4-Leiter-pH/ORP-Analysator PH450

Der PH450 pH-Analysator bietet die höchste Genauigkeit in der Branche und verfügt über eine fortschrittliche Temperaturkompensationsfunktion, programmierte Kalibrierstandards, Stabilitätsprüfungen und Online-Sensor- und Analysator-Diagnosen für verifizierbare Ergebnisse. 

Dieser multivariable 4-Leiter-Analysator kombiniert pH- mit Temperatur- und ORP (Redox)-Messungen, die alle über die verschiedenen Ausgangsfunktionen genutzt werden können: zwei mA-Stromausgänge, vier unabhängige SDPT-Kontaktausgänge und HART. Dynamische Sensorprüfung und Reinigungszyklusfunktionen sorgen für eine problemlose und genaue Analyse mit minimalem Wartungsaufwand. 

Einzigartige Bedienerschnittstelle

Der PH450 verfügt über eine hochauflösende einfache Touchscreen-Menüstruktur mit fünf Sprachoptionen, sodass Informationen für den Bediener deutlich erkennbar und leicht zugänglich sind. Wählen Sie einfach die gewünschte Sprache, woraufhin Bildschirmanweisungen dafür sorgen, dass die optimale Konfiguration für die jeweilige Anwendung gewählt wird.

 

Ideal für Reinstwasseranwendungen

Der PH450 bietet Selbstdiagnose und Prozesstemperaturkompensation für präzise pH-Messungen in Reinstwasser. Eines dieser Temperaturkompensationsverfahren, die Methode NEN6411, berücksichtigt die Dissoziation von Wasser in starken Säurelösungen und Laugen, was besonders nützlich für pH-Messungen in Rein- und Reinstwasser ist, wie sie in der Wasserchemie der Energieerzeugung vorkommen.

