污泥热水解厌氧消化工艺热系统设计探讨

Discussion on Design of Thermal System of Sludge Thermal Hydrolysis/Anaerobic Digestion Process

北京某污水处理厂泥区升级改造,采用热水解作为预处理进行强化厌氧消化。热水解-厌氧消化工艺中的热系统,主要是供热及换热系统,是整个设计考虑的核心环节。分析了换热系统的技术方案及工艺参数选择,比较了换热器选型,交代了整个换热系统及附属系统的设计,说明了启动后整个系统的运行情况。供热系统利用厌氧消化所产沼气作为能源,在厂区新建一座沼气锅炉房并保留原热水锅炉房,保证热水解系统的蒸汽用量的同时兼顾厂区采暖;换热系统对热水解后污泥采取两次换热,一次换热在新建热交换间、二次换热在消化池内完成,整个换热系统的冷却水由厂区新建的冷却水泵房提供。改造后热水解厌氧消化系统所产气量完全达到厂区运行能量需求,并且会有至少12%的能量节余。同时,指出了热系统设计中低品位热能难回收、冷却水选用、污泥换热方案以及剩余能源未全部利用等问题,并提出了优化建议。本项目已处于调试阶段,消化池完成常规启动,所产沼气量满足新建蒸汽锅炉房内单台蒸汽锅炉的要求,同时满足单条热水解处理线的蒸汽需求,热系统运行良好,保障了整个工艺的正常高效运行。

There was an upgrading project of sludge treatment zone in a WWTP in Beijing,and thermal hydrolysis process( THP) was used as pre-treatment process for enhanced anaerobic digestion.Thermal system in THP/anaerobic digestion process included heat supply system and heat exchange system,which were the core part of the whole design considerations. The technical solutions and process parameters of heat exchange system were analyzed,exchanger selection was compared,the design of the heat exchange system and ancillary systems were explained,and the operation of whole system after the start-up was introduced. The heat supply system used anaerobic digestion biogas production as an energy source. A new biogas boiler room in the plant was built and the original hot water boiler room was remained to ensure the amount of steam for THP and plant heating. Heat exchange system performed twice heat exchange for sludge after THP,once in the heat exchange room and once in the digestion tank.Cooling water in the heat exchange system was provided by the new cooling water pump house. After the upgrading,anaerobic digestion biogas produced by THP/anaerobic digestion process could fully meet the energy demand,and there were savings of at least 12% energy. Meanwhile,several problems during design were pointed out,such as difficulty in low-grade heat recovery,the choice of cooling water,sludge heat exchange program and no full utilization of the remaining energy,and optimization suggestions were proposed. The project has been in the commissioning phase. Routine start-up of digester was completed.The amount of produced biogas could meet the single steam boiler requirements and the needs of a single THP line. Thermal system is running well,protecting normal and efficient operation of entire process.