GB548873A - Improvements in or relating to tubulous boiler plant - Google Patents

Abstract

548,873. Cellulose. BABCOCK & WILCOX, Ltd. April 24, 1941, No: 5320. Convention date, July 27, 1940. [Class 2 (ii)] [Also in Groups XII, XI and XIII] The Specification as open to inspection under Sect. 91 describes a cyclic process, which is disclosed in U.S.A. Specifications 2,285,876 and 2,238,456, for the treatment of cellulosic fibrous material by the sulphite process and for the recovery of products for conversion to magnesium bisulphite for reuse. Fibrous material is fed into a digester 10, Fig. 1 (Cancelled), mixed with magnesium bisulphite and circulated through a steam heater 208. When the cooking operation has been completed the digester is discharged into a tank 12 and the pulp and liquid are then pumped to filters 13, 14, the filtrate from which passes to tanks 16, 17. The liquor from the tank 17 is fed to a wash tower 18 where it contacts with hot gases from a furnace 50 in which concentrated residual liquors are burnt, and the liquor from the tank 17 is thus freed from sulphur dioxide, which passes on with the gases to absorption towers 28, 29. The residual liquor is pumped from tower 18 to a tank 19, where it is neutralized by the addition of magnesium oxide and then passes to a tank 20, evaporators 21 and tank 23, from which it is fed to the boiler furnace 50. Ashes carried from the furnace by the furnace gases and containing magnesium oxide are led to cyclone separators 25 and'then pass to a storage tank 26 and. to a tank 30 where they are mixed with liquor from tank 16 and then supplied to the absorption towers 28, 29. During its passage through the towers the magnesium oxide in suspension combines with the sulphur dioxide in the gases to form magnesium sulphite and bisulphite in solution, which is pumped through a cooler 34 to a filter 40 and thence to a system 43 for absorbing sulphur dioxide from sulphur burners 41. The fortified liquor then passes to a tank 44 and digester acid tank 11. This subject-matter does not appear in the Specification as accepted.