Abstract:
Method and apparatus for Scrubbing exhaust streams to approach Zero Emissions with utility in Coal Fired Electricity Generation. The Scrubbing “Ionized” Rainstorm Tunnel (S.I.R.T.) a.k.a. Natural State Hydrologic Cycle Emulator comprises a tunnel that sprays exhaust streams with “ionized” water, cost effectively scrubbing toxic constituents mimicking the atmospheric and hydrologic cycle. Various tunnel configurations greatly increase dwell times beyond that of other methods to any chosen scrubbing agent allowing for more complete absorption of all toxic emissions i.e. sulfates, nitrates, heavy metals and volatile organic compounds produced by combustion of coal or other dirty fuels. The design incorporates advantageous removal points for further micro and nano effluent treatment and simplified sequestration of Carbon Dioxide if desired. A Nozzle Automated Positioning and Retrieval System (NAPRS) allows for continuous operation of boilers or other processes as failed spray nozzle heads can be serviced outside the tunnel without down time.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to the following U.S. Provisional Application No. 60/615,685, filed Oct. 5, 2004, and is incorporated herein by reference. Inventors: Hood,Ian F.; (Toronto,Canada); Poulos,Steven D.; (Toronto,Canada) 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Coal is the most abundant and easily recovered form of energy source currently extant for all of the world&#39;s countries irrespective of their level of technological advancement and so is employed for power generation wherever it is feasible. Coal powered electricity generation emits huge quantities of CO2 into the atmosphere and so coal is one of the biggest contributors to greenhouse gas emissions and therefore global warming. Coal burning also emits acid rain components (NOx &amp; SOx) and toxic heavy metals (Hg &amp; U). The present invention simplifies the process of recovering and/or sequestering of all toxic and greenhouse gas emissions far more inexpensively than all other prior apparatus and methods by emulating the cleansing attributes of the hydrologic cycle.  
         [0003]     An additional benefit of the present method is the ease of recovery of waste heat that is usually vented to the atmosphere, for district heating or local industrial processes furthering efficiency of the Rainstorm Tunnel at eliminating greenhouse gas emissions.  
       INVENTION SUMMARY  
       [0004]     The chief utility of the invention its unique design that allows for: 
        1. dramatically reduced construction and operating costs over other methods of exhaust gas scrubbing     2. ease of maintenance     3. ease of scalability     4. penultimate scrubbing control device efficiency        
 
         [0009]     The invention can consist of either a single tunnel or have multiple tunnels run in series or parallel and each to any length depending on the volume of the effluent and the configuration of the power plant/effluent generating process and/or its site. The chief efficiency of the invention comes from the use of “ionized” water in a tunnel with spray nozzles, but any scrubbing agent extant can be used depending on the constituent contamination of the effluent gas and how close to ‘zero emission’ it is desired that any specific installation of “The Rainstorm Tunnel” process needs to be.  
         [0010]     The Key to the invention is its emulation and compression of the Hydrologic Cycle in its operation. In nature the Hydrologic Cycle uses chiefly sunlight, gravity, electrical discharges (lightning) and precipitation to cleanse the air. The vortices created due to wind forces of a storm combined with the resident time of particulates within moisture-laden environments and their exposure to sunlight add to the cleansing and purifying of pollutant air. The Rainstorm Tunnel compresses the effects of the larger natural environment into an overall linear controlled environment that emulates the Hydrologic Cycle to carefully control all variables for maximum efficiency. The device scrubs the effluent with a pressurized rain/spray that absorbs the toxic constituents using water that has been de-agglomerized and polarized (“ionized”) through processes known to those skilled in the art. De-agglomerized and polarized (“ionized”) water readily absorbs and dissolves soluble compounds at a much higher rate than normal. The addition of ozone and sunlight to the Rainstorm Tunnel creates photochemical smog that can then be cleansed by the rain/spray. Residence time in the rain/spray is the increased by orders of magnitude over all other prior art contributing to the efficiency of the Rainstorm tunnel in removing toxic cleansing effluent from exhaust streams. The rain/spray is collected by gravity in the bottom of the tunnel and/or is pumped to a settling tank to precipitate the fly ash and the resultant effluent liquor is then received in an electro-coagulation tank and /or passed through a membrane to collect the remaining dissolved toxic metals and oxides of sulfur and nitrogen. The laminar flow effect in the tunnel sees some gas moving by spray force and by tunnel shape in helical motion along the outer edges of the tunnel, while gases in the center are seen as traveling at different velocities and targeted to be spray-blown into the ponding sections at the base of the tunnel to be further mixed with the outer streams. Additional vortices created are the effects of the central flow folding into the outer flows at approximately the inner most edge of the helical fence/rib version or varying the orientation of the spray nozzles along the length of the tunnel. The chaotic or non-chaotic result of gas volume factors