Low-quality coal cold plasma ignition method for thermal power plant

Abstract

The application discloses a low-quality coal cold-state plasma ignition method for a thermal power plant, which adopts waste ion exchange resin in a water treatment plant of the thermal power plant, mixes the waste ion exchange resin into coal after pretreatment, grinds the mixture to obtain a mixed fuel, and uses the mixed fuel in a plasma coal powder ignition burner to ignite a boiler of the thermal power plant in a cold state. When the mixed fuel is ignited by the plasma coal powder ignition burner, the waste ion exchange resin powder is ignited first, and after being heated, the waste ion exchange resin powder is rapidly decomposed and volatilized to burn and release a large amount of energy, further ignites the coal powder entering along with the mixed fuel, expands the plasma ignition energy in the initial ignition stage, and improves the ignition success rate. The application adopts the waste ion exchange resin and the coal powder to mix and burn for ignition, can improve the coal powder combustion rate, improve the ignition condition, processes the waste ion exchange resin generated in the water treatment section of the thermal power plant, realizes self-production and self-treatment of the hazardous waste, reduces the environmental protection approval link, realizes the hazardous waste utilization, and reduces the plasma ignition and hazardous waste disposal cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal power plant ignition, in particular to a low-quality coal cold-state plasma ignition method for thermal power plants. BACKGROUND

[0002] Thermal power generation has always been dominant in China's energy structure and will continue to dominate in the future for a period of time, so energy-saving technologies related to thermal power generation still need to be continuously developed.

[0003] At the same time, an important resource required for thermal power generation is coal. Low-quality coal refers to coal or coal sorting products with high impurity content such as minerals, sulfur, and water. Regardless of its coal rank and coal type, it is low in utilization efficiency due to high impurity content. Therefore, large-scale upgrading and utilization of this part of resources is of great significance.

[0004] Plasma oil-free ignition and stable combustion technology is an effective energy-saving method for replacing oil with coal during the ignition process of coal-fired boiler in thermal power plants. During the commissioning and cold-state startup of power plant boilers, using plasma coal powder ignition technology can save a large amount of fuel oil and generate significant economic benefits. Currently, plasma coal powder ignition technology has gradually become more perfect through development and has been adapted to many furnace types in China, becoming a commonly used energy-saving technology for coal-fired boilers in thermal power plants.

[0005] Currently, the plasma coal powder ignition burner used in existing thermal power plants is generally composed of a plasma arc ignition mechanism, a nozzle, a wind powder pipe, a thick-thin separator, and a main burner, and mainly adopts a three-stage powder feeding expansion combustion method. Its combustion process can be divided into three regions, namely, an ignition combustion zone, a mixing combustion zone, and a strengthening combustion zone. After the coal powder raw material is fed into the plasma ignition burner, part of the coal powder is ignited in the high-temperature "nucleus" region of the plasma igniter, i.e., the ignition combustion zone, and then the ignited coal powder flame ignites the subsequent fed coal powder, expands the combustion in the mixing combustion zone, and finally realizes the complete burnout of the input coal powder in the strengthening combustion zone, thereby achieving the purpose of ignition and stable combustion.

[0006] During plasma ignition, although the core temperature is as high as 10,000 K or more, the temperature range decreases sharply as the distance between the plasma hot nucleus increases, resulting in insufficient overall thermal energy of the plasma. Therefore, the coal powder burnout rate is low during the initial stage of plasma coal powder cold-state ignition, and ignition difficulties often occur during use. Although the multi-stage amplification principle is applied to the current plasma igniter, making the coal powder and air feeding ratio and air speed of the system more conducive to the working conditions of ignition, so that the coal powder can be successfully ignited and continuously burned. However, the current related plasma coal powder ignition technology is better applied to high-quality bituminous coal, and in the case of low-quality coal such as lignite, it still needs external energy input for assistance, otherwise it is not easy to ignite.

