MX2014008803A

MX2014008803A - Desiccant based honeycomb chemical filter and method of manufacture thereof.

Info

Publication number: MX2014008803A
Application number: MX2014008803A
Authority: MX
Inventors: Deepak Pahwa; Anil Kumar Choudhary
Original assignee: Desiccant Rotors Internat Pvt Ltd
Priority date: 2012-01-20
Filing date: 2013-01-19
Publication date: 2015-08-05
Also published as: CN104470632A; WO2013108117A1; BR112014017899A8; AU2013210811A1; CA2865123A1; KR20150003716A; EP2804694A1; AU2017208389A1; BR112014017899A2

Abstract

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.

Description

DESICANTE BASED ON CHEMICAL FILTER OF PANAL AND METHOD OF MANUFACTURE OF THE SAME FIELD OF THE INVENTION The present invention relates to a chemical filter for the removal of air pollutants present in industrial or domestic environments. More particularly, the present invention relates to a desiccant based on a honeycomb chemical filter. The present invention also relates to a method for manufacturing a desiccant based on a honeycomb chemical filter.

As stated above, this invention relates to a desiccant based on a chemical filter, such as a honeycomb chemical filter, for the removal of air pollutants present in industrial or domestic environments. The present invention also provides a method for making a desiccant based on a honeycomb chemical filter.

The contaminants to be removed are typically gaseous pollutants but may also comprise contaminants in the form of fine droplets of liquid which are not easily removable by conventional means.

The term "desiccant" as used herein is intended to cover a desiccant or macroporous desiccants or microporous. The desiccant or dryers based on a honeycomb matrix used in the invention are impregnated with different impregnating materials. The invention also provides methods for the removal of gaseous pollutants, pollutants and odors from industrial processes using the chemical filter. This invention also relates to a process for manufacturing desiccant or macroporous / microporous desiccants based on the honeycomb matrix impregnated with different impregnants to remove gaseous pollutants contained in the air or odors in the air.

It is well recognized that it is difficult to handle the molecular pollutants carried by the air due to the difficulty in counting and / or measuring those particles present in a given area. This difficulty is mainly due to the fact that the gases are different from the particles. The impact of contaminants on productivity as well as on human life, if not properly addressed, can be severe. The presence of chemical pollutants even at concentrations of parts per billion (ppb) can alter the chemical properties of the surrounding environment and adversely affect human life and productivity. Traditional filters have been insufficient to protect a given environment against gaseous pollutants, particularly inorganic contaminants such as ammonia, amines, ozone, sulfur oxides, nitrogen oxides, sulfides and other molecular pollutants that remain undetectable by particle counters.

BACKGROUND OF THE INVENTION The problem in the technique should be understood from the following discussion of some solutions available for the removal of volatile organic components that form a significant part of the molecular pollutants carried by the air, particularly in an industrial environment.

A problem in the art has been to ensure that as long as the odor is controlled, there is no sacrifice on the level of humidity that is desirable for comfort and human health. However, the administration of an appropriate level of humidity as well as odor control present a particular problem, since existing dehumidifying devices remove too much moisture from the air or are inefficient in the removal of odors.

Odors in industrial environments, and also in non-industrial environments such as passenger compartments of transport vehicles, are due to volatile organic compounds present in circulating air. These organic compounds are formed at high levels but at relatively low concentrations of the exhaust system of engines, solvents, gas turbines, cogeneration plants, petrochemical plants, and 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 (mainly amines), sulfur-containing materials (mercaptans and thioethers) ) and halogen-containing materials, especially hydrocarbons substituted with chlorine but also organic chlorides and bromides. The presence of these compounds in a gas flow is recognized as a health risk and / or causes the gas flow to have an unpleasant and undesirable odor.

A traditional method for the recovery of wet air solvent comprised an adsorption system which typically was operated until the concentration of solvent in the exit gas flow reached a detectable present anticipated level. When this level was reached, the flow of gas to the adsorbent was interrupted. The adsorbent bed then contained solvent, other condensable organic contaminants, and some amount of water depending on the relative humidity of inlet of the gas flow loaded with solvent.

This method was later modified by the introduction of an inert gas or hot steam, either saturated or superheated, which displaces the solvent from the adsorbent to produce a solvent / water mixture after condensation. Typically two beds of adsorbent were used, where one adsorbed while the other bed underwent regeneration.

Additional developments in the regeneration and recovery of adsorbent bed solvents involve the use of inert gases or condensation air at low temperature of the gas solvent / regeneration air. However, these techniques are not directly applicable in all situations where it is regulated.

