Coke oven raw gas waste heat recovery coupling coking ammonia water regeneration method and device

Abstract

The invention discloses a method and a device for coke oven raw gas waste heat recovery coupled with coking ammonia water regeneration. The method comprises the following steps: carrying out primary heat exchange on coke oven raw gas generated by a coke oven and heat conduction oil by utilizing an ascending pipe heat exchanger; the heat-conducting oil subjected to primary heat exchange is conveyed to a reboiler of an ammonia distillation section and is subjected to secondary heat exchange with ammonia distillation wastewater from an ammonia distillation tower; ammonia gas generated by secondary heat exchange is introduced into the ammonia distillation tower to participate in an ammonia distillation reaction of residual ammonia water to obtain ammonia water, so that waste heat recovery of coke oven raw gas and regeneration of coking ammonia water are realized. The waste heat recovery process of the coke oven raw gas and the ammonia water vapor recovery process are coupled, so that the heat exchange efficiency of the coke oven raw gas and efficient utilization of waste heat can be improved, and the cost of the whole technological process is reduced.

Description

Technical Field

[0001] This invention relates to the technology of waste heat recovery and utilization of coke oven gas in the metallurgical industry, and more specifically, to a method and apparatus for waste heat recovery of raw coke oven gas coupled with coking ammonia water regeneration. Background Technology

[0002] With the increasingly severe environmental problems such as global warming, CO2 emission reduction has become a common challenge for humanity. The steel industry accounts for more than 15% of total CO2 emissions, and steel companies will face enormous pressure to reduce carbon emissions in the long term. The blast furnace-converter process remains the main process in steel production, with blast furnace ironmaking accounting for over 80% of CO2 emissions and over 70% of energy consumption. Therefore, blast furnace ironmaking is crucial for the steel industry to reduce energy consumption and CO2 emissions. One of the raw materials for blast furnace ironmaking is coke, which is produced through coke oven processes. It is estimated that 10% of the carbon emissions per ton of steel produced in the entire process come from coking. In addition, there are a large number of independent coking plants in China, resulting in substantial CO2 emissions from the coking industry, making CO2 emission reduction a significant challenge.

[0003] Emissions from the coking process are mainly concentrated in the combustion of blast furnace gas and coke oven gas, as well as some carbon dioxide emissions from the coking process itself. Additionally, reducing carbon dioxide emissions can be achieved by lowering the overall energy consumption of the coke oven production process.

[0004] The coke oven is a key piece of equipment and a major energy source in coking plants. The heat expenditure of a coke oven mainly consists of three parts: first, the high-temperature waste heat carried out by the red-hot coke exiting the coking chamber, accounting for approximately 37%; second, the medium-temperature waste heat carried out by the high-temperature raw coal gas discharged from the coke oven riser pipe, accounting for approximately 33%; and third, the low-temperature waste heat carried out by the exhaust gas discharged from the coke oven flue, accounting for approximately 17%. Among these, the raw coal gas is formed by the release of volatiles from coking coal during the coking process, typically at a temperature of around 600–800℃, and its sensible heat accounts for approximately 33% of the coke oven's heat expenditure. To lower the temperature of the raw coal gas for subsequent coking processes, traditional processes use ammonia injection for rapid cooling of the high-temperature raw coal gas, drastically reducing its temperature to 80–85℃. This process not only wastes a large amount of the raw coal gas's sensible heat but also consumes a significant amount of ammonia, water, and electricity, increasing wastewater discharge. The high-temperature waste heat from the red-hot coke has been recovered and used for power generation through dry quenching technology; the low-temperature waste heat from the flue gas has also been recovered using coal conditioning, coal drying, and heat pipe technology; however, the 800℃ raw coal gas discharged from the top riser pipe of the coke oven has the second highest heat output from the coke oven, and this medium-temperature waste heat is the last technical hurdle to be overcome in the recovery and utilization of coke oven waste heat and energy.

