5.2 Indirect Heating of Thermal Fluids
Many operations, requiring energy delivery to a liquid-phase (and/or fluid) stream, require a physical barrier between the fossil combustion products (energy release) and the process stream.
5.2.1 Process Uses
Processes that use high (and/or variable) pressure systems, separation/purification operations, multiphase operations, systems impeded by oxidation (or other possibly reactive/degrading components of combustion), and strictly maintained closed-loop systems are common boundaries to direct heating of process streams. More specific operations include:
- Purification, recovery, and separations.
- Chemicals and refinery distillation towers, reboilers, and flash evaporators for polymer processing, slurry separations/purification, brine treatment, etc.
- Pressurized process streams (in chemical reactors, etc.).
- Processes and products sensitive to oxidation, other reaction-driven degradation, and/or general fouling (in chemical, food, pharmaceutical processing, etc.).
- Vat or batch systems maintaining a heated fluid (such as paint/dye blenders, food deep fryers, refinery-bottoms
storage and subsequent processing, reactor/fermentation vessels, crystallizers, etc.).
- Thermal fluid, closed-loop-heating systems for processes requiring especially high and smoothly controlled
- Systems requiring high temperatures over large areas such as calcium chloride crystallizers.
- Pipe line tracing.
- Distillation and reactor feed lines whereby preheating feed components simplifies the energy delivery and/or chemistry complexity of any downstream operation.
- Heat tracing viscous material (crude, confectionery, polymer melts, etc.) pipelines to reduce electric-driven pumping rquirements.
- Tool heating (including plastics/rubber extruders, molds), paper mill platens and rollers, metal fabrication equipment, laminate setting, and others.
- General polymer processing. Polymer processing plants may require high temperature (> 400 °F) energy delivery to several unit operations because of high “pure” polymer melting points (maintained for extrusion, molding, etc.), and endothermic and/or equilibrium limited reactions (whereby light byproducts, often water, must be continuously evaporated and removed for effective/efficient reactor output). Polyester and Nylon are good examples of major international commodities often utilizing thermal fluids systems throughout their production cycle.