Patent Publication Number: US-9404650-B2

Title: Boiler with improved hot gas passages

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35USC §119(e) of U.S. provisional patent application 61/222,050, filed on Jun. 30, 2009. For the US only, the specification of the foregoing provisional patent application is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This description relates to the field of boilers for heating a fluid. More particularly, this description relates to boilers with tubes. 
     BACKGROUND 
     Boilers for heating a cold fluid (e.g. water, steam, thermal oil or any other heating medium) with a hot fluid (e.g. hot gases) with tubes are well known. Many improvements were provided in the past. In order to enhance the efficiency, number of isolated passages was increased by adding separators, plates or baffles among the tubes. These additional parts among the tubes are exposed to the hot fluid and thus require maintenance and decrease the availability of the boiler. These additional parts could also generate noise nuisance. 
     In order to enhance the efficiency, economizers are provided to be installed outside the boiler for saving energy released in the hot fluid escaping from the boiler. This type of economizer is separated to the boiler and need an external assistance (e.g. pump) for the circulation of the cold fluid trough the economizer. The external assistance consumes energy and thus decreases the global efficiency of the boiler. 
     Also, the transfer of the hot fluid from one passage to another is done with a particular pattern of tubes at the ends of the passages. That increases the number of types of tube to keep in inventory at the different level of the supply chain. 
     SUMMARY 
     According to an aspect, there is provided a boiler for heating a cold fluid with a hot fluid. The boiler comprises: a lower drum; an upper drum; a plurality of right tubes for conveying the cold fluid, each of the right tubes fluidly connecting the lower drum and the upper drum, the right tubes forming a right wall, each of the right tubes comprising at least one left inwardly extending portion extending toward a left wall; and a plurality of left tubes for conveying the cold fluid, each of the left tubes fluidly connecting the lower drum and the upper drum, the left tubes forming the left wall facing the right wall, each of the left tubes comprising at least one right inwardly extending portion, each extending toward the right wall; wherein the at least one right inwardly extending portion is contiguous to and staggered with the at least one left inwardly extending portion, forming at least two passages between the right wall and the left wall, each one of the at least two passages having first and second ends and being substantially isolated from each other between each of its respective first and second ends; in use, the hot fluid circulates in the at least two passages and heats the right tubes and the left tubes, thereby heating the cold fluid. 
     According to another aspect, there is provided a boiler for heating a cold fluid with a hot fluid. The boiler comprises: a lower drum; an upper drum; a plurality of tubes for conveying the cold fluid, each of the tubes fluidly connecting the lower drum and the upper drum, the tubes forming at least two passages each having first and second ends and being substantially isolated from each other between each of its respective first and second ends; and an end wall disposed at one end of the at least two passages, fluidly connecting the at least two passages; the end wall comprising a cavity allowing the hot fluid passing from one to another of the at least two passages by the cavity, wherein, in use, the hot fluid circulates in the at least two passages and heats the tubes, thereby heating the cold fluid. 
     According to another aspect, there is provided a boiler for heating a cold fluid with a hot fluid. The boiler comprises: a lower drum; an upper drum; a plurality of tubes for conveying the cold fluid, each of the tubes fluidly connecting the lower drum and the upper drum, the tubes forming a passage having first and second ends; and an additional exchanger; the additional exchanger comprising a cold inlet, a cold outlet, a hot inlet and a hot outlet; the cold inlet being fluidly connected to the lower drum, the cold outlet being fluidly connected to the upper drum, the hot inlet being fluidly connected to one end of the passage for receiving the previously cooled hot fluid; wherein in use, the hot fluid circulates in the passage and heats the tubes, thereby heating the cold fluid, then the hot fluid crosses the additional exchanger and exhausts by the hot outlet, the cold fluid, being subjected to a difference in temperature between the cold inlet and the cold outlet, flows upwardly from the lower drum to the upper drum crossing the additional exchanger thereby heating the cold fluid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
         FIG. 1  is a partial cut-out perspective of a boiler  10  in accordance with an embodiment; 
         FIG. 2  is another partial cut-out perspective of the boiler  10 ; 
