Normal-pressure fixed bed gasification device and gasification method suitable for forming carbon-rich fine slag

Abstract

The invention provides a normal-pressure fixed bed gasification device and gasification method suitable for forming carbon-rich fine slag, and belongs to the technical field of coal gasification. Formed carbon-rich fine slag is added from the top of the gasification furnace; oxygen is firstly preheated by steam in an oxygen heater, and then enters a gasifying agent mixing tank of steam, carbon dioxide and oxygen to be mixed; the mixed gasification agent is introduced from the bottom of the gasification furnace, oxygen and the formed carbon-rich fine slag are subjected to a combustion reaction to release a large amount of heat, steam and hot carbon in the furnace further react under the high-temperature condition to generate carbon monoxide and hydrogen, and carbon dioxide and carbon generate carbon monoxide gas at the same time; generated synthesis gas is discharged from the top of the furnace and enters a sensible heat recoverer after being dedusted by a cyclone dust collector; and the synthesis gas discharged from the sensible heat recoverer enters a synthesis gas cooler, is cooled and washed, and is output and delivered. By integrating raw material adaptation, process optimization and system energy-saving design, efficient resource conversion and comprehensive energy utilization of the gasified fine slag are achieved.

Description

Technical Field

[0001] This invention provides an atmospheric pressure fixed-bed gasification device and gasification method suitable for forming carbon-rich fine slag, belonging to the field of coal gasification technology. Background Technology

[0002] Fluidized bed coal gasification technology is one of the core methods for the clean and efficient utilization of coal. With the large-scale application of this technology, a large amount of gasification slag is generated. This slag is mainly carried out by the gasification gas stream, and is obtained after preliminary washing, flocculation sedimentation, and pressure filtration. It has a high moisture content and contains 20%-40% residual carbon. Currently, its disposal methods mainly involve open-air stockpiling and landfilling, which not only releases harmful gases and generates dust pollution, but also leaches heavy metals under rainwater runoff, causing serious pollution to soil and water bodies. Only a small amount of gasification slag undergoes carbon-ash separation to obtain carbon-rich components, which are used to prepare high-value-added products such as adsorbent materials and composite materials. Therefore, achieving large-scale utilization of gasification slag is urgently needed.

[0003] Carbon-rich fine slag undergoes a high-temperature gasification process of 1400-1600℃, resulting in a high degree of carbon graphitization and low gasification reactivity. This makes fluidized bed and entrained flow bed technologies unsuitable for its secondary gasification. Fixed bed gasifiers, however, offer advantages such as long residence time and no material entrainment, promising suitable reaction conditions for the regasification of carbon-rich fine slag. Fixed bed gasification typically requires 5-50mm lumps as feedstock, necessitating the processing of the carbon-rich fine slag into molds with sufficient mechanical strength. Researchers have explored molding processes for carbon-rich fine slag to address this issue (e.g., patent CN 119776033 A). However, currently, no atmospheric pressure fixed bed gasification device suitable for molding carbon-rich fine slag has been developed.

[0004] The apparatus and process provided by this invention aim to solve the gasification problem of formed carbon-rich fine slag. Summary of the Invention

[0005] This invention aims to provide an atmospheric pressure fixed-bed gasification device and method for shaped carbon-rich fine slag, to solve the technical bottlenecks in the prior art, such as the difficulty in large-scale and high-value utilization of gasified fine slag, and the unsuitability of carbon-rich fine slag for conventional secondary gasification due to its poor reactivity. By integrating raw material adaptation, process optimization, and system energy-saving design, efficient resource conversion and comprehensive energy utilization of gasified fine slag are achieved.

[0006] The specific technical solution is as follows:

[0007] An atmospheric pressure fixed-bed gasification unit suitable for forming carbon-rich fine slag includes an oxygen heater, a gasifying agent mixing tank, a gasifier jacketed steam drum, a sensible heat recovery steam drum, a gasifier, a cyclone dust collector, a sensible heat recovery unit, and a syngas cooler.

