Abstract: The process of producing particulate, solid, pourable and free-flowing useful materials from water-containing preparations thereof by spray-drying in a hot gas stream under normal pressure wherein the hot gas stream is superheated steam, terminating the spray-drying of the materials before they are completely dry or damaged by heat effects, and then (a) mixing the spray-dried materials with an auxiliary component which is capable of binding residual quantities of water from the materials, or (b) further drying the spray-dried materials under conditions that will not damage the materials, or (c) post-treating the spray-dried materials in a manner as to homogenize the residual moisture in the materials.

Abstract: The invention relates to a process for the recovery of heat and chemicals from a mixture of ashes and spent liquor by carrying out the final concentrating (2) of the liquor, and its feeding (8) into the soda recovery unit (5), under pressure and at a temperature higher than the atmospheric boiling point of the liquor. According to the invention, the ashes (1) are not mixed with the waste liquor (7) until after the final concentrating (2) of the liquor, and the mixture is further expansion evaporated (4) before the thus concentrated pressurized liquor is fed into the soda recovery unit (5).

Abstract: A system and method of concentrating spent caustic at a refinery has a multi-stage flash drum for separating a spent caustic stream into an overhead output stream including vaporized water and volatile organic compounds, and a concentrated spent caustic output stream. The system also has a condenser for condensing the overhead output stream, and a separator for separating the condensed overhead output stream into a volatile organic compound stream, a liquid hydrocarbon stream and a water stream. The system further has an ejector for applying a vacuum to the flash drum to vaporize the spent caustic stream at a reduced temperature, and to the separator to remove the volatile organic compound stream. The volatile organic compounds are removed from the overhead of the separator through the ejector to a burner of a fired heater.

Abstract: A high pressure evaporation vessel which is operated at a predeterminate pressure above atmospheric pressure, is connected to a low pressure expansion vessel which is operated at a predeterminate pressure below the pressure prevailing in the high pressure evaporation vessel, through a U-shaped siphon tube. The U-shaped siphon tube contains a liquid column absorbing the pressure difference existing between the high pressure evaporation vessel and the low pressure expansion vessel.

Abstract: A caustic alkali solution is concentrated to high density or high caustic alkali concentration by evaporation under high pressure at elevated temperature and expansion of the thus obtained concentrated caustic alkali solution to low pressure, preferably below atmospheric pressure. The pressure difference between the high pressure evaporator and the low pressure expansion vessel is absorbed gradually by a pressure difference absorber, preferably comprising a liquid column in a U-shaped siphon tube, so that corrosion and erosion are reduced considerably.

Abstract: A feedforward control system for a multiple-effect evaporator is provided wherein control is based on maintaining desired values for inferential variables of concentration and boiling point rise for a solution of a solid inorganic substance.

Abstract: The addition of a small amount of hydrogen or a hydrogen-liberating compound such as a metal hydride to a caustic solution serves to suppress the corrosive effect of the solution on nickel-based surfaces. Typical nickel-based surfaces include caustic evaporator surfaces which contain a caustic solution maintained at a temperature of from about 130.degree. C. to about 180.degree. C. A preferred metal hydride is sodium borohydride which is preferably present in an amount of from about 5 ppm to about 100 ppm. Concentrated caustic solutions containing less than 0.5 ppm of nickel can be prepared by this process.

Abstract: An improved cooling system is provided for hot, aqueous caustic solutions, such as received from evaporators employed for the concentration of electrolytically produced dilute caustic solutions. The improved cooling system consists of at least one closed loop circuit in which the hot caustic solution circulates under pressure and in the absence of air. The circuit includes suitable heat exchanger means, for example, a shell and tube device or other known heat transfer apparatus. The novel system not only allows the maintenance of controlled cooling rates, reduces scale formation on heat exchanger surfaces, improves caustic yield and quality due to lessening of carbonate formation but also improves the energy balance of the evaporation process.