CN111410996B

CN111410996B - Control method of biomass gasification furnace

Info

Publication number: CN111410996B
Application number: CN202010296788.0A
Authority: CN
Inventors: 许东来; 胡旭东
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2020-04-15
Filing date: 2020-04-15
Publication date: 2021-06-25
Anticipated expiration: 2040-04-15
Also published as: CN111410996A

Abstract

A control method of a biomass gasification furnace relates to the field of automatic control. The applied device mainly comprises: the method mainly emphasizes the application of the combination of the camera and the temperature sensor in detecting the calorific value information of gas-producing combustible gas, simultaneously introduces a calorific value coefficient concept, and adopts a fuzzy-PID composite controller with Smith estimation to enable the temperature in the downdraft biomass gasifier to be in an optimal gasification state during temperature loop control.

Description

Control method of biomass gasification furnace

Technical Field

The invention relates to the field of automatic control, in particular to a control method of a biomass gasification furnace.

Background

With the development of economy and society, fossil fuels are becoming exhausted and environmental pollution is becoming serious. The biomass energy sources (such as rice straws, cotton stalks and branches) in China are quite rich, and the biomass gasification furnace can relieve the situation of energy shortage and reduce the environmental pollution degree by taking the agriculture and forestry biomass energy sources such as straws and cotton stalks as raw materials to prepare combustible gas. At present, the biomass gasification furnace production line in China has the problems of high labor intensity of workers, severe working environment, unstable gas production and low heat value. The invention provides a biomass gasification furnace control scheme which can improve gas production stability and gasification efficiency.

Disclosure of Invention

The invention aims to design a control method of a biomass gasification furnace in order to improve the gas production stability and the gas production efficiency of the biomass gasification furnace.

The technical scheme provided by the invention is an intelligent control method of a biomass gasification furnace, which is characterized by comprising the following steps: the system mainly comprises a downdraft biomass gasifier 1, a gasifying agent air inlet valve 2, a plurality of temperature sensors 3 around a hearth, a Roots blower 4, a temperature sensor 5 at a long-time open fire position and a data acquisition camera 6. The method mainly solves the problems of enabling the temperature in the gasification furnace to reach the optimal gasification temperature, enabling the gasification effect to be optimal and analyzing the heat value condition of the generated mixed gas.

The downdraft biomass gasifier, the gasifying agent air inlet valve and the plurality of temperature sensors on the periphery of the hearth form a temperature control ring. And when the temperature is controlled, a Smith-fuzzy-PID composite controller is adopted to control the opening degree of the air inlet valve.

As shown in fig. 2, when the temperature deviation is greater than the deviation set value, the change-over switch is turned to the fuzzy control position, and the Smith-fuzzy control is used for ensuring the response speed of the gasification furnace system; when the deviation is smaller than the set value, the change-over switch is arranged at the PID control position and Smith-PID control is adopted to ensure the problem error of the system.

The temperature sensor at the ever-burning fire, the data acquisition camera and the computer form a gas production heat value analysis system. The flame image information collected by the camera is processed and analyzed by a computer and is compared with the data in the expert database in combination with the temperature information of the thermocouple of the ever-burning fire, so that whether the calorific value of the combustible gas in the produced gas is within the specified range can be obtained.

And a heat value coefficient concept is introduced during data comparison, and the heat value coefficient is formed by combining flame area, height and temperature factors capable of reflecting heat values.

The invention has the beneficial effects that: the temperature control ring controlled by Smith-fuzzy-PID can make the downdraft biomass gasification furnace system more stable, the robustness is strong, and the gas production quality is improved; the gas production heat value analysis system provides reference significance for remote control and large-scale development of the biomass gasification industry.

Drawings

FIG. 1 is a schematic diagram of the main components of a downdraft gasifier system.

Fig. 2 is a block diagram of a control system configuration.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in the figure, biomass raw materials enter a gasification furnace 1 through a feeding hole, contact with a gasification agent introduced into the gasification furnace through an air inlet valve 2, generate mixed gas containing combustible gas such as carbon monoxide, hydrogen, methane and the like, nitrogen and carbon dioxide in the gasification furnace through complex physical and chemical reaction, the generated mixed gas is pumped out from the bottom of the gasification furnace through a variable-frequency Roots blower 4, most of the mixed gas enters a subsequent gas storage device or other links through a pipeline after passing through a purification system, and a small part of the mixed gas is combusted at a long open fire to be used for gas heat value detection.

During the temperature control in the stove, a plurality of sensors 3 around the furnace transmit the temperature to PLC, control the aperture of admission valve 2 after analysis, contrast in order to reach the demand of adjusting the temperature in the stove. When the temperature deviation is larger than the set deviation, the deviation and the change rate of the deviation are used as input of fuzzy control to adjust the opening degree of the air inlet valve 2 in a Smith-fuzzy control mode, and when the deviation is smaller than the set value, the opening degree of the air inlet valve 2 is controlled by a Smith-PID (proportion integration differentiation), wherein the set value of the deviation is written by a configuration software connected with a PLC (programmable logic controller), and can be set to be 10 ℃, and the control mode has good adjusting effect on the temperature of the hearth.

