Subsection Utilization Research Of Wast Heat From Low-temperature Exhaust In Building Ceramics Industry

In China’s steel,power generation,metallurgy,cement,chemical industry and other industries,the amount of waste heat resources has exceeded more than 43 million standard coal every year.At present,the utilization of waste heat from high temperature flue gas represented by steel industry has been widely used,but the utilization of waste heat from low temperature flue gas represented by ceramic construction enterprises is lack of relevant application.This paper first conducts an on-site investigation of the waste heat of the typical building ceramic industry,determines that the waste heat utilization object is the flue gas with a temperature range of 150℃～200℃,and tests the flue gas composition.Based on this,the organic Rankine cycle power generation technology and lithium bromide absorption refrigeration technology,which are relatively mature and widely used in the current low-grade waste heat utilization method,are analyzed.Based on the Aspen Plus software,this paper selects appropriate physical parameters and modules for modeling of the organic Rankine cycle and lithium bromide absorption refrigeration systems,and uses other literature data to verify the effectiveness of the model.When studying the organic Rankine cycle power generation system,this paper focuses on analyzing the compatibility of the four dry working fluids R227 ea,R245fa,R236 ea and R123 with the system at different heat source temperatures,and analyzes the influence of pinch temperature difference,evaporating pressure,condensing pressure and system superheat on system performance.The temperature difference of the pinch point mainly affects the economy of the system,and different working fluids have their optimal pinch point temperature difference to make the system economy reach the best;In terms of evaporating pressure,higher evaporating pressure can make the system achieve higher thermal efficiency,but the existence of the optimal evaporation pressure makes the system more economical,and different heat source temperatures correspond to different optimal evaporation pressures,so that the system can achieve greater net work;In terms of condensing pressure,the increase in condensing pressure has a negative impact on the thermal efficiency,net work,exergy loss and economy of the system,so the condensing pressure should be reduced as much as possible in combination with the cooling water temperature;When the flue gas temperature is constant,the degree of superheat mainly affects the net power and economy of the system.Under the same evaporation pressure,both of them decrease with the increase of the degree of superheat.When studying the single-effect lithium bromide absorption refrigeration system,this paper analyzes the influence of the system’s dilute solution concentration,flow rate,and highand-low side pressures on the system performance at different waste heat temperature sections.When the waste heat temperature is constant and other conditions remain unchanged,the system COP,economy,etc.all decrease with the increase of the system’s dilute solution concentration,pressure on high pressure side and system dilute solution flow rate,but these three parameters affect each other;The pressure on the low pressure side determines the quality of the output exergy of the system.As the pressure on the low pressure side of the system increases,the exergy loss of the system increases.Whether it is an organic Rankine cycle power generation system or a single-effect lithium bromide absorption refrigeration system,the selection ranges of the above parameters are different,and the parameters affect each other,and there are different optimization results under different indicators.Therefore,a unified optimization index is needed in each waste heat temperature section to configure each parameter reasonably.This paper proposes a multifactor comprehensive evaluation index based on the analytic hierarchy process to optimize the selection of system operating parameters for different temperature sections.Taking the flue gas at the entrance of a desulfurization tower in a factory in Jiajiang County as an example,the waste heat recovery is guided according to the parameter optimization results.The results show that the lithium bromide absorption refrigeration system in this example is a better choice.