SC25V 12mm with Built-in Temperature and External Liquid Earth

Yokogawa is continuously improving our pH sensing portfolio and designing new sensors that integrate the latest improvements in the industry. The SC25V is the latest addition to the family, and Yokogawa's first combination pH sensor in a 12 mm design that 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.

  • External titanium Liquid Earth
  • Pt1000 integration in pH compartment giving highly accurate temperature compensation
  • ATEX certified : ATEX II1G Ex ia IIC T3...T6 Ga
  • 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 10 μS/cm
  • Variopin connector
  • SC25V-ALP25 for chemically harsh applications and high temperatures
  • SC25V-AGP25 for all General Purpose applications

Overview:

After extraction from sugar cane or sugar beets, juice must be purified to remove the many other organics and minerals that accompany it.
 The processing to accomplish this is heavily dependent on reliable pH measurement and control as illustrated.

Application Note
Overview:

Introduction

Two types of polymerization reaction are used to produce styrene-butadiene copolymers, the emulsion type and the solution type. This section addresses volatile organic compound (VOC) emissions from the manufacture of copolymers of styrene and butadiene made by emulsion polymerization processes. The emulsion products can be sold in either a granular solid form, known as crumb, or in a liquid form, known as latex.

Copolymers of styrene and butadiene can be made with properties ranging from those of a rubbery material to those of a very resilient plastic. Copolymers containing less than 45 weight percent styrene are known as styrene-butadiene rubber (SBR). As the styrene content is increased over
45 weight percent, the product becomes increasingly more plastic.

As shown in below figure, fresh styrene and butadiene are piped separately to the manufacturing plant from the storage area. Polymerization of styrene and butadiene proceeds continuously through a train of reactors, with a residence time in each reactor of approximately 1 hour. The reaction product formed in the emulsion phase of the reaction mixture is a milky white emulsion called latex. The overall polymerization reaction ordinarily is not carried out beyond a 60 percent conversion of monomers to polymer, because the reaction rate falls off considerably beyond this point and product quality begins to deteriorate.

crumb1

Because recovery of the unreacted monomers and their subsequent purification are essential to economical operation, unreacted butadiene and styrene from the emulsion crumb polymerization process normally are recovered. The latex emulsion is introduced to flash tanks where, using vacuum flashing, the unreacted butadiene is removed. The butadiene is then compressed, condensed, and pumped back to the tank farm storage area for subsequent reuse. The condenser tail gases and
 noncondensables pass through a butadiene adsorber/desorber unit, where more butadiene is recovered.

Some noncondensables and VOC vapors pass to the atmosphere or, at some plants, to a flare system. The latex stream from the butadiene recovery area is then sent to the styrene recovery process, usually taking place in perforated plate steam stripping columns. From the styrene stripper, the latex is stored in blend tanks.

From this point in the manufacturing process, latex is processed continuously. The latex is pumped from the blend tanks to coagulation vessels, where dilute sulfuric acid (H2SO4 of pH 4 to 4.5) and sodium chloride solution are added. The acid and brine mixture causes the emulsion to break, releasing the styrene-butadiene copolymer as crumb product. The coagulation vessels are open to the atmosphere.
Leaving the coagulation process, the crumb and brine acid slurry is separated by screens into solid and liquid. The crumb product is processed in rotary presses that squeeze out most of the entrained water. The liquid (brine/acid) from the screening area and the rotary presses is cycled to the coagulation area for reuse.

Typical Process Details:

crumb2Fluid: Crumb slurry


  1. Fluid composition (normal):
    Water: 95% wt

    Polymer: 4.06% wt

    Fatty acid: 0.2% wt

    Extender oil: 0% wt. (Max. 1.45% wt)
    Rosin acid: 0.078%wt
  2. Acidity (min/orm/Max): 0.0/3.6/14.0
  3. Fluid design conditions P@T: 1.033 Kg/cm2- 
g@115 degC
  4. Boiling point @ operating pressure: 100 degC 

    Dew point @ operating pressure: 100 degC
    Boiling point @ atmospheric pressure: 100 degC

    Dew point @ atmospheric pressure: 100 degC
  5. Density: 980 kg/m3 (Norm)
  6. Fluid able to foul

Max. pressure: 1.033 kgf/cme-g Tempe: 62 degC

Crumb rinsing and dewatering

Typical Problems:

This is indeed a tough application. The rubber tends to stick on the holder. The rubber does not tend to stick on the glass very much.

Remedies:

To mount the holders in such a way that they can swing with the process flow and make them easy to remove for manual cleaning: 0.5 or 1 m immersion fittings hanging on the hoisting cable on a hook.

Solutions:

  • Sensor: SC25V series
  • 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

Alternatively, SENCOM sensor can be used. (SC25F)

Sensor Holder:

The FD20-P37 comes with hoisting cable made of SS316. When the holder is mounted this way, just hangs in the vessel, then it can swing with the flow. Otherwise the rubber slurry may damage the sensor if the holder is mounted rigidly. Most probably the sensor protection cage must be removed to prevent the polymer to fill the cage.

Overview:

In stable dispersion of fine particles is the pre-requisite for the selective flocculation technique involving separation of ultra-fine valuable particles from the gangue. Among mineral processing techniques selective flocculation technique is known to have outstanding potential of capturing the particles of particular mineral in slurry of mixed mineral system by selective adsorption of water soluble polymers known as flocculants.

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.

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

 

Features

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

 

  • 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.

 

 

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.

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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