Controlling temperatures in chemical processing is one of the most essential aspects of the entire procedure. By simply reducing or increasing the temperature by a few degrees during chemical processing, dramatic effects and reactions can occur to the end product, the National Renewable Energy Laboratory reported.
The chemical industry relies on cooling and heating of base, intermediate and final products. Additionally, heating, cooling and reheating processes in containers, reactors and autoclaves is necessary for most chemical processing plants.
Many facilities in the industry use shell and tube chemical heat exchangers for a wide variety of duties including:
- Cooling products that are high in viscosity, such as latex.
- Heating, cooling and reheating solvents such as toluene, which is often used in paint thinners.
- Heating and cooling different solutions and acids and bases such as sodium hydroxide.
- Reducing any contamination between solutions or solvents.
Chemical processing is dependent on heat transfer from a temperature gradient and fluid flow velocity through heat changers, the Rensselaer Polytechnic Institute reported. However, heat exchangers can also be used for boiling or condensing specific solutions or acids to get them to more accurate levels.
"As the equation shown above, the heat transfer area (or contact area) is directly proportional to the heat transfer rate," the Rensselaer Polytechnic Institute stated. "If the heat transfer area increases, heat transfer rate increases as well. A common way to increase heat transfer area is adding fins to the surface. It is cheap to put fins to the heat transfer area but fins also increase fouling, especially in bio-process."
Controlling reactor temperatures
Reactor temperatures also have to be controlled in chemical processing. The temperature can affect numerous qualities such as the production rate, operating costs and the final product, Chemical Processing reported.
Continuous reactors are used to keep temperatures steady without oscillation, which can be achieved by using heat exchangers to maintain the jacket temperature on the reactor. Additionally, reactors need to limit operator intervention significantly and to trim down the consumption of utilities.
However, batch reactors need fast heat up or cool down processes and to control the response to load disturbances, the source reported. To meet the requirements of these chemical processing standards, chemists have to closely observe equipment temperatures to make sure the end product is not damaged.
The National Renewable Energy Laboratory explained that heat exchangers are used for batch reactors with a pump-around loop to control the temperature and agitate the process, as well.