A process and system for briquetting particulate matter such as moisture-containing bituminous and sub-bituminous coal includes partially drying and feeding the particulate matter to a briquetting apparatus under conditions such that water vapor is released from the particulate matter during feeding. The released water vapor substantially displaces or prevents the ingress of a large proportion of other gaseous components from the atmosphere surrounding an/or intermixed with the particulate matter. The particulate matter is surrounded by and intermixed with a gaseous component containing 70% to 100% by volume of water vapor where it enters the briquetting apparatus, such that when the particulate matter is compressed, the water vapor liquefies and the pressure buildup in the thus-formed briquettes is minimized. This reduction in the pressure buildup reduces blow-back of gases as the coal fines are formed into briquettes.
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31. A system for briquetting particulate matter, comprising:
a briquetting apparatus;
means for feeding particulate matter to the briquetting apparatus under gas-forming conditions of temperature and pressure in which a condensable gas is released from the particulate matter during feeding, wherein the condensable gas is allowed to displace and/or prevent the ingress of other non-condensable gaseous components such that the particulate matter is surrounded by and/or intermixed with a gaseous component containing 70-100% by volume of the condensable gas;
a briquette forming part for forming briquettes from the particulate matter, the briquettes being formed by the briquette forming part under conditions of temperature and pressure which cause the condensable gas to condense, thereby reducing gas pressure buildup during briquette formation and gas blow-back through the particulate matter being fed to the briquette forming part of the briquetting apparatus; and
a precompactor for precompacting and feeding the particulate matter to the briquette forming part of the briquetting apparatus, wherein in use the precompactor and the precompacted particulate matter define a tortuous path to further assist in reducing blow-back of gases through the particulate matter being fed to the briquette forming part of the briquetting apparatus, wherein
the briquette forming part of the briquetting apparatus includes a pair of rollers through which the particulate bituminous matter passes, at least one of the rollers having pockets formed therein for assisting in defining the shape of the briquettes, and the rollers are rotatable at peripheral roll speeds from 113.1 m/min to 188.5 m/min and are configured to apply a loading within a range of 115 kn/cm to 150 kn/cm.
16. A process for briquetting particulate matter, comprising:
partially drying the particulate matter;
feeding the particulate matter to a briquetting apparatus under gas-forming conditions of temperature and pressure in which a condensable gas is released from the particulate matter during feeding, wherein the condensable gas is allowed to displace and/or prevent the ingress of other non-condensable gaseous components such that the particulate matter is surrounded by and/or intermixed with a gaseous component containing 70-100% by volume of the condensable gas; and
forming briquettes in a briquette forming part of the briquetting apparatus, wherein briquettes are formed from the particulate matter under temperature and pressure conditions which cause the condensable gas to condense, thereby reducing gas pressure buildup during briquette formation and gas blow-back through the particulate matter being fed to the briquette forming part of the briquetting apparatus,
wherein the process further comprises using a precompactor to feed the partially dried particulate matter to the briquette forming part of the briquetting apparatus, and applying back pressure to said particulate matter using said precompactor and precompacted particulate matter to define a tortuous path to assist in further reducing blow-back of gases through the particulate matter being fed to the briquette forming part of the briquetting apparatus, wherein
the briquette forming part of the briquetting apparatus includes a pair of rollers through which the particulate bituminous matter passes, at least one of the rollers having pockets formed therein for assisting in defining the shape of the briquettes, and the process further comprises
rotating the pair of rollers at peripheral roll speeds from 113.1 m/min to 188.5 m/min and applying a loading with the rollers within a range of 115 kn/cm to 150 kn/cm.
0. 89. A system for briquetting particulate matter, comprising:
a briquetting apparatus;
means for feeding particulate matter to the briquetting apparatus under gas-forming conditions of temperature and pressure in which a condensable gas is released from the particulate matter during feeding, wherein the condensable gas is allowed to displace and/or prevent the ingress of other non-condensable gaseous components such that the particulate matter is surrounded by and/or intermixed with a gaseous component containing 70-100% by volume of the condensable gas;
a briquette forming part for forming briquettes from the particulate matter, the briquettes being formed by the briquette forming part under conditions of temperature and pressure which cause the condensable gas to condense, thereby reducing gas pressure buildup during briquette formation and gas blow-back through the particulate matter being fed to the briquette forming part of the briquetting apparatus; and
a precompactor for precompacting and feeding the particulate matter to the briquette forming part of the briquetting apparatus, wherein in use the precompactor and the precompacted particulate matter define a tortuous path to further assist in reducing blow-back of gases through the particulate matter being fed to the briquette forming part of the briquetting apparatus, wherein
the briquette forming part of the briquetting apparatus includes a pair of rollers through which the particulate bituminous matter passes, at least one of the rollers having pockets formed therein for assisting in defining the shape of the briquettes, and the rollers are rotatable at peripheral roll speeds from 25.1 m/min to 188.5 m/min and are configured to apply a loading within a range of 60 kn/cm to 150 kn/cm, wherein the diameters of the rollers are within a range of 400 mm to 600 mm and wherein the rollers are rotatable at speeds from 20 rpm to 100 rpm.
