Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L5/00—Solid fuels
  • C10L5/02—Solid fuels such as briquettes consisting mainly of carbonaceous materials of mineral or non-mineral origin
  • C10L5/06—Methods of shaping, e.g. pelletizing or briquetting
  • C10L5/10—Methods of shaping, e.g. pelletizing or briquetting with the aid of binders, e.g. pretreated binders

Definitions

• This invention concerns a coal briquetting process, and more especially it concerns a process for "cold" briquetting.
• the present invention provides a cold coal briquetting process which is a modification of that of UK Patent Application No 87/03410 (Publication No.2 187 754A), and comprises mixing fine coal with a binder comprising 5-15% sugar solution of a concentration of at least 25% by weight and up to 5% of hardening accelerator for the sugar solution, selected from iron oxide, calcium carbonate, calcium phosphate and aluminium oxide, each optionally with an acid, and p-toluene sulphonic acid, forming the mixture into briquettes, hardening the resulting green briquettes.
• a binder comprising 5-15% sugar solution of a concentration of at least 25% by weight and up to 5% of hardening accelerator for the sugar solution, selected from iron oxide, calcium carbonate, calcium phosphate and aluminium oxide, each optionally with an acid, and p-toluene sulphonic acid
• Preferred coals are high rank non-caking coals, especially those having low smoke emissions such as anthracite.
• the coal is of a particle size mainly below 3mm, and anthracite duff is especially suitable.
• the invention is also applicable to coals for power stations or steam raising and to coal blends containing caking coal components and/or treated coals e.g. by mild oxidation or by pyrolysis.
• the coal may be crushed or be the direct product of coal cutting.
• the sugar solution preferably contains 50% or more of solids, by weight. It is believed that most refined or unrefined sugars may be used, and the solution may contain other components provided these do not significantly adversely affect the physical and combustion properties of the resulting briquettes.
• the hardening agents ferric oxide, calcium carbonate, calcium phosphate, and aluminium oxide are readily available at low price in such forms as iron ore, limestone, phosphate rock and bauxite. These may be used alone or together in total amounts of 0.5 to 3%.
• Phosphoric acid or sulphuric acid may be used in amounts of up to 2% in admixture with any one or more ferric oxide, calcium carbonate and aluminium oxide.
• an organic acid, p-toluene sulphonic acid may be used in place of phosphoric or sulphuric acid, either alone or in admixture with the above accelerators. Routine testing should, of course, be carried out to ensure that any individual coal/binder mix is satisfactory.
• the briquetting step of the present invention includes all methods of forming agglomerates from fine coal, and these agglomerates may be of any size or shape according to market requirements. There may be mentioned forming agglomerates by extrusion, ringroll - or roll-pressing, die-pressing, rotary table pressing and pelletising, e.g. on a disc pelletiser.
• the process may include a self-hardening stage to permit the green briquettes to gain strength, but the briquettes tend to have inadequate water resistance.
• a hot curing step is included to speed up the hardening stage and to make the briquettes water resistant, and this may be carried out at temperatures of the order of 200 to 300°C, suitably for about half an hour or more.
• Hot curing may be conveniently carried out by passing the briquettes on a conveyor through an oven, in an inert or partially inert gas atmosphere which may contain any of nitrogen, carbon dioxide, water vapour and oxygen. It is to be noted that the hot curing step does not correspond to a carbonisation step, and thus not only are there energy savings, but the solid yield on a dry basis is very high. Additionally, there is a reduced risk of pollution.
• the release of the green briquettes from the press moulds may be improved, if desired, by prewarming the moulds and/or by sprinkling coal fines or graphite uniformly across the press surface in contact with the mix prior to and during the briquetting of the mix.
• the water resistance and appearance of the briquettes may be improved by an additional treatment with a spray or bath of a waterproofing agent.
• a spray or bath of a waterproofing agent Several agents are known or have been proposed including, for example, aluminium acetate.
• the product was admixed with 8% okf a prepared solution of unrefined molasses sugar (brown sugar) comprising 75% sugar solids and 25% water, and 1% phosphoric acid and 1% iron ore, and the mixture was formed into briquettes using a hydraulic mould-and-plunger press.
• An initial mean crushing strength of 4.5 kg was measured for the green briquettes.
• the briquettes were cured at 250°C for 11 ⁇ 2 hours under a mixture of air and nitrogen and after cooling exhibited a mean crushing strength of 87 kg, and an excellent water resistance.
• Example 1 The procedure of Example 1 was repeated, but using a commercial starch-derived glucose syrup, containing 80% of sugar solids by weight, comprising dextrose, maltose and higher sugars and 20% water, by weight. Crushing strengths of 3.5 kg and 70 kg were obtained for the green and cured briquettes, respectively, and an excellent water resistance was observed.
• Example 1 The procedure of Example 1 was repeated, but using a solution of glucose(dextrose), containing 65% sugar solids and 35% water, by weight and adding 1% phosphoric acid and 2% iron ore. Crushing strengths of 2.5 kg and 80 kg were obtained for the green and cured briquettes, respectively, and an excellent water resistance was observed.
• Example 3 The procedure of Example 3 was repeated, but using time at 250°C was reduced to half an hour. After immersion in water for one day, the crushing strength of the briquettes was 126kg.
• Example 1 The procedure of Example 1 was repeated, but using a solution of refined sugar (sucrose) containing 65% of sugar solids and 35% of water, by weight, and adding 1% p-toluene sulphuric acid alone. After curing at 250°C for half an hour, followed by immersion in water for one day, the crushing strength of the briquettes was 105kg.
• sucrose refined sugar
• p-toluene sulphuric acid 1%

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Geology (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Manufacture And Refinement Of Metals (AREA)

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Cited By (6)

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Citations (5)

• 1987
  • 1987-09-16 GB GB878721757A patent/GB8721757D0/en active Pending
• 1988
  • 1988-08-25 EP EP88307880A patent/EP0308095A1/fr not_active Withdrawn
  • 1988-08-25 GB GB8820224A patent/GB2209763B/en not_active Expired - Lifetime
  • 1988-08-29 ZA ZA886408A patent/ZA886408B/xx unknown
  • 1988-09-15 CN CN88106787A patent/CN1020747C/zh not_active Expired - Fee Related

Patent Citations (5)

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