METHOD FOR AVOIDING AND EXTINGUISHING A DEFLAGRATION IN MATERIALS CAPABLE OF DEFLAGRATION

Abstract

The invention relates to a method for processing and/or handling solids and/or mixtures capable of deflagration, in particular for processing materials capable of deflagration in the chemical and pharmaceutical industry, wherein the processing and/or handling is carried out in an environment under a reduced pressure of <500 mbara and, when a deflagration cannot be ruled out measures for extinguishing the deflagration are commenced, where the processing and/or handling comprises one or more process steps selected from a group consisting of filtration, milling, sieving, mixing, homogenization, granulation, compacting, dispensing, drying, storage and transport in a transport vessel and also other steps in apparatuses having mechanical internals.

Claims

1. Method for processing and/or handling one or more solids and/or mixtures capable of deflagration, wherein processing and/or handling is carried out in an environment under a reduced pressure of <500 mbara and a deflagration is detected before breaking of the reduced pressure and the deflagration is subsequently extinguished by maintaining or restoring the underpressure.

2. Method for processing and/or handling one or more solids and/or mixtures capable of deflagration, wherein processing and/or handling is carried out in an environment under a reduced pressure of <500 mbara and a deflagration is detected before breaking of the reduced pressure and the deflagration is subsequently stopped by introduction of an extinguishing agent into an apparatus which is under underpressure, where the extinguishing agent is optionally water or water admixed with one or more surfactants and the pressure in the apparatus is <700 mbar at beginning of an introduction of the extinguishing agent.

3. Method according to claim 1, wherein a deflagration is detected by pressure increase in an apparatus after disconnection of a source of underpressure not being greater than the leakage rate and/or a thermal buildup of pressure in the apparatus.

4. Method according to claim 2, wherein the introduction of the extinguishing agent is effected automatically when a limit value for the pressure is reached.

5. Method according to claim 1, wherein a deflagration is detected by a temperature increase in the solid or mixture capable of deflagration and/or in a gas space of an apparatus which is greater than that brought about by the introduction of energy being observed after disconnection from a source of underpressure.

6. Method according to claim 1, wherein a deflagration is detected by a temperature increase in the solid or mixture capable of deflagration and/or in gas space of an apparatus which is greater than that brought about by the introduction of energy being observed during processing in the presence of an effective source of underpressure.

7. Method according to claim 1, wherein a deflagration is detected by decomposition gases being found in an apparatus after disconnection from a source of underpressure.

8. Method according to claim 1, wherein a deflagration is detected by decomposition gases being found during processing in the presence of an effective source of underpressure.

9. Method according to claim 1, wherein the solid capable of deflagration is selected from the group consisting of acetylenes, acetylides, 1,2-dienes, azirines, epoxides, azo compounds, diazo compounds, hydrazines, azides, peroxides, ozonides, hydroxylamines, nitrates, N-oxides, 1,2-oxalates, nitro and nitroso compounds, chloramines, fluoramines, chlorates, perchlorates, iodosyl compounds, sulfonyl halides, sulfonyl cyanides, Grignard reagents and organolithium compounds.

10. Method according to claim 1, wherein the mixture comprises consists of at least one material capable of deflagration selected from the group acetylenes, acetylides, 1,2-dienes, azirines, epoxides, azo compounds, diazo compounds, hydrazines, azides, peroxides, ozonides, hydroxylamines, nitrates, N-oxides, 1,2-oxalates, nitro and nitroso compounds, chloramines, fluoramines, chlorates, perchlorates, iodosyl compounds, sulfonyl halides, sulfonyl cyanides, Grignard reagents and organolithium compounds.

11. Method according to claim 1, wherein the processing and/or handling comprises one or more processes selected from the group consisting of filtration, milling, sieving, mixing, homogenization, granulation, compacting, dispensing, drying, storage and transport in a transport container and also other steps in apparatuses having mechanical internals.

