Knowledge Info

Angstrom Advanced Hydrogen Electrolysis Plant:

Angstrom Advanced Inc. designs, manufactures and supplies variety of scientific instruments and Hydrogen & Nitrogen plants for academic and industrial fields.  Our instruments and plants have been delivered to many renowned organizations. Our goal is to provide our customers with the best products with highest standard of service at cost efficient pricing. With the best rates and a highly trained staff, we guarantee to meet your needs and work with you to obtain your project goals.

Knowledge base: Hydrogen Generating Plant

Overview

Electrolysis is the passage of a direct electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes and separation of materials.

The main components required to achieve electrolysis are:

  • An electrolyte: a substance containing free ions which are the carriers of electric current in the electrolyte. If the ions are not mobile, as in a solid salt then electrolysis cannot occur.
  • A direct current (DC) supply: provides the energy necessary to create or discharge the ions in the electrolyte. Electric current is carried by electrons in the external circuit.
  • Two electrodes: an electrical conductor which provides the physical interface between the electrical circuit providing the energy and the electrolyte. Electrodes of metal, graphite and semiconductor material are widely used. Choice of suitable electrode depends on chemical reactivity between the electrode and electrolyte and the cost of manufacture.

Electrolysis Process

The key process of electrolysis is the interchange of atoms and ions by the removal or addition of electrons from the external circuit. The required products of electrolysis are in some different physical state from the electrolyte and can be removed by some physical processes. For example, in the electrolysis of brine to produce hydrogen and chlorine, the products are gaseous. These gaseous products bubble from the electrolyte and are collected.

A liquid containing mobile ions (electrolyte) is produced by

  • Solvation or reaction of an ionic compound with a solvent (such as water) to produce mobile ions
  • An ionic compound is melted (fused) by heating
  • An electrical potential is applied across a pair of electrodes immersed in the electrolyte.

Each electrode attracts ions that are of the opposite charge. Positively charged ions (cations) move towards the electron-providing (negative) cathode, whereas negatively charged ions (anions) move towards the positive anode.

At the electrodes, electrons are absorbed or released by the atoms and ions. Those atoms that gain or lose electrons to become charged ions pass into the electrolyte. Those ions that gain or lose electrons to become uncharged atoms separate from the electrolyte. The formation of uncharged atoms from ions is called discharging.
The energy required to cause the ions to migrate to the electrodes, and the energy to cause the change in ionic state, is provided by the external source of electrical potential.

 

Hydrogen Plant Industrial Uses

  • Production of aluminium, lithium, sodium, potassium, magnesium
  • Coulometric techniques can be used to determine the amount of matter transformed during electrolysis by measuring the amount of electricity required to perform the electrolysis
  • Production of chlorine and sodium hydroxide
  • Production of sodium chlorate and potassium chlorate
  • Production of perfluorinated organic compounds such as trifluoroacetic acid
  • Production of electrolytic copper as a cathode, from refined copper of lower purity as an anode.
  • Electrometallurgy is the process of reduction of metals from metallic compounds to obtain the pure form of metal using electrolysis. For example, sodium hydroxide in its molten form is separated by electrolysis into sodium and oxygen, both of which have important chemical uses. (Water is produced at the same time.)
  • Anodization is an electrolytic process that makes the surface of metals resistant to corrosion. For example, ships are saved from being corroded by oxygen in the water by this process. The process is also used to decorate surfaces.
  • Electroplating is used in layering metals to fortify them. Electroplating is used in many industries for functional or decorative purposes, as in vehicle bodies and nickel coins.
  • Production of hydrogen for fuel, using a cheap source of electrical energy.

