Customer Cases
Coal-Fired Boiler Filter Bag Replacement
A PS155T baghouse solution for hot, humid, and seasonally changing flue gas
A paper mill in Northeast China needed to replace the filter bags in the pulse-jet baghouses serving two 75 t/h coal-fired boilers. The previous system repeatedly experienced bag blinding, rising differential pressure, unstable dust emissions, and cage corrosion after seasonal shutdowns.
Aokai reviewed the complete operating conditions and supplied PS155T coal-fired boiler filter bags. Our technicians also supported bag and cage installation, filter bag precoating, fluorescent powder leak testing, and startup.
Project result: The boiler baghouses have operated steadily through multiple heating cycles. The customer reported better overall system stability than before the shutdown maintenance.
The Project
The customer operates two captive coal-fired boilers at a paper mill in Northeast China. During the annual shutdown, the mill carried out complete maintenance of the No. 1 and No. 2 boiler dust collection systems and replaced the existing filter bags.
The flue gas treatment process is:
Coal-fired boiler → SCR + SNCR → pulse-jet baghouse → wet desulfurization → stack
To prepare the boilers for the next heating season, the customer needed a filter bag solution that could handle high temperature, high humidity, chemical exposure, and seasonal changes in operating conditions.
Key Project Data
| 75 t/h × 2 | 180,000 m³/h | 130–150°C | ≤10 mg/m³ |
|---|---|---|---|
| Boiler capacity | Rated flue gas volume | Operating temperature | Required dust emission concentration |
Findings from the On-Site Inspection
Aokai Recommendations
Based on the actual site conditions, Aokai’s technical engineers recommended the following improvements:
- Remove rust and apply anti-corrosion treatment to the clean-air plenum, tube sheet, and access doors.
- Replace the filter bags and matching filter cages.
- Improve the operation and maintenance of the cleaning system and ensure stable pulse-jet cleaning.
- Control ammonia injection in the DeNOx system to reduce the risk of NH₃ slip.
- Replace the aged sealing strips.
- Conduct a comprehensive fluorescent powder leak test before the heating season.
- Standardize boiler startup and shutdown procedures to reduce operating stress on the filter bags.
The Solution: Aokai PS155T Boiler Filter Bags
Aokai recommended PS155T filter bags for the two pulse-jet baghouses. PS155T was selected for the project’s 130–150°C operating temperature and the hot, humid flue gas conditions commonly found in coal-fired heating and circulating fluidized bed boiler applications.
Why PS155T Was Selected
- Resists hydrolysis under humid flue gas conditions
- Resists acidic and alkaline components
- Releases collected dust more easily during pulse cleaning
- Adapts to seasonal changes in boiler operation
- Suitable for boiler, power, steel, cement, and district-heating baghouses
Filter bag selection must still be based on actual process data. Temperature alone is not enough. Moisture, oxygen, sulfur compounds, ammonia slip, acid dew point, dust properties, and abnormal temperature excursions must also be considered.
Why This Boiler Baghouse Project Worked
The project addressed the filter bags and the surrounding system at the same time:
- Aokai reviewed the complete operating conditions.
- PS155T was selected for the temperature, humidity, chemistry, and cleaning method.
- The cages, tube sheet, seals, and installation quality were checked.
- The new bags were precoated before full operation.
- Fluorescent powder leak testing was completed before continuous service.
If new boiler filter bags become blinded shortly after replacement, another bag change may only provide temporary relief. The upstream denitration system, moisture conditions, pulse cleaning, air leakage, cages, tube sheet, and startup procedure should also be inspected.
Project Operating Parameters
| Parameter | Project condition |
| Customer application | Paper mill captive boiler |
| Boiler quantity | Two boilers |
| Boiler capacity | 75 t/h each |
| Fuel | Coal |
| Denitrification | SCR + SNCR |
| Desulfurization | Wet desulfurization |
| Dust collector | Pulse-jet baghouse |
| Cleaning control | Differential-pressure and timer-based cleaning |
| Cleaning pressure | 0.2–0.4 MPa |
| Operating temperature | 130–150°C |
| Rated flue gas volume | 180,000 m³/h |
| Filtration velocity | ≤0.76 m/min |
| Required dust concentration | ≤10 mg/m³ |
| Selected filter bag | Aokai PS155T |
Coal-Fired Boiler Filter Bag Replacement The Result
After installation and commissioning, the two baghouses returned to service for the next heating season.
According to the customer’s operating feedback:
- The system remained stable through multiple heating cycles
- Overall operating stability improved compared with the previous period
- The maintenance work provided a more reliable basis for continuous seasonal operation
The project’s required dust concentration was no more than 10 mg/m³. Exact before-and-after emission, differential-pressure, and filter-life figures are not stated because they were not included in the available project record.
