Improvements relating to the drying and cleaning of small or fine coal,or other particulate materials,containing components of different specific gravities

摘要

971,583. Drying coal &c. HEAD, WRIGHTSON & CO. Ltd. Oct. 24, 1963 [Nov. 12, 1962], No. 42731/62. Addition to 970,643. Heading F4G. [Also in Division B2] In the apparatus and process of the parent Specification for drying and cleaning coal or other particulate material containing components of different S.G. the material is discharged from the fluidized bed or beds by overflowing therefrom at substantially the whole periphery of the bed. The modifications of the parent Specification comprise: (i) A containing wall 10, Fig. 2, adjustable in height, enclosing the periphery of the fluidized drying and de-dusting bed of material so as to provide a substantially full peripheral overflow 125 for material discharging from the bed. A launder 126 may surround the wall to receive the discharged material, which launder is subdivided by plates 127 into several compartments each having a separate outlet which may lead via a connected pipe 129 having valves (not shown) to deliver the material into a further fluidized bed of magnetite to cleanse the material. (ii) A sensing mechanism for controlling the rate of extraction of the fraction of higher S.G. together with its associated magnetite from a lower cleansing bed, comprises two sensing devices arranged in the offtake to operate either electrically or pneumatically a rotary valve in the offtake. (iii) Means for controlling the mass flow rates of the gaseous medium to the various parts of the apparatus either manually or automatically. The means may comprise: (a) A manual valve 162, Fig. 7, in supply line 4 in accordance with a rotameter 163 or the like measuring the flow rate. (b) A valve 154 in the feed line 3 automatically controlled through signals of the pressure differential existing in the bed between two spaced points e.g. tappings 147 and 148. (c) A damper (not shown) at the inlet to a low-pressure blower supplying heated air to the upper drying bed which is controlled in dependence of the gas temperature and pressure variations at the waste gas outlet of the apparatus to atmosphere. (iv) Means for controlling the temperature of the gaseous medium to maintain it above the dewpoint comprising a valve in the fuel supply line E to the furnace 31 controlled in dependence of the temperature above the bed a. (v) Utilizing two blowers or fans operating with different delivery pressures to supply different beds. (vi) Primary and secondary cyclone separators 165, 166 for removal of dust from the medium leaving the apparatus, the clean gas exhausting to atmosphere at 181 by a fan (not shown). (vii) The perforate support 2 may (a) be of generally inverted conical form composed of adjacent inner and outer sections respectively inclined to the horizontal at different angles (Figs. 11 and 12, not shown) having a slowly rotating rake for sweeping the upper surface of the support. (b) Comprises three annular surfaces inclined to the horizontal to enable particles to move under gravity (Figs. 13, 14, not shown), a central down pipe and one or more additional down pipes leading from the trough between the outer and next adjacent of the annular surfaces and having rotary paddles operative in the trough to sweep the discard product to the additional pipe or pipes. (viii) Launder fitted with a perforated bottom surface mounted about the containing wall to receive the discharged material from the overflow to which air is supplied to fluidize the bed formed on the surface. (ix) The cleaned coal and discard product from the bed (b) pass respectively to screens 21, 22 from which the undersize products pass to an elevator 196 for passage down a shoot 197 to a magnetic separator 199, the magnetic product passing to a hopper 201 for return to the bed (b). Specification 970,644 also is referred to.