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Dr. Kim Choon Ng
KAUST's project on “Hybrid Multi-Effect Adsorption Desalination: An Emerging High Efficiency and Low Cost Desalination" was named a winner in this year's Global Technology Challenge at Saudi Water & Power Forum (SWPF).
The challenge was launched by the Aramco Entrepreneurship and GE ecomagination and the winners were announced Tuesday at the opening of the Saudi Water & Power Forum. The competition was developed in partnership with GE as a way to promote a culture of technology-based entrepreneurship and venturing in the Kingdom. Because Saudi Arabia is expected to invest heavily in seawater desalination technologies and solar energy in the coming decades, the focus of the competition was on seawater desalination using renewable energy.
KAUST News spoke with Dr. Kim Choon Ng, visiting professor at KAUST’s Water Desalination and Reuse Center (WDRC) about the project, his academic association with KAUST began and how this continuing research partnership between the University and National University of Singapore (NUS) is bringing groundbreaking technology to Saudi Arabia’s water treatment industry.
As you mention, water is key for the country’s economic growth. All activities are dependent on the supply of good water. Currently in the Kingdom of Saudi Arabia thermal desalination is still the dominant method of water desalination. There are basically two reasons for this.
One is the high salinity of the seawater surrounding the Kingdom, particularly in the Gulf region with salinity reaching as high as 45000 ppm (parts-per-million).
Secondly, the seawater in the Gulf is also prone to algae blooms from time to time. It may occur two or three times per year. Only thermal desalination can handle these drastic fluctuations in deep-water quality realms. So that’s why thermal desalination is still the key dominating method of desalination.
Also, thermal desalination is normally co-located with thermal power plants where electricity is generated through steam turbines. Only low-pressure steam at low exergy is being let off to run the thermally driven cycle such as the multi-stage-flashing -- what we call the MSF or the MED (Multi-Effect Distillation processes).
This is very effective because low exergy steam is of not much use in producing electrical energy through the turbines; yet they have very high latent heat -- which can be utilized for the thermo desalination.
That’s why at the Water Desalination and Reuse Center (WDRC) I concentrated on thermo desalination. Through the KAUST-NUS special academic program (SAP) I completed a pilot plan at the WDRC from 2009 to 2013 and invented the Adsorption Desalination process for the thermo desalination.
That part of the work has been completed and currently we are embarking on phase two. That is to do hybridization of this basic adsorption technology with the existing MED processes.
Adsorption desalination is also a thermally driven process where we use those absorbents such as silica gel that has very high affinity for water vapor. So when a high saturated silica gel is exposed to water vapor, it will draw water vapor rapidly onto the surface of the silica gel.
When this happens in a closed environment, which we call evaporator, the saline solution will evaporate and the resulting vapor gets absorbed by the silica gel, while the salt concentration remains with the solution. This process can take place a very low temperature, usually around less than 5 degrees Celsius.
By the same token, when there’s a vapor uptake in the evaporator you can actually produce cooling, used for air conditioning. In order to maintain the temperature constant in the evaporator we supply chilled water at 12 degrees Celsius, coming out at 7 degrees Celsius -- which can then be used for air conditioning. This process is a batch-operated process.
The other bit which previously absorbed the water will at the same time undergo what’s called a desorption process where a heat source is supplied at low temperature; and this is another unique advantage of adsorption desalination because it utilizes heat at low temperate, 60 to 80 degrees Celsius. Which is very suitable for solar.
The Kingdom is blessed with very much solar energy, as you know. Saudi Arabia receives about 2,400 kilowatt hour per meter square per year. We can collect the solar thermal heat by more than 50% through ordinary stationary collectors.
This means that we can get about 1200 to 1300 kilowatt hour per meter square per year in the Kingdom. Basically, this heat source can then be used to power the adsorption cycle. This gives rise to the possibility for developing a solar-driven AD cycle in Saudi Arabia.
My solar park is on the roof of KAUST’s Building 2. From there we collect the energy and the thermal energy is stored in the storage tanks next to the AD plant in Building 7. We employ that energy to run the AD cycle using fully automatic controls. So the research fellows do not actually need to be down there. They could be at their offices but, through computers, they can see the operation of the plant.
