System and method for coupling household garbage gasification with coal-fired unit combustion

Abstract

The invention provides a household garbage gasification coupling coal-fired unit combustion system and method. The system comprises a coal-fired boiler, a dry garbage warehouse, a garbage gasification device and a purification device. The household garbage in the dry garbage warehouse is conveyed to an inlet of the garbage gasification device for gasification treatment of the household garbage, and combustible gas is generated; an outlet of the garbage gasification device is connected with an inlet of the purification device, so that the gasified combustible gas is purified in the purification device, and purified combustible gas is obtained; and an outlet of the purification device is connected with a special combustible gas burner at the hearth of the coal-fired boiler, so that the purified combustible gas is conveyed into the coal-fired boiler, and the purified combustible gas and the pulverized coal are mixed for combustion in the coal-fired boiler. According to the system, domestic garbage disposal and flexible peak regulation of the coal-fired unit are efficiently coupled, domestic garbage gasified fuel gas can help the coal-fired unit to stably burn under low load, pollution of domestic garbage to the environment is reduced, the energy utilization efficiency of the coal-fired unit is improved, and deep peak regulation of the coal-fired unit is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization, and particularly relates to a system and method for coupling the gasification of domestic waste with the combustion of a coal-fired unit. Background Art

[0002] With the acceleration of the urbanization process, the annual output of domestic waste in China has increased sharply, and the annual clearing volume has reached 263.5 million tons. However, the traditional landfill and incineration disposal methods are facing severe challenges. The landfill method occupies land resources and has the risk of leachate pollution; although the incineration method can achieve volume reduction, it has problems such as low energy conversion and power generation efficiency (22%-26%), potential risks of fly ash and dioxin pollution, etc. Moreover, waste incineration power plants are mainly built in the suburbs of cities, with high land acquisition and construction costs, and are often challenged by the environmental protection public opinions of surrounding residents. At the same time, the scale of existing coal-fired power generation units in China is huge, and it is urgent to explore a low-carbon transformation path under the background of the "dual carbon" strategy and the flexible peak shaving transformation of coal power. How to achieve the collaborative innovation of efficient and clean disposal of domestic waste and low-carbon operation of the coal power system has become a major technical proposition in the environmental protection and energy fields.

[0003] There is a natural cross-field coupling demand between domestic waste and coal-fired power generation units. Existing waste-coal power co-disposal technologies mainly focus on the co-combustion of refuse-derived fuel (RDF) and coal. However, the RDF preparation process has high energy consumption, and elements such as Cl and K generated by in-furnace co-combustion are prone to cause corrosion and slagging problems on the boiler heating surface. Thermochemical gasification technology can decompose the organic components of domestic waste, realizing the harmless disposal of domestic waste while converting low-grade solid fuels into high-grade homogeneous combustible gases (CH4, H2, CO). Among them, heavy metals enter the bottom slag for solidification, without generating dioxin pollution. The combustible gas becomes clean gas after dechlorination and can enter the furnace through a burner to be co-combusted with pulverized coal, improving the flame stability at low loads and eliminating the high-chlorine corrosion problem of conventional waste fuels. Gasification technology is considered a new option for further realizing the harmlessness and resource utilization of domestic waste compared with incineration power generation. The purified gas coupled with the co-combustion of a coal-fired power generation unit can improve the power generation efficiency of energy; domestic waste, as a renewable energy source, co-combusted with pulverized coal can replace coal and thus reduce carbon emissions.

[0004] Therefore, the present invention proposes a system and method for coupling the gasification of domestic waste with the combustion of a coal-fired unit. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art, and provides a system and method for coupling the gasification of domestic waste with the combustion of a coal-fired unit.

[0006] On the one hand, the present invention provides a system for coupling the gasification of domestic waste with the combustion of a coal-fired unit, the system includes a coal-fired boiler, a dry waste storage, a waste gasification device and a purification device;

[0007] The domestic waste in the dry waste storage is transported to the inlet of the waste gasification device for gasification treatment of domestic waste to generate combustible gas;

[0008] The outlet of the waste gasification device is connected to the inlet of the purification device to transport the combustible gas to the purification device for purification to obtain purified combustible gas;

[0009] The outlet of the purification device is connected to a dedicated combustible gas burner at the furnace of the coal-fired boiler to send the purified combustible gas into the coal-fired boiler, so that the purified combustible gas and pulverized coal are co-fired in the coal-fired boiler.

