Fixed bed gasifier and ash and slag discharge method

Abstract

The present invention discloses a fixed-bed gasifier and ash and slag discharge method, comprising a furnace body, the upper end of which is connected to a high-pressure silo via a material guide pipe, an air outlet provided at the upper portion of the furnace body, a temperature measuring tube provided within the upper portion of the furnace body, and several thermocouples provided at different heights for measuring temperature within the temperature measuring tube, a conical lower portion of the furnace body, a solid material discharge area provided at the lower portion of the furnace body, at least two sets of auxiliary agent inlets provided at the lower portion of the furnace body, and a residual carbon treatment mechanism connected to the outlet end of the solid material discharge area. The present invention significantly simplifies the gasification furnace's reaction gas distribution and ash discharge structures, enabling direct dry ash discharge control. When the slag melting operation range is required, the residual carbon combustion and ash melting processes are separated from the gasifier body, and the ash melting operation is completed using a small combustion device. The ash and slag discharge of the gasifier is precisely controlled, and operations such as starting, stopping, and hot standby of the gasifier are simplified, significantly improving the reliability and availability of the fixed-bed gasifier and achieving the discharge of solid and liquid slag.

Description

Technical Field

[0001] The invention belongs to the field of gasifiers, in particular to a fixed bed gasifier and an ash and slag discharge method. Background Art

[0002] Fixed-bed (also known as moving-bed) gasifiers are the oldest type of coal gasification equipment. They feature mature technology, reliable equipment, flexible production operations, and high thermal efficiency in the coal conversion process. Despite the advancements in modern coal gasification technology, such as raw materials and environmental protection, fixed-bed gasification still holds considerable promise. The adoption of slag removal significantly increases fixed-bed gasification's processing capacity under pressurized conditions, while also improving its environmental performance. Fixed-bed gasifiers offer key advantages over other technologies, including simplified feedstock preparation, high methane yields, a high-value tar byproduct, and high thermal efficiency. Their significantly lower oxygen consumption, in particular, makes them particularly attractive for use in coal gasification combined cycle power generation.

[0003] To date, most fixed-bed gasifiers have required grates, which not only support the bed material in the furnace but also distribute the gasifying agent. The grates guide the ash produced during the gasification process into a pressurized ash bin. Large grates have complex structures, high investment and maintenance costs, and low operational reliability. Fixed-bed gasifiers with liquid slag discharge convert the ash into a molten state at a temperature above the ash melting point, making the liquid easier to flow. Furthermore, due to the increased gasification reaction temperature, the gasifier's generation strength increases, meeting the needs of modern coal chemical industry. However, existing slag-type fixed-bed gasifiers have difficulty controlling slag and a narrow operating window. The resulting slag pool places high demands on the nozzle materials and refractory materials of the gasifier, which are expensive. Furthermore, the cleaning and maintenance cycles after slag blockage are long and costly. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a fixed bed gasification furnace and an ash and slag discharge method.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A fixed bed gasification furnace comprises a furnace body, the upper end of the furnace body is connected to a high-pressure silo via a material guide pipe, an air outlet is provided at the upper part of the furnace body, a temperature measuring tube is provided inside the upper part of the furnace body, a plurality of thermocouples at different heights for measuring temperature are provided inside the temperature measuring tube, a solid material discharge area is provided at the lower part of the furnace body, at least two groups of auxiliary agent inlets are provided at the lower part of the furnace body, and the outlet end of the solid material discharge area is connected to a residual carbon processing mechanism.

[0007] The carbon residue processing mechanism includes a connected carbon residue cyclone combustion cylinder and a slag quenching cylinder. The carbon residue cyclone combustion cylinder is provided with an auxiliary agent introduction port. The lower part of the furnace body is provided with a control valve connected to the carbon residue cyclone combustion cylinder.

[0008] The carbon residue cyclone combustion cylinder and the slag quenching cylinder are both arranged vertically, and the inlet end of the carbon residue cyclone combustion cylinder is connected to the solid material discharge area.

[0009] A discharge controller is provided in the solid material discharge area.

[0010] The residual carbon cyclone combustion cylinder is tilted with one end higher than the other end, the slag quenching cylinder is vertically arranged, the control valve is connected to the feed end of the residual carbon cyclone combustion cylinder, the flue gas return pipe is connected to the side wall of the residual carbon cyclone combustion cylinder, and the inlet end of the residual carbon cyclone combustion cylinder is connected to the solid material discharge area.

[0011] The carbon residue cyclone combustion tube and the slag quenching tube are both arranged vertically, the control valve is connected to the side wall of the carbon residue cyclone combustion tube, the solid material discharge area is connected to the side wall of the carbon residue cyclone combustion tube, and the flue gas return pipe is connected to the inlet end of the carbon residue cyclone combustion tube.

[0012] An ash tank is installed at the outlet end of the fixed material discharge zone.

[0013] The residual carbon treatment mechanism includes an ash melting control tube and a slag quencher. The ash melting control tube is connected to the outlet of the solid material discharge zone. A pneumatic valve is installed at the bottom of the ash melting control tube and is provided with an additive inlet. The slag quencher is equipped with a balancing pipe, which is connected to the conical bottom area of ​​the gasifier and is provided with a venting port and a supplementary gas inlet. The pneumatic valve extends obliquely upward from bottom to top, with the higher end of the pneumatic valve connected to the inlet of the slag quenching port and the lower end of the pneumatic valve connected to the ash melting control tube. The height difference between the connection point with the slag quencher and the connection point with the ash melting control tube is no less than the diameter of the pneumatic valve pipe. The outlet pressure of the pneumatic valve is adjusted by controlling the supplementary gas flow and the balancing pipe valve to control the discharge rate of the molten slag through the pneumatic valve.

