CN108916866B

CN108916866B - Sleeve type multi-fuel circulating-bubbling combined fluidized bed boiler

Info

Publication number: CN108916866B
Application number: CN201810442475.4A
Authority: CN
Inventors: 陈巨辉; 韩坤; 张宗云; 李铭坤; 宋美琪; 陈纪元; 马明
Original assignee: Harbin University of Science and Technology
Current assignee: Harbin University of Science and Technology
Priority date: 2018-05-10
Filing date: 2018-05-10
Publication date: 2021-01-15
Anticipated expiration: 2038-05-10
Also published as: CN108916866A

Abstract

A sleeve type multi-fuel circulating-bubbling combined fluidized bed boiler is a boiler which integrates two circulating-bubbling beds into a whole. The fluidized bed of the fluidized bed boiler is divided into a circulating fluidized bed and a bubbling fluidized bed, so that the processes of coal particle combustion and biomass gasification can be simultaneously carried out in separate beds; the two beds are directly used for heat transfer, and a water-cooled wall is laid outside the bubbling bed, so that the effects of energy transfer and product isolation are achieved, and meanwhile, the occupied space of the product is saved; the combustible gas generated by biomass gasification can be collected and utilized, and no oxynitride can be separated out from the biomass under the gasification condition. The invention solves the problems that the prior circulating fluidized bed boiler can not fully utilize the waste heat when burning single fuel, and the discharge of oxynitride pollutes the environment and the like.

Description

Sleeve type multi-fuel circulating-bubbling combined fluidized bed boiler

Technical Field

The invention relates to the technical field of fuel gasification and combustion, in particular to a sleeve type multi-fuel circulation-bubbling combined fluidized bed boiler.

Background

At present, the industrialized gasification technologies mainly include fixed bed gasification technology, fluidized bed gasification technology and entrained flow gasification technology. The fixed bed gasification technology is the simplest and the most widely applied, but the fixed bed is difficult to adapt to large fuel treatment amount and small production scale; the raw materials mostly use high-quality lump coal, which undoubtedly increases the fuel cost; the gasification temperature is low, the problems of secondary pollution and the like of phenol water are easily caused, the environmental protection pressure is high, and the national environmental protection requirement cannot be met;

the fluidized combustion technology is rapidly developed in recent years, and has the characteristics of strong combustion adaptability, capability of combusting fuel with low heat value, high moisture and high ash content, high combustion efficiency, flexible combustion temperature regulation and the like, and has unique advantages in the technical field of fuel gasification and combustion. The bubbling fluidized bed boiler has wide fuel adaptability, can especially burn inferior fuel, and is often used in the fields of biomass gasification, combustion and the like. The circulating fluidized bed boiler is a new boiler type developed on the basis of a bubbling fluidized bed boiler, and has the characteristics of low-temperature combustion, good mixing effect in the bed, excellent fuel adaptability and the like, so that the circulating fluidized bed boiler has wide social benefits and application prospects. However, the existing fluidized bed boiler is limited to single-bed combustion, mainly uses single fuel for combustion, has large heat loss, and can not fully utilize the residual heat after the fuel is combusted.

Disclosure of Invention

The invention provides a technical scheme of biomass-coal combined gasification-combustion of a circulating-bubbling fluidized bed, which aims to increase the utilization rate of fuel to the maximum extent, reduce the fuel cost, fully utilize the heat generated by the circulating fluidized bed and the bubbling fluidized bed, further reduce the discharge of oxynitride, obtain combustible gases such as hydrogen and the like, and realize the graded utilization of energy.

The technical scheme of the invention is as follows: a sleeve type multi-fuel circulating-bubbling combined fluidized bed boiler is characterized in that a hearth is divided into two regions, the middle region is a circulating fluidized bed riser part, and the peripheral region is a bubbling fluidized bed part. In which coal is burned in a circulating fluidized bed and biomass is gasified in a bubbling fluidized bed. Water-cooled walls are arranged around the bubbling bed.

In the circulating fluidized bed, coal is fed from a feed inlet, high-speed airflow is sprayed into a riser from the bottom, and the coal and bed materials are blown around to fill the whole space of the riser. The coal is burned in the riser, releasing heat. The heat released after the coal is burnt is transferred to the bubbling fluidized bed through the pipe wall and is used as a heat source for the gasification of the bubbling fluidized bed. The combustion products pass through a cyclone, the flue gases are discharged from a flue gas outlet at the top of the riser, while the unburned carbon particles and bed material are returned to the circulating fluidized bed for renewed combustion.

