A system and method for preparing coke in batches

Abstract

The present invention relates to the technical field of deep processing of petroleum heavy oil and coal tar pitch, and specifically to a system and method for intermittently preparing coke. The system includes a coking furnace, a reaction vessel and a hot carrier gas system, wherein one or more blowers are installed on the inner furnace wall of the coking furnace, one or more reaction vessel racks are placed in the coking furnace, the reaction vessel is placed on the reaction vessel rack, the thickness of the reaction vessel is 300-500mm, and the hot carrier gas system includes an incinerator, a circulating fan and a nitrogen supplement control device; the coking furnace air outlet is connected to the incinerator air inlet, the incinerator air outlet is connected to the circulating fan, the circulating fan is connected to the nitrogen supplement control device, and the nitrogen supplement control device is connected to the coking furnace air inlet. The present invention selects multiple thin-layer reaction vessels as coking reactors, greatly shortens the distance of heat transfer in coke, reduces the temperature difference, and makes the temperature distribution in the coke block more uniform.

Description

Technical Field

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

[0002] Coking is the process of thermally polymerizing macromolecular hydrocarbon compounds such as heavy petroleum oil, petroleum residue, coal tar pitch, etc. to generate larger molecular coke products. Most of the current coking technologies are developed based on the traditional delayed coking technology through optimization or improvement. According to the different goals of using coking technology, delayed coking technology can be divided into two categories: one is the delayed coking technology for the purpose of producing more light oil products, which often uses heavy petroleum oil or petroleum residue as raw materials, and light oils such as naphtha, diesel, and wax oil as main products, and petroleum coke products as by-products. The development direction of this type of technology is that with the development and progress of technology, the yield of light oil products will gradually increase, the production cycle will gradually extend, and the production scale of a single set of equipment will gradually increase. For example, patent document 201610061496.2 optimizes the process flow of delayed coking, first condenses the high-temperature oil and gas, and then treats the oil and gas separately, so as to obtain a higher yield of liquid products. Patent documents 200910065261.0 and 200910065262.5 use a process of first reducing viscosity and then coking, which can also increase the yield of liquid products, reduce the tendency of coking in the heating furnace, and extend the start-up cycle. This type of delayed coking technology is often used in large-scale production units in refineries that process more than hundreds of thousands of tons of raw materials annually.

[0003] The other type is delayed coking technology with needle coke as the main product. This type of technology uses needle coke as the main product and aims to improve the properties and yield of needle coke products. For example, patent documents 201811374496.3 and patent document 201810743620.2 add a polymerization tower in front of the coking tower, which first undergoes a polymerization to generate a portion of intermediate phase asphalt, and then enters the coking tower for a coking reaction. This can improve the performance of the needle coke. The scale of the device for producing needle coke is relatively small, and the common device scale is 50,000 tons / year.

[0004] In addition to the above-mentioned delayed coking technology, there is also an intermittent kettle coking technology, which is generally used in smaller-scale production processes with relatively high quality requirements for coke products. Patent document 201910728396.4 uses an intermittent coking kettle to produce high-regular carbon microcrystalline asphalt coke that meets the requirements of lithium battery negative electrode materials. This method is to remove light components from the raw asphalt in the coking kettle through dry distillation and further condense the aromatic components to generate asphalt coke. The key technology is to control the appropriate heating rate and coking reaction time to control the crystal form of 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, which have been widely used in petrochemical and coal chemical industries. They can produce products such as petroleum coke and needle coke with different performances according to the needs of raw materials and product markets of different compositions. These cokes provide rich raw materials for the carbon material industry. With the continuous development of the carbon material industry, various functional carbon materials have continuously improved the 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 put forward higher requirements for the homogeneity of coke, which actually requires the molecular size and molecular structure of coke to be the same or similar. From the production technology point of view, 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 view of 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 cokes of different properties are 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, the temperature difference between the high temperature of the kettle wall and the coke in the center of the kettle is generally 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] The uneven distribution of temperature field is determined by the characteristics of the coking tower selected for delayed coking and intermittent kettle coking technology. Therefore, delayed coking and intermittent kettle coking technology cannot meet the requirements for producing high-performance coke products. Summary of the invention

[0007] The purpose of the present invention is to overcome the problem of uneven temperature field distribution in the existing coking technology. The present invention provides a system and method for intermittent preparation of coke, which can not only solve the problem of uneven temperature field distribution, but also produce coke products with better homogeneity. At the same time, the method also has the advantages of low investment, simple operation and stable product quality.

