Design And Simulation Of Afterheat Recycling System Of Aerobic Composting In Cold Region

The large yield and low utilization rate of straw and animal manure in Heilongjiang Province seriously threaten its ecological environment.Aerobic composting is an effective method to deal with straw and livestock manure.However,Heilongjiang Province is located in a cold region.Aerobic composting is faced with some problems,such as the difficulty of natural heating of pile body,the difficulty of maintaining high temperature of pile body,the high energy consumption of composting equipment and the long composting cycle.In this study,based on the actual situation of aerobic composting in cold region,a set of waste heat recovery system of aerobic composting with high efficiency,low energy consumption,economy and operability was constructed to make full use of waste heat of composting,reduce the restriction of low temperature on aerobic composting in cold region,and improve the efficiency of aerobic composting.The main research contents and conclusions of this paper are as follows:(1)The control variable method was used to study the ventilation rate(0m~3/(min·m~3),0.05m~3/(min·m~3),0.20m~3/(min·m~3),0.35m~3/(min·m~3))and ventilation frequency(0min/h,10min/h,20min/2h,30min/3h)of aerobic compost.Effect on the efficiency of aerobic composting.The results showed that the experimental group with ventilation rate of 0.20m~3/(min·m~3)and ventilation frequency of 20min/2h showed absolute advantages in temperature,water content,organic matter,C/N,p H,EC,etc.The maximum temperature of the reactor reached 61℃and above 50℃for 5.37days.(2)The plate-fin waste heat recovery system was introduced into the aerobic composting system to systematically study the effects of waste heat recovery on the efficiency of aerobic composting under different ambient temperatures(11.4-13.4℃and 7.1-8.6℃).The results show that waste heat recovery can effectively improve the efficiency of aerobic compost,which can be shown as faster reactor heating,longer high temperature period and higher maximum temperature of the reactor.The experimental group of waste heat recovery also showed absolute advantages in water content,organic matter,C/N,p H,EC and other aspects.When the ambient temperature ranged from 11.4℃to 13.4℃,it took 1.62 days for the reactor temperature to reach 50℃,7.15 days for the reactor temperature above 50℃,and the maximum temperature was 63.8℃in the waste heat recovery group.Compared with the normal composting group,the time for the waste heat recovery group to reach 50℃was 0.55 days shorter,the maintenance time for the temperature above 50℃was 1.42 days longer,and the maximum temperature was 2.8℃higher.When the ambient temperature is 7.1～8.6℃,the maximum temperature of the reactor body in the waste heat recovery group is 62.4℃,and it can be maintained above 50℃for 5.61 days.The maximum temperature of the normal compost group was 41.2℃,which did not meet the requirements of innocuity.(3)Apply ANSYS to simulate and verify the heat exchange process of waste heat recovery.The results show that waste heat recovery can effectively improve the air temperature,and the simulation accuracy of waste heat recovery is more than 91%.When the ambient temperature is 11.4～13.4℃,the air can be raised by 4.72℃at the highest;When the ambient temperature is 7.1～8.6℃,the air can be raised by 5.46℃at most.