A system and method for preparing coke

Abstract

The present invention belongs to the technical field of deep processing of petroleum heavy oil and coal tar pitch, and specifically relates to a system and method for preparing coke. The system comprises: a coking furnace, a hot carrier gas system and an oil and gas recovery system; wherein the coking furnace comprises M coking chambers connected in parallel, a hot carrier gas inlet main pipeline, a hot carrier gas outlet main pipeline and a gas guide main pipeline, wherein M≥4, and the present invention adopts multiple coking chambers connected in series, which realizes continuous production in a macro sense and improves production efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep processing of petroleum heavy oil and coal tar pitch, and in particular relates to a system and method for preparing coke. Background Art

[0002] Coking is the process of thermally polymerizing macromolecular hydrocarbon compounds, such as heavy petroleum oil, petroleum residue, and coal tar pitch, to produce even larger coke products. Most current coking technologies are developed through optimization or improvement based on traditional delayed coking technology. Depending on the objectives of using coking technology, delayed coking can be divided into two categories: one is delayed coking technology aimed at increasing the production of light oil products. This type of technology often uses heavy petroleum oil or petroleum residue as feedstock, with light oils such as naphtha, diesel, and wax oil as primary products, and petroleum coke as a by-product. This type of technology is developing towards increasing the yield of light oil products, extending the production cycle, and increasing the production scale of a single unit as technology advances. For example, Patent Document 201610061496.2 optimizes the delayed coking process by condensing high-temperature oil and gas before separately treating the oil and gas, thereby achieving a higher yield of liquid products. Patents 200910065261.0 and 200910065262.5 employ a process of first visbreaking and then coking, which can also increase liquid product yields, reduce coking in the heating furnace, and extend the operating cycle. This type of delayed coking technology is commonly used in large-scale refinery production facilities that process hundreds of thousands of tons of raw materials annually.

[0003] Another type of technology involves delayed coking, which primarily produces needle coke. This technology aims to improve the properties and yield of needle coke. For example, patent documents 201811374496.3 and 201810743620.2 add a polymerization tower before the coking tower. This process initially polymerizes the pitch to produce a portion of mesophase, which then enters the coking tower for coking. This improves the properties of the needle coke. Needle coke production facilities are relatively small, with a typical scale of 50,000 tons / year.

[0004] In addition to the delayed coking technology mentioned above, there is also an intermittent kettle coking technology, which is generally used in smaller-scale production processes with relatively high coke product quality requirements. Patent document 201910728396.4 uses an intermittent coking kettle to produce high-structured carbon microcrystalline pitch coke that meets the requirements of lithium battery negative electrode materials. This method is to remove light components from the raw asphalt through dry distillation in the coking kettle and further condense the aromatic components to produce pitch coke. The key technology is to control the appropriate heating rate and coking reaction time to control the crystal form of the coke. Patent documents 200910012506.3, patent document 201110353712.8, and patent document 201310496046.2 also use intermittent kettle coking technology and also produce needle coke products by controlling the appropriate heating rate and coking reaction time.

[0005] Delayed coking technology and intermittent kettle coking technology are both traditional heavy oil processing technologies that have been widely used in the petrochemical and coal chemical industries. They can produce products such as petroleum coke and needle coke with different performance according to the different raw materials and product market needs. These cokes provide a rich source of raw materials for the carbon materials industry. With the continuous development of the carbon materials industry, various functional carbon materials have continuously increased their requirements for the structure and properties of raw coke. For example, in addition to strict control of the macroscopic indicators of coke, products such as lithium battery negative electrode materials, graphite electrodes, and high-purity graphite also place higher requirements on the homogeneity of coke. In fact, this requires that the molecular size and molecular structure of the coke tend to be the same or similar. From a production technology perspective, only when the coking reaction occurs under the same temperature and the same time conditions can coke with the same or similar molecular size and molecular structure be produced, and the high performance and stable quality of downstream carbon material products can be guaranteed. In response to the increasingly high performance requirements of downstream products for coke, the coke products produced by the existing delayed coking and intermittent kettle coking technologies can no longer meet them, because these two coking technologies cannot control the temperature distribution in the coking reactor to be sufficiently uniform. For example, the temperature at the feed inlet of the delayed coking tower is the highest, and the temperature in the middle of the tower is the lowest. The temperature difference is generally 40-60°C. Due to the uneven distribution of reaction temperature in the coking tower, needle coke of different properties is often produced in the same coking tower, and the coke in some parts even fails to meet the indicators of needle coke. The intermittent kettle coking technology also has obvious temperature unevenness. Since the kettle wall needs to be heated to provide heat to the kettle, under normal circumstances, the temperature difference between the high temperature of the kettle wall and the coke in the center of the kettle is also more than 50°C, resulting in excessive coking of the coke near the kettle wall and insufficient coking of the coke in the center of the kettle.

[0006] Uneven temperature distribution is a result of the characteristics of the coking towers used in delayed coking and intermittent kettle coking technologies. Consequently, these technologies cannot meet the requirements for producing high-performance coke products. To address this issue and produce more homogeneous coke products, the present invention provides a coking method that utilizes a suitable coking furnace structure and a corresponding heating method to achieve uniform temperature distribution and consistent reaction times within the furnace. This method can produce coke products with a uniform crystalline structure, meeting the quality requirements of the raw coke in downstream carbon material production processes. Summary of the Invention

[0007] The purpose of the present invention is to solve the problem of uneven temperature field distribution in the coking furnace existing in the existing coking technology, and propose a new coking method to ensure that all raw materials undergo coking reaction under the same temperature conditions and can produce coke products with uniform crystal structure.

