Heat treatment process and system for increasing pitch yield

Abstract

A pitch production system using coal tar or decant oil for coal- or petroleum-based pitch is disclosed. Thermal treatment of distillate fractions from the pitch production process increases the overall pitch production yield. Thermal treatment systems and processes are disclosed in the embodiments. While the heaviest distillate with the highest molecular weight is thermally treated, other embodiments contemplate thermal treatment of various combinations of distillate fractions. The thermal treatment system involves heat soaking the distillate at a high, nearly constant temperature between 459 and 535°C using near-constant flow. A fraction of the thermally treated distillate may be reintroduced into the pitch production system as part of a continuous process.

Description

[Technical field]

[0001] This application claims priority to currently pending U.S. patent application Ser. No. 16 / 520,135, filed Jul. 23, 2019, the contents of which are incorporated herein by reference in their entirety. The present invention relates to improvements in the production of carbon-based pitches. More specifically, the present invention relates to the thermal treatment of distillation by-products from coal tar and petroleum processing to optimize pitch yield while minimizing quinoline insolubles and mesophase formation in the pitch. [Background technology]

[0002] Coal is a vital starting material in the manufacture of many useful products on which the modern world has come to depend. In particular, bituminous coal mined from the ground may be heated in furnaces called "coke ovens" to produce coke and coal tar by cracking, or carbonizing, the coal. Coke is widely used as a fuel and as a source of reagents in steelmaking. Coal tar is a dark liquid removed from coal in the coking process and is useful as a component of seal coats used to seal roads, asphalt, roofs, treated wood, and other construction materials. Coal tar is a complex mixture of about 10,000 compounds, primarily aromatic and semi-aromatic, that generally boil at temperatures ranging from 50° C. to over 550° C., including, but not limited to, benzene, toluene, xylene, indene, phenol, naphthalene, benzothiophene, quinoline, methylnaphthalene, acenaphthene, fluorene, phenanthrene, anthracene, carbazole, fluoranthene, pyrene, tetracene, triphenylene, chrysene, benzo(a)pyrene ("BaP"), coronene, and benzo(ghi)perylene. Coal tar can therefore be distilled into a series of fractions, with various components separated and recovered, each of which may be commercially viable in its own right. A significant fraction of the distilled coal tar material is coal tar pitch residue. This material is used to manufacture anodes for aluminum smelting and electrodes for electric arc furnaces used in the steel industry. In assessing the qualitative properties of coal tar pitch, the industry focuses on the ability of the coal tar pitch material to provide a suitable binder for use in anode and electrode manufacturing processes. Softening point, specific gravity, % quinoline insolubles, and coke value all play a role in characterizing the coal tar pitch for its applicability in these various manufacturing processes and industries. Pitch can also be obtained from petroleum, rather than coal. In such cases, oils obtained from catalytic cracking of petroleum, such as decant oil or ethylene cracker bottoms ("ECB"), can be used as starting materials for the production of petroleum pitch. Decant oil is produced from catalytic cracking and distillation of petroleum in petroleum refineries. Decant oil is storage stable, has a high boiling point, and also contains aromatic and heterocyclic compounds. ECB is less thermally stable than decant oil, and therefore its distillation product may explode during storage, making it less preferred. Coal tar and petroleum pitch production processes may be similar to each other, and may even use the same equipment, but the operating conditions are different. Alternatively, petroleum and coal tar pitch production systems may differ from each other. Furthermore, petroleum pitch may have different properties compared to coal tar pitch in terms of softening point, quinoline insolubles ("QI") %, or coke value. Often, blends of petroleum pitch and coal tar pitch in specific ratios are used to address raw material shortages, costs, and desired properties of the final product.

[0003] There are many ways to produce coal tar or petroleum pitch. For example, FIG. 1A shows one embodiment of such a process. This prior art distillation process starts with a feedstock of wet crude 1. The wet crude 1 can be either coal tar or a petroleum-based oil such as decant oil or ECB. The wet crude 1 is introduced into the first tower C1 through C1 feed line 10, which is a pipe or conduit that transfers the wet crude 1 starting material to the first tower C1. The C1 feed line 10 may be narrow compared to the internal volume of the first tower C1, so that the wet crude 1 is under high pressure in the C1 feed line 10. When the wet crude 1 enters the first tower C1 through orifice 11, it experiences a "flash" or a sudden change in pressure, which causes the constituent parts to be separated into low and high boiling components. The first tower C1 is a dehydration vessel that heats the contents at a specific temperature to remove light ends components. Alternatively, the C1 feed line 10 may pass through a heat exchanger to increase the temperature of the wet crude material 1 before entering the column. The first column C1 is primarily used to remove water to produce a "dry tar" or "dry oil" (depending on the starting material) at the bottom of the column, not exceeding a certain water content. For example, a heater such as a steam heater may be used to heat the first column C1 to a temperature of about 160° C. to fractionate the C1 distillate 12, which contains water vapor and light molecules with relatively low boiling points (e.g., water, light oil containing benzene, toluene, and xylene, commonly referred to as "BTX"). Said C1 distillate 12 rises to the top or "overhead" region of the first column C1 and is removed through the C1 vapor line 13. The remaining, heavier molecules, including polycyclic aromatic hydrocarbons ("PAHs"), fall to the bottom of the column. "Bottoms" refers to the fraction with heavy components that separate at the bottom of the distillation column as a result of their mass and high boiling point. Thus, C1 bottoms contain PAHs and other heavy molecules and are often referred to as “dry tar / oil”14.

[0004] The dry tar / oil 14 from C1 bottoms is transferred to the second column C2 through the connecting C1-C2 transfer line 15 for further distillation. Thus, the dry tar / oil from the first column C1A is the feed for the second column C2. The second column C2 is a fractionation column providing a multi-stage distillation. A distillation column with multiple stages provides optimal recovery and purity of useful chemicals. The distillation column has a number of trays 20 spanning at least a portion of the diameter of the column, which serve as stages for the formation of the distillation condensate and aid in the further separation of the components in the reflux of the components. The distillation column also includes random or structured packing 21, which aids in the separation as the vapor molecules rise through the packing. Regardless of the column configuration, the boiling vapor travels upward through the column and the liquid flows downward by gravity. At any given stage, the vapor entering from below is hotter than the liquid flowing downward. This convective contact between the vapor and the liquid transfers heat from the vapor to the liquid. This vaporizes the lower boiling lighter components in the liquid and condenses the heavier components in the vapor. This vaporization of the lights and condensation of the heavier components occurs in successive stages to separate and purify the recovered chemicals. Distillation in the second column C2 typically occurs by heating the second column C2 with a heater at atmospheric pressure from a minimum temperature of about 250-270°C to a maximum of 360°C. Light ends 22, including naphthalene (which can be sold as such or used to make dyes and plastics), may be removed in this stage or may be further concentrated to refined chemical oil ("RCO"), which distills at 210-315°C. The light ends 22 are removed from the second column C2 through a vapor line 23. A portion of the light ends 22 is returned to the second column C2 for reflux to achieve further distillation and separation. The C2 bottoms obtained from the second column C2 are commonly referred to as "topped tar / oil" 25 (again depending on the starting material) and contain high molecular weight aromatic hydrocarbons such as PAHs, and constitute the middle and heavy distillates.

[0005] The topped tar / oil 25 from the C2 bottoms is transferred from the second column C2 to the third column C3 through the C2-C3 transfer line 26. Additional tar and pitch, including topped tar, intermediate pitch or soft pitch, characterized as soft pitch 27, having a softening point of about 40-125°C, preferably about 90°C (depending largely on the desired final softening point of the final pitch), may be added to the C2-C3 transfer line 26 and combined with the topped tar / oil 25 as additional feed to the third column C3 if additional volume is required or to adjust the characteristics of the incoming feed. This third distillation column C3 may contain packing 21 and / or trays, the contents of which are heated by heaters to temperatures above 315°C. However, care must be taken at this stage, as mesophase begins to form at temperatures of 390°C. The mesophase is a precursor to coke and will appear as solid particles in the resulting pitch. However, the term "mesophase" as used herein refers only to "reportable" mesophases larger than 4 μm. "Embryonic" mesophases below 4 μm are not considered mesophases for the purposes of this disclosure. Coke in the pitch should be avoided in this particular manufacturing process because it reduces the functionality of the pitch when used in anode preparation for aluminum production and electrodes for steelmaking, limits the ability of the pitch to adequately wet the coke in the mixing step to make carbon artifacts such as anodes or electrodes, and leads to poor electrical conductivity in the resulting products. Therefore, a vacuum may be used in the third column C3 to lower the boiling points at which the components separate and distill.

[0006] Various fractions are obtained from the third column C3, each of which is a mixture of various components. For example, a first middle fraction 35 may be distilled first and removed from the third column C3 through a distillate line 36. The first middle fraction 35 is a mixture of various carbon-based molecules, such as molecules having at least 12 carbons and thus having a high molecular weight. Such molecules may be referred to as carbon black feedstock ("CBF") and may be sold to the carbon black industry to produce raw materials for the rubber industry. A portion of the first middle fraction 35 may be returned to the third column C3 for reflux and further separation. A second middle distillate fraction 38 may be removed from third column C3 through distillate line 39. The second middle distillate fraction 38 may contain compounds used in the manufacture of creosote wood preservative, which may be separated from the remaining distillate for further purification and use in other applications, such as railroad tie treatment, utility poles, and other wood preservative applications. A portion of the second middle distillate fraction 38 may be returned to third column C3 for reflux and further separation. The heavy fraction 41 further comprises higher molecular weight components. The heavy fraction may be removed from the third column C3 through vapor line 42. The heavy fraction 41 is a co-product and may comprise carbon black feedstock. A portion of the heavy fraction 41 may be returned to the third column C3 for reflux and further separation. What remains in the C3 bottoms of the third column C3 is coal tar pitch 50. This pitch 50 is a thick black liquid containing a mixture of chemicals such as PAHs, and is the desired end product of the pitch production system described above. The pitch can be removed from the third column C3 through pitch outlet line 51 and used for subsequent applications. This pitch 50 is characterized by various qualities such as softening point, specific gravity, QI%, coke value, etc. to determine its quality and applicability in various manufacturing processes and industries. The distillation process can be adjusted so that various fractions of the distillate are removed at different times and / or in different volumes to selectively modify the resulting characteristics of the pitch 50 produced as desired. For example, coal tar pitch 50 having a Mettler softening point of about 108-140° C. and a QI of 10-20% or less can be used as a binder in anode and electrode production. An even lower QI is required for impregnated pitch.

[0007] In a second embodiment of prior art pitch production, as shown in Figure 1B, wet crude material 1 feedstock is flashed through orifice 11 into first tower C1 and dewatered. Light oil and water are removed as C1 distillate 12, and dry tar / oil 14 is transferred through transfer line 15 to second tower C2. Second column C2 is a multi-stage fractionator, as in other prior art processes, heated by heaters to a temperature of about 250-270° C. at atmospheric pressure. In this embodiment, however, light fraction 22 is distilled off from second column C2 via vapor line 23, and middle fraction 38 is distilled off via distillate line 39. Light fraction 22 may include refined chemical oils ("RCO") and other light distillate oils. Middle fraction 38 may include creosote, which may be further separated and refined. Light and middle fractions 22, 38 may be combined and stored together, or may be further processed to produce refined creosote. In this embodiment, the topped tar / oil 25 in the C2 bottoms is then transferred to the fourth (third in this embodiment) column C4 through the C2-C4 transfer line 26' and may be introduced or flashed into the fourth column C4 through the orifice 11 (which may be a sparger). This flashing separates the heavy fraction 41, such as heavy oil, from the remaining residue, allowing the heavy fraction 41 to be removed from the fourth column C4 through the vapor line 42. The components of the heavy fraction 41 may then be separated by further distillation or processing to produce carbon black pitch and other aromatics. The bottom residue of the fourth column C4 is a pitch 50, which may be a coal tar pitch if starting with coal tar, or a petroleum pitch if starting with decant oil.

[0008] A third embodiment of the prior art pitch production uses four columns to distill and / or separate oil from residue in pitch production, as shown in FIG. 1C. Specifically, wet crude material 1 is first dehydrated in a first column C1 to remove a C1 distillate 12 containing water and light oil. The dried tar / oil 14 is then distilled in a second column C2 of the distillation apparatus to remove a light fraction 22. The resulting top-off tar / oil 25 is then transferred to a third column C3 of another distillation apparatus, where a middle fraction 38 is removed. In this embodiment, the residue from the third column C3 is transferred to a fourth column C4, which is a flash column, where a sharp pressure difference is used to separate the heavy fraction 41. The remainder is the desired pitch 50.