[0007] At present, the improvement of the related technology of plasma pulverized coal ignition is mainly in the optimization of the structure of the plasma igniter, and the improvement and optimization of the related fuel are less. For example, the related patent CN201210304328.3 optimizes the fuel while improving the plasma torch, and a small amount of high-calorific value fuel is used to enhance the energy of the plasma torch during ignition with pure oxygen combustion assistance, but this method still needs the participation of external energy fuel and the establishment of a series of supporting facilities, which increases the corresponding process equipment. At the same time, the plasma torch needs to be modified to adapt to it, which has certain limitations in use.

[0008] From the above, we can see that the current plasma pulverized coal ignition technology in China is widely applicable, has significant oil-saving effect, and has achieved great economic benefits. However, there are still some problems such as not suitable for low-quality coal, low coal combustion rate during ignition, insufficient energy at the initial stage of overall ignition, the need for external energy supplement, and the increase of corresponding supporting facilities. SUMMARY

[0009] The purpose of the present application is to overcome the defects of the prior art and provide a low-quality coal cold-state plasma ignition method for thermal power plants. The method uses ion exchange resin produced in the water treatment plant of the thermal power plant, which is pretreated and mixed with low-quality coal powder. The ion exchange resin has the characteristics of high volatile matter and easy ignition. The energy released by the ion exchange resin after rapid combustion is used to further heat the low-quality coal while the plasma igniter releases energy to heat the low-quality coal. At the same time, the resource utilization of waste ion exchange resin in thermal power plants is realized, which realizes the transformation of waste into treasure and reduces the cost of ignition and the cost of hazardous waste treatment.

[0010] The present application is realized by the following technical solutions:

[0011] A low-quality coal cold-state plasma ignition method suitable for thermal power plants is used for cold-state ignition of coal-fired boilers in thermal power plants. The pulverized coal plasma ignition burner used in the thermal power plant basically adopts a three-stage combustion design. In the first stage, the pulverized coal is concentrated to maximize the content of volatile matter, so that it can burn and generate a flame when passing through the plasma "fire core" interval. The flame ignites a large amount of coal powder in the second stage for expansion combustion and ignites the third stage of combustion intensification zone, finally achieving the effect of coal powder ignition and stable combustion. However, the low-quality coal has a low calorific value and a relatively low volatile matter content, so it is not easy to ignite even after concentration in this interval.

[0012] The waste ion exchange resin has high volatile content, and the temperature of the burning stage is between 300-400 DEG C, which is lower than the temperature required by coal burning. Therefore, when the coal powder gradually moves away from the high temperature of the plasma "fire core", the energy released by the waste ion exchange resin combustion heats the surrounding low-quality coal powder again, and the surrounding unignited coal powder moves and ignites at the same time during the combustion, thereby increasing the coal combustion rate and improving the ignition success rate of the coal powder.

[0013] The waste ion exchange resin is a waste generated by the water treatment plant of the power plant, and contains cation resin, anion resin and mixed bed resin, and the ratio of the three resins is 1:1:2. The main element and industrial analysis data of the mixed waste ion exchange resin raw material and coal are as follows:

[0014] Coal air dry basis element analysis (%):

[0015] C: 75-80; H: 6-9; O: 11-13; N: 36-40; S: 1-3; Cl: 0-1;

[0016] Mixed resin air dry basis element analysis (%):

[0017] M: 44-50; H: 8-12; O: 33-39; N: 0-3; S: 4-7; Cl: 1-4;

[0018] Coal received basis industrial analysis (wt%):

[0019] M: 1-4; A: 31-35; V: 21-25; FC: 35-40; Qnet (kJ / kg): 17000-20000;

[0020] Mixed resin received basis industrial analysis (wt%):

[0021] M: 35-42; A: 0-3; V: 48-55; FC: 6-10; Qnet (kJ / kg): 16000-20000;

[0022] The received basis industrial analysis of the dried mixed resin is (wt%):

[0023] M: 10-15; A: 12-17; V: 60-67; FC: 7-11; Qnet (kJ / kg): 20000-25000;

[0024] The specific steps of the present application are as follows:

[0025] (1) The waste ion exchange resin is dried and pretreated;

[0026] (2) the dry pretreated waste ion exchange resin is mixed with low-quality coal in proportion;

[0027] (3) the mixed mixture is ground into a mixed powder;

[0028] (4) the mixed powder is sent into a plasma coal powder ignition burner for ignition.