[0014] A baffle is provided in the lower part of the furnace body, and the baffle is located above the connection position between the residual carbon cyclone combustion tube and the furnace body. The solid-free space formed at the bottom of the baffle facilitates the entry and distribution of the reflux flue gas. The lower part of the furnace body is conical, and an auxiliary internal air distribution component is provided in the auxiliary agent introduction port or the auxiliary agent inlet to allow the auxiliary agent to enter the furnace body evenly. The auxiliary agent introduction port or the auxiliary agent inlet is used to introduce oxygen and water vapor.

[0015] A method for removing ash and slag from a fixed-bed gasifier comprises the following steps:

[0016] Before starting, add some ash to the bottom of the gasifier. At this time, the fixed material discharge area is also filled with ash. Then, pre-load crushed coal on the ash layer to reach the normal material level of the gasifier. Fill the high-pressure silo with material through the coal lock and wait for use.

[0017] Oxygen and steam are introduced from the bottom of the gasifier. Superheated steam is introduced to preheat the bed material in the gasifier. Oxidation combustion reaction is carried out in the gasifier, so that the bed temperature is higher than the superheated steam temperature. The ratio of the input oxygen and steam is adjusted within the set range so that the ash at the bottom of the gasifier does not melt and remains in a dry slag state.

[0018] Solid or liquid slag discharge is carried out as needed. During solid slag discharge, the highest temperature layer in the gasifier is maintained at the middle and lower part of the gasifier or the upper part of the fixed material discharge area, and the temperature at the gasifier outlet is maintained at the set temperature. During liquid slag discharge, the residual carbon cyclone burner connected to the gasifier is used for combustion, and the flue gas generated by the combustion is sent back to the gasifier for utilization. The solid or liquid produced after combustion enters the slag quencher for cooling and then discharged. During the combustion process, oxygen and steam are introduced into the residual carbon cyclone burner to make the combustion temperature capable of melting the ash with low residual carbon.

[0019] When steady-state gasification treatment is being carried out in the gasifier, the oxygen concentration of the flue gas leaving the residual carbon cyclone combustion tube is tested to see whether the oxygen concentration is within the set oxygen concentration range. If not, the ash discharge speed is increased or decreased as needed; the gas outlet temperature of the gasifier is tested in real time. If the gas outlet temperature continues to rise, the ash discharge speed is increased; if the gas outlet temperature continues to decrease, the ash discharge speed is reduced.

[0020] The present invention significantly simplifies the air distribution structure and ash discharge structure of the reaction gas in the gasifier, and can directly perform dry ash discharge control. When it is necessary to enter the slag operation range, the process of residual carbon combustion and ash melting is separated from the gasifier body, and the ash melting operation is completed by using small combustion equipment. The ash and slag discharge of the gasifier is precisely controlled, and the start-up, shutdown, hot standby and other operations of the gasifier become simpler, which is obviously beneficial to improving the reliability and availability of the fixed-bed gasifier and realizing the discharge of solid slag and liquid slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of embodiment 1 of the present invention;

[0022] Figure 2 Schematic top view of the furnace body according to the first embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of embodiment 2 of the present invention;

[0024] Figure 4 and 5 They are schematic diagrams of the partially cutaway structure of the furnace body in different viewing angles in the second embodiment;

[0025] Figure 6 This is a schematic structural diagram of embodiment 3 of the present invention;

[0026] Figure 7 This is a structural diagram of a fourth embodiment of the present invention;

[0027] Attachment Figure 8 and 9 They are schematic diagrams of the partial structure of the furnace body from different perspectives in the fourth embodiment;

[0028] Attachment Figure 10 This is a structural diagram of embodiment 5 of the present invention. DETAILED DESCRIPTION

[0029] In order to further understand the features, technical means, specific objectives and functions achieved by the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] As attached Figure 1 and 2 As shown, the present invention discloses a fixed-bed gasifier comprising a furnace body 5, the upper end of which is connected to a high-pressure silo 2 via a material guide pipe 3. A gas outlet 8 is provided at the top of the furnace body 5 for discharging generated coal gas. A temperature measuring tube 4 is located within the upper interior of the furnace body 5, with several thermocouples positioned at different heights for temperature measurement. A solid material discharge area 7 is located at the bottom of the furnace body 5, along with at least two sets of auxiliary agent inlets. The outlet of the solid material discharge area is connected to a residual carbon treatment mechanism. The gas outlet is used to discharge the coal gas generated by the reaction. Ash is discharged from the fixed material discharge area, processed in the residual carbon treatment mechanism, and then discharged to a designated location. A pressurized coal lock is connected to the high-pressure silo, with pressurization valves located above and below the lock for pressurizing the material. The auxiliary agent inlet is primarily used to input oxygen, air, and water vapor for auxiliary heating or as a reaction gas. The auxiliary agent inlet can be arranged in multiple nozzle groups to facilitate gas delivery. Figure 1 The direction of the middle arrow indicates the reaction gas input position, that is, the auxiliary agent inlet position.

[0031] Multiple material guide pipes and temperature measuring tubes can be set. In this embodiment, three material guide pipes are set, which are divided into three routes and connected to the top of the furnace body. The screened normal pressure crushed coal, generally with a particle size of 6 to 50 mm, is added to the pressurized coal lock and first pressurized by the pressurized coal lock. The pressure can be from low pressure to high pressure 10 MPa. After pressurization, the crushed coal is sent to the pressure silo located at the top of the furnace body. The material guide pipe at the bottom of the pressure silo is connected to the top of the furnace body. The pressure block coal is moved to a stable material layer height on the upper part of the furnace body through the material guide pipe.

