Winterizing Gas Engine/Compressors
Although plant process coolers are usually winterized in some fashion, the standard gas engine drive compressor is often neglected. Figure 1 illustrates a typical engine/compressor shaft driven cooler with minimal winterization consisting of louvres only over the compressor cooler can hydrate and that choke louvres are necessary only on that section. These louvres are supposed to stop -40ºC air from freezing these bundles when driven by the fan at design speed. The engine jacket section often has no louvres in the belief that the thermostat will bypass the bundle with the majority of the coolant, thus maintaining constant engine temperature.
However, many processing plants may also use two other excellent heat sinks which are often overlooked. These are:
- Incoming plant raw gas.
This usually arrives at mean ground temperature which is usually some 25 - 35ºF cooler than atmospheric air on a hot day. - Disposal Water.
This is an excellent heat sink usually available at oil processing plants which are subject to a high water/oil ratio.
What Are The Benefits of Water Over Air Cooling?
When water is available (whether it’s river water, lake water or disposal water) it is a substantially preferred heat sink over atmospheric air. Firstly the typical water cooled shell and tube exchanger will cost less than half that the price of a comparable fin/fan aerial cooler. Secondly water temperatures usually do not exceed 70ºF in the summer compared to ambient air which may reach 90ºF. The water cooler exchange approach temperature is also better than that achieved by aerial coolers, with the result that process streams cooled by water will be typically 25ºF cooler than the same stream cooled by air on a hot summer’s day. In the case of gas compressor intercoolers, every 5ºF improvement on temperature equates to an increased throughput of 1%. Therefore 25ºF on a hot day amounts to a 5% plant debottlenecking. In the case of refrigerant plant condensers the benefits of water over air are magnified. A refrigeration system using a water condenser will use approximately 20% less power than the same system using atmospheric air. Below are three examples of recommendations made to clients over the past year for improved cooling systems using innovative heat sinks - other than atmospheric air.