[0008] This system includes the core equipment coking furnace and hot carrier gas system. The coking furnace is the core equipment for providing coking reaction for raw asphalt, and the function of the hot carrier gas system is to provide sufficient heat for the coking reaction.

[0009] To achieve the above object, the present invention provides a system for preparing coke in an intermittent manner, the system comprising a coking furnace, a reaction vessel and a hot carrier gas system, wherein one or more fans are installed on the inner furnace wall of the coking furnace, the fans are coking furnace fans, one or more reaction vessel racks are placed in the coking furnace, the reaction vessels are placed on the reaction vessel racks, the thickness of the reaction vessels is 300-500mm, and the hot carrier gas system comprises an incinerator, a circulating fan and a nitrogen supplement control device;

[0010] The coking furnace air outlet is connected to the incinerator air inlet, the incinerator air outlet is connected to the circulating fan, the circulating fan is connected to the nitrogen supplement control device, and the nitrogen supplement control device is connected to the coking furnace air inlet. Figure 1 shown.

[0011] Preferably, the coking furnace has a cubic structure, and the length of the coking furnace is 2-4 meters, the width is 1-4 meters, and the height is 2-5 meters;

[0012] The coking furnace wall is made of refractory materials and heat-insulating materials to reduce the loss of high-temperature heat in the furnace;

[0013] Among them, refractory materials and thermal insulation materials are well known in the art.

[0014] The coking furnace is provided with an air inlet for hot carrier gas on one side and an air outlet for hot carrier gas on the other side; a furnace wall on one side of the front side of the coking furnace is used as a passage for inlet and outlet of materials, and is provided with a sealing door that can be opened and closed. When the sealing door is opened, the reaction vessel rack containing raw materials / products can be pushed in and out. When the sealing door is closed, the coking furnace can be isolated from the outside to prevent gas circulation;

[0015] One or more fans are installed on the inner wall of the coking furnace to strengthen the hot air convection in the furnace, establish a uniform temperature field in the furnace, and ensure uniform temperature at each point;

[0016] One or more reaction vessel racks can be placed in the coking furnace. The reaction vessel rack refers to a movable frame that can orderly place multiple reaction vessels, such as Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 shown.

[0017] Preferably, the reaction vessel refers to a metal container with a standard size (length 800-1000 mm, width 500-800 mm, height 300-500 mm) that can hold a certain volume of asphalt / coke, which is characterized by a thin layer structure (height only 300-500 mm), and the upper end of the reaction vessel can be open or semi-open to ensure that the oil and gas generated during the reaction process can be discharged smoothly. Figure 7 As shown, further preferably, the dimensions of the reaction vessel are 800 mm in length, 600 mm in width and 300 mm in height.

[0018] Preferably, the hot carrier gas system further comprises an oxygen content measuring device, and the oxygen content measuring device is located at the air inlet of the coking furnace.

[0019] The nitrogen supplement control device and the oxygen content measuring device are commonly used measuring devices in the art. Preferably, the hot carrier gas system is mainly composed of an incinerator, a circulating fan, a nitrogen supplement control device, an oxygen content measuring device, and a series of pipe valves. The fuel gas and air are burned in the incinerator to burn off the oil and gas in the gas from the coking furnace. The high-temperature flue gas generated by the combustion is pressurized by the circulating fan and circulated to the coking furnace to provide heat for the coking reaction.

[0020] The present invention provides a method for preparing coke in an intermittent manner, comprising the following steps:

[0021] 1) Loading: Load the raw asphalt into the reaction vessel, place the reaction vessel with asphalt on the reaction vessel rack, then push the reaction vessel rack into the coking furnace, and close and seal the coking furnace door;

[0022] 2) Heating: Start the circulating fan, pass the gas and air into the incinerator for combustion, start the first stage of heating, adjust and control the oxygen content of the gas at the coking furnace inlet, and then continue the second stage of heating, and control the oxygen content of the gas at the coking furnace inlet and the pressure of the coking furnace;

[0023] 3) Coking reaction: When the temperature in the coking furnace rises to the reaction temperature, the heating rate and constant temperature time are controlled according to the requirements of the coking reaction to achieve the coking reaction at a precise temperature;

[0024] 4) Cooling: After the reaction is completed, gradually lower the temperature in the coking furnace; then stop the hot carrier gas system;

[0025] 5) Unloading: After the temperature in the coking furnace drops, open the coking furnace door to obtain coke.

