A system and method for purifying high-dust and high-chlorine coal tar

Abstract

The present invention belongs to the technical field of coal chemical industry, and specifically relates to a system and method for purifying high-dust and high-chlorine coal tar. The system includes a first separation device and a second separation device. The first separation device is provided with a connected rough washing section and a fine washing section. The top of the rough washing section is provided with a raw coal tar inlet; the bottom of the first separation device is provided with an agitator, and the top is provided with a second oil and gas discharge port; the bottom of the fine washing section is provided with a heavy tar outlet, and the top is provided with a light tar reflux inlet; a heavy tar reflux inlet is provided between the heavy tar outlet and the light tar reflux inlet; the second separation device is connected to the second oil and gas discharge port and the fine washing section, respectively, for performing three-phase separation on the gas discharged from the second oil and gas discharge port to obtain light tar. The system can be used for the purification of high-dust and high-chlorine coal tar. The dust content and chlorine content of the obtained light tar and heavy tar are both low, and the coal tar can be comprehensively utilized without generating waste residue, which is economical and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of coal chemical industry, and in particular relates to a system and method for purifying high-dust and high-chlorine coal tar. Background Art

[0002] At present, coal tar in my country is mainly produced as a by-product of semi-coke using bituminous coal and lignite as raw materials. The annual production of semi-coke in my country is about 30 million tons. The production of coal tar is refined on the basis of semi-coke production. According to the annual output of semi-coke, the annual output of coal tar is about 3 million tons. With such a large output of coal tar, its processing process is diverse. Due to various factors, the development of domestic coal tar processing industry is still in its early stages, with small scale, low technical level, few products and poor environmental protection level.

[0003] There are two common coal tar processing technologies in China: one is coal tar distillation separation technology, which uses the different properties of the components in coal tar, but there are many components with similar properties, and separates various fractions by distillation technology, so that the products of the components to be extracted, such as anthracene, phenol, naphthalene, etc., are concentrated into the corresponding fractions, and then further separated by physical or chemical methods; the other is to catalytically hydrogenate coal tar to produce fuel oil products. The lignite pyrolysis and upgrading process, including gas heat carrier and solid heat carrier processes, has a large dust content in the coal tar, which can reach up to 30%. Most of the dust particles are micron-sized, and the viscosity of the heavy components in the coal tar will also increase.

[0004] Due to the high dust and chlorine content in coal tar, it is completely uneconomical to use it directly as fuel and cannot meet environmental protection requirements. Existing centrifugal separation, distillation process, delayed coking and other technologies cannot purify high-dust and high-chlorine coal tar to meet the requirements, making it impossible to effectively further process coal tar.

[0005] Chinese patent document CN103666513A discloses a separation and upgrading process for high-dust coal tar, which includes filtering dust from high-dust coal tar in sequence, feeding into a feed tank, preheating to above 200-250°C in a preheater, and then feeding into a distillation tower for distillation to obtain a light component. The light component is distilled from the top of the distillation tower, and then preheated in a preheater to remove the dust from the coal tar, and then fed into a tower condenser to condense into a liquid to form light tar. The coal powder content in the dedusted coal tar in this process is less than 0.01wt%, but the process cannot effectively remove chlorine in the coal tar, and a large amount of chlorine still remains in the dedusted coal tar, affecting subsequent processing. Summary of the invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problems in the prior art that when purifying coal tar, the dust and chlorine content cannot be fully reduced, and the requirements for subsequent processing of coal tar cannot be met, thereby providing a high-dust and high-chlorine coal tar purification system and method.

[0007] To this end, the present invention provides the following technical solutions.

[0008] The present invention provides a high-dust and high-chlorine coal tar purification treatment system, comprising:

[0009] a first separation device for removing dust and chlorine; a washing section is provided in the first separation device, and the washing section includes a rough washing section and a fine washing section connected from bottom to top, and a raw coal tar inlet is provided at the top of the rough washing section; a stirrer is provided at the bottom of the first separation device; a second oil and gas discharge outlet is provided at the top of the first separation device; a heavy tar outlet is provided at the bottom of the fine washing section, and a light tar reflux inlet is provided at the top; a heavy tar reflux inlet is provided between the heavy tar outlet and the light tar reflux inlet;

[0010] The second separation device is connected to the second oil and gas outlet and the fine washing section respectively, and is used for performing three-phase separation on the gas discharged from the second oil and gas outlet to obtain light tar.

[0011] The second separation device is connected to the fine washing section via a light tar reflux pump; the light tar reflux pump is connected to the top of the fine washing section and refluxes part of the light tar to the fine washing section;

[0012] The second separation device is also provided with a non-condensable gas discharge outlet and an oily wastewater discharge outlet;

[0013] The bottom of the fine washing section is connected to a heavy tar reflux pump, and part of the heavy tar refluxes to the fine washing section.

