Ultra-low emission flue gas treatment system suitable for whole-bundle straw gasification coupling combustion boiler

Abstract

The utility model discloses an ultralow emission flue gas treatment system suitable for a whole bundle straw gasification coupling combustion boiler, which comprises a boiler, the upper part of the boiler is connected with an SNCR ammonia water spraying device, the flue gas outlet of the boiler is connected with the flue gas inlet of dust removal equipment, the flue gas outlet of the dust removal equipment is connected with the flue gas inlet of an SCR reactor, and the flue gas outlet of the SCR reactor is connected with the flue gas inlet of the SCR reactor. A flue gas outlet of the SCR reactor is connected with a flue gas inlet of the deacidification tower, a flue gas outlet of the deacidification tower is connected with a flue gas inlet of the bag-type dust collector, and a flue gas outlet of the bag-type dust collector is connected with the chimney. The flue gas treatment system is combined with the original boiler body, so that the flue gas treatment equipment is distributed at a proper position in the boiler body, and the beneficial conditions of temperature, pressure and the like of the flue gas in the original boiler body are fully utilized, so that part of environment-friendly flue gas pretreatment equipment can be omitted, the investment is reduced, and the treatment efficiency of environment-friendly equipment can be improved; and the environment-friendly operation cost is reduced, and the efficiency of a subsequent boiler body heat exchange device is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of flue gas purification and treatment, and in particular relates to an ultra-low emission flue gas treatment system suitable for a whole-bundle straw gasification coupled combustion boiler. Background Art

[0002] Most of the existing biomass direct heat and steam supply devices are: gasification in a gasifier first and then combustion in a gas boiler. This method of utilizing biomass by gasification first and then combustion has high requirements for biomass fuel entering the furnace. Traditional straws include rice straw, wheat straw and corn straw, etc. These straws need to be crushed first, and then pre-processed by briquetting to make them into shaped fuels of a certain density and size before they can enter the gasifier for gasification. This greatly increases the cost of biomass straw utilization and is not conducive to comprehensive promotion. At present, the form of direct decoupled gasification and combustion of whole bundles of straw without crushing or briquetting has become a development trend, and whole bundles of straw gasification coupled combustion boilers have also emerged.

[0003] At present, biomass emission standards are becoming more and more stringent, and many places have introduced ultra-low emission standards for biomass. The specific emission requirements are as follows: Particles ≤ 10 mg / Nm 3 , sulfur dioxide ≤35 mg / Nm 3 , nitrogen oxides ≤50 mg / Nm 3 , ammonia slip (SNCR+SCR) ≤ 3.8 mg / Nm 3 (Requirements vary slightly from place to place). The traditional method of comprehensive utilization of biomass and flue gas treatment is: the boiler body only considers the calorific value conversion and utilization rate of the fuel, and the waste gas generated is discharged from the flue at the tail of the boiler, and then the flue gas treatment facilities are used to treat the flue gas to meet the emission standards. The traditional ultra-low emission facilities for flue gas treatment of biomass boilers are: SDS baking soda desulfurization + bag dust removal + flue gas heating + SCR catalytic reaction tower denitrification. This traditional ultra-low emission process has high deacidification costs and will cause a surge in environmental protection operating costs. In order to meet the reaction temperature requirements of SCR, the flue gas temperature in front of the SCR catalytic reaction tower needs to be increased. Generally, steam heating or direct heating with fuels such as natural gas is used, which leads to a surge in flue gas heating costs. This flue gas treatment method that is completely separated from the boiler body will lead to an increase in investment costs for flue gas treatment equipment and an increase in operating costs.

[0004] Therefore, it is urgent to develop a flue gas treatment system that comprehensively considers factors such as the fuel conversion efficiency of biomass, the ultra-low emission requirements of flue gas, and the operating costs of flue gas treatment to meet the delayed ultra-low emission requirements. Utility Model Content

[0005] Technical problems solved: In response to the above technical problems, the utility model provides an ultra-low emission flue gas treatment system suitable for whole-bale straw gasification coupled combustion boilers, which can not only save some environmental protection flue gas pretreatment equipment and reduce investment, but also improve the treatment efficiency of environmental protection equipment, reduce environmental protection operating costs, and also improve the efficiency of subsequent boiler body heat exchange devices.

