Process heaters – are the units used at oil refineries for heating process mediums utilizing the heat released in the process of the fuel combustion. Process heaters in oil refineries fall into tube heaters and gaseous, liquid, and solid production waste incinerators.
Depending on a heat transfer mode, configuration and number of combustion chambers, position of burners, and the number of process streams and the type of heat flux to tubes, tube heaters fall into the following types:
- Vertical – cylindrical with bottom burners of radiant and radiant-convection types;
- Box-type with the bottom position of burners and upward combustion gas withdrawal and with vertical or horizontal radiant wall tubes;
- Narrow chamber type with an upward withdrawal of combustion gases and central horizontal radiant tubes;
- Sectional or cylindrical heaters with a coiled tube and bottom burners;
- Multi-chamber box heaters with vertical coiled tubes and a common convection.
Box tube heaters are intended for heating raw hydrocarbon fluids and various heat transfer agents. Heaters are fabricated as per individual designs, taking into consideration their thermal efficiency and local conditions.
The so-called “soft lining” and thermal insulation allow manufacturing fully prefabricated heaters, decreasing the heater thermal inertia and heat loss. The heater design provides an easy access for inspections and repairs of coiled tubes. The heaters are outfitted with up-to-date short-flame burners. Spraying of liquid fuel and feed of air are performed by high-pressure fans, though the heaters can operate using the stack effect.
Depending on the design, the burners can be located in the heater bottom part or on the sides. If necessary, an extra coil can be installed in the heater for steam overheating and air heating. The heaters are outfitted with instrumentation and controls and firefighting equipment as per the effective regulations.
