e) sewage treatment plant sludge digester heating (engine fired on
digester gas), and
process heating and hot water use.
high temperature hot water heating (and district heating)
absorption chillers, and
additional power generation.
188.8.131.52 Steam. Steam, measured in pounds per square inch (lb/in2) or
kilograms per square centimeter (kg/cm2) is produced in heat recovery
boilers and is usually generated at about 125 lb/in2 (8.79 kg/cm2) for
larger systems. It is possible to generate steam at higher pressures;
however, the highest operating steam temperature is limited to about 100deg.
F (38deg. C) below the exhaust temperature. The most cost-effective steam
conditions for heat recovery may be saturated 15 lb/in2 steam (1.05
kg/cm2). Care must be taken in design of heat recovery systems to insure
that the exhaust temperature is above the dew point. This usually limits
the minimum exhaust temperature to between 300deg. F (148deg. C) and 350deg.
F (177deg. C). Economic analysis of design options will assist in selecting
the best configuration. Some of the uses for cogeneration steam are:
d) steam turbine drive and combined cycle applications (such as
back pressure turbines with steam exhausted to other uses,
f) condensing turbines with condensate cycled back to heat
recovery boiler feedwater, and
process steam uses.