Method and apparatus for dispensing a fluidizable solid from a pressure vessel

Abstract

An improvement in a process for dispensing a fluidizable solid from the lower portion of a pressure vessel equipped with a weighing device, a closable supply, a discharge, and a source of three gas flows, a first of which is applied within the vessel at a level above the solid to be fluidized, a second of which is applied within said vessel in a lower portion thereof, and a third of which is applied within the discharge orifice of the vessel, which discharge orifice terminates in a chamber, which improvement involves determining the amount of solid dispensed and determining the throughflow of gas in relationship to the amount of solid dispensed to maintain a constant gas/solid ratio while maintaining the pressures such that the pressure applied to the lower portion of the vessel is greater than the pressure applied at a level above of the solids which, in turn, is greater than the pressure applied to the discharge orifice, all of which are greater than the pressure maintained within the chamber, and an apparatus for carrying out the process embodying control devices to maintain the desired constant predetermined gas/solid ratio.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method of dispensing a fluidizable solid from a pressure vessel having a weighing device and closable supply and discharge, wherein of three gas flows which are supplied to the solid and are at various pressure values P₁, P₂, P₃, the gas flow at medium pressure P₂ is conducted into the vessel above the solid and the gas flow at relatively high pressure P₁ is conducted into the lower vessel region for fluidizing the solid, and the gas flow or relatively low pressure P₃ is conducted into the discharge connected thereto, the latter opening into a chamber at very low pressure P₄, and the quantity of solid taken from the vessel being weighed and also to an apparatus for carrying out the method.

2. Discussion of the Prior Art

Some method steps and the apparatus required for these in the method described hereinbefore are known from publications: German Auslegeschrift No. 1,140,863, German Pat. No. 1,147,756 and German Auslegeschrift No. 1,148,938.

Further developments on the basis of these have led to a known procedure and an apparatus such as is illustrated in FIG. 1 and FIG. 3 of the accompanying drawings and will be described in detail hereinafter.

In FIG. 1, the apparatus includes a pressure vessel 1 having a closable charging aperture 2 through which solid 3 is introduced and a closable discharge 4, 19. Conduits 5, 7 and 8 are connected to gas pressure sources and a pressure reducing valve 12 is provided. The gas pressure conduit 7 leads into a chamber 9 formed between the vessel bottom end 10 and a second bottom end 11 which is arranged above bottom 10 and which is gas-pervious. A weighing device 14 for the solid 3 is connected to the vessel 1. There is a dispensing or consumption chamber 17 in which a very low pressure P₄ prevails.

The known apparatus illustrated operates as follows:

With the discharge 4 closed, the pressure vessel 1 is filled with a solid 3 in powder form. The charging aperture 2 is closed and the gas pressure sources 5, 7, 8 are connected, the gas pressure source 5 being used for regulating the top pressure P₂ the gas pressure source 7 for fluidizing the solid at pressure P₁ and the gas pressure source 8 for supplying the "conveying gas" at pressure P₃. The gas supplied to the chamber 17 and providing pressure P₄ is the gas from the pressure source through 7 and the gas from the pressure source through 8. The prerequisite for conveying the fluidized solid is that the pressure relationship should be P₁ >P₂ >P₃ >P₄, P₁ being the pressure of the second gas pressure source through 7, P₂ the pressure of the first gas pressure source through 5, P₃ the pressure of the third gas pressure source through 8 and P₄ the pressure in the chamber 17. By means of the weighing apparatus 14 the quantity of solid to be dispensed from the vessel is determined. The known method is based on the relationship shown in FIG. 3, according to which the conveyed quantity of solid present preset desired value, the pressure P₂ is adjusted. Also the actual value of the quantity of solid dispensed is continuously monitored by means of the control device 13 and taking the predetermined gas/solid ratio into account is converted into the desired value for the regulation of the air quantity.

