Abstract:
A method and apparatus for cleaning carbon oxides, sulfur oxides and nitrogen oxides, from stack gas, from combustion of coal, combustion of natural gas or propane, or from a cement kiln by reaction using calcium zeolite and sodium zeolite catalysts. The method also includes cleaning the catalytic beds with nitrogen to remove the collected reactants and recover a fertilizer product and the catalysts for reusable.

Description:
BACKGROUND AND SUMMARY 
       [0001]    This invention relates to cleaning of stack gases such as those from coal fired power plants, from natural or propane burning heating plants or from cement kilns. The stack gases exhausted from each such facility is controlled by environmental regulations. Such regulations require abatement of carbon monoxide (CO), carbon dioxide (CO 2 , nitrogen oxide (NOx), sulfur oxide (SOx) as well as halogens such as chloride and fluorides and trace metals particularly, mercury, lead, zinc. 
         [0002]    Various methods and apparatus have been proposed for abating these pollutants in stack gases. It is proposed that the stack gases be mixed with ammonia or urea and then passed through a catalyst in which the ammonia reacts selectively with the nitrous oxides to form nitrogen gas in water vapor, or combustion of a sulfur-containing fossil fuel in the presence of a calcium carbonate or magnesium carbonate to form calcium sulfate or magnesium sulfate. See U.S. Pat. Nos. 8,181,451, 7,968,068, 6,706,246, 5,525,317, 5,237,939, 4,185,080, and 4,051,225. Reducing nitrogen in stack gas passing the stack gas through a heat exchange having a SCR catalyst. See U.S. Pat. No. 5,918,555. Reduction of sulfur oxide content in stack gases by catalyzed oxidation to sulfur trioxide in the presence of an absorbent or combusting sulfur-containing fuel in a combustion zone charged with a slurry in sulfuric acid solution. See U.S. Pat. Nos. 5,540,755, 4,649,034, 4,284,015, and 4,185,080. Catalytically converting unburned hydrocarbons and carbon monoxide to carbon dioxide and reducing nitrogen oxides to nitrogen subsequent to the combustion of fossil fuels while absorbing sulfur oxide, where the catalytic material is physically combined onto a dry powder of an adsorbent matrix select from calcium aluminate, calcium aluminate cement, barium titanate, and calcium titanate. See U.S. Pat. No. 4,483,259. It has also been proposed to pass the stack gases through a catalyst bed of a combination of active metals on the surface that is capable of reducing or converting sulfur oxides, carbon monoxide and hydra carbons to inert compounds such as carbon dioxide, water and nitrogen. See U.S. Pat. No. 7,399,458. Levels of mercury in stack gases from coal combustion have also been reduced by introducing a sorbent composition into the gas stream in a zone where temperature is greater than 500° C., where the sorbent composition comprises an effective amount of nitrate salt and/or a nitrite salt. See U.S. Pat. Nos. 7,468,170 and 7,731,781. 
         [0003]    These previous proposals had a number of drawbacks. Many require addition of another gas or liquid such as ammonia or sulfuric acid, or the presence of an active metal catalyst. Also, they have involved production of stack gases such as carbon dioxide, which is now itself regulated as pollutant, and production of a waste material which itself presents a disposal problem sometimes as a hazardous waste. 
         [0004]    There is still a need for a method and apparatus to effectively remove carbon monoxide, carbon dioxide, nitrous oxides, and sulfur oxides, as well as trace metals such as mercury, from stack gases without consuming expensive catalysts, injection of additional gases and solids, and without creating waste products that do, themselves, present the problems in disposal. 
         [0005]    This problem in cleaning of stack gases is of particular concern in coal fire power plants because of the release of volatiles such as coal tar, sulfur oxides, and other active pollutants. These proposals also involve flaring methane gas which could reduced with energy recovery. A variety of methods have been proposed for reducing pollutants released from coal fired power plants. One method of cleaning coal flue gases is the use of scrubbers that inject a liquid or slurry into a gas stream that washes various pollutants, such as acidic compounds, from the flue stream. Another type of cleaning is the use of an exhaust burner that combusts volatile materials and other compounds to reduce pollution. The burner may also burn uncombusted methane present in the exhaust stream. Another type of cleaning that may be used is carbon capture that collects and stores carbon dioxide, such as by compressing the carbon dioxide and storing it in a geological formation. Other types of cleaning flue gases from coal fired plant have also been proposed and are known to those having skill in the art. 
