CN112300817A

CN112300817A - Pyrolysis gasification method for household garbage

Info

Publication number: CN112300817A
Application number: CN201911235383.XA
Authority: CN
Inventors: 孙敏; 马晓建; 李洪亮
Original assignee: Shanghai Minjian Environmental Protection Technology Co ltd
Current assignee: Shanghai Minjian Environmental Protection Technology Co ltd
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2021-02-02

Abstract

The invention relates to the technical field of garbage pyrolysis treatment, in particular to a household garbage pyrolysis gasification method, which comprises the following steps: crushing and drying the garbage, transferring the dried garbage into a granulator, conveying steam of the dryer into a primary heater for heating, then heating in the granulator, cooling to obtain granular garbage, transferring the granular garbage into a pyrolysis gasifier, conveying the steam of the granulator into a secondary heater for heating, then heating in the pyrolysis gasifier to generate pyrolysis slag and pyrolysis gas, conveying the pyrolysis gas into a cooling condenser, and respectively discharging the obtained pyrolysis liquid and the pyrolysis gas. The invention solves the problems of large energy consumption and uneven distribution in the pyrolyzer in the garbage granulation process in the prior art, and can reduce the operation cost of granulation by combining the granulation process and the garbage treatment process; the garbage is granulated and can be distributed in the pyrolyzer.

Description

Pyrolysis gasification method for household garbage

Technical Field

The invention relates to the technical field of garbage pyrolysis treatment, in particular to a household garbage pyrolysis gasification method.

Background

With the rapid economic development and the accelerated urbanization process of China, the production amount of urban domestic garbage is continuously increased, great harm is caused to the environment, and the urban domestic garbage becomes an important factor influencing the survival and sustainable development of human beings. The traditional landfill and composting method has the defects of large occupied area, long treatment period and serious pollution; and harmful substances such as dioxins are generated in the waste incineration process.

The volume reduction and decrement degree of the garbage pyrolysis is high, three products of gas, liquid and coke can be obtained, different requirements are met, and the method is gradually favored. The traditional garbage pyrolysis method is to dehydrate and crush the household garbage, then carry out drying pyrolysis, and condense and separate pyrolysis liquid after pyrolysis to obtain fuel oil. A conventional process flow diagram is shown in fig. 1.

The method disclosed in patent CN106590803A adopts a flat-die extrusion granulator to granulate the garbage, and adopts mechanical granulation, which is large in energy consumption and complex in equipment. The method disclosed in patent CN108148633A, which uses solids as heat carrier for pyrolysis, needs corresponding solid heating and circulating equipment, and is complex and demanding. Patent CN103382433A discloses a method for preparing combustible gas by utilizing steam pyrolysis gasification domestic garbage, which can avoid the generation of a large amount of tar after the gasification of municipal domestic garbage, has low gasification temperature and high gas production rate, but the pyrolysis process needs a large amount of heat energy, and corresponding energy-saving measures are needed for reducing consumption.

In the prior art, the household garbage is crushed and dried and then directly enters a pyrolyzer, so that the following problems exist:

(1) the shape and size of the waste are irregular, which presents problems of dispersion, distribution in the pyrolyzer. When a fixed bed pyrolyzer is adopted, if the fixed bed pyrolyzer is externally heated, the garbage is unevenly heated; when a moving bed is adopted, the movement of materials can be interrupted or even blocked due to poor dispersion performance; when a fluidized bed is adopted, the retention time of materials in the pyrolyzer is not easy to be uniform.

(2) The garbage is granulated and then enters a pyrolyzer, and when mechanical granulation is adopted, the energy consumption is high, and the equipment is complex.

(3) When the garbage is only subjected to pyrolysis reaction, tar is generated, and the normal operation of equipment is adversely affected.

(4) The solid heat carrier is adopted for heating, corresponding solid heating and circulating equipment is needed, and the equipment is complex and high in requirement.

(5) The pyrolysis process needs a large amount of heat energy, and corresponding energy-saving measures are needed for reducing consumption.

