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 plasma solid waste treatment system and method

technical field

The invention relates to the technical field of harmless disposal of hazardous waste and solid waste, and more particularly, to a system and method for the treatment of oxygen-deficient plasma solid waste.

Background technique

With the development of society and economy, people's living standards are getting higher and higher, the annual output of solid waste in my country is getting higher and higher, and the types are more and more complex, especially the vigorous development of the petrochemical industry, various products are used in daily life In various fields, more and more solid wastes are produced. The long-term existence of solid wastes will seriously pollute the soil and water sources, and cause irreversible effects on the environment.

In recent years, the frequent occurrence of pollution problems has frequently sounded alarm bells to people. The state and relevant departments have also actively issued policies to restrict the discharge of industrial and domestic solid waste, and increased the treatment of solid waste in different fields, which has made the solid waste treatment industry develop rapidly. No matter what type of solid waste is incinerated, the relevant standards have strict requirements on the temperature inside the incinerator, the residence time of flue gas, and the weight loss on ignition.

From the analysis of the solid waste treatment industry, it is known that there are many kinds of treatment methods for solid waste at present, of which three are the most common, namely sanitary landfill, incineration and composting. Sanitary landfills are the most widely used; incineration is usually limited to coastal areas; composting works well, but it is only used selectively in individual areas, with greater limitations.

The heavy metals in the flue gas of various solid waste incineration mainly include mercury, cadmium, lead, etc. and their compounds. During the incineration process, oxides and halides are formed due to high temperature gasification and volatilize into the flue gas. Heavy metals are easy to accumulate in the human body, leading to chronic poisoning.

Whether the hazardous solid waste is directly incinerated or incinerated after gasification cracking, the inorganic non-metallic substances such as chlorine, fluorine, and sulfur contained in the solids will be converted into corresponding acid gases in the flue gas, and the It also contains pollutants such as smoke, nitrogen oxides, and heavy metal compounds. The direct discharge of this part of the pollutants will have an impact on the local atmospheric environment.

The products of organic matter incineration are carbon dioxide, water, nitrogen oxides, sulfur dioxide and other gases; the products of organic matter gasification are carbon monoxide, hydrogen, methane and other combustible gases.

Dioxins are organic substances remaining in flue gas, which need special attention because of their high toxicity and impact on the environment and human health. The precursors of dioxins include various chlorinated benzenes. Due to the presence of dioxin precursors and necessary catalysts in solid hazardous waste or domestic waste, dioxins will be generated at a suitable temperature. The optimum temperature for dioxin formation is 300 to 500 °C.

The decomposition of dioxin is generally 2 seconds in the furnace at about 850 °C, or 1 second in the furnace at about 1000 °C.

Solid waste will emit flue gas after the incineration process. In general incinerators, because the furnace temperature is controlled at about 850 °C, it is not conducive to the complete incineration and decomposition of dioxins, and the incomplete decomposition. The smoke contains dioxins.

In order to reduce the emission of dioxins in the solid waste treatment process, a secondary combustion chamber needs to be installed downstream of the flue gas flow direction of the incinerator to control the flue gas temperature and increase the flue gas residence time.

Re-synthesis reaction and heterogeneous catalytic reaction of precursors are the main mechanisms of dioxin formation in solid waste incineration. A large number of experimental results have proved that the conditions for re-synthesizing dioxin are carbon, oxygen, chlorine source, transition metal catalysis, and a specific temperature range of 200-400 °C. The presence of oxygen is necessary in the re-synthesis reaction. With the increase of oxygen concentration, the concentration of dioxins in solid waste combustion also increases. Experiments observed that under anoxic conditions, the concentration of dioxins began to decrease.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide an oxygen-deficient gasification plasma solid waste treatment system and method, which integrates gasification, melting, and secondary combustion chambers into one, cancels the setting of the secondary combustion chamber behind the conventional incinerator, and makes The solid waste treatment process is simpler, the disposal process is optimized, the disposal efficiency is improved, and the energy recovery rate is significantly improved.

