A high-efficiency desulfurization tower for coal underground gasification coal gas

Abstract

The utility model relates to coal underground gasification technical field discloses a kind of high-efficiency desulfurization tower for coal underground gasification coal gas, wherein desulfurization tower includes desulfurization tower body, upper section inner component assembly, lower section inner component assembly, liquid extraction component and liquid processing component.Upper section inner component assembly is metal regular packing layer, and lower section inner component assembly includes multilayer sieve plate structure, liquid extraction component collects liquid from upper section space and guides to the outside of tower body, and liquid processing component is injected to lower section space after filtering treatment to the liquid discharged.The utility model solves the technical problem that traditional desulfurization tower desulfurization efficiency is low, and the ability to resist synthetic gas component fluctuation is poor, and easy to produce foaming liquid overflow by two-section inner component combination, liquid extraction filtration injection mechanism, realizes the technical effect of efficient desulfurization, stable operation, anti-foaming.

Description

Technical Field

[0001] This utility model relates to the field of underground coal gasification technology, and more specifically, it relates to a high-efficiency desulfurization tower for underground coal gasification. Background Technology

[0002] Underground coal gasification technology directly converts coal into product gas through controlled combustion and gasification reactions in underground coal seams. This product gas can be used as a feedstock for fuel production, chemical production, and power generation. The product gas generated through underground coal gasification typically contains effective components such as CO, CO2, H2, and CH4, as well as inorganic sulfur, organic sulfur, coal tar, and coal slag dust particles. These sulfur-containing impurities are toxic to catalysts in downstream chemical production processes, causing irreversible damage, reducing production efficiency, and even leading to safety accidents. Therefore, sulfur-containing impurities must be removed before using the product gas as feedstock for downstream syngas chemical industries.

[0003] Existing technologies typically employ desulfurization towers to remove sulfur-containing impurities from crude syngas. The crude syngas is brought into countercurrent contact with the desulfurization absorbent in the desulfurization tower, and the sulfur-containing components in the syngas are removed into the desulfurization absorbent by utilizing the dissolving and absorbing properties of the desulfurization absorbent.

[0004] However, traditional desulfurization towers suffer from low desulfurization efficiency, high equipment investment, unstable operation, and poor ability to withstand fluctuations in syngas composition. In particular, the crude syngas produced by underground coal gasification technology has a high tar content. During the desulfurization process, coal tar and the desulfurization absorbent form a bubble-prone system, continuously generating a large amount of foam during gas-liquid contact, causing flooding or even submersion of the desulfurization tower, drastically deteriorating the desulfurization effect and affecting the normal and stable operation of the unit. The reasons for these technical problems are: First, the internal structure of traditional desulfurization towers is simple and cannot simultaneously meet the requirements of high mass transfer efficiency and impurity resistance; second, coal tar and solid particulate impurities in the crude syngas promote foam generation during gas-liquid contact after entering the desulfurization absorbent, and traditional desulfurization towers lack measures to remove impurities from the absorbent; third, the uneven liquid distribution in traditional desulfurization towers leads to gas-liquid two-phase flow deviation, reducing mass transfer efficiency. Utility Model Content

[0005] This invention provides a high-efficiency desulfurization tower for underground coal gasification, solving the technical problems of low desulfurization efficiency, unstable operation, poor ability to resist syngas composition fluctuations, and easy foam flooding in traditional desulfurization towers.

[0006] This utility model discloses a high-efficiency desulfurization tower for underground coal gasification gas, comprising: a desulfurization tower body, wherein the lower part of the desulfurization tower body has a gas inlet, the upper part has a gas outlet, the top has a liquid inlet, and the bottom has a liquid outlet; an upper section internal component assembly, disposed in the upper section space of the desulfurization tower body, the upper section internal component assembly being a structured metal packing layer; a lower section internal component assembly, disposed in the lower section space of the desulfurization tower body, the lower section internal component assembly including a multi-layer sieve plate structure; and a liquid extraction assembly disposed in the upper section space and the lower section space. Between the spaces, a liquid collection unit is used to collect the liquid flowing down from the upper space and guide it to the outside of the desulfurization tower body; a liquid treatment component is set outside the desulfurization tower body and connected to the liquid extraction component, used to filter the liquid discharged from the liquid extraction component and reinject the treated liquid back into the lower space; wherein, the liquid extraction component includes an extraction tray and a liquid collection pipe, the extraction tray has a gas through hole for gas to pass through, the upper end of the liquid collection pipe is located on the upper surface of the extraction tray, and the lower end penetrates the extraction tray and extends to the outside of the desulfurization tower body.

