CN111156499B

CN111156499B - Clean combustion method for straw bundle burning

Info

Publication number: CN111156499B
Application number: CN202010112457.7A
Authority: CN
Inventors: 姚宗路; 贾吉秀; 赵立欣; 邓云; 丛宏斌; 霍丽丽; 郝先荣
Original assignee: Institute of Environment and Sustainable Development in Agriculturem of CAAS
Current assignee: Institute of Environment and Sustainable Development in Agriculturem of CAAS
Priority date: 2020-02-24
Filing date: 2020-02-24
Publication date: 2020-12-08
Anticipated expiration: 2040-02-24
Also published as: CN111156499A

Abstract

The invention discloses a clean combustion method for straw bundling, belongs to the field of straw utilization, and aims to solve the problems of incomplete process flow, high emission of nitrogen oxides and carbon monoxide in bundling and the like in a straw bundling method. The invention comprises the working procedures of raw material pretreatment, clean combustion and central heating; the method comprises the following steps of picking and bundling field straws, stacking and storing the field straws, dehydrating and drying the field straws and the like to obtain raw materials, then pretreating the raw materials to obtain clean combustion fuel, realizing clean semi-gasification combustion of the straw bundles through a clean combustion process, and finally performing heat exchange through circulating water of a boiler for central heating. The invention adopts the air distribution grading technology, and carries out combined application of the processes of air distribution grading, raw material grading, flue gas backflow and the like in the combustion process of the straw bundle, so that the combustion efficiency of the straw can be improved to a greater extent, the pollutant emission is reduced, and reference is provided for realizing the clean resource utilization of the straw.

Description

Clean combustion method for straw bundle burning

Technical Field

The invention belongs to the field of straw utilization, and particularly relates to a straw bundle burning method.

Background

The straw bundling technique is a better straw energy utilization mode, and is to pick up and bundle loose straws in the field and burn the straws in a special biomass boiler. The energy density is improved after the straw is bundled, the storage and transportation cost is reduced, meanwhile, the burning efficiency and the boiler heat supply efficiency are greatly improved through the semi-gasification burning of the bundled and burned straw, and the straw bundling and burning device has good economic benefits. In recent years, scholars at home and abroad carry out a great deal of research on straw bundling and burning technology and develop research work aiming at perfecting the straw bundling and burning theory and optimizing the straw bundling and burning technology and the boiler structure.

The foreign straw bundling combustion technology has earlier development, the development is faster in the aspects of research, development and popularization of bundling boiler equipment, and the method is mainly focused on the developed Europe such as Denmark, Poland, Sweden, Finland, Czech and AustriaThe country. Denmark already started the combustion utilization of the whole bundle of straws in the 70 s of the 20 th century, and in the 90 s, Denmark formulated the subsidy plan and system of biomass straw boilers, and the more the boiler flue gas emission result for burning biomass is better, the more the subsidy is obtained, thereby stimulating the research and development enthusiasm of boiler manufacturers, and leading various high-performance biomass boilers to be rapidly developed, the combustion efficiency of the boiler is increased from 75% in 1995 to 87% in 2002, and the CO emission is increased from 6250 mg/m in 1995³Reduced to less than 1250 mg/m in 2002³. The Polish MetalERG company has exported 800 EKOPAL series boilers since 1993, has installed 700 EKOPAL RM series boilers in China, and has about 84 MW total power. The straw bundling boiler produced by the Czech Step Trurnov company has the power of 100 kW to 5000 kW, and is mainly used for heat supply of companies, residential areas, government agencies, farmhouses and the like and cogeneration of heat and power in partial areas.

However, the problems of imperfect bundling process flow, poor technical applicability, high emission of nitrogen oxides and carbon monoxide in bundling and the like still exist in the actual operation of the straw bundling and burning boiler.

Disclosure of Invention

The invention aims to provide a clean combustion method for straw bundling, which aims to solve the problems of incomplete process flow, high emission of nitric oxide and carbon monoxide in bundling and the like in the straw bundling method.