Therefore, a domestic garbage treatment pyrolysis method which is simple in equipment, low in operation cost, stable in operation and energy-saving is found, and the method has important significance for reduction, recycling, stabilization, harmless treatment and disposal of the domestic garbage.

Disclosure of Invention

In view of the above disadvantages of the prior art, the present invention provides a method for pyrolysis and gasification of domestic garbage, which is used to solve the problems of high energy consumption and uneven distribution in a pyrolyzer during the garbage granulation process in the prior art. The invention can reduce the operation cost of granulation by combining the granulation and the garbage treatment processes; the garbage is granulated and can be distributed in the pyrolyzer.

In order to attain the above and other related objects,

the invention provides a pyrolysis and gasification method of household garbage, which comprises the following steps:

step one, crushing the garbage, adding the crushed garbage into a dryer for drying, and conveying steam of the dryer into a primary heater to obtain dried garbage for later use;

transferring the dried garbage into a granulator, conveying superheated steam in a primary heater into the granulator, heating the dried garbage to 150-300 ℃ by the superheated steam, keeping the temperature for 30-60 min, conveying the steam of the granulator into a secondary heater, and cooling to obtain granular garbage for later use;

transferring the granular garbage into a pyrolysis gasifier, conveying steam in a secondary heater into the pyrolysis gasifier, pyrolyzing and gasifying the granular garbage at 500-900 ℃ for at least 30min by the steam to generate pyrolysis slag and pyrolysis gas, and discharging the pyrolysis slag to obtain the pyrolysis gas for later use;

and step four, conveying the pyrolysis gas and the steam in the pyrolysis gasifier to a cooling condenser, and cooling and condensing the pyrolysis gas and the steam in the pyrolysis gasifier to obtain pyrolysis liquid and pyrolysis gas which are respectively discharged.

The granulation and the garbage treatment process are combined, and the dried steam is heated again in the granulation process and then heated and granulated, so that the plastic in the garbage is melted and mixed with other components, and the granulation operation cost can be reduced; according to the types of plastics in the garbage, the operation temperature of the granulator is controlled to be 150-300 ℃, the retention time is 30-60 min, and most of the plastics in the garbage are melted. The garbage is granulated and can be distributed in the pyrolyzer. The pyrolysis and gasification are combined, and the tar generated in the pyrolysis process is gasified and reformed by steam, so that the yield of pyrolysis gas can be improved, and the generation of tar can be reduced; the pyrolysis gasification condition is optimized, the pyrolysis gas can be directly converted into the synthesis gas, the subsequent processing is convenient, and the tar is better recycled. Steam is used as a gasifying agent and a heat carrier for pyrolysis and gasification in the pyrolysis process, so that the heat utilization rate is high, the heat transfer coefficient is large, and the equipment is simple. The drying, the granulation and the pyrolysis gasification are combined, secondary steam generated by the drying is fully utilized, and the energy consumption is reduced.

The steam outlet of the dryer is connected with the steam inlet of the primary heater, and the steam outlet of the primary heater is connected with the steam inlet of the granulator; the steam outlet of the granulator is connected with the steam inlet of the secondary heater, and the steam outlet of the secondary heater is connected with the steam inlet of the pyrolysis gasifier; and the gas outlet of the pyrolysis gasifier is connected with the gas inlet of the cooling condenser. The drying, granulation and pyrolysis gasification are combined, secondary steam generated by drying is fully utilized, energy consumption is reduced, and energy utilization rate is improved. The secondary steam generated in the drying process enters a primary heater, is heated by an external heat source to become superheated steam, and enters a granulator to provide heat required by plastic melting. And (3) steam (still in an overheated state) discharged from the granulator enters a secondary heater, is heated by an external heat source, is heated to 500-900 ℃, is used as a heat carrier and a gasifying agent in the pyrolysis gasification process, and enters the pyrolysis gasifier. The garbage is subjected to pyrolysis and gasification reaction under the action of high-temperature steam (500-900 ℃) to generate pyrolysis slag and gas. The gas contains non-condensable components (pyrolysis gas) and condensable components, the gas generated in the pyrolysis gasification process enters a cooling condenser, the condensable components are condensed into liquid, and the liquid and the gas are separated to obtain pyrolysis liquid and the pyrolysis gas.

