CN106524138A - Drop tube furnace device and method for reducing NOx discharge of blended coal combustion - Google Patents

Abstract

The invention belongs to the field of subsidence furnaces, and discloses a subsidence furnace device for reducing NOx emissions from mixed coal combustion, comprising a subsidence furnace body, a powder feeding pipeline assembly and a flue gas classification circulation assembly, and the powder feeding pipeline assembly includes two Secondary air pipe, two primary air powder pipes and main flue gas pipe. The flue gas graded circulation assembly includes the main flue gas pipe and two flue gas circulation pipes. In the upper part of the furnace, the two primary air powder pipes are respectively primary air powder pipe A and primary air powder pipe B. One end of the main flue gas pipe is connected to the flue gas outlet A of the settling furnace body and the other end is respectively Connect the two flue gas circulation pipes. The invention reduces NOx emission while improving incomplete combustion of pulverized coal, increasing the burnout rate of pulverized coal, and is beneficial to the capture and storage of CO ₂ .

Description

A settling furnace device and method for reducing NOx emissions from mixed coal combustion

technical field

The invention belongs to the field of sinking furnaces, and more particularly relates to a sinking furnace device and method for reducing NOx emissions from mixed coal combustion.

Background technique

As my country's industrialization continues to advance, energy consumption continues to increase, improving energy utilization and improving consumption structures have become urgent problems to be solved. Coal is the leading fuel for China's energy consumption. In 2014, coal accounted for 66% of energy consumption. Industrial coal combustion in power plants and other industries produces a large amount of carbon dioxide, sulfide, and nitrogen oxides, causing serious pollution to the environment and bringing about the greenhouse effect. , acid rain and other hazards. The "National Environmental Statistical Bulletin" (2014) pointed out that my country's nitrogen oxide emissions were 20.78 million tons, and industrial nitrogen oxide emissions were 14.048 million tons, accounting for about 67.6% of the national nitrogen oxide emissions.

Reducing _CO2 and NOx emissions has become a global concern. At present, NOx emission reduction technologies are divided into two categories: one is flue gas denitrification technology, which requires a catalyst to complete the denitrification reaction, and this technology is expensive; the other is low NOx combustion technology, among which pulverized coal combustion technology is considered to be a A new combustion technology that simultaneously controls CO ₂ and NOx emissions. In recent years, combustion has attracted great attention. Studies have found that under the combustion conditions of pulverized coal, the combustion of pulverized coal is unstable and the burnout rate is reduced. In order to improve the combustion instability and increase the burnout rate of pulverized coal, the method of increasing the oxygen concentration is adopted. With the increase of the oxygen concentration, the ignition characteristics are improved, the burnout rate is increased, and the combustion tends to be stable; the NOx generation is constantly increasing. . Increasing oxygen concentration, improving combustion characteristics and reducing NOx emissions are contradictory.

Combustion flue gas circulation technology, due to the incomplete combustion of pulverized coal, the flue gas mainly contains CO ₂ , CO, NOx and unburned carbon, etc., the flue gas is circulated to the furnace for reburning, CO and unburned carbon particles enter the furnace for further combustion, improving The burnout rate of pulverized coal is improved, and the CO ₂ concentration in the flue gas is further increased, and the experimental research can be as high as 98%, which is beneficial to the capture and storage of CO ₂ . The NOx in the flue gas is reduced, which reduces the formation of NOx. The research found that the reduced NOx in the flue gas is mainly concentrated in the upper part of the furnace, and the pulverized coal releases a large amount of reducing volatiles in the initial stage of combustion. The NOx is reduced by the volatiles released from pulverized coal.

In power plant boilers, the input coal types are variable, and the parameters of the coal types used in practice are quite different from the designed coal types, which seriously affects the economy and safety of power plant boilers. At present, co-combustion technology is widely used in large coal-fired power plant boilers. Large coal-fired power plant boilers are usually equipped with multi-layer burners along the height of the furnace. The distance along the course of the pulverized coal in the furnace is also different. With the limited space and distance in the furnace, the fuel residence time and the delay mixing time will have a great influence on the combustion economy and emission characteristics. At the same time, under the mixed combustion of pulverized coal in the "furnace", the blending ratio of different coal types will also have a great impact on the economy and emission characteristics of combustion. As far as the "outside the furnace" blending combustion method is concerned, coal types with different characteristics are blended outside the furnace according to a certain proportion and then sent to the furnace for combustion. Coals are in an oxygen-deficient state, which inhibits the ignition of low-volatile coals.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides a settling furnace device and method for reducing NOx emissions from mixed coal combustion, so that pulverized coal of different coal types can be circulated through flue gas classification under combustion conditions, Change the amount of circulating flue gas at different inlet positions, reduce NOx emissions, and improve pulverized coal burnout rate and combustion stability.