The technical scheme adopted by the present invention to solve the technical problem is: constructing a plasma solid waste treatment system for oxygen-deficient gasification, including a belt conveyor, a lock tank, a rotary feeder, a plasma gasification melting reaction furnace, a waste heat recovery boiler, an alkali washing towers, wet electrostatic precipitators, induced draft fans and gas cabinets;

The solid waste is transferred to the lock tank through the belt conveyor, and the lock tank outlet is connected to the upper part of the plasma gasification melting reaction furnace through the rotary feeder. The gas inlet in the middle of the plasma gasification melting reaction furnace is connected to the oxygen vapor pipeline. The liquid molten slag at the bottom of the gasification melting reaction furnace is connected through a slag discharge port and a slag discharge chute, and the upper gas outlet of the plasma gasification melting reaction furnace is connected with the waste heat recovery boiler. The precipitator is connected, and the oxygen-deficient gasification reaction occurs in the plasma gasification melting reaction furnace to generate syngas. The syngas recovers heat through the waste heat recovery boiler, and then passes through the alkali washing tower and the wet electrostatic precipitator in turn to complete the gas purification, and then is stored in the gas through the induced draft fan. inside the cabinet.

In the above scheme, the lower part of the plasma gasification and melting reaction furnace is uniformly distributed with a plurality of plasma torches located on the same plane, and a plurality of uniformly distributed secondary oxidation air nozzles are arranged above the plasma torches. A plurality of evenly distributed tertiary oxidation air nozzles are arranged above the mouth.

In the above solution, the inlet of the wet electrostatic precipitator is provided with a trace oxygen online monitor.

In the above solution, a regulating valve is provided on the inlet pipeline of the induced draft fan.

In the above solution, the lock tank is provided with a nitrogen sealing tube.

In the above solution, both the alkaline washing tower and the wet electrostatic precipitator are connected to the sewage circulating pool.

The present invention also provides a solid waste treatment method of the oxygen-deficient gasification plasma solid waste treatment system, comprising the following steps:

Step 1: The solid waste is sent to the lock tank at the top of the plasma gasification melting reaction furnace through the belt conveyor, and the lock tank is sealed with nitrogen gas, and the solid waste enters the plasma gasification melting reaction furnace evenly;

Step 2: After the solid waste enters the plasma gasification melting reactor, the organic matter in the solid waste and the oxygen vapor undergo oxygen-deficient gasification reaction. The oxygen content in the plasma gasification melting reactor is controlled to be less than 0.5%, and the oxygen vapor passes through the plasma gas. The secondary oxidation tuyere and the tertiary oxidation tuyere in the gasification melting reactor enter the plasma gasification melting reactor;

Step 3: Plasma torches uniformly distributed in the circumferential direction of the melting zone at the bottom of the plasma gasification melting reaction furnace generate a high-temperature plasma arc, so that the melting zone at the bottom of the plasma gasification melting reaction furnace is maintained at 1300-1500 ° C, and at the same time, through the high-energy effect of the plasma arc, the The solid waste in the furnace accelerates the pyrolysis and gasification;

Step 4: The inorganic matter of the solid waste enters the melting zone at the bottom of the plasma gasification melting reactor, and the inorganic matter of the solid waste and the heavy metals are melted into liquid slag at high temperature;

Step 5: The organic matter in the solid waste is converted into synthesis gas under the oxygen-deficient atmosphere in the plasma gasification melting reaction furnace, and the gas outlet temperature of the plasma gasification melting reaction furnace is kept above 1000 °C;

Step 6: The synthesis gas recovers heat through the waste heat recovery boiler, and then passes through the alkaline scrubber and the wet electrostatic precipitator in sequence to complete the gas purification, and then stores it in the gas cabinet through the induced draft fan.

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

The plasma generated in the plasma gasification melting reactor is generated by the plasma torch using 380V alternating current. The plasma temperature can reach 4000℃～7000℃, and the jet velocity exceeds 200m/s. Under a high-intensity heat source, the activity energy of elementary particles is far greater than the action of any intermolecular chemical bonds. The microscopic motion of matter is dominated by atomic thermal motion, and the original matter is broken into atomic matter to destroy harmful components or make them lose their vitality. , thereby transforming complex substances into simple harmless substances.

