OCR Text |
Show ash particles is measured, and this temperature is assumed to be in equilibrium with the surrounding gas. At the exit of the furnace in a utility boiler, this assumption is very accurate, because the particles are small, combustion is essentially completed, and the temperature profiles are small. Thus, OTM measurements will be very close to the gas temperature. The data presented in this paper are from a series of tests conducted at a number of utility boilers all owned and operated by New England Power (NEP). NEP is investigating ways of better characterizing the furnace performance and controlling slagging and fouling problems when utilizing a number of new coals. The units in question were all designed for high quality low-slagging coals which could be transported along the eastern seaboard. However, future emission control regulations are aimed at reducing S02 emissions by 1995. Therefore, NEP is considering a wide range of coals with low sulfur contents which could comply with these regulations while ensuring that slagging and fouling can be controlled using current sootblowing practice. Furnace exit gas temperature (FEGT) measurement is a direct technique for quantifying the effects of furnace deposits on boiler operation. As ash deposition occurs, heat transfer to the waterwalls decreases and FEGT increases. Deposits must be removed periodically using sootblowers to allow efficient boiler operation and to prevent overheating of convective pass tubes. Table 1 lists the test sites studied in this series. Testing has been performed on three different boiler designs with a number of different low and medium volatile bituminous eastern coals. The FEGT measurement range during this program was 2100° to 2850°F. Although improvements to the OTM design have occurred during this testing period, all of the tests were considered successful. Table 1. OTM Demonstrations at NEP Firing Capacity Date Site Arrangement (MW) Coal Type 8/89 Salem Harbor #1 Front wall 81 Medium volatile bituminous 11/89 Salem Harbor #3 Front wall 160 Medium volatile bituminous 11/90 Salem Harbor #3 Front wall 160 Low and medium v lume bitumin u 12/90 Salem Harbor #3 Front wall 160 Medium volatile bitumin us . f 5/91 Brayton Pint #2 Tangential 255 Low and medium ,. v latile bituminous 5/91 Brayton Point #3 Opposed wall 620 Medium volatile bituminous 4 |