| The cement grinding process is an important part of the cement production process,it is not only directly related to the quality of cement(especially the fineness and particle size distribution),but also has an important impact on the cement output and energy consumption.The particle size distribution of the cement in the ball mill grinding is more reasonable,particle spherical degree is high,can satisfy the requirement about the quality of the cement in the concrete industry.But it is well known that the energy of the ball mill utilization rate is very low and the effective energy utilization rate of the grinding work is only about 3%~5%,most of the energy is consumed by the collision,friction heating and noise.Between the steel ball/steel forging and the body liner,the friction and the collision led to the grinding power consumption is high.For the cement clinker grinding,at present,the main use of the combined grinding system which was composed of the roller press and the ball mill.In this system,the material sufficient pre-crushed by the roll press and the particle size graded by the V-type separator,so that the material size can be controlled about <1 mm,which can effectively alleviate the pressure of crushing material in the ball mill.For the slag grinding,at present,mainly adopts vertical mill grinding system and ball mill grinding system,and the latter's grinding power consumption is higher,especially the production of high specific surface area of the slag powder.The reason is that,on the one hand,the slag is hard to wear,on the other hand,the current proportion of the metal grinding medium is larger,which increases the work ing load of the ball mill.It can be seen that the “burden reduction” of the grinding medium in the grinding mill is an effective way to reduce the power consumption of the ball mill.Therefore,in the fine grinding mill with a small proportion,strong grinding ability of the ceramic grinding medium to replace the larger proportion,the strong impact of the metal grinding medium become a new research topics to reduce the grinding power consumption in the ball mil.In this paper,through the design of four factors and four levels of the orthogonal experiments to determine the main factors of the experiment:(1)grinding medium filling rate;(2)grinding medium gradation;(3)grinding aids content;(4)ball mill speed.Each influencing factor was taken at four levels and the grinding experiment of ceramic grinding medium and metal grinding medium was carried out according to the orthogonal experiment table of L16(45).By measuring the specific surface area of cement clinker and slag,the results of 45?m sieve residue,particle size distribution,compressive strength and slag activity were used to compare the grinding performance of ceramic grinding medium and metal grinding medium,and analyzing the best experimental conditions and regularity of the ceramic grinding medium to the cement clinker and the slag grinding as the reference data of the industrial practice.The influence of each experimental factor on the grinding performance of the cement clinker is different,in which the filling rate of grinding medium > boll mill speed > grinding medium gradation > grinding aids content.In addition,the optimum experimental conditions for the metal grinding medium by orthogonal test are: the filling rate is 31.0%,the gradation is ?30 : ?20 : ?17 : ?14 : ?12 = 10% : 10% : 10% : 35% : 35%,the grinding aids content is 0.15%,the ball mill speed is 95 r/min.And the optimum experimental conditions for the ceramic grinding medium by orthogonal test are: the filling rate is 37.2%,the gradation is ?30 : ?20 : ?17 : ?14 : ?12 = 10% : 10% : 10% : 35% : 35%,the grinding aids content is 0.15%,the ball mill speed is 85 r/min.The grinding performance of the metal grinding medium and the ceramic grinding medium under the optimum experimental conditions is different,in which the fineness of the ceramic grinding medium is slightly higher,the particle gradation of the cement is more reasonable,especially for the cement strength development,the main role of 3~32 ?m particles increased by about 3.5%.At the same time,on the basis of a slight decrease in compressive strength of 3d,the compressive strength of 28 d increased by about 5.9MPa,and the standard consistency water consumption decreased by about 2.5%.In addition,the cement particles roundness ground by the ceramic grinding medium increased by about 8.5%,spherical particles increased,so that the appearance of the cement particles have been optimized.Therefore,the effect of the ceramic grinding medium on the cement clinker grinding is better than the metal grinding medium,so the ceramic grinding medium apply to grinding cement clinker can improve the performance of the cement.Under the similar experimental conditions,the fineness of slag powder ground by the ceramic grinding medium is higher than that of the metal grinding medium,and the range of the particle size distribution is narrow,and the particle size is uniform,and the particle group is more consistent with the Rosin-Rammler distribution,and the activity of the slag is high.In addition,the particles roundness of the slag powder ground by the ceramic grinding medium higher than that of the metal grinding medium about 2.5%,optimizing the appearance of the slag powder.Therefore,the ceramic grinding medium apply to grinding slag can improve the performance of the slag powder.In the industrial practice,the ceramic grinding medium(ceramic ball/ceramic forging)used in grinding cement clinker and slag,in order to ensure the capacity of the impact,the grinding warehouse in the ball mill must adhere to use the metal grinding medium(steel ball).In the use of the ceramic grinding medium instead of the metal grinding medium(steel ball/steel forging)in the second warehouse and the third warehouse of the ball mill,we must improve the filling rate,change the grading principle,from the “middle more,both sides less” to the “front less,behind more”,in order to give full play to the advantages of high efficiency and energy saving grinding.In the cement combined grinding system,the steel forging in the second warehouse of the ball mill replaced into ceramic ball can improve the grinding efficiency,reduce the operating current of the ball mill,reduce the material temperature,the discharge temperature,save the tons of the cement power consumption about 4.5 kw/h.At the same time,the particle composition of the cement product was optimized,and the particle content of 3~32 ?m was increased from 60.65% to 63.45%,increased by about 2.80%,which was beneficial to improve the late strength of the cement,and the particle content of ?45?m increased from 87.35% to 90.11%,increased by about 2.76%,increased the content of qualified powder in the cement products,improved the quality of cement products and improved the adaptability to the concrete admixtures.In the slag grinding system,the steel ball/steel forging in the second warehouse and the third warehouse of the ball mill replaced into ceramic forging can improve the grinding efficiency,reduce the operating current of the ball mill,reduce the material temperature,the discharge temperature,save the tons of the slag power consumption about 8.0 kw/h,and improved the fineness and the activity of the slag powder,and obviously reduced the content of Cr6+ in the slag powder,which effectively solves the problem of the Cr6+ pollution in the cement. |
PDF Full Text Request