0. 79. A process for briquetting particulate matter, comprising:
partially drying the particulate matter; feeding the particulate matter to a briquetting apparatus under gas-forming conditions of temperature and pressure in which a condensable gas is released from the particulate matter during feeding, wherein the condensable gas is allowed to displace and/or prevent the ingress of other non-condensable gaseous components such that the particulate matter is surrounded by and/or intermixed with a gaseous component containing 70-100% by volume of the condensable gas; and
forming briquettes in a briquette forming part of the briquetting apparatus, wherein briquettes are formed from the particulate matter under temperature and pressure conditions which cause the condensable gas to condense, thereby reducing gas pressure buildup during briquette formation and gas blow-back through the particulate matter being fed to the briquette forming part of the briquetting apparatus,
wherein the process further comprises using a precompactor to feed the partially dried particulate matter to the briquette forming part of the briquetting apparatus, and applying back pressure to said particulate matter using said precompactor and precompacted particulate matter to define a tortuous path to assist in further reducing blow-back of gases through the particulate matter being fed to the briquette forming part of the briquetting apparatus, wherein
the briquette forming part of the briquetting apparatus includes a pair of rollers through which the particulate bituminous matter passes, at least one of the rollers having pockets formed therein for assisting in defining the shape of the briquettes, and the process further comprises
rotating the pair of rollers at peripheral roll speeds from 25.1 m/min to 188.5 m/min and applying a loading with the rollers within a range of 60 kn/cm to 150 kn/cm, wherein the diameters of the rollers are within a range of 400 mm to 600 mm and wherein the process comprises rotating the rollers at speeds from 20 rpm to 100 rpm.
1. A process for briquetting particulate bituminous matter containing moisture, comprising:
partially drying the particulate bituminous matter under process conditions including a temperature of above 100° C. and for a period which will raise the temperature of the particulate bituminous matter to above 90° C. and decrease the total moisture content of the particulate bituminous matter to between 1% and 10% by weight of the particulate bituminous matter;
maintaining the temperature of the partially dried particulate bituminous matter above 80° C. whilst feeding the particulate bituminous matter towards a briquette forming part of a briquetting apparatus along a feed path from which the ingress of ambient air is excluded, thereby causing water vapor driven from the particulate bituminous matter to substantially displace ambient air and other gasses from the interstices between the particles of the particulate bituminous matter as the particulate bituminous matter moves towards the briquette forming part of the briquetting apparatus;
feeding the partially dried particulate bituminous matter into the briquette forming part of the briquetting apparatus, wherein feeding the partially dried particulate bituminous matter into the briquette forming part of the briquetting apparatus comprises using at least one precompaction auger, and applying a back pressure to said particulate bituminous matter using said precompaction auger and precompacted particulate bituminous matter to define a tortuous path to assist in further reducing blow-back of gases through the particulate bituminous matter being fed to the briquetting forming part of the briquetting apparatus; and
briquetting the particulate bituminous matter in the briquette forming part of the briquetting apparatus at a pressure which is sufficient to cause the entrained water vapor to condense, wherein
the briquette forming part of the briquetting apparatus includes a pair of rollers through which the particulate bituminous matter passes, at least one of the rollers having pockets formed therein for assisting in defining the shape of the briquettes, and the process further comprises
rotating the pair of rollers at peripheral roll speeds from 113.1 m/min to 188.5 m/min and applying a loading with the rollers within a range of 115 kn/cm to 150 kn/cm.
0. 56. A process for briquetting particulate bituminous matter containing moisture, comprising:
partially drying the particulate bituminous matter under process conditions including a temperature of above 100° C. and for a period which will raise the temperature of the particulate bituminous matter to above 90° C. and decrease the total moisture content of the particulate bituminous matter to between 1% and 10% by weight of the particulate bituminous matter;
maintaining the temperature of the partially dried particulate bituminous matter above 80° C. whilst feeding the particulate bituminous matter towards a briquette forming part of a briquetting apparatus along a feed path from which the ingress of ambient air is excluded, thereby causing water vapor driven from the particulate bituminous matter to substantially displace ambient air and other gasses from the interstices between the particles of the particulate bituminous matter as the particulate bituminous matter moves towards the briquette forming part of the briquetting apparatus;
feeding the partially dried particulate bituminous matter into the briquette forming part of the briquetting apparatus, wherein feeding the partially dried particulate bituminous matter into the briquette forming part of the briquetting apparatus comprises using at least one precompaction auger, and applying a back pressure to said particulate bituminous matter using said precompaction auger and precompacted particulate bituminous matter to define a tortuous path to assist in further reducing blow-back of gases through the particulate bituminous matter being fed to the briquetting forming part of the briquetting apparatus; and
briquetting the particulate bituminous matter in the briquette forming part of the briquetting apparatus at a pressure which is sufficient to cause the entrained water vapor to condense, wherein
the briquette forming part of the briquetting apparatus includes a pair of rollers through which the particulate bituminous matter passes, at least one of the rollers having pockets formed therein for assisting in defining the shape of the briquettes, and the process further comprises rotating the pair of rollers at peripheral roll speeds from 25.1 m/min to 188.5 m/min and applying a loading with the rollers within a range of 60 kn/cm to 150 kn/cm, wherein the diameters of the rollers are within a range of 400 mm to 600 mm and wherein the process comprises rotating the rollers at speeds from 20 rpm to 100 rpm.
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0. 57. A process according to claim 56, wherein the process comprises rotating the pair of rollers at peripheral roll speeds from 28.3 m/min to 188.5 m/min.
0. 58. A process according to claim 56, wherein the process comprises rotating the pair of rollers at peripheral roll speeds from 31.4 m/min to 188.5 m/min.
0. 59. A process according to claim 56, wherein the process comprises rotating the pair of rollers at peripheral roll speeds from 34.5 m/min to 188.5 m/min.
0. 60. A process according to claim 56, wherein the process comprises rotating the pair of rollers at peripheral roll speeds from 37.7 m/min to 188.5 m/min.
0. 61. A process according to claim 56, wherein the diameters of the rollers range from 400 mm to 550 mm.
0. 62. A process according to claim 56, wherein the diameters of the rollers range from 400 mm to 460 mm.
0. 63. A process according to claim 56 wherein the method comprises partially drying the particulate bituminous matter under process conditions which raise the temperature of the particulate bituminous matter to between 105° C. and 150° C.
0. 64. A process according to claim 56, wherein the pair of rollers includes a first roller and a second roller, and the process further comprises rotating the second roller at a peripheral roll speed of between 10% faster and 10% slower than the peripheral roll speed of the first roller.
