Field of the Invention
The invention relates to a process for production of Diethyleneglycol Dinitrate (DEGDN). In particular, the invention relates to a process for production of a low moisture content DEGDN.
Background of the invention
Diethylene glycol dinitrate (DEGDN) is a nitrated alcohol ester produced by the action of concentrated nitric acid. Usually a mixed acid comprising concentrated nitirc acid and strong sulfuric acid are used for nitration of diethylene glycol (DEG) to produce DEGDN.
W. H. Rinkenbach, Industrial Engineering Chemistry vl9 p925 (1927) discloses that Diethylene glycol dinitrate is a colorless, odorless, viscous, oily liquid, with specific gravity of 1.4092 at 0°C and 1.3846 at 20°C. Its freezing point is -11.5°C under a standard atmosphere. The theoretical boiling point of approximately 197°C is difficult to confirm as the compound begins to decompose and spontaneously inflames at or slightly below this temperature. It is readily miscible in most non-polar solvents, methanol, and cold acetic acid. Solubility in water (4.1 gm/L at 24 °C) and ethanol is very low. While chemically similar to a number of powerful high explosives, pure diethylene glycol dinitrate is extremely hard to initiate and does not propagate a detonation wave. It inflames only with difficulty (requiring localized heating to decomposition point) unless first atomized, and bums placidly even in quantity.
Mixed with nitrocellulose and extruded under pressure, diethylene glycol dinitrate forms a tough colloid whose characteristics (good specific impulse, moderate bum rate and temperature, great resistance to accidental ignition and casual handling) make it well suited as a solid propellant for rocketry. It was widely used in this capacity, by both sides, during World War II. It also found use as a "productive" desensitizer (one that contributes to the overall power of the explosion rather than having a neutral or negative effect) in nitroglycerine and nitroglycol based explosives such as dynamite and blasting gelatin. It is also used as plasticizer for energetic materials.
US Patent No. 4,251,455 to Gebauer discloses a process for the continuous manufacture of a nitric acid ester of a polyhydric alcohol by reacting the polyhydric alcohol with nitrating acid. This patent addresses the problem of storage of less stable waste acids, that are obtained during the manufacture of dinitrodiglycol. Such disadvantage is avoided by nitrating polyhydric alcohol in a closed cycle from fortified waste acid. This cycle has a preferred residence time of less than about 15 minutes, preferably about 2 to 5 minutes.
US Patent No. 4,352,699 also addresses the problem of unstable spent acid obtained during the process of nitrating diethylene glycol. This patent discloses that diethylene glycol and trimethylolethane can be co-nitrated and a storage stable spent acid obtained if one employs during the nitration an excess of from about 60 to about 100% by weight of nitric acid over that stoichiometrically required for the nitration.
The processes disclosed in the prior arts are concerned with the problems of safety in the process of nitration of diethylene glycol. However, the prior arts have not discussed the quality of the final product achieved. None of the prior arts has discussed about the effect of presence of moisture in DEGDN.
Object of the Invention
The object of the invention is to provide a continuous/ batch process for the manufacture of DEGDN that is safe and fast, and enhances the quality and stability of the product.
In another objective of the invention, the DEGDN produced according the process of the present invention contained Not More Than (NMT) 0.12 % moisture, which resulted in to enhancement in the efficacy of the product.
Further objective of the invention is to provide an automatic continuous manufacturing process of DEGDN is achieved, for the large scale commercial production of DEGDN, by use of fully automatic remote controlled continuous running plant, equipped with several built in safety parameters. Further improvement in the quality of DEGDN achieved by minimization of moisture contents in the ready for use final product with out compromising the safety parameters.
Summary of the Invention
A process for manufacturing diethyleneglycol dinitrate (DEGDN) comprises:
(i) nitrating diethylene glycol (DEG) with a mixed acid in a nitrator to form
DEGDN and spent acid, (ii) separating the DEGDN from spent acid in a separator, (iii) neutralizing the DEGDN with soda solution in a washing tank, (iv) washing the neutralized DEGDN with water in a washing tank to remove
impurities, (v) optionally adjusting the pH of DEGDN to neutral using soda solution, (vi) separating the DEGDN from water in a separator, (vii) storing the DEGDN in a storage tank containing water, and (viii) transferring said DEGDN to a drying vessel for drying the DEGDN by adding
anhydrous calcium chloride (fused) in an amount of 8-12% by weight to
DEGDN and leaving for 8-12 hours to reduce the moisture content of
DEGDN to 0.12%.
