NITRATION WITH NITRATING MIXTURES 159from the top and bottom and throws it out at a tangent. The stream of liquid
hits the cooling coil. Then the liquid flows partly upward and partly downward
between the coil, some of it being reflected by the coil.
The shape of the nitrator bottom should also be carefully selected for a given
stirring system. The efficiency of mixing with a propeller or turbine is higher when
the nitrator has a conical or spherical bottom.
FIG. 33. Diagram of a nitrator with a draw-lift turbine and a cooling
coil (circulation of the liquid content is marked with arrows).The construction of nitrators for the continuous production of nitro compounds
is somewhat different. Figure 90 (p. 374) shows a schematic diagram of one type of
continuous nitrator. Nitrators for preparing nitric esters (e.g. nitroglycerine, nitro-
cellulose) are of yet another design. New types of nitrators based on the principle of
passing two streams of reacting liquids (organic substance and nitrating acid)
through an injector, are now being introduced (Vol. II). They may bring about
a radical change in many existing designs of nitration plant.
PRODUCT SEPARATION AND DISCHARGE OF THE NITRATORWhen the reaction has been completed the nitrator contents must remain at
rest for some time to allow the product to separate from the spent acid. This maybe done in the nitrator itself or the mixture may be transferred into a special set-
tler-separator. The latter is more advantageous if the next nitration is to be carried
out in the nitrator immediately after the first reaction.
The nitrator is discharged either through an outlet located in the bottom (Fig.
34) or by forcing the contents out by means of compressed air (Fig. 35). In the
latter case the nitrator lid should fit tightly and the fume outlet should also close
tightly with a valve. If the nitrator itself has been used as a separator, the spent