The Study And Process Design For Preparation Of Hemihydrate Calcium Sulfate Whiskers By Waste Calcium Chloride

Calcium sulfate whisker is a new type of high performance inorganic material with wide application range.It has excellent mechanical and physical properties,such as high strength,high temperature resistance,high modulus,and loss resistance.Its surface is easy to deal with,good compatibility,non-toxic.It can be made of high-strength,wear-resistant,lightweight reinforced composite materials.is a new material with wide application prospect.At present,the raw materials used in the production of calcium sulfate whiskers is basically natural gypsum.As a non-renewable resource,natural gypsum will inevitably face exhaustion problem.Based on this problem,this paper presents the preparation of calcium sulfate whiskers by using waste calcium chloride as raw material,which can reduce the cost of raw materials and conserve natural gypsum resources.Ammonia waste liquid is a kind of waste liquid produced by ammonia process during soda production.The main groups of waste liquid are calcium chloride and sodium chloride.There are many soda plants in China,and the scale is large.A large amount of waste and waste residue discharged every year.If not dealt with and free discharge,it will bring serious environmental costs.The traditional treatment of ammonia-alkali waste is discharged to the embankment.The Factories place it naturally,waste liquid can be discharged after meeting the environmental requirements.Many ammonia-alkali plants now use multiple enrichment methods for waste liquid to recycle calcium salts and sodium chloride.But this method has little improvement on the value of waste liquid.It is the key of treating the waste liquid to treat the ammonia waste liquid and improve the waste value at the same time.In this paper,the preparation of calcium sulfate whisker and the treatment of ammonia waste liquid in ammonia alkali plant are combined.Half water calcium sulfate whisker was prepared by improved atmospheric pressure acidification method.The prepared calcium sulfate whisker has the appearance of white,no impurities,good crystal appearance,and the ratio of long and diameter is big.The process of preparing the half water calcium sulfate whisker with ammonia waste liquid was investigated experimentally.The best technological conditions were obtained by experiment.We got the best process conditions: the additive was SDS,its concentration was 2.5g/L,the concentration of calcium chloride was 20g/L,n(calcium ion): n(Sulfate ion)=1:5,boiling time was 1 hour,pH was 2,standing time was 2 hours.Filter Cake was dried at 150? to get the final product.Under these conditions,its diameter was in 2?m~3?m,length was in70?m~100?m,and the length-diameter ratio of the hemihydrate calcium sulfate whiskers prepared by calcium chloride could reach 50,the color of the products was pure white and the products did not contain impurities.The process design of 300 tons of half water calcium sulfate whisker per year was carried out in this paper.The process flow was determined.And I did the material balance of each unit,the heat balance of important equipment,and calculation of equipment selection.The equipment specifications was determined.Finally I drew the P&ID of process design,the drawing of the layout of equipment and workshop,and the drawing of the layout of factory.