0. 65. A process according to claim 56 in which water vapor prior to undergoing condensation comprises 70% to 100% of the gas in the interstices between particles.
0. 66. A process according to claim 56 in which the particulate bituminous matter is chosen from a group consisting of organic materials including wood dust, peat, lignite, brown coal, anthracite and bituminous and sub-bituminous coals.
0. 67. A process according to claim 56 wherein the formed briquettes undergo evaporative cooling for preventing spontaneous combustion.
0. 68. A process according to claim 67 wherein evaporative cooling is achieved by a spray arrangement for lowering the temperature of the briquettes to below 50° C. and maintaining the moisture level close to the equilibrium moisture level of the briquettes.
0. 69. A process according to claim 56 wherein partially drying the particulate bituminous matter takes place in a flash dryer, in which the particulate bituminous matter is injected into a hot gas stream flowing through a conduit, the particulate bituminous matter being entrained by the hot gas stream which causes the temperature of the particulate bituminous matter to be increased, and the gas stream with the entrained particulate bituminous matter then passing through one or more cyclones in which the particulate bituminous matter is separated from the gas stream.
0. 70. A process according to claim 69 wherein the separated gas stream leaving the cyclone or cyclones is partially recycled to the flash dryer with the excess gas being vented, the vented portion of the gas stream passing through a fines removing device for removing fines that pass with the gas stream through the cyclones.
0. 71. A process according to claim 70 wherein the portion of the gas stream that is recycled to the flash dryer is reheated prior to injection of the particulate bituminous matter into the flash dryer, with the amount of gas that is vented corresponding to the volume of combustion product gas and the volume of non-condensed water vapor driven off from the particulate bituminous matter.
0. 72. A process according to claim 56 including rotating the rollers at differing speeds for applying a predetermined amount of shear to the particulate bituminous matter as it passes between the rollers and is formed into briquettes.
0. 73. A process according to claim 56 wherein the ratio of the briquette pocket width to roller diameter falls within the range of 0.05 to 0.15.
0. 74. A process according to claim 56 wherein the particulate bituminous matter is fed to the briquette forming part of the briquetting apparatus at a temperature ranging from 100° C. to 120° C.
0. 75. A process according to claim 56 wherein the condensable gas generates a pressure ranging from 100 kPa to 200 kPa (absolute) within the briquette forming part of the briquetting apparatus.
0. 76. A process according to claim 56 wherein the temperature of the particulate bituminous matter is maintained above 100° C. whilst feeding the particulate bituminous matter towards the briquetting forming part of the briquetting apparatus.
0. 77. A process according to claim 56 wherein the particulate bituminous matter is partially dried such that the total moisture content is between 5% and 8% by weight of the particulate bituminous matter.
0. 78. A process according to claim 56 wherein the briquetting forming part of the briquetting apparatus serves to distort the shape of the particulate bituminous matter to substantially eliminate voids between particles and cause the condensed water vapor to be re-adsorbed into the particulate bituminous matter and individual particles to be chemically bonded together.
0. 80. A process according to claim 79, wherein the process comprises rotating the pair of rollers at peripheral roll speeds from 28.3 m/min to 188.5 m/min.
0. 81. A process according to claim 79, wherein the process comprises rotating the pair of rollers at peripheral roll speeds from 31.4 m/min to 188.5 m/min.
0. 82. A process according to claim 79, wherein the process comprises rotating the pair of rollers at peripheral roll speeds from 34.5 m/min to 188.5 m/min.
0. 83. A process according to claim 79, wherein the process comprises rotating the pair of rollers at peripheral roll speeds from 37.7 m/min to 188.5 m/min.
0. 84. A process according to claim 79, wherein the diameters of the rollers range from 400 mm to 550 mm.
0. 85. A process according to claim 79, wherein the diameters of the rollers range from 400 mm to 460 mm.
0. 86. A process according to claim 79 wherein the method comprises partially drying the particulate bituminous matter under process conditions which raise the temperature of the particulate bituminous matter to between 105° C. and 150° C.
0. 87. A process according to claim 79, wherein the pair of rollers includes a first roller and a second roller, and the process further comprises rotating the second roller at a peripheral roll speed of between 10% faster and 10% slower than the peripheral roll speed of the first roller.
0. 88. A process according to claim 79, wherein a ratio of a pocket width to roller diameter ranges from 0.05 to 0.15.
0. 90. A system according to claim 89, wherein the rollers are rotatable at peripheral roll speeds from 28.3 m/min to 188.5 m/min.
0. 91. A system according to claim 89, wherein the rollers are rotatable at peripheral roll speeds from 31.4 m/min to 188.5 m/min.
0. 92. A system according to claim 89, wherein the rollers are rotatable at peripheral roll speeds from 34.5 m/min to 188.5 m/min.
0. 93. A system according to claim 89, wherein the rollers are rotatable at peripheral roll speeds from 37.7 m/min to 188.5 m/min.
0. 94. A system according to claim 89, wherein the diameters of the rollers range from 400 mm to 550 mm.
0. 95. A system according to claim 89, wherein the diameters of the rollers range from 400 mm to 460 mm.
0. 96. A system according to claim 89, wherein the pair of rollers includes a first roller and a second roller, and the second roller is rotatable at a peripheral roll speed of between 10% faster and 10% slower than the peripheral roll speed of the first roller.
0. 97. A system according to claim 89, wherein a ratio of a pocket width to roller diameter ranges from 0.05 to 0.15.
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This application is a reissue application of U.S. patent application Ser. No. 12/244,909, filed Oct. 3, 2008, now U.S. Pat. No. 8,070,839, which is a continuation of U.S. application Ser. No. 10/545,174, filed Nov. 16, 2005, now U.S. Pat. No. 7,892,302, which is a national phase of international application PCT/AU2004/000158, filed Feb. 11, 2004, which designated the U.S. and claimed benefit claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/446,267, dated Feb. 11, 2003, the entire contents of each of which are hereby incorporated by reference.
