Study On Establishment Of The Cleaner Production Index System And Its Evaluation Methods Of Mangesium Industry With Pidgeon Process

As a new type of the applied materials, magnesium and magnesium alloys are widely used in aerospace, military, civilian and other areas because they can meet the strict requirements of weight loss, energy saving and environmental protection in auto industry as well as the demands of higher integration, lighter volume in electronic device. The thermal reduction and molten salt electrolysis are the two main current methods in producing the magnesium and magnesium alloys in the world. As the impact of raw materials, cost and the other factors, Pidgeon technics is the main method in magnesium industry in China. Although Pidgeon technics fits neatly to our national conditions, there are many issues in each steps of refining magnesium. The utilization efficiency of energy and resources is low while pollutant emissions are comparing large. Therefore it is important and urgent to implement the cleaner production in magnesium industry. Scientific management and advanced technology are the two major measures to achieve the aim of saving energy, consuming lower energy, reducing pollutants discharge, maintaining the human health and protecting the eco-environment.The establishment of the index system and its assessment methods is the most important links in the cleaner production quantitative management. It will benefit the indexing management of cleaner production and provides assessing scales of its effect. Under the designing principle of orderly stages, full-scale content, being scientific, conciseness, continuity, cleaner production index system of refining magnesium in Pidgeon technics is posed through theoretical analysis, expert advice and frequency methods. The index system includes quantitative and qualitative indexes. Quantitative indexes include resources consumption, energy consumption, comprehensive utilization, technology and pollutants discharge which can be summarized in detailed such as the consumption of dolomite, ferrosilicon, fluorite and fresh water, life expectancy of reducing pots, the consumption of coal, power and coal in magnesium alloy section, energy utilization, industrial water recycling rate, comprehensive utilization rate of wasted solid, burned magnesia yield coefficient, reduction furnace efficiency, refining yield, reduction period, quality levels, purity of crude magnesium, the emissions of wasted gas, SO2 and dust, wasted solid in unit product, the removal efficiency of SO2 and TSP. Qualitative indexes include environmental management, health and safety, quality of raw material, technology features and pollutants discharge. Qualitative indexes can be summarized in detailed such as whether passing the ISO14000 and ISO9000 certification, controlling the total pollutants within the national and local requirements, passing cleaner production audit, the implementation of EIA system, the implementation of three simultaneousness in environmental protection, labor security and sanitation of construction project, quality standards of dolomite, fluorite, ferrosilicon and pelletizing. Besides the above-mentioned point, the indexes also include whether existing production section of magnesium alloy, using computer ingredients, grinding production and making the balls in linkage enclosing production lines, whether the range of activity meeting the requirements of state policy, the kind of calcining kiln and reduction furnace, whether existing temperature controlled in the processes of refining, calcining and reducing, using machinery to remove ash, clean cans, feed material and mould magnesium, whether Ringemann blacken is less than 1, SO2, TSP and the noises meet the emission standards.Because the index values in index system of cleaner production are a continuous process moving from quantitative to qualitative, the concept of attribution rate of index value is described to be obscure. Fuzzy set mathematics can solve the contradiction between complexity of the system and the accuracy of evaluation by translating complicated and uncertain factors issues into simple evaluation model with the foundation of figures. Therefore fuzzy set mathematics is drawn into the assessment of cleaner production which is also widely used in economic management activities. With the help of integrated assessment method in fuzzy set mathematics, all factors which impact quality in cleaner production can be evaluated all sidedly and precisely.That the current situations of all connections in firms before or after the cleaner production are evaluated and the opportunities of cleaner production are distinguished to find out the weak connections to assess and decide the degree of cleaner production by using the maximum membership principle. The key of using fuzzy set mathematical method to evaluate the cleaner production is to determine membership grade and weight coefficient of indexes in fuzzy relationship matrix. In this paper, the weight coefficient of indexes is determined by using Analytic Hierarchy Process (AHP) which can combine the experts'advices with analysts'judgments directly and effectively. Such index system can provide scientific, effective and feasible assessment to cleaner production. The membership grade of indexes is calculated by related functions. In this paper, rise and drop semi-trapezium and semi-rectangle distribution function are adopted respectively as quantitative and qualitative membership functions. Rise and drop semi-trapezium distribution function is a linear function with multiple extreme values while there are several levels corresponding to the extreme values. In this index system, the indexes are divided into four grades such as the international advanced level, the domestic advanced level, the general domestic level and elimination level.In this paper, Life Cycle Assessment (LCA) and integrated assessment in fuzzy set mathematics are chosen to analyze a case in Ningxia whose level of cleaner production is the domestic advanced. This firm locates the domestic advanced level through calculation, which matches up to situation reflected via the experimental data. The results prove the feasibility and effectiveness of index system and assessment methods. In connection with the firms'malpractices reflected through fuzzy assessment and analysis of cleaner production, a number of improved suggestions are given in terms of reinforcing management, improving technic, increasing utilization efficiency of resource, decreasing pollutant discharge.In this context, the index system and assessment method of cleaner production in pidgeon technics of refining magnesium are not only to determine the cleaner production level in this industry, create a platform for the comparison between firms and take an important step forward to establishing assessment criteria of cleaner production in magnesium industry, but also to help firms to understand their own production more intuitively especially the shortage, to allocate the resources with pertinence and selectivity in production practice. Achieving optimal allocation of resources plays a very important role of exploring cleaner production potential of firms.