On the whole, granulation is carried out before pyrolysis of the garbage, the dispersing performance of the garbage in a pyrolyzer is improved, and the pyrolyzer is simple in structure and convenient to operate. The garbage is granulated by a heating method, so that the energy consumption is low. The latent heat of secondary steam in the garbage drying process is further used for heating and granulating the garbage, and the energy-saving effect is obvious. Steam is used as a heat carrier and a gasifying agent for pyrolysis and gasification in the pyrolysis and gasification process, so that the heat transfer efficiency is high, and the gas yield is high.

In an embodiment of the present invention, the particle size of the pulverized garbage in the first step is 10-200 mm.

Firstly crushing the household garbage, and then feeding the household garbage into a dryer; the particle size after crushing is 10-200 mm, and the later heating granulation is facilitated.

In an embodiment of the invention, the particle size of the pulverized garbage in the first step is 10-100 mm.

In an embodiment of the invention, the temperature of the dryer in the first step is 60-100 ℃, and the water content of the dried garbage is less than or equal to 15%.

The garbage is heated by an external heat source (steam) in the dryer, moisture in the garbage is vaporized and converted into secondary steam, and the garbage is converted into dry garbage with low moisture content. The operation temperature of the dryer is controlled below 100 ℃, and the properties and the forms of the components in the garbage are not changed, and the moisture content is only reduced. The operation temperature of the dryer is controlled at 80 ℃, and the drying speed is higher, so that the drying process is prevented from being too long.

In an embodiment of the invention, the temperature of the dryer in the first step is 80-100 ℃, and the water content of the dried garbage is less than or equal to 12%.

In one embodiment of the invention, the temperature for heating the garbage in the second step is 150-300 ℃, and the heating time is 30-60 min; specifically, the operation temperature of the granulator is controlled to be 150-300 ℃, and the retention time is 30-60 min.

And conveying the dried garbage to a granulator. In the granulator, the waste is directly heated by the superheated steam, wherein the plastic is transformed into a molten state and mixed with the non-molten components to form a mixture containing the molten plastic. The mixture is cooled, and the plastic therein solidifies to shrink and form solid particles with the other components. Such an operation is then convenient to transport and enables an improved dispersion in the pyrolysis gasifier. Wherein, the secondary steam generated in the drying process enters a primary heater, is heated by an external heat source to become superheated steam, and enters a granulator to provide heat required by plastic melting.

In an embodiment of the invention, the temperature for heating the garbage in the second step is 250-300 ℃, and the heating time is 30-45 min. In an embodiment of the present invention, the pyrolysis gasification temperature in the third step is 500-900 ℃, and the pyrolysis gasification time is 30-60 min.

In an embodiment of the present invention, the pyrolysis gasification temperature in the third step is 700 to 800 ℃, and the pyrolysis gasification time is 30 to 45 min.

As described above, the pyrolysis gasification method of domestic garbage according to the present invention has the following beneficial effects: the granulation and the garbage treatment process are combined, and the dried steam is heated again in the granulation process and then heated and granulated, so that the plastic in the garbage is melted and mixed with other components for granulation, and the granulation operation cost can be reduced; according to the types of plastics in the garbage, the operation temperature of the granulator is controlled to be 150-300 ℃, the retention time is 30-60 min, and most of the plastics in the garbage are melted. The garbage is granulated and can be distributed in the pyrolyzer. The pyrolysis and gasification are combined, and the tar generated in the pyrolysis process is gasified and reformed by steam, so that the yield of pyrolysis gas can be improved, and the generation of tar can be reduced; the pyrolysis gasification condition is optimized, the pyrolysis gas can be directly converted into the synthesis gas, the subsequent processing is convenient, and the tar is better recycled. Steam is used as a gasifying agent and a heat carrier for pyrolysis and gasification in the pyrolysis process, so that the heat utilization rate is high, the heat transfer coefficient is large, and the equipment is simple. The drying, the granulation and the pyrolysis gasification are combined, secondary steam generated by the drying is fully utilized, and the energy consumption is reduced.

