A PROCESS FOR THE EXPLOSION-PROOF STORAGE OF NITROUS OXIDE

Abstract

A process for the explosion-proof storage of nitrous oxide in the liquid phase in a container comprising filling the container with nitrous oxide and an inert component selected from nitrogen, oxygen, carbon dioxide, water, argon, helium, krypton, xenon and mixtures thereof, and keeping it at a temperature of 190 to 273 K, wherein (i) the container has in all three spatial directions an inner distance between two opposite interior walls of 10 cm, (ii) the concentration of the inert components comprises 2 to 20 wt.-% in total, based on the nitrous oxide in the liquid phase, and (iii) compounds selected fromgases having a flammable range with air at 293.15 K and 101.3 kPa abs,liquids having a flash point of 366.15 K at 101.3 kPa abs, andmixtures thereof are kept at 0 to 2 wt.-% in total, based on the nitrous oxide in the liquid phase.

Claims

1.-15. (canceled)

16. A process for the explosion-proof storage of nitrous oxide in the liquid phase in a container comprising filling the container with nitrous oxide and an inert component selected from nitrogen, oxygen, carbon dioxide, water, argon, helium, krypton, xenon and mixtures thereof, and keeping it at a temperature of 190 to 273 K, wherein (i) the container has in all three spatial directions an inner distance between two opposite interior walls of 10 cm, (ii) the concentration of the inert components comprises 2 to 20 wt.-% in total, based on the nitrous oxide in the liquid phase, and (iii) compounds selected from gases having a flammable range with air at 293.15 K and 101.3 kPa abs, liquids having a flash point of 366.15 K at 101.3 kPa abs, and mixtures thereof are kept at 0 to 2 wt.-% in total, based on the nitrous oxide in the liquid phase.

17. A process according to claim 16, wherein the container has in all three spatial directions an inner distance between two opposite interior walls of 15 cm.

18. A process according to claim 16, wherein the container has an inner volume of 500 L to 100 m.sup.3.

19. A process according to claim 16, wherein the concentration of the inert components comprises 2.1 to 15 wt.-% in total, based on the nitrous oxide in the liquid phase.

20. A process according to claim 16, wherein the inert component is selected from nitrogen, carbon dioxide and mixtures thereof.

21. A process according to claim 16, wherein the concentration of nitrous oxide in the liquid phase is 82 to 98 wt.-%.

22. A process according to claim 16, wherein the gases having a flammable range with air at 293.15 K and 101.3 kPa abs are selected from hydrogen, carbon monoxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, methane, ethane, propane, n-butane, 2-methylpropane, 2,2-dimethylpropane, ethene, propene, but-1-ene, but-2-ene, 2-methylprop-1-ene, acetylene, methylacetylene, 1-butine, chloromethane, bromomethane, chloroethane, vinyl chloride, dimethyl ether, methyl ethyl ether, methyl vinyl ether, formaldehyde, hydrogen sulfide, methyl mercaptan, mono phosphane, methyl phosphine, diborane and stibine.

23. A process according to claim 16, wherein the liquids having a flash point of 366.15 K at 101.3 kPa abs are selected from methyl ethyl amine, diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-propylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, ethylenediamine, pyrrolidine, piperidine, n-pentane, 2-methylbutane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, cyclopentane, cyclohexane, 1,3-butadiene, 2-butine, 1-pentene, 2-pentene, 2-methylbut-1-ene, 2-methylbut-2-ene, 2-methyl-1,3-butadiene, 1-octene, cyclopentene, cyclopentadiene, cyclohexene, 1,4-cyclohexadiene, benzene, toluene, xylenes, ethylbenzene, furan, pyrrol, 1-chloropropane, 2-chloropropane, 1-chlorobutane, 2-chlorobutane, chlorobenzene, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, tert.-butanol, pentanols, diethyl ether, 2,3-dihydrofuran, 2,5-dihydrofuran, tetrahydrofuran, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, acetone, 2-butanone, 2-pentanone, 3-pentanone, crotonaldehyde, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate and methyl propionate.