[0009] The above prior art pitch production processes can produce pitch yields of 15-60% calculated from one of the starting coal tar and decant oil materials, depending on the process parameters. Process optimization and product yield increases, while significant, have been difficult to determine, and producing a commercially saleable product on an industrial scale has proven even more difficult. One method for optimizing yield involves thermal treatment (also called thermal treatment or heat soaking) of the distillates and by-products used as feedstocks in pitch production. It is recognized that the thermal treatment process has three main parameters: temperature, pressure, and residence time. Numerous attempts have been made to identify ways to improve pitch yield (and other properties) through the use of heat treatment, but the capabilities vary widely and few have been commercially successful at the industrial production levels necessary for commercial development. Each reference discloses a wide range of times and temperatures, the mechanisms leading to increased yields are poorly understood, and there is insufficient disclosure of the actual times and temperatures associated with specific yields.

[0010] US Patent 3,140,248 discloses the preparation of binder pitches using a soaking step. Petroleum fractions with boiling points between 200 and 650°C are catalytically cracked and then thermally cracked. The hot residue from the pyrolysis is treated in a soaking zone at temperatures between 480 and 590°C for 4 to 20 minutes at 2.1 to 27.6 bar (30 to 400 psi). Short residence times and high linear velocities are preferred to minimize coking. The use of soaking coils is disclosed but not described in detail. U.S. Patent No. 3,318,801 discloses a heat soak drum and short tube heater. The heat soak drum is used at temperatures of 340-425°C and 0-2.1 bar(g) (0-30 psi(g)) for 3-90 minutes. The heating tube induces rapid heating to 425-510°C at 1.7-17.2 bar(g) (25-250 psi(g)) for 2-30 minutes. U.S. Patent No. 3,673,077 discloses heat soaking for the production of binder pitch to increase the toluene insolubles ("TI"). The conditions are 350-450°C, a pressure of about 5.2 bar(g) (75 psi(g)), and a residence time of 15 minutes to 25 hours. Optionally, air is passed through the reactor. U.S. Patent No. 4,039,423 discloses the thermal treatment of decant oil to form a petroleum pitch. Conditions include 413-524°C, 15.2-30.3 bar(g) (220-440 psi(g)), and residence times of 3-300 minutes. Turbulent continuous flow conditions are preferred over laminar flow to minimize coke formation and keep the QI in suspension. This also increases efficient mixing of the materials and reduces reaction times. The softening point of the product ranges from 79-135°C. EP 1739153 discloses the use of thermal treatment of coal tars and distillates under an inert atmosphere. Conditions are 340-400°C, less than 10.0 bar(g) (145 psi(g)), and a residence time of 3-10 hours. A preferred embodiment is 370-400°C, 1.0 bar(g) (14 psi(g)), and 4-6 hours. Thermal treatment under inert conditions is speculated to increase molecular planarity and stability of the reaction products, limiting side reactions. This improves wettability, graphitizability, and reaction yields. Starting materials include anthracene oil. US Patent No. 8,757,651 discloses the use of thermal treatment of coal tar distillate at 350-440°C and pressures of 3.5-8.3 bar(g) (50-120 psi(g)) for pitch production. Residence times range from 1-7 hours. The starting material is creosote oil with a low QI. It is speculated that thermal treatment can polymerize the relatively low molecular weight components into larger molecules. Downstream distillation of the product is contemplated to separate the different species. The final product may have a coke value of 55-70% and a softening point of 90-140°C. A QI of less than 15% is also a goal. Batch and continuous thermal treatments are contemplated, but no reactor details are given. US Patent No. 9,222,027 discloses heat treatment using an electrically heated tubular reactor operating at high velocity and pressure. Salt and molten metal baths are also disclosed. Conditions are 450-560°C, 34.5-62.1 bar(g) (500-900 psi(g)), and residence time 1-2 minutes. Laminar and turbulent flow in the reactor pipes are addressed, with turbulent flow being preferred. Reynolds numbers for turbulent flow are generally accepted as greater than 4000. Reynolds numbers greater than 10,000 are preferred, with best experimental results obtained at 25,000. Speculation is given for the use of Reynolds numbers greater than 50,000, but no empirical or experimental data is available. US Patent Publication No. 20170121834 discloses the production of petroleum pitch using thermal processing. A soaker reactor is used at temperatures ranging from 360-460°C and 14.8-18.3 bar (215-265 psi) for 15 minutes to 5 hours. An inert environment, or at least oxygen-free, is required. Starting materials include decant oil, lubricant extracts, and gasoline.

[0011] Despite these efforts, there is still room for improvement, as the prior art solutions have not achieved commercial success. Thus, what remains unknown in the art is a method and apparatus for thermal treatment that can be applied to coal tar and petroleum by-products and that produces predictable and reproducible results in commercial scale operations. A significant limitation to the application of the prior art is the production of excessive coke or mesophase after thermal treatment, which prevents continuous processing of the starting material. This is typically due to overapplication of the treatment or excessive variation in the time and temperature of the treatment. Prior art teachings that utilize recycle of the contents of the batch reactor identify the recycle as detrimental to pitch quality. Summary of the Invention [Problem to be solved by the invention]

[0012] A thermal treatment process is disclosed in which coal tar or distillate by-products from petroleum production are subjected to thermal treatment with particular emphasis on time, temperature, and pressure parameters to minimize coking and mesophase formation. A corresponding coal tar or petroleum pitch production process utilizing the thermal treatment process is disclosed. [Means for solving the problem]

[0013] Specifically, the thermal treatment process of the present invention utilizes heavy distillates from downstream pitch production and decant oil from petroleum production as starting materials. The thermal treatment process of the present invention thermally treats these starting materials at specific temperatures, pressures, and residence times to recover additional pitch and increase the overall pitch yield. Thus, the thermal treatment process of the present invention increases the efficiency of the overall pitch production while benefiting from otherwise less economical by-products. Control of the relevant temperature, pressure, and residence time variables in the thermal treatment process is crucial to minimize QI levels and avoid mesophase formation. The present invention utilizes high temperature ranges that can exceed 510°C and pressure ranges that exceed 4.1-20.7 bar(g) (60-300 psi(g)) to keep the starting materials and reactants in the liquid phase, so that they are constantly moving throughout the thermal treatment system. However, since mesophase is known to form at approximately 390°C, the present invention contemplates minimizing residence times in the corresponding processes to minimize the possibility of mesophase formation and subsequent coking. The present invention also attempts to achieve as much turbulent heating of the feedstock followed by plug flow in the reactor section of the thermal treatment device as is physically possible in real world conditions, with the goal being to maintain a continuous and consistent flow through the system so that the starting materials are exposed to heat nearly equally, which we uniquely identify as "near-uniform flow." References to plug flow herein should be understood as near-uniform flow. Longer time in the system increases the likelihood of mesophase formation and coking, which can be addressed by lowering the temperature, but is not preferred. The thermally treated starting material can then be returned as additional feed to the pitch production process as part of a continuous process to increase yields.

[0014] In addition, it has been noted that the softening point of commercially used pitches is likely to increase in the future. Currently, most commercial pitches and pitch blends have softening points in the range of 90-150°C. The decrease in pitch softening point is a result of the high PAH content, and reducing this content will increase the softening point. Many of the PAH compounds are potentially carcinogenic, and some states and countries are becoming increasingly sensitive to public and environmental exposure to these substances. Thus, removing more of these high PAH compounds will remove potentially carcinogenic compounds, but will also result in an increase in the softening point, and therefore may increase the softening point of pitches in the future. Heavy fractions contain many highly aromatic compounds, and it is known that an increase in the amount of heavy fraction removed during pitch production will result in a higher softening point for the resulting pitch. A method to utilize this additional removed heavy fraction would be beneficial, especially if it could be used for further pitch generation. The systems and processes disclosed herein provide such benefits. The heat treatment and pitch production system and process, together with its features and advantages, will become more apparent with reference to the following detailed description and accompanying drawings. [Brief description of the drawings]

[0015] [Figure 1A] FIG. 1 is a schematic diagram of a first embodiment of a prior art system for producing pitch from wet crude coal tar or decant oil. [Figure 1B] FIG. 1 is a schematic diagram of a second embodiment of a prior art system for producing pitch. [Figure 1C] FIG. 1 is a schematic diagram of a third embodiment of a prior art system for producing pitch. [Figure 2A] FIG. 1 is a schematic diagram of a first embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from coal tar. [Figure 2B] FIG. 1 is a schematic diagram of a second embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from coal tar. [Figure 2C]FIG. 2 is a schematic diagram of a third embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from coal tar. [Figure 3A] FIG. 1 is a schematic diagram of a first embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from petroleum by-products such as decant oil. [Figure 3B] FIG. 1 is a schematic diagram of a second embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from petroleum. [Figure 3C] FIG. 1 is a schematic diagram of a third embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from petroleum. [Figure 3D] FIG. 1 is a schematic diagram of a fourth embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from petroleum by-products such as decant oil. [Figure 3E] FIG. 1 is a schematic diagram of a fifth embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from petroleum. [Figure 3F] FIG. 1 is a schematic diagram of a sixth embodiment of a pitch production system of the present invention incorporating thermal processing to produce increased yields of pitch from petroleum. [Figure 4A] 1 is a schematic diagram of a first embodiment of a heat treatment system of the present invention. [Figure 4B] FIG. 2 is a schematic diagram of a second embodiment of a heat treatment system of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Like reference numbers refer to like parts throughout the several views.

[0017] As shown in the accompanying drawings, the present invention relates to thermal treatment systems 300, 300' and pitch production systems 100, 100', 100" (from coal tar) and 200, 200', 200" (from petroleum) utilizing such systems. For example, FIGS. 2A-2C illustrate various embodiments for producing coal tar pitch 150 from coal tar 102, and FIGS. 3A-3C show various embodiments for producing petroleum pitch 250 from decant oil 203. Various thermal treatment systems 300, 300' that can be used with any of the pitch production systems are shown in FIGS. 4A-4B.

[0018] Coal tar Turning first to the coal tar pitch production system, a first embodiment of a pitch production system 100 (shown diagrammatically in FIG. 2A) begins with the dewatering of coal tar 102. The crude coal tar 102 will likely have some water or moisture from the initial coking process, but the moisture should be less than about 4% by weight so as not to slow down the tar processing. The coal tar 102 is transferred in a C1 feed line 110 to a first tower C1 for dewatering. The C1 feed line 110 passes through at least one heat exchanger (not shown) where heat from other elements of the system is applied to the C1 feed line 110 to preheat the tar 102 in the C1 feed line 110 while simultaneously cooling other components. The heat exchangers disclosed herein and in the figures do not mix the components, but are in sufficient contact to allow for the transfer of heat from hot to cold components. This allows for efficient use of heat generated within the system. This is especially important in industrial scale production where the cost of heating the components of the system can be very expensive and may require large amounts of fuel. To use the heat efficiently, multiple heat exchangers may be placed throughout the system. In at least one embodiment, the heat exchangers may include routing of various distillate lines to simultaneously cool the corresponding distillate for storage and heat other components, such as the tar 102 feedstock. In other embodiments, heat exchange oil may be used in the heat exchangers to heat the cooler components.