[0005] Chinese Patent Publication No. CN105605954A proposes a heat pipe-type waste heat recovery system for anti-adhesion raw coal gas. This system draws out the raw coal gas from the riser pipe for heat exchange. However, this system has complex heat exchange equipment, poor heat exchange efficiency, and also poses coal gas safety issues. Furthermore, it requires a large space on the furnace roof, resulting in high investment costs, poor heat exchange efficiency, and poor practicality. Chinese Patent Publication No. CN101888200A discloses a method and device for recovering waste heat from coke oven raw coal gas. This method mainly improves the refractory lining bricks of the riser pipe by using silicon carbide refractory lining bricks. By installing a semiconductor thermoelectric generator module on the outer wall of the riser pipe, the coke oven raw coal gas inside the riser pipe is used as the heat source for the semiconductor thermoelectric generator, and the riser pipe acts as the collector for the semiconductor thermoelectric generator, thus realizing the recovery of waste heat from the coke oven raw coal gas inside the riser pipe. This method has complex equipment, involves electrical issues under high-temperature conditions, poses safety concerns, and does not consider the temperature fluctuations of the coal gas, which could lead to instability in the power generation process. As can be seen from the previous analysis, since the riser pipe waste heat recovery is located at the top of the coke oven and there are a large number of riser pipes, the heat exchange device should be as simple as possible. At the same time, the heat exchange effect, the feasibility of installation at the top of the oven, and the investment and usability also need to be considered. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method and apparatus for coking waste gas waste heat recovery coupled with coking ammonia water regeneration. By coupling the coking waste gas waste heat recovery process with the ammonia water steam recovery process, the heat exchange efficiency of coking waste gas and the efficient utilization of waste heat can be improved, the overall process cost can be reduced, the production process can be simplified, the operation can be easily controlled, industrial production can be realized, and energy consumption in the coking and ironmaking processes can be reduced, resulting in significant environmental and economic benefits.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a method for recovering waste heat from coke oven raw gas coupled with the regeneration of coking ammonia water. The method utilizes a riser heat exchanger to perform a primary heat exchange between the coke oven raw gas and heat transfer oil. The heat transfer oil after the primary heat exchange is sent to the reboiler of the ammonia stripping section to perform a secondary heat exchange with the ammonia stripping wastewater from the ammonia stripping tower. The ammonia gas generated by the secondary heat exchange is introduced into the ammonia stripping tower to participate in the ammonia stripping reaction of the remaining ammonia water to obtain ammonia water, thereby realizing the recovery of waste heat from coke oven raw gas and the regeneration of coking ammonia water.

[0009] Preferably, it includes the following steps:

[0010] S1, the coke oven gas passes through the riser tube of the riser heat exchanger, and the heat transfer oil is introduced into the tube cavity of the riser heat exchanger. The coke oven gas and the heat transfer oil flow in opposite directions, and the waste heat of the coke oven gas is recovered through a single heat exchange.

[0011] S2, the heat transfer oil after the first heat exchange is transported through the pipeline to the reboiler of the ammonia stripping section, where it undergoes a second heat exchange with the ammonia stripping wastewater from the ammonia stripping tower, turning the ammonia stripping wastewater into ammonia gas. The heat transfer oil after the second heat exchange returns to the riser heat exchanger to continue participating in the first heat exchange.

[0012] S3, the ammonia gas obtained through secondary heat exchange participates in the ammonia stripping reaction in the ammonia stripping tower. The ammonia gas enters the ammonia stripping tower from the bottom and flows upward. The remaining ammonia water enters the ammonia stripping tower from the middle after heat exchange and flows downward. The gas generated at the top of the tower through the ammonia stripping reaction is condensed by the total condenser to obtain ammonia water. The ammonia stripping wastewater coming out from the bottom of the ammonia stripping tower enters the reboiler to participate in secondary heat exchange, thereby realizing the regeneration of coking ammonia water.

[0013] Preferably, in step S1, the inner wall of the heat exchange tube is made of high-temperature heat-resistant steel with a roughness of 0.03 to 0.05 micrometers.

[0014] Preferably, in step S1, the coke oven gas is coke oven gas produced during the coke oven production process; and the heat transfer oil is selected as high-temperature resistant heat transfer oil.

[0015] Preferably, in step S1, the inlet temperature of the coke oven gas is 650-800°C and the outlet temperature is 500-550°C; the inlet temperature of the heat transfer oil is 60-75°C and the outlet temperature is 280-320°C.

[0016] Preferably, in step S2, the temperature of the ammonia gas is 140–160°C.

[0017] Preferably, in step S3, the remaining ammonia water is selected from the sprayed ammonia water used for coke oven gas cooling, and the ammonia content in the remaining ammonia water is 5850-5980 mg / L.

[0018] Preferably, in step S3, the heat exchanger used for the heat exchange of the remaining ammonia water is the heat transfer oil after the first heat exchange, and the temperature of the remaining ammonia water after the heat exchange is 90-95°C.

[0019] Preferably, in step S3, the temperature of the gas at the top of the tower is 100–104°C.

[0020] Preferably, in step S3, the gas at the top of the tower is condensed by the total condenser and then enters the reflux tank to obtain ammonia water. Part of the ammonia water enters the finished ammonia water tank, and part of the ammonia water flows back from the top to the ammonia stripping tower to participate in the ammonia stripping reaction.

[0021] Preferably, in step S3, the ammonia content in the wastewater from the bottom of the ammonia stripping tower is ≤100mg / L.