[0014] The high-dust and high-chlorine coal tar purification treatment system also includes a pyrolysis furnace, which is connected to the bottom of the first separation device through a residual oil pump, and the residual oil pump is reflux-connected to the middle position of the rough washing section;

[0015] The pyrolysis furnace is communicated with the bottom of the rough washing section, and is used to pass the pyrolysis oil and gas generated by pyrolysis into the rough washing section.

[0016] A tower plate is arranged between the light tar inlet of the fine washing section and the bottom of the fine washing section. The tower plate is specifically arranged below the heavy tar reflux inlet and / or above the heavy tar reflux inlet. The types of tower plates include distillation tower plates such as flow-through sieve plates, floating valve tower plates, bubble cap tower plates, and tongue-shaped tower plates; the tower plate arranged below the heavy tar reflux inlet is a flow-through sieve plate, and the tower plate arranged above the heavy tar reflux inlet is one or more of the distillation tower plates such as flow-through sieve plates, floating valve tower plates, bubble cap tower plates, and tongue-shaped tower plates.

[0017] A tower plate is arranged between the bottom of the fine washing section and the pyrolysis oil and gas inlet. The tower plate is a herringbone open-hole tower plate. The tower plates are staggered in the vertical direction on the opposite side walls in the rough washing section. The tower plates are inclined downward. There are 6 to 15 tower plates in number, and the angle between the tower plates and the vertical direction is 30 to 60 degrees.

[0018] At least two agitators are arranged at the bottom of the first separation device; the agitators are arranged at the bottom in a diagonal form, so as to circulate the tar at the bottom of the first separation device and prevent dust deposition and coking in dead corners.

[0019] The pyrolysis furnace is a coal dry distillation furnace, and the furnace type is a vertical furnace, a rotary furnace, a belt furnace, etc.

[0020] When the pyrolysis reaction is carried out, it is also necessary to introduce materials such as coal or coke into the pyrolysis furnace to cause the residual oil to undergo pyrolysis reaction to fix dust and absorb chlorine.

[0021] The number of each unit structure in the first separation device and the second separation device can be adjusted according to actual production conditions.

[0022] The present invention also provides a method for purifying high-dust and high-chlorine coal tar, which uses the above-mentioned high-dust and high-chlorine coal tar purification system, comprising the following steps:

[0023] (1) After being preheated, the raw coal tar enters the rough washing section for fractionation and washing to obtain first oil gas and residual oil; wherein, part of the residual oil is refluxed to the rough washing section;

[0024] (2) The first oil and gas enter the fine washing section, and after fractionation and washing in the fine washing section, the second oil and gas and heavy tar are obtained;

[0025] (3) After the second oil and gas are separated into three phases, light tar, non-condensable gas and oily wastewater are obtained.

[0026] The step (2) further includes the step of returning part of the heavy tar to the fine washing section after the heavy tar has been heat exchanged with the raw coal tar; and / or,

[0027] The step (3) also includes a step of returning part of the light tar to the fine washing section.

[0028] The step (1) also includes a step of allowing part of the residual oil to enter a pyrolysis furnace for pyrolysis reaction to obtain pyrolysis products and pyrolysis oil and gas; wherein the pyrolysis oil and gas are introduced into the bottom of the rough washing section.

[0029] The dust content of the raw coal tar is greater than 1.5wt%, the chlorine content is 50-2000ppm, the initial distillation point is greater than 75°C, the 50% distillation temperature is 240-300°C, and the 80% distillation temperature is 350-400°C;

[0030] The light tar fraction is a distillate with an initial boiling point of 250°C in the raw coal tar and a density of 700 to 900 kg / m 3 ;

[0031] The heavy tar fraction is a distillate of 200-350°C from the raw coal tar, with a density of 900-1020 kg / m 3 .

[0032] The temperature at the top of the first separation device is 75-150°C; the temperature at the bottom of the first separation device is 300-450°C.

[0033] The reflux temperature of the light tar is 20-45°C;

[0034] The extraction temperature of the heavy tar is 200-350°C, and the reflux temperature is 80-250°C;

[0035] The temperature of the raw coal tar after preheating is 75 to 200°C.

[0036] The pressure of the first separation device is -0.1 to 0.25 MPaG.

[0037] The technical solution of the present invention has the following advantages:

