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Gas-to-Gas Heat Exchangers

The same design that is used in a Ljungström® Air Preheater can be used for another purpose in a power plant. Downstream of the Ljungström® Air Preheater, there are several pieces of equipment designed to clean up the flue gas before it exits the power plant through the stack. At each step, the flue gas loses some heat. If it loses too much, by the time it reaches the stack it does not have enough energy to disperse properly. A power plant that has its discharge settle as a cloud over a residential area is in serious trouble.

That is what a Ljungström® Gas-Gas heater is used to prevent. Located just before the stack, the unit salvages heat from the flue gas just before it goes into the scrubber (which removes sulfurs) and then puts it back into the cleaned flue gas. This provides the cleaned flue gas with enough heat to rise out of the stack and disperse.

Ljungström® Gas-Gas heaters tend to be shallow, as the amount of heat transferred is relatively small compared to the air preheaters. There are also two other main diferrences.  The Ljungström® Gas-Gas heater operates in very low temperatures. The combination of low temperature and sulfur content require the unit to be designed with the consideration that there will be a significant amount of sulfuric acid condensation. For this reason, we used enameled element and flake glass lining to prevent the equipment from corroding away.

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