[0008] The water jacket of the gasifier is connected to the steam drum of the gasifier jacket;

[0009] The bottom of the gasifier is connected to a gasifying agent mixing tank, which is equipped with a steam inlet, a carbon dioxide inlet, and an oxygen inlet. The oxygen inlet is equipped with an oxygen heater. The externally supplied oxygen is first preheated by steam in the oxygen heater and then enters the gasifying agent mixing tank for mixing. The shaped carbon-rich fine slag is added to the gasifier from the top, and the mixed gasifying agent is introduced from the bottom of the gasifier. The oxygen reacts with the shaped carbon-rich fine slag to release a large amount of heat. Under high temperature conditions, the steam reacts further with the hot carbon in the furnace to generate carbon monoxide and hydrogen, and the carbon dioxide reacts with the carbon to generate carbon monoxide.

[0010] The gasifier is also connected to a cyclone dust collector, which is connected to a sensible heat recovery unit. The syngas generated in the gasifier is discharged from the top of the furnace, and after being removed by the cyclone dust collector, it enters the sensible heat recovery unit.

[0011] The gasifier and the steam drum of the sensible heat recovery unit form a loop connection; the steam drum of the sensible heat recovery unit is connected to the sensible heat recovery unit; the sensible heat recovery unit is connected to the syngas cooler; the syngas exiting the sensible heat recovery unit enters the syngas cooler, and after cooling and washing, it is output and sent out.

[0012] Furthermore, the gasifier includes a feeding device, a furnace body, and a slag discharge device;

[0013] The feeding device includes a raw material silo, an automatic feeder at the top of the raw material silo, and a manual slide valve at the bottom of the raw material silo; the shaped carbon-rich fine slag is conveyed to the automatic feeder by a belt and added into the furnace body by the automatic feeder.

[0014] The furnace body has a bottom gasifying agent inlet and a top syngas outlet. The gasifying agent comes into counter-current contact with the formed carbon-rich fine slag to improve thermal efficiency and reduce heat loss. A grate is located at the bottom of the furnace body to support the fuel layer and evenly distribute the gasifying agent. A radar and hydraulic focus detector are installed at the top of the furnace body for real-time monitoring and data accuracy. The furnace body is equipped with a two-section water jacket: an upper water jacket and a lower water jacket. The upper water jacket structure significantly reduces manufacturing costs due to its lower operating temperature. A manhole is also provided on the furnace body.

[0015] The ash discharge device is located on the lower side of the bottom of the furnace body and includes two ash bins arranged side by side. Each ash bin is equipped with a manual ash bin slide valve at the bottom.

[0016] An atmospheric pressure fixed-bed gasification method suitable for forming carbon-rich fine slag, employing the aforementioned atmospheric pressure fixed-bed gasification device for forming carbon-rich fine slag; the method includes the following steps:

[0017] The shaped carbon-rich fine slag is conveyed by belt to the raw coal bunker at the top of the gasifier, and then added to the gasifier in a timed and quantitative manner by an automatic feeder;

[0018] The externally supplied oxygen is first preheated by steam in an oxygen heater, and then mixed in a vaporizing agent mixing tank containing steam, carbon dioxide and oxygen.

[0019] The mixed gasifying agent is introduced from the bottom of the gasifier. Oxygen reacts with the shaped carbon-rich fine slag to release a large amount of heat. Under high temperature conditions, steam reacts further with the hot carbon in the furnace to generate carbon monoxide and hydrogen. Carbon dioxide reacts with carbon to generate carbon monoxide.

[0020] The generated synthesis gas is discharged from the top of the furnace, and after being removed by a cyclone dust collector, it enters the sensible heat recovery unit.

[0021] The syngas exiting the sensible heat recovery unit enters the syngas cooler, and after cooling and washing, it is output and sent out.

[0022] The gasifier of this invention uses a fixed-bed gasifier with a high aspect ratio to gasify the shaped carbon-rich fine slag feed. This ensures that, under the same gasification intensity and gas volume, the taller furnace body provides a longer flow path and a longer residence time for solid particles and reactant gases, thereby improving the carbon conversion rate of the shaped carbon-rich fine slag.

