(195b) Ejector Refrigeration Cycle for Natural Gas Plant Waste Heat Recovery in Hot Climates

Natural gas processing plants (gas plants) use refrigeration systems to provide the cooling duty required by the process. Typical designs of such plants use vapor compression refrigeration systems.  At the same time, the plants located in the hot climates (e.g. Middle East) also include large air cooled heat exchangers to cool down process streams which have temperatures between 180 deg. F and 250 deg. F.  This work explores a possibility to use such low grade waste heat to provide energy required to power vapor absorption refrigeration which can (partially) replace the vapor compression refrigeration systems.

The challenge in designing vapor absorption refrigeration systems is the need to remove the heat of absorption at relatively low temperatures (e.g. 70 deg F).  In desert climates, it is not possible to remove heat at such low temperatures.

An alternative is to utilize an ejector refrigeration system, which is similar to a vapor compression system except for the method of compressing the refrigerant. An ejector is used instead of a mechanical compressor to compress the refrigerant vapor from the evaporator to the condenser. Advantages of ejector refrigeration system over conventional compression systems include much lower or insignificant power consumption, no moving parts (except the liquid solution pump) and, hence, no requirement for lubrication, the relatively low capital cost, simplicity of operation, reliability and very low maintenance cost.

This work presents evaluation of different refrigerants and the system design for an ejector refrigeration cycle for gas plant applications in desert conditions.