         FIG. 3  is a front perspective of a tube arrangement  34  of the boiler  10 ; 
         FIG. 4  is a rear perspective of the tube arrangement  34 ; 
         FIG. 5  is a rear perspective of the boiler  10 ; 
         FIG. 6  is a scheme of a pattern  86  of tubes of the boiler  10 ; 
         FIG. 7  is a scheme of a pattern  96  in accordance with another embodiment; 
         FIG. 8  is a scheme of a pattern  112  in accordance with another embodiment; 
         FIG. 9  is a scheme of a pattern  126  in accordance with another embodiment; 
         FIG. 10  is a scheme of a pattern  138  in accordance with another embodiment; 
         FIG. 11  is a schematic view of a circulation of a hot fluid in a boiler in accordance with another embodiment; 
         FIG. 12  is a schematic view of a circulation of a hot fluid in a boiler in accordance with another embodiment; and 
         FIG. 13  is a schematic view of a circulation of a hot fluid in a boiler in accordance with another embodiment. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DETAILED DESCRIPTION 
     Referring now to the drawings and more particularly to  FIG. 1  and  FIGS. 2, 3 and 4 , there is respectively shown from the front and from the rear a boiler  10  in accordance with an embodiment. The boiler  10  is usually installed in a closed circuit, not shown, for heating a fluid and delivering it through a boiler outlet  12  as an external flow. The fluid circulates in a network comprising radiators, exchangers or turbines which decrease the temperature of the fluid, then the fluid flows back into the boiler  10  through a boiler inlet  76  to be heated again. According to an embodiment, the fluid is warm water or steam; it could also be a high specific heat capacity fluid or other convenient fluid or heating medium. 
     The boiler  10  comprises a housing  14  enclosing a lower drum  16 , an upper drum  18  and a plurality of tubes  20  fluidly connecting the lower drum  16  and the upper drum  18 . The boiler inlet is connected to the lower drum  16  and/or to the economizer inlet  62  for receiving the fluid coming from the network which is called the cold fluid. A burner  22  produces a hot fluid  24 , usually hot gases from combustion, which circulate among the tubes  20  for heating the cold fluid. The cold fluid being heated in the tubes  20  naturally migrates from the lower drum  16  to the upper drum  18 . The lower drum  16  and the upper drum  18  are fluidly connected by a front down corner  26  and a rear down corner  28  for creating a high rate cold fluid internal flow downwardly from the upper drum  18  to the lower drum  16 . 
     At the rear, the boiler  10  comprises an economizer  30 , also referred to as an additional exchanger receiving from the top or the bottom hot fluid  32  usually hot gases, previously cooled by the tubes  20 . The economizer  30  heats the cold fluid which, due to a difference in temperature between a lower cold fluid inlet and an upper cold fluid outlet, naturally flows from the lower drum  16  and flowing up to the upper drum  18 . 
     Referring to  FIG. 3 , there is shown a tube arrangement  34  of the boiler  10  according to an embodiment. The tube arrangement  34  comprises a plurality of left tubes  36  for conveying the cold fluid. Each of the left tubes  36  fluidly connects the lower drum  16  and the upper drum  18 . The tubes may be connected to the drums by welding directly or by means of ferrules. The left tubes  36  form a left wall  38 . According to an embodiment, each of the left tubes  36  comprises two right inwardly extending portions  40 ,  42  each extending toward a right wall  44 . The tube arrangement  34  further comprises a plurality of right tubes  46  for conveying the cold fluid. Each of the right tubes  46  fluidly connects the lower drum  16  and the upper drum  18 . The right tubes  46  form the right wall  44  facing the left wall  38 . According to an embodiment, each of the right tubes  46  comprises two left inwardly extending portions  48 ,  50 , each extending toward the left wall  38 . 
     The right inwardly extending portion  40  is contiguous to and staggered with the left inwardly extending portion  48  and the left inwardly extending portion  50 , forming three passages  52 ,  54 ,  56  between the left wall  38  and the right wall  44 . Of course all references to the left and the right are for convenience of description only. They can be reversed depending of the observer&#39;s point of view. This description is therefore meant to cover any mirror image of the device shown in the Figures. 
     Each one of the three passages  52 ,  54 ,  56  has first end  58  and second end  60  and are substantially isolated from each other between each of its respective first and second ends  58 ,  60 . In use, the hot fluid circulates in the three passages  52 ,  54 ,  56  and heats the left tubes  36  and the right tubes  46 , thereby heating the cold fluid. According to another embodiment, there are only one left inwardly extending portion and one right inwardly extending portion which are contiguous and staggered and which would create at least two passages. 
