Method for recovering hydrogen during hydroprocessing of oxygenate-containing feedstocks - Patent Application 20070122999

Abstract

The present invention relates to a method and process plant for partially hydroprocessing a feedstock containing oxygenates, comprising: introducing the feedstock, a quantity of make-up hydrogen, and recycle gas into a catalytic hydrotreating process under conditions to convert 30 to 95% of the oxygenates to hydrocarbons to provide a partially hydroprocessed product stream; adding a quantity of recycled wash water containing at least 0.1% by weight of oxygenates to a stream comprising at least 50% by weight of the partially hydroprocessed product stream, optionally in combination with an additional quantity of wash water, to provide a combined hydroprocessed product stream; cooling the combined hydroprocessed product stream and separating it into a vapor product fraction, a liquid aqueous fraction, and a liquid product fraction; withdrawing a first quantity of the liquid aqueous fraction as a waste stream; and introducing a second quantity of the liquid aqueous fraction as the quantity of recycled wash water, which has the associated advantage of minimizing withdrawal of oxygenates in the wash water because the wash water is at least partially saturated with oxygenates.

Description

[Technical Field]

[0001] Field of invention The present invention relates to the field of upgrading liquids derived from the pyrolysis of solid feedstocks. [Background technology]

[0002] technical challenges Oxygenates derived from biological feedstocks or from the pyrolysis of solid feedstocks, such as mixed municipal waste, mixed or sorted plastic waste, and forestry waste, can be upgraded to high-quality hydrocarbons to provide a liquid product (simply pyrolysis oil or raw pyrolysis oil) that can be used as a transportation fuel or petrochemical feedstock. This product can also be richer in oxygenates than typically required for hydrocarbon transportation fuels, with the intention of subsequent hydroprocessing elsewhere or using such oxygenate-rich products. Summary of the Invention [Problem to be solved by the invention]

[0003] If the final product is enriched in oxygenates, the processing conditions and intermediate products will be different from the intermediate products and other hydroprocessing processes where the final product is quantitatively converted to hydrocarbons. This also means that the intermediate processes for purifying the intermediate product will be different; specifically, the presence of oxygenates in the product may result in a higher amount of product soluble in the wash water, reducing yield.

[0004] The inventors have determined that this yield loss can be reduced by full or partial recycling (reuse) of the wash water, such that washing is performed with a stream that is already saturated with oxygenates and therefore has no ability to remove oxygenates.

[0005] definition The unit "MPag" will be understood to indicate MPa gauge, i.e. pressure above ambient.

[0006] Nm 3 The unit is "normal" m 3 , i.e. the amount of gas that would be taken up by this volume at 0°C and 1 atmosphere.

[0007] As used herein, the term "hydrogen to liquid oil ratio" or "H2:oil ratio" means the volumetric ratio of a hydrogen gas stream to a liquid oil stream, and is defined as Nm 3 / m 3 where the gas phase is reported at normal conditions (0° C., 1 atmosphere) and the liquid phase is reported at standard conditions (25° C., 1 atmosphere), in accordance with art practice.

[0008] When concentrations are stated in % by weight (wt%), this is to be understood as % by weight / weight.

[0009] When referring to the concentration of oxygenates or other molecular groups, it is intended to mean the concentration of all molecules of such molecular groups, not functional groups.

[0010] For convenience, the terms "pyrolysis" and "thermochemical cracking" are used broadly herein to refer to any cracking process in which solid materials are partially decomposed at high temperatures (typically 250°C to 800°C or 1000°C) in the presence of sub-stoichiometric amounts of O (including no added oxygen). The products are typically a combination of liquid and gas streams and a quantity of solid char. The terms are intended to include the processes known as pyrolysis and hydrothermal liquefaction, both in the presence and absence of a catalyst. For convenience, the product of such a pyrolysis process may be referred to as pyrolysis oil, but should be understood to include any pyrolysis process.

[0011] In the following, a hydrocarbon feedstock is a material comprising molecules containing hydrogen and carbon, and possibly heteroatoms, i.e. other elements such as oxygen, sulfur, nitrogen, etc.

[0012] In this specification, the term "section" means a physical section that includes a unit or combination of units for performing one or more steps and / or sub-steps.

[0013] The terms plastic or polymer derived feedstock, or waste plastic or waste polymer, should be understood to include mixed or separated waste containing at least 50%, 80%, or 90% by weight of plastics and other synthetic polymers.

[0014] Biological feedstocks can also be defined by tracing their origin, 14 It can also be defined by a C content exceeding 0.5 ppt (parts per trillion) of the total carbon content.