Description

EXAMPLES

[0080] The invention will be described below for the mixing of 1000 kg of dichlofluanid (Euparen) with 1000 kg of kieselguhr in a paddle mixer operated under reduced pressure. The paddle drier has a volume of 5 m.sup.3. A vacuum of 50 mbar is set in the mixer by means of a vacuum pump having a pumping power of 350 m.sup.3/h. Charging is effected via a vacuum lock with running stirrer shaft. The leakage rate of the mixer was determined as 50 l/h before charging. A pressure sensor and a temperature sensor are installed in the gas space of the mixer. Water can be added via a valve at a rate of 100 m.sup.3/h to extinguish a deflagration. After the mixing operation is complete, the pressure in the mixer is brought to ambient pressure by introduction of nitrogen. (The introduction of the inert gas nitrogen ensures that the product is not damaged by possible oxidation processes).

[0081] Dichlofluanid and the mixture with kieselguhr are capable of deflagration according to the test VDI2263-1. The speed of deflagration determined in accordance with VDI2263-1 is 2 mm/sec in the case of ignition from below and 0.14 mm/sec for ignition from above. A potential ignition source is present in the mixing operation due to a running mixer blade.

Example 1Detection of an Incipient Deflagration By Means of a Pressure Increase and Stopping of the Deflagration by Means of a Further Reduction In the Pressure

[0082] After switching off the mixing device, the apparatus is disconnected from the vacuum source by closing the valve in the connecting conduit to the vacuum pump, but no gas is introduced to break the vacuum. A deflagration is triggered at the stirrer blade which has been heated by running along the wall and this deflagration spreads in a conical fashion around the point of ignition. The pressure increases due to the gases liberated in the decomposition. After 5 minutes, the pressure has risen to the alarm value of 70 mbar. The plant operator restores the connection to the vacuum within one minute, and the pressure is decreased to 50 mbar within 5 minutes. The pressure is kept at 50 mbar for 30 minutes, and the apparatus is subsequently disconnected again from the vacuum source by closing the valve in the connecting conduit to the vacuum pump. No further pressure increase is observed over the next 15 minutes. The reduced pressure is broken by introduction of nitrogen, and the drier can be emptied safely.

The deflagration has been extinguished in the vacuum.

Example 2Detection of an Incipient Deflagration By Means of a Pressure Increase and Stopping of the Deflagration By Introduction of Water

[0083] After switching off the mixing device, the apparatus is disconnected from the vacuum source by closing the valve in the connecting conduit to the vacuum pump, but no gas is introduced to break the vacuum. A deflagration is triggered at the stirrer blade which has been heated by running along the wall and this deflagration spreads in a conical fashion around the point of ignition. The pressure increases due to the gases liberated in the decomposition. After 5 minutes, the pressure has risen to the alarm value of 70 mbar. After a further 10 minutes, the plant operator restores the connection to the vacuum; when the pressure has increased to 400 mbar under this, the pressure is lowered over a period of 8 minutes to 100 mbar and increases to 150 mbar over a further 20 minutes. The plant operator activates the introduction of water; 1000 l of water are introduced and the mixing device is then switched on again.

The deflagration is stopped by the introduction of water.

Example 3Detection of an Incipient Deflagration By Means of an Increase in Temperature and Stopping of the Deflagration By Means of a Further Reduction In the Pressure

[0084] After switching off the mixing device, the apparatus is disconnected from the vacuum source by closing the valve in the connecting conduit to the vacuum pump, but no gas is introduced to break the vacuum. A deflagration is triggered at the stirrer blade which has been heated by running along the wall and this deflagration spreads in a conical fashion around the point of ignition. The temperature in the gas space increases due to the hot gases liberated in the decomposition. The temperature in the gas space increases to the alarm value of 40 C. after 8 minutes. The plant operator restores the connection to the vacuum within 1 minute, and the pressure is decreased to 50 mbar over a period of 5 minutes. The temperature drops to <30 C. The pressure is maintained at 50 mbar for 30 minutes; the apparatus is subsequently disconnected again from the vacuum source by closing the valve in the connecting conduit to the vacuum pump. No further temperature increase is observed over the next 30 minutes. The reduced pressure is broken by introduction of nitrogen, and the drier can be emptied safely.

The deflagration has been extinguished in the vacuum.