Drawings

FIG. 1 shows a process flow diagram of the pyrolysis of waste in the prior art.

FIG. 2 is a process flow chart of a pyrolysis gasification method of household garbage according to an embodiment of the present invention.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

Example 1

A pyrolysis and gasification method for household garbage comprises the following steps:

step one, crushing the garbage, adding the crushed garbage into a dryer for drying, wherein the particle size of the crushed garbage is 10-200 mm, the temperature of the dryer is 80 ℃, the water content of the dried garbage is 15%, and conveying steam of the dryer into a primary heater to obtain the dried garbage for later use;

step two, transferring the dried garbage into a granulator, conveying superheated steam in a primary heater into the granulator, heating the dried garbage to 150 ℃ by the superheated steam, keeping the temperature for 60min, conveying the steam of the granulator into a secondary heater, and cooling to obtain granular garbage for later use;

transferring the granular garbage into a pyrolysis gasifier, conveying steam in a secondary heater into the pyrolysis gasifier, pyrolyzing and gasifying the granular garbage at 500 ℃ for 60min by the steam to generate pyrolysis slag and pyrolysis gas, and discharging the pyrolysis slag to obtain the pyrolysis gas for later use;

Example 2

step one, crushing the garbage, adding the crushed garbage into a dryer for drying, wherein the particle size of the crushed garbage is 10-100 mm, the temperature of the dryer is 100 ℃, the water content of the dried garbage is 12%, and conveying steam of the dryer into a primary heater to obtain the dried garbage for later use;

step two, transferring the dried garbage into a granulator, conveying superheated steam in a primary heater into the granulator, heating the dried garbage to 250 ℃ by the superheated steam, keeping the temperature for 35min, conveying the steam of the granulator into a secondary heater, and cooling to obtain granular garbage for later use;

transferring the granular garbage into a pyrolysis gasifier, conveying steam in a secondary heater into the pyrolysis gasifier, pyrolyzing and gasifying the granular garbage at 700 ℃ for 40min by the steam to generate pyrolysis slag and pyrolysis gas, and discharging the pyrolysis slag to obtain the pyrolysis gas for later use;

Example 3

step one, crushing the garbage, adding the crushed garbage into a dryer for drying, wherein the particle size of the crushed garbage is 10-100 mm, the temperature of the dryer is 95 ℃, the water content of the dried garbage is 14%, and conveying steam of the dryer to a primary heater to obtain the dried garbage for later use;

step two, transferring the dried garbage into a granulator, conveying superheated steam in a primary heater into the granulator, heating the dried garbage to 250 ℃ by the superheated steam, keeping the temperature for 50min, conveying the steam of the granulator into a secondary heater, and cooling to obtain granular garbage for later use;

transferring the granular garbage into a pyrolysis gasifier, conveying steam in a secondary heater into the pyrolysis gasifier, pyrolyzing and gasifying the granular garbage at 700 ℃ for 50min by the steam to generate pyrolysis slag and pyrolysis gas, and discharging the pyrolysis slag to obtain the pyrolysis gas for later use;

Example 4

step two, transferring the dried garbage into a granulator, conveying superheated steam in a primary heater into the granulator, heating the dried garbage to 200 ℃ by the superheated steam, keeping the temperature for 60min, conveying the steam of the granulator into a secondary heater, and cooling to obtain granular garbage for later use;

transferring the granular garbage into a pyrolysis gasifier, conveying steam in a secondary heater into the pyrolysis gasifier, pyrolyzing and gasifying the granular garbage at 900 ℃ for 30min by the steam to generate pyrolysis slag and pyrolysis gas, and discharging the pyrolysis slag to obtain the pyrolysis gas for later use;

