SC25F Digital SMART SENCOM™ pH 12 mm Sensor with Build-in Temperature and External Liquid Earth

The SC25F is Yokogawa's first 12mm combination design digital SMARTpH sensor. It includes an integral temperature element and a Liquid earth electrode. This design provides a large electrolyte volume giving the sensor longer life than most comparable pH electrodes.

  • Solid Titanium LE electrode for stable measurements
  • Integral Pt1000 element for enhanced pH accuracy
  • Versatile in-line, immersion or off-line installation
  • CIP and Steam cleaning possible
  • large internal KCL volume giving the sensor a longer life time
  • low conductivity applications possible from 10µS
  • SC25F-ALP25 for chemically harsh applications and high temperature
  • SC25F-AGP25 for all General Purpose applications
  • Easy setup by sensor specific characteristics stored in the sensor itself
  • Simple maintenance by comprehensive design
  • CE, ATEX, CSA and FM Approval. However *Can only be used General Purpose at this time, because FLXA21 SENCOM™ module and SPS24 Interface box are pending ICECx, ATEX, FM and CSA approval*

WU11 Connection Cable

The WU11 interconnection cable is specified for reliable transfer of digital signals between the SENCOM™ sensors and Yokogawa FLXA™ analyzer. It is espically designed to be installed in a heavy industrial environment. The cable is water proof, IP67, allowing it to be submerged as a whole. The cable has a wide temperature operation range which is sufficient for most of the applications. The materials used for the cable are flame retardant to resist the spread of fire.

  • Double shielding to protect connected devices for interference from high voltages and currents
  • Available in four different lengths. Long cable runs up to 100 m (328 ft) are possible
  • Easy connection to a SENCOM pH Sensor by one 5- pins molded connector, and to the analyzer by 5 wired pins
  • Flame retardant recognized by UL (fileno. E124763) and CSA (fileno. LL105324)
  • IP67
  • Operating temperature from - 40ºC up to + 85°C (-40ºF up to +185°F)
Overview:

Wet scrubbers are used in utilities, paper mills, and chemical plants to remove sulfur dioxide (SO2) and other pollutants from gas streams. Undesirable pollutants are removed by contacting the gases with an aqueous solution or slurry containing a sorbent. The most common sorbents are lime, Ca(OH)2, and limestone, CaCO3

Industries:
Application Note
Overview:

For control of batch neutralization, a pH measurement coupled with a timer-controlled chemical feed scheme provides very satisfactory results.

This system can be adapted for either acid waste or alkaline waste neutralization.

Overview:

In flue gas desulfurization systems that use magnesium hydroxide (Mg(OH)2) slurry, the consumption of the desulfurization agent (Mg(OH)2) is controlled by using online pH analyzers. A great concern in the pH measurement is heavy staining of the pH electrodes by the Mg(OH)2 slurry. To ensure accurate measurement, frequent cleaning of the electrodes with an acid is required, adding to both maintenance workload and cost.

Industry:Chemical, Power

Application Note
Overview:

Introduction 

A process and apparatus for removing SO2 from a gas stream having the steps of scrubbing the SO2 with an ammonia scrubbing solution and removing any aerosols generated by the scrubbing in a wet electrostatic precipitator. The scrubbing solution is maintained at a pH between 6 and 8 to increase the speed of absorption of SO2, to Increase the ratio of sulfite to bisulfite which also facilitates the oxidation of SO2, and to avoid the need to use exotic, corrosion resistant alloys. Ammonium sulfate, a valuable fertilizer, can be withdrawn from the scrubbing solution.

Scrubbing as a Function of pH in a 10% Ammonium Sulfate Solution

Process background 

Fossil fuels are burned in many industrial processes. Electric power producers, for example, burn large quantities of coal, oil, and natural gas. Sulfur dioxide (“SO2”) is one of the unwanted byproducts of burning any type of fossil fuel. It is known to cause acid rain, and to have serious negative health effects on people, animals, and plants. A great deal of research has been done to find a way to economically remove SO2 from flue gas streams before it enters the atmosphere.