ratio to helical wavelength and amplitude factors are calculated depending on the volume and constituency of the effluent stream using present day understandings of vortex design, absorption factors due to gas pressure, distance and time traveled within control device, material surface texture and area, and variables relating to the introduced agent properties. It is the intention of the Rainstorm Tunnel that a degree of the momentum of the swirling action within a helical vortex is maintained to provide a continuous and maximal surface absorption, velocity and residence time as in nature as apposed to other methods of screening, filtering, catalytic chemical reductions, combustion modifications, and precipitating that require significantly more process energy and often require complete retooling of existing power plants. The Rainstorm Tunnel can eliminate or reduce the size of dust collectors, the need for coal preparation prior to burning, lime input for SO2 scrubbing, bag-houses, electrostatic precipitators, complex multiple grid piping systems, pure oxygen and low nitrogen combustors and the attendant maintenance problems and costs. The Rainstorm Tunnel using custom designed spray nozzles to create optimal droplet sizes and GWPT&#39;s proprietary Nozzle Auto-Positioning &amp; Retrieval System (NAPRS) for ease of maintenance can accommodate varying coal fired plant layouts and effluent stream volumes and constituents with ease and flexibility. Virtually any process known for scrubbing exhaust can be attached to the rain tunnel for final polishing so that the released gas stream to the atmosphere can be totally benign to the environment. It is the intention of the Rainstorm Tunnel to reduce or eliminate the need and therefore the cost of implementation for the most of these processes. Because of this flexibility and simplicity, due to its artful design, the Rainstorm Tunnel can also be segmented and portable to a degree impossible with other systems of screening and filtering and settling. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  shows a plan view of the Rain Tunnel attached to an existing coal fired power plant.  
         [0012]      FIG. 2  shows a elevation of the Rain tunnel attached to an existing coal fired power plant.  
         [0013]      FIG. 3  shows an oblique view of a helically fenced version of the Rain Tunnel  
         [0014]      FIGS. 4   a  to  4   b   1  show a cross-sectional detail of various versions of the Rain Tunnel with piping outside the tunnel 
         FIG. 4   a  fixed nozzle version that has maintenance access from the interior of the tunnel      FIG. 4   a   1  fixed nozzle version detail      FIG. 4   b  Nozzle Auto-Positioning and Retrieval System (NAPRS) cross section      FIG. 4   b   1  Nozzle Auto-Positioning and Retrieval System (NAPRS) detail          
         [0019]      FIG. 5  shows a wall detail for piping embedded in the tunnel  
         [0020]      FIG. 6  Rain Tunnel Isometric 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     In accordance with the present invention briefly described herein  FIG. 2  shows a greatly simplified system for removing all toxic constituents of any gaseous effluent stream at any temperature with or without heat exchangers ( 6 ) via spray nozzles ( 15 ), using “ionized” water, steam or slurry spray introduced artfully into a sloped or horizontal tunnel to create a vortex in the exhaust stream thereby increasing its dwell time in the spray. The helical interior shaped version ( FIG. 3 ) creates ideal conditions to maximize the spray contact time with the exhaust stream. The single, double or triple helical fence/rib ( 7 ) embodied in the present invention minimizes construction complexity and cost as the fence/rib integrally strengthens the Rainstorm Tunnel&#39;s structure.  FIG. 3  shown represents a single helix, high fence &amp; high frequency configuration. An actual tunnel variation may incorporate as little as one or a multiple of helical grooves/fences along the tunnel surface made of stainless steel with welded on rebar or other high strength/ high temperature resistant concrete/plastic/composite material to become integral with a formed concrete/plastic/composite tunnel and drains therein to act as ponding and collection devices. A Rainstorm Tunnel version having only spray nozzles ( FIGS. 4   a ,  4   a   1 ,  4   b ,  4   b   1 ) will impart the beneficial vortex, centrifugal and ponding effects without the impediment of a fence by having the piping on the outer periphery of the walls of the tunnel with some of the nozzle heads extensible into the very centre of the tunnel to penetrate the central vortex created in the tunnel using the Nozzle Auto-Positioning &amp; Retrieval System (NAPRS).  FIGS. 4   b  &amp;  4   b   1  illustrate a tunnel section and enlargement of the Nozzle Auto-Positioning &amp; Retrieval System (NAPRS). Illustrated in  FIG. 4   b   1  is the detail of the installed aspect of the NAPRS hydraulic spray-head moving device. “Ionized” water enters through main pipes ( 16   b ) which connect to the distribution pipes ( 17 ) which are held to the exterior of the SIRT by clamps ( 26 ) bolted to brackets ( 19 ) welded to a plate ( 24 ) which is bolted to the SIRT wall ( 9 ). The distribution pipes ( 17 ) feed pressurized “ionized” water to the connected feeder pipes ( 18 ) through the telescoping hydraulically operated feeder pipe extension ( 22 ) that penetrates the SIRT wall( 9 ) and its liner( 25 ) moving through a sleeve ( 23 ) to position the spray head ( 15 ) The hydraulic fluid is fed by hoses( 37 ) and the moving feeder pie extension( 22 ) and the feeder pipe( 18 ) are held to the brackets by bolts ( 21 ).  