When the mixed gas becomes a calorific value for analysis, the combustion flame information collected by the camera 6 and the flame temperature information collected by the temperature sensor at the long open fire are transmitted into a computer, and the height, area and temperature information of the flame are extracted after image processing. f. of₁＝T_R,T_RIndicating the thermocouple measured temperature. Formula f for flame height information₂＝max{y_p,i}-min{y_p,iDenotes wherein y is_p,iAn ordinate representing the ith point of the flame region; for area information

Representing, wherein M and N respectively represent the row number and the column number of the pixel matrix, and N represents the number of pixels occupied by the flame area; the temperature information uses the average temperature above the thermocouple end as a criterion, and the expression of the average temperature is as follows:

a is the number of pixels in the flame region above the top of the thermocouple, y_rOrdinate, y, representing the center of the top of the thermocouple_jIndicating the ordinate, R, of a pixel point_qThe abscissa range of the flame region is represented, T (i, j) is temperature information of each pixel point in the flame region above the top of the thermocouple, and the temperature information of each pixel point can be obtained by a bicolor method; the gas calorific value coefficient is represented by α, and the expression thereof can be defined as:

in the formula f_θ(θ ═ 1,2,3,4) respectively represent thermocouple temperature values and area, flame height, temperature information in the image, ω is_θIndicating the heat value of the reaction gasCoefficient of relationship of (1), k_θRepresenting the degree of importance of the factor to the calorific value reaction, k_θSatisfy the requirement of

ω_θAnd k_θOmega can be obtained by experimental calibration_θAnalyzing different data of certain processed factor and thermocouple fed back temperature information and different heat value data of gas after content analysis and calculation during calibration, determining the relationship of the factor and the heat value of the reaction gas by using a scatter plot method so as to determine the relationship coefficient, k, of the factor_θThe calibration is determined by the relation coefficient of the reaction heat value of each factor, and the more linear degree of the reaction heat value of a factor is, the k of the factor is_θThe larger, k_θThe specific value (θ ═ 1,2,3,4) can be found by genetic algorithm optimization. The gas heat value coefficient can reflect the height of the gas heat value, whether the gas heat value is in a set value or not can be obtained by comparing the heat value coefficients, the set target heat value maximum value is firstly compared, the maximum value and the minimum value of the gas heat value coefficient are calculated according to a formula and are placed in a database, and the gas heat value can be judged whether the gas heat value is in the set value or not by comparing the heat value coefficient calculated in actual operation with the database setting coefficient.

The invention has wide practical prospect in the large-scale project of biomass gasification cogeneration, and provides reference for detecting the heat value of the mixed gas in the chemical process.

Claims

1. A biomass gasification furnace control method is applied to a device comprising: the system comprises a downdraft biomass gasifier, a gasifying agent inlet valve, a plurality of temperature sensors around a hearth, a Roots blower, a temperature sensor at a long open fire position and a data acquisition camera;

a temperature control ring is formed by the downdraft biomass gasifier, the gasifying agent air inlet valve and a plurality of temperature sensors around the hearth; controlling the opening of the air inlet valve by adopting a Smith-fuzzy-PID composite controller during temperature control; when the temperature deviation is larger than the deviation set value, the change-over switch is switched to the fuzzy control position, and the response speed of the gasification furnace system is ensured by utilizing Smith-fuzzy control; when the deviation is smaller than a set value, the change-over switch is arranged at a PID control position and is controlled by Smith-PID;

the method is characterized in that:

when the mixed gas is analyzed to form a calorific value, transmitting combustion flame information acquired by a camera and flame temperature information acquired by a temperature sensor at an open flame into a computer, and extracting height, area and temperature information of flame after image processing;

f₁＝T_R,T_Rindicating the thermocouple measured temperature;

formula f for flame height information₂＝max{y_p,i}-min{y_p,iDenotes wherein y is_p,iAn ordinate representing the ith point of the flame region;

for area information

Representing, wherein M and N respectively represent the row number and the column number of the pixel matrix, and N represents the number of pixels occupied by the flame area;

the temperature information uses the average temperature above the thermocouple end as a criterion, and the expression of the average temperature is as follows:

a is the number of pixels in the flame region above the top of the thermocouple, y_rOrdinate, y, representing the center of the top of the thermocouple_jIndicating the ordinate, R, of a pixel point_qThe abscissa range of the flame area is represented, T (i, j) is temperature information of each pixel point in the flame area above the top of the thermocouple, and the temperature information of each pixel point is calculated by a bicolor method;

the gas calorific value coefficient is represented by α, and the expression thereof is defined as:

in the formula f_θ(θ ═ 1,2,3,4) respectively represent thermocouple temperature values and area, flame height, temperature information in the image, ω is_θCoefficient of relationship, k, representing the calorific value of the reaction gas of the factor_θRepresents the factor pairImportance of the calorific value reaction conditions, k_θSatisfy the requirement of

ω_θAnd k_θObtained by experimental calibration; comparing the thermal value coefficient to obtain whether the thermal value of the produced gas is within the set value.