A process for drying DEGDN comprises:
(i) transferring the manufactured DEGDN carefully into a Stainless Steel bucket,
(ii) weighing the bucket as W1, and transferring the contents into a SS bowl with lid,
(iii) re-weighing the bucket to calculate the transferred product to the bowl,
(iv) repeating the steps (i) to (iii), if required,
(v) calculating the total transferred quantity of DEGDN into the bowl,
(vi) calculating the quantity of anhydrous calcium chloride @ 10% of the DEGDN taken in the bowl,
(vii) transferring this weighed calcium chloride in to the bowl slowly, to avoid any spurting / spillage of the product, covering the bowl with lid, and stirring the contents with wooden /Teflon stick occasionally, while keeping the bowl covered with lid otherwise,
(viii) resting the contents for 8 to 12 hours and transferring the total contents into another bowl by passing through Mesh #100 sieves to obtain the dried DEGDN product, eliminating the particles of calcium chloride in the product.
Detailed Description of the Invention
The invention will now be described with reference to the accompanying drawing which is a flow sheet of the process.
Mixed acid of HNO3 & H2SO4, in the ratio 60:40 is taken in a tank T1 and diethylene glycol (DEG) is taken in a tank T2. Both, the mixed acid and diethylene glycol are pumped in the ratio 2.5:1 into a nitrator tank T3. The rate of flow of mixed acid and diethylene glycol from tank T1 and T2 into a nitrator tank T3 is maintained in such a way that the temperature during reaction in the nitrator tank T3 is maintained at below 15°C. The nitrator tank is provided with a coil (C) for circulation of brine solution comprising of 25-35% sodium nitrate, 0.5-1.5% sodium bicarbonate and 0.25-0.75%) bisulphate for cooling and maintaining the temperature below 15°C in the nitrator tank T3. A stirrer is also provided into the nitrator to facilitate the reaction between mixed acid and DEG. The nitration time is between 8-20 minutes. During this period the reaction between the mixed acid and DEG in the nitrator forms DEGDN and spent acid in the form of emulsion. Said emulsion is overflown from nitrator tank T3 to a separator tank T4. Since spent acid is heavy it settles down at the bottom of separator tank T4 and DEGDN being lighter floats on the surface of the spent acid. Acidic DEGDN is overflown to a soda water tank T5 containing 12-14% soda solution or the spent acid from outside is pumped from the bottom of separator tank T4 to enable the acidic DEGDN to overflow from the top of the separator tank T4 to soda water tank T5 containing 12-14% soda solution to neutralize the acid. During neutralization the NaNO3 and Na2SO4 are formed and removed as waste. The DEGDN is pumped to washing tank T6 where the DEGDN is washed with water with the appropriate pH. There after the DEGDN is transferred to storage tank T8. The total time for neutralization, washing and pH adjustment steps in tanks T5 and T6 varies between 1.0-1.5 hrs. The stored DEGDN in tank T8 is dried with 8-12% of CaCl2 for 8-12 hrs. to reduce the moisture content of the DEGDN to less than 0.12% in a Stainless Steel Bowl/tank T9. The dried DEGDN so obtained is stable and quality product.
Detail process of Drying DEGDN
Transfer the manufactured DEGDN carefully in to SS bucket. Weigh the bucket as Wl. Transfer the contents in to a SS bowl with lid. Reweigh the bucket to calculate the transferred
product to the bowl. Repeat the process, if required. Calculate the total transferred quantity of DEGDN into the bowl.