[0022] A second aspect of the present invention provides an apparatus for recovering waste heat from coke oven raw gas coupled with regenerating coking ammonia water, comprising:

[0023] A riser heat exchanger is used to exchange heat between heat transfer oil and coke oven gas in a primary heat exchange process. The riser heat exchanger includes a riser for coke oven gas and a cavity for heat transfer oil. The cavity is fitted onto the riser and has a heat transfer oil inlet and a heat transfer oil outlet.

[0024] A reboiler is used to vaporize the ammonia stripping wastewater from the ammonia stripping tower into ammonia gas. The reboiler is connected to the heat transfer oil inlet and heat transfer oil outlet of the riser heat exchanger via pipelines. The reboiler is equipped with a wastewater inlet and an ammonia gas outlet.

[0025] An ammonia stripping tower is used to perform an ammonia stripping reaction on the remaining ammonia water. The bottom of the ammonia stripping tower is provided with a wastewater outlet connected to the wastewater inlet of the reboiler, the lower part is provided with an ammonia inlet connected to the ammonia outlet of the reboiler, the middle part is provided with a first ammonia water inlet connected to the remaining ammonia water, the upper part is provided with a second ammonia water inlet, and the top is provided with an ammonia outlet.

[0026] A total condenser is used to condense the top gas coming out of the top of the ammonia stripping tower; the total condenser is connected to the ammonia outlet at the top of the ammonia stripping tower.

[0027] The finished ammonia water tank is used to store the ammonia water generated after condensation in the total condenser. The finished ammonia water tank is connected to the total condenser through a return tank.

[0028] The apparatus for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration is used to perform the method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration as described in the first aspect of the present invention.

[0029] Preferably, the inner wall of the riser pipe is made of high-temperature steel with a roughness of 0.03 to 0.05 micrometers.

[0030] Preferably, the cavity is cylindrical.

[0031] Preferably, it also includes a residual ammonia water tank and a residual ammonia water heat exchanger; the residual ammonia water in the residual ammonia water tank enters the ammonia stripping tower through the first ammonia water inlet after passing through the residual ammonia water heat exchanger; the residual ammonia water heat exchanger is provided with a first inlet and a first outlet, the first inlet is connected to the heat transfer oil outlet of the riser heat exchanger, and the first outlet is connected to the heat transfer oil inlet of the riser heat exchanger.

[0032] The beneficial effects of this invention are:

[0033] 1. This invention couples the recovery of waste heat from coke oven raw gas and the recovery and regeneration of coking ammonia water in the coke oven riser pipe. The heat exchange device is directly installed on the riser pipe and heat exchange is carried out using heat transfer oil. This greatly simplifies the process, reduces investment, improves heat exchange effect, and reduces the increase in energy consumption and energy loss caused by temperature changes throughout the process.

[0034] 2. This invention utilizes heat transfer oil as a heat exchange medium to conduct countercurrent heat exchange with the raw coke oven gas in the coke oven riser pipe. After heat exchange, the heat transfer oil enters the ammonia water evaporation and recovery process through a pipeline. The heat transfer oil is used to heat the ammonia stripping wastewater in the reboiler. After heating, the wastewater in the ammonia stripping wastewater re-enters the distillation tower for ammonia stripping, achieving the separation of ammonia gas and water, and finally obtaining a high concentration of ammonia water.

[0035] 3. This invention utilizes the coke oven gas generated during the coking process of steel plants to exchange heat with heat transfer oil, thereby realizing the recovery of waste heat from the coke oven gas in steel plants. At the same time, the heat absorbed by the heat transfer oil is used in the ammonia stripping section to exchange heat with the ammonia stripping wastewater, thus achieving efficient utilization of recovered waste heat. This invention couples the process of waste heat recovery from coke oven gas with ammonia water steam recovery, providing a new path for the recovery of waste heat from coke oven gas and the steam recovery and utilization of residual ammonia water in the coking process.

[0036] 4. This invention effectively avoids the wall-hanging and blockage problems caused by tar condensation in the waste heat recovery process of coke oven raw gas, and finds a new path for the heat source of the ammonia stripping section; it effectively avoids the problems of complex heat exchange equipment, poor heat exchange effect, gas safety issues, large space occupation, high investment, poor heat exchange effect and practicality of some current waste heat recovery systems. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the scaling in the device for recovering waste heat from coke oven raw gas and regenerating coking ammonia water according to the present invention.

