Translate

Saturday, October 24, 2015

Fossil-fuel Fired Boilers

Utility companies have been using fabric filters on coal-fired boilers since the mid 1970s and
because of the advances in their design and operation, fabric filters have become a preferred
technology for the control of particulate matter (Cushing 1990). Utility use of fabric filters is
expected to increase as emission limits become more stringent and regulatory attention to air
toxics increases. Fabric filters can also be integrated with acid gas controls providing an added
dimension not possible with some other forms of particulate control.
Based on a survey conducted by the Electric Power Research Institute (EPRI) in 1989, there
were 99 fabric filters operating on utility boilers representing 21,359 MWof generating capacity
(Cushing 1990). Since the mid 1980s the application of fabric filters downstream of acid
gas control equipment has increased substantially. Worldwide, industrial and utility use of fabric
filters is even more dramatic as over 300 pulse-jet fabric filters are treating exhaust gas
from coal-fired boilers alone (Belba 1992).
Table 1  lists some coal-fired boilers that use fabric filters for controlling particulate matter
emissions that use either the reverse gas or shake/deflate cleaning method. The fabric most
commonly used in the applications depicted on Table 1 is woven glass. Fabric coatings used
include Teflon, silicon graphite, and other proprietary acid resistant coatings.

                         Table 1 .  Fabric filter performance data


Design efficiencies of the fabric filters depicted on Table 1  ranged from 98 to 99.9%. The
lowest particulate emission rates were found on units using reverse-gas cleaning and ranged

from 0.005 to 0.03 lb/MMBtu. Particulate emissions from fabric filters using reverse-gas cleaning with sonic assistance ranged from 0.008 to 0.125 lb/MMBtu. The units using shake/
deflate cleaning had particulate emissions of 0.007 to 0.07 lb/MMBtu.
Table 2 lists some coal-fired boilers that use fabric filters with pulse-jet cleaning. This table
gives you an idea of the different combinations of bag material and A/C ratios that are being
used successfully at different sites. Woven glass and felted fabrics are the most common bag
materials used. Fabric filters using 16 oz/yd2 woven fiberglass bags were found to be less efficient
in particulate matter collection than fabric filters using 22 oz/yd2 bags. Fabric filters
using 22 oz/yd2 bags achieved particulate emission levels consistently less than 0.02 lb/
MMBtu (Belba 1992).


                                   Table 2. Pulse-jet fabric filter performance data



0 comments:

Post a Comment