Implementing the oxygen-deficient gasification plasma solid waste treatment system and method of the present invention has the following beneficial effects:

1. The present invention can convert organic matter in solid waste into valuable syngas resources through the improved plasma gasification melting technology, greatly reduce the emission of nitrogen oxides and other pollutants, recover the energy available in waste, and realize waste Disposal reduction and resource utilization.

2. Through the improved plasma gasification melting technology, the present invention can convert harmful substances in solid waste into inert glassy substances, prevent the discharge of heavy metal pollutants, and realize harmless waste disposal.

3. The invention suppresses the regeneration of dioxins and other harmful substances in the syngas through high-temperature and oxygen-poor combustion, promotes the further cracking of macromolecular organics such as tar, improves the efficiency of cold gas, and reaches the international advanced level of gas emission indicators.

4. The present invention improves the design of the plasma gasification melting reactor, so that the outlet temperature and residence time of the plasma gasification melting reactor can completely replace the function of the secondary combustion chamber, and the oxygen-deficient environment in the plasma gasification melting reactor is further improved. The generation of dioxin is curbed, so that the conventional secondary combustion chamber is no longer necessary for solid waste disposal, and the process flow is greatly simplified.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

Fig. 1 is the schematic diagram of the oxygen-deficient oxidation plasma solid waste treatment system of the present invention;

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

Detailed ways

In order to have a clearer understanding of the technical features, objects and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in Figure 1, the oxygen-deficient gasification plasma solid waste treatment system of the present invention includes: a belt conveyor 2, a lock tank 3, a rotary feeder 4, a plasma gasification melting reaction furnace 1, a slag discharge port 5, a waste heat recovery boiler 6, Alkali washing tower 7, trace oxygen online monitor 13, wet electrostatic precipitator 8, sewage circulation pool 9, induced draft fan 10, regulating valve 11, gas cabinet 12, plasma torch 14, secondary oxidation nozzle 15 and tertiary oxidation nozzle 16.

The lower part of the plasma gasification melting reaction furnace 1 is uniformly distributed with a plurality of plasma torches 14 located on the same plane. A plurality of secondary oxidation air nozzles 15 are arranged above the plasma torches 14 , and a plurality of secondary oxidation air nozzles 15 are arranged above the secondary oxidation air nozzles 15 . There are evenly distributed tertiary oxidation tuyere 16 .

The inlet of the wet electrostatic precipitator 8 is provided with a trace oxygen online monitor 13 , the inlet pipeline of the induced draft fan 10 is provided with a regulating valve 11 , and the lock tank 3 is provided with a nitrogen sealing pipe. Both the alkaline washing tower 7 and the wet electrostatic precipitator 8 are connected to the sewage circulating pool 9 .

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

The solid waste is sent to the lock tank 3 at the top of the gas plasma melting reaction furnace 1 through the belt conveyor 2, and nitrogen is introduced into the lock tank 3 through a nitrogen sealing pipe for sealing to prevent the plasma melting reaction furnace 1. Syngas enters lock tank 3. The plasma gasification melting reaction furnace 1 provides a space for the solid waste to react with the oxidant. The solid waste is in a certain proportion before entering the plasma gasification melting reaction furnace 1 to ensure good temperature control in the furnace.

The solid waste materials with qualified proportions enter the plasma gasification melting reaction furnace 1 uniformly through the lock tank 3 at the top of the plasma gasification melting reaction furnace 1, and the organic matter and oxygen vapor in the solid waste in the plasma gasification melting reaction furnace are subjected to oxygen deficiency. The oxygen content in the plasma gasification melting reaction furnace is less than 0.5%, and the oxygen content in the syngas is monitored in real time by the trace oxygen online monitor 13 . The remaining inorganic matter in the solid waste enters the high temperature zone at the bottom of the plasma gasification melting reaction furnace 1. The high temperature zone is the melting zone at the bottom of the plasma gasification melting reaction furnace 1. Three plasma torches 14 are evenly distributed at the bottom of the plasma gasification melting reaction furnace. The high temperature plasma arc is generated, so that the melting zone at the bottom of the plasma gasification melting reaction furnace 1 can be maintained at 1500° C., and the power of the plasma torch 14 can be adjusted online. The inorganic substances in the solid waste are melted into liquid slag at high temperature, and the harmful substances such as heavy metals in the solid waste are wrapped in the liquid slag. After cooling, the liquid slag becomes an inert glassy substance, which can be used as a common building material.