[0019] In at least one embodiment, the coal tar 102 has an initial temperature of about 50° C. The coal tar 102 is heated to about 160° C. as the C1 feed line 110 passes through at least one, and possibly two or more, heat exchangers. Thus, the coal tar 102 is at a temperature of at least 160° C. when it enters the first column C1. The coal tar 102 is under pressure, for example, about 6.9 bar (100 psi), as it is pumped through the C1 feed line 110. The first column C1 is an atmospheric column at a pressure of about 1 atm (about 14.7 psia). As the coal tar 102 enters the first column C1 through the orifice 111, the sudden pressure drop causes the coal tar 102 to flash and initiate separation of its components. Preferably, since there is no reboiler or other heater to heat the first column C1, the heat of the first column C1 is generally that of the incoming wet coal tar 102, which is at least 160°C. The water vapor and distillate gas oil (such as BTX) travel up the first column C1 and may be removed by the C1 vapor line 113 and condensed by a cooling water condenser at a maximum temperature of about 75° C. before being recovered as the C1 distillate 112. Water distills at a temperature of approximately 100° C. The gas oils also distill at about the same temperatures: benzene (80° C.), toluene (110° C.) and sometimes xylene (144° C.). Therefore, these gas oils and water are distilled and recovered together. The gas oils make up about 1% of the coal tar feedstock, are immiscible in water, and are decanted as the top layer of the C1 distillate 112 and pumped for storage. The specific gravity of the gas oils must be monitored and not be too high, for example, not more than about 0.92 at 15.5° C., beyond which separation from the condensed water may be insufficient. This may occur if the wet coal tar 102 for the first column C1 is too high. Distillation in the first column C1 is continued until the dried tar 114 recovered in the C1 bottoms is reduced to a moisture content of about 2.5% by weight or less, preferably less than 0.5%, and may be characterized as having a specific gravity of at least 1.15 at 15.5° C. The dried tar 114 may then be removed from the first column C1 through a transfer line 115, which may pass through at least one heat exchanger to increase the temperature of the dried tar 114 to about 250-270° C. before entering the second column C2 for tar topping.

[0020] In the second column C2, the dry tar 114 is further distilled to recover a light fraction 122 in a process called "tar topping" because the lowest boiling fraction of the dry tar 114, i.e., the overhead fraction, is removed. This fraction may include crude naphthalene as RCO. The incoming dry tar 114 is already at a temperature of about 250-270°C when it enters the second column C2 and may be pumped under flow control at a C2 feed flow rate based on the heater, vacuum and condenser system associated with the second column C2. The second column C is an atmospheric column at a pressure of 1 atm and has distillation trays 120 below the dry tar 114 feed point. In at least one embodiment, there are 20-30 trays in the second column C2. Additionally, there may be at least one packed column section or packing 121 above the dry tar 114 feed point to increase the purity of the light fraction 122 as it distills. A heater, such as a fired process heater reboiler or other suitable heat source, may be attached to the second column C2 to heat the bottoms contents to a temperature of about 350-360° C. and distill an additional light fraction 122. The light fraction 122 vapor travels up the second column C2 and is typically removed through distillate line 123 at a rate of about 15-22% of the C2 feed rate. The light fraction 122 is then condensed in a condenser to convert it to liquid form, which may include RCO along with naphthalene, or may even be water cooled in a heat exchanger. Preferably, the light fraction 122 may have a naphthalene content of 55-65% and may be further processed in a purification unit to separate and purify the naphthalene. The light fraction 122 also preferably has a maximum specific gravity of 1.03 at 70° C. The characteristics of the light fraction 122 are also shown in Tables 1 and 2 below. At least a portion of the light fraction 122 is returned to the top of the second column C2 and refluxed to limit the amount of high boiling compounds in the light fraction 122 and to increase the naphtha content of the light fraction 122. It should be noted throughout this disclosure that all distillation and vapor streams may alternatively be removed and stored for further use in the future and inserted into these processes at appropriate times, as is well known to those skilled in the art. This liquid C2 reflux condenses the high boiling compounds in the vapor above the feed point and improves the separation efficiency of the overhead rectification section of the second column C2.The light fraction 122 may be refluxed at at least 10% of the C2 feed rate to increase the naphthalene content in the light fraction 122. Approximately 15-22% of the original coal tar 102 may be removed as the light fraction 122. The C2 bottoms contain topped tar 125 and are transferred through transfer line 126 to the third column C3 to produce pitch at the desired softening point. Heat is retained along transfer line 126 so that the topped tar 125 entering the third column C3 is at approximately the same temperature as the C2 bottoms. Optionally, soft pitch 127 may be added to transfer line 126 prior to the third column C3 to combine with the topped tar 125 to form the C3 feedstock for temperature control, feed augmentation, or residual oil removal from the added soft pitch. The third column C3 is preferably a vacuum column operating at a pressure of about 40-100 mbar absolute (about 0.77-1.9 psia absolute). The third column may also have a combination of trays 120 and a packed top section 121 for multi-stage distillation. A heater (such as, but not limited to, a fired process heater reboiler) may be used to heat the C3 column bottoms to a temperature of about 350-360°C and boil off the heavy oil distillate from the topside tar 125 by recirculation of the C3 bottoms liquid. When the topping tar 125 is distilled in the third column C3, the distillate vapor rises in the column and is condensed by recycling various distillates. Specifically, a first middle distillate 135 is extracted through a distillate line 136 and can be externally cooled with other processes, heat transfer oil streams, or water for condensation. The fraction has the characteristics described in Tables 1 and 2 below. The first middle distillate 135 is an intermediate carbon black feedstock that is mainly produced as a blended oil to support the quality of other products. A portion of it may be refluxed back to the third column C3 or sent to storage and sale. Less than about 5% of the initial coal tar 102 is distilled as the first middle distillate 135.

[0021] The second product from the third column C3 is a second middle distillate 138, which may contain components used as creosote, such as WEI-C or AWPA creosote base oil. The second middle distillate 138 is removed through a distillate line 139 and may be externally cooled and condensed with other processes, heat transfer oil streams, or water. Approximately 13-22% of the total crude tar 102 is distilled as the second middle distillate 138. The second middle distillate 138 may have the characteristics described in Tables 1 and 2 below, and / or may be characterized by a maximum of 10% distillation up to 300° C., a maximum of 65-90% distillation up to 355° C., and in certain cases (especially in Europe) a maximum of 10 ppm benzo(a)pyrene. At least a portion of the distilled second middle distillate 138 may be returned or recycled to the third column C3 for reflux. The creosote contained in the second middle distillate 138 is very useful in other industries, such as wood preservatives, so monitoring for quality control may be performed by monitoring the distillation range and the content of benzo(a)pyrene. The quality of the second middle distillate 138 is controlled by its production rate (preferably in the range of 14-20% of the total crude coal tar 102) and the temperature at which it is recycled to the third column C3 for reflux (preferably in the range of 100-115°C). The third product obtained from the distillation of the topside tar 125 in the third column C3 is a heavy fraction 141, which may be removed through a distillate line 142 and condensed with other processes, a heat transfer oil stream, or external cooling with water. This heavy fraction 141 is also a mixture of components, including primarily carbon black feedstock, but with additional components not found in the first middle distillate 135, as shown in Table 1 below, which elevate the PAH level and boiling point of the heavy fraction 141. Additionally, the heavy fraction 141 has a very low, essentially zero, concentration of QI and toluene insolubles. The fraction may also be characterized by up to 10% distillation by 355° C. At least a portion of the heavy fraction 141 may be returned to the third column C3 for further distillation and separation by reflux. Approximately 14% of the total crude tar 102 may be distilled off as the heavy fraction 141.

[0022] The various distillates for the first embodiment of the coal tar production system 100 generally have the characteristics shown in Tables 1 and 2 below, with the amounts of the components varying depending on the target softening point of the pitch produced. [Table 1]

[0023] [Table 2]

[0024] The residue remaining in the C3 bottoms is the desired coal tar pitch 150, whose quality is determined by, but not limited to, its softening point, the percentage of distillate up to 355°C, the QI and the toluene insolubles. All three of the above parameters are controlled by the C3 bottoms liquid temperature and the heavy fraction 141 production rate. Preferably, the resulting pitch 150 has a softening point in the range of 100-140°C and a QI of 20% or less. Furthermore, the final pitch 150 preferably has an ash content of 0.4% or less and a distillate up to 355°C of 4% or less. The system 100 and process can produce a pitch yield of at least about 40%. The pitch 150 is removed from the third column C3 via pitch outlet line 151 for storage, transport, use or sale.

[0025] The pitch production system 100 also includes a thermal treatment system 300. Details of the thermal treatment system 300 are shown more fully below with reference to Figures 4A and 4B, but it should be noted that the thermal treatment process 300 may increase the total pitch 150 yield by 2-10%, totaling about 42-50% yield. In certain embodiments, the pitch yield may increase to a preferred target of 44% total pitch yield. This additional pitch 150 is obtained by thermally treating the distilled heavy fraction 141 at a specific preselected temperature and residence time, and then introducing the thermally treated product into a third column C3 for further distillation and separation of the pitch in the pitch production system 100, as shown in Figure 2A.

[0026] The present invention also includes a second embodiment of a coal tar pitch production system 100', as shown diagrammatically in FIG. 2B. Coal tar 102 is heated to about 160-170° C. under a pressure of about 6.9 bar (100 psi) as it passes through at least one heat exchanger (not shown) in a C1 feed line 110. The coal tar 102 is flashed into a first column C1 through an orifice 111, where the C1 feed line 110 and the first column C1 meet in fluid communication. The first column C1 is a dehydrator under atmospheric pressure of about 900 mmHg (17.4 psia) in this embodiment. The pressure difference between the C1 feed line 110 and the first column C1 flashes the wet coal tar 102 to separate water vapor and light oils (such as benzene, toluene, and xylenes) as a C1 distillate 112. As previously mentioned, the residue remaining at the bottom of first column C1 is dry tar 114, which remains in first column C1 until the moisture content of dry tar 114 is about 2.5% or less, preferably 0.5% or less, which has similar characteristics to the dry tar 114 described above. The dried tar 114 is transferred through C1-C2 transfer line 115 to second column C2, which may be a fractionator or a multi-stage distillation column as described above. Here, second column C2 may be under vacuum at a pressure of about 120-180 mmHg (2.3-3.48 psia) and heated to an internal temperature of about 182-230° C. In this second embodiment of production system 100′, a light fraction 122′ is distilled and recovered by distillate line 123. The light fraction 122′ may have the composition and characteristics shown in Table 3 below. A middle fraction 138′ is also distilled and removed from second column C2. The middle fraction 138′ may have the composition and characteristics shown in Table 3 below. The C2 bottoms are heated by a heater (not shown) to a temperature of about 350-365° C. to recycle the residue and assist in the distillation. The distilled light and middle fractions 122', 138' may be combined and stored together, or may be stored separately and later processed, such as for producing refined creosote that can be sold or used for other purposes. The C2 bottoms contain topped tar 125', which may have similar characteristics as those described above, at a temperature of about 350-365°C and a pressure of about 180-220 mmHg (3.48-4.25 psia). However, in this second embodiment of the pitch production process 100', the topped tar 125' is transferred from the second column C2 to the fourth column C4 through a C2-C4 transfer line 126'. The fourth column C4 is a flash column, rather than the fractionator third column C3 described above. The topped tar 125' may be flashed into the fourth column C4' through an orifice 111 (such as a sparger or other suitable inlet opening). The fourth column C4 may be under vacuum, at a pressure of about 40-70 mmHg (0.77-1.35 psia). As the topping tar 125 is flashed to the fourth column C4, a heavy fraction 141' may separate at a temperature of about 290-365° C. and be removed through a distillate line 142. This heavy fraction 141' has the composition and characteristics shown in Table 3 below. The heavy fraction 141' is then transferred to a thermal treatment system 300, described below, for thermal treatment to increase pitch production. After passing through the thermal treatment system 300, the thermally treated product is introduced into the C1-C2 transfer line 115 and added to the C2 feedstock for additional fractionation and distillation. The yield of pitch 150' produced through this process is increased by 20-40% over the initial yield of the heavy fraction 141' without thermal treatment.

[0027] The various distillates produced by the second preferred embodiment of the pitch production system may have the characteristics of Table 3.

[0028] [Table 3]

[0029] In a third embodiment of a pitch production system 100″ shown in FIG. 2C , coal tar 102 is heated to about 124-184° C. under a pressure of about 10.9-11.1 bar (158-161 psi) as it passes through at least one heat exchanger (not shown) in a C1 feed line 110. The coal tar 102 is flashed into a first column C1 through an orifice 111 where the C1 feed line 110 and the first column C1 meet in fluid communication. The first column C1, in this embodiment, is heated to about 51.7 mm Hg (15.6 psi). sia atmospheric pressure dehydration apparatus. The pressure differential between the C1 feed line 110 and the first column C1 flashes the wet coal tar 102 to separate water vapor and light oil (such as BTX) as a C1 distillate 112 having a temperature of about 115° C. As previously mentioned, the residue remaining at the bottom of the first column C1 is a dry tar 114, which remains in the first column C1 until the water content of the dry tar 114 is 2.5% or less, preferably about 0.5% or less, and the temperature is about 230° C., which may have similar characteristics to the dry tar 114 described above.