The technical scheme of the invention is as follows: a clean combustion method for straw bundle combustion comprises the working procedures of raw material pretreatment, clean combustion and central heating:

step 1: in the clean bundling stage in the bundling pretreatment, the soil content of the straw is lower than 8%; the water content of the straw should not exceed 20%;

and a step 2: clean combustion, wherein straw bundles are combusted and sequentially pass through a main combustion reaction chamber, a volatile component combustion chamber and a straw charcoal combustion chamber, one side of the main combustion reaction chamber is ignited and provided with primary air, and the air distribution excess air coefficient is controlled to be 1.0-1.2; and (3) preparing secondary air in the volatile component combustion chamber, controlling the coefficient of excess air to be 0.8-1.0, and preparing tertiary air in the straw charcoal combustion chamber, and controlling the coefficient of excess air to be 1.2-1.5.

Step 3: and (4) central heating.

In the clean combustion process, according to the requirement of heating scale, a continuous bundling combustion boiler with power of more than 700kW is adopted, and the continuous bundling combustion boiler is divided into a chain grate type, an inclined feeding type and a horizontal feeding type according to the feeding mode.

In another mode, in the clean combustion process, according to the requirement of heating scale, a sequencing batch bundling combustion boiler with power less than 700kW is adopted, and according to the combustion mode, the method is divided into an upper ignition type, a lower ignition type and a side ignition type; the process adopts an intermittent bundling burning process, and comprises a counter-current layer burning type and a forward layer burning type.

Further, in the central heating step, the heating area is more than 10000m²The continuous bundling burning boiler in the working procedure 2 is adopted for large-scale central heating.

Further, in the central heating step, the heating area is less than 10000m²The small-scale central heating adopts the intermittent bundling and burning process in the working procedure 2.

The invention has the following characteristics:

(1) the invention adopts the air distribution grading technology, and carries out combined application of the processes of air distribution grading, raw material grading, flue gas backflow and the like in the combustion process of the straw bundle, so that the combustion efficiency of the straw can be improved to a greater extent, the pollutant emission is reduced, and reference is provided for realizing the clean resource utilization of the straw.

(2) The invention effectively analyzes the whole technical process flow of straw bundle combustion heating, and comprises the pretreatment means before straw combustion, technical characteristics in the straw combustion process, a high-efficiency clean straw combustion air distribution method and technical process selection of heating requirements.

Drawings

FIG. 1 is a process flow diagram of the process of the present invention;

fig. 2 is a schematic diagram of the present invention.

Detailed Description

The invention comprises the working procedures of raw material pretreatment, clean combustion and central heating; the method comprises the following steps of picking and bundling field straws, stacking and storing the field straws, dehydrating and drying the field straws and the like to obtain raw materials, then pretreating the raw materials to obtain clean combustion fuel, realizing clean semi-gasification combustion of the straw bundles through a clean combustion process, and finally performing heat exchange through circulating water of a boiler for central heating.

Step 1: the raw material pretreatment process comprises field straw, clean bundling, straw bundle storage and transportation, bundle burning pretreatment and the like. In the cleaning and bundling stage, a bundling machine with a vibrating screen or other soil screening devices is adopted for picking and bundling the corn straws in the field, so that the soil content is ensured to be lower than 8%; in the stage of storing and transporting straw bundles, the burning of the straws to be stacked and stored is strictly controlled to control the moisture, the water content of rice straws, wheat straws, corn straws and the like is not more than 20 percent, the long edge of a straw stack is parallel to the main wind direction of the local year, a water rolling slope is arranged from the top of a stack to a knot top, and a ventilation opening or a heat dissipation opening is required to be reserved during stacking; in the pre-treatment stage of bundle burning, the waste heat of the boiler is mainly utilized to carry out pre-treatment such as primary drying and dehydration on the straw bundles, so that the water content of the straw bundles is reduced to below 15%.

And a step 2: the clean combustion process mainly comprises clean combustion, a bundling boiler and a bundling process, wherein according to the requirement of heating scale, continuous bundling boilers generally larger than 700kW are adopted, and the continuous bundling boilers can be divided into a chain grate type, an inclined feeding type and a horizontal feeding type according to the feeding mode; a sequencing batch type bundling boiler which is less than 700kW is mainly divided into an upper ignition type, a lower ignition type and a side ignition type according to a combustion mode.

Step 3: the central heating process has a heating area of more than 10000m²The method is called large-scale central heating and corresponds to a continuous bundling boiler and a continuous heating process in the working procedure 2; less than 10000m for heating area²The method is called small-scale central heating and corresponds to an intermittent bundling boiler and an intermittent bundling process in the working procedure 2. (the above-mentioned specific process is prior art.)