[0010] Optionally, the system further includes a first fan, and the first fan is arranged in the pipeline between the outlet of the purification device and the dedicated combustible gas burner at the furnace of the coal-fired boiler.

[0011] Optionally, the system further includes a second fan, and the second fan is arranged in the pipeline between the outlet of the waste gasification device and the inlet of the purification device.

[0012] Optionally, the system further includes a third fan, and the third fan is connected to the waste gasification device to inject a gasification agent into the waste gasification device.

[0013] Optionally, the system further includes a coal mill, and the coal mill is connected to the coal-fired boiler to transport pulverized coal to the coal-fired boiler.

[0014] Optionally, the waste gasification device is further connected to the coal mill to transport the slag at the bottom of the waste gasification device to the coal mill for grinding.

[0015] Optionally, the waste gasification device adopts a downdraft domestic waste gasification furnace.

[0016] Optionally, the system further includes a waste conveyor, and the waste conveyor is respectively connected to the dry waste storage and the waste gasification device to transport domestic waste.

[0017] Optionally, the system further includes a denitration device, an air preheater, a dust removal device, an induced draft fan, a desulfurization device and a chimney connected in sequence; wherein, the coal-fired boiler is connected to the denitration device.

[0018] On the other hand, the present invention provides a method for gasifying domestic waste and coupling it with the combustion of a coal-fired unit, using the system for gasifying domestic waste and coupling it with the combustion of a coal-fired unit described above; the method includes:

[0019] Transport the domestic waste in the dry waste storage to the waste gasification device for gasification treatment of domestic waste to generate combustible gas;

[0020] Transport the combustible gas to the purification device for purification to obtain purified combustible gas;

[0021] Transport the purified combustible gas into the coal-fired boiler so that the purified combustible gas and pulverized coal are co-combusted in the coal-fired boiler.

[0022] The combustion system and method of the domestic waste gasification-coupled coal-fired unit of the present invention can realize the reduction and harmless treatment of domestic waste through this system, convert the complex solid domestic waste into homogeneous and clean gas, rely on the existing coal-fired boiler to realize the co-combustion of gas and pulverized coal, help to break through the safety bottleneck of unstable pulverized coal flame during deep peak shaving of coal-fired units, and replace the incinerator to achieve more efficient power generation of renewable energy from domestic waste, forming a new way for the cross-field integrated and large-scale comprehensive utilization of domestic waste and coal; this system efficiently couples the domestic waste treatment with the flexible peak shaving of coal-fired units. The gasified gas of domestic waste can help the coal-fired unit to stably burn at low load, reduce the environmental pollution caused by domestic waste, improve its energy utilization efficiency, and achieve deep peak shaving of coal-fired units. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of a combustion system of a domestic waste gasification-coupled coal-fired unit in an embodiment of the present invention;

[0024] Figure 2 It is a schematic flow diagram of a combustion method of a domestic waste gasification-coupled coal-fired unit in another embodiment of the present invention. Detailed Embodiments

[0025] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0026] As Figure 1 shown, one aspect of the present invention provides a combustion system of a domestic waste gasification-coupled coal-fired unit. The system includes a coal-fired boiler 1, a dry waste storage 2, a waste gasification device 3, and a purification device 4.

[0027] The domestic waste in the dry waste storage 2 is transported to the inlet of the waste gasification device 3 for domestic waste gasification treatment to generate combustible gas.

[0028] The outlet of the waste gasification device 3 is connected to the inlet of the purification device 4 to transport the combustible gas to the purification device 4 for purification to obtain purified combustible gas. Among them, in this embodiment, the waste gasification device 3 can adopt a downdraft domestic waste gasification furnace.

[0029] The outlet of the purification device 4 is connected to a dedicated combustible gas burner at the furnace of the coal-fired boiler 1 to send the purified combustible gas into the coal-fired boiler 1, so that the purified combustible gas and pulverized coal are mixed and burned in the furnace of the coal-fired boiler 1.