It is known that volatile organic compounds can be removed from the air by adsorption as a rotating thermal adsorption. Air flows that need treatment can be found in most chemical and manufacturing plants, and especially those that use solvents. At concentration levels of 500 to 15,000 ppm, the recovery of VOC from the steam used to thermally regenerate the activated carbon adsorbent is economically justified. Concentrations above 15,000 ppm are typically found in the explosive range and require the use of a hot inert gas instead of air for regeneration. While, for below about 500 ppm, recovery is not economically justifiable, environmental concerns often dictate recovery by adsorption followed by destruction. Activated carbon is the traditional adsorbent for these applications, and represents its second greatest use.

U.S. Patent No. 4,421,532 describes a process for the recovery of VOCs from industrial waste gases by rotary thermal adsorption including the use of hot inert gases circulating in a closed cycle to desorb VOCs.

A device used to dry air in closed areas such as a home, ship or building at 0.001 pounds of water per pound of air is discussed in U.S. Patent No. 4,134,743. This document describes a process and apparatus wherein the adsorbent body is a wheel of sheets or thin layers of fibrous material containing approximately 10 to 90% by weight of a freely divided molecular sieve material. The apparatus includes means for passing air to be processed in one direction through the wheel and means for passing a flow of regenerative air in countercurrent to the air to be processed. In addition, it provides a cooling flow in a direction under current with the air flow.

U.S. Patent No. 4,887,438 describes an air conditioning system aided by desiccant to distribute dehumidified refrigerated air to a conditioned space on the basis of an adsorbent wheel. Meckler teaches the use of a drying wheel coated with silica gel, or a preferred hygroscopic salt, lithium chloride, to remove moisture from the air. This citation teaches the use of residual heat from the cooling condenser to heat the reactivation air and employs an injection of liquid refrigerant to the compressor to increase the pressure ratio in a positive displacement compressor to counteract the problem of "thermal overflow". Thermal overflow is the associated heat conducted from the desiccant wheel to the treated air that occurs after exposure of the wheel to the hot regeneration air. This associated heat is added to the total cooling load on the cooling system.

U.S. Patent No. 5,242,473 discloses a gas dehumidifying apparatus which exhibits better dehumidification efficiency to provide a gas treated with a high level of dryness using two dehumidifying rotors, where the second rotor uses a synthetic zeolite. The gas to be dehumidified is first passed to a rotor covered with silica gel and then to the rotor coated with zeolite. The rotors are regenerated by supplying a flow of hot gas through the second rotor and then the first rotor, so that the adsorbent in the first rotor is regenerated at a temperature lower than that of the zeolite in the second rotor. A portion of the treated gas is used to counter-flow the rotors after regeneration.

Of the techniques for removing volatile organic pollutants at low concentrations of a gas flow by adsorption the most common is exemplified in U.S. Patent No. 4,402,717. This document teaches an apparatus for removing moisture and odor from a gas flow comprising a cylindrical honeycomb structure made of corrugated paper, uniformly coated with an adsorbent and formed in the form of a disk or wheel. The multiplicity of parallel flow passages coated with adsorbent formed by the corrugations in the paper serves as gas passageways which are separated as a zone for the removal of water and the components that cause the smell in the gas, and as a zone for the regeneration of the adsorbent. The zones for the removal and regeneration are continuously deflectable since the wheel rotates circumferentially around its center line. Labyrinth seals separate the outer side of the rotating structure from the cylindrical wall of the sealed case.

One of the problems associated with attempts of the previous technique for using a honeycomb matrix is the adsorbent that is used. Hydrophilic adsorbents such as silica gel are typically chosen for dehumidification applications, but are poor adsorbents for the removal of volatile organic contaminants. One such process combination is discussed in U.S. Patent No. 5,181,942. On the other hand, hydrophobic adsorbents, such as higher silica zeolites are typically recommended for VOC removal applications, but are poor adsorbents for dehumidification applications. Thus, applications for dehumidification and VOC removal may typically require both types of adsorbents.

Attempts have therefore been made to be able to use a single adsorbent for both operations. In addition, paper coated with adsorbent and some adsorbent salts may have a limited range of moisture and temperature within which they may retain their structural integrity. This failure also limits the regeneration medium to dry gases and air at a moderate temperature. The contact between the adsorbent and the gas flow and consequently the adsorbent capacity for the VOCs is limited to very thin layers of adsorbent on the surface of the fiber. This feature also limits the final life of the adsorbent wheel, resulting in frequent replacement of the wheel.

It is recognized that chemical filtration strategies are ideal for use in the control of molecular pollution carried by the air. However, the use of the honeycomb matrix based on desiccants has generally not been considered due to the difficulty in ensuring moisture and chemisorption control.

Filters are generally devices such as a membrane or a layer that is designed to block or contain objects or substances and allow others to pass through it. Filtration media are generally of three types - mechanical, biological and chemical. Chemical filters are preferred for the removal of gaseous pollutants in a given environment since they provide air purification by absorption and absorption of odors by impregnated adsorbents / adsorbents such as potassium permanganate for a controlled oxidant action.

