Types of Condensate Recovery Systems
Most steam-using equipment generates large quantities of condensate. Although reusing this condensate as boiler feed water or for cleaning offers many advantages, choosing the right type of system can be difficult. The following article introduces various types of condensate recovery systems in use today to help with the selection process.
Condensate Recovery Methods
The progressive development of newer tools and methods used for condensate recovery has lead to ever more efficient and economical systems.
Positive Pressure Condensate Recovery
The simplest method of condensate recovery dates as far back as the first half of the 19th century, when steam traps were first invented. This method, also known as 'positive pressure condensate return', uses steam pressure at the steam trap inlet to pump the condensate towards the area where it is to be reused.
No special equipment is required, so this condensate recovery method can be implemented quite easily. However, the height and distance accross which condensate can be transported is limited by trap inlet steam pressure.
Condensate Recovery Using a Centrifugal Pump
Centrifugal pumps have been used in condensate recovery applications since the early 1900’s. Condensate is first collected in a condensate tank, and then pumped using a centrifugal pump to the location(s) where it is to be reused. Advantages of using this method include the ability to recover condensate over farther distances and greater heights, and the fact that it is not dependant on steam pressure at the inlet of the steam trap.
Using a centrifugal pump enables large amounts of condensate to be recovered for reuse even in areas with higher pressure (depending on the capacity and lift head of the centrifugal pump). Pumps with a high lift head also make it possible for the recovered condensate to be directly used as boiler feed water.
One problem associated with this type of pump is cavitation, which can impair discharge performance. Cavitation occurs inside the pump if there is not enough pressure from the water head. So when pumping high temperature condensate, a water head of 3-5 m [10-16 ft] is usually required.
Condensate Recovery Using a Mechanical Pump
In the mid 1900’s, a mechanical pump was developed that uses gases such as steam or compressed air as the motive medium for pumping condensate. This was in part created to solve the problem of centrifugal pump cavitation. When mechanical pumps are used, centrifugal force is not involved so there is no danger of cavitation. Furthermore, this pump does not need electricity so this type of pump also has the benefit of being suitable for use in explosion-proof areas.
The popularity of mechanical pumps has increased in recent years because of greater variety in options available such as models with built-in steam traps and larger discharge capacities.
Specialized Condensate Recovery Pumps
A specialized condensate recovery pump was developed around the same time as the mechanical pump. Its conception is based on the installation of an ejector at the inlet side of a centrifugal pump to solve the problem of cavitation. The ejector forces pressurized high temperature condensate into the centrifugal pump and makes condensate recovery possible without the fear of cavitation even at filling heads of approximately 1 m [3 ft].
In addition to enabling the direct recovery of high temperature condensate back to the boiler, other important benefits of a condensate recovery pump include reduced space requirements, lower labor costs, and no necessity to use an elevated tank. All these features and more made this a widely popular and extremely effective energy-savings measure during the oil crisis in the 1970’s. This pump still remains a mainstream tool for condensate recovery applications for closed systems that recover high temperature condensate directly to the boiler.
For more details on how to decide the most suitable type of condensate recovery system for your factory or plant, refer to the next article on Open vs. Closed Condensate Recovery.
|Introduction to Condensate Recovery||Open vs. Closed Condensate Recovery|