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REFEX application and solution overview

The Refex electrode is exceptionally resistant to applications containing poisons, even those with components such as cyanide, ammonia and sulfides. This immunity is achieved because the polymeric reference junction is non-porous and prevents process material from invading and contaminating the electrode internals, causing drift and inevitable failure.

Here are a few examples where REFEX sensors can make a difference

Potable Water

REFEX Water Treatment pH Systems are designed to give reliable, continuous real time measurement of water quality in water treatment systems. Designed to be operated as a side steam, each system is supplied complete with a purpose built flowcell assembly that houses the measurement electrodes. REFEX pH electrodes are provided. The robust reference sensor uses a highly stable, rapid response, non-porous polymeric interface instead of a traditional porous liquid junction as used by all conventional reference electrodes. The non-porous nature of the electrode interface prevents the loss of electrolyte into the flow stream, preventing the rapid degradation of the measurement and costly frequent replacement of “consumable” probes. REFEX electrodes typically last 5 times longer than conventional electrodes in water treatment applications. The electrode is also highly resistant to fouling and coatings, greatly reducing maintenance overhead and providing high measurement uptime when in service.

Download REFEX Potable Water pH System Information Here
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Optimized Coagulation

Deviations from optimum coagulation conditions (i.e. coagulant chemical dosing rates and pH) can seriously affect treatment performance in water treatment plants. Coagulant chemicals are often sensitive to pH and perform best when pH is maintained within a tight range. Less than optimal conditions can have significant impact on residual coagulant concentration, turbidity, particle counts, NOM (Natural Organic Matter) and micro organisms making the proper control of coagulant dosage and coagulation pH important operational challenges.

Often, turbidity and NOM removal performance is best achieved at pH ranges from 5 to 6, while at pH > 6, NOM removal efficiency lessens significantly and requires higher dosage of coagulant. It is clear that rapid and large variation in raw water quality represents major operational challenges to ensure optimal coagulation conditions suitable to the actual raw water quality are maintained.

REFEX solid state reference electrodes provide instantaneous response to pH change. This very important measurement quality is vital where chemical dosing is required to maintain optimal conditions as slow response can lead to both over- and under-dosing of often expensive correction chemicals – increasing costs directly with greater use of correction chemicals and indirectly by lowering coagulation efficiency.

The slow response of conventional electrodes in correction chemical control systems leads to over-shoot of set points (Fig. 1) and therefore greater chemical usage – correction chemicals are needed to correct for the overcorrection!

REFEX reference electrodes provide rapid response because their entire wetted surface is electrochemically active. This helps to prevent pH over-shoot (Fig. 2), resulting in significant chemical savings and improved operational efficiency.

Download REFEX Optimized Coagulation Information Here

Ultra Pure Water

The REFEX Ultra-Pure Water pH System is designed to give reliable, continuous real time measurement of water quality in water purification and distribution systems. Designed to be operated as a side steam, the system is supplied complete with a purpose built flowcell assembly that houses the measurement electrodes.

REFEX reference and glass pH separates are provided. The robust reference sensor uses a highly stable non-porous polymeric interface instead of a traditional porous liquid junction as used by all conventional reference electrodes. The non-porous nature of the electrode interface prevents the loss of electrolyte into the flow stream, a serious problem in all conventional probes. The maintenance of the reference cell in this way prevents the rapid degradation of the measurement, greatly reduces the maintenance overhead and no longer requires the frequent replacement of “consumable” probes.

Where needed, an optional Conductivity sensor with low cell constant can be fitted into the measurement loop as an additional parameter.

To complete the package, a multi-parameter analyzer unit is used to give and transmit real time pH, conductivity and temperature information to local SCADA and control systems.

Download REFEX Ultra Pure Water pH System Information Here
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Oil & Gas Refineries, Petrochemical/Chemical Processes and ETP

Traditional pH and ORP sensors with porous/open reference junctions that are used in processes containing aggressive and toxic chemicals often fail because of reference electrode poisoning. Chemicals from within the process diffuse through the built-in porous/open junction(s) necessary for this type of sensor to operate and poison the Ag/AgCl electrode within the reference half cell. Poisoning of the reference electrode leads to severe measurement performance issues and premature demise of the sensor. Apart from the high expense that comes about from the frequent replacement of these failing sensors, there is also the cost of safely [and legally] handling and disposing of what can be highly contaminated sensors. Improper disposal of contaminated sensors can have a significant impact on the environment and expose companies to additional cost risk through litigation and penalty

