Patent Publication Number: US-2012031987-A1

Title: Process heater system

Description:
RELATED APPLICATION 
     This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 61/370,804 filed on Aug. 4, 2011. The entire disclosure of this provisional application is hereby incorporated by reference. 
    
    
     BACKGROUND 
     An industrial process heater can comprise a main combustion chamber, an afterburner, and an exhaust stack. The main combustion chamber volatizes an industrial load (e.g., dry paint, powder coating, varnish, epoxy, oil, and/or grease). A supplemental combustion chamber which is a first zone (or zone one) of the afterburner, completes the combustion of non-hazardous volatized organic material. Combustion gas passes from the supplemental combustion chamber to a second zone (or zone two) of the afterburner. The combustion gas dwells for at least half a second in the afterburner, and then passes to the exhaust stack for exhaust outside the envelope of the industrial facility. 
     SUMMARY 
     A system is provided wherein stack-exhaust heat is captured and transmitted for use as an energy source for the industrial envelope. For example, the stack-exhaust heat can be used to radiantly heat the envelope of the industrial facility. Alternatively, the recovered heat can be used to heat water or another liquid. In either or any event, material combusted in the afterburner is a recycled alternative fuel, not a solid waste. 
    
    
     
       DRAWINGS 
         FIG. 1  is a schematic side view of a process heater system for an industrial zone. 
         FIG. 2  is a schematic top view of the process heater system. 
         FIG. 3  is a schematic view of a radiant-heat pipe straightened to show temperature distribution along its length. 
         FIGS. 4-7  are sectional views of different regions of the radiant-heat pipe. 
         FIGS. 8 and 9  are each diagrams of heating control procedures. 
         FIG. 10  is a schematic view of a liquid-heating cycle for the process heater system. 
     
    
    