[0015] When hydrogen and hydrogen concentrations are referred to, this is generally understood to be the element hydrogen molecule, unless it is specified that the hydrogen is part of another molecule.

[0016] When referring to oxygen content, it is generally understood that atomic oxygen is part of another molecule unless specifically stated to refer to the molecular element oxygen. [Means for solving the problem]

[0017] Resolving the issue The conversion of pyrolysis oil to stabilized products containing moderate amounts of oxygenates can be carried out cost-effectively while reducing hydrogen consumption by partial hydrocracking.

[0018] Conversion of oxygenates to transportation fuels by partial hydroprocessing will result in partially water-soluble products. To minimize yield losses, it has been suggested to use oxygenate-containing wash water, e.g., recycled wash water, even if it contains other impurities, so that additional oxygenated products are not drawn off in the wash water.

[0019] The hydrocarbonaceous feedstock according to the present disclosure can be provided by a thermochemical cracking process plant section, which can be one of many variations, including a rotary furnace, a fluidized bed, a transport bed, or a circulating fluidized bed, as is well known in the art. This cracking converts the pyrolysis feedstock at high temperatures into solids (char), high-boiling liquids (tar), and a gas fraction. The gas fraction includes a condensable fraction (pyrolysis oil or condensate, C5+ compounds) and a non-condensable fraction (pyrolysis gas, including pyrolysis off-gas) at standard temperatures. For example, the thermochemical cracking process plant section (pyrolysis section) can include a pyrolyzer unit (pyrolysis reactor), cyclones and / or filters for removing particulate solids such as char, and a cooling unit to thereby produce a pyrolysis off-gas stream and a pyrolysis oil stream, i.e., a condensed pyrolysis oil. The pyrolysis gas stream contains light hydrocarbons, such as C1-C4 hydrocarbons, typically HO, CO, and CO2. Typically, the term pyrolysis oil includes condensates and tars, and pyrolysis oil streams from the pyrolysis of biomass are sometimes referred to as bio-oil or bio-crude. Pyrolysis oil is a liquid substance resulting from the depolymerization of solids treated in pyrolysis, rich in a blend of molecules, typically consisting of over 200 compounds, primarily oxygenates such as acids, sugars, alcohols, phenols, guaiacols, syringols, aldehydes, ketones, furans, and other mixed oxygenates. Thermochemical decomposition of non-biological wastes with appropriate compositions, such as plastic fractions or rubber containing used tires, generally yields products with low oxygen content unless O2 is added to the decomposition process, generally providing hydrocarbon feedstocks with structures that mirror the solid pyrolysis feedstocks.

[0020] For purposes of this invention, the pyrolysis section may be fast pyrolysis, also known in the art as flash pyrolysis. Fast pyrolysis refers to the thermochemical decomposition of solid feedstocks, typically in the absence of O2, at temperatures typically in the range of 350-650°C, e.g., about 500°C, and for reaction times of 10 seconds or less, e.g., 5 seconds or less, e.g., about 2 seconds. Fast pyrolysis is carried out, for example, by autothermal treatment in a fluidized-bed reactor. The latter, also known as autothermal cracking, is characterized by the use of air as a fluidizing gas, optionally with an inert or recycle gas. This allows the partial oxidation of pyrolysis compounds produced in the pyrolysis reactor (autothermal reactor) to provide the energy for pyrolysis, while simultaneously improving heat transfer. So-called catalytic fast pyrolysis can use catalysts. Acid catalysts, typically containing zeolites free of active metals, can be used to upgrade pyrolysis vapors and can operate in either in-situ mode (where the catalyst is placed within the pyrolysis reactor) or ex-situ mode (where the catalyst is placed in a separate reactor). The use of a catalyst has the advantage of stabilizing the pyrolysis oil and facilitating hydroprocessing, and can also increase the selectivity to desired pyrolysis oil compounds.

[0021] In some cases, hydrogen is added to catalytic pyrolysis, which is called reactive catalytic fast pyrolysis. When catalytic pyrolysis is carried out at high hydrogen pressures, e.g., above 0.5 MPa, it is often called catalytic hydropyrolysis. Catalysts for upgrading in the presence of hydrogen are usually composed of one or more metals active for hydrogenation, e.g., metals from Group 6 or Groups 8, 9, and 10.

[0022] The pyrolysis step may be fast pyrolysis carried out without the presence of a catalyst and hydrogen, i.e., the fast pyrolysis step is not catalytic fast pyrolysis, hydropyrolysis or catalytic hydropyrolysis, which allows for a simpler and cheaper process.