Calculate the quantity of anhydrous calcium chloride @ 10% of the DEGDN taken in the bowl. Transfer this weighed calcium chloride in to the bowl (drying vessel) slowly, to avoid any spurting / spillage of the product. Cover the bowl with lid. Stir the contents with wooden /Teflon stick occasionally, while keeping the bowl covered with lid otherwise. Rest the contents for 8 hours and transfer the total contents into another bowl by passing through Mesh #100 sieves to avoid the particles of calcium chloride in the dried product.
Weigh either the calcium chloride retained on the mesh in bowl or the dried product, to estimate the loss during drying process.
The details of various initial experiments carried out to arrive at an optimum situation is listed as under
Moisture analysis in DEGDN at Lab scale
Initial Moisture before addition of anhydrous Calcium Chloride = 0.64 %
(Table Removed)
Moisture analysis in DEGDN at Plant scale
Initial Moisture before addition of anhydrous Calcium Chloride = 0.62 %
Quantity of DEGDN taken = 45 kg
Quantity of Calcium Chloride taken = 4.5 kg
Moisture contents after One hour = 0.40%
Moisture contents after Two hour = 0.25%
Moisture contents after Four = 0.18%
Moisture contents after Six hour = 0.15%
Moisture contents after Eight hour = 0.12%
De sensitization of DEGDN for safe transportation
Transfer dried DEGDN and ethyl acetate in the ration of 65:35 in to a SS mixing bowl and mix the contents for 10 minutes. Transfer the mixed contents in to narrow mouth aluminum container. Close the container with closure system so as it becomes air tight. The aluminum containers may further be placed in foam lined wooden box to avoid damage to the aluminum containers during transportation.
Table 1 Table 1 illustrates the details of DEGDN produced by the process of the present invention
(Table Removed)
It does not include drying steps.
Illustration of the various steps of the process for preparing DEGDN
Nitration:
The nitrator (T3) is composed of a SS vessel, equipped with a mechanical stirrer and cooling coils for the removal of reaction heat. The temperature is maintained constant by a thermostatic system. The stirring (S) is realized by means of a turbine wheel placed at the bottom of the nitrator shell, with the coils (C) disposed in such a way, so as to obtain the action of a centrifugal pump.
The raw materials (DEG and Mixed acid) are introduced from the top of nitrator (T3) along the shaft of the stirrer (S). They are drawn towards the bottom of the turbine (S), where they are instantaneously mixed together. The centrifugal force of the wheel hurls the emulsified liquid towards the wall of the nitrator (T3). The emulsion slowly rises in spiral movement; part of it leaves the nitrator from an overflow, while the rest is again drawn to the centre of the nitrator and on to the turbine.
The action of the turbine wheel can be illustrated in the following way, the reaction fall on a disc rapidly rotated in a horizontal plane. Under the effect of centrifugal force, the liquids are spread out in extremely thin layers, which forms a very fine emulsion of uniform sized droplets. The reaction will then have the same duration for all of them.
As the liquid motion is quite regular (also due to the presence of baffles welded inside the vessel) the particles are obliged to follow the long circular path from the bottom to the top of the vessel. The permanence in the nitrator is uniform for the great majority of the molecules and by choosing a nitrator of approximate dimension, the permanence can be set at the minimum necessary for the complete termination of the reaction.
Declared Capacity = 210 liters Useful capacity = 180 liters
Cooling System
The removal of heat in the nitartor is done by a series of several sets of SS spiral coils (C) in parallel, which occupy the greater part of the vessel (T3) and through which the cooling medium circulates. The centre of the nitrator is left free for the descent of the reactants.
The heat exchange coefficient obtained is extremely high. It usually exceeds 700 k cal per hour per m per degree centigrade. This allows the use of brine at a much higher temperature (-2°C) than with other nitrating systems, with practically no danger of un stability of DEGDN in the nitrator, as a matter of fact, water at 14 degree-centigrade can be employed as a cooling
agent.
The cooling surface of the nitrator, is 0.05 m2 per liter of useful capacity, its useful capacity is approx. 180 liters for 600 kg of DEGDN produced per hour, during the operation, the same nitrator contains approx 100 kg of formed DEGDN or during course of formation.