         [0022]     Helical fencing ( FIG. 3 ) for certain applications may be constructed from identical modules arranged along a given calculated path for each particular application, and may move through various frequencies within the path length. The high pressure spray nozzles ( 15 ) that are arrayed along the fence/rib or embedded in the walls of the tunnel can be angled to impart radial and axial momentum to the effluent gas, and may be positioned alternatively in any location along the tunnel wall being fed from supply pipes running longitudinally or spirally inside, outside or embedded in the tunnel wall. This advantageously results in a decrease in the necessary size and power of the induced draft fans as the gas will mix and flow naturally by the vortex created by the fence/rib and the spray and causing a natural centrifuge effect. Illustrated is the advantageous embodiment of the invention wherein the axial cross sectional  FIG. 1  shows induced draft fans ( 2 ) moving exhaust gas into a downward sloped tunnel ( 7 ), in which heat exchangers ( 6 ) can be installed to create process steam for steam stripping of volatile gases and sulfurs and/or heat removal for district heating/industry plus the necessary preheat of the rain/spray and reheating of the effluent gas discharged to the atmosphere if desired. The Rainstorm Tunnel can also enter the ground to take advantage of ground source cooling. Subsequently the new stack dimensions are dramatically reduced and therefore have less impact on the local esthetics. It is within the scope and intention of the Rain Tunnel to purify gases to medical or food grade quality to produce a revenue stream from the said purified gases for tunnel operators. The initial parts of the tunnel can contain, in the case of a coal fired generating station, a series of helically shaped or standard heat exchanger pipes ( 6 ) to preheat the slurry or “ionized” water and/or create steam to be used in steam stripping volatiles from the effluent gas if desired, the configuration of which will depend on the constituent effluent gas. From the initial stage the tunnel proceeds to a to a chamber ( 14 ) in which the initial highly concentrated liquor is collected to be pumped to sedimentation tanks ( 13 ) and then to electro-coagulation processing ( 12  ) and/or membranes and/or ozonation and/or any other existing prior art process necessary to purify the liquor and its off-gas. From the chamber the tunnel proceeds upward and can contain one and as many as three helical fence/ribs ( 7 ) positioned spirally along the tunnel wall and such ribs have advantageously spaced spray nozzles ( 15 ) along its interior edge to maximize exposure to and dwell time of the exhaust gas in the “ionized” water or slurry spray and/or steam. Alternatively the nozzles themselves ( 15 ) embedded in the tunnel wall can impart a cyclonic effect by their aspect with some of the nozzle heads extensible into the very centre of the tunnel to penetrate the central vortex created in the tunnel. Alternatively the Nozzle Auto-Positioning &amp; Retrieval System (NAPRS)( 4   b ,  4   b   1 ), which the nozzles( 15 ) can be mounted on, can move the feeder pipes( 18 ) telescoping them through the tunnel wall ( 9 ) to either hydraulically or manually move them for ease of maintenance and safety of the workers as the workers would never have to enter the tunnel nor the tunnel shutdown for maintenance ( FIG. 6 ). The resultant is a controlled linear cyclonic rainstorm. Parameters will include a sound wave analysis to avoid potential reverberation resulting in sound and if deemed necessary reverse wave sound deadening equipment installed (noise canceling). The ribs can also act as heat exchangers if so desired by embedding piping within them or eventuating them as pipes illustrated in  FIG. 3 . The feeder pipes( 18 ) for the spray nozzles ( 15 ) are modularized and sectioned off for ease of maintenance. The helical fence/rib in the sloped or horizontal tunnel ( 9 ) creates multiple natural collection points/pools as temporary storage of the liquor in the tunnel which then can be siphoned to the main drains ( 8 ) and once the concentration of contaminants in the runoff liquor has reached the desired level then the liquor can be piped away for further processing. The resultant purified exhaust is released to the atmosphere via the vent stack ( 10 ).  