[0023] In one embodiment, the pyrolysis is hydrothermal liquefaction. Hydrothermal liquefaction refers to the thermochemical conversion of solid raw materials, such as plastic waste, biomass, municipal solid waste, or sewage sludge, into a primarily liquid component by treating them in a high-temperature, high-pressure aqueous environment for a sufficient period of time to decompose the solid biopolymer structure. Typical hydrothermal treatment conditions include temperatures in the range of 200-500°C, particularly 300-450°C, and operating pressures in the range of 4-40 MPag, particularly 25-35 MPag. Compared to pyrolysis, such as fast pyrolysis, this technology has the advantages of lower operating temperatures, higher energy efficiency, and a lower yield of high-boiling products.

[0024] In one embodiment, pyrolysis further includes passing the solid feedstock through a solid feedstock preparation section, which may include, for example, drying to remove moisture and / or grinding to reduce particle size. For example, water / moisture in the solid feedstock that vaporizes in the pyrolysis section condenses in the pyrolysis oil stream, thereby carrying out the process, which may be undesirable. Furthermore, the heat used to vaporize the water removes the heat required for pyrolysis. Removing water and reducing the particle size of the solid feedstock improves the thermal efficiency of the pyrolysis section.

[0025] Finally, other related thermochemical decomposition methods include intermediate or slow pyrolysis, where conditions are lower and generally have longer residence times - these methods are also known as carbonization or torrefaction. The main advantage of these thermochemical decomposition methods is their low investment costs, but they may have specific advantages for certain feedstocks and specific product requirements, such as the desire for biochar as an associated product.

[0026] When large amounts of solid products are produced, for example, in processes for producing biochar or when it is desired to thermochemically convert used tires to recover unconverted carbon black particles, it can be beneficial to filter the liquid products as part of the thermochemical conversion process, with the benefit of minimizing downstream catalyst deactivation.

[0027] The liquid feedstocks obtained from thermochemical cracking are not of sufficient quality to be used, for example, as transportation fuels: they have too high a boiling point, poor stability, or contain undesirable heteroatoms, and therefore require hydroprocessing to be upgraded to a practical and economically viable feedstock.

[0028] Accordingly, we propose a method for hydroprocessing a liquid oil stream by reacting the liquid oil stream with hydrogen in the presence of a hydroprocessing catalyst that is resistant to sulfur poisoning. The catalyst may be a sulfided catalyst containing one or more of nickel, cobalt, molybdenum, and tungsten, typically operated at an inlet temperature of 130-200°C, or a metal catalyst containing one or more of nickel, palladium, and platinum, typically operated at an inlet temperature of 80-130°C. The pressure is often 0.5-2 MPa, but can be up to 15 MPa, and the liquid hourly space velocity (LHSV) is 0.1-5 h -1 This allows for the formation of a stable liquid oil flow.

[0029] In one embodiment, the hydroprocessing catalyst is in a sulfided form, such as NiMoS or CoMoS. The catalyst may be pre-sulfided by exposure to sulfur-containing flow paths, or may be sulfided in situ or immediately prior thereto by sulfur present in, for example, pyrolysis oil, so that the sulfided catalyst remains sulfided and thus active due to the presence of sulfur.

[0030] Catalytically active materials, particularly in the initial hydroprocessing of conjugated double bonds, e.g., hydroprocessing, typically consist of an active metal (either elemental metal, such as nickel, cobalt, tungsten, and / or molybdenum, or, in some cases, nickel and precious metals, such as platinum and / or palladium) and a refractory support (such as alumina, silica, or titania, or a combination thereof). Initial hydroprocessing conditions can include moderate temperatures in the range of 120-200°C, moderate pressures in the range of 0.5-5 MPa, and liquid hourly space velocities (LHSVs) in the range of 0.1-5. Under certain conditions, high pressures up to 15 MPa may be required.

[0031] Final hydroprocessing (e.g., hydroprocessing conditions) generally include high temperatures in the range of 250-400°C, high pressures in the range of 3-15 MPa, and liquid hourly space velocities (LHSV) in the range of 0.1-4, optionally with intermediate cooling by quenching with cold hydrogen, feed, or product. Generally, one or more of lower temperatures, increased liquid hourly space velocities, limited catalyst activity, and reduced hydrogen availability can result in low degrees of polymerization and thus limited conversion of oxygenates to hydrocarbons, thereby reducing hydrogen consumption. Those skilled in the art will recognize that selecting appropriate conditions for a desired degree of polymerization in this multidimensional space will be accomplished by routine experimentation.