24. A process according to claim 16, wherein (iii) compounds selected from gases having a flammable range with air at 293.15 K and 101.3 kPa abs, liquids having a flash point of 366.15 K at 101.3 kPa abs, and mixtures thereof are kept at 0 to 1 wt.-% in total, based on the nitrous oxide in the liquid phase.

25. A process according to claim 16, wherein nitrogen oxides having a N to O ratio of 1 are kept at a concentration at which the amount of nitrogen present in these nitrogen oxides is 0 to 1000 wt.-ppm in total, based on the nitrous oxide in the liquid phase.

26. A process according to claim 16, wherein nitrogen monoxide and nitrogen dioxide are kept at a concentration at which the amount of nitrogen present in these nitrogen oxides is 0 to 1000 wt.-ppm in total, based on the nitrous oxide in the liquid phase.

27. A process according to claim 24, wherein the nitrogen oxides having a N to O ratio of 1 are kept at a concentration at which the amount of nitrogen present in these nitrogen oxides is 0 to 10 wt.-ppm in total, based on the nitrous oxide in the liquid phase.

28. A process according to claim 16, wherein the liquid phase in the container is kept at 223 to 263 K.

29. A process according to claim 16, wherein the nitrous oxide is stored for 1 hour.

30. A process according to claim 16, wherein the nitrous oxide is stored for 1 week.

Description

EXAMPLES

Experimental Set-Up and Execution

[0099] The experimental set-up for determining the potential explosiveness of liquid nitrous oxide containing samples was based on the commonly known UN-GAP named as a test to determining if a substance has explosion properties, published in the Manual of Tests and Criteria, 7.sup.th revised edition, United Nations, New York and Geneva, 2019, part I, section 11, test series 1, but with some adjustments as described in the following. The test was designed to determine the sensitivity to detonative shock of a certain substance or substance mixture.

[0100] The experimental set-up used in the below experiments is shown in FIG. 1. The meanings of the labels used therein are summarized together for a better overview. [0101] (A) gas cylinder mounted in upside down direction [0102] (B) corner valve [0103] (C) HPLC pump [0104] (D) valve [0105] (E) pressure retaining valve [0106] (F) three-way valve [0107] (G) valve [0108] (H) explosion-proof wall [0109] (I) tube with a 8 mm Swagelok connection [0110] (J) blast cap with RDX explosive [0111] (K) metal foil (membrane) [0112] (L) detonator [0113] (M) shock absorber [0114] (N) safety valve [0115] (O) remote-controlled pneumatic valve [0116] (P) off-gas pipe

[0117] The experiments were performed by either using a 2 steel tube with an internal diameter of 2 inch (relating to 5.08 cm) and an inner length of about 40 cm, or a 4 steel tube with an internal diameter of 4 inch (relating to 10.16 cm) and an inner length of about 50 cm. Such tubes are also often called GAP-tubes, but for the sake of simplicity only called tubes in the following. For each experiment, a blast cap (J) containing 160 g RDX/wax (95/5 w/w) together with a detonator (L) was mounted to the tube (I) and separated from the nitrous oxide sample space by a metal foil (K). RDX is a commonly used explosive, also known as hexogen, or chemically as 1,3,5-trinitroperhydro-1,3,5-triazine. According to the recommendations of the UN-GAP testing manual, hollow glass microspheres with a diameter of ca. 50 m were added to simulate cavitation. In the case of the 2 tube 0.25 g of the microspheres were added, while in the 4 tube 2.1 g of microspheres were used. The top of the tube was closed with a threaded closure containing an inlet pipe and an outlet pipe, and a removable cooling coil mounted around the tube (not shown in FIG. 1). The bottom side of the tube prepared in this way was then put into a wood block as a shock absorber (M). The above-described set-up was located in an explosion-proof bunker and separated from the dosing equipment by an explosion-proof wall (H).

[0118] Before filling in the respective nitrous oxide sample, the system was purged free of air by passing pure gaseous nitrous oxide through it. After the purging, the tube (I) was cooled down by circulating a cooling liquid through the mounted cooling coil, and the test sample filled in. In case of pure nitrous oxide, nitrous oxide 5.0 with a nitrous oxide concentration of 99.999% was used. For the experiments with a nitrous oxide/carbon dioxide mixture, a premixed nitrous oxide/carbon dioxide mixture was used. Mixtures with ammonia or cyclopentene were prepared by separately adding nitrous oxide and ammonia or cyclopentene, respectively. The same principally applied for mixtures of nitrous oxide and nitrogen with the difference that nitrogen was added as a gas to a predetermined final pressure. The amount filled in was determined by weighing.

