Reverse Osmosis Desalination Plant in Nuweiba City (Case Study)

Transcription

1 North & South Sinai Company for Water and Wastewater ( NSSCWW ) Reverse Osmosis Desalination Plant in Nuweiba City (Case Study) Dr. Eng. Ibrahim Khaled El-Sayed Chairman 1

2 Introduction Desalination is a process removing dissolved minerals from the saline water. Many technologies have been developed for the sea and brackish water, but the most common and widely used process is the reverse osmosis (RO). The RO desalination plant consists of 4 major systems; pretreatment system, high pressure pumps, membrane systems, and post-treatment. RO membranes are 3 types; spiral wound, hollow fiber & plate and frame. The major parameters affecting the RO plant performance are the feed water temperature, pressure and salinity. 2

3 Objectives of the study This case study is carried out to study : the influence of main design and operating parameters on the RO plant performance the cost analysis of the RO plant the evaluation of the overall system reliability for longterm automatic operation for a certain maintenance procedure 3

4 Considered Plant The considered plant has been constructed at Nuweiba City in South Sinai, Egypt. It started the actual production on August The required electrical power for the plant is supplied from the local electrical power network. The saline water is supplied from 8 beach wells near the coast of Aqaba Gulf. The salinity of feed sea water is in the order of ppm. The plant consists of 5 units; each has a capacity of 1000 m 3 /day. 4

5 Considered Plant 5

6 Considered Plant 6

7 Experimental Procedures The plant consists of the following main systems : 1. Intake : saline water is pumped from the beach wells through the deep well pumps to a PVC header and then to the sand filters (activated carbon filters) 2. Raw water pre-treatment unit : the water is sterilized to prevent the growth of bacteria and algae activated carbon (AC) filtration is most effective in removing organic contaminants from saline water. After new design by PX system, the activated carbon increased from 12 filters to 24 filters the plant is provided with one cartridge filter which ensure that particles larger than 5 microns, carried over from the dual media filters will not enter the membranes This system changed from 1 filter to 5 cartridge filters (1 micron) 7

8 Experimental Procedures 3. RO membrane units: the membrane stainless steel skid consists of 15 vessels; each one contains 5 elements of membranes of spiral wound type. Total elements 75 SU820. After using PX system, the total 24 vessels 120 elements TM Post-treatment system : it consists of chlorinating to allow chlorine residual and ph adjusting within the acceptable range of 7.5 to 8.5 ppm. This system is suitable for the new capacity 5. The plant is completely automatically controlled using PLC and SCADA system The pressure required to operate Nuweiba RO plant is bar. 8

9 Experimental Procedures 1- Sand Filter 2- Carbon Filter 3- Raw Water Tank 4- Feed Pump 5- Cartridge Filter 6- High Pressure Pump 7- Turbocharger 8- RO Membrane 9- Aerated Tank 10- Flushing Pump 11- Chemicals Tank 9

10 Experimental Procedures Simply activated carbon filters (Sand Filters) 10

11 Experimental Procedures Cartridge Filters 11

12 Experimental Procedures Chemical Pre-treatment 12

13 Experimental Procedures High Pressure Pump 315 kw 13

14 Experimental Procedures Degasifier 14

15 Experimental Procedures Turbocharger (before PX) 15

16 Experimental Procedures P X 16

17 Pressure Exchanger (PX) PX is an isobaric energy recovery device that transfers pressure from the membrane reject stream to a seawater membrane feed stream with extremely high efficiency : High Pressure IN High Pressure OUT Low Pressure IN Low Pressure OUT 17

18 Pressure Exchanger (PX) 18

19 Experimental Procedures During the normal operation, the following data have been recorded daily : 1. The pressure before and after each filter, pump, turbocharger and RO element 2. Temperature before and after each RO element 3. Thermal conductivity before and after each RO element. Salinity of a stream is calculated from the measured thermal conductivity 4. The mass flow rate of both the product water and brine 19

