CN101850350A - A new treatment method of oxygen-enriched gasification of municipal solid waste - Google Patents

Abstract

The invention discloses a novel treatment method for oxygen-enriched gasification of urban solid waste, comprising the following steps: (1) pretreatment of urban domestic waste; (2) oxygen-enriched pyrolysis and gasification of garbage; (3) gasification gas purification; 4) Gasification gas reuse; (5) Sewage treatment and energy saving. Due to the oxygen-enriched conditions, the nitrogen content entering the reactor is less, so the nitrogen oxides produced during the reaction process are also very small, which provides assistance for subsequent purification and reduces secondary pollution; oxygen-enriched pyrolysis gasification technology Compared with the original conventional combustion products, the combustion products produced have less nitrogen, which accounts for 60% of the total gas production. Therefore, the heat loss of the oxygen-enriched pyrolysis gasification technology is low, and the heat loss caused is only about half of the original conventional combustion. ;The generated ash can be used in paving or construction industries; no harmful gas emissions such as dioxin, no waste water, dust and other harmful substances; when dealing with urban waste, there is no need to classify garbage; no fuel other than garbage is required.

Description

A new treatment method of oxygen-enriched gasification of municipal solid waste

technical field

The invention relates to the technical field of urban solid waste treatment, in particular to an oxygen-enriched pyrolysis gasification method for waste that reduces secondary pollution, greatly improves product calorific value and saves energy.

Background technique

There are many methods of garbage disposal, such as landfill, composting and incineration, which are relatively mature methods. Garbage pyrolysis treatment has attracted widespread attention for its advantages of high energy recovery rate and low pollution. Pyrolysis will become a very promising garbage treatment method to replace traditional garbage treatment methods. Research on pyrolysis technology started as early as the 1930s. Pyrolysis combustion technology has the characteristics of uniform gas and coke properties and sufficient combustion. It is currently used in the direct gasification of shaft furnaces developed by Nippon Steel Works--Molten solid waste incineration system, represented by Mitsui Shipbuilding and Yuxijia Co., Ltd. Rotary kiln type solid waste gasification - melting and so on. In recent years, experts and scholars at home and abroad have put forward some valuable theories and methods in the research on pyrolysis theory. Most of these methods focus on the experimental analysis or theoretical analysis of single-component waste pyrolysis, which is still far from practical application. Different from biomass pyrolysis, the composition of waste is complex, and the optimal pyrolysis temperature of each waste composition is different, which makes there is a big difference between theoretical analysis and practical application.

Oxygen-enriched combustion technology was proposed by Horne and Steinburg in 1981, which has the advantages of sufficient combustion, greatly reduced smoke emission, and high efficiency. The current main research and application fields of oxygen-enriched combustion technology include power plant boilers, magnetic fluid power generation technology, fuel cells, IGCC and combined energy production systems, etc., and the combustion objects include coal powder, garbage, natural gas and coke oven gas, etc.; however, the existing heat However, there are still problems such as low combustion efficiency, large smoke exhaust, and carbon dioxide emissions; the simple oxygen-enriched combustion of municipal solid waste cannot fundamentally solve the problems of solid phase (heterogeneous phase) combustion and difficult control.

Contents of the invention

The purpose of the present invention is to combine oxygen enrichment with gasification, determine the process route and method of oxygen-enriched pyrolysis gasification of solid domestic waste, and design a systematic treatment method, aiming to solve the problems existing in the above methods and realize waste reduction , Harmless and resourceful.