[0026] Preferably, in the first stage of step 2), the temperature of the circulating gas reaches 100-150°C, and the oxygen content of the gas at the air inlet of the coking furnace is controlled to be less than 3%. In the second stage, the temperature of the circulating gas reaches the temperature at which the asphalt undergoes a coking reaction, and the oxygen content of the gas at the air inlet of the coking furnace is controlled to be less than 3%. The pressure inside the coking furnace is controlled to be a slightly positive pressure, that is, the internal pressure of the coking furnace is 0-500Pa, and the pressure inside the coking furnace is controlled by adjusting the emission of flue gas.

[0027] Preferably, the step 2) also includes, after starting the hot carrier gas system, discharging a portion of the high-temperature flue gas when the oxygen content in the hot carrier gas exceeds 3%, and simultaneously adding a portion of nitrogen into the hot carrier gas so that the oxygen content in the hot carrier gas is not higher than 3%.

[0028] Preferably, the reaction temperature in step 3) is not more than 500°C. If a multi-stage temperature coking reaction is required, the heating and cooling rate between the temperature stages is less than 15°C / hour when the reaction temperature is not less than 350°C, and the total constant temperature time is 20-70 hours.

[0029] Preferably, in step 4), the temperature in the coking furnace is lowered to no more than 100° C. before the carrier gas system is stopped.

[0030] In the present invention, the oxygen content in the hot carrier gas is controlled by adjusting the flue gas emission and the nitrogen supplementation, the temperature of the coking furnace is controlled by adjusting the temperature of the flue gas at the outlet of the incinerator, and the pressure in the coking furnace is controlled by adjusting the flue gas emission and the nitrogen supplementation.

[0031] The temperature of the coking furnace is controlled by adjusting the temperature of the flue gas at the outlet of the incinerator. The adjustment method is: when the temperature inside the coking furnace is low, the temperature of the flue gas at the outlet of the incinerator is increased; when the temperature of the coking furnace is high, the temperature of the flue gas at the outlet of the incinerator is reduced.

[0032] The pressure inside the coking furnace is controlled by adjusting the flue gas emission and the nitrogen supplement. The adjustment method is: when the pressure inside the coking furnace is low, increase the nitrogen supplement; when the pressure inside the coking furnace is high, reduce the nitrogen supplement and increase the flue gas emission.

[0033] The equipment and process of the present invention are simple, the operation is flexible, the maximum temperature can reach 500° C., and it can be used to prepare a variety of coke products with uniform structures.

[0034] Compared with the existing delayed coking and intermittent kettle coking technologies, the advantages of the present invention are:

[0035] (1) The present invention controls the temperature field distribution in the coking chamber to be more uniform, and the temperature distribution deviation is ≤±1°C.

[0036] (2) The temperature distribution inside the coke of the present invention is more uniform. The coking reaction is a weak endothermic process and requires continuous external heat supply to keep the reaction temperature constant. Therefore, the present invention uses multiple thin-layer reaction vessels as coking reactors, which greatly shortens the distance that heat is transferred in the coke, reduces the temperature difference, and makes the temperature distribution in the coke block more uniform. Experiments have shown that the difference between the highest temperature on the coke surface and the lowest temperature in the coke center is less than 5°C, which is much better than the temperature field distribution of delayed coking and intermittent kettle coking technology.

[0037] (3) The coking reaction temperature can be controlled flexibly and accurately, and the coking reaction can be accurately controlled to proceed under the optimal temperature conditions.

[0038] (4) The present invention can control the coking reaction of raw materials under multiple different temperature conditions, thereby obtaining an ideal coke crystal structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a simplified process flow diagram of the present invention;

[0040] Figure 2 It is a three-dimensional diagram of a coking furnace of the present invention;

[0041] Figure 3 A top view of a coking furnace according to the present invention;

[0042] Figure 4 A three-dimensional diagram of a reaction vessel rack according to the present invention;

[0043] Figure 5 It is a front view of the reaction vessel rack of the present invention;

[0044] Figure 6 It is a left view of the reaction vessel rack of the present invention;

[0045] Figure 7 It is a schematic diagram of the structure of the reaction vessel of the present invention;

[0046] Figure 8 This is a distribution diagram of temperature measurement points in a coking furnace according to Example 2 of the present invention;

[0047] Reference numerals:

[0048] 1. Air inlet, 2. Air outlet, 3. Reaction vessel rack, 4. Reaction vessel, 5. Fan. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with specific embodiments.

