Condensate Return

Over the last couple months, we’ve been focusing on boilers; specifically, we’ve talked about boilers based on fuel options, and we’ve also discussed determining capacity needed.  Today I want to talk about improving your boiler’s efficiency, and one way to do that is to monitor the condensate returned to the boiler with a goal of maintaining a return temperature of around 180 degrees.

Let’s dive into specifics.  One type of energy steam contains is latent energy or latent heat.  According to mobile-dictionary.reverso.net, latent heat is the heat evolved or absorbed by unit mass or unit amount of substance when it changes phase without change of temperature.  In a dry cleaning plant, when steam is supplied to a process, the steam releases latent energy to supply the piece of equipment with the steam it needs to function and then condenses to a liquid condensate.  That condensate still has energy, and if pumped back into the boiler, makes the boiler run more efficiently.  How?  First, less new make-up water is required, which helps keep water costs down.  Second, that water is already hot, so less energy is required to heat the water.  Third, most of the corrosive dissolved Oxygen has been removed from the water, reducing system corrosion.

Do these three things to make sure your plant is set up properly:

• Always T upwards off of the supply and return header to the equipment connections
• Always put a check valve after every steam trap
• Confirm that all steam traps are in good working condition

This last point is exceptionally important as equipment will not work properly without steam supply and as a result, it’s constantly blowing steam by heating the condensate return system above the 180 degree target temperature.  Then the pump can’t pump water into the boiler at over around 200 degrees so it takes longer to fill the boiler which equals more cost to run the pump longer. Also, remember that increased return water temperature equals malfunctioning steam traps that allow steam to blow through the trap and heat the return water.  This can result in more than 14% flash steam loss.  It’s basically like you’re putting a brick on the steam pedal of a puff iron, and its blowing steam all the time the boiler is up to pressure.  Double utility cost hit when the steam is blowing by heating the return water which causes the pump to run longer using more electricity and the boiler to cycle more often because the pressure is being lost through the malfunctioning steam trap. All this can be detected by checking the return tank water temperature, if you are regularly running over 185 degrees.