[0032] Once the material level in the high-pressure silo reaches the lower limit, the pressurized coal lock is responsible for delivering pressurized coal briquettes to the silo, ensuring a constant supply of material. This ensures that the guide pipe is always filled with material. As long as the material level in the gasifier moves downward, the coal in the guide pipe will also move downward to replenish the material. This maintains a constant material level on the gasifier's upper surface, ensuring a sufficient supply of material. Since the material is added to the gasifier through the guide pipe without a free fall, fine coal dust that falls is prevented from being carried away by the rising gas flow and exiting the gasifier, resulting in a low dust content in the outlet gas.

[0033] Multiple temperature measuring tubes can be used to measure temperatures at different heights in the gasifier charge layer. This allows for consistent temperature uniformity across the gasifier's cross-section. Temperature measuring elements with varying insertion depths are placed at various heights around the bottom of the furnace, enabling more precise temperature control.

[0034] In addition, the structure of the furnace body is divided into the upper part, the middle part and the lower part. The structure of the middle part of the furnace body is from small to large, and the lower part of the furnace body is cone-shaped. The upper part is the coal inlet and gas outlet area, the middle part is the main reaction area, and the lower part is the residual carbon combustion area, which is used for ash and slag discharge.

[0035] like Figure 6 As shown, the middle part of the furnace body is a structure from small to large. The expansion of the cross-sectional area is conducive to the opportunity for the accumulated coal to stretch outward. In the case of some weakly cohesive coal, it can help split the coal particles, reduce aggregation, and improve permeability. On the other hand, the expansion of the cross-section reduces the friction force from the solid on the inner surface of the gasifier, which is conducive to protecting the inner surface structure of the gasifier.

[0036] In the gasifier, lump coal added to the top of the gasifier comes into countercurrent contact with hot gases from the bottom. The coal is dried and dehydrated, then distilled to remove volatiles. The semi-coke then reacts with the water vapor and carbon dioxide in the gas to form a gas primarily composed of CO and H₂. The remaining carbon residue enters the bottom of the gasifier. At the bottom, pure oxygen or air, along with some water vapor, is introduced. The oxygen burns the carbon residue, generating heat that heats the carbon dioxide and water vapor. These heat then flows upward with the hot gas flow, providing the energy required for the gasification reaction, distillation, and drying process. Once the carbon residue is nearly completely burned, the remaining material is ash, which is the result of the conversion of inorganic matter from the raw coal.

[0037] The furnace body is designed with a shallow conical bottom, with an opening at the bottom of the cone serving as a solid material discharge area for ash and slag. Multiple inlets for gasification reaction gases (oxygen or air, water vapor, and carbon dioxide, etc.) are located at different heights and along the circumference of the furnace cone. Different gas composition ratios, such as water vapor to oxygen ratios, can be used at different heights. Furthermore, the flow rate of reaction gases entering at different heights should be adjusted based on the cross-sectional area of ​​the gasifier to be covered. After entering the cone, the oxygen in the gasification gas reacts with the residual carbon in the solid material, burning it and releasing a large amount of heat. The heat released by combustion heats the water vapor and carbon dioxide produced, raising the temperature. The high-temperature gas continues to rise and reacts with the residual char after dry distillation and devolatilization. The cooler reaction gas first countercurrently contacts the ash produced by the combustion, cooling it. Once the gas heats up, it continues to combust with the residual carbon. The water vapor to oxygen ratio in the gasification reaction gas is adjustable and can be adjusted appropriately to achieve the discharge of solid or liquid materials.

[0038] The cone angle of the lower part of the furnace body is set to ensure that the solid movement in the straight section of the gasifier can always maintain uniform flow. The cone angle is in the range of 10-60 degrees, preferably between 20-40 degrees.

[0039] There are different options for the connection structure of the fixed body discharge area at the lower part of the furnace body.

[0040] Example 1, as Figure 1 As shown, a horizontal discharge controller 5 is provided in the fixed material discharge area 7, which is a spiral feeding structure, and the fixed material discharge area 7 is connected to the ash tank 6. The solid particle ash that has been cooled moves to the outlet of the solid material discharge area at the bottom of the gasifier cone. By providing a discharge controller in the solid material discharge area, the discharge controller can be a variety of mechanisms, including horizontal spirals, vertical spirals, small grate, etc. The spiral feeding structure discharges the ash from the solid material discharge area to the ash tank, and then discharges it from the ash tank to a designated location. The spiral feeding structure itself contains a cooling heat exchange surface to further cool the ash, and the change in the speed of the spiral can control the ash discharge speed. In this way, the need for a conventional gasifier to have a grate of the same diameter as the gasifier is avoided. The grate structure is complex, the cost is high, and the operation and maintenance requirements are high. This reduces the cost of equipment.

[0041] Example 2, as Figure 3-5As shown, the carbon residue processing mechanism includes a connected carbon residue cyclone burner 11 and a slag quenching cylinder 12. The carbon residue cyclone burner 11 is tilted, with one end higher than the other, while the slag quenching cylinder 12 is vertically arranged. A control valve 10 is connected to the feed end of the carbon residue cyclone burner 11. A flue gas return pipe 9 is connected to the side wall of the carbon residue cyclone burner 11. The inlet end of the carbon residue cyclone burner 11 is connected to the solid material discharge area 7. The discharge controller is vertically arranged in the solid material discharge area. Gas can be extracted from the flue gas return pipe for oxygen concentration analysis. Figure 3 The direction of the arrows in the middle represents the reaction gases (oxygen and water vapor) input at various locations.

[0042] After the coal gasifies within the furnace, the coke gasification reaction completes, and the solid particle size decreases significantly. The carbon content of the solids, which contain residual carbon and minerals, is between 50% and 70%. At the very bottom of the conical zone, where the solids enter the gasifier, they remain in a solid particle state. When a low steam-to-oxygen ratio is supplied to the furnace, the coke gasification is primarily directed upwards from the lower conical zone. Residual carbon combustion does not occur here, and inorganic solids containing residual carbon are discharged through the solids discharge zone.