[0038] In the diagram, 1 is the riser heat exchanger; 11 is the riser pipe; 12 is the tube cavity; 2 is the reboiler; 3 is the ammonia stripping tower; 4 is the total condenser; 5 is the reflux tank; 6 is the finished ammonia water tank; 7 is the residual ammonia water tank; and 8 is the residual ammonia water heat exchanger. Detailed Implementation

[0039] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] In response to the current requirements for carbon emission reduction and energy conservation and cost reduction in production, and also to the problem that a large amount of waste heat from coke oven gas in the coking process is not being fully utilized, current waste heat recovery systems suffer from complex heat exchange equipment, poor heat exchange efficiency, and gas safety issues, as well as requiring a large space, resulting in high investment costs, poor heat exchange efficiency, and poor practicality. This invention provides a method for coke oven gas waste heat recovery coupled with coking ammonia water regeneration. This method not only provides a new approach for efficient heat exchange in coke oven gas systems, but also offers a new pathway for reducing energy consumption through ammonia water evaporation and recovery. By coupling the coke oven gas waste heat recovery process with the efficient reuse of waste heat, the heat exchange efficiency of coke oven gas and the efficient utilization of waste heat can be improved, reducing the overall process cost, simplifying the production process, making operation easier to control, enabling industrialized production, reducing energy consumption in the coking and ironmaking processes, and yielding significant environmental and economic benefits.

[0041] Combination Figure 1 As shown, the method for recovering waste heat from coke oven raw gas coupled with the regeneration of coking ammonia water of the present invention utilizes a riser heat exchanger 1 to perform a primary heat exchange between the coke oven raw gas and heat transfer oil. The heat transfer oil after the primary heat exchange is sent to the reboiler 2 of the ammonia stripping section for a secondary heat exchange with the ammonia stripping wastewater from the ammonia stripping tower 3. The ammonia gas generated by the secondary heat exchange is introduced into the ammonia stripping tower 3 to participate in the ammonia stripping reaction of the remaining ammonia water to obtain ammonia water, thereby realizing the recovery of waste heat from coke oven raw gas and the regeneration of coking ammonia water.

[0042] Combination Figure 1 As shown, the method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration of the present invention specifically includes the following steps:

[0043] S1, the coke oven gas passes through the riser pipe 11 of the riser heat exchanger 1, and the heat transfer oil is introduced through the tube 12 of the riser heat exchanger 1. The coke oven gas and the heat transfer oil flow in opposite directions, and the waste heat of the coke oven gas is recovered through a single heat exchange.

[0044] Coke oven gas is the raw gas produced during the coke oven production process in steel enterprises. It mainly contains hydrogen and methane, as well as small amounts of long-chain alkanes, benzene compounds, and tar containing small amounts of dust. High-temperature resistant heat transfer oil, such as heat transfer oil resistant to 350℃, is selected.

[0045] Coke oven gas and heat transfer oil undergo primary heat exchange using a riser heat exchanger 1. The coke oven gas passes through the riser pipe 11 of the riser heat exchanger 1, while the heat transfer oil enters through the tube 12 of the riser heat exchanger 1. The coke oven gas and heat transfer oil flow in opposite directions, achieving waste heat recovery from the coke oven gas through primary heat exchange. The inlet temperature of the coke oven gas is 650–800℃, and the outlet temperature is 500–550℃. The inlet temperature of the heat transfer oil is 60–75℃, and the outlet temperature is 280–320℃.

[0046] The aforementioned riser heat exchanger 1 is a self-designed component, comprising a riser pipe 11 and a cylindrical cavity 12 welded to its outer wall. Coke oven gas generated in the coke oven is introduced into the riser pipe 11. The inner wall of the riser pipe 11 is made of high-temperature heat-resistant steel with a roughness of 0.03–0.05 micrometers to prevent carbon buildup on the inner wall. Heat transfer oil is introduced into the cavity 12 to exchange heat with the coke oven gas introduced into the riser pipe 11. The specifications of the riser heat exchanger 1 can be determined according to actual conditions, for example, the following specifications: the inner diameter of the riser pipe 11 is 500–550 mm, the outer diameter of the cavity 12 is 650–680 mm, and the length of the heat exchange section is 1.8–2.2 meters.

[0047] S2, the heat transfer oil after the first heat exchange is transported through the pipeline to the reboiler 2 of the ammonia stripping section, where it undergoes a second heat exchange with the ammonia stripping wastewater from the ammonia stripping tower 3, turning the ammonia stripping wastewater into ammonia gas. The heat transfer oil after the second heat exchange returns to the riser heat exchanger 1 to continue participating in the first heat exchange.

[0048] During the secondary heat exchange process, the ammonia-steaming wastewater is converted into ammonia gas at a temperature of 140–160°C.

[0049] S3, the ammonia gas obtained through secondary heat exchange participates in the ammonia stripping reaction in ammonia stripping tower 3. The ammonia gas enters ammonia stripping tower 3 from the bottom and flows upward. The remaining ammonia water enters ammonia stripping tower 3 from the middle after heat exchange and flows downward. The gas generated at the top of the tower after the ammonia stripping reaction is condensed by the total condenser 4 to obtain ammonia water. The ammonia stripping wastewater coming out from the bottom of ammonia stripping tower 3 enters the reboiler 2 to participate in secondary heat exchange, thereby realizing the regeneration of coking ammonia water.

