Indirect Air Heater Overview
Indirect air heaters are used as the hot air source to dry chemically sensitive products. In order to effectively heat the end product and avoid contamination by the products of combustion, indirect fired air heaters use a heat medium, such as a heat exchanger, to transfer heat to the end product. By using heat exchangers, indirect fired air heaters can provide relatively high thermal efficiencies. Stelter & Brinck’s Indirect Air Heaters are 72-90% thermally efficient, depending upon the application.
These process heaters are mainly used in food, chemicals, pharmaceuticals, and other product manufacturing where the taste, look or feel of the end product may be altered by combustion flue gases or particulates. For example, in cigarette manufacturing, the paper must be flavored using tobacco extracts or else the taste will be inferior. However, before being applied to cigarette paper, the extracts must first be spray dried to a powder form. In order to create the “smooth” smoke taste that tobacco is known for, the spray driers use indirect fired process air heaters as their heat source. Because indirect fired air heaters do not contaminate the airstream with the by-products of combustion the tobacco flavor remains “pure”.
Indirect fired air heaters are used in conjunction with fluid bed dryers, spray dryers, and air cap dryers, among various other applications. Not only are indirect fired air heaters ideal for applications in which the product is chemically sensitive, but indirect heaters are also good for products that need temperature uniformity.