Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/26—Drying gases or vapours
  • B01D53/28—Selection of materials for use as drying agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
  • B01J20/2805—Sorbents inside a permeable or porous casing, e.g. inside a container, bag or membrane
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
  • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
  • B01J20/3234—Inorganic material layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/30—Physical properties of adsorbents
  • B01D2253/34—Specific shapes
  • B01D2253/342—Monoliths
  • B01D2253/3425—Honeycomb shape
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
  • B01D2257/708—Volatile organic compounds V.O.C.'s
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/90—Odorous compounds not provided for in groups B01D2257/00 - B01D2257/708
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F2203/00—Devices or apparatus used for air treatment
  • F24F2203/10—Rotary wheel
  • F24F2203/1032—Desiccant wheel
  • F24F2203/1036—Details

Definitions

• the present invention relates to a chemical filter for removal of contaminants from air present in industrial or domestic environments. More particularly, the present invention relates to a desiccant based honeycomb chemical filter. The present invention also relates to a method for the manufacture of a desiccant based honeycomb chemical filter.
• this invention relates to a desiccant based chemical filter, such as a honeycomb chemical filter, for the removal of contaminants from air present in industrial or domestic environments.
• the present invention also provides to a method for the manufacture of a desiccant based honeycomb chemical filter.
• the contaminants to be removed are typically gaseous contaminants but can also comprise contaminants in the form of fine liquid droplets which are not easily removable by conventional means.
• the term 'desiccant' as used herein is intended to cover both macroporous and microporous desiccant or desiccants.
• the desiccant or desiccants based honeycomb matrix used in the invention is impregnated with different impregnating materials.
• the invention also provides methods for removal of gaseous contaminants, pollutants and odors from industrial processes using the said chemical filter.
• This invention also relates to a process for manufacturing macroporous /microporous desiccant or desiccants based honeycomb matrix impregnated with different impregnants for removing gaseous contaminants contained in air or odour in the air.
• Odours in industrial environments, and also in non-industrial environments such as passenger compartments of transportation vehicles are due to volatile organic compounds present in the circulating air. These organic compounds are formed in high levels but at relatively low concentrations from engine exhaust, solvents, gas turbines, cogeneration plants, petrochemical plants, and in many industrial processes where waste gases contain materials such as solvent vapors, inks, paints, etc.
• Volatile organic compounds comprise not only hydrocarbons, whether saturated, unsaturated, or aromatic, but also contain oxygenated materials such as alcohols, esters, ethers, and acids, nitrogen containing compounds (principally amines), sulfur containing materials (mercaptans and thioethers) and halogen-containing materials, especially chlorine-substituted hydrocarbons but also organic fluorides and bromides.
• oxygenated materials such as alcohols, esters, ethers, and acids
• nitrogen containing compounds principally amines
• sulfur containing materials mercaptans and thioethers
• halogen-containing materials especially chlorine-substituted hydrocarbons but also organic fluorides and bromides.
• a traditional method for solvent recovery from humid air comprised an adsorption system which typically was operated till the solvent concentration in the outlet gas stream reached a detectable preset breakthrough level. When this level was reached, the flow of gas to the adsorber was stopped. The adsorbent bed then contained solvent, other condensable organic contaminants, and some amount of water dependent on the inlet relative humidity of the solvent laden gas stream.
• This method was subsequently modified by the introduction of a hot inert gas or steam, either saturated or superheated, which displaces the solvent from the adsorbent to produce a solvent/water mixture upon condensation.
• a hot inert gas or steam either saturated or superheated
• two adsorber beds were used, where one was adsorbing while the other bed underwent regeneration.
• Further developments in regenerating and recovering solvents from adsorbent beds involve the use of inert gases or air and low temperature condensation of the solvent from the regenerating gas/air. However, these techniques are not directly applicable in all given situations where required.
• U.S. Pat. No. 4,421 ,532 discloses a process for the recovery of VOCs from industrial waste gases by thermal swing adsorption including the use of hot inert gases circulating in a closed cycle to desorb the VOCs.
