Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10F—DRYING OR WORKING-UP OF PEAT
  • C10F5/00—Drying or de-watering peat
• • 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
  • C10L9/00—Treating solid fuels to improve their combustion

Definitions

• the invention relates to a process for dewatering and decarboxylating water- and carboxyl groups-containing fines of low grade fuel, in which process the fines are shaped into coherent bodies and the coherent bodies are consecutively heated to a temperature of 150-375°C in the presence of the water originally present in the said fines, at a pressure which is higher than the vapour pressure of the water and the selected temperature and the heated bodies are separated from the water.
• Solid fuel which contains more than 10% by weight, and more particularly more than 40% by weight of bound and/or unbound water (herein referred to as low-grade fuel) can suitably be subjected to thermal upgrading.
• This fuel is designated as low-grade because its weak or crumbly consistency gives it poor handleability and because the calorific value lies too far below that of normally used fuels such as hard coal or oil.
• Examples of such fuel are young coal (such as brown coal), peat, lignite, wood and carbon-containing waste (such as compost).
• Young coal for example, generally contains 40-70% by weight of water and peat contains 80-90% by weight.
• the water in said fuels occurs in a number of forms, namely as inherent or absorbed water, as a constituent in compound organic substances, as chemically bound water (for example water of crystallization) and as potentially present water, i.e. water that forms from chemically bound oxygen and hydrogen during upgrading of the fuel.
• thermal upgrading There are various ways of upgrading low-grade fuel, the most commonly used route being thermal upgrading. Examples of the various possibilities of achieving thermal upgrading include:
• An advantage of thermal upgrading in the presence of water is that the formation of gas from the fuel (largely as a result of decarboxylation) already begins at 300°C, whereas under dry conditions (at a pressure lower than the water vapour pressure at the selected temperature) the formation of gas is fairly insignificant below 400°C.
• the present invention does not relate to the above-mentioned slurry process, but to a fixed-bed process which has been known for some time and in which the fuel, not in a pumpable slurry but essentially without additional water, is heated in a fixed bed under such conditions that the driven-off water remains liquid.
• fixed bed-type processes include all processes in which a charge of solid fuel or a continuous stream of solid fuel is heated without the charge first having been converted into a pumpable slurry in water. Such processes may, for example, make use of a fixed bed, a moving bed or a fluidized bed.
• Fleissner process which essentially comprises the heating in a vessel of a quantity of fuel (see US patent specification No. 1,632,829 and Industrial and Engineering Chemistry, December 1930 (Vol. 22, No. 12, pp. 1347-1360)).
• the fuel is present in a fixed bed and is heated by passing saturated steam into the vessel, which steam partially condenses.
• the condensed steam and the water originating from the fuel percolate downwards through the fixed bed and are drained off at the bottom of the vessel.
• Said process is used on a considerable scale in practice.
• the invention relates to such a process, in which on the one hand liquid water is indeed present during the heating, but on the other hand, there is so little water that the charge to be heated is in the solid state.
• the fuel in the reactor in which the heating takes place must have as uniform as possible a particle size, which size is situated between certain limits.
• the upper limit is imposed by the requirement that the through- heat time must be sufficiently short, i.e. that the interior of the largest particles must be capable of being heated to the required temperature sufficiently fast to arrive at an economic process.
• the lower limit is imposed by the requirement that the smallest particles must not be washed out of the bed and by the fact that the proportion of inherent moisture increases with the percentage of small fuel particles (drainage from the bed deteriorates).
• the invention provides a process for upgrading fines of low grade fuel, in which process the fines are shaped into coherent bodies and the coherent bodies are consecutively heated to a temperature of 150-375°C in the presence of the water originally present in the said fines, at a pressure which is higher than the vapour pressure of the water at the selected temperature and the heated bodies are separated from the water, characterized in that the said fines have a particle size of less than 25 mm and that the said heated and separated bodies are kept at a temperature and pressure at which the water vaporizes and decarboxylation takes place, thus producing coherent bodies having a reduced content of water and of carboxyl groups.
