A quick guide to condensate recovery
One of the best energy-saving measures for most steam systems is returning condensate to the boiler instead of dumping it to drain. Installing condensate recovery systems or enhancing existing systems are highly effective in improving steam plant efficiency. Here’s an overview of condensate recovery and why it deserves your attention.
What is condensate?
Condensate is purified water. It is distilled water. It may have some chemical treatment left in it which in itself is valuable. Most of all, it is hot water. It is fairly obvious that it is less expensive to regenerate hot condensate back into steam than it would be to heat cold makeup water into steam. Every BTU (heat energy) is valuable and that which remains in the condensate is no exception. In the past, the focus of condensate removal was generally in main steam process areas only. Condensate contains heat, chemicals and water. It is usually as much as one third of the cost of generating steam!
Where else can I return condensate?
Condensate from light load locations are definitely places worth considering, such as Drip and Tracer lines. Generally, condensate from these location have not been widely returned, mainly because the loads at a drip station are low for each location, but when the number of locations are counted, the amount of returnable condensate can be surprisingly high.
Why return condensate and reuse it?
There are too many advantages to return condensate, the list below is just a few reasons that might just get you started.
Financial reasons: Condensate is a valuable resource and even the recovery of small quantities is often economically justifiable. The discharge from a single steam trap is often worth recovering.
Un-recovered condensate must be replaced in the boiler house by cold make-up water with additional costs of water treatment and fuel to heat the water from a lower temperature.
Water charges: Any condensate not returned needs to be replaced by make-up water, incurring further water charges for the local water supplier.
Maximizing boiler output: Colder boiler feedwater will reduce the steam rate of the boiler. The lower the feedwater temperature, the more heat, and thus fuel needed to heat the water, thereby leaving less heat to raise steam.
Boiler feedwater quality: Condensate is distilled water, which contains almost no total dissolved solids (TDS). Boilers need to be blown down to reduce their concentration of dissolved solids in the boiler water. Returning more condensate to the feedtank reduces the needs for blowdown and thus reduces the energy lost from the boiler.
How to recover condensate?
Steam Traps retain steam within the process for its heat, while releasing condensate and incondensable gases as needed.
Condensate should ideally run away from a steam trap by gravity – but often it needs to be pumped using electrical or mechanical condensate pumps.
Automatic pump traps act as conventional steam traps, but when back pressure rises, pump traps automatically switch to pumping mode to remove condensate.
A deaerator head is important to mix returned condensate, flash steam and cold make-up water as they are fed into the feedwater tank.
Flash steam is released from hot condensate when its pressure is lowered. Use it, don’t waste it. Collect in a flash vessel and use for heating, and recover any associated condensate.
Closed-loop, pressurized flash steam recovery allows virtually all the energy from both the condensate and its flash steam to be used, reducing steam-raising costs and increasing boiler efficiency.
Use condensate and flash steam from boiler blowdown to heat the boiler feedtank.
When should I return condensate?
The return of condensate obviously has too many advantages that simply shouldn’t be ignored. No matter how much condensate your company generates per day it should never be put to waste. So start today and stop throwing your money down into the drain!
A good start point to improve condensate recovery is to commission a professional steam trap survey to identify where improvements could be achieved. The survey will give an estimate of the potential financial gains through upgrades–providing information to justify maintenance budgets.
Content provided by Spirax Sarco, originally published in Steam News Magazine.