[0038] 1. The high-dust and high-chlorine coal tar purification treatment system provided by the present invention comprises a first separation device and a second separation device, wherein the first separation device is provided with a connected rough washing section and a fine washing section, and a raw coal tar inlet is provided at the top of the rough washing section; an agitator is provided at the bottom of the first separation device; a second oil and gas discharge outlet is provided at the top of the first separation device; a heavy tar outlet is provided at the bottom of the fine washing section, and a light tar reflux inlet is provided at the top; a heavy tar reflux inlet is provided between the heavy tar outlet and the light tar reflux inlet; the second separation device is respectively connected to the second oil and gas discharge outlet and the fine washing section, and is used for performing three-phase separation on the gas discharged from the second oil and gas discharge outlet to obtain light tar. The system can be used for the purification of coal tar with high dust content and high chlorine content. A washing section is arranged in the first separation device, and the washing section includes a connected rough washing section and a fine washing section. When the raw coal tar is passed into the rough washing section, a first oil gas is generated after evaporation. The first oil gas flows upward and contacts with the tar flowing out of the fine washing section, the raw coal tar and the residual oil in the rough washing section, so as to effectively adsorb dust and reduce the dust content of the first oil gas. After the first oil gas enters the fine washing section, it is fractionated and heavy tar with low dust content is obtained at the bottom of the fine washing section. The second oil gas is extracted from the top of the fine washing section and light tar with extremely low dust content is obtained after three-phase separation. The tar adsorbing dust (referred to as dusty tar) will be deposited at the bottom of the first separation device and formed into residual oil after heating and concentration. As the chlorine in the raw coal tar is distilled and washed in the first separation device, part of the chlorine will be discharged from the first separation device along with the oil and gas and enter the second separation device. As the three-phase separation proceeds, the chlorine is dissolved in the sewage, reducing the chlorine content in the light tar. Another part of the chlorine will exist in the tar and deposit at the bottom of the first separation device. The tar is concentrated to form residual oil. Through the pyrolysis reaction, the chlorine is adsorbed in the pyrolysis product and discharged. The light tar and heavy tar obtained by this system have low dust and chlorine contents.

[0039] The processing system can be adjusted according to actual production requirements and is suitable for processes with different production volume requirements.

[0040] 2. The present invention provides a method for purifying high-dust and high-chlorine coal tar. In this method, the raw coal tar enters the rough washing section for fractionation to produce a first oil and gas. The coal tar in the rough washing section washes the first oil and gas and absorbs dust in the oil and gas. After absorbing the dust, the coal tar is deposited at the bottom of the first separation device. At the same time, the first oil and gas produced in the rough washing section enters the fine washing section for fractionation to form a second oil and gas. The heavy tar and light tar in the fine washing section wash the oil and gas again, further reducing the amount of dust in the oil and gas. The second oil and gas is discharged from the second gas discharge port and enters the second separation device. After three-phase separation, light tar, non-condensable gas and oily wastewater with low dust content are obtained. Part of the light tar enters the fine washing section again to supplement the liquid phase reflux, and can also control the top temperature of the first separation device. The non-condensable gas can be used as a raw material or fuel gas for preparing LNG and LPG. The chlorine in the gas will enter the oily wastewater, so that the chlorine content in the light tar is relatively low. The first oil and gas will obtain heavy tar while being fractionated in the fine washing section. After the heavy tar and the raw coal tar are heat exchanged, the raw coal tar reaches the preheating temperature, and the temperature of the heavy tar is reduced, so that the heat is recovered. The dusty tar enters the bottom of the first separation device, and forms residual oil after being heated and concentrated. Part of the residual oil enters the middle position of the rough washing section to form liquid reflux, and the other part enters the pyrolysis furnace for pyrolysis, and the reaction generates pyrolysis oil and gas and pyrolysis products (pyrolysis coke or semi-coke). The chlorine in the residual oil is adsorbed into the micropores of the pyrolysis coke or semi-coke, and a large amount of chlorine is removed; the pyrolysis oil and gas enter the rough washing section for separation and washing. After passing through the first separation device, the dust, heavy components and chlorine in the pyrolysis oil and gas can be effectively removed.

[0041] 3. In the method for purifying high-dust and high-chlorine coal tar provided by the present invention, controlling the temperature at the bottom of the first separation device helps to increase the yield of light coal tar and heavy coal tar; the pressure of the first separation device cooperates with the pressure of the pyrolysis furnace, which helps to separate the fractions and the recovery rate of coal tar; and the temperature and pressure at the bottom of the first separation device and the pressure of the pyrolysis furnace cooperate with each other, which can save energy and improve the recovery rate of coal tar. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 The high-dust and high-chlorine coal tar purification treatment system in Example 1 of the present invention;

[0044] Figure 2 Schematic diagram of the arrangement structure of the tray in the rough wash section in Example 1 of the present invention;

[0045] Reference numerals:

[0046] 1-residue oil outlet; 2-heat exchanger; 3-fine washing section; 4-rough washing section; 5-residue oil pump; 6-cooler; 7-pyrolysis furnace; 8-heater; 9-agitator; 10-second separation device; 11-light tar reflux pump; 12-heavy tar reflux pump; 13-tower plate; 14-tower wall;

[0047] 3-1-heavy tar outlet; 3-2-heavy tar reflux inlet; 3-3-light tar reflux inlet; 3-4-second oil and gas outlet;

[0048] 4-1-Raw coal tar inlet; 4-2-Residue oil reflux inlet; 4-3-Pyrolysis oil and gas inlet;

[0049] 7-1-pyrolysis furnace charge port; 7-2-pyrolysis product outlet; 7-3-pyrolysis oil and gas outlet;

[0050] 10-1- Second oil and gas inlet; 10-2- Non-condensable gas outlet; 10-3- Light tar outlet; 10-4- Oily wastewater outlet. DETAILED DESCRIPTION

