S F Bush
A mechanism for the wall initiation and termination of radical chains is put forward for use with models of homogeneous chlorination reactions. Some estimates of thermodynamic and rate constant values are made.
S F Bush with P A Sinclair.
This note summarises the design of new large chlorinators for a projected single stream chloromethanes plant taking 2500 M3/hr of methyl chloride and producing methylene chloride and chloroform down to a weight ratio of 0.7 to 1. This design is based on the CIRL theory of chlorination stability and is sized for operation at 45 psig (current operation 25-30 psig). The control strategy proposed is designed to be implemented by any combination of manual single loop and computer control; numerical values have still to be supplied.
S F Bush with P A Sinclair
An analysis is presented of the mixing of chlorine and methyl chloride in the dip-pipes of chlorinators of Rocksavage type. Conclusions are drawn about the length of pipe needed for adequate mixing.
See also the section on Applications to existing products and processes.
S F Bush with P A Sinclair.
A method is described which has been used at CIRL and elsewhere to solve sets of algebraic equations arising from models of chemical reactions in well-stirred flow reactors. Application has also been made to the solution of sets of 150 or more equations arising from the reaction stability models. In both classes of problem the jacobian matrix is relatively stiff. The present method is a natural extension of the approximate implicit method for solving stiff differential equations and in the chemical kinetics case is advantageously combined with the reaction models input procedure described in an earlier report.
S F Bush
Experimental studies of the terylene polymerization reaction in thin films have shown that, although the back reaction is known to occur, the overall rate of reaction appears nonetheless to vary as the square of the polymer ends concentration and inversely as the film thickness (Ref 2).
This note explains this observation in analytical terms and determines the relative importance of liquid diffusion and vapour diffusion rates in the achieved rates of polymerization. The results appear to apply to both Terylene and Nylon 6.6 polymerizations.
[1] S F Bush, M J Shires, M A L Sita-Lumsden, CIRL Research Note, 5th October 1970, “Some results from a study of the possible applications of mathematical models to the continuous terylene processes”.
[2] B R Hefford, K Porter, 11th June 1968, “Terylene fast polymerization kinetics . . .”
S F Bush with M J Shires and M A L Sita-Lumsden.
Results obtained from an examination of various aspects of the PTA process are given. These include esterification rate measurements, CP5 residence time measurements, an elucidation of the thin film results, a design of pre-polymeriser coil, a relationship between throughput, revolution speed and plate spacing in the CP5 design and an outline of a first model of the batch esterifier.
S F Bush
Also as Mond Division Report, J D Birchall, 9th March 1970.
The fundamentals of crysallisation are briefly reviewed. Industrial crystallisation operations are usually characterised (a) by the presence of impurities in the solutions, liquors etc. from which crystals grow; (b) the use of large vessels etc. in which the conditions are non-uniform and largely unknown and (c) unsteady conditions of operation due to changes in parts of the plant before and after the crystallisation unit, stoppages due to scale formation, failures etc. Impurity effects can be of paramount importance, but often these can be characterised by laboratory experiments so that the effect on product quality of changes in plant conditions can be understood qualitatively.
The most profitable research would be in refining laboratory characterisation techniques, in the development of instruments for the on-line monitoring of important crystallisation variables, in particular supersaturation and in eliminating factors that cause fluctuation in operating conditions, particularly scale formation.
Research in the general field of crystallisation has a number of functions. The solution of specific plant problems as they arise is difficult unless there exists background knowledge of the theory and of techniques and experience of past problems. Such knowledge and experience is especially valuable when new processes fail to perform as planned. If crysallisation is properly regarded as phase transformation in its broadest sense, then research in the field is vital because of much common theory in aspects as apparently remote as the crystalisation of salt, the strength of metals, the formation of bone, the properties of plastics, rain-making, ceramics, strong materials etc.
S F Bush with M J Shires.
The data enclosed is a summary of the two main alternative designs put forward by CIRL for a prototype unit to vaporise 7500 lbs/hr of adipic acid in the presence of an 8 : 1 molar ratio of ammonia to adipic acid.
S F Bush
A number of principles to be followed in the design or modification of chlorinators is given. Design is intended to facilitate both optimum start-up and steady running.
S F Bush with P A Sinclair
An important method of manufacture of 1.1.1.-trichloroethane proposed by Mond Division is the vapour-phase chlorination of 1.1.-dichloroethane made from liquid-phase hydrochlorination of VC,
CH2 = CHCl + HCl → fast → CH3.CHCl2.
For this process the organic feed is conveniently brought to a preferred reaction temperature of 400-410 oC by mixing with reacted product, the whole to run autothermally. Factors limiting design on the 25,000 tons per year scale are (a) the stability of the reaction to external disturbances, particularly flow disturbances and (b) the difficulty of ensuring that the preferred steady reaction temperature can be sustained even with no flow disturbances.
The theory and models worked out for the chloromethanes process have been applied to this proposed new process with a view to (a) predicting if a process based on a chloremethanes-type reactor would be satisfactory on the scale proposed, and (b) if so, what size should the semi-technical reactor be to give adequate experimental proof of the design and the control scheme. The intricate programming and many attendant calculations have been carried out by P A Sinclair.
This note gives an interim account of the conclusions reached in this study, which is continuing, and which has involved several recomputations from changed kinetic data.
See also the section on Development of new Products and Processes.
