classic | mobile
 

Search...

SA Instrumentation & Control Buyers' Guide

Technews Industry Guide - IIoT 2018

Technews Industry Guide - Maintenance, Reliability & Asset Optimisation

 

Acoustic process analytics
November 2011, Flow Measurement & Control


Europe’s largest production facility for ammonia and nitrogen fertiliser in Sluiskil, The Netherlands, produces up to 4000 tonnes of nitric acid per day to make nitrogen fertilisers. The plant has an automated filling station for transferring the nitric acid onto tanker trucks where the driver uses a memory card to enter the quantity and concentration into the station’s control system. The automatic filling requires both concentration and mass flow measurement.

These functions are usually implemented with mass flow meters that utilise the Coriolis effect. These meters measure the mass flow and the density, which is proportional to the concentration, by means of phase shifts in the vibration of the measuring tube and changes in the resonance frequency. The filling station at Sluiskil is equipped with such a Coriolis measuring system, however, nitric acid is a challenging fluid even for robust measuring methods and rugged instruments. Sluiskil experienced frequent process disruptions and failures of the measurement systems which had a negative impact on the performance of the plant. As a result, the production engineers started to look for alternative methods in order to ensure the continuous availability of the filling station. Unexpectedly, they found the solution in ultrasonics.

Acoustic process analytics

Ultrasonic flow measurement with transducers clamped to the outside of pipes is a well-established technology, particularly in the chemical industry, where aggressive and toxic fluids are often encountered. Much less common, however, is the application of this technology in the field of process analysis eg, for concentration measurement. For flow measurement, the difference of the transit times of an ultrasonic signal in and against the direction of flow is determined and used to calculate the flow velocity. Concentration measurement on the other hand uses the signal’s transit time to determine the specific speed of sound for the fluid. The speed of sound in a fluid depends on the fluid’s adiabatic compressibility and density, and also on its temperature. It is a material-specific quantity, so the mass flow can be calculated from the volume flow and the density. Determining the actual mass flow, therefore merely requires combining these two ultrasonic measurement functions. As clamp-on transducers are not in direct contact with the fluid, ultrasonic technology is particularly suitable for the measurement of challenging materials. Because of positive experiences with Flexim’s Fluxbus ultrasonic flow meters, the Sluiskil engineers presented their idea to Joost van Parreeren, director of the Benelux branch of Flexim.

Unlike ultrasonic volume flow measuring equipment, which can be set up in less than half an hour, concentration and mass flow required more extensive measurement preparation. Until now, there was little data on sound velocity as a property of the characteristics of this type of material. It was therefore necessary first to determine a set of curves representing the relationship between concentration and the speed of sound at various temperatures. If a good measuring effect was observed in the concentration range of interest, the method would be deemed suitable for use in the process. Laboratory tests demonstrated that, in the relevant range of measurement, it was possible to determine the concentration of nitric acid by measuring the speed of sound. The Flexim laboratories in Berlin set about determining the characteristic concentration curves for nitric acid and the corresponding co­efficients were transferred to the Piox S transmitter.

However, initial installation of ultrasonic measuring equipment in the process resulted in disappointment. It seemed the effort had been in vain.

Achieving success through quick temperature measurement

“The first measurement results came as a very unpleasant surprise,” recalls van Parreeren. Naturally, the initial reaction was to question the accuracy and reliability of the ultrasonic technology. “However,” van Parreeren however insisted, “ultrasonic measurement is not imprecise.” Closer inspection revealed that the difficulties did not originate from the sound velocity measurement.

The tank plant is equipped to deliver nitric acid at various levels of concentration, with 60 and 68% being most common, the lower concentration achieved by dilution with water. The dilution process is however exothermic, causing the temperature of the liquid to rise and it was found that the inability to measure this change in temperature accurately was the weak link in the system. The Pt 100 clamp-on probes that were initially used measured the temperature at the outer surface of the pipe, which made them unable to respond quickly enough to rapid temperature changes of the liquid. The manufacturer of the measuring equipment advised the plant engineers to refit the measuring point with a built-in thermo-element.

