RU2437030C1 - Heat treatment method of crude urban ore - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: crude urban ore is loaded to the reactor; mixture of hot air, water vapours and light volatiles is supplied to reactor lower part; urban ore undergoes subsequent drying, pyrolysis and gasification processes. Solid non-organic substances are removed from reactor lower part; as well as pyrolysis and gasification products are removed from heat chamber in the form of thermal gas. Temperature mode in the reactor is controlled by controlling the hot air flow via two air pipelines, with arrangement of recirculation circuit as to gas mixture of water vapours and light volatiles, which is heated to temperature of 500-700°C owing to thermal gas heat from drying zone to gasification zone. Air for gasification of solid carbon residue is heated at temperature of not more than 500°C. Temperature in drying zone is maintained within 120-350°C.

EFFECT: increasing utilisation efficiency of urban ore and improving the quality of fuel gas owing to removing the moisture accumulated during drying of urbane ores and its return to gasification.

2 cl, 1 dwg

Description

The present invention relates to methods for processing municipal solid waste (MSW) containing plastics, paper, wood, textiles, glass, leather, rubber and other organic components by pyrolysis and gasification in a thermoset to produce combustible gas (thermogas).

The problem of solid waste disposal is currently relevant, as its solution is associated with ensuring the normal functioning of the population, the sanitary state of cities and settlements, the environment and resource conservation.

There are a number of ways of processing solid waste in the combustion mode. The most common is the method of direct burning of solid waste in furnaces with grates. The disadvantage is atmospheric air pollution with toxic combustion products, which can only be prevented by using expensive flue gas treatment.

More promising are methods based on the heat treatment of solid waste by gasification and pyrolysis processes to produce fuel gas. Its cleaning is simplified due to its smaller volume. MSW is included in the class of high-ash solid fuels that can be processed by pyrolysis followed by gasification of the solid carbon residue. MSW contains a significant amount of organic substances: paper, wood, plastics, rubber and the like, which when heated without oxygen, form a combustible gas. Solid inorganic residues formed after heat treatment are non-aggressive to the environment.

A number of methods are known based on sequential layer-by-layer heat treatment of solid organic fuels in an oxidizing gas stream in shaft-type furnaces (US patent No. 2796390, IPC F23G 5/027, 1957 and US patent No. 2798032, IPC F23G 5/027, 1957 .).

As an analogue, you can take the gasification method (US Patent No. 4732091, IPC F23G 5/027, 1988), according to this method, municipal solid waste is loaded into the upper part of a vertical shaft furnace. MSW passes successively a series of chambers separated by horizontal gratings, on which the MSW is pyrolyzed, followed by the combustion of the solid carbon residue of the vapor-air gasifying agent. Fuel gas is discharged from the upper part of the reactor with a temperature of 430-450 ° C, and the combustion temperature is 870-930 ° C. The main disadvantage of this method is the use of moving gratings, which are prone to rapid contamination and wear.

A known method of thermal processing of solid waste containing solid organic part, water and a solid non-combustible part (RF Patent No. 2079051, IPC F23G 5/027, 1994), which can be taken as a prototype.

According to this method, partially combustible solid waste is loaded into a reactor (shaft type furnace), where drying, pyrolysis and gasification of combustible solid waste components are carried out sequentially. An oxygen-containing oxidizing gas, such as air, is supplied to that part of the reactor where a solid carbon residue is accumulated and is directed countercurrently through a solid waste layer, sequentially through a series of zones (drying, pyrolysis and coking, combustion and gasification, cooling). By filtering the gas into the MSW layer, gas is preheated in the solid carbon residue layer and hot gaseous products transfer their heat to the loaded MSW. The temperature distribution in the reactor is as follows: in the drying zone - up to 200 ° C, in the pyrolysis and coking zone - from 200 to 800 ° C. The maximum temperature in the combustion and gasification zone is maintained within 700-1400 ° С, and the temperature of the product - gas at the outlet is lower than 400 ° С.

The disadvantages of this method are: firstly, the regulation of the temperature regime of the process by maintaining the necessary ratio of mass fractions of combustible and non-combustible components of solid waste, which requires mandatory thorough preparation of solid waste; secondly, the increased humidity of the fuel gas at the outlet, which, having successively passed all the zones, is saturated with moisture in the drying zone, which, in turn, causes a decrease in its calorific value, requires the installation of a condenser to condense moisture from the fuel gas.

