{"id":32731,"date":"2023-12-12T12:13:01","date_gmt":"2023-12-12T10:13:01","guid":{"rendered":"https:\/\/obera.fr\/advice\/industrial-dedusting-technologies\/"},"modified":"2025-04-15T11:11:28","modified_gmt":"2025-04-15T09:11:28","slug":"technologies-depoussierage-industriel","status":"publish","type":"post","link":"https:\/\/obera.fr\/en\/our-tips\/technologies-depoussierage-industriel\/","title":{"rendered":"Industrial dedusting technologies"},"content":{"rendered":"\n<p>There are two <strong>main dust removal routes<\/strong>: dry and wet. The dry process includes dust collectors with filter layers (bag filters, pockets, cartridges), mechanical (cyclones) and electrostatic (electrostatic precipitators); the wet process includes scrubbers, venturi scrubbers, bubble columns and wet electrostatic precipitators. The <a href=\"https:\/\/obera.fr\/en\/our-tips\/depoussiereur-fixe-mobile-central-local-quels-criteres\/\">choice of a dust collector<\/a> depends on<strong> expected performance<\/strong>, budgetary constraints and the industrial processes to be dedusted, in particular the size of the particles emitted.<\/p>\n\n<h2 class=\"wp-block-heading\">Layer dust collectors (bag filters, pockets, cartridges)<\/h2>\n\n<p>The principle: dusty air passes through a porous filter medium, retaining all particles larger than the porosity of the medium.  <\/p>\n\n<p>The <strong>device comprises a box with a dust collection hopper at its base<\/strong>. The box contains rows (vertical or horizontal) of filter elements (bags, pockets, cartridges) through which the dusty airflow passes. This will have first encountered a deflector at the casing inlet. By inertial impaction, it separates the larger particles from the air stream, allowing them to fall into the hopper.  <\/p>\n\n<p>The remaining dust will then settle on the surface of the filter media. The dust-free air stream exits the filter layer formed by the porous walls of the filter elements. The particles, deposited continuously, agglomerate to form a layer that contributes to air filtration: the filter cake. The latter enhances dust collection efficiency. On the other hand, it <strong>increases pressure drop<\/strong> (clogging is measured by the difference in static pressure between upstream and downstream of the filter medium). This requires either replacement of the media (disposable paper, felt, etc.), or periodic cleaning (on or off) to regenerate the filter media.<\/p>\n\n<p>In general, to ensure continuity of operation, unclogging operations are carried out automatically and sequentially on one <strong>part of the filter media assembly<\/strong>, with the other part continuing filtration. On the other hand, manual declogging requires intervention at the end of the process, or even shutdown. The filter clogging time until a critical pressure drop is reached must be aligned with the process duration.<\/p>\n\n<p>The main methods for cleaning filter elements are :<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong> Mechanical shaking<\/strong>, which causes a wave of deformation in the fabric of the sleeves to cause the filter cake to fall.<\/li>\n\n\n\n<li><strong>Unclogging by reversing the flow of air inside the pores of the filter media<\/strong>. It takes effect automatically once a load loss limit or a set time has been reached.<\/li>\n\n\n\n<li><strong>Pneumatic bag cleaning using compressed air injection <\/strong>(jet-pulse), which momentarily counteracts filtration and loosens dust from the filter. It has the disadvantage of resuspending dust, some of which settles on adjacent media; hence the use of element group cleaning to limit this phenomenon.  <\/li>\n<\/ul>\n\n<p><strong> Bag filters<\/strong> require a low filtration speed to maintain filter regeneration. In fact, during cleaning operations during operation, the upward flow velocity must not clash with the sedimentation velocity of the cleaned particles. Filtration speed varies between 0.6 and 6cm\/s depending on the dust and gas to be treated and the type of filter media. Filtration speed or filtration rate is also expressed in m3\/h.m\u00b2.<\/p>\n\n<p>Filter media come in a variety of structures: fabrics, needled felts, composites, membranes, ceramics. They are made from synthetic (PET, nylon), mineral (glass) or organic (cellulose) materials. <strong> These fibers are treated to improve properties<\/strong> such as chemical resistance, conductivity, hydrophobicity, oleophobicity, adhesiveness and wettability.  <\/p>\n\n<p>The choice of filter element depends on the concentration of dust in the flow to be treated, the nature of the dust, the composition of the gases, the required efficiency, the cleaning method, temperature resistance and economic constraints.<\/p>\n\n<p>The<strong>capture efficiency of a dust collector<\/strong> is lowest for particles with diameters between 0.1 and 0.5\u00b5m (too large to be collected by diffusion, too small to be collected by impaction or interception). At 0.1\u00b5m, efficiency reaches 95%. Above 0.5\u00b5m, it is greater than 99%. If necessary, a HEPA H13 or H14 safety filtration stage can be added for particularly low emission concentrations.<\/p>\n\n<p>This dedusting technique achieves a <strong>high level of separation<\/strong> and can be adapted to a wide range of dust emission concentrations. Layer filter technology is the most widely used in industry for gas\/solid separation, as bag or cartridge dust collectors combine good efficiency with attractive operating costs.<\/p>\n\n<h2 class=\"wp-block-heading\">Mechanical dust collectors: cyclones, decanters<\/h2>\n\n<h3 class=\"wp-block-heading\">Cyclones<\/h3>\n\n<p>The <strong>operating principle<\/strong>: dusty air rotates in a cyclone; centrifugal force presses the dust against its wall, where it agglomerates and settles in the hopper. The purified air rises through the center of the cyclone to the outlet at the top.<\/p>\n\n<p>Dust separation is all the more effective when :<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong> cyclone radius is small <\/strong>(increases centrifugal force)<\/li>\n\n\n\n<li><strong> high particle concentration<\/strong> (promotes agglomeration)<\/li>\n\n\n\n<li><strong>high particle density<\/strong> (faster path to the wall)<\/li>\n\n\n\n<li><strong>low airflow temperature<\/strong> (reduces gas viscosity, increases cyclonic effect)<\/li>\n<\/ul>\n\n<p>High airflow at the cyclone inlet helps collect fine particles.<\/p>\n\n<p>Cyclones do not meet air pollution regulations. They generally act as <a href=\"https:\/\/obera.fr\/en\/produits\/depoussiereurs-industriels\/\">primary dust collectors <\/a>or pre-separators for <strong>coarse particles or slag, for example<\/strong>. Their low cost and simplicity make them ideal for this application. Cyclones will be chosen to collect particles of the order of 10\u03bcm and above.  <\/p>\n\n<h3 class=\"wp-block-heading\">Decanters<\/h3>\n\n<p>The larger particles are pre-separated by settling in an enclosure (expansion box, settling chamber). An air velocity of 5m\/s for dusty air allows particles larger than 30\u00b5m to settle.<\/p>\n\n<h2 class=\"wp-block-heading\">Wet dust collectors: scrubbers, venturi, bubble columns<\/h2>\n\n<figure class=\"wp-block-image alignright size-large is-resized\"><img decoding=\"async\" width=\"576\" height=\"1024\" src=\"https:\/\/obera.fr\/wp-content\/uploads\/2023\/12\/na-k-576x1024.jpg\" alt=\"na k\" class=\"wp-image-26793\" style=\"width:303px;height:auto\" srcset=\"https:\/\/obera.fr\/wp-content\/uploads\/2023\/12\/na-k-576x1024.jpg 576w, https:\/\/obera.fr\/wp-content\/uploads\/2023\/12\/na-k-169x300.jpg 169w, https:\/\/obera.fr\/wp-content\/uploads\/2023\/12\/na-k-768x1365.jpg 768w, https:\/\/obera.fr\/wp-content\/uploads\/2023\/12\/na-k-864x1536.jpg 864w, https:\/\/obera.fr\/wp-content\/uploads\/2023\/12\/na-k-1152x2048.jpg 1152w, https:\/\/obera.fr\/wp-content\/uploads\/2023\/12\/na-k-scaled.jpg 1440w\" sizes=\"(max-width: 576px) 100vw, 576px\" \/><\/figure>\n\n<p>How it works: <strong>dusty air is brought into contact with a washing liquid<\/strong>.  <\/p>\n\n<p>We are looking for the wetting effect of the particle. Contact between liquid and dust is encouraged:  <\/p>\n\n<ul class=\"wp-block-list\">\n<li>or by condensation of the steam around the particle,  <\/li>\n\n\n\n<li>or by adding surfactants to make the dust adhere to the drop of liquid.  <\/li>\n<\/ul>\n\n<p>The<strong>dedusted air is separated from the dusty liquid<\/strong> by centrifugation or inertia. Dust separation is all the more important the more intimate the mixture or the smaller the drops (without being too fine to separate from the air).  <\/p>\n\n<p>In a scrubber, air circulates from bottom to top, and sprayers eject water droplets against the current.<\/p>\n\n<p>A venturi<strong>accelerates the speed of the <\/strong>dusty<strong>air <\/strong>, while a convergent diffuser increases the impact between particles and spray droplets. Then a diverter slows down the speed, allowing dust to clump together. Finally, the air flow passes through a cyclone-type separator where dust is captured by centrifugation and inertia. The dust-free air flow rises through the <strong>center of the cyclone to the central outlet at the top<\/strong>.<\/p>\n\n<p>Scrubbers and venturi scrubbers are effective for particles between 0.5 and 1 \u03bcm. Below 0.5\u00b5m, capture efficiency is accompanied by high pressure drop, and therefore higher energy consumption. However, the capture of submicron particles increases with dust concentration.<\/p>\n\n<p><strong>Capture efficiency also increases with water and air flow rates<\/strong>. This multiplies the probability of dusty air\/water contact. In addition, increasing these flows in the venturi throat proportionally increases the efficiency of venturi scrubbers. Particle collection is mainly influenced by the speed of the water spray.<\/p>\n\n<p>Up to 200\u00b5m, the addition of a surfactant and an increase in the drop height improve dust capture for droplets of around 3mm. This is because the surfactant increases the <strong>deformation of the drop<\/strong> as it falls, and therefore its contact surface.<\/p>\n\n<p>The transfer of dust from a gaseous to a liquid phase can generate significant treatment, water and energy costs compared to the dry process. Scrubbers are used to solve safety problems associated with <strong>explosive dusts and flammable gases<\/strong>, or when the air to be treated is approaching water saturation.<\/p>\n\n<p>The wet process also features bubble columns to remove dust from the air. This is distributed evenly over the cross-section of the column in the form of fine bubbles. The efficiency of<strong> dust<\/strong> collection<strong> increases with the height of the liquid<\/strong>, and hence the time taken for the bubble to travel through it.  <\/p>\n\n<p>Reducing air flow helps to reduce bubble diameter and increase collection efficiency. Moreover, this efficiency increases with: particle size between 1.5 and 20 \u00b5m (stable above that, below 1\u00b5m: low efficiency), the use of surfactants, and the size of gas distribution orifices. The lower collection efficiency of nanometric particles can be improved by bubble fineness, bubbling regime and the addition of packing to improve bubble residence time.  <\/p>\n\n<p>The construction and installation of bubble columns is fairly straightforward, and relatively inexpensive. However,<strong>capture efficiency remains low<\/strong> compared with bag filters or electrostatic precipitators.<\/p>\n\n<h2 class=\"wp-block-heading\">Electrostatic precipitators, electrostatic precipitators or electrostatic precipitators<\/h2>\n\n<p>The<strong> principle of dust collection<\/strong> involves electrically charging the particles, then using electrostatic interactions to deflect them from the path of the dusted flow. The charged dust then travels to an electrode with the opposite electrical charge, where it agglomerates.  <\/p>\n\n<p>Emitting electrodes (often wires) and receiving electrodes (plates) form the device. A negative voltage is applied to the anodes, which emit electrons in their vicinity. This has the effect of ionizing the<strong> gas molecules which, attracted by the cathodes<\/strong>, collide with and electrically charge the dust in their path. In turn, the charged dust is attracted to the plates, where it agglomerates. Filter efficiency is maintained by periodically cleaning the plates using various techniques: vibration, hammering, washing. The dust is collected in a hopper and then discharged.<\/p>\n\n<p>The efficiency of an electric <a href=\"https:\/\/obera.fr\/en\/produits\/depoussiereurs-industriels\/fixes\/\">stationary dust collector<\/a> depends on :<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>dust resistivity<\/strong> (between<sup>106<\/sup> and<sup>1014<\/sup> \u03a9.cm).