Application Of Smokeless Coal

Application of smokeless coal
Smokeless coal blocks are mainly used in industries such as fertilizers (nitrogen fertilizers, synthetic ammonia), ceramics, manufacturing and forging; Smokeless pulverized coal is mainly used in the metallurgical industry for blast furnace injection (blast furnace injection coal mainly includes anthracite, lean coal, lean coal, and gas coal).
It can also be used for filtration and purification treatment of domestic and industrial water supply. The usage parameters are determined according to the form of the filter tank. Generally, the paving thickness of the double-layer filter material is 300-400mm; the normal filtration rate is 10-14m/h, and the forced filtration rate is 14-18m/h; The thickness of the three-layer filter material paving is 450mm, with a normal filtration rate of 18-20m/h and a forced filtration rate of 20-25m/h. The backwashing of the filter tank adopts water flushing, water vapor flushing, or supplemented by surface flushing.
calciner
The function of the decomposition furnace is to complete the endothermic reaction of carbonate decomposition under the condition of solid suspension in hot gas.
CaCO3=CaO+CO2↑
In the case where the provided heat cannot completely decompose the raw material, the decomposition process can be considered based on the partial pressure of CO2 reaching a certain equilibrium state. Generally speaking, the equilibrium temperature of the decomposition furnace is in the range of 850-900 ℃. The temperature distribution inside the decomposition furnace is related to the following factors.
1) The heat release rate of combustion into gas phase.
2) The heat transfer rate from air to solid raw material powder.
3) The heat absorption rate during the decomposition of raw material particles.
Compared with using bituminous coal, due to the lower volatile content of anthracite coal, a relatively larger decomposition furnace is required to achieve the same raw material decomposition rate and coal powder burnout degree, or to require a higher operating temperature, or to grind anthracite coal finer.
When the temperature of the third air is low, the gas evaporated from anthracite often cannot generate enough heat to raise the temperature. Therefore, feeding coal powder directly into the rising flue gas with a temperature range of usually 1000-1200 ℃ can ensure coal powder combustion.
Additionally, it should be noted that the combustion rate and burnout time also depend on the O2 content in the flue gas. Operating the decomposition furnace with a higher air excess coefficient can shorten the burnout time, but usually increasing the air excess coefficient will increase the gas flow through the preheater. As a result, it will cause a large pressure difference and high exhaust gas temperature, which will increase the load on the main exhaust fan of the kiln, and the unit heat consumption of the entire kiln system will also increase.
Changing the feeding method of raw materials is quite important. When using smokeless coal operation, it is best to have an appropriate lag time for the mixing of smokeless coal and raw material powder to ensure the ignition of smokeless coal. Therefore, the raw materials fed into the decomposition furnace need to be graded and controlled to form a relatively high temperature zone at the bottom of the decomposition furnace. The best way to determine whether the raw material has achieved the expected effect in the decomposition furnace is to detect the decomposition rate of the raw material entering the kiln. If the decomposition rate of the raw material entering the kiln has achieved the expected effect, it indicates that the combustion of anthracite in the decomposition furnace is appropriate.
burner
The new dry process cement production line is equipped with modern burners, which are equipped with appropriate flame adjustment devices to enable smokeless coal to burn at the kiln head without any problems. The function of a burner is not only to transport and distribute coal powder, but also to maintain the ideal length of the flame and a suitable gas flow field. The length of the flame is very important for new dry kilns. If the flame is too short, the latent heat of coal can only be released in a small volume, and the temperature of the flame will become very high locally. On the contrary, if the flame length is prolonged, the temperature will decrease. The length of the flame is mainly controlled by the driving force of the burner.
The driving force of the burner=primary air (kg/s) x burner tip wind speed (m/s)
When the driving force of the burner increases, the flame length shortens.
The type of raw coal is not very important for the length of the flame, only requiring that the burning time of a single coal particle is less than its residence time in the flame.
If the goal is to maintain the same flame length between anthracite and bituminous coal, then it is necessary to compensate for the burnout time of coal powder. The simple approach is to grind the smokeless coal finer.
The high-temperature secondary air will quickly heat the volatile matter of the coal powder entering the burner and quickly discharge it. Once the coal powder leaves the end of the burner, the coke particles will ignite, so the effectiveness of the cooling machine will have a certain impact on the use of smokeless coal.
The use of smokeless coal on the burner of the rotary kiln head requires the following conditions to be met:
1) Coal powder can achieve sufficient fineness that meets the requirements to ensure combustion and flame formation.
2) Control reliable and stable coal powder feeding.
3) The primary component of the burner must have sufficient driving force and be adjustable.
4) The burner must be able to generate flames with sufficient internal circulation of air in the combustion zone to ensure that the smokeless coal ignites as soon as possible.
5) Use bituminous coal or fuel oil to assist combustion when starting the cold kiln or when the kiln condition is abnormal.