[0032] In general, the process is moderately exothermic, typically resulting in a temperature rise of 5-20°C. However, depending on the extent of hydrogenation and hydrodeoxygenation, it can be highly exothermic, with temperatures rising up to 100°C.

[0033] In addition to hydroprocessing to remove heteroatoms, additional steps may be desired to obtain a product of suitable quality. These steps may include isomerization, hydrocracking, hydrodearomatization, among others, depending on the feedstock characteristics and product requirements.

[0034] Catalytically active materials in isomerization typically include an active metal (either an elemental noble metal such as platinum and / or palladium, or a sulfide base metal such as nickel, cobalt, tungsten, and / or molybdenum), an acidic support (typically a molecular sieve having a topology that exhibits high shape selectivity, e.g., MOR, FER, MRE, MWW, AEL, TON, and MTT), and a refractory support (such as alumina, silica, or titania, or a combination thereof).

[0035] The isomerization conditions are a temperature of 250 to 400°C, a pressure of 2 to 10 MPa, and a liquid hourly space velocity (LHSV) of 0.5 to 8.

[0036] Catalytically active materials for hydrocracking have similar properties to those for isomerization and typically include an active metal (either an elemental noble metal such as platinum and / or palladium, or a sulfide base metal such as nickel, cobalt, tungsten, and / or molybdenum), an acidic support (typically a molecular sieve with a topology that exhibits high cracking activity, e.g., MFI, BEA, and FAU), and a refractory support (e.g., alumina, silica, or titania, or a combination thereof). The difference between catalytically active materials for isomerization is usually the nature of the acidic support. Acidic supports can have different structures (even amorphous silica-alumina can be used for hydrocracking) and can have different acidities due to factors such as the silica:alumina ratio.

[0037] Hydrocracking conditions are temperatures of 250-400°C, pressures of 3-20 MPa, and liquid hourly space velocities (LHSV) of 0.5-8, optionally with intermediate cooling by quenching with cold hydrogen, feed, or product.

[0038] Other types of hydroprocessing are also contemplated, such as hydrodearomatization (HDA). Catalytically active materials in hydrodearomatization typically include an active metal (typically an elemental noble metal such as platinum and / or palladium, but also possibly sulfide base metals such as nickel, cobalt, tungsten, and / or molybdenum) and a refractory support (e.g., amorphous silica-alumina, alumina, silica, or titania, or combinations thereof).

[0039] The conditions for hydrodearomatization are a temperature of 200 to 350°C, a pressure of 2 to 10 MPa, and a liquid hourly space velocity (LHSV) of 0.5 to 8.

[0040] The supply of hydrogen for hydroprocessing is a significant cost, and reducing the amount of hydrogen required can be a driving force for cost reduction. Hydroprocessing consumes hydrogen per volume of oil, which is H 2: This is called the oil consumption ratio. In the case of complete hydroprocessing, the H2:oil consumption ratio is 50 Nm 3 / m 3 ~1000Nm 3 / m 3 However, to minimize the risk of coke deposition on the catalyst due to hydrogen starvation, the H2:oil consumption ratio is set to 200 Nm 3 / m 3 In this case, the oil consumption ratio is up to 1000 Nm 3 / m 3 It is common to operate them with a safety factor of 2, 4, or 8 so that they will operate within this range.

[0041] Hydroprocessing in general, and especially for oxygenate feedstocks, is carried out with an excess of hydrogen to increase reaction rate and minimize the risk of coke deposition on the catalyst. The excess hydrogen is usually recycled to minimize hydrogen consumption and associated costs. However, because reaction rate and process equilibrium depend on the hydrogen partial pressure, the presence of other compounds such as methane and carbon dioxide in the recycle gas reduces this effect of hydrogen, at the expense of more expensive equipment, or requires higher total pressures. For example, when the H2:oil consumption ratio is 200 Nm 3 / m 3 In this case, if the purity of the H2-rich gas in the process is 80 vol% (volume %), and a safety factor of 2 is used, the gas:oil ratio is 500 Nm 3 / m 3 This becomes:

[0042] The product stream from hydroprocessing is a two-phase gas / liquid stream. The liquid phase, which is of suitable quality for final or downstream use, may contain significant amounts of high-boiling hydrocarbons and oxygenates, while the hot gas phase contains unreacted hydrogen and gaseous products. The gaseous products are primarily liberated heteroatoms, including oxygen (as HO or CO and CO), nitrogen (as NH), sulfur (as HS), and halides such as chlorides (as HCl or NHCl). Additionally, lighter hydrocarbons and oxygenates may also be present in the hot gaseous phase, especially if hydrogenation is incomplete. Due to the excess hydrogen and associated costs, hydrogen recycling is desirable.

