urbaf2

TNT MANUFACTURE 357

Trinitration. The nitrator is filled with DNT and nitrating mixture is added

(Table 84).

TABLE 84

TRINITRATION OF DNT

Nitration acid

HNO 3

H 2 SO 4

H 2 O

Quantity of nitrating mixture

Temperature of nitration :

on mixing reagents

after ,, ,,

Time

17.5-18.5%

81.5-82.5%

• 164% of theoretical

72-77°C

115°C

6-6½ hr

German method................................

This method known from the description of the process at the Krümmel.
factory was used by the German explosives industry during World War II. Figure 82
represents a flow diagram of the manufacture of TNT by this method.
The characteristic features of the method were:
(1) two-stage mononitration, i.e. a preliminary and a final one;
(2) use of a nitrating mixture prepared from fresh acids for mononitration;
(3) purification of MNT prior to further nitration to DNT;
(4) low temperature during the trinitration process (max. 96°C);
(5) exclusive use of iron in the plant; such units as the washing vessels for TNT
being constructed from materials other than wood.
Mononitration. For the nitration of toluene a mixture T 1 of the composition:
HNO 3 28%
H 2 SO 4 56%
H 2 O 16%
was used.

The nitrating mixture is prepared from fresh concentrated nitric acid, 55%

regenerated nitric acid (from the denitration of spent acid), and 96% sul-

phuric acid recovered by distillation. The mixture of acids is fed into the nitrator

from a metering tank through a vacuum started siphon. Toluene is conveyed to

the nitrator from another metering tank by means of compressed nitrogen. Air

is considered as too dangerous to use, because the explosibility of mixtures of

toluene vapour with air.

Plant for mononitration consists of two cast iron pre-nitrators, each having

a capacity of 0.5 m3 and a main cast iron nitrator of 15 m^3 capacity. Toluene and

acid are run into the pre-nitrators, a toluene to acid ratio of 1 : 2.5 being maintained.

The mixture is transferred to the main nitrator through an overflow in the quantity

necessary to fill the nitrator (10-12 m^3 ). A temperature of 34-40°C is maintained
in both nitrators by means of a cooling coil.