The hydrogen separation reformer using Pd-alloy membrane is a novel hydrogen production system for on-site hydrogen station for fueling fuel cell vehicles. In the hydrogen separation reformer, hydrogen is generated by steam methane reforming process using natural gas and the generated hydrogen permeates across the Pd-alloy membrane. Since hydrogen generation and separation proceed simultaneously in a single reactor without limitation of equilibrium, the hydrogen separation reformer is more compact and more energy efficient than a conventional reformer. Tokyo Gas Co., Ltd. and Mitsubishi Heavy Industries Ltd. have developed a 40 Nm3/h-H2-class pilot system with energy efficiency of more than 80% and durability of more than 8000 hours. In addition, Tokyo Gas Co., Ltd. and NGK Spark Plug Co., Ltd. have developed a compact and low cost module with membrane on catalyst for the hydrogen separation reformer.
As represented by the launch of fuel cell vehicle (FCV) and the construction of hydrogen fueling station aimed the spread of FCV, the use of hydrogen as a secondary energy is just before the commercialization stage. As a high purity hydrogen is required in this field, the quality of purification technology becomes a very important element. Pressure Swing Adsorption (PSA) is the most practical technology and the purification system (equipment) using PSA technology is most useful on the view of cost performance, simple operation, safe and stability. In this paper, we introduce the history of the development, a principle and application of the PSA.
Organic chemical hydrides such as methlcyclohexane have recently received much attention as hydrogen carrier for efficient hydrogen storage and transport. For the widespread of energy system with organic chemical hydrides to build hydrogen-based economy, it is necessary to develop compact and efficient dehydrogenating systems suitable for commercial buildings, office complex, or hydrogen-supplying stations. Membrane reactors with inorganic membranes such as hydrogen selective silica membrane have high potential to reduce the volume and increase efficiency of dehydrogenating system. This review describes recent development in the field of hydrogen separation from organic chemical hydrides to supply high-purity hydrogen with membrane reactors.
In this study, we developed a novel membrane reactor consisted of CO shift catalysts and a membrane for CO2 separation. First, we developed facilitated transport membranes for CO2 separation. We tested several carriers to achieve high CO2 permeance (1x10-4mol/m2skPa) and high CO2/H2 selectivity (100). We successfully achieved the target values even at the elevated temperature (160°C). In addition, the developed membrane had good stability. It was confirmed that high performance was maintained stably for 400 hours at 160°C. Secondly, we developed CO shift catalysts, which have high activity for the CO shift reaction at low temperature region. As a result, we succeeded in the development of both precious metal-based catalysts, and Cu-based catalysts. Thirdly, a membrane reactor could be fabricated by combining the developed CO2 selective membranes and CO shift catalysts. Observed CO and CO2 concentrations at the feed-side exit of the membrane reactor were lower than 10 ppm and 1%, respectively. Using membrane reactor it is possible to reduce both CO and CO2 to lower than equilibrium level. Finally, we performed trial design of the total system of a hydrogen station equipped with the developed membrane reactor and evaluated the effect of the membrane reactor on downsizing of the total system and improvement of efficiency.
Hydrogen is attracting attention as a clean fuel that produces no CO2 emission at the stage of use. In Japan, fuel cell vehicle, which is a car running by converting hydrogen to electrical energy, is commercially available now. Hydrogen can be produced using existing equipment, but hydrogen recovery decreases, because specifications of impurities in hydrogen for fuel cell vehicles are so severe. As a result, production efficiency of high-purity hydrogen is reduced. If high-purity hydrogen is produced from fossil fuel at low production efficiency, CO2 emissions increase. To solve these problems, we developed a new hydrogen purification system with a hybrid-type membrane that features CO2 membranes and H2 membranes arranged in alternating stages. In this system, H2 or CO2 was respectively permeated through each type of membranes, and the partial pressure of H2 or CO2 was alternatively increased. Therefore, this system can increase the recovery rate of high-purity hydrogen up to over 90%, as well as simultaneously recovering by-product CO2. Recently, the system was scaled up to pilot plant. In this plant we are conducting long life tests at 2MPa(20 bar) by using gases produced from steam reforming of propane.
The analysis of stability mechanism and structure of gas-interface of nanobubble are become to be important for applying nanobubbles to cleaning, nanoscale ultrasound contrast and drug delivery. The determination of nanobubble concentration was established, the control of nanobubble diameter were investigated with loading Ir2O3 nanoparticle on platinum surface and the weight of nanobubble was studied with centrifugation of electrolyzed solution. In the case of ionic strength above 0.10 mol dm-3, the density of oxygen-nanobubble including gas-liquid interface layer which move together is higher than that of solution. The lifetime of hydrogen nanobubbles was about three hrs, while that of oxygen nanobubbles was above 60 days. The layer may be thought to be rigid like a wall which reduces the diffusion rate of hydrogen and oxygen molecules to bulk solution and stabilizes nanobubbles.