Method for converting tar / crude benzene in coke oven raw gas into combustible gas

Abstract

The invention relates to a method for converting tar / crude benzene in coke oven raw gas into combustible gas. When the coke oven is built, CO2 vent holes are formed in the oven top of a carbonization chamber, and meanwhile, the space temperature of the oven top of the carbonization chamber is increased by increasing the height of a combustion chamber or reducing the coal charging height of the carbonization chamber to reduce the heating horizontal height of the coke oven; during coking of the coke oven, when the temperature of the furnace top space of the carbonization chamber reaches 710-1050 DEG C, CO2 gas is introduced into the furnace top space of the carbonization chamber through the CO2 vent hole; the CO2 reacts with tar / crude benzene organic steam in the high-temperature raw coke oven gas to generate combustible gas; the method provided by the invention can realize flexible regulation and control of the ratio of tar to fuel gas products, is beneficial to inhibition of carbon deposition, improves the resource utilization efficiency of CO2, reduces greenhouse gas emission, and provides a new way for conversion of tar, crude benzene and fuel gas in the coking industry.

Description

Technical Field

[0001] The invention relates to the technical field of coke oven coking, in particular to a method for converting tar / crude benzene in coke oven raw gas into combustible gas. Background Art

[0002] Industrial coke oven coking is a key process in coal conversion. Coke ovens pyrolyze coal in a high-temperature, oxygen-free environment, producing byproducts such as coke, coke oven gas, and coal tar. Coke oven gas is a combustible gas rich in hydrogen, methane, and carbon monoxide, while organic products such as coal tar and crude benzene are liquid products composed of various aromatic hydrocarbons and heterocyclic compounds. These products are obtained after coal coking and through gas purification processes such as raw gas cooling, desulfurization, and benzene washing. They are often used in the extraction of fine chemical raw materials.

[0003] During the high-temperature coking process, the raw gas from the coke oven top contains light fuel gas and tar / crude benzene gas. The tar / crude benzene gas content is affected by a variety of factors, including the type of coking coal, the structure of the coke oven's carbonization and combustion chambers, the coking temperature, and the coking process. Adjusting the quality of the coal blending process based on market demand can regulate the yield of tar or fuel gas. For example, when chemical raw materials are in short supply, higher tar and crude benzene yields are beneficial for extracting high-value-added chemicals such as benzene and naphthalene. Conversely, when demand for fuel gas is high, converting tar / crude benzene into fuel gas and increasing coke oven gas yield is more economically viable. The coking process consumes a large amount of fuel gas to heat the coke ovens, which in turn generates significant CO2 emissions. With increasingly stringent environmental protection requirements, companies face the significant challenge of reducing CO2 emissions. Therefore, flexibly controlling the relative yields of coal tar and fuel gas during the coking process and realizing resourceful utilization of CO2 have become urgent challenges for coking plants.

[0004] Currently, improving the gas-to-tar yield ratio during coking relies primarily on modifying the coal quality of the charged coal and optimizing coking process conditions, such as increasing the volatile matter content of the coal blend, raising the coking temperature, and adjusting the heating method. However, these methods have limitations in terms of controllability and operability. For example, while increasing the coking temperature can promote the secondary cracking of tar / crude benzene to produce gas, it also increases coke oven energy consumption, increases CO₂ emissions in the coke oven flue gas, and exacerbates damage to the coke oven combustion and carbonization chamber walls. Conventional technologies for addressing CO₂ emissions during coking primarily focus on absorbing CO₂ from the exhaust gas through tail gas purification systems, but lack methods for resource utilization of CO₂. For example, Chinese patent application publication number CN110144228A discloses a "clean coking production process and system." The clean coking production system includes a coke oven flue gas CO2 absorption system. Pretreated coke oven flue gas enters the CO2 absorption system, where the CO2 in the flue gas fully contacts and is absorbed by an alkaline absorption liquid, generating corresponding carbonate substances. This removes CO2 from the flue gas and reduces CO2 emissions during the coking production process. Chinese patent application publication number CN119607831A discloses a "carbon dioxide capture and wastewater resource treatment method based on cavitation flotation," which introduces a solution containing calcium and magnesium ions into the flue gas to absorb CO2.

