Research On Application Of Waste Heat In Paper-making Wastewater

Energy-saving and emission-reduction are much valued in China and abroad because of the problem of energy shortage and environmental damage which brought by the rapid increasment of global economy.Lots of industrial wastewater is produced in China every year and the paper-making wastewater is the most.There is large amounts of recyclable waste heat in paper-making wastewater.Recovery and usage of the heat could both save energy and improve the environment.Therefore,this thesis carried out the research on recovery and using of waste heat in paper-making wastewater.Paper-making process consumes lots of hot water and high temperature steam,so the waste water produced in the process contains much recyclable heat.Wastewater source heat pump is an energy-efficient technology which could recover low temperature heat from wastewater and produce high temperature water or air.The technology is very useful for the application of waste heat in paper-making wastewater.This thesis discussed the necessity of recovery and usage of waste heat in paper-making wastewater from several aspects about the energy-saving and emission-reduction policies of government,energy and environment situation,the needs of paper-making enterprises and so on.Research on the temperatures and qualities of wastewater in different wastewater treatment periods showed that the reclaimed water after wastewater treatment system is a very good low grade heat source and could satisfy the requirements of the recovery and usage of waste heat.The heat recovered from the wastewater could be made full use of because there are large demands for heat in the enterprise and surrounding areas.A wastewater source heat pump system with cascade utilization of wasteheat was proposed in this thesis.The waste heat of wastewater can be cascaded recovered through preheating the fresh water and then being the heat source of the heat pump.Analysis of the system COP indicates that the preheating could improve the system COP remarkably.Economic evaluation is necessary for this project.Through the analysis and calculation about revenues and expenses,financial internal rate of return is higher than the selected industry benchmark yield,financial net present value is greater than zero,the project of recovery and usage of waste heat in paper-making wastewater could profit well.The sensitivity analysis is done from the initial investment,annual operating costs,annual operating income to find that the project's ability to resist risks is strong.The project could make full use of waste heat in paper-making wastewater with only a little electric energy.It could reduce the consume of fossil fuels and production of greenhouse gases,soot and cinder the wastewater source heat pump system.