The installation of a special T-type precision thermo-element proved to be successful and using the correct temperature data, the Piox S transmitter delivered the correct mass flow results. “Everybody at Sluiskil is delighted with an excellently adapted measuring system and the successful implementation of genuine multiparameter measurement,” says van Parreeren. “At a comparatively low cost, the system measures the concentration in addition to the volume and mass flow without being worn out by the aggressive fluid.”

Further use of this adapted ultrasonic flow measurement technology is planned by by the engineers at Sluiskil.

For more information contact Peter Jones Electronic Equipment, +27 (0)11 608 2944, pjelec@iafrica.com, www.peterjones.co.za


Credit(s)
Supplied By: Peter Jones Electronic Equipment
Tel: +27 11 608 2944
Fax: +27 11 608 3825
Email: sales@peterjones.co.za
www: www.peterjones.co.za
Share via email     Share via LinkedIn   Print this page

Further reading:

  • Picomag for utility measurement
    December 2018, Endress+Hauser, Flow Measurement & Control
    In industrial process measurement and automation, demand is steadily rising for simple, reliable and maintenance-free measuring instruments in a pocket-sized format. The new Picomag from Endress+Hauser ...
  • Optisonic biogas flowmeter
    December 2018, KROHNE, Flow Measurement & Control
    The new Optisonic 7300 Biogas ultrasonic flowmeter from Krohne has been specially designed to measure dry and wet biogas with variable composition. The meter provides additional functions like calculation ...
  • Environmental challenges in the mining industry
    November 2018, Endress+Hauser, Flow Measurement & Control
    Endress+Hauser’s water quality measurement instruments.
  • Improved fuel management for mine fleets
    November 2018, Endress+Hauser, Flow Measurement & Control
    In the current economic climate, most companies are looking to make their Rands go further. This is especially the case when it comes to fuel, as modern industries cannot operate without it and diesel ...
  • Clearly visible flow measurement
    November 2018, Instrotech, Flow Measurement & Control
    To check the flow processes in pipeline systems and for insight into the interior of process pipes, many flow indicators are used in which the flowing medium sets a rotor turning and thus, to a large ...
  • Open channel flow
    October 2018, WIKA Instruments, Flow Measurement & Control
    WIKA constructs a Parshall flume for local effluent application.
  • Electromagnetic flowmeter
    October 2018, Instrotech, Flow Measurement & Control
    Kobold’s new model EPS electromagnetic flowmeter has a standard accuracy of ±0,3% of reading stability of zero. The new developed, microprocessor-controlled UMF2 converter guarantees highest accuracy ...
  • Foxboro’s top performing intelligent vortex flowmeters
    September 2018, EOH Process Automation Solutions, Flow Measurement & Control
    The 84 series measures volumetric and mass flow of saturated and super-heated steam.
  • Magnetic flowmeter with IO-Link
    September 2018, ifm Electronic RSA, Flow Measurement & Control
    The new SM4 type flow meter from ifm electronic operates according to Faraday’s law of induction. The conductive medium flowing through a pipe in a magnetic field generates a voltage which is proportional ...
  • Clamp-on ultrasonic flow measurement
    September 2018, Instrotech, Flow Measurement & Control
    Kobold’s portable DUC-MP and the stationary DUC-MF are designed for continuous non-intrusive flow measurement where accurate and drift-free operation is required for liquids in filled pipes. The devices ...
  • The art of craft
    August 2018, Endress+Hauser, Flow Measurement & Control
    “An explosion of art and science coming together to build a drinking masterpiece” – Urban Dictionary.
  • Powerful diagnostics for flowmeter intelligence
    August 2018, Emerson Automation Solutions, Flow Measurement & Control
    Emerson has launched the latest version of its Smart Meter Verification software for Coriolis and magnetic flowmeters, providing verification on demand and empowering process engineers, technicians and ...

 
 
         
Contact:
Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronic Buyers Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Other
Terms & conditions of use, including privacy policy
PAIA Manual





 

         
    classic | mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.