[0051] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0052] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0053] Example 1

[0054] This embodiment provides a high dust and high chlorine coal tar purification system. Figure 1 As shown, including,

[0055] The first separation device is provided with a washing section for removing dust and chlorine from coal tar. The washing section includes a connected rough washing section 4 and a fine washing section 3 from bottom to top. The side wall of the rough washing section 4 is provided with a raw coal tar inlet 4-1, a residual oil reflux inlet 4-2 and a pyrolysis oil and gas inlet 4-3. The raw coal tar inlet 4-1 and the residual oil reflux inlet 4-2 are both above the pyrolysis oil and gas inlet 4-3. The raw coal tar and the residual oil are sprayed downward in the rough washing section for fractionation to produce the first oil and gas and dusty tar. The first oil and gas and the pyrolysis oil and gas flow upward into the fine washing section. The raw coal tar and the residual oil are sprayed downward to absorb the dust in the gas and reduce the dust content of the gas. The side wall of the fine washing section 3 is provided with a heavy tar outlet 3-1, a heavy tar reflux inlet 3-2, a light tar reflux inlet 3-3 and a second oil and gas outlet 3-4. After the first oil gas and pyrolysis oil gas enter the fine washing section, they will be further fractionated to produce the second oil gas and heavy tar. The refluxed light tar and heavy tar will spray downward to further absorb the dust in the gas and reduce the dust content. The second oil gas will be discharged from the second oil gas outlet 3-4. The heavy tar outlet 3-1 is set at the bottom of the fine washing section, below the heavy tar reflux inlet 3-2 and the light tar reflux inlet 3-3. The light tar reflux inlet 3-3 is located at the top of the fine washing section 3, and the heavy tar reflux inlet 3-2 is located below the light tar reflux inlet 3-3. After the heavy tar is discharged from the heavy tar outlet 3-1, it enters the heat exchanger 2 through the heavy tar reflux pump 12, and exchanges heat with the raw coal tar to make the raw coal tar reach the preheating temperature. This step can recycle the heat of the heavy tar and does not need to provide a heat source for preheating the raw coal tar, which is energy-saving and environmentally friendly. After the heat exchange, part of the heavy tar enters the fine washing section 3 again through the heavy tar reflux inlet 3-2, and part of it is collected as a product. The dusty tar falls to the bottom of the first separation device. The bottom of the first separation device is provided with an agitator 9 for stirring the dusty tar to prevent the coal tar from solidifying and clogging the equipment and pipelines. The agitator is a propeller blade propulsion agitator. A heater 8 is also provided at the bottom of the first separation device to provide heat and control the temperature at the bottom of the first separation device. The dusty tar is gradually concentrated by heat to form residual oil. In this embodiment, the trays of the rough wash section are herringbone perforated trays, which are staggered on the opposite side walls of the rough wash section in the vertical direction and arranged obliquely downward. The number of trays is 15, and the angle between the tray 13 and the tower wall 14 (vertical direction) is 30°. Figure 2 As shown, the trays of the fine washing section are arranged above and below the heavy tar reflux inlet, the tray at the upper position is a floating valve tray, and the tray at the lower position is a through-flow sieve tray. There are two agitators, which are arranged at the bottom diagonally and tilted downward to circulate the residual oil.

[0056] The second separation device 10 is used for performing three-phase separation on the second oil and gas, and is connected to the second oil and gas outlet 3-4 and the fine washing section 3 respectively, wherein a cooler 6 is arranged between the second separation device 10 and the second oil and gas outlet 3-4. After being cooled by the cooler, the second oil and gas enter the second separation device 10 from the second oil and gas inlet 10-1 for three-phase separation to obtain light tar, non-condensable gas and oily wastewater. The non-condensable gas is discharged from the non-condensable gas outlet 10-2, and the oily wastewater is discharged from the oily wastewater outlet 10-4. The second separation device 10 and the fine washing section 3 are connected through a light tar reflux pump 11. After the light tar is discharged from the light tar outlet 10-3, it enters the light tar reflux pump 11. Part of the light tar refluxes to the fine washing section through the light tar reflux inlet 3-3 to supplement the liquid phase reflux and control the top temperature of the second separation device. Part of the light tar flows out as a product and is collected.

[0057] As a preferred embodiment, the high dust and high chlorine coal tar purification treatment system also includes a pyrolysis furnace 7, which is connected to the residual oil discharge port 1 at the bottom of the first separation device through a residual oil pump 5, and the residual oil pump 5 is refluxed to the middle position of the rough washing section 4. After the residual oil is discharged from the bottom of the first separation device, it passes through the residual oil pump 5, and part of the residual oil is refluxed to the rough washing section through the residual oil reflux inlet 4-2, and part of the residual oil enters the pyrolysis furnace through the pyrolysis furnace charge port 7-1 for pyrolysis, and pyrolysis produces pyrolysis oil gas and solid pyrolysis products. After the pyrolysis oil gas is discharged from the pyrolysis oil gas outlet 7-3, it enters the rough washing section through the pyrolysis oil gas inlet 4-3 for separation, and the solid pyrolysis product is discharged from the pyrolysis product outlet 7-2. In this embodiment, when the pyrolysis reaction is carried out again, the coal enters the pyrolysis furnace through the pyrolysis furnace charge port 7-1 to carry out pyrolysis reaction with the residual oil to produce blue carbon, which will adsorb the chlorine in the residual oil and reduce the chlorine content of the pyrolysis oil gas.