         [0006]    Zeolite has also been proposed as a material to absorb carbon dioxide, then to be able to regenerate the zeolite material. See “Carbon Dioxide Capture Using a Zeolite Molecular Seive Sampling System for Isotopic Studies ( 13 C and  14 C) of Respiration,”  Radiocarbon,  47, 441-451 (2005), “Absorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources”,  ChemSusChem  2009, 2, 796-854,  NIST Provides Octagonal Window of Opportunity for Carbon Capture, NIST Techbeat , Feb. 7, 2012. However, these uses of zeolite involved large particle sizes of zeolite, for example between 1/32 and 1/16 inch in size in a low pressure to provide for adsorption of carbon dioxide and later regeneration. The effectiveness of these processes have been affected by the presence of moisture. 
         [0007]    The presently disclosed method uses more finely ground zeolite as described below to more effectively clean carbon oxides, sulfur oxides and nitrogen oxides from stack gases. The method of cleaning stack gases disclosed comprises the steps of: (a) providing in a stack or flue adapted to pass stack gases a first catalytic flow-through bed of calcium zeolite comprising zeolite particles of a majority between 44 μm and 64 μm in size adapted to reduce carbon oxides from the stack gases, (b) providing in the stack adapted to pass stack gases positioned adjacent the first catalytic flow-through bed, a second catalytic flow-through bed of a blend between 25 and 75% of sodium zeolite and calcium zeolite comprising zeolite particles of a majority between 65 μm and 125 μm in size adapted to reduce nitrogen oxides from the stack gases, (c) providing in the stack adapted to pass stack gas positioned adjacent the second catalytic flow-through bed, a third catalytic flow-through bed of calcium zeolite comprising zeolite particles of a majority between 78 μm and 204 μm adapted to reduce sulfur oxides in the stack gases. The method further include passing stack gases selected from the group consisting of volatiles from combustion of coal or from combustion of natural gas or propane or flue gases from a cement kiln sequential through the first catalytic bed, the second catalytic bed, and the third catalytic bed each reducing pollutants and collecting solids in the catalytic beds and providing gas exiting the third catalytic bed with at least 90% reduction in sulfur oxides, nitrogen oxides, and carbon oxide. The particle size ranges of calcium zeolite and the calcium zeolite/sodium zeolite blend is indicative of the surface area, number, of exposed zeolite pores, and ion exchange capacity of the calcium and sodium/calcium zeolite in the catalytic flow-through beds. 
         [0008]    The first catalytic flow-through bed, the second catalytic flow-through bed and the third catalytic flow-through bed may be provided between screens of between 150 and 350 mesh. This enables the catalytic beds to contained in position without falling out of the bed, while maintaining the catalytic beds as flow through beds without appropriate pressure drop across each bed. The beds can be maintained in any desired cross section given cross-sectional area of the stack and with a depth corresponding to the flow rate of stack gases through the stack. 
         [0009]    The method can be extended by purging solids and liquids from the first catalytic bed, the second catalytic bed, and the third catalytic bed by intermittently passing nitrogen through the beds to remove solids and liquids reaction product formed in the beds from the stack gases. This embodiment enables the solids and liquids collected in the catalytic flow-through beds to be reacted with nitrogen to form nitrate compounds and be recovered as a useable product such as fertilizer. This step of purging the catalytic flow-through beds may be performed by liquid nitrogen to increase the efficiently of the recovery of solids and liquids from the catalytic flow-through beds and make the recovered product more useful as a fertilizer product. 
         [0010]    This method also provides a way of removing other such as aluminum oxides, mercury compounds and trace metals such as zinc, lead, uranium and rare earth metals from the stack gas stream. An added benefit of the present method is that methane, which is typically flared and wasted, can be recovered, and moisture typically a problem is reduced as part of the recovered product and taken off as hydrogen and oxygen gas in the cleaned stack gas. 
         [0011]    Furthermore, the first catalytic flow-through bed, the second catalytic flow-through bed, and the third catalytic flow-through bed can be provided in a system that allows for continuous reduction and cleaning of stack gas while another part of the same beds or like beds are purged to capture of fertilizer products and other commercial products and clean the beds for reuse. For example, two or more series of beds could be provided in parallel so one series of beds were in use to clean the stack gas while one or more other series of beds was be purged of collected solids and liquids and cleansed for reuses. Another approach is to assemble the beds on rotating disks. This enables the catalytic flow-through beds to be maintained in operation cleaning the stack gases while other parts the same catalytic flow-through bed or a bed of similar composition to be cleaned of collected solids and liquids for reuse. The later approach has the advance of allowing the individual beds to be taken out of use separately as desired, rather than require all beds in a series to be taken off line at once for purging to removing collected solids and liquid and clean for reuse. 