Gaseous pollutants can be inorganic and organic. To remove gaseous pollutants, the selection of adsorbents to adsorb gas or adsorbent / impregnated gas reagents is very important for chemical filter media. As discussed above, a single chemical filter medium may not adequately control multiple contaminants or classes of AMC.

BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to provide a desiccant based on the honeycomb chemical filter, where the desiccant is generated in situ, and impregnated with oxidizing chemical compounds, acidic or alkaline chemical compounds, or reducing chemical compounds to remove / contain gaseous contaminants, where the percentage of loading of impregnants is significantly higher than what is possible in the technique.

The main objective of the present invention is to increase the removal capacity of gaseous pollutants, whether they are acidic, alkaline or organic and to increase the life of the chemical filter through the use of larger quantities of impregnants.

A further object of the invention is to produce a desiccant based on a honeycomb matrix or without activated carbon or hydrophobic zeolite for impregnation with different impregnants / reagents to remove gaseous contaminants.

Another object of the invention is to provide a desiccant based on a honeycomb matrix where the loss of pressure is minimized. The desiccant may or may not contain activated carbon or hydrophobic zeolite and may or may not be impregnated with impregnants to improve the removal of different contaminants.

An object of the invention is to provide a recess based on a honeycomb matrix chemical filter that provides an energy saving, and can be with or without activated carbon or hydrophobic zeolite and can be impregnated with different impregnants or not be impregnated, allowing the time a better control of the smell.

Accordingly, to overcome the problems encountered in the foregoing technique, the present invention provides a honeycomb matrix comprising a desiccant prepared in situ, to be used as a chemical filter, as described below.

The present invention provides a desiccant based on a honeycomb chemical filter comprising a matrix formed of a substrate having a cascade generated in situ or deposited thereon, the desiccant being selected from the group consisting of silicates of metal, silica gel, molecular sieves, activated alumina, activated carbon and hydrophobic zeolite, and any mixture thereof, the substrate being further impregnated with one or more of an oxidizing agent, or an alkali metal hydroxide or strong or weak acids, or reducing agents.

The substrate comprises an inorganic substance or an organic substance or a mixture thereof.

In a further embodiment, the substrate is in the form of a fiber or a pulp.

In a further embodiment, the inorganic fiber is selected from the group consisting of fiberglass, Kraft paper, ceramic paper and any combination thereof, and is preferably a glass fiber.

In another embodiment, the desiccant is selected from a silicate of metal and silica gel or a combination of silicate with activated carbon and / or a hydrophobic desiccant such as the selected zeolites of HISIV and ZS-5.

The metal silicate is selected from potassium silicate and sodium silicate, preferably where the silicate is a neutral grade sodium silicate.

In a preferred embodiment, in the sodium silicate, the ratio of Si02 to Na20 is in the range of 1: 2.0 to 1: 4.0, preferably in the range of 1: 3.

In another embodiment of the invention, the impregnated material is selected from the group consisting of potassium permanganate, sodium permanganate, potassium hydroxide, sodium hydroxide, phosphoric acid and sodium thiosulfate.

In a further embodiment of the invention, the loading of material impregnated in the matrix is in the range of 4% to 40%, preferably approximately 20%.

In a further embodiment of the invention, the binder is preferably absent.

In a further embodiment of the invention, the basic weight of the substrate is in a range of 50 g to 150 g, preferably in the range of 80 to 120 g.

The present invention also provides a method for manufacturing a honeycomb chemical filter based on a desiccant, comprising the steps of: (i) dehydrating a honeycomb matrix based on macroporous or microporous desiccant / desiccants at a temperature of 100 ° C or more; (ii) impregnating the dehydrated desiccant-based honeycomb matrix with suitable impregnants and then drying the matrix with moisture content retention in the range of 15-30%.

The method when used in a situation comprising in situ generation for the desiccant comprises the following steps: (i) treating a substrate material with a desiccant forming material or a desiccant selected from the group consisting of silicates of metal, silica gel, molecular sieves (hydrophilic or hydrophobic), activated alumina, activated carbon, and any mixture of the same, where the material forming desiccant is in the form of a solution with a concentration in the range of 15-40%; (ii) drying the treated material to reduce the moisture content thereof to a range of 15-40%; (iii) soaking the substrate matrix in salt or metal salts or water soluble strong or weak acids to form a hydrogel and obtain a gel matrix; (iv) washing the gel matrix obtained in step iii to remove excess reagents and undesirable products; (v) drying the gel matrix under controlled temperature conditions to convert the hydrogel into an airgel matrix; (vi) treating the airgel matrix with one or more of an oxidizing agent, or an alkali metal hydroxide, or strong or weak acids, or reducing agents; (vii) drying the treated airgel matrix of step (vi) above at a temperature in the range of 50-140 ° C to obtain the guillotine filter.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a solution to the problems in the art of ensuring maximum efficiency in the adsorption of chemical contaminants using a honeycomb-based chemical filter using a desiccant. Honeycomb matrices can be formed from a variety of substrates such as a plastic sheet, thin sheet metal / aluminum, strata of organic and / or inorganic fiber that are similar to "paper" and that can be very porous. The deposition or loading of a desiccant material on the substrate it is a function, in general, of the substrate of choice, the amount of decant that is going to be deposited or charged, and the temperature at which the air / matrix is intended to be used. Among the known techniques for the deposition or desiccant charge on the substrate to prepare the matrix is the coating, impregnation and synthesis in situ.