• U.S. Pat. No. 4, 134,743 discloses a process and apparatus where the adsorbent body is a wheel of thin sheets or layers of fibrous material containing about 10 to 90% by weight of a freely divided molecular sieve material.
• the apparatus includes a means for passing air to be processed in one direction through the wheel and a means for passing a regenerative air stream countercurrent to the air to be processed.
• a cooling stream is provided in a direction co-current with the air stream.
• U.S. Pat. No. 4,887,438 discloses a desiccant assisted air conditioning system for delivering dehumidified refrigerated air to a conditioned space based on an adsorbent wheel.
• Meckler teaches the use of a desiccant wheel coated with silica gel, or a preferred hygroscopic salt, lithium chloride, to remove moisture from air.
• This citation teaches the use of waste heat from the refrigeration condenser to heat the reactivation air and employs a liquid refrigerant injection into the compressor to increase the pressure ratio in a positive displacement compressor to counter the problem of "thermal dumpback".
• Thermal dumpback is the associated heat conducted from the desiccant wheel to the treated air which occurs following the exposure of the wheel to heated regeneration air. This associated heat adds to the overall cooling load on the refrigeration system.
• U.S. Pat. No. 5,242,473 discloses a gas dehumidifying apparatus which exhibits improved dehumidification efficiency to provide a treated gas with a high dryness level employing two dehumidifier rotors, wherein the second rotor uses a synthetic zeolite.
• Gas to be dehumidified is passed first to a silica gel coated rotor and then to the zeolite coated rotor.
• the rotors are regenerated by supplying a stream of heated gas through the second rotor and then the first rotor so that the adsorbent in the first rotor is regenerated at a lower temperature than the zeolite in the second rotor.
• a portion of the treated gas is used to countercurrently cool the rotors following regeneration.
• adsorbent that is used.
• Hydrophilic adsorbents such as silica gel are typically chosen for dehumidification applications, but are poor adsorbents for volatile organic contaminant removal.
• hydrophobic adsorbents such as high silica zeolites are typically recommended for VOC removal applications, but are poor adsorbents for dehumidification application.
• applications for both dehumidification and VOC removal may typically require both types of adsorbents.
• adsorbent-coated paper and some adsorbent salts have a limited range of humidity and temperature within which they can maintain structural integrity. This failure also limits the regeneration medium to dry, moderate temperature gases and air. Contact between the adsorbent and gas stream and hence adsorbent capacity for VOCs is limited to very thin layers of adsorbent on the surface of the fiber. This feature also limits the ultimate life of adsorbent wheel, resulting in frequent wheel replacement.
• Filters are generally devices such as a membrane or a layer that is designed to block or contain objects or substances while letting others through. Filtration media are generally of three types - mechanical, biological and chemical. Chemical filters are preferred for removal of gaseous contaminants in a given environment since they provide air purification by both adsorbing and absorbing odours by adsorbents/impregnated adsorbents such as potassium permanganate by controlled oxidizing action.
• Gaseous contaminants either could be inorganic or organic.
• selection of adsorbents to adsorb gas or reactants for adsorbing gas/impregnates is very important for the chemical filter media. As discussed above, a single chemical filter media may not adequately control multiple contaminants or classes of AMC.
• One object of the present invention is to provide a desiccant based honeycomb chemical filter where the desiccant is generated in situ, and impregnated with oxidizing chemicals, acidic or alkaline chemicals, or reducing chemicals to remove/contain gaseous contaminants, where the loading percentage of the impregnants is significantly higher than thought possible in the art.
• the primary object of the present invention is to increase the capability of removing gaseous contaminants whether, acidic, alkaline, or organic and increase chemical filter life by the use of higher amounts of impregnants.
• a further object of this invention is to produce a desiccant based honeycomb matrix with or without active carbon or hydrophobic zeolite for impregnation with different impregnants/reactants to remove gaseous contaminants.
• Another object of the invention is to provide a desiccant based honeycomb matrix where pressure loss is minimized.