[0050] The residual ammonia water is selected from the sprayed ammonia water used for coke oven gas cooling, and the ammonia content in the residual ammonia water is 5850-5980 mg / L. After heat exchange, the temperature of the residual ammonia water reaches 90-95℃.

[0051] The ammonia stripping tower 3 used in the above-mentioned ammonia stripping reaction has a wastewater outlet at the bottom connected to the wastewater inlet of the reboiler 2, an ammonia inlet at the bottom connected to the ammonia outlet of the reboiler 2, a first ammonia inlet in the middle connected to the remaining ammonia water, a second ammonia inlet at the top, and an ammonia outlet at the top. The ammonia stripping tower 3 can be equipped with 24 trays. In the above-mentioned ammonia stripping reaction process, ammonia gas enters from the fourth tray of the ammonia stripping tower 3 and flows upward. The remaining ammonia water, after being heated by the heat exchanger (the heat exchanger uses heat transfer oil after the first heat exchange), reaches a temperature of 90-95℃ and enters from the 15th tray of the ammonia stripping tower 3 and flows downward. During the ammonia stripping process, the gas at the top of the tower is condensed by the total condenser 4 and enters the reflux tank 5 and then the finished ammonia water tank 6. Some of the ammonia water flows back from the twentieth tray into the ammonia stripping tower 3 to continue participating in the ammonia stripping reaction.

[0052] After the ammonia stripping process is completed, the ammonia stripping wastewater coming out of the bottom of ammonia stripping tower 3 is tested to measure the effectiveness of the ammonia stripping process. In the method of the present invention, the ammonia content in the ammonia stripping wastewater coming out of the bottom of ammonia stripping tower 3 is ≤100mg / L.

[0053] Combination Figure 1 As shown, the present invention also provides an apparatus for coking oven waste heat recovery coupled with coking ammonia water regeneration, for performing the above-mentioned coking oven waste heat recovery coupled with coking ammonia water regeneration method, which includes a riser heat exchanger 1, a reboiler 2, an ammonia stripping tower 3, a total condenser 4, and a finished ammonia water tank 6.

[0054] Combination Figure 1 As shown, the riser heat exchanger 1 is used to exchange heat between heat transfer oil and coke oven gas. The riser heat exchanger 1 includes a riser pipe 11 through which the coke oven gas passes and a cavity 12 through which the heat transfer oil passes. The cavity 12 is fitted onto the riser pipe 11 and has a heat transfer oil inlet and a heat transfer oil outlet. In a specific embodiment, the inner wall of the riser pipe 11 is made of high-temperature steel with a roughness of 0.03 to 0.05 micrometers to prevent carbon buildup on the inner wall. The inner diameter of the riser pipe 11 is 500 to 550 mm. The cavity 12 is cylindrical and welded to the outer wall of the riser pipe 11. The outer diameter of the cavity 12 is 650 to 680 mm, and the length of the heat exchange section is 1.8 to 2.2 meters.

[0055] Combination Figure 1 As shown, the reboiler 2 is used to vaporize the ammonia stripping wastewater from the ammonia stripping tower 3 into ammonia gas; the reboiler 2 is connected to the heat transfer oil inlet and heat transfer oil outlet of the riser heat exchanger 1 through pipes respectively, and the reboiler 2 is provided with a wastewater inlet and an ammonia gas outlet.

[0056] Combination Figure 1 As shown, the ammonia stripping tower 3 is used to perform ammonia stripping reaction on the remaining ammonia water; the bottom of the ammonia stripping tower 3 is provided with a wastewater outlet connected to the wastewater inlet of the reboiler 2, the lower part is provided with an ammonia inlet connected to the ammonia outlet of the reboiler 2, the middle part is provided with a first ammonia water inlet connected to the remaining ammonia water, the upper part is provided with a second ammonia water inlet, and the top is provided with an ammonia outlet.

[0057] Combination Figure 1 As shown, the total condenser 4 is used to condense the top gas coming out of the top of the ammonia stripping tower 3; the total condenser 4 is connected to the ammonia outlet at the top of the ammonia stripping tower 3.

[0058] Combination Figure 1 As shown, the finished ammonia water tank 6 is used to store the ammonia water generated after condensation in the total condenser 4. The finished ammonia water tank 6 is connected to the total condenser 4 through a reflux tank 5. The reflux tank 5 is connected to the second ammonia water inlet of the ammonia stripping tower 3 through a pipe, so that some of the ammonia water can flow back to the ammonia stripping tower 3 to continue participating in the ammonia stripping reaction.