In order to achieve the above object, the present invention adopts the following technical solutions: a novel treatment method for oxygen-enriched municipal solid waste, comprising the following steps:

(1) Municipal solid waste pretreatment: store the municipal solid waste in the garbage pit, after crushing, screening and pressing, input it into the rotary kiln for drying and dehydration, and control the moisture content within 25%;

(2) Oxygen-enriched pyrolysis gasification of garbage: The pretreated municipal solid waste is sent into the gasifier through the feeder, and oxygen-enriched gas is used as the gasification medium. Incomplete combustion, gasification reaction occurs, and combustible gas is generated;

(3) Purification of gasification gas: the combustible gas is purified by a purification system consisting of Venturi and at least two-stage water washing towers, and the ash and tar in the gas are removed and stored in the gas cabinet;

(4) Gasification gas reuse;

(5) Sewage treatment and energy saving: After the above steps (1) and (2), the landfill leachate passes through the grid to trap larger impurities and floating objects in the water, and then flows into the sewage regulating tank by itself, and the effluent of the sewage regulating pond is lifted to Coagulation, sedimentation and air flotation integrated tank, the effluent after coagulation, sedimentation and air flotation treatment enters the anaerobic hydrolysis and acidification tank, and the effluent of the hydrolysis and acidification tank is lifted to the anaerobic treatment stage by pump; the gas generated in the garbage pit is pumped out by the pump and directly transported to In the gasification furnace, a large amount of hot steam is generated during the washing process of the first-stage water washing tower to supply heat to the rotary kiln to dry the garbage through the heat exchanger, and at the same time, the exhaust gas after combustion in the internal combustion engine is also passed into the rotary kiln to dry the garbage.

Municipal solid waste belongs to solid fuel, and its element composition is mainly C, H and O. In addition, although it also contains N, S and some other trace elements, for the gasification reaction, due to the small amount of N, S and other elements, thus can be ignored. At the same time, compared with coal, municipal solid waste has a lower carbon content, and the H/C and O/C ratios are quite high, so that it has a higher volatile content, but its calorific value is lower than that of ordinary coal. In addition, due to the low content of N, S and other elements in municipal solid waste, the amount of pollution emissions formed by N and S components in the thermal conversion process is relatively low, and its activity of fixing carbon is much higher than that of coal. These characteristics determine that MSW is more suitable for gasification.

In order to fully dehydrate and mix the garbage before entering the gasifier, improve the operation of the gasifier, and increase the calorific value of the garbage entering the furnace, first store the garbage in the garbage pit to prolong the parking time of the garbage in the pit (staying time) The time is about 7-10 days), and at the same time, before the garbage enters the gasifier, it is further dried through the rotary kiln; after step 1, the moisture content of the municipal solid waste is controlled within 25%, and then the pretreated The municipal solid waste is transported to the gasification furnace. The gasification process developed by this invention uses rich oxygen as the gasification medium, and has the characteristics of controlling the operating temperature in different areas. The gas components are O ₂ , CO, H ₂ , CH ₄ and CnHm, etc. , the calorific value of the produced gas can reach 3000kcal/m ³ ;

In step 2, the garbage is conveyed by the belt after being crushed, screened, squeezed and dehydrated, and sent into the gasifier through the uniform feeder, and part of the garbage is burned with oxygen to provide the heat required for thermal decomposition. Under the condition of oxygen, a thermal decomposition reaction occurs, and volatile matter and coke are precipitated. The volatile matter stays in the high-temperature reaction zone and undergoes a secondary reaction. Venturi dust removal and water washing coke removal are used to purify the gas. A large amount of water is sprayed to quickly cool down the gas, reduce the residence time of the gas in the dioxin-forming temperature range, and take away the tar.

The high calorific value gas purified in step 3 is stored in the gas storage tank. Due to the high calorific value of this kind of gas, it can be used as raw material gas for synthesis, and it can also be adapted to various combustion furnaces.

Sewage treatment includes landfill leachate, production wastewater, etc. The leachate is discharged to the sewage adjustment tank for collection and then enters the sewage treatment facility for treatment. The relevant process is as follows:

The landfill leachate passes through the grid to trap larger impurities and floating objects in the water, and then flows into the regulating tank by itself; the effluent from the regulating tank is lifted by the pump to the integrated pool of coagulation, sedimentation and air flotation, where the pH value is adjusted and harmful microorganisms are removed; The effluent after coagulation, sedimentation and air flotation treatment enters the anaerobic hydrolysis acidification tank, which reduces the concentration of suspended solids in the sewage and effectively eliminates the inhibitory effect of poisons on microorganisms; Improve the biodegradability of wastewater, on the other hand reduce the COD in wastewater, etc.

