MED

Az Zour North facility is Kuwait’s first independent desalination plant and power station, accounting for up to 20% of the country’s desalination capacity and up to 10% of its energy capacity – Kuwait

A quick aerial view of the state of Kuwait brings one of the country’s most pressing challenges into sharp focus – meeting the water needs of a growing population in a landscape dominated by desert sands. In a recent study, the World Resources Institute ranked Kuwait among the top ten countries globally that are likely to face extremely high water stress by 2040. With average annual precipitation of just 121mm per year and no permanent rivers or lakes, it is no surprise that more than 90% of water for domestic and industrial needs and up to 60% of total water supply in Kuwait is currently met through seawater desalination plants. These desalination plants are energy-intensive. To keep them running and meet the growing demand for electricity across the country, Kuwait’s Ministry of Electricity and Water plans to significantly increase generation capacity in the decades to come.

Az Zour North Phase 1: Securing Kuwait’s Water and Energy Supplies

The Az Zour North Phase 1 Independent Water and Power Plant (IWPP) in southern Kuwait, approximately 100km from central Kuwait City, is one of the most important projects set up to secure Kuwait’s water and energy future. Launched in 2013, the landmark facility was the first public-private partnership (PPP) in Kuwait, with the government’s share at 60% and the remaining 40% owned by a consortium of private owners: France’s ENGIE (17.5%), Japan’s Sumimoto Corporation (17.5%) and Kuwait’s AH Al Sagar & Brothers (5%). With construction completed in December 2015, the desalination plant has a production capacity of up to 107 million gallons a day (MGD) of desalinated water. It comprises 10 multiple effect distillers (MED) and a potabilisation plant to provide drinking water. It accounts for up to 20% of Kuwait’s desalination capacity, making it the largest desalination facility in the country. The power behind the desalination process is provided through a 1.5GW combined cycle gas turbine (CCGT) power plant which can generate up to up to 10% of the country’s energy capacity. The power plant is equipped with five GE 9FA gas turbines, two GE steam turbines and five heat recovery steam generators (HRSGs). The plant both feeds electricity into the national grid and helps generate steam for the desalination process. Operations and maintenance services at Az Zour North are carried out by the Az Zour North Operations and Maintenance (AZN O&M) Company, a joint venture between ENGIE and Sumitomo. GE Power provided technical instruction during equipment installation and has a multi-year agreement to provide maintenance and repairs services for the gas and steam turbines at the power plant until 2034.

Unique Challenges for a Unique Region

Forging ahead with a project as unique as the Az Zour North IWPP posed several technical challenges, some very region-specific. For example, in the Middle East the reliability of operations and efficiency are very important. That is quite different from Europe, where the focus for gas turbines is often preservation, low-load operations and cycling. There were also very specific requirements in Kuwait to be able to run for extended periods of time on liquid fuel instead of gas, which can lead to issues such as fuel leaks and coking. Maximising the reliability of gas turbines in a harsh desert environment is not easy, but is of utmost importance for the stability of the grid. Remaining on schedule with the construction and delivery of a project of this size – the largest desalination plant in Kuwait – was equally challenging. According to Adel Masaad, Gulf & Pakistan leader for GE’s Power Services business: “The main challenge was that the first gas turbine was contractually required to be in commercial operation a little over 18 months after signing the EPC contract, followed by the second and third shortly after. This required extensive work to get the civil, mechanical and electrical infrastructure and balance of the plant to be ready to support commissioning of the first gas turbine.” The logistics of having all the required equipment delivered on time was also critical to the success of the project. “Despite the tight deadlines, the first gas turbine and generator were placed on foundations in July 2014, eight months after contract signature,” says Masaad. “Subsequent deliveries were well ahead of requirements, meaning that critical project milestones were achieved and Phase 1 of the North plant began operating at full capacity within two years of the project’s launch.”

Unlocking Future Efficiency and Growth

In an effort to continuously improve operations, AZN O&M and GE have now started to explore means to further strengthen the reliability and performance of assets at the Az Zour North facility. With GE successfully completing the digital transformation of Kuwait Ministry of Electricity & Water’s Sabiya CCGT power station earlier this year, GE and AZN O&M are together exploring the possibility of adopting new digital technologies at Az Zour North to further strengthen resource utilisation and productivity at the site. These digital solutions can give industrial businesses a complete, integrated view of assets and equipment. Connected machines equipped with data sensors can collect vast amounts of information into a centralised and secured data platform. The analysis of this data can provide insights to predict and diagnose equipment problems before they happen, reducing unplanned downtime. The success of the PPP model employed with the Az Zour North Phase 1 IWPP has also set a precedent for future growth paths in Kuwait’s utilities sector. Under the 2035 development plan, the Kuwaiti government has announced plans to boost foreign direct investment through public-private partnerships, adopting a more synergistic approach to driving long-term economic growth and diversification.

