When to Use a Clean Steam Generator for Humidification

August 12, 2015  |  Eric Erpenbeck, Mechanical Engineering Manager

Steam generation often requires chemical injection into the steam distribution piping in order to neutralize the mild acids that occur from condensing steam.    When the steam system serves humidification loads for space air quality, Owners are forced to decide whether to directly inject steam into the air stream or isolate the chemical with a clean steam generator.

Understanding Your System

With the improvement of water treatment processes such as reverse osmosis units and FDA approved chemicals, many institutions are using direct steam injection.  However the costs of operating new central plant equipment as well as the additional costs for FDA approved chemicals are growing.  In addition to the increased central plant maintenance costs, another disadvantage of direct steam injection is a decrease in condensate return which results in a reduction of system efficiency.

Another option is to install a clean steam generator (also called a steam to steam heat exchanger).  With a clean steam generator, all humidification related condensate is returned to the central steam plant, while potentially eliminating the need for high end FDA approved chemicals.

Weighing the advantages

Depending upon the existing central plant water treatment equipment, capital and maintenance costs of a clean steam generator can be higher as more equipment and controls are required, however these additional costs can be outweighed by the operational savings of makeup water and chemical costs in the central plant.

The right answer for a given facility always depends on its unique circumstances. Maintenance personnel usually want to use direct injected steam, preferring to avoid the extra equipment (and extra upkeep) associated with a clean steam generator. The central plant, on the other hand, usually prefers the use of clean steam generators which return condensate and reduce the need for more makeup water as well as help reduce total chemical costs.

Generally, clean steam generators are more cost-effective for the long-term use.  Savings on chemicals and condensate return for the entire steam system will often exceed additional capital and maintenance costs associated with clean steam generators.  However, those considering a clean steam generator should consider their ability to maintain it, the health and comfort requirements of your facility, and the prospect for savings over the long term. After careful cost analysis, you may find that it is a worthwhile investment.

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