Patent GB-1431591-A (GB)
Title: Method and apparatus for making compacted pellets of solid phase carbon dioxide
IPC: C01B32/55
Filed: 1973-08-21
Abstract: 1431591 Extruding solid carbon dioxide CHEMETRON CORP 21 Aug 1973 [28 Aug 1972] 39635/73 Heading B5A [Also in Divisions F2 and F4] Carbon dioxide rods, issuing from extrusion passages 52, Figs. 2 and 3, of a roller and ring extruder, are subjected to a back pressure applied by resilient spring members 76 to prevent rupture of the rods arising from the escape of entrapped CO 2 . The orifices 52 extend radially outwardly through an annular die wall provided with an annular interior groove 115, within which a freely rotatable roller 80 engages with an orbiting motion around the groove to effect the extrusion. The die passages 52 have a 30 degree inlet taper, followed by a taper of 3 to 5 degrees. The passages 52, Fig. 7, are arranged in upper and lower rows, and as upper and lower pairs of adjacent passages in each row opening out into a respective upper, and a lower pocket 64, defined between side walls 58 projecting from the die wall, and either an upper or lower surface of a flange 66 projecting from the die wall between the side walls 58. The members 76 comprise spring steel of generally "U"-shape, with one member being provided in each pocket 64 for a pair of passages and with the upper and lower members 76 of aligned pockets 64 each being secured against the die face, about a centring pin 78, by spools 74 and washers 70 secured by bolts 72. Each arm of a member 76 is resiliently urged against a pocket side wall 58, from which it is displaced in exerting back pressure on the extrusions, which are broken off either by their own weight or by contact with an annular conical deflector (77), Fig. 1 (not shown), surrounding the die. In operation, the carbon dioxide is extruded from snow formed by the injection of CO 2  liquid from. nozzles 204 spaced at 90 degree intervals around the interior of the die wall. The injection. is effected automatically in synchronism with the orbiting of the roller 80, and in sequence from adjacent nozzle pairs, into the region B, Fig. 3, of clearance between the die wall and roller, as the injection is similarly terminated from the adjacent nozzle pairs within the region A, in which the roller 80 exerts extrusion pressure on the snow. The automatic control of the liquid CO 2  delivery to the nozzles 204 is effected from a valve 156 on the underside of the die, Figs. 2 and 5, to a chamber 168 of which valve liquid CO 2  is constantly delivered from an inlet conduit 26, via a passage through the die 42a, 148, 162, and valve inlet port 166. The liquid CO 2  is delivered to each nozzle 204, via a passage through the die 42b, 154, 200, terminating, in a valve outlet port 196 in a stationary valve seat plate 158. The ports 196 are spaced at 90 degree intervals around the plate 158, and are obturated and opened in the required sequence by a closure plate 186, comprising an approximately 180 degree segment which continuously rotates, under spring bias against the plate 158, so that the adjacent nozzle pairs sequentially inject and cease to inject the CO 2 . The closure plate 186 is rotated by a. pin connection 194 to a plate 182, keyed to a shaft 174 which is rotated, via a pin 180 and slot 172a connection, by a shaft 82 on which the roller 80 is mounted for its orbiting motion about the axis 32 of the die. CO 2  gas is vented through filters 132 into upper and lower annular chambers 122, 146 around the die, and from the upper chamber 122 at a pair of outlets 124, 126, 128, with communication of the lower chamber 146 with the upper being provided by radial passages 42c and vertical passages 42. The filters 132 comprise stainless steel of 0À31 inch thickness having 0À30 inch diameter perforations, and comprise radially extending "V"- shaped corrugations of 45 degree angle and which enlarge in the outward radial direction. The filtering effect is enhanced by a layer of CO 2  snow which forms between the filters and the side edges of the roller 80.