20 Experimental Procedures Site experimental work has been carried out on one RO unit of the plant to study the effect of feed water temperature, pressure and salinity on the productivity of the unit. The change in the salinity of feed water was carried out by adding product water to the feed saline water. The pressure of the feed water was changed by the pump and by passing the feed water. To study the effect of temperature of the feed water, tests are carried out during different times of the year with different ambient temperatures. The results are measured by the same instrumentation attached to the RO desalination plant. 20

21 Results & Discussion Effect of feed water pressure on the productivity The productivity increases from 7.2 to % corresponding to an increase in the feed pressure from to 72.4 bar respectively 21

22 Results & Discussion Effect of feed water temperature on the productivity The productivity increases from 74.4 to 112.8% corresponding to an increase in the feed temperature from 10 to 32 C respectively 22

23 Results & Discussion Effect of feed water pressure on the product water salinity The product salinity decreases from 1500 to 300 ppm corresponding to an increase in the feed pressure from to 72.4 bar respectively 23

24 Results & Discussion Effect of feed water salinity on the productivity The plant productivity decreases from 120 to 100.8% as the feed water salinity increases from to ppm respectively 24

25 Results & Discussion Effect of feed water salinity on the product water salinity The salinity of feed water increases from 67 to 350 ppm corresponding to an increase in the feed water salinity from to ppm respectively 25

26 Economical Analysis Pump 1. Power Consumption Cost Without PX With PX kw kwh/m 3 kw kwh/m 3 Sea Water Pump Filter Pump Additive Pump Product Pump RO H.P. Pump Circulation Pump Total Power Cost (Without PX) = 7.8 * 0.22 = LE/m 3 Power Cost (Using PX) = 3.2 * 0.22 = LE/m 3 26

27 Economical Analysis 2. Chemical Requirements Cost Item gr/m 3 Cost (LE/m 3 ) Ca O Cl (Pre + Post) H Cl (30%) Anti Scalant Na O H Others Total Chemical Cost = 0.52 LE/m 3 27

28 Economical Analysis 3. Maintenance & Repairs Cost Operation Name Cost (LE/m 3 ) Cartridge filter 0.03 Pumps and motors 0.08 Controls and electrical, etc Instrument, etc Miscellaneous 0.05 Total 0.24 Maintenance & Repairs Cost = 0.24 LE/m 3 28

29 Economical Analysis 4. Capital Cost Without PX Capital Cost = 5,500,000 LE/Unit Unit = 1000 m 3 /day Working Days = 335 days/year Expected Life Time = 10 years Using PX Capital Cost = 5,500,000 LE/Unit Design Modify = 1,500,000 LE Unit = 2000 m 3 /day Working Days = 335 days/year Expected Life Time = 10 years Capital Cost = / = LE/m 3 Capital Cost = / = LE/m 3 29

30 Economical Analysis 5. Labour & Administration Cost Labor & Administration Cost = 0.50 LE/m 3 6. Cost of Wells & Plant Civil Work Civil Work Cost = LE/m 3 Total Cost per One Cubic Meter Total Cost without PX Total Cost using PX = LE/m 3 = LE/m 3 By using PX, the total cost decreased by 33%. 30

31 Conclusions The following conclusions are obtained based on 5-year operation : 1. The RO system is found to be sensitive to the variation in the feed water temperature, pressure and salinity : Higher feed water temperature increases the plant productivity Increasing the feed water pressure increases the plant productivity but decreases the permeate salinity Higher feed water salinity reports lower productivity and higher product water salinity 31

32 Conclusions The following conclusions are obtained based on 5-year operation : 2. The cost analysis of the RO plant (without PX) reveals that the major factors affecting the product water cost are the power consumption cost (35%) and capital cost (33.6%) while the chemical treatment represents 10% of the total cost 3. The cost analysis of the RO plant (using PX) reveals that the major factors affecting the product water cost are the power consumption cost (21.5%) and capital cost (31.8%) while the chemical treatment represents 16% of the total cost 32

33 THANK YOU 33