Coking device coke gasification method

Abstract

The invention discloses a coke gasification method of a coking device. Pure oxygen and carbon dioxide are mixed and then enter the gasifier together with steam as a gasification medium from the bottom of the gasifier to be in countercurrent contact with petroleum coke from the reaction part for gasification reaction, and generated crude gasified gas is led out from the top of the gasifier and enters a cyclone dust remover after heat exchange cooling and heat recovery; further dedusting and desulfurizing through a dedusting and desulfurizing system, then entering a decarburization tower to be in countercurrent contact with lean alkali liquor from an alkali liquor regeneration tower to remove carbon dioxide in the crude gasified gas, and conveying the decarburized gasified gas to a fuel gas system; the rich alkali liquor absorbing the carbon dioxide is extracted from the bottom of the decarburization tower, pressurized and sent to the alkali liquor regeneration tower, the regenerated poor alkali liquor returns to the decarburization tower to serve as an absorbent, and the carbon dioxide removed from the alkali liquor regeneration tower is sent out of the device, or a part of the carbon dioxide is sent out of the device, and the other part of the carbon dioxide is circulated back to the inlet of the gasifier to be mixed with pure oxygen. The temperature of the gasifier can be reduced, the operation severity of gasifier equipment is reduced, and the calorific value of gasified gas is improved.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals, and specifically relates to a method for coke gasification in a coking unit. Background Technology

[0002] As global oil resources become increasingly heavier and of lower quality, the requirements for heavy oil processing technologies are becoming more stringent. Flexible coking, developed based on fluidized bed coking technology, is an important heavy oil processing route. Compared to delayed coking, flexible coking eliminates the need for a heating furnace, avoiding coking problems in the furnace tubes and allowing for the processing of heavier feedstocks. Furthermore, flexible coking is a continuous operation, converting most of the petroleum coke into coal gas in a closed system, making it more environmentally friendly and increasingly attractive in the face of declining oil quality.

[0003] The conventional gasification system process for a flexible coking unit is as follows: Air is pressurized by the main blower, then mixed with steam and enters the gasifier. Inside the gasifier, it comes into contact with petroleum coke from the reaction section, undergoing a gasification reaction at high temperatures. The heat required for the gasification reaction is provided by the heat released from the combustion of oxygen in the air with the coke. The flexible gas product exiting the gasifier undergoes a series of cooling processes, including direct contact cooling with cold coke, generation of medium-pressure steam, and preheating of boiler feedwater. After further dust removal and desulfurization, purified flexible gas is sent to the plant's fuel system for partial replacement of fuel gas or for other uses.

[0004] Because air is used as the gasification medium, and approximately 78% of the air is inert nitrogen, which accounts for about 50% of the total volume of the flexible gas, the calorific value of the flexible gas is relatively low. Therefore, it cannot completely replace fuel gas and needs to be blended with natural gas, which greatly limits its application. Furthermore, the burners of furnaces using flexible gas as fuel require special designs or modifications, resulting in significant equipment investment. Additionally, the main blower consumes a large amount of power, with most of it used to pressurize the inert nitrogen gas, which is essentially inefficient energy consumption and leads to substantial energy waste. Summary of the Invention

[0005] The purpose of this invention is to provide a coke gasification method for coking plants to solve the problem of low calorific value of flexible gas produced by coking plants in the prior art.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A method for coke gasification in a coking unit, characterized in that:

[0008] Pure oxygen and carbon dioxide, mixed with steam, enter the gasifier from the bottom as the gasification medium. Petroleum coke from the reaction section, heated to 600–700°C, enters the gasifier from the top. Inside the gasifier, the gasification medium and petroleum coke come into countercurrent contact, undergoing a gasification reaction. The reaction temperature in the gasifier is 800–1000°C, preferably 900–950°C. The crude gasified gas generated in the gasifier is drawn out from the top of the gasifier, and after heat recovery through a heat exchanger, it enters a cyclone separator to remove most of the entrained coke particles. After further dust removal and desulfurization by the dust removal and desulfurization system, the gas enters the decarbonization tower and comes into countercurrent contact with the lean alkali solution from the alkali regeneration tower to remove carbon dioxide from the crude gasification gas. The decarbonized gasification gas is sent to the fuel gas system and can be used as fuel. The rich alkali solution after absorbing carbon dioxide is drawn out from the bottom of the decarbonization tower, pressurized and sent to the alkali regeneration tower for regeneration. The regenerated lean alkali solution is returned to the decarbonization tower. The carbon dioxide removed by the alkali regeneration tower is sent out of the device, or part of it is sent out of the device and the other part is recycled back to the gasifier inlet to mix with pure oxygen.

[0009] The present invention discloses a method for coke gasification in a coking unit, wherein the further technical feature is that the pure oxygen is preferably derived from a green hydrogen unit.