Zusätzliche Merkmale

  • Fähigkeit zur gleichzeitigen Bestimmung von pH-, ORP- oder rH- und Temperaturwerten mit dem gleichen Sensor
  • Vollständige PID-Regelung gleichzeitig für Säure- und Alkalizugabe möglich
  • Doppelt hochimpedant für differentielle pH/ORP-Messungen  
  • Erweiterte Diagnose, Prozesstrendgrafiken und Bildschirm-Logbücher zur Datenspeicherung
  • Zwei mA-Ausgänge und vier SPDT-Relaiskontakte mit Anzeige im Display
  • Hart®-Kommunikation
  • FM Klasse 1, Div.2, Gruppe ABCD, T6 für Ta-20 bis 55°C
  • IP66/NEMA4X 1/2 DIN-Gehäuse für Feld- und Schalttafelmontage
  • Drei Sets vorgegebener pH-Pufferstandards (NIST, USA und DIN) decken die gebräuchlichsten pH-Kalibriermethoden ab.
  • Unterstützt zahlreiche Temperaturkompensationselemente und Sensortypen
Messprinzip Elektrochemisch
Eingangsbereiche pH: -2 bis 16 pH
ORP: -1500 bis 1500 mV
rH: 0 bis 100 rH
Temperatur: -30 bis 140 °C (Pt1000)
Übertragungssignale: Allgemein: Zwei potentialfreie Ausgänge von 4 bis 20 mA DC mit gemeinsamem Minuspol. Maximallast 600 Ω. Bidirektionale digitale HART®-Kommunikation, dem mA1-Signal (4 bis 20 mA) überlagert.
Ausgangsfunktion: Linearer oder nichtlinearer (21-stufige Tabelle) Ausgang für pH, Temperatur, ORP oder rH.
Steuerungsfunktion: PID-Regelung.
Burn out-Funktion: Burn up (21,0 mA) oder Burn-out (3,6 mA) auf Signalausfall gemäß NAMUR NE43.
Halten: Die mA-Ausgänge sind auf den letzten bzw. einen festen Wert während der Kalibrierung/Inbetriebnahme eingefroren.
Kontaktausgänge Allgemein: Vier SPDT-Relaiskontakte mit Anzeige im Display.
Schaltleistung:
  Höchstwerte 100 VA, 250 V AC, 5 A
  Höchstwerte 50 W, 250 V DC, 5 A
Status: Hohe/niedrige Prozessalarme, ausgewählt aus pH, ORP und Temperatur. Konfigurierbare Verzögerungszeit und Hysterese. Störungsmeldung.
Steuerungsfunktion: Ein/Aus, PID-Betriebszyklus oder gepulste Frequenzregelung.
Waschen: Kontakt kann zum Starten von manuellen Waschzyklen oder solchen mit Intervallzeit verwendet werden.
Halten: Kontakt kann zum Signalisieren des Hold-Status verwendet werden.
Ausfall: Kontakt S4 ist als Ausfallsicherheitskontakt programmiert.
Kontakteingang Waschzyklus-Fernstart.
Temperaturkompensationsfunktion Automatisch oder manuell. Kompensation gemäß Nernstscher Gleichung. Prozesskompensation durch konfigurierbaren Temperaturkoeffizienten, NEN6411 für Wasser oder starke Säuren/Basen oder programmierbare Matrix.
Kalibrierung Halbautomatische 1- oder 2-Punkt-Kalibrierung mit vorkonfigurierten NIST-, US-, DIN-Puffertabellen 4, 7 und 9 oder mit benutzerdefinierten Puffertabellen mit automatischer Stabilitätsprüfung. Manuelle Justage auf Laborprobe.
Anzeige Grafische Anzeige VGA (320 x 240 Pixel) LCD mit LED-Hintergrundbeleuchtung und Touchscreen.
Gehäuse Aluminiumgussgehäuse mit chemisch beständiger Beschichtung; Polycarbonat-Abdeckung mit flexiblem Fenster aus Polycarbonat, Schutzgrad IP66/NEMA 4X/CSA Typ 3S
Spannungsversorgung PH450G-A:
  Netzfrequenz; 100 bis 240 V AC, zulässiger Bereich; 90 bis 264 V AC
  Netzfrequenz; 50/60 Hz, zulässiger Bereich; 50 Hz ±5 %, 60 Hz ±5 %
  Stromverbrauch; 15 VA
PH450G-D:
  Netzfrequenz; 12 bis 24 V DC, zulässiger Bereich; 10,8 bis 26,4 V DC
  Stromverbrauch; 10 W
Umwelt- und Betriebsbedingungen Umgebungstemperatur: -20 bis 55 °C (-5 bis 130 °C)
Lagertemperatur: -30 bis 70 °C (-20 bis 160 °C)
Luftfeuchtigkeit: 10 bis 90 % r. F. bei 40 °C (100 °C) (nicht kondensierend)
pH-Eingang ≤0,01 pH
ORP-Eingang ≤1 mV
Temperatur ≤0,3 °C (≤0,4 °C für Pt100)
Sprungantwort  < 4 s für 90 % (pH 7 – pH 4)

Verlängerungs-Anschlussbox BA10/WTB10

Bei größeren Entfernungen zwischen der Messstelle und dem Analysator, insbesondere wenn die Entfernung die Länge der Standard-Elektrodenkabel überschreitet, bietet dieses Anschlusszubehör eine zweckmäßige Möglichkeit zum Anschluss der Sensorkabel an das Messinstrument.

Übersicht:

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

Industrien:
Applikations-beschreibungen
Übersicht:

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.

Applikations-beschreibungen
Übersicht:

The term "cooling tower" is used to describe both direct (open circuit) and indirect (closed circuit) heat rejection equipment. Cooling towers are heat-transfer units, used to remove heat from any water-cooled system. The cooled water is then re-circulated (and thus, recycled) back into the system. Since the process water is re-circulated, the mineral concentration increases as a result of the evaporation.

