{"id":82485,"date":"2024-04-09T15:48:29","date_gmt":"2024-04-09T13:48:29","guid":{"rendered":"https:\/\/obera.fr\/our-advice\/quels-procedes-ameliorent-qualite-air-eliminant-cov\/"},"modified":"2025-04-15T11:20:01","modified_gmt":"2025-04-15T09:20:01","slug":"quels-procedes-ameliorent-qualite-air-eliminant-cov","status":"publish","type":"post","link":"https:\/\/obera.fr\/en\/our-tips\/quels-procedes-ameliorent-qualite-air-eliminant-cov\/","title":{"rendered":"What processes improve air quality by eliminating VOCs?"},"content":{"rendered":"\n<p>Two families of <strong>VOC treatment processes<\/strong> extract VOCs from ambient air:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>Recovery processes<\/li>\n<\/ul>\n\n<p><strong>Recuperative processes aim to capture VOCs<\/strong> for reuse. They include adsorption with desorption, absorption, condensation and membrane separation.   <\/p>\n\n<ul class=\"wp-block-list\">\n<li>Destruction process  <\/li>\n<\/ul>\n\n<p>Destructive processes include <strong>VOC oxidation<\/strong> (catalytic, thermal), biological treatment, adsorption without desorption, etc <strong>.<\/strong> <\/p>\n\n<h2 class=\"wp-block-heading\">Adsorption<\/h2>\n\n<figure class=\"wp-block-image alignright size-full is-resized\"><img decoding=\"async\" width=\"774\" height=\"461\" src=\"https:\/\/obera.fr\/wp-content\/uploads\/2024\/09\/adsorption.png\" alt=\"Drops of water entering a material and remaining there\" class=\"wp-image-33956\" style=\"width:393px;height:auto\" srcset=\"https:\/\/obera.fr\/wp-content\/uploads\/2024\/09\/adsorption.png 774w, https:\/\/obera.fr\/wp-content\/uploads\/2024\/09\/adsorption-300x179.png 300w, https:\/\/obera.fr\/wp-content\/uploads\/2024\/09\/adsorption-768x457.png 768w\" sizes=\"(max-width: 774px) 100vw, 774px\" \/><\/figure>\n\n<p><strong>VOC molecules<\/strong> bind to a solid material with a large specific surface area, through the action of Van der Waals forces. A wide range of adsorbent materials are available: activated carbon, zeolite, silica gel, activated alumina and resin. Activated carbon is the most widely used. Characterized by its high specific surface area (800 to 2000 m\u00b2\/g), it comes in powder, grain or fabric form. When the activated carbon is saturated, either the <strong>material is changed <\/strong>and treated as waste (powder), or it is regenerated by recovering VOCs through desorption. In this case, either the total pressure is reduced (vacuum desorption), or<strong>the temperature is increased<\/strong><a href=\"https:\/\/obera.fr\/en\/our-tips\/cov-aspiration-vapeurs-solvants\/\">(steam<\/a>, air or hot neutral gases). The VOCs are then recycled into production&#8230;      <\/p>\n\n<p>Absorption, or gas scrubbing, is based on contact between air containing VOCs and a liquid solvent. Soluble VOCs pass into the liquid. Water is used for water-soluble VOCs. For less soluble VOCs,<strong>silicone oil replaces water<\/strong>. These two techniques are not widely used, as water is not very effective and oil is quite costly.    <\/p>\n\n<h2 class=\"wp-block-heading\">Condensation<\/h2>\n\n<p>This involves transforming the gaseous VOC into a liquid, by lowering the temperature to -40\u00b0C for mechanical condensation (using a compressor and heat exchanger) and &#8211; 180\u00b0C for cryogenic condensation (using liquid nitrogen). <strong>The liquid is then separated from the air<\/strong> for recovery. This technique is used for polluted air with a high concentration of VOCs, the latter having a boiling point of at least 40\u00b0C. Condensation is suitable for polluted air flows of less than 1000<sup>m3\/h.<\/sup>   <\/p>\n\n<h2 class=\"wp-block-heading\"><strong>Membrane separation<\/strong><\/h2>\n\n<p>Air polluted with VOCs passes through a <strong>semi-permeable membrane,<\/strong> retaining the VOCs as it passes. The flow rate treated by membrane separation is less than 100<sup>m3\/h<\/sup>. Separation efficiency depends on the structure of the membrane, its <strong>cut-off<\/strong> threshold <strong>and filtration operating conditions<\/strong>. The technique is costly and sensitive to variations in flow rates and concentrations.   <\/p>\n\n<h2 class=\"wp-block-heading\"><strong>Thermal oxidation<\/strong><\/h2>\n\n<p>The aim is to burn the VOCs at at least 750\u00b0, transforming them into<sub>CO2<\/sub> and water. A VOC concentration in excess of <sup>10g\/m3<\/sup> is required to balance the <strong>energy and heat<\/strong> input of <strong>combustion<\/strong>. Otherwise, the process becomes very energy-intensive. When VOCs are halogenated or sulfurated, toxic by-products may be formed, requiring additional neutralization treatment.   <\/p>\n\n<h2 class=\"wp-block-heading\"><strong>Catalytic oxidation<\/strong><\/h2>\n\n<p>To the previous technique, a <strong>precious metal or metal oxide<\/strong> catalyst is added. This oxidizes VOCs at temperatures between 250\u00b0 and 400\u00b0. The aim is to reduce the energy consumption associated with oxidation. However, certain elements (heavy metals, phosphorus, <sub>SO2<\/sub>) contribute to catalyst poisoning and deactivation.     <\/p>\n\n<h2 class=\"wp-block-heading\"><strong>Microbiological treatments<\/strong><\/h2>\n\n<p><strong>Microbes<\/strong> are used <strong>aerobically to break down VOCs into<sub>CO2<\/sub><\/strong> and water. The microbial culture is either fixed or dispersed in a mobile or stationary liquid phase. A distinction is made between biofilters, biopercolators and bioscrubbers.  <\/p>\n\n<h3 class=\"wp-block-heading\"><strong>Biofilter<\/strong><\/h3>\n\n<p>The <strong>bacteria attach themselves to an organic support <\/strong>(peat, wood, etc.) through which the VOC-polluted air flows. To maintain biological activity, the bacteria are occasionally sprayed with water and additional nutrients. <\/p>\n\n<h3 class=\"wp-block-heading\"><strong>Biopercolator<\/strong><\/h3>\n\n<p>Bacteria attach themselves to a <strong>solid<\/strong> support <strong>, mineral or lining<\/strong>. A biofilm is formed, up to several millimeters thick. Continuous watering distributes water and nutrient supplements. This creates a liquid film around the biofilm, in which oxygen and VOCs are absorbed and then transferred to the biofilm.   <\/p>\n\n<h3 class=\"wp-block-heading\"><strong>Biolaveur<\/strong><\/h3>\n\n<p>VOCs are absorbed in a spray washing tower, then <strong>biodegraded in an activation tank<\/strong> containing suspended biomass. Bioscrubbers, using an oil\/water emulsion, can treat compounds that are poorly soluble in water or toxic to microorganisms. <\/p>\n\n<h3 class=\"wp-block-heading\"><strong>Choice of treatment<\/strong><\/h3>\n\n<p>It depends on the nature of the VOCs to be treated, their minimum, <strong>maximum and average<\/strong> concentration <strong>in the polluted air<\/strong>, and its physical conditions (temperature, relative humidity, presence of dust or other pollutants, etc.).  <\/p>\n\n<p>If the process emits one or two VOCs to be treated, and the VOC(s) is (are) cost-effective to reuse, a recovery technique may be chosen; subject to an adequate VOC concentration and polluted air flow rate.  <\/p>\n\n<p>With 3 or more VOCs, it&#8217;s best to opt for a destructive technique.<\/p>\n\n<p>It should be noted that more than 30% of manufacturers <a href=\"https:\/\/obera.fr\/en\/produits\/traitement-cov\/filtre-atex-mobile-mobfan-4500\/\">choose activated carbon-based treatment<\/a>.<strong> <\/strong>allowing a wide range of flow rates for both destructive and recuperative applications. They also eliminate olfactory nuisances. <\/p>\n","protected":false},"excerpt":{"rendered":"<p>wo families of VOC treatment processes extract VOCs from ambient air:<\/p>\n<p>Recovery processes<\/p>\n<p>Recuperative processes aim to capture VOCs for reuse. They include adsorption with desorption, absorption, condensation and membrane separation. <\/p>\n","protected":false},"author":4,"featured_media":81941,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_robots_primary_cat":"none","_seopress_titles_title":"What processes improve air quality by eliminating VOCs?","_seopress_titles_desc":"Two families of VOC treatment processes extract VOCs from ambient air: recovery processes & destruction processes.","_seopress_robots_index":"","footnotes":""},"categories":[309],"tags":[18],"class_list":["post-82485","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\/82485","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=82485"}],"version-history":[{"count":1,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts\/82485\/revisions"}],"predecessor-version":[{"id":82487,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/posts\/82485\/revisions\/82487"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/media\/81941"}],"wp:attachment":[{"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/media?parent=82485"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/categories?post=82485"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/obera.fr\/en\/wp-json\/wp\/v2\/tags?post=82485"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}