In terms of energy saving, on the one hand, in order to maintain the negative pressure in the garbage pit, use the pump to pump out the gas generated in the garbage pit, and directly pass it into the gasifier. Secondly, a large amount of hot steam is generated during the first water washing process to supply heat to the rotary kiln through the heat exchanger. At the same time, the exhaust gas after combustion in the internal combustion engine is also passed into the rotary kiln to dry the garbage.

Compared with the prior art, the present invention has the following advantages: (1) Owing to having oxygen-enriched conditions, the nitrogen content entering the reactor is less, so the nitrogen oxides produced in the reaction process are also very few, which provides a great deal of room for subsequent purification. (2) The combustion products produced by the oxygen-enriched pyrolysis gasification technology have less nitrogen, which accounts for 60% of the total gas production, than the original conventional combustion products, so the oxygen-enriched pyrolysis gas The heat loss of chemical technology is low, and the heat loss caused is only about half of the original conventional combustion; (3) The mixed gas is a mixture containing carbon monoxide, a small amount of nitrogen, alkanes and hydrogen, which greatly improves the scope of application of the generated gas (4) The ash produced can be used for paving or construction; (5) No harmful gas emissions such as dioxin, no waste water, dust and other harmful substances; (6) When dealing with urban waste, it is not necessary to classify the waste (7) fuel other than rubbish is not required.

Description of drawings

Fig. 1 is a fluid figure (one) of municipal refuse treatment process of the present invention;

Fig. 2 is the fluid diagram (two) of municipal refuse treatment process of the present invention;

Fig. 3 is a schematic diagram of the influence of oxygen enrichment amount on gasification time, unburned rate and reaction temperature when the equivalence ratio is 0.27;

Fig. 4 is a schematic diagram of the influence of oxygen enrichment on product calorific value when the equivalence ratio is 0.25;

Fig. 5 is a schematic diagram of the sewage treatment process of the present invention;

Explanation of reference numerals: 1-feeder, 2-gasifier, 3-venturi, 4-first-stage water washing tower, 5-second-stage water washing tower, 6-gas cabinet.

Detailed ways

The content of the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Example:

Please refer to Fig. 1 and shown in Fig. 2, a kind of treatment method of oxygen-enriched oxidation of novel municipal solid waste, comprises the following steps:

(1) Municipal solid waste pretreatment: store the municipal solid waste in the garbage pit, after crushing, screening and pressing, input it into the rotary kiln for drying and dehydration, and control the moisture content within 25%;

(2) Oxygen-enriched pyrolysis gasification of garbage: The pretreated municipal solid waste is sent into the gasification furnace 2 through the feeder 1, and oxygen-enriched gas is used as the gasification medium. Incomplete combustion in the furnace 2, gasification reaction occurs, and combustible gas is generated;

(3) Purification of gasification gas: the combustible gas is purified by a purification system consisting of Venturi 3, the first-stage water washing tower 4 and the second-stage water washing tower 5, and the ash and tar in the gas are removed and stored in the gas cabinet 6;

(4) Reuse of gasification gas; the synthesis gas produced through the above steps is mainly hydrogen and carbon monoxide, with high calorific value and greatly improved scope of application. It can be used as raw material gas for chemical synthesis, heavy oil burner raw material gas, internal combustion engine, etc., expanding the scope of reuse of gasification gas.

(5) Sewage treatment and energy saving: Please refer to Figure 5. After the above steps (1) and (2), the landfill leachate passes through the grid to trap larger impurities and floating objects in the water, and then flows into the sewage regulating tank by itself. The effluent from the regulating tank is pumped to the coagulation-sedimentation-air-flotation integrated pool, and the effluent after coagulation-sedimentation-air flotation treatment enters the anaerobic hydrolysis and acidification tank, and the effluent from the hydrolysis and acidification tank is pumped to the anaerobic treatment stage; The generated gas is directly transported to the gasifier, and a large amount of hot steam is generated during the washing process of the first-stage water washing tower to supply heat to the rotary kiln for drying garbage through the heat exchanger, and at the same time, the exhaust gas after combustion in the internal combustion engine is also passed into the gasifier. The rotary kiln dries the garbage.