[0058] Example 2

[0059] This embodiment provides a method for purifying high-dust and high-chlorine coal tar, using the system provided in Example 1. The specific method includes the following:

[0060] The raw coal tar is heat exchanged with heavy tar to preheat the raw coal tar. The temperature after preheating reaches 155°C and enters the rough washing section. The temperature at the bottom of the rough washing section (that is, the bottom of the first separation device) is 350°C and the pressure is -2.0 kPaG. The raw coal tar is sprayed downward and distilled to obtain the first oil and gas. The first oil and gas flows upward. The sprayed coal tar washes the first oil and gas, absorbs the dust in the first oil and gas, forms dusty tar, and is deposited at the bottom of the first separation device.

[0061] The first oil and gas enter the fine washing section and are distilled to obtain the second oil and gas. The temperature at the bottom of the fine washing section is 280°C and the pressure is -2.5kPaG. The second oil and gas flow upward, and the heavy tar and light tar refluxed in the fine washing section wash the second oil and gas and adsorb dust. The dusty tar flows downward, and the heavy tar is produced from the fine washing section at a production temperature of 280°C. After passing through the heavy tar reflux pump, it is heat exchanged with the raw coal tar to preheat the raw coal tar. Part of the heavy tar after heat exchange is refluxed to the fine washing section to provide liquid phase reflux. The reflux temperature of the heavy tar is 185°C. Part of the heavy tar is further cooled and output as a product for collection. The second oil and gas is discharged from the second oil and gas outlet 3-4 at the top of the first separation device. The temperature at the top of the first separation device is 90°C. After cooling, it enters the second separation device. After the second oil and gas are separated into three phases, non-condensable gas, light tar and oily wastewater are obtained, and the non-condensable gas and oily wastewater are collected. After the light tar is refluxed by the light tar reflux pump 11, the reflux temperature of the light tar is 25°C. Part of the light tar enters the fine washing section to supplement the liquid phase reflux, and part of the light tar is collected as a product. The dusty tar from the fine washing section and the rough washing section is deposited at the bottom of the first separation device. The heater heats the bottom of the first separation device to make the temperature reach 350°C. The dusty tar is gradually concentrated by heat to form residual oil. After passing through the residual oil pump, part of the residual oil enters the rough washing section, and the other part enters the pyrolysis furnace to react with coal to generate pyrolysis oil gas and lignite. The temperature in the pyrolysis furnace is 600°C and the pressure is -1.75kPaG. The chlorine in the residual oil will be adsorbed and fixed in the lignite, reducing the chlorine content in the pyrolysis oil gas. The pyrolysis oil gas is passed into the bottom of the rough washing section, mixed with the first oil gas in the rough washing section, and distilled.

[0062] The parameters of the raw coal tar are as follows: dust content 6.8wt%, chlorine content 870ppm, density 1042kg / m 3 , initial distillation point 75℃, 50% distillation temperature 270℃, 80% distillation temperature 380℃;

[0063] The parameters of light tar are: moisture 0.25%, density (20℃) 890kg / m 3 , toluene insoluble matter 0.2%, chloride ion content 4.8ppm;

[0064] The parameters of heavy tar are: moisture 0.05%, density (20℃) 1005kg / m 3 , toluene insoluble matter 0.27%, chloride ion content 7.5ppm.

[0065] Example 3

[0066] This embodiment provides a method for purifying high-dust and high-chlorine coal tar, using the system in Embodiment 1. The specific method includes the following:

[0067] After heat exchange with heavy tar, the temperature of the raw coal tar reaches 180°C and enters the rough washing section. The temperature at the bottom of the rough washing section is 420°C and the pressure is 0.10MPaG. It sprays downward and distills to obtain the first oil and gas. The first oil and gas flows upward, and the sprayed coal tar washes the first oil and gas, absorbs the dust in the first oil and gas, forms dusty tar, and is deposited at the bottom of the first separation device.