[0050] The present invention is an intermittent coking technology, the process flow is as follows Figure 1As shown, the specific implementation process is:

[0051] (1) Loading: At the beginning of operation, the raw asphalt must be loaded into the reaction vessel, and multiple reaction vessels filled with asphalt are placed on the reaction vessel rack as required. Then, the reaction vessel rack is pushed into the coking furnace, and the coking furnace door is closed and sealed.

[0052] (2) Start the hot carrier gas system: Start the circulating fan to circulate the gas, then burn the gas with an appropriate amount of air in the incinerator and mix it with the gas from the coking furnace to gradually heat up the circulating gas. When the temperature of the circulating gas reaches the range of 100-150°C, start to adjust and control the oxygen content of the coking furnace inlet gas within the specified concentration range, where the oxygen content is less than 3%, then continue to heat up the circulating gas, and control the oxygen content of the coking furnace inlet gas to less than 3% and the pressure of the coking furnace within the specified range, where the pressure range is 0-500Pa.

[0053] (3) Coking reaction: The temperature of the coking furnace can be controlled by adjusting the flue gas temperature of the incinerator. When the temperature in the coking furnace rises to the reaction temperature, the heating rate, constant temperature time and other parameters are controlled according to the temperature curve of the coking reaction to meet the needs of the coking reaction. In order to produce coke products with regular crystal structures, it is usually necessary to carry out polymerization reactions under multiple temperature conditions. First, react at a lower temperature to allow the components with high reaction activity in the raw materials to react first, and then heat to a higher temperature to allow the components with low reaction activity to react fully. The reaction rate can be controlled by using the temperature segment reaction method, and a regular coke crystal structure can also be obtained.

[0054] (4) Cooling: After the reaction is completed, keep the circulating gas circulating normally, keep the incinerator able to completely burn the oil and gas components in the coking furnace gas, keep the oxygen content in the gas and the pressure in the coking furnace within the specified range, and gradually reduce the temperature of the incinerator flue gas, thereby slowly reducing the temperature of the coking furnace. When the temperature in the coking furnace drops below 100°C, stop the circulation system.

[0055] (5) Unloading: After the temperature in the coking furnace drops below 100°C, open the coking furnace door and ventilate the flue gas in the coking furnace. When the temperature reaches a safe range, pull out the reaction vessel rack and unload the coke product in the reaction vessel.

[0056] Embodiment 1, 2

[0057] The coking furnace used in the embodiment has a length of 2.2 meters, a height of 2.2 meters, and a width of 1 meter.

[0058] The size of the reaction vessel is 0.8 (length) X 0.6 (width) X 0.3 (thickness) meters. The reaction vessel rack can hold 3 vertical rows of reaction vessels, with 5 layers of reaction vessels in each vertical row, for a total of 15 reaction vessels at a time.

[0059] This example uses high temperature coal tar pitch as raw material, and the raw material composition and properties are listed in Table 1.

[0060] Each example undergoes the following steps in sequence: loading, heating, coking reaction, cooling, and unloading. The coking reaction of Example 1 is divided into four temperature sections: 360°C, 400°C, 450°C, and 480°C, and the heating rate between each temperature section is 10°C / hour; the coking reaction of Example 2 is also divided into four temperature sections: 360°C, 400°C, 460°C, and 500°C, and the heating rate between each temperature section is 10°C / hour. The temperature curves of the coking reaction stages of each example are listed in Table 2, and the coke yield and properties are also listed in Table 2.

[0061] Under the conditions of Example 2, the temperature values ​​at 5 positions in the coking furnace were measured to observe the uniformity of the temperature distribution in the coking furnace. The volatile matter of the coke product in the reaction dish corresponding to the 5 positions in the coking furnace was also measured to observe the uniformity of the product properties at each position in the coking furnace. The 5 temperature measurement points and the 5 coke sampling points correspond to each other, which are the 4 end points and the center point of the reaction dish rack (see Figure 8 ), the temperature distribution of each point and the volatile matter test results of coke are listed in Table 3. The results show that the coking furnace has a very uniform temperature distribution at different temperatures, and the quality of coke is also very uniform.