[0059] Combination Figure 1 As shown, the device for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration also includes a residual ammonia water tank 7 and a residual ammonia water heat exchanger 8; the residual ammonia water in the residual ammonia water tank 7 enters the ammonia stripping tower 3 through the first ammonia water inlet after passing through the residual ammonia water heat exchanger 8; the residual ammonia water heat exchanger 8 is provided with a first inlet and a first outlet, the first inlet is connected to the heat transfer oil outlet of the riser heat exchanger 1, and the first outlet is connected to the heat transfer oil inlet of the riser heat exchanger 1.

[0060] Example 1

[0061] This embodiment employs a method of recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration to recover waste heat from coke oven raw gas. The specific process is as follows:

[0062] The coke oven gas is the raw coke oven gas produced during the coking process. The riser heat exchanger is a self-designed system. The riser tube carries the raw coke oven gas, and its inner wall is made of high-temperature heat-resistant steel. A cylindrical cavity is welded to the outer wall of the riser tube, and heat transfer oil resistant to 350℃ is introduced into the cavity to exchange heat with the raw coke oven gas. The inner diameter of the riser tube is 500mm, the outer diameter of the cavity is 650mm, and the height of the heat exchange section is 1.8 meters. Coke oven gas and heat transfer oil flow counter-currently. The inlet temperature of the coke oven gas is 650℃, and the outlet temperature is 500℃. The inlet temperature of the heat transfer oil is 60℃, and the outlet temperature is 280℃. After one heat exchange, the heat transfer oil is transported via pipeline to the reboiler in the ammonia stripping section, where it undergoes a second heat exchange with the ammonia stripping wastewater from the ammonia stripping tower. This converts the wastewater into ammonia vapor at 140℃, which then enters the ammonia stripping tower for the ammonia stripping reaction. The ammonia stripping tower has 24 trays. The ammonia vapor obtained from the second heat exchange enters from the fourth tray and flows upward. The residual ammonia water with a concentration of 5850 mg / L, after heat exchange, reaches a temperature of 90℃ and enters from the 15th tray of the ammonia stripping tower, flowing downward. After the ammonia stripping process, the gas at the top of the tower passes through a condenser, enters a reflux tank, and then enters the finished ammonia water tank. Part of the ammonia water flows back into the ammonia stripping tower from the twentieth tray. The gas temperature exiting from the top of the tower was 100℃. After ammonia stripping was completed, the wastewater was tested to evaluate the effectiveness of the stripping process. The test results showed that the ammonia content in the wastewater was 95 mg / L.

[0063] Example 2

[0064] This embodiment employs a method of recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration to recover waste heat from coke oven raw gas. The specific process is as follows:

[0065] The raw coke oven gas is the raw coal gas produced during the coking plant's production process. The riser heat exchanger is a self-designed system. The raw coke oven gas flows through the riser pipe, and its inner wall is made of high-temperature heat-resistant steel. A cylindrical cavity is welded to the outer wall of the riser pipe, and heat transfer oil with a temperature resistance of 350℃ is introduced into the cavity to exchange heat with the raw coke oven gas introduced into the pipe. The inner diameter of the riser pipe is 520mm, the outer diameter of the cavity is 660mm, and the height of the heat exchange section is 2 meters. Coke oven gas and heat transfer oil flow counter-currently. The inlet temperature of the coke oven gas is 700℃, and the outlet temperature is 520℃. The inlet temperature of the heat transfer oil is 65℃, and the outlet temperature is 290℃. After one heat exchange, the heat transfer oil is transported via pipeline to the reboiler in the ammonia stripping section, where it undergoes a second heat exchange with the ammonia stripping wastewater from the ammonia stripping tower. This converts the wastewater into ammonia vapor at 145℃, which then enters the ammonia stripping tower for the ammonia stripping reaction. The ammonia stripping tower has 24 trays. The ammonia vapor obtained from the second heat exchange enters from the fourth tray and flows upward. The residual ammonia water with a concentration of 5900 mg / L, after heat exchange, reaches a temperature of 92℃ and enters from the 15th tray of the ammonia stripping tower, flowing downward. After the ammonia stripping process, the gas at the top of the tower passes through a condenser, enters a reflux tank, and then enters the finished ammonia water tank. Part of the ammonia water flows back into the ammonia stripping tower from the twentieth tray. The gas temperature exiting from the top of the tower was 102℃. After ammonia stripping was completed, the wastewater was tested to evaluate the effectiveness of the stripping process. The test results showed an ammonia content of 90 mg / L in the wastewater.