[0029] In step (1), the dry pretreatment of the waste ion exchange resin is as follows: the waste ion exchange resin is sent into a dryer for dry treatment; the waste ion exchange resin and hot flue gas are indirectly heated in the dryer, the dry temperature in the dryer is controlled at 85-95 DEG C, the dryer rotation speed is 0.2 r / min, and the dry time is 2 hours.

[0030] The dryer is a horizontal dryer, and a flue gas pipeline is arranged in the dryer, and flue gas with a temperature of 130 DEG C after purification treatment of a thermal power plant is used as a heat source; in the dryer, the gas flows through the tube, and the material flows through the shell; the dryer is under negative pressure, and the negative pressure is controlled at-50 Pa.

[0031] In step (2), the dry pretreated waste ion exchange resin is mixed with low-quality coal in proportion, and the mixing is as follows: the dry pretreated waste ion exchange resin and the low-quality coal are mixed in the mixer at a mass ratio of 3:7.

[0032] In step (3), the mixed mixture is ground into a mixed powder, and the temperature is controlled below 90 DEG C during the grinding.

[0033] In step (4), the mixed powder is sent into the plasma coal powder ignition burner for ignition, and the mixed powder must first pass through the ignition combustion zone at the center of the plasma coal powder ignition burner.

[0034] The low-quality coal has a received base ash mass of greater than 30%, and a calorific value of less than 20000 kJ / kg.

[0035] The present application uses a plasma ignition burner as an ignition device for cold-state starting of a boiler, the plasma ignition burner adopts a multi-stage expansion combustion design; the waste ion exchange resin powder is mixed in the coal powder and used as an ignition energy source, the energy released by the combustion of the waste ion exchange resin powder is used to expand the energy of the entire plasma ignition system, and the coal powder combustion rate is improved.

[0036] The present application has the following advantages:

[0037] The present application is suitable for use in plasma ignition of low-quality coal, does not need input of other external energy sources, saves energy consumption during ignition, and reduces the ignition cost of the coal-fired boiler.

[0038] The application uses waste ion exchange resin, utilizes ignition energy and high volatile content of the waste ion exchange resin which is easy to ignite at the plasma ignition, first ignites the waste ion exchange resin in an instant, and then utilizes the energy released by the combustion of the waste ion exchange resin to further increase the energy of the periphery of the unburned low-quality coal powder, so as to increase the combustion rate of the coal powder particles and improve the ignition success rate.

[0039] The application utilizes the waste ion exchange resin produced by the water treatment plant of the thermal power plant, realizes the resource utilization of the waste, and realizes the transformation of waste into treasure.

[0040] The application is suitable for the existing plasma coal powder igniter, and can be easily implemented by using the existing equipment.

[0041] In the waste ion exchange resin, the volatile content is high, and the ash content is low. In the initial stage of cold-state ignition, the generation amount of fly ash combustibles is reduced, and the risk of accidents such as ignition of the preheater, ash removal equipment, or reburning of the tail flue of the boiler is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The flowchart of the application is shown. DETAILED DESCRIPTION

[0043] In order to make the purpose, advantages and related technical solutions of the application patent more clear and explicit, the application patent will be further described below in combination with the drawings and examples. The examples described below are only used to illustrate the application patent, and are not used to limit the application patent.

