What is Thermocompressor ?
Thermocompressor is a type of ejector used to convert low pressure to medium pressure steam with the use of high pressure steam. It mixes both low and high pressure steam to generate intermediate pressure thus making low pressure or flash steam useful for process.
High pressure steam is used to create high velocity which mixes with low pressure stream as shown in the fig 1.1
Types of Thermocompressor
- Fixed Nozzle type
In fixed nozzle type thermo compressor, there is no regulation of the spindle, Control of thermo compressor is done by regulating steam pressure by external control valve as shown in fig 1.1.
2. Variable Nozzle type
In variable nozzle type thermocompressor, Variation in motive steam is done by regulating spindle which enables varying cross sectional area for the flow of steam at the nozzle. This type of thermocompressor is used where either motive Steam, or Suction steam or intermediate steam condition varies and specific flow or pressure is required to be maintained at discharge end in fig 1.2
When to explore thermocompressor ?
Utilizing flash steam directly in the process is most cost effective, efficient and simpler process. All efforts to be taken to utilize Flash or lower pressure steam directly in process. If direct use of flash steam is not available, option of thermocompressor may be explored for raising flash or low steam pressure to medium pressure and then utilizing it in process.
Precaution to taken while selecting thermocompressor
It must be noted that thermocompressor works well in its design envelop and functioning detoriates significantly beyond its design envelop. Therefore most care to be taken while designing the thermocompressor. Motive pressure cannot be lower than design and diffential pressure must not increases while operation otherwise thermocompressor will not work. Steam properties for motive steam also plays high role in design, steam should be saturated or slightly superheated.
Thermocompressor can be arranged in almost any direction but horizontal and vertical is preferred because of the ease in condensate drain as shown in fig 1.3
Typical arrangement of thermo compressor is shown in fig 1.4, where High Pressure or medium pressure condensate is collected in flash separator. Flash steam is separated and fed to thermo compressor for compressing it to medium / intermediate pressure steam. Quantity of intermediate steam is sum of motive and flash steam. Additional qty of steam to be withdrawn with the Pressure reducing station.
Advantages of Thermocompressor
- Easy to handle large volume
- Stationary equipment and no moving part.
- Simple in design and construction.
- Lower capital investment.
- Minimum maintenance requirement.
- Safe for hazardous area and silent operation
- Can be constructed with various materials
- Long operational life expectancy.
Common Cause of poor performance
- Lower Motive pressure.
- Higher differancial pressure
- Motive steam not dry
- Variation in discharge pressure.
- Motive steam excessive superheat.
- Nozzle worn-out or chocked
- Steam leakage high to low pressure
- Alignment issue with nozzles.