Download REFEX Oil and Gas Process Information Here

Petroleum Refining – Sour Water Stripper

Used to remove gases such as ammonia and dissolved hydrogen sulfide from sour water, sour water strippers present an extremely challenging pH measurement application. Strippers are operated at about 80°C to facilitate removal of these gases. Hydrogen sulfide can block a porous pH reference with precipitated silver from the reference electrolyte whilst ammonia and cyanide poison the reference electrode and prevent it working by forming a complex with silver ions. These applications can be so aggressive that traditional porous reference electrodes may last only a few days before being rendered useless. Refex sensors do not suffer these effects because the unique polymeric reference is non-porous and an impermeable barrier to poisoning from the process stream. Consequently, the typical lifetime of a Refex sensor in this application exceeds 12 months and represents a significant savings in operating costs

Download REFEX Oil and Gas Process Information Here
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Oil Refinery Desalter Wash and Brine Water

Crude Oil contains many contaminants that must be removed before refining processes can be carried out. Typical contaminants are salts such as KCl, NaCl, MgCl and CaCl and solids such as sand.

The salts are removed by mixing wash water to the crude feed to a desalter vessel and assisted by electrolysis within the vessel itself. The wash water should be as clean as possible but is often steam condensate collected from other parts of the refinery, so pH should be monitored real time and wash water diverted to a sour water stripper or be otherwise treated should pH be out of spec.

The “cleaned oil” proceeds to the refinery for processing. The brine underflow from the desalter is directed to waste water treatment and from there either recycled or safely discharged into the environment.

Both the wash water feed and brine discharge are challenging measurements. Wash water can have a pH of 5.5 –7.0 and can be contaminated with Ammonia and Phenols. Temperatures can be >100°C. The brine effluent can contain sulfides, heavy metals, and oil plus sediment and sand – this mixture is often very abrasive and electrode erosion, fouling and poisoning is an ever present risk.

REFEX pH combination and separate reference electrodes have a patented NON-POROUS, ionically conductive interface that separates wash water and brine effluent from the electrode’s Ag/AgCl reference half cell and KCl electrolyte. This is 100% resistant to H2S and Ammonia poisoning and prevents electrode fouling.

REFEX sensors combine ultra-fast response to pH changes (prevents over/under shoot of pH setpoints) and extremely long-life (low maintenance) to provide real and measureable savings in terms of chemical costs and manpower/replacement parts.

Download REFEX Oil and Gas Process Information Here

Oil Refinery Wastewater Treatment

Refinery wastewater contains challenging contaminants that must all be removed before the water is either recycled for reuse in the plant or discharged to the environment. Contaminants include residual hydrocarbons, sulphur and chloride salts from sour crude refining, ammonia, cyanides, hydrofluoric acid, benzene and toluene.

To eliminate these contaminants, the wastewater is subjected to a coagulation process where Alum and polymers are added. These create a ”floc’ that captures the contaminants in a sludge that can be dried and disposed of. Accurate pH measurement and control is vital to ensure coagulation and floc is optimal.

Refinery wastewater is oily/dirty and can soon destroy typical traditional pH probes, even those labeled and promoted for “severe service” The non-porous nature of REFEX pH probes makes them the best solution for this type of extreme application

Download REFEX Oil and Gas Process Information Here
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Chlor-Alkali

Chlor-Alkali – Chlorinated and Waste Brine

Chlorine gas is produced in a membrane cell chlor-alkali process. Saturated brine is introduced into a high voltage electrolysis cell where chloride ions are oxidized to chlorine gas at the anode. To optimise yield while minimising corrosion damage to the expensive electrolysis membrane cell, brine pH must be carefully controlled between pH 2.00 and pH 4.00 by the addition of HCl.

Depleted brine from the cell is re-saturated with salt in a recirculation system for reuse over and over again. After leaving the electrolysis cell, the pH of the brine is adjusted to between 10 and 12 so that impurities in the brine (such as metals and sulphates) can be removed by precipitation. pH measurement and control by the addition of Hydrochloric Acid (HCl) and Sodium Hydroxide (NaOH) is critical throughout the entire process.

The challenges of reliably measuring pH in brine applications are severe. KCl is typically used in pH probe reference junctions because the equivalent conductance of a Potassium ion (K+) and a Chloride ion (Cl-) are almost the same. The equivalent conductance of a Sodium ion is much less, a Hydronium ion much higher, causing significant asymmetry potentials in the electronic circuit. This leads to measurement error and accelerated KCl diffusion across the electrode junction. Chlorinated brine pH is measured close to the electrolysis cell electrodes where very high electrical currents are present. These currents cause ground loops in the pH measurement circuit, creating offsets and shortening electrode life. In short, pH measurement in the process using traditional electrodes quickly becomes sluggish and inaccurate, causing waste of pH correction chemicals and impacting plant performance and yield.