[0043] Typically, separation of the liquid and vapor phases is performed in a high-temperature, high-pressure separator (operating at conditions approximating process conditions), e.g., 11 MPa and 240°C. If all catalysts are sulfided and the process is operated in the presence of sulfur, this separation may be performed downstream of all hydroprocessing steps, but typically only the first step of hydroprocessing uses a sulfided catalyst, in which case the first step separation is performed downstream of the hydrodeoxygenation catalyst and upstream of the noble metal isomerization or hydrocracking catalyst. If additional (or all) catalysts are sulfided, separation typically occurs after all sulfided catalysts.

[0044] The gas phase contains excess H, small heteroatom molecules such as H0, CO, CO, NH, H2S, and HCl, as well as C1-C5 hydrocarbons and oxygenates. To separate the excess H from the remainder of the gas phase, the gas phase can be cooled, for example to 50°C, and separated in a high-pressure, low-temperature separator.

[0045] If the high-temperature vapor phase contains water and light hydrocarbons, the condensate in the cryogenic separator will have three phases: a vapor phase, a hydrocarbon-rich liquid nonpolar phase, and a water-rich liquid polar phase. Because many nonpolar gases, e.g., CO2, CO, and paraffins, have high solubility in the liquid nonpolar phase and salts, such as NH4Cl, have high solubility in the polar phase, these compounds may be withdrawn from the high-pressure cryogenic separator with the liquid condensate, but because of the low solubility of H2, it will remain primarily in the vapor phase.

[0046] Salts such as ammonium chloride are undesirable in the product and can solidify on the equipment. Because salts are highly soluble in liquid water and can be easily separated from the gas stream by lowering the temperature, adding wash water after the thermal separator is common to remove these impurities. This removes the salts from the liquid product. However, if the product is only partially hydroprocessed, it will contain oxygenates that are partially soluble in water. This means that a product purification step by adding wash water will remove not only the salts but also the valuable oxygenates.

[0047] A practical addition of wash water preferably involves mixing liquid water with the hot stream under conditions (pressure, temperature, relative amount of water) that result in only partial evaporation of the water, since some amount of liquid water is highly desirable for the wash step, especially when the product is in the liquid phase. The combined stream is then cooled to form a liquid product phase, a water phase, and a gas phase. Because hydrocarbons are non-polar and have very low solubility in water, the water phase contains ppm wtOnly a small concentration of hydrocarbons enters the wash water. On the other hand, oxygenates are highly polar and, depending on the nature of the oxygenate, have some degree of solubility in water. As a result, the intended amount of oxygenates is extracted (removed) along with the wash water.

[0048] To minimize the amount of product recovered in the wash water, it is proposed to use wash water that is at least partially saturated with oxygenates. This can be achieved cost-effectively by recycling the wash water, but contrary to the common practice of purifying the wash water before recycling, it is desirable in this case to recycle the wash water containing dissolved oxygenates. In this way, no additional oxygenates are drawn off, resulting in a higher overall process yield.

[0049] To prevent salt buildup in the wash water, a certain amount of the liquid aqueous phase must be withdrawn. This can be done as a purge to the general waste hydroprocessing process, or the water can be purified in a closed loop, for example by evaporation and recycling the purified water. When determining the purge amount, the water produced by the hydrodeoxygenation must also be taken into account. In many cases, this produced water is a significant contributor to the process's wash water consumption.

[0050] However, if the product is only partially hydroprocessed, the amount of condensed nonpolar hydrocarbons will be low. This is especially true when the feedstock is high-boiling, since in this case most of the ambient product liquid is withdrawn in the high-pressure, high-temperature separator. Furthermore, if the moderate amount of condensed nonpolar hydrocarbons is dominated by slightly more polar compounds, such as light oxygenates, the solubility of minor amounts of nonpolar gases will be low. As a result, CO2 and CO are withdrawn less from the cold vapor phase, and the purity of the recycle gas will be lower.

[0051] A common method for purifying gas streams in hydroprocessing plants is the use of amine scrubbers, which reversibly capture, among other things, CO2 and H2S in an aqueous amine solution. However, if the gas being purified also contains water-soluble compounds such as methanol, ethanol, and formic acid, these compounds will also be captured in the amine scrubber, but not reversibly.