[0030] This third embodiment of the system 100″ differs from the previous embodiment in that it uses four columns for distillation and separation of oil in pitch production. Specifically, the dried tar 114 is transferred to the second column C2, which is a fractionator through the C1-C2 transfer line 115 and can be heated to a temperature of about 262° C. by a heater (not shown). A light end 122″ is distilled off from this second column C2 and can be refluxed for further separation. The light end 122″ has the characteristics shown in Table 4 below and can include RCO and other gas oils. The resulting topped tar 125″ is produced in the bottom of the second column C2 and is transferred to the third column C3 through the C2-C3 transfer line 126 for further distillation. In the third column C3, the tar may be heated to a temperature of about 330° C. with a heater (not shown) to distill a middle distillate 138″, which may have the characteristics shown in Table 4 and may include creosote and certain carbon black feed compounds. The middle distillate 138″ may be refluxed to the third column C3 for further distillation and cracking. The resulting soft pitch 127″ is produced in the bottom of the third column C3 and may be close to the desired pitch, but may have a softening point that is too low (such as in the range of about 90° C.). To increase the softening point of the pitch, more oil must be removed. Thus, the soft pitch 127" is transferred through the C3-C4 transfer line to a fourth column, C4, which may be a flash column that utilizes a differential pressure to remove oil from solids. For example, the fourth column, C4, may be under a vacuum of about 1 psia. The differential pressure causes the heavy fraction 141" to distill off, leaving the desired coal tar pitch 150" at the bottom of the fourth column, which may be removed for further use or sale. The heavy fraction 141" may be at a temperature of about 310°C and a pressure of about 0.11 psi(g), and may further have the characteristics shown in Table 4 below. As described in more detail below, process 100" continues with thermal treatment of the distilled heavy fraction 141" through thermal treatment system 300. After being thermally treated, the heavy fraction 141" is either combined with the topsoil tar 125" as C3 feedstock or introduced separately into third column C3 for distillation of the middle fraction 138" and subsequent distillation of the heavy fraction 141" from newly produced additional pitch.

[0031] The distillate produced by the third preferred embodiment of the coal tar pitch production system 100″ may have the characteristics of Table 4.

[0032] [Table 4]

[0033] Petroleum Pitch Petroleum products may be used as starting materials for the production of petroleum pitch 250, as shown in Figures 3A-3C. For example, as shown in Figure 3A, petroleum fractions such as decant oil are generally identified as oil 203 and are used as starting products for pitch production. Decant oil 203 is a mixture of heavy oils obtained from the catalytic cracking of petroleum. Decant oil is similar in many ways to coal tar 102, except that it contains more aliphatic hydrocarbons from petroleum, which makes the chemistry of the decant oil 203 processing more complex. However, many of the steps are similar. In certain embodiments, ECB may be used as the oil 203 for pitch production 200, either independently or in combination with decant oil. However, ECB is difficult to handle reliably as a starting reagent, especially since it has low stability as a vapor and may exhibit a tendency to explode. ECB is also generally not suitable for the production of impregnated pitch. Decant oil may be preferred in at least one embodiment due to its very high storage stability and ease of handling. Although the petroleum pitch production systems 200, 200', 200" are described with respect to the use of decant oil 203 as a starting material, it should be understood that heavy oil or compositions thereof obtained from petroleum cracking (such as catalytic cracking) having suitable sulfur, carbon or coke value characteristics may be used as the starting material.

[0034] The dewatering and distillation characteristics of the petroleum pitch production systems 200, 200', 200" shown in Figures 3A-3C and 3D-3F may be similar to those of the coal tar production systems s100, 100', 100" of Figures 2A-2C, respectively. However, the petroleum pitch production systems 200, 200', 200" may have different operating parameters at each step. Those skilled in the art should note that the operating parameters for coal tar may be equally applicable to petroleum unless specifically identified as different. Furthermore, as shown in Figures 3A-3C, the thermal treatment process 300, 300' may be performed as the first step of the process prior to dehydration and distillation of the starting material in the case of petroleum pitch 250 production, whereas it is performed after dehydration and distillation in the case of coal tar pitch 150 production. This is mainly because the chemical composition of decant oil is free of heavy components and generally has a low water content upon delivery compared to coal tar. Thus, the decant oil distillation by-product is generally not suitable for independent thermal treatment. Thus, the input of the thermal treatment system 300, 300' in the petroleum pitch production systems 200, 200', 200" is the decant oil 203. The thermal treatment system 300, 300' is described in more detail below with reference to Figures 4A and 4B. The system may be the same as the system used to produce the coal tar pitches 150, 150', 150".

[0035] Referring to FIG. 3A, in a first embodiment of pitch production system 200, decant oil 203 is first processed through thermal treatment system 300 and then sent to the remaining distillation system. The specific processing path is determined by whether it is a batch or continuous process and the water content. To the extent that decant oil 203 does not require dehydration, as described below with respect to FIGS. 3A-3C, the C1 dehydrator may be omitted and streams 326′ and 215 may be combined as would be known to one skilled in the art. To the extent that a C1 dehydrator is required or potentially as part of a continuous process, decant oil 203 or the combined light fraction 222, first middle fraction 235, second middle fraction 238, heavy fraction 241, or any combination or subcombination thereof may be reintroduced to thermal treatment system 300 or the C1 dehydrator, as described in further detail below. In that case, as shown in Figures 3D-3F, the decant oil 203 may alternatively be sent to the C1 dehydrator via input stream 310A. After dehydration, the decant oil may be returned to thermal treatment via output stream 215A for introduction into thermal treatment system 300, as described below. Additionally, as part of a continuous system, distillate stream 243 may be returned via input stream 310A for reintroduction into the first column C1 dehydrator. In an embodiment using dehydrator C1, the material is introduced and flashed into the first column C1 dehydrator. The pressure differential between the incoming thermally treated oil and first column C1 separates light oils such as naphtha or BTX (benzene, toluene, and xylenes) from the remainder of the decant oil 203, which is removed as C1 distillate 212 via distillate line 213. As described in more detail below, BTX and other light oils may be extracted from reactor 320. The remaining dried oil 214 is transferred to fractionator column 2 C2 via C1-C2 transfer line 215 or returned to thermal treatment as described above. This column C2 is preheated in a heater to a temperature of about 350-365° C. to distill off the light ends 222 from the oil (which may include RCO and creosote). The light ends 222 may also be sent to recycle through system 200 for further thermal treatment and through light ends stream 224 for further distillation. The C2 bottoms residue includes top-cut heat treated oil 225, which is transferred to a heat exchanger to raise the temperature of top-cut oil 225 to about 375-415°C before entering the third column C3 where it is further distilled. As top-cut oil 225 is distilled, various distillates may be removed from the petroleum pitch 250. Specifically, a first middle distillate 235, which corresponds to the carbon black feedstock and other components, may be distilled first. A second middle distillate 238 may be extracted and contain slightly heavier molecules. A heavy distillate 241 may be distilled last and have the heaviest oils and components. Each of these distillates may be combined in various combinations and sent to recycle through system 200 for further thermal treatment and distillation through a first middle distillate stream 237, a second middle distillate stream 240, and a heavy distillate stream 243, respectively. It should be noted that pitch 250 must be removed before recycling through thermal treatment, as described below. 3A, the various distillate streams 224, 237, 240, and 243 may all be combined in any combination or subcombination to form a single input for combination with the fresh decant oil 203 entering the thermal treatment system 300 at the beginning of the pitch production process 200, or may be introduced into the C1 dehydrator as needed. However, the various distillate streams 224, 237, 240, and 243 may also be applied separately to the thermal treatment system 300 for recycle.

[0036] A second embodiment of pitch production system 200', as shown in FIG. 3B, is very similar but has a different distillation procedure. Specifically, both light fraction 222' and middle fraction 238' may be distilled in a second column C2 heated to 350-415° C. The resulting tops 225' are then transferred to a fourth column C4, which is a flash column as described above. The heavy fraction 241' is distilled in this fourth column C4 to produce a resultant petroleum pitch 250'. Each of the light fraction 222', middle fraction 238' and heavy fraction 241' may be sent for recycling through system 200' and may be combined for reinjection into thermal treatment system 300 or may be separately injected for further thermal treatment and distillation of light fraction stream 224, middle fraction stream 240 and heavy fraction stream 243, respectively.

[0037] A third embodiment of pitch production system 200'', shown in FIG. 3C, is similar except that it uses four columns for the dehydration and distillation process. In this case, light fraction 222'' is removed in the second column C2 fractionator to produce tops 225'', middle fraction 238'' is removed from the third column C3 fractionator to produce soft pitch 227', and heavy fraction 241'' is removed from the fourth column C4 flash column to produce final petroleum pitch 250''. Each of light fraction 222'', middle fraction 238'', and heavy fraction 241'' may be sent for recycling through system 200'' for further thermal treatment and distillation via light fraction stream 224, middle fraction stream 240, and heavy fraction stream 243, respectively, and may be combined for reinjection into thermal treatment system 300 or may be fed separately. In a preferred embodiment, the light fraction 222', the middle fraction 238' and the heavy fraction 241' may have the properties shown in Table 5 below as derived from the second embodiment of the petroleum pitch production system 200', although the distillates derived from the other embodiments may be similar.

[0038] [Table 5]

[0039] Heat Treatment The present invention also includes thermal treatment systems 300, 300' for heating the distillate from the coal tar pitch production 100, 100', 100" or the starting decant oil from the petroleum pitch production 200, 200', 200". Each of the thermal treatment systems 300, 300' uses specific temperatures and retention times to concentrate the thermally treated material to produce additional pitch that would not occur without the thermal treatment, thereby increasing the overall pitch production yield. It should be noted that these systems are intended to be interchangeable and constitute alternative embodiments of any of the systems described herein.

[0040] 4A illustrates a first embodiment of a thermal treatment system 300. The input to the system 300 is from a pitch production system, such as a combination of a heavy distillate 141 from a coal tar pitch production 100, a decant oil 203 or a light distillate 222 from a petroleum pitch production 200, a middle distillate 238 (or first and second middle distillates 235, 238), and a heavy distillate 241. Regardless of type, the input enters the thermal treatment system 300 through a thermal treatment input stream 310. The feed material may have a temperature in the range of 265-300°C, moving at a flow rate of about 4-9 MT / hr, and a pressure of about 3.3-7.5 bar(g) (47.86-108.78 psi(g)); more preferably a temperature in the range of 273-293°C, a flow rate of about 5.5-9 MT / hr, and a pressure of about 3.5-6.5 bar(g) (50.76-94.27 psi(g)); even more preferably a temperature of about 278-288°C, a flow rate of about 6.5-9 MT / hr, and a pressure of about 3.8-5.5 bar(g) (55.11-79.77 psi(g)); most preferably a temperature of about 283°C, a flow rate of about 7 MT / hr, and a pressure of about 4.5 bar(g) (65.27 psi(g)). It should be noted that the disclosed flow rates are not intended to be process limitations. For flow rates beyond the above ranges, one need only recalculate the remaining variables according to this specification. The thermally treated input stream 310 may be a pipe or other conduit having a diameter of about 2 inches. A pump 311, such as but not limited to a pressure pump, is used on the thermally treated input stream 310 to move the input material therethrough and pressurize it to a pressure of about 6.2-11.7 bar(g) (89.92-169.69 psi(g)), more preferably a pressure of about 7.2-9.7 bar(g) (104.42-140.69 psi(g)), even more preferably a pressure of about 7.5-8.7 bar(g) (108.78-126.18 psi(g)), and most preferably a pressure of about 8.8 bar(g) (127.63 psi(g). The thermal treatment input stream 310 delivers the input material to a heat exchanger 312 which increases the temperature of the input material to about 455-490°C, more preferably about 470-490°C, even more preferably about 475-490°C, and most preferably about 480°C.The input material is transferred from the heat exchanger 312 through line 313 (which may be heated) to the process heater 314, preferably with turbulent flow therein. The process heater 314 may be any type of thermal reactor, such as, but not limited to, induction heating. For example, in at least one embodiment, the process heater 314 may include a soaking coil 315 made of a thermally conductive material that facilitates heat transfer, the soaking coil 315 being in fluid communication with the line 313. It should be understood that "thermally conductive" is intended to mean a material that transfers heat or facilitates heat transfer, and not a particular heating mechanism or regime. Although not required, turbulent flow of the input stream of material is highly desirable within the process heater 314. At least one power source 316 may be present, providing, for example, alternating current (AC), direct current (DC), or other type of work, power, or energy to the process heater 314 to heat the thermal coil 315. It should be noted that the application of energy may be of any known type, such as induction heating, a flame, molten material such as salt or metal, electric coils, etc. The only constraint is that heat be applied in the specified amount. As the input material passes through the coil 315 and process heater 314, it is brought to a temperature of about 475-510°C and a pressure of about 4.2-11.7 bar(g) (60.92-169.69 psi(g)), more preferably about 490-510°C at about 5.2-9.7 bar(g) (75.42-140.69 psi(g)), even more preferably about 495-510°C at about 5.5-8.7 bar(g) (79.77-126.18 psi(g)), and most preferably about 500°C at about 6.8 bar(g) (98.63 psi(g)). The heated material exits the process heater 314 through a reactor output line 317 and travels to the reactor 320. The reactor output line 317 may be of smaller diameter than the previous input stream 310, for example, about 5 / 4 inch (31.75 mm) for high velocity or turbulent flow. The reactor 320 may include multiple vessels, pipes, or conduits through which the heated material passes to achieve a desired retention or residence time within the system 300 for thermal processing. Thus, the reactor 320 may have a variety of lengths, shapes, sizes, and configurations known to those skilled in the art to achieve the desired retention time. Without wishing to be bound by theory, the heated material is introduced into the reactor 320 and passes therethrough as a continuous stream, which generally moves with uniform or near uniform plug flow and velocity, within the limitations of conventional piping or reservoir flow characteristics. However, preferably, the length to diameter ratio is about 10:1 for an elongated vessel.