The coating or impregnation are chosen where the desiccant powder is produced in bulk and is intended to be used for industrial applications other than HVAC air treatment. In situ synthesis is generally chosen in the case of a desiccant material such as silica gels and metal silicates.

In the desiccant-based honeycomb chemical filter of the invention, the desiccant is generated in situ, and impregnated with oxidizing chemical compounds, acidic or alkaline chemical compounds to remove / contain gaseous contaminants, and the percentage of loading of impregnants is significantly greater than is possible in the technique.

In a surprising discovery, this has resulted in an increase in the removal capacity of gaseous pollutants, either acidic, alkaline, or organic and an increase in the life of the chemical filter through the use of larger quantities of impregnants.

The honeycomb matrix based on desiccant can be produced with or without activated carbon or hydrophilic zeolite, for impregnation with different impregnants / reagents to remove gaseous pollutants. Another significant feature of the invention is that the loss of production in the honeycomb matrix based on desiccant is minimized. The desiccant may or may not contain activated carbon or hydrophobic zeolite and may or may not be impregnated with impregnants to improve the removal of different contaminants.

The desiccant-based honeycomb matrix chemical filter of the invention also provides an energy saving, and can do so with or without activated carbon, and can be impregnated with different impregnants or not be impregnated, while allowing better control of the odor.

As stated above, the air to be treated, particularly the air from the outside, generally contains several gaseous contaminants, for example VOCs, odor and the like. It is desirable to remove those through the desiccant matrix. In the air to be treated, particularly when air is precooled almost to saturation, those gaseous contaminants are sometimes soluble in water and condense together in the macroporous desiccant mainly through capillary adsorption. The previous technique contains some references to the use of microporous casts. However, these desiccants generally have limited capillary adsorption and therefore Limited adsorption of gaseous pollutants.

The above technique also shows a limited loading capacity for both the desiccant and any impregnant due to the fact that generally the desiccant is coated or impregnated on the substrate. In this way, the adsorption in these cases is a surface phenomenon. This necessarily results in the use of less dense paper, typically in the range of 20 to 80 g in thickness. The requirement for coating the substrate is generally a limiting factor in the choice of substrate, and it was considered ineligible to increase the density of the substrate without compromising the surface area required for adsorption.

The problems encountered in the prior art are solved in the present invention by providing a honeycomb matrix comprising a desiccant prepared in situ for use as a chemical filter, as described hereinafter.

The invention is achieved by means of a honeycomb matrix based on macroporous or microporous desiccant. The substrate is constituted by several inorganic or organic substances or combinations thereof. The substance can be a fiber or pulp. The inorganic fiber is selected from glass fibers, Kraft paper, ceramic paper, etc. and it is preferably fiberglass. The desiccants also they can be synthesized in situ preferably comprising metal silicate / silica gel which provides a high adsorption capacity.

The invention will now be described with reference to an exemplary non-limiting embodiment where fiberglass is used as the substrate. The process comprises laminating glass fiber treated / impregnated with water in the form of a honeycomb or as a block. The matrix is treated with water soluble salts (divalent or trivalent) or any acid (organic or inorganic) to convert the hydrated glass silicate into the active desiccant material with a pore diameter in the range of 10-70 A °, a pore volume of 0.10-0.80 g / cc and a surface area of 300-700m2.

The desiccant-based honeycomb matrix is generally a flat and / or corrugated sheet of fiberglass substrate where the active desiccant has been synthesized in the pores. In fiberglass substrate used in the invention is a highly porous material having a fiber diameter of 4-15 microns, a fiber length of 6-10 mm, a thickness in the range of 0.10-0.75 mm. The binder content of the glass fiber substrate used in the process is not greater than 8% and the preferred binder used to produce the substrate is polyvinyl alcohol or a 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 honeycomb matrix based on desiccant is also reduced.

Generally, the need to add an external binder is avoided where the water soluble silicate desiccant is generated in situ. The silicate material itself performs the function of a desiccant once treated with the appropriate reagents. However, when the desiccant is to be coated on the matrix, it is possible to add an additional binder material. Water-soluble silicates can be used for this purpose. Alternatively, commercially available binders can also be used where the desiccant is coated on the matrix.

