Abstract:
A tuyere cooling system which includes a coolant circuit for a body section and nose section. A valve is operable to connect the coolant circuits in series or to disconnect flows to the nose section of the tuyere so that if the nose of the tuyere tears during operation, the flow of coolant to the nose section of the tuyere may be cut off without affecting the overall operation of the blast furnace.

Description:
This application is a continuation of PCT application No. PCT/CA03/00766 filed on May 29, 2003, which claims priority from U.S. provisional application No. 60/383,777 filed on May 30, 2002 the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates in general to tuyeres, and, more specifically, to a tuyere cooling system. 
     DESCRIPTION OF THE PRIOR ART 
     The use of blast furnaces in the manufacture of metals has been well known for many years. Blast furnaces generally include a blowpipe which connects a hot-blast system with a tuyere which blows hot air into the hearth of the blast furnace. However, due to the high temperature (around 1100° C.) of the hot-blast system, the tuyere is required to be cooled during use in order to protect it from being overheated. 
     In prior art tuyere cooling systems which only require one water circuit, if the nose section tears or breaks, the entire water circuit must be shut down to avoid letting any water enter the hearth of the furnace and subsequently the entire furnace is shut down since there is no cooling for the tuyere. This causes a delay in the manufacturing process while the tuyere is replaced. 
     Alternatively, the tuyere is cooled using two separate water circuits. One water circuit is used to cool the nose section of the tuyere while a second water circuit is used to cool the remaining tuyere body. In this manner, if the nose of the tuyere tears off during operation, the high pressure water circuit may be immediately turned off to prevent water from entering the hearth while operation of the blast furnace continues. While the air continues to be blasted into the hearth, the body of the tuyere is cooled by the lower pressure water circuit. However, by requiring two separate water circuits, the cost for operating a blast furnace is increased since each water circuit requires a separate set of pumps, heat exchangers, piping and controls for 
     Therefore, it is an object of the present invention to obviate or mitigate some of the above-described disadvantages. 
     SUMMARY OF THE INVENTION 
     A tuyere comprises a body section, a nose section and a cooling system. The cooling system includes a first coolant passageway extending through said body section and having an inlet and an outlet A second coolant passageway extending through the nose section and has an inlet and an outlet, and a valve assembly operable in a first condition to connect the coolant passageways in series so that coolant flows sequentially through the sections and operable in a second condition to inhibit flow through one of the passageways whilst maintaining flow in another. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the invention will now be described by way of example only with reference to the appended drawings wherein: 
         FIG. 1  is a sectional view of a tuyere and blowpipe assembly; 
         FIG. 2  is a section view taken along the line II—II of  FIG. 1 ; 
         FIG. 3  is a schematic diagram of a tuyere cooling system with the valves in a first position; 
         FIG. 4  is an enlarged view of a portion of the cooling system shown in  FIG. 3  with valves in the first position; and 
         FIG. 5  is a view similar to  FIG. 4  with valves in the second position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning to  FIG. 1 , a tuyere and blowpipe assembly  10 , located within a wall  11  of a blast furnace, includes a blowpipe  12  with a ceramic lining  14  to introduce air into the furnace. The blowpipe  12  is connected to a tuyere  16  which is mounted in the wall  11 . The tuyere  16  generally comprises a body section  16   a  and a nose section  16   b . Passageway  18  within the tuyere  16  allows a fluid coolant, such as water, to pass through and cool the tuyere  16  during operation of the blast furnace. As shown in  FIGS. 2 and 3 , the passageway  18  is subdivided into two sets, a body passageway  18   a  for cooling the body section  16   a  and a nose passageway  18   b  for cooling the nose section  16   b.    
     As may be more clearly seen in  FIG. 3 , body passageway  18   a  has an inlet  19   a  and an outlet  21   a  and forms a separate path through the body  16   a  of the tuyere while nose passageway  18   b  suitably has an inlet  19   b  and an outlet  21   b  and is located as an annular passage at the nose  16   b  of the tuyere  16 . The passageway  18   a  is formed between inner and outer shells  50 ,  52  of the body section  16   a  by radial partitions  54 . The partitions  54  terminate alternately adjacent the outer shells  52  and an internal wall  56  concentric to the inner shell  50  to define a serpentine flow path circumferentially around the body section  16   a . The internal wall  56  and inner shell  50  define an annular return path for contra flow within the nose section  16   b.    
     The inlet  19   a  of the body passageway  18   a  is connected, by a supply conduit  24 , to a coolant source  22  which provides a fluid coolant via pump  23  for cooling the tuyere  16 . The outlet  21   a  of the body passageway  18   a  is connected by a pipe  23  to a valve assembly  25  comprising a three-way valve  28  and a two-way valve  38 , both controlled by an operating mechanism  41 . The coolant flows from the outlet  21   a  to an input  26  of the three-way valve  28  which has two outputs  30  and  32 . One of the outputs  30  of the three-way valve  28  is connected by pipe  31  with the inlet  19   b  of the nose passageway  18   b  while the other output  32  is connected to a coolant discharge  34  which leads to a reservoir  35 . The direction of the fluid coolant flow is controlled by a rotatable valve member  33 . 
