Abstract: A method is disclosed for controlling retention time in a reactor, such as an autoclave, having a plurality of compartments separated by dividers with underflow openings. A retention time of the reaction mixture is calculated and compared with an optimal retention time, and the volumes of the reaction mixture in the compartments are adjusted while maintaining the flow rate of the reaction mixture, so as to change the retention time to a value which is closer to the optimal retention time. The reactor may include a level sensor in the last compartment for generating volume data; a control valve for controlling the liquid level in the last compartment; and a controller which receives volume data from the level sensor and controls operation of the control valve.

Abstract: A method and apparatus for controlling a temperature within a reactor vessel such as an autoclave operating at elevated temperature and pressure. The apparatus includes a preheating vessel for preheating a feed material such as an aqueous slurry. The preheating vessel forms part of a preheating control system providing the primary means of temperature control within the reactor vessel. The apparatus also comprises secondary means for heating and cooling the reactor. Feed material temperature is increased or decreased by the preheating control system, based on the reactor temperature. Where the preheating control system is at or near its capacity for heating or cooling, the secondary heating or cooling means is activated to bring the reactor temperature within an optimum range.

Abstract: A method is disclosed for controlling retention time in a reactor, such as an autoclave, having a plurality of compartments separated by dividers with underflow openings. A retention time of the reaction mixture is calculated and compared with an optimal retention time, and the volumes of the reaction mixture in the compartments are adjusted while maintaining the flow rate of the reaction mixture, so as to change the retention time to a value which is closer to the optimal retention time. The reactor may include a level sensor in the last compartment for generating volume data; a control valve for controlling the liquid level in the last compartment; and a controller which receives volume data from the level sensor and controls operation of the control valve.

Abstract: A method for removing elemental sulfur from a hot gas stream, such as an autoclave vent gas, while simultaneously cooling the gas stream. The method results in conversion of sulfur in the hot gas stream to the form of solid, non-sticky sulfur allotropes such as rhombic sulfur while avoiding formation of sticky sulfur allotropes such as monoclinic sulfur, thereby avoiding scaling and fouling of plant equipment. According the method, the hot gas stream is contacted with an aqueous medium containing a particulate material inside a quench vessel having a first inlet for the hot gas stream, a second inlet for the aqueous medium, and an outlet for removing a sulfur-containing liquid fraction from the vessel. At least a portion of the sulfur contained in the hot gas stream, along with other condensable materials, becomes incorporated into the aqueous medium and is subsequently drained from the vessel.

Abstract: A method for removing elemental sulfur from a hot gas stream, such as an autoclave vent gas, while simultaneously cooling the gas stream. The method results in conversion of sulfur in the hot gas stream to the form of solid, non-sticky sulfur allotropes such as rhombic sulfur while avoiding formation of sticky sulfur allotropes such as monoclinic sulfur, thereby avoiding scaling and fouling of plant equipment. According the method, the hot gas stream is contacted with an aqueous medium containing a particulate material inside a quench vessel having a first inlet for the hot gas stream, a second inlet for the aqueous medium, and an outlet for removing a sulfur-containing liquid fraction from the vessel. At least a portion of the sulfur contained in the hot gas stream, along with other condensable materials, becomes incorporated into the aqueous medium and is subsequently drained from the vessel.

Abstract: A method and apparatus are disclosed for controlling a temperature within a reactor vessel such as an autoclave operating at elevated temperature and pressure. The apparatus includes a preheating vessel for preheating a feed material such as an aqueous slurry. The preheating vessel forms part of a preheating control system which provides the primary means of temperature control within the reactor vessel, and the reactor temperature is used as the setpoint for the preheating control system. The apparatus also comprises secondary means for heating and cooling the reactor. The feed material temperature is increased or decreased by the preheating control system, based on the reactor temperature. This is sufficient to heat or cool the reactor under most process conditions. Where the preheating control system is at or near its capacity for heating or cooling, the secondary heating or cooling means is activated to bring the reactor temperature within an optimum range.