[0007] This utility model discloses a desulfurization method, which uses the aforementioned high-efficiency desulfurization tower for underground coal gasification to perform the following steps: Rough syngas enters the lower section space through a gas inlet, and undergoes preliminary desulfurization by passing through a multi-layer sieve structure from bottom to top and contacting the desulfurization absorbent; the pre-desulfurized rough syngas enters the upper section space through the gas passage of the liquid extraction component; the liquid flowing down from the upper section space collects in the liquid extraction component and is guided to the outside of the desulfurization tower body; the guided liquid is filtered in the liquid treatment component to remove solid particles and coal tar impurities, and then reinjected into the lower section space as the desulfurization absorbent; the rough syngas entering the upper section space undergoes deep desulfurization by counter-current contact with the lean desulfurization absorbent from the liquid distribution component through a metal structured packing layer; the desulfurized syngas is discharged through the gas outlet, and the rich desulfurization absorbent, which has absorbed sulfur-containing impurities, is discharged through the liquid outlet.

[0008] Furthermore, the liquid treatment assembly includes a filtration device, a reflux pump, and a reinjection pipeline. The inlet of the filtration device is connected to the outlet of the liquid extraction assembly. The filtration device contains a filter medium, which is a porous material layer or a filter screen, used to trap solid particles and coal tar impurities in the liquid. The inlet of the reflux pump is connected to the outlet of the filtration device, and the outlet is connected to the reinjection pipeline. The reinjection pipeline is connected to a liquid reinjection port opened on the side wall of the desulfurization tower body, and the position of the liquid reinjection port corresponds to the upper area of ​​the lower section space.

[0009] Furthermore, a liquid dispersion structure is provided at the end of the reinjection pipe. The liquid dispersion structure includes a horizontally arranged annular distribution pipe and multiple radial branch pipes. The annular distribution pipe is connected to the reinjection pipe, and the inner ends of the multiple radial branch pipes are connected to the annular distribution pipe. The radial branch pipes are evenly distributed along the circumference of the annular distribution pipe, and multiple small holes are opened on the radial branch pipes.

[0010] Furthermore, the liquid treatment assembly also includes a bypass pipeline and a switching valve. The bypass pipeline connects the outlet of the filtration device to the solution regeneration device conveying pipeline outside the desulfurization tower body. The switching valve is located at the connection position between the reinjection pipeline and the bypass pipeline, and the switching valve is a three-way valve.

[0011] Furthermore, the structured metal packing layer is formed by vertically stacking multiple structured metal packing units, each of which has a regularly arranged corrugated structure that forms an inclined flow channel; the structured metal packing unit is a standard orifice plate corrugated packing or Mellapak series packing.

[0012] Furthermore, the multi-layer sieve plate structure is arranged at intervals along the vertical direction. Each layer of the sieve plate structure includes a sieve plate tray, a downcomer, an overflow weir, and a tray support structure. The sieve plate tray is a horizontally arranged circular plate with multiple sieve holes evenly distributed on it. The overflow weir is located at the edge area of ​​the sieve plate tray and is a vertically arranged arc-shaped baffle. The downcomer connects two adjacent layers of sieve plate structures, with its upper end connected to the overflow area of ​​the upper sieve plate structure and its lower end extending into the space below the sieve plate tray of the lower sieve plate structure.

[0013] Furthermore, it also includes a liquid distribution component, which is disposed at the top of the upper space. The liquid distribution component is a tray-type liquid distributor. The tray-type liquid distributor includes a main liquid tank, multiple auxiliary liquid tanks, and multiple spray holes. The main liquid tank is an annular tank and is connected to a liquid inlet. The multiple auxiliary liquid tanks are evenly distributed radially, and the outer end of each auxiliary liquid tank is connected to the main liquid tank. The spray holes are disposed at the bottom of the auxiliary liquid tanks and are arranged at equal intervals along the length of the auxiliary liquid tanks.

[0014] Furthermore, it also includes a bottom assembly, which is located at the bottom of the desulfurization tower body; the bottom assembly includes a bottom space, a liquid level detection device, and a liquid level regulating device, wherein the liquid level detection device is a liquid level gauge installed on the side wall of the bottom space, and the liquid level regulating device is a liquid level regulating valve installed on the liquid outlet pipe.

[0015] Furthermore, a high-temperature cyclone separator is installed upstream of the gas inlet of the desulfurization tower body. The high-temperature cyclone separator is connected to the product well outlet of the underground coal gasification unit, and a rotating airflow channel is formed inside the high-temperature cyclone separator.

