What defines a waste heat boiler?

A waste heat boiler is fundamentally characterized by its function as a heat exchanger that utilizes hot gases or liquids produced during industrial processes. The primary purpose of this type of boiler is to capture and repurpose waste heat that would otherwise be emitted into the atmosphere or lost in the industrial operation. By doing so, it enhances energy efficiency by converting residual thermal energy into useful steam or hot water.

This process typically involves the hot exhaust gases generated from combustion processes—such as those from turbines or internal combustion engines—passing through tubes within the boiler. As these gases flow through, they transfer their heat to the water or another medium circulating in a closed loop, effectively producing steam or heating water for various applications. This method not only conserves energy but also reduces operating costs and environmental emissions.

The other options provided do not accurately describe the defining characteristics of a waste heat boiler. The focus on solid fuels or the recycling of steam does not capture the primary mechanism of utilizing waste heat from industrial processes. Additionally, while some waste heat boilers may have unique designs, this is not a defining feature, as their fundamental operation remains centered on heat exchange efficiency.