Patent GB-995124-A (GB)
Title: Combined heat interchanger and electrostatic precipitator
IPC: F23J1/00
Filed: 1964-04-09
Abstract: 995,124. Thermal regenerators. AEROTEC INDUSTRIES Inc. April 9, 1964 [April 18, 1963], No. 14704/64. Heading F4K. [Also in Division B2] A combined heat interchanger and electrostatic precipitator, e.g. for removing dust from furnace exhaust gases and heating incoming air in a powdered fuel power plant, comprises an ionizing unit 10, 11, 12 or 13, with ionizing electrodes 14 and grounded electrodes 15, and a unit 16, 17, 18 or 19 containing a bed of granular material 21 of low electrical conductivity in contact with an electrode 26 setting up a voltage gradient across the material, so that charged dust particles are deposited on the material, and the material also acts as a thermal regenerator. In Fig. 1, a system of dampers, e.g. 27a, 28a, 33a, 39a, are arranged so that exhaust gases from the furnace, after passing through the ionizing units 10-13, pass through alternate units 16, 18, where dust is deposited, and the material becomes hot. The gases then pass to the stack (arrows 32, 46). Incoming air (arrows 38, 42), passes through previously heated units 17, 19, to the furnace through passages 40, 44. At predetermined intervals of, say, one minute, all dampers are changed over, so that the exhaust gases pass through cooled units 17, 19 and the incoming air through the heated units 16, 18. A control device may delay the changeover until the temperature of the outgoing gases is above the dew point, to prevent moisture being trapped in the system to prevent dilution of incoming air by exhaust gases remaining in the units 16-19 at changeover, dampers such as 27a, 30a, may be changed over slightly before dampers such as 33a, so that air is flushed backwards through unit 17 to the stack. Dampers such as 48 permit an ionizing unit to be shut off, and dust removed by rapping. The material 21 may be limestone, to absorb acid from the exhaust gases, or ceramic. It is discharged periodically by gravity into a hopper, cleaned, and returned to a feed hopper for re-filling units 16-19, limestone being replaced when necessary. In another embodiment, Fig. 8, the precipitating units 58A-60A are in two side-by-side tiers (one shown), one tier acting as a precipitator and being heated, while the other tier heats incoming air, with the change-over controlled by dampers. To clean the units, inlet and outlet dampers 68, 69 are closed, and high velocity air admitted by door 63A, leaving by door 64A. Normally open doors 81-86 are closed, being opened in sequence one by one, so that all the cleaning air passes upwards through each half of a unit in turn, agitating the material and removing the dust. To prevent premature discharge of the charge on the dust particles before reaching the precipitator units, the width of the ducts downstream of the ionizer units should be at most slightly greater than the distance between grounded electrodes in the ionizer, and no grounded surface should have a small radius of curvature. Thus the ducts may be subdivided, appropriate parts of the dividing walls being attached to the dampers, and grounded rods are placed where this is not possible, so that no point within the ducts is too far from a grounded surface.