The gas temperature at the outlet of the plasma gasification melting reactor 1 is controlled at 1000°C, and the enlarged upper space ensures that the gas residence time in the furnace is within 3-5s. The oxygen environment further inhibits the re-synthesis of dioxins. The improved plasma gasification melting reactor 1 can meet the requirements of the gas emission index without the need for a rear secondary combustion chamber. Through the monitoring of the exhaust gas in the test process, the gas emission data obtained, the dioxin is 0.00004-0.26ng-TEQ/m ³ , the sulfur dioxide is less than 5ppm, and the nitrogen oxide is 69-84ppm. The indicators are much better than the national standards. . The test verifies that in the improved high temperature plasma gasification melting reaction furnace 1, in the oxygen-deficient atmosphere, the gas emission results after the elimination of the secondary combustion chamber fully meets the requirements of the national pollutant emission standards.

Example 2

Another treatment method of the oxygen-deficient gasification plasma solid waste treatment system of the present invention is as follows:

The solid waste is sent to the lock tank 3 at the top of the plasma gasification melting reaction furnace 1 through the belt conveyor 2, and the lock tank 3 is sealed with nitrogen to prevent the synthesis gas in the plasma gasification melting reaction furnace 1 from entering the lock tank. Tank 3. The plasma gasification melting reaction furnace 1 provides a space for the solid waste to react with the oxidant, and a certain proportion of solid waste is carried out before entering the plasma gasification melting reaction furnace 1 to ensure good control of the temperature in the furnace. Generally, according to the properties of different solid wastes, the solid waste is adjusted, and the calorific value of the solid waste into the furnace is not less than 3000Kcal/kg, the moisture content is not higher than 20%, and the solid waste is crushed to 50-100MM.

At the same time, in order to control the melting point of the ash to be less than 1500℃, a certain proportion of flux is added to the solid waste treatment material. The main component of the flux is CaO, and the typical ratio of solid waste to flux is 100:1. The solid waste materials with qualified ratio enter the plasma gasification and melting reaction furnace 1 through the lock tank 3 at the top of the plasma gasification melting reaction furnace 1, and the waste organic matter and oxygen vapor in the solid waste in the plasma gasification melting reaction furnace 1 are depleted. In the oxygen gasification reaction, the oxygen content in the plasma gasification melting reaction furnace 1 is lower than 0.5%, and the oxygen content in the syngas is monitored in real time by the trace oxygen online monitor 13 .

The remaining inorganic matter in the solid waste enters the high temperature zone at the bottom of the plasma gasification melting reactor 1, and the bottom high temperature zone is the bottom melting zone of the plasma gasification melting reactor 1. Three plasma torches are evenly distributed at the bottom of the plasma gasification melting reactor 1. 14. High temperature plasma arc is generated, which can maintain the melting zone at the bottom of the plasma gasification melting reaction furnace at 1300-1500 °C, and the torch power can be adjusted online. The inorganic substances in the solid waste are melted into liquid slag at high temperature, and the harmful substances such as heavy metals in the solid waste are wrapped in the liquid slag. After cooling, the liquid slag becomes an inert glassy substance, which can be used as a common building material.

The embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the inspiration of the present invention, without departing from the scope of protection of the present invention and the claims, many forms can be made, which all belong to the protection of the present invention.

