Nitro Aromatic Compounds
TNT with its almost legendary explosive power is probably the best known of all nitro aromatic compound substances; however, it is by no means the most important. Nitration of toluene is today used primarily in the production of polyurethane, which has become much more important in recent years. Nitration of benzene results in mononitro-benzene (MNB), which is the basis of a second key input product in the chemical industry, namely aniline. Up to 95 percent of the entire global production of MNB is thus used as the primary material for isocyanates (MDI), pharmaceuticals, rubber chemicals and most of the dyes with which we are familiar.
Nitro aromatic compounds are obtained in a multi-stage, large-scale process. Mononitration takes place in the first reaction tank, and dinitration in a subsequent second tank. To ensure that the process proceeds in a controlled manner, a mixture of highly concentrated sulphuric acid and nitric acid is added to the overflow of the corresponding stages. After nitration in the reaction tanks, the liquid is pumped to a separator so that the nitrated aromatic compound can be separated from the waste acid. After the reaction mixture of the second nitration stage has been separated, the dinitro aromatic compounds are pumped to a multi-stage washing process to enable a high degree of purity to be achieved for the substances. The dinitro aromatic compounds are then recovered in a drier in the form of a crystalline substance.
Recovering nitro aromatic compounds
Excellent team right down to the smallest seal
Separators with a solid-wall bowl design, increasingly from the TTC series, are normally used to separate the nitro aromatic compound from the waste acid after the nitration process and also from water after washing. The purity of the nitro aromatic compounds obtained in this way is excellent. Separation takes place in a very small space, thereby significantly increasing the safety of the installation. Chamber-type separators of the type TKC 100 are successfully used in practical applications for cleaning the sulphuric acid.
This increases the operating lives of the separators in the nitration stages by up to 100 percent as sulphuric acid cleaned in this way significantly extends the intervals between the cleaning cycles of the solid-wall bowl machines.
With its aggressive media, the nitration process poses extremely stringent demands on separator design in the nitration stages. A challenge that GEA Westfalia Separator has successfully mastered: from the bowl and all other components that come into contact with product right through to the smallest seal, everything has been consistently designed for this process. The problem is particularly acute when processing nitrated toluene or xylene from the waste acid; special material (Incoloy 825) is used in virtually all cases where the components come into contact with product. And with liquid centripetal pumps for both phases, the separators meet the requirement for safely discharging both the acid and the organic phase under pressure.
Another popular benefit of the TTC separators is the location of the discharge drain hole on the bottom of the bowl. This prevents the operator from coming into contact with the extremely toxic organic substances.
Throughout the world, virtually all well-known manufacturers of nitro aromatic compounds use separators supplied by GEA Westfalia Separator – and most of them have been doing so for many decades. There are specific reasons why GEA Westfalia Separator has continued to be the main supplier for this application. The new TTC generation continues this story of success by meeting the customer‘s need for higher feed capacities, increasingly strict installation requirements and operator safety.
Process line for nitro aromatic compounds
- Nitro aromatic compounds (process animation)1:16 min.
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