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Entrance Desalination technology

Desalination Technology is developing globally very fast these days. More and more desalination technologies getting applied into the conventional water treatment business today. DME does follow and support this development on an international basis starting from the first idea up to commodity products.

In order to give some direction what technology is available today this area will give a basic direction.

Following the navigation of this side you will find fundamentals such as on the right listed.

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Classification of Desalination Technologies

Desalination technology is used by humans since thousands of years. Being in the desert surrounded by sand and rocks or being on the sea sailing through salty waters, always fresh water is needed every day to keep the human body in a balanced hydrate mode.

Nature started using desalination processes from the very first moment. Different concentration levels drive everything alive on our planet. Humans started using first evaporation and condensation processes to purify unusable water. In the last century the number of processes to desalinate water and other liquids has gone through a very big development. New processes have been found, existing processes have been improved.

Overviewing all known desalination processes of today we may find a large number in a lot of science areas. In order to give this convolute of technology a systematic structure a larger group of desalination experts and scientists developed a Classification of Desalinaiton Technology (CDT) system.

This Classification of Desalinaiton Technoogy system is based on the natural working principles of chemistry, physics and biology. It starts as low as electrochemistry and nuclear physics. From here on it is building up its structure. Under the five main science fields 20 subordinated science areas have been found describing all natural working principles in desalination systems.

In order to structure all known desalination technologies a general structure was build up to the Classification of Desalinaiton Technology system (CDT):

The first classification level does divide in transient phase and stable phase technologies.
The second level classes represent the separation processes  of desalination technologies.
The third level classes show the main technology, in some cases without further structure.
The fourth level classes are split in advanced sub-desalination technologies.
In total there were 51 desalination technologies found and classified inside CDT.

As of today the used technologies mainly are Multi-Stage Flash and Reverse Osmosis they can be found within the structure at the third level.

Everybody is free to make use of this CDT but is asked to make a reference to DME GmbH on behalf of all people being involved, please.

We will keep developing CDT and you are free to participate in this discussion!

(more details LINK)

Desalination Technology in use

Today three technologies are dominating the international market. These are Multi-Stage Flash (MSF), Multiple-Effect Distillation (also Multi Effect Distillation or MED) and Reverse Osmosis (RO).

Looking into a global installed capacity in 2016 of about 90 mio m³/d app. 90% of this water is produced by these three technologies.

Multi-Stage Flash (MSF) takes app 20%, Multiple-Effect Distillation (also Multi Effect Distillation or MED) app. 5% and Reverse Osmosis (RO) app 65% of this.

The number of installed plants differs very much because a single MSF plant today easily does  produce 60.000 m³/d versus a RO plant very often produces 5.000 m³/d or less. Today more then 50 different desalination technologies are classified.

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Future Desalination Technology

Saving material and energy per ton of water produced is the main target of all developments in desalination. Due to this basic attempt every of the today known technology has to prove its benefits against the established ones. Not pointing out every new technology three of them are selected and briefly described at this stage (2017).

Obviously an idea for a technology needs to develop. On the right hand side you can see an overview of different technologies. This sketch does illustrate the state of science knowledge and in the same way the state of Development, Technology and Art.

Legend: State of science knowledge values

0 Very high, 1 High, 2 Medium, 3 Low, 4 Very low

In this context DME does illustrate some of the know how build up and some of the support given so far in this field of activities preforming. In order to classify the development of a technology DME did introduce the

– Desalination Technology Development Benchmark –

also called “DesTeDeBe”. You will find more details “here (LINK)”

Some of the latest developments in technology are now benchmarked here. In order you want to know more, please get in contact with DME.

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Multiple-Effect Distillation (MED)

Multiple-Effect Distillation (also Multi Effect Distillation or MED) is a thermal distillation technology based on evaporation and condensation processes in multiple stages, called effects, that is mainly used for desalination. In most MED plants, the seawater enters all the effects in parallel and is raised to the boiling point after being preheated on tubes. The seawater is either sprayed or otherwise distributed onto the surface of the evaporator tubes in a thin film to further rapid boiling and evaporation. The tubes are heated by steam from a boiler or some other source, which is condensed on the opposite side of the tubes (inside). The condensate from the boiler steam is recycled to the boiler for reuse. Only a portion of the seawater applied to the tubes in the effects evaporates. The remaining feed water is collected and fed to the last effect, from where it is removed by a brine pump. The tubes in the various effects are heated in turn by the vapours arose from the previous effect. This vapour is condensed to a fresh water product, while giving off heat to evaporate a portion of the seawater feed in the effects. This continues for several effects, with 4 or 16 effects being found in a typical large plant. The remaining seawater of each effect flows to the next effect through pipes by gravity. Generally, these plants are powered by low temperature heat leading to Top Brine Temperatures (TBT) of 55-70°C and are combined with mechanical vapour compressors or thermal vapour compressors. The number of effects directly correlating with the Performance Ratio (PR). In contrast to this, the PR is not significantly influenced by TBT. Depending on the TBT, pre-treatment of the feed and usage of anti-scalants is necessary. Furthermore, corrosion problems limit the usage of cheap construction materials.