[0023] Using a fixed-bed gasifier with a high aspect ratio to gasify the shaped carbon-rich fine slag feed helps to establish a gentler and more stable axial temperature gradient from the furnace head (combustion zone) to the furnace tail (outlet), maintain a more stable high-temperature zone, and provide a wider reaction window for the shaped carbon-rich slag with lower reactivity.

[0024] The fixed-bed gasifier adopts a two-stage water jacket design, optimized for different operating conditions and technical requirements of each stage. This design saves costs while achieving multiple functions: the lower jacket effectively prevents the furnace body from burning through and produces a large amount of process steam as a byproduct; the upper jacket is used to recover low-temperature waste heat from the system, improving overall energy efficiency.

[0025] The beneficial effects of the technical solution of this invention are as follows:

[0026] 1. Solve the problem of disposing of gasification slag;

[0027] 2. Compared with traditional processing methods and gasification devices, this invention can improve gasification efficiency and syngas quality, with a carbon conversion rate of up to 95%;

[0028] 3. In the design of this device, two-stage jacket protection and corrosion-resistant grate prevent equipment burn-through and corrosion, while gasifying agent premixing and dual coke detection monitoring ensure stable and controllable furnace conditions.

[0029] 4. This high length-to-diameter ratio gasifier gasifies difficult-to-gasify carbon-rich fine slag, providing ideas for the design of gasification devices for other difficult-to-gasify raw materials. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the device structure of the present invention;

[0031] Figure 2 This is a schematic diagram of the gasifier structure of the present invention. Detailed Implementation

[0032] The specific technical solution of the present invention will be described in conjunction with the accompanying drawings.

[0033] like Figure 1 As shown, an atmospheric pressure fixed-bed gasification device suitable for forming carbon-rich fine slag includes an oxygen heater 9, a gasifying agent mixing tank 8, a gasifier jacketed steam drum 1, a sensible heat recovery steam drum 4, a gasifier 3, a cyclone dust collector 7, a sensible heat recovery unit 6, and a syngas cooler 5.

[0034] The water jacket of gasifier 3 is connected to the steam drum 1 of the gasifier jacket;

[0035] The bottom of the gasifier 3 is connected to the gasifying agent mixing tank 8, which is equipped with a steam inlet, a carbon dioxide inlet and an oxygen inlet. The oxygen inlet is equipped with an oxygen heater 9. The externally supplied oxygen is first preheated by steam in the oxygen heater 9 and then enters the gasifying agent mixing tank 8 for mixing. The shaped carbon-rich fine slag is added to the gasifier 3 from the top, and the mixed gasifying agent is introduced from the bottom of the gasifier 3. The oxygen reacts with the shaped carbon-rich fine slag to release a large amount of heat. Under high temperature conditions, the steam reacts further with the hot carbon in the furnace to generate carbon monoxide and hydrogen, and the carbon dioxide reacts with the carbon to generate carbon monoxide.

[0036] The gasifier 3 is also connected to the cyclone dust collector 7, which is connected to the sensible heat recovery unit 6. The synthesis gas generated in the gasifier 3 is discharged from the top of the furnace and enters the sensible heat recovery unit 6 after being removed by the cyclone dust collector 7.

[0037] Gasifier 3 and sensible heat recovery steam drum 4 form a loop connection; sensible heat recovery steam drum 4 is connected to sensible heat recovery unit 6; sensible heat recovery unit 6 is connected to syngas cooler 5; syngas exiting sensible heat recovery unit 6 enters syngas cooler 5, and after cooling and washing treatment, it is output and sent out.

[0038] like Figure 2 As shown, the gasifier 3 includes a feeding device, a furnace body, and a slag discharge device;

[0039] The feeding device includes a raw material silo 311, an automatic feeder 31 is provided at the top of the raw material silo 311, and a manual slide valve 310 is provided at the bottom of the raw material silo 311; the shaped carbon-rich fine slag is conveyed to the automatic feeder 31 by a belt and added into the furnace body by the automatic feeder 31.