         [0012]    In another embodiment, an additional fourth catalytic flow-through bed of calcium zeolite comprising zeolite particles between 44 μm and 64 μm in size may be positioned in the stack gas before the first catalytic bed, with an electrical charge beneath said fourth catalytic flow-through bed to facilitate collection aluminum oxides and other aluminum compounds from from the stack gases before passing through the first catalytic bed. This embodiment enables aluminum compounds to be separately capture and recovered as a separate product that can be a substitute for bauxite to produce aluminum, particularly where the beds are provided on rotating disks so the beds can separately taken off line for removal of collected solids and liquids. This is particularly useful with some coals high in aluminum oxides and given bauxite ore is not readily available in some location. If the aluminum compounds are not separately recovered by recovered in the first catalytic flow-through bed the aluminum compounds go into the fertilizer products recovered using this method. 
         [0013]    Irrespective of the embodiment of the present method and apparatus that is employed at least 95% or 99% reduction in sulfur oxides, nitrogen oxides and carbon oxides compared to the content in the stack gases delivered to the a first catalytic flow-through bed. The present method can also be useful for focusing on collection of sulfur oxides where sulfur oxides are particularly a problem such as in coal fired plants of 50 to 100 KW. These plants are targeted by EPA for conversion to natural gas or propane fired plants at considerable cost. The present method allow these plants to continue to operate as coal fired power plants and meet the EPA sulfur oxide standards for sulfur emission. The method also results coal-fired power plants of less the 50 KW to continue to operate, where these power plant would otherwise are targeted to shutdown because of inability to comply with new EPA sulfur oxide standards. 
         [0014]    Also disclosed is apparatus of cleaning carbon oxides, sulfur oxides, nitrogen oxides from stack gases comprising: (a) assembling an stack adapted to pass stack gases selected from the group consisting of volatiles from combustion of coal or from combustion of natural gas or from flue gas from cement kiln, (b) assembling in the stack adapted to pass stack gases a first catalytic flow-through bed of calcium zeolite comprising zeolite particles of a majority between 44 μm and 64 μm in size adapted to reduce carbon oxides from the stack gases, (c) assembling in the stack adapted to pass stack gases positioned adjacent the first catalytic flow-through bed, a second catalytic flow-through bed of a blend between 25 and 75% of sodium zeolite and calcium zeolite comprising zeolite particles of a majority between 65 μm and 125 μm in size adapted to reduce nitrogen oxides from the stack gases, (d) assembling in the stack adapted to pass stack gas positioned adjacent the second catalytic flow-through bed, a third catalytic flow-through bed of calcium zeolite comprising zeolite particles of a majority between 78 μm and 204 μm adapted to reduce sulfur oxides in the stack gases. The method results in the stack gases flowing through the first catalytic bed, the second catalytic bed, and the third catalytic bed adapted to collect solids in the catalytic beds so that stack gases exiting the third catalytic have at least 90% reduction in sulfur oxides, nitrogen oxides and carbon oxide. This apparatus may be utilized to provide at least 95% or 99% cleaning of the stack gas. 
         [0015]    The first catalytic flow-through bed, the second catalytic flow-through bed and the third catalytic flow-through bed may each be assembled between screens of between 150 and 250 mesh to provide for flow-through while maintaining the zeolite particles in the beds. The beds can be accommodate any desired cross section according the cross-sectional area of the stack, with a depth corresponding to the flow rate of stack gases through the stack. 
         [0016]    The first catalytic flow-through bed, the second catalytic flow-through bed, and the third catalytic flow-through bed can be assemble with parallel series of the first catalytic flow-through bed, the second catalytic flow-through bed and the third catalytic flow-through bed in a system that allows for continuous reduction and cleaning of stack gas while one or more series of like beds are purged to capture of fertilizer products and other commercial products and clean the beds for reuse. Another approach is to assemble the beds on rotating disks. This enables the catalytic flow-through beds to be maintained in operation cleaning the stack gases while other parts the same catalytic flow-through bed or a bed of similar composition is cleaned of collected solids and liquids for reuse. The later approach has the advance of allowing the individual beds to be taken out of use separately as desired, rather than require all beds in a series to be taken off line at once for purging to removing collected solids and liquid and clean for reuse. The first catalytic bed, the second catalytic bed, and the third catalytic bed may each be assembled on a rotating disk so a part of the bed or a similar bed can be maintained to continue to clean stack gas without interruption, while another portion of the bed or a similar bed is cleaned for reuse. 