[0008] To achieve the above objectives, the present invention provides a system for producing coke. The system comprises a coking furnace, a hot carrier gas system, and an oil and gas recovery system. The coking furnace is the core equipment for the coking reaction of the raw asphalt, the hot carrier gas system provides sufficient heat for the coking furnace, and the oil and gas recovery system recovers and separates the hydrocarbon components generated during the coking reaction into gas, light oil, and heavy oil products.

[0009] The coking furnace comprises M or more coking chambers 8 connected in parallel, a hot carrier gas inlet main pipe 6, a hot carrier gas outlet main pipe 12 and a gas guide main pipe 10, wherein M is greater than or equal to 4;

[0010] The coking chamber includes a reaction vessel, an inlet and outlet channel, and a sealing door is installed in the inlet and outlet channel.

[0011] A reaction vessel rack is placed in the coking chamber, and the reaction vessel is placed on the reaction vessel rack. An air duct is designed on the top of each coking chamber. A group of hot gas coils 21 are arranged inside the wall between two adjacent coking chambers and inside the outer walls of the first coking chamber and the last coking chamber.

[0012] One end of each group of hot air coils is the air inlet end, and the other end is the air outlet end. The air outlet end of each group of hot air coils is connected to the air inlet end of the adjacent group of hot air coils. The air inlet end of the hot air coils inside the first coking chamber near the outer wall is connected to the air outlet end of the hot air coils inside the last coking chamber near the outer wall. A flow control valve is installed on each connecting pipeline.

[0013] A hot carrier gas inlet pipe 7 and a hot carrier gas outlet pipe 11 are respectively installed on the hot carrier gas coil connecting pipelines in the outer walls of the first coking chamber and the last coking chamber and the hot carrier gas coil connecting pipelines in the walls of the two adjacent coking chambers, and a flow control valve is installed on the hot carrier gas inlet pipe and the hot carrier gas outlet pipe; the inlet pipe 7 of each group of hot carrier gas coils is connected to the hot carrier gas inlet main pipe 6, and the outlet pipe 11 of each group of hot carrier gas coils is connected to the hot carrier gas outlet main pipe 12, and the outlet pipe is also connected to the inlet pipe of the adjacent group of hot carrier gas coils (the hot carrier gas coils in the walls at both ends of the coking furnace are considered adjacent), and a flow control valve is installed on each connecting pipeline.

[0014] The air guide pipe 9 in each coking chamber wall is connected to the main air guide pipe 10;

[0015] The hot carrier gas system includes a burner 3 and a circulating fan 4, and the oil and gas recovery system includes a fractionating tower 13, a cooler 19, a separator 16 and a vacuum pump 17;

[0016] The air outlet of the burner 3 is connected to the hot carrier gas inlet main pipe 6, the air inlet of the burner 3 is connected to the circulation fan 4, the circulation fan 4 is connected to the hot carrier gas outlet main pipe 12, the gas guide main pipe 10 is connected to the feed port of the distillation tower 13, the top air outlet of the distillation tower 13 is connected to the condenser 19 and the separator 16, and the separator 16 is connected to the vacuum pump 17.

[0017] The coking furnace is composed of multiple adjacent coking chambers of identical structure and size (thin-layer cubic structure). The thin-layer cubic structure of the coking chamber means that its width is only 0.5-1.5 meters, which can ensure uniform temperature distribution within the coking chamber. A reaction vessel rack is placed in each coking chamber.

[0018] Preferably, the outer wall of the coking furnace is installed with a thermal insulation layer to reduce energy loss caused by heat dissipation.

[0019] The thermal insulation layer is made of materials well known in the art.

[0020] Preferably, the coking chamber further comprises two or more reaction vessels.

[0021] Preferably, each coking chamber has a depth of 2-4 meters, a height of 2-5 meters, and a width of 0.5-1.5 meters, wherein:

[0022] One side of each coking chamber serves as a passage for loading and unloading materials, and is designed with a sealed door that can be opened and closed. When the sealed door is open, it can meet the needs of the pallet frame truck loaded with raw materials / products to push in and out. When the sealed door is closed, it can ensure that the coking chamber is separated from the outside and prevent gas circulation. The reaction vessel rack refers to a movable frame that can orderly place multiple reaction vessels. The reaction vessel refers to a thin-layer metal container with standardized dimensions that can hold a certain volume of asphalt / coke. The length of the reaction vessel is 800-1000 mm, the width is 500-800 mm, and the height is 300-500 mm. The thin layer means that the height of the reaction vessel is only 300-500 mm, which reduces the heat transfer distance and can ensure uniform temperature distribution in the reaction vessel. The upper end of the reaction vessel can be open or semi-open, as long as the generated oil and gas are discharged smoothly.

[0023] An air guide pipe is designed on the top of each coking chamber, through which the oil and gas generated in the coking chamber are guided out of the coking chamber, and the oil and gas guided out of each coking chamber are collected into a main air guide pipe 10, and then the main air guide pipe 10 sends the oil and gas to the distillation tower 13.

