Gasifier lock bucket slag discharge method and system

Abstract

The present invention discloses a slag discharge method and system for a gasifier lock bucket, and relates to the field of coal chemical industry. The method comprises: (1) a pressure relief step, wherein all the pressure relief gas in the lock bucket is discharged into a waste gas treatment device; (2) a gas stripping step, wherein after the pressure relief step is completed, gas stripping gas is introduced into the lock bucket to gasify the toxic and harmful gases dissolved in the slag water, and a mixture of the gas stripping gas and the toxic and harmful gases gasified from the slag water is also discharged into the waste gas treatment device; (3) after the step (2) is completed, slag discharge, flushing, pressurization and slag collection are performed in sequence, and after the slag collection is completed, the pressure relief step described in step (1) is returned to complete a slag discharge cycle. The method of the present invention protects the environment and also protects the workers around the slag pool from being harmed by toxic and harmful gases.

Description

Technical Field

[0001] The present invention relates to the technical field of coal chemical industry, and in particular to a method and system for discharging slag from a locking bucket of a gasifier. Background Art

[0002] Entrained-bed gasifiers generally discharge slag in liquid form, and are mostly equipped with a lock bucket slag discharge system. The typical working steps of the lock bucket slag discharge system are:

[0003] Step 1: After the slag collection is completed, the pressure relief step is entered. In this pressure relief step, the lock hopper inlet valve is closed and the lock hopper pressure relief valve is opened to relieve the pressure in the lock hopper;

[0004] Step 2: After the pressure relief is completed, the slag discharge step is started. In this slag discharge step, the lock bucket outlet valve is opened, and the slag and slag water in the lock bucket are discharged into the slag pool;

[0005] Step 3: After the slag discharge is completed, the flushing step begins. In this flushing step, the lock bucket flushing valve is opened to flush the lock bucket;

[0006] Step 4: After flushing, enter the pressurization step. In this pressurization step, open the lock bucket pressurization valve and pressurize the lock bucket with high-pressure water or high-pressure gas;

[0007] Step 5: After the pressure charging is completed, the slag collection step is entered. In the slag collection step, the lock bucket inlet valve is opened, and the lock bucket starts to collect the slag. After the slag collection step is completed, the pressure relief step in step 1 is returned to complete a slag discharge cycle.

[0008] In the slag discharge step, the slag water discharged with the slag contains gases such as hydrogen sulfide, ammonia, carbon monoxide, carbonyl sulfide and hydrogen cyanide, which pollute the environment and harm human health. The problems of the currently widely used lock bucket slag discharge method are listed as follows:

[0009] 1. Usually, the pressure relief step is controlled to minimize the toxic and harmful gases emitted by the lock bucket during slag discharge. The lock bucket pressure is reduced as much as possible during the pressure relief step in order to release the toxic and harmful gases dissolved in the slag water to the greatest extent. The pressure relief gas is generally discharged directly into the atmosphere (0MPaG); or at the beginning of the pressure relief, due to the high lock bucket pressure, the pressure relief gas is discharged to the flare equipment (the flare equipment is positive pressure and has a relatively high back pressure (generally between 0.01MPaG and 0.2MPaG)), and the pressure relief gas is discharged to the atmosphere after the lock bucket pressure is reduced. This disposal method pollutes the atmosphere. There are also cases where the pressure relief gas is led to the slag pool, and the pressure relief gas is discharged to the atmosphere through the slag pool. Because the slag pool is a semi-open structure, even if the slag pool is equipped with an induced draft fan, some toxic and harmful gases will be emitted into the working environment, which not only pollutes the air, but also endangers the personal health of the workers around the slag pool. In recent years, there has also been a process of introducing depressurized gas into an activated carbon bed with very low resistance drop, and then discharging it into the atmosphere after being adsorbed by the activated carbon. This treatment method only converts gaseous pollutants into solid pollutants, and the activated carbon that adsorbs toxic and harmful gases becomes hazardous solid waste, which requires further treatment by a qualified unit. At the same time, the adsorption effect needs to be further verified.

[0010] 2. Even if the pressure relief gas is discharged into the atmosphere and the pressure in the lock bucket is reduced to normal pressure by simply reducing the pressure, some toxic and harmful gases will still be emitted into the low-altitude air near the slag pool during the process of slag and slag water being discharged from the lock bucket into the slag pool, which not only pollutes the air but also endangers the health of workers near the slag pool.

[0011] The above two problems have long existed and are common in coal chemical enterprises. They not only pollute the air and deteriorate the working environment around the slag pool, but also seriously damage the health of the workers because many enterprises use cars to transport slag. However, the lock bucket slag discharge technology is not the research and development focus of coal gasification technology. The research focus of various research institutions and engineering companies is on extending the operation cycle and reducing oxygen and coal consumption. The environmental protection and occupational health problems caused by the currently widely used lock bucket slag discharge method have not attracted much attention. Summary of the invention

[0012] The researchers of the present invention have conducted focused research on the environmental and occupational health issues caused by the gasifier bucket slag discharge, and proposed a new gasifier bucket slag discharge method and system, which solves the problem that the currently widely used bucket slag discharge method causes toxic and harmful gases to pollute the atmosphere and endanger the health of on-site workers.

