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State of the art technology:
Continuous casting solutions for oil and grease caused troubles in cooling water systems
The challenge
Since the 1960s continuous casting became more and more important in modern steel production. More than 80% of the worldwide production and more than 95% of the German steel fabrication use this process.
The need of optimizing and maximizing every important parameter of the manufacturing process leads us to the consideration of the secondary cooling. Improvement of this part of the facility provides for more safety, less maintenance and other measurable savings.
There are two main causes for scaling and clogging issues in cooling water systems of continuous casting plants: calcium fluoride and oil and grease which get into the system through lubrication. The mechanisms of malfunction caused by oil and grease usually are:
- oil and grease are left inside the cooling tower
→ cooling capacity and efficiency are decreased
→ water temperature becomes higher
- concentration of oil and grease in cooling water
→ sticking to strainers, spray nozzles
and water pipes
→ risk of decreasing flow rates,
spray water amount, cooling effect
- oil and grease stick to filter media
→ decrease of filter capacity and efficiency
- oil leakage from backwash water systems
→ oil and grease return back into the cooling system
and concentrate
→ stick to surrounding equipment
A proper operating cooling water system and the avoidance of production failure require a careful water treatment with the best available technique.
The solution
Depending on the specific requirements of a cooling water system in the continuous caster plant, there are several possible approaches to reach the goals. Kurita developed an array of special products which generate highest prosperity.
fig 1.: possible spots of applications
- Against oil stain at the cooling tower: dosage of Kurita Polyclean into the return water at the top of the cooling tower with 6-8 ppm
- In case of clogging of strainers, spray nozzles and water pipes: 40-60 ppm Coagulant is recommended to be dosed at the scale pit
- Filter cleaning: 50-100 ppm Kurita Diclean has to be added to the backwash water of the sand filters in order to keep filters clean and efficient. Dosing point: Pipeline of the backwash water
- Oil leakages from backwash water treatment: use of an organic coagulant, which is to be added 1-3 ppm to the back wash waste water
fig. 2: study of water pipe before and after treatment
fig. 3: study of sand filter material during treatment
Conditions:
| inlet water | outlet water before treatment | outlet water after treatment | |
| pH [-] | 8.5 | 8.2 | 7.6 |
| suspendend solids [mg/l] | 15 | <10 | <10 |
| turbidity [ntu] | 1.9 | 1.4 | 1.3 |
| oil and grease [mg/l] | 3.3 | 3.1 | <1 |
The result
The optimal treatment for a specific continuous caster plant depends on many different factors. The consideration of the entire system is necessary to develop the optimal concept.
As oil and grease can lead to several huge problems in the cooling water system they need to be avoided in the distribution system, in the cooling tower and in the sand filters. The variety of Kurita proprietary advanced cooling water products provides the ideal basis for the optimal treatment.
The application of the Kurita scaling inhibitor and filter conditioner improved the steel plant performance significantly. The sand filters worked more efficient, the backwash frequency decreased and the water quality improved. The amount of biocide demand was reduced about 20 % and the number of failures was reduced remarkably.
Beside the about 15% saving of the water treatment costs the new treatment provided a considerable increase of plant safety and operational reliability.