GB459445A - Improvements in nitration processes - Google Patents

Abstract

<PICT:0459445/IV/1> In the manufacture of solid, including fibrous, nitro-compounds or nitric acid esters, the liquid used for the nitration or for precipitating or washing the nitrated product is separated from the solid product by using a continuously operating centrifuge in which there is no relative movement in the direction of rotation between those parts of the apparatus with which the product comes in contact during its passage therethrough. By minimizing friction, the danger of explosion is reduced. The process is applicable to continuous processes for the nitration of aromatic substances in which solid products are obtained such as m-dinitrobenzene, and o-chlornitrobenzene. It is particularly applicable to the production of explosive products such as cellulose nitrate. In an example, cotton linters, cellulose pulp, or other nitrifiable form of cellulose is subjected to nitration in any desired manner. The nitrating mixture is run off, preferably through a vessel having a stirrer, in a constant stream, the speed of which may be controlled automatically by a flap valve moved by the centrifuge. The mixture then passes into a continuously acting reciprocating centrifuge, the acid and nitrocellulose being separated continuously. The product is washed in a stabilizing vessel. The apparatus may be enclosed and maintained under reduced pressure, and the acid vapour may be conducted to a recovery plant. The process may be combined with a continuous nitration process, e.g. the passage of a paper web through the nitrating acid. As shown, the nitrated material is introduced through a pipe 4 into the dome-shaped hopper 6 of the centrifuge. The basket 1 carries a piston 3 working in a cylinder mounted on the pusher member 2 whereby the basket is caused to reciprocate. The basket and pusher member are mounted on a horizontal shaft and rotate at the same speed. During the centrifuging operation the material which collects on the inner wall of the basket is moved intermittently towards the discharge end and into the pipe 5. The process is continuous. If desired, a similar apparatus could be used in which the pusher member reciprocates instead of the basket.