[0016] This invention employs a two-section internal component combination of an upper section with a structured metal packing layer and a lower section with a multi-layer sieve plate structure. This allows the desulfurization tower to simultaneously meet the requirements of high mass transfer efficiency and impurity resistance, overcoming the limitation of a single internal component structure being unable to simultaneously meet multiple performance requirements. By incorporating a liquid extraction component and a liquid treatment component, the liquid flowing down from the upper section is extracted and filtered to remove solid particles and coal tar impurities before being reinjected into the lower section. This reduces the impurity content in the desulfurization absorbent in the lower section and decreases the possibility of foam formation during gas-liquid contact. A tray-type liquid distributor is installed at the top of the upper section, achieving uniform distribution of the desulfurization absorbent at the top of the packing layer and preventing gas-liquid two-phase flow deviation. This invention solves the technical problems of low desulfurization efficiency, unstable operation, and easy foam flooding in traditional desulfurization towers, achieving the technical effects of improved desulfurization efficiency, enhanced operational stability, and suppression of foam formation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the device; In the diagram: 1. Coal underground gasification unit; 2. Crude syngas from the product well outlet; 3. High-temperature cyclone separator; 4. Crude syngas from the cyclone separator outlet; 5. Rich absorbent solution at the bottom of the tower; 6. Absorbent solution regeneration unit; 7. Lean absorbent solution for desulfurization; 8. Intermediate extracted absorbent; 9. Extracted liquid filtration unit; 10. Solution reinjection pump; 11. Desulfurization absorption solution reinjected to the lower part; 12. Clean syngas after desulfurization at the top of the tower; 13. Subsequent syngas utilization unit; 14. Tray-type liquid distributor; 15. Structured metal packing; 16. Intermediate liquid extraction unit; 17. Sieve plate; 18. Bottom level gauge; 19. Bottom level regulating valve. Detailed Implementation

[0018] Underground coal gasification technology directly converts coal into product gas through controlled combustion and gasification reactions in underground coal seams. This product gas can be used as a feedstock for fuel production, chemical production, and power generation. In the underground coal gasification process, an oxidant is injected into the coal seam through an injection well, forming a combustion zone, a gasification zone, and a pyrolysis zone within the coal seam. The high-temperature product gas flows downstream from the gasification zone and is eventually transported to the surface from the product well.

[0019] The product gas generated from underground coal gasification typically contains effective components such as CO, CO2, H2, and CH4, as well as inorganic sulfur, organic sulfur, coal tar, and coal slag dust particles. These sulfur-containing impurities are toxic to catalysts in downstream chemical production processes, causing irreversible damage, reducing production efficiency, and even leading to safety accidents. Therefore, sulfur-containing impurities must be removed before using the product gas as feedstock for downstream syngas chemical industries.

[0020] Existing technologies typically employ desulfurization towers to remove sulfur-containing impurities from crude syngas. This is achieved by counter-current contact between the crude syngas and the desulfurization absorbent within the tower, utilizing the absorbent's ability to dissolve and absorb sulfur-containing components. However, traditional desulfurization towers suffer from low desulfurization efficiency, high equipment investment, unstable operation, and poor resistance to fluctuations in syngas composition. Particularly concerning is the high tar content in the crude syngas produced by underground coal gasification technology. During desulfurization, the coal tar and absorbent form a bubble-prone system, continuously generating large amounts of foam during gas-liquid contact. This can cause flooding or even submersion of the desulfurization tower, drastically deteriorating the desulfurization effect and affecting the normal and stable operation of the plant.

[0021] The reasons for the above technical problems are as follows: First, the internal structure of traditional desulfurization towers is simple and cannot simultaneously meet the requirements of high mass transfer efficiency and impurity resistance; Second, after coal tar and solid particulate impurities in crude syngas enter the desulfurization absorbent, they promote foam generation during the gas-liquid contact process, while traditional desulfurization towers lack measures to remove impurities from the desulfurization absorbent; Third, the uneven liquid distribution in traditional desulfurization towers leads to gas-liquid two-phase flow deviation and reduced mass transfer efficiency.

[0022] According to an embodiment of this invention, a high-efficiency desulfurization tower for underground coal gasification gas is used to desulfurize the crude syngas from underground coal gasification product wells. The high-efficiency desulfurization tower for underground coal gasification gas includes at least a desulfurization tower body, upper internal components, lower internal components, a liquid distribution component, a liquid extraction component, a liquid treatment component, and a tower bottom component.