The basic weight of the substrate used in the process is 50-150 g, preferably between 80 to 120 g. The fiber used in the preparation of these substrates can be electrical grade fiber. The flat sheet to be corrugated is first passed through the desired concentration of aqueous sodium silicate solution (15-40%, preferably 30%), with or without activated carbon material or hydrophobic zeolite. The sheets are dried in a drying chamber, preferably using infrared heating, to ensure that the moisture content is in the desired range of 15-40%, preferably 20%. Although other types of water-soluble silicates can also be used, such as silicate potassium, sodium silicate is preferred due to its cost, high solubility of its byproducts, higher binding strength and easy availability.

It is preferable to use neutral grade water soluble silicate, preferably sodium silicate, to impregnate the glass fiber substrate. It is observed that the presence of a high alkali content in the alkali grade silicate compared to the neutral grade requires the use of a large amount of reagents. The use of sodium silicate alkali grade also results in a higher gelation rate than sodium silicate neutral grade. The gelation rate adversely affects the characteristics of the desiccants.

The process of in situ synthesis of the desiccant material on the substrate can be effected simultaneously with the deposition of activated carbon and / or hydrophobic zeolite material such as HISIV or ZSM05. The use of the activated carbon material and / or hydrophobic zeolite improves the level of odor removal and also provides a significant improvement in the structural strength of the substrate itself. The activated carbon (and / or a hydrophobic zeolitic material) in powder form is mixed with water-soluble silicate or any binder-inorganic or organic-before formation of the desiccant in situ. This allows the capture / encapsulation of carbon particles activated or hydrophobic zeolite within the desiccant, thereby improving odor control, VOC adsorption, and the structural strength of the matrix itself.

The corrugated sheet is produced by passing the flat sheet impregnated with silicate (or silicate and activated carbon or hydrophobic zeolite) through a serrated roller. The moisture content of the leaves impregnated with silicate or silicate and activated carbon or hydrophobic zeolite, the degree of the water-soluble sodium silicate, the corrugated rolls, the cleaning control on the adhesive rolls and the heat of the curing of the adhesive are important to produce a unit with a single coating. The corrugated sheet and flat sheet are pressed together using additional rollers of the same material that was used for the corrugation. It is preferable to avoid the use of adhesive while producing the single coating, even with the same water-soluble sodium silicate used for impregnation, to avoid spraying or higher pressure stocks after the synthesis. This is achieved by retaining a higher moisture content in the flat sheet.

The unique coating that is a combination of flat and corrugated sheets can be converted into a block or a cylindrical shape. The neutral grade sodium silicate is preferably applied to ensure the adhesion of individual coatings sequentially before stacking or roll up. The application of Si02: Na20 in the range of 1: 2.0 to 1: 4.0 preferably 1: 3.0 before rolling or stacking the coating gives additional resistance to the honeycomb matrix. The honeycomb matrix that is produced is then dried to improve the adhesion of the sheets. If the ratio of Si02: Na20 is < 2, the bond strength is weaker and if the ratio of Si02: Na20 is higher than 4.0 the adhesive strength is lower.

Another advantage of using neutral grade silicate is the drying rate. The loss of moisture is affected by the ratio of Si02: Na20 because the water retention is direct fusion of the alkalinity. A higher silicate ratio retains less water. The drying of more alkaline silicates of the ratio Si02: Na20 in the range 2.0-2.6 is less than that of the silicate having SiO2: Na20 in the range of 3.0-3.3.

The honeycomb matrix produced above either in block or cylindrical form is then soaked in salt / water soluble metal salts or acid / strong inorganic or organic acids in different proportions and other forms of solution to produce silicate hydrogel. The reaction between water-soluble sodium silicates with metal salts to form insoluble metal silicate hydrogel is given in the following table.

Na2Si03 + Al2 (SO4) 3 ® Al2 (Si03) 3 + Na2S04 Na2Si03 + MgSO4- > MgSi03 + Na2S04 Na2Si03 + MgCl2 - > MgSi03 + NaCl Na2Si03 + A1C13 ® Al2 (Si03) + NaCl Na2Si03 + HC1 ® H2Si03 + NaCl The washing of the gel matrix is essential to remove by-products and excess reagents formed during the synthesis of the active materials. The acidity of the gel matrix due to the presence of excess reagents deteriorates the building material used in the system. The hydrogel is washed at controlled pH. The gelation pH of the matrix or the concentration of reagent / reagents, temperature, reaction time used in the process change the characteristics of the active material, such as pore size, porosity, pore volume and surface area.