[0010] The present invention discloses a coke gasification method for a coking unit, further characterized in that: the petroleum coke from the reaction section is heated by a cold coke heater and enters the gasifier from the top of the gasifier; the crude gasification gas generated in the gasifier is drawn out from the top of the gasifier and enters the cold coke heater to directly contact and exchange heat with the petroleum coke from the reaction section; the crude gasification gas after preliminary cooling is drawn out from the top of the cold coke heater, and after further heat recovery by a gasification gas heat recovery unit, it enters a cyclone separator; the rich alkali solution after absorbing carbon dioxide is drawn out from the bottom of the decarbonization tower, pressurized by a rich alkali solution pump, and sent to the alkali regeneration tower.

[0011] The present invention discloses a method for coke gasification in a coking unit, wherein the volume ratio of pure oxygen to carbon dioxide is 0.15 to 0.4, preferably 0.25 to 0.35.

[0012] The present invention discloses a coke gasification method for a coking unit, the further technical feature of which is that the gasifier and the cold coke heater both adopt a fluidized bed with a bed linear velocity of 0.1 m / s to 2 m / s, preferably 0.2 to 1 m / s.

[0013] The advantages of this invention compared to the prior art are:

[0014] 1) This invention eliminates the main fan system of the device, reducing the footprint and equipment maintenance costs; at the same time, it makes up for the energy consumption generated by using pure oxygen.

[0015] 2) The gasification medium of the present invention is a mixture of steam, pure oxygen and carbon dioxide. Carbon dioxide and pure oxygen replace the nitrogen in the original main air, which can reduce the inert (nitrogen) component in the gasified gas product from about 50% to 0, thereby increasing the calorific value of the gasified gas by nearly 100%, greatly enhancing the usability and application flexibility of the gasified gas.

[0016] 3) The gasification medium of the present invention is a mixture of steam, pure oxygen and carbon dioxide. When carbon dioxide enters the gasifier, it can increase the partial pressure of carbon dioxide in the gasifier. According to chemical equilibrium, it can suppress the generation of carbon dioxide in the gasified gas, increase the content of effective components such as carbon monoxide and hydrogen in the synthesis gas, and reduce carbon dioxide emissions.

[0017] 4) This invention uses a mixture of carbon dioxide and pure oxygen to enter the gasifier, which can reduce the intensity of oxidation and combustion in the gasifier, reduce the temperature of the gasifier, reduce the operational severity of the gasifier equipment, and reduce equipment costs.

[0018] 5) When the present invention preferably uses the by-product oxygen of the green hydrogen device as the gasification medium, it can solve the problem of the outlet of the by-product oxygen of the green hydrogen device; and it is environmentally friendly and pollution-free.

[0019] 6) After the carbon dioxide contained in the gasified gas is removed by the decarbonization tower, it can be used as fuel gas for the whole plant or for other purposes, which can further improve the calorific value of the gasified gas.

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of the invention. Attached Figure Description

[0021] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the following detailed description to explain this application, but do not constitute a limitation thereof.

[0022] Figure 1 A simplified flow chart of a coke gasification method for a coking unit according to the present invention.

[0023] The reference numerals in the figure are:

[0024] 1. Alkali regeneration tower; 2. Gasifier; 3. Cold coke heater; 4. Rough gasification gas; 5. Gasification gas heat recovery unit; 6. Cyclone dust collector; 7. Decarbonization tower; 8. Rich alkali pump. Detailed Implementation

[0025] The specific embodiments of this application are described in detail below. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0026] like Figure 1As shown, the pure oxygen used comes from the green hydrogen unit. The pure oxygen from the green hydrogen unit (referred to as green oxygen) is mixed with carbon dioxide from the alkali regeneration tower 1 and then enters the gasifier 2 from the bottom along with steam as the gasification medium. Petroleum coke from the reaction section (e.g., the reactor) is heated to 600–700°C by the cold coke heater 3 and then enters the gasifier from the top. The gasification medium is evenly distributed by a gas distributor (not shown in the figure) and then evenly mixed and contacted with the hot coke (or hot coke) from the cold coke heater 3 within the gasifier 2 to carry out the coke gasification reaction. The gasification reaction is endothermic, and the heat required for the reaction is provided by the oxidation and combustion of some of the coke and oxygen. The reaction temperature in the gasifier is 800–1000°C, preferably 900–950°C, and the volume ratio of pure oxygen from the green hydrogen unit to carbon dioxide from the alkali regeneration tower is 0.15–0.4, preferably 0.25–0.35.

[0027] Both the gasifier and the cold coke heater adopt a fluidized bed with a bed linear velocity of 0.1 m / s to 2 m / s, preferably 0.2 to 1 m / s.

[0028] The crude gas generated by the reaction is drawn out from the top of the gasifier 2 and enters the cold coke heater 3 to directly contact the cold coke from the reactor for heat exchange and recovery of heat from the high-temperature gasified gas. The crude gasified gas 4 after preliminary cooling is drawn out from the top of the cold coke heater 3 and enters the gasified gas heat recovery unit 5 to further recover heat. The gasified gas heat recovery unit 5 includes, but is not limited to, a medium-pressure steam generator, a boiler feedwater preheater, etc.

