Study On The Technology Of Preparing Industrial Gelatin With Chrome-containing Leather Shavings

Chromium-containing leather shavings are considered a solid waste in the production process.Due to the low utilization of raw leather,only 35% of the raw leather is made into finished leather.Most of the remaining raw hides are treated as leather solid waste,it’s annual output exceeds 1.4 million tons.Leather solid waste contains a large amount of collagen resources,and the content is about 80% calculated by the absolute dry leather scraps.Therefore,the recycling of the solid wastes not only solves the dangers caused by solid hazardous wastes,but also benefits the development of leather production enterprises.In this paper,the process of preparing industrial gelatin using chromiumcontaining leather scraps and the optimization of the reaction kettle are studied.The preparation process of industrial gelatin is mainly from three aspects: Industrial gelatin was prepared by using the alkali method and the acid method,and dried using anhydrous ethanol.The reactor was mainly optimized in terms of structural modeling,heat transfer method,and agitator.It will be elaborated from the following sections:First,the optimal process of industrial gelatin was explored by acid and alkali processes.CaO was mainly used as a pretreatment for the production of industrial gelatin by the alkaline method.Through single factor experiment,the effects of CaO on the pretreatment time,dosage,extraction temperature,time,liquid ratio,pH and other aspects of chromium-containing leather shavings were studied.The optimal preparation process was determined by the performance parameters of industrial gelatin,namely viscosity and yield.Its optimal process route was: The pretreatment time of CaO was 4d,the amount of CaO was 16% of the weight of the dry leather scraps.It was washed with water to neutrality,the ratio of extracting liquid was 6,the temperature was 100℃,the time was 6h,and the pH was 8.The yield of industrial gelatin was as high as 54.5%,and the viscosity was 14.5 mPa · S.Oxalic acid was mainly used for the pretreatment of industrial gelatin produced by acid method.Through single factor experiment,the effects of oxalic acid soaking time,oxalic acid dosage,hydrolysis temperature,time,liquid ratio,and pH were investigated separately.Its optimal process route was: The oxalic acid pretreatment time was 5d,the amount of the oxalic acid was 8% of the weight of the dry leather shavings.It was washed with water to neutrality,the gel extraction liquid ratio was 6,the temperature was 90 ℃,the time was 8h,and the pH was 9.The yield of finished industrial gelatin was 58%,and the viscosity was 13 mPa ·S.Through the experimental investigation of the alkali method and the acid method,the performance index of the finished industrial gelatin completely meets the industry standard of industrial gelatin,which provides a certain technical reference for the production enterprises.Second,because the melting point of industrial gelatin is relatively low,the requirements for the production environment are also more stringent.Threfore,there is a major problem in the process of the production of industrial gelatin in the factory.In June to-September,due to the hot and humid weather,industrial gelatin production cannot be carried out.In order to solve the problem of difficult production of industrial gelatin in summer,this article mainly explored the use of anhydrous ethanol to dry industrial gelatin,and the use of quicklime to recycle anhydrous ethanol.The main factors explored were: The temperature of the collagen hydrolysate,the amount of anhydrous ethanol,the time of interaction with the collagen hydrolysate,the concentration of the collagen hydrolysate,and the amount of quicklime during the ethanol recovery.The best process was explored: The temperature of the collagen hydrolysate was 25 ~ 35 ℃,the amount of anhydrous ethanol was 4.25 times that of the collagen hydrolysate,the amount of precipitated collagen was independent of the action time,the concentration of the collagen hydrolysate was 30%,the ratio of the amount of quicklime to the amount of anhydrous ethanol mixture was 1: 2.5.Finally,the reactor used for the hydrolysis of chromium-containing leather shavings was optimized.The enamel material is selected as the inner wall material of the reactor mainly through the hydrolysis conditions of chrome containing leather scraps;During the process of heating hydrolysis in the reactor,due to the presence of some chromium-containing leather shavings,therefore,the internal components cannot be selected for heating the kettle body,but a jacket heating method was required;Finally,the agitator inside the reactor was optimized and selected.The CFD fluid numerical simulation software was used to perform fluid numerical simulation on straight-blade turbine blades,frame blades,and combined turbine and frame blades.Through the analysis and comparison of the velocity cloud diagram,velocity vector diagram and radial velocity distribution curve at different height from the bottom of the buss,it is determined that the combined impeller is the best choice for the agitator.