Study On A New Type Of Diesel Particulate Filters

Nowadays, people pay more and more attention to the particulate pollution made bydiesel engine, industrial furnace and waste incineration. In numbers of dust removaltechnology on filtration, such as mechanical dust collector, electrostatic dust collector,filter collector and wet-scrubber, for its low cost and high filter efficiency, bag-dustcollector (one method of filter collector) was widly used in the field of flue gas cleaningboth in China and abroad. But while the traditional bag-dust collector was used on filteringthe off-gas made by diesel engine or other equipment, it’s hard to filter submicron particlesand the particles were easy to be adhered to the bag. Thus a innovative method wasproposed in this research: Bag filter combining with pre-paved powder membrane to filterthe off-gas made by diesel engine. It’s a new type of diesel particulate filters. According tothis, at first a basic experiment on filtering simulate smoke by stainless steel sintered fiber feltcombining with powder has been performed, the result became evidence to laterexperiments,(experimental parameter: expanded perlite particle diameter should be from150~300mesh and more, the thickness between0.5-3mm, smoke particle sizeD50=0.183μm). Then, we made the experiment on bag-dust collector with pre-pavedpowder membrane to filter the off-gas made by diesel engine,(experimental parameter:expanded perlite particle diameter should be from500~1000mesh、D90=27.78μm, thethickness between0.2-1mm, smoke particle size D50=0.181μm). Finally, it’s theexperiment on deashing and recovering effects of the bag,(experimental parameter: thepulse pressure reached to0.4-0.8Mpa, the duration was0.05-0.15s,the number of timeswas below8). The main conclution was as follow:(1) In the basic experiment, the main point is the influence of fiber felt precision,powder size, powder thickness, filter speed and time. The result is that the fiber feltprecision made less effect on filter efficiency, while the pre-paved powder took a moreimportant role. When the powder size decreased, the thickness increased, or the filter speedbecame higher, the filter efficiency all performed as firstly increased and then decreased.Under the condition of following: filter speed was3m/min,the powder thickness was1.5mm, and the perlite particle diameter was200~250mesh,the best efficiency in primeperiod should be95.746%, and after30mins, reached to98.499%.Meanwhile, it’s foundthat in the stable period of high efficiency, the powder size, thickness and filter speed madevery small influence to filter efficiency, almost above98%. （2）In the experiment on bag dust collector with pre-paved powder to filter theoff-gas made by diesel engine, the influence study was mainly made among powderthickness, filter speed, off-gas concentration, the feed way and material of bag. The resultis that the efficiency was proportional to the powder thickness, and had an inverserelationship with filter speed. While the powder size was500mesh, the powder thicknessis1mm, filter speed was0.2m/min, the initial efficiency can reach to77.952%, after120mins, up to99.594%, and also the efficiency was kept above98%. Off-gasconcentration also made some effects to the filter efficiency. Under the condition of highconcentration, the increase speed was much higher than low concentration,and more stable.On-line feeding was more efficient than feed before filtering. While the powder size was500mesh,the filter speed was0.2m/min, the feeding amount was controled as2.5L/h, thethickness was0.5mm,the on-line feeding efficiency was to64.186%in prime period. After80mins, efficiency was up to99.719%, and kept to be above98%during360mins.Material of bag has great effect on filter efficiency, when coated bag combining with1mmpowder at0.2.m/min, the prime period efficiency should be more than99.9%, and kept tobe above99.9%during180mins. On the other hand, smaller particle diameter made higherefficiency. All the particle classification efficiency would be promoted as time goes by.about the pressure drop, increasing on powder thickness and filter speed would rise thepressure drop up. While the filter efficiency decreased, the rising speed became slower.onthe other side, the smoke concentration and feed way made little influence on the pressuredrop.(3)The experiment on deashing and recovering effects of the bag maily stuied on theinfluence made by the pulse of air impress, the duration and the number of times. Theresult indicated that the recover efficiency made by pre-paved powder was proportional toall the above3items. When the pulse of air impress reached to0.8Mpa, the duration was0.1s,in6times, the recovering effiency could be83.6%, contrast with the bag withoutpowder pre-paved, the recovering effiency could only been to18.7%.