[0119] Once the tube (I) was filled with the respective test sample and cooled down to a set temperature of 247 K2 K (26.15 C.2 C.), the blast cap (J) was brought to detonation by the detonator (L). Depending on the severity of the demolition, the experimental result was either classified as negative (non-explosive) or positive (explosive). A test was classified positive if the tube was fragmented into shrapnel, and negative if the tube was at the most only ruptured but stayed mostly in one piece.

Control Experiment with Water

[0120] As a control experiment for a negative test result, a 4 tube was filled with water at room temperature and the blast cap (J) brought to detonation. The tube was only deformed.

Example 1 (Comparative)

[0121] A 2 tube containing 0.25 wt.-% of hollow glass microspheres was filled with 400 g of pure nitrous oxide and cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.). At this temperature, nitrous oxide has a density of 1025 kg/m.sup.3. The blast cap (J) was then brought to detonation and the tube was ruptured only to a length of ca. 20 cm. No shrapnel was formed. The test was classified as negative. A tabular overview including a comparison with the other examples is given in table 1.

[0122] Example 1 confirmed that even pure, liquid nitrous oxide in a 2 tube at a temperature of 247 K2 K (26.15 C.2 C.) having a density of 1025 kg/m.sup.3 is not detonation sensitive to a shock wave.

Example 2 (Comparative)

[0123] As pure nitrous oxide in a 2 tube at 247 K2 K (26.15 C.2 C.) is not detonation sensitive to a shock wave, pure nitrous oxide was tested under the same set temperature in a 4 tube containing 2.1 wt.-% of hollow glass microspheres. The 4 tube was filled with 3650 g pure nitrous oxide and cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.). The blast cap (J) was then brought to detonation and the tube was fully ruptured forming shrapnel. The test was classified as positive. A tabular overview including a comparison with the other examples is given in table 1.

[0124] In contrast to the experimental set-up with a 2 tube, pure nitrous oxide in a 4 tube at a temperature of 247 K2 K (26.15 C.2 C.) is detonation sensitive to a shock wave.

Example 3 (Inventive)

[0125] As pure nitrous oxide in a 4 tube at 247 K2 K (26.15 C.2 C.) is detonation sensitive to a shock wave, it was tested whether a low content of nitrogen in nitrous oxide would prevent triggering a detonation by a shock wave. Therefore, a 4 tube containing 2.1 wt.-% of hollow glass microspheres was filled with 4215 g of pure nitrous oxide and then pressurized with nitrogen to a pressure of 30.1 bar abs. The composition thus obtained contained 97.8 wt.-% nitrous oxide and 2.2 wt.-% nitrogen in the liquid phase. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was ruptured to a length of ca. 13 cm. No shrapnel was formed. The test was classified as negative. A tabular overview including a comparison with the other examples is given in table 1.

[0126] Example 3 shows that even a content of only 2.2 wt.-% nitrogen in nitrous oxide is already sufficient to suppress the detonation sensitivity to a shock wave in a 4 tube.

Example 4 (Inventive)

[0127] As nitrogen was confirmed to be able to suppress the detonation sensitivity of nitrous oxide to a shock wave, it was tested whether also carbon dioxide is able to suppress the detonation sensitivity. Therefore, a 4 tube containing 2.1 wt.-% of hollow glass microspheres was used, but filled with 3341 g of pure nitrous oxide and 440 g of carbon dioxide. The composition thus obtained contained 88.4 wt.-% nitrous oxide and 11.6 wt.-% carbon dioxide. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was only bulged and not ruptured. The test was classified as negative. A tabular overview including a comparison with the other examples is given in table 1.

[0128] Example 4 shows that a content of 11.6 wt.-% carbon dioxide in nitrous oxide suppresses the detonation sensitivity to a shock wave in a 4 tube.