• the decarboxylated bodies obtained by the process according to the invention have a very low water content, a very high calorific value and, surprisingly, are of a considerably reduced size, have a high strength and have good dusting properties.
• a very important advantage of the process according to the invention is that the separation of the upgraded fuel and the driven-off water is much simpler and cheaper, draining off being sufficient, and that the upgraded end product is obtained in convenient form and does not dust.
• the bodies may, for example, be obtained by extruding, by briquetting, by pressing (tablet making) and by compaction (ramming).
• a very attractive method in which the shaping of the bodies can be combined with their supply to the space in which the upgrading treatment takes place consists of supplying the fines to the upgrading space via an extrusion press or via a solids pump for overcoming high pressure.
• the pressure which is applied for the purpose of shaping the bodies depends inter alia on the type of fuel, but it is usually between 0.1 and 25 kN/cm 2 and preferably between 1 and 15 kN/ cm 2 .
• bodies having a largest dimension between 10 and 150 mm.
• such bodies give a sufficiently rapid upgrading and, on the other, they present no problem when separating the formed water from the bodies. It is preferred that during the heating of the bodies no fines are present having a particle size of less than 5 mm and preferably less than 10 mm.
• a binder can be added to the fines before the bodies are shaped.
• binders are bitumen, residual petroleum fractions, and coal tar.
• a principle known per se is advantageously applied to the present invention, namely that after the heating of the bodies and removal of the liquid water, the pressure in the upgrading space is reduced and/or the temperature is raised so that steam forms, thereby promoting the decarboxylation and facilitating the separation of fuel and water. During this second heating period under the changed conditions, the upgrading treatment is continued.
• Victoria brown coal an Australian brown coal having a water content of 53.9% by weight and a calorific value of 12.89 kj (3078 cal/g)
• a quantity of 533.8 g of tablets was heated at a temperature of 250°C for 60 min. at a pressure of 45 bar; during heating the tablets remained in contact with the separating water, which remained liquid (the water vapour pressure at 250°C is approx. 40 bar). The formed water was subsequently drained off.
• the tablets were heated for 60 min. at 360°C at a pressure of 40 bar, during which treatment all the present water and all the forming separating water was in the vapour state (the water vapour pressure at 360°C is approx. 190 bar).
• Upgrading may therefore be said to have taken place with regard to transportability (the fuel takes up considerably less space).
• the product has also been upgraded with regard to its combustion properties, since the calorific value of the fuel after the treatment was 31,82 kj (7600 cal/g) (which is more than double the original value).
• the end product therefore still represented 92.1% of the calorific capacity of the starting product, concentrated into 37% of the original volume and into 37.4% of the original weight. Upgrading may therefore most certainly be said to have taken place.
• the water content of the treated tablets was approx. 1% by weight.
• the tablets were subjected to a drop shatter test (modified ASTM D 440).
• a drop shatter test modified ASTM D 440.
• the elements to be tested are dropped a number of times in a conditioned manner and after the test the weight percentage of the fraction of small particles in the residues is analysed:
• Morwell brown coal an Australian brown coal having a water content of 61.2% by weight and a calorific value of 10.89 kj (2600 cal/g)
• wks compacted at a pressure of 5.0 kN/cm 2 to form uniform tablets (the same dimensions as in Example 1).
• the tablets were then heated at 340°C at a pressure of 156 bar for 1 min. (the vapour pressure of water at 340°C is approx. 149 bar) in the presence of some inherent moisture.
• the end product had a water content of 34.6% by weight and a calorific value of 20.77 kj (4960 cal).

Landscapes

• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Hydrogen, Water And Hydrids (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

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Family Applications (1)

Country Status (12)

Family Cites Families (6)

• 1980
  • 1980-05-02 CA CA351,160A patent/CA1127846A/en not_active Expired
  • 1980-05-14 EP EP19800200456 patent/EP0019969B1/en not_active Expired
  • 1980-05-27 YU YU142780A patent/YU40878B/xx unknown
  • 1980-05-28 ES ES491904A patent/ES8102181A1/es not_active Expired
  • 1980-05-28 PL PL22456480A patent/PL132146B1/pl unknown
  • 1980-05-28 BR BR8003335A patent/BR8003335A/pt unknown
  • 1980-05-28 AR AR28121680A patent/AR220984A1/es active
  • 1980-05-28 NZ NZ19387080A patent/NZ193870A/xx unknown
  • 1980-05-28 RO RO80101257A patent/RO82629A/ro unknown
  • 1980-05-28 TR TR2108680A patent/TR21086A/xx unknown
  • 1980-05-28 GR GR62063A patent/GR68474B/el unknown
  • 1980-05-28 AU AU58830/80A patent/AU532194B2/en not_active Ceased

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