Abstract:
A kiln fuel system and method for producing cement. The system includes a tank for storing a fuel and a suction heater for drawing and preheating the fuel from the tank. A pressure station pressurizes the preheated fuel and a heater heats the preheated and pressurized fuel. A burner receives the fuel from the heater and ignites the fuel to form a flame and heat the concrete. The fuel is preferably a bitumen/water fuel mixture. A burner valve train is provided for regulating an amount and mixture of fuel and air supplied to the burner, preventing the flow of fuel to the burner upon detection of a predetermined condition, regulating an amount of heated and pressurized fuel supplied to the burner and providing a source of pressurized air for controlling a size of the flame produced by the burner. A slop tank is connected to the tank for receiving the fuel upon detecting a temperature of the fuel is above a predetermined value in the suction heater or above a predetermined pressure in the pressurizing station. A thermal heating device is connected to both the suction heater and heater for aiding in heating the fuel to a desired temperature, the thermal heating device includes a thermal oil supply and a thermal oil pump for providing the heated thermal oil supply to both the suction heater and heater. A filter is provided for screening the fuel prior to being pressurized.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to kiln fuel systems and, more specifically, to a method and apparatus for storing, conveying and igniting a fuel consisting substantially of bitumen and water within a kiln. 
     2. Description of the Prior Art 
     Numerous types of fuel delivery systems designed for kilns have been provided in the prior art. For example, U.S. Pat. Nos. 3,595,544; 4,234,106; 5,339,75 1; 5,806,442 and 5,837,052 all are illustrative of such prior art. While these units may be suitable for the particular purpose to which they address, they would not be as suitable for the purposes of the present invention as heretofore described. 
     U.S. Pat. No. 3,595,544 
     Inventor: George T. Curtis 
     Issued: Jul. 27, 1971 
     This invention relates to the combination of a rotary kiln for sintering raw material into sinter having drive means connected to the rotary kiln for rotating the rotary kiln, heating means disposed adjacent one end of the rotary kiln for directing a heated fluid through the rotary kiln to sinter the raw material as the new raw material passes through the rotary kiln from the other end of the rotary kiln to the one end of the rotary kiln, and control means associated with the rotary kiln for controlling the operation of one of the drive means and the heating means. 
     U.S. Pat. No. 4,234,106 
     Inventor: Donald E. Rywak et al. 
     Issued: Nov. 18, 1980 
     A series of operatively interconnected fuel flow regulators are adapted to meter and direct the flow of particulate fuel from a fuel conveying system into the burners of a furnace or kiln. Each regulator is fed by a conveying system and includes a feeder housing having a flow metering impeller and feed rotor arrangement. Each housing includes an adjustable fuel orifice communicating with a respective burner. 
     U.S. Pat. No. 5,339,751 
     Inventor: James R. Tutt 
     Issued: Aug. 23, 1994 
     A firing system is provided for charging a plurality of incoming combustible fuel modules containing a known amount of a parameter of interest into a heated zone of a rotating kiln. The firing system separates incoming fuel modules into a plurality of stages based on the parameter amount in each fuel module. The system then removes fuel modules from the plurality of stages in a selected order to maintain an average parameter amount for fuel modules charged into the kiln at substantially a preselected level. The system charges fuel modules into the kiln in the selected order. The system determines an optimum time to charge each fuel module into the rotating kiln to maintain an average amount of the parameter of interest supplied to the kiln substantially at the preselected level. 
     U.S. Pat. No. 5,806,442 
     Inventor: Ernie Aldred et al. 
     Issued: Sep. 15, 1998 
     A feeding apparatus for feeding whole tires into a cement kiln comprising a feed opening in the shell of the kiln, a passageway including a sleeve extending within and outside the kiln, an arcuate sector valve device for closing the passageway and timed to open so as to allow the tires to fall into the kiln through the passageway. The sector valve having an outer perforated wall and an inner wall, the perforated wall allowing ambient air to circulate between the outer and inner wall to keep the outer wall cool for contact with the tires. A transfer device is provided for transferring the tires onto the feeding apparatus wherein the transfer device includes fingers while the feeding apparatus includes a fork receiving tray interdigitated with the fingers to pick up the tires as the kiln rotates. 
