The ignition temperature of the pulverized coal gas stream is higher than that of the coal why

The ignition temperature of coal is the temperature at which the coal is mixed with the oxidant in the stationary state, and the combustible gas with higher temperature is released after the coal is heated, and the diffusion rate is relatively slow, and the concentration is relatively high, therefore, the ignition temperature of the measured coal is relatively low;

The ignition temperature of pulverized coal gas flow is the temperature at which pulverized coal is mixed with air in the forced flow state, and the flammable gas released after the pulverized coal gas flow is heated has a relatively fast diffusion speed and a relatively low concentration, so the ignition temperature of the measured pulverized coal gas flow is relatively high.

Because the fineness of pulverized coal is small, it carries a lot of oxygen.

The basic measures for combustion from the gas flow of pulverized coal are:

1) Appropriately increase the primary air temperature and increase the primary temperature can reduce the ignition heat demand, so that the pulverized coal gas can quickly reach the ignition temperature after entering the furnace. Of course, the level of the primary air temperature is determined according to different types of coal, and the primary air temperature can be lower for coal with high volatile content.

2) Properly control the primary air volume and the primary air volume is small, which can reduce the ignition demand and facilitate the rapid ignition of pulverized coal airflow. However, the minimum primary air volume should also meet the oxygen demand for volatile combustion, and the primary air volume of coal with high volatile content should be larger.

3) The finer the finer the finer the coal powder, the larger the relative surface area, the smaller the thermal resistance of the coal itself, the faster the volatilization analysis, and the easy to achieve complete combustion when ignited. However, the pulverized coal is too fine, and the power consumption of the plant should be increased, so a reasonable economic fineness should be determined according to different coal types.

4) Reasonable.

Primary and secondary wind speeds.

The primary and secondary wind speed has a great impact on the ignition and combustion of pulverized coal airflow. Because.

The primary and secondary wind velocities affect the reflux of hot flue gas, thereby affecting the heating of pulverized coal gas flow1. The influence of the second wind speed.

Sooner or later, the primary and secondary air mixes, which affects the progress of the combustion stage;The primary and secondary wind speeds also affect the strength of the airflow disturbance in the later stage of combustion, thereby affecting the completeness of fuel combustion. Therefore, it is necessary to choose the appropriate one according to the type of coal and the type of burner.

Primary and secondary wind speeds.

5) Maintaining the appropriate high temperature and appropriate high furnace temperature in the combustion area is the basic condition for the ignition and stable combustion of pulverized coal gas flow. The furnace temperature is high, the pulverized coal gas flow is rapidly heated and ignited, and the combustion reaction is also rapid, and the conditions are provided to ensure complete combustion. Therefore, when burning anthracite or other inferior coal, the combustion zone is often set up in the combustion area or other measures are taken to increase the furnace temperature.

Of course, when increasing the furnace temperature, it is necessary to consider the possibility of preventing the formation of slagged.

6) Appropriate furnace volume and reasonable furnace shape furnace volume size, determine the length of the fuel residence time in the furnace, thereby affecting its complete combustion degree, so the fire, poor combustion performance of the fuel, the furnace volume should be larger, this fuel also requires to maintain the high temperature of the combustion area, so it is often necessary to choose the thin and tall furnace with a small cross-sectional size of the furnace burning area.

7) When the boiler load is maintained within the appropriate range, the boiler load is low, and the temperature in the furnace drops, which is not conducive to ignition and combustion, and the combustion stability becomes worse. When the boiler load is too high in the past, the fuel stays in the furnace for a short time and does not burn completely. At the same time, due to the increase in furnace temperature, there is also the possibility of slagging and other problems.

Therefore, the boiler load should be dispatched as much as possible within the permissible range.

After the pulverized coal enters the furnace, the water in it is first evaporated under the flame, high-temperature flue gas and radiant heating of the furnace wall, and then the volatile matter escapes into combustible gas.

Combustible gases have high chemical activity, low ignition temperature, and low energy required for ignition, so volatiles ignite quickly after escaping. The heat generated by the combustion of the escaping volatiles heats the coke to the ignition temperature, causing the coke to ignite and burn. It can be seen that the higher the volatile content of the coal in the flame, the high temperature flue gas and the receipt of the national emblem of the furnace wall.

