Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
  • B03B9/00—General arrangement of separating plant, e.g. flow sheets
  • B03B9/005—General arrangement of separating plant, e.g. flow sheets specially adapted for coal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
  • B03D3/00—Differential sedimentation
  • B03D3/06—Flocculation
• • 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 OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L9/00—Treating solid fuels to improve their combustion

Definitions

• This invention relates to an improved method of preparing mined coal for its end use and in particular to the preparation of mined coal, as a feedstock for power generating stations.
• Co-pending patent application 55574/80 relates to a process of deashing coal which comprises crushing mined coal into small sized particles, subjecting said mined coal to wetting with a hydrocarbon liquid and forming agglomerates of carbonaceous material in said coal, separating said carbonaceous agglomerates from non carbonaceous material present in said coal, subjecting said carbonaceous agglomerates to vapour separation treatment in the absence of oxidizing gases to separate the hydrocarbon liquid fromsaid carbonaceous material to produce the deashed coal product and recycling said hydrocarbon liquid for use in wetting said mined coal.
• the present invention provides a method of separating an agglomerated mixture of coal particles and a liquid hydrocarbon to form finely divided coal and recover the hydrocarbon liquid which comprises disintegrating said agglomerates and subsequently and/or simultaneously subjecting agglomerates to vapourphase separation in the presence of steam and in the absence of oxidizing gases to recover the liquid hydrocarbon from the finely divided coal particles.
• all of said agglomerates are above 1mm in size, said steam temperature is above 200oC the residence time of the coal particles in the steam stripping zone is less than 5 seconds and at least 70% of the coal product comprises particles less than 0.3mm and final product oil content less than 2.5%.
• Comminution of the agglomerates prior to the vapour phase separation may be carried out in any conventional comminution device.
• the agglomerates are subjected to initial attrition to reduce the particle size of the agglomerates and subsequently passing said agglomerates into the path of a high velocity stream of steam to further reduce the coal particle size and to separate such hydrocarbon liquid into a vapour phase.
• the velocity and the internal shape of the particle entrainer may be chosen to be sufficient to disintegrate the agglomerates.
• said agglomerates are passed into a high velocity stream of steam to simultaneously separate they hydrocarbon liquid and to form the finely divided coal particles.
• the system at a commercial scale would still utilize underwater storage (tanks or ponds) of the coal-oil agglomeration stage product and the slurry reclamation and de-watering systems as specified in the prior process of 55574/80.
• This feed material would be then fed to the front end of a conveying pipe to which superheated steam would also be fed.
• An initial short section of the conveying pipe would be used to achieve disintegration of the feed and the ramainder to accomplish removal of the oil from the coal surfaces to the gas stream.
• Disengagement of the solids from the dry vapours would be achieved in a high efficiency cyclone system with the solids discharging to a storage hopper prior to independent delivery of the fuel to the burners. This then could be performed in lean or dense or phases in steam or air.
• the cyclone overhead vapours are then totally condensed, and the hydrocarbon liquids separated and returned to the agglomeration system.
• Control of the residual oil level of the particulate coal product may be achieved in this system by control of the inlet steam temperature and steam to oil mass ratio both of which strongly influence the kinetics of mass transfer of the oil from the coal surfaces. Further, the product is steam blanketed throughout the stripping and storage systems and no oxidation of the particulate material or spontaneous combustion prior to the burners need be risked.
• the present invention provides a method of preparing mined coal for use as fuel in steam generation comprising crushing mined coal into small sized particles subjecting said mined coal to wetting with a hydrocarbon liquid and forming agglomerates of carbonaceous material, separating said carbonaceous material from non carbonaceous material present in said coal and subsequently distintegrating said agglomerates and simultaneously and/or subsequently subjecting the disintegrated agglomerates to a vapour phase separation in the presence of steam and in the absence of oxidizing gases to recover said hydrocarbon liquid and form finely divided coal particles as steam generating fuel.
• a plant for preparing and delivering fuel to a steam generator comprising a storage for a slurry of crushed, mined coal, apparatus for agglomerating said coal with a hydrocarbon liquid, separation means for separating said coal agglomerates from the water phase of said slurry, comminution apparatus to disintegrate said agglomerates, means to dispense said disintegrated agglomerates into a stripper through which steam is passed at vapour phase separating conditions to vaporize said hydrocarbon liquid from said coal particles, separation apparatus to separate said coal particles and recover said hydrocarbon liquid and means to convey said coal particles to. said steam generator.