[0013] On the one hand, the present invention provides a slag discharge method for a gasifier lock bucket, comprising the following steps: (1) a pressure relief step, discharging the pressure relief gas in the lock bucket into a waste gas treatment device; (2) a gas stripping step, after the pressure relief step is completed, introducing gas stripping gas into the lock bucket to gasify the toxic and harmful gases dissolved in the slag water, and the mixture of the gas stripping gas and the toxic and harmful gases gasified from the slag water is also discharged into the waste gas treatment device; (3) after the step (2) is completed, slag discharge, flushing, pressurization and slag collection are performed in sequence, and after the slag collection is completed, the pressure relief step described in step (1) is returned to complete a slag discharge cycle.

[0014] Conventional lock bucket slag removal system mainly includes lock bucket, slag pool and slag picker etc. The lock bucket slag removal system is located downstream of the entrained flow gasifier, connected to the high pressure gasifier, opens the lock bucket inlet valve, closes the lock bucket pressure relief valve, and collects slag in the lock bucket.

[0015] In normal operation, there is a mixture of slag and slag water at the bottom of the gasifier. The slag and slag water are discharged through different outlets of the gasifier. Only slag is discharged into the lock bucket, but it is inevitably mixed with a small amount of slag water (the slag water discharged with the slag contains gases that are toxic and harmful to the human body); before the lock bucket is connected to the gasifier to collect slag, the inside of the lock bucket is pre-filled with water (as described below). During the slag collection, there will be slag and a large amount of slag water in the lock bucket. After the slag is collected, the lock bucket pressure relief valve is opened to discharge the toxic and harmful high-pressure gas in the lock bucket into the atmosphere, and the lock bucket outlet valve is opened to allow the slag and a large amount of slag water to finally be discharged from the bottom of the lock bucket into the slag pool.

[0016] The slag (and slag water) discharged from the gasifier is collected in the lock bucket of the lock bucket slag discharge system, which is the slag collection step (also known as the lock bucket slag collection step).

[0017] After the slag collecting step, a pressure relief step (lock bucket pressure relief step) is implemented.

[0018] In the method of the present invention, in the depressurization step of step (1), all the depressurized gas is discharged into a waste gas treatment device. The waste gas treatment device can be any non-polluting or low-polluting waste gas treatment device, preferably a flare device. The waste gas treatment device can treat toxic and harmful gases in the depressurized gas to avoid air pollution.

[0019] In the conventional decompression step, the decompression gas is directly or indirectly discharged into the atmosphere. In contrast, in step (1) of the method of the present invention, the decompression gas is completely discharged into the waste gas treatment equipment. Toxic and harmful gases in the decompression gas are removed in the waste gas treatment equipment to avoid air pollution.

[0020] Compared with the conventional situation that the decompression gas is discharged into the atmosphere and the final decompression pressure is basically as low as the atmospheric pressure, in step (1) of the method of the present invention, the final decompression pressure of the decompression step of the present invention must be higher than the atmospheric pressure, because the waste gas treatment equipment generally requires the intake pressure to be between 0.01MPaG and 0.3MPaG, and the toxic and harmful gases remaining in the slag water are more, and the remaining toxic and harmful gases can be further removed in the gas stripping step of step (2) of the present invention. In the method of the present invention, in the gas stripping step of step (2), the slag water is subjected to gas stripping, and the dissolved toxic and harmful gases are deeply removed. The concentration of toxic and harmful gases in the slag water of the gasifier lock bucket is reduced by the gas stripping method. Although the toxic and harmful gases in the slag water cannot be completely separated, the concentration of toxic and harmful gases in the slag water after gas stripping is much lower than its equilibrium concentration under atmospheric pressure. In this way, when the slag water is discharged from the lock bucket and enters the slag pool, no toxic and harmful gases will be emitted, thereby protecting the environment around the slag pool and the health of the workers around the slag pool. Another important function of the gas stripping step is that the gas stripping gas used for stripping toxic and harmful gases is introduced into the slag water, which provides conditions for the residual pressure relief gas in the previous step, i.e., the pressure relief step, to be discharged to the waste gas treatment equipment. After adding the gas stripping step, the pressure of the residual pressure relief gas can be increased to a pressure higher than the pressure required by the waste gas treatment equipment (for example, the pressure relief gas can be allowed to enter the flare equipment by increasing it to a pressure higher than the back pressure of the flare equipment), so that the residual pressure relief gas is also discharged to the waste gas treatment equipment, and the residual toxic and harmful gases in the slag water (more than the pressure relief to normal pressure) can be further removed in the gas stripping step.

[0021] In the method of the present invention, in step (3), the slag discharge, flushing, pressurizing and slag collection steps are all conventional operations. In the slag discharge step, the slag in the lock bucket and the slag water after gas lift are discharged together and enter the slag pool; in the flushing step, the slag discharge residue in the lock bucket is first flushed and enters the slag pool, and then the lock bucket is filled with flushing water; in the pressurizing step, the lock bucket flushing valve is closed and the lock bucket is pressurized. The gasifier is in a high-pressure state. Before connecting the lock bucket and the gasifier, if the lock bucket is not filled with water and pressurized, there will be a great impact after directly opening the connecting valve.