[0023] A high-temperature cyclone separator 3 is installed upstream of the gas inlet of the desulfurization tower. The high-temperature cyclone separator 3 is connected to the product well outlet of the underground coal gasification unit 1. The high-temperature cyclone separator 3 is a gas-solid separation device. A rotating airflow channel is formed inside the high-temperature cyclone separator 3. Centrifugal force is used to separate solid dust particles and suspended droplets in the crude syngas from the airflow and allow them to settle to the bottom collection area. The crude syngas, after preliminary gas-solid separation, is discharged from the top outlet of the high-temperature cyclone separator 3. The outlet of the high-temperature cyclone separator 3 is connected to the gas inlet of the desulfurization tower via a gas transmission pipeline, completing the transportation of crude syngas from the underground coal gasification unit 1 to the desulfurization tower.

[0024] The desulfurization tower is a vertical cylindrical pressure vessel. A gas inlet is located at the bottom of the tower to receive crude syngas that has undergone preliminary gas-solid separation, supplied from the high-temperature cyclone separator 3. A gas outlet is located at the top of the tower to output the desulfurized syngas. A liquid inlet is located at the top of the tower to receive lean desulfurization absorbent from the solution regeneration unit 6. A liquid outlet is located at the bottom of the tower to output rich desulfurization absorbent that has absorbed sulfur-containing impurities. The desulfurization tower is vertically divided into an upper section and a lower section, with the upper section located above the lower section.

[0025] The upper internal components are located within the upper space and consist of 15 layers of structured metal packing. Each 15-layer structured metal packing unit is vertically stacked, with a regularly arranged corrugated structure forming numerous inclined flow channels. This allows for thorough contact between the gas flowing upwards within these channels and the liquid flowing downwards along their surfaces. The 15-layer structured metal packing is fixed to the inner wall of the desulfurization tower body by a supporting member, a ring-shaped support beam welded to the inner wall of the desulfurization tower body.

[0026] In some embodiments, the structured metal packing unit 15 is a standard orifice plate corrugated packing or a Mellapak series packing. The standard orifice plate corrugated packing has regularly arranged holes on its corrugated plate, which increases the turbulence of the gas and liquid phases and improves the mass transfer efficiency.

[0027] The lower internal components are located within the lower space and include a multi-layer sieve plate structure 17, which is spaced vertically. Each sieve plate structure 17 includes a sieve tray, a downcomer, an overflow weir, and a tray support structure. The sieve tray is a horizontally arranged circular plate with multiple uniformly distributed sieve holes. The sieve holes are circular through holes that penetrate the sieve tray, allowing gas to pass through from bottom to top. The overflow weir is located at the edge of the sieve tray and is a vertically arranged arc-shaped baffle. The lower end of the overflow weir is fixedly connected to the upper surface of the sieve tray, and the arc-shaped structure of the overflow weir and the edge of the sieve tray together form an overflow area. A downcomer connects two adjacent sieve tray structures 17. The downcomer is a vertically arranged cylindrical channel. The upper end of the downcomer connects to the overflow area of ​​the upper sieve tray structure 17, and the lower end extends into the space below the sieve tray of the lower sieve tray structure 17. Liquid flows from the upper sieve tray structure 17 to the lower sieve tray structure 17 through the downcomer. The tray support structure includes multiple support beams arranged radially. The outer ends of the support beams are fixed to the inner wall of the desulfurization tower body, and the inner sides of the support beams support the lower surface of the sieve tray.

[0028] The liquid distribution assembly is located at the top of the upper section of the space. The liquid distribution assembly is a tray-type liquid distributor 14. The tray-type liquid distributor 14 includes a main liquid tank, multiple auxiliary liquid tanks, and multiple spray holes. The main liquid tank is an annular tank, fixed to the upper part of the inner wall of the desulfurization tower. The interior of the main liquid tank forms an annular receiving space. The main liquid tank is connected to the liquid inlet, and the desulfurization absorbent lean liquid from the solution regeneration device 6 enters the main liquid tank. The auxiliary liquid tanks are strip-shaped tanks, and multiple auxiliary liquid tanks are evenly distributed radially. The outer end of each auxiliary liquid tank is connected to the main liquid tank. Multiple spray holes are opened at the bottom of the auxiliary liquid tanks, and the spray holes are arranged at equal intervals along the length of the auxiliary liquid tanks. The desulfurization absorbent lean liquid flows from the main liquid tank into the auxiliary liquid tanks, and then is evenly sprayed onto the top surface of the metal structured packing layer 15 through the spray holes.