• the desiccant may or may not contain active carbon or hydrophobic zeolite and may or may not be impregnated with impregnants for enhanced removal of different contaminants.
• a further object of the invention is to provide a desiccant based honeycomb matrix chemical filter that provides an energy saving, and may be with or without active carbon or hydrophobic zeolite, and may be impregnated with different impregnants or un-impregnated, while also enabling enhanced odour control.
• the present invention provides a honeycomb matrix comprising a desiccant prepared in-situ, for use as a chemical filter, as described herein below.
• the present invention provides a desiccant based honeycomb chemical filter comprising a matrix formed of a substrate having a desiccant generated in situ or deposited thereon, said desiccant being selected from the group consisting of metal silicates, silica gel, molecular sieves, activated alumina, activated carbon or hydrophobic zeolite, and any mixture thereof, said substrate being further impregnated with one or more of an oxidizing agent, or an alkali metal hydroxide, or strong or weak acid(s), or reducing agents.
• the substrate comprises an inorganic substance or an organic substance or a mixture thereof.
• the substance is in the form of a fiber or a pulp.
• the inorganic fiber is selected from the group consisting of glass fiber, Kraft paper, ceramic paper and any combination thereof, and is preferably a glass fiber.
• the desiccant is selected from a metal silicate and silica gel or combination of metal silicate and activated carbon and/or a hydrophobic desiccant such as zeolites selected from HISIV and ZSM-5
• the metal silicate is selected from potassium silicate and sodium silicate, preferably where the silicate is a neutral grade sodium silicate.
• the ratio of Si0 2 to Na 2 0 is in the range of 1 :2.0 to 1 :4.0, preferably in the range of 1 :3.
• the impregnated material is selected from the group consisting of potassium permanganate, sodium permanganate, potassium hydroxide, sodium hydroxide, phosphoric acid and sodium thiosulphate.
• the loading of the impregnated material in the matrix is in the range of 4% to 40 %, preferably about 20%.
• the binder is preferably absent.
• the basic weight of the substrate is in the range of 50 to 150 gsm, preferably in the range of 80 to 120 gsm.
• the present invention also provides a method for manufacture of a desiccant based honeycomb chemical filter, comprising the steps of
• the method when used in a situation comprising in situ generation fo desiccant comprises the following steps
• a substrate material with a desiccant forming material or a desiccant selected from the group consisting of metal silicates, silica gel, molecular sieves (hydrophillic or hydrophobic), activated alumina, activated carbon, and any mixture thereof, wherein the desiccant forming material is in the form of a solution with a concentration in the range of 15 - 40 %; (ii) drying the treated material to reduce moisture content thereof to a range of 15-40%;
• step iii washing the gel matrix obtained in step iii to remove excess reactants and unwanted by-products;
• step (vii) drying the treated aerogel matrix of step (vi) above at a temperature in the range of 50 - 140°C to obtain said chemical filter.
• the present invention provides a solution for the problems in the art of ensuring maximum efficiency in adsorption of chemical contaminants using a honeycomb based chemical filter using a desiccant.
• Honeycomb matrixes can be formed from a variety of substrates such as plastic sheet, metal/aluminum foil, organic and/or inorganic fiber substrates which are "paper" like, and which may be quite porous.
• the deposition or loading of a desiccant material on the substrate is a function, generally, of the substrate of choice, the amount of desiccant that is to be deposited or loaded, and the temperature at which the air/matrix is intended for use.
• known techniques for deposition or loading the desiccant on the substrate to prepare the matrix are coating, impregnation and in situ synthesis.
• Coating and impregnation are chosen where the desiccant powder is produced in bulk and are intended for industrial applications other than HVAC air treatment.
• In situ synthesis is generally chosen in case of desiccant material such as silica gels and metal silicates.
• the desiccant is generated in situ, and impregnated with oxidizing chemicals, acidic or alkaline chemicals to remove/contain gaseous contaminants, and the loading percentage of impregnants is significantly higher than thought possible in the art.