The solution to these problems is a pH probe using a REFEX solid state non-porous reference interface – an electrochemically active, ionically conductive interface that forms an impenetrable barrier between the process brine and the Ag/AgCl reference electrode in 2.8 mol /l KCl electrolyte. Non-porous REFEX electrodes are immune to KCl loss/diffusion, ground-Loop currents (a liquid Earth should always be used), fouling and poisoning.

REFEX pH and REFEX ORP combined electrodes are the only ones that can withstand all chlor-alkali application challenges. The patented REFEX non-porous reference interface has solved many of the measurement problems of the past.

Download REFEX Chlor-Alkali Information Here

Municipal Waste Water Treatment

Sulfides build up in waste water systems due to the anaerobic (without oxygen) conditions that such plant is operated under. As with sour water applications in the petroleum industry, the non-porous polymeric Refex reference is a barrier to these dissolved sulfides in the process stream, preventing their ingress to the reference cell and subsequent precipitation of silver from the reference electrolyte. pH measurement loops using Refex reference electrodes do not exhibit the pronounced measurement drift and rapid failure rates common with traditional porous reference electrodes. Measurement remains stable and long term performance provides significant savings in both replacement probes and labor costs.

REFEX Water Treatment pH/ORP Measurement Systems are designed to give reliable, continuous real time measurement of water quality in both water purification and waste water applications. Designed to be operated as a side steam, the system is supplied complete with a purpose built flowcell assembly that houses the measurement electrodes.

 

REFEX reference and glass pH/ORP separates are provided with the system. The robust reference sensor uses a highly stable non-porous polymeric interface instead of a traditional porous liquid junction as used by all conventional reference electrodes. The active reference area is the whole of the outside surface of the electrode and this super large “jumbo” contact area means that the electrode is supremely resistant to coatings, even in the harshest of applications. Poisoning effects are eliminated because the polymeric reference material is conductive to ions but not porous; the reference can operate electrically but electrolyte and process fluids are not exchanged.

 

Systems are available with combination probes and electrode/reference separates: all are configured from the REFEX standard electrode range depending upon application requirements.

 

Many users have their own preferred pH analyzer type/brand. REFEX sensors will interface with any of the high dual impedance instruments available in today’s market. However, where no preference is given, we will be happy to source and supply a suitable multi-parameter analyzer unit that will interface with local SCADA and control systems. Talk to us about your requirements.

Download REFEX Water Treatment Information Here
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Biotechnology

Biotechnology

Biotechnology processes are carried out in a sterile and highly controlled environment to prevent contamination and loss of material. Loss can be very expensive, with some media costing astronomical amounts of money. To prevent cross contamination between batches, pH probes are often discarded after only being used once. The porous nature of traditional probes makes them impossible to clean completely, hence the disposable approach. REFEX probes can solve this issue as they are intrinsically non-porous and totally cleanable. Furthermore, the reference junction material is resilient to sterilization, with tests proving that REFEX reference probes can be sterilized many, many times without loss of effectiveness or operation.

Download REFEX Sterilization Test Information Here

pH Neutralization in Industrial Waswater

There are many regulatory requirements at both State and Federal level regarding the discharge of wastewater from industrial manufacturing facilities. Any company that discharges any sort of effluent into sewer systems, lakes, streams or the ocean is required to neutralize this effluent before discharge. Non-compliance can result, at a minimum in financial penalties and may include other consequences such as remediation of damage caused. It is in the best interests of any company (and depending upon local rules, can be compulsory) to record discharged effluent characteristics such as pH at the point where it leaves their facility.

Application Note

Delignification of pulp is carried out to brighten the pulp and make it ready for paper manufacture. Lignin is naturally brown in color and affects the quality of the final paper product, so must be removed. Most lignin is removed by “cooking” early on in the paper making process, but it is not possible to remove 100 percent of the lignin by cooking alone as this damages the pulp fibers. Bleaching is therefore used to complete delignification of raw pulp stocks after cooking.
Bleaching is a multistage process and the number of stages used is largely dictated by the final brightness of the pulp required. The most common process is the ECF (elemental Chlorine free) method as this is more environmentally friendly than earlier Chlorine bleaching methods.

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