Actual SWCG chlorine rate compared to theory

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Regarding the cell configuration, electrolyzers may be constructed in either unipolar or bipolar design (Figure 8).

A unipolar (or “tank- -type”) electrolyzer (Figure 8a) consists of alternate positive and negative electrodes held apart by porous separators, i.e., membranes.

Positive electrodes are all coupled together in parallel, as are the negative electrodes, and the whole assembly is immersed in a single electrolyte bath (“tank”) to form a unit cell.

A plant-scale electrolyzer is then built up by connecting these units electrically in series.

The total voltage applied to the whole electrolysis cell is the same as that applied to the individual unit cells.

On the other hand, in a bipolar electrolyzer a metal sheet (or “bipole”) connects electrically adjacent cells in series.

As seen in Figure 8b, the electrocatalyst for the negative electrode is coated on one face of the bipole and that for the positive electrode of the adjacent cell is coated on the reverse face.

In this case, the total cell voltage is the sum of the individual unit cell voltages.

Therefore, a series-connected stack of such cells forms a module that operates at a higher voltage and lower current than the tank-type (unipolar) design.

To meet the requirements of a large electrolysis plant, these modules are connected in parallel so as to increase the current.

These two different cell configurations present different electrode reactions.

For the unipolar configuration, the same electrochemical reaction (either the HER or the OER) occurs on both sides of each electrode.

On the other hand, in the bipolar configuration, two different reactions (HER and OER) take place simultaneously on the opposite sides of each electrode not directly connected to the power source.

This means that one side of each electrode acts as a cathode and the other as an anode (although both sides are at the same potential), with the exception of the two end electrodes that are connected to the DC power source.

The resulting cell voltage for these two basic configurations is quite different.

For typical industrial processes, the unipolar configuration presents a cell voltage of about 2.2 V and the bipolar configuration has a value of 2.2 × (n − 1) V (where n is the number of electrodes).

Owing to the simplicity of the unipolar configuration, this type of electrolyzer is easy to fabricate and requires low maintenance, but presents high electrical currents at low voltages, causing large Ohmic losses.

On the other hand, the bipolar configuration has lower Ohmic losses in the electrical circuit connectors; however, it demands much higher precision in its design and manufacturing to prevent electrolyte and gas leakage between cells.

The gap between electrodes must also be considered during cell design.

It corresponds to the distance that the ions have to travel within the electrolyte.

A smaller gap has the advantage of less resistance to ionic transportation.

However, if the gap is too small, it can induce electric sparks, posing an explosion hazard.

An optimum electrode gap must be identified for each particular cell.

The electrolyte flow forces convective mass transfer in the cell.

At high current densities, electrochemical reactions are limited by the electrolyte mass transfer. Stirring and/or inducing turbulence reduces the concentration gradients in the electrolyte and enhances mass transfer.

An electrolyzer’s operating cell voltage is directly related to its energy consumption and electrical efficiency.

The cell is considered inefficient if a higher voltage is required to produce an equivalent hydrogen mass, while keeping the current constant.

The operating current density also defines the electrolyzer’s energy efficiency.

Conventional water electrolyzers generally run at current densities ranging from 1000 to 3000 A m −2 .

The current density determines the rate of hydrogen production, with higher current densities leading to higher rates of the electrochemical reactions.

However, fast bubble formation resulting from an increased rate of gas production also increases the overpotential due to the bubbles’ resistance.

Therefore, current density should be kept within a certain range, with compromises between the gas production rates and the energy efficiency.

The operating temperature is another important parameter.

Conventional alkaline water electrolyzers are designed to run at temperatures of around 80‐90 C.

Increasing the operating temperature has the advantage of decreasing the equilibrium cell voltage.

However, high temperatures increase water loss due to evaporation and require highly resistant materials to maintain the equipment’s structural integrity.

 
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Electrolytic generation of halogen biocides

Nov 11, 1976 - Diamond Shamrock Corporation

Patent # 4,100,052

The present invention generally relates to an electrolytic cell for the generation of low cost halogen biocidally active agent for the treatment of a sewage or other liquid effluents especially those waters of a fresh water swimming pool or cooling towers.

More particularly, the present disclosure relates to an improved electrolytic cell having a bipolar configuration which is used in line with the pumps generally associated with the distribution of waters in swimming pools or cooling towers or other liquid effluents for the generation of chlorine from affluent containing low levels of chloride.

This employs an enclosure connected in line with the liquid distribution system of the facility containing a series of parallel planar plates to be utilized as electrodes arranged such that the effluent flows through the parallel planar matrix of plates and is treated thereby with the chlorine being electrolytically produced from within the confines of the electrolytic cell.
 
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1976-11-11: Application filed by Diamond Shamrock Corp

1984-06-06: Assigned to LECTRANATOR CORP., CHARDON, OH 44024.

Lectranator became Autopilot.

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The name Lectranator was changed to Autopilot in July 1995.

Aquacal bought Lectranator in 1992.

 
We use bipolar cells, that offer a much higher performance level than conventional monopolar cells. This means more chlorine per amp, increasing the efficiency and speed of the procedure.

 
LECTRANATOR — 0427168

Filed: 1978-07-11

Registered: 1980-04-25

Registrant: DIAMOND SHAMROCK CORPORATION. 717 Harwood Street. Dallas, Texas. UNITED STATES OF AMERICA.

Registration Expiry Date: 2025-04-25

Current owner: AUTOPILOT SYSTEMS, INC., (A FLORIDA CORPORATION),

5755 POWERLINE ROAD, FORT LAUDERDALE, FLORIDA 33309-2074, UNITED STATES OF AMERICA

 
In May 1992, the Lectranator Chlorine Machine business was purchased from Olin Corporation (NYSE).

Lectranator, in production since 1978, utilizes the principles of electrolytic generation to make liquid chlorine in the pool.

The factory was moved in October 1992, from Cleveland, Ohio to Ft. Lauderdale, Florida.

In July 1995, Lectranator Company was renamed AutoPilot Systems, Inc.

 
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A monopolar cell is probably the easiest configuration and consists of one, or multiple (parallel connected) anodes (DC positively charged members) and cathodes (DC negatively charged members) joined to the power source by separate power connections.

Conversely, in the bipolar configuration, the electrode serves as both an anode and a cathode.

Except for the terminal electrodes, where the positive and the negative power input points are located, each electrode has a MMO coated portion (anode) and a non-MMO coated portion (cathode).

DC current is delivered to the positive coated terminal electrode face, emitted from that electrode face through the electrolyte, then it is received on the cathode face of the adjacent plate and passes through the plate to the anode face of the same electrode.


 
The IECG contains the control electronics and bipolar electrodes that electrically produces chlorine when energized with DC current.

Chlorine is generated as pool water containing salt passes through the cell.

The chlorine production can be varied by either adjusting the sanitizer output level on the control panel and/or by varying the number of hours the IECG is on each day.

The IECG automatically reverses the cell electrode blades every few hours to help clean the cell.

This process does not interrupt the production of Chlorine.

 

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