In the bubbling fluidized bed, biomass enters through the inlet 2. Meanwhile, water cooling walls are arranged on the periphery of the bubbling fluidized bed, the water is gasified into high-temperature steam by using the waste heat of the bubbling fluidized bed, the flow speed of the generated high-temperature steam is controlled by a throttle valve, and the generated high-temperature steam is introduced to the bottom of the bubbling fluidized bed to fluidize bed materials and biomass and promote heat transfer. The biomass and steam are subjected to gasification reaction in a high-temperature environment to generate combustible gas, and the combustible gas is collected through an exhaust port at the top of the bubbling fluidized bed.

Each fluidized bed is provided with an independent fluidizing system, wherein the fluidizing of the circulating fluidized bed is realized by an air source provided by an air blower, and the air source enters the bed through an air distribution plate to serve as a fluidizing medium; the fluidization of the bubbling fluidized bed is realized by feeding high-temperature water vapor generated by a water-cooled wall of a boiler into the bottom of the bubbling fluidized bed through the regulation of a throttle valve to serve as a fluidizing medium. In the circulating fluidized bed, the cyclone separator and the whole material circulating channel are arranged outside the whole boiler and extend from the top of the riser of the circulating fluidized bed to a lower position at one side of the circulating fluidized bed. In the circulating fluidized bed, a feed inlet 1 is provided for feeding coal. And a feeding hole 2 is formed in the outer side of the bubbling fluidized bed and used for introducing biomass. Water cooling walls are arranged around the bubbling fluidized bed. The bubbling fluidized bed and the circulating fluidized bed are in an isolated state, and the reactions of the fuel in the bubbling fluidized bed and the circulating fluidized bed are not interfered with each other.

Compared with the prior art, the invention has the following beneficial effects: according to the invention, the fluidized bed is divided into two areas, so that the processes of coal combustion and biomass gasification are simultaneously carried out in a separated bed manner. Meanwhile, the heat of the circulating fluidized bed is directionally transferred to the bubbling fluidized bed to be used as a heat source for biomass gasification. The waste heat of the bubbling fluidized bed is fully absorbed by the water of the water-cooled wall and gasified into high-temperature steam. The flue gas generated by combustion flows out of the top of the circulating fluidized bed, and the gasification products flow out of the top of the bubbling fluidized bed. Realizes the directional transfer of substances and energy among beds, fully utilizes the heat generated by each step of reaction, reduces the discharge of oxynitride,

and the combustible gas can be collected.

Drawings

FIG. 1 is a front view of a fluidized bed in an embodiment of the present invention;

wherein: 1. the biomass gasification furnace comprises a coal feeding port 2, a biomass feeding port 3, a circulating bed air inlet 4, a bubbling bed high-temperature steam inlet 5, a water-cooled wall 6, a cyclone separator 7, a flue gas outlet 8, a gasification product collecting port 9, a bubbling fluidized bed 10 and a circulating fluidized bed;

FIG. 2 is a sectional view of a fluidized bed in an embodiment of the present invention;

FIG. 3 is a three-dimensional schematic of a fluidized bed in an embodiment of the invention.

Detailed Description

A sleeve type double-circulation multi-fuel combined fluidized bed boiler works according to the following principle:

1. circulating the fluidized bed:

during the coal passed through feed inlet 1 entering circulating fluidized bed, the air was sent into from the bottom through the grid plate by the air-blower, and coal and air mixed combustion emit a large amount of reaction heats, and its main chemical reaction who takes place has:

the reactions are exothermic reactions, the reaction temperature is 800-950 ℃, and heat generated by coal combustion is transferred into the bubbling fluidized bed to provide energy (heat source) for biomass gasification. The flue gases produced are discharged from the top of the riser via a gas outlet at the top of the riser under the action of a cyclone, while the unburnt carbon particles and bed material are returned to the circulating fluidized bed for renewed combustion.

2. Bubbling fluidized bed:

water cooling walls are arranged around the bubbling fluidized bed, the water is gasified into high-temperature steam by using the waste heat of the bubbling fluidized bed, the flow rate of the generated high-temperature steam is controlled by a throttle valve, and then the high-temperature steam is sent to a nozzle of the bubbling fluidized bed, so that the fluidization of particles is realized.

