KR100476139B1 - Hydrogen sulfide removal device and hydrogen sulfide removal capacity restoration method - Google Patents

Abstract

The apparatus and method of the present invention provide for restoring hydrogen sulfide removal capacity in nitrogen treated carbonaceous charcoal that is released for hydrogen sulfide capacity when used to remove hydrogen sulfide from a gas and to remove hydrogen sulfide from a gas stream. do. The apparatus has a matrix of removable containers containing nitrogenous carbonaceous charcoal. The method involves passing a hydrogen sulfide containing gas through the vessel and washing the carbonaceous charcoal consumed with water by performing a flush / dynamic wash through the vessel to remove most of the hydrogen sulfide reactants. By using this method, the initial hydrogen sulphide ratio of the nitrogenous carbonaceous charcoal is restored and the vessel can be recycled several times.

Description

Hydrogen sulfide removal device and hydrogen sulfide removal capacity restoration method

The present invention relates to an apparatus for removing hydrogen sulfide in the range of 0.1 to 100 ppm using nitrogen treated carbon and a method for restoring hydrogen sulfide removal capacity of the nitrogen treated carbon, in particular, compared to a conventional scrubber and odor control unit. A small and efficient hydrogen sulfide removal means.

Various methods are known for removing hydrogen sulfide. Typically, high levels of hydrogen sulphide, for example, at least 100 ppm are experienced when controlling malodor in municipal wastewater treatment plants. Generally, removal is accomplished by wet scrubbing with sodium hydroxide and / or sodium hypochlorite in the wastewater stream. In addition, activated carbon beds used to disinfect off-gases to remove odors, in particular hydrogen sulfide, are a very large and useful space in the treatment plant.

The prior art includes activated carbon impregnated with salts such as sodium hydroxide (caustic soda) or potassium hydroxide (caustic potash) and conventional activated carbon containing oxygen and water by oxidation of hydrogen sulfide to elemental sulfur. It is known to remove hydrogen sulfide from the gas stream. That is, it is expressed as following Equation 1.

[Formula 1]

Also, in some cases small amounts of sulfuric acid have been observed as reactants, but this phenomenon is generally considered to be an insignificant and unnecessary side reaction due to the presence of iron or other ash impurities. Elemental sulfur produced by Equation 1 is deposited in the porous structure of carbon until the active moiety that reacts with the catalyst is blocked.

Conventional methods for regenerating activated carbon that are inactivated in this manner rely on solvents or heat treatment to remove accumulated elemental sulfur. The solvent used in this method is very harmful, expensive and inconvenient to use. Solvents selected from various fields, namely carbon disulfide, are not only expensive and highly toxic, but also highly volatile and flammable. Water, the cheapest, safest and most convenient solvent, cannot be used for regeneration because elemental sulfur is not soluble in water.

Heat treatment techniques may also be used to restore hydrogen sulfide capacity in conventional carbon that is inactivated by exposure to hydrogen sulfide. Elemental sulfur is sublimed at a temperature above 445 ° C. and therefore can be removed from the carbon surface by hot gas such as nitrogen or steam or by direct heating. Where steam or other oxidizing or reducing agents are present, various other sulfur compounds may be produced. Since the treatment generates a significant amount of sulfur vapor, post-treatment facilities, such as acid scrubbers or Claus plants, are generally required. In addition, the treatment is energy intensive and requires materials of construction that must withstand high temperatures and corrosive gases. As a result, the usefulness of the heat treatment method is limited.

In general, caustic-impregnated carbon is regenerated by contact with concentrated caustic solutions in which elemental sulfur is well dissolved. Since solutions containing concentrated sodium or potassium hydroxide are corrosive and toxic, these methods are also harmful, expensive and inconvenient to use. In general, the heat treatment method is inadequate for caustic impregnated carbon because the impregnant produces aerosols that promote vaporization of the carbon tissue at high temperatures and corrode conventional structural materials. Similar problems arise when transition metals are used to impregnate carbon. In addition, the use of oxidants is generally required to restore the function of the transition metal impregnated carbon catalyst. In addition, the treatment produces significant amounts of sulfided off-gases that require extensive aftertreatment.

Surprisingly, the nitrogenous carbon used in the present invention has significantly different hydrogen sulfide removal chemistry. The nitrogen treatment was observed to convert hydrogen sulfide to diluted sulfuric acid rather than elemental sulfur. All the reactions can be represented by the following formula (2).

