Rendering Cooker Flash Steam Recovery

Summary

​The aim of this project was to design an improved system for recovering heat from rendering cooker condensate while it is still at high pressure. A common type of heat recovery is to use a flash steam recovery vessel to pre-heat the boiler feed water. This is usually done by installing a flash vessel between the cooker and the boiler feed tank and using a steam heat exchanger to condense the flash steam by pre-heating the boiler feed water.

This flash vessel is normally operated at less than 2 bar pressure so that it does not interfere with the operation of the cooker steam traps. The result is that the maximum temperature the boiler feed water can be heated to is typically less than 130°, limited by the pressure and therefore temperature of the flash steam. This lower temperature limits the amount of heat that can be recovered.

Objectives

The primary objective of this project was to demonstrate an alternate means of recovering waste flash steam from the rendering process.

Key findings

This research has provided proof of concept for an innovative heat recovery system that is cheaper and more efficient than conventional systems. This project recovers the heat from the cooker condensate while it is still at high pressure.

Benefits to industry

This project demonstrated that savings can be accurately calculated simply using condensate temperature measurements, and calculating a percentage saving, rather than needing to go to the expense of measuring gas or water flow.

Future research

The heat recovery system was designed and built in Sydney and transported to site. There have been numerous issues with the pipework and controls. Generally, the issues have been resolved and a final design is being discussed prior to major modifications being made.

Heat recovery at higher pressures offers double the heating of the conventional lower pressure systems. It is expected that it will be cheaper to install, as there are less components.