In order to achieve the above object, according to one aspect of the present invention, a settling furnace device for reducing NOx emissions from mixed coal combustion is provided, which is characterized in that it includes a settling furnace body, a powder feeding pipeline assembly and a flue gas classification circulation assembly, Wherein, the powder feeding pipeline assembly includes a secondary air pipe and two primary air powder pipes, the flue gas classification circulation assembly includes a main flue gas pipe and two flue gas circulation pipes, and the secondary air pipe is installed vertically In the upper part of the hearth of the furnace body of the settling furnace, it is used to transport pure oxygen into the hearth to support combustion, and the two primary air powder pipes are respectively vertically installed on the inner wall of the secondary air pipe and extend into the furnace respectively, the two primary air powder pipes are respectively primary air powder pipe A and primary air powder pipe B and they are respectively used to send coal powder A and coal powder B into the furnace. One end of the main flue gas pipe is connected to the flue gas outlet A of the settling furnace body and the other end is connected to two flue gas circulation pipes respectively, and the two flue gas circulation pipes are flue gas circulation pipe A and flue gas circulation pipe A respectively. The flue gas circulation pipe B and they are all used to transport the flue gas produced by the combustion of pulverized coal into the furnace, wherein the end of the flue gas circulation pipe A away from the main flue gas pipe is at the same outlet end of the primary air powder pipe A On the horizontal plane A, so that the flue gas and pulverized coal A are fully mixed, and the end of the flue gas circulation pipe B away from the main flue gas pipe is on the same horizontal plane B as the outlet end of the primary air powder pipe B, so that the flue gas and pulverized coal B Mix well, and the level A and the level B are different heights.

Preferably, the powder feeding pipeline assembly also includes an inlet cooling water device, the inlet cooling water device is installed on the inner wall of the secondary air pipe and passes through the secondary air pipe, so as to The air powder pipe, the flue gas circulation pipe and the secondary air pipe are forced convection heat exchange for cooling, and the two primary air powder pipes and the two flue gas circulation pipes all pass through the inlet cooling water device.

Preferably, the main flue gas pipe is provided with a flue gas circulation vacuum pump for transporting flue gas.

Preferably, the settling furnace device also includes a flue gas sampling and analysis assembly, and the flue gas sampling and analysis assembly includes an outlet cooling water device, a filter device, a flue gas analysis vacuum pump and an external flue gas analyzer, and the outlet cooling The water device is installed at the flue gas outlet B of the settling furnace body, so as to cool the flue gas coming out of the settling furnace body from the flue gas outlet B, and the flue gas outlet B of the settling furnace body The filter device, the flue gas analysis vacuum pump and the flue gas analyzer outside the furnace are connected in sequence, the filter device is used to realize the gas-solid separation in the flue gas, the flue gas analysis vacuum pump is used to transport the flue gas, Flue gas analyzers are used to measure NOx levels.

Preferably, the filter device has a glass fiber filter cartridge.

Preferably, the flue gas circulation pipe A and the flue gas circulation pipe B are respectively provided with mass flow meters for controlling the flow of flue gas entering the furnace body of the settling furnace.

Preferably, an observation hole is provided on the side wall of the furnace for observing the flame and flue gas in the furnace body of the settling furnace, and the inspection hole is covered with a sealing cover made of a transparent material. Both the horizontal plane A and the horizontal plane B are located above the observation hole.

Preferably, an in-furnace flue gas analyzer is arranged at the sampling hole.

Preferably, thermocouples are arranged on the body of the settling furnace.

According to another aspect of the present invention, there is also provided a method for reducing NOx emissions by using the settling furnace device, characterized in that, the method is as follows:

Pulverized coal A and pulverized coal B are respectively sent from the primary air powder pipe A and the primary air powder pipe B into the reverse pipe for combustion, and the flue gas from the flue gas outlet A of the settling furnace body passes through the flue gas circulation pipe A and the flue gas circulation pipe B is delivered to the outlet end of the primary air powder pipe A and the outlet end of the primary air powder pipe B, and the flue gas flow into the furnace is controlled by a mass flow meter to realize the distribution of the flue gas flow, thereby reducing NOx emission.

Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

1) The present invention reduces NOx emissions while improving incomplete combustion of pulverized coal, increasing the burnout rate of pulverized coal, and is beneficial to the capture and storage of CO ₂ .