According to above-described method within the invention uniform delivery of solid is achieved since the control of the volumes of solid and gas, taking normal conditions into account for the gas, avoids the use and any disadvantageous operation of the pressure reducing valve 12 which was described initially. The known pressure reducing valve 12 operating as a proportional controller without servo force is not necessary in the apparatus within the invention. However, to maintain desired pressure conditions a manually adjustable pressure reducing valve can be arranged at the valve 18 (in desulphurisation, e.g., 11/2 to 2 atmospheres excess pressure) between the gas pressure source 7, 8 and the valve 18,18a.

A further advantage is that pressure fluctuations in the chamber 17 do not cause any sudden changes in the gas delivery quantity, whereby pulsating conveyance is obviated. Furthermore there are no longer the excessive gas quantities delivered when the immersion lance is put in and taken out, which led to the throwing-out of molten metal initially described. Blockages owing to inadequate fluidisation no longer occur. It is of particular practical importance that the gas-solid ratio remains constant, which is of significance more particularly when using the invention in the field of metallurgy. For example, it has been found possible by the above method to increase to 95 percent the capacity of torpedo ladles, which was limited to 80 percent with the previously described known methods.

It should be stressed that the use of the above methodwithin the invention has been found to be advantageous also for the introduction of other fine-grain or powder-form solids into molten metal baths, e.g., for the introduction of silicon or aluminium into iron melts.

It is to be understood that the apparatus of the present invention is characterized by a first source of gas flow disposed in an upper region of the pressure vessel, i.e., terminating in the upper region or portion of the pressure vessel. By the term "upper region or portion" is meant the upper half of the vessel, similarly with respect to the second source of gas located in the lower portion of the vessel, it should be understood that the term "lower portion" refers to the bottom half of the vessel. Preferably, this latter second source of gas is disposed in an inverted conically shaped at the bottom of the vessel and terminates in a confined region defined by an inside wall of the inverted conically shaped zone and a liner disposed thereover which is gas-pervious. Preferably, the first gas source is disposed at the top of the vessel, and in any event, above the means for supplying solid to the vessel.

Claims

1. In a process for dispensing fluidizable solid from the lower portion of a pressure vessel having a weighing device at which said solid is dispensed, a closable supply, a discharge, a source of three gas flows, one of which is applied within the vessel at a level above the solid to be fluidized at a pressure p₂, a second of which is applied within said vessel in the lower portion of said vessel at a pressure p₁, a third of which is applied within the discharge orifice at a pressure p₃, said discharge orifice terminating in a chamber maintained under a pressure p₄, the improvement which comprises determining the amount of solid dispensed at said weighing device, determining the throughflow quantity of gas flow, said throughflow quantity of gas flow being the sum of the amount of gas having a pressure p₁ and the amount of gas having a pressure p₃ and regulating the amount of gas and amount of solid to maintain a predetermined constant gas/solid dispensed ratio under conditions such that p₁ >p₂ >p₃ >p₄.

2. An improvement according to claim 1 wherein the ratio of gas to solid dispensed is regulated by varying the pressure of the gas at pressure p₂.

3. An improvement according to claim 2 wherein the throughflow quantity of gas is controlled in response to the throughflow quantity of solid determined to have been dispensed at said weighing device.

4. A method according to claim 1 wherein the throughflow quantity of the gas flow is controlled by varying only the gas flow at pressure p₃ and maintaining the gas at pressure p₁ at constant pressure.

5. A method according to claim 1, wherein the solid is in powder form and is dispensed into a metal melt.

6. A method according to claim 5, wherein a desulfurizing agent is fluidized and dispensed from said vessel at a rate between 40 and 250 kg/min, the gas/solid ratio is maintained at a value in the range from 2 to 20 Nl/kg and said agent is directed into a pig iron desulphurization process through an immersion lance.

7. A method according to claim 6 wherein the desulfurizing agent is calcium carbide.

8. A method according to claim 6 wherein the solid throughflow rate is between 100 and 140 kg/min and the gas/solid ratio is between 4 and 10 Nl/kg.

