Research on the energy and ecological efficiency of mechanical equipment remanufacturing systems

According to the characteristics of mechanical equipment remanufacturing system, the dynamic performance of energy consumption and emission is explored, the equipment energy efficiency and emission analysis model is established firstly, and then energy and ecological efficiency analysis method of the remanufacturing system is put forward, at last, the energy and ecological efficiency of WD615.87 automotive diesel engine remanufacturing system as an example is analyzed, the way of energy efficiency improvementnt and environmental friendly mechanism of remanufacturing process is put forward.

Where, E input is the input energy, E si is the consumed energy of the ith startup process, Q S is the frequency of startup, E uj is the consumed energy of jth standby process, Q U is the frequency of standby, E mk is the consumed energy of kth working process, Q M is the frequency of working, E lost is the lost energy.
Energy efficiency indicator is expressed as the ratio of effective energy to the total input energy (or be expressed as specific energy consumption) in working process , shown in equation (2) (2) Where, EN is energy efficiency, E c is the effective energy in working process, E st is the total input energy of remanufacturing system.

Ecological efficiency analysis method
As shown in figure 1, in this study, material and energy flow is comprehensively considered, and by means of LCA (Life Cycle Assessment) method [2] and CLCD (Chinese Core Life Cycle Database) [3] , environmental emissions is expressed by material consumption and energy consumption integrated, shown as equation (3): Where, P i is the ith environmental emissions, E m is the mth energy consumption, M j is the jth material consumption, f im and f ij is respectively represent the emission factor of mth energy and jth material consumption.
By equation (3), the energy flow and the material flow are integrated into the ecological efficiency analysis. The ecological efficiency is measured in broad measurement, which is given in equation (4 Where, EO i is the ecological efficiency indicator , V is the value or amount of product, which can be shown as the form of product output, sales volume, profit, etc, EI i is the ith environmental impact potential, which can be expressed as global warming potential, acidification potential, etc. According to the life cycle inventory of input information (material and energy consumption), referred to CLCD database, the resource consumption and environmental emissions (such as CO 2 , CFCs, SO 2 , etc.) can be get, and after classification, characterization, normalization and weights [4][5] , the environmental impact potential index EI is obtained, given in equation (5) : Where, G i is the amount of the ith substance in the inventory, EK i is the environmental characterization indicator of the ith substance, R k is the kth environmental normalization indicator, V k is the weight of the kth environmental indicator .

Case study
Take the WD615.87 diesel engine remanufacturing system for example, when the old machine is recycled, it will goes through the processed as: disassembly --cleaning --testing --repairing-assembly. From investigation, the disassembly and assembly devices are usually pneumatic wrenches and wind triggers, the cleaning device is ZQX-135 cleaning machine, the testing device is CEW2001 magnetic inspection machine, and the repair devices is CMD-AS arc spraying machine and automatic nanobot plating equipment [6]. The energy and material consumption of the engine remanufacturing is shown in table 1. It is clearly that the highest energy efficiency is in the cleaning process, the lowest energy efficiency is in repairing phase, the reason for this situation is that there are a lot of uncertainties of old parts damage conditions (such as crack, fatigue or wear), and the repairing process and device will be different due to different damage conditions, sometimes there are presence of miscalculation for the damage condition and wrong process and device are selected, which make the lower energy efficiency. Therefore, in old parts repairing phase, it is necessary to pay attention to the specific damage and appropriate repairing process and devices selection. Also repairing transformation plan should be well designed and unnecessary energy waste are avoided.

Environmental impact analysis.
According to ISO 14042 [7] , environmental impact potentials of CRDP (Chinese Resource Depletion Potential), GWP (Global Warming Potential) and AP (Acidification Potential) are selected. In which, CRDP is determined mainly by coal, oil, natural gas, iron, aluminum and other non-renewable resources and energy, GWP is determined by the emissions of CH 4 , CO 2 , CO, NOx, etc , SO 2 , NOx, H 2 S, HCL and other gases determine the potential of AP [8]. According to equation (3) and (5), the engine remanufacturing inventory and the results of characterization and normalization are shown in table 2. From the result it can be conclude that, each 10000 yuan RMB of engine remanufacturing profit will produce 25.2 units comprehensive environmental impact potential, and produce 3.3, 1 and 1.95 environmental impact potential of CRDP, GWP and AP respectively. It is illustrated that the engine remanufacturing produces lower environmental impact of greenhouse effect, and more Chinese resource consumption. Although the engine remanufacturing saves resources, however, compared with other environmental impact, it is also necessary to search measures of reducing resources and energy input, especially electricity, which would reduce large environmental impact of CRDP, GWP and AP at the same time, because the electricity production will produce large amount of CO 2 and SO 2 .

Conclusion
Based on the analysis of energy and materials consumption and environmental emissions of the remanufacturing system, energy and ecological efficiency analysis method for remanufacturing system is presented. The WD615.87 diesel engine remanufacturing as an example is used to demonstrate and verify the effectiveness of this method. The research results could provides basic theory and method of energy efficiency and environmental emissions dynamic characteristics for the remanufacturing system analysis , which with important research significance and application value.