Performance Testing of Heat Recovery Steam Generators

1 августа, 2013

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There are major differences in the way the HRSGs behind GTs are tested compared to conventional boilers, even WHRBs. The HRSG is treated as part of a combined cycle power plant (CCPP) instead of a stand-alone steam generator.

• For HRSGs behind GTs PTC 4.4 is applied and not PTC 4.

• The performance test is a direct test.

TABLE 1.8

Differences in Measurements of Losses and Credits between PTC 4.1 and PTC 4

Loss	PTC 4 Item	PTC 4.1	PTC 4.1 Abb. Test	H/Cp Potential Difference	Notes
1a	Dry gas loss	Yes	Yes	Yes	—
1b	Moisture loss from H2 and H2O	Yes	Yes	No	No change
1c	Moisture in air loss	Yes	No	No	No change
	H2O vapor in fuel loss	No	No	—	New item
2	Unburned carbon loss	Yes	Yes	—	No change
3	Surface radiation and convection loss	Yes	Yes		As noted earlier, the calculation procedure is different, and PTC 4 generally yields greater loss for coal-fired units
4	Sensible heat of residue loss	Yes	No	Yes	Users may agree on residue split if not measured
New	Hot air quality control equipment loss	No	No		New item added to distinguish the loss due to the hot air quality control equipment separate from the steam generator
	Entering dry air and moisture in dry air credit	Yes	No	Yes
	Sensible heat in fuel credit	Yes	No	Yes	—
	Auxiliary equipment power credit	Yes	No	—	No change
	Loss and credits for sorbent reactions	No	No		Different from prior industry values published by the ABMA

• No separate efficiency guarantees are demanded of HRSGs as the guarantees for total CCPP are given.

• HRSG is required to only demonstrate the (1) gas pressure loss and (2) steaming conditions of HP, IP, and LP steam circuits at the specified loads with the GT exhaust gas supplied at specified quantities and temperatures.

• Steam pressures and temperatures are noted along with inlet and exhaust gas pressures and temperatures of the HRSG. It is normal to adopt this direct method and perform the test that lasts at least 2 h.

• The plant must be running at nearly the same load as the test load, for some time before and some time after the test, to attain a steady-state condition.

• There should be no blowdown during test.

• The drum levels at the beginning and end of the test should be nearly the same.

• The frequency of test readings can be at more than 10 min for all primary readings except for flowmeter readings that must be recorded every 5 min.

• The code specifies the measuring tolerances (Table 1.9).

TABLE 1.9

Tolerances for Direct Measurement of Parameters (PTC 4.4)

Variable	Variation
Water flow to ECON	±2%
ECON recirculation flow	±3%
DeSH water flow	±4%
Blowdown flow	±4%
Fuel flow to gas turbine	±2%
Supplemental fuel flow	±2%
GT power output	±2%
GT to boiler	±10°F
Stack gas temperature	±10°F
Water temperature to ECON	±10°F
Steam temperature at DeSH exit	±10°F
Ambient temperature	±5°F
Barometric pressure	±1%
Steam pressure	±2%
Flow
Air	±2%
Heat recovery steam generator gas	±2%
GT exhaust	±2%