CN105879579A - Method and system for realizing reduction of heavy metal and NOx pollutant emission of power station boiler - Google Patents

Abstract

The invention discloses a method and a system for reducing heavy metal and nitrogen oxide (NOx) pollutant emissions from power plant boilers, which belong to the technical field of flue gas pollutant control. In this system, the raw coal is transported to the pyrolysis furnace and coal mill through the belt, the top outlet of the pyrolysis furnace is connected to the boiler burner, the bottom outlet of the pyrolysis furnace is connected to the activation furnace, and the activation furnace is connected to the reformer, and the reformer passes through the pipeline and The injection system is connected to the boiler flue. The specific method is to pyrolyze part of the coal fired in the boiler through the pyrolysis furnace, and the generated pyrolysis gas is transported to the boiler reburning burner for reburning, thereby reducing NOx emissions in the boiler; the coke at the bottom of the pyrolysis furnace is transported to the activation furnace through the discharge system. High-temperature activation, the activated coke is modified by the modifier, and then transported to the injection pipe by the pneumatic conveying pipeline, and the modified activated coke is sprayed into the boiler flue through the injection pipe, and the activated coke absorbs and removes the flue gas in the flue heavy metal pollutants, etc. The invention effectively reduces the discharge of heavy metals and NOx of the boiler.

Description

A method and system for reducing the emission of heavy metals and NOx pollutants from power plant boilers

technical field

The invention discloses a method and a system for reducing heavy metal and NOx pollutant emissions from power plant boilers, which belong to the technical field of flue gas pollutant control. Specifically, the activated coke obtained by pyrolysis in the pyrolysis furnace is modified and sprayed into the flue as an adsorbent, and the pyrolysis gas is used for reburning in the boiler to achieve the purpose of reducing heavy metal pollutants and NOx emissions.

technical background

my country is a big coal producing country in the world, and it is also a big coal burning country. In 2013, China's total coal consumption was 3.61 billion tons. A large amount of NOx and trace heavy metal elements (mercury, arsenic, lead, cadmium, chromium) in coal are released. Heavy metals are enriched and difficult to degrade in the environment. Heavy metals and their compounds discharged to the outside world are harmful to human health and the ecological environment. Taking mercury as an example, mercury released from flue gas from coal-fired power plants is the main source of atmospheric mercury pollution. A large amount of gaseous mercury will be formed during coal combustion, and gaseous mercury will be emitted into the atmosphere along with the flue gas. The "Emission Standards of Air Pollutants for Thermal Power Plants" implemented in January 2012 added mercury emission indicators, stipulating that the emission limit of mercury and its compounds in thermal power plants in my country is 0.03mg/m3. Therefore, it is necessary to strengthen research on the control of mercury pollution emissions from coal-fired power plants, further explore reasonable ways to control mercury emissions, and develop efficient, economical, and environmentally friendly mercury oxidation catalysts, which will have far-reaching significance for the future control of mercury emissions from coal-fired power plants in my country.

At present, the mercury pollution control of coal combustion is mainly through the following three methods: mercury removal before combustion, mercury removal during combustion and mercury removal after combustion. Mercury removal before combustion is mainly through the washing and heat treatment of raw coal to separate mercury from raw coal and not participate in combustion; mercury removal during combustion mainly uses improved combustion methods to reduce NOx while suppressing part of mercury emissions; combustion In post-removal of mercury, in addition to using the existing flue gas treatment equipment of the power plant to optimize the coordinated removal of gaseous mercury, spraying modified mercury removal sorbents in the tail flue of the boiler can effectively reduce the mercury content in the flue gas.

Activated coke is a granular material with dual properties of adsorption and catalysis, with lignite as the main raw material. Activated coke has the characteristics of activated carbon, but at the same time it overcomes the disadvantages of high price, low mechanical strength and easy crushing of activated carbon. The modified active coke is loaded with a modifier, which greatly improves the ability to adsorb mercury.