[0029] The liquid extraction assembly is located at the transition position between the upper and lower sections of the desulfurization tower. It collects the liquid flowing down from the upper section and guides it to the outside of the tower. The assembly includes an extraction tray and a collection pipe. The extraction tray is a horizontally positioned circular plate with multiple gas through-holes evenly distributed across it. These through-holes allow gas to enter the upper section from the lower section. The collection pipe is located in the central area of ​​the extraction tray. It is a vertically extending cylindrical pipe with its upper opening on the upper surface of the extraction tray and its lower end extending through the tray to the outside of the desulfurization tower. The collection pipe connects to a liquid extraction port on the side wall of the desulfurization tower. Liquid flowing down from the upper section collects on the upper surface of the extraction tray and then flows into the collection pipe, from where it is discharged to the outside of the desulfurization tower through the collection pipe and the liquid extraction port.

[0030] The liquid treatment assembly is located outside the desulfurization tower body and is connected to the liquid extraction assembly. The liquid treatment assembly filters the liquid discharged from the liquid extraction assembly and reinjects the treated liquid into the lower section space. The liquid treatment assembly includes a filter device 9, a reflux pump, and a reinjection pipeline. The inlet of the filter device 9 is connected to the liquid extraction outlet. The filter device 9 contains a filter medium, which is a porous material layer or filter screen. The filter medium mechanically filters the passing liquid, trapping solid particles and coal tar impurities. The inlet of the reflux pump is connected to the outlet of the filter device 9. The reflux pump is a centrifugal pump or a positive displacement pump, providing the power to transport the filtered liquid. The reinjection pipeline is connected to the outlet of the reflux pump and connects to a liquid reinjection port on the side wall of the desulfurization tower body. The location of the liquid reinjection port corresponds to the upper area of ​​the lower section space. The filtered liquid re-enters the lower section space through the reinjection pipeline and the liquid reinjection port, participating in gas-liquid contact as the desulfurization absorbent in the lower section space.

[0031] Furthermore, to avoid disturbing the gas flow in the lower space due to the reinjected liquid, a liquid dispersion structure is installed at the end of the reinjection pipe. The liquid dispersion structure includes a horizontally arranged annular distribution pipe and multiple radial branch pipes. The annular distribution pipe is connected to the reinjection pipe, and the inner ends of the multiple radial branch pipes are connected to the annular distribution pipe. The radial branch pipes are evenly distributed along the circumference of the annular distribution pipe, and multiple small holes are opened on the radial branch pipes. The reinjected liquid is sprayed out in the form of a fine stream through the small holes, reducing the impact on the gas flow.

[0032] The reboiler assembly is located at the bottom of the desulfurization tower body. It is used to accumulate and buffer the liquid flowing down from the lower section. The reboiler assembly includes a reboiler space, a level detection device, and a level regulating device. The reboiler space is the containment space at the bottom of the desulfurization tower body, and its height is determined according to the required liquid buffering capacity. The level detection device is a level gauge installed on the side wall of the reboiler space, which monitors the liquid level in real time. The level regulating device is a level regulating valve 19, located on the liquid outlet pipe. The opening of the level regulating valve 19 is adjusted according to the liquid level detected by the level detection device. By adjusting the opening of the level regulating valve 19, the outflow rate of the liquid in the reboiler space is controlled, maintaining a stable liquid level within the reboiler space.

[0033] Furthermore, to adapt to the operational needs of the underground coal gasification unit 1 under different loads, the liquid treatment component also includes a bypass pipeline and a switching valve. The bypass pipeline connects the outlet of the filter unit 9 to the delivery pipeline of the solution regeneration unit 6 outside the desulfurization tower. The switching valve is located at the connection point between the reinjection pipeline and the bypass pipeline. The switching valve is a three-way valve, and its state is adjusted to control the flow direction of the filtered liquid. When the underground coal gasification unit 1 operates under lower loads or uses air gasification, the volume of crude syngas and its tar and dust content are lower, reducing the likelihood of foaming in the system. In this case, the switching valve switches to bypass mode, and the filtered liquid is directly sent to the solution regeneration unit 6 without being reinjected into the lower space. The lower space serves only as a gas flow channel. When the underground coal gasification unit 1 operates under normal or high loads, the switching valve switches to reinjection mode, and the filtered liquid is reinjected into the lower space through the reinjection pipeline.