[0024] A set of hot air coils is arranged inside the walls of every two adjacent coking chambers. When hot air flows through these coils, the heat carried by the hot air is transferred to the coking chamber through radiation and convection, heating the asphalt or coke in the reaction vessel. The hot air coils are arranged sequentially according to the coking chambers, connected end to end. That is, the hot air coils are placed in the first coking chamber first. Once the first coking chamber is arranged, the outlet of the first coking chamber's hot air coils is connected to the inlet of the second coking chamber's hot air coils. Once the second coking chamber is arranged, the outlet of the second coking chamber's hot air coils is connected to the inlet of the third coking chamber's hot air coils. This pattern repeats until the last coking chamber is arranged, and the outlet of the last coking chamber's hot air coils is connected to the inlet of the first coking chamber's hot air coils. In this way, the hot air coils of the coking furnace form a circulation system. A hot carrier gas inlet pipeline and a hot carrier gas outlet pipeline, namely a hot carrier gas inlet pipe 7 and a hot carrier gas outlet pipe 11, are installed on each group of hot carrier gas coils. Each hot carrier gas inlet pipe is connected to the hot carrier gas inlet main pipe 6, and each hot carrier gas outlet pipe is connected to the hot carrier gas outlet main pipe 12. Flow control valves are installed on the hot carrier gas inlet pipeline and the hot carrier gas outlet pipeline.

[0025] The hot carrier gas system is mainly composed of a burner 3, a circulating fan 4, and a series of pipe valves. The gas 1 and air 2 are burned in the burner 3, and the high-temperature flue gas is mixed with the circulating hot carrier gas to form a high-temperature hot carrier gas. The hot carrier gas is sent to the inlet pipe inlet of the hot carrier gas coil in the outer wall of the first coking chamber through valve control (the valve of the inlet pipe of the hot carrier gas coil in the outer wall of the first coking chamber is open, and the valves of the inlet pipes of other coking chambers are all closed). The hot carrier gas passes through the 1st, 2nd, 3rd, ..., M-4, and M-3 coking chambers in sequence along the coil. The temperature of the hot carrier gas gradually decreases, and the temperature of these coking chambers is also Correspondingly, a temperature distribution that decreases in sequence is formed, and a temperature gradient appears between two adjacent coking chambers. The hot carrier gas is controlled to flow out of the outlet pipe of the hot carrier gas coil between the M-3 and M-2 coking chambers (at this time, the hot carrier gas outlet pipe valve between the M-3 and M-2 coking chambers is open, and the hot carrier gas outlet pipe valves between other coking chambers are all closed) as circulating hot carrier gas. After the circulating hot carrier gas is pressurized by the circulating fan 4, a part of it is sent to the burner 3 for heating and recycling, and the excess part is discharged through the valve controlling the flow rate 5.

[0026] In this case, the temperature of the first coking chamber is the highest, and then the temperatures of the 1st, 2nd, ..., M-3, and M-2 coking chambers decrease in turn. Among the heated coking chambers, the temperature of the M-2 coking chamber is the lowest. The Mth coking chamber enters the cooling state, the M-1th coking chamber has been cooled to room temperature and is in the unloading and loading state, and the M-2th coking chamber has completed loading and entered the heating state.

[0027] The maximum temperature of the coking reaction is the main control indicator of the present invention. In this case, the temperature of the first coking chamber is the highest. The temperature of the first coking chamber can be controlled by adjusting the burner outlet temperature, and the temperature gradient between the coking chambers can be controlled by adjusting the flow rate of the circulating hot carrier gas.

[0028] After the reaction time of the first coking chamber is completed, the inlet valve of the hot carrier gas coil between the first and second coking chambers is opened, and the inlet valve of the hot carrier gas coil between the first and M coking chambers is closed. Then, the outlet valve of the hot carrier gas between the M-2 and M-1 coking chambers is opened, and the outlet valve of the hot carrier gas between the M-3 and M-2 coking chambers is closed. At this time, the high-temperature hot carrier gas enters the coking furnace through the inlet pipe of the hot carrier gas coil between the first and second coking chambers via the hot carrier gas inlet manifold 6, exits the coking furnace through the outlet pipe of the hot carrier gas coil between the M-2 and M-1 coking chambers, and enters the circulation fan 4 through the hot carrier gas outlet manifold 12. In this case, the temperature of the second coking chamber becomes the highest temperature, and then the temperatures of the second, third, ..., M-3, and M-2 coking chambers decrease in sequence. Among the heated coking chambers, the temperature of the M-1 coking chamber is the lowest. The first coking chamber begins to cool down, and the temperature of the Mth coking chamber drops to room temperature and is in the unloading and loading state. The M-1th coking chamber has completed loading and started to enter the heating state.

[0029] When the reaction time of the second coking chamber is completed, the high-temperature hot carrier gas is introduced into the next coking chamber using the same method. In this way, for each coking chamber, the process of loading, heating, highest temperature coking, cooling, and unloading is completed. For the entire coking furnace, the raw asphalt is continuously converted into coke with special properties.

[0030] The oil and gas recovery system primarily consists of a fractionating tower 13, a condenser 19, a separator 16, a vacuum pump 17, and a series of pipes and valves. During production, the valves in the gas pipes at the top of the coking chambers where materials are being unloaded or loaded are closed, while the valves in the gas pipes at the tops of all other coking chambers are opened. The oil and gas generated during the reaction in each coking chamber are then transported to the fractionating tower 13 via the gas manifold 10. There, the oil and gas are condensed and separated into light oil 15, heavy oil 14, and gas 18. The gas 18 is then extracted by the overhead vacuum pump 17 and transported out of the device.

