When absorption chillers were first introduced, steam from an external source was used to concentrate the lithium bromide. Over the years, direct boiling of the diluted bromide has become the method of choice, and this is what is used in today’s absorption chillers.
The entire absorption chiller seems very simple, mechanically. Pumps are needed to circulate the bromide and water. A heat source is required. Heat exchangers, spray trees, tubing bundles, electrical controls, etc., complete the system. The entire operation depends upon circulating the right mix of water and lithium bromide through unobstructed piping. But there is another aspect of the absorption chiller that literally fouls up the workings of the chiller — corrosion. Lithium bromide, a highly corrosive brine, readily attacks ferrous metals such as steel.
The corrosion process generates hydrogen gas that reduces the internal vacuum inside the chiller. With the reduction in vacuum, the unit operates poorly. In addition, the debris resulting from the corrosion fouls narrow openings in spray headers, heat exchangers, etc.
Proper operation of absorption chillers, therefore, does not merely depend upon servicing the mechanical aspects of the unit. An understanding of lithium bromide chemistry is also required...
...This is, then, the chemical mechanism whereby lithium bromide attacks the internal metal components of absorption chillers. It cannot be ignored because the action creates havoc on the workings of the unit. Owners and operators of absorption chillers must deal with its chemistry as well as its mechanical systems.