 

Components of The Hydrogen Generator by Water Electrolysis

  • Bipolar pressurized Electrolyser
  • The cell of electrolyser is divided into anode cell and cathode cell
  • Hydrogen is generated in cathode side
  • Oxygen is generated in anode side
  • Electrolyser is filled with electrolyte KOH mixed with DM water (30% KOH)
  • On Electrical Side Rectifying transformer is used to change high AC voltage electricity to low voltage electricity and then through rectifying to become DC power
  • The positive pole of DC power is connected to the anode of electrolyser, cathode of electrolyser directly comes from transformer
  • Rectifying transformer and rectifier are two main part of Electric power supply unit.
  • Cathodic reaction is 4H2O+4e == 2H2+4OH-
  • Anodic reaction is 4OH == O2+2H2O+4e-
  • The pressure of the system is raised to and maintained at the set pressure by means of regulating valve.
  • The electrolyte at the bottom of hydrogen and oxygen separators is pumped back to electrolyser after filtering and cooling, to complete one process cycle.
  • Hydrogen & oxygen generated in electrolyser mixed with electrolyte are sent to Hydrogen and oxygen separators, there hydrogen and oxygen are separated with electrolyte due to gravity.
  • Hydrogen and oxygen gases are allowed to pass through hydrogen and oxygen coolers separately and are cooled to the temperature of 30~40°C,
  • The hydrogen is allowed to pass through a pd deoxo unit and hydrogen dryer to remove its moisture and oxygen .
  • Electrolyte tank is used for storing electrolyte and feed water.
  • Electrolyte pump makes the electrolyte, pumps it in the system and back in the pump
  • Feed water pump is a piston pump, used to pressurize feed water into the system

Main Electrical Components of a Hydrogen Generator by Water Electrolysis

  • Transformer & Rectifier
  • The transformer changes the voltage from AC 415 V to the low voltage value required
  • Rectifier Changes the Low voltage to DC Current to be supplied to electrolyser.
  • The capacity of rectifying transformer is designed as per the size of electrolyser.
  • At the input of rectifying transformer, a current and voltage measurement is provided with interlocks to protect the system in case of some malfunctions.
  • Rectifying component includes rectifying components, control with interlocks.
  • Rectifier function is to stabilization of current and voltage
  • The voltage can be regulated from 0.6~1.05 times of the rated voltage
  • The rated current of rectifier is 1.1 times of the rated current of electrolyser.

Hydrogen Generator Safety Interlock

Safety is our number one concern at Angstrom Advanced. Hydrogen Generators are built with many safety devices and interlock devices such as:

  • DC voltage indication
  • Current indication
  • Current overflow indication
  • Phase lack indication
  • Cooling water malfunction
  • High temperature of SCR

Hydrogen Plant Electrolyser

Oxygen and electrolyte from anode side are pumped into oxygen separator, there oxygen separates with electrolyte under the action of gravity, then oxygen passes through oxygen cooler, be cooled to the temperature of 30~425℃, where after it passes through oxygen demister to remove liquid water from gas. The electrolyte at the bottom of oxygen separator is pumped back to oxygen side cell of the electrolyser after filtering and cooling, oxygen side circulation is finished.

According to the capacity and work pressure of hydrogen generator, the handling capacity of 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 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, the equation is: There is a hydrogen buffer tank between hydrogen generator and hydrogen purification equipment; it is used to remove dissociative water from hydrogen and to keep the pressure of hydrogen purification unit stable. Hydrogen flows into purifier though this buffer. The action of purification equipment is to purify the hydrogen generated by hydrogen generator. The oxygen is removed though chemical reaction under the action of catalyst, and water is removed by the way of adsorption.2H2O==2 H2+O2.

Hydrogen, oxygen and electrolyte are sent to hydrogen and oxygen separators installed in auxiliary equipment frame, there hydrogen and oxygen are separated with electrolyte under the action of gravity, hydrogen and oxygen gases pass through hydrogen and oxygen coolers separately and are cooled to the temperature of 30~425℃, then pass through hydrogen and oxygen demisters to remove liquefied water from gases, then hydrogen and oxygen are supplied out. The pressure of the system is raised to and maintained at the set pressure by means of regulation valve. The electrolyte at the bottom of hydrogen and oxygen separators is pumped back to electrolyser after filtering and cooling, then, one circle is finished.

The hydrogen from water electrolysis has the advantages of high purity and simple composition, normally only has the impurities like oxygen and water, it is easy to purify it to much higher purity used in electronic industry.

