Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/1005—Forming solid beads
  • C03B19/102—Forming solid beads by blowing a gas onto a stream of molten glass or onto particulate materials, e.g. pulverising
  • C03B19/1025—Bead furnaces or burners

Definitions

• the invention relates to a method for obtaining spherical solid particles, in particular those for use as jet beads, as fillers for plastics, as reflective beads or the like.
• glass blasting beads have been used regularly for the various purposes mentioned above.
• Glass spheres of this type are produced in a separate manufacturing process using a large amount of energy and raw materials at considerable expense.
• finely ground glass powder of the desired glass type and composition is used as the raw material for the production of glass beads.
• this glass powder is precisely metered from the storage container into the hot zone of a powerful gas burner.
• the glass granules are carried along with the flame into a subsequent expansion chamber.
• the glass particles immediately melt and take on the desired spherical shape in the molten state in the entrained flow.
• the size of the resulting glass beads practically depends exclusively on the weight of the glass particle from which the beads are formed.
• conventional glass jet beads are subjected to tempering below the so-called relaxation temperature.
• surface coatings of the glass balls are provided for special applications to increase the service life.
• Post-treated glass blasting beads can be used, for example, to refine the surface structure of aircraft parts or other workpieces made of aluminum or aluminum-magnesium alloys.
• the invention is based on the object of obtaining spherical solid particles which have conventionally produced glass blasting beads of comparable quality features and possible uses, at a substantially lower cost.
• this object is achieved by melting ash in the furnace of a hard coal-fired power station and cooling melted ash particles in the entrained flow. separates cooled ash in at least one filter from the flue gas stream of the power plant, removes the separated filter ash and then subjects it to at least one sorting process for grain size, weight, surface shape and / or surface structure selection.
• the invention utilizes ashes from the power plant process as the previous residual material for the production of a high-quality and previously extremely expensive spherical abrasive product.
• Particularly good and perfectly spherical grains can be from the filter ash removed from the prefilter of an electrostatic filter.
• the filter ash should preferably be separated from the flue gas flow on the cold side of the flue gas duct, ie after an air preheater. This leaves the spherical solid particles formed in the entrained flow sufficient time to harden into the inner core of the balls.
• a melting-chamber furnace in particular a melting chamber with U-furnace, in which a particularly high proportion of intended spherical solid particles is obtained is preferably used as the furnace.
• grain size The selection according to grain size, weight, surface design and / or surface structure takes place in a predominantly conventional manner. Different grain size classes can be obtained within the filter ash, for example in the range of 0.2 to 0.3 mm preferred in practice. The grain size is selected, for example, by sieving the ash particles removed from the filter.
• the ash particles are subjected to a screening.
• a screening For example, throwing sighting can be provided.
• a roll separation by means of roller spirals is used, for example, to select the desired spherical particles with a smooth surface.
• the method according to the invention is explained in more detail below using an example which has been tried and tested in practice with reference to the drawing.
• the drawing shows: 1 shows a basic illustration of that part of a coal-fired power plant with smelting chamber firing, from the electrostatic filter of which ash is removed for the production of spherical solid particles, and schematically further treatment stages of the " fly ash " and
• Fig. 2 is a greatly enlarged illustration of some
• a melting chamber 3 is provided with a ceiling burner arrangement 4, to which a mixture of hard coal dust and carrier air is supplied via a dust line, not shown. In addition, flying dust is usually introduced into the melting chamber.
• the temperature in the melting chamber 3 is set so that the ash is melted. Liquid ash is drawn off from the melting chamber 3 via a melting chamber outlet 5 and removed as slag in a conventional manner.
• the flue gas to be used for the power plant process enters from the melting chamber 3 into a vertical boiler section 6 from below. Melted ash particles are entrained with the flue gas and cooled in the region of the boiler section 6 via radiant heat exchangers.
• a boiler section 7 which is arranged downstream of the boiler section 6 and is also arranged essentially vertically and in a falling manner, touch heating surfaces 8 ensure further cooling and use of the sensible Heat of the flue gas for the power plant process.
• the process according to the invention for the extraction of spherical solid particles is integrated in the power plant process known to this extent.
• the filter ash is removed from the lower funnel of the first or pre-filter stage 20 for the purposes of the invention.
• the solid particles have an already very uniform and different power plant parameters, including also dependent on the grain size of the hard coal fuel and the fly dust in the melting chamber. Surprisingly, they are to a very large extent of an almost optimal spherical shape.
• the term "spherical” is not limited to a purely spherical shape; Depending on the setting of the power plant process or depending on the intended application of the end product to be obtained, oval, egg-shaped beads may also be suitable or selected. In the example described here, the aim is to obtain spherical particles which are as uniform as possible and have essentially the same grain size and smooth surface structure.
• the ash particles drawn off from the removal funnel of the prefilter 20 are first sieved through one or more sieves 22 with a suitable mesh size in order to select the particles with the correct grain size.
• the thinner ash particles and the oversize particles are then separated from the desired solid particles.
• the screened ash particles of the correct grain size are then subjected to a screening process in a classifier 24, in which the spherical solid profiles are separated from light parts of the same grain size.
• a roll separation with at least one roller spiral 26.
• the desired spherical particles with a smooth surface are separated from those with a rough or uneven surface.
• the spherical solid particles obtained after the various sorting processes in the sorting devices 22, 24 and 26 are processed in a suitable aftertreatment device.
• Block 28 - subjected to an annealing process in which the spherical bodies are heated to a temperature below the relaxation temperature and then suitably cooled.
• the thermal aftertreatment can be carried out analogously to the tempering of the glass known in the production of glass -beam beads.
• FIG. 2 shows some of those ash particles on a substantially enlarged scale which were removed from the funnel 21 of the electrostatic filter stage 20 in a test carried out in practice. It has been shown that from the ash particles obtained in a certain "coal-fired power plant of the applicant in the prefilter 20, over 90% spherical beads with glass spheres are of comparable smooth surface. These spheres 30 had a yellowish color and were almost comparable to transparent with glass spheres The deformed or crystalline ash particles 32 were only obtained in comparatively small proportions in the total amount of ash removed from the prefilter 20.
• the filter pre-stage 20 already represents a sorting process with the aid of which the first selection of the solid particles takes place, in this case by separation from the flue gas stream.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Processing Of Solid Wastes (AREA)

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Cited By (3)

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Citations (3)

• 1988
  • 1988-07-05 DE DE19883822646 patent/DE3822646A1/de active Granted
• 1989
  • 1989-06-08 WO PCT/EP1989/000642 patent/WO1990000529A1/de not_active Ceased

Patent Citations (3)

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