         [0017]    Also disclosed is the fertilizer product made by the processes described in the previous application. This product may include trace metals as such zinc compounds, lead compounds mercury compounds, uranium compounds, and rare earth metal compounds, as well as sulfate and fluoride compounds beneficial in fertilizers. 
         [0018]    Other details, objects and advantages of the present invention will become apparent from the description of the preferred embodiments described below in reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The following description is described of the accompanying drawings: 
           [0020]      FIG. 1  is a schematic illustrating a coal-fired boiler for electric power generation using stack gases that are cleaned and solid/liquid products recovered in accordance with the present method and apparatus; 
           [0021]      FIG. 2A  is an enlarged portion of part of the stack gas cleaning and recovery apparatus shown in  FIG. 1  where three catalytic flow-through beds are utilized; 
           [0022]      FIG. 2B  is an enlarged portion of part of the stack gas cleaning and recovery apparatus shown in  FIG. 1  where four catalytic flow-through beds are utilized; 
           [0023]      FIG. 3  is a cross-section taken along line  3 - 3  of  FIG. 2A  or  FIG. 2B ; 
           [0024]      FIG. 4  is a schematic illustrating a test facility designed to test the cleaning of stack gases and recovery of solids and liquids with the present method and apparatus; 
           [0025]      FIG. 5  is an enlarged portion of the test facility shown in  FIG. 4 ; and 
           [0026]      FIG. 6  is an illustration corresponding to  FIG. 5  in top view showing the movement of catalytic flow-through beds in  FIG. 5 ; 
           [0027]      FIG. 7A  is a graph illustrating CO 2  before and after cleaning; 
           [0028]      FIG. 7B  is a graph illustrating SO 2  before and after cleaning; and 
           [0029]      FIG. 7C  is a graph illustrating NO before and after cleaning. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Referring to  FIG. 1 , schematic illustrating a coal-fired boiler for electric power generation using stack gases that are cleaned and solid/liquid products recovered. A coal fired boiler  10  is shown utilizing the stack gas cleaning and recovery apparatus and method of the present invention. Fresh air intake  12  flows through preheater  14  to supply preheated fresh air to the boiler  10  for coal firing. The stack gases  16  from boiler  10  pass through preheater  14  whereby heat is transferred to the fresh air intake  12 . 
         [0031]    The stack gases  16 , now cooled by preheater  14 , are conveyed to an emission control unit  18  where the stack gases  16  are circulated to inlet  20  to emission control system  18 , where the stack gases  16  are allowed to rise through the emission control system  18  and through gas cleaning apparatus  22 . The stack gases  16  at this point include pollutants according carbon monoxide, carbon dioxide, nitrogen oxides and sulfur oxides. The stack gases  16  also includes water and particulates such as aluminum oxides, mercury compounds, zinc compounds lead compounds, and other particulate matters such as uranium and rare earth metals, as well as halogens such as fluoride and chloride. 
         [0032]    With reference to  FIGS. 2A-B , gas cleaning apparatus  22  may comprise first catalytic flow-through bed  24 , second catalytic bed  26  and third catalytic flow-through bed  28  as shown in  FIG. 2A  or through first catalytic flow-through bed  24 , second catalytic flow-through bed  26 , third catalytic flow-through bed  28  and fourth catalytic flow-through bed  30  as shown in  FIG. 2B . In  FIG. 2A , the rising stack gases  16  in gas cleaning apparatus  22  first flow through the first catalytic flow-through bed  24  followed by the adjacent second catalytic flow-through bed  26 , and then followed by the third catalytic flow-through bed  28 . When fourth catalytic flow-through bed  30  is utilized as shown in  FIG. 2B , gas stack  16  in stack  32  first flow through fourth catalytic flow-through bed  30  and then through the adjacent first catalytic flow-through bed  24 . 