The present invention relates to a process and system for briquetting materials, especially, but not limited to, those that contain moisture. The present invention is especially suitable for briquetting organic materials that contain moisture, such as peat, lignite, brown coal, sub-bituminous coal, bituminous coal and anthracite.
The present invention is particularly suited to briquetting organic material containing moisture, such as peat, lignite, brown coal, sub-bituminous coal and bituminous coal. The present invention is especially suited to briquetting sub-bituminous and bituminous coals and, for convenience and ease of description, the invention will be described with reference to the briquetting of sub-bituminous and bituminous coals. However, it will be understood that the invention is not limited to briquetting bituminous and sub-bituminous coals and that the invention may be used to briquette other organic or inorganic materials, and indeed any other materials that may or may not contain moisture.
Sub-bituminous coals have relatively high moisture levels (up to 35% moisture, by weight). Not only does this reduce the calorific value of the coal, it almost completely excludes sub-bituminous coals from export markets due to the poor economics associated with transporting the very high moisture levels associated with those coals. Removal of this moisture requires a thermal drying stage due to the chemically combined nature of most of the water in sub-bituminous coals. However, removal of the water causes further problems that prevent greater acceptability and use of such coals. In particular, once dried, the sub-bituminous coals suffer serious spontaneous combustion problems and considerable size degradation. Consequently, the drying process tends to increase the quantity of fines associated with the coals.
Bituminous coals are higher rank coals that have a higher calorific value and lower inherent moisture content than sub-bituminous coals. Although more amenable to transport than sub-bituminous coals, bituminous coals can suffer from production of excessive fines during mining, washing and handling operations. Such fines are difficult to use and represent a loss of product. Free surface moisture also causes difficulties with fine bituminous coals and can be as high as 25% by weight. This causes problems because it reduces the available energy content of the coal and can have a serious impact on the handling properties of the coal.
With many metallurgical and higher ranks steam coal, the grindability of the coal is such that the percentage of fine material in the total cleaned coal is sufficient to result in marketing difficulties even if the moisture content is reduced to an otherwise acceptable value. A possible solution to overcome this difficulty involves briquetting of the coal to form larger particles of the coal. However, the briquetting solution must provide for restructuring of the fines into a commercially attractive, handleable and durable form whilst not increasing production costs beyond the threshold of overall profitability.
Briquetting of coal has been carried out since the late nineteenth century. The traditional approach to coal briquetting involved mixing the coal particles with binders to bind the coal particles together into a larger mass. Binders that have been tried include organic binders such as coal-tar pitch, petroleum bitumen and asphalt, wood tar, synthetic and natural resins, starch, sulphite liquors, sugars and molasses, cellulose compounds, vegetable pulps, alginates, glue or gum, albumates, casein, peat, lignite and wood. Inorganic binders that have been used include cement, clay, lime, magnesia, gypsum, sodium or other alkali silicates. Compound binders comprising blends of two or more of the above have also been tried.
The criteria by which binders used in briquetting of coal have been judged include:
Experience with coal briquettes that incorporate binders has shown that a generally applicable coal binder that meets all of the above criteria has not yet been found. For example, pitch, bitumen and asphalt give adequate strength and moisture resistance but result in smoking combustion, toxicity problems, change to coking properties, high cost and high processing costs. Starch provides good strength and clean burning but is expensive and has poor weathering resistance. Sulphate liquor binders burn with little smoke but produce toxic sulphur dioxide emissions and have poor weathering properties. Sugars, particular molasses, have inferior moisture and weathering resistance and may suffer mould growth during storage. Cellulose-type binders typically suffer from low strength and rapid deterioration, with the briquettes tending to disintegrate in the early stages of combustion. It has been reported that the inorganic binders all suffer relatively low strengths, poor weathering resistance and high ash levels after combustion.
The necessity to add the binder component to the briquette also unavoidably increases the complexity and cost of briquette production.
In order to try to avoid some of the difficulties involved with producing briquettes using binders, various attempts have been made to produce binderless briquettes. For example, U.S. Pat. No. 2,937,080 in the name of Komarek et al. describes a process for briquetting coal by feeding coal particles into a hot gas stream in a flash dryer. The coal particles are entrained by the gas stream and are heated by the gas stream to cause water to evaporate from the coal. The coal particles are transported by the gas stream to a cyclone separator, where the hot, dried coal particles are separated from the gas stream. The separated coal particles drop into a hopper and pass through the rolls of a briquetting apparatus to form the briquettes. This patent states that the temperature of the coal just before it reaches the briquetting machine should be just below the softening point, e.g. of nascent plasticity, of the coal for maximum efficiency and operation. The patent further stated that many coals can be compressed into suitable agglomerates within the temperature range of about 300° F. to 700° F. (about 149° C. to 371° C.).
U.S. Pat. No. 5,046,265 in the name of Kalb describes an integrated process for drying and briquetting sub-bituminous coals. In this process, coal is dried in a flash dryer under conditions that promote degradation of the coal particles. In particular, the coal particles are fed to a hot gas stream in a flash dryer and the thermal shock of the particles entering the hot gas stream causes degradation of the coal particles. The thus-treated coal particles are then separated from the gas stream by a series of cyclones. The separated gas is at least partially recycled to the flash dryer. The dried coal particles are fed to degasification/pre-compaction augers that compress the coal and remove gas therefrom before it is fed to the briquetting machine. In this regard, it will be appreciated that the dried coal particles have gas filling the interstitial spaces between the particles of coal and that the pre-compaction augers compress the coal and reduce the interstitial volume, thereby driving gas out of the coal. The gas liberated from the coal by the pre-compaction augers is treated by a small volume fan and dust collector. The pre-compacted coal is subsequently fed to a briquetting machine.