Industry:Refining, Food and Beverage, Power, Oil and Gas, Pulp and Paper, Chemical

Industrien:
Applikations-beschreibungen
Übersicht:

The proliferation of microorganisms and the resultant formation of slime is a problem which commonly occurs in aqueous systems. Problematic slime producing microbes may include bacteria, fungi and/or algae. Slime deposits typically occur in many industrial aqueous systems including cooling water systems, pulp and paper mill systems, petroleum operations, clay and pigment slurries, recreational water systems, air washer systems, decorative fountains, food, beverage, and industrial process pasteurizers, sweetwater systems, gas scrubber systems, latex systems, industrial lubricants, cutting fluids, etc.

Industry:Refining, Food and beverage, Power, Oil and Gas, Pulp and Paper, Chemical

Industrien:
Applikations-beschreibungen
Übersicht:

There are a number of suppliers of oil and fat products used for edible purposes. These products include, but are not limited to olive oil, peanut oil, soybean oil, sunflower oil, lard, shortening, butter, and margarine. The raw materials for these products include animal by-products, fleshy fruits (palm and olive), and oilseeds. 

Industry:Food and Beverage

Applikations-beschreibungen
Übersicht:

One of the primary applications for high purity water is for boiler feed water. The measurement of pure water pH can be one of the quickest indicators of process contamination in the production or distribution of pure water. Effective chemical treatment of the feed water is vital in maintaining the useful operating life and minimizing maintenance costs of the boiler.

Industry:Power, Pharmaceutical, Common

Industrien:
Applikations-beschreibungen
Übersicht:

Process liquid analyzers such as pH meters, conductivity meters, ORP meters, and density meters play an important role at electrolysis plants in the control of concentrations of various process solutions. This requires both precision and stability under harsh conditions that include highly corrosive substances, high temperatures, and many impurities.

Übersicht:

Most zinc are produced at hydrometallurgically, where a high-grade zinc product can be obtained and valuable metals mixed in the raw material can be recovered. In the hydrometallurgy, the raw material of zinc concentrate is roasted and then dissolved in sulfuric acid to remove impurities. The process called leaching and pH control of the leachate is important.

Industry:Chemical, Power

Industrien:
Applikations-beschreibungen
Übersicht:

Problems at the wet end of a paper machine can rarely be corrected down stream. That is why monitoring and controlling pH in pulp stock is critical to the paper making process. Essentially, at every stage in the manufacture of paper, correct pH values play a vital role. Variations in the pH value at the head box have a negative effect on the quality of the paper produced.

Übersicht:

Cyanide-bearing wastewater from mining and electroplating facilities and certain types of chemical plants is toxic and must be treated by oxidation with chlorine or chloride to bring the cyanide concentration within regulatory limits.

Industry:Electrical and Electronics

Applikations-beschreibungen
Übersicht:

Fish perform all their bodily functions in water. Because fish are totally dependent upon water to breathe, feed and grow, excrete wastes, maintain a salt balance, and reproduce, understanding the physical and chemical qualities of water is critical to successful aquaculture. To a great extent water determines the success or failure of an aquaculture operation.

Übersicht:

Introduction

cobb1Paper is used in a broad array of products essential for everyday life, from newspapers, books, magazines, printing, writing papers to cardboard boxes and bags, paper napkins, sanitary tissues etc. We are daily surrounded by paper products.

The most important use of paper is writing. The quality of paper used for printing or writing should be good and it depends on many parameters. One of the parameters is Cobb, which needs to be controlled.

What is Cobb Control?

Cobb control is nothing but the control of quality and binding of pulp in such a fashion that whatever is written by any source such as ink, etc on paper it should not spread as well as leave its impression on back side of the paper.

How is Cobb Variation Minimized?

Cobb variation is minimized by maintaining pH of the pulp in the range of 5-6 pH. Before processing, the raw pulp pH is in the range of 7-8. This should be controlled and brought down to acidic range i.e. 5 to 6 pH. This is very essential for following reasons.

