CN111550795A - Oxygen-deficient gasification plasma solid waste treatment system and method - Google Patents

Abstract

The invention relates to a system and a method for treating solid waste by oxygen-deficient gasification plasma, wherein the system comprises a belt conveyor, a lock tank, a rotary feeder, a plasma gasification melting reaction furnace, a waste heat recovery boiler, an alkaline tower, a wet electric dust collector, an induced draft fan and a gas holder; solid garbage is transferred into a locking tank through a belt conveyor, an outlet of the locking tank is connected with the upper part of a plasma gasification melting reaction furnace through a rotary feeder, a gas inlet in the middle of the plasma gasification melting reaction furnace is connected with an oxygen steam pipeline, liquid slag at the bottom of the plasma gasification melting reaction furnace is connected with a slag discharging chute through a slag discharging port, and oxygen deficiency gasification reaction occurs in the plasma gasification melting reaction furnace to generate synthesis gas. The invention integrates gasification, melting and secondary combustion chambers, and cancels the arrangement of a secondary combustion chamber arranged behind a conventional incinerator, so that the solid waste treatment process is simpler, the treatment process is optimized, the treatment efficiency is improved, and the energy recovery rate is obviously improved.

Description

Oxygen-deficient gasification plasma solid waste treatment system and method

Technical Field

The invention relates to the technical field of harmless treatment of hazardous waste and solid waste, in particular to a system and a method for treating the solid waste by using under-oxygen gasification plasma.

Background

Along with the development of society and economy, the living standard of people is higher and higher, the annual solid waste yield of China is higher and higher, the variety is more and more complicated, especially the vigorous development of petrochemical industry, various products are applied to various fields of life, the solid waste generated along with the development is more and more, and the long-term existence of the solid waste can seriously pollute soil and water sources and cause irreversible influence on the environment.

In recent years, the pollution problem is frequent, and people are frequently warned. The state and related departments also actively set policies to restrict the discharge of industrial and domestic solid wastes and increase the treatment of the solid wastes in different fields, so that the solid waste treatment industry is rapidly developed. Regardless of the type of solid waste to be incinerated, the relevant standards impose strict requirements on the temperature inside the incinerator, the residence time of the flue gas, the amount of thermal ignition, and the like.

From the analysis of the solid waste treatment industry, there are many methods of treatment of solid waste, the most common of which are three, sanitary landfill, incineration and composting. The application of sanitary landfill is the widest; incineration is usually limited to coastal areas; the composting effect is good, but only a certain area is selectively used, and the limitation is large.

Heavy metals in various solid waste incineration flue gases mainly comprise mercury, cadmium, lead and the like and compounds thereof, and oxides and halides formed by high-temperature gasification are volatilized into the flue gases in the incineration process. Heavy metals are easily accumulated in the human body, resulting in chronic poisoning.

Because the dangerous solid waste is directly incinerated or incinerated after gasification and cracking, inorganic nonmetallic substances such as chlorine element, fluorine element, sulfur element and the like contained in the solid can be converted into corresponding acid gas in the flue gas, and the flue gas also contains pollutants such as smoke dust, nitrogen oxide, heavy metal compounds and the like. The direct emission of this portion of the pollutants can have an impact on the local atmospheric environment.

The products of the incineration of the organic matters are gases such as carbon dioxide, water, nitrogen oxides, sulfur dioxide and the like; the products of the gasification of organic matters are combustible gases such as carbon monoxide, hydrogen, methane and the like.

Dioxins are residual organic substances in flue gas, and have great influence on environment and human health due to high toxicity, so special attention needs to be paid. The precursor of dioxin includes various chlorobenzene substances, and because the precursor of dioxin and necessary catalyst exist in solid hazardous waste or household garbage, the dioxin can be generated at proper temperature. The optimal generation temperature of the dioxin is 300-500 ℃.

The decomposition of dioxin is generally that the dioxin stays in a hearth for 2 seconds at about 850 ℃, or stays in the hearth for 1 second at about 1000 ℃.

The solid waste can discharge flue gas after the incineration process, and the general incinerator is not beneficial to the complete incineration and decomposition of dioxin substances because the hearth temperature of the general incinerator is controlled to be about 850 ℃, and the flue gas which is not completely decomposed contains dioxin.

In order to reduce the discharge of dioxin-like substances in the solid waste treatment process, a secondary combustion chamber is required to be arranged at the downstream of the flue gas flowing direction of the incinerator for controlling the temperature of the flue gas and increasing the residence time of the flue gas.

