Flue Gas Conditioning for Coal Boilers (FGC)
For #Dust Emission Reduction and #Gypsum Quality Improvement

Flue Gas Conditioning

Simply explained

WELCOME! Let me explain Flue Gas Conditioning.

The best way to reduce fly ash resistivity in electro static precipitators.

SO3 is injected into the flue gas duct

Before the ESP to reduce fly ash resistivity.

The minimized resistivity maximizes the impact of ESP

Back corona is eliminated and the filter can run at full performance.

You don’t need to enlarge the ESP

To increase gypsum quality and reduce solid emission.


  • Supply of turnkey equipment
  • Supply of rental units
  • Supply of test units
  • ESP Assessmentation
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Optimize ESP Performance with Flue Gas Conditioning 

Pentol Flue Gas Conditioning is a simple and reliable way to optimize ESP efficiency. With a market share of 100% in Europe, we offer the best available technology to comply with particle emission legislation and reduce carry-over of dust into the FGD unit, increasing the gypsum quality and reducing wast water treatment cost.
Pentol Flue Gas Conditioning has more or less the same effect as building an additional ESP field. Without the need for space, of course. And without changing the ductwork of your plant. And at a fraction of the cost. Pentol Flue Gas Conditioning reduces solid emission…
  • by increasing the efficiency of your ESP
  • by reducing the fly ash resistivity
  • by injecting SO3 into the flue gas stream.
On the following pages, we would like to show how this works.
Action principle

Modify fly ash resistivity to let the ESP run on its design point

ESP top view (without conditioning)
Fly ash has an electrical resistivity that is been made use of by the electrostatic precipitator (ESP). The ESP produces a huge electrical field where the dust is collected on large steel plates. The collection speed depends on the fly ash resistivity. Typically, coal with low sulfur level tends to produce fly ash with high resistivity. The ESP cannot build up an electric field that is strong enough to collect high resistivity particles, leading to higher than usual emissions or a break through of the ESP at high load.
ESP with conditioning (SO3 injection into flue gas duct)
Pentol Flue Gas Conditioning adds a small amount of SO3 to the flue gas. Just enough to reduce the fly ash resistivity, the ESP can now collect the dust properly and is running at its design capacity. Changing coal is getting easier, as the operator can simply increase or decrease the injection of SO3, preventing the need to mix different coals.
Avoid back corona   There are 2 reasons why back corona is no longer an issue with flue gas conditioning:  1. The resistivity of the ash is so low, that the electrical current flowing through the deposits is no longer an issue.  2. Because the deposits are no longer baked to the plates by the electrical current, the deposits are easily removed while rapping the plates. Not only is back corona completely eliminated, this also means that the lifetime of the precipitator plates and electrodes is extended.  

Increased whiteness of gypsum

In most countries, exceeding the emission limit forces the reduction of power production of the unit. The loss of production pays the cost of a complete Pentol FGC unit in a few days. This is why Pentol keeps mobile rental units available for testing, wherever an urgent need arises.
For plants equipped with FGD who sell their gypsum, a similar situation exists with FGD availability. If FGD is polluted by dust, the washers need to be cleaned regularly and the dust particles hinder the particle grow of the gypsum, resulting in a grey, watery gypsum of low quality. With Pentol Flue Gas Conditioning, whiteness and humidity of the gypsum are easily increased to comply with your buyer’s specification.
Dosing skid

Working Principle

Fully automatic dosing systems: precise, protected and easy to use.
Liquid, elemental sulphur is stored in a steam heated tank. By means of a dosing pump, the sulfur is transported into the sulphur burner. Together with pre-heated air, the sulphur is converted to SO2. After the sulphur burner, the SO2/air gas mixture is passing the 2-stage converter unit, oxidizing the SO2 to SO3. Now the SO3 is available for reaction in the flue gas duct. No SO3 is stored in any place and the correct quantity is produced automatically by the system.
In the flue gas duct, the SO3 is condensed immediately at the dosing point and reacts with the fly ash particles, resulting in a lower fly ash resistivity of these particles. Ash particles with lower resistivity have a higher migration velocity and are collected on the dust collector plates. The dust layer adhering to the collector plate is not working as an insulator anymore, allowing the current of the ESP to work in the electric field instead of heating up the dust layer on the plate. The obvious effect is a very high efficiency of the ESP and easy removal of the dust from the plates. In fact, after a few days of operation, the ESP will be cleaned by the SO3 and after rapping the bare metal is visible. Cycles between rapping of the plates can be extended for lower emissions and reduced stress of the ESP. To receive a quote, please talk to a sales engineer in order to find the best possible product for your application.

Containerized Flue Gas Conditioning System

All equipment is tested in our factory, reducing start up time on site considerably. All equipment is installed inside of 20 foot containers. This makes the system simple to install while protecting all elements from the influence of weather or dust. Worldwide we have a great range of rental units in all sizes and treatment modes.

Increase of ECO-efficiency


A large reduction in solid emission

Dust load

Reduced dust load entering FGD, the, therefore, more reliable operation of FGD with less cleaning cycles

Gypsum quality

The whiteness of gypsum and particle size (from FGD) is increased

Economy and use

Easy to operate. No special personal required to operate the system

Increasing the efficiency of the ESP, by reducing the Fly Ash Resistivity

Pentol develops products and services for the power industry. Our goal is to help our customers reduce emission and increase the performance of coal and oil-fired power stations. Pentol looks back on more than 30 years of successful treatment of boilers and looks forward to a cleaner world.
Ask our staff for a presentation or training. Did we get your attention? We would love to hear from you and discuss any questions you might have personally. Pentol has more than 100 units operating in Europe and successful references in Asia, Middle East and Central America and we are proud to share them with you!

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TECHNOLOGY – FlueGasConditioning for Coal » EN
TECHNOLOGY – Rauchgaskonditionierung