REFEX Application Overview

The Refex electrode is exceptionally resistant to applications containing poisons 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 details on applications where REFEX sensors can make a difference

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.

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.

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.

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 condensate from other parts of the refinery, so pH should be monitored real time and wash water diverted to a sour water stripper or otherwise treated should pH be out of spec.

From the desalter, the cleaned oil is directed into the refinery process. The underflow is brine that is directed to waste water treatment and from their either recycled or discharged.

Both the wash water feed and brine discharge are challenging measurements. Wash water can have a pH of 5.5 –7.0 and be contaminated with Ammonia and Phenols. Temperatures can >100°C. The brine effluent can contain sulfides, heavy metals, and oil plus sediment and sand – this cocktail 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.