[0043] Oxygen and water vapor are introduced through the control valve to fluidize the solid material in the solid material discharge area and push it toward the residual carbon cyclone combustion tube. Simultaneously, solid material from the lower conical section of the furnace body is continuously replenished to the solid material discharge area. The gas flow rate to the control valve directly determines the speed of the solid material push, thereby achieving control over the discharge speed of the solid material at the conical bottom of the gasifier. Oxygen and water vapor are also introduced into the residual carbon cyclone combustion tube during combustion.

[0044] The solid particles leaving the control valve and the solid material discharged from the discharge controller are combined and enter the feed end of the carbon residue cyclone burner. The reaction gas (oxygen and water vapor) enters the carbon residue cyclone burner rapidly along the tangential direction from the feed end. The oxygen and water vapor introduced into the carbon residue cyclone burner are mainly used to re-swirl the solid material that may have settled to the bottom of the carbon residue cyclone burner so that it can come into contact with oxygen and ensure that the carbon residue is completely burned.

[0045] In the carbon cyclone burner, oxygen rapidly combusts the solid carbon residue until it is completely consumed. The heat released by combustion raises the temperature above the ash melting point of the minerals, transforming the solid ash into molten slag. The cyclone burner is tilted to facilitate the flow of molten slag toward the other end. The molten slag flows out of the end and ultimately falls into the slag quencher, where it is quenched by water and solidified. The solidified slag is discharged through the slag lock and pressure system.

[0046] In addition, a baffle plate 14 is installed in the lower portion of the furnace body 5. This baffle plate 14 is located above the connection between the carbon residue cyclone combustion tube 11 and the furnace body 5. The lower portion of the furnace body is conical in shape. The auxiliary agent introduction port or inlet is equipped with an auxiliary internal air distribution component to ensure uniform entry of the auxiliary agent into the furnace body. The auxiliary agent introduction port or inlet is used to introduce oxygen and water vapor. The baffle plate is located in the conical bottom area above the direction of the airflow of the carbon residue combustion flue gas entering the conical bottom area. Its width is slightly wider than the outer dimensions of the airflow. This baffle plate provides flow space for the gas to enter the deep conical bottom area and facilitates uniform distribution.

[0047] This second embodiment can achieve the purpose of discharging solid materials as needed.

[0048] Example 3, as Figure 6 As shown, the carbon residue cyclone burner 11 and slag quenching cylinder 12 are both arranged vertically, the control valve 10 is connected to the side wall of the carbon residue cyclone burner 11, the solid material discharge area 7 is connected to the side wall of the carbon residue cyclone burner 11, and the flue gas return pipe 9 is connected to the inlet end of the carbon residue cyclone burner 11, which is a vertical furnace structure. The control valve is connected to the carbon residue cyclone burner 11 tangentially, cutting into the side wall circumferentially. Figure 6 The direction of the arrows in the figure indicates the reaction gases (oxygen and water vapor) input at various locations.

[0049] The gas flow entering the control valve 10 propels the solid material toward the carbon residue cyclone combustion tube. More oxygen is added to the solid flow from the control valve, and together, they rapidly enter the carbon residue cyclone combustion tube in a tangential manner. The solid carbon residue from the solid material discharge area is inherently at a high temperature, such as 1000°C or above. Once oxygen comes into contact with the carbon residue, the carbon residue is burned. The heat released by the combustion causes the solid to burn out, potentially exceeding its melting point and forming slag. As the slag rotates, it flows downward along the tube wall and eventually flows into the slag quenching tube at the bottom for cooling. An additional oxygen inlet is also provided below the solid material inlet to continue providing sufficient oxygen for carbon residue combustion. This additional oxygen also enters the combustion tube in a tangential manner, increasing the time the solid rotates along the tube wall and ensuring complete combustion of the carbon residue.

[0050] In the third embodiment, molten slag is formed by high-temperature combustion, which is used for the purpose of liquid material discharge.

[0051] Example 4, as Figure 7-9 As shown, the carbon residue cyclone combustion cylinder and the slag quenching cylinder are both arranged vertically, and the inlet end of the carbon residue cyclone combustion cylinder is connected to the solid material discharge area. Compared with the embodiment 3, the fourth embodiment does not have a separate flue gas return pipe. Figure 7 The direction of the arrows in the figure indicates the reaction gases (oxygen and water vapor) input at various locations.

[0052] Because the carbon residue cyclone burner 11 is located directly below the solid material discharge area 7, one end of the control valve 10 is connected to the lower portion of the furnace body 5, and the other end of the control valve 10 is connected to the carbon residue cyclone burner 11. This connection is tangential to the circumference of the combustion chamber cylinder. Oxygen enters the carbon residue cyclone burner tangentially. A portion of the solid material is discharged directly from the solid material discharge area at the bottom of the furnace body into the carbon residue cyclone burner. Another portion of the solid material is flow-controlled by the reaction gas input through the control valve. Together with another set of input reaction gases, the carbon residue solids are fed tangentially into the carbon residue cyclone burner. Oxygen contacts the carbon residue, burning it to ashes. The molten slag flows down the combustion chamber wall into the slag quenching tube at the bottom. The high-temperature flue gas generated by the combustion rises and enters the conical bottom of the furnace body. In this solution, the gas flow rate leaving the combustion chamber is set to be sufficiently high to prevent the solid material at the conical bottom of the gasifier from directly falling into the carbon residue cyclone burner. An auxiliary air distribution assembly 15 can be provided within the furnace body to ensure more uniform gas discharge into the furnace body.