The element is further dried under specified conditions to convert the hydrogel into an airgel. It was observed that the type of silicate, types of salts, their pH, concentration, temperature and time during which the gel is aged or otherwise treated, greatly affects the characteristics of the gel such as pore diameter, pore volume , surface area, adsorption capacity etc. The other important factors that affect the characteristics of the gel are the salt content and the surface tension of the liquid medium when it evaporates from the pores of the gel.

The manufacture of the chemical matrix filter The desiccant-based honeycomb of the invention comprises laminating the glass fiber substrate treated / impregnated with water-soluble sodium silicate (with or without carbon or hydrophobic zeolite) in cylinder or block form, treating this element with one or more water divalent / trivalent salts or organic or inorganic acids-strong or weak, soluble in water, to convert water-soluble sodium silicate into active material, and then impregnate the active material with different impregnants.

The produced airgel is submerged / impregnated with a solution of oxidizing agents, alkaline solution and weak acid solution or any suitable reagent to remove gaseous pollutants of different concentration at a different temperature during a different soaking time. When the honeycomb is impregnated sufficiently with solution, the excess of impregnation is drained and conserved in another container after adjusting the concentration.

The time required for total 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 to free moisture and evaporate the water and taken out of the mixture leaving the impregnating material inside the pores of honeycomb silicate airgel material and / or silicate and carbon hydrogel activated or hydrophobic zeolite.

Preferably, the drying temperature of the impregnated honeycomb material is in the range of 50-140 ° C. The exposure time in heating varies with the quality and quantity of materials, heating efficiency and other factors. After preparation, the honeycomb matrix impregnated with impregnant is preserved until ready for use. The impregnation steps are described below: to. dehydration of the honeycomb matrix based on macroporous or microporous desiccant / desiccant b. impregnation with impregnation / impregnation c. drying of the honeycomb matrix based on macroporous or microporous desiccant / desiccants.

In our experiments the preferred impregnants used are potassium and sodium permanganate, sodium or potassium hydroxide, weak acids such as phosphoric acid, and a reducing agent such as sodium thiosulfate. The loading of impregnants depends on several factors such as types of desiccants, concentration of impregnants, soaking time, temperature, number of dives, etc.

Impregnation with Potassium Permanganate and Sodium Permanganate The honeycomb matrix supported by macroporous or microporous desiccant material (with or without activated carbon) is impregnated with a permanganate solution of potassium / sodium in a range of 5 to 40%, preferably at a concentration of 15% in the case of potassium permanganate and 30% in the case of sodium permanganate, 10 ° C to 90 ° C, more preferably of 70 ° C for 5 to 60 minutes, more preferably for 15 minutes, to obtain the maximum impregnant load without affecting the mechanical strength of the matrix and the water adsorption capacity / CTC. Table 1 gives details of the factors that affect the percentage of loading of impregnant (KMn04 against NaMn04) and capacity of adsorption of the matrix based on impregnated honeycomb desiccant.

TABLE 1 A. CONCENTRATION OF IMPREGNANTS B. REMOVAL TIME OF KMn04 AND NaMn04 C. TEMPERATURE OF KMn04 AND NaMn04 D. KMn04 and NaMn04 (Macro against Micro) The concentrations, soaking time, solution temperature, successive immersion and surface properties of the active material play an important role in achieving the double objective of loading and absorption. The method of impregnation of alkali, preferably sodium or potassium hydroxide, or acid, preferably phosphoric acid and reducing agent such as sodium thiosulfate with micro or macropores and / or with hybrid desiccant (metal silicate and acid-insoluble activated carbon) is described here later. An activated carbon suspension is prepared in water-soluble sodium silicate solution and the honeycomb matrix is wound into a block or cylinder. The honeycomb matrix is supported with sodium silicate soluble in water and activated carbon is treated with a salt solution as described earlier. The desiccant material, whether macroporous or microporous (and with or without activated carbon), the supported honeycomb matrix is impregnated with different concentrations of impregnants.

Impregnation with Potassium Hydroxide The honeycomb matrix supported on macroporous or microporous desiccant material (with or without activated carbon and / or hydrophobic zeolitic material) is impregnated with potassium hydroxide solution in the range of 2 to 15%, more preferably 6%, of 10 ° C to 50 ° C, more preferably at 30 ° C for 5 to 60 minutes, more preferably for 15 minutes to obtain the maximum impregnation load without affecting the mechanical strength of the matrix and water adsorption capacity. CTC Table 2 gives the details of the factors that accept the impregnated load percentage (KOH) and adsorption capacity in the impregnated honeycomb matrix.

