Biomass circulating fluidized bed boiler with low heating value and high moisture

Abstract

The utility model discloses a biomass circulating fluidized bed boiler with low calorific value and high moisture, which comprises a hearth, a feeding device, a returning device, a secondary tuyere, an air distribution plate, a cyclone separator and a tail flue, castable is laid in the hearth to form a heat insulation hearth, and the hearth is divided into an upper area, a middle area and a lower area. The furnace bottom is provided with an air distribution plate, the air distribution plate is provided with an air cap communicated with a primary air box, a feeding device and a material returning device, the material returning device is communicated with the preheating mixing area at the lower part of the hearth, the upper part of a cyclone separator is communicated with the hearth heat exchange area at the upper part of the hearth, and the bottom of the cyclone separator is communicated with the material returning device; the secondary tuyere communicates with a hearth combustion area in the middle of the hearth. The device is designed for urban garbage, industrial wastes and agricultural wastes, is suitable for fuels with low heat value, high moisture and high chlorine element content, can effectively solve the problems of insufficient combustion of the fuels and generation of dioxin, and has wide application prospects.

Description

Technical Field

[0001] The utility model relates to the technical field of circulating fluidized bed boilers, in particular to a biomass circulating fluidized bed boiler with low calorific value and high moisture content, which is applied to waste incineration and biomass power generation equipment. Background Technique

[0002] In order to handle garbage and other waste, waste incineration boilers and biomass power generation boilers have been widely used. However, the fuels used in these boilers generally have low calorific values and high water contents, and are not easy to burn completely. The amounts of chlorine-containing garbage, chlorine-containing plastics and other chlorine-containing waste in the fuels are generally large. When the incineration temperature is lower than 800 °C, dioxins are easily generated due to incomplete combustion of the fuel. Dioxins are a class of colorless, odorless and highly toxic fat-soluble substances, and their toxicity is 130 times that of cyanide and 900 times that of arsenic, seriously endangering human health and the safety of other organisms. To solve the problem of incineration of garbage and other waste, at present, grate waste incinerators are usually used to incinerate garbage. Although the temperature level in the furnace can be increased to avoid the generation of dioxins, it is difficult to be large-sized due to the limitation of the grate.

[0003] At present, the daily treatment capacity of the mainstream grate furnaces on the market is generally within 1000 tons per day. When using a traditional circulating fluidized bed boiler to incinerate garbage, the garbage treatment capacity can far exceed the level of 1000 tons per day, having the advantage of being large-sized. However, when incinerating garbage with low calorific value and high moisture content, since the preheating combustion space in the furnace is small, the fluctuations in the characteristics of the fuel entering the furnace have a great impact on the temperature in the furnace, the fuel burns incompletely, the temperature level in the furnace is lower than 800 °C, resulting in a large amount of dioxins being generated, and the dioxin content in the boiler emissions exceeding the standard. Therefore, how to handle these waste has become a severe problem faced by today's society. Content of the Utility Model

[0004] To solve the above technical problems, the utility model designs a biomass circulating fluidized bed boiler with low calorific value and high moisture content. The biomass circulating fluidized bed boiler is designed for municipal waste, industrial waste (such as rubber, plastics, etc.), and agricultural waste, and is suitable for fuels with low calorific value, high moisture content and high chlorine element content, and can effectively solve the problems of incomplete fuel combustion and dioxin generation, having broad application prospects.

[0005] The utility model adopts the following technical solutions:

[0006] A biomass circulating fluidized bed boiler with low calorific value and high moisture content, comprising a furnace, a feeding device, a return device, a secondary air inlet, a distributor plate, a cyclone separator and a tail flue. The interior of the furnace is lined with castable to form a heat-insulating furnace. The furnace is divided into three regions: upper, middle and lower. From bottom to top, they are: a preheating and mixing zone, a furnace combustion zone and a furnace heat exchange zone. A distributor plate is arranged at the bottom of the furnace, and air caps are arranged on the distributor plate to communicate with the primary air box. The feeding device and the return device are connected to the preheating and mixing zone at the lower part of the furnace. The upper part of the cyclone separator is connected to the furnace heat exchange zone at the upper part of the furnace, and the bottom of the cyclone separator is connected to the return device. The secondary air inlet is connected to the furnace combustion zone in the middle of the furnace, and the top of the cyclone separator is connected to the tail flue.

[0007] Preferably, a superheater is arranged in the furnace heat exchange zone.

[0008] Preferably, an economizer and an air preheater are sequentially arranged in the tail flue.

[0009] Preferably, the economizer adopts a multi-stage layout structure form.