[0030] Specifically, domestic waste is successively collected, sorted, compressed and dewatered, dried, and crushed, and then transported to the dry waste storage bin 2 of the coal-fired power plant for storage. Subsequently, it is conveyed to the top of the waste gasification device 3 and continuously fed into the gasification furnace hearth by a sealed spiral feeder arranged at the top. The gasification process of the waste raw material in the down-draft domestic waste gasification furnace is a multi-stage thermochemical conversion process. There are four main reaction zones in the furnace, namely drying, pyrolysis, oxidation, and reduction. The domestic waste first enters the drying layer (100°C - 200°C) of the gasification furnace, and through contact with high-temperature gas, the moisture is removed to form dry materials. The materials then fall downward to the pyrolysis layer (300°C - 600°C), where in an oxygen-deficient environment, the organic matter undergoes pyrolysis cracking, and long-chain molecules decompose into volatile gases (such as CO2, CH4, CO, H2), liquid tar, and solid coke. The mixed products after drying and pyrolysis continue to move downward to the high-temperature oxidation layer (700°C - 1200°C). The gasifying agent (air) is injected from the middle of the furnace body by the third blower 7. The coke undergoes a violent exothermic reaction with oxygen (C + O2 → CO2), and the released heat maintains the high temperature of the system. At the same time, part of the tar is oxidized and decomposed. In the subsequent reduction layer (600°C - 1000°C), the hot coke undergoes endothermic reduction reactions with CO2 and H2O (C + CO2 → 2CO, C + H2O → CO + H2) to generate a combustible synthesis gas rich in CO and H2, and the residual tar is further cracked into small-molecule gases. The unique co-directional flow design of the down-draft gasification furnace enables the pyrolysis gas to pass through the high-temperature oxidation zone, realizing the secondary cracking of tar and significantly reducing the tar content in the synthesis gas. Finally, the synthesis gas is discharged from the bottom, and the ash slag is removed by the slag discharge system. Through regulating the flow rate of the gasifying agent, temperature gradient, and material residence time throughout the process, the efficient conversion of domestic waste into combustible gas (4MJ / Nm 3 ~6MJ / Nm 3 ) is achieved.

[0031] The combustible gas from the outlet of the waste gasification device 4 is sent to the purification device 4 for purification processes such as dust removal, tar removal, and dechlorination to form purified combustible gas. Finally, the purified combustible gas enters the dedicated combustible gas burner of the coal-fired boiler 1. At this time, the purified combustible gas and pulverized coal are mixed and burned in the furnace. The combustible gas can replace 2% - 10% of the coal with the same calorific value, and realize the stable combustion of low-concentration pulverized coal corresponding to an auxiliary load of 15%Pe - 25%Pe of the unit. At the high temperature of 1200°C - 1400°C in the boiler, a small amount of chlorides and fly ash carried by the gasified gas can be turned into harmless flue gas and conventional solid waste through high-temperature treatment, realizing the multi-stage harmless purification treatment of the whole process of domestic waste.

[0032] The system for burning domestic waste gasification coupled with a coal-fired unit of the present invention can achieve the reduction and harmless treatment of domestic waste, convert the complex solid domestic waste into homogeneous clean gas, and rely on the existing coal-fired boiler to achieve the co-combustion of gas and pulverized coal, which helps to break through the safety bottleneck of unstable pulverized coal flame during deep peak shaving of coal-fired units, and replace the incinerator to achieve more efficient power generation of renewable energy from domestic waste, forming a new way for the cross-field integrated and large-scale comprehensive utilization of domestic waste and coal; this system efficiently couples the disposal of domestic waste with the flexible peak shaving of coal-fired units. The gasified gas from domestic waste can help the coal-fired unit to stably burn at low loads, reduce the environmental pollution caused by domestic waste, improve its energy utilization efficiency, and achieve deep peak shaving of coal-fired units.

[0033] Exemplarily, as Figure 1 shown, the system further includes a first fan 5, and the first fan 5 is arranged in the pipeline between the outlet of the purification device 4 and the dedicated combustible gas burner at the furnace of the coal-fired boiler 1.

