Recovering condensate can lead to considerable energy and water savings in any industrial plant using steam, in addition to improving process working conditions.
An efficient condensate return system is necessary to transport the condensate from the steam-using equipment to the boiler.
Keep in mind that the condensate has already been treated for use in a boiler and contains useful heat. It would be a great waste not to reuse it. This reuse of condensate reduces the amount of heat that the boiler will have to provide to convert it back to steam and reduces the chemicals needed to treat the water, which also prevents the steam system from accidents.
Condensate return systems can be divided into three main categories:
Blowdown lines to traps (a).
Unpumped discharge lines from the traps (b).
Pumped return lines (c).
Blowdown lines to traps
Condensate flow from process equipment to its steam trap is usually by gravity. The condensate return system for this piping can be sized for practical purposes to the same size as the trap, assuming the trap is sized correctly. The trap should be mounted a minimum of 200 mm below the equipment being trapped to provide a column of water above the trap.
Unpumped discharge lines
On the discharge side of the trap, the condensate lines should carry the condensate, as well as any uncondensable gas carried through the process, and the revaporate released from the condensate by the pressure drop as it passes through the trap.
Regarding the revaporate, remember that when steam releases its specific enthalpy of evaporation, condensate is formed at the same temperature and pressure as the steam from which it condenses. When this condensate is discharged at a lower pressure, the energy it contains is greater than that which it can sustain while remaining liquid.
Pumped return lines
Unpumped condensate lines, individual or common, are often connected to a receiver tank, and then pumped back to the boiler.
The pumps do not run continuously, and usually have an on/off type of drive. This must be taken into account when sizing the condensate piping from the pump, because the discharge velocity of the pump will be higher than the actual condensing velocity of the process equipment. Depending on the pump type this discharge rate can vary from 1.5 to 6 times the actual condensing rate.
Long pumped supply lines also require special attention if water hammer is to be avoided in them. Water being pumped can gain a significant amount of movement and can continue to move through the pipeline when the pump stops. This can create an area of low pressure in the pipeline, behind the moving water pocket, which can cause a reverse flow when the amount of movement has been exhausted. To prevent this, a suitably sized vacuum breaker can be mounted at the start of the discharge line, along with a check valve to protect the pump.
The Water Harvesting Solutions (Wahaso) team brings experience, expertise and a passion for water conservation to every customer project. We incorporate a holistic approach to system design and construction, working to integrate multiple renewable water sources along with multiple uses of treated water to maximize overall water savings.
You can contact us through our phone number 800-580-5350 or review all of our equipment and merchandise in stock through our website https://wahaso.com/ and if you are interested in doing a project with us, you can get a free quote through https://wahaso.com/free-estimate/.