[0052] The use of amine scrubbers for gas purification involves very low pressure drop, so the scrubber can be placed in line with a recycle gas compressor whose role is to pressurize the high pressure gas to match the process pressure, while compensating for the reactor pressure drop of perhaps 1 MPa. [Brief explanation of the drawings]

[0053] [Figure 1] Figure 1 shows the layout of a method for recycling wash water without purification. [Figure 2] Figure 2 shows the layout of the process when fresh wash water is added. DETAILED DESCRIPTION OF THE INVENTION

[0054] Figure 1 In Figure 1, a feedstock containing oxygenates (2) is pressurized in a feed pump (FP) and heated with reactor effluent (10) in a heat exchanger (HX) before being combined with makeup hydrogen gas (4) compressed in a makeup gas compressor (MUGC) and recycle gas (6) compressed in a recycle gas compressor (COMP). This feedstock stream (8) is directed to a hydrodeoxygenation reactor (HDO) containing one or more catalysts configured by controlling conditions, including composition, temperature, pressure, and liquid hourly space velocity, to provide the desired hydrodeoxygenation conversion of the reactor feed stream (8). Conditions can be selected to support only a limited range of reactions, for example, by limiting temperature, residence time, or hydrogen availability. The reactor effluent (10) is cooled, and the cooled reactor effluent (12) is directed to a high-temperature, high-pressure separator (HHPS) to provide a first product stream (14) and a vapor stream (16). The vapor stream (16) is combined with a wash water stream (18), and the combined stream (20) is cooled in a cooler (C) and introduced as a cold combined stream (22) into a three-phase separator (TPS), from which condensed sour water (28) and light products (24) are separated from light gases (32), which are then directed to a recycle compressor (COMP). A portion of the condensed sour water (28) is pressurized in a recycle pump (RP) and introduced as wash water, and another portion (30) is withdrawn from the system. The first product stream (14) and light products (24) may be withdrawn as a combined product stream (26).

[0055] In other embodiments, additional water may be added to the recycled wash water, and the process may include additional steps, including purification of the recycled light gas (32) and hydroprocessing other than hydrodeoxygenation (HDO), such as olefin hydrogenation, hydrodearomatization, isomerization, etc. These process steps may be in-line with the hydrodeoxygenation process or may be located upstream or downstream of the process shown in FIG.

[0056] In further embodiments, the product stream (26) can be introduced into a fractionation process to provide products for specific applications based on boiling point, such as naphtha for gasoline, naphtha for use in steam cracking, aviation fuel, automotive diesel or marine fuel, etc. The product stream (26) or fractions thereof can also be directed to further hydroprocessing steps, such as isomerization, hydrocracking and hydrodearomatization.

[0057] In a further embodiment, the hydrogen-rich gas phase (32) may be purified to increase the effective hydrogen pressure in the process.

[0058] Figure 2 A comparative process is shown in Figure 2. Here, a feedstock containing oxygenates (2) is pressurized in a feed pump (FP) and heated with reactor effluent (10) in a heat exchanger (HX) before being combined with makeup hydrogen gas (4) compressed in a makeup gas compressor (MUGC) and recycle gas (6) compressed in a recycle gas compressor (COMP). This feedstock stream (8) is introduced into a hydrodeoxygenation reactor (HDO) containing one or more catalysts configured by controlling conditions, including composition, temperature, pressure, and liquid hourly space velocity, to provide the desired hydrodeoxygenation conversion of the reactor feed stream (8). Conditions can be selected to support only a limited range of reactions, for example, by limiting temperature, residence time, or hydrogen availability. The reactor effluent (10) is cooled, and the cooled reactor effluent (12) is directed to a high-temperature, high-pressure separator (HHPS), which provides a first product stream (14) and a vapor stream (16). The vapor stream (16) is combined with a fresh wash water stream (18), and the combined stream (20) is cooled in a cooler (COOL) and introduced as a low-temperature combined stream (22) into a three-phase separator (TPS), from which condensed sour water (30) and light products (24) are separated from light gases (32), which are introduced into a recycle compressor (COMP). In this manner, all of the condensed sour water (28) is withdrawn for hydroprocessing in the plant. The first product stream (14) and light products (24) may be withdrawn as a combined product stream (26).

[0059] Description of the embodiment A first broad aspect of the invention is a method for partially hydroprocessing a feedstock containing oxygenates, comprising the steps of: introducing the feedstock, a quantity of make-up hydrogen, and a recycle gas into a catalytic hydrotreating process under conditions to convert 30 to 95% of the oxygenates to hydrocarbons to provide a partially hydroprocessed product stream; adding a quantity of recycle wash water containing at least 0.1 wt. % oxygenates to a stream comprising at least 50 wt. % of the partially hydroprocessed product stream, optionally in combination with an additional quantity of wash water, to provide a combined hydroprocessed product stream; cooling the combined hydroprocessed product stream and separating it into a vapor product fraction, a liquid aqueous fraction, and a liquid product fraction; withdrawing a first quantity of the liquid aqueous fraction as a waste stream; and introducing a second quantity of the liquid aqueous fraction as the quantity of recycle wash water.

