The Substance Flow Analysis And Evaluation Of High Alumina Coal Fly Ash Utilization Process

Coal fly ash is a typical industrial solid waste.Because of its large amount and serious harm to the environment,the utilization of coal fly ash has been the hot research topic.Extracting alumina from coal fly ash is one of the high value-added and effective ways to utilize fly ash.Extracting alumina from coal fly ash with soda lime sintering is one of the effective methods.Currently,some companies have applied this technology and built the industrial symbiosis chain based on the high alumina fly ash processes in China.However,due to extracting aluminum from high alumina fly ash is a new type of solid waste recycling technology,resources,the environment and other problems are also presented in the course of its operation.In order to mentain the long-term and stable development of this industrial symbiosis chain,we need to quantify and evaluate the environmental impacts and resource efficiency of this chain.In order to carry out material flow analysis and various substance flows of the extracting aluminum from high alumina fly ash,this work provides in-depth on-site investigation,combined with the necessary experiments to obtain the adequate supporting data.The indicators of relative environmental emissions and aluminum resources production ratio are proposed.Quantitative evaluation of environmental and resource problems of the exacting aluminum industrial symbiosis chain is presented on the basis of the results of material flow analysis.The main achievements of this work are as follows:1.The multi-attribute evaluation method based on material flow analysis is presented.These attribute includes the environment,resources,and value.Based on input and output table of the material flow analysis,the indicators to evaluate the extracting aluminum industrial symbiosis chain from high alumina fly ash are proposed.2.In this work,we carry out the material flow analysis of the extracting aluminum industria symbiosis chain on the basis of the supporting data.The results show that the consumption of one ton of coal fly ash produced 0.314 tons of alumina,the by-product of 0.49 tons activated calcium silicate,and 1.13 tons of red mud.3.The aluminum,silicon substance flow analysis of this industrial symbiosis chain are carried out.The results show that the aluminum yield was 64.6%of the whole chain,which was less than the yield from the ordinary aluminum industry(about 80%).Aluminum in the dissolution process has suffered serious losses;the dissolution rate was 74.5%,less than the ordinary aluminum industry(about 90%).Since the dissolution of the crude liquid alumina process of the final product,the loss of aluminum is only 0.04 tons.The aluminum losses of this industrial symbiosis chain are at the beginning of sintering dissolution process.4.The lead and chromium flow analysis of this industrial symbiosis chain are carried out.The results show that about half of lead and chromium was carried in by high alumina fly ash,the others by other raw materials.Both these two heavy metal elements eventually was moved into the red mud,some are entered into the flue gas and the activated calcium silicate byproduct,and a small amount of heavy metals pass into the products alumina.The heavy metal content in the product is complied with the requirements of national standards.5.The environmental and resource multi-attribute evaluation are presented.The results show that the lead emission of this industrial symbiosis chain was less than Bayer process,and the chromium emission of this process was fair with Bayer process.The aluminum resource production ratio of this industrial symbiosis chain is approximately 268.61 yuan/ton.