[0031] The pressure of each coking chamber is controlled to be slightly positive, i.e. 0-500Pa. The pressure of each coking chamber of the coking furnace is controlled by adjusting the vacuum degree of the inlet of the tower top vacuum pump and the opening of the valves on each air guide pipe.

[0032] The present invention provides a method for preparing coke, comprising the following steps: when the number of coking chambers is M (M≥4), the method comprises the following steps:

[0033] A. Initial stage:

[0034] Before the coking system is started, the coking furnace, hot carrier gas system, and oil and gas recovery system are all in their initial state, that is, all coking chambers in the coking furnace are at room temperature and pressure; all equipment in the hot carrier gas system is in a closed state, and the gas in the hot carrier gas pipeline is at room temperature and static; all equipment in the oil and gas recovery system is in a closed state, and no oil and gas flows from the coking furnace to the oil and gas recovery system;

[0035] B. Start-up phase

[0036] 1) Loading: Load the raw asphalt into the reaction vessels. Place multiple reaction vessels filled with asphalt on a reaction vessel rack. Place the reaction vessel rack in the coking chamber, and then close and seal the coking chamber door. Follow this procedure to load the raw asphalt into each coking chamber.

[0037] 2) Hot carrier gas circulation: start the circulation fan, pass the gas and air into the burner for combustion, mix them with the circulating hot carrier gas of the circulation fan to form a mixed hot carrier gas, open the hot carrier gas coil inlet pipe valve on the outer wall of the first coking chamber (all other hot carrier gas coil inlet pipe valves are closed), open the hot carrier gas coil outlet pipe valve between the M-3 and M-2 coking chambers (all other hot carrier gas coil outlet pipe valves are closed), control the hot carrier gas to enter the coking chamber from the inlet pipe of the hot carrier gas coil on the outer wall of the first coking chamber, pass through the 1st, 2nd, 3rd, ..., M-3 coking chambers in sequence, and finally discharge from the coking furnace from the outlet pipe of the hot carrier gas coil between the M-3 and M-2 coking chambers, and circulate to the circulation fan through the hot carrier gas outlet main pipeline;

[0038] 3) Oil and gas processing: Under the hot carrier gas circulation route described in 2), except for the M-1th coking chamber which does not produce oil and gas at room temperature, all other coking chambers are in a heated state and produce oil and gas. In this case, the valve of the air guide pipe on the top of the M-1th coking chamber is closed, and the valves on the air guide pipes on the top of the other coking chambers are opened. The oil and gas produced by each coking chamber is collected into the main air guide pipe through the air guide pipe on the top of the coking chamber, and then enters the fractionating tower, where gas, light oil and heavy oil products are separated;

[0039] 4) Heating and coking reaction: Under the hot carrier gas circulation route described in 2), the first coking chamber is at the highest temperature. The temperatures of the first, second, third, ..., M-2 coking chambers decrease in sequence. The M-2 coking chamber is the coldest coking chamber heated by the hot carrier gas. The M-1 coking chamber is at room temperature and is in a loading and unloading state. When the coking reaction time of the first coking chamber is completed, the hot carrier gas circulation route is switched.

[0040] C. Cyclic reaction stage

[0041] When the coking reaction time of the first coking chamber is completed, the hot carrier gas circulation route is switched to cool down the coke product in the first coking chamber and discharge the coke, so that the reaction temperature of the second coking chamber is raised to the highest level. The method of switching the hot carrier gas circulation route is as follows:

[0042] Open the air inlet valve of the hot carrier gas coil between the 1st and 2nd coking chambers, close the air inlet valve of the hot carrier gas coil inside the outer wall of the 1st coking chamber, then open the air outlet valve of the hot carrier gas coil between the M-2nd and M-1st coking chambers, close the air outlet valve of the hot carrier gas coil between the M-3rd and M-2nd coking chambers, open the air guide valve on the top of the M-1st coking chamber, and close the air guide valve on the top of the Mth coking chamber. At this time, the hot carrier gas enters the coking furnace from the hot carrier gas inlet pipe between the 1st and 2nd coking chambers, passes through the 2nd, 3rd, 4th, 5th, ... M-2th coking chambers in sequence, and finally exits the coking furnace from the hot carrier gas coil outlet pipe between the M-2nd and M-1st coking chambers. The 2nd coking chamber is the coking chamber with the highest temperature, the M-1st coking chamber is the coking chamber with the lowest temperature among the coking chambers heated by the hot carrier gas, and the Mth coking chamber cools down to room temperature and is in the loading and unloading state. When the coking reaction time of the 2nd coking chamber is completed, the hot carrier gas circulation route is switched;