[0041] For example, in at least this first embodiment, the reactor output line 317 is in fluid communication with a first vessel 321 and delivers the heated material to the first vessel 321. Due to the high temperature of the heated material, the interior volume of the first vessel 321 is under an inert gas 318, such as, but not limited to, nitrogen or argon gas, to keep oxygen out of the first vessel 321. The first vessel 321 may have a variety of shapes and / or diameters as described above, and in at least one embodiment, may have a length of about 16 m and a diameter of 0.3 m (about 14 inches). The vessel may also be insulated to retain heat from the heated material and maintain a temperature of about 500° C. The first vessel 321 is also under a pressure of about 6-7 bar(g) (87-101.5 psi(g)), which, together with the temperature, acts to keep the heated material in a liquid phase so that it moves easily through the system 300. While true adiabatic conditions are practically impossible, it is intended that the temperature of the first vessel 321 (and the corresponding segment of any other embodiment, including the specifically contemplated single vessel embodiment) be maintained at a substantially constant level over a significant portion of the cross-section of the heated material passing therethrough, conveniently identified as a "substantially constant temperature." For purposes of this preferred embodiment, plus or minus 30°C, more preferably plus or minus 10°C, and most preferably plus or minus 5°C, is considered to be substantially uniform. Furthermore, to the extent practical, it is intended that the heated material will pass through the vessel as uniformly as possible in a near uniform flow.

[0042] The heated material enters the first vessel 321 from the bottom and the liquid level rises as additional heated material is delivered to the first vessel 321. The heated material moves in the first vessel 321 essentially in plug flow, so that all molecules of the heated material move through the first vessel 321 at approximately the same speed, as far as possible. Given the dynamics of the fluid interaction with the interior surface of the vessel, overall plug flow is unlikely to be achieved, but it should be understood that the design of the vessel and reactor 320 should, overall, achieve as close to equal flow as possible. Changes in flow or flow rate within the first vessel 321 should be avoided. This is to keep the movement of the molecules of the heated material in the reactor 320 as uniform as possible so that the residence time of the molecules can be known. The longer the residence time, the more the molecules of the heated material are exposed to a given reaction temperature, and the higher the risk of mesophase formation, which can lead to coke formation. Thus, turbulence helps create a nearly uniform plug flow, but not so much that some molecules move quickly while others get caught in eddies or local recirculations. This inconsistency caused by excessive turbulence is believed to lead to inconsistencies in the heat treatment process 300 and thus to be detrimental to the quality of the additional pitches 150, 250 formed by the process. As the heated material rises through the first vessel 321, vapor containing light chains 322 is generated in the liquid front. These light chains 322 may include short carbon chain molecules that could not be combined with other molecules or that are broken off as by-products during pitch production. These light chains 322 may be removed and collected from the first vessel 321 by scrubbing or any other non-condensable gas recovery method for further processing. Without being bound by theory, this vapor material aids in the uniformity of the flow through the vessel. When the level of the heated material rises to a predetermined exit point in the first vessel 321, the material enters an intermediate reactor line 323 that is in fluid communication with the first vessel 321 and the second vessel 324. The intermediate reactor line 323 may be smaller than or about the same size as the first or second vessels 321, 323. In at least one embodiment, intermediate reactor line 323 is about 3 inches in diameter, preferably up to one-fifth the diameter of first vessel 321. The line transports heated material from first vessel 321 to second vessel 324 for further holding.

[0043] In at least one embodiment, the second vessel 324 may be a standpipe or other similar elongated structure having a diameter of about 6 inches and a length of about 5 meters. The vessel is desirably of minimal size to prevent further reaction and insulated to conserve heat of the material and maintain a temperature of about 500° C. The heated material also moves through the second vessel 324 by pseudo-constant flow or plug flow (used interchangeably herein) as described above. The reactor output line 325 is in fluid communication with the second vessel 324 and transfers the heated material from the second vessel 324 to the heat exchanger 312, which may be the same heat exchanger 312 as described above or a different heat exchanger, but is preferably the same. The reactor output line 325 may be of a similar diameter to the reactor output line 317, for example about 1.25 inches, for high speed transfer. The heated material exiting reactor 320 and returning to heat exchanger 312 may lose some heat as it travels through reactor 320 and may have a temperature at this point of about 465-510°C, more preferably about 480-510°C, even more preferably about 485-510°C, and most preferably about 490°C. At this point the heated material is cooled in heat exchanger 312 to a temperature of about 275-325°C and a pressure of about 3.7-11.7 bar(g) (53.66-169.69 psi(g)), more preferably about 280-315°C and 5.2-9.7 bar(g) (75.42-140.69 psi(g)), even more preferably about 288-305°C and 5.0-8.7 bar(g) (72.52-126.18 psi(g)), and most preferably about 300°C and 6.5 bar(g) (94.27 psi(g)), and the pressure is slightly reduced. This heat treated material contains additional pitch produced by exposure to the heat treatment. To obtain this additional pitch, the heat treated material is carried away from the heat exchanger 312 by an output line 326 that intersects the pitch production system 100, 100', 100", 200', 200', 200" at various locations (depending on the embodiment and type of system) to deliver the heat treated product for additional pitch extraction by distillation and removal of oil.Specifically, the output line 326 may intersect with the C2-C3 transfer line 126 of the coal tar pitch production system 100 and 100" to provide additional C3 feedstock, as shown in Figures 2A and 2C, respectively; or enter the C1-C2 transfer line 115 of the coal tar pitch production system 100' to provide additional C2 feedstock, as shown in Figure 2B; or enter directly into the first column C1 in the petroleum pitch production system 200, 200', 200" for dehydration and subsequent distillation, as shown in Figures 3A-3C. Other embodiments may introduce the thermally treated product at a different point along the pitch production system. In the coal tar embodiment, combining the thermally treated material with the topped tar 125, 125" or dried tar 114 further reduces the temperature, flow rate and pressure, resulting in a C3 or C2 feedstock at about 358-375°C and flow rates of about 98-130 m, respectively. 3 / hr, and a pressure of about 2.3 to 5.5 bar(g) (33.35 to 79.77 psi(g)), more preferably about 362 to 373°C, about 99 to 120 m 3 / hr, and about 2.5-4.9 bar(g) (36.26-71.07 psi(g)), even more preferably about 364-370°C, about 99-110 m 3 / hr and about 2.8 to 4.5 bar(g) (40.61 to 65.27 psi(g)), most preferably about 367°C, about 99 m 3 / hr and about 3.5 bar(g) (50.76 psi(g)). It should be noted that in any continuous process, other oils contained in the heat treated material must be separated from the pitch produced by the heat treatment before these remaining other oils are reintroduced into the heat treatment system for further processing and additional pitch production. Without being bound by theory, it will generally be understood that if a pitch material is heat treated, the pitch should be separated by distillation before being reintroduced into the heat treatment, due to the high likelihood of mesophase or coke formation during additional heat treatment.

[0044] The residence time of the heated material in the thermal treatment system 300 may be interchangeably referred to as "residence time" or "holding time". It is the duration of the thermal treatment process and may be defined as the time it takes for the heated material to make a circuit from the heat exchanger 312 through the reactor 320 and back to the heat exchanger 312 for cooling. This circuit defines the time during which the heated material is exposed to high temperatures of about 500° C., i.e., the time during which care must be taken to avoid mesophase formation. The residence time may vary depending on the exact temperature and pressure of the system, with higher temperatures or pressures correspondingly shorter residence times. In at least one embodiment, the thermal treatment system 300 includes heating the input material to a temperature of about 500° C. and a pressure of about 6.0-7.0 bar(g) (87-101.5 psi(g)) for about 3-7 minutes, preferably 7 minutes. The various distillate cuts from the pitch production systems 100, 100', 100" are fairly well defined and characterized as described above. Thus, the consistency of the coal tar starting material, the heavy cut 141, means that retention times and reaction temperatures are relatively predictable, although the inherent relationships between the various parameters are somewhat complex. Below are some representative ranges of operating parameters for the heavy cut thermal treatment process:

[0045] [Table 6]

[0046] Additional calculations of parameters for predicting pitch yield at various flow rates for the thermal treatment of heavy coal tar fractions are shown below in Table 7, which is based on the same complex relationships as above. [Table 7]

[0047] A second embodiment of a thermal treatment system 300' is shown in FIG. 4B. This may also be used in connection with any of the pitch production systems. Without such thermal treatment, pitch may be produced in an amount of about 15-25% of the original decant oil 203. Using the thermal treatment described herein in system 300', the yield increases by about 25-30%, resulting in a total pitch yield of about 40-50%. If the distillate is recycled and further thermally treated, the total pitch yield may increase to about 60-80%, depending on the starting material and the quality level of the distillate. In this embodiment of the thermal treatment system 300', the components of the reactor 320' may differ slightly from those previously described, as may some of the operating parameters of the overall thermal treatment system 300'. As a non-limiting example of a pre-test plan, the input material may have a temperature of about 49-104°C, a flow rate of about 7.2-13.1 MT / hr, and a pressure of about 1.4-4.8 bar(g) (20-70 psi(g)) as it enters the thermal treatment system 300'. The pressure pump 311 may be a high pressure feed pump operating at about 2 gpm at 20.7 bar(g) (300 psi(g)), although other speeds and pressures are contemplated. The pressure pump 311 may increase the flow rate of the input material to about 20.3 MT / hr and the pressure to about 13.8-18.0 bar(g) (200-260 psi(g)) before the input material enters the heat exchanger 312. Heat exchanger 312 raises the temperature of the input material to approximately 413-430° C. by passing a hotter component (e.g., a heated product from downstream in system 300′) through heat exchanger 312. From there, the material is transferred to process heater 314 where it is further heated to a temperature of approximately 465-500° C. depending on the characteristics of the input material.

[0048] As in the previous embodiment, the process heater 314 may be inductively heated or a soaking coil and may be powered by any suitable power source 316, such as, but not limited to, a transducer of the type shown operating at 1 MW power. There may be multiple connections from the power source 316 to the process heater 314 and / or the coil 315 therein, which may be at regular intervals, such as every 3 revolutions of the coil 315, although any configuration that provides sufficient power to the process heater 314 is contemplated. The process heater 314 may have a sufficient length of coil 315 therein to maintain and heat the input material to the desired target temperature before it leaves the process heater 314 through a reactor exit line 317. The reactor exit line 317 is in fluid communication with the first vessel 321' of the reactor 320'. This first vessel 321' may be a plug flow reactor as previously described. The heated material enters the first vessel 321' from the bottom and rises at a substantially uniform rate to avoid turbulence and maintain the same flow rate for all molecules of the heated material. The first vessel 321' may be at a pressure in the range of about 6.9-13.8 bar(g) (100-200 psi(g)), preferably 6.9-12.1 bar(g) (100-175 psi(g)), and may be under an inert gas 318, such as nitrogen or argon, to limit the oxygen present in the first vessel 321' given the high temperatures. The heated material may be at a temperature of preferably about 482.2-496°C when it enters the first vessel 321'. As the material travels upward in the first container 321' it may lose some heat, for example about 20-30°C.