[0010] Preferably, the temperature of the distributor plate is controlled within the range of 880°C to 900°C.

[0011] Preferably, the flue gas temperature at the outlet of the furnace combustion zone is controlled within the range of 900°C to 1050°C.

[0012] Preferably, the flue gas temperature at the outlet of the furnace heat exchange zone is controlled within the range of 800°C to 900°C.

[0013] Preferably, the oxygen content in the furnace combustion zone is controlled within the range of 2.5% to 3.5%.

[0014] The beneficial effects of the present utility model are as follows: (1) The present utility model can improve the combustion efficiency and has a wide fuel adaptability. After fuels with low calorific value and high moisture content (such as municipal solid waste, rubber, etc.) enter the adiabatic combustion space of the furnace, due to the characteristics of high heat capacity and high material concentration in this space, the fuels are instantaneously heated by the high-temperature flue gas and materials, enabling preheating and drying. And due to the characteristics of the fluidized bed boiler, the fuels are strongly mixed, allowing the fuels to burn stably and continuously in the combustion space. This utility model can adapt to the fluctuations of fuel characteristics, such as changes in calorific value, moisture content, etc., enabling the boiler to have a high adaptability to fuels with large variations in such characteristics; (2) The present utility model can effectively reduce the generation of pollutants such as dioxins. This utility model adopts a circulating fluidized bed boiler. There are a large number of circulating materials in the furnace, and the temperature level in the furnace is relatively uniform, making it easy to control the combustion effect. At the same time, an arch structure is adopted in the combustion zone of the furnace, with high internal heat capacity and high material concentration. The combustion temperature can be controlled within the range of 900°C to 1050°C, and the residence time of the fuel in the furnace exceeds 2 s. Theoretical research and practical experience show that when plastic waste with a relatively high chlorine content is burned at a temperature higher than 800°C and the residence time exceeds 2 s, it can be completely burned and no dioxin-like substances will be produced after combustion; (3) The present utility model can realize the large-scale of the waste incinerator. Due to the characteristics of the circulating fluidized bed boiler, the waste treatment capacity is large when using this utility model, enabling the realization of equipment large-scale. And there are no mechanical transmission components, improving the reliability of the boiler and reducing the maintenance and repair costs of the equipment. Brief Description of the Drawings

[0015] Figure 1 is a schematic structural diagram of the present utility model;

[0016] Figure 2 is a schematic structural diagram of the furnace in the present utility model;

[0017] In the figure: 1, furnace; 2, feeding device; 3, return device; 4, secondary air inlet; 5, air distribution plate; 6, cyclone separator; 7, tail flue; 8, superheater; 9, economizer; 10, air preheater; I, preheating and mixing zone; II, furnace combustion zone; III, furnace heat exchange zone. Detailed Embodiments

[0018] The technical solutions of the present utility model will be further specifically described below through specific embodiments in conjunction with the drawings:

[0019] Embodiment: As Figure 1 shown, a biomass circulating fluidized bed boiler for fuels with low calorific value and high moisture content is composed of a furnace 1, a feeding device 2, a return device 3, a secondary air inlet 4, an air distribution plate 5, a cyclone separator 6, a tail flue 7, a superheater 8, an economizer 9, an air preheater 10, etc.

[0020] AsFigure 2 As shown in the figure, the furnace is divided into three regions: the upper, middle, and lower regions, which are, from bottom to top: the preheating and mixing zone I, the furnace combustion zone II, and the furnace heat exchange zone III. The inside of the furnace is lined with castable refractory to form an adiabatic furnace. Fuel enters the preheating and mixing zone from the feeding device at the lower part of the front wall. Primary air enters the furnace from the air distribution plate at the bottom of the furnace to fluidize the circulating material. Secondary air enters the furnace from the secondary air inlet. After being preheated, dried, and mixed in the preheating and mixing zone, the fuel enters the furnace combustion zone for combustion. The fine particles and circulating ash generated by combustion rise with the flue gas and enter the furnace heat exchange zone to exchange heat with the working medium in the superheater. Then the flue gas enters the cyclone separator, and the separated circulating ash returns to the furnace from the return device at the lower part of the rear wall to continue the material circulation. The flue gas enters the tail flue of the boiler to exchange heat with the tail heating surface.

[0021] The evaporative water-cooled screen is removed from the middle and lower parts of the furnace, and refractory castable is lined inside to form an adiabatic furnace structure, reducing the heat absorption of the furnace and ensuring stable combustion of low calorific value and high moisture fuel in the furnace. The inlet of the tail flue is connected to the cyclone separator, and tail heating surfaces such as superheater, economizer, and air preheater are arranged according to design requirements to heat the working medium in the heating surface and reduce the flue gas discharge temperature. The economizer adopts a multi-stage layout structure to supplement the preheating and evaporative heating surfaces and ensure the load-carrying capacity of the boiler.