[0053] Example 5, as Figure 10 As shown, the residual carbon processing mechanism includes an ash melting control cylinder 16 and a slag quencher 17. The ash melting control cylinder 16 is connected to the outlet end of the solid material discharge area 7. A pneumatic valve 18 is installed at the bottom of the ash melting control cylinder 16. An auxiliary agent inlet is provided on the ash melting control cylinder 16. The slag quencher 17 is equipped with a balance pipe 19. The balance pipe 19 is provided with a vent 20. The pneumatic valve extends obliquely from bottom to top, and the higher end of the pneumatic valve is connected to the inlet of the slag quenching port, and the lower end of the pneumatic valve is connected to the ash melting control cylinder. The height difference between the high end and the low end is greater than one pipe diameter, and a valve is provided on the balance pipe. A supplementary gas pipe 21 is located above the quencher. This is controlled by the supplementary gas flow rate and the balancing pipe valve. The air seal separating the ash melting control tube and the quencher when the pneumatic valve is filled with liquid is utilized to adjust the relative pressure between the pneumatic valve outlet and the gasifier. This pressure, primarily the pressure above the slag quencher, influences the liquid level at the pneumatic valve outlet, thereby controlling the rate at which molten slag is discharged through the pneumatic valve. The vent is primarily used for startup and shutdown of the gasifier. During shutdown, the balancing pipe valve is closed and the vent is quickly opened. The low pressure at the pneumatic valve outlet quickly discharges liquid molten slag from the cone bottom area, the ash melting control tube, and the pneumatic valve into the quencher, ensuring that the ash melting control tube and the pneumatic valve are filled with normal, unmelted granular solid material, facilitating the next restart of the gasifier. Figure 10 The arrows in the figure indicate the reaction gases (oxygen and water vapor) fed in at various locations. The connection point with the slag quenching port is located higher than the connection point with the ash melting control cylinder.

[0054] Oxygen, primarily a component of the reaction gas, is introduced into the ash melting control tube. This oxygen burns the residual carbon contained in the solids emerging from the conical bottom area of ​​the furnace body, molten by the heat released by combustion. Reaction gas and auxiliary fuel gas are introduced at the pneumatic valve, primarily for system startup heating. During normal operation, the oxygen and fuel combust here, further raising the temperature to ensure the molten slag maintains good fluidity. The slag flows through the flat pipe section of the L-valve to the slag quencher. When the ash is solid, it has little fluidity. Without airflow toward the pneumatic valve outlet, the solids are unlikely to migrate vertically toward the valve outlet. However, once the ash becomes fluid, liquid ash can flow through the flat pipe section of the pneumatic valve to the slag quencher. As the dry ash in the ash melting control tube (including the conical bottom area of ​​the furnace body) is heated and melted, flowing out of the bottom of the tube, the dry ash at the bottom of the furnace body moves downward to continue combustion of the residual carbon, ultimately achieving the purpose of slag removal from the gasifier. The pneumatic valve is configured in an inclined, tilted shape, primarily to provide a gas seal. This means that when the horizontal section of the L-valve is filled with liquid molten slag, gas from the upper portion of the quencher will not flow from the horizontal section to the ash melting control cylinder, minimizing the chance of solids flowing out with the liquid. A gas balance pipe removes excess gas from the upper portion of the slag quencher. A supplementary gas connection is also provided at the upper portion of the slag quencher, allowing nitrogen and other gases to be introduced when the quencher pressure needs to be increased. By controlling the valve on the balance pipe, the flow rate of the supplementary gas, and the valve on the vent line, the slag discharge rate is assisted in controlling the rate at which the gasifier reacts to produce ash. In addition to the special-shaped L-valve described above, the pneumatic valve can also be U-shaped. Example 5 is also applicable to other types of gasifier bottom structures, such as conventional flat-bottom or round-bottom gasifiers.

[0055] In each of the above embodiments, oxygen and water vapor can be selectively introduced, with the appropriate ratio and number of input channels selected based on actual needs to meet the requirements of normal gasification reaction and slag removal. Auxiliary combustion can be installed in the pipe section before the outlet of the special-shaped L-valve as needed to maintain the fluidity of the slag, which is not shown in the figure.

[0056] When the gasifier is performing gasification treatment, oxygen and water vapor are mainly introduced into the lower part of the furnace body and enter the conical area at the bottom of the furnace body. According to the needs of use, part of the reaction gas can be introduced with the help of the auxiliary air distribution component installed in the furnace body to make the reaction gas distribution more uniform.

[0057] The furnace body does not directly undergo combustion reactions and is basically not exposed to extreme high temperatures. Therefore, the furnace body can be made of more common refractory materials, and on-site cast refractory materials are also applicable. Two or three layers of cast refractory materials can be used, and the innermost layer can be a refractory material with good wear resistance, such as high-aluminum refractory materials. In the cone bottom area of ​​the gasifier, due to the heat dissipation of the outer shell, part of the slag forms a solidified ash layer on the surface of the refractory material, so that the refractory material is protected. In areas involving molten slag, it is necessary to minimize heat loss through the selection and thickness design of refractory materials to avoid a large amount of slag solidifying and depositing on the tube wall and the wall of the device after cooling, causing blockage. Necessary external heating measures can be set as needed.

[0058] The present invention also provides a method for removing ash and slag from a fixed-bed gasifier, comprising the following steps:

[0059] Before starting, load some ash into the bottom of the gasifier. At this time, the fixed material discharge area is also full of ash. Then pre-load crushed coal on the ash layer to reach the normal material level of the gasifier. Fill the high-pressure silo with material through the coal lock and wait for use.