         [0033]    First catalytic flow through bed  24  is calcium zeolite comprised of zeolite particles with a majority between 44 μm and 64 μm in size. By a “majority” in the particle size range means here, as well as elsewhere in this application, that is highest in like particle size increments but that it necessarily is not 50% of the particle sizes in the zeolite of the bed. The particle size range of the calcium zeolite is indicative of the surface area, number of exposed pores, and ion exchange capacity of the calcium zeolite effective in the first catalytic flow-through bed. The calcium zeolite is a calcium-sodium-potassium aluminosilicate that is relative high calcium oxide greater than 2.75% by weight. Typical chemical analyses of calcium zeolite are (i) 2.85% calcium oxide (CaO), 2.85% potassium oxide (K 2 O), 0.98% manganese oxide (MgO), 0.06% manganese oxide (MnO), 0.19% titanium dioxide (TiO 2 ), 0.05% potassium oxide (P 2 O 5 ), 0.03% sodium oxide (Na 2 O), 11.43% aluminum oxide (Al 2 O 3 ), 1.26% ferric oxide (Fe 2 O 3 ) and 66.35% silicon dioxide (SiO 2 ), and (ii) 3.4% calcium oxide (CaO), 3.0% potassium oxide (K 2 O), 1.5% manganese oxide (MgO), 0.05% potassium oxide (P 2 O 5 ), 0.3% sodium oxide (Na 2 O), 12.1% aluminum oxide (Al 2 O 3 ), 1.6% ferric oxide (Fe 2 O 3 ) 70.0% silicon dioxide (SiO 2 ). The remainder may comprise of other oxides (R 2 O 3 ). A source for calcium zeolite, amongst others, is St. Cloud Mining Company mines at Winston and Truth or Consequences, New Mexico 87901. 
         [0034]    The depth and breadth of the first bed  24  is determined by the flow rate of the stack gases  16  and the physical dimensions of the stack  32  and gas cleaning apparatus  22  through which stack gases  16  are conveyed. First catalytic flow-through bed  24  is provided as a flow through bed held in position by lower screen  34  and upper screen  36  each of between 150 and 350 mesh designed to hold the zeolite particles of calcium zeolite in position in the bed, while allowing flow through of the stack gases  16  with the desired flow rate. 
         [0035]    The primary function of first catalytic flow-through bed  24  is to reduce carbon monoxide and carbon dioxide in the zeolite bed. First catalytic flow-through bed  24  also captures ash and other particular matter as well as aluminum oxide if the fourth catalytic flow-through bed  30  is not provided as shown in  FIG. 2A . 
         [0036]    The stack gases  16  in stack cleaning apparatus  22  then flow through second catalytic flow-through bed  26  positioned adjacent first catalytic flow-through bed  24 . Second catalytic flow-through bed  26  is comprised of a blend between 25 and 75% of sodium zeolite and calcium zeolite with a majority of the zeolite particles between 65 μm and 125 μm in size. The particle size range of sodium zeolite and calcium zeolite in the blend is indicative of the surface area, number of exposed zeolite pores, and ion exchange capacity of the sodium zeolite/calcium zeolite blend effective in the second catalytic flow-through bed. The source of the calcium zeolite can be the same as that used to provide first catalytic flow-through bed  24 , but with a majority particle size between 65 μm and 125 μm. The sodium zeolite may be natural sodium-potassium clinoptilolite that is relative high sodium oxide greater than 2.75% by weight. Typical chemical analyses of a sodium zeolite are (i) 3.5% sodium oxide (Na 2 O), 3.8% potassium oxide (K 2 O), 11.9% aluminum oxide (Al 2 O 3 ), 0.7% ferric oxide (Fe 2 O 3 ), 0.8% calcium oxide (CaO), 0.4% manganese oxide (MgO), 0.02% manganese oxide (MnO), 0.1% titanium oxide (TIO 2 ) and 69.1% silicon dioxide (SiO 2 ), and (ii) 3.03% sodium oxide (Na 2 O), 3.59% potassium oxide (K 2 O), 10.27% aluminum oxide (Al 2 O 3 ), 0.86% ferric oxide (Fe 2 O 3 ), 1.77% calcium oxide (CaO), 0.00% potassium oxide (K 2 O), 0.4% manganese oxide (MgO), 0.02% manganese oxide (MnO), 0.11% titanium oxide (TIO 2 ), 69.1% silicon dioxide (SiO 2 ), and 13.09% LOI. The remainder may comprise other oxides (R 2 O 3 ). A source of the sodium zeolite, amongst others, is the St. Cloud mines in Ash Meadows, Nev. Again the size and depth of the second flow-though bed is determined by the physical dimensions of the stack  32  and the flow rate through the stack  32  at second catalytic flow-through bed  26  in the gas cleaning apparatus  22 . 
