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  Process to prepare adsorbents from organic fertiilizer and their applications for removal of acidic gases from wet air streamsUSPTO Application #: 20060014639Title: Process to prepare adsorbents from organic fertiilizer and their applications for removal of acidic gases from wet air streams Abstract: The invention is directed to an adsorbent comprising: a) 20-30% porous carbon with incorporated organic nitrogen species; and b) 70-80% inorganic matter. The invention is directed to a method of making an adsorbent which comprises: a) thermally drying dewatered sewage sludge to form granulated organic fertilizer; and b) pyrolyzing said the organic fertilizer at temperatures between 600 and 1000° C. The invention is additionally directed to the process of removing acidic gases from wet air streams comprising putting an adsorbent in contact with the wet air stream and allowing the adsorbent to adsorb the acidic gases. (end of abstract) Agent: Darby & Darby P.C. - New York, NY, US Inventors: Teresa J. Bandosz, Andriy Bahryeyev, David C. Locke USPTO Applicaton #: 20060014639 - Class: 502417000 (USPTO) Related Patent Categories: Catalyst, Solid Sorbent, Or Support Therefor: Product Or Process Of Making, Solid Sorbent, Free Carbon Containing, And Specified Adde Active Sorbent Material The Patent Description & Claims data below is from USPTO Patent Application 20060014639. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application claims the benefit of priority under 35 U.S.C. .sctn. 119 based upon Ser. No. 60/253,860, filed Nov. 29, 2000, the entire disclosure of which is incorporated herein by reference. [0002] Numerous references, including patents, patent applications and various publications, are cited and discussed in the description of this invention. The citation and/or discussion of such references is provided merely to clarify the description of the present invention and is not an admission that any such reference is "prior art" to the invention described herein. All references cited and discussed in this specification are incorporated herein by reference in their entirety and to the same extent as if each reference was individually incorporated by reference. 1. FIELD OF THE INVENTION [0003] The invention is directed to an adsorbent comprising: a) 20-30% porous carbon with incorporated organic nitrogen species; and b) 70-80% inorganic matter. The invention is directed to a method of making an adsorbent which comprises: a) thermally drying dewatered sewage sludge to form granulated organic fertilizer; and b) pyrolyzing said the organic fertilizer at temperatures between 600 and 1000.degree. C. The invention is additionally directed to the processes of removing acidic gases from wet air streams comprising putting an adsorbent in contact with the wet air stream and allowing the adsorbent to adsorb the acidic gases. 2. BACKGROUND OF THE INVENTION [0004] Growing concerns about the environment has resulted in development of new environmentally friendly technologies, new materials, and new ways to reduce and minimize wastes [Manahan, S. E. Environmental Chemistry, 6th ed., CRC Press: Boca Raton, Fla., 1994]. One of the wastes produced by contemporary society in abundant quantity is municipal sewage sludge, euphemistically often referred to as biosolids. Biosolids are a mixture of exhausted biomass generated in the aerobic and anaerobic digestion of the organic constituents of municipal sewage along with inorganic materials such as sand and metal oxides. According to the United States Environmental Protection Agency (EPA), 6.9 million tons of biosolids (dry basis) were generated in 1998 and only 60% were used beneficially [Biosolid Generation, Use, and Disposal in The United States: EPA530-R-99-009, September 1999; www.epa.gov]. The EPA report estimates an annual 2% increase in the quantity of biosolids produced. [0005] The abundance of raw sewage sludge produces one of the major environmental problems of contemporary civilization. Various methods have been proposed for its disposal [Manahan S. E. Environmental Chemistry, 6th ed., CRC Press: Boca Raton, Fla., 1994]. Ocean dumping was popular until recently, however is no longer an option because of stricter environmental regulations [Biosolid Generation, Use, and Disposal in The United States: EPA530-R-99-009, September 1999; www.epa.gov]. Among the most often used methods of disposal are landfilling, cropland application, and incineration [Manahan S. E. Environmental Chemistry, 6th ed.; CRC Press: Boca Raton, Fla., 1994.]