Abstract: Commercial production of sulfuric acid is almost entirely accomplished nowadays using the contact process. And the trend is to increase conversion efficiency and reduce emissions of unconverted sulfur dioxide. By using a special combination of contact catalyst beds, a single contact single absorption (SCSA) system can be engineered to achieve the conversion and emission capabilities of conventional double contact double absorption systems. Thus, the complexity and cost of incorporating a second absorption tower and associated heat exchanger in the system can be omitted. In the SCSA system, the initial catalyst bed or beds comprise vanadium oxide catalyst and the last catalyst bed or beds comprise platinum catalyst operating at a much lower temperature than the initial beds.

Abstract: A contact process, sulfuric acid system and method are disclosed for producing sulphuric acid with improved operating efficiency in humid environments. The system comprises a pre-drying absorber for pre-drying humid air with weak sulfuric acid. Weak sulfuric acid from the pre-drying absorber is provided to a subsystem comprising two sulfur trioxide absorbers and a heat exchanger for the recovery of heat via steam production. This arrangement allows for a marked increase in steam production (i.e. energy efficiency). In a separate improvement, the emission apparatus for the system can be simplified using a peroxide tail gas scrubber comprising upper and lower scrubber sections in which the upper scrubber section consists essentially of tray type scrubbers.

Abstract: The invention relates to a continuous process for purifying a gas containing 60-99 percent SO2 (sulfur dioxide) by volume and 1 to 40 percent steam by volume, followed by synthesis of SO3 (sulfur trioxide) without first drying the gas, and to an apparatus for carrying out said method.

Abstract: A side stream subsystem can be used to remove impurity species from the recirculating alkali metal chloride solution in certain electrolysis systems. Silicon and/or aluminum species can be removed via precipitation after introducing an alkali metal hydroxide and magnesium chloride in a side stream line in the subsystem. The invention can allow for a substantial reduction in raw material and capital costs.

Abstract: Nanofiltration can be used to improve a hydrometallurgical process in which valuable metal is extracted from ore or tailings by leaching with a suitable lixiviant. The process requires at least two nanofiltration subsystems in which raffinate from a solvent extraction process is treated in a nanofiltration subsystem, after which permeate therefrom is combined with a pregnant solution stream and is treated in a second nanofiltration subsystem. This arrangement can lead to advantages in the amount of lixiviant recovered, in the raw materials required, in the effluent produced, in the size of plant, and in overall cost.

Abstract: Commercial production of sulfuric acid is almost entirely accomplished nowadays using the contact process. And the trend is to increase conversion efficiency and reduce emissions of unconverted sulfur dioxide. By using a special combination of contact catalyst beds, a single contact single absorption (SCSA) system can be engineered to achieve the conversion and emission capabilities of conventional double contact double absorption systems. Thus, the complexity and cost of incorporating a second absorption tower and associated heat exchanger in the system can be omitted. In the SCSA system, the initial catalyst bed or beds comprise vanadium oxide catalyst and the last catalyst bed or beds comprise platinum catalyst operating at a much lower temperature than the initial beds.

Abstract: High strength, low salt solutions of alkali hypochlorite (e.g. sodium hypochlorite) can advantageously be produced in a system comprising a subsystem in which alkali hydroxide solution and chlorine are reacted to produce alkali hypochlorite and salt solids in a crystallizer, while drawing a vacuum in the crystallizer. In a system comprising a chlor-alkali plant, the alkali hydroxide solution and chlorine can be directly obtained (i.e. without concentrating) from the electrolyzer in the plant. A net energy savings in the system can be achieved and water consumption in the chlor-alkali plant can be substantially decreased by returning chlorinated condensate from the crystallizer to the recycle line in the chlor-alkali plant. Salt can be efficiently recovered by redissolving the salt solids produced in depleted brine and returning it directly to the electrolyzer. As a result, high strength, low salt hypochlorite can be produced without the need to evaporate caustic.

Abstract: A side stream subsystem can be used to remove impurity species from the recirculating alkali metal chloride solution in certain electrolysis systems. Silicon and/or aluminum species can be removed via precipitation after introducing an alkali metal hydroxide and magnesium chloride in a side stream line in the subsystem. The invention can allow for a substantial reduction in raw material and capital costs.

