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Measure aqueous ammonia inline
NH3 concentration in real time

LiquiSonic® determines the ammonia content in water directly in the pipeline or in the tank. No sampling, no bypass, and no waiting time.

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Real-time measurement

Continuous monitoring without delay

Maintenance-free

No moving parts or wear components

Maximum accuracy

Precise measurement even under difficult conditions

Reduced operating costs

Cost-efficient solution with a short payback period

The concentration of ammonia in water (also called aqueous ammonia, ammonia solution, NH4OH) can be determined continuously and inline using ultrasound. LiquiSonic® measures the speed of sound and temperature in the medium and converts both values into NH in real time3concentration.

  • Measurement range: 0–35 wt% NH3 in water at max. 30 °C or from 95 wt% NH3

  • Measurement principle: Measurement of the speed of sound with integrated temperature compensation, independent of color, turbidity, and conductivity

  • Installation: DN 80 pipe sensor as a wafer flange, optionally PFA-coated; or 40-40 Ex immersion sensor with flange

  • Explosion protection: ATEX and Ex (the 40-40 Ex immersion sensor is approved for Zone 0)

  • Maintenance: no moving parts, no wear; regular calibration is not required

How does ammonia measurement with ultrasound work?

The sensor sends an ultrasonic pulse through the medium and measures its transit time over a known distance. This determines the speed of sound in the medium, which changes with the ammonia content in the liquid. Since the speed of sound also depends on temperature, the sensor records the temperature as well. The assignment of speed of sound and temperature to concentration is done using a previously defined product data set. For aqueous ammonia, this covers the entire range from 0-35 wt% and 95-100 wt%.

Why not titration, conductivity, density, or refractometry?

Each of these methods basically works, but for aqueous ammonia each one reaches a specific limit. The Titration is unbeatable in accuracy as a reference method, but it remains a spot sample. Because ammonia can off-gas between sampling and analysis, sample handling determines the result. In addition, the labor effort remains. The Conductivity is tricky for a weak base. The degree of dissociation decreases as concentration increases, conductivity reaches a maximum in the low percentage range and then decreases again. A measured value can therefore correspond to two different concentrations, and dissolved salts further distort the picture.

Density and Coriolis measurements use a relationship that is usable in itself. Density decreases significantly as ammonia content increases, but it responds sensitively to off-gassing bubbles and to the installation situation. Refractometers and optical methods require a clean window. Deposits, turbidity, and condensate directly affect the measured value. A pH measurement is too ambiguous in the concentration range relevant here.

Speed-of-sound measurement is independent of color, turbidity, and conductivity, and works without moving parts, electrodes, or an optical window.

Problems a lab sample does not solve

The result comes too late

The sample provides an exact value, but for a point in time that has long passed by the time the result arrives. Between two samples, the plant is operating blind, and deviations are only noticed when it is too late.

Ammonia evaporates

NH3 has a considerable partial pressure within an aqueous solution and escapes, promoted by heat, storage time, and any opening or transfer pumping. Anyone who designs dosing based on a (outdated) nominal value will underdose aged product without realizing it.

Every sample is an occupational safety issue

Ammonia solution at this concentration is corrosive, and the vapors irritate the eyes and respiratory tract. Sampling from an operating line means extensive safety measures, a permit process, and a residual risk that becomes smaller with every avoided sample.

Temperature-compensated measured values

In an unheated tank farm, the medium temperature fluctuates. Methods without precise integrated temperature measurement then deliver values that cannot be compared over months or years.

Application examples

Aqueous ammonia is typically delivered at about 25 wt%. It is then dosed and diluted to significantly lower levels, while wash and working solutions, for example, may be above that depending on the process. Typically, it is only checked by spot sampling, and this is exactly where emission, quality, and cost risks arise.

The following industries benefit directly from continuous concentration measurement:

 

Flue gas treatment

Operations management and emissions officers

Waste incineration and refuse-derived fuel power plants, biomass and coal-fired power plants, cement, glass, lime, and steel plants.

  • Dose reducing agent according to NOxload
  • NOxreliably comply with limit values
  • NH3limit slip

Production & filling

Process and quality managers

Absorption of gaseous NH3 in water, adjustment to specification, filling of product and solutions.

  • Specification compliance for every batch
  • less rework and repackaging
  • Batch documentation without manual work

Tank farm & logistics

Goods receipt and maintenance

Receipt by tanker truck, storage tanks, transfer pumping, and distribution in the plant.

  • Check concentration upon receipt
  • Detect incorrect filling
  • Make off-gassing losses visible

Exhaust air & gas scrubbing

Gas scrubbers and recovery

Coke plants, fertilizer and melamine plants, exhaust air scrubbers in the food and agricultural industries, emergency gas scrubbers.

  • Keep wash solution at the optimum absorption point
  • Control loading and regeneration
  • Document availability in the event of an incident

Refrigeration and energy technology

Absorption refrigeration and heat pumps

Ammonia/water in absorption refrigeration systems, waste heat utilization, industrial cooling circuits.

  • Monitor circulating solutions
  • Detect performance drops early
  • Measure concentration instead of calculating it

Planning & plant engineering

Engineering firms and EPC projects

New plants and retrofits in which a measuring point for aqueous ammonia must be specified.