[0060] This has the related advantage that withdrawal of oxygenates in the wash water can be minimized because the wash water is at least partially saturated with oxygenates. The withdrawal of the first amount of said liquid aqueous fraction can be done as a purge (removal) or by a purification process.

[0061] A second aspect relates to the process according to the first aspect, wherein the liquid aqueous fraction comprises at least 0.1 wt. %, at least 0.2 wt. %, or at least 0.5 wt. % oxygenates. .

[0062] This has the associated advantage of providing a liquid aqueous fraction that removes minimal oxygenates from the process.

[0063] One embodiment relates to the method according to the first embodiment, wherein the liquid aqueous fraction comprises less than 20%, less than 10%, or less than 5% by weight of oxygenates, and the amount of oxygenates bound in the liquid aqueous fraction is moderate.

[0064] A third embodiment is a method for preparing a liquid aqueous fraction comprising: wt or at least 100 ppm wt and less than 15% or less than 10% by weight of inorganic salt.

[0065] Such a process allows for the hydroprocessing of feedstocks containing inorganic salts, with the associated advantage of recycling wash water with salt recovery capabilities.

[0066] A fourth embodiment relates to a process according to the first three embodiments, wherein the ratio of the mass of wash water to the mass of the amount of wash water and said combined hydroprocessed product stream is greater than 1:50, 1:20 or 1:10 and less than 1:1, 1:2 or 1:5.

[0067] This has the associated advantage of balancing the convenience of a process that has relatively low amounts of water in the partially hydroprocessed product stream against the increased level of removal of water soluble impurities such as salts.

[0068] A fifth embodiment relates to a method according to the first four embodiments, wherein a certain amount of said liquid aqueous fraction is directed to a purge.

[0069] This has the associated advantage of continuously removing impurities and product water from the process, but centralizing the purification of the purified water in the process plant's hydroprocessing system.

[0070] A sixth aspect relates to the method according to the fifth aspect, wherein the amount of liquid aqueous fraction directed to purging is greater than 5%, greater than 10% or greater than 15% of the liquid aqueous fraction.

[0071] This has the associated advantage of a high purge, corresponding to a process where the net production of water is greater than that required as wash water, although the oxygen content is typically 5%, 10%, or even up to 50% for pyrolyzed biological feedstocks.

[0072] At the same time, the amount introduced into the purge must be limited to less than 95% or even less than 90% to ensure there is a remaining amount of liquid aqueous fraction for recycle.

[0073] A seventh aspect relates to a process according to the fifth or sixth aspects, with the associated advantage that the amount of liquid aqueous fraction directed to the purge is less than 50%, less than 25% or less than 15%, a moderate purge corresponding to a process in which the net production of water is less than that required as wash water, which is typically the case for pyrolysis feedstocks with low biological content and oxygen content less than 5%. To ensure removal of salts and other impurities from the process, the amount of liquid aqueous fraction introduced to the purge can be more than 2%, more than 5% or more than 10%.

[0074] An eighth embodiment relates to the method according to the fifth, sixth or seventh embodiment, wherein the amount of liquid aqueous fraction directed to the purge is separated with a concentrated salt brine or precipitate and an amount of purified water by use of evaporation, membrane separation or precipitation.

[0075] This has the associated benefit of reducing the amount of wasted water introduced into the waste stream.

[0076] A ninth aspect relates to a process plant configured to carry out a method according to any of the above aspects. [Example]

[0077] example To illustrate the benefits of the present disclosure, methods using pure make-up wash water and recycled wash water were studied.

[0078] The method studied involves partially hydroprocessing a liquid feedstock produced by hydrothermal liquefaction of forest wastes to produce a fuel containing hydrocarbons and oxygenates (HC+Oxyg). The liquid feedstock contains a certain amount of chloride, and a wash to remove the chloride is required to obtain sufficient product. The hydroprocessed product stream has the composition shown in Table 1, Stream 12, and is then washed and separated into gas, sour water, and products in either Example 1, which uses recycled wash water in accordance with this disclosure and Figure 1, or Example 2, which uses pure or purified wash water in accordance with the comparative process in Figure 2. For practical reporting, the amounts of nitrogen and chloride are reported based on the results of an aqueous solution of NH4 + and Cl - Even though the compounds contain ionic forms such as HCl and NH3, they are reported as NH3 and HCl, respectively.