. Other methods that have been used to dispose of or utilize municipal sewage sludge [Biosolid Generation, Use, and Disposal in The United States: EPA530-R-99-009, September 1999; www.epa.gov], include road surfacing, conversion to fertilizer, compression into building blocks, and carbonization [Manahan, S. E. Environmental Chemistry, 6th ed., CRC Press: Boca Raton, Fla., 1994; Biosolid Generation, Use, and Disposal in The United States: EPA530-R-99-009, September 1999; www.epa.gov; Sutherland, J. U.S. Pat. No. 3,998,757 (1976); Nickerson, R. D.; Messman, H. C., U.S. Pat. No. 3,887,461 (1975)]. Specifically, the residue of incineration can be used in construction materials or road surfacing. [0006] Although incineration is effective in reducing the volume of sludge and produces useful end products, cleaning of the flue gases generated requires effective and expensive scrubbers. The application of raw sewage sludge as a fertilizer produces odor problems and is also associated with the risk of contamination of the soil by heavy metals and pathogens. A more efficaceous and safer alternative is the pyrolytic carbonization of sludge to obtain useful sorbents [Piskorz J, Scott D S, Westerberg, I B. Flash pyrolysis of sewage sludge, Ind. Proc. Des. Dev. 1996; 25: 265-270; Chiang, P C., You, J H. Use of sewage sludge for manufacturing adsorbents, Can. J. Chem. Eng. 1987; 65: 922-927; Lu, G Q, Low J C F, Liu C Y, Lau A C. Surface area development of sewage sludge during pyrolysis, Fuel 1995; 74: 3444-3448; Lu G Q, Lau D D. Characterization of sewage sludge-derived adsorbents for H.sub.2S removal. Part 2: surface and pore structural evolution in chemical activation. Gas Sep. Purif. 1996; 10: 103-111; Lewis F M. Method of pyrolyzing sewage sludge to produce activated carbon, U.S. Pat. No. 4,122,036 (1977)]. [0007] Since 1976, several patents have been issued on carbonization of sewage sludge and various applications of the final materials [Nickerson, R. D.; Messman, H. C., U.S. Pat. No. 3,887,461 (1975); Lewis, F. M. U.S. Pat. No. 4,122,036 (1977); Kemmer, F. N.; Robertson, R. S.; Mattix, R. D. U.S. Pat. No. 3,619,420 (1971)]. The carbonization of sludge was first patented by Hercules, Inc. [Sutherland, J. Preparation of activated carbonaceous material from sewage sludge and sulfuric acid. U.S. Pat. No. 3,998,757 (1976)]. The process was further investigated by Chiang and You [Chiang, P C., You, J H. Use of sewage sludge for manufacturing adsorbents, Can. J. Chem. Eng. 1987; 65: 922-927] and Lu, et al. [Lu, G Q, Low J C F, Liu C Y, Lau A C. Surface area development of sewage sludge during pyrolysis, Fuel 1995; 74: 3444-3448; Lu G Q, Lau D D. Characterization of sewage sludge-derived adsorbents for H.sub.2S removal. Part 2: surface and pore structural evolution in chemical activation. Gas Sep. Purif. 1996; 10: 103-111]. Both simple pyrolysis and pyrolysis after addition of chemical activation agents such as zinc chloride or sulfuric acid were used. Carbonization of sludge in the presence of chemical activating agents such as zinc chloride and sulfuric acid produces new sorbents, with patented applications in such processes as removal of organics in the final stages of water cleaning [Lewis, F. M. U.S. Pat. No. 4,122,036 (1977)] and removal of chlorinated organics [Kemmer, F. N.; Robertson, R. S.; Mattix, R. D. U.S. Pat. No. 3,619,420 (1971)]. [0008] The process of carbonization of biosolids has been studied in detail using different chemical agents and various conditions [Chiang, P. C.; You, J. H. Can. J. Chem. Eng. 1987, 65, 922; Lu, G. Q; Low J. C. F.; Liu, C. Y.; Lau A. C. Fuel 1995, 74, 3444; Lu, G. Q.; Lau, D. D. Gas Sep. Purif. 1996, 10, 103; Lu, G. Q. Environ. Tech. 1995, 16, 495]. The sorbents obtained had relatively high surface area (100-200 m.sup.2/g for physical activation and up to 400 m.sup.2/g for chemical activation) and developed microporosity. As suggested by Chiang and You, the high content of inorganic matter, usually around 75%, together with the microporosity promotes the adsorption of organic species such as methyl ethyl ketone or toluene [Chiang, P C., You, J H. Use of sewage sludge for manufacturing adsorbents, Can. J. Chem. Eng. 1987; 65: 922-927]. In general, materials obtained as a result of the treatment have surface areas between 100 and 500 m.sup.2/g, but their performance as adsorbents has been demonstrated to be much worse than that of activated carbons. The ability of these adsorbents to remove organics such as phenols, or sulfur dioxide and hydrogen sulfide [Lu, G. Q.; Lau, D. D. Gas Sep. Purif. 