[0049] In an embodiment, the first vessel 321' may include a disengagement zone 328 defined along a portion thereof, preferably near the top of the vessel 321'. The disengagement zone 328 has a larger diameter (and therefore a larger internal volume) than the remainder of the first vessel 321'. In an embodiment, this additional space may allow vapors, including small hydrocarbon molecules that did not form the pitch 150, 250 in the pitch production process, to separate from the liquid and be removed as LCl 322'. This extraction may also limit foaming, which is undesirable because it creates turbulence. These LCl's 322' rise to the top of the first vessel 321'. The LCl's 322' may be at a temperature of about 437.8-443.3°C and may be removed from the first vessel 321' at a point preferably above the disengagement zone 328. The removed LCl's 322' may be sent to a condenser where it is condensed and / or pyrolyzed in a pollution control device. LC2 333 may be produced as bubbles and / or vapor in the disengagement zone 328. LC2 333 contains non-condensable gases and may be removed from the disengagement zone 328 of the first vessel 321' and transferred to the second vessel 324'. In a preferred embodiment, additional light chain LC2 333 enters the second vessel 324' at the longitudinal midpoint of the vessel. As the level of heated material in the first vessel 321' rises to a certain level, the liquid heated material leaving the first vessel 321' is also transferred through the intermediate reactor line 323' to the second vessel 324'. The heated material from the first vessel 321' is combined with the LC2 333 in the second vessel 324' for additional plug flow through the second vessel 324'. The second vessel 324' is also under an inert gas 318, which may be the same or different from the gas in the first vessel 321'. The heated material is at substantially the same temperature and pressure in the second vessel 324' as in the first vessel 321', although some losses may occur as the heated material passes through the reactor 320'. The vapors that collect at the top of the second vessel 324' may be removed as light chains LC3 340, which may then be combined with LC1 322' and condensed back into liquid form. The combined LC1 322' and LC3 340 may contain naphtha, which may be refined and separated in a naphtha refinery for sale or further use. The remainder of LC1 322' and LC3 340 may be pyrolyzed as described above. The bottom of the second vessel 324' contains the thermally treated material, which is then returned to the heat exchanger 312 through the reactor output line 325 for cooling. After cooling, the thermally treated material returns to the pitch production system 100, 100', 100", 200', 200', 200", depending on the embodiment and type of system, with similar crossover points as described above. Alternatively, the heat treated material may be returned from reactor 320' to column C1 and the temperature reduced by conventional means. The residence time of the heat treatment process using the second embodiment of the system 300' will vary depending at least on the temperature used. For example, a heated coal tar material at a temperature of about 482.2-500°C will pass through the heat treatment process 200' with a retention time of about 10-20 minutes, whereas a temperature of about 537.8°C may only last about a 5 minute retention time. For even lower reaction temperatures, retention times of up to 60 minutes are possible. These are just a few non-limiting examples.

[0050] It has been found that a single pass of the input material through the thermal treatment system 300' of the present invention increases the pitch yield by a factor of 2.5, resulting in a total pitch yield of about 40%, compared to about 15% without thermal treatment. Additional pitch 150, 250 can be generated even more, if not multiple times, by recycling the input material and passing it at least once through the thermal treatment system 300'. However, the increased pitch loading risks mesophase accumulation. Therefore, in some embodiments, it may be beneficial or even necessary to pass the thermal treatment product through distillation to remove the resulting pitch 150, 250, without recycling it back to the thermal treatment system 300'. This limits or prevents mesophase formation in the pitch 150, 250.

[0051] Compared to the coal tar 102 starting material, the decant oil 203 has a large variation in composition and concentration from batch to batch. This causes an increased complexity in the relationship between temperature, retention time, and pressure. However, the desired pitch parameters of >47% coke value and <0.7% mesophase control the upper and lower limits of the acceptable pitch yield increase, as too much or too little increase will produce pitch with either insufficient coke value or too much mesophase. From the above limits, the relationship between retention time and temperature for the thermally treated decant oil can be described as follows: 25=0.1((1.8×T r +32)-T c )+0.1(R t ) where T is the percent yield increase relative to the yield obtained without heat treatment (determined by the desired pitch parameters of at least 47% coke value and 0.7% submesophase); r is the reaction temperature in degrees Celsius; T c is 653, and R t is the retention time in minutes. The first 0.1 indicates the % increase in yield for each degree Fahrenheit, and the second 0.1 indicates the % increase in yield for each additional minute. Depending on the constraints of a particular system, the above formula can be modified to fit the retention time R t or reaction temperature T r can also be expressed as follows: R t =250-(1.8×T r +32)+T c

number

[0052] In a preferred embodiment according to the present invention, in the case of the thermal treatment of the decant oil 203, T r The reaction temperature is in the range of 454 to 483 °C, and R tRetention times range from 3 to 25 minutes. Interestingly, the 25% yield increase (corresponding to "25" and "250" in the above formula) applies equally well to decant oil 203 starting materials with API gravities between -5 and 0. Yields higher or lower than above tend to produce either unacceptable levels of mesophase or insufficient coke values. As is commonly understood in the petroleum industry, API gravity and specific gravity (SP) are related as follows:

number

[0053] Thus, although the gravity of the decant oil 203 in the petroleum pitch production 200" may vary depending on the operating parameters of the system 200", the above equation applies equally well to various gravity of the decant oil 203 starting material. The above equations for predicting reaction temperature and reaction time, for average reactor gradients, provide representative ranges, shown below in Table 8, for operating parameters for the thermal treatment process of petroleum distillates using the thermal treatment system 300′ disclosed herein.

[0054] [Table 8]

[0055] The above and other features of preferred embodiments herein may be illustrated by the following non-limiting examples. EXAMPLES

[0056] The following examples provide experimental data derived in determining and / or testing certain parameters of the pitch producing system and / or thermal treatment system described herein. Reference to specific embodiments is made where appropriate.

[0057] Example 1 Determination of Heavy Fraction Removal Rate An experiment was conducted to determine the maximum flow rate at which the heavy fraction 141 could be removed from the third column C3 of the first embodiment of the above coal tar pitch production system 100 without compromising the overall performance of the pitch production system 100. Thermal treatment of the heavy fraction 141 is important for the separation of B(a)P as well as to maintain a high softening point (e.g., about 130° C., Mettler process) of the resulting pitch 150. Assuming a goal of increasing pitch yield by 5%, the flow rate required for thermal treatment system 300 was calculated as follows: Assuming an annual tar production of approximately 300,000 MT / year, 5% of this figure is approximately 15,000 MT / year, which is the additional pitch required. Dividing this 15,000 MT / year rate by 30% of the projected yield is approximately 50,000 MT / year, which, when divided by 300 days / year of operation, gives a flow rate for thermal treatment system 300 of 166 MT / day or 7 MT / hour to achieve an additional 5% pitch yield. Coal tar pitch production system 100 may typically be operated at a rate of about 31.5 MT / hr for pitch production. In order for heavy fraction 141 to pass through thermal treatment process 300 at a rate of about 7 MT / hr, the rate of pitch production would need to be similarly reduced. For this reason, testing was performed to determine whether a sufficient reduction in pitch production rate could be achieved to achieve additional pitch yield without disrupting the existing pitch production process. To test this, a thermal processing draw of heavy fraction 141 was simulated experimentally by partially closing the valve from third column C3 to distillate line 142 by various amounts. This limited the flow rate of the oil draw. Four valve positions with different closure percentages were tested, starting with 55% closure (normal position), then 35%, 30% and 25% closure. For each valve position, the flow rate was measured to monitor the simulated draw of heavy fraction 141. The heat load was also measured to monitor the effectiveness of the system, and the softening point (Mettler) of the resulting pitch was measured as a quality control for the pitch production process. Other parameters were also measured as controls. B(a)P and distillation interval were also measured to better understand the impact of separation. The results of these tests are summarized in Table 9 below.

[0058] [Table 9]

[0059] The results show that the heavy distillate 141 heat treatment flow rate can be reduced while maintaining normal operation of the pitch production system 100. This is demonstrated by the effect of the reduced flow rate on the heat load. The process conditions at 55%, while being standard operating conditions, do show some of the normal variation, as seen by the second middle distillate tray temperature differing from the normal temperature of 210° C. It should be noted that while normal operation was maintained, the second middle distillate cooling loop exceeded its maximum. This caused the second middle distillate tray temperature to increase as the experiment progressed, which resulted in an increase in the first middle distillate yield. Reaching the second middle distillate cooling maximum is problematic, especially when the additional cooling load is removed due to a decrease in the heavy distillate rate. Overall, both the thermal management and experimental results indicate that the tower is undercooled. This effect increases as additional flow is removed from the management loop. Thus, additional cooling may be required to overcome the loss of cooling load or to reduce the energy input. Taken together, the above results indicate that heat treatment using a flow rate of 7 MT / hr is possible, but additional cooling may be required for low-PAH creosote production.

[0060] Example 2 Determination of Reactor Temperature To further design the full-scale application of the thermal processing system 300, several base cases were evaluated, especially for the process heater 314 temperature. Here, temperatures of 420, 445, 471, 497, and 522°C were evaluated. The lower limit of this evaluation is based on preliminary autoclave results that showed reactivity limits. The upper limit is based on the autoignition temperature of the heavy fraction (measured at 542°C). For safety reasons, the final reactor temperature is limited to 522°C. Previous experiments have shown that the heavy fraction can be treated at a temperature of 550° C. for 5.2 minutes without forming mesophase or coke. Further previous experiments with long retention times have yielded the data shown in Table 10 below.

[0061] [Table 10]

[0062] Based on these historical data, kinetic simulations were determined using a heavy fraction flow rate of 7 MT / hr and a desired overall pitch yield of 30%, as identified from Example 1. These kinetic calculations provide the data shown in Table 11 below.

[0063] [Table 11]

[0064] The maximum hold time used in the laboratory is 5.2 min. As can be seen from Table 11, most of the calculated results far exceeded this time. Therefore, these kinetic calculations may overestimate the reaction rate.

[0065] Example 3 Testing Various Temperatures and Holding Times - Coal Tar Tests were conducted to evaluate the feasibility of thermal processing the heavy fraction to convert it into pitch. These initial experiments were performed at various temperatures from 365 to 510°C and hold times ranging from 4.5 minutes to 2 hours. Reaction constants were derived from these results. To determine if the reaction was endothermic or not, two additional experiments were performed adiabatically, ensuring that the reactor was sufficiently insulated to ensure that the measured reactor temperature was due to the heavy fraction inside and not due to the oven temperature. The experiments were performed using a plug flow reactor. All experiments were carried out in the same general manner. The heavy fraction was placed in a feed tank and passed through the reactor by a rotary pump. The reactor was housed in an oven with a preheater, and different sizes of reactors ranging from 299 to 330 mL were also used. The heavy fraction was pumped through the reactor to obtain a given retention time at a given temperature. After the oven, the heavy fraction was passed to a waste or sample tank after the temperature was reduced through a cooling coil. Sample collection was carried out after the reactor temperature was stabilized. In most experiments, a 1000 g sample was collected. Heat tracing was added to all pipes to ensure the heavy end was liquid throughout the experiment. The feed tank was maintained at 100°C, the cooling coils at 180°C, and the sample and waste tanks at 150°C. Temperature sensors were placed in multiple locations on the preheater and reactor to track the temperature profile of the heavy end. A nitrogen purge flow was used to provide an inert atmosphere during the experiment. The experiments were run at high pressure to overcome the vapor pressure of the heavy end. Experiments were typically run at approximately 6.9 bar(g) (100 psi(g)). The heat-treated oil obtained had to be distilled to confirm the pitch yield of the samples. For the distillation, a vacuum distillation was prepared. Each distillation was carried out with about 400 g of sample in a round-bottom flask. The distillation column used was a Vigreux column with a length of 1 m. All samples were distilled under full vacuum. The bottom temperature was set at 250 °C at the beginning of the distillation and then gradually increased until enough oil was distilled to obtain the expected yield. When the pitch was not in the appropriate melting range of 105-130 °C, the distillation was carried out again from the beginning. During the second distillation, the bottom temperature was increased or decreased so that more or less distillate was distilled off to produce a higher or lower melting pitch, respectively. Several analyses were performed on the heat treated oil, pitch and distillate. The heat treated oil was measured by Fourier transform infrared spectroscopy (FTIR) to calculate aromaticity. The melting point of the pitch was measured. To be acceptable the melting point had to be between 105-130°C. The QI of the pitch was measured. It was desirable to have a QI as low as possible. The pitch was also analyzed for B(a)P. Gas chromatography (GC) was performed on the distillate to calculate the conversion of compounds in the heavy fraction and to calculate reaction constants. A portion of the oil was also measured by gas chromatography mass spectroscopy (GCMS) and compared with the GC results. Data from the various studies are summarized in Table 12 below.