[0060] When preparing for startup, the reaction gas (oxygen + water vapor) is input from the conical bottom of the furnace body. Superheated steam is introduced to preheat the bed material, and then pure oxygen is gradually added. The temperature of each layer at different heights in the gasifier can be detected by temperature measuring tubes arranged in the gasifier. When the oxidation combustion reaction begins clearly, the bed temperature will be higher than the superheated steam temperature. The ratio of the input water vapor to oxygen is adjusted within the range of 4 to 8. The principle is to ensure that the ash and slag produced in the bottom area of ​​the gasifier cone will not melt and remain in a dry slag state. This continues until the temperature gradient of each layer of the gasifier reaches normal operating conditions. The water vapor and oxygen ratio of each reaction gas series can be independently set and adjusted as needed.

[0061] For slag discharge methods, there are solid slag discharge and liquid slag discharge solutions.

[0062] For solid slag removal scheme, such as Figure 1 As shown in the figure, after the gasifier temperature gradient reaches the desired temperature, the spiral discharge controller at the bottom of the gasifier is activated to discharge ash, moving the highest temperature layer in the gasifier bed downward and controlling it in the lower middle portion of the gasifier or in the upper conical bottom area, thereby ensuring that the gas outlet temperature at the upper portion of the gasifier falls within the set range. Temperature measuring points can be set at the conical bottom of the furnace body to determine the temperature of the residual carbon combustion in the conical bottom area. The characteristics of the discharged dry ash can also be used to adjust the overall water vapor and oxygen mixture ratio to optimize the efficiency of the gasification process.

[0063] For liquid slag removal scheme, such as Figure 3As shown, the gas burner (not shown) on the carbon residue cyclone burner is activated, and the heat generated by the combustion gas preheats the refractory materials in the combustion chamber and the flue gas outlet duct. Subsequently, a control valve is used to discharge the solid material discharge area at the bottom of the furnace body into the carbon residue cyclone burner. Simultaneously, oxygen is introduced into the carbon residue cyclone burner. The solids or liquids produced after combustion enter the slag quenching tube, while the reaction gases enter the conical bottom of the gasifier from the top. As the temperature of the solids from the conical bottom of the gasifier increases and contains a sufficient amount of carbon residue, the combustion chamber reaches a temperature above the ash melting point. After combustion, the solids are converted into slag, which is finally cooled in the slag quenching tube.

[0064] At different positions of the gasifier, multiple reaction gases are input respectively. The reaction gases in different channels are composed of water vapor and oxygen or air. The ratio of water vapor and oxygen can be set accordingly according to the type of coal, mineral content, ash melting point, production requirements and operating pressure.

[0065] During steady-state operation, the high-pressure silo is always filled with material. The feed pipe maintains a stable feed level in the upper portion of the gasifier. As the drying, distillation, and gasification processes progress, solid carbon residue and minerals enter the conical bottom of the gasifier. The discharge controller continuously discharges the solid material into the carbon residue cyclone burner, where pure oxygen combusts the carbon residue. High-temperature flue gas returns to the conical bottom area to provide heat for the gasification reaction. Most of the oxygen enters the carbon residue cyclone burner for carbon combustion, while a small amount enters the gasifier directly through the conical bottom. The ash discharge rate should be commensurate with the gasification reaction capacity. The incoming oxygen should essentially combust any carbon residue in the ash discharge. The flue gas exiting the carbon residue cyclone burner should contain a low oxygen concentration, such as 0.5% to 2%, typically less than 1%. Oxygen concentration is determined through online gas sampling and analysis. The outlet temperature trend is a key indicator of gasifier operation stability. A sustained increase in outlet gas temperature indicates an upward shift in the furnace fire layer, necessitating an increase in the ash discharge rate. If the ash removal rate is too high, the oxygen flow during carbon residue combustion will be insufficient to consume all the carbon residue, resulting in a lack of oxygen in the flue gas exiting the carbon residue cyclone burner, and the carbon and ash content in the slag discharge increases. Therefore, by monitoring parameters such as the gasifier gas outlet temperature, the temperature gradient within the bed layers, the oxygen concentration in the carbon residue combustion flue gas, and the carbon content in the slag discharge, the ash removal rate of the gasifier can be indirectly or directly controlled. For fixed-bed gasifier operations, precise ash and slag removal ensures more stable operation.

[0066] Multiple sets of temperature measurements can be arranged inside the furnace body, mainly used to determine whether the air distribution of the gasifier is uniform across the entire cross section.

[0067] When preparing to shut down the gasifier, the steam-to-oxygen ratio in the reaction gases can be adjusted to increase the mixture. Ash discharge from the conical bottom area of ​​the gasifier and oxygen supply to the residual carbon cyclone combustion chamber can then be stopped. After a period of steam purge, the gasifier can enter hot standby mode. If an emergency shutdown is required, the L gas and all oxygen flows can be stopped, followed by a brief steam purge. The gasifier should be in safe hot standby mode.

[0068] When the gasifier is restarted from the hot standby state, reaction gas is input at different positions, and the ratio of water vapor to oxygen in each reaction gas series is appropriately increased first; the control valve discharge and the oxygen combustion of the residual carbon cyclone burner are started, and the gasifier basically enters the operating state. After that, the ratio of water vapor to oxygen in each reaction gas is adjusted to the normal state, so that the gasifier enters stable operation.

[0069] Molten slag operation can be adapted to a wide range of coal types with ash melting points, but is more preferred for coal types with medium and low ash melting points (such as FT at 1100-1350°C). At this time, if the gasifier operating temperature is too low, the gasifier processing capacity cannot be improved. Molten slag operation allows the gasifier to operate at a higher temperature, such as 1500-1800°C. The reaction at high temperature can significantly improve the gasification effect.

[0070] In actual operation, when gasifying coal with a high ash melting point, the gasifier operates normally and the residual carbon cyclone burner also burns the residual carbon normally, but the ash particles may remain in a solid state and be sent to the quencher for cooling. In this way, the same gasification and ash removal effects can be achieved.

