Abstract: A process and apparatus for the recovery of metals such as silver from phosphate flue dust. The process includes the steps of blending chloride salt and the flue dust to produce a blended material, roasting the blended material in an oxygen bearing atmosphere to oxidize carbon in the blended material producing a gas and to react chloride salt with the metal in the blended material producing a water soluble metallic salt, dissolving the metallic salt in water to produce a solution, filtering the solution to remove solids, and precipitating metals from the filtered solution with the precipitate ready for conventional smelting. The preferred embodiment of the apparatus includes a flue dust hopper and mill and a salt hopper and mill for feeding the dust and salt to a radiant tube dryer and a radiant tube asher for blending and roasting the materials, and a spray chamber at the outlet of the asher for separating solids and gases, where certain of the solids go into solution.

Abstract: A carburetor with a fuel nozzle in the throat, an upstream butterfly valve, a downstream butterfly valve, a first vacuum actuator for controlling the upstream butterfly valve as a function of vacuum in the throat, and a second vacuum actuator for controlling pre-mix air supply to the fuel nozzle as a function of vacuum downstream from the downstream butterfly valve. A cold start control for disabling the second vacuum actuator for a predetermined period of time at starting to block flow of pre-mix air to the fuel nozzle, including a cold start valve with a thermal responsive bimetal and a resistance heater for timing of the cold start operation. A main fuel control valve with an idle bypass passage therethrough, and means for adjusting the rate of flow through the idle bypass passage.