Many municipal water, nutrient processing, as well as wastewater handling plants are switching over from the usage of chlorine disinfectants as well as biocides to safer as well as to a greater extent than environmentally friendly point-of-use as well as on-demand generated chemicals. The primary reasons for this modify are that conventional chlorine agents require carry past times tankers on accident-prone highways or railroads, ever increasing security as well as environmental regulations regarding toxic gases as well as chemic spills, as well as the required volume storage of these hazardous materials at the sites where they are used. Safer as well as inwards many cases to a greater extent than effective chemicals bring been developed that tin supervene upon chlorine. For example, later many trial as well as fault attempts to notice a way to effectively command Legionnaires’ disease, it was flora that chlorine dioxide (CIO2) was i the few chemic agents that could consistently as well as safely disinfect Legionella bacteria (see References). Add to this the mightiness to industry these safer chemicals at the locations that usage them, as well as alone when needed, as well as the advantages inwards total larn obvious.
Two pop substitute chemicals for chlorine are sodium hypochlorite (NaOCI) as well as chlorine dioxide (CIO2) both of which tin last manufactured via mini-plants (aka, generators) that are delivered to the halt users’ site every bit a consummate packet as well as provide the disinfectants on-demand as well as every bit needed. In many cases, these mini-plants piece of employment automatically as well as tin last employed inwards unmanned locations such every bit municipal H2O handling sites.
These electrochemical generators usage the procedure of electrolysis every bit the footing for the production of these disinfecting as well as biocide chemicals. Recalling our scientific discipline classes, electrolysis is a mutual method of separating bonded elements as well as compounds past times passing an electrical electric current through them. It involves applying a voltage betwixt ii electrodes (anode as well as cathode) which are submerged inwards a conductive solution (electrolyte). When a voltage is applied to the electrodes, electrical electric current flows as well as inwards plow breaks downward the molecules inside the solution into its components (Figure 1).
Figure 1 shows usage of the procedure that is used to create sodium hypochlorite (NaOCI), which is to a greater extent than commonly known every bit identify bleach when sold every bit a solution containing 5-6% of NaOCI. However, instead of a static vessel every bit shown inwards Figure 1, modern electrochemical generators catch the electrolyte solution continuously through i or to a greater extent than tubes that bring the electrodes mounted inside them. As the electrolytic solution flows through these tubes (electrolytic cells), the electrolysis procedure continuously separates the molecular components. In some instances, the solution is run through the dual-electrode electrolytic cells to a greater extent than than i time to farther refine as well as dissever the resulting chemicals. (Note: Batteries piece of employment past times a contrary procedure from electrolysis; they generate electricity past times way of galvanic or voltaic cells that comprise anode as well as cathode electrodes that are inwards contact alongside an electrolyte solution or gel.)
Historically, the mightiness supplies that provide the driving forcefulness for electrochemical generators bring evolved from basic transformer as well as diode rectifiers, to transformer as well as SCR (silicon-controlled-rectifier) mightiness sources, to modern as well as to a greater extent than sophisticated mightiness sources. The evolution of the switchmode mightiness provide greatly reduced the size as well as substantially improved the efficiency of these mightiness sources. In addition, switchmode mightiness supplies bring the mightiness to provide electronic signals for status data (volts, amps, temperature, etc.), remote control, as well as communications to as well as from a PLC (Programmable Logic Controller) or a local/remote computerized controller.
The vast bulk of switchmode mightiness supplies are designed to piece of employment every bit regulated voltage mightiness sources. These supplies regulate the output voltage real exactly regardless of the amount of electrical current drawn from the supply, upwardly to its blueprint limit. For example, a 1500-watt provide tin provide a 12-volts output spell providing from 0 to 125 amperes of current. Once the maximum electrical current of 125-amps is reached, the provide is designed to plow over into a current-limit trend (where the output voltage is automatically reduced or the provide shuts down).
Figure 2 higher upwardly shows the loop diagram of a typical sodium hypochlorite generator. The usage of the arrangement shown higher upwardly that is called the Electrolyzer consists of multiple electrolytic cells (tubes containing electrodes), connected inwards series, through which the electrolytic solution is pumped as well as inwards plow separated into its primary chemic components (e.g., sodium hypochlorite solution as well as hydrogen gas) via electrolysis. The electrochemical procedure for manufacturing chlorine dioxide is like to the higher upwardly except it starts alongside a solution of sodium chlorite.