[0068] The first oil and gas enter the fine washing section and are distilled to obtain the second oil and gas. The temperature at the bottom of the fine washing section is 350°C and the pressure is 0.09MPaG. The second oil and gas flow upward, and the heavy tar and light tar refluxed in the fine washing section wash the second oil and gas and adsorb dust. The dusty tar flows downward, and the heavy tar is produced from the bottom of the fine washing section at a production temperature of 350°C. After passing through the heavy tar reflux pump, it is heat exchanged with the raw coal tar to preheat the raw coal tar. Part of the heavy tar after heat exchange is refluxed to the fine washing section to provide liquid phase reflux. The reflux temperature of the heavy tar is 190°C. Part of the heavy tar is further cooled and output as a product for collection. The second oil and gas is discharged from the second oil and gas outlet 3-4 at the top of the first separation device. The temperature at the top of the first separation device is 150°C. After cooling, it enters the second separation device. After the second oil and gas are separated into three phases, non-condensable gas, light tar and oily wastewater are obtained, and the non-condensable gas and oily wastewater are collected. After the light tar is refluxed by the light tar reflux pump, the reflux temperature of the light tar is 40°C. Part of the light tar enters the fine washing section to supplement the liquid phase reflux, and part of the light tar is collected as a product. The dusty tar from the fine washing section and the rough washing section is deposited at the bottom of the first separation device. The heater heats the bottom of the first separation device to make the temperature reach 420°C. The dusty tar is gradually concentrated by heat to form residual oil. After passing through the residual oil pump, part of the residual oil enters the rough washing section, and the other part enters the pyrolysis furnace to react with coal to generate pyrolysis oil gas and lignite. The temperature in the pyrolysis furnace is 650°C and the pressure is 0.11MPaG. The chlorine in the residual oil will be adsorbed and fixed in the lignite, reducing the chlorine content in the pyrolysis oil gas. The pyrolysis oil gas is passed into the bottom of the rough washing section, mixed with the first oil gas in the rough washing section, and distilled.

[0069] The parameters of the raw coal tar are as follows: dust content 10.2wt%, chlorine content 1008ppm, density 1122kg / m 3 , initial distillation point 95℃, 50% distillation temperature 280℃, 80% distillation temperature 400℃;

[0070] The parameters of light tar are: moisture 0.3%, density (20℃) 921kg / m 3 , toluene insoluble matter 0.1%, chloride ion content 5.2ppm;

[0071] The parameters of heavy tar are: moisture 0.03%, density (20℃) 1015kg / m 3, toluene insoluble matter 0.25%, chloride ion content 8.7ppm.

[0072] Comparative Example 1

[0073] This comparative example provides a method for purifying high-dust and high-chlorine coal tar. The system used is different from that of Example 1 only in that the heavy tar and light tar are not refluxed, and the purification method is the same as that of Example 2.

[0074] Experimental results: Due to the lack of reflux of light tar and heavy tar, a large amount of dust and heavy tar components are carried out by the second oil and gas with higher temperature. After three-phase separation, the dust content in coal tar reaches more than 2%. The mixture of light tar, water and heavy tar in the second separation device is difficult to separate.

[0075] Comparative Example 2

[0076] This comparative example provides a method for purifying high-dust and high-chlorine coal tar. The system used is different from that of Example 1 only in that the heavy tar is not refluxed, and the purification method is the same as that of Example 2.

[0077] Experimental results: After removing the heavy tar reflux, the light tar reflux will evaporate with the second oil and gas rising in the tower, reducing the temperature of the first oil and gas at the top of the rough washing section. A small amount of heavy tar and dust falls into the rough washing section, but the second oil and gas still carries a large amount of dust out of the fine washing section. After three-phase separation, the dust content in the coal tar reaches more than 1.5%, and the light tar, water and heavy tar are mixed and difficult to separate in the second separation device.

[0078] Comparative Example 3

[0079] This comparative example provides a method for purifying high-dust and high-chlorine coal tar. The system used is different from that of Example 1 only in that the light tar is not refluxed, and the purification method is the same as that of Example 2.

[0080] Experimental results: When light tar is not refluxed, the yield of heavy tar is low, the second oil and gas is not further cooled and washed with the light tar, and part of the heavy tar is carried out of the fine washing section by the second oil and gas. After three-phase separation, the dust content in the light tar reaches more than 0.6%, and the light tar, water and heavy tar are mixed and difficult to separate in the second separation device.

[0081] Comparative Example 4

[0082] This comparative example provides a method for purifying high-dust and high-chlorine coal tar, using the purification system provided in Example 1, and the method is as follows:

[0083] The raw coal tar is heat exchanged with heavy tar to preheat the raw coal tar. The temperature after preheating reaches 155°C and enters the rough washing section. The temperature at the bottom of the rough washing section (that is, the bottom of the first separation device) is 350°C and the pressure is -2kPaG. The raw coal tar is sprayed downward and distilled to obtain the first oil and gas. The first oil and gas flows upward. The sprayed coal tar washes the first oil and gas, absorbs the dust in the first oil and gas, forms dusty tar, and is deposited at the bottom of the first separation device.

