Page 294 - Sustainable On-Site CHP Systems Design, Construction, and Operations

Operation and Maintenance Services 267

The HRSG may also have a separate superheater section and an economizer. Like any
boiler, it is very important to maintain a reliable water conditioning system to control
scale build up. The CHP plant operators must test and chemically treat the HRSG water
on a daily basis.
Further, like any boiler, the HRSG must be opened for cleaning and inspection once
a year. There are many installations where air quality regulations require a significant
reduction in exhaust emissions. In these cases, catalysts are often installed in the HRSG.
The catalyst sections should be visually inspected and a section should be removed
and tested in a laboratory to determine the remaining service life. The NO catalyst
x
requires ammonia injection and the delivery and injection system must be cleaned and
inspected periodically.
STG
In addition to the schedule in Table 16-1, the steam turbine internals must also be
inspected periodically. The frequency of the inspection depends on the steam conditions
and operation, but, if possible, should not exceed 3 years (see Table 16-2). It is important
to check the lube oil system for proper level and quality before starting the unit and
while it is in operation.

Steam Turbine Chillers and Absorption Chillers
Maintenance requirements on steam turbine–driven centrifugal chillers are identical to
the STG on the turbine side. The chiller end must be leak checked and maintained with
the proper amount of refrigerant. The evaporator and condenser heat exchangers must
be cleaned and inspected at least once a year. Condensing water must be provided and
maintained at the proper temperature to achieve the overall efficiency of the chiller. If a
cooling tower is used, the operator must maintain an effective water conditioning and
chemical treatment program to protect the condenser tubes from fouling and corrosion.
Maintaining absorption chillers is unique in that it has no internal moving parts. A
constant flow of water through the evaporator and through the condenser will main-
tain a stable heat transfer process within the unit. Since steam or hot water is used to
separate the water and lithium bromide in the generator section, the heat transfer in the
condenser is greater than with centrifugal units, therefore the cooling water supply is
even more important.

Plant Auxiliaries
A CHP plant has a number of auxiliary systems that support the CTG, engines, genera-
tors, and HRSG, or hot water heat recovery unit. Most of the equipment is common to

Maintenance
Annual permit inspection
Open all ducts—inspect, for loose insulation, all internal panels, catalyst and clean
Drain and open mud and steam drums and clean
Replace safeties (send out existing for recertification)

TABLE 16-1 Typical HRSG Maintenance Schedule