U.S. Pat. No. 5,046,265 specifies seven parameters as being critical to the briquetting process, these being:
The overall process system described in U.S. Pat. No. 5,046,265 is stated as being able to convert high inherent moisture (30% to 35%), low BTU value (8,200 BTU per pound to 8,800 BTU per pound), sub-bituminous coals, and the like into a high BTU (11,000 BTU per pound to 11,500 BTU per pound), low moisture (approximately 5% to 8%) product which at the same time has acceptable handleability characteristics in the context of the current market place and user infrastructure system.
International Application PCT/CA90/00056 (International Publication WO 90/10052) describes a briquetting process for briquetting bituminous coals without the use of extraneous binders. This system uses high temperature, high pressure mould forming of the coal fines material in an apparatus incorporating a high pressure roll-type briquetting press. The system incorporates a positive pressure, controlled oxygen, gas re-circulation flash dryer and a direct briquette product to feed a heat exchange system for high system efficiency.
In a first aspect, the present invention provides a process for briquetting particulate matter containing moisture comprising the steps of partially drying the particulate matter, feeding the partially dried particulate matter to a briquetting apparatus under conditions such that water vapor is released from the particulate matter during feeding and passing the particulate matter through the briquetting apparatus to form briquettes.
The term “feeding the partially dried particulate material to the briquetting apparatus” encompasses the steps involved in transferring the partially dried particulate matter from when it is separated from the dryer gas stream to when it enters the briquetting apparatus. It may include transfer through conduits or chutes, short term storage in a hopper or vessel and final feeding to the briquetting apparatus.
Preferably, the partially dried particulate matter is fed to the briquetting apparatus under conditions such that water vapor is released from the particulate matter whereby the released water vapor substantially displaces and/or prevents the ingress of a large proportion of other gaseous components from the atmosphere surrounding and/or intermixed with the particulate matter. More preferably, the particulate matter that is fed to the briquetting apparatus is surrounded by and/or intermixed with a gaseous component containing from 70% to 100% by volume water vapor at the point where it enters the briquette-forming part of the briquetting apparatus. As a result, when the particulate matter is compressed during briquette formation, the water vapor condenses or liquefies and the pressure buildup of gaseous material in the thus-formed briquette is minimised. The present inventors have also discovered that previous difficulties caused by the presence of large proportions of non-condensable gases mixed with the particulate matter (which include blow-back of the gases through the particulate feed material which can disrupt the flow of particulate matter to the briquetting apparatus, explosive break-up of the briquettes as they are removed from the briquetting apparatus and porous briquettes of diminished strength) are minimised or avoided in the present invention.
In a second aspect, the invention provides a process for briquetting particulate matter including:
The invention extends to a system for briquetting particulate matter including:
Whilst water vapor is the most common condensable gas that is used, other condensable gases such as freon may also be used in cases where the particulate matter is more temperature sensitive or moisture sensitive. By the term ‘condensable gas’ is meant any gas that will tend to condense during the briquette forming process.
The method of the present invention may be used for the briquetting of organic and inorganic materials, as well as materials such as sludges which are partly organic and partly inorganic. Examples of inorganic materials include magnesium and calcium oxides, alumina and red mud. The method and system is particularly suitable for the briquetting of organic materials, such as wood dust, vegetable matter, peat, brown coal lignite, sub-bituminous coal and bituminous coals. The method of the present invention is especially suitable for briquetting brown coals, lignite, sub-bituminous and bituminous coals.
The method of the present invention involves the step of partially drying the particulate matter. It is preferred that the step of partially drying the particulate matter takes place in a flash dryer, and in particular a gas recycle flash dryer. In the process the particulate matter is injected into a hot gas stream flowing through a conduit. The particulate matter is entrained by the hot gas stream which causes the temperature of the particulate matter to be increased. This commences the drying process. The gas stream with entrained particulate matter then passes through one or more cyclones in which the particulate matter is separated from the gas stream.
The separated gas stream leaving the cyclone or cyclones is partially recycled to the gas recycle flash dryer with the excess gas being vented. The vented portion of the gas stream preferably passes through a baghouse or any other suitable device for removing fines that pass with the gas stream through the cyclones.
The portion of the gas stream that is recycled to the gas recycle flash dryer suitably passes through a fan, compressor or the like and a gas heater or furnace, which again increases the temperature of the gas stream prior to injection of the particulate matter into the flash dryer. The amount of gas that is vented through the baghouse corresponds largely to the volume of combustion product gas generated in the gas heater together with the volume of non-condensed water vapor driven off from the particulate matter within the system. The particulate matter recovered from the separating cyclone is in a partially dried state. By “partially dried”, it is meant that the moisture content of the particulate matter has been reduced from the moisture content of the feed particulate matter, but that further moisture can be removed therefrom.
The partially dried particulate matter is then transferred and fed to the briquetting apparatus. The transfer and feeding of the particulate matter from the cyclones to the briquetting apparatus may take place using any apparatus known by the person skilled in the art to be suitable for transferring particulate matter. Some examples include augers, conveyer systems and pneumatic conveyers.
It is a feature of the first aspect of the present invention that further drying of the partially dried particulate matter takes place during feeding of the particulate matter to the briquetting apparatus. As will be readily understood by the person of skill in the art, further drying of the particulate matter during feeding to the briquetting apparatus causes the release of moisture from the particulate matter. The moisture is released in the form of water vapor and the water vapor acts to displace non-condensable gases, such as nitrogen, carbon dioxide and other gases from the atmosphere that surrounds or intermixes with the particulate matter. As a result, the gaseous component of the mixture of particulate matter and gas that is fed to the briquetting apparatus has a high level of water vapor. It will be appreciated that water vapor is a condensable gas and that the pressure applied to the particulate matter during the briquetting process can cause the water vapor to liquefy, thereby greatly reducing the volume of the gaseous components that pass through the briquetting apparatus. This assists in preventing blow-back of gases through the particulate matter being fed to the briquetting apparatus, as well as improving the quality of the briquettes thus formed by minimising porosity caused by trapped non-condensable gases and possible explosive breakdown of briquettes caused by pockets of compressed non-condensable gases trapped inside the briquettes.