• said comminution apparatus omitted, and the velocity of steam and the internal shape of the particle entrainer which constitutes said stripper is selected to disintegrate said agglomerate.
• An example of one configuration of such a system at the pilot plant or commercial scale is shown in Figure 1.
• unstripped agglomerates are recovered from a storage pond or tank 3 and pumped to a set of dewatering screens 4.
• Dewatered agglomerates are then fed to a small hopper/ feeder 5 at the front end of the stripper and waste water is pumped out through line 6.
• Agglomerates fed to the stripping tube 7 are picked up by the conveying steam 12 and pass through an initial short length of pipe constructed internally to disintegrate the agglomerate material as it passes through.
• the remainder of the tube provides the additional residence time for oil vapourisation. Stripped solids then pass with the steam and hydrocarbon vapours to a cyclone 8 where the solids are disengaged. The overhead vapours are then totally condensed in condenser 9, hydrocarbon liquids separated with any coal fines from the water and returned to the agglomeration plant. Solids exit from the cyclone to a surge hopper 10 from which they are then air conveyed by line 13 to the burners 11 of the power generator plant.
• a sample of coal was treated to the oil agglomeration process as set out in pending application 55574/80.
• the agglomerating oil used was a light gas oil with a boiling range of 240-340oC.
• the ash content was reduced from 26% on the feed coal (DCB, dry coal basis), to 13.6% on the agglomerate (DCB).
• the particle size of the agglomerates is given in Table 1 and the particle size of the coal particles within the agglomerates is shown in Table 2.
• the oil and water contents of the agglomerates were 12.3% (total agglomerate basis - TAB) and 4.8% respectively.
• a continuous steam stripping rig was utilized in these examples.
• the rig is shown in Figure 2.
• Saturated steam generated in boiler 21 at 100 psig passes through a pressure reducing valve 22 dropping the pressure into the 0-4 psig range.
• the steam then passes into a superheater 23 and from the superheater through a jet 24 into an entrainer 25.
• Agglomerates are also fed from Hopper 27 to the entrainer 25 through a rotary valve 28. Breakdown of the agglomerates occurs under action of the steam jet within the entrainer 25 and the particles are then transported through a carrier pipe 29 of approximately lm in length within which oil is vapourized from the agglomerate surface.
• the stripped solids are separated from the steam and oil in a cyclone 30.
• the steam and oil are passed through a water cooled condenser 31 from which the oil and water can be separated as distinct liquid phases.
• the solids are passed through ball valve 32.
• the agglomerates Prior to feeding to the steam stripping unit, the agglomerates were part broken up in a rod mill and screened to a top size of 1.18 mm.
• TAB residual oil levels
• stripping model was devised which shows the effectiveness the invention at the higher steam temperatures available power stations and also treats a much lower particle size range based on complete comminution of the agglomerates.
• Development of this model for the kinetics of hydroiarbon and water removal from the product of a coal-oil agglomeration process is based primarily on consideration of that product in its disintegrated form. Exposure of the full surface area of the finely ground constituent particles provides potential for heat and mass transfer at greater rates than those obtained experimentally in the fluid bed steam stripping of the primary agglomerate product.
• hydrocarbon is present in the agglomerate as surface film on coal particles and in interpart icle bridges as shown in Figure 2,
• micropores within individual particles are water filled but that this would account for less than 2wt.% water on dry coal basis, (iii) the bulk of the water present occupies a portion of the remaining interparticle voidage not occufile by hydrocarbon.
• Evaporation of hydrocarbon from the films on coal particles and of the water droplets is accomplished by contacting the disintegrated agglomerate material with superheated steam.
• the model monitors heat and mass transfer as a function of time thus determining the rates of hydrocarbon stripping from the coal particles, water evaporation and degree of solids heating. Required mass ratios of steam to hydrocarbon and the initial degree of superheat in the steam are predicted.
• the physical system represented by the model is that of pneumatic conveying of agglomerate material in a steam atmosphere. A number of stages can be identified in the system.
• the model considers (i) and (ii) to be instantaneous and examines stripping as a function of contact time with steam i.e. operations (iii) and (iv) are included. Condensation, is not included in the model.
• the stripping model was run with the following input conditions.
• Particular size after disintegration ranged from 6 to 100 microns.

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

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Cited By (4)

Citations (7)

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• 1981
  • 1981-05-12 JP JP56501548A patent/JPS57500929A/ja active Pending
  • 1981-05-12 EP EP81901210A patent/EP0051623B1/en not_active Expired
  • 1981-05-12 WO PCT/AU1981/000055 patent/WO1981003337A1/en active IP Right Grant
  • 1981-05-13 ZA ZA00813167A patent/ZA813167B/xx unknown
  • 1981-05-13 CA CA000377518A patent/CA1158439A/en not_active Expired

Patent Citations (7)

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