     U.S. Pat. No. 5.837,052 
     Inventor: David Bridson Oates 
     Issued: Nov. 17, 1998 
     Contaminated coal ash, for example flyash contaminated with carbon is introduced to hot clinker in a cooler downstream of a cement kiln; the carbon is combusted in the cooler to provide a cement clinker having an effective content of flyash free of carbon; this permits use of flyash contaminated with carbon without the need for separate special steps for carbon removal; volatile contaminants of contaminants having a volatile component, for example absorbed ammonia are similarly removed in the cooler by volatilization. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention relates generally to kiln fuel systems and, more specifically, to a method and apparatus for storing, conveying and igniting a fuel consisting substantially of bitumen and water within a kiln. 
     A primary object of the present invention is to provide a kiln fuel system that will overcome the shortcomings of prior art devices. 
     A further object of the present invention is to provide a kiln fuel system which is able to use a mixture consisting substantially of bitumen and water as a kiln fuel as an economically viable substitute for conventionally used fuel oil. 
     Another object of the present invention is to provide a kiln fuel system having a bottom fill storage tank or tanks to eliminate foaming of the bitumen/water fuel mixture. 
     A yet further object of the present invention is to provide a kiln fuel system able to preheat the fuel to a desired selectable temperature. 
     A still further object of the present invention is to provide a kiln fuel system able to pressurize the fuel to a desired pressure for delivery. 
     An even further object of present invention is to provide a kiln fuel system able to heat the pressurized fuel to as desired selectable temperature. 
     Yet another object of the invention is to provide a kiln fuel system able to vary the length and shape of the flame produced within the kiln. 
     Yet another object of the present invention is to provide a kiln fuel system using a bitumen and water fuel having physical, chemical and combustion characteristics which have little impact on the final quality of the cement produced by a dry process. 
     Still yet another object of the present invention is to provide a kiln fuel system having emission characteristics below those required by International Environmental and Safety Regulations. 
     Another object of the present invention is to provide a kiln fuel system that is simple and easy to use. 
     A still further object of the present invention is to provide a kiln fuel system that is economical in cost to manufacture. 
     Additional objects of the present invention will appear as the description proceeds. 
     The bitumen/water fuel mixture of the present invention is stored at ambient temperature in bottom filled fuel tank. Alternatively, a plurality of bottom filled fuel tanks may be used. The fuel is extracted from the tank by a suction heater, the suction heater preheating the fuel using an indirect heat exchanger with thermal oil as the heat medium. The pre heating selectively raises the temperature of the fuel to substantially 40° C. before carrying the fuel to a high pressure pump station. The high pressure pump station increases the fuel pressure to be atomized by the burner. After pressurizing, the fuel is fed via a conduit to a high pressure heater station. The temperature of the fuel is increased in the high pressure heater station to substantially 70° C. by one or more indirect heat exchangers using thermal oil as the heat medium. The pressurized and heated fuel is fed through another conduit to the burner valve train in which it is filtered. The burner valve train is comprised of a plurality of pressure gauges, regulating valves, check valves, a quick shut off switch and mass flow meter for monitoring and adjusting the flame within the kiln. 
     The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying drawing, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying drawing, like reference characters designate the same or similar parts throughout the several views. 
     The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims. 
     To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific construction illustrated and described within the scope of the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     Various other objects, features and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views. 