[0022] In one embodiment of the method of the present invention, in step (1), the final pressure relief pressure of the pressure relief step is 0.05 MPaG to 0.5 MPaG. In the actual operation of the lock bucket slag discharge of the fluidized bed gasifier, the final pressure relief pressure of the pressure relief step is determined according to the requirements of the supporting waste gas treatment equipment. The intake pressure required by the waste gas treatment equipment is generally between 0.01 MPaG and 0.3 MPaG. Considering the flow resistance of various parts such as equipment and pipelines, the final pressure relief pressure of the pressure relief step is generally between 0.05 MPaG and 0.5 MPaG, preferably between 0.1 MPaG and 0.3 MPaG. When the pressure of the pressure relief gas is higher than the intake pressure required by the waste gas treatment equipment (such as the back pressure of the flare equipment), the pressure relief gas is continuously discharged into the waste gas treatment equipment; until the final pressure relief pressure is reached, the pressure relief gas can no longer be discharged into the waste gas treatment equipment, and is further brought into the waste gas treatment equipment through step (2).

[0023] In one embodiment of the method of the present invention, in step (2), the stripping gas is selected from nitrogen, or other gases that are harmless to the human body, insoluble or slightly soluble in water and can be received by the waste gas treatment equipment.

[0024] In one embodiment of the method of the present invention, in step (2), the pressure of the stripping gas introduced is in the range of 0.1 MPaG to 1.0 MPaG, preferably in the range of 0.4 MPaG to 0.7 MPaG. In actual operation, the air intake pressure required by the waste gas treatment equipment is generally between 0.01 MPaG and 0.3 MPaG. Considering the static pressure of the slag water and the flow resistance of various parts such as the equipment and pipelines, the stripping gas pressure is generally in the range of 0.1 MPaG to 1.0 MPaG, preferably in the range of 0.4 MPaG to 0.7 MPaG, so as to ensure that the stripping gas and the mixture of toxic and harmful gases stripped from the slag water can enter the waste gas treatment equipment.

[0025] In other words, in the method of the present invention, the stripping gas pressure>the final pressure relief pressure>the inlet pressure required by the waste gas treatment equipment (for example, the flare back pressure).

[0026] In one embodiment of the method of the present invention, in step (2), air stripping gas is introduced into the lock bucket, and the air stripping intensity ranges from 1Nm 3 Air stripping gas / 1m 3 Slag water to 10Nm 3 Air stripping gas / 1m 3 Between slag and water, preferably 2Nm 3 Air stripping gas / 1m 3 Slag water to 4Nm 3 Air stripping gas / 1m 3The higher the gas lift intensity, the less toxic and harmful gases remain in the slag water. However, too high a gas lift intensity will consume more gas lift gas, and the gas lift effect will become less and less obvious.

[0027] The air lift strength has the meaning commonly recognized in the art. In the present invention, the air lift strength is the air lift strength of 1m 3 The standard cubic volume of lift gas required for slag water.

[0028] In a further embodiment of the method of the present invention, in step (2), gas stripping is introduced into the lock bucket, and the stripping time is generally 3 minutes to 10 minutes, preferably 4 minutes to 6 minutes. 3 Air stripping gas / 1m 3 Slag water to 4Nm 3 Air stripping gas / 1m 3 Within the gas lift intensity range of the slag water, the gas lift of toxic and harmful gases in the slag water in the lock bucket can be completed by introducing gas for 3 to 10 minutes, preferably 4 to 6 minutes.

[0029] In one embodiment of the method of the present invention, in step (2), the stripping gas enters the lock bucket through the lower pipe opening of the lock bucket, or the stripping gas enters the pipeline connected to the lower part of the lock bucket; preferably, the stripping gas enters the lock bucket through the lower pipe opening of the lock bucket, in order to improve the stripping effect. In step (2), a pipe opening can be added at the lower part of the lock bucket, and the stripping gas enters the lock bucket at the lower part of the lock bucket to strip the slag water; if the existing production device is technically upgraded and there is no available pipe opening at the lower part of the lock bucket, the stripping gas can also be connected to the pipeline connected to the lower part of the lock bucket. In this way, the stripping gas can indirectly enter the lower part of the lock bucket to strip the slag water. Preferably, the stripping gas directly enters the lock bucket through the lower pipe opening of the lock bucket. The lower part of the lock bucket refers to the lowest possible position of the lower section of the lock bucket. Introducing the stripping gas at the lowest possible position of the lower section of the lock bucket is conducive to better exerting the stripping effect.

[0030] In one embodiment of the method of the present invention, in step (2), a stripping gas distributor is arranged in the lock hopper to improve the stripping effect, minimize the solubility of toxic and harmful gases in the slag water, and save the use of stripping gas. The stripping gas distributor shall not have an adverse effect on the slag discharge. In the present invention, the particle size of the slag from the entrained flow gasifier is about 1-4 mm, and the particles are very loose, and such slag discharge will not have a significant adverse effect on the operation of the stripping gas distributor.

[0031] In one embodiment of the method of the present invention, in step (2), the stripping gas distributor can be a tubular distributor, and the main pipe and branch pipe of the tubular distributor are provided with a certain number of small holes, and the opening direction of the small holes is either downward or obliquely downward. In step (2), the stripping gas distributor can also be other types of gas distributors, preferably a tubular distributor.