There is a hydrogen buffer tank between hydrogen generator and hydrogen purification equipment; it is used to remove dissociative water from hydrogen and to keep the pressure of hydrogen purification unit stable. Hydrogen flows into purifier though this buffer. The action of purification equipment is to purify the hydrogen generated by hydrogen generator. The oxygen is removed though chemical reaction under the action of catalyst, and water is removed by the way of adsorption.

Hydrogen O2/H2 Separator

Hydrogen and oxygen come separately into H2 separator and O2 separator, where they are cooled by cooling water and separated from the mixture of gas-lye by gravity. After that H2 gas come into the H2 washer for lye drop to be removed which is contained in gas by DM water, at the same time the gas is cooled by coil-piped cooler which is erected in the washer. Finally, the hydrogen through the demister which locates at the top of washer to eliminate the water drop, then flows into the hydrogen drying unit via pneumatic valve for further purification. Oxygen processing will be expelled to atmosphere.

Hydrogen Generator Lye System

The function of lye is to improve the electrical-conduction performance during water electrolysis. Under normal operation condition, the consumption of lye will be nearly zero. Generally, the supplementary of lye will be needed once per year if necessary and the quantity will be a very small. For preparation of lye, solid caustic potash is put into the lye tank which is filled with two-third of DM water inside and then the lye pump will be started to agitate and dissolve caustic potash into the DM water.

The alkaline solution (electrolyte) combined together from the hydrogen (oxygen) separators return to the electrolytic cells via the collection pipe and the filter in which the foreign substances will be removed from the solution, then it will be returned to the electrolyzer via lye pump.

Hydrogen Generator Cooling Water

Cooling water serves for the following purposes:

A) Cooling the SCR element in the rectifier

B) Cooling the lye by means of the lye coolers inside of H2/O2 separators and hence the operation temperature of electrolyzer is to be controlled in the range of 80-90 Celsius degrees

C) Cooling hydrogen and oxygen by the cooler in washer and their temperature at the outlet of cooler is not more than 40 Celsius degrees at the outlet of H2 washer

Hydrogen Generator Control Cabinet

The control cabinet is the key part of the entire monitoring system to maintain the safety and stable running of the Hydrogen Generator. The regulating of operating pressure of hydrogen generator ensures that the generator will be able to operate under the required working pressure. The control arithmetic used in this system is PID algorithm. The pressure transmitter samples the system pressure and is transferred to PLC through the safety barrier to compare with the working pressure set-point, the arithmetic result gained from PLC will be converted to be standard signal of 4~20mA DC from the analogue output module and then into a standard gas signal of 0.02~0.1Mpa through the electric-pneumatic converter, and the pneumatic signal controls the opening of pneumatic regulating valve so that the operating pressure is to be kept at the set-point value.

Angstrom Advanced hydrogen control system allows the plant to actively control generator parameters.

Angstrom hydrogen control systems integrated into the hydrogen generator automatically controls purity and dew point. Actively controlling hydrogen at optimum levels in the hydrogen generator will:

• Warn the user of excess limit monitored parameters

• Optimize efficiency

• Maximize generator capacity

• Provide safe hydrogen supply

• Automatically cut off power to rectifier in case of excess pressure is reached

Hydrogen Generator Gas Analysis System

Hydrogen is sampled to the hydrogen gas analysis system via sampling tube, in which the mini-lye drop is separated from it by the gas-moisture separator, then it goes into the online analyzer to check the O2 content in hydrogen after its pressure will be reduced. Before the product H2 is transmitted into the corresponding storage tank, it will be sampled into the separated moisture meter to measure their dew-point, the corresponding signal will be sent into programmable logic controller for display and monitoring. The control program will decide the product H2 and product H2 to be sent into their corresponding storage system or not, depending a certain conditions

Angstrom Advanced Nitrogen Generator by Pressure Swing Adsorption:

Applications of a Nitrogen Generator

Petroleum industry
In the petroleum industry, nitrogen is an indispensable component in a number of processes. Most commonly, nitrogen is used to create an inert environment for preventing explosions and for fire safety and to support transportation and transfer of hydrocarbons. Additionally, nitrogen is used for pipeline testing and purging, cleaning technological vessels and cleaning liquefied gas carriers and hydrocarbon storage facilities.
Metallurgy
The metal industry generally utilizes nitrogen as a means of protecting ferrous and non-ferrous metals during annealing. Also, nitrogen is helpful in such standard industry processes as neutral tempering, cementing, hard brazing, stress relieving, cyanide hardening, metal-powder sintering and extrusion die cooling.