Example 5

step two, transferring the dried garbage into a granulator, conveying superheated steam in a primary heater into the granulator, heating the dried garbage to 250 ℃ by the superheated steam, keeping the temperature for 60min, conveying the steam of the granulator into a secondary heater, and cooling to obtain granular garbage for later use;

transferring the granular garbage into a pyrolysis gasifier, conveying steam in a secondary heater into the pyrolysis gasifier, pyrolyzing and gasifying the granular garbage at 800 ℃ for 30min by the steam to generate pyrolysis slag and pyrolysis gas, and discharging the pyrolysis slag to obtain the pyrolysis gas for later use;

Examples 1-5 energy consumption of each step of the pyrolysis gasification method of domestic garbage in the whole pyrolysis gasification process of garbage is shown in table 1:

table 1

Recording items	Step one/kJ.kg^-1	Step two/kJ.kg^-1	Step three/kJ.kg^-1	Step four/kJ.kg^-1	kg/kJ^-1
						Example 1	552	56	600	60	1268
Example 2	579	58	660	80	1377
						Example 3	561	57	672	80	1370
Example 4	561	57	816	90	1542
						Example 5	561	57	768	85	1471

Comparative tests were carried out on example 1 and the prior art, the results being shown in table 2:

table 2

Name of item	Example 1	Prior Art	Remarks for note
				Garbage low calorific value MJ/kg	7.96	7.96	50 percent of water, 30 percent of organic matters and 20 percent of inorganic matters
The process consumes MJ/kg	1.38	2.07	The reduction is 33.3 percent
				Consumption ratio	17.3％	26％	--

In conclusion, the domestic garbage pyrolysis gasification method carries out granulation before garbage pyrolysis, improves the dispersion performance of the garbage in the pyrolyzer, and has the advantages of simple structure and convenient operation. The garbage is granulated by a heating method, so that the energy consumption is low. The latent heat of secondary steam in the garbage drying process is further used for heating and granulating the garbage, and the energy-saving effect is obvious. Steam is used as a heat carrier and a gasifying agent for pyrolysis and gasification in the pyrolysis and gasification process, so that the heat transfer efficiency is high, and the gas yield is high. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. The method for pyrolyzing and gasifying the household garbage is characterized by comprising the following steps of:

transferring the dried garbage into a granulator, conveying superheated steam in a primary heater into the granulator, heating the dried garbage to 150-300 ℃ by the superheated steam, keeping the temperature for 30-60 min, conveying the steam of the granulator into a secondary heater, and cooling the solid to obtain granular garbage for later use;

and step four, conveying the pyrolysis gas generated in the step three to a cooling condenser, and respectively discharging the pyrolysis liquid and the pyrolysis gas obtained after cooling and condensing.

2. The pyrolysis and gasification method for household garbage according to claim 1, wherein the pyrolysis and gasification method comprises the following steps: the size of the garbage in the first step is 10-200 mm.

3. The pyrolysis and gasification method for household garbage according to claim 1 or 2, characterized by comprising the following steps: in the first step, the temperature of the dryer is 60-100 ℃, and the water content of the dried garbage is less than or equal to 15%.

4. The pyrolysis and gasification method for household garbage according to claim 3, wherein the pyrolysis and gasification method comprises the following steps: in the first step, the temperature of the dryer is 80-100 ℃, and the water content of the dried garbage is less than or equal to 12%.

5. The pyrolysis and gasification method for household garbage according to claim 1, wherein the pyrolysis and gasification method comprises the following steps: and in the second step, the heating temperature of the garbage is 150-300 ℃, and the heating time is 30-60 min.

6. The pyrolysis and gasification method for household garbage according to claim 1 or 5, wherein: and in the second step, the heating temperature of the garbage is 250-300 ℃, and the heating time is 30-45 min.

7. The pyrolysis and gasification method for household garbage according to claim 1, wherein the pyrolysis and gasification method comprises the following steps: the pyrolysis gasification temperature in the third step is 500-900 ℃, and the pyrolysis gasification time is 30-60 min.

8. The pyrolysis and gasification method for household garbage according to claim 1 or 7, wherein: the pyrolysis gasification temperature in the third step is 700-800 ℃, and the pyrolysis gasification time is 30-45 min.