1996, 10, 103; Lu, G. Q. Environ. Tech. 1995, 16, 495] have been tested so far; their capacity for the adsorption of SO.sub.2 reported by Lu was less than 10% of the capacity of Ajax activated carbon [Lu, G. Q. Environ. Tech. 1995, 16, 495]. Lu and coworkers used the sorbents obtained from sludge by chemical activation as media for the removal of hydrogen sulfide [Lu G Q, Lau D D. Characterization of sewage sludge-derived adsorbents for H.sub.2S removal. Part 2: surface and pore structural evolution in chemical activation. Gas Sep. Purif. 1996; 10: 103-111]. Their removal capacity was only 25% of that of Calgon activated carbons and the mechanism and efficiency of the process were not studied in detail. [0009] Since hydrogen sulfide is the main source of odor from sewage treatment plants the possibility of using sewage sludge as a source of adsorbents for H.sub.2S is appealing. The idea is even more attractive when the mechanism of adsorption of hydrogen sulfide is taken into account. As proposed elsewhere [Hedden K, Huber L, Rao B R. Adsorptive Reinigung von Schwefelwasserstoffhaltigen Abgasen VDI Bericht 1976; 37: 253; Adib F, Bagreev A, Bandosz T J. Effect of surface characteristics of wood based activated carbons on removal of hydrogen sulfide. J. Coll. Interface Sci. 1999; 214: 407-415; Adib F, Bagreev A, Bandosz T J. Effect of pH and surface chemistry on the mechanism of H.sub.2S removal by activated carbons. J. Coll. Interface Sci. 1999; 216: 360-369] H.sub.2S is first adsorbed in the water film present on the carbon surface, followed by dissociation and adsorption of HS.sup.- in the micropores. In the next step, HS.sup.- is oxidized to various sulfur species. The speciation of the final products of oxidation depends on the pH of the activated carbon surface [Adib F, Bagreev A, Bandosz T J. Effect of pH and surface chemistry on the mechanism of H.sub.2S removal by activated carbons. J. Coll. Interface Sci. 1999; 216: 360-369; Adib F, Bagreev A, Bandosz T J. Analysis of the relationship between H.sub.2S removal capacity and surface properties of unimpregnated activated carbons. Environ. Sci. Technol. 2000; 34: 686-692; Adib F, Bagreev A, Bandosz T J. Adsorption/oxidation of hydrogen sulfide on nitrogen modified activated carbons. Langmuir 2000; 16: 1980-1986]. This mechanism is based on the study on unmodified carbons [Adib F, Bagreev A, Bandosz T J. Effect of surface characteristics of wood based activated carbons on removal of hydrogen sulfide. J. Coll. Interface Sci. 1999; 214: 407-415; Adib F, Bagreev A, Bandosz T J. Effect of pH and surface chemistry on the mechanism of H.sub.2S removal by activated carbons. J. Coll. Interface Sci. 1999; 216: 360-369; Adib F, Bagreev A, Bandosz T J. Analysis of the relationship between H.sub.2S removal capacity and surface properties of unimpregnated activated carbons. Environ. Sci. Technol. 2000; 34: 686-692]. In the case of catalytic carbons containing nitrogen it was proposed that nitrogen-containing basic centers located in the micropores are the high energy adsorption sites playing an important role in the oxidation of hydrogen sulfide to sulfuric acid [Adib F, Bagreev A, Bandosz T J. Adsorption/oxidation of hydrogen sulfide on nitrogen modified activated carbons. Langmuir 2000; 16: 1980-1986.]. The latter as the final product makes the regeneration feasible using simple methods such as washing with water [Adib F, Bagreev A, Bandosz T J. On the possibility of water regeneration of impregnated activated carbons used as hydrogen sulfide adsorbents, Ind. Eng. Chem. Res. 2000; 39: 2439-2446; Bagreev A, Rahman H, Bandosz T J. Study of H.sub.2S adsorption and water regeneration of spent coconut-based activated carbon. Environ. Sci. Technol. 2000; 34: 4587-4592]. In the case of catalytic carbons such as Centaur.RTM. the basic centers are introduced using the special urea modification process [Matviya T M, Hayden R A. Catalytic Carbon. U.S. Pat. No. 5,356,849 (1994)]. Since sewage sludge contains a considerable amount of organic nitrogen, carbonization of such species can lead to the creation of basic nitrogen groups within the carbon matrix which again have been proven to be important in the oxidation of H.sub.2S [Adib F, Bagreev A, Bandosz T J. Adsorption/oxidation of hydrogen sulfide on nitrogen modified activated carbons. Langmuir 2000; 16: 1980-1986; Matviya T M, Hayden R A. Catalytic Carbon. U.S. Pat. No. 5,356,849 (1994)]. Another advantage to the use of sludge as a starting material is the presence of significant amounts of iron added to the raw sludge as a dewatering conditioner; iron is also considered to be a catalyst for H.sub.2S oxidation [Katoh H., Kuniyoshi I., Hirai M., Shoda M. Studies of the oxidation mechanism of sulfur containing gases on wet activated carbon fibre. Appl. Cat. B: Environ. 