[0032] Another aspect of the present invention provides a gasifier lock bucket slag discharge system, which comprises: a lock bucket, which is located below the gasifier, and a lock bucket inlet valve is arranged on the connecting pipeline between the lock bucket and the gasifier, and the connection or disconnection between the gasifier and the lock bucket is controlled by opening or closing the lock bucket inlet valve; an exhaust gas treatment device, which is located above the lock bucket, and a lock bucket pressure relief valve is arranged on the connecting pipeline between the lock bucket and the exhaust gas treatment device at the top of the lock bucket, and the pressure relief gas in the lock bucket is released by opening the lock bucket pressure relief valve. The slag is discharged to the waste gas treatment equipment; a stripping gas supply pipeline is connected to the lower part of the lock bucket so that the stripping gas can pass into the lock bucket from the lower part of the lock bucket; a slag pool is located below the lock bucket, and a lock bucket outlet valve is arranged on the connecting pipeline between the lock bucket and the slag pool, and the slag and slag water in the lock bucket are discharged into the slag pool by opening the lock bucket outlet valve; a slag scooping machine is used to scoop out the slag discharged from the lock bucket into the slag pool and transport it to the slag bucket, and then transport it away from the gasification furnace lock bucket slag discharge system through transportation equipment.

[0033] Conventional lock bucket slag removal system mainly includes lock bucket, slag pool and slag picker etc. The lock bucket slag removal system is located downstream of the entrained flow gasifier, connected to the high pressure gasifier, opens the lock bucket inlet valve, closes the lock bucket pressure relief valve, and collects slag in the lock bucket.

[0034] In normal operation, there is a mixture of slag and slag water at the bottom of the gasifier. The slag and slag water are discharged through different outlets of the gasifier. Only slag is discharged into the lock bucket, but it is inevitably mixed with a small amount of slag water (the slag water discharged with the slag contains gases that are toxic and harmful to the human body); before the lock bucket is connected to the gasifier to collect slag, the inside of the lock bucket is pre-filled with water (as described below). During the slag collection, there will be slag and a large amount of slag water in the lock bucket. After the slag is collected, the lock bucket pressure relief valve is opened to discharge the toxic and harmful high-pressure gas in the lock bucket into the atmosphere, and the lock bucket outlet valve is opened to allow the slag and a large amount of slag water to finally be discharged from the bottom of the lock bucket into the slag pool.

[0035] The present invention improves the traditional lock bucket slag discharge method. In the conventional lock bucket slag discharge system, the pressure relief gas is discharged directly or indirectly into the atmosphere. The present invention eliminates the pipeline for discharging the pressure relief gas directly or indirectly into the atmosphere, and adds a pipeline for discharging the pressure relief gas to the waste gas treatment equipment. The pressure relief gas is discharged to the waste gas treatment equipment. After the pressure relief gas is discharged into the waste gas treatment equipment, environmental pollution can be reduced.

[0036] The lock bucket slag discharge system of the present invention is additionally provided with a gas stripping gas supply pipeline, which is used to introduce gas stripping gas into the slag water in the lock bucket. After the slag water is gas stripped, the toxic and harmful gases dissolved therein are deeply removed, thereby reducing the concentration of toxic and harmful gases in the slag water in the lock bucket of the gasifier. Although the toxic and harmful gases in the slag water cannot be completely separated out, the concentration of toxic and harmful gases in the slag water after gas stripping is much lower than its equilibrium concentration under atmospheric pressure. In this way, when the slag water is discharged from the lock bucket into the slag pool, no toxic and harmful gases will be emitted, thereby protecting the environment around the slag pool and the health of the workers around the slag pool. Another important function of the gas stripping gas supply pipeline is to introduce a certain pressure of gas stripping gas into the slag water, which provides conditions for more pressure relief gas to be discharged to the waste gas treatment equipment. After adding a gas lift gas supply pipeline to supply a certain pressure of gas into the lock bucket, the pressure of the depressurized gas can be increased to a pressure above the pressure required by the waste gas treatment equipment, so that the depressurized gas can be fully discharged to the waste gas treatment equipment (for example, increasing the pressure to above the back pressure of the flare equipment can allow the depressurized gas to enter the flare equipment), and the remaining toxic and harmful gases in the slag water (more than when the pressure is released to normal pressure) can be further removed.

[0037] In the system of the present invention, the "lower part of the lock bucket" refers to the lowest possible position of the lower section of the lock bucket. Introducing gas lift gas at the lowest possible position of the lower section of the lock bucket is conducive to better exerting the gas lift effect.

[0038] In one embodiment of the system of the present invention, a pipe opening is opened in the conical section at the lower part of the lock bucket, and the number of the pipe openings can be one or more. The stripping gas supply pipeline is connected to the pipe opening, so that the stripping gas can pass into the lock bucket from the lower part of the lock bucket to strip the slag water and remove toxic and harmful gases in the slag water.

[0039] In one embodiment of the system of the present invention, if the existing lock bucket slag discharge system of the gasifier that has been put into production is technically upgraded, and there is no available pipe opening at the bottom of the lock bucket, then a connecting port is set between the lock bucket outlet and the lock bucket outlet valve on the pipeline connecting the lower part of the lock bucket to the slag pool to connect the gas stripping gas supply pipeline. Through this connection method, only one connecting port is needed, so that the gas stripping gas can indirectly enter the lower part of the lock bucket to strip the slag water.

