Closed Pressure Vessel Research Articles

Compressed hydrogen generation using chemical hydride

In a closed pressure vessel, the reaction of sodium borohydride (NaBH 4 ) with Pt-LiCoO 2 catalyst and a stoichiometric amount of water drastically increases the pressure owing to the generation of large quantities of hydrogen gas by synergism of hydrogen pressure and the catalyst (gravimetric hydrogen density per unit weight of NaBH 4 and H 2 O including the Pt-LiCoO 2 catalyst is 9.0 wt.%, volumetric hydrogen density per unit weight of NaBH 4 and H 2 O including the Pt-LiCoO 2 catalyst is 101 kg H 2 /m −3 ). The hydrogen densities are high enough to reach the US Department of Energy (DOE) targets for use in a fuel cell vehicle (FCV) and also for other applications such as a fuel cell uninterrupted power supply (FCUPS).

Hazard evaluation of self-decomposition materials by the combination of pressure and heat flux measurements

Thermal decomposition of unstable chemicals is always accompanied by heat release and gas generation. To ascertain such relationship, a heat flux calorimeter C80D fitted with a pressure-sensitive transducer provided simultaneous knowledge about pressure and heat flux behavior of a reactive agent. Consequently, (d P/d t) max was a parameter to reflect the characteristics of gas production potential during decomposition with the rate of reaction, which can be determined by thermal data, and was considered as a criterion to evaluate the hazardous characteristics for unstable substance. The results were compared with those in the UN standard PVT tests and the modified closed pressure vessel test (MCPVT), which have intense outer heating. It indicates that the decomposition measured in the C80D represents the inherent factor of materials and rate of reaction is the dominant factor to contribute to the intensity of the decomposition in other PVTs.

Decomposition of methyl ethyl ketone peroxide and mixtures with sulfuric acid

Abstract The fact that an explosion starts at a lower ambient temperature when methyl ethyl ketone peroxide (MEKPO) is not sufficiently neutralized, is demonstrated with a highly sensitive small-scale calorimeter (C80D). The data indicate that MEKPO might undergo acid and redox decompositions in addition to thermal decomposition in the accidental scenario. Meanwhile, experimental results of modified closed pressure vessel tests (MCPVT) suggest that the decomposition is much more active for MEKPO in the presence of sulfuric acid. Under such conditions, the maximum pressures and the maximum rates of pressure rise are significantly higher than those of pure MEKPO.

The “Mini Closed Pressure Vessel Test (MCPVT)” as a screening or classification test for explosive properties of organic peroxides

Tests according to the UN Recommendations on the Transport of Dangerous Goods for the determination of explosive properties of organic peroxides have been compared with screening criteria for explosivity based on measurements in a closed mini-autoclave (MCPVT). It will be shown that an additional screening test may be helpful but the information obtained from the UN tests are more important to characterise the specific properties of a substance under different conditions.

