Process heat integration means heat that was previously cooled off is recovered and reused in another unit operation.. With direct process heat integration, heat is transferred directly from one process stream to the other in a single heat exchanger.
The two streams need to be fairly close to each other, and there should not be any dangers involved if the streams mix in case of a leak.
The result is a reduced load on both the heating and cooling utility systems.
There are numerous examples in chemical plants where direct process heat integration can be utilized, for example:
In this example heat from a process gas stream is recovered and used for preheating the feed gas of a direct fired heater. A shell-and-tube is replaced by a compact heat exchanger, increasing heat recovery and reducing gas consumption. The result is an increase in heat recovery by 1.7 MW (5.814 MMBtu/h).
Direct process heat integration
Payback period for heat recovery system as a function of fuel price.
Payback period (years)