A specific startup and shutdown procedure should be supplied by the baghouse vendor.
Improper startup and shutdown can damage the equipment. If hot moist gases are to be filtered,
the baghouse must be preheated to raise the interior temperature in the baghouse above
the dew point to prevent condensation and potential corrosion problems. This can be done by
using heaters in each compartment or by burning a clean fuel such as natural gas before filtering
gases from a coal-fired boiler.
The baghouse must also be brought on-line slowly to avoid permanent damage to the fabric.
Clean filters do not have a protective dust cake on them and are sensitive to dust abrasion and
penetration by fine particles. Penetration can lead to permanent residual pressure drop. In
some applications, bags are precoated with a protective dust layer prior to bringing the unit online.
This protective dust can be the same dust from the process or other material such as pulverized
limestone. In all cases, the filter velocity should always be kept low until a sufficient
dust cake is built up on the bags. This is indicated by a pressure drop of 1 to 2 inches H2O. The
gas flow can then be slowly increased to the designed rate (McKenna and Greiner 1982).
A suggested startup and shutdown list for baghouse system operators is given below.
Startup
Improper startup and shutdown can damage the equipment. If hot moist gases are to be filtered,
the baghouse must be preheated to raise the interior temperature in the baghouse above
the dew point to prevent condensation and potential corrosion problems. This can be done by
using heaters in each compartment or by burning a clean fuel such as natural gas before filtering
gases from a coal-fired boiler.
The baghouse must also be brought on-line slowly to avoid permanent damage to the fabric.
Clean filters do not have a protective dust cake on them and are sensitive to dust abrasion and
penetration by fine particles. Penetration can lead to permanent residual pressure drop. In
some applications, bags are precoated with a protective dust layer prior to bringing the unit online.
This protective dust can be the same dust from the process or other material such as pulverized
limestone. In all cases, the filter velocity should always be kept low until a sufficient
dust cake is built up on the bags. This is indicated by a pressure drop of 1 to 2 inches H2O. The
gas flow can then be slowly increased to the designed rate (McKenna and Greiner 1982).
A suggested startup and shutdown list for baghouse system operators is given below.
Startup
- Make sure all collector components are in working order and in proper mode.
- Do not allow higher-than-design filtering velocities or air flow.
- Avoid passing through (below) the dew point within the baghouse when dirty gases are present. The system should be preheated to above the dew point with clean, hot air before the introduction of flue gas. During normal operation, maintain the temperature approximately 25 degrees above the dew point level. The gas dew point level can be obtained by making process exhaust gas measurements (acid concentration, moisture, and gas temperature) and appropriate calculations or by looking it up in literature such as The Handbook of Chemistry and Physics.
- Operate the bypass system to assure its readiness in an emergency situation.
- Check all indicating and monitoring devices for proper operation.
Shutdown
- Purge the collector with clean (hot when necessary) dry air before allowing the gas temperature to descend below the dew point. This is imperative when bringing a unit off-line.
- Do not store dust in the collector. Many maintenance workers have resigned after spending a day with pick and shovel inside a dust collector hopper.
- The bags should be "cleaned down" after dust flow ends, but not overcleaned. The operator should allow for one or two cleaning cycles then stop the cleaning process.
- Finally, the operator should check to see that all components are in the proper shutdown mode.
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