The Electrochemical Ammonia Compression Technology Based On The Fuel Cell Structure

Ammonia is one of the most common and important basic chemical raw materials in the world.It can be used in many fields,such as chemical industry,agriculture and medical industry.There are various disadvantages of traditional mechanical compression technology used for ammonia compression.By contrast,the electrochemical gas compression technology,which has attracted wide attention in recent years,has many obvious advantages,such as high efficiency,energy saving,noise free,environmentally friendly.In this thesis,a new electrochemical ammonia compression technology based on fuel cell structure was developed.Low-cost hydrogen storage alloys,instead of Pt catalysts,is utilized for preparation of a membrane electrode assembly(MEA).Using indigenously designed equipment of fuel cell structure,ammonia has been compressed by the new electrochemical method successfully.High pressure gas over 600 kPa is obtained.In this thesis,hydrogen storage alloy powders in suitable particle size were prepared.Fabrication process of the MEA was explored.Charge-discharge test of fabricated MEAs was carried out,which proved the feasibility of hydrogen absorption of the hydrogen storage alloy in the MEA by electrochemical method.The effects of electrode area and material on capacity of MEA,as well as the cycle stability and storage performance of the MEA were investigated.The MEA made by MmNi3 73Coo.74Mn0.41Al0.19 has the largest capacity of 305mAh·g-1 among the three sorts of materials adopted,and the best cycle stability,retains 93.8%of the maximum capacity after 25 cycles.LaNi4.5Co0.5 material performs best in term of storage performance.On the basis of mastering the capacity characteristics of the MEA,the ammonia compression equipment was assembled.It is indicated by the controlled trials that the optimal working conditions of ammonia compression are temperature of 60? and intake humidity of 60%.Under the optimal working conditions,ammonia compression on different applied voltages were investigated.Composition of the obtained high pressure gas was analyzed as well.Furthermore,electrochemical characteristics of the MEA were investigated,effects of leakage and back diffusion in the ammonia compressor were discussed,and the efficiency of ammonia compression was calculated.Accroding to the experimental results,the maximum pressure achieved by ammonia compression increases,while the required time decreases with the applied voltage between 1.5?3.0V The pressure of ammonia achieved 672.4kPa within 32 minutes at the applied voltage of 3.0V.Content of ammonia in the compressed gas on different applied voltages is 86 to 94%.The polarization curve of the MEA shows that the current density increases obviously with the applied voltage above 1.2V,corresponding well with the range of applied voltage in ammonia compressing.At different applied voltages,the current efficiency of ammonia gas compression is between 46 and 49%,and the utilization efficiency of hydrogen storage alloy increases with applied voltage,up to 60.5%.