Abstract: A gaseous species can be separated from an aqueous donor mixture and absorbed in an aqueous recipient mixture using a membrane separation apparatus while maintaining a large temperature difference (e.g. greater than 30° C.) between the two aqueous mixtures. A composite membrane is employed which comprises a non-porous membrane adjacent a porous membrane. The non-porous membrane is permeable to the gaseous species. The porous membrane has a porosity greater than 50% and is hydrophobic. In one embodiment, the composite membrane is oriented such that the porous membrane faces the aqueous recipient mixture and is impermeable thereto at the recipient mixture pressure. The invention is particularly suitable for separating chlorine dioxide from chlorine dioxide reaction liquor and absorbing in chilled water.

Abstract: A liquid distribution trough contained within a tower for the purpose of mass or thermal exchange between at least a first liquid and a second fluid; the trough having an upper section and a lower section; the lower section for receiving the first liquid; a horizontal dividing member separating the upper section from the lower section and having at least one dividing member portion defining an aperture to allow for passage of the liquid fluid from the lower section to the upper section; a feed conduit means in communication with the lower section to provide feed first liquid flow to the lower section; the lower section having at least one inlet portion defining a liquid inlet in communication with the feed conduit means; and a first baffle adjacent the inlet portion operably impacted by the first liquid flow and to hinder preferential flow along the walls of the trough and the dividing member. The trough and tower are of particular value in a sulphuric acid plant and a carbon dioxide capture plant.

Abstract: A side stream subsystem can be used to remove impurity species from the recirculating alkali metal chloride solution in certain electrolysis systems. Silicon and/or aluminum species can be removed via precipitation after introducing an alkali metal hydroxide and magnesium chloride in a side stream line in the subsystem. The invention can allow for a substantial reduction in raw material and capital costs.

Abstract: Nanofiltration can be used to improve a hydrometallurgical process in which valuable metal is extracted from ore or tailings by leaching with a suitable lixiviant. The process requires at least two nanofiltration sub-systems in which raffinate from a solvent extraction process is treated in a nanofiltration subsystem, after which permeate therefrom is combined with a pregnant solution stream and is treated in a second nanofiltration sub-system. This arrangement can lead to advantages in the amount of lixiviant recovered, in the raw materials required, in the effluent produced, in the size of plant, and in overall cost.

Abstract: Nanofiltration membranes have been identified that can unexpectedly provide for competitive removal of silica and sulfate from brine in alkaline conditions. Such membranes are known as monolithic nanofiltration membranes and are particularly suitable for removing silica and sulfate impurities from a brine stream in a brine electrolysis plant.

Abstract: Sodium chlorate is produced industrially via electrolysis of brine and is thus an energy intensive process. An improved cathode for this and other industrial processes is a low nickel content stainless steel whose surface has been suitably modified. With an appropriate amount of surface roughening, the cathode provides for improved overvoltages during electrolysis while still maintaining corrosion resistance.

Abstract: A process for reducing the concentration of perchlorate in an aqueous concentrated multi-component salt solution comprising treating the salt solution with an amphoteric ion-exchange resin to provide an adsorbed perchlorate and multi anion-containing resin and a perchlorate depleted solution; and removing the perchlorate depleted solution. The multi-anion are selected from chloride, chlorate, perchlorate, sulphate, and dichromate, present in electrolytic processes for the production of sodium chlorate.

Abstract: A liquid distribution trough contained within a tower for the purpose of mass or thermal exchange between at least a first liquid and a second fluid; the trough having an upper section and a lower section; the lower section for receiving the first liquid; a horizontal dividing member separating the upper section from the lower section and having at least one dividing member portion defining an aperture to allow for passage of the liquid fluid from the lower section to the upper section; a feed conduit means in communication with the lower section to provide feed first liquid flow to the lower section; the lower section having at least one inlet portion defining a liquid inlet in communication with the feed conduit means; and a first baffle adjacent the inlet portion operably impacted by the first liquid flow and to hinder preferential flow along the walls of the trough and the dividing member. The trough and tower are of particular value in a sulphuric acid plant and a carbon dioxide capture plant.

Abstract: A process for reducing the concentration of perchlorate in an aqueous concentrated multi-component salt solution comprising treating the salt solution with an amphoteric ion-exchange resin to provide an adsorbed perchlorate and multi anion-containing resin and a perchlorate depleted solution; and removing the perchlorate depleted solution. The multi-anion are selected from chloride, chlorate, perchlorate, sulphate, and dichromate, present in electrolytic processes for the production of sodium chlorate.