|||||IIIIUSOO5779 767A United States Patent (19) 11 Patent Number: 5,779,767 Golden Et Al
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|||||IIIIUSOO5779 767A United States Patent (19) 11 Patent Number: 5,779,767 Golden et al. (45) Date of Patent: Jul. 14, 1998 54 USE OF ZEOLITES AND ALUMINAN 4.477364 10/1984 Garcia ..................................... 252/42 ADSORPTION PROCESSES 4493.75 1/1985 Hogan et al. ........ ... 55/68 4.507,271 3/1985 Van Deyck et al., 95/106 X 75 Inventors: Timothy Christopher Golden. 4.541851 9/1985 Bosquain et al. ... ... 55/208 Allentown, Pa.; Mohammed Ali 4,696.680 9/1987 Ghate et al. ..... ... 95/03 4,711,645 12/1987 Kumar ...... 55.26 Kalbassi. Walton-on-Thames, England: 4.713,090 2/1987 Yokoe et al. ... ... 95/96 Fred William Taylor. Allentown, Pa.; 4,762.537 8/1988 Fleming et al. ..... 95/902 X Rodney John Allam, Guildford. 4775,396 10/1988 Rastelli et al. ..... ... 55/58 England 4,795,735 1/1989 Liu et al. .............................. 95/139 X 4,986.835 1/99 Uno et al. ................................... 95/99 73) Assignee: Air Products and Chemicals, Inc. 5,137.548 8/1992 Grenier et al. 55/23 Allentown, Pa. 5.232.474 8/1993 Jain .............. ... SS/26 5,417,950 5/1995 Sheu et al. .... 95/902 X 5,475.150 12/1995 Rastelli et al. .......................... 568/699 21 Appl. No.: 814,749 5514204 5/1996 Sheu et al. .................. ... 9.5/121 X 22 Filed: Mar. 7, 1997 5.531.808 7/1996 Ojo et al. ...... 95/101 X 5.531.809 7/1996 Golden et al. ............................ 95/10 51 Int. Cl. .................................... BOD 53/047 5536,301 7/1996 Lansbarkis et al. 95/126 X 52 U.S. Cl. ........................ 95/96; 95/106; 95/121: 5,614.000 3/1997 Kalbassi et al. ............................ 95/96 95/126; 95/129; 95/139; 95/145; 95/902; 5,656,064 8/1997 Golden et al. .............................. 95/96 96/108: 96/43 FOREIGN PATENT DOCUMENTS 58 Field of Search ....................... 95/96-106, 117-26, 95/139, 141, 145, 902: 96708, 121. 130 073501 8/1985 European Pat. Off. O449576 3/1991 European Pat. Off. References Cited 3045451 7/1981 Germany . 56 3702190 1/1987 Germany . U.S. PATENT DOCUMENTS 1648,547 5/1989 U.S.S.R. 58.6961 8/1976 United Kingdom . 2.944,627 7/1960 Skarstrom ................................ 183f4.7 3.273,314 9/1966 Quinn ........................................ 95/145 3.274,125 9/1966 Clarke et al. .. ... 252/466 Primary Examiner-Robert Spitzer 3.287,884 11/1966 Scofield .................................... 95/145 Attorney, Agent, or Firm-Geoffrey L. Chase 3.557,025 1/1971 Emerson et al. ... 252/463 3,619, 130 1 1/1971 Ventriglio .......... 95/139 X 57 ABSTRACT 3.865,924 2/1975 Gidaspow et al. ... 423/230 3.899,310 8/1975 Chi et al. .................................. 95/141 A process for the adsorption of at least carbon dioxide, water 4.012206 3/1977 Macriss et al. 95/125 X and oxides of nitrogen and preferably acetylene from a feed 4.127,395 11/1978 McKey et al. 95/22 X gas, comprises contacting the feed gas with an adsorbent 4,130,484 12/1978 Marwill et al. 95/106 X mixture of a zeolite and an alumina. The process may be 4,134,743 1/1979 Macriss et al. .... 95/125 X operated as a swing adsorption process comprising contact 4,153,429 571979 Matthews et al. ........................ 95/17 ing the gas with the adsorbent at a first temperature and 4,183,728 1/1980 Leitzke et al. ..... 95/117 X pressure to adsorb at least carbon dioxide, water and oxides 4.249.95 2/1981 Sircar et al. ................................ 55/26 of nitrogen therefrom and periodically regenerating the 4.251924 2/1981. Becket al...... 95/22 X adsorbent by reducing the pressure and or increasing the 4.264,340 47981 Sircar et al. ................................ 95/99 4.420,419 12/1983 Ogawa et al. 502/68 temperature to which the adsorbent is exposed. 4.433,981 2/1984 Slaugh et al. .. ... 55/59 4,477.264 10/1984 Kratz et al. ................................. 