2) The flow of flue gas is controlled by a mass flow meter, and when coal type A and coal type B are input into the settling furnace, they are burned on different levels to realize the reduction of NOx in the flue gas by the volatile matter released by different coal types at the initial stage of combustion. Its emission characteristics affect the experiment.

3) Through the flow control of different branch flue gas pipes by the mass flowmeter, the experiment of the influence of different proportions of flue gas on the NOx emission characteristics in different branch flue gas pipes is realized.

4) As far as the pulverized coal is mixed and burned in the "furnace", the present invention realizes the control of the different residence time and delayed mixing time of the pulverized coal injected into the furnace at different furnace heights, so as to better explore the residence time and The effect of delayed mixing time on combustion improves the "oxygen rush" phenomenon of different coal types at the initial stage of combustion.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

Referring to Fig. 1, a settling furnace device for reducing NOx emissions from mixed coal combustion includes a settling furnace body 10, a powder feeding pipeline assembly and a flue gas classification circulation assembly, wherein,

The upper end of the settling furnace body 10 is the air powder and flue gas inlet end, the lower end is the flue gas outlet end, the wind powder and flue gas inlet end are connected to the powder feeding pipeline assembly and the flue gas classification circulation assembly, and the flue gas outlet end is Connect the flue gas classification circulation component;

The settling furnace has a furnace 13; the powder feeding pipeline assembly includes a secondary air pipe and two primary air powder pipes, and the flue gas classification circulation assembly includes a main flue gas pipe 17 and two flue gas circulation pipes, so The secondary air pipe is vertically installed on the upper part of the furnace 13 of the settling furnace body 10, and is used to deliver pure oxygen to the furnace 13 to support combustion. The secondary air pipe has two conveying The gas branch pipes are respectively the gas transmission branch pipe A7 and the gas transmission branch pipe B8. The two primary air powder pipes are respectively installed vertically on the inner wall of the secondary air pipe and extend into the furnace 13 respectively. The air powder pipes are primary air powder pipe A1 and primary air powder pipe B2 respectively and they are respectively used to send coal powder A and coal powder B into the furnace 13, and one end of the main flue gas pipe 17 is connected to the settling The flue gas outlet A21 of the furnace body 10 and its other end are respectively connected to two flue gas circulation pipes, the two flue gas circulation pipes are flue gas circulation pipe A3 and flue gas circulation pipe B4 respectively and they are used for The flue gas generated by the combustion of pulverized coal is transported into the furnace 13, preferably, a flue gas circulation vacuum pump 16 is provided on the main flue gas pipe for transporting the flue gas. The end of the flue gas circulation pipe A3 away from the main flue gas pipe 17 is on the same horizontal plane A as the outlet end of the primary air powder pipe A1, so that the flue gas and coal powder A can be fully mixed, and the flue gas circulation pipe B4 is far away from the main flue gas One end of the gas pipe 17 is on the same horizontal plane B as the outlet end of the primary air powder pipe B2, so that the flue gas and the pulverized coal A are fully mixed, and the heights of the horizontal plane A and the horizontal plane B are different. If different coals are fed into the furnace at the same position, the high volatile coals will be ignited first, and a large amount of oxygen will be consumed in the early stage of combustion, making the low volatile coals in a state of oxygen deficiency, which will inhibit the low volatile coals from igniting, making The phenomenon of "grabbing oxygen" is intensified, which is not conducive to the complete combustion of pulverized coal. The distance from different fuels to the furnace outlet is different, which realizes the control of the residence time and delayed mixing time of different coal types in the furnace, and improves the "oxygen rush" phenomenon of different coal types at the initial stage of combustion. The flue gas is circulated to the inlet of pulverized coal, and the pulverized coal releases a large amount of reducing volatiles (CO, CH ₄ , H ₂ , etc.) and intermediate products (such as NH ₃ , HCN, etc.) Reducing substances are reduced to N ₂ , reducing the generation of NOx.

Further, the powder feeding pipeline assembly also includes an inlet cooling water device, the inlet cooling water device is installed on the inner wall of the secondary air pipe and passes through the secondary air pipe for cooling the primary air The powder pipe, the flue gas circulation pipe and the secondary air pipe are forced convection heat exchange for cooling, and the two primary air powder pipes and the two flue gas circulation pipes all pass through the inlet cooling water device. The inlet cooling water device has a first cooling water inlet 5 and a first cooling water outlet 6 .