[0044] As shown in the drawings, Figure 1 A cold-state plasma ignition method for low-quality coal of a thermal power plant, specifically comprising the following steps:

[0045] The waste ion exchange resin obtained from the water treatment plant of the thermal power plant has a high water content. The waste anion exchange resin, the waste cation exchange resin, and the mixed bed resin are mixed in a ratio of 1:1:2 to form the waste ion exchange resin. The element analysis and the industrial analysis of the prepared waste ion exchange resin raw material are shown in Table 1:

[0046] Element analysis of the mixed resin (dry basis) (%):

[0047] M: 46.48; H: 10.73; O: 35.11; N: 0.21; S: 5.57; Cl: 2.72;

[0048] Industrial analysis of the mixed resin (received basis) (wt%):

[0049] M: 39.46; A: 0.89; V; 51.38; FC; 8.27; Qnet (kJ / kg): 17530;

[0050] Table 1

[0051]

[0052] Therefore, the waste ion exchange resin raw material needs to be dried before being used. The waste ion exchange resin is sent into a dryer for drying treatment. The dryer is a horizontal dryer, which is internally arranged with a flue gas pipeline, and uses flue gas with a temperature of about 130°C after purification treatment of a thermal power plant as a heat source. In the dryer, the gas goes through the tube, and the material goes through the shell. The pressure in the dryer is negative, and is controlled at-50 Pa. The waste ion exchange resin and the hot flue gas are indirectly heated in the dryer, the drying temperature in the dryer is controlled at 85-95°C, the rotation speed of the dryer is 0.2 r / min, and the drying time is 2 hours. The dried mixed resin is received for the proximate analysis as shown in Table 2 (wt%):

[0053] M: 12.53; A: 14.65; V; 63.71; FC 9.11; Qnet (kJ / kg): 23665;

[0054] Table 2

[0055]

[0056] Secondly, the prepared waste ion exchange resin raw material is mixed with low-quality coal, and the waste ion exchange resin raw material and the low-quality coal are mixed in a mass ratio of 3:7 and sent into a mixer for uniform mixing. The elemental analysis and the proximate analysis of the low-quality coal are as follows:

[0057] Proximate analysis of coal on an air-dry basis (%):

[0058] C: 77.02; H: 7.18; O: 12.22; N: 38.25; S: 1.66; Cl: 0;

[0059] Proximate analysis of coal on a received basis (wt%):

[0060] M: 2.38; A: 33.5; V; 25.87; FC; 38.25; Qnet (kJ / kg): 18280;

[0061] Thirdly, the mixed raw material of the low-quality coal mixed with the waste ion exchange resin is sent into a coal mill for grinding. The temperature of the entire coal grinding system is basically controlled below 90°C to ensure that the resin does not decompose and stick due to high temperature during the grinding process. In the entire grinding process, the high-temperature area where the mixed raw material is located is the inlet of the coal mill, and the temperature of the hot air at this position is about 350°C. However, the cold mixed raw material is in contact with the hot air for a short time, and the temperature decreases rapidly afterwards. The thermal decomposition temperature of the resin needs to be above 220°C, and the resin is sent to the subsequent process before the thermal decomposition temperature is reached under this process condition, so the waste ion exchange resin is not greatly affected.

[0062] Subsequently, the mixed raw materials are fed into the plasma coal dust ignition burner and first pass through the central ignition combustion zone. This zone is the high temperature "fire core" zone of the plasma coal dust igniter burner, the central temperature of which is greater than 10000K. By using high energy, the coal dust and the ion exchange resin powder collide, fragment and reduce the ignition energy required in the gas phase in this very short time (1-2S) through the high temperature zone. Among them, the ion exchange resin powder has a high volatile content, and its volatile begins to separate and gradually pyrolyze and burn at a temperature > 300℃. When it passes through this zone, the volatile is heated and burned while releasing a large amount of energy to the surrounding coal dust.

[0063] When the coal dust passes through the high temperature "fire core" zone of the igniter burner, although it collides and fragments with the waste ion exchange resin in the gas phase to reduce the ignition energy required, due to the low volatile content and high fixed carbon and ash content in the coal dust, the stage of its sustained combustion and emission of a large amount of energy is in the fixed carbon combustion stage, and the ignition energy required is higher than that of the ion exchange resin particles. Therefore, a large amount of carbon powder is not ignited or not completely burned. And because the energy produced by the combustion of the volatile of the ion exchange resin particles continues to heat the surrounding carbon powder, not only does it heat and burn the volatile of the unburned carbon powder, but also it heats and burns the fixed carbon part of the burned carbon powder, thereby improving the carbon powder combustion rate in the first stage combustion zone.