It has been flora that inwards many electrochemical processes, including the production of disinfecting agents, that measure voltage-regulated mightiness supplies make non ever provide the ideal mightiness profile for these processes. In fact, inwards many instances, the mightiness supplies are existence forced to piece of employment at a fixed voltage as well as at roughly their maximum electrical current rating. If these operating weather condition are maintained for long periods of time, the provide volition internally heat-up as well as prematurely fail, therefore shutting downward the production of the disinfecting agents.
Why does this move on as well as how tin it last avoided? As described above, during the electrochemical process, inwards companionship to plow over along upwardly alongside the continuous electrolysis procedure alongside constantly flowing electrolyte solutions, the mightiness provide must provide a high plenty voltage to overcome the impedance betwixt the ii electrodes as well as the solution surrounding them, and, to a greater extent than importantly, to provide a high plenty electrical current density (amperes) to effectively dissever the molecules during the brusk fourth dimension (determined past times the flow rate) that the solution comes inwards contact alongside the electrodes. By using a switchmode mightiness provide that is designed to piece of employment inwards a “constant-current” trend (instead of constant-voltage, every bit is the norm) the electrochemical procedure has been flora to create chemicals much faster, alongside consistent high quality, without forcing the mightiness provide into an overload state.
There are a publish of ways of providing current-mode mightiness supplies for enhanced electrochemical applications. One method is to usage Programmable Power Supplies. These supplies are designed to last manually or remotely programmed to piece of employment inwards a voltage-mode and/or a electrical current mode, at a specific voltage as well as electrical current range, along alongside other specified parameters. As an added bonus these supplies commonly include a series digital communications port that allows it “talk” to local or remote estimator controllers. Additionally, these supplies tin last connected inwards parallel to the electrodes, or to groups of electrodes, when an electrochemical procedure requires to a greater extent than electrical current than i provide tin provide. For example, Lambda Americas’ model ZUP10-80/U programmable mightiness supplies is adjustable from 0 to 10-volts alongside 0 to 80-amps (800 watts total). This type of provide is existence used inwards its “constant-current” trend to efficiently create disinfectant as well as biocide chemicals at many unmanned, non-air conditioned, municipal H2O handling sites. In some applications, ii or to a greater extent than ZUP supplies are connected inwards parallel to provide the necessary amount of electrical current for the electrochemical process.
Another method of providing a “constant-current” trend mightiness provide is to modify the blueprint of a voltage regulated supply. This tin last done past times adding circuits that monitor the supply’s output electrical current to preclude an overload, nonetheless keep a “constant-current” profile from the supply. For example, Lambda Americas has produced modified versions its HWS-CC 1500-watt provide to make exactly this. In electrochemical applications that create disinfectant as well as biocide chemicals, a publish of these “current-mode” supplies are connected to dissimilar sets of electrodes, and/or, inwards parallel, to back upwardly dissimilar output electrical current requirements for diverse models of electrochemical generators. Obviously, generators that create higher output rates of chemicals require higher electrical current levels.
Lambda’s HWS-CC Series Power SuppliesThis newspaper has focused on the techniques as well as benefits related to advanced switchmode mightiness supplies for mini-electrochemical generators (self-contained plants) that create disinfecting as well as biocide chemicals on-site. It should last noted that electrolysis processes are used extensively inwards many other chemic as well as industrial areas, some of which are listed below.
- Production of aluminum, copper, sodium
- Anodizing
- Production of hydrogen (e.g., for the cars as well as fuel cells of the future)
- Electroplating as well as polishing
- Large waste matter H2O handling plants
- Factory as well as mightiness flora cooling towers - recirculating H2O treatments
In summary, the application of switchmode mightiness supplies operating inwards a “constant-current” trend has been shown to provide pregnant improvements inwards electrochemical self contained mini-plant generators that are used to create disinfecting as well as biocide chemicals. These benefits include:
- Improved current-density command for consistent electrolysis
- Enhanced lineament of the resulting chemicals
- Higher efficiencies as well as improved rule of the mightiness sources
- Reduced infinite as well as weight
- Power Supplies run into international Safety as well as Power Factor Correction (PFC) standards
- Availability of digital communications, remote control, as well as status signals
- Substantial reduction of downtime
References:
http://en.wikipedia.org/wiki/Electrolysis
http://www.medscape.com/viewarticle/520378
http://www.lambdapower.com/ http://www.doh.wa.gov/ehp/dw/Publications/alternate_disinfectants.htm
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