Waste Heat Recovery

Whether you are looking at stack gas heat recovery, through the use of Waste Heat Recovery Units (WHRU), or trying to optimise streams to reach your pinch point, Graham Hart (Process Technology) Ltd. have supplied units to meet most requirements.

With process modelling capabilities at our finger tips, our Chemical Engineers can work with you to meet your requirements.

Do you have a process that is dumping huge quantities of energy? Can some of that energy be recovered and used in the process? Get it right and you save so much money that you are a hero. Get it wrong and it will cost your company more than the value of the energy recovered. You need help. It is a very complex field and one where many factors need to be considered and you need a partner with a feel for what is important and what can be ignored.

In an ideal world you have a hot dry gas going to atmosphere and you cool it down using one of our cross flow heat exchangers to heat an incoming stream. The heat transfer is forced convection and the duty is straight forward.

At the other extreme you have a hot gas laden with dust and you need to cool this down and use the heat. On this occasion you need to use one of our direct contact heat exchangers, where the hot gas passes through a shower of liquid.

Between these two extremes lies the real world where most problems lie.

So what do we need to know? Well, the quantity of stack (or waste) gas (Kg/hr) and its temperature are a good start. Also its composition. Are halides present. As an example, common stainless steels do not like chlorides. You need also to consider what you are going to use the recovered heat for. Ideally you need to put it back into the process by for example pre-heating an input stream but as a last resort it can be used for heating water to clean an area.

Identifying the best use of heat in a process can be very complex and to achieve optimal results, must consider a wide range of factors, ranging from identifying heat sources and demand, through to how it will affect the process control. Upfront planning and working closely with thermal design engineers can pay dividends.

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