1995; 6: 255-262; Stejns M, Mars P. Catalytic oxidation of hydrogen sulphide. Influence of pore structure and chemical composition of various porous substances. Ind. Eng. Chem. Prod. Res. Dev. 1977; 16: 35-41; Cariaso, O. C. and Walker P L. Oxidation of hydrogen sulphide over microporous carbons. Carbon 1975; 13: 233-239]. [0010] Primarily caustic-impregnated carbons have been used as adsorbents of hydrogen sulfide at sewage treatment plants. Because of the presence of KOH or NaOH their pH is high, which ensures that hydrogen sulfide is oxidized to elemental sulfur. The process is fast and caustic impregnated carbons have high hydrogen sulfide breakthrough capacity. Such materials have a H.sub.2S breakthrough capacity measured using accelerated test (not suitable for virgin carbons and other adsorbents), which should be around 140 mg/g. In one example of its use, the New York City Department of Environmental Protection installed 118 carbon vessels in 12 sewage treatment plants. Each vessel contains about 10 tons of activated carbon adsorbent. [0011] Caustic-impregnated carbons, although efficient for H.sub.2S removal, have many disadvantages which recently have attracted the attention of researchers toward alternative sorbents, unmodified activated carbons. The disadvantages of caustic-impregnated carbons are as follows: [0012] 1) Limited capacity for physical adsorption of VOCs (volatile organic compounds) due to the presence of caustic materials in the carbon pore system. [0013] 2) Low self-ignition temperature, which may result in fire inside the carbon vessel. [0014] 3) Special safety precautions in dealing with caustic materials have to be applied. [0015] 4) High density because of the presence of water. [0016] 5) Higher cost than that of unmodified carbons. [0017] The results of recent studies have shown that at very low concentrations of hydrogen sulfide (as is present at sewage treatment plants), unmodified carbons can work effectively as adsorption/oxidation media. Thus, there is a great interest in the development of new types of adsorbents for use in sewage treatment facilities. 3. SUMMARY OF THE INVENTION [0018] This invention is directed to an adsorbent comprising: a) 20-30% porous carbon with incorporated organic nitrogen species; and b) 70-80% inorganic matter. This invention is further directed to a method of making an adsorbent which comprises thermally drying dewatered sewage sludge to form granulated organic fertilizer and pyrolyzing said the organic fertilizer at temperatures between 600 and 1000.degree. C. This invention is directed to the process of removing acidic gases from wet air streams comprising putting an adsorbent comprising 20-30% porous carbon with incorporated organic nitrogen species and 70-80% inorganic matter in contact with the wet air stream and allowing the adsorbent to adsorb the acidic gases. This invention is further directed to the process of removing acidic gases from wet air streams comprising forming an adsorbent by thermally drying dewatered sewage sludge to form granulated organic fertilizer and pyrolyzing said organic fertilizer at temperatures between 600-1000.degree. C., putting said adsorbent in contact with the wet air stream, and allowing the adsorbent to adsorb the acidic gases. 4. BRIEF DESCRIPTION OF THE FIGURES [0019] FIG. 1. (A) TG, (B) DTG, and (C) DTA curves for pyrolysis of sludge-derived fertilizer in air (solid heavy lines) and nitrogen (solid thin lines). [0020] FIG. 2. Nitrogen adsorption isotherms for ash and the sludge derived materials. [0021] FIG. 3. Development of porosity with increasing pyrolysis temperature. [0022] FIG. 4. Pore size distributions for ash and the sludge derived materials. [0023] FIG. 5. Comparison of the pore size distribution for SLC-1 and SLC-3 and their acid-washed counterparts. [0024] FIG. 6. pKa distributions for the materials studied. [0025] FIG. 7. FTIR curves for the initial sludge, ash and SLC-2 and SLC-4. Continue reading... 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