     FIG. 1 is a block diagram of the kiln fuel system of the present invention; 
     FIG. 2 is a block diagram of the kiln fuel system of the present invention illustrating a device for controlling the fuel temperature through conduction using thermal oil as the heat medium; 
     FIG. 3 is a block diagram of the thermal oil pumping station used in the kiln fuel system of the present invention; 
     FIG. 4 is a block diagram of the high pressure pump station having a three spindle pump used in the kiln fuel system of the present invention for reducing shear on the fuel; 
     FIG. 5 is a block diagram of the high pressure pump station having additional elements used in the kiln fuel system of the present invention; 
     FIG. 6 is a block diagram of the high pressure heater station used in the kiln fuel system of the present invention for providing control of the pressurized fuel temperature through conduction using thermal oil as the heat medium; 
     FIG. 7 is a block diagram of the high pressure heater station used in the kiln fuel system of the present invention having additional elements; and 
     FIG. 8 is a block diagram of the burner valve train used in the kiln fuel system of the present invention. 
    
    
     DESCRIPTION OF THE REFERENCED NUMERALS 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, the Figures illustrate the kiln fuel system of the present invention. With regard to the reference numerals used, the following numbering is used throughout the various drawing figures. 
       10  kiln fuel system of the present invention 
       12  bottom filled fuel tank 
       14  bitumen/water fuel mixture 
       16  suction heater 
       18  conduit between tank and high pressure pump station 
       20  high pressure pump station 
       22  burner 
       24  kiln 
       26  filters of high-pressure pump station 
       28  pump of high-pressure pump station 
       30  safety valves of high-pressure pump station 
       32  slop tank 
       34  conduit between high pressure pump station and high pressure heater station 
       36  high pressure heater station 
       38  safety valves in high pressure heater station 
       40  high pressure heater in high pressure heater station 
       42  temperature controlled flow valve in high pressure heater station 
       44  fuel line thermostat in high pressure heater station 
       46  burner train valve 
       48  indirect heat exchanger 
       50  thermal oil supply 
       52  thermal oil pump 
       54  thermostat 
       56  second  3 -way temperature control valve 
       58  temperature control valve 
       60  pumps 
       62  valve shut-off switches 
       64  return line 
       66  conduit from temperature control valve to high pressure heater station 
       68  quick shut off switch 
       70  mass flow meter 
       72  regulating and check valves 
       74  pressurized air intake 
       76  conduit between burner valve train and burner 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, FIGS. 1 through 8 illustrate the kiln fuel system of the present invention indicated generally by the numeral  10 . 
     A block diagram of the kiln fuel system  10  is shown in FIG.  1 . The kiln fuel system  10  includes a bottom filled fuel tank  12  for storing a bitumen/water fuel mixture. Alternatively, any number of bottom filled fuel tanks  12  may be connected to the system  10  for supplying the bitumen/water fuel mixture. The bitumen/water fuel mixture is indicated by the arrows labeled with the numeral  14  which show the path followed by the bitumen/water fuel mixture  14  through the kiln fuel system  10 . The bitumen/water fuel mixture  14  is stored at ambient temperature in the bottom filled fuel tank  12 . The tank  12  is designed to prevent foaming of the bitumen/water fuel mixture  14 . The bitumen/water fuel mixture  14  is extracted from the tank  12  by a suction heater  16 . The bitumen/water fuel mixture  14  passes from the tank  12  to the suction heater  16  through a conduit  18 . The suction heater  16  preheats the bitumen/water fuel mixture  14  to a temperature of substantially 40° C. The heating of the bitumen/water fuel mixture  14  is performed by an indirect heat exchanger  48  using thermal oil as a heat medium. The indirect heat exchanger  48  includes a thermal oil supply  50  and a thermal oil pump  52 . The pre heating of the bitumen/water fuel mixture  14  accelerates the flow rate from the storage tank  12  to a high pressure pump station  20 . 
     The preheated bitumen/water fuel mixture  14  is carried through the conduit  18  to the high pressure pump station  20 . The temperature of the bitumen/water fuel mixture  14  within the conduit  18  is able to be selectively controlled and regulated with a temperature control valve  22  and a thermostat  24  as shown in FIG.  2 . The temperature control valve  22  forms a portion of a thermal oil valve station. The thermostat  24  and temperature control valve  22  automatically control the temperature of the bitumen/water fuel mixture  14  being delivered to the high pressure pump station  20 . 
