Improved hydrogen storage properties of MgH_2 catalyzed with K_2NiF_6

In this study, the hydrogen storage properties of MgH-X wt% KNiF（X = 5, 10, 15, 20, and 50） were investigated for the first time. From the analysis of the onset desorption temperature and isothermal de/absorption kinetics, it was shown that MgH+ 5 wt% KNiFsample has the best performance. The 5wt% doped sample started to release hydrogen at about 260 °C, which was a reduction of about 95 °C and 157 oC compared with the as-milled and as-received MgH. In addition, the de/absorption kinetics of the MgH+ 5 wt% KNiFwere also improved significantly compared to the un-doped MgH. The apparent activation energy for hydrogen desorption exhibited the decrement from 167.0 k J/mol for as-milled MgHto 111.0 k J/mol with the addition of 5 wt% KNiF. Moreover, the X-ray diffraction spectra displayed the formation of new phases of KF, KH, MgNi and MgNiHby doping the KNiFwith MgHafter the dehydrogenation and rehydrogenation processes. The scanning electron microscope results revealed that MgHdoped with 5 wt% KNiFdemonstrated the smallest particle size compared to the as-received and as-milled MgH. It is believed that the formation of in situ active species of KF, KH, and MgNi could provide a synergetic catalytic effect in enhancing the hydrogen sorption properties of MgH.

Application of Liquid Nitrogen Cold Trap for Purification of Hydrogen Gas Stream Generated from NaBH4

The feasibility of using liquid nitrogen cold trap （LNCT） for the removal of water vapour and alkaline mist from the hydrogen gas stream which is generated from the catalytic and acidic decomposition of sodium borohydride is investigated. Practically, the target application is mobile fuel cells based on hydrogen production from storage in chemical hydrides. The LNCT would be used as a one step purification method with less cost and space requirements instead of applying the conventional purification techniques. Two catalysts were investigated for the production of hydrogen from the aqueous solution of NaBH4 in a small scale packed bed reaction column. The hydrogen generated from the catalytic decomposition of NaBH4 was accompanied by limited quantity of water vapour and alkaline mist. Nonetheless, higher quantities were generated when applying the acidic decomposition of NaBH4 and consequently the utilization of LNCT for H2 purification has proved useful and lead to a reduction in the content of these impurities; thereby the concentration of hydrogen in the outlet stream has increased.

Experiment and simulation research of storage for small grain steel silo

Knowing the temperature distribution in silo is a convenient and efficient way to control the process of grain storage.A three-dimensional(3-D)numerical model was used to study the temperature variation in small grain steel silo under quasi-steady state.In this study,experiments were conducted and porous media model was adopted.Results of numerical simulation and experiment were compared and the results indicated that grain temperature was influenced by temperature of the wall,grain stacking height,and the distance between grain and wall.The higher the wall temperature,the more the temperature increases.If the wall temperature is low,the effect of wall temperature on temperature distribution is significant.The temperature at the top part of grain varied obviously with the changes of temperature in air layer.Overall,numerical simulation results coincided with experimental results and the model established in this study is valuable for predicting grain temperature in steel silo.

Adaptive Virtual Synchronous Generator Considering Converter and Storage Capacity Limits

A virtual synchronous generator(VSG)control has been proposed as a means to control a voltage source converter interfaced generation and storage to retain the dynamics of a conventional synchronous generator.The storage is used to provide the inertia power and droop power in the VSG control to improve the frequency stability.Since the parameters in the VSG control can be varied,it is necessary for it to be tuned to be adaptive,in order to achieve an optimal response to grid frequency changes.However,the storage cannot provide infinite power and the converter has a strict power limitation which must be observed.The adaptive VSG control should consider these limitations,which have not been considered previously.This paper proposes an adaptive VSG control aimed at obtaining the optimal grid supporting services during frequency transients,accounting for converter and storage capacity limitations.The proposed control has been validated via hardware-in-the-loop testing.It is then implemented in storage co-located with wind farms in a modified IEEE 39-bus system.The results show that the proposed control stabilizes the system faster and has better cooperation with other VSGs,considering storage and converter limits.