     The outlet  21   b  of the nose passageway  18   b  is connected by a pipe  37  to input  36  of a two-way valve  38  while the output  40  of the two-way valve  38  is connected to the coolant discharge  34  leading to the reservoir  35  The flow of the fluid coolant within the two-way valve  38  is controlled by a rotatable valve member  39 . 
     A pressure relief valve  43  may also be installed at the input  36  of the two-way valve  38 . The pressure relief valve  43  is used to monitor the pressure within the cooling system and if the pressure reaches a predetermined maximum limit, the pressure relief valve  43  provides an outlet for the excess pressure to be released. Furthermore, the relief valve  43  may be used for testing purposes. Air pressure may be introduced to the system using the relief valve as an input so that leaks within the system may be identified. 
     The alternate positions of the rotational valve member  33  and  39  in the first and second positions are respectively shown in  FIGS. 4 and 5 . In the first position ( FIG. 4 ), rotational valve member  33  is placed so that it may receive the fluid coolant from the input  26  and direct the fluid coolant back through output  30  to the inlet  19   b  of nose passageway  18   b  of the tuyere  16 . Likewise, the rotational valve member  39  is located such that the fluid coolant from the outlet of the nose passageway  18   b  flows from the input  36  to the coolant discharge  34  via the output  40 . 
     In the second position ( FIG. 5 ), the rotational valve member  33  is positioned so that the fluid coolant from the outlet  21   a  of the body passageway  18   a  is directed from the input  26  to the coolant discharge  34 , via the output  32 . Meanwhile, rotational valve member  39  is positioned so that no fluid coolant flows from the outlet  21   b  to the coolant discharge  34 . 
     Conjoint Movement of the valve members  33 ,  39  between the first and second positions is provided by the operating mechanism  41  that includes levers  60 ,  62  connected to valve members  33 ,  39 . The levers  60 ,  62  are connected by a link  64  and a handle  66  is connected to one of the levers  60 . 
     In operation, the fluid coolant is pumped from the coolant source  22  to the inlet  19   a  of the body passageway  18   a . The coolant flows through the body of the tuyere  16  to cool the body section  16   a . After the fluid coolant has passed through the body section  16   a , the fluid coolant exits the body section  16   a  via the outlet  21   a  and flows to the input  26  of the three-way valve  28 . Since the valves are in the first position, the fluid coolant is then directed by the rotatable valve member  33  back to the inlet  19   b  of the nose passageway  18   b  via output  30 . The fluid coolant then flows around the nose section  16   b  and exits via the outlet  21   b  and flows to the input  36  of the two-way valve  38 . The fluid coolant is then directed by the rotational valve member  39  to the coolant discharge  34 . The fluid coolant then flows within the coolant discharge  34  to the reservoir  35  whereby the coolant is preferably cooled and returned to the coolant source  22 . Reverse flow past the valve  28  to the outlet  30  is prevented. 
     If the nose section  16   b  of the tuyere  16  tears off or leaks during operation, the handle  60  is rotated so that the rotational valve members  33  and  39  cause the valves  28  and  38  to be placed in the second position shown in  FIG. 5  so that fluid coolant flow to the nose section  16   b  is cut off. However, the body section  16   a  of the tuyere  16   b  will still be cooled by the fluid coolant. 
     In the second position (as shown in  FIG. 5 ), the fluid coolant is pumped into the inlet  19   a  of the body passageway  18   a  from the source  22  and flows around the body section  16   a  as shown by arrows  42 . After exiting the outlet  21   a  of the body passageway  18   a , the fluid coolant flows to the input  26  of the three-way valve  28 . In this second position, the rotational valve member  33  directs the fluid coolant to the coolant discharge  34  via the output  32 . The fluid coolant then flows to the coolant discharge  34  and subsequently to the reservoir  35  where the fluid coolant may be cooled before being sent back to the source  22 . Since the nose section has been torn, no fluid coolant flows from the outlet  21   b  of the nose passageway  18   b  to the input  36  of the two-way valve  38 . Reverse flow from the discharge is prevented by the valve  38 . By placing the valves in the second position, the flow rate of the fluid coolant flowing in the body section  16   a  is increased because of the coolant path. When the valves are rotated from the first position to the second position, the flow of fluid coolant through the body passageway  18   a  is uninterrupted, so as to maintain cooling of the body. 
     It will be appreciated that the valve member  39  essentially operates as a check valve to inhibit flow from the discharge  34  to the nose section cooling passage  34   b . Accordingly, a check valve may be used in place of the rotary valve  38  where conditions permit. Alternatively, the discharge from the valves  28 ,  38  may be separated to remove the possibility of a reverse flow and obviate the need for the valve  38 . Conjoint operation of the valve members  33 ,  39  may be achieved automatically by electrical or hydraulic operators if required although the simplicity of a manual valve is preferable in most installations. 
     By using a single water circuit to cool the tuyere, the cost of the tuyere cooling system may be reduced. Furthermore, if the nose section of the tuyere tears or leaks during operation, the entire furnace does not have to be shut down to repair the tuyere, instead, the tuyere may be replaced at a more convenient time such as a scheduled furnace shutdown for maintenance. 
     Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the present application.