As a cooling agent (Brine solution) 25-35% sodium nitrate solution to which are also added about 1% of sodium bicarbonate and 0.5% sodium biphosphate. This solution does not corrode the SS cooling coils, the iron pipes does not leave a scale in the pipelines and in case of leak in the cooling coil does not react with mixed acid. The cooling of nitrator is automatically adjusted by means of 3 way pneumatic controlled valve, which modifies the brine flow through the coils in order to maintain the nitration temperature constant. This directly sends back the brine surplus in order to keep the flow from cooling unit to the refrigerating plant constant
Drowning system (Safety) (not shown for the sake of simplicity)
In case of danger, the nitrator charge can be drowned by remote control or it is automatically drowned by the safety system in to a large drowning tank filled with water.
For the emergency drowning, the nitrator is provided with a large bottom opening, closed with a shutter held in place by a spring. The spring may be released by hand or by means of compressed air.
The drowning orifice is not at the centre but on the side of nitrator bottom, the reason is that the suction produced by the turbine wheal on the centre of vessel is so strong that it could not be entirely emptied, while the opposite effect manifest itself towards the rim and the liquid is pushed out of the orifice.
The diameter of the orifice is large enough to drown the charge in about 10 seconds. A more rapid discharge may be dangerous on account of excessive heating caused by the blunt
contact of the acid with the mass of water in the drowning tank.
Separation
In continuous separator (T4) of DEGDN where the emulsion is introduced tangentially in correspondence with the middle layer of emulsion so as to obtain the movement of this layer only. It is thus possible to obtain considerable increase in the clashing of the small drops and an increase in the intake intensity of the same, compare with separation by simple rest, thus overcoming the surface tension and /or the resistance opposed to the superficial layer by the impurities which surrounding the drop of DEGDN.
To keep the emulsion in a slight movement presents also the advantage, in case of the separation of the DEGDN from the spent acid, of avoiding dangerous local rises of temperature, which are well known causes of the decomposition or of explosion.
The shape of the separator (T4) has been particularly studied a stream -lined, resistance -free flow of the fluids. The interior of the separator is empty, in contrast to other continuous separator. Its internal valve has a highly polished surface and there is no pocket or dead comer where any drop of DEGDN may remain stagnant. Sight glass (not shown) is placed at the convenient places for control. Temperature probes at various heights indicate the temperature of different layers. There is one drowning system of the nitrator, and the two phases (DEGDN and spent acid) are drowned in the same drowning tank.
Dilution of spent acid
In order to avoid in the long run, an after separation of DEGDN in the storage tank, the spent acid as usually diluted just after leaving the separator (T4), to 1-3 % according to outside temperature (with 60% nitric acid) according to solubility of DEGDN in spent acid increases with increasing water contents.
The addition of the water to spent acid takes place in the pipe leaving the spent acid separator variable overflow valve (not shown).
In order to ensure a complete solution of the DEGDN (even if a considerable quantity of it should be carried away with the acid), the diluted acid flow continuously to vessel equipped
with stirrer and cooling coil called spent acid diluter.
The spent acid dilution is carried out continuously and automatically by means of proportional system, it is in fact the opening of the spent acid variable overflow valve, which controls the opening of the diluting water feeding valve.
The temperature inside the spent acid diluter is automatically controlled and in case of temperature increase the cooling water valve opens.
Washing
The acidic DEGDN containing about 5-7 % Nitric acid and a small amount of sulphuric acid flow from the top over flow of the semi static separator (T4) through a series of three washer (T5, T6, T7) where it washes directly under stirring with a 12-14% soda solution.
The acid is neutralized (in T5) forming nitrates, sulphates and CO2.
The quantity of soda water to be added depends on the quantity of nitric acid dissolved in the DEGDN, which in turn is related to the spent acid composition. A slight excess of soda will take care of possible surplus of nitric acid.
In any case the soda solution flow is automatically controlled by a pH meter installed at the outlet of the first washer (T5).
The washer consists of vessels with high speed stirrers (S) which produces a very fine and non detonating emulsion.