The primary air carries pulverized coal through the primary air powder pipe A1 and the primary air powder pipe B2 into the furnace 13 for combustion, and the pure oxygen is sent into the furnace 13 through the secondary air pipe A and the secondary air powder pipe B to support combustion, providing fuel for combustion. Adequate oxygen. The flue gas is extracted from the flue gas outlet A21 by the flue gas circulation vacuum pump 16, first passes through the main flue gas pipe 17, and then is transported from the flue gas circulation pipe A3 and the flue gas circulation pipe B4 into the furnace 13 for staged combustion. The purpose of the inlet water cooling section It is mainly to protect the primary air powder pipe A1 and primary air powder pipe B2, the branch flue gas pipe A and the branch flue gas pipe B, and prevent the coal powder from igniting in advance and the temperature is too high to cause the pipe to expand and deform due to heat.

Further, the settling furnace device also includes a flue gas sampling and analysis assembly, which includes an outlet cooling water device, a filter device 18, a flue gas analysis vacuum pump 20, and a flue gas analyzer 19 outside the furnace, and the outlet cooling The water device is installed at the flue gas outlet B22 of the settling furnace body 10, so as to cool the flue gas coming out of the settling furnace body 10 from the flue gas outlet B22, and the flue gas of the settling furnace body 10 The gas outlet B22 is sequentially connected to the filter device 18, the flue gas analysis vacuum pump 20 and the flue gas analyzer 19 outside the furnace. The filter device 18 is used to realize gas-solid separation in the flue gas, and the flue gas analysis vacuum pump 20 is used The flue gas is transported, and the flue gas analyzer 19 outside the furnace is used to measure the content of NOx. The cooling water device at the outlet end has a second cooling water inlet 14 and a second cooling water outlet 15 . Preferably, the filter device 18 has a glass fiber filter cartridge. The flue gas passes through the outlet cooling water device at the flue gas outlet B, and then is output after water cooling and heat exchange. The glass fiber filter cartridge realizes the gas-solid separation in the flue gas. The fly ash particles are collected by the glass fiber filter cartridge, and the flue gas components enter the flue gas. The gas analyzer 19 measures the concentration of NOx in the flue gas in real time.

Further, the flue gas circulation pipe A3 and the flue gas circulation pipe B4 are respectively provided with mass flow meters 9 for controlling the flow of flue gas entering the body 10 of the settling furnace. The flow meter controls the flow rate circulating to the flue gas circulation pipe A3 and the flue gas circulation pipe B4. Different coal types entering the furnace through the primary air powder pipe A1 and the primary air powder pipe B2 have different volatile content, and the reduction gas released at the initial stage of combustion The amount of volatile matter is different. By adjusting the flow meter, a high proportion of flue gas reaches the flue gas circulation pipe near the primary air powder pipe containing high volatile coal types; a low proportion of flue gas reaches the flue gas circulation pipe containing low volatile matter. The flue gas circulation pipe near the primary air powder pipe of the coal type makes the NOx amount reasonably distributed to different branch flue gas pipes, and is more effectively reduced.

Further, the side wall of the furnace 13 is provided with an observation hole 12 for observing the flame and flue gas in the furnace body 10 of the settling furnace, and the observation hole 12 is covered with a seal made of a transparent material. cover, the horizontal plane A and the horizontal plane B are both located above the observation hole 12 . Preferably, the observation hole 12 is provided with an in-furnace flue gas analyzer 19 for measuring the content of NOx in the flue gas in the furnace.

Further, thermocouples 11 are arranged on the furnace body 10 of the settling furnace. The furnace body 10 of the settling furnace is heated in three stages, and the thermocouple 11 is installed in each stage to control the temperature in the furnace.

According to another aspect of the present invention, there is also provided a method for reducing NOx emissions by using the settling furnace device, the method is as follows:

Pulverized coal A and pulverized coal B are sent to the furnace 13 for combustion through the primary air powder pipe A1 and the primary air powder pipe B2 respectively, and the flue gas from the flue gas outlet A21 of the furnace body 10 of the settling furnace passes through the flue gas circulation pipe A3 and flue gas circulation The pipe B4 is sent to the outlet near the primary air powder pipe A1 and the outlet end of the primary air powder pipe B2, and the flue gas flow into the furnace 13 is controlled by the mass flow meter 9 to realize the distribution of the flue gas flow, thereby realizing Reduce NOx emissions.

