Disclosed is a process system and a process for converting the sulfur-containing flue gas into the sulfuric acid. The process system comprises: a flue gas preheater, which for preheating the sulfur-containing flue gas to 15˜30° C. above its dew point, and the flue gas preheater has a glass tube as a heat exchange tube; a flue gas fan for boosting the pressure of the preheated acid process gas and transporting one part of which to a combustion furnace, and the other part of which to a process gas steam heater; a sulfuric acid steam condenser for condensing SO.sub.3 generated by the combined reactor into sulfuric acid. The device of the present invention can resist the fluctuation of SO.sub.2 concentration in the feed gas, and can realize considerable economic benefits and rational utilization of energy.

Improved systems and methods are disclosed for producing sulfur dioxide using oxygen and submerged combustion. By incorporating a vapour phase combusting step in addition to the submerged combusting step, the downstream sulfur condenser may be made substantially smaller with reduced complexity and cost. Further, energy recovery is simplified and improved.

Improved systems and methods are disclosed for producing sulfur dioxide using oxygen and submerged combustion. By incorporating a vapour phase combusting step in addition to the submerged combusting step, the downstream sulfur condenser may be made substantially smaller with reduced complexity and cost. Further, energy recovery is simplified and improved.

A process plant for production of sulfuric acid from a process gas comprising SO2, including a process gas inlet, a first SO2 converter having an inlet and an outlet, a first condenser having a gas inlet, a gas outlet and a liquid outlet, a gas mixing device having a first inlet, a second inlet and an outlet, a process gas heater having an inlet and an outlet, a second SO2 converter having an inlet and an outlet, a second condenser having a gas inlet, a gas outlet and a liquid outlet, one or more means for cooling and storage of sulfuric acid and a purified process gas outlet.

Sulfur trioxide is produced from a feed stream comprising sulfur-containing compounds and dissolved metals, such as alkali metals, in a plant comprising an incineration furnace, a waste heat boiler, a dilution air heater, a dust removal absorber and an SO.sub.2 converter. The plant may further comprise a sulfuric acid condenser for the production of sulfuric acid.

The invention relates to a continuous process for purifying a gas containing 60-99 percent SO.sub.2 (sulfur dioxide) by volume and 1 to 40 percent steam by volume, followed by synthesis of SO.sub.3 (sulfur trioxide) without first drying the gas, and to an apparatus for carrying out said method.

The invention relates to a continuous process for purifying a gas containing 60-99 percent SO.sub.2 (sulfur dioxide) by volume and 1 to 40 percent steam by volume, followed by synthesis of SO.sub.3 (sulfur trioxide) without first drying the gas, and to an apparatus for carrying out said method.

Sulfur trioxide is produced from a feed stream comprising sulfur-containing compounds and dissolved metals, such as alkali metals, in a plant comprising an incineration furnace, a waste heat boiler, a dilution air heater, a dust removal absorber and an SO.sub.2 converter. The plant may further comprise a sulfuric acid condenser for the production of sulfuric acid.

The invention relates to processes for the extraction of products from titanium-bearing minerals. In particular embodiments the invention relates to methods of recycling sulphuric acid used in a titanium dioxide extraction process. The invention also relates to methods for minimising chromophore contamination in calcined titanium dioxide. The process may also comprise steps for removing contaminants from recycled acid or desirable products.

The invention describes a process for producing sulfuric acid by catalytic oxidation of SO.sub.2 to SO.sub.3 and subsequent absorption of the SO.sub.3 in sulfuric acid, wherein the SO.sub.3 is introduced into a first absorption stage (primary absorber) and at least partly absorbed there in concentrated sulfuric acid, wherein the SO.sub.3 not absorbed in the first absorption stage is supplied to a second absorption stage (secondary absorber) for the further absorption in concentrated sulfuric acid, and wherein the sulfuric acid is cooled after passing through the two absorption stages. The cooling of the sulfuric acid is effected in at least two heat exchangers connected in parallel, wherein one of the at least two heat exchangers is operated as partial evaporator and is cooled with boiler feed water/steam and the other one is cooled with cooling water and operated as pure acid cooler.