[0040] In a further embodiment of the system of the present invention, the stripping gas supply line is capable of supplying a stripping gas with a strength in the range of 1 Nm 3 Air stripping gas / 1m 3 Slag water to 10Nm 3 Air stripping gas / 1m 3 Between slag and water, preferably 2Nm 3 Air stripping gas / 1m 3 Slag water to 4Nm 3 Air stripping gas / 1m 3The gas lift between slag and water. The higher the gas lift intensity, the less toxic and harmful gases remain in the slag and water. However, too high a gas lift intensity will consume more gas lift, and the gas lift effect will become less and less obvious.

[0041] The air lift strength has the meaning commonly recognized in the art. In the present invention, the air lift strength is the air lift strength of 1m 3 The standard cubic volume of lift gas required for slag water.

[0042] In a further embodiment of the system of the present invention, the stripping gas supply pipeline is a pressure pipeline capable of supplying stripping gas with a pressure range of 0.1MPaG to 1.0MPaG, preferably 0.4MPaG to 0.7MPaG. In actual operation, the inlet pressure required by the waste gas treatment equipment is generally between 0.01MPaG and 0.3MPaG. Considering the static pressure of the slag water and the flow resistance of various parts such as the equipment and pipelines, the stripping gas supply pipeline can supply stripping gas with a pressure range of 0.1MPaG to 1.0MPaG, preferably 0.4MPaG to 0.7MPaG, so as to ensure that the stripping gas and the mixture of toxic and harmful gases stripped from the slag water can enter the waste gas treatment equipment.

[0043] In one embodiment of the system of the present invention, a stripping gas distributor is provided in the lock bucket. This improves the stripping effect, minimizes the solubility of toxic and harmful gases in the slag water, and saves the use of stripping gas. If a stripping gas distributor is provided inside the lock bucket, only one pipe opening is required in the cone section at the bottom of the lock bucket. If the stripping gas supply pipeline is connected by providing a connection port between the lock bucket outlet and the lock bucket outlet valve, a stripping gas distributor is not required.

[0044] The stripping gas distributor is fixed at the lower part of the lock bucket, and the main pipe is connected to the pipe opening of the cone section at the lower part of the lock bucket. The stripping gas distributor shall not have an adverse effect on slag discharge. In the present invention, the particle size of the slag from the entrained flow gasifier is about 1-4 mm, and the particles are very loose, so such slag discharge will not have a significant adverse effect on the operation of the stripping gas distributor.

[0045] In a further embodiment of the system of the present invention, the stripping gas distributor is a tubular distributor, and a certain number of small holes are opened in the main pipe and branch pipes of the tubular distributor, and the opening direction of the small holes is either downward or obliquely downward. The stripping gas enters the main pipe of the gas distributor through the pipe opening opened in the cone section at the bottom of the lock bucket, and then enters each branch pipe from the main pipe. The stripping gas evenly enters the bottom of the lock bucket to perform a stripping operation on the slag water. The stripping gas distributor can also be other types of gas distributors, preferably a tubular distributor.

[0046] In one embodiment of the system of the present invention, the waste gas treatment device is a non-polluting or low-polluting waste gas treatment device. The waste gas treatment device can treat toxic and harmful gases in the depressurized gas to avoid air pollution.

[0047] In a further embodiment of the system of the present invention, the exhaust gas treatment device is a flare device.

[0048] Compared with the prior art, the method of the present invention has the following beneficial effects:

[0049] 1. The method of the present invention improves the traditional lock bucket slag discharge method. In the pressure relief step, the depressurized gas is discharged to the waste gas treatment equipment. After the depressurized gas is discharged into the waste gas treatment equipment, environmental pollution can be reduced.

[0050] 2. The method of the present invention newly adds a gas stripping step of introducing gas stripping gas from the lower part of the lock bucket after the pressure relief step and before the slag discharge step. By introducing gas stripping gas of a certain pressure into the lock bucket, conditions are provided for the residual pressure relief gas in the pressure relief step to be discharged to the waste gas treatment equipment; after the residual pressure relief gas is discharged into the waste gas treatment equipment, environmental pollution can be further reduced;

[0051] The newly added gas stripping step of the method of the present invention can deeply remove the toxic and harmful gases dissolved in the slag water, so that the solubility of the toxic and harmful gases in the slag water is much lower than the equilibrium concentration under atmospheric pressure. In this way, when the slag is discharged by the lock bucket, no toxic and harmful gases will be emitted from the slag water, thereby protecting the environment around the slag pool and the health of the workers around the slag pool.

[0052] In the existing fluidized bed gasification furnace lock hopper system including a lock hopper, waste gas treatment equipment, slag pool, etc., a step is added to the existing lock hopper slag discharge method, which achieves a significant effect of greatly (cumulatively) increasing the amount of toxic and harmful gases discharged into the waste gas treatment equipment.

[0053] 3. The present invention improves the traditional lock bucket slag discharge system by eliminating the pipeline for discharging the pressure relief gas directly or indirectly to the atmosphere and adding a pipeline for discharging the pressure relief gas to the waste gas treatment equipment. After the pressure relief gas is discharged into the waste gas treatment equipment, environmental pollution can be reduced.