Claims (7)

1. An oxygen-deficient gasification plasma solid waste treatment system is characterized in that, comprising belt conveyor, lock tank, rotary feeder, plasma gasification melting reactor, waste heat recovery boiler, alkali washing tower, wet electrostatic precipitator, Fans and gas cabinets; The solid waste is transferred to the lock tank through the belt conveyor, and the lock tank outlet is connected to the upper part of the plasma gasification melting reaction furnace through the rotary feeder. The gas inlet in the middle of the plasma gasification melting reaction furnace is connected to the oxygen vapor pipeline. The liquid molten slag at the bottom of the gasification melting reaction furnace is connected through a slag discharge port and a slag discharge chute, and the upper gas outlet of the plasma gasification melting reaction furnace is connected with the waste heat recovery boiler. The precipitator is connected, and the oxygen-deficient gasification reaction occurs in the plasma gasification melting reaction furnace to generate syngas. The syngas recovers heat through the waste heat recovery boiler, and then passes through the alkali washing tower and the wet electrostatic precipitator in turn to complete the gas purification, and then is stored in the gas through the induced draft fan. inside the cabinet. 2 . The oxygen-deficient gasification plasma solid waste treatment system according to claim 1 , wherein a plurality of plasma torches located on the same plane are evenly distributed in the lower part of the plasma gasification melting reaction furnace, and a plurality of plasma torches are arranged above the plasma torches. 3 . There are a plurality of uniformly distributed secondary oxidation air nozzles, and a plurality of uniformly distributed tertiary oxidation air nozzles are arranged above the secondary oxidation air nozzles. 3 . The oxygen-deficient gasification plasma solid waste treatment system according to claim 1 , wherein a trace oxygen online monitor is provided at the inlet of the wet electrostatic precipitator. 4 . 4 . The oxygen-deficient gasification plasma solid waste treatment system according to claim 1 , wherein a regulating valve is provided on the inlet pipeline of the induced draft fan. 5 . 5 . The oxygen-deficient gasification plasma solid waste treatment system according to claim 1 , wherein a nitrogen sealing tube is arranged on the lock tank. 6 . 6 . The oxygen-deficient gasification plasma solid waste treatment system according to claim 1 , wherein the alkaline washing tower and the wet electrostatic precipitator are both connected to the sewage circulating pool. 7 . 7. The solid waste treatment method of the oxygen-deficient oxygenation plasma solid waste treatment system according to claim 1, characterized in that, comprising the following steps: Step 1: The solid waste is sent to the lock tank at the top of the plasma gasification melting reaction furnace through the belt conveyor, and the lock tank is sealed with nitrogen gas, and the solid waste enters the plasma gasification melting reaction furnace evenly; Step 2: After the solid waste enters the plasma gasification melting reactor, the organic matter in the solid waste and the oxygen vapor undergo oxygen-deficient gasification reaction. The oxygen content in the plasma gasification melting reactor is controlled to be less than 0.5%, and the oxygen vapor passes through the plasma gas. The secondary oxidation tuyere and the tertiary oxidation tuyere in the gasification melting reactor enter the plasma gasification melting reactor; Step 3: Plasma torches uniformly distributed in the circumferential direction of the melting zone at the bottom of the plasma gasification melting reaction furnace generate a high-temperature plasma arc, so that the melting zone at the bottom of the plasma gasification melting reaction furnace is maintained at 1300-1500 ° C, and at the same time, through the high-energy effect of the plasma arc, the The solid waste in the furnace accelerates the pyrolysis and gasification; Step 4: The inorganic matter of the solid waste enters the melting zone at the bottom of the plasma gasification melting reactor, and the inorganic matter of the solid waste and the heavy metals are melted into liquid slag at high temperature; Step 5: The organic matter in the solid waste is converted into synthesis gas under the oxygen-deficient atmosphere in the plasma gasification melting reaction furnace, and the gas outlet temperature of the plasma gasification melting reaction furnace is kept above 1000 °C; Step 6: The synthesis gas recovers heat through the waste heat recovery boiler, and then passes through the alkaline scrubber and the wet electrostatic precipitator in sequence to complete the gas purification, and then stores it in the gas cabinet through the induced draft fan.

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