An Explanation of Industrial Process Heating Technologies

Boiler providing steam for process heat.

Process heating technologies can be grouped into four general categories based on the type of fuel consumed: fuel, steam, electric, and hybrid systems (which utilize a combination of energy types). These technologies are based upon conduction, convection, or radiative heat transfer mechanisms - or some combination of these. In practice, lower-temperature processes tend to use conduction or convection, whereas high-temperature processes rely primarily on radiative heat transfer. Systems using each of the four energy types can be characterized as follows:

Fuel-based process heating systems generate heat by combusting solid, liquid, or gaseous fuels, then transferring the heat directly or indirectly to the material. Hot combustion gases are either placed in direct contact with the material (i.e., direct heating via convection) or routed through radiant burner tubes or panels that rely on radiant heat transfer to keep the gases separate from the material (i.e., indirect heating).  Examples of fuel-based process heating equipment include furnaces, ovens, red heaters, kilns, melters, and high-temperature generators.

Steam-based process heating systems introduce steam to the process either directly (e.g., steam sparging) or indirectly through a heat transfer mechanism. Large quantities of latent heat from steam can be transferred efficiently at a constant temperature, useful for many process heating applications. Steam-based systems are predominantly used by industries that have a heat supply at or below about 400°F and access to low-cost fuel or byproducts for use in generating the steam. Cogeneration (simultaneous production of steam and electrical power) systems also commonly use steam-based heating systems. Examples of steam-based process heating technologies include boilers, steam spargers, steam-heated dryers, water or slurry heaters, and fluid heating systems.

Electricity-based process heating systems also transform materials through direct and indirect processes. For example, electric current is applied directly to suitable materials to achieve direct resistance heating; alternatively, high-frequency energy can be inductively coupled to suitable materials to achieve indirect heating. Electricity-based process heating systems are used for heating, drying, curing, melting, and forming. Examples of electricity-based process heating technologies include electric arc furnace technology, infrared radiation, induction heating, radio frequency drying, laser heating, and microwave processing.

Hybrid process heating systems utilize a combination of process heating technologies based on different energy sources and/or heating principles to optimize energy performance and increase overall thermal efficiency. For example, a hybrid boiler system may combine a fuel-based boiler with an electric boiler to take advantage of access to lower off-peak electricity prices. In an example of a hybrid drying system, electromagnetic energy (e.g., microwave or radio frequency) may be combined with convective hot air to accelerate drying processes; selectively targeting moisture with the penetrating electromagnetic energy can improve the speed, efficiency, and product quality as compared to a drying process based solely on convection, which can be rate-limited by the thermal conductivity of the material. Optimizing the heat transfer mechanisms in hybrid systems offers a significant opportunity to reduce energy consumption, increase speed/throughput, and improve product quality.

For more information, visit www.ivesequipment.com or call (877) 768-1600.

Understanding Condensate Pumps on a Steam Distribution System

Diagram of industrial steam system
(courtesy of Watson McDaniel)

A condensate pump is a type of pump used to pump the condensate (water) produced in an industrial steam system. The primary application for the condensate pump is pumping condensate from a process application or condensate collection area back to the condensate return system.

In certain cases, the steam pressure of the system may be sufficient to push the condensate through the steam traps and condensate return lines, back to the condensate holding tank in the boiler room. In most practical situations, however, one or more condensate return pumps are required to assist in overcoming gravity, pressure drops from long piping runs, and back pressures in return lines.

Condensate Return Pumps are either electrically-driven centrifugal pumps or non-electric mechanical pumps that use steam pressure as the motive force to pump the condensate. Non-electric pumps are referred to as Pressure Motive Pumps (PMPs).

A facility will often have a separate area that contains various components required for the generation of steam, such as a boiler, condensate holding or deaerator (DA) tank, boiler feed pump, water treatment, etc. Regulated by the boiler control system, the boiler feed pump sends condensate from the holding tank back to the boiler.

Pressure Motive Pumps (PMPs) are non-electric pumps which return condensate back to the boiler room; using steam pressure as the motive force. PMPs can be supplied as stand-alone units – which include a pump tank, the internal operating mechanism, and a set of inlet and outlet check valves, or: as a packaged system – which also includes the vented receiver tank (to collect the condensate) mounted on a common base.

The following is a comprehensive document, courtesy of Watson McDaniel, that provides a good general understanding of steam and condensate systems, traps and condensate pumps. 

Understanding Condensate Pumps on a Steam Distribution System from Ives Equipment

For more information, contact:

Ives Equipment
www.ivesequipment.com
(877) 768-1600