[0054] 4. The system of the present invention improves the traditional lock bucket slag discharge system. A gas stripping gas supply pipeline is added at the lower part of the lock bucket, and gas stripping gas with a certain pressure can be introduced from the lower part of the lock bucket. The pressurized gas stripping gas can increase the pressure of the pressure relief gas at the upper part of the lock bucket, providing conditions for more pressure relief gas to be discharged to the waste gas treatment equipment; more pressure relief gas discharged to the waste gas treatment equipment can bring more toxic and harmful gases into the waste gas treatment equipment, reducing environmental pollution;

[0055] The system of the present invention adds a gas stripping gas supply pipeline at the lower part of the lock bucket, which can strip the slag water in the lock bucket, thereby deeply removing the toxic and harmful gases dissolved in the slag water, making the solubility of the toxic and harmful gases in the slag water much lower than the equilibrium concentration under atmospheric pressure. In this way, when the lock bucket discharges slag, no toxic and harmful gases will be emitted from the slag water, thereby protecting the environment around the slag pool and the health of the workers around the slag pool.

[0056] Adding a lift gas supply pipeline to the existing fluidized bed gasifier lock hopper system, which mainly includes lock hopper, slag pool, slag scoop machine and other equipment, can achieve the significant effect of greatly (cumulatively) increasing the amount of toxic and harmful gases discharged into the waste gas treatment equipment, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 The present invention is a schematic diagram of slag discharge using a gasifier lock bucket slag discharge system.

[0058] Figure 2 The present invention is a schematic diagram of another gasifier hopper slag discharge system for slag discharge.

[0059] Figure 3 Schematic diagram of the gas stripping gas distributor of the present invention.

[0060] Description of reference numerals:

[0061] 1-lock bucket; 2-slag pool; 3-slag scoop machine; 4-slag bucket; 5-lock bucket inlet valve (double valve); 6-lock bucket pressure relief valve; 7-lock bucket air lift valve; 8-lock bucket outlet valve (double valve or single valve); 9-lock bucket flushing valve; 10-lock bucket pressure charging valve; 11-flushing water tank; 12-auxiliary slag discharge water pump; 13-auxiliary slag discharge water pump inlet valve; 14-self-circulation valve. DETAILED DESCRIPTION

[0062] The gasifier lock bucket slag discharge method and system of the present invention are further described with reference to the attached drawings. The following description is for illustrative purposes only and is by no means construed as limiting the lock bucket slag discharge method of the present invention. It should be understood that the content disclosed in the present invention also includes any scheme and all variations that can be learned from the teachings provided herein.

[0063] like Figure 1-3 As shown, after the lock bucket 1 finishes collecting slag, it enters the pressure relief step, closes the lock bucket inlet valve 5, opens the lock bucket pressure relief valve 6, and the pressure relief gas first enters the flushing water tank 11 to separate the slag water that may be entrained, and then is discharged to the flare equipment. The maximum back pressure of the flare equipment is 0.1MPaG. When the lock bucket 1 is depressurized, the pressure of the lock bucket 1 is used as the control parameter, and the pressure relief gas is controllably discharged to the flare equipment through the automatic control system.

[0064] When the lock hopper 1 is depressurized to 0.2 MPaG, the gas lift step begins. Open the gas lift valve 7 at the bottom of the lock hopper and pressurize at 2 Nm 3 Nitrogen / 1m 3 When the gas lift intensity of the slag water is high, gas lift gas is introduced into the lock bucket 1 from the lower part of the lock bucket 1, and the gas lift time is about 5 minutes. Figure 1 It is shown that the air is introduced into the lock bucket 1 through the pipe opening provided in the cone section at the bottom of the lock bucket 1; Figure 2 The figure shows that the gas is introduced through the connection port provided on the pipeline connecting the lower part of the lock bucket 1 and the slag pool 2, more specifically, the gas is introduced through the connection port provided at the lock bucket outlet valve. The toxic and harmful gases dissolved in the slag water are gas-lifted out, and after passing through the lock bucket pressure relief valve 6, they first enter the flushing water tank 11 to separate the slag water that may be entrained, and then are discharged into the flare equipment.

[0065] The stripping gas uses nitrogen with a pressure of 0.5 MPaG to ensure that the stripping gas together with the toxic and harmful gases stripped from the slag water can enter the flare equipment through the lock hopper pressure relief valve 6.

[0066] In order to improve the gas lift effect and minimize the residual amount of toxic and harmful gases in the slag water, a gas lift gas distributor is set in the lock bucket 1. The gas lift gas distributor shall not affect the slag discharge. The gas lift gas distributor can also save the use of gas lift gas. The gas lift gas distributor can be a tubular distributor. For a schematic diagram of the tubular distributor, see Figure 3 The main pipe and branch pipe of the tubular distributor are provided with a certain number of small holes, and the opening direction of the small holes is either downward or obliquely downward. Other types of gas distributors are also possible, and a tubular distributor is preferred.