[0029] After being cooled by the gasification gas heat recovery unit 5, the gasified gas enters the cyclone separator 6 to remove most of the entrained coke particles. The coke powder (or coke pulverizer) exits from the bottom of the cyclone separator 6 and is recovered for coke processing. Alternatively, the coke powder (or coke pulverizer) can be sent to the coke processing unit for further processing via self-pressurization. The gasified gas with preliminary dust removal is drawn from the top of the cyclone separator 6 and further dusted and desulfurized by the wet dust removal and desulfurization system before entering the bottom of the decarbonization tower 7. There, it comes into countercurrent contact with the lean alkali solution from the alkali regeneration tower 1 to remove carbon dioxide from the gasified gas. The carbon-removed gas (i.e. purified flexible gas) flows out from the top of the decarbonization tower 7 and is sent to the fuel gas system for use as fuel. The rich alkali solution after absorbing carbon dioxide is drawn out from the bottom of the decarbonization tower 7, pressurized by the rich alkali solution pump 8, and sent to the top of the alkali solution regeneration tower 1. The carbon dioxide in the rich alkali solution is removed by stripping. The regenerated lean alkali solution is drawn out from the bottom of the alkali solution regeneration tower 1 and returned to the top of the decarbonization tower 7 as an absorbent. Most of the carbon dioxide removed from the alkali solution regeneration tower 1 is recycled back to the inlet of the gasifier 2 and mixed with pure oxygen as a gasification medium. A small amount of carbon dioxide generated is sent out of the device.

Claims

1. A method for coke gasification in a coking unit, characterized in that: Pure oxygen and carbon dioxide, mixed with steam, enter the gasifier from the bottom as the gasification medium. Petroleum coke from the reaction section, heated to 600-700℃, enters the gasifier from the top. Inside the gasifier, the gasification medium and petroleum coke come into countercurrent contact, undergoing a gasification reaction. The reaction temperature in the gasifier is 800-1000℃. The crude gasified gas generated in the gasifier is drawn out from the top, cooled by a heat exchanger to recover heat, and then enters a cyclone separator to remove most of the entrained coke particles. After further dust removal and desulfurization by the dust removal and desulfurization system, the gas enters the decarbonization tower and comes into countercurrent contact with the lean alkali solution from the alkali regeneration tower to remove carbon dioxide from the crude gasification gas. The decarbonized gasification gas is then sent to the fuel gas system. The rich alkali solution, after absorbing carbon dioxide, is drawn out from the bottom of the decarbonization tower, pressurized, and sent to the alkali regeneration tower for regeneration. The regenerated lean alkali solution is returned to the decarbonization tower. The carbon dioxide removed by the alkali regeneration tower is sent out of the device, or part of it is sent out of the device and the other part is recycled back to the gasifier inlet to mix with pure oxygen.

2. The coke gasification method for a coking unit according to claim 1, characterized in that: The pure oxygen comes from the green hydrogen unit.

3. The coke gasification method for a coking unit according to claim 1, characterized in that: The reaction temperature of the vaporizer is 900~950℃.

4. The coke gasification method for a coking unit according to claim 1, characterized in that: The petroleum coke from the reaction section is heated by the cold coke heater and enters the gasifier from the top. The crude gasification gas generated in the gasifier is drawn out from the top of the gasifier and enters the cold coke heater to directly contact and exchange heat with the petroleum coke from the reaction section. After preliminary cooling, the crude gasification gas is drawn out from the top of the cold coke heater and further heat is recovered by the gasification gas heat recovery unit before entering the cyclone separator. The rich alkali solution after absorbing carbon dioxide is drawn out from the bottom of the decarbonization tower, pressurized by the rich alkali solution pump, and sent to the alkali regeneration tower.

5. The coke gasification method for a coking unit according to claim 1, characterized in that: The volume ratio of pure oxygen to carbon dioxide is 0.15 to 0.

4.

6. A coke gasification method for a coking unit according to claim 1 or 5, characterized in that: The volume ratio of pure oxygen to carbon dioxide is 0.25 to 0.

35.

7. The coke gasification method for a coking unit according to claim 1, characterized in that: The gasifier uses a fluidized bed with a bed linear velocity of 0.1 m / s to 2 m / s.

8. The coke gasification method for a coking unit according to claim 7, characterized in that: The gasifier uses a fluidized bed with a bed linear velocity of 0.2~1m / s.

9. A coke gasification method for a coking unit according to claim 4, characterized in that: The cold coke heater uses a fluidized bed with a bed linear velocity of 0.1 m / s to 2 m / s.

10. A method for coke gasification in a coking unit according to claim 9, characterized in that: The cold coke heater uses a fluidized bed with a bed linear velocity of 0.2~1m / s.

Images