urbaf2

386 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

a minimum. The nitro compound, separated from acid in the separator (4) (see

the diagram in Fig. 87) flows to the washing column (6,), fed with fresh water. A mix-

ture of the nitro compound and water flows off at the top of the column to the

separator (7 1 ), where the nitro compound separates from acid washings. The washings

(being the upper layer in the separator) are drained away, while the nitro compound

flows to the next column (6 2 ), fed with the water from the third separator (7 3 ). A calcu-

lated weight of alkali is added to column (6 2 ) to neutralize any acid present. The

neutralized mixture of the nitro compound and wash water flows off at the top

of column (6 2 ) to separator (7 2 ) The water separated from the nitro compound is

drained away while the nitro compound is transferred to column (6 3 ), whence it

overflows to separator (7 3 .) The nitro compound from the third separator passes

to further nitration or to a drier, while water is led to column (6 2 )

The equipment is made of stainless steel, those parts that hold alkaline or neutral

liquids may be made of carbon steel. The washing columns are equipped at the

bottom with air injectors for emulsifying the nitro compounds in water. To avoid

any hazards the plant is not equipped with mechanical stirrers.

To remove any acid present the TNT is water-washed, neutralized with a solu-

tion of sodium hydrogen carbonate, then with a solution of sodium sulphite and

finally washed several times with water.

SCHEMATIC DIAGRAM OF A PLANT FOR CONTINOUS TNT

MANUFACTURE

A schematic diagram of such a plant is shown in Fig. 100. Separate buildings are

denoted :

1. Packing department


2. Granulation


3. Sulphite washing and TNT drying


4. TNT washing


5. Nitration of nitrotoluene to di- and tri-nitrotoluene


6. Absorption


7. Concentration of sulphuric acid


8. Concentration of nitric acid


9. Preparation of washing solutions


10. Compressor house


11. Boiler house


12. Acid storage tanks for di- and tri-nitrotoluene


13. Acid storage tanks for mononitration


14. Distillation and mononitrotoluene separation plant


15. Toluene and mononitrotoluene separation tanks


16. Mononitration plant


17. Mononitrotoluene washing plant


18. Safety embankments


19. Safety walls for shielding passages.
    A schematic diagram of a plant operated by the A. B. Bofors system is shown
    in Fig. 101.