[0043] Open the inlet valve of the hot carrier gas coil between the 2nd and 3rd coking chambers, close the inlet valve of the hot carrier gas coil between the 1st and 2nd coking chambers, then open the outlet valve of the hot carrier gas coil between the M-1st and Mth coking chambers, close the outlet valve of the hot carrier gas coil between the M-2nd and M-1st coking chambers, open the valve of the top air guide pipe of the Mth coking chamber, and close the valve of the top air guide pipe of the 1st coking chamber. At this point, the hot carrier gas enters the coking furnace from the inlet pipe of the hot carrier gas coil between the 2nd and 3rd coking chambers, passes through the 3rd, 4th, 5th, 6th, ... M-1st coking chambers in sequence, and finally exits the coking furnace from the outlet pipe of the hot carrier gas coil between the M-1st and Mth coking chambers. The 3rd coking chamber is the hottest coking chamber, and the Mth coking chamber is the coldest among the coking chambers heated by the hot carrier gas. The 1st coking chamber has cooled to room temperature and is ready for loading and unloading. When the coking reaction time of the third coking chamber is completed, the hot carrier gas circulation route is switched;

[0044] Open the air inlet valve of the hot carrier gas coil between the 3rd and 4th coking chambers, close the air inlet valve of the hot carrier gas coil between the 2nd and 3rd coking chambers, then open the air outlet valve of the hot carrier gas coil between the Mth and 1st coking chambers, close the air outlet valve of the hot carrier gas coil between the M-1st and Mth coking chambers, open the air duct valve on the top of the 1st coking chamber, and close the air duct valve on the top of the 2nd coking chamber. At this time, the hot carrier gas enters the coking furnace from the hot carrier gas coil inlet pipe between the 3rd and 4th coking chambers, passes through the 4th, 5th, 6th, 7th, ... Mth coking chambers in sequence, and finally exits the coking furnace from the hot carrier gas coil outlet pipe between the Mth and 1st coking chambers. The 1st coking chamber is the one with the lowest temperature among the coking chambers heated by the hot carrier gas. The reaction temperature of the 4th coking chamber reaches the highest, the 3rd coking chamber begins to cool down, and the 2nd coking chamber cools down to room temperature and is in the loading and unloading state. When the reaction in the 4th coking chamber is completed, the hot carrier gas circulation route is switched in sequence;

[0045] By switching the hot carrier gas circulation routes in sequence in this manner, the coking furnace of the present invention can be operated and produced in a continuous cycle.

[0046] Preferably, the pressure of the coking chamber is controlled at 0-500 Pa, and the pressure of the coking chamber is controlled by adjusting the inlet vacuum degree of the vacuum pump at the top of the fractionating tower and the valve opening on the gas guide line.

[0047] Preferably, step 12) further includes discharging a portion of the pressurized hot carrier gas through a circulating fan, adjusting the discharge volume to control the pressure of the hot carrier gas circulation system within the coking chamber, and delivering the remaining portion to the burner as circulating hot carrier gas. The pressure of the hot carrier gas circulation system is controlled to be below 0.2 MPa, ensuring that the temperature of the coking chamber does not exceed 500°C.

[0048] Preferably, the coking chamber is heated in a step-type mode, the step temperature difference of the coking chamber is 30-80°C, more preferably 30-50°C, and the total reaction time at each step temperature is 20-70 hours, more preferably 40-60 hours.

[0049] Each coking chamber in the coking furnace of the present invention is heated in a step-type mode, and the maximum temperature can reach 500° C., and can be used to prepare a variety of coke products with uniform structures.

[0050] The coke oven of the present invention realizes the separate treatment of hot carrier gas and oil and gas, forms two independently controlled heating systems and oil and gas recovery systems, and improves heat utilization efficiency.

[0051] Compared with the existing delayed coking and intermittent kettle coking technologies, the advantages of the present invention are:

[0052] (1) The present invention adopts a two-layer structure model, providing the same coking reaction temperature and the same coking reaction time for all raw pitches, and finally obtaining a coke product with uniform structure and properties. Among the two thin-layer structures, one is a coking chamber with a thin-layer structure, which is only 0.5-1.5 meters wide, ensuring uniform temperature distribution in the coking chamber. Tests have shown that when the temperature range is controlled at 300-500°C, the temperature deviation of each point in the coking chamber is within the range of ±2°C; the other thin-layer structure is a reaction dish with a height of only 300-500 mm, which is about one-tenth of the thickness of coke in the prior art. This thin-layer reaction dish greatly shortens the distance of heat transfer and ensures a more uniform temperature distribution in the coke layer during the reaction. Tests have shown that the temperature difference between the center and the surface of the coke layer during the reaction is ≤5°C. Therefore, the temperature difference between the highest temperature point and the lowest temperature point in the coking furnace of the present invention is ≤7°C, while the temperature difference in the coke layer in the existing delayed coking and kettle coking technologies exceeds 40°C. By comparison, it can be seen that the present invention greatly improves the temperature distribution in the coking reactor, providing conditions for producing uniform coke products.

[0053] (2) The hot carrier gas and oil and gas are processed separately, which maximizes the oil and gas yield and effect.

[0054] (3) The coking chambers are connected in series, so that each coking chamber forms a different temperature distribution, which increases the temperature difference between the hot carrier gas entering the coking furnace and the hot carrier gas leaving the coking furnace, effectively improving the thermal efficiency.

[0055] (4) Flexible operation, the maximum coking temperature and coking reaction time can be flexibly adjusted to meet the quality requirements of various coke products.