In the bubbling fluidized bed, a certain amount of biomass is fed from a feed inlet 2, high-temperature steam is taken as a gasification medium and is fed into a hearth from the bottom through a nozzle, and heat released by coal combustion in the circulating fluidized bed is transferred to the bubbling fluidized bed to be used as a heat source for biomass gasification. The reaction of the water vapor and the biomass at high temperature comprises the thermal decomposition reaction of the biomass, the reduction reaction of water vapor-carbon, the shift reaction of CO and the water vapor, the methanation reaction and the like.

(1) Thermal decomposition reaction of biomass: the carbohydrate bonds of the macromolecules are broken up and volatiles (mainly including hydrogen, carbon monoxide, carbon dioxide, methane, tars and other carbohydrates) are evolved, leaving the carbon to form the matrix for further reactions. The biomass will undergo irreversible thermal decomposition reactions above 150 ℃.

(2) Steam-carbon reduction reaction:

(3) shift reaction of CO with steam:

(4) methanation reaction:

the reaction is essentially endothermic and the combustible gas produced flows out through a vent at the top of the bubbling fluidized bed, where it is then collected. The temperature of the bubbling fluidized bed after gasification is reduced to 200-350 ℃. However, in the circulating fluidized bed, the combustion of coal generates heat continuously, and then the heat is transferred to the bubbling fluidized bed, so that the temperature of the bubbling fluidized bed is maintained in a relatively stable state.

The overflow height in the two beds can be adjusted by the air supply volume of the independent air supply system respectively. The bubbling fluidized bed and the circulating fluidized bed are in an isolated state, and the reactions of the fuel in the bubbling fluidized bed and the circulating fluidized bed are not interfered with each other and only transfer heat. The gasification products and the flue gas are respectively discharged from different exhaust ports, and the combustible gas generated by the reaction in the fluidized bed can be collected.

Claims

1. A sleeve type multi-fuel circulating-bubbling combined fluidized bed boiler is characterized in that: the internal structure of the fluidized bed is divided into an inner nested area and an outer nested area, the inner layer is a circulating fluidized bed for carrying out coal combustion reaction, the outer layer is a bubbling fluidized bed for carrying out biomass gasification reaction, and water-cooled walls are arranged around the bubbling fluidized bed; the coal feeding port penetrates through the bubbling fluidized bed to the circulating fluidized bed; a biomass feed port is introduced into the bubbling fluidized bed; the top of the circulating fluidized bed is communicated with the cyclone separator, the top end of the cyclone separator is provided with a flue gas outlet, the lower end of the cyclone separator is provided with a feed back pipe, the feed back pipe extends through the bubbling fluidized bed and then returns to the circulating fluidized bed,

in the circulating fluidized bed, coal is fed from a coal feeding port, high-speed airflow is sprayed into a lifting pipe from the bottom, the coal and bed materials are blown to the periphery to fill the whole space of the circulating fluidized bed, the coal is combusted in the circulating fluidized bed to release heat, the heat released after the coal is combusted is transferred to the bubbling fluidized bed through a pipe wall to be used as a heat source for the gasification of the bubbling fluidized bed, combustion products pass through a cyclone separator, flue gas is discharged from a flue gas outlet at the top of the cyclone separator, unburned carbon granules and bed materials are returned to the circulating fluidized bed to be combusted again,

in the bubbling fluidized bed, biomass enters from a biomass feed inlet, water cooling walls are arranged around the bubbling fluidized bed at the same time, water is gasified into high-temperature steam by using the waste heat of the bubbling fluidized bed, the flow rate of the generated high-temperature steam is controlled by a throttle valve, the generated high-temperature steam is introduced to the bottom of the bubbling fluidized bed, bed materials and the biomass are fluidized to promote heat transfer, the biomass and the steam are subjected to gasification reaction in a high-temperature environment to generate combustible gas, and a gasification product collecting port at the top of the bubbling fluidized bed is used for collecting the combustible gas;

the bubbling fluidized bed and the circulating fluidized bed are in an isolated state, and the reactions of the fuel in the bubbling fluidized bed and the circulating fluidized bed are not interfered with each other;

and steel with good heat conductivity is adopted around the circulating fluidized bed.