[0022] During the operation of the boiler, the primary hot air required for combustion enters from the primary air box at the bottom of the furnace and is fluidized under the action of the air caps arranged on the air distribution plate, serving as the fluidizing air of the boiler. Secondary air enters the furnace from the secondary air inlet and participates in combustion. The primary air and secondary air have a strong disturbing effect on the fuel in the furnace, enabling the fuel entering the furnace to be quickly dried and mixed, which is beneficial to complete combustion.

[0023] By adopting the present utility model, by adjusting the primary air volume and secondary air volume, the combustion can be precisely adjusted, the temperature of the air distribution plate is controlled within the range of 880°C to 900°C, the flue gas temperature at the outlet of the furnace combustion zone is controlled within the range of 900°C to 1050°C, the flue gas temperature at the outlet of the furnace heat exchange zone is controlled within the range of 800°C to 900°C, and the oxygen content is controlled within the range of 2.5% to 3.5%, so as to achieve the purpose of controlling combustion. For a circulating fluidized bed boiler burning waste fuel and various waste fuels with a high chlorine element content, after the fuel enters the furnace, due to the large heat capacity and high temperature level in the furnace, the fuel is fully preheated, dried, and mixed, and can be completely burned. Moreover, the combustion temperature of 900°C to 1050°C and a residence time of more than 2 s can ensure complete combustion of the fuel and prevent the generation of harmful substances such as dioxins.

[0024] By adopting the present utility model, the evaporative water-cooled screen is removed from the middle and lower parts of the furnace, and refractory castable is lined inside to form an adiabatic furnace structure, reducing the heat absorption of the furnace and enabling the use of low calorific value and high moisture fuel to ensure stable combustion of the fuel in the furnace.

[0025] By adopting the utility model, by using an economizer with a multi-stage layout structure form, the preheating and evaporation heating surfaces are supplemented, the feed water temperature is increased, and the boiler's load-carrying capacity is ensured.

[0026] The above-described embodiments are only a preferred solution of the utility model, and do not impose any form of limitation on the utility model. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. A biomass circulating fluidized bed boiler with low calorific value and high moisture content, comprising a furnace, a feeding device, a return device, a secondary air inlet, a wind distribution plate, a cyclone separator and a tail flue, characterized in that, The refractory castable laid inside the furnace is an adiabatic furnace. The furnace is divided into three regions: upper, middle, and lower. From bottom to top, they are: preheating and mixing zone, furnace combustion zone, and furnace heat exchange zone. A wind distribution plate is provided at the furnace bottom, and air caps are arranged on the wind distribution plate to communicate with the primary air box. The feeding device and the return material device are connected to the preheating and mixing zone at the lower part of the furnace. The upper part of the cyclone separator is connected to the furnace heat exchange zone at the upper part of the furnace, and the bottom of the cyclone separator is connected to the return material device. The secondary air nozzles are connected to the furnace combustion zone in the middle of the furnace, and the top of the cyclone separator is connected to the tail flue.

2. A biomass circulating fluidized bed boiler with low calorific value and high moisture content according to claim 1, characterized in that, A superheater is provided in the furnace heat exchange zone.

3. A biomass circulating fluidized bed boiler with low calorific value and high moisture content according to claim 1, characterized in that, A economizer and an air preheater are successively arranged in the tail flue.

4. A biomass circulating fluidized bed boiler with low calorific value and high moisture content according to claim 3, characterized in that, The economizer adopts a multi-stage layout structure form.

5. A biomass circulating fluidized bed boiler with low calorific value and high moisture content according to claim 1, characterized in that, The temperature of the wind distribution plate is controlled within the range of 880°C to 900°C.

6. A biomass circulating fluidized bed boiler with low calorific value and high moisture content according to claim 1, characterized in that, The flue gas temperature at the outlet of the furnace combustion zone is controlled within the range of 900°C to 1050°C.

7. A biomass circulating fluidized bed boiler with low calorific value and high moisture content according to claim 1, characterized in that, The outlet flue gas temperature of the furnace heat exchange zone is controlled within the range of 800°C to 900°C.

8. A biomass circulating fluidized bed boiler with low calorific value and high moisture content according to claim 1, characterized in that, The oxygen content in the furnace combustion zone is controlled within the range of 2.5% to 3.5%.

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