     As can be seen in FIG. 2 the supply of thermal oil  50  is conducted to the suction heater  16  through a closed loop system by the thermal oil pump  52 . The temperature of the oil is continuously regulated by a thermostat  54  communicating with the first  3 -way temperature control valve  22  and a second  3 -way temperature control valve  56  able to mix or divert the thermal oil from and to the conduit  18 . The thermal oil of a selected temperature is divergently conducted to the suction heater  16  and to a high pressure heater  36  having a respective return conduit. The bitumen/water fuel mixture  14  is also conducted through the suction heater  16  where, by conduction through the thermal oil conduit, the temperature is selectively raised. The selective temperature is controlled by the thermostat  54  communicating with the first 3-way temperature control valve  22 . The first 3-way temperature control valve  22  mixes or diverts the thermal oil through the suction heater  16 . 
     FIG. 3 shows the conduction of thermal oil from the thermal oil supply  50  to the oil line thermostat  54  back to both the suction heater  16  and high pressure heater station  36 . The thermal oil is conducted from the thermal oil supply  50  through a temperature control valve  58  by one or more pumps  60 . The temperature of the thermal oil is selectively controlled through the thermostat  54  communicating with the temperature control valve  58 . The temperature control valve  58  is able to mix or divert the thermal oil from or to the return line  64 . The return line  64  provides the thermal oil from the thermostat  54  to either the suction heater  16  or the high pressure heater station  36 . The thermal oil pumping station  48  can have a redundant pumping device including valve shutoff switches  62  whereby a pump  60  can be removed from service without shutting down the system. 
     The bitumen/water fuel mixture  14  which is preheated in the suction heater  16  is fed through the conduit  18  and into the high pressure pump station  20  which sufficiently increases the pressure of the bitumen/water fuel mixture  14  which is to be atomized by a burner  22  within the kiln  24 . The high pressure pump station  20  is comprised of one or more systems having filters  26  for screening unwanted particle matter suspended in the fuel  14  and a pump  28  for increasing the pressure to a predetermined amount as is shown in FIG. 4. A three spindle pump is preferably used to reduce shear on the fuel. The high-pressure pump station  20  is also equipped with safety valves  30 . If it is determined that the pressure of the bitumen/water fuel mixture  14  within the high pressure pump station  20  exceeds the predetermined amount, the bitumen/water fuel mixture  14  within the tank  12  is directed to a slop tank  32 . In addition, a plurality of valves providing easy access to components of the system for servicing and, with regards to the use of redundant systems, the valves provide access for servicing system components without shutting down the entire system  10 . A redundant system is illustrated in FIG. 5 wherein a desired pump  60  can be removed from service without shutting down the system by shutting a particular combination of switches  30 . 
     After being pressurized in the high pressure pump station  20 , the bitumen/water fuel mixture  14  is fed via a conduit  34  to the high pressure heater station  36 . The high pressure heater station  36  includes a high pressure heater  40  for increasing the temperature of the bitumen/water fuel mixture  14  to approximately 70° C. using one or more indirect heat exchangers and thermal oil as a heat medium as is shown in FIGS. 2,  6  and  7 . The high pressure heater station  36  is equipped with either a high pressure heater  40  and a fuel line thermostat  42  as shown in FIG. 6 or a plurality of high pressure heaters  40  and a plurality of safety valves  38  connected to the fuel line thermostat  42  as shown in FIG.  7 . The redundant system illustrated in FIG. 7 allows a desired pump  40  to be removed from service without shutting down the system. This is performed by shutting a combination of the switches  38 . If it is determined that the pressure of the bitumen/water fuel mixture  14  within the high pressure heater section  36  exceeds a predetermined value the bitumen/water fuel mixture  14  within the tank  12  is directed to the slop tank  32 . In addition, a plurality of valves are provided for facilitating servicing of components of the system  10 . With regards to the use of multiple heat exchangers, the valves allow for servicing system components without shutting down the entire system. 