[0034] The gas outlet of the desulfurization tower is connected to the downstream syngas utilization unit 13 via a gas pipeline. The downstream syngas utilization unit 13 is a chemical synthesis unit or a power generation unit, used to utilize the desulfurized syngas for chemical product production or power generation. The liquid outlet of the desulfurization tower is connected to the solution regeneration unit 6 via a liquid pipeline. The solution regeneration unit 6 is used to desulfurize and regenerate the rich desulfurization absorbent that has absorbed sulfur-containing impurities. It separates the sulfur-containing components in the rich desulfurization absorbent after desorption or reaction conversion, regenerating the rich desulfurization absorbent into a lean desulfurization absorbent. The lean outlet of the solution regeneration unit 6 is connected to the liquid inlet of the desulfurization tower via a liquid pipeline, realizing the recycling of the desulfurization absorbent.

[0035] According to an embodiment of this invention, the operation process of a high-efficiency desulfurization tower for underground coal gasification includes: Step 1: The crude syngas from the underground coal gasification product well passes through a high-temperature cyclone separator 3 to remove some solid dust impurities and suspended droplets, and then enters the bottom of the lower section of the desulfurization tower through the gas inlet. The temperature of the crude syngas is 275 to 300 degrees Celsius.

[0036] In step two, the crude syngas moves upwards in the lower section space, passing sequentially through the multi-layer sieve plate structure 17. At each sieve plate structure 17, the crude syngas passes upwards through the sieve holes on the sieve plate tray, maintaining a certain thickness of liquid layer on the tray. As the gas passes through the liquid layer, it comes into contact with the liquid, and some of the sulfur-containing impurities in the gas dissolve into the liquid. The liquid on the sieve plate tray flows laterally, overflowing into the downcomer at the overflow weir, and then flows to the next sieve plate structure 17 through the downcomer. The flow directions of the gas and liquid are approximately perpendicular and intersecting. The liquid flowing down from the upper section space and filtered by the liquid treatment component before being reinjected serves as the desulfurization absorbent in the lower section space, contacting the gas on the sieve plate structure 17.

[0037] Step 3: The crude syngas that has undergone preliminary desulfurization in the lower section enters the upper section through the gas passage on the extraction tray of the liquid extraction component. At the same time, the liquid flowing down from the upper section collects on the upper surface of the extraction tray and flows into the liquid collection pipe, and is discharged to the outside of the desulfurization tower body through the liquid extraction outlet.

[0038] Step four: The discharged liquid enters the filtration device 9 of the liquid treatment assembly. The filtration device 9 uses a filter medium to trap any solid particles and coal tar impurities that may be present in the liquid. The filtered clean liquid is pressurized by a return pump and then reinjected into the upper area of ​​the lower section space through a return pipe and a liquid return port, continuing to be used as the desulfurization absorbent in the lower section space. The filtration process reduces the content of solid particles and coal tar in the desulfurization absorbent in the lower section space, reducing the possibility of foam formation during gas-liquid contact.

[0039] In some embodiments, step four further includes: when the underground coal gasification unit 1 is operating at a low load, the filtered liquid is switched to bypass mode by switching valves. The filtered liquid is not reinjected into the lower space but is directly sent to the solution regeneration unit 6. At this time, the lower space is only used as a gas flow channel, which simplifies the operation.

[0040] Step 5: The crude syngas entering the upper space continues to move upwards within the upper space, passing through 15 layers of structured metal packing. The lean desulfurization absorbent from the solution regeneration unit 6 enters the liquid distribution assembly through the liquid inlet. In the tray-type liquid distributor 14, the lean desulfurization absorbent flows from the main liquid tank into multiple auxiliary liquid tanks, and is then evenly sprayed onto the top surface of the 15 layers of structured metal packing through spray holes at the bottom of the auxiliary liquid tanks. The lean desulfurization absorbent flows downwards within the 15 layers of structured metal packing, fully contacting the crude syngas flowing upwards on the large contact area formed on the packing surface. Remaining sulfur-containing impurities in the crude syngas dissolve into the lean desulfurization absorbent, which then absorbs these impurities and transforms into desulfurization absorbent. Because the tray-type liquid distributor 14 achieves uniform liquid spraying, it avoids gas-liquid two-phase flow deviation and ensures high mass transfer efficiency.

[0041] Step Six: After deep desulfurization in the upper section, the sulfur impurity content of the syngas has been reduced to within the specified limits. The desulfurized syngas leaves the desulfurization tower body through the gas outlet and enters the downstream syngas utilization unit 13. The desulfurization absorbent liquid, which has absorbed sulfur impurities, flows from top to bottom in the upper section and reaches the extraction tray of the liquid extraction component. Part of the desulfurization absorbent liquid is extracted, filtered, and reinjected according to the processes in Steps Three and Four. The remaining desulfurization absorbent liquid continues to flow downward into the lower section, participates in the gas-liquid contact in the lower section, and finally flows to the bottom space of the tower.