Study on decomposition of hydroxylamine/water solution

Abstract The risk evaluation of decomposition of hydroxylamine(HA)/water solution was studied experimentally. The thermal property of HA/water solution was studied from the calorimetric data obtained using the differential thermal analysis (DTA). The intensity of decomposition was studied on the basis of the results of the mini closed pressure vessel test (MCPVT) and the pressure vessel test (PVT) in addition to the steel tube test. The thermal property of HA/water solution was evaluated on the basis of results of the DTA. The heat-release onset temperatures using the no-treated stainless steel cells were more than 70 K below those measured using the GSC. This result implies that the heat-release onset temperature depends on the materials of sample cell. On the other hand, the heat of reaction did not depend on the materials of sample cell. The intensity of the thermal decomposition was investigated on the basis of results of the MCPVT, the PVT and the steel tube test. The intensity of the thermal decomposition increased as the HA concentration increased in the MCPVT. The intensity of the thermal decomposition increased greatly when the HA concentration was beyond 80wt.% in the MCPVT. It was elucidated that the thermal decomposition of HA 70wt.%/water solutions was very violent in the PVT. In addition, HA/water solutions of more than 80wt.% concentration could detonate in the steel tube test. HA 80 wt.% water/solution was easily detonated by a detonator without RDX in the steel tube test. In addition, the decomposition hazard of HA/water solution by the metal ion and the iron powder was studied in this paper. The thermal stability of HA85%/water solution with the iron ion or the iron powder was discussed on the basis of the heat-release onset temperature by the DTA. The heat-release onset temperatures decreased when the concentration of the iron ion or the iron powder increased in the DTA measurements. The reactiveness of HA/water solution with the metal ion of iron, manganese, nickel, chromium and copper was examined by measuring the mass loss of HA/water solution after the metal ion was added to HA/water solution at room temperature. The reactiveness of HA/water solution with the iron powder was also studied in this paper. The ferrous ion, the ferric ion and the iron powder reacted with HA/water solution. Ignition automatically began when the 0.2wt.% ferric ion solution was added to HA85wt.%/water solution. The mass loss rate depended on the HA concentration greater than the iron ion concentration. The mass loss rate increased when an amount of the iron powder increased. On the other hand, the decomposition reaction of HA85wt.%/water solution with Cu2+ was calm compared to that of the iron ion. HA/water solution did not react with Mn2+, Ni2+ and Cr3+ at room temperature.

Risk evaluation of methyl ethyl ketone peroxide and mixtures with sulfuric acid

The fact that an explosion starts at a lower ambient temperature when methyl ethyl ketone peroxide (MEKPO) is not sufficiently neutralized, is demonstrated with a highly sensitive small scale calorimeter (C80D). Meanwhile, experimental results of modified closed pressure vessel tests (MCPVT) suggest that the decomposition is much more active for MEKPO in the presence of sulfuric acid. Under such conditions the maximum pressures and the maximum rates of pressure rise are significantly higher than those of pure MEKPO.

Risk evaluation of decomposition of hydroxylamine/water solution at various concentrations

AbstractThe thermal property of HA/water solution was studied from the calorimetric data obtained using differential thermal analysis (DTA). The intensity of decomposition was studied from results of a mini closed pressure vessel test (MCPVT), and a pressure vessel test (PVT), in addition to the steel tube test.The thermal analysis was conducted to evaluate the ease of thermal decomposition using DTA. The heat‐release onset temperatures using the no‐treated stainless steel cells were more than 70° C below those measured using the gold‐coated stainless steel cells. This result implies that the heat‐release onset temperature depends on the materials of the sample cell.The intensity of the thermal decomposition was investigated using the MCPVT, the PVT, and the steel tube test. The intensity of the thermal decomposition increased as the HA concentration increased in the MCPVT. The intensity of the thermal decomposition increased greatly when the HA concentration was beyond 80% (wt.) in the MCPVT. It was determined that the thermal decomposit ion of HA 70%/water solutions was very violent in the PVT. In addition, HA/water solutions of more than 80% concentration could detonate in the steel tube test.

A closed pressure vessel test screen for condensed-phase explosive properties in organic materials

Screening criteria for explosivity based on measurements in a mini-autoclave were recently proposed. A predictive test of these criteria has now been carried out. It has been necessary to reduce the scope of the screen, but the criteria proposed for detonability and other Class 1 properties have been confirmed. A method has been specified to allow further testing and inter-laboratory studies. To co-ordinate these activities, a working group has been formed.

A review of United Nations tests for explosivity

In attempting to develop a closed pressure vessel test for assessing explosivity, arising from propagation of detonation, deflagration or thermal explosion, some difficulties were encountered in relation to United Nations test methods. This led to a review of these methods and comparisons of their performance according to available data. The review supports the contention of several authors that the UN methods are not optimal. Agreement between methods for a given property tends to be poor and some tests appear inherently unreliable. This is especially the case with the various vented pressure vessel tests, which are capable of both under- and over-estimating explosive potential depending on the particular circumstances. The need for improving the situation is clear and is highlighted by the current move to a globally harmonised system for classifying dangerous materials. It is intended that such a system will cover storage and supply as well as transport. In the additional circumstances, reliable assessment of explosivity is arguably even more important than in the transport situation. One step forward could be to introduce a closed vessel test. In the short term, however, such a test could only be introduced as a limited screen due to the vagaries of the current tests.