[0084] The first oil and gas enter the fine washing section and are distilled to obtain the second oil and gas. The temperature at the bottom of the fine washing section is 180°C and the pressure is -2.5kPaG. The second oil and gas flow upward, and the heavy tar and light tar refluxed in the fine washing section wash the second oil and gas and adsorb dust. The dusty tar flows downward, and the heavy tar is produced from the fine washing section at a production temperature of 180°C. After passing through the heavy tar reflux pump, it is heat exchanged with the raw coal tar to preheat the raw coal tar. Part of the heavy tar after heat exchange is refluxed to the fine washing section to provide liquid phase reflux. The reflux temperature of the heavy tar is 125°C. Part of the heavy tar is further cooled and output as a product for collection. The second oil and gas is discharged from the second oil and gas outlet 3-4 at the top of the first separation device. The temperature at the top of the first separation device is 90°C. After cooling, it enters the second separation device. After the second oil and gas are separated into three phases, non-condensable gas, light tar and oily wastewater are obtained, and the non-condensable gas and oily wastewater are collected. After the light tar is refluxed by the light tar reflux pump, part of the light tar enters the fine washing section to supplement the liquid phase reflux. The reflux temperature of the light tar is 25°C, and part of the light tar is collected as a product. The dusty tar from the fine washing section and the rough washing section is deposited at the bottom of the first separation device. The heater heats the bottom of the first separation device to make the temperature reach 350°C. The dusty tar is gradually concentrated by heat to form residual oil. After passing through the residual oil pump, part of the residual oil enters the rough washing section, and the other part enters the pyrolysis furnace to react with coal to generate pyrolysis oil gas and lignite. The temperature in the pyrolysis furnace is 600°C and the pressure is -0.5kPaG. The lignite will absorb the chlorine overflowing from the residual oil, reducing the chlorine content in the pyrolysis oil gas. The pyrolysis oil gas is passed into the bottom of the rough washing section, mixed with the first oil gas in the rough washing section, and distilled.

[0085] In this comparative example, due to the low reflux temperature of heavy tar, the bottom temperature of the fine washing section is low, a large amount of heavy tar falls into the bottom of the tower, the amount of residual oil sent out increases, the dust concentration of the residual oil decreases, and the oil yield decreases.

[0086] The parameters of the raw coal tar are as follows: dust content 6.8wt%, chlorine content 870ppm, density 1042kg / m 3 , initial distillation point 75℃, 50% distillation temperature 270℃, 80% distillation temperature 380℃;

[0087] The parameters of light tar are: moisture 0.25%, density (20℃) 850kg / m 3, toluene insoluble matter 0.08%, chloride ion content 4.5ppm;

[0088] The parameters of heavy tar are: moisture 0.10%, density (20℃) 985kg / m 3 , toluene insoluble matter 0.24%, chloride ion content 6.8ppm.

[0089] Comparative Example 5

[0090] This comparative example provides a method for purifying high-dust and high-chlorine coal tar, using the purification system provided in Example 1, and the method is as follows:

[0091] The raw coal tar is heat exchanged with heavy tar to preheat the raw coal tar. The temperature after preheating reaches 85°C and enters the rough washing section. The temperature at the bottom of the rough washing section (that is, the bottom of the first separation device) is 180°C and the pressure is -2.0 kPaG. The raw coal tar is sprayed downward and distilled to obtain the first oil and gas. The first oil and gas flows upward. The sprayed coal tar washes the first oil and gas, absorbs the dust in the first oil and gas, forms dusty tar, and is deposited at the bottom of the first separation device.

[0092] The first oil and gas enter the fine washing section and are distilled to obtain the second oil and gas. The temperature at the bottom of the fine washing section is 285°C and the pressure is -1.95 kPaG. The second oil and gas flow upward, and the heavy tar and light tar refluxed in the fine washing section wash the second oil and gas and adsorb dust. The dusty tar flows downward, and the heavy tar is produced from the fine washing section at a production temperature of 180°C. After passing through the heavy tar reflux pump, it is heat exchanged with the raw coal tar to preheat the raw coal tar. Part of the heavy tar after heat exchange is refluxed to the fine washing section to provide liquid phase reflux. The reflux temperature of the heavy tar is 120°C. Part of it is further cooled and output as a product for collection. The second oil and gas is discharged from the second oil and gas outlet 3-4 at the top of the first separation device. The temperature at the top of the first separation device is 65°C, and it enters the second separation device after cooling; after the second oil and gas are separated into three phases, non-condensable gas, light tar and oily wastewater are obtained, and the non-condensable gas and oily wastewater are collected; after the light tar is refluxed by the light tar reflux pump, the reflux temperature of the light tar is 25°C, part of the light tar enters the fine washing section to supplement the liquid phase reflux, and part of the light tar is collected as a product. The dusty tar from the fine washing section and the rough washing section is deposited at the bottom of the first separation device. The heater heats the bottom of the first separation device to make the temperature reach 285°C. The dusty tar is gradually concentrated by heat to form residual oil. After passing through the residual oil pump, part of the residual oil enters the rough washing section, and the other part enters the pyrolysis furnace to react with coal to generate pyrolysis oil gas and lignite. The temperature in the pyrolysis furnace is 620°C and the pressure is -0.05kPaG. The chlorine in the residual oil will be adsorbed and fixed in the lignite, reducing the chlorine content in the pyrolysis oil gas. The pyrolysis oil gas is passed into the bottom of the rough washing section, mixed with the first oil and gas in the rough washing section, and distilled.

