Study On The Factors Affecting The Oil Absorption Performance Of Calcined Coal Series Kaolin

Calcined coal series kaolin is an important industrial raw material,which is widely used in a lot of fields.Among these fields,the most widely used industry is the papermaking industry,which makes coal series kaolin available for resource utilization.However,the low oil absorption value of calcined coal series kaolin cannot meet the needs of the papermaking industry and limits the application of coal series kaolin.Therefore,how to increase the oil absorption value of calcined coal series kaolin has become an important way to solve the application of kaolin.Coal series kaolin were chosen as research objects.In view of low oil absorption value of calcined coal series kaolin,following works have been primarily conducted:1)Shanxi coal series kaolin were treated with microwave irradiation,the effects of microwave radiation on coal series kaolin and the factors affecting the oil absorption value were analyzed.2)The type,content of additives and calcination system that increase the oil absorption value of coal series kaolin were studied.The influence of additives on the oil absorption performance and the reasons for increase were constructed.3)Experiment results demonstrate the relationship between the oil absorption performance of calcined coal series kaolin and its particle size distribution.Main results and conclusions are summarized as follows:(1)In the microwave irradiation experiment of kaolin,the oil absorption value of coalseries kaolin increased and then decreased over time.The oil absorption value is the highest74.4 g/100g at 17.5 min,which is 61%higher than the oil absorption value of the original kaolin.The edges and corners of the kaolin will begin to thermal aggregation under the microwave for 15 min,and local high temperature will occur at the edge of the kaolin layer.When the microwave is irradiated for 20 min,the high temperature will cause part of the kaolin sintering.The oil absorption value of kaolin is related to the average pore size of adsorption,but not to the specific surface area.A small amount of mullite will form pores with a larger pore size,which will promote the oil absorption value of calcined coal-based kaolin..(2)In the experiment to improve the oil absorption performance of coal series kaolin,the best additive is boric acid.When the addition amount of boric acid is 5%,the highest oil absorption value of calcined coal series kaolin sample is 87.4 g/100g.The calcination system is calcined to 1000?,and the heating rate is 5?/min,holding time 2 h.(3)Adding a small amount of boric acid can reduce the K element of the sample,so that the sintering phenomenon can be suppressed to a certain extent.The mechanism is that boric acid can interact with the K₂O in the coal series kaolin to generate metastable substances after adding boric acid,which are finally volatilized under the high temperature,reducing the content of K element in coal series kaolin.However,excessive addition of boric acid will produce a liquid phase to promote sintering,and the porosity of the sample will decrease,resulting in a decrease in oil absorption.The oil absorption value of the sample is related to the size and distribution of the pore size.If the sample has excellent oil absorption performance,its internal pore size should not be too large and the proportion of large pore volume should be large.The oil absorption value of the sample is also related to the particle size distribution.The more concentrated the particle size distribution,the greater the oil absorption value.(4)Ultrasonic treatment will reduce the oil absorption value of calcined coal series kaolin samples,and the oil absorption value of the sample will decrease with the treatment time increasing.When the ultrasonic treatment time is 60 min,the oil absorption value of the sample is reduced 18.0%compared with the unsonicated sample.After ultrasonic treatment,the specific surface area of the sample will has a certain increase,but the adsorption average pore size and the percentage of pore volume with pore diameter>50 nm of the sample continue to decrease with the increase of the ultrasonic treatment time.The smaller the average pore size and the percentage of macropore volume,the lower the oil absorption value.