[0066] Example 3

[0067] This embodiment employs a method of recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration to recover waste heat from coke oven raw gas. The specific process is as follows:

[0068] The raw coke oven gas is the raw coal gas produced during the coking process. The riser heat exchanger is a self-designed device. The raw coke oven gas passes through the riser pipe, and its inner wall is made of high-temperature heat-resistant steel. A cylindrical cavity is welded to the outer wall of the riser pipe, and heat transfer oil resistant to 350℃ is introduced into the cavity to exchange heat with the raw coal gas introduced into the pipe. The inner diameter of the pipe is 540mm, the outer diameter of the cavity is 670mm, and the height of the heat exchange section is 2.2 meters. Coke oven gas and heat transfer oil flow counter-currently. The inlet temperature of the coke oven gas is 750℃, and the outlet temperature is 540℃. The inlet temperature of the heat transfer oil is 70℃, and the outlet temperature is 310℃. After one heat exchange, the heat transfer oil is transported via pipeline to the reboiler in the ammonia stripping section, where it undergoes a second heat exchange with the ammonia stripping wastewater from the ammonia stripping tower. This converts the wastewater into ammonia vapor at 155℃, which then enters the ammonia stripping tower for the ammonia stripping reaction. The ammonia stripping tower has 24 trays. The ammonia vapor obtained from the second heat exchange enters from the fourth tray and flows upward. The residual ammonia water with a concentration of 5950 mg / L, after heat exchange, reaches a temperature of 95℃ and enters from the 15th tray of the ammonia stripping tower, flowing downward. After the ammonia stripping process, the gas at the top of the tower passes through a total condenser, enters a reflux tank, and then enters the finished ammonia water tank. Part of the ammonia water flows back into the ammonia stripping tower from the twentieth tray. The gas temperature exiting from the top of the tower was 103℃. After ammonia stripping was completed, the wastewater was tested to evaluate the effectiveness of the stripping process. The test results showed an ammonia content of 88 mg / L in the wastewater.

[0069] Example 4

[0070] This embodiment employs a method of recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration to recover waste heat from coke oven raw gas. The specific process is as follows:

[0071] Coke oven gas is the raw coal gas produced during the coking plant's production process. The riser heat exchanger is a self-designed system. The riser pipe carries the raw coal gas, and its inner wall is made of high-temperature heat-resistant steel. A cylindrical cavity is welded to the outer wall of the riser pipe, through which heat transfer oil flows, exchanging heat with the coke oven gas. The riser pipe has an inner diameter of 550mm, an outer cavity diameter of 680mm, and a height of 2.2 meters. The coke oven gas and heat transfer oil flow counter-currently. The inlet temperature of the coke oven gas is 800℃, and the outlet temperature is 550℃. The inlet temperature of the heat transfer oil is 75℃, and the outlet temperature is 320℃. After the first heat exchange, the heat transfer oil is transported via pipeline to the reboiler in the ammonia stripping section, where it undergoes a second heat exchange with ammonia stripping wastewater from the ammonia stripping tower. This converts the wastewater into ammonia vapor at 160℃, which then enters the ammonia stripping tower for the ammonia stripping reaction. The ammonia stripping tower used in the ammonia stripping reaction has 24 trays. Ammonia vapor obtained from the secondary heat exchange enters from the fourth tray and flows upwards. Residual ammonia water with a concentration of 5980 mg / L, after heat exchange, reaches a temperature of 95℃ and enters from the 15th tray, flowing downwards. After the ammonia stripping process, the gas at the top of the tower passes through a total condenser, enters a reflux tank, and then flows into the finished ammonia water tank. Part of the ammonia water flows back into the ammonia stripping tower from the twentieth tray. The temperature of the gas exiting from the top of the tower is 104℃. After ammonia stripping, the wastewater is tested to evaluate the effectiveness of the process. The test results show that the ammonia content in the wastewater is 81 mg / L.

[0072] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for recovering waste heat from coke oven raw gas coupled with regeneration of coking ammonia water, characterized in that, The coke oven gas and heat transfer oil are exchanged in a primary heat exchange using a riser heat exchanger. The heat transfer oil after the primary heat exchange is sent to the reboiler of the ammonia stripping section for a secondary heat exchange with the ammonia stripping wastewater from the ammonia stripping tower. The ammonia gas generated in the secondary heat exchange is fed into the ammonia stripping tower to participate in the ammonia stripping reaction of the remaining ammonia water to obtain ammonia water, thus realizing the waste heat recovery of the coke oven gas and the regeneration of coking ammonia water.

2. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 1, characterized in that, Includes the following steps: S1, the coke oven gas passes through the riser tube of the riser heat exchanger, and the heat transfer oil is introduced into the tube cavity of the riser heat exchanger. The coke oven gas and the heat transfer oil flow in opposite directions, and the waste heat of the coke oven gas is recovered through a single heat exchange. S2, the heat transfer oil after the first heat exchange is transported through the pipeline to the reboiler of the ammonia stripping section, where it undergoes a second heat exchange with the ammonia stripping wastewater from the ammonia stripping tower, turning the ammonia stripping wastewater into ammonia gas. The heat transfer oil after the second heat exchange returns to the riser heat exchanger to continue participating in the first heat exchange. S3, the ammonia gas obtained through secondary heat exchange participates in the ammonia stripping reaction in the ammonia stripping tower. The ammonia gas enters the ammonia stripping tower from the bottom and flows upward. The remaining ammonia water enters the ammonia stripping tower from the middle after heat exchange and flows downward. The gas generated at the top of the tower through the ammonia stripping reaction is condensed by the total condenser to obtain ammonia water. The ammonia stripping wastewater coming out from the bottom of the ammonia stripping tower enters the reboiler to participate in secondary heat exchange, thereby realizing the regeneration of coking ammonia water.

3. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S1, the inner wall of the heat exchange tube is made of high-temperature heat-resistant steel with a roughness of 0.03 to 0.05 micrometers.

4. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S1, the coke oven gas is the coke oven gas produced during the coke oven production process; the heat transfer oil is selected as high-temperature resistant heat transfer oil.

5. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S1, the inlet temperature of the coke oven gas is 650-800℃ and the outlet temperature is 500-550℃; the inlet temperature of the heat transfer oil is 60-75℃ and the outlet temperature is 280-320℃.

6. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S2, the temperature of the ammonia gas is 140–160°C.

7. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S3, the remaining ammonia water is selected from the sprayed ammonia water used for coke oven gas cooling, and the ammonia content in the remaining ammonia water is 5850-5980 mg / L.

8. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S3, the heat exchanger used for the heat exchange of the remaining ammonia water is the heat transfer oil after the first heat exchange, and the temperature of the remaining ammonia water after the heat exchange is 90-95℃.

9. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S3, the temperature of the gas at the top of the tower is 100–104°C.

10. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S3, the gas at the top of the tower is condensed by the total condenser and then enters the reflux tank to obtain ammonia water. Part of the ammonia water enters the finished ammonia water tank, and part of the ammonia water flows back from the top to the ammonia stripping tower to participate in the ammonia stripping reaction.

11. The method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 2, characterized in that, In step S3, the ammonia content in the ammonia stripping wastewater coming out of the bottom of the ammonia stripping tower is ≤100mg / L.

12. A device for recovering waste heat from coke oven raw gas coupled with regenerating coking ammonia water, characterized in that, include A riser heat exchanger is used to exchange heat between heat transfer oil and coke oven gas in a primary heat exchange process. The riser heat exchanger includes a riser pipe and a cavity through which the heat transfer oil passes. The cavity is fitted onto the riser pipe and has a heat transfer oil inlet and a heat transfer oil outlet. A reboiler is used to vaporize the ammonia stripping wastewater from the ammonia stripping tower into ammonia gas. The reboiler is connected to the heat transfer oil inlet and heat transfer oil outlet of the riser heat exchanger via pipelines. The reboiler is equipped with a wastewater inlet and an ammonia gas outlet. An ammonia stripping tower is used to perform an ammonia stripping reaction on the remaining ammonia water. The bottom of the ammonia stripping tower is provided with a wastewater outlet connected to the wastewater inlet of the reboiler, the lower part is provided with an ammonia inlet connected to the ammonia outlet of the reboiler, the middle part is provided with a first ammonia water inlet connected to the remaining ammonia water, the upper part is provided with a second ammonia water inlet, and the top is provided with an ammonia outlet. A total condenser is used to condense the top gas coming out of the top of the ammonia stripping tower; the total condenser is connected to the ammonia outlet at the top of the ammonia stripping tower. The finished ammonia water tank is used to store the ammonia water generated after condensation in the total condenser. The finished ammonia water tank is connected to the total condenser through a return tank. The apparatus for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration is used to perform the method for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration as described in any one of claims 1 to 11.

13. The apparatus for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 12, characterized in that, The cavity is cylindrical.

14. The apparatus for recovering waste heat from coke oven raw gas coupled with coking ammonia water regeneration according to claim 12, characterized in that, It also includes a residual ammonia water tank and a residual ammonia water heat exchanger; the residual ammonia water in the residual ammonia water tank passes through the residual ammonia water heat exchanger and then enters the ammonia stripping tower through the first ammonia water inlet; the residual ammonia water heat exchanger is provided with a first inlet and a first outlet, the first inlet is connected to the heat transfer oil outlet of the riser heat exchanger, and the first outlet is connected to the heat transfer oil inlet of the riser heat exchanger.

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