回收低温余热的热电耦合电解制氢系统及性能评估

Heat-power coupled electrolytic hydrogen production system with low-temperature waste heat recovery and its performance evaluation

固体氧化物电解制氢时,水以气态进行电解,但仅依靠电解产物冷却所释放的热能不足以将液态给水蒸发气化,电解制氢系统存在供热缺口。为解决该问题,基于高温热泵技术,提出了通过热泵吸收外界低温余热(<100℃)制取较高温热能(>100℃),以满足给水蒸发气化用热的系统工艺方法,设计了系统流程,研究了热泵系统关键参数对系统性能的影响,并通过建模仿真的手段评估了该系统的制氢性能。研究结果表明:①利用热泵吸收环境中的低温余热,制取较高温热能使电解给水蒸发,具有技术可行性,该方法同样适用于系统内部电解产物所携带余热的回收再利用;②外界余热温度越高,越有利于降低系统的制氢能耗,直流电解功率为1 MW的电解制氢系统,对余热源的热需求约为138 kW;当余热源为水且温降在5℃时,水的需求量约为20 t/h;③假设外界余热不计入制氢能耗,利用热泵集成外界余热时,系统理论单位制氢能耗约3.5 kW·h/m^(3),全部为电能消耗。结论认为,通过热泵吸收低温余热向高温电解制氢系统供热的系统工艺,开辟了一种低品位余热向高品位氢能转化的新思路、新途径和新方法,具有广阔的应用前景。

During hydrogen production by solid oxide electrolysis,water is electrolyzed in the form of steam,but the heat energy released from electrolysate through cooling is not sufficient for feed water evaporation,which results in a heating gap in the electrolytic hydrogen production system.To address this problem,this paper proposes a systematical process method to meet the heat demand of feed water evaporation.In this method,the high-temperature heat pump technology is used,which applies a heat pump to absorb external low-temperature waste heat(<100℃)to produce high-temperature heat energy(>100℃).A systematical procedure is designed.In addition,the influences of key parameters of the heat pump system on the system performance are studied,and the hydrogen production performance of this system is evaluated by means of modeling and simulation.And the following research results are obtained.First,the proposed system applies a heat pump to absorb ambient low-temperature waste heat to produce high-temperature heat energy for the evaporation of electrolysis feed water,which indicates its technological feasibility.This method is also applicable in recovering the waste heat carried by the elecrolysate inside the system.Second,the energy consumption of hydrogen production decreases as ambient waste heat temperature increases.The heat demand to the waste heat source is 138 kW for the electrolytic hydrogen production unit with 1 MW of DC electrolysis power.When the waste heat source is water and its temperature drop is 5℃,the demand rate of water is about 20 t/h.Third,if it is assumed that the ambient waste heat is excluded from the energy consumption of hydrogen production and is integrated by using a heat pump,the theoretical specific energy consumption of hydrogen production is about 3.5 kW·h/m^(3),all of which is electricity.In conclusion,the system process which applies a heat pump to absorb low-temperature waste heat to supply heat for the high-temperature electrolytic hydrogen production system provides a new idea,means and method for converting low-grade waste heat into high-grade hydrogen energy,presenting a promising application prospect.