[0005] In addition, the temperature of the raw gas discharged from the top space of the coke oven carbonization chamber to the riser is about 700-750℃. In the conventional raw gas treatment process, an ammonia spraying device is set in the gas collecting pipe to cool the raw gas. After cooling by ammonia spraying, not only the high-temperature thermal energy of the raw gas in this temperature range is wasted, but also the tar organic vapor in the raw gas is condensed into tar, which is easy to clog and corrode the pipeline during the subsequent gas purification process. Summary of the Invention

[0006] The present invention provides a method for converting tar / crude benzene in coke oven raw gas into combustible gas. By introducing CO2 into the top space of the coke oven carbonization chamber, tar / crude benzene vapor is converted into fuel gas. Flexible regulation of the ratio of tar and fuel gas products can be achieved, while the resource utilization efficiency of CO2 is improved and greenhouse gas emissions are reduced. This provides a new way for the coking industry to achieve the conversion of tar, crude benzene and fuel gas.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for converting tar / crude benzene in coke oven raw gas into combustible gas. When the coke oven is built, a CO2 vent is opened on the top of the carbonization chamber. During coking in the coke oven, when the temperature of the top space of the carbonization chamber reaches 710-1050°C, CO2 gas is introduced into the top space of the carbonization chamber through the CO2 vent. The CO2 reacts with the tar / crude benzene organic vapor in the high-temperature raw gas to generate combustible gas, thereby increasing the combustible gas yield and reducing the tar yield.

[0009] Along the length of the coke oven, CO2 vents are opened on the top of each carbonization chamber in the area from the second vertical fire channel on the coke side to the second vertical fire channel on the machine side; when the temperature of the top space of a carbonization chamber reaches the set temperature, CO2 gas is introduced into the top space of the corresponding carbonization chamber.

[0010] The number of the CO2 vent holes is 1 to 7 along the length of the corresponding carbonization chamber.

[0011] The flow rate of CO2 gas introduced from the CO2 vent into the top space of the carbonization chamber is 0.1-1.7m 3 / t·min, where t represents per ton of dry coal.

[0012] The process of introducing CO2 gas into the top space of the carbonization chamber from the CO2 vent begins when the temperature of the top space of the carbonization chamber reaches the set temperature and ends when coking is completed.

[0013] The coke oven is a top-loading coke oven or a ramming coke oven; the carbonization chamber top space height is increased by reducing the coal loading height in the carbonization chamber, or the coke oven heating level is reduced when designing a new coke oven, so as to ensure that the carbonization chamber top space temperature reaches 710-1050°C.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1) By introducing CO2 into the top space of the coke oven carbonization chamber, tar / crude benzene vapor is converted into fuel gas, which can achieve flexible control of the ratio of tar to fuel gas products;

[0016] 2) Utilizing the thermal energy of high-temperature raw coal gas to realize the resource utilization of CO2, improving the resource utilization efficiency of CO2, reducing greenhouse gas emissions, and providing a new way for the coking industry to realize the conversion of tar, crude benzene and gas;

[0017] 3) Compared with the conventional method of directly extracting the raw gas from the furnace top through the riser and then cooling it, this method can effectively avoid the waste of high-temperature heat energy of the raw gas and the environmental pollution caused by the subsequent recovery of chemical products in the gas purification process system;

[0018] 4) The high-temperature heat energy of the raw gas in the coke oven carbonization chamber roof space is fully utilized to smoothly convert tar / crude benzene organic vapor into low-molecular-weight fuel gas, effectively reducing the tar vapor content in the raw gas. Compared with the conventional process of cooling the raw gas through a riser, this method can alleviate pipeline blockage and corrosion to a certain extent.

[0019] 5) Compared with the conventional process that easily causes carbon deposition in the top space of the carbonization chamber, the present invention can inhibit the generation of carbon deposition to a certain extent by using the weak oxidant CO2 to produce a Boudouard reaction (C+CO2→2CO) with tar vapor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the temperature variation curve of the top space of the coke oven carbonization chamber of the present invention. DETAILED DESCRIPTION

[0021] The present invention discloses a method for converting tar / crude benzene in coke oven raw gas into combustible gas. When the coke oven is built, a CO2 vent is opened on the top of the carbonization chamber. During coking in the coke oven, when the temperature of the top space of the carbonization chamber reaches 710-1050°C, CO2 gas is introduced into the top space of the carbonization chamber through the CO2 vent. The CO2 reacts with the tar / crude benzene organic vapor in the high-temperature raw gas to generate combustible gas, thereby increasing the combustible gas yield and reducing the tar yield.