  1. This ensures proper binding of the fiber
  2. Cobb is controlled
  3. Further it also helps in maintaining paper 
machine run ability at head box.

How is Cobb Control Done?

Cobb control is done by addition of Alum (which is in the range of 2-3 pH) and rosin to pulp. When alum and rosin are mixed with pulp after a certain distance pH of the mixture is measured and if it is not in the desired range the transmitter will control the Alum dosing via controller so that pH of the pulp is maintained. Rosin on the other side has no such controlled action. It will be getting dosed to the pulp continuously in a specific quantity. It is the Alum whose dosing is controlled depending upon pH variations.

Application Overview

By installing pH loop in paper industry not only the Cobb control is done but also customer can achieve the following:

  1. 20% saving in Alum consumption
  2. Eliminate corrosion problem in approach flow 
pipelines, pumps and other equipment. This is because if alum dosing is not controlled, there are chances that more Alum is dosed and it can lead to corrosion of pipes and components.

Summary

Measurement points:

After Rosin tank:

cobb2

Typical problems: Cleaning of sensor in such installations

Remedies: Using retractable fitting this optimum level of pH can be achieved by using Yokogawa's 4-wire pH Analyser with suitable retractable fitting and sensor. Our manual retractable fitting PR10 with Titanium ball valve is designed for use in pulp industry where frequent
cleaning of the sensor is required. For cleaning one has to take out pH sensor, close the ball valve so that the sample will not come out, clean the sensor, open the ball valve and then put back the cleaned sensor. The pH sensor will be a combination electrode having double junction electrodes, which provide long time stability and a prolonged lifetime. In our 4-wire pH analyser on 2nd mA output we have PI control facility. The speed of the alum dosing pumps can be controlled as per pH variations with the help of this feature.

Übersicht:

The treatment of wastewater from pulp and paper plants is a serious environmental concern. Yokogawa's submersion holder with an ultrasonic+air-jet cleaner (customized product) can reduce the manual cleaning frequency to just once every one or two months.

Industry:Pulp & Paper

Industrien:
Applikations-beschreibungen
Übersicht:

Continuous technology improvement is ongoing in the pulp & paper industry to obtain the best possible performance. Problems at the wet end (stock preparation) can rarely be corrected downstream. That is why monitoring and controlling pH in pulp stock is critical to the paper making process. Essentially, at every stage in the manufacture of paper, correct pH values play a vital role.

Applikations-beschreibungen
Übersicht:

Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure.

Übersicht:

Continuous technology improvement is ongoing in the pulp & paper industry to obtain the best possible performance. The improved plant performance translates to the higher quality improvement and lower cost, and simultaneously environmental friendly plant operation.

Industrien:
Übersicht:

Wastewater from electroplating facilities and certain types of chemical plants contains toxic forms of hexavalent chromium such as chromate and dichromate. The hexavalent chromium in this wastewater must be reduced before the water can be discharged. This requires a two-step process: hexavalent chromium (CR6) is reduced to trivalent chromium (CR3); and CR3 is precipitated as chromium hydroxide.

Industry:Electrical and Electronics

Applikations-beschreibungen
Übersicht:

Removal of free oil and grease from a wastewater stream reduces the potential for equipment problems to occur further downstream. There are three forms of oil encountered in wastewater treatment at a refinery. 

Industrien:
Applikations-beschreibungen
Übersicht:

Sour Water is the wastewater that is produced from atmospheric and vacuum crude columns at refineries. Hydrogen sulfide and ammonia are typical components in sour water that need to be removed before the water can be reused elsewhere in the plant. Removal of these components is done by sending the sour water from the process to a stripping tower where heat, in the form of steam, is applied.

Applikations-beschreibungen
Übersicht:

Power plant boiler houses designed to burn coal or high sulfur oil are required by Federal and State pollution regulations to "scrub" (remove) sulfur dioxide from flue gasses to meet emission limits. SO2 in flue gasses is known to be harmful to the environment, as it is one contributor to the formation of acid rain. pH control is critical for the proper functioning of the scrubber system.

