Ceramic ball valves applied to Pulverized coal injection system
Currently, in high furnace of metallurgy technique, techniques of high wind, high temperature, refined steel, injection oxygen enrichment have been widely used to save cost and increase production. Furnace injection techniques have been widely used for some places where lack of coke and small high furnace. Actually, for places where does not lack of coke, high furnace injection has not been adopted. Along with lacking of coke, cost increasing of coke meanwhile ceramic lined pipe, elbow and valves are growing maturely, more and more steel factories adopt high furnace injection techniques.
1. Meaning of pulverized coal injection
Pulverized coal injection is an important revolution for high furnace metallurgy. Pulverized coal injection refers that injecting refined coal from high furnace to replace coke and offer heat and reducer. The significance of pulverized coal injection list as below:
1) Using cheap coal to replace expensive furnace coke, which can reduce coke ratio and cost of metallurgy significantly.
2) Pulverized coal injection could be a way of adjusting furnace conditions.
3) Pulverized coal injection could adjust furnace working conditions and make furnace work smoothly.
4) It can increase wind temperature and create oxygen-enriched blast. Coal injection could reduce theoretical burring temperature before wind.
After High furnace injects coal fines, coal gas increases meanwhile it will consume heat to warm coal fines.
The amount heat that injecting coal fines brings is a few. When coke enters tuyere, coke will be well heated up to 1450~1500℃.The temperature of coal fines will be less than 100℃.
The hydrocarbon in the coal fines needs heat to decompose.
The coal fines have more hydrogen than coke brings. Hydrogen increases reducing power and penetration diffusion capacity, which will be helpful for ore reduction and improve high furnace operation.
Coal injection replace partial coke, which will relieve lack of coke and reduce investments of building coking plant
Currently ceramic is applied for pipe and valves, which have solved abrasive problem of coal injection, reduce cost and increase working performance.
2. Introduction of pulverized coal injection process
It mainly includes two procedures: coal fines making and injection:
1) Coal fines producing system adopt vertical middle-speed fast grinding. Electric motor actuated reducer makes millstone rotated. Raw material will be sent to millstone from feed port of feeder. Under pressure of centrifugal force, raw material will enter roller way from all around and become powder with power of roller way.
2) Under weight of roller way and pressure device, raw material will become powder. Because there is not only rolling between roller way and millstone, raw material will get several stresses, which will increase grinding capacity and efficiency. Hot air enters tuyere and millstone from bottom body.
Because there is air distributing ring in the gap of rotated millstone and bottom body, it can be evenly distributed in the millstone along with air of air distributing ring.
3) Grinded material will be blew up. Qualified powder will go out along with air and these collected by dust collector are finished products. Bigger powder will be redistributed in the millstone under effect of air distributing ring and get reground. This procedure will cycle and recycle all the time. These small steel pieces mixed with material in the millstone will be blew out from rotated millstone and fall down on the bleeding hole. Foreign material will be cleaned as long as bleeding hole is open periodically.
Injection system make us of high pressure air to inject coal fines from injection tank to high furnace directly.
During this procedure, high-speed col fines will abrade elbow, pipe and valves seriously, so all pipe, elbow and vales of injection system should be lined with ceramic. Usually fully lined ceramic ball valve are applied. Structure ceramic has performance of high hardness, high strength, anti-corrosive and anti-abrasive. After grinding seat and ball precisely, ceramic ball valves could reach zero leakage, which can make sure of excellent sealing performance and have a very long service life under seriously erosion of high-speed coal fines.