• the desiccant based honeycomb matrix can be made with or without active carbon or hydrophobic zeolite, for impregnation with different impregnants/ reactants to remove gaseous contaminants. Another significant feature of the invention is that pressure loss is minimized in the desiccant based honeycomb matrix.
• the desiccant may or may not contain active carbon or hydrophobic zeolite and may or may not be impregnated with impregnants for enhanced removal of different contaminants.
• the desiccant based honeycomb matrix chemical filter of the invention also provides an energy saving, and may be with or without active carbon, and may be impregnated with different impregnants or un-impregnated, while also enabling enhanced odour control.
• air to be treated generally contains several gaseous contaminants, e.g. VOCs, odour, and the like. It is desirable to remove these through the desiccant matrix.
• gaseous contaminants e.g. VOCs, odour, and the like.
• gaseous contaminants are sometime water soluble and together are condensed in the macro porous desiccant mainly through capillary adsorption.
• the prior art contains some references to the use of microporous desiccants. However, these desiccants generally have limited capillary adsorption and therefore limited adsorption of gaseous contaminants.
• the prior art also shows a limited loading capability for both the desiccant and any impregnants due to the fact that generally the desiccant is coated or impregnated on the substrate.
• adsorption in these cases is a surface phenomena. This necessarily results in the use of less dense paper, typically in the range of 20 to 80 gsm thickness.
• the requirement of coating of the substrate is generally a limiting factor in the substrate choice, and it was considered unfeasible to increase the density of the substrate without compromising on the surface area required for adsorption.
• honeycomb matrix comprising a desiccant prepared in- situ, for use as a chemical filter, as described herein below.
• the invention is achieved by a macroporous or microporous desiccant based honeycomb matrix.
• the substrate is made from various inorganic or organic substances or combinations thereof.
• the substance can be a fiber or pulp.
• the inorganic fiber is selected from glass fibre, Kraft paper, ceramic paper, etc. and is preferably glass fiber.
• the desiccants that can be synthesized in situ preferably comprise metal silicate/ silica gel which provide a high adsorption capacity.
• the process comprises laminating water glass treated/ impregnated glass fiber in the shape of either a honeycomb or as a block.
• the matrix is treated with either water soluble salts (whether divalent or trivalent) or any acid (whether organic or inorganic) to convert the water glass silicate into the active desiccant material with a pore diameter in the range of 10 - 70 A 0 , a pore volume of 0.10-0.80gm/cc and surface area of 300-700 m 2 .
• the desiccant based honeycomb matrix is generally a flat and/or corrugated sheet of the fiber glass substrate where the active desiccant has been synthesized into the pores.
• the fiber glass substrate used in the present invention is a highly porous material having the fiber diameter of 4-15 micron, fiber length 6-10mm, thickness in the range of 0.10-0.75 mm.
• the binder content of the fiber glass substrate used in the process is not greater than 8% and the preferred binder used in making substrate is polyvinyl alcohol or combination with acrylic. It is advisable to use a low content of organic binder in the substrate so that the percentage of organic content in the desiccant based honeycomb matrix is also reduced.
• the need for adding an external binder is avoided where the water soluble silicate desiccant is generated in situ.
• the silicate material itself carries out the function of a desiccant once treated with suitable reactant/s.
• Water soluble silicates can be used for this purpose, .
• binders may also be used where the desiccant is coated on the matrix.
• the basic weight of the substrate used in the process is 50-150 gsm, preferably between 80 to 120 gsm.
• the fiber used in the making of such substrates can be of electrical grade fiber.
• the flat sheet that is to be corrugated is first passed through the desired concentration of water glass solution (from 15-40%, preferably 30%), with or without active carbon material or hydrophobic zeolite.
• the sheets are dried in a drying chamber, preferably using infra-red heating to ensure that the moisture content is in the desired range of 15-40%, preferably 20%.
• water soluble silicates such as potassium silicate can also be used, sodium silicate is preferable due to its cost efficiency, high solubility of its byproducts, higher bonding strength and easy availability.
