Coal Powder Preparation

1. Physical Characteristics of Coal Powder
The main physical properties of pulverized coal have the following aspects:
(1) The general pulverized coal particle diameter ranges from 0 to 1000 μm, and most of the particles are 20-50 μm;
(2) The density of pulverized coal has a small density of pulverized coal, and the newly-grown pulverized coal has a bulk density of about (0.45-0.5) t/m3, and the bulk density after storage for a certain period of time is (0.8-0.9) t/m3;
(3) Pulverized coal has fluidity. Pulverized coal particles are very fine. The unit mass of coal powder has a large surface area, and the surface can adsorb a large amount of air, thereby making it fluid.


2. Physical and Chemical Indicators
Volatile: mainly composed of water, hydrocarbon oxides and hydrocarbons.
Ash: Generally should be controlled below 10% or lower.
Moisture: It should be controlled below 6%. When using coal powder, enterprises should not use the water index as a quality index to measure the quality of coal powder.
Sulfur: generally should be controlled below 1.0% or lower.
Hastelloy index: The grindability of coal is a comprehensive physical property related to the hardness, strength, toughness and brittleness of coal. The larger the HGI value, the same amount is specified under the condition of consuming a certain amount of energy. The finer the fineness of the powdered coal sample milled into the powder, or the less the energy consumed when the same amount of coal sample is ground to the same fineness.

3. Production of Coal Powder
The preparation of pulverized coal refers to the process of processing raw coal into coal powder with the same particle size and moisture content as the blast furnace coal injection requirements by the coal mill. The requirements for pulverized coal in the blast furnace injection system are: 80% or more with a particle size of less than 74 μm and a moisture content of not more than 1%.

4. Application Project of Coal Powder
(1) Cement industry
The fuel used for calcining cement clinker is mainly coal, which usually needs to be processed into coal.
The pulverized coal is injected into the kiln for combustion, and the combustion intensity and the formed flame are required to satisfy the clinker calcination.
Claim. Calcination of high quality clinker requires high quality and stable supply of pulverized coal.
Vertical mill has high grinding efficiency and low noise.
Simple process, small footprint, low civil construction cost and low power consumption (compared to ball mills), energy saving 10%~15%), strong drying ability and so on.
The fineness of coal powder in the cement industry is generally 90um, D90 through the sieve.

(2) Power industry:
Boiler is one of the main equipment of thermal power plant, its role is to make fuel in the furnace, Combustion and heating the working medium in the pot to a sufficient quantity and quality
The advantages are mainly applicable to lignite with high volatile lean coal and bituminous coal and raw coal with total moisture ≤ 35%.
The fineness of coal powder in the power industry is generally 90um, D90 through sieve. 


(3) Metallurgical industry:
In the metallurgical industry, blast furnace ironmaking is often used, and blast furnace injection of pulverized coal through the tuyere has become a festival.
The most effective measures is for improving the smelting process. It can not only replace the increasingly scarce coke,
The fineness of coal powder in the metallurgical industry is generally 80um, and D80 is screened. 


(4) Chemical industry:
Anthracite is a coal with a higher degree of metamorphism. It is the main chemical coal and carbon.
The fineness of pulverized coal has different requirements according to different processes, and the range is usually 80 to 325 mesh. 


5. Solutions
According to customer requirements, it can be divided into two types: vertical grinding powder processing and medium-speed grinding powder processing.

(1) LM Vertical Grinding Powder Processing



a. Advantages
 Easy and Reliable Operation
Automatic control devices equipped, remote control can be realized, the operation is easy and simple.
 Environmental Protection
Small vibration, less noise.
 Low Cost
The energy consumption of grinding system is lower 30%-by special material.
 Convenient Maintenance
Turn the rockerers by oil jack to maintain the roller shell and liner within short time,and reduce the downtime.

b. Customized Solutions--LM Series Vertical Grinding Mill
One -Step: Coal Preparation System
One-step coal preparation system refers to a system of simultaneous drying and milling. It is widely used in cement, chemicals, coal, electricity and other sectors. It has many advantages, such as small footprint, simple process and compact layout, low energy consumption and low noise. And also it is a comprehensive plant which integrates crushing, milling, drying, separation and transportation. 


c. Preparation Process:
The coal is fed into warehouse for storage by belt conveyor, and then into the inside of LM vertical by closed-end quantitative feeder. The system of hot air sends hot air into internal LM vertical mill to dry the coal mixing. The coal which firstly enters into the grinding chamber enter into the impulse explosion-proof dust collector to collect powder through roller disc grinding with dynamic and static separator powder classifying. Then the summary collected powdered coal come into the finished pulverized coal warehouse for storage by screw conveyor (also by pneumatic conveying, etc.). And at last, the powder is transported by tanker as required. The entire system has a system of nitrogen and carbon dioxide fire extinguishing system to provide fire and explosion protection. And the key components are mounted with explosion-proof valve to prevent equipment damage. 


(2) Medium-Speed Grinding Powder Processing 


a. Advantages
 Low operation cost and high durability
Only the blade need be replaced during maintenance, curved shovel blade can prolong the service life of roller and ring.
 Bevel gear internal transmission
Higher transmission efficiency, save space and lower the investment costs.
 Low Maintenance Cost
Internal thin oil lubrication system, which realize lubrication in the main bearing and drive bearing by adding no more oil pumps.
 Overall streamlined design with elegant appearance
Reduce airflow resistance and dust accumulation.

b. Customized Solutions—MTW Series Trapezium Mill
Two-step coal powder system is a solution for drying and pulverizing separation. The temperature of grinding chamber is relatively low, mainly represented by pendulum mill comes from continental trapezoid mill, so the process is relatively simple and easy to control the system. The host device adopts overall drive bevel gear, internal lubrication system, oil temperature measurement and others of the world’s advanced technology, which has a number of independent patent property rights.
The whole system has a small footprint, low overall investment, low operating costs, high efficiency, environment protection and many other advantages. 


c. Coal powder Process
The coal within the coal storage is delivered into drying equipment for drying by conveyer equipment (optional on demand), into the surge bin by lifting machines and other equipments before grinding. The dried raw coal is fed into the interior of MTW European version by constant feeder (or vibrator feeder). The ground powder enters into powered collector (or special explosion-proof pulse dust removal for coal mill) to be collected along the pipe. Then the finished pulverized coal is stored by refined coal warehouse through the pneumatic conveying system (optional pneumatic conveying mode), and transported by the tanker as required. The entire system has a system of nitrogen and carbon dioxide fire extinguishing system to provide fire and explosion protection. And the key components are mounted with explosion-proof valve to prevent equipment damage. 13.jpg


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