[Formula 2]

Since sulfuric acid can be mixed with water, it is strongly adsorbed by carbon so that when Equation 2 does not change the basic properties of the catalytic site in any way and the sulfuric acid produced by the reaction cannot be removed upon contact with water Not so, it may be possible to reclaim spent nitrogen treated carbon by washing sulfuric acid with water. Any aqueous sulfuric acid removed from carbon can be diluted, ie, neutralized, for treatment by any known technique that is carried for sulfuric acid calibration or used directly in other plant processes.

The nature of the catalytic site reacting to equation 2 is unknown. However, comparing the removal chemistry of nitrogen treated carbon with that of conventional carbon made from the same raw material and having similar adsorption properties and similar levels of ash and iron, it gives carbon the increased activity of Formula 2 above. It becomes clear that this is nitrogen treatment. Surprisingly, it has been found in the present invention that despite the known ability of sulfur compounds to weaken conventional catalysts, hydrogen sulfide and sulfuric acid do not react with the catalyst site. It has also been found that, despite the ability of sulfuric acid to strongly adsorb on the carbon surface, large amounts of acid can be removed from the carbon surface.

It is therefore an object of the present invention to provide an apparatus for removing hydrogen sulfide and for regenerating the spent nitrogenous carbon used in such removal with water. Another object of the present invention is to provide a physically small and very efficient processing unit which advantageously uses the chemical properties of nitrogen treated carbon.

1 is a front view of the malodor control unit of the present invention.

FIG. 2 is a side view of the malodor control unit shown in FIG. 1. FIG.

3 is a plan view of the unit shown in FIG.

4 to 6 are front, side and top views of the matrix configuration of the container of the present invention.

6A is a perspective view of a container matrix and a vertical tube.

7 is a side view of the container of the present invention.

8 is a cross-sectional view of the container shown in FIG.

FIG. 9 shows an end cover used for the container shown in FIG. 7. FIG.

FIG. 10 is a partial cross-sectional front view of the container shown in FIG. 7 mounted to the control unit shown in FIGS. 1-3. FIG.

11 to 18 are graphs showing test results of a housing according to the invention with the advantages of removal and restoration.

The present invention provides an apparatus and method for removing hydrogen sulfide at levels below 50 ppb, preferably at levels between 10 and 30 ppb. There is no odor at this level. The apparatus utilizes a removable container with a nitrogenous carbonaceous charcoal bed, preferably a bed 3 to 4 in. (7.62 to 10.16 cm) deep. The nitrogen treated charcoal used in the bed not only provides a very good removal capacity, but also affects the economic recovery of the hydrogen sulfide removal capacity of the carbonaceous charcoal selected to convert hydrogen sulfide to sulfuric acid. In a preferred embodiment of the invention, the carbon consumed is washed by water in a continuous or batch process until the wastewater reaches a hydrogen ion index (pH) of 1.5 times the initial acidity. Typically, the hydrogen ion index is 0.8 to 1.2, but the hydrogen ion index used advantageously is 2.5. This water wash regenerates the hydrogen sulfide removal capacity of the nitrogenous carbon. Upon re-exposure to hydrogen sulfide, carbon again becomes useful for hydrogen sulfide removal. In this manner, the cycle of exposure and regeneration can be repeated as many times as necessary or until the restored hydrogen sulfide capacity reaches an unusable performance level.

The apparatus uses a container matrix consisting of containers stacked in multiple rows. The matrix is connected to a gas source containing hydrogen sulfide with respect to the discharge port. The size of the unit comprising the matrix is substantially smaller than a conventional scrubber or odor control unit using activated carbon. In addition, the fans and water used to facilitate the movement of gas and regeneration fluid are substantially less than in conventional odor control units. Other advantages of the present invention will become apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.

1 to 3, the malodor control unit 10 of the present invention includes a housing 11 well made of plastic such as polypropylene or polyethylene. Preferably, at the top of the housing 11 is a cover unit 12 comprising an outlet channel 13 and an inlet channel 14. As shown in more detail in FIG. 3, the inlet channel 14 provides converging walls 16, 17 and end walls 18. The inlet channel 14 communicates with a plurality of vertical tubes 19, and the inlet port 21 is provided with a cover or control unit (not shown) by a blower (not shown) having a capacity of 10,000 cfm for use in municipal wastewater treatment systems and the like. 10) to a fumes or offgas source that is delivered to. Base plate 22 and top member 23 seal channel 14.

