OBTAINING DICARBOXYLIC ACID WITH DIRECT HEATING OF OFF-GAS WITH FLAME Russian patent published in 2016 - IPC C07C51/265 C07C63/26 C07C63/15 C07C63/24 C07C63/16 C07C51/44 

FIELD: chemistry.

SUBSTANCE: claimed invention relates to method for obtaining aromatic dicarboxylic acid, which includes (a) oxidation of aromatic compound in at least on oxidiser, which results in obtaining oxidised off-gas and oxidised product, containing aromatic dicarboxylic acid; (b) introduction of at least part of said oxidised off-gas into system for extraction of solvent, which results in obtaining solvent-depleted off-gas and removed solvent; (c) addition of hot combustion products into said solvent-depleted off-gas, which results in obtaining heated off-gas, containing volatile organic compound (VOC); and (d) passing, at least, part of said heated off-gas through turboexpander, in which, at least, 50 mole percent of hydrocarbyl compounds, present in said solvent-depleted off-gas, leaving said system for solvent extraction, are passed through said turboexpander. The invention also relates to method for obtaining terephthalic acid, which includes (a) oxidation of paraxylene in at least one oxidiser, which results in obtaining oxidised off-gas and oxidised product, containing terephthalic acid; (b) introduction of at least part of said oxidised off-gas into system for solvent extraction, which results in obtaining solvent-depleted off-gas and removed solvent; (c) addition of hot combustion products into said solvent-depleted off-gas, which results in obtaining heated VOC-containing off-gas, and (d) passing of at least part of said heated off-gas through turboexpander, in which at least 50 mole percent of hydrocarbyl compounds, present in said solvent-depleted off-gas, leaving said system for solvent extraction, are passed through said turboexpander, where said hot combustion products are added to said solvent-depleted off-gas in amount, sufficient for supporting said heated off-gas at temperature, which is at least 5°C higher than its local condensation temperature throughout in the process of said heated off-gas passing through said turboexpander, and where temperature of said heated off-gas is, at least, 10°C higher than temperature of said solvent-depleted off-gas, where amount of thermal energy, supplied to said solvent-depleted off-gas by said hot combustion product, is in the range 100-1000 Watt per kilogram of said aromatic compound, supplied into said installation for oxidation.

EFFECT: method relates to improved extraction of power on shaft from off-gas of xylene oxidation reaction while bringing cost of sewage water processing to minimum Larger power on shaft is obtained by application of off-gas, required for functioning primary air compressor, even with preferable relatively low oxidation temperature.

25 cl, 1 dwg