[0056] (5) The present invention adopts multiple coking chambers connected in series, which realizes continuous production on a macro level and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A front perspective structural diagram of a coking furnace used in the present invention;

[0058] Figure 2 A rear perspective structural diagram of a coking furnace used in the present invention;

[0059] Figure 3 It is a process flow chart and a schematic diagram of the coking chamber switching operation method of the present invention;

[0060] Figure 4 This is a schematic diagram of the coil structure with top inlet and bottom outlet;

[0061] Figure 5 This is a schematic diagram of the bottom-in and top-out coil structure;

[0062] Figure 6 This is a three-dimensional diagram of the reaction vessel rack;

[0063] Figure 7 This is the front view of the reaction vessel rack;

[0064] Figure 8 This is the left view of the reaction vessel rack;

[0065] Figure 9 Figure 1 is a diagram of the reaction vessel structure;

[0066] Figure 10 This is a distribution diagram of temperature measurement points in the coking furnace of Example 4;

[0067] Reference numerals:

[0068] 1. Gas, 2. Air, 3. Burner, 4. Circulating fan, 5. Exhaust gas, 6. Hot carrier gas inlet main pipeline, 7. Hot carrier gas inlet pipe, 8. Coking chamber, 9. Air guide pipe, 10. Gas guide main pipeline, 11. Hot carrier gas outlet pipe, 12. Hot carrier gas outlet main pipeline, 13. Distillation tower, 14. Heavy oil, 15. Light oil, 16. Separator, 17. Vacuum pump, 18. Gas, 19. Cooler, 20. Valve, 21. Hot carrier gas coil. DETAILED DESCRIPTION

[0069] The present invention will be further described below with reference to specific embodiments.

[0070] The delayed coking technology is to heat the raw asphalt to about 500°C in a short period of time, and then enter the coking tower for polymerization coking reaction. Due to the high reaction temperature and fast reaction speed, it is difficult to achieve directional and orderly polymerization. The molecular structure of the coke varies greatly and can only be used as ordinary coke. However, if the coking reaction temperature and polymerization reaction speed are controlled, directional polymerization can be achieved to obtain a coke product with a similar molecular structure and orderly arrangement. This coke can be used to prepare lithium battery negative electrode materials or other carbon materials. The present invention adopts a method of connecting multiple coking chambers in series, and adjacent coking chambers naturally form a temperature distribution that decreases in sequence. For each coking chamber, as the hot carrier gas inlet and outlet pipelines are switched in sequence, each coking chamber undergoes the same reaction process from low temperature to high temperature, and the temperature distribution in the coking chamber is uniform. In this way, by strictly controlling the coking reaction temperature and reaction time in each coking chamber, an ideal coke product can be obtained.

[0071] The process of the present invention is as follows Figure 3As shown, the implementation process is as follows: (1) Hot carrier gas circulation system: fuel gas 1 is combined with an appropriate amount of air 2 to burn in the burner 3 and is mixed with the circulating hot carrier gas from the circulating fan 4 to form a mixed hot carrier gas, which enters the coking chamber from the hot carrier gas coil inlet pipe 7 on the outer wall of the first coking chamber, passes through the 1st, 2nd, 3rd, ..., M-3, M-2 coking chambers in turn, and finally exits the coking furnace from the hot carrier gas coil outlet pipe 11 between the M-3rd and M-2nd coking chambers and circulates to the circulating fan 4 through the hot carrier gas outlet main pipe 12. After being pressurized by the circulating fan, a part of it is sent to the burner 3 as circulating gas, and the other part is sent to the exhaust gas 5 of the device. (2) Loading: In the state of the hot carrier gas circulation system described in (1), the M-1th coking chamber is in the unloading and loading state, and the raw asphalt is loaded into the reaction vessel (see the reaction vessel structure diagram). Figure 9 ), place multiple reaction vessels filled with asphalt on the reaction vessel rack as required (see the reaction vessel rack structure diagram Figure 6 、 Figure 7 、 Figure 8 ), then push the reaction vessel rack into the coking chamber, close and seal the coking chamber door. (3) Heating and coking reaction. The reaction temperature of each coking chamber is controlled by adjusting the temperature and flow of the hot carrier gas. Under the state of the circulation system described in (1), the temperature of the first coking chamber is the highest, and then the temperatures of the 1st, 2nd, 3rd, ..., M-3, and M-2 coking chambers decrease in sequence to form a temperature ladder. Among the heated coking chambers, the temperature of the M-2nd coking chamber is the lowest, and each coking chamber reacts under its own temperature ladder. The M-1th coking chamber is in the loading and unloading state. After the coking reaction in the first coking chamber is completed, the hot carrier gas circulation line is switched to make the temperature of the second coking chamber the highest. Thereafter, the temperatures of the 2nd, 3rd, 4th, ..., M-2, and M-1 coking chambers decrease in sequence, and the Mth coking chamber is in the loading and unloading state. Similarly, after the second coking chamber completes the coking reaction, the hot carrier gas circulation line is switched in sequence. In this way, after a series of switching hot carrier gas lines, the raw asphalt in each coking chamber has undergone the processes of loading, coking reaction from low temperature to high temperature, and unloading. Among them, the highest temperature and the reaction time at the highest temperature are the key control conditions of the present invention. (4) Oil and gas treatment. The oil and gas produced by each coking chamber are combined through the air guide pipe 9 and the main air guide pipe 10 at the top of the coking chamber and enter the distillation tower 13. The gas 18, light oil 15 and heavy oil 14 products are separated in the distillation tower. The pressure of the coking chamber is controlled by the vacuum pump 17 and the relevant valve 20 at the top of the distillation tower.