The re-synthesis reaction and the precursor heterogeneous catalytic reaction are the main mechanisms for generating dioxin in solid waste incineration. A large number of test results prove that the condition for re-synthesizing the dioxin is carbon, oxygen, chlorine source and transition metal catalysis, and has a specific temperature range of 200-400 ℃. The presence of oxygen is essential in the re-synthesis reaction, and as the oxygen concentration increases, the concentration of dioxin produced in the combustion of solid waste also increases. It was experimentally observed that the dioxin production concentration began to decrease under anoxic conditions.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a system and a method for treating the solid waste by the oxygen-deficient gasification plasma, wherein a gasification chamber, a melting chamber and a secondary combustion chamber are integrated, and the arrangement of the secondary combustion chamber behind a conventional incinerator is cancelled, so that the solid waste treatment process is simpler, the treatment process is optimized, the treatment efficiency is improved, and the energy recovery rate is obviously improved.

The technical scheme adopted by the invention for solving the technical problems is as follows: constructing an oxygen-deficiency gasification plasma solid waste treatment system, which comprises a belt conveyor, a locking tank, a rotary feeder, a plasma gasification melting reaction furnace, a waste heat recovery boiler, an alkaline tower, a wet electric dust collector, an induced draft fan and a gas holder;

solid waste changes over into to the lock jar through the belt feeder, and the lock jar export links to each other through rotary feeder and plasma gasification melting reacting furnace upper portion, plasma gasification melting reacting furnace middle part gas inlet links to each other with oxygen steam pipeline, plasma gasification melting reacting furnace bottom liquid slag is connected through row cinder notch and row's sediment chute, the upper portion gas outlet of plasma gasification melting reacting furnace with waste heat recovery boiler links to each other, the gas holder pass through the draught fan with wet-type electrostatic precipitator links to each other, takes place the reaction of oxygen deficiency gasification in the plasma gasification melting reacting furnace and produces the synthetic gas, and the synthetic gas passes through waste heat recovery boiler and retrieves the heat, then loops through alkaline tower and wet-type electrostatic precipitator and accomplishes after gas purification and store in the gas holder through the draught fan.

In the scheme, a plurality of plasma torches which are positioned on the same plane are uniformly distributed at the lower part of the plasma gasification melting reaction furnace, a plurality of uniformly distributed secondary oxidation air nozzles are arranged above the plasma torches, and a plurality of uniformly distributed tertiary oxidation air nozzles are arranged above the secondary oxidation air nozzles.

In the above scheme, the inlet of the wet electric dust collector is provided with a trace oxygen on-line monitor.

In the above scheme, the inlet pipeline of the induced draft fan is provided with the regulating valve.

In the scheme, the lock tank is provided with the nitrogen sealing pipe.

In the scheme, the alkaline tower and the wet electric dust collector are both connected with the sewage circulating tank.

The invention also provides a solid waste treatment method of the under-oxygen gasification plasma solid waste treatment system, which comprises the following steps:

step 1: the solid waste is conveyed into a locking tank at the top of the plasma gasification melting reaction furnace through a belt conveyor, nitrogen is introduced into the locking tank for sealing, and the solid waste uniformly enters the plasma gasification melting reaction furnace;

step 2: after the solid waste enters a plasma gasification melting reaction furnace, organic matters in the solid waste and oxygen steam are subjected to oxygen-deficient gasification reaction, the oxygen content in the plasma gasification melting reaction furnace is controlled to be lower than 0.5%, and the oxygen steam enters the plasma gasification melting reaction furnace through a secondary oxidation air nozzle and a tertiary oxidation air nozzle in the plasma gasification melting reaction furnace;

and step 3: plasma torches are uniformly distributed at the periphery of a melting zone at the bottom of the plasma gasification melting reaction furnace to generate high-temperature plasma arcs, so that the melting zone at the bottom of the plasma gasification melting reaction furnace is maintained at 1300-1500 ℃, and meanwhile, the solid waste in the furnace is promoted to be pyrolyzed and gasified in an accelerated manner through the high-energy effect of the plasma arcs;

and 4, step 4: inorganic matters of the solid waste enter a melting zone at the bottom of the plasma gasification melting reaction furnace, and the inorganic matters and heavy metals of the solid waste are melted into liquid slag at high temperature;

and 5: organic matters in the solid waste are converted into synthesis gas in an oxygen-deficient atmosphere in the plasma gasification melting reaction furnace, and the temperature of a gas outlet of the plasma gasification melting reaction furnace is kept above 1000 ℃;

step 6: the synthesis gas is subjected to heat recovery by a waste heat recovery boiler, then is subjected to gas purification by an alkaline tower and a wet electric dust collector in sequence, and then is stored in a gas holder by a draught fan.