[0006] Technical solution: An ultra-low emission flue gas treatment system suitable for a whole-bale straw gasification coupled combustion boiler, comprising a boiler, the upper part of which is connected to an SNCR ammonia water injection device, the flue gas outlet of the boiler is connected to the flue gas inlet of a dust removal device, the flue gas outlet of the dust removal device is connected to the flue gas inlet of an SCR reactor, the flue gas outlet of the SCR reactor is connected to the flue gas inlet of a deacidification tower, the flue gas outlet of the deacidification tower is connected to the flue gas inlet of a bag filter, and the flue gas outlet of the bag filter is connected to a chimney.

[0007] Preferably, a superheater and an evaporator are respectively provided in the second flue and the third flue of the boiler.

[0008] Preferably, the dust removal equipment is a cyclone dust collector.

[0009] Preferably, a catalyst layer is provided above the interior of the SCR reactor.

[0010] Preferably, an economizer and an air preheater are sequentially arranged between the flue gas outlet of the SCR reactor and the flue gas inlet of the deacidification tower.

[0011] Preferably, an induced draft fan is provided on the pipe connecting the smoke outlet of the bag filter and the chimney.

[0012] Beneficial effects: The flue gas treatment system is combined with the original boiler body, so that the flue gas treatment equipment is distributed in the appropriate position in the boiler body, making full use of the favorable conditions of the flue gas in the original boiler body, such as temperature and pressure, which can not only save some environmental protection flue gas pretreatment equipment and reduce investment, but also improve the treatment efficiency of environmental protection equipment, reduce environmental protection operation costs, and also improve the efficiency of subsequent boiler body heat exchange devices;

[0013] The flue layout is shorter than the traditional process flow, the smoke resistance is small, the induced draft fan power consumption is low, and the operating cost is saved;

[0014] The cyclone dust collector is installed after the boiler evaporator to reduce dust in the subsequent SCR device, economizer and air preheater, thus preventing blockage and salt corrosion of subsequent equipment.

[0015] SCR is installed in front of the economizer, in the flue of the boiler body, with a temperature of about 380°C. Denitrification uses medium-high temperature SCR catalyst, with high denitrification efficiency and low ammonia slip value, which fully meets the emission requirements of nitrogen oxides and ammonia slip; and the denitrification agent can be provided by the SNCR system, eliminating the need for ammonia evaporation, dilution and ammonia injection equipment, saving investment costs;

[0016] The deacidification adopts high-efficiency slaked lime deacidification. Compared with the traditional slaked lime dry method, it has high desulfurization efficiency and can ensure ultra-low emission requirements of sulfur dioxide; compared with the traditional baking soda dry method, it can save the cost of desulfurization consumables and reduce operating costs;

[0017] Compared with the traditional ultra-low process, the medium and high temperature SCR denitrification catalyst utilizes the original high-temperature flue gas without consuming additional steam or fuel, which greatly saves energy loss and reduces operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of an ultra-low emission flue gas treatment system suitable for a whole-bundle straw gasification coupled combustion boiler of the utility model;

[0019] Serial numbers in the figure: 1. Boiler, 1-1. SNCR ammonia water injection device, 2. Dust removal equipment, 3. SCR reactor, 4. Deacidification tower, 5. Bag filter, 6. Draft fan, 7. Chimney. DETAILED DESCRIPTION

[0020] The technical solution of the utility model is further described in detail below in conjunction with the accompanying drawings. Example 1

