Abstract: This invention provides for the recovery of lignin and other by-products from the pulping of fibrous plant material. In accordance with this invention, solvents and filtrates are recovered and recycled for reuse. This results in significant solvent and energy savings. Filtrates from the bleaching and delignification of the pulp are recycled for reuse in pulping, separation, and recovery of lignin and other by-products which results in significant energy savings and mitigation if not the elimination of pollution typically associated with bleaching. This invention also relates to products derived from the process and apparatus for carrying out the process. Lignins of various molecular weights and by-products of the pulping process are also recovered. The lignins are precipitated in high yields and at a high rate from a black liquor produced by pulping wood at high temperature and pressures. As a by-product of this process a purified furfural product is recovered.

Abstract: Lignin is precipitated in high yields and at high rates from a black liquor produced by pulping wood at high temperatures and pressures with an aqueous lower aliphatic alcohol solvent. The lignin is precipitated by diluting the black liquor with water and an acid to form a solution with a pH of less than about 3, an alcohol content of less than about 30% by volume and a temperature of less than about 75.degree. C. The precipitated lignin, when subsequently dried, is in the form of a powder which requires little or no crushing to convert it into a fine uniform size suitable for use without further significant processing.

Abstract: An improved distillation method and apparatus are provided for recovering hydrous ethanol from fermentation or synthetic feedstocks. Substantial energy savings are realized by utilizing a pair of stripper-rectifier towers in which overhead vapors from one tower operating at a higher pressure supply the heat required for the other tower operating at a lower pressure and by preheating the feedstock in multiple heat exchange steps. The feedstock is split into two portions of unequal size, the larger portion being supplied to the higher pressure tower and the smaller portion to the lower pressure tower.

Abstract: A process for the removal of sulfur dioxide and other contaminants and the recovery of ammonium sulfate as a by-product from a hot waste gas stream comprising cooling the waste gas stream to a temperature below 120.degree. F., passing said waste gas stream in sequence through at least two separate absorption zones utilizing as an absorbent a recirculated aqueous salt solution of ammonium sulfite-bisulfite, withdrawing and oxidizing a portion of said aqueous ammonium sulfite-bisulfite salt solution under pressures and temperatures sufficient to substantially convert the salts to sulfate salts, and recycling the ammonia and sulfur dioxide vapors liberated during oxidation to the first absorption zone.

Abstract: An improved distillation method is provided for obtaining motor fuel grade anhydrous ethanol from fermentation or synthetic feedstocks. A three tower system is used comprising a stripper-rectifier tower in which the dilute feedstock is converted to a concentrated ethanol stream, a dehydrating tower in which water is removed from the concentrated ethanol stream by azeotropic distillation, and a stripper tower for recovering the azeotropic agent. The invention effects substantial energy savings by utilizing the heat content of the overhead vapors from the stripper-rectifier tower to supply the heat required for the dehydrating and stripper towers and by preheating the feedstock in stages utilizing the heat content of the overhead vapors from the dehydrating and stripper towers, the heat content of the overhead vapors from the stripper-rectifier tower and the heat content of the bottoms from the stripper-rectifier tower.

Abstract: A crude alcohol-containing mixture comprising a saturated aliphatic alcohol of not more than three carbon atoms and associated impurities is processed in a three-tower distillation system to permit recovery of the desired alcohol product in highly concentrated and purified form. In the first tower the crude feed is subjected to extractive distillation with water to remove substantially all the impurities overhead. An aqueous bottoms stream from the first tower containing 5 to 10 wt.% alcohol and only minor amount of impurities is fed to the second tower where the alcohol product is concentrated and recovered. Overhead and intermediate purge streams containing low boiling and hgh boiling impurities are removed from the second tower and are fed to the third tower along with the overhead from the first tower. Stripped aqueous effluent is withdrawn from the bottom of the second tower and is recycled in part to the first tower.

Abstract: A process for removing sulfur dioxide and other contaminants from a hot waste gas stream in which the waste gas stream is cooled to a temperature below 100.degree.F and then passed in sequence through two separate absorption zones utilizing as the absorbent a recirculated aqueous solution of ammonium sulfite-bisulfite salts. Heat is continuously withdrawn from the recirculated salt solution in each zone. The absorbent solution in the first zone has an initial pH of from 6 to 7.2 and a salt concentration of from 1 to 20% by weight. The absorbent solution in the second zone has an initial pH of from 5.2 to 6.5 and a salt concentration, lower than said first zone of, from 0.1 to 5% by weight. The process provides for the efficient absorption and substantial removal of SO.sub.2, SO.sub.3 and particulate contaminants and for the economic recovery and use of heat from stack gases of a variety of industrial and commercial operations.