[0071] For the operation of coal with particularly high ash melting point, the ratio of water vapor and oxygen in the reaction gas is flexibly adjusted so that the residual carbon is completed at the conical bottom of the gasifier. The operation of the gasifier can be based on Figure 1 The scheme shown is as follows: two reaction gases are fed into the conical bottom of the gas furnace, and one reaction gas is fed into the solid material discharge area.

[0072] Because the ash melting operation occurs outside the gasifier, the reaction gas used for residual carbon combustion can be primarily oxygen. Two reaction gas paths at the conical bottom of the gasifier can independently combust with the residual carbon. Properly increasing the proportion of water vapor in the reaction gas promotes the water-gas shift reaction in the gasifier, producing more hydrogen, significantly reducing the load on downstream catalytic converters. This also increases methane production, further reducing oxygen consumption and improving overall energy conversion efficiency.

[0073] In addition, the gas reaction gas enters the gasifier through multiple series of nozzle groups, and each series includes multiple groups of nozzles. The ratio of water vapor to oxygen in the reaction gas of each series can be set independently, and the flow distribution between each series can vary with the different operating conditions of the gasifier. After each series of reaction gas enters the gasifier, the gas will be naturally redistributed in the gasifier. Using the highest possible height for the bed layer in the middle of the gasifier will be beneficial to the redistribution of the gas over the entire cross section. Setting auxiliary air distribution components in the conical bottom area of ​​the gasifier as needed will be beneficial to the redistribution of the gas, such as Figure 8 As shown in the figure, in terms of operation, an appropriate steam / oxygen ratio is employed to enable the gasification reaction to proceed at the highest possible temperature in the central region of the gasifier, including the conical bottom, while preventing ash melting. This helps maintain a large and uniform solid particle size, ultimately facilitating the most uniform distribution of the reaction gases within the gasifier. After the primary char in the coal is gasified, the residual carbon to mineral ratio can range from 2:1 to 1:1. At this point, the ash particles are still separated by residual carbon, limiting the chance of ash particles agglomerating even at moderately high temperatures. The initial mineral composition of the coal is an internal factor affecting the solid form reaching the conical bottom of the gasifier, while the steam / oxygen ratio is an external factor. Appropriate configuration of the reaction gases in each train and appropriate ash discharge rate control ensure that the residual carbon required for combustion is minimized in the conical bottom and burned as much as possible outside the conical bottom. This improves the solid particle size in the conical bottom region, thereby facilitating uniform distribution of the reaction gases.

[0074] The fixed-bed gasifier of the present invention can be used to produce low-to-medium calorific value syngas from low-pressure gasification, as well as high-pressure syngas for pressurized chemical production or power generation. Operating at approximately 4.0 MPa, it can be used for coal gasification combined cycle power generation and general chemical synthesis needs, such as ammonia synthesis. Operating at approximately 6.5 MPa yields a syngas pressure that meets downstream methanol synthesis requirements, eliminating the need for syngas recompression. Using higher pressures (e.g., 10 MPa) can help increase the methane concentration in the syngas, which is highly advantageous in substitute natural gas production processes and optimizes the thermal efficiency of the entire production process.

[0075] Oxygen and steam are introduced from the bottom of the gasifier. Superheated steam is introduced to preheat the bed material in the gasifier. Oxidation combustion reaction is carried out in the gasifier, so that the bed temperature is higher than the superheated steam temperature. The ratio of the input oxygen and steam is adjusted within the set range so that the ash at the bottom of the gasifier does not melt and remains in a dry slag state.

[0076] Solid or liquid slag discharge is carried out as needed. During solid slag discharge, the highest temperature layer in the gasifier is maintained at the middle and lower part of the gasifier or the upper part of the fixed material discharge area, and the temperature at the gasifier outlet is maintained at the set temperature. During liquid slag discharge, the residual carbon cyclone burner connected to the gasifier is used for combustion, and the flue gas generated by the combustion is sent back to the gasifier for utilization. The solid or liquid produced after combustion enters the slag quencher for cooling and then discharged. During the combustion process, oxygen and steam are introduced into the residual carbon cyclone burner so that the combustion temperature can melt the residual carbon.

[0077] When steady-state gasification treatment is being carried out in the gasifier, the oxygen concentration of the flue gas leaving the residual carbon cyclone combustion tube is tested to see whether the oxygen concentration is within the set oxygen concentration range. If not, the ash discharge speed is increased or decreased as needed; the gas outlet temperature of the gasifier is tested in real time. If the gas outlet temperature continues to rise, the ash discharge speed is increased; if the gas outlet temperature continues to decrease, the ash discharge speed is reduced.

[0078] The present invention has the following characteristics through structural design:

[0079] 1. Set up a high-pressure silo and a material guide pipe, and use the direct feeding of the material guide pipe to ensure the stability of the material level above the gasifier and prevent the coal dust from being carried over before the coal gas leaves the gasifier.

[0080] 2. Set up multiple groups of extended temperature measuring tubes to realize real-time temperature measurement at different positions, track and monitor the temperature at various points of the gasifier cross section and bed height, and accurately grasp the actual working conditions in the gasifier.

[0081] 3. The middle part of the gasifier adopts a gradually enlarged size to facilitate gas distribution and protect the inner surface of the gasifier.

[0082] 4. The bottom of the gasifier is set to be conical. The residual carbon and solid ash after the main gasification reaction are discharged from the outlet of the solid material discharge area at the conical bottom of the furnace body, avoiding large rotating equipment and saving costs.

[0083] 5. The gasification reaction gas is divided into multiple routes and fed into the gasifier according to the needs, and the reaction gases in different routes are

[0084] The ratio of reactive gases, oxygen and water vapor can be adjusted individually to meet different reaction requirements.

[0085] 6. The solid ash containing residual carbon enters the residual carbon cyclone combustion tube through the control valve or spiral control, and the oxygen burns the residual carbon.