For the flue gas produced by the combustion of pulverized coal in the device, not only the mixed combustion of different coal types in the furnace is realized, but also the flue gas is graded into the flue gas from the flue gas pipe, and the NOx in the flue gas is volatilized by the pulverized coal combustion. Partial reduction, reducing the amount of NOx generated.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (10)

1. A settling furnace device for reducing NOx emissions from mixed coal combustion, characterized in that it comprises a settling furnace body of furnace, a powder feeding pipeline assembly and a flue gas classification circulation assembly, wherein the powder feeding pipeline assembly includes a secondary air pipe and two primary air powder pipes, the flue gas classification circulation assembly includes the main flue gas pipe and two flue gas circulation pipes, the secondary air pipe is installed vertically in the furnace chamber of the settling furnace body The upper part of the furnace is used to deliver pure oxygen into the furnace to support combustion. The two primary air powder pipes are respectively installed vertically on the inner wall of the secondary air pipe and extend into the furnace respectively. The primary air powder pipes are respectively the primary air powder pipe A and the primary air powder pipe B and they are respectively used to send coal powder A and coal powder B into the furnace, and one end of the main flue gas pipe is connected to the settling furnace The flue gas outlet A of the furnace body and its other end are connected to two flue gas circulation pipes respectively, and the two flue gas circulation pipes are flue gas circulation pipe A and flue gas circulation pipe B respectively, and they are used to supply The flue gas produced by the combustion of pulverized coal is transported in the furnace, wherein the end of the flue gas circulation pipe A away from the main flue gas pipe is on the same horizontal plane A as the outlet end of the primary air powder pipe A, so that the flue gas and pulverized coal A Fully mixed, the end of the flue gas circulation pipe B away from the main flue gas pipe and the outlet end of the primary air powder pipe B are on the same level B, so that the flue gas and coal powder A are fully mixed, and the level A and the level B has different heights. 2. A settling furnace device for reducing NOx emissions from mixed coal combustion according to claim 1, wherein the powder feeding pipeline assembly also includes an inlet cooling water device, and the inlet cooling water device is installed on the on the inner wall of the secondary air pipe and pass through the secondary air pipe for forced convection heat exchange and cooling of the primary air powder pipe, flue gas circulation pipe and secondary air pipe. Both the powder pipe and the two flue gas circulation pipes pass through the inlet cooling water device. 3. A settling furnace device for reducing NOx emissions from mixed coal combustion according to claim 1, characterized in that a flue gas circulation vacuum pump is arranged on the main flue gas pipe for transporting flue gas. 4. A settling furnace device for reducing NOx emissions from mixed coal combustion according to claim 1, characterized in that the settling furnace device also includes a flue gas sampling and analysis assembly, and the flue gas sampling and analysis assembly includes an outlet End cooling water device, filter device, flue gas analysis vacuum pump and furnace flue gas analyzer, the outlet end cooling water device is installed at the flue gas outlet B of the settling furnace body for cooling the settling furnace The flue gas that the furnace body comes out from the flue gas outlet B, the flue gas outlet B of the settling furnace body is connected to the filter device, the flue gas analysis vacuum pump and the flue gas analyzer outside the furnace in sequence, and the filter device is used for The gas-solid separation in the flue gas is realized, the flue gas analysis vacuum pump is used to transport the flue gas, and the flue gas analyzer outside the furnace is used to measure the content of NOx. 5 . A settling furnace device for reducing NOx emissions from coal blending combustion according to claim 1 , wherein the filter device has a glass fiber filter cartridge. 6 . 6. A kind of settling furnace device for reducing NOx emissions of mixed coal combustion according to claim 1, characterized in that, the flue gas circulation pipe A and the flue gas circulation pipe B are respectively provided with a mass flow meter to It is used to control the flow of flue gas entering the furnace body of the settling furnace. 7. A kind of downhill furnace device for reducing NOx emission of mixed coal combustion according to claim 1, characterized in that, the side wall of the furnace is provided with an observation hole for observing the downturn furnace furnace body The observation hole is covered with a sealing cover made of transparent material, and the horizontal plane A and the horizontal plane B are both located above the observation hole. 8. A settling furnace device for reducing NOx emissions from coal blending combustion according to claim 1, characterized in that an in-furnace flue gas analyzer is arranged at the sampling hole. 9. A settling furnace device for reducing NOx emissions from coal blending combustion according to claim 1, characterized in that a thermocouple is arranged on the settling furnace body. 10. A method for reducing NOx emissions by using the settling furnace device according to any one of claims 1 to 9, characterized in that, the method is as follows: Pulverized coal A and pulverized coal B are respectively sent from the primary air powder pipe A and the primary air powder pipe B into the reverse pipe for combustion, and the flue gas from the flue gas outlet A of the settling furnace body passes through the flue gas circulation pipe A and the flue gas circulation pipe B is delivered to the outlet end of the primary air powder pipe A and the outlet end of the primary air powder pipe B, and the flue gas flow into the furnace is controlled by a mass flow meter to realize the distribution of the flue gas flow, thereby reducing NOx emission.