Angstrom Advanced Knowledge base: Hydrogen Generating Plant

Angstrom Advanced Hydrogen Generating Plant by Water Electrolysis

Oxygen and electrolytes from the anode side are pumped into an oxygen separator, where oxygen separates with electrolytes under the effects of gravity, then oxygen passes through an oxygen cooler. There, the oxygen is cooled to a temperature of 30~425℃, where it then passes through an oxygen demister to remove liquid water from gas. The pressure of the system is raised to and maintained at a set value by means of a pressure regulation valve. The electrolytes at the bottom of the oxygen separator are pumped back to the oxygen cell of the electrolyser. After filtering and cooling, oxygen side circulation is finished.

According to the capacity and work pressure of a hydrogen generator, the handling capacity of its hydrogen purifier is determined. In order to guarantee the quality of hydrogen after purification, we use purified hydrogen as regeneration gas.

The total system includes a hydrogen generator, hydrogen purifier, electrical and control unit as well as a hydrogen buffer tank and a storage container. In this unit, water is decomposed into hydrogen and oxygen through electrolysis, for which the equation is 2H₂O==2H₂+O₂. There is a hydrogen buffer tank between the hydrogen generator and hydrogen purification equipment; it is used to remove dissociative water from hydrogen and to keep the pressure of the hydrogen purification unit stable. Hydrogen flows into the purifier though this buffer. The purpose of purification equipment is to purify the generated hydrogen. The oxygen is removed through a chemical reaction under catalytic effects, and water is removed by way of adsorption.

The hydrogen from water electrolysis has the advantages of high purity and simple composition, and normally only has impurities such as oxygen and water. It is easy to purify the hydrogen to much higher purity levels for use in the electronic industry.

Angstrom Advanced Knowledge base: Atomic Force Microscope/Scanning Probe Microscope

STM relies on “tunneling current” between the probe and the sample to sense the topography of the sample. The STM probe, a sharp metal tip (in the best case, atomically sharp), is positioned a few atomic diameters above a conducting sample which is electrically biased with respect to the tip. At a distance under 1 nanometer, a tunneling current will flow from sample to tip. In operation, the bias voltages typically range from 10 to 1000 mV while the tunneling currents vary from 0.1 to10 nA. The tunneling current changes exponentially with the tip-sample separation, typically decreasing by a factor of two as the separation is increased 0.2 nm. The exponential relationship between the tip separation and the tunneling current makes the tunneling current an excellent parameter for sensing the tip-to-sample separation. In essence, a reproduction of the sample surface is produced by scanning the tip over the sample surface and sensing the tunneling current. STM relies on a precise scanning technique to produce very high-resolution, three-dimensional images of sample surfaces. The STM scans the sample surface beneath the tip in a raster pattern while sensing and outputting the tunneling current to the SPM Controller. The digital signal processor (DSP) in the Controller controls the Z position of the Piezo Scanner based on the tunneling current error signal. The STM operates in both “constant height” and “constant current” data modes, depending on the Feedback Gain settings. The DSP always adjusts the height of the tip based on the tunneling current error signal, but if the feedback gains are set extremely low (e.g., Integral Gain < 15 and Proportional Gain < 15), the piezo remains at a nearly constant height while tunneling current data is collected. With the Feedback Gains high (e.g., Integral Gain >15 and Proportional Gain >15), the Scanners Piezo height changes to keep the tunneling current nearly constant, and changes in piezo height are used to construct the image. The exponential relationship between tip-sample separation and tunneling current allows the tip height to be controlled very precisely.