[0042] Step seven: The desulfurization absorbent flowing into the bottom space of the tower has absorbed a large amount of sulfur-containing impurities, becoming a rich desulfurization absorbent. This rich absorbent accumulates in the bottom space and forms a certain liquid level. The liquid level detection device monitors the liquid level in the bottom space in real time, and the liquid level regulating device adjusts the opening of the liquid level regulating valve 19 according to the detected liquid level, controlling the outflow rate of the rich desulfurization absorbent through the liquid outlet to maintain a stable liquid level in the bottom space. The outflowing rich desulfurization absorbent is sent to the solution regeneration device 6 for desulfurization regeneration treatment. The regenerated lean desulfurization absorbent then re-enters the desulfurization tower body for recycling.

[0043] This embodiment employs a two-stage internal component combination of 15 layers of upper-section structured metal packing and 17 layers of lower-section multi-layer sieve plate structure, enabling the desulfurization tower to simultaneously meet the requirements of high mass transfer efficiency and impurity resistance. The 15 layers of structured metal packing feature excellent mass transfer performance, low pressure drop, and uniform fluid distribution, allowing for deep desulfurization of the already preliminarily desulfurized crude syngas in the upper section, achieving the expected desulfurization targets. The multi-layer sieve plate structure 17 is characterized by its simple structure, strong impurity resistance, and resistance to foaming systems. It is highly adaptable to the characteristics of crude syngas entering the desulfurization tower, such as high impurity content, high coal tar content, easy foaming, and large gas volume fluctuations, avoiding internal component blockage or performance degradation caused by high impurity content in the lower section of the desulfurization tower. By adopting a two-stage internal component combination, the limitations of a single internal component structure in simultaneously meeting multiple performance requirements are overcome, solving the problems of low desulfurization efficiency and unstable operation in traditional desulfurization towers.

[0044] This embodiment employs a liquid extraction component and a liquid treatment component to extract and filter the liquid flowing down from the upper section, removing solid particles and coal tar impurities before reinjecting it into the lower section as the desulfurization absorbent. The filtration process reduces the impurity content in the lower section's absorbent, minimizing the effect of impurities on foam formation during gas-liquid contact. By utilizing a liquid extraction, filtration, and reinjection mechanism, the adverse effects of coal tar and solid particle impurities in the crude syngas promoting foam formation in the absorbent are overcome. This solves the problem of continuous foam generation, flooding, and even tower submersion in desulfurization towers when processing tar-rich crude syngas, leading to a sharp deterioration in desulfurization efficiency.

[0045] This embodiment utilizes a tray-type liquid distributor 14 installed at the top of the upper section, enabling the lean desulfurization absorbent to be uniformly sprayed onto the top surface of the structured metal packing layer 15. The lean desulfurization absorbent flows from the main liquid tank into multiple auxiliary liquid tanks, and then is sprayed out through multiple spray holes at the bottom of the auxiliary liquid tanks. The spray holes are evenly spaced along the length of the auxiliary liquid tanks, and the auxiliary liquid tanks are uniformly distributed radially, achieving uniform liquid distribution at the top of the packing layer. The use of the tray-type liquid distributor 14 overcomes the unfavorable factors of uneven liquid distribution in traditional desulfurization towers, which leads to gas-liquid two-phase flow deviation, and solves the problem of low mass transfer efficiency in traditional desulfurization towers.

[0046] In summary, this embodiment achieves efficient desulfurization, stable operation, and anti-foaming effects through the synergistic effect of the two-stage internal components combination, liquid extraction, filtration and reinjection mechanism, and tank-type liquid distributor 14. This makes the desulfurization tower have the advantages of small footprint, low investment, low energy consumption and high desulfurization efficiency, and is particularly suitable for the desulfurization treatment of crude syngas from underground coal gasification products.

Claims

1. A high-efficiency desulfurization tower for underground coal gasification, characterized in that, include: The desulfurization tower body has a gas inlet at the bottom, a gas outlet at the top, a liquid inlet at the top, and a liquid outlet at the bottom. The upper internal components are disposed in the upper space of the desulfurization tower body, and the upper internal components are a structured metal packing layer. The lower internal components are disposed in the lower space of the desulfurization tower body, and the lower internal components include a multi-layer sieve plate structure. A liquid extraction component is disposed between the upper and lower sections of the space and is used to collect the liquid flowing down from the upper section and guide it to the outside of the desulfurization tower body. A liquid treatment component is disposed outside the desulfurization tower body and connected to the liquid extraction component, used to filter the liquid discharged from the liquid extraction component and reinject the treated liquid into the lower space. The liquid extraction assembly includes an extraction tray and a collection pipe. The extraction tray has a gas passage for gas to pass through. The upper end of the collection pipe is located on the upper surface of the extraction tray, and the lower end passes through the extraction tray and extends to the outside of the desulfurization tower body.