     The passages  52 ,  54 ,  56  are substantially isolated from each other. The left tubes  36  are substantially contiguous between themselves along their length. The right tubes  46  are similarly disposed. Moreover, the right inwardly extending portion  40  is proximate to or in contact with the left inwardly extending portion  48  and the left inwardly extending portion  50 . In another embodiment (not shown), insulation is disposed between the tubes. 
     Turning now to  FIG. 4 , there is shown the tube arrangement  34  including the piping of the economizer  30 . The economizer  30  is located between the lower drum  16  and the upper drum  18  and comprises a cold inlet  62 , a cold outlet  64 , a hot inlet  66  and a hot outlet  68 . The cold inlet  62  is fluidly connected to the lower drum  16  by a lower piping  70 . The cold outlet  64  is fluidly connected to the upper drum  18  by an upper piping  72 . The hot inlet  66  is fluidly connected to second end  60  of upper passages  74  for receiving the previously cooled hot fluid  32 . The hot inlet  66  is above the hot outlet  68 , so that the previously cooled hot fluid  32  has a downward movement while the cold fluid has an upward movement. According to another embodiment, the hot inlet  66 , the hot outlet  68 , the cold inlet  62  and the cold outlet  64  can be reversed. 
     In use, the previously cooled hot fluid  32  circulates through the economizer  30  and exhausts by the hot outlet  68 . The cold fluid, due to a difference in temperature between a cold inlet  62  and a cold fluid outlet  64 , naturally flows upward from the lower drum  16  to the upper drum  18  crossing the economizer/additional exchanger  30  thereby heating the cold fluid. Such a disposition does not need any external assistance like a pump to be operative. An additional inlet  76  is fluidly connected to the cold inlet  62  for receiving additional cold fluid in the boiler  10  and inserting the additional cold fluid directly in the economizer  30  for pre-heating it before circulating in the tube arrangement  34 . The additional inlet  76 , can also receive the cold fluid flowing back from the network instead of the boiler inlet  13 . 
     Referring now to  FIG. 5 , there is shown the rear of the boiler  10 . A duct  78  is disposed for receiving the previously cooled hot fluid  32 , for conveying it to the hot inlet, not shown, for receiving the previously cooled hot fluid  32  from the hot outlet, not shown, and for exhausting it by a hot fluid output  80 . A receptacle  82  is disposed at the bottom for receiving condensates  84 . 
     Referring now to  FIG. 6 , there shown a pattern  86  of one of the left tubes  36  and one of the right tubes  46  fluidly connecting the lower drum  16  and the upper drum  18 . The right inwardly extending portion  40  is contiguous to the left inwardly extending portion  48  and to the left inwardly extending portion  50 , such that three passages  52 ,  54 ,  56  are formed between the left wall  38  and the right wall  44 . The left inwardly extending portion  50  is contiguous to the right inwardly extending portion  40  and to the right inwardly extending portion  42 , such that three passages  54 ,  56 ,  88  are formed between the left wall  38  and the right wall  44 . The right inwardly extending portion  42  is contiguous to the upper drum  18 , such that two passages  88 ,  90  are formed between the left wall  38  and the right wall  44 . 
     Side plates  92  are disposed outside and against the left wall  38  and the right wall  44  forming four additional passages  94  with the right inwardly extending portions  40 ,  42  and the left inwardly extending portions  48 ,  50 . Such a pattern results in nine passages  52 ,  54 ,  56 ,  88 ,  90 ,  94  with two right inwardly extending portions  40 ,  42  and two left inwardly extending portions  48 ,  50 . 
     Referring now to  FIG. 7 , there is shown a pattern  96  of a right tube  98  and a left tube  100  according to another embodiment. A right inwardly extending portion  102  is contiguous to a left inwardly extending portion  104  and to another left inwardly extending portion  106 , so that three passages  108  are formed. The right inwardly extending portion  102  is longer than the left inwardly extending portions  104 ,  106 . Sections of the passages  108  depend on a length  110  of each inwardly extending portion. 