In normal operating conditions, the neutralization heat evolved in the first washer is such that the temperature does not exceed the 35 degree centigrade. This is an appropriate temperature for the washing conditions. In case of overheating (over 40 degree centigrade) the first washer is equipped with a double jacket and the heat excess is removed by means of cold water. In order to cut down the soda water consumption, and in order that complete neutralization will always be ensured, a control system, based on the pH value of the effluent water, has been designed, which gives a steady record of the alkalinity, an automatically stops the transfer of DEGDN to storage. In this respect a pH meter is installed at the outlet of
last washer and automatically stops the DEGDN transfer to the storage if the pH value is lower than the set limit.
From the last washer, DEGDN / Water emulsion flows in to an another semi static separator, where the DEGDN separated from its wash water and sent by means of water injector to the storage /catch tank (T8) for storage. From the storage tank, the desired amount of DEGDN is transferred to a drying vessel (T9) for drying.
Automation (Control Panel)
It is clear from the above that a plant equipped with indicators and remote control can easily be made completely automatic. Such a realization has permitted the application of following systems (not shown):
Automatic preparation of unit for a start up.
Automatic control of nitration temperature.
Automatic control of the interface leveling the acid separator,
Automatic control of spent acid dilution.
Automatic control of the neutralization,
Programmed draining of the DEGDN from the vessels at the end of production and
shut down the plant.
Automatic preparation of unit for a start up
This system consist of a succession of electric and electro pneumatic impulses setting in operation successively the various electrical items such a pumps, stirrers, compressors and opening or closing the valves controlling the filling of the vessels.
Automatic control of nitration temperature
This system is composed of a controller with a proportional and integral action. This
instrument controls the pneumatic valves for the regulation of the brine through coil of the
nitrator.
This group is fully automatic and the operator does not need to intervene during production.
Automatic control of the interface leveling the acid separator
This system is based on the calibrated float, floating on the spent acid and sinking in the DEGDN is mounted on the separator neck, the float is free to move vertically.
In the highest position the float spindle rest against a mobile pneumatic nozzle, which
receives the air from the amplifier? If the nozzle is closed (acid level too high), the pressure in the membrane increases air regulating valve closes, thus decreasing the pressure in bellows and in the pneumatic drive of the variable overflow which opens, letting the acid flow out. The acid level becoming too low, the nozzle opens, air regulating valve opens and the overflow closes. This cycle is repeated every 4-5 seconds, by the float moving 2-3 mm. The amplitude of the variations gradually decreases, due to the speed control valve. The nozzle and its set bellows must have a gentle vertical movement.
Automatic control of spent acid dilution
The automatic control of the water dilution in the spent acid consists in the pneumatic control of a valve on the water pipe from a constant level tank. The pneumatic signal comes from the separators variable overflow valve; when the valve completely open, the air presssure is at its lowest and the water flow is at the highest point. When the valve is closed, the air pressure is at its highest point and there is no water flow
Automatic control of the neutralization
This control is obtained by mean of an electronic regulator with a proportional and integral action with a pre set setting point.
An electrode placed in a pocket at the outlet of the first washer transmits the pH variations to the regulator acting on an electro pneumatic transducer. This apparatus practically control the opening of the pneumatic soda solution feeding valve.
The regulator gives to the system a very high stability with a view of damping the signal pulsation and controlling their intensity and the scale range.
Programmed draining of the DEGDNfrom the vessels at the end of production and shut down the plant
The system consists in the complete sequence of operations required to complete the work from the movement of stopping the feed pumps, these operations are the following:
Stopping of the nitrator stirrer
Displacement of all DEGDN from nitrator and from the separator by means of spent
acid from overhead tank flowing through the bottom of the nitrator
Partial evacuation of the spent acid from the acid separator
Repetition of displacement in order to collect any DEGDN remaining on the wall of
the vessels
Emptying of the nitrator and acid separator
Stopping of pumps, stirrers etc.
Emptying of the washers and last separator
Rinsing of vessels
The sequence of the operations is controlled by a matrix programmer provided with pins. The column of matrix is successively fed by means of a step by step system. The time between the steps being constant except during the displacement phases, as the time required for thios operation can not be determined exactly.