[0021] Reference Figure 1 , an ultra-low emission flue gas treatment system suitable for a whole-bale straw gasification coupled combustion boiler, comprising a boiler 1, the boiler being a whole-bale straw gasification coupled combustion boiler, the upper part of the furnace of the boiler 1 being connected to the SNCR ammonia water injection device 1-1, the injected ammonia water can not only remove a part of the nitrogen oxides, but also provide a denitrification agent - ammonia gas for the subsequent medium and high temperature SCR catalyst, eliminating the need for ammonia evaporation, dilution and ammonia injection equipment, saving investment costs. The flue gas comes out of the furnace, passes through the superheater and evaporator of the second flue and the third flue in turn, and the flue gas temperature drops to about 380°C, and then enters the dust removal device 2, removes the medium and large particles of dust in the flue gas, and then enters the SCR reactor 3, the upper part of the SCR reactor 3 is provided with two layers of denitration catalyst layers, the denitration catalyst is the residual ammonia of the SNCR ammonia water injection device 1-1, at this flue gas temperature, the denitration efficiency of the denitration filter bag can reach 85~95%, and the ammonia escape is extremely low, and the nitrogen oxides of the flue gas after denitration and dust removal are ≤50 mg / Nm 3After that, the flue gas passes through the vertical economizer and air preheater for heat exchange, and the flue gas temperature drops to about 140℃; then, the flue gas enters the dry deacidification tower 4, and the deacidification agent uses high-efficiency slaked lime. Compared with the traditional baking soda deacidification, high-efficiency slaked lime is cheap, has a low calcium-sulfur ratio, and has a deacidification efficiency similar to baking soda, which can greatly reduce the deacidification cost. After the dry deacidification tower, the flue gas SO2≤35 mg / Nm 3 ; Then, the flue gas enters the bag filter 5. The bag is made of pure PTFE+PTFE film material to ensure that the dust is ≤10 mg / Nm 3 The flue gas after the bag filter meets the ultra-low emission requirements, passes through the induced draft fan 6, and is discharged through the chimney 7 to meet the emission standards.

[0022] The dust removal device 2 is a cyclone dust collector.

[0023] The embodiments of this specific implementation method are all preferred embodiments of the utility model, and are not intended to limit the protection scope of the utility model. Therefore, all equivalent changes made based on the structure, shape, and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. An ultra-low emission flue gas treatment system suitable for whole-bundle straw gasification coupled combustion boiler, characterized in that: The invention comprises a boiler (1), wherein the upper part of the boiler (1) is connected to an SNCR ammonia water injection device (1-1), the flue gas outlet of the boiler (1) is connected to the flue gas inlet of a dust removal device (2), the flue gas outlet of the dust removal device (2) is connected to the flue gas inlet of an SCR reactor (3), the flue gas outlet of the SCR reactor (3) is connected to the flue gas inlet of a deacidification tower (4), the flue gas outlet of the deacidification tower (4) is connected to the flue gas inlet of a bag filter (5), and the flue gas outlet of the bag filter (5) is connected to a chimney (7).

2. The ultra-low emission flue gas treatment system suitable for whole-bale straw gasification coupled combustion boiler according to claim 1, characterized in that: The second flue and the third flue of the boiler (1) are respectively provided with a superheater and an evaporator.

3. The ultra-low emission flue gas treatment system suitable for whole-bale straw gasification coupled combustion boiler according to claim 1, characterized in that: The dust removal equipment (2) is a cyclone dust collector.

4. The ultra-low emission flue gas treatment system suitable for whole-bale straw gasification coupled combustion boiler according to claim 1, characterized in that: A catalyst layer is provided above the interior of the SCR reactor (3).

5. The ultra-low emission flue gas treatment system suitable for whole-bale straw gasification coupled combustion boiler according to claim 1, characterized in that: An economizer and an air preheater are arranged in sequence between the flue gas outlet of the SCR reactor (3) and the flue gas inlet of the deacidification tower (4).

6. The ultra-low emission flue gas treatment system suitable for whole-bale straw gasification coupled combustion boiler according to claim 1, characterized in that: An induced draft fan (6) is provided on the pipeline connecting the smoke outlet of the bag filter (5) and the chimney (7).

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