مهدی گوگل

Freshwater, which accounts for less than 1% of world water resources, is rapidly decreasing due to extreme levels of withdrawals and the influence of seawater in areas under tension. This decreasing trend has reached a critical level in the Middle East since the water per capita in this area is much lower than the world average. Desalination is an approach for reducing water stress by producing freshwater from seawater, saline groundwater, drainage water, and wastewater in the coastal and inland areas. During these processes, rejected streams with high salinity as a sub-product are produced in which disposing of them is costly. A large amount of concentrated water containing the remaining compounds discharge into the environment and is potentially considered as a serious problem. Inland desalination due to the impossibility of disposing the produced brine is different from the desalination of seawater. In desalination of underground saline waters, fouling occurs with water-soluble salts and sedimentation reduces the production of water with a certain amount of energy during these processes. Therefore, the evolution of desalting technologies makes it cheaper, more reliable, and less productive.

The wet cooling towers are one of the main consumers of water in oil and gas refineries as well as petrochemical companies for producing cooling water. If an optimum selection of cooling systems is considered in the design phase and retrofit operations in a factory، considerable water consumption savings will be achieved. For modifying existing systems to determine the best optimal option among all the alternatives available، the mathematical modeling and optimization of such plans can replace expensive laboratory or pilot plant methods previously used. In this study، using the mixed integer linear programming along with the operational experiences of the first superstructure plan، a network of cooling towers was created. In the next step، the most favorable model is regarded in two scenarios to reduce raw water consumption and cooling tower blowdown production with producing demine water (DM) required by the factory. The optimum scenario results in producing 200 m3h-1 DM water and reducing 480 m3h-1 cooling tower blowdown and 200m3h-1 raw water consumption. This scenario results are confirmed and it is now installed in ammonia plant (unit 1). The functions of NPV، IRR، and Payback are used to determine the economic criteria of the plan.