The technical result of the proposed technical solution is to increase the efficiency of technological operations for processing solid waste, expressed in the exclusion of costs for the preliminary preparation of solid waste and improving the quality of fuel gas (thermogas) by supplying a heated mixture of air, water vapor and light volatile gasification.

The technical result is achieved in that in a method for the thermal processing of unsorted municipal solid waste, which includes continuous loading of waste into the reactor, feeding a mixture of hot air, water vapor and light volatiles to the lower part of the reactor, sequential drying, pyrolysis and gasification and subsequent removal from the lower part of the reactor solid inorganic substances, as well as the withdrawal from the gasification zone of the products of pyrolysis and gasification in the form of thermogas, organize a recirculation loop through a gas mixture of water vapor and light their volatiles, heated to a temperature within 5000 ° C-7000 ° C due to the heat of thermogas, from the drying zone, while the air for gasification of the solid carbon residue is heated up to not higher than 500 ° C and fed through two ducts to the gasification zone, in one of which to the heated air is supplemented with a heated mixture of water vapor and light volatiles from the drying zone. The temperature in the drying zone is maintained within the range of 120-3500 ° C.

The drawing schematically shows a diagram of a method. Unsorted MSW is loaded into a shaft-type reactor 1. MSW passes sequentially through the zones of drying 2, pyrolysis 3 and gasification 4. The inorganic residue is removed from the slag removal zone 5 at the bottom of the reactor. Thermogas is taken from the heat chamber in gasification zone 4 and cooled sequentially in heat exchangers 6 and 7. A mixture of water vapor and light volatiles is taken from drying zone 2 and sent to heat exchanger 6 for heating, then sent to gasification zone 4 for further use in the gasification process. The air is heated in the heat exchanger 7 and served in the gasification zone 4 through two ducts. A mixture of water vapor and light volatiles from the heat exchanger 6 is mixed into one of the ducts, thereby forming a recirculation loop of the mixture of water vapor and light volatiles.

The proposed method is implemented as follows: unsorted municipal solid waste is loaded into a shaft type reactor (thermoreactor). MSW undergo a drying process in drying zone 2, where the temperature of the MSW reaches 120-350 ° С, the layer of MSW is heated and dried by heat exchange with filtration of the gas flow supplied from the pyrolysis zone 3. Moisture removed from the MSW in the form of water vapor and light volatile compounds with a temperature of at least 120 ° C are collected in a collector and sent to a heat exchanger 6 for heating to a temperature in the range of 500-700 ° C due to the heat of the thermogas. A heated mixture of water vapor and light volatiles together with hot air is fed under a layer of solid carbon residue (TOC) to organize the gasification process.

Then the MSW enters the pyrolysis zone 3, where due to heat exchange with the gas stream, the temperature gradually rises to 1300 ° C. The combustible components of MSW are pyrolyzed, a solid carbon residue is formed - coke and gaseous products - pyrolysis gas, which are taken to a heat chamber located under the pyrolysis zone, and then taken from the reactor, sequentially cooled in two heat exchangers: in heat exchanger 6 to a temperature of no higher than 800 ° С , in the heat exchanger 7 to a temperature not exceeding 400 ° C.

MSW, gradually descending into the lower part of the reactor, in the form of MSW enter the gasification zone 4. In the gasification zone, the MSW interacts with the hot steam-air mixture supplied from below from the countercurrent, forming fuel gas. A mixture of pyrolysis and fuel gases (thermogas) is collected in a heat chamber, from where, after passing through two-stage cooling in heat exchangers - first in a heat exchanger 6 with a mixture of water vapor, then in a heat exchanger 7 with cold air, it is supplied to the consumer.

Claims (2)

1. A method for the thermal processing of unsorted municipal solid waste, including continuous loading of waste into the reactor, feeding a mixture of hot air, water vapor and light volatiles to the lower part of the reactor, sequential drying, pyrolysis and gasification, and subsequent removal of solid inorganic substances from the lower part of the reactor, as well as the conclusion from the gasification zone of the products of pyrolysis and gasification in the form of thermogas, characterized in that they organize a recirculation loop through a gas mixture of water vapor and light volatile, heating mine to a temperature in the range of 500-700 ° C due to the heat of the thermogas from the drying zone, while the air for gasification of the carbonaceous solid residue is heated no higher than 500 ° C and fed through two ducts to the gasification zone, in one of which they produce heated air the addition of a heated mixture of water vapor and light volatiles from the drying zone. 2. The method according to claim 1, characterized in that the temperature in the drying zone is maintained within 120-350 ° C.