Study On New Type Gasifying Briquette Composite Binder And Process For The Alumina Industry

Development of briquette technology can not only alleviate the situation that supply exceeds demand in pulverized coal and demand exceeds supply in block coal, but also reduce harm to the environment due to the direct combustion of pulverized or block coal, which is very important to build the resource-economical and environment-friendly society of our country. In addition, the study on gasifying briquette composite binder and process of alumina industry broadens the applied range of briquette. So it will have broad market and significant social benefit.In this paper, new type binder and process were developed to solve the problem of poor performance and high cost of gasifying briquette binder in alumina enterprises using the method of six sigma management theory. Firstly, basal formulation was obtained from common materials. Then a cost-effective and environment-friendly composite binder formulation was obtained based on the reduction of price and enhancement of performance. Finally, the effect on strength of moulding and drying process and its mechanism were investigated.The main contents obtained in the paper were as follows:1) Orthogonal design was used in experiment where kaolin, bentonite and sodium humate were used as briquette binder. The results indicated that bentonite and kaolin had a significant influence on the high temperature performance, with sodium humate on the room temperature performance. Also we knew that the optimal formula, that is basal formulation, was obtained under conditions of1%addition of kaolin,4%addition of bentonite and3%addition of sodium humate.2) The acid activation-mixture of alkali extraction technique was used in this paper, with8%addition of hydrochloric acid as the activator, which made the room temperature strength improve a lot. Then the mixture of peat and lignite, six times of paet by weight, was used as raw material of the extraction of humic acid. The largest room temperature strength was obtained when the amount of sodium hydroxide was15%. Finally mixture experiment was used with sodium carbonate, sodium phosphate tribasic and sodium hydroxide as three factors. The results indicated that the optimal proportion of the three is about0.37,0and 0.64from the response optimization, which helped to get the room temperature strength of0.91MPa.3) Sodium chloride was used as reinforcing material of room temperature strength. When the amount of sodium chloride added to50%, room temperature strength increased to1.23MPa, which shows the significant enhancement of sodium chloride. The enhancement of high temperature performance was achieved by modification of bentonite. When the amount of modified bentonite was2%, the high temperature strength was0.76MPa, and the thermal stability was up to80%. Semi-dry process was used, with5%addition of sodium carbonate solution, called odium agent,30%addition of moisture content, three days of storage time and three times of extrusion.4) Response surface methodology was used to arrange experiments in the paper. The experimental data was firstly processed utilizing the method of multi-factorial total probability formula evaluation. Then based on the regression analysis and model building, the optimum formula was obtained under conditions of4.5%addition of modified lignite,2%addition of sodium-modified bentonite,1%addition of kaolin and20%addition of sodium chloride, which beneficial to the environment can meet the requirement of gas furnace5) The briquetting pressure, particle components of the raw coal, briquetting temperature, mixing time, moisture content, dry time and temperature affected to the briquette performances were investigated. The optimized technical parameters were as follows:briquetting pressure of four times, particle components of the raw coal of60%of the particle size ranging from0～0.85mm and40%from0.85～3mm, mixing time of two minutes, moisture content of18%, dry time of two and a half hours and dry temperature of150℃. Then the mechanism was studied by porosity and drying degree. The optimized drying degree of the briquette developed in the paper was12.3%, which would be increaced if the porosity increased in the process of cold forming with binder.