[0034] Specifically, the purified combustible gas purified by the purification device 4 enters the dedicated combustible gas burner at the furnace of the coal-fired boiler 1 under the boosting action of the first fan 5 (boosting by 2000 Pa).

[0035] Exemplarily, as Figure 1 shown, the system further includes a second fan 6, and the second fan 6 is arranged in the pipeline between the outlet of the waste gasification device 3 and the inlet of the purification device 4.

[0036] Specifically, the combustible gas at the outlet of the waste gasification device 3 is sent to the purification device 4 by the action of the second fan 6 for purification processes such as dust removal, tar removal, and dechlorination to form purified combustible gas.

[0037] Exemplarily, as Figure 1 shown, the system further includes a third fan 7, and the third fan 7 is connected to the waste gasification device 3 to inject gasifying agent into the waste gasification device 3.

[0038] Specifically, during the waste gasification process, gasifying agent (air) is injected into the waste gasification device 3 by the third fan 7.

[0039] Exemplarily, as Figure 1 shown, the system further includes a coal mill 8, and the coal mill 8 is connected to the coal-fired boiler 1 to convey pulverized coal into the coal-fired boiler 1. Specifically, in this embodiment, the number of coal mills 8 can be multiple, and the ground pulverized coal is conveyed into the coal-fired boiler 1 through multiple coal mills 8.

[0040] Exemplarily, the waste gasification device 3 is also connected to the coal mill 8 to convey the slag at the bottom of the waste gasification device 3 into the coal mill 8 for grinding.

[0041] Specifically, the domestic waste gasification furnace slag can also be reused. The slag at the bottom of the waste gasification device 3 is rich in porous coke, which can be sorted by methods such as gravity flotation and further used as an adsorbent in other fields. The carbon-containing furnace slag after sorting can also be transported to the coal mill 8, ground into powder in the coal mill 8, and then enter the coal-fired boiler 1 through the burner for combustion, so that the calorific value of domestic waste can be fully utilized, and the furnace slag is also converted into harmless solid waste after high-temperature treatment.

[0042] Exemplarily, as Figure 1 shown, the system further includes a waste conveyor 9, and the waste conveyor 9 is respectively connected to the dry waste storage 2 and the waste gasification device 3 to transport domestic waste.

[0043] Exemplarily, as Figure 1 shown, the system further includes a denitration device 10, an air preheater 11, a dust removal device 12, an induced draft fan 13, a desulfurization device 14 and a chimney 15 connected in sequence; wherein, the coal-fired boiler 1 is connected to the denitration device 10.

[0044] Specifically, the flue gas after the co-combustion of the purified combustible gas and pulverized coal in the coal-fired boiler 1 is first drawn by the induced draft fan 13 and enters the denitration device 10, and heat exchange is carried out at the air preheater 11. After heat exchange, the flue gas first enters the dust removal device 12 to capture and remove particulate matter, then enters the desulfurization device 14 for spray desulfurization, and finally enters the chimney 15 and is discharged into the atmosphere.

[0045] In this embodiment, the flue gas after the co-combustion of the purified combustible gas and pulverized coal can utilize the purification devices (denitration, dust removal, desulfurization, etc.) at the tail of the coal-fired unit to finally achieve ultra-low emissions of pollutants.

[0046] As Figure 2 shown, another aspect of the present invention provides a method S100 for co-combusting domestic waste gasification and a coal-fired unit, using the system for co-combusting domestic waste gasification and a coal-fired unit described above; the structure of the system for co-combusting domestic waste gasification and a coal-fired unit has been described in detail above and will not be elaborated here.

[0047] The method S100 for co-combusting domestic waste gasification and a coal-fired unit of the present invention specifically may include:

[0048] S110. Transport the domestic waste in the dry waste storage to the waste gasification device for domestic waste gasification treatment to generate combustible gas.

[0049] Specifically, the domestic waste in the dry waste storage 2 is transported to the waste gasification device 3 through the waste conveyor 9 for biochemical waste gasification treatment to generate combustible gas.

