The present invention relates to a process for monitoring and for controlling a nitrating process, in particular for the nitration of toluene, with the aid of a computer-assisted, matrix-specific calibration model and a process model.
Various nitration processes are known in the prior art. For example, toluene is nitrated with nitric acid to yield nitrotoluidines by way of intermediate dye products. It is also known to nitrate toluene with mixed acids to yield nitrotoluene and dinitrotoluene. Dinitrotoluene is, for example, processed further to yield diamines, diisocyanates, trinitrotoluene or phloroglucinol.
For economic reasons, the aim in the course of nitration is to conduct the nitration with as small an excess of acid as possible. To this end, it is known from the state of the art to take samples from the process manually and to examine them analytically in the laboratory. The process is then readjusted manually when required.
One disadvantage of such manual sampling and adjustment is the high cost of labor for the sampling and for the laboratory analysis. Another disadvantage is that the effort increases linearly with the number of measuring-points. Furthermore, manual sampling is problematic from the point of view of industrial safety, since, particularly in the case of 2-nitrotoluene, it is a question of working with a substance that is detrimental to health. Therefore in the course of handling 2-nitrotoluene, the wearing of respiratory protection at all times as a precaution is prescribed.
Another disadvantage of manual sampling with subsequent laboratory analysis is the fact that readjustment of the process can only be effected irregularly and after relatively long time-intervals. This may result in use of a relatively large excess of acid; the plant cannot then be operated in optimal manner, either technically or economically.