According to a still further aspect of the invention there is provided a system for briquetting particulate matter containing moisture including:
a briquetting apparatus having a briquette forming part;
means for partially drying the particulate matter;
means for feeding the partially dried particulate matter to the briquetting apparatus, and
means for creating conditions such that water vapor is released from the particulate matter during feeding.
The briquetting apparatus is suitably of the kind that includes briquetting rollers. In briquetting apparatus of this kind, the particulate matter is fed to the rollers. The rollers compress the particulate matter. One or more of the rollers preferably has pockets formed therein, which pockets assist in defining the shape of the briquettes. The rollers also apply an amount of shear to the particulate matter as it passes through the briquetting apparatus. It is believed that applying shear as well as compression is important in forming briquettes from certain feed materials such as bituminous coals and sub-bituminous coals.
In order to assist in feeding the particulate matter to the briquetting apparatus or briquetting rollers, it is preferred that one or more feed augers are used to feed the particulate matter. The feed augers are beneficial as they precompact the particulate matter, reduce voidage, and ensure a consistent supply of particulate matter to the briquetting apparatus. Moreover, the feed augers generate a more tortuous path for escaping gas displaced from between the particles during compaction which also assists in minimising or avoiding blow-back of gases through the particulate matter being fed to the briquetting apparatus.
In a preferred embodiment of the present invention, the particulate matter is fed to the rollers of the briquetting apparatus in an essentially horizontal direction.
The present inventors have also found that the relationship between roll size and briquette pocket width to roll diameter is quite important in forming briquettes, especially when forming briquettes from brown sub-bituminous or bituminous coals. Therefore, in a second aspect, the present invention provides a process for briquetting particulate material in which the particulate material is fed to a briquetting apparatus including two or more rollers through which the particulate material passes, at least one of said rollers including one or more briquetting pockets, characterised in that the diameter of the rollers ranges from 100 mm to 600 mm and the ratio of the briquette pocket width to roll diameter falls within the range of 0.05 to 0.15.
In a preferred embodiment of the second aspect of the present invention, the roll diameters fall within the range of 400 mm to 550 mm and the ratio of the briquette pocket width to roll diameter is about 0.08.
In an especially preferred embodiment, the method of the second aspect of the present-invention is used in conjunction with the method of the first aspect of the present invention.
In order to more fully explain the present invention, an embodiment of the invention will now be described with reference to
In the flow diagram shown in
When the moist coal feed is fed into the flash heater riser tube 14, the coal is entrained in the gas stream. As the gas is hot, the temperature of the coal increases and this causes some of the moisture contained in the coal to be converted to water vapor.
The gas stream and entrained coal are then fed to separating cyclones 20, 22. First cyclone 20 separates large fractions of the coal from the gas stream. The separated larger fraction of coal passes through conduit 24 into a collection hopper 26. The gas leaving first cyclone 20 passes through a conduit 28 and into second cyclone 22. In second cyclone 22, finer particles of coal are separated from the gas. The finer particles of coal travel through conduit 30 and into collection hopper 26. Some of the finer coal may also be fed to the heater 18 as a fuel.
The gas leaving second cyclone 22 passes through conduit 32. A portion of the gas travelling through conduit 32 is vented via baghouse 34 and vent 36. The remaining portion of gas is recycled via fan 16 and gas heater 18 to the flash heating riser tube 14.
As a portion of the gas stream in the flash dryer or heating riser tube is recirculated, it will be appreciated that the gas stream in the flash dryer has a significant quantity of water vapor therein. Furthermore, the quantity of water vapor in the gas stream will increase following injection of the moist coal into the gas stream because water will be removed from the moist coal in the gas stream. The presence of significant quantities of water vapor in the gas stream circulating through the flash dryer 14 and careful control of other constituents of the gas stream, especially its oxygen content, can ensure that the danger of explosion within the flash dryer is minimised or avoided.
It will also be appreciated that combustion product gas added at gas heater 18, together with the water vapor generated from the product drying displaces gas through vent 36 in order to maintain constant system pressures. The amount of gas vented through vent 36 is equivalent to the amount of combustion gas injected at the gas heater 18 plus the water vapor generated from the drying of the particulate matter.
The partially dried coal that is collected in collection hopper 26 is then fed by a feed auger 37 to briquetting apparatus 38. The partially dried coal passes from feed auger 37 into feed hopper 39 under conditions such that water vapor continues to be released from the coal. This further reduces the moisture content of the coal and also results in the released water vapor displacing non-condensable gases, such as nitrogen, carbon dioxide and other gases, particularly from the environment of the feed hopper 39. As a result, the amount of non-condensable gases intermixed with the coal being fed to the briquetting apparatus 38 is reduced and the amount of water vapor in the gaseous atmosphere intermixed with the coal is increased. Preferably, the gaseous atmosphere comprises 70% to 100% and more preferably 80% to 100% by volume H2O at this point. In a situation where the gaseous atmosphere is not sufficiently saturated, supplemental water vapor can be introduced directly into the briquetting apparatus 38 into the feed hopper 39 or 39A.
