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The unsung hero of boilerhouse efficiency

08 May 2018

Chris Coleman argues that truly efficient condensate recovery can boost productivity and improve regulation, at a much lower cost to steam users in the food industry. 

Boilerhouse managers and operators constantly battle with rising energy prices and so reducing energy consumption is at the top of most wish lists as it is no longer enough to strike a good deal on energy supplies or achieve high levels of productivity. Today there is an expectation to do both, while complying with a complex web of regulation. Striking the right balance can make a crucial, tangible contribution to revenue flow, but, with ageing equipment and economic uncertainty coming into play, this is virtually impossible to achieve. Until, that is, you consider the use of condensate and the heat that may otherwise be wasted.

The value of condensate
While it is widely known that condensate is hot, it is often not considered as a useful resource. Condensate generated by a steam heating system will normally have about 25% of the energy that the steam had, and contains little to no dissolved solids.

Draining condensate, rather than re-using it, can trigger water and effluent management costs, which can be significant. Similarly, draining condensate can make it harder to comply with the regulatory standards around environmental effluent. In many countries, including the UK, condensate often has to be cooled before it can be drained which, again, will come at an extra cost.

Recovering and re-using as much condensate as possible can offer financial advantages. 

Condensate – and the heat energy it carries – is too valuable to be tipped down the drain. But how can it be put to better use?

• Boiler feedwater: If condensate is not used as feedwater, the boiler must be topped up continually with cold water. This is costly in terms of both water and energy because the cold feedwater needs to be heated. In contrast, condensate is already hot, which reduces the need for (and cost of) fresh water and treatment chemicals. It also requires much less energy than cold make-up water does to be ready for use.

• Flash steam recovery: Flash steam can be harvested and re-used. This is formed when high pressure condensate is exposed to a large pressure drop, often created during the blowdown process. A flash vessel is just one method that can be used to recover energy by separating flash steam from condensate. As condensate enters the flash vessel, flash steam is produced and can be piped from the top of the vessel to the feedtank through the deaerator.

The use of both a flash vessel and plated heat exchanger pack will allow up to 80% of the energy from the rejected Total Dissolved Solids (TDS) water to be recovered which can also result in fuel savings, a reduction in carbon dioxide emissions, and the elimination of unsightly plumes of steam.

The recovery process
In the food industry, steam is mostly generated for process. How it is recovered can broadly be summarised in three important steps.

1. Steam traps are used to remove condensate from the steam system.  A steam trap survey can often offer some invaluable insight into the performance of a given system, and will almost certainly reveal impressive savings potential through reduced fuel consumption, fuel emissions, water, and effluent charges.

2. Pumps are used to return any condensate not captured by steam traps to the boiler feedtank.

3. Condensate is mixed with other types of feedwater to heat it within the feedtank.

Condensate recovery is a process that is genuinely capable of boosting boiler efficiency, saving energy, enhancing equipment lifespan and complying with legislation – all of which can generate substantial savings.

A report  – The unsung hero of boiler house efficiency: How condensate recovery can transform steam system performance –  is available to download at http://sxscom.uk/boilerhouseefficiency

Chris Coleman is boilerhouse national specialist at Spirax Sarco.


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