The invention has better environmental protection property by oxygen deficiency combustion, namely gasification, the gas quantity to be treated generated by combustion is 1/10 of the gas quantity to be treated by conventional combustion, the yield of pollutants such as nitrogen oxides, sulfides and the like in the gas is far lower than that of the incineration process, and the invention has the characteristics of high efficiency and energy saving.

Plasma generated in the plasma gasification melting reaction furnace is generated by a plasma torch by adopting 380V alternating current. The plasma temperature can reach 4000-7000 ℃, and the jet velocity exceeds 200 m/s. Under a high-intensity heat source, the activity energy of basic particles is far greater than the action of any intermolecular chemical bond, the microscopic motion of substances is mainly atomic thermal motion, and original substances are broken into atomic substances to destroy harmful components or lose the activity of the harmful components, so that complex substances are converted into simple harmless substances.

The system and the method for treating the solid waste by the under-oxygen gasification plasma have the following beneficial effects:

1. according to the invention, through an improved plasma gasification melting technology, organic matters in solid waste can be converted into precious synthesis gas resources, the discharge amount of pollutants such as nitrogen oxides is greatly reduced, the available energy in the waste is recovered, and the reduction and the resource of waste disposal are realized.

2. The invention can convert harmful substances in solid waste into inert glass-state substances by an improved plasma gasification melting technology, thereby completely eradicating the discharge of heavy metal pollutants and realizing the harmless treatment of waste.

3. According to the invention, by high-temperature oxygen-deficient combustion, the regeneration of harmful substances such as dioxin in the synthesis gas is inhibited, the further cracking of macromolecular organic matters such as tar is promoted, the cold gas efficiency is improved, and the gas emission index reaches the international advanced level.

4. The invention improves the design of the plasma gasification melting reaction furnace, so that the outlet temperature and the retention time of the plasma gasification melting reaction furnace can completely replace the function of the secondary combustion chamber, and the oxygen-deficient environment in the plasma gasification melting reaction furnace further restrains the generation of dioxin, so that the conventional secondary combustion chamber is not necessary to treat solid waste any more, and the process flow is greatly simplified.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic diagram of an oxygen-deficient gasification plasma solid waste treatment system according to the present invention;

FIG. 2 is a schematic flow diagram of the method of the present invention for an oxygen-deficient gasification plasma solid waste treatment system.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in fig. 1, the solid waste treatment system of the present invention comprises: the device comprises a belt conveyor 2, a locking tank 3, a rotary feeder 4, a plasma gasification melting reaction furnace 1, a slag discharge port 5, a waste heat recovery boiler 6, an alkaline washing tower 7, a trace oxygen online monitor 13, a wet electric precipitator 8, a sewage circulating pool 9, an induced draft fan 10, a regulating valve 11, a gas holder 12, a plasma torch 14, a secondary oxidation air nozzle 15 and a tertiary oxidation air nozzle 16.

A plurality of plasma torches 14 which are positioned on the same plane are uniformly distributed at the lower part of the plasma gasification melting reaction furnace 1, a plurality of uniformly distributed secondary oxidation air nozzles 15 are arranged above the plasma torches 14, and a plurality of uniformly distributed tertiary oxidation air nozzles 16 are arranged above the secondary oxidation air nozzles 15.

An inlet of the wet electric precipitator 8 is provided with a trace oxygen on-line monitor 13, an inlet pipeline of the induced draft fan 10 is provided with a regulating valve 11, and a nitrogen sealing pipe is arranged on the lock tank 3. The alkaline tower 7 and the wet electric dust collector 8 are both connected with a sewage circulating tank 9.

As shown in fig. 2, the treatment method of the solid waste treatment system of the oxygen-deficient gasification plasma of the invention is as follows:

solid waste sends the processing materials into a locking tank 3 at the top of a gas plasma melting reaction furnace 1 through a belt conveyor 2, and nitrogen is introduced into the locking tank 3 through a nitrogen sealing pipe for sealing so as to prevent synthetic gas in the plasma melting reaction furnace 1 from entering the locking tank 3. The plasma gasification melting reaction furnace 1 provides a space for the reaction of solid waste and an oxidant, and the solid waste is proportioned before entering the plasma gasification melting reaction furnace 1 so as to ensure the good control of the temperature in the furnace.

