SO3 Monitor
#Measuring and #Analyzing

SO3 Monitoring

Simply explained

WELCOME! Let me explain our SO3 Monitor

The most reliable measurement techniques for safe data processing.

Continuous SO3 Measurement

Online Monitoring

Many well-known operators of fossil fueled power plants and industrial factories have relied

on the unsurpassed accuracy of this instrument, constantly developed since 1989

The SO3 or H2SO4 in the gas sample is absorbed as sulphate ions (SO42-) in an aqueous solution of propan-2-ol in water.

The solution is passed through a bed of barium chloranilate. The acid chloranilate ions created are measured in a continuous flow photometer. By maintaining a constant ratio of flow rates for the gas and the propan-2-ol absorbing solution, the concentration of acid chloranilate ions can be directly related to the sulphate ion concentration in the absorbing solution, and hence the SO3 concentration in the gas. Above acid dew point temperature > 130 °C


  • Supply of turnkey equipment
  • Supply of rental units
  • Supply of test run

[Situation]   »   [Challenge]   »   [Pentol]   »   [Plan]   »   [Action]   »   [Results] 


How much SO3 do you generate?

In power generation, SO3 measurements provide data to allow the operator to burn fuel in the most efficient way to minimize corrosion of the plant and limit acid discharges to the environment. Monitoring of SO3 is also important where it is formed as a by-product, e.g. in De-NOx systems.
In processes where H2SO4 is used or ore with large amounts of sulphur is processed, the SO3 monitor can measure SO4 2- ions and show emission as mg/Nm³ or ppm.
Action principle


The Pentol SO3 monitor has been designed to meet a wide range of measuring requirements.

  • 1 – 200 ppm SO3
  • Flue gas temperature up to 400°C (up to 550°C with special probes)
  • The instrument is portable and suitable for long- and short-term measurements
  • The unit is auto-calibrating in a user-defined cycle
  • An optional RS232 connector allows to log measurements on a laptop

Questions regarding function, support, and sales are answered via online chat support and e-mail to, as fast as possible.

The Pentol SO3-monitor is based on a wet-chemical process.

The gas sample is measured by means of a heated probe. In the probe head, the sample is cooled down and diluted in a mixture of isopropanol and water. The SO3 condenses and reacts with the sulfuric acid in the liquid phase, eliminating all problems related due to insufficient heating is known from manual measurements.

The sample is then transported to the instrument by the peristaltic pump and reacts with bariumchloranilate, colouring the sample according to the SO3 concentration. The concentration is then measured with a photometer that can be calibrated automatically.

This procedure allows measuring repeatedly and very accurate directly in the plant or in laboratories.


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TECHNOLOGY – SO3 Monitoring


TECHNOLOGY – Monitor de SO3