[0050] S120. Transport the combustible gas to the purification device for purification to obtain purified combustible gas.

[0051] Specifically, transport the combustible gas to the purification device 4 for purification to obtain purified combustible gas.

[0052] S130. Transport the purified combustible gas into the coal-fired boiler so that the purified combustible gas and pulverized coal are co-combusted in the furnace of the coal-fired boiler.

[0053] Specifically, transport the purified combustible gas into the coal-fired boiler 1 so that the purified combustible gas and pulverized coal are co-combusted in the furnace of the coal-fired boiler 1.

[0054] The method for burning a domestic waste gasification-coupled coal-fired unit of the present invention efficiently couples the domestic waste treatment with the flexible peak shaving of the coal-fired unit. The gasified gas of domestic waste can help the coal-fired unit to stably burn at low loads, reduce the environmental pollution caused by domestic waste, improve its energy utilization efficiency, and achieve deep peak shaving of coal-fired power units. Through this method, the reduction and harmless treatment of domestic waste can be realized, the complex solid waste can be transformed and synthesized into homogeneous and clean gas, and the existing coal-fired boiler is relied on for gas and pulverized coal blending and combustion assistance, which helps to break through the safety bottleneck of unstable pulverized coal flame during deep peak shaving of coal-fired power units, and replace the incinerator to achieve more efficient power generation of renewable energy from domestic waste, forming a new way for the integrated and large-scale comprehensive utilization of domestic waste and coal across fields.

[0055] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims

1. A system for coupling the gasification of domestic waste with the combustion of a coal-fired unit, characterized in that, The system includes a coal-fired boiler, a dry waste storage, a waste gasification device, and a purification device; The domestic waste in the dry waste storage is conveyed to the inlet of the waste gasification device for domestic waste gasification treatment to generate combustible gas; The outlet of the waste gasification device is connected to the inlet of the purification device to convey the combustible gas to the purification device for purification to obtain purified combustible gas; The outlet of the purification device is connected to a dedicated combustible gas burner at the furnace of the coal-fired boiler to send the purified combustible gas into the coal-fired boiler, so that the purified combustible gas and pulverized coal are co-fired in the coal-fired boiler.

2. The system according to claim 1, characterized in that, The system further includes a first fan, and the first fan is arranged in the pipeline between the outlet of the purification device and the dedicated combustible gas burner at the furnace of the coal-fired boiler.

3. The system according to claim 1, wherein The system further includes a second fan, and the second fan is arranged in the pipeline between the outlet of the waste gasification device and the inlet of the purification device.

4. The system according to claim 1, wherein The system further includes a third fan, and the third fan is connected to the waste gasification device to inject a gasifying agent into the waste gasification device.

5. The system according to any one of claims 1 to 4, characterized in that, The system further includes a coal mill, and the coal mill is connected to the coal-fired boiler to convey pulverized coal into the coal-fired boiler.

6. The system according to claim 5, characterized in that The waste gasification device is further connected to the coal mill to convey the slag at the bottom of the waste gasification device into the coal mill for grinding.

7. The system according to any one of claims 1 to 4, characterized in that, The waste gasification device adopts a downdraft domestic waste gasification furnace.

8. The system according to any one of claims 1 to 4, characterized in that, The system further includes a waste conveyor, and the waste conveyor is respectively connected to the dry waste storage and the waste gasification device to convey domestic waste.

9. The system according to any one of claims 1 to 4, characterized in that, The system further includes a denitration device, an air preheater, a dust removal device, an induced draft fan, a desulfurization device, and a chimney that are connected in sequence; wherein, the coal-fired boiler is connected to the denitration device.

10. A method for coupling the gasification of domestic waste with the combustion of a coal-fired unit, characterized in that, A system for burning a domestic waste gasification-coupled coal-fired unit according to any one of claims 1 to 9; the method includes: Convey the domestic waste in the dry waste storage to the waste gasification device for domestic waste gasification treatment to generate combustible gas; Convey the combustible gas to the purification device for purification to obtain purified combustible gas; Convey the purified combustible gas into the coal-fired boiler, so that the purified combustible gas and pulverized coal are co-fired in the coal-fired boiler.

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