[0064] Subsequently, more ignited carbon powder enters the second stage expanded combustion zone. Because a large amount of carbon powder is ignited in the first stage, a stable secondary coal dust ignition source is formed, and at this time, most of the waste ion exchange resin powder in the coal dust and waste ion exchange resin powder brought in by the primary air is first ignited and releases energy to ignite the surrounding coal dust, thereby expanding the energy of the ignition source and realizing that a large amount of coal dust brought in by the primary air is ignited. In the first and second combustion zones, the volatile in the previously input waste ion exchange resin powder is basically completely burned out, and the fixed carbon part is mostly burned. Most of the volatile in the coal dust is burned, and a small part of the fixed carbon is also burned.

[0065] In the last enhanced combustion zone, the above-mentioned ignited carbon powder and waste ion exchange resin powder in the first and second stages form a stable ignition source for igniting the third stage coal dust and waste ion exchange resin powder raw materials fed in.

[0066] In the present ignition method, a large amount of energy is released due to the combustion of the waste plasma resin powder in the raw material, the energy of the plasma igniter is expanded, and more carbon powder mixed therewith is combusted, thereby greatly improving the combustion rate and burnout rate of the carbon powder and reducing the content of unburned fixed carbon and the like in the fly ash. This can reduce the risk of accidents such as ignition of the preheater, ash removal equipment, or the flue gas of the tail of the boiler.

[0067] It should be understood that, for those skilled in the art, improvements and changes can be made according to the above description, and all these improvements and changes shall also belong to the scope of the present patent.

Claims

1. A method for cold plasma ignition of low-quality coal in a thermal power plant, characterized in that: The specific steps are as follows: (1) Dry the waste ion exchange resin; (2) The dried and pretreated waste ion exchange resin is mixed with low-quality coal in a certain proportion. (3) Grind the mixed mixture into powder to obtain a mixed powder; (4) The mixed powder is fed into the plasma coal powder ignition burner for ignition; The waste ion exchange resin mentioned in step (1) is obtained from the water treatment room of a thermal power plant. The waste ion exchange resin includes cation exchange resin, anion exchange resin and mixed bed resin, and the ratio of the three resins is 1:1:

2.

2. The method for cold plasma ignition of low-quality coal in a thermal power plant according to claim 1, characterized in that: The pretreatment of waste ion exchange resin by drying in step (1) is as follows: the waste ion exchange resin is sent into a dryer for drying; the waste ion exchange resin and hot flue gas are indirectly heated in the dryer, the drying temperature in the dryer is controlled at 85-95℃, the dryer speed is 0.2r / min, and the drying time is 2 hours.

3. The method for cold plasma ignition of low-quality coal in a thermal power plant according to claim 2, characterized in that: The dryer is a horizontal dryer with flue gas pipelines inside. It uses flue gas at 130°C after purification treatment in a thermal power plant as a heat source. Inside the dryer, the gas flows through the tube side and the material flows through the shell side. The dryer is under negative pressure, which is controlled at -50Pa.

4. The method for cold plasma ignition of low-quality coal in a thermal power plant according to claim 3, characterized in that: Step (2) involves mixing the dried and pretreated waste ion exchange resin with low-quality coal in a specific ratio as follows: The dried and pretreated waste ion exchange resin and low-quality coal are fed into a mixer and mixed evenly in a mass ratio of 3:

7.

5. The method for cold plasma ignition of low-quality coal in a thermal power plant according to claim 1, characterized in that: In step (3), the mixture is ground into powder to obtain mixed powder. During the grinding process, the temperature is controlled below 90°C.

6. The method for cold plasma ignition of low-quality coal in a thermal power plant according to claim 1, characterized in that: In step (4), the mixed powder is fed into the plasma pulverized coal ignition burner for ignition. It must first pass through the ignition and combustion zone in the center of the plasma pulverized coal ignition burner.

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