[0066] [Table 12-1]

[0067] [Table 12-2]

[0068] These data showed an increase in pitch yield (%) for the temperatures and holding times tested, suggesting that thermal treatment of heavy distillates can increase pitch yield. The results of an adiabatic experiment to test whether the reaction was endothermic are shown in Table 13 below. [Table 13]

[0069] Example 4 Testing of Various Temperatures and Hold Times - Petroleum Various laboratory scale tests were conducted on the thermal treatment of petroleum derived decant oil at various temperatures and retention times. The raw decant oil was subjected to heat soaking in a constant autoclave at 200 psi(g). A slight lag time occurred as the decant oil was heated to the desired temperature. After heat treatment to the desired temperature, the product was quenched to stop the heat soaking and limit mesophase formation. The pitch produced during the thermal treatment process was isolated by distillation to remove unreacted decant oil, and the resulting pitch was characterized by coke value and mesophase. The results of these experiments are summarized in Table 14 below.

[0070] [Table 14]

[0071] Each of the above experiments produced acceptable pitches characterized by a coke value of >47% and <0.7% mesophase. Since the described preferred embodiment is susceptible to numerous modifications, variations and changes in detail, it is intended that all matters set forth in the above description and accompanying drawings be interpreted in an illustrative and not a limiting sense. The scope of the invention should therefore be determined by the appended claims and their legal equivalents. The invention has thus been described. Yet another aspect of the present invention may be as follows. [1] A method for deriving pitch from a preselected starting material, comprising the steps of: Selecting a starting material from the group consisting of: (i) petroleum-based decant oil; and (ii) coal tar-based heavy distillate oil; introducing said starting materials in a flowable liquid phase into a conduit constructed at least in part of a conductive material that facilitates heat transfer; applying heat in a controlled manner to the thermally conductive portion of the conduit containing the starting material to raise the temperature of the starting material to between 459 and 535° C. at a pressure between about 3.2 and 20.7 bar(g) (46 and 300 psi(g)); maintaining a near equal flow of the starting material through at least a portion of the thermally conductive section of the conduit at a substantially constant temperature for a time sufficient to convert a portion of the starting material to pitch while limiting mesophase formation in the combined stream to 0.7% or less; reducing the temperature of the combined stream to between 275 and 385°C; separating said pitch from said combined stream to obtain a pitch yield of (i) at least 25% for said petroleum based decant oil, and (ii) at least 15% for said coal tar based heavy distillate; A method comprising: [2] The method according to [1], wherein the starting material is a coal tar-based heavy distillate oil that has been elevated in temperature to a range of 475 to 510°C at a pressure in the range of about 3.2 to 10.7 bar(g) (46 to 155 psi(g)). [3] The method according to [2], wherein the approximately uniform flow occurs at the approximately constant temperature for a time period ranging from 3.0 to 49.2 minutes. [4] The method according to [2] above, wherein the pitch yield is in the range of 15 to 45%. [5] The method of [2], wherein the temperature is about 475°C, the pressure is about 3.2 bar(g) (about 46.2 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 49.2 minutes, resulting in a pitch of about 45%. [6] The method of [2], wherein the temperature is about 510°C, the pressure is about 10.7 bar(g) (about 155 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 3 minutes, resulting in a pitch of about 15%. [7] The method according to [1], wherein the starting material is a coal tar-based heavy distillate oil that has been elevated in temperature to a range of 490 to 510°C at a pressure in the range of about 4.2 to 8.7 bar(g) (60.7 to 126 psi(g)). [8] The method according to [7], wherein the approximately uniform flow occurs at the approximately constant temperature for a time in the range of 4.3 to 23.6 minutes. [9] The method according to [7] above, wherein the pitch yield is 20 to 40%.

[10] The method of [7], wherein the temperature is about 490°C, the pressure is about 4.2 bar(g) (about 60.7 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 23.6 minutes, resulting in a pitch of about 40%.

[11] The method according to [7], wherein the temperature is about 510°C, the pressure is about 8.7 bar(g) (about 126 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 4.3 minutes, resulting in a pitch of about 20%.

[12] The method according to [1], wherein the starting material is a coal tar-based heavy distillate oil that has been elevated in temperature to a range of 495 to 510°C at a pressure in the range of about 4.5 to 7.7 bar(g) (65.1 to 111.5 psi(g)).

[13] The method according to

[12] , wherein the approximately uniform flow occurs at the approximately constant temperature for a time in the range of 5.7 to 16.3 minutes.

[14] The method according to

[12] , wherein the pitch yield is in the range of 25 to 35%.

[15] The method according to

[12] , wherein the temperature is about 495°C, the pressure is about 4.5 bar(g) (about 65.1 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 16.3 minutes, resulting in a pitch of about 35%.

[16] The method of

[12] , wherein the temperature is about 510°C, the pressure is about 7.7 bar(g) (about 111.5 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 5.7 minutes, resulting in a pitch of about 25%.

[17] The method according to [1], wherein the starting material is a coal tar-based heavy distillate oil that has been elevated in temperature to about 500°C at a pressure of about 5.8 bar(g) (about 83.9 psi(g)).

[18] The method according to

[17] , wherein the near uniform flow occurs at the nearly constant temperature for about 7.4 minutes, resulting in a pitch of about 30%.

[19] The starting material is a petroleum-based decant oil having an API gravity in the range of -5 to 0, and the starting material is subjected to a pressure of about 5.5 to 20.7 bar(g) (80 to 300 psi(g)) at a substantially constant temperature for a time according to the following formula: 25=0.1((1.8×T r +32)-T c )+0.1(R t ) [In the formula, T r is the reaction temperature in degrees Celsius, T c is 653, and R t is the retention time in minutes], resulting in at least a 25% increase in pitch yield, the pitch having a coke value of at least 47% by mass.

[20] The method according to [1], wherein the starting material is a petroleum-based decant oil that has been elevated to a temperature in the range of 459 to 496°C at a pressure in the range of about 5.5 to 20.7 bar(g) (80 to 300 psi(g)).

[21] The method according to

[20] , wherein the approximately uniform flow occurs at the approximately constant temperature for a time period ranging from 1 to 25 minutes.

[22] The method according to

[20] , wherein the pitch yield is in the range of 40 to 54.3% and the coke value is 47.3 to 50.5 mass%.

[23] The method according to

[20] , wherein the temperature is about 496°C and the near uniform flow occurs at the nearly constant temperature for about 1 minute to produce about 54% pitch having a coke value of about 47.3% by mass.

[24] The method according to

[20] , wherein the temperature is in the range of 468 to 482°C, and the near uniform flow occurs at the nearly constant temperature for about 10 minutes to produce pitch having a coke value in the range of 47.3 to 50.5 mass% in the range of about 43 to 54.3%.

[25] The method according to

[20] , wherein the temperature is in the range of 459-471°C, and the near uniform flow occurs at the nearly constant temperature for about 20 minutes to produce pitch having a coke value in the range of 47.7-50.1% by mass in the range of about 40-47.5%.

[26] The method according to [1], wherein the conduit further comprises a heat transfer section through which the starting material flows turbulently, and a reactor section through which the starting material flows at an approximately uniform flow rate.

[27] The method according to

[26] , wherein the temperature of the starting material is increased in the heat transfer section and maintained at a substantially uniform level in the reactor section.

[28] The method according to [1], further comprising the additional step of warming the starting material prior to introduction into the conduit.

[29] The method according to

[28] , wherein the warming step and the temperature reducing step are accomplished simultaneously in a common heat exchanger.

[30] A pitch product having a mesophase content of less than 0.7%, derived from a starting material selected from the group consisting of (i) petroleum-based decant oil and (ii) coal tar-based heavy distillate oil, introducing said starting materials in a flowable liquid phase into a conduit constructed at least in part of a conductive material that facilitates heat transfer; applying heat in a controlled manner to the thermally conductive portion of the conduit containing the starting material to raise the temperature of the starting material to between 459 and 535° C. at a pressure between about 3.2 and 20.7 bar(g) (46 and 300 psi(g)); maintaining a near uniform flow of the starting material through at least a portion of the thermally conductive portion of the conduit at a substantially constant temperature for a time sufficient to convert a portion of the starting material to pitch; reducing the temperature of the combined stream to between 275 and 385°C; separating said pitch portion from said merged stream; 2. A pitch product derived by a process comprising:

[31] The method according to

[30] , wherein the starting material is a coal tar-based heavy distillate oil that has been elevated in temperature to a range of 475 to 510°C at a pressure in the range of about 43.2 to 10.7 bar(g) (46 to 155 psi(g)).

[32] The method according to

[31] , wherein the approximately uniform flow occurs at the approximately constant temperature for a time in the range of 3.0 to 49.2 minutes.

[33] The method according to

[31] above, wherein the yield of the pitch is in the range of 15 to 45%.

[34] The method according to

[31] , wherein the temperature is about 475°C, the pressure is about 3.2 bar(g) (about 46.2 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 49.2 minutes, resulting in a pitch of about 45%.

[35] The method according to

[31] , wherein the temperature is about 510°C, the pressure is about 10.7 bar(g) (about 155 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 3 minutes, resulting in a pitch of about 15%.

[36] The method according to

[30] , wherein the starting material is a coal tar-based heavy distillate oil that has been elevated in temperature to a range of 490 to 510°C at a pressure in the range of about 4.2 to 8.7 bar(g) (60.7 to 126 psi(g)).

[37] The method according to

[36] , wherein the approximately uniform flow occurs at the approximately constant temperature for a time in the range of 4.3 to 23.6 minutes.

[38] The method according to

[36] above, wherein the pitch yield is 20 to 40%.

[39] The method according to

[36] , wherein the temperature is about 490°C, the pressure is about 4.2 bar(g) (about 60.7 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 23.6 minutes, resulting in a pitch of about 40%.

[40] The method according to

[36] , wherein the temperature is about 510°C, the pressure is about 8.7 bar(g) (about 126 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 4.3 minutes, resulting in a pitch of about 20%.

[41] The method according to

[30] , wherein the starting material is a coal tar-based heavy distillate oil that has been elevated in temperature to a range of 495 to 510°C at a pressure in the range of about 4.5 to 7.7 bar(g) (65.1 to 111.5 psi(g)).

[42] The method according to

[41] , wherein the approximately uniform flow occurs at the approximately constant temperature for a time in the range of 5.7 to 16.3 minutes.

[43] The method according to

[41] above, wherein the pitch yield is in the range of 25 to 35%.

[44] The method according to

[41] , wherein the temperature is about 495°C, the pressure is about 4.5 bar(g) (about 65.1 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 16.3 minutes, resulting in a pitch of about 35%.

[45] The method according to

[41] , wherein the temperature is about 510°C, the pressure is about 7.7 bar(g) (about 111.5 psi(g)), and the near uniform flow occurs at the nearly constant temperature for about 5.7 minutes, resulting in a pitch of about 25%.

[46] The method according to

[30] , wherein the starting material is a coal tar-based heavy distillate oil that has been elevated in temperature to about 500°C at a pressure of about 5.8 bar(g) (about 83.9 psi(g)).

[47] The method according to

[46] , wherein the near uniform flow occurs at the nearly constant temperature for about 7.4 minutes, resulting in a pitch of about 30%.