Industrien:
Übersicht:

Sodium chlorate is an inorganic compound with the chemical formula NaClO3. It is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 300 °C to release oxygen and leave sodium chloride. Several hundred million tons are produced annually, mainly for applications in bleaching paper.

Übersicht:

Application Description

Many Ethanol plants running today are using a combination style pH electrode with a non-flowing reference to measure pH in the Mash Slurry transfer line from the Mash slurry mix tank to cook.  The Mash is being pumped out of the Mash Slurry tank is at approximately 82 °C and  2 to 4 bar (180 °F and 40 to 60 psig).

The original pH electrode systems that were installed during plant construction are online retractable assemblies and are mounted in orientations from completely horizontal to completely vertical and everywhere in between.

The Problem

The combination probe that is being used will typically drift out of calibration very quickly.  Also, the probe is damaged sometimes from excessive removal from the process.  The reason this probe drifts out of calibration is due to the fact that the non-flowing reference system plugs and becomes fouled by the mash passing by it.  pH measurements are only as good as the reference required to make this measurement.  If the reference is not doing its job, the measurement electrode will drift.

Process Overview

Product Recommendations

Yokogawa manufactures a multi-probe holder called the FF20 – flow through fitting or the FS20, which is pH chamber assembly with ½” NPT process connections.  With these holders we use a combination electrode, part number:  SC21C-AGC55 for measurement and reference and a separate temperature sensor part number: SM60-T1.  The Yokogawa electrode system works due to the fact that the SC21C-AGC55 combination probe uses a pressurized reference system.  By using plant air regulated to a KCl reservoir, the SC21C-AGC55 utilizes a positive flowing reference that does not foul. 

Plants using this system typically check the pH measurement against a grab sample and only make adjustments if the sample and the online measured values are more than 0.2 pH difference from one another.  Typically, the system will not need daily or weekly calibrations.  Most plants will pull the electrodes once a month for cleaning and calibration in a standard 4 and 7 buffer solutions.

Installation Considerations

The Yokogawa pH system is not retractable from the process.  It is usually best to put the Yokogawa pH electrodes in a by-pass or recirculation line that you can add isolation valves for isolating the probes from the process for maintenance and calibration.  The probe assembly should be mounted downstream of the Slurry Tank transfer pump.  Ideally it will be in a recirculation line going back into the tank or into the suction side of the slurry pump.

The picture below shows an installation that is actually flowing from left to right.  The arrows indicate the direction of the mash flow through the recirculation line and back into the suction side of the pump.  You will get an idea of the installation of the Yokogawa probes and the pressurized reference KCl reservoir from this picture.  The reservoir pressure is typically set 1 to 2 psig above the slurry line pressure.  The KCl reservoir will require refilling every 2-3 months for most applications

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

Applikations-beschreibungen
955 KB
Applikations-beschreibungen
Übersicht:

Introduction

The Combined Effects of pH and Percent Methanol on the HPLC Separation of Benzoic Acid and Phenol:

Many mobile-phase variables can affect an HPLC (High Performance Liquid Chromatograph) separation. Among these are pH and the percent and type of organic modifier. The pKa of a weak acid is the pH at which the acid is equally distributed between its protonated (uncharged) and unprotonated (charged) forms. This is illustrated by the Henderson–Hasselbalch equation:

pH = pKa + log ([A_]/[HA]

where [A_] is the concentration of the weak acid in its unprotonated form
and [HA] is the concentration of the weak acid in its protonated form.
 

If the weak acid is equally distributed between its two forms, ([A_]/[HA]) = 1, log ([A_]/[HA]) = 0, and pH = pKa. If the weak acid is not equally distributed between its two forms, then the pH will be either less or greater than the pKa of the weak acid.

