Research And Practice Of Three-product HM Cyclone With Dual-medium-supply On The Second Stage Cyclone For Reducing Reject Content In Middlings

On-line adjusting specific gravity of the second stage cyclone of three-product heavy medium(abbr.HM)cyclone is a problem that has puzzled the development of coal preparation technology.As a result,the reject content in the middlings is too large(generally over 30%),the middlings' quality is hard to guarantee.At present,when most coking coal preparation plants in China adopt three-product HM cyclone process,the method of replacing the underflow port is often used to adjust the separation effect of the second stage cyclone.When replacing the underflow port,the production system must be shutdown,the adjustment is lagged,which affects the production,and the effect is not obvious.Therefore,it is of great significance to develop a new type of three-product HM cyclone which can realize specific gravity on-line adjustment of the second stage cyclone to improve the middling' quality.In view of the dual-medium-supply technology has been developed and applied to the first stage cyclone of the three-product HM cyclone,the thesis applies the concept to the second stage cyclone of the three-product HM cyclone,introduces the concepts of internal circulation area and external circulation area,and proposes to reconstruct the existing three product HM cyclone,that is,to add an additional medium supply port on the second stage cyclone cylinder,whose medium comes from correct medium of the correct medium segment of the D&R screens of clean coal,middlings,and reject and circulating water.On the premise of not affecting the large system,a small medium supply system to the second stage cyclone is formed.That is the developed three-product HM cyclone with dual-medium-supply on the second stage cyclone to solve high reject content in middlings problem.The test site is at Guantai coal preparation plant,which is a coking coal plant.The main separation equipment is an 850/600 pressure-feed three-product HM cyclone,and the reject content in middlings is 25.61% in average.The second stage cyclone of the three-product HM cyclone was reconstructed to the dual-mediumsupply mode for industrial test.The suspension for the additional supplied medium is composed of middlings correct medium,reject correct medium,and circulating water,adjusting their proportion to adjust the density of the suspension.On the premise of ensuring the quality of clean coal,sampling and testing are carried out to compare the change of reject content in middlings.The test results that reject content in middlings can reduced to 7.8% when the "middlings correct medium + circulating water" is used as the second stage cyclone additional feeding medium,and the separation effect of the second stage cyclone is obviously improved.From the view of the site construction,the project workload is not large,the number of additional auxiliary equipment is less,and it is easy to realize and operate.Under the condition of single medium system,using the process of three-product HM cyclone with dual-medium-supply on the second stage cyclone,the purpose of reducing the reject content in middlings is achieved,the original intention of on-line adjusting the separation accuracy of the second stage cyclone is realized,and a new way to solve the accurate separation of the second stage cyclone of three-product HM cyclone is explored.The three-product HM cyclone with dual-medium supply on the second stage cyclone and the developed process package are the first at home and abroad,which enriches the family of three-product HM cyclones,makes a beneficial attempt for the accurate separation and fine production,and fills the blank in the research field of specific gravity on-line adjustment of the second stage cyclone of three-product HM cyclone.There are 44 figures,35 tables and 80 references in this paper.