The Synthesis Of CaO₂with Carbide Slag By The Circulation Process Of Liquid Phase

The preparation of acetylene by the hydrolysis of calcium carbide-which has a good prospect-is one of the most fundamental reactions in chemical industry. And the carbide slag that comes from the preparation reaction has become a big problem and is brothering plenty of related enterprises for a long time.The main component of the carbide slag is calcium hydroxide which has many uses.However, due to factors such as technical lack,mostly the carbide slag was not exploited and directly discarded as wastes which results in the waste of resources and pollution,In this study,the Ca2+in the carbide slag was extracted through the reaction between carbide slag and NH4Cl,and then one important chemical product-CaO2was synthetised. At the same time NH4Cl was recreated.Firstly the raw material carbide slag was analyzed by XRD and some other ways.And the test methods were made according to some related national standards、 industry standards、some related theses and the actual situation in the lab. The raw material carbide slag and the carbide slag which was exposed in the air for several months were both analyzed by XRD;The content of calcium and magnesium was determined by using the EDTA titration method;The pH of carbide slag suspensoid was determined by a precision tester;In addition, the volatile components and the insolubles in hydrochloric acid were determined.Secondly the treatment of carbide slag by using NH4Cl was studied.By using the NH4Cl solution,the carbide slag was treated and the Ca2+was extracted and the impurities were removed at the same time. Effects of various factors on the experiment were studied by single factor experiment, in order to determined the optimum process parameters.And the optimum process parameters was the feeding mode:carbide slag�'NH4Cl,the dosage of carbide slag:120%of theoretical value,the stirring intensity:300r/min, the reaction time:30min.On this condition,the Calcium extraction rate can reach83.3%, and the coefficient of utilization of NH4Cl can reach98.5%.The experiments showed that ammonium chloride extraction technique was simple, effective,and operable. Thirdly is the synthesis of calcium peroxide, by using the mixed solution obtained in previous step (includes calcium chloride and ammonia),and hydrogen peroxide.Through the single factor experiment, the better parameters was determined, and on the basis of the results of the single factor experiments,several factors were elected to design orthogonal experiment,to determine the optimum process parameters.The reasonable process parameters which were determined by the single factor experiment were the feeding mode was mixed solution�'H2O2, the stabilizer concentration:about8%, the mixed liquid dosage should be controlled at1.2times, and the mixed solution concentration should be less than0.2mol/L, the reaction time:not more than30min, the stirring intensity:<600r/min. Through the analysis of the results of the single factor experiment, combined with the actual condition of the lab, the4parameters-the stabilizer dosage, reaction time, dosage of mixed liquid and stirring intensity were selected as test factors.The L16(44)orthogonal experiment was designed, with the yield of CaO2as test object (combined with the purity of the product). The best process parameters were stabilizer dosage:9%, reaction time:20min,the mixed solution dosage:1.05times, the stirring intensity:500r/min. Under these conditions, the yield reached to94.69%, and the purity reached to69.74%.The product was characterized and discussed through XRD and SEM. At the same time, the filtrate that came from the synthetic reaction of calcium oxide, mainly contains NH4Cl.Obviously it can be used in the Ca2+extraction step of carbide slag, and realizes the circulation process.At last, the recycling process of Ca2+extraction solution-the circulation process of liquid phase has been proved by experiments. Firstly the content of NH4Cl in the filtrate was determined by the method of argentometry.Then one proving experiment was designed according to the parameters and conclusions of extraction process of carbide slag by NH4Cl. The result of the proving experiment is:the extraction rate of Ca2+can reach to84.13%-almost as the same as the extraction rate of Ca2+by NH4Cl.It proves that the Ca2+extraction solution can be recreated and the circulation process of liquid phase is feasible.