[0062] Table 1 Composition and properties of high temperature coal tar pitch

[0063]

[0064]

[0065] Table 2 Reaction temperature curves and coke results of Examples 1 and 2

[0066]

[0067] Table 3 Coking furnace temperature distribution and coke uniformity

[0068]

[0069]

[0070] Example 3

[0071] The coke obtained in Example 2 was used as a raw material, calcined at 1250°C for 1.5 hours, and then ground into powder, with a D50 of 13 microns. It was then graphitized at 2600°C to prepare a negative electrode material for a lithium battery, and a batch of half-cells were made for testing. The average results were:

[0072] Average specific capacity of the first charge: 368.36mAh / g

[0073] Average specific capacity of first discharge: 347.02mAh / g

[0074] First average coulombic efficiency: 94.2%

[0075] Average specific capacity of secondary charge: 350.94mAh / g

[0076] Secondary discharge average specific capacity: 348.61mAh / g

[0077] Secondary average coulombic efficiency: 99.3%

[0078] It can be seen from the test results of the half-cell that the coke of the present invention can be used to prepare a lithium battery negative electrode material with good performance.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A system for preparing coke in an intermittent manner, characterized in that: The system comprises a coking furnace, a reaction vessel and a hot carrier gas system, wherein one or more fans are installed on the inner wall of the coking furnace, one or more reaction vessel racks are placed in the coking furnace, the reaction vessels are placed on the reaction vessel racks, the thickness of the reaction vessels is 300-500mm, and the hot carrier gas system comprises an incinerator, a circulating fan and a nitrogen supplement control device; The coking furnace air outlet is connected to the incinerator air inlet, the incinerator air outlet is connected to the circulating fan, the circulating fan is connected to the nitrogen supplement control device, and the nitrogen supplement control device is connected to the coking furnace air inlet; The reaction vessel rack refers to a movable frame for orderly placing a plurality of reaction vessels.

2. The intermittent coke preparation system according to claim 1, characterized in that: The coking furnace has a cubic structure, with a length of 2-4 meters, a width of 1-4 meters, and a height of 2-5 meters; The coking furnace is provided with an air inlet for hot carrier gas on one side and an air outlet for hot carrier gas on the other side; a furnace wall on one side of the front side of the coking furnace serves as a channel for inlet and outlet of materials.

3. The intermittent coke preparation system according to claim 1, characterized in that: The upper end of the reaction vessel is open or semi-open.

4. The intermittent coke preparation system according to claim 1, characterized in that: The hot carrier gas system also includes an oxygen content measuring device, which is located at the front end of the coking furnace air inlet.

5. A method for preparing coke in an intermittent manner based on the system according to any one of claims 1 to 4, comprising the following steps: 1) Loading: Load the raw asphalt into the reaction vessel, then put it into the coking furnace, and close and seal the coking furnace door; 2) Heating: Start the circulating fan, pass the gas and air into the incinerator for combustion, start the first stage of heating, adjust and control the oxygen content of the gas at the coking furnace inlet, and then continue the second stage of heating, and control the oxygen content of the gas at the coking furnace inlet and the pressure of the coking furnace; 3) Coking reaction: When the temperature in the coking furnace rises to the reaction temperature, control the heating rate and constant temperature time; 4) Cooling: After the reaction is completed, gradually lower the temperature in the coking furnace; then stop the hot carrier gas system; 5) Unloading: After the temperature in the coking furnace drops, open the coking furnace door to obtain coke.

6. The method according to claim 5, characterized in that In the step 2), the temperature of the circulating gas in the first stage is raised to 100-150°C, and the oxygen content of the gas at the coking furnace inlet is controlled to be less than 3%. In the second stage, after the temperature of the circulating gas reaches the asphalt coking reaction temperature, the oxygen content of the gas at the coking furnace inlet is controlled to be less than 3%, and the internal pressure of the coking furnace is 0-500Pa.

7. The method according to claim 5, characterized in that The step 2) also includes starting the hot carrier gas system, and when the oxygen content in the hot carrier gas exceeds 3%, discharging a portion of the high-temperature flue gas, and simultaneously adding a portion of nitrogen into the hot carrier gas, so that the oxygen content in the hot carrier gas is not higher than 3%.

8. The method according to claim 5, characterized in that The reaction temperature in step 3) is not greater than 500°C.

9. The method according to claim 8, characterized in that When the multi-stage temperature coking reaction is carried out in step 3), the heating and cooling rate between the two temperature stages is less than 15°C / hour when the reaction temperature is not less than 350°C, and the total constant temperature time is 20-70 hours.

10. The method according to claim 5, characterized in that In the step 4), the temperature in the coking furnace is lowered to no more than 100° C., and then the carrier gas system is stopped.

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