55/25 30 Claims, 3 Drawing Sheets U.S. Patent Jul. 14, 1998 Sheet of 3 5,779,767 s - O Co in to Lo N Co (N : c o o o o o os d d C H) (OHLX W H 9 2 H2O TWNOILOW U.S. Patent Jul. 14, 1998 Sheet 2 of 3 5,779,767 >< C y N < Z. > d - < CN) bo E o t 1 - O Co N to Lo O O. O. O. O. O O H) OHLX WHI8 O TWNOILOW U.S. Patent Jul. 14, 1998 Sheet 3 of 3 5,779,767 s CO O O C C C C C C O C C C C C C O) OO N CO O r CO s S 2OO Woc/2H2O 8dd 5,779,767 2 USE OF ZEOLTES AND ALUMNA IN removal followed by Zeolites like 13X for the removal of ADSORPTION PROCESSES CO. More recently, all alumina PSA systems have been described (U.S. Pat. No. 5,232.474). The advantages of the BACKGROUND OF THE INVENTION all alumina system include lower adsorbent cost, vessel The invention relates to the field of adsorption processes 5 design which does not need screens to separate the two including pressure swing adsorption (PSA), temperature adsorbents and better thermal stability in the adsorption Swing adsorption (TSA) and hybrids of the two and provides vessel during blowdown and repressurisation. Also, recent processes for the removal of carbon dioxide, water and Patents (U.S. Pat. No. 5,137,548) have taught the use of low optionally acetylene and other impurities from a gas using regeneration temperature (regeneration temperature a maxi improved adsorbents. mum of 50° C. above feed temperature) thermal swing In conventional processes for cryogenic separation of air adsorption (TSA) cycles. However, alumina adsorbents by to recover N and/or O., feed air is compressed, then cooled themselves are not effective for removing all nitrogen oxides through expansion to low temperature before introduction to and some hydrocarbons during PSA and low temperature a two-stage distillation column. Unless water and CO are TSA operation. Therefore, a layering of adsorbents has been removed from the air before cooling. these components will 15 proposed as in U.S. Pat. No. 4477.264, and GB 1586961. block heat exchangers employed for cooling the gas prior to However, the layering of adsorbents is difficult when more distillation. Also, other air impurities can cause both freeze exotic bed geometries, like radial bed flow adsorbers are out and safety problems. For example, nitrogen oxides employed (U.S. Pat. No. 4.541.851). Thus, the difficulty including NO and NO can form polymeric species NO facing the industry is to find a single absorbent capable of and NO during reaction with O. from air. These higher removing various air impurities so that layering of adsor nitrogen oxides freeze at temperatures which are present in bents can be avoided. Layering of adsorbents can cause the main heat exchanger. Consequently, these impurities problems including: must also be removed prior to the cold box. In addition. 1. a need for screens to separate materials. hydrocarbon impurities, especially acetylene, present in the 2. different densities of materials can lead to localised feed air can cause explosion hazards if they enter the cold 25 fluidisation problems and channelling. box. If acetylene enters the cold box it concentrates in the 3. difficult bed loading for radial flow vessels, and liquid oxygen section of the distillation column creating a 4. different adsorption characteristics for air leading to axial severe safety problem. Thus, in addition to the removal of temperature fluctuations in the bed. water and CO other air impurities including nitrogen An early description of a PSA drier is U.S. Pat. No. oxides and acetylene must be removed prior to the cold box. 2.944,627. Using purge to feed ratios greater than 1.0 on an There is also significant interest in removal of trace CO actual volume of gas basis it was found that using an and water from synthesis gas prior to cryogenic separation alumina adsorbent the product air was devoid of water, CO of CO and H. Typically CO and H are produced by steam and oil vapour. No mention of acetylene or nitrogen oxides reforming methane to produce synthesis gas containing CO. is made. 35 German Patent Publication DE 3045451 (1981) describes H CO. HO and CH. The bulk of the CO is then a PSA process which operates at 5°-10° C. 880 KPa removed in an absorption unit. The trace levels of CO and adsorption pressure and 98 KPa regeneration pressure. Feed water which exit the scrubber must then be removed to low air is passed through a layer of 13X particles to remove the levels before introduction into the cryogenic distillation bulk of water vapour and CO and then through a final layer process. Traditionally, this is accomplished in a TSA process of alumina for final clean-up. The alumina section can using zeolites. Improved adsorbents for CO and water constitute 20-80% of the bed volume. The bed layering is removal from air will also be useful for this application. claimed to reduce formation of "cold spots" in the adsorbent Two methods generally used for such carbon dioxide beds. removal are temperature swing adsorption (TSA) and pres U.S. Pat. No. 4.711.645 described a PSA process for sure swing adsorption (PSA). 45 removal of water and CO utilising alumina for water In each of these techniques, a bed of adsorbent is exposed removal followed by a zeolite for CO removal.