FIG. 2 shows the principle of the present invention, in which the continuous type bundling-burning boiler and the sequencing batch bundling-burning boiler both use clean burning mode, the burning mode mainly includes 3 times of counter-current air distribution technology, the primary air is equipped to generate main burning reaction to generate volatile components and coke and other products, the secondary air is equipped to burn volatile components generated by main burning, and the tertiary air is equipped to realize the full burning of coke and residual combustible gas; wherein the heat is gradually transferred to the raw material layer from the combustion layer, and the processes of drying, volatile analysis and pyrolysis combustion of the raw material are realized.

To continuous type bundle burning boiler mainly including chain grate formula, slope feeding formula, horizontal feeding formula, all can realize the continuous feeding and the continuous scarfing cinder of straw bundle, guarantee combustion state and furnace temperature stable, intelligent degree is higher, is applicable to that heating area exceeds 10000m²The demand for heating.

The intermittent bundling and burning boiler mainly comprises an upper ignition type, a lower ignition type and a side ignition type, the charging and burning circulation can be continued only after raw material filling, burning and slag removal, the whole burning process is unstable, the intermittent boiler needs to be shut down when raw materials are replaced, so that the temperature is reduced during material changing, an intelligent heat storage water tank is additionally arranged to ensure that the water outlet temperature is stable, the floor area is small, the heating scale is not too large, and the intermittent bundling and burning boiler is suitable for heating with the heating area smaller than 10000m²The demand for heating.

Example (b):

the specific process comprises the following steps: taking a square bundle of straws as an example, igniting one side of the straw bundle and preparing primary air, controlling the air distribution excess air coefficient to be 1.0-1.2, enabling one side of the straw bundle to generate combustion reaction, and generating volatile combustible gas and straw carbon, wherein the volatile gas mainly comprises CO and H₂、CxHy、CO₂Composition is carried out; secondary air is prepared in the volatile component combustion chamber, the excess air coefficient is controlled to be 0.8-1.0, and the combustible gas in the flue gas is fully combusted; the tertiary air is prepared in the straw charcoal combustion chamber, the excess air coefficient is controlled to be 1.2-1.5, the straw charcoal and the residual combustible gas are fully combusted, and the combustion efficiency of the boiler is improved. Straw bundle is at the combustion process, and the heat is by burning side to unburned side through heat conduction mode transmission, realizes processes such as the drying dehydration of straw, volatile analysis play and pyrolysis burning among the heat transfer process, finally reaches the raw materials grading and the hierarchical effect of air distribution among the straw bundle combustion process, improves combustion efficiency, effectively reduces pollutants such as NOx, CO and discharges in the flue gas. In the processes of main combustion reaction, volatile component combustion reaction and combustion of coke and residual combustible gas, heat is transferred to the coke and residual combustible gas by means of radiation heat exchange and convection heat exchangeThe circulating water is used for heating energy.

Claims

1. A clean combustion method for straw bundle burning is characterized in that: the method comprises the following working procedures of raw material pretreatment, clean combustion and central heating:

and a step 2: clean combustion, wherein straw bundles are sequentially combusted through a main combustion reaction chamber, a volatile component combustion chamber and a straw charcoal combustion chamber, one side of the main combustion reaction chamber is ignited and provided with primary air, and the air distribution excess air coefficient is controlled to be 1.0-1.2; preparing secondary air in the volatile component combustion chamber, controlling the coefficient of excess air to be 0.8-1.0, preparing tertiary air in the straw charcoal combustion chamber, and controlling the coefficient of excess air to be 1.2-1.5;

according to the requirement of heating scale, a continuous type bundling burning boiler with power larger than 700kW is adopted, and the continuous type bundling burning boiler is divided into a chain grate type, an inclined feeding type and a horizontal feeding type according to a feeding mode;

according to the requirement of heating scale, a sequencing batch type bundling burning boiler with power less than 700kW is adopted, and according to a burning mode, the method is divided into an upper ignition type, a lower ignition type and a side ignition type; the process adopts an intermittent bundling burning process, and comprises a counter-current layer burning type and a forward layer burning type;

step 3: in the process of central heating and intermittent bundling, an intelligent heat storage water tank is additionally arranged on an intermittent boiler;

in the central heating step, the heating area is more than 10000m²The large-scale central heating adopts a continuous bundling burning boiler in the working procedure 2; less than 10000m for heating area²The small-scale central heating adopts the intermittent bundling and burning process in the working procedure 2.