     Referring now to  FIG. 8 , there is shown a pattern  112  of a right tube  114  and a left tube  116  according to another embodiment. A base portion  118  of the right tube  114 , comprised between two left inwardly extending portions  120 , is distant to a virtual base plan  122  comprising other base portions  124  of the right tube  114 . 
     Referring now to  FIG. 9 , there is shown a pattern  126  of a right tube  128  and a left tube  130  according to another embodiment. A right inwardly extending portion  132  comprises a flat portion  134  which is contiguous to two left inwardly extending portions  136 . 
     Referring now to  FIG. 10 , there is shown a pattern  138  of a right tube  140  and a left tube  142  according to another embodiment. The right tube  140  and the left tube  142  fluidly connect a lower drum  144  and an upper drum  146 . The lower drum  144  comprises two lower manifolds  148  fluidly connected between themselves. Similarly, the upper drum  146  comprises two upper manifolds  150  fluidly connected between themselves. The right tube  140  fluidly connects one of the lower manifolds  148  to one of the upper manifold  150  and the left tube  142  fluidly connects the other lower manifold  148  to the other upper manifold  150 . 
     Returning now to  FIG. 3 , the tube arrangement  34  further comprises a dividing plate  152  disposed along the passage  94  for dividing a circulation of the hot fluid in a portion of the at least one passage in two separate fluxes. The tube arrangement  34  further comprises a limiting plate  154  disposed across the passage  94 , limiting a section of a portion of passage  94 . 
     Returning now to  FIG. 1 , the boiler  10  further comprises an end wall  156  disposed at one end  60  of the passages  52 ,  94 ,  54 , fluidly connecting the passages  52 ,  94 ,  54 . The end wall  156  comprises a cavity  158  allowing the hot fluid  24  to pass from the passage  52  to passages  94 ,  54  by the cavity  158 . Other arrangements for cavity  158  are possible where the hot fluid  24  passes from passage  52  to passage  94 , but not to passage  54 . Cavity  158  can also be arranged to provide an end passage between two single longitudinal passages or any other combination (e.g., two passages to one, two passages to two, etc.). According to dispositions of cavities in the end walls, several circulations of hot fluid are envisioned as un-exclusively depicted on  FIG. 11 ,  FIG. 12  and  FIG. 13 , concurrently referred to. 
       FIG. 11  shows a circulation  160  according to another embodiment. A hot fluid  161  is generated in a passage  162  and divided into two passages  164  in the back. In the front, the hot fluid  161  is transferred from the two passages  164  into two passages  166 . In the back, the hot fluid  161  is transferred from the two passages  166  into two passages  168 . In the front, the hot fluid  161  is transferred from the two passages  168  into two passages  170 . Each portion of the hot fluid crosses through five passages in the boiler. 
       FIG. 12  shows a circulation  172  according to another embodiment. A hot fluid  175  is generated in a passage  174  and divided into two passages  176  in the back. In the front, the hot fluid  175  is transferred from the two passages  176  into two passages  178 . In the back, the hot fluid  175  is transferred from the two passages  178  into a passage  180 . In the front, the hot fluid  175  is transferred from the passage  180  into a passage  184 . In the back, the hot fluid  175  is transferred from the passage  184  into a passage  182 . In the front, the hot fluid  175  is transferred from the passage  182  into a passage  186 . Each portion of the hot fluid crosses through seven passages in the boiler. 
       FIG. 13  shows a circulation  188  according to another embodiment. A hot fluid  191  is generated in a passage  190  and transferred into a passage  192  in the back. In the front, the hot fluid  191  is transferred from the passage  192  into a passage  194 . In the back, the hot fluid  191  is transferred from the passage  194  into a passage  196 . In the front, the hot fluid  191  is transferred from the passage  196  into a passage  198 . In the back, the hot fluid  191  is transferred from the passage  198  into a passage  200 . In the front, the hot fluid  191  is transferred from the passage  200  into a passage  204 . In the back, the hot fluid  191  is transferred from the passage  204  into a passage  202 . In the front, the hot fluid  191  is transferred from the passage  202  into a passage  206 . Each portion of the hot fluid  191  travels through nine passages in the boiler. 
     While embodiments have been described above and illustrated in the accompanying drawings, it will be evident to those skilled in the art that modifications may be made therein without departing from the essence of this description. Such modifications are considered as possible variants comprised in the scope of the description.