         [0037]    The primary purpose of the second flow through bed  26  is to capture and reduce nitrogen oxides (NOx) in the stack gas  16 . The second catalytic flow through bed  26  is also effective in reduce water and metal compounds such as mercury, lead, uranium and other trace materials. Again, a lower screen  38  and an upper screen  40  may be provided with mesh sizes between 150 and 350 mesh to maintain the zeolite particles in the third catalytic flow-through bed  28 , while allowing the desire flow rate through of stack gas  16 . 
         [0038]    On exiting the second catalytic flow-through bed  26 , the stack gases  16  flow through the adjacent third catalytic flow-through bed  28 . The third catalytic flow-through bed is comprised of calcium zeolite similar in chemical analysis to the first catalytic flow-through bed  24  with a majority of zeolite particles size between 78 μm and  204 . The particle size range of calcium zeolite is again indicative of the surface area, number, of exposed zeolite pores, and ion exchange capacity of the calcium zeolite in the third catalytic flow-through bed. 
         [0039]    The third catalytic flow-through bed  28  is primarily to reduce sulfur oxides present in the stack gas  16 . The third catalytic flow through bed may also reduces sulfur acids, calcium compounds and ash in the stack gas  16 . The composition of calcium zeolite in third catalytic flow through bed  28  may be of the same composition as the first catalytic flow through bed  24 , but with zeolite particle of different particle size as described. Again, a lower screen  42  and an upper screen  44  is with mesh size between 150 and 350 mesh is provided to maintain the zeolite particles in the third catalytic flow through bed  28 . 
         [0040]    Where a fourth catalytic flow through bed  30  is provided as shown in  FIG. 2B , the fourth catalytic flow-through bed is provided in the stack gas  16  adjacent the first catalytic flow-through bed  24 . This embodiment provides that the gas stream  16  may flow through the fourth catalytic-flow-through bed  30  before flowing through the first catalytic flow-through bed  24 . The composition of the fourth catalytic flow-through bed  30  is the same as the first catalytic flow-through bed, namely, comprised of calcium zeolite with a majority of the zeolite particles between 44 μm and 64 μm in size. The zeolite particles in fourth catalytic flow-through bed are maintained in position by lower screen  46  and upper screen  48  with a mesh size between 150 and 350, while allowing flow of stack gas  16  though the bed. An electrical charge is also provided on the lower screen  46  to provide that the fourth catalytic flow-through bed  30  attracts and retains aluminum particles from stack gas  16 . The particle size range of calcium zeolite is again indicative of the surface area, number, of exposed zeolite pores, and ion exchange capacity of the calcium zeolite in the fourth catalytic flow-through bed. 
         [0041]    Thus, the stack gas  16  flowing through gas cleaning apparatus  22  is substantially cleaned of aluminum compounds carbon dioxide, carbon monoxide, nitrogen oxides, sulfur oxides. It may also clean mercury compounds, zinc compounds, lead compounds, water and other trace particulate in the stack gas  16 . The cleaning of the stack gases  16  flow through first catalytic flow-through bed  24 , second catalytic flow-through bed  26 , third catalytic flow-through bed  28  and, if present, fourth catalytic flow-through bed  30  provides at least 90%, 95%, or 99% reduction in aluminum compounds, sulfur oxides, nitrogen oxides and carbon oxides from the stack gases  16 . Where the fourth catalytic flow-through catalytic bed  30  is provided as shown in  FIG. 2B , aluminum oxide may be largely separately collected and separately processed to recovered as explained below. 
         [0042]    To demonstrate the operation of the present method and apparatus the test facility shown in  FIGS. 4 through 6  was assembled and operated to perform tests as described below. As shown in  FIG. 4 , the gas cleaning apparatus  22  has the first catalytic through-flow bed  24 , second catalytic through-flow bed  26 , third catalytic through-flow bed  28  and fourth catalytic through-flow bed  30  (where used). Each of the catalytic through-flow beds may be individually rotated using the handle  60  and the gear assembly  58  shown in  FIGS. 5 and 6 . Stack gas  16  is brought up though stack  12  and through the first catalytic through-flow bed  24 , second catalytic through-flow bed  26  and third catalytic through-flow bed  28  or the first catalytic through-flow bed  24 , second catalytic through-flow bed  26 , third catalytic through-flow bed  28  and fourth catalytic through-flow bed  30  in gas cleaning apparatus  2  as shown in  FIGS. 4 and 5 . 