Chemical and petrochemical industries
The primary and very important application of nitrogen in chemical and petrochemical industries is the provision of inert environment aimed at ensuring general industrial safety during cleaning and protection of process vessels. Besides, nitrogen is used for pipelines pressure testing, chemical agents transportation, and regeneration of used catalysts in technological processes.

Paint-and-varnish industry
Paint and varnish production uses nitrogen for the creation of an inert environment in process vessels to ensure safety, as well as for oxygen displacement during packing in order to prevent polymerization of drying oils.

Pharmaceutical industry
In pharmaceutical industry, nitrogen finds application in pharmaceuticals packaging, and ensuring against explosion and fire safety in activities where fine dispersed substances are used.

Electronics
In electronics, nitrogen serves as an antioxidant in the manufacture of semi-conductors and electric circuits, heat treatment of finished products, as well as in blowing and cleaning.

Glass industry
In the glass production, nitrogen proves efficient as a cooling agent for bow oven electrodes, oxidation inhibitor during process procedures, as well as air cooler.

 

 Benefits for using PSA Nitrogen Generator

  • High Reliability: Proven PSA technology, simple engineering design, few moving parts and international standardized manufacturing techniques ensure minimal maintenance and maximum reliability.
  • Low Cost: Patented high-efficiency control system reduces air consumption, and saves power.
  • Automatic Control: Unattended operation fully controlled by PLC automatically. Touch-screen control, display and alarm system enables the system to be operated by one touch. Display also show working parameters, and provides filter changing reminders, and trouble shooting instructions.
  • Easy Installation: Skid mounted for easy installation and movement.
  • Long Service-life: Exclusive bed containment system extends Carbon Molecular Sieve (CMS) bed life to more than ten years.
  • Minimal Maintenance: The generator has highly-reliable valves and no other moving parts. Filter elements are easily replaced.

 

 Nitrogen Generator Carbon Molecular Sieve

PSA nitrogen generator uses carbon molecular sieve as sorbent, produces nitrogen by making use of the PSA principle. Under certain pressure, carbon molecular sieve has different oxygen/nitrogen adsorption capacity, i.e. much more oxygen adsorption capacity than nitrogen adsorption capacity.PLC controls pneumatic valve on/off to realize two towers alternate adsorption and desorption as per pressure change, carries out oxygen/nitrogen separation and produces nitrogen with desired purity.
This system generates nitrogen by separating nitrogen and oxygen in from air.
CMS (Activated Carbon Molecular Sieve) is a specially treated material that is used in separating air.

Figure 3－1: Activated Carbon Molecular Sieve（CMS）

The distance of CMS is between the nitrogen molecules and oxygen molecules, this is the main cause of oxygen molecules are smaller and lighter than nitrogen molecule. This leads to the Oxygen molecules to be absorbed first by the Carbon Molecular Sieve.

Nitrogen Plant Components

PSA Nitrogen Generator can be divided into three units:

  • Air compressor and purification system
  • Oxygen and nitrogen separation unit
  • Nitrogen storage and flow control system

Nitrogen Generator Compressor

Angstrom Advanced will provide a compressor or the end user can source the compressor on his own. The specifications vary on each model generator and will be provided by Angstrom Advanced.

Specified generator is fully automatic, compact, and skid-mounted. Each generator comes pre-tested and ready to be installed upon delivery. We believe that our system meets all of specific needs, with the most reliability, convenience and at the best price.

Nitrogen Generator Storage Tank

The main function of the Nitrogen storage tank is to buffer the pressure wave when nitrogen produced, avoiding unqualified airflow rate when nitrogen over-consumption. It also avoids minimal storage (lower than standard purity) due to long downtime. The nitrogen tank should be provided with at least ten minutes backup. The nitrogen flow can be shown on the flow meter after the nitrogen storage tank.