What should I do if the resistance of the dust removal bag is too high (high pressure difference)?

Excessive resistance (high pressure difference) of the dust removal bag is the most common operating problem of bag filters. The core reason is that the dust layer on the surface of the filter bag is not effectively removed, the filter bag itself is blocked/ineffective, or the system airflow/parameters are abnormal. If not dealt with in a timely manner, it can lead to an increase in fan load, a sharp decrease in air volume, and even filter bag damage and dust collector shutdown. The solution needs to follow the principle of "emergency resistance reduction and operation first, then step-by-step investigation to find the root cause, and finally targeted treatment+long-term prevention". The following are the full process solutions that can be implemented on site, suitable for various bag filter scenarios such as industrial boilers, mines, building materials, and chemicals:

1、 Urgent handling: Quickly reduce pressure difference to ensure temporary operation of equipment

If the pressure difference has exceeded the design value (normal pressure difference of 1000-1500Pa, emergency is required if it exceeds 2000Pa), first stabilize the operation through simple operations to avoid the expansion of the fault:

Optimize cleaning parameters: temporarily increase the cleaning frequency (such as from once every 30 minutes to once every 10-15 minutes), extend the single valve spraying time (such as from 0.1s to 0.15-0.2s), and the offline cleaning system can increase the offline cleaning time;

Improve dust cleaning power: Check the compressed air pressure and temporarily increase it to 0.5-0.6MPa (usually 0.4-0.5MPa, do not exceed 0.6MPa to avoid damaging the filter bag), ensuring that the compressed air is free of oil and water (oil/water will aggravate the sticking of the bag, and the condensed water in the air storage tank needs to be drained in advance);

Reduce the load on the filter bag: Close the inlet valve of the dust collector appropriately to reduce the processing air volume (lower the surface air speed of the filter bag to avoid rapid thickening of the dust layer). If it is a multi chamber dust collector, the high resistance chamber can be taken offline and cleaned separately before being put into operation;

Manual assisted dust cleaning: For the filter bag in the offline room, low-pressure (0.2-0.3MPa) compressed air is blown back from the inside of the filter bag to remove loose dust on the surface (to avoid damage to the filter material caused by high-pressure direct blowing).

2、 Step by step investigation: Accurately locate the core cause of high resistance

After an emergency, it is necessary to troubleshoot in the order of "easy first, difficult second, system first, filter bag second" to eliminate problems one by one. The following are 90% of the fault points and troubleshooting methods that may occur on site:

Troubleshooting 1: Dust cleaning system malfunction (the most common cause, accounting for over 60%)

The failure of dust cleaning is the direct cause of the inability to remove the dust layer. The focus is on checking the pulse valve, spray pipe, compressed air, and dust cleaning program:

Pulse valve: whether there is no spraying, air leakage, or weak spraying (feel the pulse valve body with your hand, no vibration=no spraying, continuous air leakage=membrane damage);

Spray nozzle: whether the spray nozzle is blocked or misaligned (due to dust adhesion or debris blockage, causing the airflow to be unable to align with the filter bag opening);

Compressed air: whether the air storage tank/refrigerated dryer has not been drained and degreased in a timely manner (compressed air with water/oil will adhere to dust, forming "oil sludge/cement" that sticks to the filter bag), and whether the pressure has been below 0.4 MPa for a long time;

Dust cleaning program/valve: Whether the PLC program is disordered (incorrect dust cleaning interval and spraying time settings), whether the offline valve/lift valve for offline dust cleaning is not tightly closed (airflow short circuit, filter bag still passes through the air during dust cleaning, dust cannot be blown off).

Troubleshooting 2: Filter bag itself problem (core fault, accounting for 25%)

The filter bag is the core carrier of resistance, and problems can be classified into four categories: stuck bag, blockage, aging/damage, and improper installation. On site, it can be judged by observing in the offline room and touching the filter bag by hand:

Paste bag (most common): A layer of damp/sticky dust adheres to the surface of the filter bag, making it sticky and difficult to fall off when touched by hand. This is often due to smoke condensation, high moisture content, or the stickiness of the dust itself (such as cement, fly ash, desulfurization dust);

Filter bag blockage: Fine dust enters the internal pores of the filter material (non surface dust layer), causing the filter bag to become hard and swollen. Even after cleaning, no dust falls off. This is often due to the filter material not being coated, high inlet dust concentration, or long-term low cleaning frequency, resulting in dust layer compaction;

Aging/damage: The filter bag is brittle, loose, and has holes. The damaged area can cause local dust accumulation, increase the load on the surrounding filter bag, and increase the resistance;

Installation issues: Poor sealing between the filter bag opening and the flower board (air leakage), excessive wrinkling/stretching of the filter bag, or deformation of the cage bone (abrasion of the filter bag, resulting in uneven airflow distribution).

Troubleshooting 3: Abnormal system operating parameters (indirect cause, accounting for 10%)

If the temperature, humidity, air volume, and dust concentration of the flue gas exceed the design values, it will accelerate the increase in resistance of the filter bag. Please focus on checking:

Flue gas temperature: whether it is too low (below dew point temperature, condensation on the bag) or too high (causing softening and scaling of the filter material);

Moisture content: whether it exceeds the standard (such as water in the flue gas after wet dust removal or high humidity in the flue gas after raw material drying);

Handling air volume: whether it exceeds the design value (due to excessively high air speed on the surface of the filter bag, rapid thickening of the dust layer, and delayed dust cleaning);

Inlet dust concentration: whether it far exceeds the design (such as the failure of front-end pre dust removal equipment (cyclone, settling chamber), and the direct entry of coarse dust into the bag filter).

Troubleshooting 4: Auxiliary system malfunction (easily overlooked, accounting for 5%)

Malfunctions in the ash hopper, flue, and fan can cause poor airflow and dust backflow, indirectly increasing the resistance of the filter bag

Ash accumulation/blockage in the ash hopper: Material hanging or bridging on the inner wall of the ash hopper, malfunction of the ash discharge valve (non rotation, jamming), resulting in the ash hopper being filled with ash, the bottom of the filter bag being buried by dust, and the airflow being unable to pass through;

Flue blockage: Dust accumulation in the inlet/outlet flue, guide plate, and fan impeller, resulting in increased system air resistance and uneven airflow distribution inside the dust collector;

Sealed air leakage: Air leakage occurs at the dust collector housing, manhole door, and flange, causing external cold air to enter and causing condensation of smoke, which exacerbates the sticking of bags.

GB/T 7714:

SALEEM M,RAMACHANDRAN S,RAMARAO B V.The effect of operating conditions on resistance parameters of filter media and limestone dust cake for uniformly loaded needle felts in a pilot scale test facility at ambient conditions[J].Separation and Purification Technology,2013,111:112-120.

MLA 9th:

Saleem,Muhammad,et al."The Effect of Operating Conditions on Resistance Parameters of Filter Media and Limestone Dust Cake for Uniformly Loaded Needle Felts in a Pilot Scale Test Facility at Ambient Conditions."Separation and Purification Technology,vol.111,2013,pp.112–120.

APA 7th:

Saleem,M.,Ramachandran,S.,&Ramarao,B.V.(2013).The effect of operating conditions on resistance parameters of filter media and limestone dust cake for uniformly loaded needle felts in a pilot scale test facility at ambient conditions.Separation and Purification Technology,111,112–120.