For example, if [A_] < [HA], ([A_]/[HA]) < 1, log ([A_]/[HA]) < 0, and pH < pKa. Thus, a weak acid exists primarily in its protonated form at a pH below the pKa and therefore has a greater affinity for the nonpolar stationary phase. If [A_] > [HA], ([A_]/[HA]) > 1, log ([A_]/[HA]) > 0, and pH > pKa. Thus, a weak acid exists primarily in its unprotonated form at a pH above the pKa and therefore has a greater affinity for the polar mobile phase.

Fig 1 - full-factorial experimental design

Fig. 1 - A three-level, two-factor
full-factorial experimental design

Organic modifiers also have an effect on the retention of solutes in HPLC. In the reversed-phase mode (polar mobile phase, nonpolar stationary phase), the most polar solute component will elute first. This is because the most polar component interacts least with the nonpolar stationary phase.

As the polarity of the mobile phase is increased, those solute components that were previously highly retained (nonpolar components) will be retained even more.

Two species that are of public interest because of their classification as moderate environmental and health hazards are benzoic acid (pKa = 4.202) and phenol (pKa = 9.98). The purpose of this study is to investigate the combined effects of pH and percent methanol on the reversed-phase HPLC separation of these compounds.

A three-level, two-factor fullfactorial experimental design will be used to specify nine mobile phases for consideration in this study. The levels of pH were chosen to bracket the pKa value of benzoic acid (below, near,
and above 4.202). It was not possible to study a mobile phase with a pH > 7.5 owing to the pH range limit of the column. A methanol/water mobile phase was selected for this study because methanol is readily available in most undergraduate labs and relatively inexpensive. In addition, both solutes elute in a relatively short time, making completion of this lab during one or two lab periods possible.

Table 1. Mobile Phases Specified by the Experimental Design
 
Phase No. Methanol % pH
1 25 3.0
2 25 4.5
3 25 6.0
4 50 3.0
5 50 4.5
6 50 6.0
7 75 3.0
8 75 4.5
9 75 6.0

Major Observation

At low mobile-phase methanol concentration (25%), as pH increases, the retention time of phenol appears to be unaffected, whereas the retention time of benzoic acid decreases significantly. Over the pH range investigated, the mobile-phase pH is below the pKa of phenol. Thus, phenol will remain in its protonated form and should be unaffected by these mobile-phase changes. However, as pH increases, benzoic acid shifts from its protonated to its unprotonated form, decreasing its affinity for the nonpolar stationary phase and decreasing its retention time.

At intermediate (50%) and high (75%) mobile-phase methanol concentrations, as pH increases, the retention time of phenol remains unaffected by increases in pH while the retention time of benzoic acid decreases. This is consistent with the behaviour at low methanol concentration.

At pH 3.0, as percent methanol increases, the retention times of both phenol and benzoic acid decrease significantly. Because both solutes are polar, increasing mobile-phase polarity causes both to be retained less tightly. At pH 4.5 (slightly above the pKa of benzoic acid) and pH 6.0 (well above the pKa of benzoic acid) as percent methanol increases, the retention times of phenol and benzoic acid decrease. This is consistent with the retention behaviour at pH 3.0.

Typical Process Details

  • Customer plant: Bulk drug plant
  • Application: This is 4 cycle application. There will 
be a pipe connected to inlet which allows process to flow through the column and the same will be sent out from another pipe at outlet.
  • pH measurement is typically required at both the inlet and outlet. Temp: 30-40°C. pH range shall be 7 to 7.5. Between this range the customer can take necessary action to control his process.
  • Conductivity max. 300 micro siemens/cm.
  • Cycle 1: Process contains 95% liquid methanol, 
2% liquid ammonia, 3% water.
  • Cycle 2: Process contains 30% liquid methanol, 
70% water.
  • Cycle 3: Process contains 90% liquid methanol, 
5% liquid ammonia, 3% water, 2% sugar content.
  • Cycle 4: The column will be cleaned by flushing 
with DM water.
Übersicht:

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

Applikations-beschreibungen
Übersicht:

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

 

 

Übersicht:

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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