[0072] Examples 1-4

[0073] The coking furnace used in Examples 1-4 consists of multiple coking chambers, and adopts a step-type temperature increase mode and controls the polymerization reaction time at each step temperature to simulate the reaction effect under the conditions of multiple coking chambers connected in series. Figure 1 、 Figure 2This is a basic structural diagram of the coking furnace used in the present invention, but the number of coking chambers shown in the figure is not limited, and the number and size of the coking chambers can be increased or decreased according to the needs of the production scale.

[0074] The coking chamber is 2.2 meters deep, 2.2 meters high and 1 meter wide. The reaction vessel dimensions are 0.8 meters long, 0.6 meters wide and 0.3 meters high. The reaction vessel rack can hold three vertical rows of reaction vessels, with five layers of reaction vessels in each vertical row, for a total of 15 reaction vessels at a time.

[0075] There are hot air coils on both sides of the coking chamber. Figure 4 、 Figure 5 , use hot flue gas as hot carrier gas for heating, and control the temperature of the coking chamber by adjusting the flue gas temperature.

[0076] This embodiment simulates 8 coking chambers connected in series. In a coking furnace system consisting of 8 coking chambers, the state of each coking chamber is different at any time, as shown in Table 1:

[0077] Table 1 Status of each coking chamber at any time

[0078] Coking chamber number state temperature 5 Coking reaction highest temperature 6 Coking reaction Maximum temperature-△t 7 Coking reaction Maximum temperature-2△t 8 Coking reaction Maximum temperature-3△t 1 Coking reaction Maximum temperature-4△t 2 Raw materials have been loaded and are heating up Above room temperature 3 Unloading products and loading raw materials Room temperature 4 Cooling down Above room temperature

[0079] For a coking chamber, the stages experienced in a cycle include: loading raw materials, heating, reaction at a series of stepped temperatures, reaction at the highest temperature, cooling, and unloading.

[0080] In the embodiment, high-temperature coal tar pitch was used as the raw material (the composition and properties of the raw material are listed in Table 2). The control conditions of the coking chamber were as follows: the maximum coking temperature of the coking chamber was controlled at two temperatures: 490°C and 500°C, the temperature difference of each step was 30°C, and the reaction time (heating plus constant temperature) at each step temperature was controlled at two conditions: 6 hours and 8 hours. Within this condition range, the coking reaction temperature curve and the coke yield and properties are listed in Tables 3 and 4, respectively.

[0081] Under the conditions of Example 4, the temperature values ​​at 5 locations in the coking chamber were measured to observe the uniformity of the temperature distribution in the coking chamber. The volatile matter of the coke product in the tray at 5 locations in the coking chamber was also measured to observe the uniformity of the product properties at each location in the coking chamber. The 5 temperature measurement points correspond to the 5 coke sampling points, which are the 4 end points and the center point of the pallet frame car (see Figure 10 ), and the temperature distribution at each point and the volatile content of the coke are listed in Table 5. The results show that the coking chamber has a very uniform temperature distribution at different temperatures, with a deviation within ±2°C. The coke quality is also very uniform. The maximum difference in volatile content among the five coke samples is 0.2%. After calcination at 1400°C, the true density of all five coke samples is 2.14 g / cm3, indicating very uniform properties.

[0082] Table 2 Composition and properties of high temperature coal tar pitch

[0083] project index <![CDATA[Density, kg / m 3 > 1282.1 Ash content, % 0.05 Softening point, ℃ 97 Coking value, % 43.6 Carbon content, % 92.01 Hydrogen content, % 4.65 Sulfur content, % 0.68 Nitrogen content, % 1.21 Oxygen content, % 1.40

[0084] Table 3 Reaction temperature curves and coke results of Examples 1 and 2

[0085]

[0086]

[0087] Table 4 Reaction temperature curves and coke results of Examples 3 and 4

[0088]

[0089] Table 5 Coking chamber temperature distribution and coke uniformity

[0090]

[0091]

[0092] Example 5

[0093] The coke obtained in Example 4 was used as raw material, calcined at 1250°C for 1.5 hours, and then ground into powder with a D50 of 16 μm. The powder was then graphitized at 2600°C to prepare a negative electrode material for lithium batteries. A batch of half-cells were made and tested, and the average results were:

[0094] Average specific capacity of the first charge: 370.10mAh / g

[0095] Average specific capacity of the first discharge: 347.69mAh / g

[0096] First average Coulombic efficiency: 93.9%

[0097] Average specific capacity of secondary charge: 352.72mAh / g

[0098] Secondary discharge average specific capacity: 350.15mAh / g

[0099] Quadratic average coulombic efficiency: 99.3%

[0100] From the test results of the half-cell, it can be seen that the coke of the present invention can be used to prepare a lithium battery negative electrode material with good performance.

[0101] Any content not described in detail in the present invention can be based on conventional technical knowledge in the art.

