The sulphidation of alkali-cellulose

Abstract

Sulphidation of cellulose 3 3 Note: The word cellulose is often used in this paper for alkali-cellulose. If cellulose is meant as pure material this is indicated as pure cellulose. is a necessary operation in the production of rayon. The process is normally carried out in a rotating drum, filled with cellulose chips. CS 2 is fed into the drum as a liquid, which evaporates due to the heat of reaction. The reaction occurs mainly between the gas and the chips. The heat of reaction is partly removed by cooling the wall of the drum in order to keep the contents below a critical temperature of 38°C. This study consists of three parts: firstly, the rate of reaction and the heat of reaction have been measured in small-scale experiments; secondly, the heat transfer between cellulose of different degrees of sulphidation and the drum wall has been studied in small drums of various diameters; thirdly, a mathematical model has been developed to predict the conversion rate in commercial reactors, using the basic data from the small-scale experiments. The results of the design calculation match the data taken from the large industrial reactors as long as the conversions are not too high. A discrepancy between theory and experiment remains, amounting to 15 per cent of the total reaction time, due to the fact that in the very last stage of the process, in which nearly all CS 2 has been used, the transfer of CS 2 gas from the space above the filling to the bulk of the chips becomes an unknown rate-determining factor.