The pyrolysis and gasification process of garbage in the pyrolysis gasification device belongs to the chemical reaction process of multi-phase multi-component system. Under certain conditions of temperature, pressure, and original reactants, the entire device is regarded as a closed ideal reaction system, and the analysis of the entire waste oxygen-enriched pyrolysis gasification system under different conditions (equivalent ratio, oxygen-enriched gasification system) Quantity) when the thermodynamic equilibrium state is reached, the calorific value of the gas, the content of hydrogen and carbon monoxide in the gas, and the content of nitrogen in the product are investigated. At the same time, the changes of the reaction speed, reaction completeness and reaction temperature under oxygen-enriched conditions are investigated.

The equilibrium constant method and the Gibbs minimum free energy method are commonly used to deal with the chemical equilibrium of complex systems in chemical thermodynamics. Here, the Gibbs minimum free energy method is used: under isothermal and isobaric conditions, the minimum Gibbs free energy of the system is used as the balance The criterion is that under a certain temperature and pressure, the original reaction substances such as air and garbage are added to the waste incinerator to perform various complex chemical reactions. When the system reaches a chemical equilibrium state, the Gibbs free energy of the entire system is the minimum. Calculate the composition and concentration of various gaseous substances in the waste pyrolysis system under this equilibrium condition under different oxygen enrichment conditions, especially the concentration of nitrogen, so as to obtain the calorific value of the gas under different components.

It can be seen from Figure 3 that with the increase of oxygen enrichment, the reaction time is shortened, the reaction temperature is higher, the reaction is more complete, and the unburned rate is greatly reduced, which is conducive to improving the gasification efficiency, improving the heat transfer efficiency and energy utilization rate ; Better ignition characteristics can be obtained, flame stability can be improved, combustion load ratio can be expanded, flame characteristics and flame shape control can be improved.

It can be seen from Figure 4 that with the increase of the oxygen enrichment degree, the nitrogen content in the product decreases, and the calorific value of the gas increases rapidly, which greatly improves the scope of application of the generated gas.

The above detailed description is a specific description of the feasible embodiment of the present invention. This embodiment is not used to limit the patent scope of the present invention. Any equivalent implementation or change that does not deviate from the present invention should be included in the patent scope of this case. middle.

Claims (1)

1. the processing method of a new city solid waste by oxygen-rich gasification is characterized in that, comprises the steps:

(1) domestic waste preliminary treatment: domestic waste is stored in the dump pit, after broken, screening, squeezing, is input to drying and dewatering in the rotary kiln, moisture is controlled in 25%;

(2) rubbish oxygen enrichment pyrolytic gasification: will send in the gasification furnace by batcher through pretreated domestic waste, and utilize oxygen rich air as gasifying medium, in the anoxic atmosphere, rubbish is imperfect combustion in gasification furnace, and the generating gasification reaction generates fuel gas;

(3) gasification gas purifies: fuel gas is through by venturi and the cleaning system purification formed of two-stage water scrubber at least, deposits gas holder in after removing ash in the combustion gas, tar;

(4) gasification gas utilizes again;

(5) sewage disposal and energy-conservation: in the grid trap water, enter the sewage regulating reservoir than gravity flow behind big impurity and the floating thing through the percolate after above-mentioned steps (1) and the step (2), the water outlet of sewage regulating reservoir is promoted to coagulating sedimentation air supporting integral pool through pump, water outlet after coagulating sedimentation air supporting is handled enters the anaerobic hydrolysis-acidification pond, and the hydrolysis acidification pool water outlet is promoted to anaerobic treatment stage with pump; Utilize pump to extract the gas that produces in the dump pit out, be delivered directly in the gasification furnace, produce a large amount of vapours and through heat exchanger heat is supplied with rotary kiln oven dry rubbish in the water-washing process of first order water scrubber, the tail gas after internal combustion engine burns simultaneously also feeds rotary kiln oven dry rubbish.

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