TABLE 2 A. CONCENTRATION OF IMPREGNANTS - macroporous against icroporous with activated carbon (hybrid desiccants) B. KOH REMOVAL TIME C. KOH TEMPERATURE Impregnation with Phosphoric Acid The honeycomb matrix supported on macroporous or microporous material (with or without activated carbon) is impregnated with phosphoric acid solution in the range of 2 to 15%, more preferably 8%, of 10 ° C to 50 ° C, most preferably from 30 ° C for 5 to 60 minutes, more preferably for 15 minutes to obtain the maximum impregnation filler without affecting the mechanical strength of the matrix and water adsorption capacity / CTC. Table 3 gives the details of the factors affecting the impregnant charge (phosphoric acid) and the adsorption capacity of the impregnated honeycomb desiccant based matrix.

TABLE 3 A. CONCENTRATION OF IMPREGNANTS - macroporous against microporous and activated carbon (hybrid desiccants) B. PHOSPHORIC ACID REMOVAL TIME C. TEMPERATURE OF PHOSPHORIC ACID D. KOH (Macro against Micro) Impregnation with sodium thiosulfate The honeycomb matrix supported on macroporous or microporous material (with or without activated carbon or hydrophobic zeolite) is impregnated with sodium thiosulfate solution in the range of 5 to 45%, preferably 15%, of 10 ° C to 50 ° C, more preferably at 30 ° C for 5 to 60 minutes, preferably for 15 minutes to obtain the maximum impregnation filler without affecting the mechanical strength of the matrix and adsorption capacity and water / CTC. Table 4 gives details of the factors that affect the percent loading of impregnant (sodium thiosulfate) and the adsorption capacity of the impregnated honeycomb desiccant based matrix: TABLE NO.4 A. CONCENTRATION OF IMPREGNANTS - macroporous against microporous and activated carbon (hybrid desiccants) B. TIME TO REMOVE THE SOLUTION OF SODIUM TIOSULFATE C. TEMPERATURE OF THE SOLUTION OF SODIUM TIOSULFATE The present invention provides several significant advantages over the methods of the prior art. Some of those are summar below. 1. Although macroporous material is generally preferred, potassium permanganate can also be impregnated at a large percentage of filler on microporous material. 2. There is an improvement in the degree of loading due to several factors, some of which are given below: (a) The grams of substrate are significantly larger than that used in the prior art. The grams generally fluctuate from 50 to 150 grams, preferably between 80 and 120 grams. This allows a greater load of desiccant on the substrate which leads to a higher impregnation load of the impregnated one; (b) the in situ formation of the desiccant is carried out in such a way that its pH is neutral and is generally minimally affected by the chemical nature of the gas, whether acidic or basic. Binders are avoided preferably and are not considered necessary for the formation of desiccant and the desiccant materials thus obtained are all active materials. This also results in the final increase in the substrate surface density of 400 to 750 grams. (c) The degree of loading also improves due to a combination of different factors such as soaking time, temperature and concentration. For example, permanganates, usually Na permanganate achieves a load of more than 30%. Additionally the necessary moisture content is maintained, in a greater adsorption capacity of the desiccant since this is synthes in situ, additional advantages include the fact that the desiccant can be bacteristatic, and not flammable. (d) The desiccant can be combined with activated carbon or hydrophobic zeolite preferably by mixing the carbon powder or a hydrophobic desiccant as a zeolitic material selected from HISIV or ZSM-05 with a suitable binder, preferably inorganic prior to in situ desiccant formation. This allows to capture / encapsulate the carbon particles inside the desiccant. This allows for an improvement in color control, VOC adsorption, and the structural strength of the matrix itself. 3. The invention allows, if required, a sacrifice of the surface area of the matrix to allow Multiple fluid geometries, and allows lower pressure drops without any sacrifice of material or significant performance. 4. An efficiency of up to 100% is achieved even in spite of the reduced contact time when carried out at frontal speeds greater than 400 to 600 fpm [2 to 3 m / sec].

Claims

1. A desiccant-based honeycomb chemical filter, characterized in that it comprises a matrix formed of a substrate having a desiccant generated in situ or deposited thereon, the desiccant being selected from the group consisting of silicates of metal, silica gel, molecular sieves , activated alumina, activated carbon and any mixture thereof, the substrate being further impregnated with one more of an oxidizing agent, or an alkali metal hydroxide, or acid or strong or weak, or reducing agents.

2. The chemical filter according to claim 1, characterized in that the substrate comprises an inorganic substance or an organic substance or a mixture thereof.

3. The chemical filter according to claim 2, characterized in that the substance is in the form of a fiber or a pulp.

4. The chemical filter according to claim 3, characterized in that the inorganic fiber is selected from the group consisting of glass fiber, Kraft paper, ceramic paper and any combination thereof.

5. The chemical filter according to claim 4, characterized in that the inorganic fiber It is fiberglass.

6. The chemical filter according to claim 1, characterized in that the desiccant is selected from a silicate of metal and silica gel or combination of metal silicate and activated carbon and / or hydrophobic desiccant such as zeolites selected from HISIV and ZSM-5.

7. The chemical filter according to claim 6, characterized in that the metal silicate is selected from potassium silicate and sodium silicate.

