GB688421A - Improvements in or relating to pebble heater apparatus - Google Patents

Abstract

Pebble-heating chambers furnishing heat for the treatment of gases which are passed in direct contact through catalytic or other hot pebbles are provided with means for regulating the pebble flow through the chamber to equalize the pebble-gas contact time. According to the invention, a shell or chamber 11 lined with refractory material 12 is designed to promote the flow of pebbles from inlet 13 to outlet 19, without causing a central conical cavity, by providing an imperforate baffle 22 over the pebble outlet, the baffle being situated between inverted cones representing the angles of pebble-repose and pebble- <PICT:0688421/III/1> <PICT:0688421/III/2> slip which have their common apex at the pebble outlet. Further, the diameter of the baffle is between 1/4 and 5/8 that of the pebble chamber and its outer periphery is situated inside and at least eight pebble diameters from the cone of pebble-repose and outside the cone of pebble-slip. In the form shown in Fig. 1, the apparatus comprises a vertically-disposed closed shell 11 having an upper pebble-inlet zone with a perforated baffle 15 and conduit 16, an intermediate heat-exchange zone above a perforated pebble-supporting dome 17, and a lower zone 25 fed from a combustion gas inlet 24. The gas after heating the pebbles passes to an outlet 14. Disposed above a pebble-outlet conduit 19 extending through the centre of the dome is an imperforate baffle 22 supported above the dome by open bars 23 at such a distance that the baffle is within the inverted cone of pebble-repose (inclined at 30 degrees to 45 degrees to the horizontal plane) and outside the inverted cone of pebble-slip (inclined at 60 degrees to 75 degrees to the horizontal plane). The vertical walls of the pebble chamber 11 are lined with common refractory material such as fire brick and superrefractory material such as silicon carbide, mullite, or alumina to withstand temperatures of 3000 DEG F. The pebbles from 1/8 to 1 inch in diameter are formed of solid refractory material such as silicon carbide, alumina, periclase, beryllia, stellite zirconia and mullite and they may either be inert or catalytic. Two or more chambers 11, Fig. 3, may be superposed, an elevator 27 being provided for raising the pebbles from the outlet of the lowest to the inlet of the highest chamber. In the lower chamber 11 the pebbles may contact with gaseous reactant materials and furnish heat for the treatment or conversion of the gases. In a modification, Fig. 6 (not shown), the flow of pebbles through the centre of the chamber is prevented by a hollow core supported by the imperforate baffle 22. In a further modification Fig. 7, (not shown), the perforate dome 17 is omitted, the imperforate baffle 22 being situated adjacent the gas chamber at the base of the shell. The pebble-inlet in this case comprises a pipe with branches spread outwardly in place of the perforated conical baffle. Specification 688,422, [Group XII], is referred to.