• neutral grade water soluble silicate preferably sodium silicate to impregnate the fiber glass substrate. It is observed that the presence of high alkali content in alkaline grade as compared to neutral grade silicate necessitates use of a large quantity of reactants. Use of alkaline grade sodium silicate also results in a higher rate of gelation than neutral grade sodium silicate. The gelling rate adversely affects the characteristics of the desiccants.
• the process of in situ synthesis of the desiccant material on the substrate can be accomplished simultaneously with the deposition of active carbon and/or hydrophobic zeolite material such as HISIV or ZS 05.
• active carbon and/or hydrophobic zeolitic material enhances the level of odour removal and also provides a significant enhancement in structural strength of the substrate itself.
• Active carbon (and/or hydrophobic zeolitic material) in the form of powder is mixed with water soluble silicate or any suitable binder-inorganic or organic_prior to the formation of the desiccant in situ.
• the corrugated sheet is produced by passing the silicate (or silicate and active carbon or hydrophobic zeolite) impregnated flat sheet through a toothed roller. Moisture content of the silicate or silicate and active carbon or hydrophobic zeolite impregnated sheets, grade of water glass, corrugated rolls, the control of clearances on the adhesive rolls and the curing heat of the adhesive are important in making a single facer unit.
• the corrugated sheet and the flat sheet are pressed together using additional rolls of the same material that is used for corrugation. It is preferable to avoid the use of adhesive while making single facer, even with the same water glass used for impregnation, in order to avoid powdering or higher pressure drops after synthesis. This is achieved by keeping higher moisture content in the flat sheet.
• the single facer that is a combination of flat and corrugated sheets can be converted into either a block or a cylindrical shape.
• Neutral grade sodium silicate is preferably applied to ensure adhesion of the single facers sequentially prior to stacking or winding.
• Application of Si0 2 : Na 2 0 in the range of 1:2.0 To 1:4.0 preferably 1:3.0 before winding or stacking of the single facer gives additional strength to the honeycomb matrix.
• the honeycomb matrix that is produced is then dried to enhance the adhesion of the sheets. If the ratio of Si0 2 :Na 2 0 is ⁇ 2, the bonding strength is weaker and if ratio of Si0 2 : Na 2 0 is above 4.0 the adhesive strength is less.
• honeycomb matrix produced above either in block or cylindrical form is then soaked in water soluble metal salt/salts or strong or weak acid/acids- inorganic or organic in different proportions and other forms of solution to produce silicate hydrogel.
• the reaction between water glass silicates with metal salts to form insoluble metal silicate hydro gel is given in table below:
• the element is further dried under specified conditions to convert the hydrogel into the aerogel. It is observed that the type of silicate, types of salts its pH, concentration, temperature and time during which the gel is aged or otherwise treated, greatly affects the gel characteristics such as pore diameter, pore volume, surface area, adsorption capacity etc., The other important factors which affects gel characteristics are salt contents and surface tension of the liquid medium as it is being evaporated from the pores of the gel.
• the manufacture of the desiccant based honeycomb matrix chemical filter of the invention comprises laminating water glass treated/impregnated glass fiber substrate (with or without carbon or hydrophobic zeolite ) in the form/shape of cylinder or block, treating this element with one or more water soluble divalent trivalent salt(s) or organic or inorganic acid(s) - strong or weak, to convert the water glass into active material, and then impregnating the active material with different impregnants.
• the produced aerogel is immersed / impregnated with a solution of oxidizing agent(s), alkaline solution and weak acid solution or any reactants suitable for removing gaseous contaminants of different concentration at different temperature for different soak time.
• oxidizing agent(s) e.g., sodium bicarbonate
• alkaline solution e.g., sodium bicarbonate
• weak acid solution e.g., sodium bicarbonate
• Time required for full impregnation varies as a function of the structure of the adsorbent, temperature and other factors.
• the honeycomb material is then placed in an oven and heated till free moisture and water evaporate or are driven out of the mixture leaving impregnating material within the pores of honeycomb silicate aerogel material and/or silicate hydrogel and activated carbon or hydrophobic zeolite.