Example 5 (Inventive)

[0129] Example 5 is based on example 4, but performed with a lower content of carbon dioxide. A 4 tube containing 2.1 wt.-% of hollow glass microspheres was filled with 3350 g of pure nitrous oxide and 320 g of carbon dioxide. The composition thus obtained contained 91.3 wt.-% nitrous oxide and 8.7 wt.-% carbon dioxide. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was only bulged and not ruptured. The test was classified as negative. A tabular overview including a comparison with the other examples is given in table 1.

[0130] Example 5 shows that also a content of 8.7 wt.-% carbon dioxide in nitrous oxide suppresses the detonation sensitivity to a shock wave in a 4 tube.

Example 6 (Inventive)

[0131] Example 6 is based on example 5, but performed with a lower content of carbon dioxide. A 4 tube containing 2.1 wt.-% of hollow glass microspheres was filled with 3320 g of pure nitrous oxide and 220 g of carbon dioxide. The composition thus obtained contained 93.8 wt.-% nitrous oxide and 6.2 wt.-% carbon dioxide. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was only bulged and not ruptured. The test was classified as negative. A tabular overview including a comparison with the other examples is given in table 1.

[0132] Example 6 shows that also a content of 6.2 wt.-% carbon dioxide in nitrous oxide suppresses the detonation sensitivity to a shock wave in a 4 tube.

Example 7 (Inventive)

[0133] Example 7 is based on example 6, but performed with an even lower content of carbon dioxide. A 4 tube containing 2.1 wt.-% of hollow glass microspheres was filled with 3615 g of pure nitrous oxide and 110 g of carbon dioxide. The composition thus obtained contained 97.05 wt.-% nitrous oxide and 2.95 wt.-% carbon dioxide. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was ruptured to a length of ca. 32 cm. The test was classified as negative. A tabular overview including a comparison with the other examples is given in table 1.

[0134] Example 7 shows that also a content of 2.95 wt.-% carbon dioxide in nitrous oxide suppresses the detonation sensitivity to a shock wave in a 4 tube.

Example 8 (Comparative)

[0135] As nitrogen and carbon dioxide are stable, inert molecules and as such not sensitive to oxidation, the behavior of ammonia as an oxidable molecule was tested in a mixture with nitrous oxide. For this test, a 2 tube containing 0.25 wt.-% of hollow glass microspheres was filled with 456 g of pure nitrous oxide and 10 g of ammonia. The composition thus obtained contained 97.9 wt.-% nitrous oxide and 2.1 wt.-% ammonia. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was ruptured to a length of ca. 22.5 cm. The test was classified as negative. A tabular overview including a comparison with the other examples is given in table 1.

[0136] Example 8 shows that 2.1 wt.-% ammonia in a 2 tube is not detonation sensitive to a shock wave.

Example 9 (Comparative)

[0137] Example 9 is based on example 8, but performed with a much higher concentration of ammonia. For this test, a 2 tube containing 0.25 wt.-% of hollow glass microspheres was filled with 275 g of pure nitrous oxide and 180 g of ammonia. The composition thus obtained contained 60.4 wt.-% nitrous oxide and 39.6 wt.-% ammonia. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was fully fragmented forming shrapnel. The test was classified as positive. A tabular overview including a comparison with the other examples is given in table 1.

[0138] Example 9 shows that a composition containing a significantly higher concentration of ammonia in nitrous oxide is, even in a 2 tube, detonation sensitive to a shock wave.

Example 10 (Comparative)

[0139] As a relatively low content of 2.1 wt.-% ammonia in nitrous oxide in a 2 tube is not detonation sensitive to a shock wave, the detonation behavior of a similar mixture was tested in a 4 tube. Therefore, a 4 tube containing 2.1 wt.-% of hollow glass microspheres was filled with 3300 g of pure nitrous oxide and 80 g of ammonia. The composition thus obtained contained 97.6 wt.-% nitrous oxide and 2.4 wt.-% ammonia. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was completely ruptured and the test classified as positive. A tabular overview including a comparison with the other examples is given in table 1.