9. In an apparatus for dispensing a fluidizable solid from the lower portion of a pressure vessel having a weighing device, a closable supply, a discharge, a source of three gas flows, a first of which terminates within the vessel at a level above the solid in an upper portion thereof, a second of which terminates within the vessel in a lower portion thereof, a third of which terminates in said discharge, said discharge connected to a chamber, the improvement which comprises means in association with said weighing device to determine the amount of a solid dispensed into said vessel, means for determining the amount of gas throughput of the gases from second and third gas sources, and regulating means for regulating the gas and solid to maintain a constant gas/solid ratio.

10. An improvement according to claim 9 wherein said regulating means is in operative association with a flow controlling means on the third gas source.

11. An improvement according to claim 9 wherein means are provided in association with the first gas source to regulate the pressure thereof, said means responsive to an actual value measured by weighing device for solid dispensed.

12. An improvement according to claim 7 wherein a control device is provided to regulate the quantity of the gas throughflow which device is responsive to the actual value of quantity of solid dispensed.

13. In a device for dispensing a fluidizable solid from a pressure vessel having a weighing device, said vessel having in its upper portion a closable feed aperture and a gas line having a first controllable gas pressure source of pressure p₂, said vessel having in the lower portion thereof a loosening bottom and a closable discharge opening, said discharge opening having a discharge line, said discharge line discharging into a chamber of pressure p₄, said vessel having in the loosening bottom and in, the discharge line a second and third line discharge having a second controllable gas pressure source for a gas stream of pressure p₁ and a third controllable gas pressure source at pressure p₃, the improvement to maintain a gas quantity/solid quantity ratio constant which comprises a first regulating means for the solid quantity which first regulating means is operable to compare the actual value of the solid quantity measured by means of the weighing device which has a preset desired value, which first regulating means is operable to adjust the pressure of the gas stream of pressure p₂ by means of said first controllable gas pressure source by synchronous adjustment thereof, a second regulating means for the gas quantity of the respective gas streams of pressures p₁ and p₃, which second regulating means receives the actual value of the gas quantity and the actual value of the solid quantity measured by the weighing device and, in the event of deviation from the gas quantity/solid quantity ratio to be maintained constant, adjusts the quantity by means of said second controllable gas pressure source to a constant preselected value, said device having magnitudes of pressures such that the following relationship is maintained: p₁ >p₂ >p₃ >p₄.

14. A device according to claim 13 wherein said second regulating means is responsive to a measuring device arranged following the second controllable gas pressure source and adjusts the gas quantity of gas at pressures p₁ and p₃, respectively, through control valves.

15. A device according to claim 13 wherein said second regulating means adjusts only the gas quantity of the gas stream at pressure p₃ by means of a control valve.

16. A process according to claim 1 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

17. A process according to claim 16 wherein said molten metal is disposed in a torpedo ladle.

18. A process according to claim 2 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at pressure p₃.

19. A process according to claim 18 wherein said molten metal is disposed in a torpedo ladle.

20. A process according to claim 4 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

21. A process according to claim 20 wherein said molten metal is disposed in a torpedo ladle.

22. A process according to claim 5 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

23. A process according to claim 22 wherein said molten metal is disposed in a torpedo ladle.

24. A process according to claim 5 wherein said molten metal is disposed in a torpedo ladle.

25. A process according to claim 5 wherein said gas/solid ratio is maintained at a value in the range from 2 to 20 Nl/kg.