[0040] The furnace body has a bottom gasifying agent inlet and a top syngas outlet, with the gasifying agent in counter-current contact with the raw materials to improve thermal efficiency and reduce heat loss. A grate 36, made of heat-resistant and corrosion-resistant material, is located at the bottom of the furnace body, serving both to support the gasified raw materials and as a gas distribution plate to ensure uniform gas distribution. A radar focus detector 32 and a hydraulic focus detector 33 are located at the top of the furnace body for real-time monitoring and data accuracy. Based on the working pressure and temperature of the gasification process, the furnace body is equipped with two water jackets: an upper water jacket 39 and a lower water jacket 35. The upper water jacket 39 structure significantly reduces manufacturing costs due to its lower operating temperature. A manhole 34 is also provided on the furnace body.

[0041] The ash discharge device is located on the lower side of the bottom of the furnace body and includes two ash bins 38 arranged side by side. Each ash bin 38 is equipped with a manual ash bin slide valve 37 at the bottom.

[0042] The present invention provides an atmospheric pressure fixed-bed gasification device and gasification method suitable for forming carbon-rich fine slag, including gasifying agent preheating, oxidation and reduction of the forming carbon-rich fine slag, dust removal, cooling and washing of the syngas, and the specific steps are as follows:

[0043] The shaped carbon-rich fine slag is conveyed by belt to the raw coal bunker at the top of the gasifier 3, and then added to the atmospheric pressure fixed bed continuous gasifier 3 in a timed and quantitative manner by the automatic feeder 31;

[0044] The externally supplied oxygen is first preheated by steam to about 150°C in the oxygen heater 9, and then mixed in the vaporizing agent mixing tank 8 containing steam, carbon dioxide and oxygen.

[0045] The mixed gasifying agent is introduced from the bottom of the gasifier 3. Oxygen reacts with the shaped carbon-rich fine slag to release a large amount of heat. Under high temperature conditions, steam reacts further with the hot carbon in the furnace to generate carbon monoxide and hydrogen. Carbon dioxide reacts with carbon to generate carbon monoxide.

[0046] The generated synthesis gas is discharged from the top of the furnace, and after being removed by the cyclone dust collector 7, it enters the sensible heat recovery unit 6, where the temperature drops from about 380-450℃ to about 145℃.

[0047] The syngas exiting the sensible heat recovery unit 6 enters the syngas cooler 5, where it is cooled and washed until its temperature drops to 40-50°C, and then it is output and sent out.

[0048] This invention optimizes the gasification process and improves overall energy efficiency through the following technical means:

[0049] Gasifying agent composition adjustment: Oxygen, steam and CO2 pipelines are set on the gasifying agent pipeline. By supplying CO2 into the furnace, it reacts with the raw materials to generate CO, thereby effectively increasing the CO content in the synthesis gas.

[0050] Uniform mixing of gasifying agents: A gasifying agent mixing tank 8 is configured to fully mix various gasifying agents before introducing them into the furnace, avoiding uneven distribution caused by adding different gasifying agents individually, which could lead to fluctuations in the furnace temperature field and ensure a stable gasification process.

[0051] Jacketed System and Process Steam Recovery: The gasifier is equipped with upper and lower water jackets, which are connected to the steam drum respectively. The lower jacket prevents the furnace body from burning through due to high temperature, while the upper jacket, in conjunction with the lower jacket, recovers the heat of reaction for the process steam required by the production system.

[0052] Syngas dust removal and waste heat recovery: The syngas produced by the gasifier first passes through a cyclone dust collector 7 to remove fine slag with high carbon content. After dust removal, the high-temperature syngas enters the waste heat recovery unit to recover sensible heat and further produce process steam.

[0053] Shared steam drum design: The lower jacket of the gasifier and the waste heat recovery unit share the same steam drum, realizing heat source integration and steam system simplification, and improving the overall energy utilization efficiency.