• the drying temperature of the impregnated honeycomb material is in the range of 50-140°C.
• the exposure time in the heating is varied with quality and quantity of materials, heating efficiency and other factors.
• impregnants used are potassium and sodium permanganate, sodium or potassium hydroxide, weak acids such as phosphoric acid, and a reducing agent such as sodium thiosulphate.
• the loading of impregnants depends on various factors such as types of desiccants, concentration of impregnants, soak time, temperature, number of dips, etc.
• Macroporous or microporous desiccant (with or without active carbon) material supported honeycomb matrix is impregnated with potassium/sodium permanganate solution in a range of 5 to 40%, preferably 15% concentration in case of potassium permanganate and 30% in case of sodium permanganate, at 10°C to 90°C, most preferably at 70°C for 5 to 60 minutes, most preferably for 15 minutes, to get the maximum impregnant loading without affecting the mechanical strength of the matrix and water/CTC adsorption capacity.
• Table 1 gives details of factors that affect percentage of loading of impregnant (KMn0 4 vs. NaMn0 4 ) and adsorption capacity of impregnated honeycomb desiccant based matrix.
• Macroporous or microporous desiccant (with or without active carbon and/or hydrophobic zeolitic material) material supported honeycomb matrix is impregnated with potassium hydroxide solution in the range of 2 to 15%, most preferably 6%, at 10°C to 50°C, most preferably at 30°C for 5 to 60 minutes, most preferably for 15 minutes to get the maximum impregnant loading without affecting the mechanical strength of the matrix and water/CTC adsorption capacity.
• Table 2 gives details of factors affecting the % of loading of impregnant (KOH) and adsorption capacity of impregnated honeycomb desiccant based matrix.
• Macroporous or microporous (with or without active carbon) material supported honeycomb matrix is impregnated with phosphoric acid solution in the range of 2 to 15%, most preferably 8%, at 10°C to 50°C, most preferably ai 30°C for 5 to 60 minutes, most preferably for 15 minutes to get the maximum impregnant loading without affecting mechanical strength of the matrix and water/CTC adsorption capacity.
• Table 3 gives details of factors affecting percentage loading of impregnant (Phosphoric acid) and adsorption capacity of impregnated honeycomb desiccant based matrix.
• Macroporous or microporous (with or without active carbon or hydrophobic zeolite) material supported honeycomb matrix is impregnated with sodium thiosulphate solution in the range of 5 to 45%, preferably 15 %, at 10°C to 50°C, most preferably at 30°C for 5 to 60 minutes, preferably for 15 minutes to get maximum impregnant loading without affecting the mechanical strength of the matrix and water/CTC adsorption capacity.
• Table 4 gives details of factors affecting % of loading of impregnant (Sodium thiosulphate) and adsorption capacity of impregnated honeycomb desiccant based matrix:
• the present invention provides several significant advantages over prior art methods. Some of these are summarized below.
• potassium permanganate can also be impregnated to a large loading percentage on microporous material. 2. There is an enhancement in the extent of loading due to several factors, some of which are given below:
• the GSM of the substrate is significantly higher than that used in the prior art.
• the GSM generally ranges from 50 to 150 gsm, preferably between 80 to 120 gsm. This enables higher desiccant loading on the substrate leading to a larger impregnate loading of the impregnate;
• Desiccant can be combined with active carbon or hydrophobic zeolite , preferably by mixing the carbon powder or a hydrophobic desiccant such as zeolitic material selected from HISIV or ZSM-05 with a suitable binder, preferably inorganic prior to formation of the desiccant in situ. This enables capture/encapsulation of the carbon particles within the desiccant. This enabies an enhancement in odour control, VOC adsorption, and in the structural strength of the matrix itself.
• zeolitic material selected from HISIV or ZSM-05
• the invention enables if required, a sacrifice of the surface area of the matrix to enable multiple fluid geometries, and allows lower pressure drops without any significant material sacrifice of the performance.

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• 2013
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