The end of the displacement or in other words, the removal of the last traces of DEGDN floating on the acid, is an operation that requires a certain amount of precision, as otherwise there is the risk of sending the spent acid in to the first washer, or of leaving too much DEGDN on the acid in the separator.
This skimming off is carried out as follows
A float, which floats in acid and sink in the DEGDN is placed in the neck of separator at the level of the overflow.
When almost all the DEGDN has been displaced, the float begins to rise. At the end of this movement the float causes the successive closing of two electric contacts which in turn causes:
The closing of the displacement spent acid valve
The opening of separator emptying valve as well as the advancement of the programme. When the acid reaches halfway of the separator, the emptying valve closes again.
SAFETY SYSTEM
The safety system has been provided to the plant has the main purpose of:
Avoiding any wrong handling before starting the operation
Bringing to the personnel's attention any abnormal operation of the plant
In case of danger, setting an action the automatic device if the personnel's
interventions fails
Allowing the personnel to work in such a way so as to avoid any damage or accident
should any piece of equipment be out of order
A- In order to be able to begin the nitration, the following conditions at least must be fulfilled The temperature in the nitrator and separator must be normal The brine and compressed air pressure must be normal The number of revolution of stirrer must be normal
The valves and flaps controlling the feeding and emptying the equipment must be in correct position
The level of feeding and drawing tank must be normal If any one of these conditions is not satisfied, the plant can not be started up
B- During the operations of plant, the irregularities, which gives a warning alarms only are Instrument compressed pressure too low Nitrator temperature too low First washer temperature too high Abnormal composition of spent acid
Bad separation between DEGDN and spent acid in the acid separator Diluting water pressure too low Fall in level in displacement spent acid overhead tank pH in first washer too low or pH in last washer too high DEGDN in last separator too high Transfer water too low
In the above cases, which do not present any immediate danger, the personnel responsible for
the operations must decide whether to stop the plant to look for the causes of the irregularities which may be quite minor. Or it may be decided to stop the nitration, with out carrying out the displacement, look for the fault and, having found it, continue the nitration
C- During the manufacture, the following irregularities causes the shutdown of the plant Nitrator, separator, spent acid diluter temperature too high Level in diethylene glycol, mixed acid and soda solution overhead tanks too low Fall in diethylene glycol, mixed acid flows Fall in rpm of any stirrer Level in drowning tank too low pH in last separator too low Fall of24 volts DC Brine pressure too low Spent acid displacement valve open
Nitrator, acid separator, washer and water separator draining valves open Nitrator or acid separator drowning
Several of these safety devices are doubled or even trebled, as for instance, if the pump filling the mixed acid feeding tank fails .the nitration stops, should this safety device fail to operate, a minimum floating in this tank causes the stoppage ; if this should fail to come in to operation, a Rota meter in the acid could causes the feeding pump to stop.
If the temperature in the nitrator or separator reaches a second high limit, the contents of these two tanks are emptied in to the drowning tank; the stirred by means of compressed air in water layer. The nitrator stirrer stops and a horn give the alarm. The contents of the washer are however stirred continuously.
D- The safety operations that may be undertaken if required are
Drowning as described under C, set in operation manually and by remote control,
from several strategical points
Stirring the washers by compressed air in case of stopping of at least one of the
washer stirrers
The safety system is partially pneumatic, partially electric
It should also be noted that the system is "FAIL SAFE", so that in case of non operation of a safety device (electrical current failure, lack of compressed air, mechanical defect etc.), the plant is palced under condition which present no danger. For example, the flow of brine through the modulating pneumatic valve controlling the nitrator temperatures is reduced by air pressure and increased by low pressure. Should there be a compressed air failure or break in the membrane, the flow increases and the risk of sudden dropping of the nitrator cooling during the nitration is thus avoided.
CONTROL SYSTEM
The remote control system related to the electric equipment, which is not situated in the manufacturing buildings (in order to avoid placing the electrical equipment in the building containing explosives) is operated either directly or by mean of 24 volts DC circuit
This control is obtained by means of compressed air for all items requiring mechanical control. This also applies to the valves (modulating or "open or closed") in the nitration house. The valves are opened and closed according to a well calculated rhythm in order to avoid any sudden flow changes or shocks.
