Washing of TNT

The product of trinitration was drained off to a separator, where a temperature of about 80°C was maintained by means of a steam heating coil. When the product had set in two layers the lower one, i.e. the spent acid in a quantity of about 5000 kg, was transferred to the detoluator, into which a mixture of MNT and DNT from a superdetoluator was run with simultaneous cooling and stirring. While maintaining a temperature of 75-80°C by cooling, some 240 kg of 50% nitric acid were introduced into the detoluator said after the mixture had been stirred for half sai hour it was cooled to 50°C. About 160 1. of acid water from the preliminary washing of TNT were then added. 

All three methods were designed to shorten the time of the operation and to Sff.tfduce the quantity of water used. The latter requirement was dictated by the necessity to reduce the pollution of streams and water-ways with toxic sulphite solutions. To accomplish this completely the sulphite solutions were evaporated In a quadruple-effect cvapoiater to a thick syrup, the syrup was then fired in a rotary kiln incinerator to give an ash which was harmless to fish and animal life., Thc number of water washes of TNT was also reduced. 

Hexanitrostilbene may be prepared by a dding a solution of TNT ia tetrahydrofuran and methanol at 5°C to aqueous sodium hypochlorite. To this mixture a 20% solution of trimethyl amine hydrochloride is added at 5—15°C. Hexanitrostilbene precipitates, and is filtered and washed with methanol and... 

The most recent UK Royal Ordnance Factory (ROF) continuous process for the manuf of TNT is described by Thomas (Ref 90b). It uses a novel method of achieving continuous counter-current contacting between heavy and light phases in the trinitration section and some of the washing stages . The plant is also designed to operate based on the use of 96—100% sulfuric acid in the trinitration stage instead of the oleum used at Radford TNT Purification. 

The first purification step is thorough washing of the TNT with hot water, in washing tanks or by emulsification, followed by neutralization with Na bicarbonate soln. This removes residual acids... 

Modern purification methods employ Na sulfite solns to react with the 0 and 7 -TNT isomers to form water soluble substances which can then be washed out of the desired a-TNT-However, these water washes form a blood-red soln — the bothersome red-water of TNT plants. Modern methods of disposing of red-water will be described in Section X... 

Water pollution can be mitigated by aeration of the wash streams formed in the sellite treatment of TNT. Further control can be achieved by incineration of the red water . However, the oxides of nitrogen and the Na2S04 ash thus formed can be troublesome. A recently developed scheme of converting this ash to Na2C03 and H2S, which can then be recycled to form sellite, looks promising... 

Sodium carbonate was added to a heated tank of washed TNT to neutralise excess acidity. It is known that the assym. isomer of TNT reacts with sodium carbonate to form unstable compounds, and decomposition led to a fire and detonation of 5 tonnes of explosive. 

Various soil remediation techniques such as incineration, soil washing, or biological soil treatment were applied in the past, but the microbiological degradation of TNT-contaminated soils is considered to be the most favorable technique as far as costs are concerned [414]. The following is a summary of these TNT remediation technologies ... 

Crude TNT contains isomers and nitrated phenolic compounds resulting from side reactions. The usual method of purification is to treat crude TNT with 4% sodium sulfite solution at pH 8-9, which converts the unsymmetrical trinitro compounds to sulfonic acid derivatives. These by-products are then removed by washing with an alkaline solution. Pure TNT is then washed with hot water, flaked and packed. It is important to remove the waste acid and unsymmetrical trinitrotoluenes together with any by-products of nitration as they will degrade the TNT, reduce its shelf life, increase its sensitivity and reduce its compatibility with metals and other materials. Trace amounts of unsymmetrical trinitrotoluenes and by-products will also lower the melting point of TNT. TNT can be further recrystallized from organic solvents or 62% nitric acid. 

The principal use of acet in the expl industry is as a solv such as, in the prepn of pentolite from PETN and TNT, in the purification of RDX and other expls, and as a gelatinizer for NC in the prepn of some propellants (eg cordite) (See spec, Ref 49, for Ordn use of acet). Acet is also used extensively in labs as a solv and for the washing of. glassware... 

The BurStds thermometer and other thermometers calibrated for total immersion should be used only for detn of sp of TNT by the Specification Method, while for routine tests the thermometers calibrated to partial immersion should be used. F or calibration of such thermometers proceed as follows a)Make a mark ca 5cm from the bottom of the bulb and at least lcm above the upper (small) mercury bulb on each special thermometer graduated in 0.1 or 0.05° b)Tie thermometers together in pairs (with a strip of rubber tubing) and be ready for calibration by custard cup method c)Wash and dry a Pyrex custard cup ca 2.5 in diam and ca 2.5 deep. In order to hold the cup and thermometers in place, use a wooden stand as shown in Fig... 

Centrifuging has been used extensively in chemical industries, including the manuf of expls. For example in the DuPont method of manuf of NC(See this vol of Encyclopedia, under Cellulose, Nitro Manufacture), the sepn of NC from the spent nitrating acid is done by centrifuging. Another example is the sepn of TNT crysts from "sellite soln(Na2S03 in water) and then from wash water, which will be described under Toluene, Trinitro Manufacture. It can be done by centrifugation or by vacuum. filtration using a "Nutsch ... 

Reinsdorf Explosion. The spent acid from the trinitration step in the manuf of TNT has been the cause of several disasters, although it had been considered safe to handle. The most noteworthy example of this occurred in the Reinsdorf factory in Ger in 1935. The hot spent add flowed down to open iron tanks, where, as the liq cooled, a mixt of di- and tri-nitrotoluenes rose to the surface. It was skimmed off from time to time and transferred to a washing tank, where it was washed with w. On skimming, a rubber glove and a shelf left on the edge of the tank with some cotton wool on it- fell into the tank. The reaction between the spent acid and the rubber and cotton wool initiated violent decompn and fire. An attempt to extinguish the flames failed, and soon the nitro compds on the surface of the spent acid expld. The expln... 

Since nitro compounds have certain specific properties, which influence the choice of methods for heating wastes, some special methods are described later in the technological section dealing with methods of the manufacture of individual nitro compounds. Diminishing water pollution by washes from the manufacture of TNT is a most complex problem. This will be discussed in detail on p. 390. 

During the trinitration the methyl group is oxidized to the carboxyl group. The trinitrobenzoic acids behave in different ways in the course of hot washing of crude TNT. Thus 2,4,6-trinitrobenzoic acid is readily decarboxylated and... 

The reaction mixture is run into a cooling crystallizer. TNT solidifies on the surface of the liquid, forming a crust which is stripped off aid washed with water. To the remaining acid 7% water is added, thus chaiging the solubility of TNT in the acid and causing a second batch of TNT to rise to the surface. 

Washing the TNT and preparing it for final purification. Crude, separated TNT, as described above, is transferred to a separator - a heated iron vessel, in which a temperature of 80°C or somewhat higher is maintained for about 3 hr in order to keep the product therein in a molten state. The remaining spent acid flows down to be then drawn off and added to the main portion of the spent acid. The molten TNT is transferred to a tank in which a preliminary washing (deacidification) is effected. For this purpose wooden tanks, shaped like truncated cones, are used. They are of about 20 m3 capacity and are equipped with stirrers (Fig. 78). 

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