[0067] After the gas lift of the lock bucket 1 is completed, the lock bucket gas lift valve 7 and the lock bucket pressure relief valve 6 are closed, and the lock bucket outlet valve 8 is opened, and the slag in the lock bucket 1 and the gas-lifted slag water are discharged into the slag pool 2 at the bottom of the lock bucket 1. The slag water in the lock bucket 1 is lifted by the gas lift gas, and the toxic and harmful gases in the slag water are deeply removed. There is almost no carbon monoxide in the slag water; the solubility of hydrogen sulfide, carbonyl sulfide and hydrogen cyanide is equivalent to 57.64%, 29.07% and 34.63% under the condition of pressure relief to normal pressure, respectively, and the solubility is greatly reduced compared with the conventional lock bucket decompression system. In the process of discharging the slag water into the slag pool 2, the emission of toxic and harmful gases is greatly reduced, which protects the environment and ensures the health of the on-site workers around the slag pool 2.

[0068] After the lock bucket 1 is discharged, the lock bucket flushing valve 9 is opened, and the flushing water enters the lock bucket 1 from the flushing water tank 11 to flush the remaining slag in the lock bucket 1, and then the lock bucket outlet valve 8 is closed, and the lock bucket 1 is continuously filled with flushing water. The flushing water pressure is relatively low, and the function of the flushing water is to fill the lock bucket with water.

[0069] After the water injection of the lock bucket 1 is completed, the lock bucket flushing valve 9 is closed, and the lock bucket pressure charging valve 10 is opened to pressurize the lock bucket 1 with high-pressure water. The high-pressure water is used to pressurize the lock bucket 1 to make it equal to the pressure of the gasifier, so that the lock bucket inlet valve can be opened smoothly without impact.

[0070] After the lock bucket 1 is pressurized, the lock bucket pressure valve 10 is closed, the lock bucket inlet valve 5 is opened, and the slag from the gasifier enters the lock bucket 1. In order to discharge slag more smoothly, the auxiliary slag discharge water pump inlet valve 13 on the inlet pipe of the auxiliary slag discharge water pump 12 is opened, and the self-circulation valve 14 is closed. The slag water with a low slag content is extracted from the upper part of the lock bucket 1, and the auxiliary slag discharge water pump 12 is used to send it to the upstream equipment of the lock bucket 1 (the upstream equipment of the lock bucket is generally a gasifier). In this way, a top-down water flow can be formed from the upstream equipment of the lock bucket 1 to the lock bucket 1. The top-down water flow helps the slag to enter the lock bucket 1. Before entering the pressure relief step after the slag collection is completed, the self-circulation valve 14 is opened first, and then the auxiliary slag discharge water pump inlet valve 13 on the inlet pipe of the auxiliary slag discharge water pump 12 is closed, so that the auxiliary slag discharge water pump 12 is in a self-circulation state, and then the pressure relief step is entered.

[0071] Based on the composition of typical coal-based gasification raw synthesis gas, with nitrogen as the lift gas, the solubility of various toxic and harmful gases in slag water under different conditions is shown in Appendix 1; the ratio of the solubility of various toxic and harmful gases in slag water under different lift intensities to the solubility of various toxic and harmful gases in slag water under reduced pressure to normal pressure is shown in Table 2.

[0072] From the data in Table 1 and Table 2, it can be seen that carbon monoxide is very easy to separate from the slag water, and it does not require gas stripping. It can be almost completely separated from the slag water by simply reducing the pressure. Due to the high solubility of ammonia, reducing the pressure has almost no effect on the separation of ammonia, and the effect of gas stripping is also very weak. After gas stripping, the solubility of hydrogen sulfide, carbonyl sulfide and hydrogen cyanide in the slag water can be significantly reduced. 3 Nitrogen / 1m 3 Under the gas lift conditions of slag water, the solubility of hydrogen sulfide, carbonyl sulfide and hydrogen cyanide is respectively equivalent to 57.64%, 29.07% and 34.63% of that under the pressure release to normal pressure conditions. The effect of gas lift is very obvious, which can greatly reduce the toxic and harmful gases emitted into the low-altitude air near the slag pool during the process of slag water being discharged from the lock bucket into the slag pool.

[0073] Table 1 Solubility of toxic and harmful gases in slag water under different conditions

[0074]

[0075] (In Table 1, “-” means no gas stripping)

[0076] Table 2 Ratio of the solubility of toxic and harmful gases in slag water to the solubility under reduced pressure to normal pressure under different gas lift intensities

[0077] Gas lift strength Carbon monoxide ammonia Hydrogen sulfide Carbonyl sulfide Hydrogen cyanide <![CDATA[1Nm 3 Nitrogen / 1m 3 Slag water]]> 1.21％ 99.90％ 79.74％ 51.16％ 58.43％ <![CDATA[2Nm 3 Nitrogen / 1m 3 Slag water]]> 0.62％ 99.68％ 57.64％ 29.07％ 34.63％ <![CDATA[4Nm 3 Nitrogen / 1m 3 Slag water]]> 0.32％ 99.25％ 37.20％ 15.64％ 19.14％ <![CDATA[6Nm 3 Nitrogen / 1m 3 Slag water]]> 0.21％ 98.83％ 27.49％ 10.70％ 13.24％ <![CDATA[8Nm 3 Nitrogen / 1m 3 Slag water]]> 0.16％ 98.42％ 21.82％ 8.13％ 10.12％ <![CDATA[10Nm 3 Nitrogen / 1m 3 Slag water]]> 0.13％ 98.02％ 18.09％ 6.55％ 8.19％

[0078] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the protection scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope of the claims of the present invention.

