The efficient processes include coal slime classification, coarse slime recovery, slime concentration and separation, slime product drying, and slime ball pressing. Of which, most important links are drying and briquetting processes of coal slurry.
Coarse slime classification, dehydration and recovery process
The hierarchical concentration equipment includes spitzkasten, cyclones, inclined plate sedimentation tanks, etc. People used to recycle the coal slurry by high-frequency vibrating dewatering sieve but now prefer centrifugal dewatering machine with higher dewatering efficiency.
Fine coal slime concentration, dehydration and recovery process
Flotation process is required when processing fine coal slurry. You should do the preparation before floatation and product dehydration after flotation well.
1.Preparation process before flotation
First, the preparations include controlling in the material granularity, concentration of floating, and the way to add flotation agent.
The use of thickeners or swirl-classified cyclone and sieve bend is to control the in-float concentration and in-float material particle size, which is a common process in coal preparation plants.
Generally, direct flotation process and low-concentration concentration flotation are the most widely used in the preparation process before flotation.
(1)Direct flotation process
Direct flotation is a new method in response to the shortcomings of concentrated flotation. That is, the original slime thickener before floating is removed, which means that and the coal slurry water in production is directly entered into the flotation machine without concentration. Finally, flotation and jigging can work simultaneously.
Coupled with the addition of flocculant in the tail coal thickener, it can effectively reduce the concentration of overflow circulating water, and better solve the problem of the accumulation of fine ash in the wash water and pollution of clean coal.
Semi-direct flotation being a special case of direct flotation is an effective method to solve the low flotation concentration.
(2) Preparation process before concentration flotation
Concentration flotation adopts the large discharge of the underflow of the thickener. When the large discharge reaches the level of the overflow, the thickener will be converted into a simple slime water channel, which becomes a direct flotation process.
The advantages of the concentration flotation are the large range of adjustment on the flotation concentration, flexible operation, and relatively low investment and production costs.
The disadvantages are that the circulating water is still easy to accumulate fine mud, and there is still a lag phenomenon when the flotation starts and stops.
2. Coal slurry smiles dehydration process after flotation
Nowadays, high-efficiency dehydration equipment such as pressure filters and diaphragm squeeze filter are increasingly used for dewatering of flotation clean coal.
Especially now the design of coking coal preparation process adopts the principle of grade separation for coal slime. Generally, the coarse slime more than 0.25mm is sorted and recovered by gravity method while fine coal slime less than 0.25mm mostly adopts flotation.
Consult the equipment
Coal Slime drying
The coal slime drying system can dry and shape the low calorific value slime, which reduces the moisture and improves the calorific value. Then the dried product through upper belt blends with other coal in the furnace to increase the amount of coal slime and reduce the costs of fuel burning in the power plant.
Mainly adopt steam extraction of steam turbine intermediate pressure cylinder as heat source, supply pressure is about 0.5MP, temperature is 200-230℃, steam supply is 4t/h, steam flows into the dryer tube bundle, and the sludge in the dryer rotation project It is heated to process the wet slime with a water content of about 28%, and then processed into a round slime ball with a water content of about 14% and a particle size of 10-40 mm by a ball press.
Coal slurry briquetting
The crushed coal slime needs drying process to meet the requirement on the moisture content less than 28% so that the further briquetting process can be made. Coal slurry ball briquetting machine is the key equipment to recycle the coal waste, and whether machine structure is reasonable will directly affect the quality of coal slime balls.
Unique value of coal slime ball
1.The coal slime balls can burn more fully in the furnace than coal slurries directly burning.
2.Coal slime ball breaks the limits of small fuel supply selectivity at pit-mouth power plant. It can increase the amount of slime usage and the share of fine coal particles in the furnace. The 50% cutting particle size is reduced to d50=3mm, which improves differential pressure from 700Pa to 1100Pa.
3.The use of coal slime ball improves the boiler combustion efficiency, reduces the furnace combustion temperature, and promotes the balanced combustion.
4.It greatly reduces the wear of the hood and the heating surface of the furnace, and improves the economy and reliability of the boiler operation.