The outlet channel 13 utilizes converging walls 16, 17 to define an outlet passage from the plurality of vessels 25 shown in more detail in FIG. 1. The outlet passage is in communication with a housing 11 comprising a plurality of containers arranged in a matrix form as shown in FIGS. 4 to 6. 4 to 6, the containers 25 are arranged in a plurality of rows equal to the number of vertical tubes 19 arranged along the length of the housing 11. As shown in FIG. 4, five vessels are connected on each side of each vertical tube 19. However, the exact number of vessels or vertical tubes is related to flow kinetics, removal rates and removal rates and other parameters known to those skilled in the art for each application. In a preferred embodiment, the matrix shown in FIGS. 4-6 is effective above all in the field of wastewater odor control in the city. As shown in Figures 5-6, each container 25 is removable as described below.

7-9, each vessel 25 includes a cylindrical envelope 26 having a plurality of holes 27 for the passage of gas. In a preferred embodiment of the present invention, the envelope 26 comprises a flexible porous plastic mat made of 300 micron polyethylene particles thermoformed. An inner conduit 28 comprising an inlet port 29 is connected to the vertical tube 19 via a pipe connector 36 for access to offgas containing hydrogen sulfide. The inner conduit 28 is preferably provided with a gas inlet hole 31 for passing gas into the annular portion 33 defined by the envelope 26 and the inner conduit 28. In addition, the inner conduit 28 is preferably made of the same material as the envelope 26. The annular portion 33 preferably has a depth of 3 to 4 in (7.62 to 10.16 cm), very preferably 4 in (10.16 cm) to contain carbonaceous charcoal. End covers 34 and 35 seal the annular portion 33. The end cover 34 may be separated for filling and removal of the nitrogenous carbonaceous charcoal. A container removal tool (not shown) is used by insertion through the inner conduit 28 to support the container 25 attached to the vertical tube 19 through the opening 37. Cylindrical envelope 26 and inner conduit 28 are preferably made of polyethylene. The end covers 34 and 35 are made of plastic material such as polypropylene or polyethylene, but may be made of other materials resistant to sulfuric acid. In a preferred embodiment, the container 25 is 3 in (7,62 cm) to provide a bed that is 20 in (50.8 cm) long, 11 in (27.94 cm) outer diameter, and 4 in (10.16 cm) deep. ) Has an inner diameter. Each container 25 is designed to accommodate approximately 30 lb (13.6 kg) of carbonaceous charcoal.

Nitrogenated carbonaceous charcoal used in the vessel 25 of the present invention is produced using bituminous materials or bituminous charcoal. Bituminous coal is pulverized and mixed with coal tar pitch of about 4 to 6% to form briquettes. The briquettes are crushed and sized to produce materials of 8 × 30 or 8 × 40 mesh, preferably 12 × 40 mesh (US standard collection of sieves). In the presence of a large amount of excess air, the material is carbonized and oxidized at temperatures between about 250 ° C. and 450 ° C. for at least 3 hours. Finally, the oxidized charcoal is cooled near ambient temperature and then impregnated with an aqueous urea solution or other nitrogen containing compound having one or more nitrogen containing functions in which nitrogen exhibits less formal oxidation than elemental nitrogen and dried nitrogen. . The amount of urea solution used was sufficient to produce a 2-4% urea load based on the dry sample weight. The impregnated and oxidized charcoal is heated to about 950 ° C. in the furnace and then maintained at that temperature for up to one hour. Immediately after this treatment, to achieve an apparent density of about 0.51 g / cc (TM-7 test method, Calgon Kagon Corporation, Pittsburgh, Penn.) For a 6 x 16 mesh (US standard collection of sieves) particle size distribution For a sufficient period of time the material is in contact with steam while maintaining a temperature of 950 ° C. After gasification, the material is cooled to ambient temperature under an inert atmosphere. The nitrogen treated carbon produced by this procedure is compared to the apparent density, adsorption properties, ash content and iron content for BPL carbon, a commercial non-impregnated gaseous activated carbon made from the same feedstock. See US Pat. No. 5,494,869, the contents of which are incorporated herein by reference.

As shown in FIG. 10, each container 25 is mounted to an associated upright tube 19 by a conductor 36. Preferably, each container 25 is mounted through an associated opening 37 in the housing 11. Side wall closures 38 (FIGS. 6A and 10) are provided to allow the container 25 to be retained in the control unit 10. In a preferred manner, the multiple rows of containers 25 can be replaced according to a predetermined principle after the carbon has been regenerated to its limit. The preferred container 25 is individually removed by the separation of the side wall closure 38 and withdrawal through the opening 37, or in a batch with the matrix and lid unit 12 of the vertical tube 19. 10) is removed. The water inlet 41 provides a source of recycled water for cleaning the multiple rows of vessels 25. Water (H ₂ SO ₄ ) is discharged through the outlet (42).

