Benefits of Waste heat Recovery
8.3 Benefits of Waste Heat Recovery
Benefits of ‘waste heat recovery’ can be broadly classified in two categories:
Direct Benefits:
Recovery of waste heat has a direct effect on the efficiency of the
process. This is reflected by reduction in the utility consumption &
costs, and process cost.
Indirect Benefits:
- Reduction in pollution:
A number of toxic combustible wastes such as carbon monoxide gas,
sour gas, carbon black off gases, oil sludge, Acrylonitrile and other
plastic chemicals etc, releasing to atmosphere if/when burnt in the
incinerators serves dual purpose i.e. recovers heat and reduces the
environmental pollution levels.
- Reduction in equipment sizes:
Waste heat recovery reduces the fuel consumption, which leads to reduction
in the flue gas produced. This results in reduction in equipment sizes
of all flue gas handling equipments such as fans, stacks, ducts, burners,
etc.
- Reduction in auxiliary energy
consumption: Reduction in equipment sizes gives additional
benefits in the form of reduction in auxiliary energy consumption
like electricity for fans, pumps etc..
8.4 Development of a Waste Heat Recovery System
Understanding the process
Understanding the process is essential for development of Waste Heat
Recovery system. This can be accomplished by reviewing the process flow
sheets, layout diagrams, piping isometrics, electrical and instrumentation
cable ducting etc. Detail review of these documents will help in identifying:
- Sources and uses of waste heat
- Upset conditions occurring in the plant due to heat recovery
- Availability of space
- Any other constraint, such as dew point occurring in an equipments
etc.
After identifying source of waste heat and the possible use of it, the
next step is to select suitable heat recovery system and equipments to
recover and utilise the same.
Economic Evaluation of Waste Heat Recovery System
It is necessary to evaluate the selected waste heat recovery system
on the basis of financial analysis such as investment, depreciation, payback
period, rate of return etc. In addition the advice of experienced consultants
and suppliers must be obtained for rational decision.
Next section gives a brief description of common heat recovery devices
available commercially and its typical industrial applications.