Process integration between individual plants at a large dairy factory by the application of heat recovery loops and transient stream analysis

Indirect heat transfer between individual plants at a large industrial site, such as at a large dairy factory, can be accomplished using a Heat Recovery Loop (HRL) operating at relatively low temperatures (20–50 °C). Direct heat transfer between plants is problematic because of the production schedule and frequent process start-ups and shutdowns that occur due to the need for regular cleaning. The dynamic operation of an industrial HRL at a large dairy factory is presented and briefly discussed. A model HRL based on a set of variable industrial stream data is used to examine the effect of heat storage capacity and HRL temperature range on the amount of heat recovery. Both HRL temperature range and a small heat storage volume can significantly improve the amount of heat recovery. The interface level in the storage tank is also modelled for different volumes and the resulting system is very dynamic and therefore good control needs to be incorporated into the HRL.

► Total site integration can be improved using a Heat Recovery Loop and an optimally sized stratified tank.
► The amount of heat recovery is dependent on the stratified tank size and the scale of stream transients.
► Optimising the stratified tank is important to maximise heat recovery.
► Variability of source and sink streams need to be accounted when optimising.