[48] ​​The starting material is a petroleum-based decant oil having an API gravity in the range of -5 to 0, and the starting material is subjected to a pressure of about 5.5 to 20.7 bar(g) (80 to 300 psi(g)) at a substantially constant temperature for a time according to the following formula: 25=0.1((1.8×T r +32)-T c )+0.1(R t ) [In the formula, T r is the reaction temperature in degrees Celsius, T c is 653, and R t is the retention time in minutes], resulting in at least a 25% increase in pitch yield, the pitch having a coke value of at least 47% by mass.

[49] The method according to

[30] , wherein the starting material is a petroleum-based decant oil that has been elevated to a temperature in the range of 459 to 496°C at a pressure in the range of about 5.5 to 20.7 bar(g) (80 to 300 psi(g)).

[50] The method according to

[49] , wherein the approximately uniform flow occurs at the approximately constant temperature for a time period ranging from 1 to 25 minutes.

[51] The method according to

[49] , wherein the pitch yield is in the range of 40 to 54.3% and the coke value is 47.3 to 50.5 mass%.

[52] The method according to

[49] , wherein the temperature is about 496°C and the near uniform flow occurs at the nearly constant temperature for about 1 minute to produce about 54% pitch having a coke value of about 47.3% by mass.

[53] The method according to

[49] , wherein the temperature is in the range of 468 to 482°C, and the near uniform flow occurs at the nearly constant temperature for about 10 minutes to produce pitch having a coke value in the range of 47.3 to 50.5 mass% in the range of about 43 to 54.3%.

[54] The method according to

[49] , wherein the temperature is in the range of 459 to 471°C, and the near uniform flow occurs at the nearly constant temperature for about 20 minutes to produce pitch having a coke value in the range of 47.7 to 50.1 mass% in the range of about 40 to 47.5%.

[55] The method according to

[30] , wherein the conduit further comprises a heat transfer section through which the starting material flows turbulently, and a reactor section through which the starting material flows at an approximately uniform flow rate.

[56] The method according to

[55] , wherein the temperature of the starting material is increased in the heat transfer section and maintained at a substantially uniform level in the reactor section.

[57] The method according to

[30] , further comprising the additional step of warming the starting material prior to introduction into the conduit.

[58] The method according to

[57] , wherein the warming step and the temperature reducing step are accomplished simultaneously in a common heat exchanger.

[59] The method of [1], wherein the separation of the pitch portion from the combined stream is accomplished by distillation.

[60] A continuous process for deriving pitch from a preselected starting material, comprising the step of recycling the combined stream described in [1] after separating the pitch portion as the starting material.

[61] A thermal treatment system for deriving pitch from a starting material selected from the group consisting of (i) petroleum-based decant oil and (ii) coal tar-based heavy distillate oil, the thermal treatment system comprising: The method includes the steps of: providing a conduit having at least one component section, the at least one component section being constructed, at least in part, from a conductive material that facilitates heat transfer, the conduit having a first end, a second end, and an intermediate portion therebetween, the first end being selectively capable of including at least a portion of the thermally conductive material portion of the conduit; the thermally conductive portion of the conduit has a maximum temperature of 459-535° C. and a maximum pressure of about 3.2-20.7 bar(g) (46-300 psi(g)); the intermediate portion of the conduit is sized and shaped to maintain a continuous, near equal flow of the starting material at a substantially constant temperature for a time sufficient to convert at least a portion of the starting material to pitch while limiting mesophase formation in the combined stream to 0.7% or less, and to obtain a pitch yield of: (i) at least 25% for the petroleum-based decant oil, and (ii) at least 15% for the coal tar-based heavy distillate. Heat treatment system.

[62] The thermal treatment system described in

[61] , wherein the intermediate portion of the conduit further comprises a reactor section.

[63] The thermal treatment system described in

[61] , wherein the thermally conductive section further includes a heating section.

[64] The heat treatment system described in

[63] , wherein the heating section is inductively heated.

[65] The heat treatment system described in

[63] , wherein the heating section is an elongated coiled conduit.

[66] The thermal processing system described in

[63] , wherein the heating section is sized to induce turbulent flow of the starting material therethrough.

[67] The thermal treatment system described in

[62] , wherein the reactor section further comprises at least one holding vessel for maintaining the starting material at a substantially constant temperature.

[68] The thermal treatment system described in

[62] , wherein the reactor section further comprises at least one holding vessel for maintaining an approximately equal flow of the starting material therethrough.

[69] The thermal treatment system described in

[62] , wherein the reactor section further comprises a plurality of vessels.

[70] The thermal treatment system described in

[62] , wherein the reactor section further comprises at least one elongated cylindrical vessel.

[71] The heat treatment system described in

[62] , wherein the reactor section further comprises an inert atmosphere.

[72] The heat treatment system described in

[62] above, further comprising a space for recovery of non-condensable gases.

[73] The thermal treatment system described in

[61] , further comprising a heat exchanger for exchanging thermal energy from the combined stream to the starting material prior to introduction into the conduit.

[74] The heat treatment system described in

[69] , wherein the plurality of containers further includes a first and a second container, the first container being sized to have a larger capacity than the second container.

[75] The thermal processing system described in

[74] , wherein the second container is of a minimum size.

[76] The thermal treatment system described in

[68] , wherein the vessel is elongated and has a length to diameter ratio of 10:1 or greater.

[77] The thermal treatment system described in

[61] , wherein the substantially constant temperature is within a range of plus or minus 30°C.

[78] The thermal processing system described in

[76] , wherein the substantially constant temperature is within a range of plus or minus 10°C.

[79] The thermal treatment system described in

[76] , wherein the substantially constant temperature is plus or minus 5°C.

[80] A distillation system for deriving a pitch having a mesophase content of 0.7% or less from a petroleum-based decant oil to increase the pitch yield by at least 25%, comprising: A thermal treatment system according to

[61] for recovering and processing the petroleum-based decant oil to derive pitch therefrom; at least one distillation column in fluid communication with the thermal treatment system for receiving the thermally treated petroleum-based decant oil and fractionating it into component fractions including pitch; a distillation system comprising:

[81] The distillation system described in

[80] , further comprising a plurality of distillation columns.

[82] The distillation system described in

[81] , wherein at least one of the distillation columns further comprises a flash distillation.

[83] The distillation system described in

[80] , wherein the decant oil is recycled to the heat treatment system after removal of the pitch in the distillation column.

[84] A distillation system for deriving a pitch having a mesophase content of 0.7% or less from a coal tar-based heavy distillate to obtain a pitch yield of at least 15%, comprising: at least one distillation column for receiving and fractionating the coal tar into component fractions including pitch and a coal tar based heavy distillate; A thermal processing system according to

[61] in fluid communication with the at least one distillation column system for receiving and processing the coal tar-based heavy distillate oil and deriving pitch therefrom; a distillation system comprising:

[85] The distillation system described in

[84] , further comprising a plurality of distillation columns.

[86] The distillation system described in

[85] , wherein at least one of the distillation columns further comprises a flash distillation.

[87] The distillation system described in

[85] , wherein at least one of the distillation columns further comprises a dehydrator.

[88] The distillation system described in

[84] , wherein the coal tar-based heavy distillate oil is recycled to the thermal treatment system after removal of the pitch in the distillation column.

Claims

1. 1. A method for deriving pitch from a starting material, comprising the steps of: introducing the starting material into a thermally conductive portion of a conduit, the starting material being in a flowable liquid phase and the conduit being constructed at least in part of a conductive material that facilitates heat transfer; applying heat in a controlled manner to the thermally conductive portion of the conduit containing the starting material to raise the temperature of the starting material to 459-535° C. at a pressure of at least about 3.2 bar(g) (46 psi(g)) while maintaining the starting material in a liquid phase; maintaining a near equal flow of the starting material through at least a portion of the thermally conductive section of the conduit at a substantially constant temperature for a time sufficient to convert a portion of the starting material to pitch while limiting mesophase production to 0.7% or less to form a combined stream containing the starting material and the pitch; reducing the temperature of the combined stream to 275-385°C; separating the pitch from the merged stream to obtain a separated pitch; A method comprising:

2. 10. The method of claim 1, wherein the starting material is a coal tar based heavy distillate that has been elevated to a temperature in the range of 475-510° C. at a pressure in excess of about 4.1 bar(g) (60 psi(g)).

3. The method satisfies one of the following: a. the near uniform flow occurs at the approximately constant temperature for a time ranging from 3.0 to 49.2 minutes; b. the yield of the separated pitch is in the range of 15-45%; c. the temperature is 475° C., the pressure is about 3.2 bar(g) (46.2 psi(g)), and the near uniform flow occurs at the near constant temperature for 49.2 minutes resulting in a pitch of 45%; and d. the temperature is 510° C., the pressure is about 10.7 bar(g) (155 psi(g)), and the near uniform flow occurs at the near constant temperature for 3 minutes resulting in a pitch of 15%; The method of claim 2.

4. 2. The method of claim 1, wherein the starting material is a coal tar based heavy distillate that has been elevated to a temperature in the range of 490-510° C. at a pressure in the range of about 4.2-8.7 bar(g) (60.7-126 psi(g)).

5. The method satisfies one of the following: a. the near uniform flow occurs at the approximately constant temperature for a time ranging from 4.3 to 23.6 minutes; b. The yield of the separated pitch is 20-40%; c. the temperature is 490° C., the pressure is about 4.2 bar(g) (60.7 psi(g)), and the near uniform flow occurs at the near constant temperature for 23.6 minutes resulting in a pitch of 40%; and d. the temperature is 510° C., the pressure is about 8.7 bar(g) (126 psi(g)), and the near uniform flow occurs at the near constant temperature for 4.3 minutes resulting in a pitch of 20%; The method according to claim 4.

6. 2. The method of claim 1, wherein the starting material is a coal tar based heavy distillate that has been elevated to a temperature in the range of 495-510° C. at a pressure in the range of about 4.5-7.7 bar(g) (65.1-111.5 psi(g)).

7. The method satisfies one of the following: a. the near uniform flow occurs at the approximately constant temperature for a time ranging from 5.7 to 16.3 minutes; b. the yield of the separated pitch is in the range of 25-35%; c. the temperature is 495° C., the pressure is about 4.5 bar(g) (65.1 psi(g)), and the near uniform flow occurs at the near constant temperature for 16.3 minutes resulting in a pitch of 35%; and d. the temperature is 510° C., the pressure is about 7.7 bar(g) (111.5 psi(g)), and the near uniform flow occurs at the near constant temperature for 5.7 minutes resulting in a pitch of 25%; The method according to claim 6.

8. 10. The method of claim 1, wherein the starting material is a coal tar based heavy distillate that has been elevated to a temperature of 500° C. at a pressure of about 5.8 bar(g) (83.9 psi(g)).

9. 9. The method of claim 8, wherein the near uniform flow occurs at the approximately constant temperature for 7.4 minutes resulting in a pitch of 30%.

10. 10. The method of claim 1, wherein the starting material is a petroleum-based decant oil that has been elevated to a temperature in the range of 459-496° C. at a pressure in the range of about 5.5-20.7 bar(g) (80-300 psi(g)).

11. The method satisfies one of the following: a. the near uniform flow occurs at the approximately constant temperature for a time period ranging from 1 to 25 minutes; b. The yield of the separated pitch is in the range of 40-54.3% and the coke value is 47.3-50.5% by mass; c. the temperature is 496° C. and the near uniform flow occurs at the near constant temperature for 1 minute to produce 54% pitch having a coke value of 47.3% by mass; d. the temperature is in the range of 468-482°C, and the near uniform flow occurs at the near constant temperature for 10 minutes to produce pitch in the range of 43-54.3% with a coke value in the range of 47.3-50.5% by weight; and e. the temperature is in the range of 459-471°C and the near uniform flow occurs at the near constant temperature for 20 minutes to produce pitch in the range of 40-47.5% with a coke value in the range of 47.7-50.1% by weight; The method of claim 10.

12. 10. The method of claim 1 further comprising the additional step of warming said starting material prior to introduction into said conduit.

13. 10. The method of claim 1 , wherein the separation of the pitch portion from the combined stream is accomplished by distillation.

14. 13. A continuous process for deriving pitch from a preselected starting material, comprising the step of recycling the combined stream of claim 1 after separating said pitch portion as said starting material.

15. The method of claim 1, wherein the starting material comprises decant oil, coal tar heavy distillate, or a combination thereof.

16. The method of claim 15, wherein the pitch separated from the combined stream has a pitch yield of: (i) at least 25% with respect to decant oil, and (ii) at least 15% with respect to coal tar based heavy distillate.

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