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Successful Commissioning of a Self-cleaning Evaporator

Another successful commissioning of a self-cleaning fluidized bed heat exchanger – the KLAREN system – in a waste water evaporation plant.The heat exchanger converted to the KLAREN system is the 1st stage of a 4-effect evaporator train to treat waste water from a plant producing dyes for textiles. The heat exchanger earlier experienced severe fouling by salts of calcium, magnesium and silica.

Due to fouling the evaporation capacity of the plant reduced to 50% in 20 days and the plant required cleaning of tubes. Subsequent to the commissioning with Klaren system the plant is operating at design evaporation capacity under stable conditions of the fluidized bed. With the KLAREN system, we make evaporator plants more sustainable.

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Business Benefit Self-Cleaning Heat Exchanger

What is the benefit of a self-cleaning heat exchanger for an evaporator?After the first period of operation we can answer this question. The answer comes from the graph that is added to this post. Previous experience of the plant showed that because of fouling of the heat exchanger tubes, the evaporation capacity of the plant reduced with 50% within 12 days of operation. After the retrofit to our technology, using a fluidized bed with cleaning particles, the evaporation capacity remained constant.Before the conversion the average production capacity was only 75% of design. So, with our technology the client has gained 33% production capacity. The benefit would be even greater in case the production loss due to the down-time for cleaning (can take between 2 and 5 days) would be considered as well.When comparing the investment for adding 33% capacity using conventional technology with the investment for a retrofit into the self-cleaning heat exchanger, a decision can be easily made. The investment for a retrofit is a factor of 3 smaller.

Self-cleaning Evaporator Pilot Unit for the Concentration of Digestate

We have successfully operated our self-cleaning evaporator pilot unit for treating digestate from a biogas plant in Germany. The aim was reducing the volume of the Digestate without facing fouling problems and maintaining high heat transfer coefficients with this viscous fluid.

Next year the pilot unit will become available for other evaporation cases.

Order for 3 Evaporator Plants

Shachi Engineering Pvt. Ltd. (Pune), our partner in India, has been granted the order for 3 new waste water treatment plants for the dye-making industry. The plants apply multi-stage evaporation of which the first and second stage will be configured with the self-cleaning technology of Klaren International. The design of the plant has been optimized for steam efficiency and to have a compact design. The order was granted after a successful project in which one of the existing evaporators of this client was revamped into the self-cleaning system and showed constant evaporation where previously fouling was an important issue.

Produced Water Concentration by Fluidized Bed Evaporators

Produced water is a by-product of oil and gas extraction. Regulations for fresh water recovery from these waters are becoming stricter, which makes operating costs for disposal expensive. Therefore, oil companies are paying more attention to systems to treat this water in an economically efficient way. A combination of forced circulation or falling film evaporation with mechanical vapor recompression (MVR) is a commonly used configuration. Vapor out of one stage evaporator is compressed and used as heat input in the shell side of the evaporator. The condensate can be re-used while the discharge can be further concentrated in crystallizers, dryers or just disposed in solar ponds for further evaporation. In some cases, the remaining liquid discharge is re-injected in wells.

Highly mineralized water is evaporated at high temperatures in the process to treat produced water. The combination of high mineral concentration and high temperatures causes these water solutions to precipitate minerals which crystallize as a scaling layer on the walls of the heat exchangers of the evaporators. Fouling of heat exchangers in this application results in:
  • Production losses or reduced operation capacity
  • Over sizing and / or redundancy of equipment
  • Increase in maintenance costs
  • Disposal of waste streams from using cleaning chemicals
A common practice to reduce the fouling effects in produced water evaporation is to use expensive softening pre-treatment plants and to limit the mineral concentration levels due to the relation between mineral concentration and fouling tendency. This adds a constrain into the maximum produced water volume reduction that can be achieved through evaporation.

To avoid problems associated with fouling and to be able to further concentrate produced water above typical concentration levels, fluidized bed heat exchangers can be used. Fluidized bed heat exchangers can be used as forced circulation evaporators by combining a regular fluidized bed heat exchanger and a flash vessel downstream the liquid outlet. And can be integrated not only in MVR configurations but also in thermo-compressor or multiple effect evaporator trains.

The capital cost of evaporation systems including fluidized bed heat exchangers is lower than of conventional forced circulation or falling film systems. This is because there is no need for expensive softening systems prior to evaporation and redundancy is not required. When a downstream Zero Liquid Discharge (ZLD) stage (crystallizer or dryer) is installed, the capital cost difference is larger. If a fluidized bed heat exchanger is used it can lower size requirements of these systems. Operating costs are also lower due to lower costs of treatment or disposal of the evaporator discharge.

More details on this topic have been presented at the Heat Exchanger Fouling and Cleaning XII – 2017 conference in Madrid, Spain, on June 11-16, 2017. A full detailed paper is available.

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Contact us at:

Klaren International BV
Hanzeweg 35N
3771 NG Barneveld
The Netherlands

Phone: +31 85 27 34 834

Any questions?

We would be happy to answer them.

+31 85 27 34 834