Why does the emission of the pulse jet bag filter housing exceed the requirements?
Besides the filter materials and filter machines, Zonel Filtech also offers free consultant on dust collector technology support, so we always can receive some technical support requirements from our clients and potential clients, when some questions are mentioned, we may edit some articles then release in our catalog to help our reader to solve the possible problems for their dust collectors, this article will explain the emission exceed problems.
As we know, the pulse jet bag filter housing is one of the highest filter efficiency dust collectors, but sometimes when we monitor the dust emission, it may exceed the requirements and bring much trouble for the end users, so we have to find the possible reasons and help to do some improvements on dust collectors so as to make the emission under the requirements, such as 20mg/Nm3 or even 5mg/Nm3, etc.
If the emission exceeds the requirements or the deep fume exhaust from the chimney, there are mainly have following possible reasons:
(1) the filter bag was installed within a short time.
The newly installed clean filter bags (w/o PTFE membrane laminated) always with a larger pore size, so the dust passing rate is higher at the beginning, and the optimal filtering efficiency has not yet been reached;
With the progress of filtration, dust accumulates on the outer surface of the filter bag to form a dust layer, which reduces the pore size on the outer surface of the filter bag and improves the dust removal efficiency. The function of a “dust filter” can remove more than 99% of fine dust.
Therefore, it is more accurate to measure the dust removal efficiency of the pulse jet bag filter after 1 month of continuous operation.
Also, the dust pre-coating works helpful, if the particle size is fine, this also can be taken into consideration.
(2) the filter bag was installed incorrectly.
The filter bag top ring has various designs, such as the steel wire ring type, cloth flange type, clamp sealing design, and so on, which have to be connected very well with the top accessories on the tube sheet, if the design is not correct, which is very easy to cause the higher emission problem, and those design are very hard to install the filter bags, so more and more dust collectors are choose the snap ring design.
The snap ring is made of elastic stripes which always adopt the metal with good elastic, such as SS301, carbon steel, and so on, and the ring will combined with a rubber strip or cloth stripe with double beams, the groove between the beams will touch with the bag tube sheet hole edges, which help to make the filter bags not drop to the hopper, also sealing well and without the dust air come out.
So when installing the filter bags, we push the ring into the bag tube sheet hole, guarantee the tube sheet edge is embedded into the groove of the top ring slowly, and finally push the rest part of the top ring to fill the whole hole, if the filter bag with good installing situation, which won’t drop to the hopper, also can not be moved, or it may cause the higher emission problem.
So have to make sure the filter bags are installed very well.
(3) The filter bag is broken.
If any filter bags are broken, the chimney will exhaust the deep color dust air, so have to find the broken filter bags and then change them to new ones.
For the small filter housing, it is very easy to locate the broken filter bags, because when the cover of the dust collector is, there will be some dust around the broken filter bag, just put them out and change will be fine;
But when the bag filter housing is big, it may be hard to find the position of the broken filter bags.
But the big bag filter housing is always designed with the offline purging system, so we can close the chamber to operating one by one, once any chamber is closed then the dust air disappears from the chimney, which means the broken filter bags were located at this chamber, so we can stop the dust collector and open this chamber to change the filter bags accordingly.
When the filter bag needs to be replaced, it is recommended to replace all the dust filter bags of the same dust collector at the same time to ensure that each filter bag has the same resistance. If only a few filter bags can be replaced, it is necessary to seal the bag mouth of the new filter bag and bury it in the dust for a few days to increase the resistance of the new filter bag, so that the resistance of the new filter bag is close to that of the old filter bag in case the new filter bags strongly crashed by dust air and broken faster.
(4) Dust collector quality problem.
For the dust collector with the air inlet channel and the air outlet channel separated only by a partition, it is necessary to check whether the middle partition plate is welded tightly. If there are welds and gaps in the middle partition, the high-concentration dust in the air inlet will enter the air outlet channel, causing dust at the outlet of the exhaust pipe. Ensuring the welding quality of the intermediate clapboard and completely separating the air inlet channel from the air outlet channel is another important aspect of quality inspection during the production and installation of the dust collector.