, the more volatiles escape, the easier it is to catch fire, the more heat is generated, and the easier it is to ignite the coke to the temperature and cause it to start burning. This is also the reason why when burning pulverized coal with a high volatile content, the pulverized coal ignites easily and the furnace is not easy to extinguish even at low loads. Pulverized coal is burned in the furnace, usually the time required for the volatiles to escape and burn out is short, while the time required for coke to burn out is long.

Therefore, the time required for coke burnout determines the time for pulverized coal to burn out. The more according to the fraction in the coal, the porosity of the coke after the volatile fraction escapes.

The higher the surface area of the coke in contact with oxygen.

The larger it is, the faster the coke burns. Therefore, coal with high volatile content is easy to burn completely due to its fast combustion rate.

This is because oxygen, an accelerant in the air, is more abundant than in other cases than in other cases.

easy to catch fire and burn completely".

The higher the volatile matter, the easier it is for the coal to catch fire, but the stability of boiler combustion does not depend entirely on the volatile content.

The flammable gas produced by the thermal decomposition of organic matter in coal at a certain temperature and under certain conditions is called "volatile matter", which is a mixture of various hydrocarbons, hydrogen, carbon monoxide and other compounds. So ......

Answer, the main factors affecting the ignition of pulverized coal are:

1. Moisture. Pulverized coal with high water content is not only difficult to grind, but also vaporizes when burned, absorbing a lot of heat. Generally, the moisture content of pure coal fiber powder is controlled below 1%.

2. Ash. In the production of cement, the ash content of coal should be controlled and stabilized, otherwise it will affect the firing condition.

3. Fixed carbon.

Carbon is the main chemical source of heat energy in pulverized coal, and a certain amount of excess air must be given to the fuel during combustion to prevent incomplete combustion.

4. Volatilization. The combustion capacity of coal separation is directly proportional to the volatile content, and the pulverized coal with high volatile content is easy to burn.

5. Calorific value. It is the most important measure of fuel performance. There are two types of calorific value: high calorific value (HHV) and low calorific value (LHV). The low calorific value takes into account the heat loss when the water in the fuel evaporates and the hydrogen burns into water vapor.

Answer] :(1) The ignition heat of the coal block is the smallest, the combustion temperature of the layer combustion furnace is 1000 1100, and the burning speed is the slowest. The capacity of the boiler is the smallest, generally not greater than 35t h, which is easy to cause incomplete combustion loss of solids.

2) The ignition heat of coal particles is relatively large, the combustion temperature of the circulating fluidized bed boiler is 850 950, the combustion speed is relatively fast, the boiler capacity can be between 35 1025t h, and the combustion efficiency of the hole is high.

3) The ignition heat of pulverized coal particles is the largest, the combustion temperature of the pulverized coal furnace is 1400 1600, the liquid slag discharge furnace can reach more than 1700, the combustion speed is the fastest, the boiler capacity can be between 65 4000t h, and the combustion efficiency is high. Nalun shed.

Summary. Pro-<>

We are glad to answer the question for you[ ] The ignition point of pulverized coal in the absence of oxygen depends on the content of volatile matter, the more volatile content, the lower the ignition point. The ignition temperature of several types of coal is roughly as follows: anthracite - 550 700 ; Bituminous coal 400 550 ; Lignite - 300 400 .

How many degrees will the pulverized coal burn in the absence of oxygen.

Dear <> is happy to answer for you[ ]The ignition point of pulverized coal in the absence of oxygen depends on the amount of volatile content of the sail skin, the more volatile content, the lower the ignition point. The ignition temperature of the ignition difference of several segments of coal is roughly as follows: anthracite - 550 700; Bituminous coal 400 550 ; Lignite - 300 400 .

Extended information: Pulverized coal is an additive commonly used in cast iron molding sand, which refers to the pulverized coal with a particle size of less than millimeters, which is an additional commonly used in cast iron molding sand. In recent years, foreign countries have combined pulverized coal and clay into a commodity market.

Adding pulverized coal to the green sand for cast iron can prevent sand defects on the surface of the casting, improve the surface finish of the casting, reduce the sand inclusion defects, improve the collapse function of the molding sand, and effectively prevent the production of pores under the skin and filial piety for the wet ductile iron parts, and the circular vortex burner can be used, and the air does not need to be preheated.

(1) The nature of the fuel, mainly the volatile content of the fuel;

2) heat dissipation conditions in the furnace;

3) The temperature of the pulverized coal gas flow, the high temperature is favorable for ignition;

4) Primary air volume and wind speed;

5) Burner structural characteristics;

6) Aerodynamic field in the furnace;

7) Boiler operating load.