[0022] Along the length of the coke oven, CO2 vents are opened on the top of each carbonization chamber in the area from the second vertical fire channel on the coke side to the second vertical fire channel on the machine side; when the temperature of the top space of a carbonization chamber reaches the set temperature, CO2 gas is introduced into the top space of the corresponding carbonization chamber.

[0023] The number of the CO2 vent holes is 1 to 7 along the length of the corresponding carbonization chamber.

[0024] The flow rate of CO2 gas introduced from the CO2 vent into the top space of the carbonization chamber is 0.1-1.7m 3 / t·min, where t represents per ton of dry coal.

[0025] The process of introducing CO2 gas into the top space of the carbonization chamber from the CO2 vent begins when the temperature of the top space of the carbonization chamber reaches the set temperature and ends when coking is completed.

[0026] The coke oven is a top-loading coke oven or a ramming coke oven; the carbonization chamber top space height is increased by reducing the coal loading height in the carbonization chamber, or the coke oven heating level is reduced when designing a new coke oven, so as to ensure that the carbonization chamber top space temperature reaches 710-1050°C.

[0027] The coking process, also known as coal dry distillation, can be categorized into low-temperature coking (500-550°C), medium-temperature coking (600-800°C), and high-temperature coking (900-1050°C), depending on the coal source and production objectives. High-temperature coking, primarily used to produce metallurgical coke, involves heating coking coal to approximately 1000°C in an airless atmosphere (high-temperature dry distillation). This process produces coke, coke oven gas, and other coking chemical products through thermal decomposition and coking.

[0028] In the coking process of coke ovens, the temperature of the carbonization chamber top space (the maximum temperature of the top space) is a key process parameter that directly affects the quality of coke and the yield of chemical products. The conventional control range is 800-850°C (modern large coke ovens, such as coke ovens with a carbonization chamber height of more than 6 meters), and under some operating conditions it may briefly reach 900°C. In the conventional coking process, when the temperature of the carbonization chamber top space is greater than 850°C, it will promote the cracking of methane (CH4→C+2H2), forming graphite on the top of the furnace and the inner wall of the riser, blocking the pipeline. Therefore, it is usually required that the continuous temperature does not exceed 900°C.

[0029] The core of the method for converting tar / crude benzene in coke oven raw gas into combustible gas is to introduce CO2 gas into the top space of the carbonization chamber after the coke oven is charged with coal and the temperature is raised to 710-1050°C. CO2 acts as a weak oxidant and reacts with the tar / crude benzene organic vapors in the raw gas to undergo Boudouard reaction and reforming reaction. The chemical process is as follows:

[0030] Boudouard reaction: C + CO2 → 2CO

[0031] Reforming reaction: C n H m +CO2→CO+H2+…

[0032] The Boudouard reaction can suppress carbon deposition in the carbonization chamber's top space, and the reforming reaction can further crack tar / crude benzene into low-molecular-weight fuel gas, thereby increasing the combustible gas yield and reducing the tar yield. Therefore, the coking method adopted in the present invention is essentially different from conventional coking methods. During the coking process, the maximum temperature of the carbonization chamber's top space is allowed to reach 1050°C.

[0033] The present invention provides three methods for achieving a carbonization chamber top space temperature of 710-1050°C: first, after an existing coke oven starts coking for a period of time, the carbonization chamber top space temperature can automatically reach 710-1050°C, meeting the application conditions; second, a newly built coke oven achieves this by reducing the coke oven heating level; third, an existing or newly built coke oven achieves this by reducing the amount of coal loaded in the carbonization chamber, thereby increasing the carbonization chamber top space height.

[0034] The said reduction of the coke oven heating level refers to reducing the heating level by increasing the combustion chamber height on the basis of conventional coke oven design when a new top-loading coal coke oven or a tamping coke oven is built. The specific reduction amount can be determined according to calculations to be between 1% and 90% of the conventional coke oven heating level.

[0035] The above-mentioned increase in the carbonization chamber top space height refers to increasing the carbonization chamber top space height on the basis of conventional coke oven design when building existing or newly constructed top-loaded coal coke ovens and ramming coke ovens. Specifically, this is achieved by reducing the original carbonization chamber coal loading height by 1% to 10%.

