Abstract: Combustion gas recirculating system for a gas-fired furnace of the type which includes a plenum with a cold air inlet duct and a warm air exhaust duct, a combustion chamber where gas is burned to form hot combustion gases, a heat exchanger in the plenum for receiving the hot combustion gases and including an outer surface configuration past which air can flow and be heated, an outlet in the heat exchanger for the hot combustion gases, and a blower for moving air through the plenum and past the heat exchanger. A recirculation duct connects the combustion gas outlet with the cold air inlet duct and a thermostatically controlled valve regulates the flow of hot combustion gases from the combustion gas outlet to the cold air inlet duct by opening when the hot combustion gases reach a predetermined temperature and closing when the hot combustion gases are below said predetermined temperature.

Abstract: A process and apparatus for the acid hydrolysis of waste cellulose to glucose of the type wherein waste cellulose is continuously fed into an inlet port of a twin screw extruder, water is continuously fed into reaction zone in the extruder downstream of the inlet port, the cellulose is continuously reacted with water in the presence of an acid catalyst at elevated temperature and pressure in the reaction zone while continuously conveying same to an outlet port of the extruder and the reacted cellulose is discharged from the extruder the elevated temperature and pressure in the reaction zone is maintained, has the elevated pressure is maintained by forming a dynamic seal zone at the upstream end of the reaction zone by providing an unthreaded and radially recessed discontinuity in the screws.

Abstract: A vertical wall surface, providing a guide for a parallel putting stroke, is provided with an opening at the mid-point through which individual golf balls are to be ejected onto a putting surface prior to each stroke. A base, top, back and end walls enclose storage for a plurality of golf balls. A bar on the top of the device, which can be depressed by a putter, actuates a release mechanism to permit a single ball to pass through the opening in the vertical wall.