  • Ex-compliant design
  • Material approval for NH3solutions
  • Connection to the process control system and control room

System technology

Measurement range and accuracy
For ammonia in water, the system is designed for up to 35 wt%. The NH is displayed and output3-concentration in weight percent as well as the underlying variables sound velocity and temperature (density also available on request). The measurement method itself can be used far beyond these limits: from −100 to 200 °C and pressures up to 500 bar. For comparable two-component applications, LiquiSonic achieves® measurement accuracies of ±0.05 wt%. We would be happy to review the value that can be guaranteed for your ammonia water measuring point together with our application team in a personal conversation.

Dynamics
The sensor performs more than 30 measurements per second. Concentration jumps, such as when switching to a different batch or in the event of incorrect filling, are detected immediately.

Materials and explosion protection
For most ammonia water applications, austenitic stainless steels are sufficient. For corrosive accompanying substances or increased purity requirements, a PFA coating of the wetted surfaces is available. The explosion protection is ATEX- and Ex-certified: the immersion sensor 40-40 Ex is approved for Zone 0, and the inline sensors are available in flameproof enclosure design.

Controller and maintenance
A LiquiSonic® controller supports up to four sensors, allowing delivery, tank, and dosing point to be displayed on one interface. The connection is digital, drift-free, and interference-resistant over distances up to 1,000 m. For transmission to the control system, 4-20 mA outputs as well as Profibus DP, Modbus, Ethernet/IP, and Foundation Fieldbus are available (the measured values are also recorded in the device). During operation, there are no wear parts, no electrodes, no seals, and no optical window, so regular calibration is not required.

Over 35 years of experience in concentration measurement

SensoTech has been a leading provider of inline measurement technology since 1990 and has established itself as a specialist in precise concentration and density measurements.

Our systems are used worldwide, including in critical applications.

35+

Years of experience

50+

Countries worldwide

ISO 9001

Certified quality

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Frequently asked questions

How can the concentration of ammonia in water be measured?

For example, via sound velocity: an ultrasonic sensor in the pipeline or in the tank measures the transit time of a sound pulse over a known distance and simultaneously records the temperature. From both variables, the LiquiSonic calculates® controller calculates the NH₃ concentration based on a product data set for ammonia water measured in the laboratory. The measurement runs in a closed system, without sampling, without bypass, and without a calming section.

What measurement range does the system cover?

Für diese Anwendung ist das System auf 0 bis 35 wt% und 95 bis 100 wt% NH₃ ausgelegt und über den gesamten Bereich temperaturkompensiert. Für vergleichbare Zweikomponenten-Messungen liefert LiquiSonic® accuracies of ±0.05 wt%. The value that can be guaranteed for a specific measuring point depends on the process conditions and is only defined as binding in the quotation.

Why does the ammonia content in the tank decrease over time?

Because ammonia has a significant partial pressure relative to an aqueous solution and therefore outgasses. Heat, long storage times, movement during transfer, and every opening of the system promote the loss. A solution delivered as 25 wt% can already be significantly below that after extended storage. Anyone designing the dosage based on the nominal value often underdoses. Continuous measurement in the storage tank makes this trend visible before it is reflected in emission or quality values.

How can the delivery be checked before it enters the tank?

A LiquiSonic® A sensor in the filling line is a typical installation point. The ammonia content of the incoming batch is displayed and recorded during transfer, so deviations and mix-ups are noticed immediately.

Does inline measurement replace titration in the laboratory?

It replaces titration as the basis, not as the reference method. As a rule, LiquiSonic takes over® ongoing monitoring and control, while the laboratory verifies and documents at longer intervals. The effort required for regular sampling is significantly reduced, along with personnel exposure to caustic solution and ammonia vapors.

Can the sensor be installed in a hazardous area?

Yes, LiquiSonic is available for this purpose® in ATEX- and Ex-certified versions. The inline sensors are available in flameproof enclosure design, with the wetted side and the surrounding area each in Zone 0 and Zone 1. The marking that can be guaranteed for your specific measuring point depends on the process conditions and is only defined as binding in the quotation.

Which materials are suitable for ammonia solutions?

For pure ammonia water applications, austenitic stainless steels are generally sufficient. Copper and copper alloys such as brass are unsuitable because ammonia attacks them and can cause stress corrosion cracking. HC2000 or a PFA coating of the wetted surfaces is advisable if there are corrosive accompanying substances in the medium, chlorides play a role, or special purity requirements apply. We coordinate the material selection with your plant.

How strongly does temperature affect the measured value?

Significantly, which is why the temperature is measured as well. The sound velocity in an ammonia solution changes with both concentration and temperature. In the LiquiSonic® sensor there is a temperature probe whose measured values are directly incorporated into the real-time evaluation. An additional temperature measuring point in the process is not necessary.

What happens if there are gas bubbles in the line?

Outgassing ammonia is a real boundary condition with this medium. The LiquiSonic® sensor can be adapted to measurement conditions with gas bubbles through signal evaluation and can determine the gas bubble content in the medium. The installation point and installation orientation are equally important for this.

How does the measured value get into the process control system?

Sensor and controller are digitally connected, drift-free and interference-free over distances of up to 1,000 m. 4-20 mA outputs as well as Profibus DP, Modbus, Ethernet/IP and Foundation Fieldbus are available. The measured values ​​are also recorded in the device. A LiquiSonic® Controller serves up to four sensors.

Does the sensor need to be calibrated, cleaned or maintained?

The process uses two physical variables and works without wearing parts. Regular calibration is not necessary and the sensors will work reliably for many years. If process conditions or the composition of the medium change, the product data set can often be adjusted before recalibration would be necessary.

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