[0102] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A system for preparing coke, characterized in that: The system comprises: a coking furnace, a hot carrier gas system and an oil and gas recovery system; wherein the coking furnace comprises M coking chambers connected in parallel, a hot carrier gas inlet main pipeline, a hot carrier gas outlet main pipeline and a gas guide main pipeline, wherein M≥4; The coking chamber includes a reaction vessel, an inlet and outlet channel, and a sealing door is installed in the inlet and outlet channel. A reaction vessel rack is placed in the coking chamber, and the reaction vessel is placed on the reaction vessel rack. An air duct is designed on the top of each coking chamber, and a group of hot gas coils are arranged inside the wall between two adjacent coking chambers and inside the outer walls of the first coking chamber and the last coking chamber; One end of each group of hot air coils is an air inlet end, and the other end is an air outlet end; wherein, the air outlet end of each group of hot air coils is connected to the air inlet end of the next group of hot air coils, and the air inlet end of the hot air coils inside the first coking chamber near the outer wall is connected to the air outlet end of the hot air coils inside the last coking chamber near the outer wall; and a flow control valve is installed on each connecting pipeline; A hot carrier gas inlet pipe and a hot carrier gas outlet pipe are respectively installed on the hot carrier gas coil connecting pipelines in the outer walls of the first coking chamber and the last coking chamber and the hot carrier gas coil connecting pipelines in the walls of two adjacent coking chambers, and a flow control valve is installed on the hot carrier gas inlet pipe and the hot carrier gas outlet pipe; The air inlet pipe of each group of hot-carrying gas coils is connected to the hot-carrying gas inlet main pipeline, and the air outlet pipe of each group of hot-carrying gas coils is connected to the hot-carrying gas outlet main pipeline; The air duct in each coking chamber wall is connected to the main air duct; The hot carrier gas system includes a burner and a circulating fan, and the oil and gas recovery system includes a distillation tower, a separator and a vacuum pump; The burner air outlet is connected to the hot carrier gas inlet main pipeline, the burner air inlet is connected to the circulation fan, the circulation fan is connected to the hot carrier gas outlet main pipeline, the gas guide main pipeline is connected to the fractionation tower air inlet, the fractionation tower top outlet is connected to the condenser and the separator, and the separator is connected to the vacuum pump; The reaction vessel rack refers to a movable frame on which a plurality of reaction vessels can be placed in an orderly manner.

2. The system according to claim 1, characterized in that The coking chamber has a depth of 2-4 meters, a height of 2-5 meters, and a width of 0.5-1.5 meters.

3. The system according to claim 1, characterized in that The length of the reaction vessel is 800-1000 mm, the width is 500-800 mm, and the height is 300-500 mm. The upper end of the reaction vessel is open or semi-open.

4. A method for preparing coke according to any one of claims 1 to 3, comprising the following steps: Open the air inlet valve of the hot carrier gas coil between the 1st and 2nd coking chambers, close the air inlet valve of the hot carrier gas coil in the outer wall of the 1st coking chamber, then open the air outlet valve of the hot carrier gas coil between the M-2nd and M-1st coking chambers, close the air outlet valve of the hot carrier gas coil between the M-3rd and M-2nd coking chambers, open the air guide valve on the top of the M-1st coking chamber, and close the air guide valve on the top of the Mth coking chamber. At this time, the hot carrier gas enters the hot carrier gas inlet between the 1st and 2nd coking chambers. The gas pipe enters the coking furnace, passes through the 2nd, 3rd, 4th, 5th, ... M-2 coking chambers in sequence, and finally exits the coking furnace from the hot carrier gas coil outlet pipe between the M-2nd and M-1st coking chambers. The 2nd coking chamber is the coking chamber with the highest temperature, and the M-1st coking chamber is the coking chamber with the lowest temperature among the coking chambers heated by the hot carrier gas. The Mth coking chamber cools down to room temperature and is in a loading and unloading state. When the coking reaction time of the 2nd coking chamber is completed, the hot carrier gas circulation route is switched; Open the air inlet valve of the hot carrier gas coil between the 2nd and 3rd coking chambers, close the air inlet valve of the hot carrier gas coil between the 1st and 2nd coking chambers, then open the air outlet valve of the hot carrier gas coil between the M-1st and Mth coking chambers, close the air outlet valve of the hot carrier gas coil between the M-2nd and M-1st coking chambers, open the top air guide valve of the Mth coking chamber, and close the top air guide valve of the 1st coking chamber. At this time, the hot carrier gas is discharged from the hot carrier gas coil between the 2nd and 3rd coking chambers. The air enters the coking furnace through the air inlet pipe and passes through the 3rd, 4th, 5th, 6th, ... M-1 coking chambers in sequence, and is finally discharged from the coking furnace from the hot carrier gas coil outlet pipe between the M-1th and M coking chambers. The 3rd coking chamber is the coking chamber with the highest temperature, and the Mth coking chamber is the coking chamber with the lowest temperature among the coking chambers heated by the hot carrier gas. The 1st coking chamber is cooled to room temperature and is in a loading and unloading state. When the coking reaction time of the 3rd coking chamber is completed, the hot carrier gas circulation route is switched.

5. The method according to claim 4, characterized in that The pressure of the coking chamber is controlled at 0-500 Pa, and the pressure of the coking chamber is controlled by adjusting the inlet vacuum degree of the vacuum pump at the top of the fractionation tower and the valve opening degree on the gas guide line.

6. The method according to claim 4, characterized in that Step 2) also includes discharging a portion of the hot carrier gas after being pressurized by the circulating fan, adjusting the discharge amount to control the pressure of the hot carrier gas circulation system, and sending the other portion to the burner as circulating hot carrier gas, and the pressure of the hot carrier gas circulation system is controlled below 0.2MPa.

7. The method according to claim 4, characterized in that The coking chamber is heated in a step-type mode, the step temperature difference of the coking chamber is 30-80° C., and the total reaction time at each step temperature is 20-70 hours.

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