Abstract: The invention provides a method of producing a carbonate or a bicarbonate of an alkali metal, in solid form, from a sulphate of the alkali metal. The method includes, in a first reaction step, reacting, in aqueous medium, a sulphate of an alkali metal with one or more alkaline earth metal sulphides, thus forming an aqueous solution of one or more sulphides of the alkali metal and one or more sulphates of the alkaline earth metal in solid form. The method also includes, in a second reaction step, in the aqueous solution of one or more sulphides of the alkali metal, reacting the one or more sulphides of the alkali metal with carbon dioxide (CO2) in gaseous form, thus forming an aqueous solution of a bicarbonate of the alkali metal and gaseous hydrogen sulphide. The method further includes, in a recovery step, recovering a carbonate or the bicarbonate of the alkali metal, in solid form, from the aqueous solution of the bicarbonate of the alkali metal.

Abstract: The invention relates to control of a wind turbine to address varying drivetrain loading. This is obtained by determining a modification signal to be set as a control signal. A signal indicative of a speed of the electrical generator a signal indicative of a requested output power are received. The signal indicative of a speed is filtering to isolate frequencies in a selected disturbance frequency band to generate a disturbance signal. The disturbance signal is phase shifted and combined with a requested output power to obtain the modification signal.

Abstract: A process to treat water includes adding a salt-forming base to the water thereby producing saline water, or thereby forming a salt in the water which is different from a salt that the water started out with, if the water started out as saline. The saline water is treated, at a temperature T1 which is above the saturation temperature of the saline water, in a first membrane separation stage to provide clean water and a first brine, the salinity of the first brine being higher than the salinity of the saline water. The first brine is cooled to a temperature T2 to precipitate some of the salt from the first brine and the precipitated salt is separated from the first brine producing a second brine, the temperature T2 being below the temperature T1 but above the freezing temperature of the first brine. The second brine is treated at a temperature T3 above the saturation temperature of the second brine in a second membrane separation stage to provide clean water and a third brine.

Abstract: A water treatment process (10) includes, in a crystallisation stage (12), passing a saline water feed (16) through an elongate conduit kept in a cold environment at a temperature below the equilibrium freezing temperature of the saline water, forming a slurry of brine and ice crystals inside the conduit, and, in a separation stage (14), separating the ice crystals from a bulk of the brine, producing a brine stream (22) and an ice stream (26). The elongate conduit is of a material, or has an inner material layer in contact with the saline water and with the slurry of brine and ice crystals, with a thermal conductivity of less than 5 W/m·K and has a length configured to ensure formation of the slurry of brine and ice crystals in the conduit at the flow rate of the saline water feed through the elongate conduit.

Abstract: A process to treat water includes adding a salt-forming base to the water thereby producing saline water, or thereby forming a salt in the water which is different from a salt that the water started out with, if the water started out as saline. The saline water is treated, at a temperature T1 which is above the saturation temperature of the saline water, in a first membrane separation stage to provide clean water and a first brine, the salinity of the first brine being higher than the salinity of the saline water. The first brine is cooled to a temperature T2 to precipitate some of the salt from the first brine and the precipitated salt is separated from the first brine producing a second brine, the temperature T2 being below the temperature T1 but above the freezing temperature of the first brine. The second brine is treated at a temperature T3 above the saturation temperature of the second brine in a second membrane separation stage to provide clean water and a third brine.

Abstract: A process for treating impure water includes adding magnesium hydroxide and/or ammonium hydroxide to the water. This neutralizes the impure water and reacts with dissolved metals in the water. The metals are precipitated as metal hydroxides/oxides, which are removed from the water. Thereafter barium hydroxide is added to the water. The barium hydroxide reacts with dissolved sulphates to produce barium sulphate and, when magnesium hydroxide is used, with dissolved magnesium, to produce magnesium hydroxide. Barium sulphate and, when present, magnesium hydroxide are removed from the water. When ammonium hydroxide is used, ammonia is stripped from the water. Carbon dioxide is then added to the water. The carbon dioxide reacts with dissolved calcium in the water. The calcium is precipitated as calcium carbonate, which is removed from the water.

Abstract: A process for treating impure water includes adding magnesium hydroxide and/or ammonium hydroxide to the water. This neutralizes the impure water and reacts with dissolved metals in the water. The metals are precipitated as metal hydroxides/oxides, which are removed from the water. Thereafter barium hydroxide is added to the water. The barium hydroxide reacts with dissolved sulphates to produce barium sulphate and, when magnesium hydroxide is used, with dissolved magnesium, to produce magnesium hydroxide. Barium sulphate and, when present, magnesium hydroxide are removed from the water. When ammonium hydroxide is used, ammonia is stripped from the water. Carbon dioxide is then added to the water. The carbon dioxide reacts with dissolved calcium in the water. The calcium is precipitated as calcium carbonate, which is removed from the water.

Abstract: A method of treating water to remove fluoride ions from the water, thereby to reduce the dissolved fluoride content of the water, is provided. The method includes, in a contacting step, contacting water containing dissolved fluoride ions with alumina, to cause the fluoride ions to react with and become bound to the alumina. In a regenerating step, the alumina, when spent, is regenerated to drive off fluoride ions bound thereto. The regenerated alumina is recycled to the contacting step where it is used to remove further fluoride ions from the water. The fluoride ions driven off the alumina in the regenerating step are passed on to downstream processing thereof.

Abstract: A method of treating water to remove fluoride ions from the water, thereby to reduce the dissolved fluoride content of the water, is provided. The method includes, in a contacting step, contacting water containing dissolved fluoride ions with alumina, to cause the fluoride ions to react with and become bound to the alumina. In a regenerating step, the alumina, when spent, is regenerated to drive off fluoride ions bound thereto. The regenerated alumina is recycled to the contacting step where it is used to remove further fluoride ions from the water. The fluoride ions driven off the alumina in the regenerating step are passed on to downstream processing thereof.

Abstract: A method and installation for forming and maintaining a slurry are disclosed. The method withdraws a slurry from a reservoir and directs it at a heap of solid material from which the slurry is drained into the reservoir, the slurry containing additional solid material from the heap to increase its specific gravity. The volume of slurry in the reservoir and its specific gravity are controlled. The installation comprises a support having a support surface which slopes to permit slurry to drain therefrom A reservoir receives slurry draining from the support and has a liquid feed. A pump withdraws the slurry from the reservoir and pumps it to a spray nozzle for spraying slurry at a heap of material on the support.

Abstract: A water treatment process for raw water containing dissolved Fe2+ and H+ cations to reduce the Fe2+ cation concentration therein involves oxidation of the Fe2cations to Fe3+ cations with the formation in the water of solid Fe(OH)3 from the Fe3+ cations. The process comprises the steps of oxygenating the water and raising the pH of the water. The oxidation of the Fe2+ cations and the fromation of the Fe(OH)3 are carried out in the presence of suspended particulate material in the water, the particulate material being present in the water at a concentration of at least 5 g/l.

Abstract: A process for treating water having anions comprising sulfur and oxygen dissolved therein involves subjecting the anions to an anaerobic biological reduction to sulfide anions dissolved in the water, followed by a biological oxidation of the sulfide anions to elemental sulfur suspended in the water. The sulfur is separated from the water. The reduction and oxidation are effected together in a series of common reaction stages in which there are oxidizing conditions which permit the biological oxidation without preventing the biological reduction.