2. The high-efficiency desulfurization tower for underground coal gasification gas as described in claim 1, characterized in that, The liquid treatment assembly includes a filtration device, a reflux pump, and a reinjection pipeline. The inlet of the filtration device is connected to the outlet of the liquid extraction assembly. The filtration device contains a filter medium, which is a porous material layer or a filter screen, used to trap solid particles and coal tar impurities in the liquid. The inlet of the reflux pump is connected to the outlet of the filtration device, and the outlet is connected to the reinjection pipeline. The reinjection pipeline is connected to a liquid reinjection port opened on the side wall of the desulfurization tower. The location of the liquid reinjection port corresponds to the upper area of ​​the lower section space.

3. The high-efficiency desulfurization tower for underground coal gasification gas as described in claim 2, characterized in that, The end of the reinjection pipe is provided with a liquid dispersion structure, which includes a horizontally arranged annular distribution pipe and multiple radial branch pipes. The annular distribution pipe is connected to the reinjection pipe, and the inner ends of the multiple radial branch pipes are connected to the annular distribution pipe. The radial branch pipes are evenly distributed along the circumference of the annular distribution pipe, and multiple small holes are opened on the radial branch pipes.

4. The high-efficiency desulfurization tower for underground coal gasification gas as described in claim 2, characterized in that, The liquid treatment assembly also includes a bypass pipeline and a switching valve. The bypass pipeline connects the outlet of the filtration device to the solution regeneration device conveying pipeline outside the desulfurization tower. The switching valve is located at the connection point between the reinjection pipeline and the bypass pipeline, and the switching valve is a three-way valve.

5. The high-efficiency desulfurization tower for underground coal gasification gas as described in claim 1, characterized in that, The structured metal packing layer is formed by vertically stacking multiple structured metal packing units. The structured metal packing units have a regularly arranged corrugated structure, which forms an inclined flow channel. The structured metal packing units are standard orifice plate corrugated packing or Mellapak series packing.

6. The high-efficiency desulfurization tower for underground coal gasification gas as described in claim 1, characterized in that, The multi-layer sieve plate structure is arranged at intervals along the vertical direction. Each layer of the sieve plate structure includes a sieve plate tray, a downcomer, an overflow weir, and a tray support structure. The sieve plate tray is a horizontally arranged circular plate with multiple sieve holes evenly distributed on it. The overflow weir is located at the edge area of ​​the sieve plate tray and is a vertically arranged arc-shaped baffle. The downcomer connects two adjacent layers of sieve plate structures. The upper end of the downcomer is connected to the overflow area of ​​the upper layer of sieve plate structure, and the lower end extends into the space below the sieve plate tray of the lower layer of sieve plate structure.

7. The high-efficiency desulfurization tower for underground coal gasification gas as described in claim 1, characterized in that, It also includes a liquid distribution component, which is located at the top of the upper space. The liquid distribution component is a tray-type liquid distributor. The tray-type liquid distributor includes a main liquid tank, multiple auxiliary liquid tanks, and multiple spray holes. The main liquid tank is an annular tank and is connected to a liquid inlet. The multiple auxiliary liquid tanks are evenly distributed radially, and the outer end of each auxiliary liquid tank is connected to the main liquid tank. The spray holes are located at the bottom of the auxiliary liquid tanks and are arranged at equal intervals along the length of the auxiliary liquid tanks.

8. The high-efficiency desulfurization tower for underground coal gasification gas as described in claim 1, characterized in that, It also includes a bottom assembly, which is located at the bottom of the desulfurization tower body; the bottom assembly includes a bottom space, a liquid level detection device and a liquid level regulating device, the liquid level detection device is a liquid level gauge installed on the side wall of the bottom space, and the liquid level regulating device is a liquid level regulating valve installed on the liquid outlet pipe.

9. The high-efficiency desulfurization tower for underground coal gasification gas as described in claim 1, characterized in that, A high-temperature cyclone separator is installed upstream of the gas inlet of the desulfurization tower. The high-temperature cyclone separator is connected to the product well outlet of the underground coal gasification unit. A rotating airflow channel is formed inside the high-temperature cyclone separator.

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