Currently we are upgrading also the solar collectors from a flat-plate collector to evacuated-tube collectors. So this upgrading process is also ongoing. Taking advantage of the fabrication period for the AD/MED hybrid plant. We are also upgrading about 350 meter squares of solar collectors to the evacuated-tube type – which has higher efficiency compared with the flat-plate.
The flat-plate collectors, although they are cost-effective, tend to collect dust in the desert environment. Whereas the evacuated-tubes have a natural gradient where the sand particles can slide over the tube surfaces. So they are less prone to accumulation of dust compared with the flat-plate collectors. That’s one of the reasons why we are upgrading from the flat-plate collectors to the evacuated-tube collectors.
Currently the AD cycle is being utilized through its first commercial pilot on a cement factory called Al-Salfa. The factory is located on the way to Medina from Thuwal, about 80 kilometers away. Every day, workers truck in about 1200 cubic meter of ground water into the quarry from the neighboring wells.
Inside the quarry there is an RO (reverse osmosis) plant with a recovery efficiency of 40%; but 60% of the RO rejects are discharged into what we call an evaporation pond. We are building this AD unit with the support of KAUST and KACST.
Actually, the Innovation and Economic Development (ETD) department at KAUST spearheads this project. The negotiation was done with KACST. We were grateful to be supported by KACST, Taqnia and KAUST for the project. This will be the first test as a demonstration pilot, a commercial pilot, so that other industry people will be able to come and observe the first commercial pilot operating before they gain confidence and get acceptance into the other industries.
Currently we are treating the RO rejects from the existing RO plant within the quarry -- so minimizing the amount of rejects to the evaporation pond. We can in fact increase the recovery ratio of pure water, using this AD technology, from 40% to about 75-80%.
Certainly. Especially in very harsh environments like a quarry plant.
RO (reverse osmosis) is a membrane-based technique where water has been pumped up to a very high pressure so as to overcome the osmotic pressure cause by the concentration of the water. So pure water molecules are pushed through the pores of the membrane while the salts are left behind in the solution. That is the RO method. The RO method is a very energy-efficient method actually; but then the maintenance costs can be high. Whereas AD (adsorption desalination) is a thermally driven method. Capital costs may be initially higher but the operating cost is very much lower, giving a lower life cycle unit cost of water.
Yes, and currently we are working on hybridizing this adsorption cycle technique together with other thermally driven cycles like MED cycles. By integrating them we get extra thermodynamic synergy between these two cycles and thereby doubling to tripling the yield for almost the same amount of heat input through the thermo cycles. So therefore we can double or triple the water production yield by hybridizing them, by integrating them together. And this is the second phase of work that I’m conducting at KAUST now.
In 2008, the KAUST inauguration team, including the Executive Vice President -- Mr. Nadhmi Al-Nasr, came to National University of Singapore (NUS). I made a presentation to them and somehow they liked the idea of low-temperature driven desalination and clean cycles. They then invited me to submit a proposal for KAUST.
At that time it was done through the Global Collaborative Research (GCR) office. So it’s through this GCR program that I came to collaborate closely with Prof. Gary Amy, the first director of WDRC, who is now Professor Emeritus. This is how I got started.
I’ve already set up a spinoff company together with KAUST and the University is also a stake holder in the start-up. The company is called Medad Technologies. In fact the Al-Safa job is done through Medad Technologies. Because I’m an academic, I do not run the company; the company has its own CEO and a team of engineers.
We are working with the licensing office of KAUST, together with NUS and are in the process of setting up a company through Innovation and Economic Development’s help. We are going to set up several offices and maybe set up offices at KAUST also eventually. This is how we are aiming to introduce the technology into the Kingdom of Saudi Arabia.
The activity is to bring adsorption desalination techniques into the desalination scene. Currently Medad is working very closely with SWCC (Saline Water Conversion Corporation) which is the key government desalination authority in the Kingdom of Saudi Arabia. We are going to embark on another experimental pilot at the Al-Jubail research center (DTRI) in the city of Dammam.