Chinese patent CN 1715471 A discloses a modified active coke and its preparation method and application. In the preparation method of modified active coke provided by the invention, the modifying agent is at least one of bromide salt, bromate salt, iodide salt, iodate salt, chloride salt and chlorate salt. This modification method is suitable for laboratory-scale research, but it is difficult to meet the injection volume of adsorbent required by coal-fired power plants with large flue gas volume. Therefore, how to carry out large-scale modification of adsorbents in coal-fired power plants is an urgent problem to be solved.

Chinese patent CN 1864809 A discloses a method for purifying flue gas using powdered activated coke. The method provided by this invention is to pass the flue gas containing pollutants through the flue gas pipe sprayed with powdered activated coke to remove the pollutants, and collect the powdered activated coke that absorbs pollutants with a dust collector to obtain purified flue gas ; Wherein, the injection amount of the powdered activated coke is 50-20000mg activated coke/m3 flue gas. This injection device realizes online continuous injection of powdered active coke, but the preparation of active coke and injection separation are realized in different places, and the coupling of the process is not realized.

In addition, the ever-increasing demand for coal and fluctuations in the coal market, especially the supply of thermal coal, have drawn more and more attention to the use of low-grade coal such as lignite, which is traditionally unsuitable for large-scale combustion as fuel. Pollutant discharge control in the process is a very important topic.

Contents of the invention

The purpose of the present invention is to propose a method and system for reducing the emission of heavy metals and NOx pollutants from power plant boilers. In this method, part of the boiler-loaded coal is pyrolyzed through a pyrolysis furnace, and the pyrolysis gas produced at the top outlet of the pyrolysis furnace is purified and transported to the boiler reburning burner for reburning to reduce NOx pollution emissions; the remaining coke at the bottom of the pyrolysis furnace is The discharge system is transported to the activation furnace for high-temperature activation. The activated coke is modified by a modifier, crushed and then transported to the injection pipeline after denitrification by a pneumatic conveying pipeline, and the modified activated coke is evenly sprayed through the injection pipeline. Spray into the boiler flue, so as to realize the adsorption and removal of heavy metal pollutants in the flue gas;

The raw coal that generates pyrolysis gas from pyrolysis in the pyrolysis furnace passes through the pyrolysis furnace once without circulation process, and the pyrolysis gas generated by pyrolysis is transported to the reburning burner of the boiler for reburning.

The coke at the bottom of the pyrolysis furnace is transported to the activation furnace through the discharge system for high-temperature activation, and the activated coke is modified by a reformer without cooling.

The modified active coke is transported to the injection pipeline by the pneumatic conveying pipeline, and evenly sprayed into the flue to absorb and remove heavy metal pollutants in the flue gas.

A system for reducing the emission of heavy metals and NOx pollutants from power plant boilers, characterized in that the raw coal is selected and transported to the coal mill 2 and the pyrolysis furnace 3 through the belt 1, and the coal mill 2 is connected to the boiler through the primary air channel 6, the main fuel burner 7-1, the top outlet of the pyrolysis furnace 3 is connected to the boiler reburning burner 7-2 through the purification system, the bottom outlet of the pyrolysis furnace 3 is connected to the activation furnace inlet 4; the activation furnace 4 is connected to the reformer 5 , the reformer 5 is connected to the injection pipeline 9 via a pipeline.

The injection pipeline 9 is arranged after the selective catalytic reduction denitrification device 8 , and the injected modified active coke adsorbent facilitates the removal by the electrostatic precipitator 10 .

The beneficial effects of the present invention include:

By spraying the activated coke produced by pyrolysis in the pyrolysis furnace in the boiler flue after modification, a mercury removal efficiency of more than 90% can be obtained, and the emission of heavy metals such as mercury can be reduced; The reburning in the reburning burner can obtain a beneficial denitrification effect. The technical equipment of the invention is simple, easy to implement and low in operation cost.

Description of drawings

Fig. 1 is a schematic diagram of the embodiment system.