26. A process according to claim 5 wherein said powder is a desulfurizing agent.

27. A process according to claim 5 wherein said solid comprises silicon.

28. A process according to claim 5 wherein said solid comprises aluminum.

29. A process according to claim 6 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

30. A process according to claim 29 wherein said molten metal is disposed in a torpedo ladle.

31. An apparatus according to claim 12 wherein said discharge is disposed vertically below said closable supply.

32. An apparatus according to claim 9 wherein said discharge is disposed vertically below said closable supply.

33. An apparatus according to claim 11 wherein said discharge is disposed vertically below said closable supply.

34. A device according to claim 13 wherein said discharge line is disposed vertically below said discharge opening.

35. In a process for dispensing via an immersion lance immersed into a metal melt fluidizable solid from the lower portion of a pressure vessel having a weighing device at which said solid is dispensed, a closable supply, a discharge, a source of three gas flows, one of which is applied within the vessel at a level above the solid to be fluidized at a pressure p₂, a second of which is applied within said vessel in the lower portion of said vessel at a pressure p₁, a third of which is applied within the discharge orifice at a pressure p₃, said discharge orifice terminating via said immersed lance in said metal melt at a pressure p₄, the improvement which comprises determining the amount of solid dispensed at said weighing device, determining the throughflow quantity of gas flow, said throughflow quantity of gas flow being the sum of the amount of gas at a pressure having a pressure p₁ and the amount of gas having a pressure p₃ and regulating the amount of gas and amount of solid to maintain a predetermined constant gas/solid dispensed ratio under conditions such that p₁ >p₂ >p₃ >p₄.

36. A process according to claim 35 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

37. A process according to claim 36 wherein said metal melt is disposed in a torpedo ladle.

38. A process according to claim 35 wherein said metal melt is disposed in a torpedo ladle.

39. A process according to claim 35 wherein the ratio of gas to solid dispensed is regulated by varying the pressure of the gas at pressure p₂.

40. A process according to claim 39 wherein said metal melt is disposed in a torpedo ladle.

41. A process according to claim 39 wherein the throughflow quantity of gas is controlled in response to the throughflow quantity of solid determined to have been dispensed at said weighing device.

42. A process according to claim 41 wherein said metal melt is disposed in a torpedo ladle.

43. A process according to claim 41 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

44. A process according to claim 43 wherein said metal melt is disposed in a torpedo ladle.

45. A process according to claim 39 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

46. A process according to claim 45 wherein said metal melt is disposed in a torpedo ladle.

47. A process according to claim 35 wherein the through flow quantity of gas flow is controlled by varying only the gas flow at pressure p₃ and maintaining the gas at pressure p₁ at constant pressure.

48. A process according to claim 47 wherein said metal melt is disposed in a torpedo ladle.

49. A process according to claim 47 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

50. A process according to claim 49 wherein said metal melt is disposed in a torpedo ladle.

51. A process according to claim 35 wherein the solid is in powder form.

52. A process according to claim 51 wherein said solid is a desulfurizing agent.

53. A process according to claim 51 wherein said solid comprises silicon.

54. A process according to claim 51 wherein said solid comprises aluminum.

55. A process according to claim 51 wherein a desulfurizing agent is fluidized and dispensed from said vessel at a rate between 40 and 250 kg/min, the gas/solid ratio is maintained at a value in the range from 2 to 20 Nl/kg and said agent is directed into a pig iron desulfurization process through said immersion lance.

56. A method according to claim 55 wherein the solid throughflow rate is between 100 and 140 kg/min and the gas/solid ratio is between 4 and 10 Nl/kg.

57. A process according to claim 55 wherein said metal melt is disposed in a torpedo ladle.

58. A method according to claim 55 wherein the desulfurization agent is calcium carbide.

59. A process according to claim 58 wherein said desulfurizing agent is calcium carbide.

60. A process according to claim 55 wherein said fluidizable solid is passed downwardly vertically from said pressure vessel into said line containing said discharge orifice and containing gas at a pressure p₃.

61. A process according to claim 60 wherein said metal melt is disposed in a torpedo ladle.

62. A process according to claim 51 wherein said gas/solid ratio is maintained at a value in the range from 2 to 20 Nl/kg. 63. A process according to claim 62 wherein said powder is fluidized and dispensed from said vessel at a rate between 40 and 250 kg/min.

64. In an apparatus for dispensing a fluidizable solid via an immersion lance, into a metal melt into which said lance is immersed, from the lower portion of a pressure vessel having a weighing device, a closable supply, a discharge, a source of three gas flows, a first of which terminates within the vessel at a level above the solid in an upper portion thereof, a second of which terminates within the vessel in a lower portion thereof, a third of which terminates in a discharge line, said discharge line discharging into a metal melt via an immersion lance immersed in said metal melt, the improvement which comprises means in association with said weighing device to determine the amount of a solid dispensed into said metal melt, means for determining the amount of gas throughput of the gases from second and third sources, and regulating means for regulating the gas and solid to maintain a constant gas/solid ratio.