     DESCRIPTION 
     Referring now to the drawings, and initially to  FIG. 1 , a process heater system  10  for an industrial envelope  11  is shown. The system  10  comprises a main combustion chamber  20 , an afterburner  30 , an exhaust stack  40 , and heat-recovery piping  50 . As is explained in more detail below, the piping  50  captures heat normally lost through the exhaust stack  40  and converts it into heat for use within the industrial envelope  11 . 
     The main combustion chamber  20  has a gas burner  21  and volatizes the industrial load. In other words, the industrial purpose of the process heater is performed in the main combustion chamber  20 . This purpose can comprise, for example, heat cleaning fixtures, parts, and/or equipment to remove non-hazardous material that is not a solid waste. 
     The afterburner  30  comprises a supplemental combustion chamber  31  having its own gas burner  32  and in communication with the main combustion chamber  20 . Often, as illustrated, the supplemental chamber  31  is within the same package perimeter as the main combustion chamber. The supplemental chamber  31  is considered the first zone of the afterburner  30  and its function is to complete the combustion of non-hazardous volatized organic material transported from the main chamber  20 . 
     The afterburner  30  comprises a second zone  33  located downstream of the supplemental combustion chamber  31 . This second zone  33  can be, as illustrated, outside the package perimeter of the chambers  20  and  31 , and vertically aligned with the exhaust stack  40 . The afterburner  30  can be sized so that combustion gas dwells therein for at least half a second. From the afterburner  30 , combustion gas passes to the exhaust stack  40  for exhaust outside the industrial envelope  11 . 
     The heat-recovery piping  50  can comprise a network of pipes which each include an adapter region  51 , an inlet region  52 , an intermediate region  53 , and an outlet region  54 . The adapter region  51  is connected to the exhaust stack  40  to receive combustion gas therefrom. An existing exhaust stack  40  can be retrofitted with the adapter region  51 . 
     The heat-recovery piping  50  can project, turn, and extend to effectively cover the industrial envelope  11 . For example, as is best seen by referring additionally to  FIG. 2 , four pipes can extend tangentially outward from the exhaust stack  40  at settings that are approximately 90° apart. That being said, in some facilities fewer pipes (e.g., a single pipe) or more pipes may be sufficient/necessary to accommodate the relevant industrial envelope  11 . 
     The pipes  50  are preferably positioned close to the ceiling and horizontally oriented. For example, the pipes  50  can be hung about twelve to sixteen feet over the floor of the industrial envelope  11 . Lower heights are possible, but may require shielding to prevent overheating of personnel. Higher heights are also possible, but may result in lost heat (e.g., about 1% per foot). The pipes  50  can be supported by beams, girders or joists. The piping  50  may also be gradually sloped downward (e.g., about ¼ inch per each ten feet length) to prevent water accumulation. 
     As is best seen by referring additionally to  FIG. 3 , combustion gas entering the pipe  50  will be at an extremely high temperature (e.g., at least 1000° F., at least 1100° F., at least 1200° F., at least 1300° F., at least 1400° F., about 1500° F. etc.). And preferably combustion gas exiting the pipe  50  will be at a much lower temperature (e.g., less than 800° F., less than 700° F., less than 600° F., less than 500° F., less than 400° F., about 300° F., etc.). 
     As shown in  FIGS. 4-7 , the radiant-heat-pipe regions  51 - 54  can each include a cylindrical housing  55  forming the gas passage. The housing  55  is made of material (e.g., radiant galvanized steel) which allows infrared heat to be emitted therefrom. The piping  50 , and thus the housing  55 , can have an OD dimension in the range of 3-5 inches (e.g., 4 inches). The heat-recovery piping  50  can also include roof-like reflectors  56  along its length to insure that any radiant heat directed upward will be reflected downward towards the desired heating area. 
     In the adapter region  51  and the inlet region  52 , the heat-recovery piping  50  includes insulation  57  on its inside surface as shown in  FIGS. 4-5 . This insulation  57  is provided to lower the radiant heat emitted by the corresponding housing  51  in regions  51 / 52  and to help retain the intense heat for transportation to regions  53  and  54 . The intermediate region  53  can include a turbulator  58  to spin the combustion gas along the interior surface of the pipe. The intermediate region  53  and the outlet region  54  can be without interior insulation. 
     Returning now back to  FIG. 2 , the process heater system  10  can additionally comprise tail piping  60  and an exhaust device  70 . The tail piping  60  conveys the now cooler combustion gas to the exhaust device  70 . To this end, it can comprise, as illustrated, a branch  61  connected to the outlet region  54  of each radiant-heat pipe  50  and a common branch  62  connecting each branch  61  to the exhaust device  70 . The exhaust device  70  (e.g., a vacuum pump or exhaust fan), pulls fluid through the pipes  50 / 60  and into a safe region of the atmosphere outside the industrial envelope  11 . Dampers  63  can be provided in each tail pipe  60  to monitor the flow rate of combustion gas therethrough. A damper  64  can be provided on the common branch  62  and a drain  65  (for accumulated moisture) can be provided upstream of the exhaust device  70 . 
     As is shown in  FIGS. 8 and 9 , a controller  80  can receive input from a thermostat  12  and convey instructions to the exhaust device  70  and/or the dampers  63 . If the industrial envelope  11  includes a conventional space heater  13  as shown in  FIG. 9 , the controller  80  can likewise control it. 
     The exhaust device  70  can be continuously run to provide the system  10  with a “self-sealing” feature insuring that combustion gas does not escape into the industrial envelope  11 . 
     As is shown in  FIG. 10 , the process heater system  10  can additionally or alternatively incorporate a liquid-heating cycle  90  (e.g., a tank  91 , a pump  92 , inlet tube  93 , heat exchanger  94 , and outlet tube  95 ). With the cycle  90 , the liquid is heated by the combustion gas passing through the heat-recovery piping  50  and stored in a tank  91 . This liquid (e.g., water) can be used for locker room showers, industrial processing steps, or other applications requiring a heated fluid. 
     Thus, the system  10  is a process heater unit with an afterburner  30  and a heat recovery system ( 50 ,  60 ,  70 ,  80 ,  90 ). The material combusted in the afterburner  30  is fuel used to provide heat or other energy for the industrial envelope  11 . This fuel material is recycled and legitimately used as an alternative fuel or ingredient. It can be produced and used for energy recovery from a non-hazardous valuable commodity secondary material with meaningful heating value and without contaminants significantly higher in concentration than traditional fuel. When the industrial load in the main combustion chamber  20  is paint, powder coating, varnish, epoxy, grease and/or oil, the secondary materials burned in the afterburner  30  are not solid wastes. 
     Although the process heater system  10 , the main combustion chamber  20 , the afterburner  30 , the exhaust stack  40 , and/or the heat-recovery elements ( 50 ,  60 ,  70 ,  80 ,  90 ) have been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. 
     REFERENCE NUMBERS 
       10  process heater system 
       11  industrial envelope 
       12  thermostats 
       13  space-heating unit 
       20  main combustion chamber 
       21  main combustion burner 
       30  afterburner 
       31  supplemental combustion chamber 
       32  supplemental combustion burner 
       33  second zone of afterburner 
       40  exhaust stack 
       50  heat-recovery piping 
       51  adaptor region 
       52  inlet region 
       53  intermediate region 
       54  outlet region 
       55  housing 
       56  reflector roof 
       57  interior insulation sleeve 
       58  turbulator 
       60  tail piping 
       61  separate branches 
       62  common branch 
       63  dampers for separate branch 
       64  damper for common branch 
       65  moisture drain 
       70  exhaust device (vacuum pump) 
       80  controller 
       90  liquid-heating cycle 
       91  tank 
       92  pump 
       93  inlet tube 
       94  heat exchanger 
       95  outlet tube