Claims

1. An atmospheric pressure fixed-bed gasification device suitable for producing carbon-rich fine slag, characterized in that, It includes an oxygen heater (9), a gasifying agent mixing tank (8), a gasifier jacketed steam drum (1), a sensible heat recovery steam drum (4), a gasifier (3), a cyclone dust collector (7), a sensible heat recovery unit (6), and a syngas cooler (5); The water jacket of the gasifier (3) is connected to the steam drum (1) of the gasifier jacket; The bottom of the gasifier (3) is connected to the gasifying agent mixing tank (8). The gasifying agent mixing tank (8) is equipped with a steam inlet, a carbon dioxide inlet and an oxygen inlet. The oxygen inlet is equipped with an oxygen heater (9). The externally supplied oxygen is first preheated by steam in the oxygen heater (9) and then enters the gasifying agent mixing tank (8) for mixing. The shaped carbon-rich fine slag is added to the gasifier (3) from the top. The mixed gasifying agent is introduced from the bottom of the gasifier (3). The oxygen reacts with the shaped carbon-rich fine slag to release a large amount of heat. Under high temperature conditions, the steam reacts with the hot carbon in the furnace to generate carbon monoxide and hydrogen. Carbon dioxide reacts with carbon to generate carbon monoxide. The gasifier (3) is also connected to the cyclone dust collector (7), which is connected to the sensible heat recovery unit (6). The synthesis gas generated in the gasifier (3) is discharged from the top of the furnace and enters the sensible heat recovery unit (6) after being dusted by the cyclone dust collector (7). The gasifier (3) and the steam drum (4) of the sensible heat recovery unit form a loop connection; the steam drum (4) of the sensible heat recovery unit is connected to the sensible heat recovery unit (6); the sensible heat recovery unit (6) is connected to the syngas cooler (5); the syngas exiting the sensible heat recovery unit (6) enters the syngas cooler (5), and after cooling and washing, it is output and sent out.

2. The atmospheric pressure fixed-bed gasification device for forming carbon-rich fine slag according to claim 1, characterized in that, The gasifier (3) includes a feeding device, a furnace body, and a slag discharge device; The feeding device includes a raw material silo (311), an automatic feeder (31) is provided at the top of the raw material silo (311), and a manual slide valve (310) is provided at the bottom of the raw material silo (311); the shaped carbon-rich fine slag is conveyed to the automatic feeder (31) by a belt and added into the furnace body by the automatic feeder (31); The furnace body is provided with a bottom gasifying agent inlet and a top syngas outlet. The gasifying agent is in counter-current contact with the shaped carbon-rich fine slag to improve thermal efficiency and reduce heat loss. The bottom of the furnace body is provided with a grate (36) to support the fuel layer and evenly distribute the gasifying agent. The top of the furnace body is provided with a radar slag detector (32) and a hydraulic slag detector (33) for real-time monitoring and ensuring data accuracy. The furnace body is equipped with two water jackets: an upper water jacket (39) and a lower water jacket (35). The upper water jacket (39) structure significantly reduces manufacturing costs due to its lower corresponding temperature. The furnace body is also provided with a manhole (34). The ash discharge device is located on the lower side of the bottom of the furnace body and includes two ash bins (38) arranged side by side. Each ash bin (38) is equipped with a manual ash bin slide valve (37) at the bottom.

3. A method for atmospheric pressure fixed-bed gasification of carbon-rich fine slag, characterized in that, The atmospheric pressure fixed-bed gasification device for forming carbon-rich fine slag, as described in claim 1 or 2, comprises the following steps: The shaped carbon-rich fine slag is conveyed by belt to the raw coal bunker at the top of the gasifier (3), and added to the gasifier (3) in a timed and quantitative manner by an automatic feeder (31). The externally supplied oxygen is first preheated by steam in the oxygen heater (9), and then mixed in the vaporizing agent mixing tank (8) of steam, carbon dioxide and oxygen; The mixed gasifying agent is introduced from the bottom of the gasifier (3). Oxygen reacts with the shaped carbon-rich fine slag to release a large amount of heat. Under high temperature conditions, steam reacts further with the hot carbon in the furnace to generate carbon monoxide and hydrogen. Carbon dioxide reacts with carbon to generate carbon monoxide. The generated synthesis gas is discharged from the top of the furnace, and after being removed by the cyclone dust collector (7), it enters the sensible heat recovery unit (6). Syngas from the heat recovery unit (6) enters the syngas cooler (5), and after cooling and washing, it is output and sent out.

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