For the Hybrid filter, the capex and the operating cost is higher than the
RABH, PJBH and ESP. It is useful to convert the existing ESP in to Hybrid
filter or Pulse Jet bag house to lower down the outlet emission level with
in same foot print area and use the existing casing of the ESP. In India
many plants are converting the ESP with this filter with mixed results.
The ESP with GCT, the capex with civil cost is higher than other filter, but
the operating cost is lower than others. It is observed in some of the plants
due to higher CO content in ESP resulted into explosion. Also, due to
constraints to maintain outlet emission level in upset condition and extra
water consumption in GCT, the ESP is not a preferred option in kiln/raw
mill application.
From the above facts, it is preferable to go for RABH or Pulse Jet Bag House
for the Kiln/Raw mill Application depending upon the guaranteed parameters
and Capital cost of both the filters.
- Cement Mill Dedusting Applications
In the dedusting system of the cement grinding plant, the filter has the function
of collecting the finished product is transported by the air stream. The gas
volumes and dust loads depend on the grinding process installed. The air
volumes coming from vertical mills are approx. twice as high as those from, ball
mills or roller presses, which are equipped with separate separators. While the
dust load of air from vertical mills is in the range of 200-500g/m3, the direct
collection of finished product is coming from separators have extremely high
dust loads of up to 1000g/m3, so the closed circuit cyclone separators are used
for the pre-collection.
For the above application, the Pulse jet bag filter, ESP and the Hybrid filter are
the available solution for the dedusting. In the present cement industries, the
Pulse Jet filter is the commonly used. In the earlier past, ESP was the option
adopted by most of the cement plants. In ESP operation, the continuous
guaranteed emission limit is very difficult to achieve in upset process conditions so
that almost all the plants are preferred to go for PJBH or by converting it to
hybrid filter.
- Cooler Dedusting
Earlier in cement industry ESP was only option for clinker cooler dedusting.
Nowadays 3 phase transformers and better controller are installed in ESP to
have better collection efficiency with an outlet emission of <10mg/Nm3. In
countries where emission norms are further stringent i.e. <5mg/Nm3 there pulse
jet bag house is preferred with low emission level with heat exchanger to
decrease inlet temperature of inlet gases in bag house. If we go for the waste
heat recovery system at cooler, then ESP is preferred because WHP require
high inlet temperature. If WHP is not considered, then both the option shall be
evaluated on capex and power cost.