The invention relates to an apparatus for producing CO.sub.2 pellets from CO.sub.2 snow, in particular, for a cleaning device for spraying surfaces to be treated with a mixed stream of a pressurized gas and CO.sub.2 pellets, includes a compressor device for compressing CO.sub.2 snow to form CO.sub.2 pellets. The compressor device includes a gear compressor. The gear compressor includes at least one compressor wheel which is mounted rotatable about a first rotation axis and has a plurality of compressing elements, and includes at least one intake wheel which has a plurality of snow intakes for accepting CO.sub.2 snow. The snow intakes are configured corresponding to the compressing elements. The intake wheel is mounted rotatable about a second rotation axis and cooperates with the at least one compressor wheel. The intake wheel includes an intake wheel sleeve with an intake wheel sleeve wall.

The invention pertains to a pellet mill 2 for forming pelleted material, the pellet mill 2 comprising: A die 4 having a cylindrical inner surface 6 with a plurality of apertures 8 formed therein and extending to the outside of the die 4, the volume bounded by said inner cylindrical surface 6 defining a die chamber 10. At least two cylindrical rollers 12, 14, 16 adapted to travel over said inner cylindrical surface 6 of the die 4 in a rolling motion. Drive means for causing relative rotation of the die 4 and the rollers 12, 14, 16, so that the rollers 12, 14, 16 will travel over the inner cylindrical surface 6 of the die 4, thereby forming wedge-shaped spaces 18, 20, 22 between the rollers 12, 14, 16 and the inner cylindrical surface 6 of the die 4. A feed system, comprising at least two conduits 24, 26, 28, one associated with each of the at least two rollers 12, 14, 16, extending into the die chamber 10, each of the conduits 24, 26, 28 having a side opening 32 for feeding the pelletizable material 30 into the wedge-shaped spaces 18, 20, 22 between the rollers 12, 14, 16 and the inner cylindrical surface 6 of the die 4, the side opening 32 extending axially along the conduit 24, 26, 28 and having an extension that is equal to the length of the rollers 12, 14, 16, wherein at least one of the conduits 24, 26, 28 is configured for feeding the pelletizable material 30 directly to a wedge-shaped space 22, which is at a higher location in the die chamber than said conduit 28.

A roll assembly temperature sensing system for a pellet mill includes: a thermal sensor (160); and a pellet mill roll assembly rotatably disposed in a rotor assembly. The pellet mill roll (140) assembly includes: a roll shaft; a bearing disposed circumferentially around the roll shaft; and a seal (150) disposed between an end of the bearing and the rotor assembly. The rotor assembly includes an area defining a die cavity adjacent to the seal (150). The thermal sensor (160) is disposed within the die cavity, and is configured to detect a temperature of the seal resulting from heat conducted from the bearing.