Product category:
Gas, Chemical, Radiation and Magnetic Sensors
News Release from: Flocare | Subject: Descaling
Edited by the Engineeringtalk Editorial
Team on 24 March 2000
British Steel Cleans Up With
Scalewatcher
A Scalewatcher unit is being used by British Steel in its BOS (Basic Oxygen Steeling) process at its Llanwern works.
British Steel is using the BOS (Basic Oxygen Steeling) process at its Llanwern works Waste gases generated in the process are laden with high levels of dust which have to be scrubbed out of the gas before it is used
The process uses water to draw off fluxes and fines together with large quantities of lime.
Waste gases from the furnace pass through a Venturi Saturator consisting of a series of high pressure water curtains.
The gas is cooled and larger dust particles removed and entrained in the water.
A high energy scrubber then sprays water into the gas to remove the fine particles.
Effluent from the scrubbers is transferred through a series of dirty water launders to the water treatment plant for cleaning.
The effluent has a very high calcium content due to lime being dissolved in the water at the furnace as part of the steel making process.
As water enters the treatment plant it is dosed with flocculent to help settle the solids.
Heavier grit particles are removed in the degritter and the resultant effluent transferred into a splitter tank where it is discharged to the clarification plant.
Lighter solids are settled in the clarifier ponds and pumped away as slurry for re-processing.
Cleaned water is recycled to the gas cleaning plant and fresh water make-up is carried out at the clarifiers.
Due to the process water being saturated with calcium and having a high pH value the pipes, sprays, in-line equipment and effluent launders rapidly became encrusted with limescale.
This necessitated regular plant shutdown for remedial work to be carried out using high pressure water jetting, manual descaling and also required frequent pipe replacement resulting in high costs.
A Scalewatcher unit was installed on the feed line to the No.
1 clarifier and at the end of a three month trial period, an inspection cover was removed some 150 metres downstream of the installation.
It was observed that instead of the thick hard scale usually found in the pipeline, the scale was just a few millimetres thick and soft.
This clearly showed the unit had been effective and had, in fact, worked along the whole length of the pipeline, preventing new scale and removing existing deposition.
Since then, the trial unit has been purchased together with a further three Scalewatcher systems.
British Steel is currently looking at other applications within Strip Products in South Wales and the North East of England and a further unit has been installed at the Llanwern Works.
Commenting, Colwyn Palmer, Operations Engineer, said: "I was very sceptical when first told about Scalewatcher, but after discussing it with the Plant Engineer we took advantage of the "Rent Before You Buy Scheme".
This allowed us to try out the unit before committing ourselves to a major purchase.
When we inspected the pipeline, I was surprised at how much scale had been removed.
We had been looking at other alternatives, but as the Scalewatcher system costs only ?10 per year in electricity to run, and there is no maintenance or consumables, it was the option we chose to take.
We are very pleased with the Scalewatcher system for this application".
Scalewatcher's patented technology works by producing a complex frequency modulated waveform.
Reacting to the varying applied field, the Scalewatcher creates an induced electric field inside the pipe whereby the crystal growth of the scaling minerals in the water is promoted.
As the crystals remain within the flow of the water, they no longer contribute to the build-up of hard pipewall deposits.
Existing scale layers are softened, and loosened scale crystals are removed from the system by the water flow.
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