Unsung hero of boiler house efficiency

It’s no longer enough to strike a good deal on energy supplies or achieve high levels of productivity: now we are expected to do both, while complying with a complex web of regulation. Striking the right balance can make that crucial, tangible contribution to your company’s revenue flow, but, with ageing equipment and economic uncertainty coming into play, the potential to achieve precisely that is virtually impossible. That is, until we consider our use of condensate and the heat we may have otherwise wasted.

The value of condensate 

While it is widely known that condensate is hot, it’s only when we consider how this translates to heat energy that we realise how useful it is as a resource. The condensate generated by the 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 often come at an extra cost. 

We might now realise that 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 feed water

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 must 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 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 you to recover up to 80% of the energy from the rejected Total Dissolved Solids (TDS) water, which can also result in fuel savings, a reduction in carbon dioxide emissions, and elimination of unsightly plumes of steam. 

Recovery process

As you’re aware, steam is usually generated for most industrial and process industries. How it is recovered can broadly be summarised in three important steps.

•  Steam traps are used to remove condensate from the steam system.  

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

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

Rising energy costs are having a major impact on all types of businesses across every industry. Saving energy from condensate is a simple, yet highly effective technique. It may not be the protagonist or the leading role in the steam system, but I believe it is the unsung hero of the boilerhouse.

Spirax Sarco’s full report, The unsung hero of boiler house efficiency is available to download: http://sxscom.uk/boilerhouseefficiency" http://sxscom.uk/boilerhouseefficiency.