[0086] a. The molten slag formed in the lower part of the gasifier cone bottom area is continuously fed into the molten slag quenching cylinder for cooling through the corresponding control valve.

[0087] 7. The slag generated by the combustion of residual carbon is cooled by water in the quencher instead of being discharged directly.

[0088] 8. The high-temperature flue gas generated by the combustion of residual carbon is returned to the conical bottom of the gasifier, and the heat is used to meet the needs of the semi-coke gasification reaction, forming a circular utilization.

[0089] 9. The gasifier is easy to start, stop, hot standby and hot start. When it stops, no large pieces of solidified slag remain in the gasifier.

[0090] 10. The conical bottom ash discharge of the gasifier can be flexibly set and operated according to different coal types and different process requirements.

[0091] a. Dry ash discharge: the residual carbon is burned in the cone bottom area. The combustion temperature is low and no slag is produced. The dry ash discharge speed is controlled by the L valve. Figure 1 shown.

[0092] b. Molten slag discharge: In the molten slag control area at the bottom or the lower part of the conical bottom of the gasifier, the residual carbon is burned at high temperature to directly produce molten slag. The molten slag is continuously discharged to the quencher for cooling through the control of the special-shaped L valve. Figure 10 .

[0093] c. The unburned carbon residue is discharged from the cone bottom area of ​​the gasifier in solid form. The ash discharge speed is controlled by the control valve and sent to the combustion chamber for high-temperature combustion. The molten slag enters the molten slag quenching cylinder for cooling. Figure 3 .

[0094] Through the above settings, different processing methods can be achieved, the residual carbon combustion and ash melting processes can be separated from the gasifier body, and the ash melting operation can be completed with small combustion equipment. The ash and slag discharge of the gasifier is precisely controlled, and the start, stop and hot standby operations of the gasifier become simpler. When the gasifier is stopped, the generated slag can be easily discharged from the conical bottom area, molten slag control area and special-shaped L-valve of the gasifier. The next time, the cold / hot start can be restarted without large pieces of solidified slag, which is obviously beneficial to improving the reliability and availability of the fixed-bed gasifier.

[0095] It should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for removing ash and slag from a fixed bed gasifier, characterized in that: Based on a fixed bed gasification furnace, the fixed bed gasification furnace includes a furnace body, the upper end of the furnace body is connected to a high-pressure silo through a material guide pipe, an air outlet is provided on the upper part of the furnace body, a temperature measuring tube is provided inside the upper part of the furnace body, and a plurality of thermocouples at different heights for measuring temperature are provided inside the temperature measuring tube, a solid material discharge area is provided at the lower part of the furnace body, at least two groups of auxiliary agent inlets are provided at the lower part of the furnace body, the outlet end of the solid material discharge area is connected to a residual carbon processing mechanism, the residual carbon processing mechanism includes an ash melting control cylinder and a slag quencher, the ash melting control cylinder is connected to the outlet end of the solid material discharge area, and the bottom of the ash melting control cylinder is installed There is a pneumatic valve, an additive inlet is provided on the ash melting control cylinder, a balance pipe is installed on the slag quencher, and a vent is provided on the balance pipe. A supplementary gas pipe is installed above the slag quencher. The pneumatic valve extends obliquely from bottom to top, and the high end of the pneumatic valve is connected to the inlet of the slag quencher, and the low end of the pneumatic valve is connected to the ash melting control cylinder. The height difference between the high and low ends of the pneumatic valve is greater than the diameter of the pneumatic valve pipeline; the crushed coal is pressurized and sent to the high-pressure silo located at the top of the furnace body. The guide pipe at the bottom of the high-pressure silo is connected to the top of the furnace body. The pressure briquette coal is moved to a stable material layer height at the top of the furnace body through the guide pipe; The method comprises the following steps: Before starting, add some ash to the bottom of the gasifier. At this time, the solid material discharge area is also filled with ash. Then, pre-load crushed coal on the ash layer to reach the normal material level of the gasifier. Fill the high-pressure silo with material through the coal lock and wait for use. During startup, multiple oxygen and steam mixtures are fed from the bottom of the gasifier, with the ratio of oxygen to steam being the same or different. Superheated steam is introduced to preheat the bed material in the gasifier, and oxidation combustion occurs in the gasifier, raising the bed temperature to a level higher than the superheated steam temperature. The ratio of oxygen and steam input is adjusted within a set range to prevent the ash and slag in the bottom of the gasifier from melting and to maintain a dry slag state. Oxygen is primarily used as the reaction gas in the ash melting control tube. This oxygen burns the residual carbon contained in the solids from the conical bottom area of ​​the furnace body. The heat released by the combustion causes the solid ash to melt and form molten slag. Reaction gas and auxiliary fuel gas are introduced into the ash melting control tube for heating during system startup. During operation, the combustion of oxygen and fuel here continues to increase the temperature to ensure good fluidity of the molten slag, allowing the molten slag to flow through the pneumatic valve to the slag quencher. When molten slag forms at the bottom of the gasifier and in the ash melting control tube, the pressure at the outlet of the pneumatic valve relative to the gasifier is adjusted by supplementing the gas flow rate and the valve of the balance pipe. This changes the liquid level of the molten liquid at the outlet and affects the discharge speed of the molten slag. This maintains a stable liquid level at the bottom of the gasifier and in the ash melting control tube, and continuously feeds the molten slag in the ash melting control tube into the slag quencher through the pneumatic valve. When the gasifier is shut down, the pressure on the upper part of the slag quencher is reduced, the vent of the balance pipe is opened, and the molten slag is quickly discharged from the bottom of the gasifier, the ash melting control tube and the pneumatic valve into the slag quencher, allowing normal granular solids to enter the ash melting control tube and the pneumatic valve, and then wait for the next cold / hot start of the gasifier.

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