[0036] In order to ensure that the furnace wall of the carbonization chamber top space can withstand the high temperature of 710 ~ 1050 ℃, the furnace wall of the carbonization chamber top space adopts high temperature resistant masonry that can withstand the corresponding temperature.

[0037] The present invention generates CO by introducing CO2 into the top space of the carbonization chamber to react with the tar / crude benzene organic vapor in the high-temperature raw coal gas, thereby increasing the CO yield and reducing the tar yield. In the prior art, the Chinese patent application with publication number CN119914896A discloses "an automatic control system and control method for oxygen-enriched coal pyrolysis intake", which introduces CO2 into the pyrolysis furnace to improve the quality of the pyrolysis gas. The article "The mechanism of the influence of CO2 as a gasifying agent on the coal char-H2O gasification reaction" (written by Bai Yonghui, "Taiyuan University of Technology") studies the influence of CO2 on the release of pyrolysis gas and the formation of coke in the coal char-H2O / CO2 co-gasification process, but the focus of the above schemes is the reaction between CO2 and coal or coke, not the reaction between CO2 and raw coal gas as described in the present invention.

[0038] The following examples are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0039] [Example]

[0040] In this embodiment, a 40kg experimental coke oven was used for simulation experiments. When the furnace temperature reached 700°C, the coking coal was put into the furnace and the temperature was continuously raised. When the temperature of the furnace top space reached 710°C, CO2 was introduced until the coking was completed. The temperature change curve of the furnace top space is shown in Figure 2. Figure 1 shown.

[0041] The properties of the coal samples used in the simulation experiment are shown in Table 1.

[0042] Table 1 Coal sample properties (industrial analysis and elemental analysis)

[0043]

[0044] Note: * is the value obtained by subtraction method.

[0045] The experimental results of each embodiment are shown in Table 2.

[0046] Table 2 Experimental results

[0047]

[0048] Note: Coal gas components include hydrogen, carbon monoxide, methane and gaseous hydrocarbon compounds of C2 and above.

[0049] By comparing Comparative Example 1 with Example 1 and by comparing Comparative Example 2 with Example 2, it can be found that the tar yield decreases after the introduction of CO2, while the gas yield increases, indicating that the introduction of CO2 can convert a portion of the tar / crude benzene into gas, thereby achieving the purpose of adjusting the ratio of gas yield to tar yield.

[0050] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for converting tar / crude benzene in coke oven raw gas into combustible gas, characterized in that: When the coke oven is being built, a CO2 vent is opened on the top of the carbonization chamber. During the coking period, when the temperature of the top space of the carbonization chamber reaches 710-1050°C, CO2 gas is introduced into the top space of the carbonization chamber through the CO2 vent. CO2 reacts with the tar / crude benzene organic vapor in the high-temperature raw gas to generate combustible gas, thereby increasing the combustible gas yield and reducing the tar yield.

2. The method for converting tar / crude benzene in coke oven raw gas into combustible gas according to claim 1, characterized in that: Along the length of the coke oven, CO2 vents are opened on the top of each carbonization chamber in the area from the second vertical fire channel on the coke side to the second vertical fire channel on the machine side; when the temperature of the top space of a carbonization chamber reaches the set temperature, CO2 gas is introduced into the top space of the corresponding carbonization chamber.

3. The method for converting tar / crude benzene in coke oven raw gas into combustible gas according to claim 1 or 2, characterized in that: The number of the CO2 vent holes is 1 to 7 along the length of the corresponding carbonization chamber.

4. The method for converting tar / crude benzene in coke oven raw gas into combustible gas according to claim 1, characterized in that: The flow rate of CO2 gas introduced from the CO2 vent into the top space of the carbonization chamber is 0.1-1.7m 3 / t·min, where t represents per ton of dry coal.

5. The method for converting tar / crude benzene in coke oven raw gas into combustible gas according to claim 1, characterized in that: The process of introducing CO2 gas into the top space of the carbonization chamber from the CO2 vent begins when the temperature of the top space of the carbonization chamber reaches the set temperature and ends when coking is completed.

6. The method for converting tar / crude benzene in coke oven raw gas into combustible gas according to claim 1, characterized in that: The coke oven is a top-loading coke oven or a ramming coke oven; the carbonization chamber top space height is increased by reducing the coal loading height in the carbonization chamber, or the coke oven heating level is reduced when designing a new coke oven, so as to ensure that the carbonization chamber top space temperature reaches 710-1050°C.

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