Solid waste materials with qualified mixture ratio uniformly enter the plasma gasification melting reaction furnace 1 through the lock tank 3 at the top of the plasma gasification melting reaction furnace 1, organic matters and oxygen steam in the solid waste in the plasma gasification melting reaction furnace are subjected to oxygen deficiency gasification reaction, the oxygen content in the plasma gasification melting reaction furnace is lower than 0.5%, and the oxygen content in the synthesis gas is monitored in real time through the trace oxygen on-line monitor 13. And (3) allowing the residual inorganic matters in the solid waste to enter a high-temperature region at the bottom of the plasma gasification melting reaction furnace 1, wherein the high-temperature region is a melting region at the bottom of the plasma gasification melting reaction furnace 1, and three plasma torches 14 are uniformly distributed at the bottom of the plasma gasification melting reaction furnace in the circumferential direction to generate high-temperature plasma arcs, so that the melting region at the bottom of the plasma gasification melting reaction furnace 1 can be maintained at 1500 ℃, and the power of the plasma torches 14 can be adjusted on line. Inorganic matters in the solid waste are melted into liquid slag at high temperature, and harmful substances such as heavy metals in the solid waste are wrapped in the liquid slag. The liquid slag becomes inert glass-state material after cooling, and can be used as common building materials.

The gas temperature at the outlet of the plasma gasification melting reaction furnace 1 is controlled at 1000 ℃, the expanded upper space ensures that the retention time of the gas in the furnace is ensured to be 3-5s, the higher outlet temperature inhibits the generation of dioxin, and meanwhile, the oxygen-deficient environment further inhibits the re-synthesis of the dioxin. The improved plasma gasification melting reaction furnace 1 can meet the requirements of gas emission indexes without a secondary combustion chamber arranged at the rear. Monitoring the exhaust gas in the test process to obtain the gas emission data that dioxin is 0.00004-0.26ng-TEQ/m³Sulfur dioxide<5ppm and 69-84ppm of nitrogen oxide, and all indexes are greatly superior to national standards. Tests prove that in the improved high-temperature plasma gasification melting reaction furnace 1, the gas emission result after the secondary combustion chamber is cancelled completely meets the requirements of national pollutant emission standards under the oxygen-deficient atmosphere.

Example 2

The invention discloses another treatment method of an oxygen-deficient gasification plasma solid waste treatment system, which comprises the following steps:

the solid waste is conveyed into a locking tank 3 at the top of the plasma gasification melting reaction furnace 1 through a belt conveyor 2, and nitrogen is introduced into the locking tank 3 for sealing so as to prevent the synthetic gas in the plasma gasification melting reaction furnace 1 from entering the locking tank 3. The plasma gasification melting reaction furnace 1 provides a space for the reaction of solid waste and an oxidant, and the solid waste is proportioned before entering the plasma gasification melting reaction furnace 1 so as to ensure the good control of the temperature in the furnace. Generally, according to the properties of different solid wastes, the solid wastes are blended, the heat value of the solid wastes entering a furnace is adjusted to be not less than 3000Kcal/kg, the water content is not more than 20 percent, and the solid wastes are crushed to 50-100 MM.

Meanwhile, in order to control the melting point of ash to be less than 1500 ℃, a certain proportion of fluxing agent is added into the solid waste treatment material, the main component of the fluxing agent is CaO, and the typical proportion of solid waste and the fluxing agent is 100: 1. Solid waste materials with qualified mixture ratio uniformly enter the plasma gasification melting reaction furnace 1 through the lock tank 3 at the top of the plasma gasification melting reaction furnace 1, waste organic matters and oxygen steam in the solid waste in the plasma gasification melting reaction furnace 1 are subjected to oxygen deficiency gasification reaction, the oxygen content in the plasma gasification melting reaction furnace 1 is lower than 0.5%, and the oxygen content in the synthesis gas is monitored in real time through the trace oxygen on-line monitor 13.