[0093] In this comparative example, the coal tar yield is low, the dust content of the bottom residue oil is relatively small, the amount of residue oil sent to the pyrolysis furnace is large, and the pyrolysis furnace consumes more heat.

[0094] The parameters of the raw coal tar are as follows: dust content 9.6wt%, chlorine content 450ppm, density 1060kg / m 3 , initial distillation point 75℃, 50% distillation temperature 300℃, 80% distillation temperature 394℃;

[0095] The parameters of light tar are: moisture 0.26%, density (20℃) 910kg / m 3 , toluene insoluble matter 0.05%, chloride ion content 5.6ppm;

[0096] The parameters of heavy tar are: moisture 0.02%, density (20℃) 1010kg / m 3 , toluene insoluble matter 0.15%, chloride ion content 8.9ppm.

[0097] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for purifying high-dust and high-chlorine coal tar, characterized in that: The high dust and high chlorine coal tar purification treatment system is adopted, including the following steps: (1) After being preheated, the raw coal tar enters the rough washing section for fractionation and washing to obtain the first oil gas and residual oil; wherein, part of the residual oil is refluxed to the rough washing section; the temperature of the preheated raw coal tar is 75-200°C; (2) The first oil and gas enter the fine washing section, and after fractionation and washing in the fine washing section, the second oil and gas and heavy tar are obtained; after the heavy tar is heat exchanged with the raw coal tar, part of the heavy tar is refluxed to the fine washing section; the extraction temperature of the heavy tar is 280-350°C, and the reflux temperature is 185-250°C; (3) After the second oil and gas are separated into three phases, light tar, non-condensable gas and oily wastewater are obtained; part of the light tar is refluxed to the fine washing section; the reflux temperature of the light tar is 20 to 45° C.; The high-dust and high-chlorine coal tar purification and treatment system comprises: The first separation device is used to remove dust and chlorine; a washing section is provided in the first separation device, and the washing section includes a rough washing section and a fine washing section connected from bottom to top, and a raw coal tar inlet is provided at the top of the rough washing section; The first separation device is provided with an agitator at the bottom; the first separation device is provided with a second oil and gas discharge port at the top; the fine washing section is provided with a heavy tar outlet at the bottom and a light tar reflux inlet at the top; a heavy tar reflux inlet is provided between the heavy tar outlet and the light tar reflux inlet; The second separation device is connected to the second oil and gas outlet and the fine washing section respectively, and is used for performing three-phase separation on the gas discharged from the second oil and gas outlet to obtain light tar.

2. The method for purifying high-dust and high-chlorine coal tar according to claim 1, characterized in that: The step (1) also includes a step of allowing part of the residual oil to enter a pyrolysis furnace for pyrolysis reaction to obtain pyrolysis products and pyrolysis oil and gas; wherein the pyrolysis oil and gas are passed into the bottom of the rough washing section.

3. The method for purifying high-dust and high-chlorine coal tar according to claim 1 or 2, characterized in that: The raw coal tar has a dust content of >1.5wt%, a chlorine content of 50-2000ppm, an initial distillation point of >75°C, a 50% distillation temperature of 240-300°C, and an 80% distillation temperature of 350-400°C; The light tar fraction is a distillate with an initial boiling point of 250°C in the raw coal tar and a density of 700 to 900 kg / m 3 ; The heavy tar fraction is a distillate of 200-350°C from the raw coal tar, with a density of 900-1020 kg / m 3 .

4. The method for purifying high-dust and high-chlorine coal tar according to claim 1 or 2, characterized in that: The temperature at the top of the first separation device is 75-150°C; the temperature at the bottom of the first separation device is 300-450°C.

5. The method for purifying high-dust and high-chlorine coal tar according to claim 1 or 2, characterized in that: The pressure of the first separation device is -0.1 to 0.25 MPaG.

6. The method for purifying high-dust and high-chlorine coal tar according to claim 1 or 2, characterized in that: The second separation device is connected to the fine washing section via a light tar reflux pump; the light tar reflux pump is connected to the top of the fine washing section and refluxes part of the light tar to the fine washing section; The second separation device is also provided with a non-condensable gas discharge outlet and an oily wastewater discharge outlet; The bottom of the fine washing section is connected to a heavy tar reflux pump, and part of the heavy tar refluxes to the fine washing section.

7. The method for purifying high-dust and high-chlorine coal tar according to claim 1 or 2, characterized in that: The high-dust and high-chlorine coal tar purification treatment system also includes a pyrolysis furnace, which is connected to the bottom of the first separation device through a residual oil pump, and the residual oil pump is reflux-connected to the middle position of the rough washing section; The pyrolysis furnace is communicated with the bottom of the rough washing section, and is used to pass the pyrolysis oil and gas generated by pyrolysis into the rough washing section.

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