| With abundant crop residues, Heilongjiang Province has the resource feasibility of promoting utilization technologies of crop residues as energy. Constructing central heat and gas supply systems with renewable energies is a developing concept that not only complies with urban-rural integrating orientation with the function of small town as “rural area serving and surrounding area promoting”, but also is a utilization strategy of renewable energy as “adapting local conditions with multi-energy complementarity”. In this thesis, the rural areas and small towns in Heilongjiang Province are taken as the target regions. Based on the quantitative study on living heat using of rural residents, the supply-demand relationship between the available amount of crop residues and living heat amount in different areas are studied. Furthermore, a living heat supply mode for rural areas and small towns with utilization technologies of crop residues as energy is proposed. The energy, economic, and environmental benefits of the heat supply system in this mode are assessed with appropriate indicators.Firstly, based on a field survey on living energy using in rural areas of Heilongjiang Province, the characteristics of living energy using of rural residents are analyzed, and the amount of annual living heat demands in rural areas in Heilongjiang Province are obtained through calculating the heat demanding indices of cooking and heating. The survey suggests that in rural areas of Heilongjiang Province, Crop residues is the major energy resource in daily life and used by most of the rural residents. However, the integrated efficiency of bio-fuels is only 27.4%. The heat demanding index of rural heating is 364MJ/(m2·a), which approximately equals to 368MJ/(m2·a) of urban energy-efficient residentials with 1-3 floors in Heilongjiang Province. The heat demanding index of rural cooking is 935MJ/(capita·a), which is lower to 1036MJ/(capita·a) of urban cooking. In rural areas of Heilongjiang Province, the annual heating demand is 1.76×1011MJ/a, which is nearly 10 times of the cooking demand.Secondly, the concept of supply capacity of crop residues as energy is proposed, by which the regional supply-demand relationship between the available amount of crop residues and living heat amount with different crop residue utilization technologies can be assessed. The zoning analysis of supply-demand relationships in rural areas of 13 prefecture-level divisions in Heilongjiang Province suggests that the crop residues in all the divisions are abundant for densification, while 7 of them are also abundant for dry distillation. All divisions except Qitaihe have the resources supply feasibilities for the mode of cooking supplied by dry distillation and heating supplied by densification, while the supply capacities in 11 of them are beyond 1.5, indicating that large portions of crop residues can be left for other use.Thirdly, based on the study on supply-demand relationships above, considering the current living heat supply mode and urban-rural integration requirement, an integrated living heat supply mode that covers small towns and its surrounding rural areas is proposed. In this mode, cooking gas is supplied by dry distillation of crop residues, coal-fired cogeneration units or coal-fired boilers are basic sources with biomass boilers as peak-shaving sources for central heating, and residential heating with densified crop residues is for remote rural areas. Taken supply capacity as the indicator, the zoning assessement of resource supply feasibility of this mode in Heilongjiang Province shows that the resource supply feasibility is excellent, 10 in 13 divisions have the supply capacities larger than 1. Moreover, in areas located in Songnen Plain and Sanjiang Plain, both of which has most of the cultivated lands of Heilongjiang and abundant crop residues, the supply capacities are larger than 1.5.Fourthly, taken the heat source subsystem with cogeneration units and biomass boilers of integrated central heating in village-town area as the research object. Based on the system characteristics, Relative Fossil Energy Savings(RFES) is proposed as the indicator of assessing the effect of substituting crop residues for fossil energy. An optimizing model with bi-objects of RFES and RPES(Relative Primary Energy Savings) is established to analyze the rational configuration and energy benefits of the heat source subsystem. The analysis results show that the B12 and B25 back pressure cogeneration units are the suitable basic heat sources for integrated central heating in village-town areas. Comparing with current heat and power supply mode in village-town areas, the integrated central heating system can achieve RFES as 10.9~32.7% and RPES as 22.1~33.1%. The energy benefits is greater with B12 units.Fifthly, taken the network subsystem of integrated central heating as the research object, two researches are conducted as follows. 1) The characteristics of temperatures and flow rates of heat medium through the heating seasons are analyzed. Results show that in the system of peak shaving at rural secondary network, both the flow variation trends and return water temperatures have large differences between rural and town primary networks, thus respective monitoring and coordinate controlling are needed. 2) Average Electricity consumption to transferred Heat quantity Ratio(AEHR) is proposed as the standard for energy consumption assessment of network. The appropriate radius of integrated central heating system in village-town area is discussed based on the calculation results of AEHR. As the discussion results, the normal appropriate radius should no larger than 7 km. If peak shaving at rural secondary network and the proportion of urban heat load is no less than 0.7, or peak shaving at central primary network and the proportion of urban heat load is no less than 0.8, the appropriate radius can be extended to 13 km.Sixthly, taking a typical village-town area in Heilongjiang Province as the example, the economic benefit of integrated central heating system is analyzed with different design programs. The results suggest that the system with densification, peak shaving at rural secondary network, and rural substations close to villages can achieve maximum economic benefit. The annual cost of the optimal program is 109.26×106yuan/a, which is 2.713×106yuan/a lower than the sum of current heating costs in this studied village-town area.With the optimal program, the cost per area and the cost per heat are 26.66yuan/(m2·a) and 56.73yuan/GJ, respectively, reducing to 80.4% and 84.5% of the corresponding values of existing urban centralized heating system. These two values of the optimal program are 2.6 and 2 times of that with the current household heating form in rural areas, while the time and effort for heating activity are saved, and the heating quality and indoor environment are both improved.Finally, the environmental benefits of integrated central heating system are assessed by an AMS/EPA regulatory model- AERMOD. The simulation results show that the maximum daily average concentrations of SO2, NOx, and TSP are 4.71, 11.01, and 4.49μg/m3, respectively, which are correspondingly only 3%, 19%, and 7% of that in current heating form. The SO2 maximum daily average concentration of current heating form is 162.53μg/m3, which is beyond the limit of 150μg/m3 set by national standard. The environmental benefits of integrated central heating system is significant, while different system designs have no obvious differences. |
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