GB808609A - Improvements in or relating to process and apparatus for the continuous manufacture of nitrocellulose - Google Patents

Abstract

<PICT:0808609/IV (a)/1> <PICT:0808609/IV (a)/2> Nitrocellulose is made by continuously bringing together separate streams of cellulose and nitrating mixture with agitation in a first reaction zone to form a slurry, continuously advancing the slurry through a plurality of successive reaction zones in a continuous alternately descending and ascending stream to form nitrocellulose, continuously agitating the slurry in each descending and ascending portion of the stream to prevent segregation of solids from the slurry and continuously withdrawing a slurry of nitrocellulose in spent nitrating mixture from the final reaction zone. The motivating force employed to advance the slurry through the succession of reaction zones is preferably hydraulic gradient only, the residence time of the slurry in the nitrator being controlled primarily by adjusting the rate of introduction of the cellulose and nitrating mixture streams. In an example, a mixture containing 43.4 parts by weight of nitric acid, 36.4 of sulphuric acid and 15.6 of water is fed into reaction chamber A (Figs. 1 and 2) at 44 DEG C. through a charge means 18 provided with four spray nozzles. Simultaneously shredded wood pulp is introduced into reaction chamber A through charge port 17. Since it is desirable to wet the cellulose rapidly with the nitrating mixture to form a reaction slurry, at least part of the stream of nitrating mixture is sprayed directly on to the stream of cellulose from the spray nozzles of the charge means 18, a number of these nozzles being arranged in a circle round the incoming stream of cellulose. At least part of the nitrating mixture may be sprayed on to the upper walls of the reaction chamber A in order to wash down cellulose dust which collects on the walls above the level of the slurry. The nitrator comprises a horizontally elongated vessel 10 provided with two baffles 11 and two baffles 12 in alternate parallel-spaced relationship separating the interior of the vessel 10 into four communicating reaction zones A-D. Each baffle 11 is in contact with both sides of vessel 10 and extends vertically downward from above the level of the slurry in the vessel 10 and terminates short of the bottom of the vessel to provide underflow communication between adjacent zones. Each baffle 12 is in contact with the bottom and both sides of vessel 10 and extends vertically upward and terminates below the level of the slurry to provide overflow communication between adjacent zones. An agitator shaft 13 provided with mixing blades 14, driving means 15 and antivibration stabilizer 16 is disposed in each of the zones. The last zone D is provided with a discharge means 19 for allowing a slurry of nitrocellulose in spent nitrating mixture to overflow from the chamber. Each of the baffles 12 is adjustable in a vertical plane by means of threaded adjusting rods 25. Vessel 10 is also provided with sight glasses 21, fume exhaust pipes 22, manual access doors 23 and drain plugs 24. The agitator in chamber A is rotated at 100 r.p.m., that in chamber B at 95 r.p.m., and those in chambers C and D at 65 r.p.m. The overflow baffles 12 are adjusted to provide an overall hydraulic gradient of about 8 inches, and the residence time of slurry in the nitrator is about 18 minutes. Nitrating mixtures containing up to 75 per cent by weight of nitric acid may be used and may effect nitration in 2 minutes. The nitrating mixtures described in Specifications 781,534 and 790,470 and consisting of mixtures of nitric acid, magnesium nitrate and water may also be used, and may effect nitration in about 10 minutes. Specification 463,437, [Group IV], also is referred to.