The residual inorganic matters in the solid waste enter a high-temperature zone at the bottom of the plasma gasification melting reaction furnace 1, wherein the high-temperature zone at the bottom is a melting zone at the bottom of the plasma gasification melting reaction furnace 1, three plasma torches 14 are uniformly distributed at the bottom of the plasma gasification melting reaction furnace 1 in the circumferential direction to generate high-temperature plasma arc, the melting zone at the bottom of the plasma gasification melting reaction furnace can be maintained at 1300-1500 ℃, and the torch power can be adjusted on line. Inorganic matters in the solid waste are melted into liquid slag at high temperature, and harmful substances such as heavy metals in the solid waste are wrapped in the liquid slag. The liquid slag becomes inert glass-state material after cooling, and can be used as common building materials.

While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (7)

1. A less-oxygen gasification plasma solid waste treatment system is characterized by comprising a belt conveyor, a locking tank, a rotary feeder, a plasma gasification melting reaction furnace, a waste heat recovery boiler, an alkaline tower, a wet electric dust collector, an induced draft fan and a gas holder;

solid waste changes over into to the lock jar through the belt feeder, and the lock jar export links to each other through rotary feeder and plasma gasification melting reacting furnace upper portion, plasma gasification melting reacting furnace middle part gas inlet links to each other with oxygen steam pipeline, plasma gasification melting reacting furnace bottom liquid slag is connected through row cinder notch and row's sediment chute, the upper portion gas outlet of plasma gasification melting reacting furnace with waste heat recovery boiler links to each other, the gas holder pass through the draught fan with wet-type electrostatic precipitator links to each other, takes place the reaction of oxygen deficiency gasification in the plasma gasification melting reacting furnace and produces the synthetic gas, and the synthetic gas passes through waste heat recovery boiler and retrieves the heat, then loops through alkaline tower and wet-type electrostatic precipitator and accomplishes after gas purification and store in the gas holder through the draught fan.

2. The solid waste treatment system of the underoxygen gasification plasma of claim 1, wherein a plurality of plasma torches located on the same plane are uniformly distributed at the lower part of the plasma gasification melting reaction furnace, a plurality of secondary oxidation nozzles are uniformly distributed above the plasma torches, and a plurality of tertiary oxidation nozzles are uniformly distributed above the secondary oxidation nozzles.

3. The underoxygen gasification plasma solid waste treatment system according to claim 1, wherein the wet electric precipitator inlet is provided with a trace oxygen on-line monitor.

4. The underoxygen gasification plasma solid waste treatment system according to claim 1, wherein an adjusting valve is arranged on the inlet pipeline of the induced draft fan.

5. The underoxygen gasification plasma solid waste treatment system according to claim 1, wherein the lock tank is provided with a nitrogen gas sealing pipe.

6. The underoxygen gasification plasma solid waste treatment system according to claim 1, wherein the caustic tower and the wet electric precipitator are both connected to a sewage circulation tank.

7. The solid waste treatment method of the underoxygen gasification plasma solid waste treatment system according to claim 1, comprising the steps of:

step 1: the solid waste is conveyed into a locking tank at the top of the plasma gasification melting reaction furnace through a belt conveyor, nitrogen is introduced into the locking tank for sealing, and the solid waste uniformly enters the plasma gasification melting reaction furnace;

step 2: after the solid waste enters a plasma gasification melting reaction furnace, organic matters in the solid waste and oxygen steam are subjected to oxygen-deficient gasification reaction, the oxygen content in the plasma gasification melting reaction furnace is controlled to be lower than 0.5%, and the oxygen steam enters the plasma gasification melting reaction furnace through a secondary oxidation air nozzle and a tertiary oxidation air nozzle in the plasma gasification melting reaction furnace;

and step 3: plasma torches are uniformly distributed at the periphery of a melting zone at the bottom of the plasma gasification melting reaction furnace to generate high-temperature plasma arcs, so that the melting zone at the bottom of the plasma gasification melting reaction furnace is maintained at 1300-1500 ℃, and meanwhile, the solid waste in the furnace is promoted to be pyrolyzed and gasified in an accelerated manner through the high-energy effect of the plasma arcs;

and 4, step 4: inorganic matters of the solid waste enter a melting zone at the bottom of the plasma gasification melting reaction furnace, and the inorganic matters and heavy metals of the solid waste are melted into liquid slag at high temperature;

and 5: organic matters in the solid waste are converted into synthesis gas in an oxygen-deficient atmosphere in the plasma gasification melting reaction furnace, and the temperature of a gas outlet of the plasma gasification melting reaction furnace is kept above 1000 ℃;

step 6: the synthesis gas is subjected to heat recovery by a waste heat recovery boiler, then is subjected to gas purification by an alkaline tower and a wet electric dust collector in sequence, and then is stored in a gas holder by a draught fan.

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