As can more clearly be seen in
The briquetting apparatus 38 is provided with two rollers 44, 46. One of the rollers 44 has briquetting pockets 44A formed therein, and the other roller is preferably smooth, as is shown at 46A, but may also be provided with pockets. As the coal passes through the rollers, it is compressed and subjected to shear. The amount of shear that is applied can be varied by virtue of the differential speed between the two rollers. Typically, the rollers are rotated at speeds from 20 rpm to 100 rpm, and preferably from 80 rpm to 90 rpm. The speed differential between the two rollers is typically between +10% and −10%. The roller 44 is mounted on an hydraulic ram 45 which is fitted with an accumulator having a gas spring 45A providing a compressive force at the nip between the rollers for compressing both the coal particles and the gaseous atmosphere that is intermixed with and surrounds the coal particles. As this gaseous atmosphere contains a substantial proportion of water vapor, the water vapor liquefies as a result of the compression. This greatly reduces the gas pressure increase during compression. It will be appreciated that if the gaseous atmosphere intermixed with the coal contained a greater proportion of non-condensable gases, the pressure-limiting condensation effect would be reduced. The pressure build-up in the gases would thus be greater resulting in gases trying to escape during compression in the briquetting apparatus by flowing back towards the feed hopper 39. This would tend to result in blow-back of the gases which interrupts the feed of coal to the briquetting apparatus. Alternatively, or in addition, the non-condensable gases could be compressed into pockets of compressed gas contained within the briquettes. When the briquettes 47 are released from the rollers 44, 46 the applied external pressure on the briquettes is released. As a result, pockets of compressed gas could potentially cause the briquettes to explode. Therefore, the present invention represents a significant advance over prior art processes known to the present inventors.
Although the embodiment shown in
The coal is prepared for the process to a particle size range of between 0 mm and 5 mm either by screening, or milling. The temperature of the drying gas, before it is mixed with the moist feed coal is governed by the moisture of the feed coal and the solids loading the flash heating riser tube. Typically, the temperature of the gas stream at point 19 shown in
The composition of the gas within the dryer is also preferably carefully controlled. The gas stream preferably has a very low oxygen content (eg below 2%, more preferably 1% or less) and a significant water vapor proportion. Typical figures for the gas composition in the dryer are given in table 1 below.
H2O
CO2
N2
O2
vol. %
vol. %
vol. %
vol. %
Before coal added
49
5
44
1
At coal separation
60
4
35
1
The particle size distribution of the feed coal that is fed in the method of the present invention can vary over a wide range. In practical terms, the limit on the upper size is determined by the maximum size of particle that can be easily dried and transported in the flash dryer, which would be 5 mm or more. Typical ranges of size distributions that have been successfully briquetted by the present inventors are shown in
The size distribution of the coal particles after drying is preferably virtually the same as before drying. There may be some degradation from thermal and mechanical effects during drying but these are usually seen as insignificant. In this aspect, the process of the present invention is different to U.S. Pat. No. 5,046,265 which deliberately caused thermal degradation of the larger coal lumps in the lower part of the dryer before they were entrained. It is believed that this approach has proved to be unsatisfactory.
The coal that is separated from the dryer and collected in collection hopper 26 is partially dried coal. As such, it still contains a level of moisture that can be removed by further drying. For bituminous coal, the moisture of the coal that is fed to the briquetter is preferably 0% to 3% above the coal's inherent moisture. This would mean a typically total moisture content for bituminous coal of between 1% and 10% by weight, more preferably between 1% and 8% by weight.
For sub-bituminous coals, the total moisture of the briquetter feed will be below the inherent moisture of the coal and typically will fall within the range of from 3% to 10% by weight. For sub-bituminous coal mined from the Collie Mine in Western Australia having an inherent moisture of 25% to 30% by weight, the optimum briquetter feed moisture content has been found to fall within the range of 5% to 7%.
Generally, the surfaces of the particles that are going to be bonded together should be essentially free of surface moisture and other foreign material.
An important feature of the process of the present invention is that the gas positioned between the coal particles after it has left the dryer, i.e. in the feed hopper 39 to the briquetter, contains 50% to 100% H2O, more preferably 70% to 100% H2O, and even more preferably 80% to 100% H2O. This is achieved through ensuring that the coal leaving the dryer still has some moisture and is at a temperature greater than 80° C. The coal continues to release water vapor as it sits in the briquetter feed hopper and this water vapor displaces the residual N2, CO2 and O2. By ensuring that the gas filling the voids between the coal is predominantly water vapor, it is possible to avoid the problems of degassing when the coal powder is compacted.
It is particularly preferred that the gas filling the voids or interstitial spaces between the particles of coal as it enters the briquetter is a gas that can be condensed at pressures in the range of 100 kPA to 200 kPa (absolute). It is specially preferred that the gas filling the voids between the particles of coals as it enters the briquetter comprises 50% to 100%, more preferably 70% to 100% and even more preferably 80% to 100% water vapor. The temperature is preferably in the range of 100° C. to 120° C., and more preferably 105° C. to 110° C., which corresponds to a vapor pressure of 120 kPA to 143 kPa (absolute).
The augers 40 and 40A that feed the coal to the briquetting apparatus act as precompactors. It is preferred that the precompactor provides a sufficiently tortuous path for escaping gas that the pressure of the vapor between the coal particles at the tip of the precompactor screw is 100 kPa to 200 kPa (absolute) and more preferably 120 kPa to 143 kPa, as was previously described.
It is preferred that the total power input to the briquetter rolls and the precompactor auger 46 should be in range of 15 to 30 kilowatt hours per ton of coal.
The two opposed rollers 44, 46 have a diameter that is preferably within the range of 100 mm to 600 mm, with the preferred diameters of the rollers being between 400 mm and 550 mm. The ratio of the briquette pocket width to roll diameter should be in the range of from 0.05 to 0.15, with the preferred ratio being about 0.08.
The rollers preferably apply loadings within the range of 60 kN to 150 kN per centimeter of roll width, with a preferred loading of 115 kN to 130 kN per centimetre of roll width for a 460 mm diameter roll. Satisfactory briquettes from bituminous and sub-bituminous coals have been achieved using these roll compaction forces.