[0140] Example 10 shows that 2.4 wt.-% ammonia in nitrous oxide does not suppress the detonation sensitivity to a shock wave in a 4 tube.

Example 11 (Comparative)

[0141] As 2.4 wt.-% ammonia in nitrous oxide is detonation sensitive to a shock wave in a 4 tube, it was tested whether the additional presence of carbon dioxide as an inert compound is able to suppress the detonation sensitivity. Therefore, a 4 tube containing 2.1 wt.-% of hollow glass microspheres was filled with 3500 g of pure nitrous oxide, 430 g of carbon dioxide and 90 g of ammonia. The composition thus obtained contained 87.1 wt.-% nitrous oxide, 10.7 wt.-% carbon dioxide and 2.2 wt.-% ammonia. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was fully ruptured forming shrapnel. The test was classified as positive. A tabular overview including a comparison with the other examples is given in table 1.

[0142] Example 11 shows that even in the presence of 10.7 wt.-% carbon dioxide the nitrous oxide composition is detonation sensitive to a shock wave in a 4 tube if 2.2 wt.-% ammonia are present.

Example 12 (Comparative)

[0143] As a further oxidable molecule, cyclopentene was tested in a mixture with nitrous oxide regarding its influence on the detonation sensitive of the mixture to a shock wave. Therefore, a 4 tube containing 2.1 wt.-% of hollow glass microspheres was filled with 940 g of pure nitrous oxide and 1654 g of cyclopentene. The composition thus obtained contained 36.2 wt.-% nitrous oxide and 63.8 wt.-% cyclopentene. The composition was cooled down to the above-mentioned set temperature of 247 K2 K (26.15 C.2 C.) and the blast cap (J) brought to detonation. The tube was fully ruptured forming shrapnel. The test was classified as positive. A tabular overview including a comparison with the other examples is given in table 1.

[0144] Example 12 shows that 63.8 wt.-% cyclopentene in nitrous oxide does not suppress the detonation sensitivity to a shock wave in a 4 tube.

TABLE-US-00001 TABLE 1 Examples 1 to 12 (set temperature 247 K 2 K) relative Ex. tube filling composition test result 1 (comp.) 2 400 g pure N.sub.2O 100 wt.-% N.sub.2O negative 2 (comp.) 4 3650 g pure N.sub.2O 100 wt.-% N.sub.2O positive 3 (inv.) 4 4215 g pure N.sub.2O 97.8 wt.-% N.sub.2O negative pressurized with 2.2 wt.-% N.sub.2 N.sub.2 to 30.1 bara 4 (inv.) 4 3341 g pure N.sub.2O 88.4 wt.-% N.sub.2O negative 440 g CO.sub.2 11.6 wt.-% CO.sub.2 5 (inv.) 4 3350 g pure N.sub.2O 91.3 wt.-% N.sub.2O negative 320 g CO.sub.2 8.7 wt.-% CO.sub.2 6 (inv.) 4 3320 g pure N.sub.2O 93.8 wt.-% N.sub.2O negative 220 g CO.sub.2 6.2 wt.-% CO.sub.2 7 (inv.) 4 3615 g pure N.sub.2O 97.05 wt.-% N.sub.2O negative 110 g CO.sub.2 2.95 wt.-% CO.sub.2 8 (comp.) 2 456 g pure N.sub.2O 97.9 wt.-% N.sub.2O negative 10 g NH.sub.3 2.1 wt.-% NH.sub.3 9 (comp.) 2 275 g pure N.sub.2O 60.4 wt.-% N.sub.2O positive 180 g NH.sub.3 39.6 wt.-% NH.sub.3 10 (comp.) 4 3300 g pure N.sub.2O 97.6 wt.-% N.sub.2O positive 80 g NH.sub.3 2.4 wt.-% NH.sub.3 11 (comp.) 4 3500 g pure N.sub.2O 87.1 wt.-% N.sub.2O positive 430 g CO.sub.2 10.7 wt.-% CO.sub.2 90 g NH.sub.3 2.2 wt.-% NH.sub.3 12 (comp.) 4 940 g pure N.sub.2O 36.2 wt.-% N.sub.2O positive 1654 g cyclopentene 63.8 wt.-% cyclopentene