Claims

1. A gasifier hopper slag removal method, characterized in that: Includes the following: (1) Pressure relief step, discharging all the pressure relief gas in the lock bucket into the exhaust gas treatment equipment; (2) a gas stripping step, after the pressure relief step is completed, introducing gas stripping gas into the lock bucket to strip out the toxic and harmful gases dissolved in the slag water, and the mixture of the gas stripping gas and the toxic and harmful gases stripped from the slag water is also discharged into the waste gas treatment equipment; (3) After step (2) is completed, slag discharge, flushing, pressurization and slag collection are performed in sequence. After slag collection is completed, the pressure relief step described in step (1) is returned to complete a slag discharge cycle.

2. The method according to claim 1, characterized in that In step (2), air is introduced into the lock bucket, and the air lift intensity ranges from 1Nm 3 Air stripping gas / 1m 3 Slag water to 10Nm 3 Air stripping gas / 1m 3 Between the slag and water.

3. The method according to claim 2, characterized in that In step (2), the air lift strength range is 2 Nm 3 Air stripping gas / 1m 3 Slag water to 4Nm 3 Air stripping gas / 1m 3 Between the slag and water.

4. The method according to claim 1, characterized in that: In step (2), the pressure of the stripping gas introduced is in the range of 0.1 MPaG to 1.0 MPaG.

5. The method according to claim 1, characterized in that In step (2), the stripping gas is selected from nitrogen, or other gases that are harmless to humans, insoluble or slightly soluble in water, and can be received by the waste gas treatment equipment.

6. The method according to claim 1, characterized in that In step (1), the final pressure of the pressure release step is 0.05 MPaG to 0.5 MPaG.

7. The method according to claim 1, characterized in that In step (1), the exhaust gas treatment equipment is a non-polluting or low-polluting exhaust gas treatment equipment.

8. The method according to claim 1, characterized in that In step (2), the stripping gas enters the lock bucket through the lower pipe opening of the lock bucket, or the stripping gas enters the pipeline connected to the lower part of the lock bucket.

9. The method according to claim 1, characterized in that: In step (2), a gas stripping gas distributor is arranged in the lock hopper.

10. The method according to claim 9, characterized in that The gas lift gas distributor is a tubular distributor, and a certain number of small holes are opened in the main pipe and branch pipe of the tubular distributor, and the opening direction of the small holes is either downward or obliquely downward.

11. A gasifier lock bucket slag discharge system for implementing the method according to any one of claims 1 to 10, characterized in that: include: A lock hopper is located below the gasifier, and a lock hopper inlet valve is arranged on the connecting pipe between the lock hopper and the gasifier, and the gasifier and the lock hopper are connected or disconnected by opening or closing the lock hopper inlet valve; An exhaust gas treatment device is located above the lock bucket, and a lock bucket pressure relief valve is arranged on the connecting pipe between the top of the lock bucket and the exhaust gas treatment device, and the depressurized gas in the lock bucket is discharged to the exhaust gas treatment device by opening the lock bucket pressure relief valve; A stripping gas supply pipeline connected to the lower part of the lock bucket so that the stripping gas can flow into the lock bucket from the lower part of the lock bucket; A slag pool, which is located below the lock bucket, and a lock bucket outlet valve is arranged on the connecting pipe between the lock bucket and the slag pool, and the slag and slag water in the lock bucket are discharged into the slag pool by opening the lock bucket outlet valve; The slag scooping machine is used to scoop out the slag discharged from the lock bucket into the slag pool and transport it to the slag bucket, and then transport it away from the gasifier lock bucket slag discharge system through transportation equipment.

12. The system according to claim 11, characterized in that A pipe opening is provided in the conical section at the lower part of the lock bucket, the number of the pipe opening is 1 or more, and the stripping gas supply pipeline is connected to the pipe opening so that the stripping gas can flow into the lock bucket from the lower part of the lock bucket.

13. The system according to claim 11, characterized in that On the pipeline connecting the lower part of the lock bucket and the slag pool, a connecting port is set between the lock bucket outlet and the lock bucket outlet valve to connect the gas stripping gas supply pipeline, so that the gas stripping gas can indirectly pass from the lower part of the lock bucket into the lock bucket through the connecting pipeline between the lower part of the lock bucket and the slag pool.

14. The system according to any one of claims 11 to 13, characterized in that: The stripping gas supply pipeline can supply stripping gas with a strength range of 1 Nm 3 Air stripping gas / 1m 3 Slag water to 10Nm 3 Air stripping gas / 1m 3 Gas lift between slag and water.

15. The system according to any one of claims 11 to 13, characterized in that: The stripping gas supply pipeline is a pressure pipeline capable of supplying stripping gas with a pressure ranging from 0.1 MPaG to 1.0 MPaG.

16. The system according to claim 11, characterized in that A gas lift gas distributor is arranged in the lock hopper.

17. The system according to claim 16, characterized in that The gas lift gas distributor is a tubular distributor, and a certain number of small holes are provided in the main pipe and branch pipe of the tubular distributor, and the opening direction of the small holes is either downward or obliquely downward.

18. The system according to claim 11, characterized in that The exhaust gas treatment equipment is a pollution-free or low-pollution exhaust gas treatment equipment.

19. The system according to claim 18, characterized in that The waste gas treatment equipment is a flare equipment.

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