<\/li>\n\n\n\n<li><strong>air velocity<\/strong> (1 to 4 m\/s)<\/li>\n\n\n\n<li><strong>dust physicochemistry<\/strong><\/li>\n\n\n\n<li><strong> electrode geometry<\/strong><\/li>\n<\/ul>\n\n<p>Below<sup>106<\/sup> \u03a9.cm, dust reaching the collecting electrode easily loses its electrical charge and can be picked up by the air flow. Above<sup>1014<\/sup> \u03a9.cm an insulating layer forms on the cathode and impedes filter efficiency.<\/p>\n\n<p>The passage of air through the electrostatic precipitator results in a low pressure drop (50-100Pa). To increase the efficiency of the electrostatic precipitator, several electric collection fields (between 2 and 6) can be placed in series, depending on the progress of the dedusting operation. This is <strong>optimal for particles larger than 100nm<\/strong>. However, when particles are smaller than 16nm, multiple single-field electrostatic filters are more efficient. And at a size of 0.2\u00b5m, this means minimum capture efficiency.<\/p>\n\n<p><strong>Small-diameter emitter electrodes<\/strong> and large-area collector electrodes increase dust collection efficiency.  <\/p>\n\n<p>Incorrect voltage settings can lead to electrode breakdown, and therefore to the risk of explosion. A wet electrostatic precipitator addresses this risk. The operating principle is identical to that of the dry electrostatic precipitator. The difference lies in the presence of a wet film on the collector electrodes, fed by a drip irrigation system. Capture<\/p>\n\n<p>The<strong> volume of an electrostatic precipitator is significant<\/strong>, as is the investment it represents. Electricity consumption, and the need for qualified personnel, make operating costs high. Electrostatic precipitators are recommended for high gas flow rates (80,000<sup>m3\/h<\/sup>). They are mainly used in heavy industry, such as the steel industry, waste incineration plants, cement works and energy production units.<\/p>\n\n<h2 class=\"wp-block-heading\">Conclusion<\/h2>\n\n<p><strong>Dust removal<\/strong> involves several effects to separate particles from the air stream: settling, impaction, centrifugation, wetting, filtration and electrostatic attraction. Dust collectors often combine several to achieve the desired level of dust removal. Other criteria come into play depending on the <strong>industrial context, such as mobility, location of the dust collector<\/strong>, etc.  <\/p>\n","protected":false},"excerpt":{"rendered":"<p>There are two main dust removal routes: dry and wet. The dry process includes dust collectors with filter layers (bag filters, pockets, cartridges), mechanical (cyclones) and electrostatic (electrostatic precipitators); the wet process includes scrubbers, venturi scrubbers, bubble columns and wet electrostatic precipitators. The choice of technology depends on expected performance, budgetary constraints and the industrial processes to be dedusted, in particular the size of the particles emitted.<\/p>\n","protected":false},"author":4,"featured_media":81752,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_robots_primary_cat":"none","_seopress_titles_title":"Industrial dedusting technologies","_seopress_titles_desc":"The choice of technology depends on expected performance, budgetary constraints and the industrial processes to be dedusted, in particular the size of the particles emitted.","_seopress_robots_index":"","footnotes":""},"categories":[309],"tags":[18],"class_list":["post-32731","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-our-tips","tag-entete-small","generate-columns","tablet-grid-50","mobile-grid-100","grid-parent","grid-50","no-featured-image-padding","resize-featured-image"],"acf":[],"_links":{"self":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts\/32731","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/comments?post=32731"}],"version-history":[{"count":8,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts\/32731\/revisions"}],"predecessor-version":[{"id":82351,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts\/32731\/revisions\/82351"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/media\/81752"}],"wp:attachment":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/media?parent=32731"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/categories?post=32731"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/tags?post=32731"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}