Tests using “centaur” carbon prepared as described above were performed to determine the H ₂ S removal level and effective regeneration cycle of the present invention. The test used a 10,000 cfm air stream with 10 ppm H ₂ S inflow at ambient temperature. The improved H ₂ S was set at 1.0 ppm. 11-18 show the test results. In general, it has been found that 8 x 16 mesh carbon with a bed depth of 4 in (10.16 cm) includes a wave front at 150 fpm. Regeneration uses water at a backflow of about 2-3 gpm / ft ³ .

The process of the present invention effectively uses a radial flow vessel in a parallel flow pattern to remove fumes that sufficiently contain H ₂ S that passes well through each vessel 25 at a rate of 150 ft / min. Removal of H ₂ S the carbon is accomplished by adsorption and catalytic conversion of H ₂ S to H ₂ SO ₄ into the study. The adsorption / reaction step is followed by a dynamic water rinse of at least 2 g / m through each selected vessel. The process advantageously regenerates individual containers or groups of containers by cleaning only a portion of the matrix and generally proceeding with regeneration in a continuous manner where carbon life can be extended.

While preferred embodiments of the invention have been described, they may be embodied in other ways within the scope of the claims herein.

Claims (10)

A method for removing hydrogen sulfide from a containing gas and restoring the hydrogen sulfide removal capacity in the discharged nitrogenated carbonaceous charcoal to the hydrogen sulfide removal capacity as used to remove hydrogen sulfide from the gas stream. Passing the gas through a plurality of vessels, each having an gas inlet port and gas outlet ports and including an envelope between the inlet port and the outlet ports, the envelope being positioned within the carbonaceous charcoal; The envelope and the outlet ports are made of a flexible porous molded particulate material so that the gas can pass through them, the charcoal is made by treatment of the carbonaceous material at a temperature of 700 ° C. or higher in the presence of a nitrogen containing compound, The nitrogenous compound is part of the charcoal feedstock or is added to the feedstock at any point during manufacture; Restoring the hydrogen sulfide capacity of the nitrogenated charcoal by flowing water through the vessels at a temperature above ambient temperature. The method of claim 1 wherein the temperature of the water is less than 100 ° C. 10. 2. The envelope of claim 1 wherein the envelope is a cylindrical envelope and has an inner conduit located within the envelope to define an annular portion and first and second end covers for closing the annular portion, the inner conduit defining gas inlet holes. And connected to a gas source containing hydrogen sulfide, said first end cover having a removable cover concentric with said inner conduit and having easy access to said conduit. (a) a housing having an interior space and a fluid inlet and outlet; (b) a plurality of fluid conduits located within the housing and in communication with the fluid inlet, respectively; (c) a plurality of vessels arranged in a plurality of rows of matrices, each row connected to one or more fluid conduits, Each vessel comprising: (i) an envelope having inlet ports respectively in communication with one or more fluid conduits and outlet ports in communication with the interior space of the housing; and (ii) the vessel between the inlet and outlet ports of the vessel. And a nitrogen treated carbonaceous charcoal located within said envelope and said outlet ports are comprised of a flexible porous molded particulate plastic material through which fluid can pass. 5. The hydrogen sulfide removal device of claim 4, wherein the housing is made of a plastic material resistant to sulfuric acid. 5. The hydrogen sulfide of claim 4, wherein the housing includes a lid, the lid having a first portion in communication with the housing inlet and the respective fluid conduit and a second portion in communication with the housing interior space and the outlet. Removal device, 7. The hydrogen sulfide removal device of claim 5 or 6, wherein the fluid conduits comprise vertical tubes. 7. The envelope of claim 6, wherein each envelope is positioned at respective ends of the envelope to define a chamber and an inner conduit spaced from the envelope to define an annular space between the ends and the envelope. A cylindrical envelope having an end wall, the envelope and the inner conduit providing communication there through to the chamber and the nitrogenated carbonaceous charcoal located therein, wherein the inner conduit is connected with one or more fluid conduits through the end wall. And the envelope communicates with the interior space of the housing through the outlet ports. 10. The apparatus of claim 8, wherein the inner conduit is made of a plastic material resistant to sulfuric acid. 10. The apparatus of claim 9, wherein the inner conduit is made of flexible porous molded particulate plastic.