     The thermal oil of a selected temperature is divergently conducted to the high pressure heater  36  having a respective return conduit as is illustrated in FIG.  2 . As is shown in FIG. 6, the bitumen/water fuel mixture  14  is also further conducted through the high pressure heater station  36  where, by conduction through the thermal oil conduit, the temperature is selectively raised. The selective temperature is controlled by the thermostat  54  communicating with the second 3-way temperature control valve  56 . The second 3-way temperature control valve  56  is able to mix or divert the thermal oil through the high pressure heater  36 . 
     The use of redundant high pressure heaters  40  is shown in FIG.  7 . These redundant high pressure heaters  40  provide control of the pressurized fuel temperature through conduction using thermal oil as the heat medium. The supply of thermal oil is conducted through a temperature control valve  44  to the high pressure heaters  40 . The bitumen/water fuel mixture  14  is also conducted through the high pressure heaters  40  whereby, during conduction through the thermal oil conduit, the temperature is selectively raised. The selective temperature is controlled by the thermostat  42  communicating with the 3-way temperature control valve  44  which is able to mix or divert thermal oil through the high pressure heaters  40 . The use of the redundant high pressure heaters  40  allows for servicing components of the system  10  without shutting down the entire system. Furthermore, the high-pressure heaters  40  are equipped with pressure safety valves  38  where if the pressure exceeds a predetermined amount the fuel is directed from the tank  12  to the slop tank  32 . 
     A conduit  66  including a temperature control valve  44  connects the thermal oil valve station for selectively controlling the temperature of the bitumen/water fuel mixture  14  and thereby regulating the heat medium through the high pressure heater station  36 . Thereby, the thermostat  42  and temperature control valve  44  automatically regulate the temperature of the bitumen/water fuel mixture  14  being delivered to a burner operating valve train  46  located downstream from the high pressure heater station  36 . 
     The pressurized heated fuel is fed via a conduit  76  into the burner valve train  46  where it is screened. The burner valve train  46  is comprised of a plurality of quick shut off switch  68 , a mass flow meter  70 , regulating and check valves  72  and a pressurized air intake  74  as shown in FIG.  8 . In addition the conduit  76  is equipped with an electrical trace heating cable and an electrical temperature controller to keep the temperature below 80° C. The quick shut-off valves  68  close the conduit  76  if a safety signal from the burner control  22  is missing and the regulating and check valves  72  control the flow in the axial and radial flow lines. The exact required fuel consumption and the flame shape can be set using these valves. The fuel is conducted through the burner valve train and the conduit  76  to the burner  22 . The burner valve train  46  serves as the control center for monitoring the performance of the fuel system, providing means for controlling such variables as the amount and mixture of fuel and air, and providing safety shut-off valves which close if any safety signal from the burner is missing. The mass flow meter indicates the flow of the bitumen/water mixture to the burner. The fine regulating valves  72  regulate the amount of heated and pressurized fuel supplied to the burner  22  and the air intake with pressure control switches  74  provide a source of pressurized air for controlling the flame size of the burner  22  within the kiln  24 . 
     The operation of the kiln fuel system  10  will now be described with reference to the figures. In operation, the kiln fuel system  10  is set up for producing cement using a dry process having a particular quality with a bitumen/water fuel mixture. The bitumen/water fuel mixture has physical, chemical and combustion characteristics which have little impact on the final quality of the cement produced. The system stores the bitumen/water fuel mixture in a fuel storage tank  20  until the fuel is needed. 