The electrical controls are in several cases transformed in to pneumatic controls by mean of pneumatic relay
The various control phases for the operation of the plant
The DEGDN production plant is controlled from the control desk in three distinct phases Preparation Start Displacement
The operation included in these three phases are indicated on the three functional diagrams Operation and functions of preparation Operation and functions of start Operation and functions of displacement
These diagrams must be used as checklist by the operator. The functions indicated in the one box are the direct resuh of those shown in the previous box.
The doubly outlined boxes indicate operations controlled from the control desk. The boxes outlined by mixed lines indicate controls and operations to be carried out by then operator.
Table 2
Table 2 provides comparative data between the process of the present invention and conventionally known process.
(Table Removed)

We Claim:
1. A process for manufacturing diethyleneglycol dinitrate (DEGDN) comprising:
(i) nitrating diethylene glycol (DEG) with a mixed acid in a nitrator (T3)
to form DEGDN and spent acid, (ii) separating the DEGDN from spent acid in a separator (T4), (iii) neutralizing the DEGDN with soda solution in a washing tank (T5), (iv) washing the neutralized DEGDN with water in a washing tank (T6) to
remove impurities, (v) optionally adjusting the pH of DEGDN to neutral using soda solution
in a washing tank (T7), (vi) separating the DEGDN from water in a separator, (vii) storing the DEGDN in a storage tank containing water, and (viii) transferring said DEGDN to a drying vessel for drying the DEGDN by
adding anhydrous calcium chloride (fused) in an amount of 8-12% by
weight to DEGDN and leaving for 8-12 hours to reduce the moisture
content of DEGDN to 0.12%.
2. The process as claimed in claim 1, wherein the temperature of the reaction mixture in the nitrator is controlled by circulating cold brine solution through coils within the nitrator.
3. The process as claimed in claim 2, wherein the temperature of the nitrator is maintained between 9 and 16°C.
4. The process as claimed in claims 2 or 3, wherein the brine solution comprises 25-35% sodium nitrate, 0.5-1.5% sodium bicarbonate and 0.25-0.75%) sodium biphosphate.
5. The process as claimed in claim 1, wherein the DEGDN is separated from spent acid by pumping additional spent acid from bottom of the separator (T4) to allow DEGDN to overflow from top outlet to the washing tank (T5).
6. The process as claimed in claim 1, wherein the ratio of mixed acid to DEG is 2.5:1.
7. The process as claimed in claim 1, wherein the mixed acid comprises nitric acid (HNO3) and sulphuric acid (H2SO4) in a ratio of 60:40.
8. The process as claimed in claim 7, wherein the mixed acid comprises +1 to -2% water (H2O).
9. The process as claimed in claim 1, wherein the concentration of soda solution
is from 12-14% by weight.
10. The process as claimed in claim 1, wherein the nitration time is 8 to 20 minutes.
11. The process as claimed in claim 1, wherein the total time for neutralization, washing and pH adjustment steps is 1.0 to 1.5 hours.
12. The process as claimed in claim 1, wherein the drying step comprises:
(i) transferring the manufactured DEGDN carefully in to a Stainless Steel bucket,
(ii) weighing the bucket as Wl, and transferring the contents into a SS bowl with lid (T9),
(iii) re-weighing the bucket to calculate the transferred product to the bowl,
(iv) repeating the steps (i) to (iii), if required,
(v) calculating the total transferred quantity of DEGDN into the bowl,
(vi) calculating the quantity of anhydrous calcium chloride @ 10% of the DEGDN taken in the bowl,
(vii) transferring this weighed calcium chloride in to the bowl slowly, to avoid any spurting / spillage of the product, covering the bowl with lid, and stirring the contents with wooden /Teflon stick occasionally, while keeping the bowl covered with lid otherwise,
(viii) resting the contents for 8 to 12 hours and transferring the total contents into another bowl by passing through Mesh #100 sieves to obtain the dried DEGDN product, avoiding the particles of calcium chloride in the product.