The pH of the ammonium sulfate solution should be kept between about four and six. This range is the result of a compromise between competing factors. On one hand, ammonium sulfate solution is capable of absorbing SO2 more rapidly when its pH is higher. The ability to absorb SO2 better implies that the size of the scrubbing tower can be smaller, thus saving capital costs. In addition, the liquid to gas (“L/G”) ratio can be smaller, meaning less liquid will be required and operating costs will be lower.

On the other hand, higher pH levels are also associated with the release of free ammonia from solution, often termed “ammonia slip.” In addition to incurring an economic loss because of lost ammonia, free ammonia in the scrubbed flue gas reacts with uncaptured sulfur dioxide and trioxide to create an ammonium sulfate/bisulfite aerosol that is visible as a blue or white plume in the stack discharge, leading to secondary pollution problems. Controlling the amount of free ammonia in the desulfurization process is in part a function of the ammonia vapor pressure, which results from a combination of pH and levels of unoxidized ammonium sulfite that remain in the absence of sufficient oxygen. Therefore, high pH values and high levels of unoxidized ammonium sulfite promote ammonia slip.

Typical Process Example 

  • Name of Application / Process: Ammonia Scrubbing
  • Location of Sensor mounting (location name): Tail Gas Scrubber Complex
  • Operating Temp / Max.Temp: 75 to 80 deg C
  • Operating Press / Max. Press: 2 to 2.5 Kg/cm2
  • Type of Installation: On Pipe ( Direct mounting ) / Flow through Chamber (By pass mounting ) /
  • Process Composition: Liquid - Scrub Acid,
    • P2O5:105 ppm,
    • AN (Ammonical Nitrogen):1326 ppm,
    • UN(Urea Nitrogen):22 ppm,
    • TN(Total Nitrogen):1348 ppm,
    • Florine:116 ppm.

Typical problems

  • Frequent cleaning, glass can be eaten away as the temperature and chemical attack glass

Remedies

  • Use of high temperature special sensor

Product Recommendation

Measurement System

Process Liquid Analyzer: 

  • 2-wire FLEXA pH/ORP Analyzer

2-wire FLEXA pH/ORP Analyzer

 

Features

  • Dual sensor measurement on 2-wire type analyser
  • Indication of sensor wellness

 

  • 4-wire PH450G pH/ORP Analyzer

4-wire PH450G pH/ORP Analyzer

Features

  • Easy touchscreen operation
  • Trending display up to 2 weeks
  • Advanced Process Temperature Compensation

Sensor Selection:

SC25 sensor from Yokogawa is the perfect sensor for this application. High temperature sensor SC25 because of its design can serve purpose.

SC25 sensors

 

 

Features SC25V

  • External titanium Liquid Earth
  • Pt1000 integration in pH compartment giving highly accurate temperature compensation
  • CIP and Steam cleaning possible
  • Large internal KCl volume giving the sensor a longer life time
  • SC25V-ALP25 for chemically harsh applications and high temperatures

Cable:

  • WU10-V-S series

Retractable fitting:

  • PR10 series

On-line measurements always present extra challenges compared to at-line measurements, for example, when maintenance needs to be done. Applications like this where the sensors have to be removed without interruptions or shut-downs the PR10 is especially suitable. Without any special tools the PR10 can be retracted safely from the process up to 5 bar.

For ease of use optional flush ports are available. In the retracted position the sensor can be kept moist, cleaned or even calibrated. This can all be done without process interruption or disassembly of the armature.

PR10 series

Tangible benefit

Better life of sensor, improve end product quality.

Note: For additional information on this application contact the local Yokogawa Process Liquid Analyzer Department

 

 

Overview:

The lifetime of a pH sensor has a significant impact on the overall annual costs of a pH measuring loop. Optimizing four key factors will decrease these costs and optimize process control and overall plant efficiency.

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