         [0000]     Note:  
         [0023]     In the helical rib design ( FIG. 3 ) each drain ( 8 ) will contain diminishing concentrations of contaminants and/or completely different contaminants both in relation to the increasing distance along the tunnel from the source of the coal smoke and what is being sprayed into the tunnel at that particular point, as both can vary to the constituents of the effluent, which would allow differing levels of further processing as the liquor at every drain ( 8 ) would not need every step of the purification process (as at each collection point the concentration and/or makeup of the runoff liquor varies and this can create diminishing returns for effort expended to cleanse the liquor). The last few drains ( 8 ) can simply have their thinly contaminated liquor returned to the first few spray nozzles allowing for much more efficient reuse of the cleansing spray as it does not have to be processed to complete purity before being reused. Only liquor that has the highest concentration of contaminant needs to be piped away for further processing by electro-coagulation, electro flocculation, precipitate settling, aeration or sequestration depending on the constituent toxicity.  
         [0024]     In simplified versions of the tunnel for effluent streams that are not highly contaminated or for small volumes of effluent the helical ribs can be eliminated and the distribution pipe itself ( 16 , 16   b ) can either be shaped in a helical or straight-line configuration. In applications where a very high pressure of “ionized” rain or scrubbing slurry mixture is needed as in a coal fired exhaust stream, the feeder pipe can be mounted inside the tunnel walls with only the spray heads exposed to the effluent in a helical or straight-line fashion or attached to the inside of the tunnel walls ( FIG. 5 ), such design placement and materials used dependant on the toxicity and corrosiveness of the effluent. In the case of a coal fired power plant the fly ash would be settled out in a pond, tank or optimally in the bottom of the tunnel( 12 ) and the resultant liquor further processed via membranes and electro coagulation( 13 ) to remove the Sulfates and Nitrates that are in the exhaust streams of coal fired boilers, smelters, incinerators and other high emission processes. Other technologies for Nox and Sox reduction in the effluent can take place before, during or after the Rainstorm Tunnel but it is the intention of the tunnel to reduce or eliminate the need for those technologies. Should the process be taken to its final and penultimate stage the carbon dioxide in the exhaust gas from the coal fired power plant or any other effluent stream, could be sprayed with a calcium and enzyme mixture for further sequestration as carbonate or compressed for industrial uses. The tunnel maintains a closed loop and processes the resultant liquor until the water is pure enough to be reused in the tunnel. Dwell time and mixing in the tunnel and therefore contact time to the spray is varied to the toxicity, temperature and density of the effluent gas by increasing or decreasing one of the following variables including but not limited to: 
    a) The fence / rib height     b) The slope of the tunnel     c) The length of the tunnel     d) The diameter of the tunnel     e) The coil tightness (frequency) of the rib along the tunnel wall     f) The density of the spray nozzles     g) The orientation of the spray nozzles     h) The pressure of the spray     i) The number of fences coiled about one another on the tunnel wall     j) The constituents of the spray     k) The size of the spray droplets     l) Surface texture on fence/ribs and tunnel wall     m) Periodically reversing or changing the aspects of the fence/rib coil on the tunnel wall     n) Eliminating the fence/rib     o) Helical arrangement of the spray nozzles/pipe     p) Straight-line arrangement of the spray nozzles/pipe     q) Materials and design of the spray nozzles/pipe     r) Positioning of the spray nozzles/pipe in the vortex     s) Embedding the pipe in the tunnel wall     t) Attaching the pipe to the tunnel wall     u) Materials and design of the tunnel     v) Sealing the tunnel and batching the effluent to increase dwell time     w) Running multiple tunnels in series or parallel     x) Any combination of the above    
 
         [0049]     It is understood that various other embodiments and modifications in the practice of the invention will be apparent to, and can be readily made by, those skilled in the art without departing from the scope and spirit of the invention described above. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the exact description set forth above, but rather that the claims be construed as encompassing all of the features of patentable novelty which reside in the present invention, including all the features and embodiments which would be treated as equivalents thereof by those skilled in the art to which the invention pertains. The “ionized” water spray main supply pipes may be introduced along the tunnel length ( 16  &amp;  16   b ) in any number and have branched piping into the tunnel at various intervals to effect the desired the result contained herein.