Heat Recovery

There are numerous manufacturing processes in industries that use relatively low temperature heat (under 250F), either in the form of hot water or low-pressure steam. Don't become biased just because many of these processes start with boiler steam at 100 to l50 psig. This is done to reduce steam transmission pipe size and cost, and as a matter of convenience or routine past practice. The actual heating is achieved by throttling the steam down at the using level.

In general manufacturing (usually the machinery or metal fabricating industries), these processes most often fall into these categories:

• Evaporation or concentration
  
• Parts washing
  
• Solution heating and cooling
  
• Degreasing
  
• Dehumidifying
  
• Process feedwater heating
  
• Boiler feedwater heating
  
• Hot water for space heating, shower rooms, cleanup, and other domestic housekeeping needs.

Many of these requirements can be met in part or in whole by reclaiming waste heat now being discharged to drain, using heat exchange, heat pumping, or a combination of both. The principal sources of waste heat in these plants include:

• Cooling (mill) water rejecting heat from air compressors, billet heaters, injection molders, refrigeration equipment, electric welders, dynamometers, extruders, air conditioners, and the like. This waste heat is usually rejected to the atmosphere using evaporative or dry-air coolers or cooling towers, or sent to drain.
  
• Refrigeration equipment rejecting heat directly to evaporative condensers.
  
• Warm water effluent from plant processes being sent to drain or to wastewater treatment plants.
  
• Excess low-pressure steam being vented to atmosphere or inefficiently used.
  
• Hot exhaust vapors being directly vented or sent to air-cooled or barometric condensers.

The following additional heating and cooling process applications represent heat exchange, heat recovery, and heat pump opportunities:

• Automotive Industry : Phosphate system heaters, plating solution coolers, paint coolers, welding and induction furnace water coolers.
  
• Metalworking Industry : Anodizing solution coolers, copper zinc, tin, and chrome plating coolers, quench oil coolers, pickling solution, and oil coolers.
  
• Steel Industry: Furnace, rolling mill, and continuous slab caster coolers, as well as scrubber and mold water coolers.
  
• Copper Industry : Electrolyte solution heaters and interchangers, sulfuric acid coolers, leach solution heaters and coolers, liquor coolers, as well as ammonia solution heaters and coolers.

And Furthermore . . .

Heat Exchangers Heat Exchanger Calculations Process Hot Water Solvent Degreasers	Thermal Storage Steam Recompression Metal Finishing Auto Paint Spray Booths
Evaporation and Concentration