FABRIC
FILTER NEWSLETTER
May 1999
No. 283
Pulse
Jet Cleans Coke Oven Off Gas
A
semi-dry FGD and pulse jet fabric filter system has been successfully
installed downstream of a group of waste heat boilers processing coke oven off
gas at Cokenergy's site in East Chicago, IN. This system is operated
continuously to meet the requirements for particulate and SO2
emissions stipulated in Cokenergy's Operating Permit.
At
the 24th Technical Conference on Coal Utilization & Fuel Systems, William
J. Morris of Marsulex Environmental Technologies (MET) described the design,
initial operation and performance testing of a Dry Flue Gas Desulfurization (DFGD)
and Modular Pulse Jet Fabric Filter (MPJFF) system.
The
initial startup of the DFGD/MPJFF posed special operational issues due to the
low initial gas flows through the system as the four coke oven batteries were
cured and put in service for the first time.
Exit
flue gas from sixteen waste heat recovery boilers is combined into a single
duct and delivered to the DFGD/MPJFF system for the removal of sulfur dioxide
and particulates. These boilers capture heat from four batteries of coke ovens
and product high pressure steam. This steam is used for generation of
electricity (94 MW maximum) and for low pressure process steam.
Sulfur
dioxide emissions are controlled by one of two 100 percent capacity spray
dryer absorber (SDA) vessels with lime slurry as the reactant. Each absorber
vessel uses a single, high-capacity, high-speed rotary atomizer, manufactured
by APV Anhydro of Denmark, to disperse the lime slurry. The motors driving the
atomizers are operated by a variable frequency drive system.
The
solids generated by the chemical reaction between SO2
and the lime slurry plus any particulate carried over from the coke ovens are
collected in the operating SDA and the MPJFFs. The MPJFF consists of 32
modules arranged in two 16-compartment units.
Each
filter compartment has 272 bags, each 6 in. in diameter and 16 ft, 3 in. long.
The bag fabric is 22 oz per square yard woven fiberglass with an
acid-resistant finish. Clean gas
exits the fabric filters into one of two 100 percent capacity ID fans and is
exhausted to the new stack. These ID fans provide draft control for the coke
oven batteries as well as moving the flue gas through the DFGD/MPJFF system.
The
initial startup of the coke oven batteries and waste heat recovery boilers
required a prolonged period (two to three months) of operation with low
temperature and low gas flow volume. Installation
of ID fan fresh air inlet dampers allow
the fan to operate at a stable load about 25 percent of design gas flow. Eight
fabric filter compartments remained unbagged for initial low temperature
operation. Delaying startup of the atomizer, minimized additional gas cooling
and potential acidic condensation which could occur in the critical areas of
the SDA and MPJFF. The partial gas bypass installed around the SDA was opened.
No fabric filter bypass is used.
Performance
tests showed an average of 0.0030 gr/DSCF outlet particulate loading which was
well below the guarantee of 0.0080 gr/DSCF. Guaranteed SO2
emissions are 275 ppmv (dry) at 8 percent O2.
CEM's SO2
readings averaged 234 ppmv and EPA method averaged 209.6 ppmv during testing.
Most
of the operating difficulties to date related to the SDA and fabric filter
have involved the pneumatic by-product handling system. At times, the SDA
by-product has been shown to have higher than expected moisture levels. Heat
tracing and insulation are planned to be added to the conveying lines of the
by-product handling system. This will alleviate most of the conveying problems
by keeping the by-product material as hot and dry as possible. The by-product
material may be recyclable into a commercial application.