     Upon initiation of the process, the bitumen/water fuel mixture  14  is drawn from the tank  12  and through a conduit  18  by a suction heater  16 . The bitumen/water fuel mixture  14  is preheated to a temperature of preferably substantially 40° C. by an indirect heat exchanger  48  including a thermal oil supply  50  and a thermal oil pump  52 . The pre heating of the bitumen/water fuel mixture  14  accelerates the flow rate from the storage tank  12  to a high pressure pump station  20 . The thermal oil is conducted from the thermal oil supply  50  through a temperature control valve  58  by one or more pumps  60 . The temperature of the thermal oil is selectively controlled through the thermostat  54  communicating with the temperature control valve  58 . The temperature control valve  58  is able to mix or divert the thermal oil from or to the return line  64 . The return line  64  provides the thermal oil from the thermostat  54  to either the suction heater  16 . The thermal oil of a selected temperature is divergently conducted to the suction heater  16 . The bitumen/water fuel mixture  14  is also conducted through the suction heater  16  where, by conduction through the thermal oil conduit, the temperature of the bitumen/water fuel mixture  14  is selectively raised. The selective temperature is controlled by the thermostat  54  communicating with the first 3-way temperature control valve  22 . The first 3-way temperature control valve  22  mixes or diverts the thermal oil through the suction heater  16 . 
     The preheated bitumen/water fuel mixture  14  is then passed to the high pressure pump station  20  which pressurizes the bitumen/water fuel mixture  14 . The high pressure pump station  20  screening unwanted particle matter suspended in the bitumen/water fuel mixture  14  through filters  26  and increases the pressure to a predetermined amount using a pump  60 . A three spindle pump is preferably used to reduce shear on the bitumen/water fuel mixture  14 . Safety valves  30  within the high pressure pump station  20  allow a desired pump  60  can be removed from service without turning off the entire system. If it is determined that the pressure of the bitumen/water fuel mixture  14  within the high pressure pump station  20  exceeds the predetermined amount, the bitumen/water fuel mixture  14  within the tank  12  is directed to a slop tank  32 . 
     The preheated and pressurized bitumen/water fuel mixture  14  is then provided to the high pressure heater station to be further heated to preferably a temperature of substantially 70° C. The high pressure heater station  36  uses the indirect heat exchanger  48  used by the suction heater  16  to further heat the preheated and pressurized bitumen/water fuel mixture  14 . The bitumen/water fuel mixture  14  is then supplied to the burner valve train  46  and then to the burner  22 . The burner valve train  46  serves as the control center for monitoring the performance of the fuel system, controlling such variables as the amount and mixture of fuel and air, and providing safety shut-off valves  68  which close if any safety signal from the burner is missing. The mass flow meter  70  indicates the flow of the bitumen/water mixture to the burner  22 . The fine regulating valves  72  regulate the amount of heated and pressurized fuel supplied to the burner  22  and the air intake with pressure control switches  74  provide a source of pressurized air for controlling the flame size of the burner  22  within the kiln  24 . The burner valve train  46  is thus able to control the length and shape of the flame produced within the kiln  24 . The bitumen and water fuel also has physical, chemical and combustion characteristics which have little impact on the final quality of the cement produced by a dry process and has emission characteristics below those required by International Environmental and Safety Regulations. 
     From the above description it can be seen that the kiln fuel system of the present invention is able to overcome the shortcomings of prior art devices by providing a kiln fuel system which is able to use a mixture consisting substantially of bitumen and water as a kiln fuel as an economically viable substitute for conventionally used fuel oil. The kiln fuel system includes a bottom fill storage tank or tanks to eliminate foaming of the bitumen/water fuel mixture. The kiln fuel system able to preheat the fuel to a desired selectable temperature, pressurize the fuel to a desired pressure and further heat the pressurized fuel to as desired selectable temperature. The kiln fuel system is also able to vary the length and shape of the flame produced within the kiln. The kiln fuel system uses a bitumen and water fuel having physical, chemical and combustion characteristics which have little impact on the final quality of the cement produced by a dry process and has emission characteristics below those required by International Environmental and Safety Regulations. Furthermore, the kiln fuel system of the present invention is simple and easy to use and economical in cost to manufacture. 
     It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
     While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. 
     Without further analysis, foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.