[0079] The properties of Example 1 are reported in Table 1. It can be seen that, due to the recycle of wash water, 896 kg / hr of sour water was withdrawn as a purge from the process in stream (30), which contained approximately 1 kg / hr of Cl. The heavy product stream (14) contained 1.9 kg / hr of Cl, corresponding to 166 ppm of Cl, and the light product stream (24) contained 3 g / hr of HCl, corresponding to 2.4 ppm of Cl. The water purge (30) contained 1.1 kg / hr (1232 ppm) of Cl and 145 kg / hr of dissolved hydrocarbons and oxygen. Residual Cl, especially in the heavy product stream, necessitated the product being directed to a stripper.

[0080] The corresponding properties for Example 2 are reported in Table 2. Here, it can be seen that, due to the recycle of wash water, 1312 kg / hr of sour water is withdrawn as a purge from the process in stream (30), which contains approximately 1.1 kg / hr of Cl. The heavy product stream (14) contains 1.9 kg / hr of Cl, which corresponds to 166 ppm of Cl, and the light product stream (24) contains 1 g / hr of HCl, which corresponds to 1.0 ppm of Cl. The water purge (30) contains 1.1 kg / hr (842 ppm) of Cl and 160 kg / hr of dissolved hydrocarbons and oxygen. In the case of Example 1, due to the heavy product stream, the product must be directed to a stripper.

[0081] Since a large amount of CO2 is present in the hydrogen-rich gas stream (32), in both process layouts this stream will typically be purified, such as with an amine wash.

[0082] These data show that recycling wash water without purification results in lower removal of water-soluble compounds (both Cl and oxygenated product). Washing with pure or purified wash water reduces the Cl concentration of the light products from 2.4 ppm Cl to 1.0 ppm Cl, but this difference is not significant because the heavy products require stripping. At the same time, washing with pure wash water pulls out 15 kg of product per hour as dissolved oxygen.

[0083] [Table 1]

[0084] [Table 2]

Claims

1. A method for partially hydroprocessing a feedstock containing oxygenates, comprising the steps of: a. introducing said feedstock, an amount of make-up hydrogen, and a recycle gas into a catalytic hydrotreating process under conditions to convert 30-95% of the oxygenates to hydrocarbons to provide a partially hydroprocessed product stream; b. adding an amount of recycle wash water comprising at least 0.1 wt. % oxygenates to a stream comprising at least 50 wt. % of said partially hydroprocessed product stream, optionally in combination with an additional amount of wash water, to provide a combined hydroprocessed product stream; c. cooling the combined hydroprocessed product stream and separating it into a vapor product fraction, a liquid aqueous fraction, and a liquid product fraction; d. withdrawing a first amount of the liquid aqueous fraction as a waste stream; e) introducing a second amount of said liquid aqueous fraction as said amount of recycled wash water.

2. 10. The method of claim 1, wherein the liquid aqueous fraction comprises at least 0.1%, at least 0.2%, or at least 0.5% by weight of oxygenates, and less than 20%, less than 10%, or less than 5% by weight.

3. the liquid aqueous fraction is at least 50 ppm ｗｔ or at least 100 ppm ｗｔ and containing less than 15% by weight or less than 10% by weight of inorganic salts.

4. 4. The method of claim 1, 2, or 3, wherein the ratio of the mass of the wash water to the mass of the amount of the hydroprocessed product stream combined with wash water is greater than 1:50, greater than 1:20, or greater than 1:10, and less than 1:1, less than 1:2, or less than 1:

5.

5. 5. The method of claim 1, 2, 3 or 4, wherein a portion of the liquid aqueous fraction is directed to a purge.

6. 6. The method of claim 5, wherein the amount of liquid aqueous fraction directed to purge is greater than 5%, greater than 10%, or greater than 15% and less than 95% or less than 90% of the liquid aqueous fraction.

7. 7. The method of claim 5 or 6, wherein the amount of liquid aqueous fraction directed to the purge is greater than 2%, greater than 5%, or greater than 10%, and less than 50%, less than 25%, or less than 15%.

8. 8. The method of claim 5, 6 or 7, wherein the amount of liquid aqueous fraction directed to the purge is separated into a concentrated salt brine or precipitate and an amount of purified water by the use of evaporation, membrane separation or precipitation.

9. A process plant configured to carry out the method according to any one of claims 1 to 8.

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