Example 4Detection of an Incipient Deflagration By Means of a Temperature Increase and Stopping of the Deflagration By Introduction of Water

[0085] After switching off the mixing device, the apparatus is disconnected from the vacuum source by closing the valve in the connecting conduit to the vacuum pump, but no gas is introduced to break the vacuum. A deflagration is triggered at the stirrer blade which has been heated by running along the wall and this deflagration spreads in a conical fashion around the point of ignition. The temperature in the gas space increases due to the hot gases liberated in the decomposition. The temperature in the gas space increases to the alarm value of 40 C. after 10 minutes. The temperature continues to increase and after a further 5 minutes reaches the switching value of 80 C., which triggers the introduction of water; 1000 l of water are introduced, and the mixing device is switched on again.

The deflagration is stopped by the introduction of water.

Example 5Detection of an Incipient Deflagration By Detection of the Decomposition Gases In Ongoing Operation and Stopping of the Deflagration By Switching Off the Mixer and Maintaining the Vacuum

[0086] In addition to the apparatus described for examples 1-4, an electrochemical sensor for detecting SO.sub.2 is installed on the pressure side of the vacuum pump. The stirrer blade runs along the wall. Some dichlofluanid decomposes locally as a result of heating.

The SO.sub.2 content in the exhaust gas from the pump increases from 0 ppm (detection limit of the sensor) to 50 ppm. The mixer is switched off. The SO.sub.2 content in the exhaust gas decreases again after 10 minutes and after 40 minutes is back at the detection limit.
The mixer is disconnected from the vacuum source, and the reduced pressure is broken by introduction of nitrogen. The drier can be emptied safely.
A deflagration has been prevented by cooling of the potential ignition source under reduced pressure.

Example 6Detection of an Incipient Deflagration By Detection of the Decomposition Gases In Ongoing Operation and Stopping of the Deflagration By Introduction of Water

[0087] In addition to the apparatus described for examples 1-4, an electrochemical sensor for detecting SO.sub.2 is installed on the pressure side of the vacuum pump.

The stirrer blade runs along the wall. Some dichlofluanid decomposes locally as a result of heating. The SO.sub.2 content in the exhaust gas of the pump increases from 0 ppm (detection limit of the sensor) to 50 ppm. The mixer is switched off. A deflagration is triggered by the heated mixer blade. The SO.sub.2 content in the exhaust gas continues to increase. After 15 minutes, it reaches a value of 200 ppm. The plant operator activates the introduction of water; 1000 l of water are introduced, and the mixing device is switched on again.
The deflagration is stopped by the introduction of water.

Example 7Detection of an Incipient Deflagration By Detection of the Decomposition Gases and Stopping of the Deflagration By Reducing the Pressure Further

[0088] In addition to the apparatus described for examples 1-4, a UV luminescence measurement cell for detecting SO.sub.2 is installed on the drier.

After switching off the mixing device, the apparatus is disconnected from the vacuum source by closing the valve in the connecting conduit to the vacuum pump, but no gas is introduced to break the vacuum. A deflagration is triggered at the stirrer blade which has been heated by running along the wall and spreads in a conical-spherical fashion around the point of ignition.
The SO.sub.2 content in the mixture increases from 0 mg/l (detection limit) to 0.5 mg/l. The plant operator restores the connection to the vacuum within 1 minute, and the pressure is reduced to 50 mbar within 5 minutes. The SO.sub.2 content in the exhaust gas decreases again after 10 minutes and reaches the detection limit again after 30 minutes.
The apparatus is subsequently disconnected again from the vacuum source by closing the valve in the connecting conduit to the vacuum pump. No further increase in the SO.sub.2 content is observed over the next 10 minutes. The reduced pressure is broken by introduction of nitrogen, and the drier can be emptied safely.
The deflagration has been extinguished in the vacuum.

Example 8Detection of an Incipient Deflagration By Detection of the Decomposition Gases and Stopping of the Deflagration By Introduction of Water

[0089] In addition to the apparatus described for examples 1-4, a UV luminescence measurement cell for detecting SO.sub.2 is installed on the drier.

After switching off the mixing device, the apparatus is disconnected from the vacuum source by closing the valve in the connecting conduit to the vacuum pump, but no gas is introduced to break the vacuum. A deflagration is triggered at the stirrer blade which has been heated by running along the wall and spreads in a conical-spherical fashion around the point of ignition.
The SO.sub.2 content in the mixer increases from 0 ppm (detection limit) to 10 mg/l. The plant operator activates the introduction of water; 1000 l of water are introduced, and the mixing device is switched on again.
The deflagration is stopped by the introduction of water.