Refining of High Nitrogen Steels in a Closed Pressure Vessel

The simultaneous removing of oxygen, sulphur and phosphorus during nitriding with nitriding from a gas phase ofthe austenitic type (18 % Cr, 9 % Ni) High Nitrogen Steels were investigated. A process named Plasma Pressure Melting Process (PPMP) was carried out in the air-tight plasma furnace equipped with the 100 kW D.C. plasma torch. Refining, nitriding and casting of the liquid steels were actualized under elevated pressure inside the furnace - up to 0.5 MPa abs . The intensity of the calcium vaporization from the liquid CaF 2 -Ca flux used as a refining agent was quantified The relation of [Ca] tot. =f(a[O]) was established based on the measurement results of the oxygen activity in the liquid steel.

Investigation of the use of a closed pressure vessel test for estimating condensed phase explosive properties of organic compounds

Following the indications of earlier work, the use of a closed pressure vessel test (a mini-autoclave system) to estimate the explosive properties of organic compounds has been investigated. The dependent variable was an explosivity ranking derived from the results of a propagation of detonation test, a heating under confinement test and a deflagration test. Tentative criteria have been derived to allow the following conclusions: • Not detonable • Not Class 1 • No explosive properties with respect to transport classification The criteria are based upon the maximum rate of pressure rise observed in the mini-autoclave and the temperature at which this occurs. They offer a more efficient screen than the decomposition energy criteria which are currently used for initial assessment of explosive properties. The importance of event temperature suggests that existing classification tests may be underestimating heating under confinement and deflagration hazards. In this case, maximum rates of pressure rise from a closed pressure vessel test might be a better basis of classification, at least for supply if not transport. Further work is necessary to test the proposed screening criteria and to assess the use of a closed pressure vessel test as a means of classification.

Fire spread in a three-dimensional pressure vessel with radiation exchange and wall heat losses

In the present study, a three-dimensional differential field model based on general orthogonal coordinates is developed. The model, which is essentially designed for closed spaces, also includes the physical effects of turbulence, strong buoyancy, full compressibility, pressure rise due to fire loading, surface-surface and surface-flame radiation exchange, and heat losses through the wall. It is based on a control-volume staggered-cell finite-difference approach with primitive variables. Results of numerical calculations based on the field model are compared with test data for a methanol fire in the NRL FIRE I test facility which is in the form of a closed pressure vessel. Reasonable comparisons of the resulting pressure and temperatures at several locations have been obtained. Also shown are the detailed velocity and temperature fields inside the vessel at different time instants after the commencement of the fire.

Problems in the determination of chromium in biological materials. Comparison of flameless atomic absorption spectrometry and neutron activation analysis

The effects of sample preparation on the analysis of chromium in biological matter have been investigated using brewer's yeast as a test material. The apparent chromium content of the yeast as determined by flameless atomic absorption spectrometry was significantly higher after destruction of the organic matter with HNO3 in a closed pressure vessel than after wet-ashing in open vessels and after direct introduction of the sample into the graphite furnace. The results obtained by neutron activation analysis without any sample preparation, which corresponded to the atomic absorption values after digestion in the pressure vessel, showed that considerable errors arise in the other methods of sample treatment. Chromium analyses of dried and ashed yeast suggest that losses of volatile organic chromium compounds may occur during heating.

Constant-volume specific heat of solid xenon

Specific heats of solid xenon were measured between 110 and 223 K in a closed pressure vessel. In this temperature interval the pressure increased from the vapor pressure of the solid at 110 K to about 1.7 kbar at the melting point. After a small correction for the nonrigidity of the container, we find that cv increases from 2.9R at 110 K to the classical Dulong-Petit value of 3R at 200 K. The behavior of the specific heat in the vicinity of the melting point depended on the treatment of the samples.