The briquetted product 47 must exit the process at a suitable temperature and moisture to reduce the likelihood of it undergoing spontaneous combustion. The product temperature should not be greater than 50° C. while it is in a stockpile 48, with a temperature of less than 40° C. being preferred. If the coal is dried below its equilibrium moisture it may tend to absorb moisture from the surrounding atmosphere which can result in the generation of significant amounts of heat (heat of absorption) which can raise the temperature of the briquette to a level where it could spontaneously combust. Consequently the briquetted product must be cooled to less than 50° C. while maintaining its moisture level close to its equilibrium moisture.
The temperature of the briquetted/compacted product as discharged from the briquetting press will be slightly higher than the temperature of the incoming hot dry fine coal feed as a result of the energy expended on the briquette by the high pressure briquetting process itself. While the exposed surface area of the material in the restructured form is vastly reduced over that of the feed material which advantageously results in a reduction in the propensity for it to undergo spontaneous ignition, it has nonetheless been demonstrated that some form of post-restructuring/briquetting cooling is necessary to prevent spontaneous combustion and to make the product handleable under normal production conditions.
Simply air cooling is not satisfactory as it also results in a reduction in the residual moisture level of the product which can have an adverse effect on the product's likelihood to spontaneously combust while in stockpiles.
As is seen in
In a specific example for briquetting a sub-bituminous coal which has an inherent moisture of 25% to 30% in its raw form, the product briquette would need to have an equilibrium moisture level of around 9% to 11%. Consequently the product moisture should be 6% to 10% when cooled, preferably 7% to 9% at a temperature of less than 40° C.
The method of the present invention provides a means for forming briquettes from a large number of particulate materials. The first aspect of the present invention avoids problems associated with degassing in prior art briquetting processes. The second aspect of the present invention avoids scale up problems that have been encountered in scaling up laboratory size briquetting processes to an industrial scale. Both aspects provide binderless briquetting of particulate material.
Those skilled in the art will appreciate that the present invention may be susceptible to variations and modifications other than those specifically described. It is to be understood that the present invention encompasses all such variations and modifications that fall within its spirit and scope.
Clark, Keith Norman, Kalb, George William, Komarek, Richard, Meakins, Ross Lawrence, Pearson, Arthur Clive
| Patent | Priority | Assignee | Title |
| Patent | Priority | Assignee | Title |
| 1453988, | |||
| 2729855, | |||
| 2937080, | |||
| 3072043, | |||
| 3800428, | |||
| 4093455, | Jun 05 1975 | Midrex Corporation | Compacted, passivated metallized iron product |
| 4187079, | Sep 13 1977 | Rheinische Braunkohlenwerke AG; ESCHWEILER BERGWERKSVEREIN AG | Method for producing form coke |
| 4248603, | Sep 29 1978 | Firma Carl Still GmbH & Co. KG; Mecan Arbed S.A.R.L. | Method and tank for producing hot briquettes |
| 4249878, | May 10 1979 | K. R. Komarek, Inc. | Briquetting press |
| 4401436, | Dec 21 1981 | ARCH COAL, INC | Process for cooling particulate coal |
| 4683814, | Feb 28 1984 | Revere Copper and Brass Incorporated | Apparatus and processes for compressing and/or biodigesting material |
| 4701184, | Feb 14 1985 | PACIFIC EDGE HOLDINGS PTY LTD | Upgrading solid fuels |
| 4702745, | May 02 1985 | Kawasaki Jukogyo Kabushiki Kaisha; ELECTRIC POWER DEVELOPMENT CO , LTD | Process for dewatering high moisture, porous organic solid |
| 4810258, | Dec 03 1984 | Western Syncoal, LLC | Low rank coal or peat having impurities removed by a drying process |
| 5017124, | Oct 04 1990 | Biomass briquetter | |
| 5046265, | Dec 04 1989 | Method and system for reducing the moisture content of sub-bituminous coals and the like | |
| 5066441, | Dec 12 1980 | INNOPHOS, INC | Process for compacting a calcium phosphate composition |
| 5067968, | Feb 28 1989 | Briquette product, and process for its production | |
| 5154662, | Aug 22 1991 | Crab extractor | |
| 5160470, | May 20 1992 | Dow Corning Corporation | Method for compacting silica fume |
| 5361513, | Nov 25 1992 | Amax Coal Industries, Inc.; AMAX COAL INDUSTRIES, INC | Method and apparatus for drying and briquetting coal |
| 5518675, | May 12 1993 | York Chemical Corporation | Method for intermixing comminuted dried materials |
| 5647300, | Oct 31 1995 | First Brands Corporation | Compacted bentonite-based absorbents |
| 6375690, | Mar 17 1995 | CURATORS OF THE UNIVERSITY OF MISSOURI OF COLUMBIA, MISSOURI, THE | Process for forming coal compacts and product thereof |
| 7892302, | Feb 11 2003 | GRIFFIN COAL MINING COMPANY PTY LIMITED, THE | Briquetting process |
| 8070839, | Feb 11 2003 | Commonwealth Scientific and Industrial Research Organisation; Tra-Det Inc.; K. R. Komarek Inc.; The Griffin Coal Mining Company Pty Limited | Briquetting process |
| 20030037485, | |||
| DE3730752, | |||
| GB1545255, | |||
| GB2063298, | |||
| JP57179294, | |||
| JP5739680, | |||
| JP5821948, | |||
| JP6164327, | |||
| WO9010052, |
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| Dec 06 2013 | Commonwealth Scientific and Industrial Research Organisation | (assignment on the face of the patent) | / | |||
| Dec 06 2013 | K. R. Komarek Inc. | (assignment on the face of the patent) | / | |||
| Dec 06 2013 | The Griffin Coal Mining Company Pty Limited | (assignment on the face of the patent) | / | |||
| Dec 06 2013 | Tra-Det Inc. | (assignment on the face of the patent) | / |
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