8. The chemical filter according to claim 7, characterized in that the silicate is a neutral grade sodium silicate.

9. The chemical filter according to claim 8, characterized in that in the sodium silicate, the ratio of Si02 to Na20 is in the range of 1: 2.0 to 1: 4.0, preferably in the range of 1: 3.

10. The chemical filter according to claim 1, characterized in that the impregnated material is selected from the group consisting of potassium permanganate, sodium permanganate, potassium hydroxide, sodium hydroxide, phosphoric acid and sodium thiosulfate.

11. The chemical filter in accordance with the claim 10, characterized in that the loading of the impregnated material in the matrix is in the range of 4% to 40%, preferably approximately 20%.

12. The chemical filter according to any of the preceding claims, characterized in that the binder is preferably absent.

13. The chemical filter according to any of the preceding claims, characterized in that the activated carbon and / or hydrophobic desiccant material such as HISIV or ZSM-5 is added together with the desiccant that is generated in situ.

14. The chemical filter according to any of the preceding claims, characterized in that the basic weight of the substrate is in the range of 50 to 150 grams.

15. The chemical filter according to any of the preceding claims, characterized in that the basic weight of the substrate is in the range of 80 to 120 grams.

16. A method for manufacturing a desiccant-based honeycomb chemical filter characterized in that it comprises the steps of (i) dehydrate a honeycomb matrix based on macroporous or microporous desiccant / desiccants to a temperature of 100 ° C or more; (ii) impregnating the honeycomb matrix based on dehydrated desiccant with suitable impregnants and then drying the matrix retaining the moisture content in the range of 15-30%.

17. The method according to claim 16, characterized in that it comprises: (i) treating a substrate material with a desiccant-forming material or a desiccant selected from the group consisting of metal silicates, silica gel, molecular sieves, activated alumina, activated carbon, and any of the same, wherein the material that Desiccant form is in the form of a solution at a concentration in the range of 15-40%; (ii) drying the treated material to reduce the moisture content thereof to a range of 15-40%; (iii) soaking the substrate matrix in salt or metal salts or water soluble strong or weak acids to form a hydrogel and obtain a gel matrix; (iv) washing the gel matrix obtained in step iii to remove excess undesirable reagents and byproducts; (v) drying the gel matrix under controlled temperature conditions to convert the hydrogel into an airgel matrix; (vi) treating the airgel matrix with one or more of an oxidizing agent, or an alkali metal hydroxide, or strong or weak acids, or reducing agents; (vii) drying the treated airgel matrix of step (vi) above at a temperature in the range of 50-140 ° C to obtain the chemical filter.

18. The method according to claim 16, characterized in that the substrate comprises an inorganic substance or an organic substance or a mixture thereof.

19. The method according to claim 16, characterized in that the substance is in the form of a fiber or a pulp.

20. The method according to claim 19, characterized in that the inorganic fiber is selected from the group consisting of fiberglass, Kraft paper, ceramic paper and any combination thereof.

21. The method according to claim 20, characterized in that the inorganic fiber is glass fiber.

22. The method according to claim 18, characterized in that the desiccant is selected from a metal silicate and silica gel.

23. The method according to claim 22, characterized in that the metal silicate is a water-soluble silicate selected from potassium silicate and sodium silicate.

24. The method according to claim 23, characterized in that the silicate comprises a neutral grade sodium silicate.

25. The method according to claim 24, characterized in that in the sodium silicate, the ratio of SIO2 to Na20 is in the range of 1: 2.0 to 1: 4.0, preferably 1: 3.

26. The method according to claim 16, characterized in that the impregnated material is selected from the group consisting of potassium permanganate, sodium permanganate, potassium hydroxide, sodium hydroxide, phosphoric acid, and sodium thiosulfate.

27. The method according to claim 26, characterized in that the loading of material impregnated in the substrate is in the range of 4% to 40%, preferably 30%.

28. The method according to any of claims 16 to 27, characterized in that the binder is preferably absent.

29. The method of compliance with any of claims 16 to 28, characterized in that activated carbon or hydrophobic zeolite is added together with the desiccant that is being generated in situ.

30. The method according to claim 16, characterized in that the moisture content of the desiccant-containing matrix is preferably 20%.

31. The method according to claim 17, characterized in that step vii is carried out at a temperature in the range of 10 ° C to 90 ° C for a period of 5 to 60 minutes.

32. The method according to claim 31, characterized in that step vii is carried out at a temperature of 70 ° C for a period of preferably 15 minutes.

33. The chemical filter according to any of claims 1 to 15 for use in the removal of contaminants from the air supply stream, the contaminants comprising gases, odorous elements or volatile organic compounds.

34. A desiccant wheel exchanger, characterized in that it comprises a chemical filter according to any of claims 1 to 15.