65. An apparatus according to claim 64 wherein said metal melt is disposed in a torpedo ladle.

66. An apparatus according to claim 64 wherein said discharge is disposed vertically below said closable supply.

67. An apparatus according to claim 66 wherein said metal melt is disposed in a torpedo ladle.

68. An apparatus according to claim 64 wherein said regulating means is in operative association with a flow controlling means on the third gas source.

69. An apparatus according to claim 68 wherein said metal melt is disposed in a torpedo ladle.

70. An apparatus according to claim 68 wherein said discharge is disposed vertically below said closable supply.

71. An apparatus according to claim 70 wherein said metal melt is disposed in a torpedo ladle.

72. An apparatus according to claim 64 wherein means are provided in associated with the first gas source to regulate the pressure thereof, said means responsive to an actual value measured by weighing device for solid dispensed.

73. An apparatus according to claim 72 wherein said metal melt is disposed in a torpedo ladle.

74. An apparatus according to claim 72 wherein said discharge is disposed vertically below said closable supply.

75. An apparatus according to claim 74 wherein said metal melt is disposed in a torpedo ladle.

76. An apparatus according to claim 64 wherein a control device is provided to regulate the quantity of the gas throughflow which device is responsive to the actual value of the quantity of solid dispensed.

77. An apparatus according to claim 76 wherein said metal melt is disposed in a torpedo ladle.

78. An apparatus according to claim 76 wherein said discharge is disposed vertically below said closable supply.

79. A process according to claim 78 wherein said powder is fluidized and dispensed from said vessel at a rate between 40 and 250 kg/min.

80. An apparatus according to claim 78 wherein said metal melt is disposed in a torpedo ladle.

81. In a device for dispensing a fluidizable solid via an immersion lance into a metal melt into which said lance is immersed from a pressure vessel having a weighing device, said vessel having in its upper portion a closable feed aperture and a gas line having a first controllable gas pressure source of pressure p₂, said vessel having in the lower portion thereof a loosening bottom and a closable discharge opening, said discharge opening having a discharge line, said discharge line discharging into a metal melt of pressure p₄ via an immersion lance immersed into said metal melt, said vessel having in the loosening bottom and in the discharge line a second and third line discharge having a second controllable gas pressure source for a gas stream of pressure p₁ and a third controllable gas pressure source at pressure p₃, the improvement to maintain a gas quantity/solid quantity ratio constant which comprises a first regulating means for the solid quantity which first regulating means is operable to compare the actual value of the solid quantity measured by means of the weighing device which has a preset desired value, which first regulating means is operable to adjust the pressure of the gas stream of pressure p₂ by means of said first controllable gas pressure source by synchronous adjustment thereof, a second regulating means for the gas quantity of the respective gas streams of pressures p₁ and p₃, which second regulating means receives the actual value of the gas quantity and the actual value of the solid quantity measured by the weighing device and, in the event of deviation from the gas quantity/solid quantity ratio to be maintained constant, adjusts the quantity by means of said second controllable gas pressure source to a constant preselected value, said device having magnitudes of pressure such that the following relationship is maintained: p₁ >p₂ >p₃ >p₄.

82. A device according to claim 81 wherein said metal melt is disposed in a torpedo ladle.

83. A device according to claim 81 wherein said second regulating means is responsive to a measuring device arranged following the second controllable gas pressure source and adjusts the gas quantity of gas at pressures p₁ and p₃, respectively, through control valves.

84. A device according to claim 83 wherein said metal melt is disposed in a torpedo ladle.

85. A device according to claim 81 wherein said second regulating means adjusts only the gas quantity of the gas stream at pressure p₃ by means of a control valve.

86. A device according to claim 85 wherein said metal melt is disposed in a torpedo ladle.

87. A device according to claim 81 wherein said discharge line is disposed vertically below said discharge opening.

88. A device according to claim 87 wherein said metal melt is disposed in a torpedo ladle.

89. A process according to claim 87 wherein said desulfurizing agent is calcium carbide.