In the figure: 1 is the coal conveying belt, 2 is the coal mill, 3 is the pyrolysis furnace, 4 is the activation furnace, 5 is the modification machine, 6 is the boiler, 7-1 is the main burner of the boiler, 7-2 is the boiler Reburning burner, 8 is a selective catalytic reduction denitrification device, 9 is an injection pipeline, and 10 is an electric dust collector.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The present invention proposes a method and system for reducing the emission of heavy metals and NOx pollutants from power plant boilers, as shown in FIG. 1 . In the embodiment, the raw coal is pyrolyzed through the coal conveying belt 1 through the pyrolysis furnace 3, and the pyrolysis product has two parts: one part is the gas product pyrolysis gas, and the other part is the solid product active coke. The pyrolysis gas is sent from the top outlet of the pyrolysis furnace 3 to the reburning burner 7-2 of the boiler through connection, as the fuel for the reburning burner; the coke at the bottom of the pyrolysis furnace 3 is transported to the activation furnace 4 through the discharge system for high-temperature activation. The activated coke is modified by the reformer 5, and then transported by the pneumatic conveying pipeline to the injection pipeline 9, and evenly sprayed into the boiler flue through the injection pipeline to absorb and remove heavy metal pollutants in the flue gas.

The present invention may be embodied in other specific forms without departing from the spirit and main characteristics of the invention. Therefore, the above-mentioned embodiments of the present invention can only be considered as descriptions of the present invention and can not limit the present invention, and the claims point out the scope of the present invention, but the above description does not all point out the scope of the present invention. Therefore, any changes within the meaning and scope equivalent to the claims of the present invention should be considered to be included in the scope of the claims.

Claims (7)

1. A method for reducing the emission of heavy metals and NOx pollutants from power plant boilers, characterized in that part of the boiler coal is pyrolyzed through a pyrolysis furnace, and the pyrolysis gas produced at the top outlet of the pyrolysis furnace is transported to the boiler reburning burner Reburning reduces NOx pollution emissions; the coke at the bottom of the pyrolysis furnace is transported to the activation furnace through the discharge system for high-temperature activation. The activated coke is modified by a reformer, and then transported to the injection pipeline by a pneumatic conveying pipeline, and passes through the injection pipeline. Evenly spray the modified activated coke into the boiler flue, so as to realize the adsorption and removal of heavy metal pollutants in the flue gas. 2. The method for reducing the discharge of heavy metals and NOx pollutants from power plant boilers according to claim 1 is characterized in that, the raw coal that is pyrolyzed in the pyrolysis furnace to generate pyrolysis gas passes through the pyrolysis furnace once, without a cycle process. 3. The method for reducing the emission of heavy metals and NOx pollutants from power plant boilers according to claim 1, characterized in that the pyrolysis gas produced by the pyrolysis furnace is transported to the reburning burner of the boiler for reburning to reduce the generation of NOx. 4. The method for reducing the emission of heavy metals and NOx pollutants from power plant boilers according to claim 1 is characterized in that the coke at the bottom of the pyrolysis furnace is transported to the activation furnace through the discharge system for high-temperature activation, and the activated coke after activation is modified by Machine modification, no cooling link. 5. The method for reducing the emission of heavy metals and NOx pollutants from power plant boilers according to claim 1 is characterized in that the modified active coke is transported to the injection pipeline by the pneumatic conveying pipeline, and the modified coke is evenly sprayed by the injection pipeline. Activated coke is sprayed into the flue to absorb and remove heavy metal pollutants in the flue gas. 6. According to claim 1, the method for reducing the discharge of heavy metals and NOx pollutants from power plant boilers is characterized in that the raw coal is transported to the coal mill 2 and the pyrolysis furnace 3 through the belt 1, and the coal mill 2 is controlled by the primary air channel Connect the main fuel burner 7-1 of the boiler 6, the top outlet of the pyrolysis furnace 3 is connected to the boiler reburning burner 7-2, the bottom outlet of the pyrolysis furnace 3 is connected to the activation furnace inlet 4; the activation furnace 4 is connected to the modification machine 5, and the modification The sex machine 5 is connected to the injection pipeline 9. 7. A kind of system that realizes the reduction of heavy metals and NOx pollutant emissions of utility boilers according to claim 6 is characterized in that, the injection pipeline 9 is arranged after the selective catalytic reduction denitrification device 8, and the modified activated coke adsorbent of injection is beneficial to ESP 10 removal.