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Multi-Stage Flash (MSF)

Multi-Stage Flash (MSF) evaporation desalination plants are based on flash evaporation in a cascade of stages (effects) at different pressure levels. In the brine-recirculation mode, the brine is recirculated through the system.

In the last stage of an MSF plant, the heated feed water is led into the pressure vessel where it partially evaporates in a flashing process due to the pressure decline. The vapour is used to preheat the feed water. The part of the brine that does not evaporate is sucked into the next stage which has a lower pressure. There, the same flashing and evaporation procedure takes place again, but at lower pressure and thus lower saturation temperature.

In this way, the feed that is used to condense the steam at every stage from the lowest pressure at the first stage to the highest pressure at the last stage is heated up continuously. The result is a low mean temperature difference between the feed water and the condensing steam, although the heat transfer is of type latent-sensible. Thus, the exergy losses are low.

The circulation of the brine mainly reduces costs for pre-treatment, but also reaches higher operation flexibility and better thermal efficiency. At the same time complexity and costs for components, construction, and maintenance rise.

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Membrane Distillation (MD)

Membrane Distillation (MD) is a thermal desalination process in which water vapour is transported through a hydrophobic porous membrane. Due to a partial pressure difference of vapour between a liquid surface and an air or gas stream, water is vaporised although the liquid phase is much below boiling temperature. A hydrophobic membrane can separate the two phases – liquid water and either vapour or vapour-gas mixture – in order to avoid the transfer of liquid or allow compact stream arrangements. Thus, MD is a non-isothermal membrane separation process with combined heat and mass transfer over the membrane. Parallel arrangement of the membranes in flat or spiral wound configuration allows generating multi-effect setups. The steam, generated over a first membrane layer can be condensed in the permeate channel using the latent heat of condensation for heating an adjacent feed channel. This way, a diversity of possible stream arrangements and system configurations arises. The main distinguishing feature is the configuration of the permeate channel. In order to minimize sensible heat transfer from the hot feed channel to the next feed channel, as it is the main drawback of direct contact configurations (Direct Contact MD (DCMD), DCMD with Liquid Gap (LGDCMD),s. Fig. (a)), either air or any other sweep gas can be filled in the permeate channel. The Air Gap (AGMD) or Sweep Gas Membrane Distillation (SGMD, s. Fig.(c)) minimize the heat transfer over the permeate channel by dividing the condensate from the membrane. The main drawback of these configurations is the higher diffusion resistance over the gas and the worse condensation due to the presence of non-condensable gases. This problem can be handled by running the system under vacuum for removing the non-condensable gases (Vacuum Membrane distillation (VMD), s. Fig. (b)). (Khayet Souhaimi & Matsuura, 2011) Besides the application of flat membranes, systems based on hollow fibre membranes are researched. The main advantage of Membrane Distillation systems is the low temperature heat (below 100 °C) at low pressure for running the system. For that cheap construction materials (plastics) can be used. As described before, the usage of membranes allows compact system setups which reduces the footprint of the plant.

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Multiple-Effect Humidification (MEH)

The Multiple-Effect Humidification (MEH) process for the extraction of water from salt-, brackish and well water represents a thermal method that is based on the well-known principle of evaporation (humidifier) and subsequent condensation (dehumidifier). The performance of this natural process was improved in the MEH process such that a major portion of the used evaporation energy remains within the process, permitting the low-temperature extraction of drinking water effectively and reasonably, without much waste heat, even in smaller units. The technical design of the process describes the natural water cycle, from evaporation (sea surface to atmosphere) to condensation (warm air in contact with cold air = rain). Thus, in a closed module, air is forced into circulation by a ventilator at atmospheric pressure. During its cycle inside the module, the air passes through the two main chambers of the system, the humidifier and the condenser, and it transports purest water (in gaseous form) from the humidifier to the condenser where it is retrieved as drinking water in liquid form. Through its various energy use options, the MEH is unique in terms of environmental sustainability. Due to the comparatively low operating temperatures, the energy required for such heating may be obtained as waste heat from operational processes or renewable energies, such as solar or geothermal power.

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MED-TVC desalination system fired by CSP solar thermal collectors commissioned in South Australia

A newly designed MED-TVC desalination system by “fischer eco solutions GmbH” was installed with a client from the field of agricultural greenhouse farming in South Australia in January 2012. The system has a nominal daily (24 hours) capacity of 10 m³ fresh water and is fired by heat from concentrating parabolic collectors (CSP).

The collector field is tracked for the diurnal variations of the suntrace in order to optimize energy yield, the derived heat is stored in hot water tanks for 24 hours per day operation of the system. The system was realized for the first time in that configuration and encourages the potential of MED-CSP water production of up to 1,000m³ daily.

More details “here”