         [0043]    The test apparatus includes stack  32  for transporting stack gas  16  to the gas cleaning apparatus  22  described above. The gas cleaning apparatus  22  is shown in further detail in  FIG. 5  with first  24 , second  26  and third  28  catalytic through-flow beds having a zeolite beds as described above. Each of the catalytic through-flow beds is connected to a central drive shaft  58  that is adapted to rotate each of the catalytic through-flow beds, individually, from a first position where stack gas  16  passes through the bed to a second position where the catalytic through-flow bed can purged by the nitrogen. A handle  60  is provided that may be translated vertically to select one of the catalytic through-flow beds and rotated to move the selected through-flow bed from the first position to the second position.  FIG. 6  is a top view of the gas cleaning apparatus  22  according to the testing apparatus shown in  FIGS. 4-5 . In this view, the catalytic through-flow beds are aligned with the stack  32 . 
         [0044]    When then gas stack  16  was stopped, the catalytic through-flow beds were each individually rotated over exit tube  50  and nitrogen gas was delivered downwardly through inlet  60  and through the rotated catalytic through-flow bed to remove solids and liquids collected on the rotated bed into the bucket shown in  FIG. 4 . The purging may also produce gases, such as oxygen (O 2 ) and nitrogen (N 2 ) that may be extracted and transported as portion of the gases (e.g. N 2 ) to a recycler and a second gas outlet that transports a portion of the gases (e.g. O 2 ) to the burner for combusting the fuel. 
         [0045]    The tests with the test facility shown in  FIGS. 4-6  included Kentucky coal fired by propane, Ohio coal fired and two tests with charcoal mixed with organic sulfur. The samples were fired by a propane burner at  62  shown in  FIG. 4  or in a combustion oven (not shown) before positioning below stack  32 . These illustrate the operation of the method and equipment. The data from these tests is set forth in table and graphic form in the Appendix to this application. 
         [0046]      FIGS. 7A-C  represent data taken from a combustion gas emissions test where charcoal and organic sulfur were combusted in a combustion oven. During a first test run, data was collected by a probe in a lower flue stack before the stack gas  16  passed through the gas cleaning apparatus  22 . During a like second test run, data was collected by a probe in the upper flue stack after the stack gas  16  passed through the gas cleaning apparatus. Data was collected every 5 seconds using a Testo 350XL portable combustion multi-gas analyzer. Data for the first test run (lower flue stack) was compared to and plotted with data for the second test run (upper flue stack) to provide an analysis of the results of the gas cleaning apparatus  22 . 
         [0047]      FIG. 7A  illustrates measured levels of carbon dioxide (ppm) before (solid line) and after (dashed line) the stack gas  16  is cleaned bypassing through the first catalytic through-flow bed  24 , second catalytic through-flow bed  26 , third catalytic through-flow bed  28  of the gas cleaning apparatus  22 . 
         [0048]      FIG. 7B  illustrates measured levels of sulfur dioxide before (solid line) and after (dashed line) the stack gas  16  is cleaned by the gas cleaning apparatus  22 . 
         [0049]      FIG. 7C  illustrates measured levels of nitrous oxide before (solid line) and after (dashed line) the stack gas  16  is cleaned by the gas cleaning apparatus  22 . 
         [0050]    It was found by the comparison of the data that carbon dioxide in the stack gas  16  was reduced by at least 95% by the coal cleaning apparatus  22 ; sulfur dioxide in the stack gas  16  was reduced by at least 99% by the coal cleaning apparatus  22 ; and nitrogen oxide in the stack gas  16  was reduced by 99% or more by the coal cleaning apparatus  22 . These results demonstrate the high effectiveness of the gas cleaning apparatus  22 . As the data in the Appendix also show, the oxygen levels in each of the tests increased with the stack gas  16  flowing through the first catalytic through-flow bed  24 , second catalytic through-flow bed  26 , third catalytic through-flow bed  28  of the gas cleaning apparatus  22  demonstrating the reduction of the carbon oxides, sulfur oxides and nitrogen oxides in the catalytic through-flow beds. 
         [0051]    While the principle and mode of operation of this invention have been explained and illustrated with regard to particular embodiments, it must be understood, however, that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.