Thursday, September 26, 2013

DESALINATION PLANTS: IT IS NOT THE WORTH THE SALT


In search of  potable water now man is desalinating sea water. As the rivers are dry and the wells of open or deep bore wells too getting deeper, there is no other alternative. But sucking sea water through pipes at great speed cause lot of harm to the marine life. Up to the 200 feet level , the sunlight can penetrate and sea life is vibrant. But all these go as waste as the high pressure tubes kill all marine life in the various processes in desalination.




DUBAI // The UAE’s largest power and desalination plant was officially opened yesterday  and, according to a senior official, customers will benefit from the improved efficiency it provides.
The Dh10 billion gas-fired M Station joins the other plants operated by the Dubai Electricity and Water Authority (Dewa) at Jebel Ali.
The complex’s rows of red-and-white stacks are a familiar landmark to the thousands of drivers who pass by on Sheikh Zayed Road every day.
Power and water bills include a fuel surcharge that is linked to the price Dewa pays for the fuel it uses at its plants.
Increased efficiency means less fuel is needed to produce a given amount of power, so the amount of surcharge paid by customers each month will be kept down.
“The surcharge is connected with the fuel [costs],” said Saeed Al Tayer, Dewa’s managing director and chief executive.
“Once you have an efficient plant it means you have more megawatts with very efficient production, and it will contribute positively [with regard] to the surcharge.
“If you compare it with Europe, efficiency there is 45 per cent, here it’s 82 per cent.”
The plant has a capacity of 2,060 megawatts and 140 million gallons of water a day.
It has six gas turbines that generate power and the hot exhaust gases are fed through boilers that heat seawater to produce steam.
The steam is either used to drive steam turbines, producing more power, or fed through the eight desalination units to produce drinkable water.
The plant’s flexible design means the amount used for each purpose can be adjusted to meet their demands. The desalination units are the largest individual ones of their kind in the world.
“We are utilising the waste heat in order to produce either water or power,” said Mr Al Tayer. “The technology is very reliable and advanced.”
The plant was opened by Sheikh Hamdan bin Rashid, Deputy Ruler of Dubai, Minister of Finance and president of Dewa.
The authority said the facility’s advanced technologies have reduced greenhouse gas emissions and generate power and water with a minimal carbon footprint.
“The inauguration of M Station is in line with our efforts to increase electricity and water production capacity to meet the economic growth in Dubai,” said Yahya Alzafin, vice president for generation.
Huge pipes draw in up to a billion gallons of water from the adjoining Arabian Gulf every day.
The pipes that feed the other Jebel Ali stations stretch one kilometre out to sea, but those serving the M Station are just offshore.
This is a precautionary arrangement to prevent operations being affected by spills from oil tankers out in the Arabian Gulf.
In the event of a spill, booms would be placed around the intakes to shield them from floating oil and enable the M Station to continue to operate, while some of the other plants might have to shut down.
There are other fail-safe features designed to ensure the lights keep shining and taps keep flowing in Dubai.
The gas turbines are able to burn diesel and, if the principal and back-up natural gas lines fail, there is enough diesel stored at the plant to keep the blades turning for 10 days.
Power plants, like everything, are affected by the blazing heat of the summer.
The operation of the gas turbines varies according to the ambient temperature – they produce more power during the cooler months of winter.
But the demand for power in winter drops by 50 per cent or more. Demand for water falls by between 10 to 15 per cent in winter.
The liquid produced by the desalination units lacks the essential minerals required in drinking water and these are added at the end of the process.
This is achieved by placing limestone from the mountains of Fujairah and Ras Al Khaimah in vessels containing the water, which absorbs the necessary salts.


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