A desalination plant arranged in 1 stage and using RO(reverse osmosis) module.Th

Question

A desalination plant arranged in 1 stage and using RO(reverse osmosis) module.The required data are in bellow table.

This course is about

membrane desalination process

i would like you to help me solve this quesion

you can assume any missing data

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1) Calculate the retention (R°) 2) Calculate the energy consumption of an 800 m'/day single stage seawater desalination plant. 3) In order to recover part of energy consumption (ERD), a turbine is included in the process; calculate the part of energy recovered 4) Determine the effective energy consumed The data necessary for the calculation are given in the table below. Permeate flow rate (V,) Applied Pressure (PApl.) Pressure drop (AP) |- | 800 m'/day 65 bar - 2 bar | 35 % Recovery factor (RR-%) 35,000 ppm Salt Concentration of NaCI (C) Pump efficiency (nPump) Turbine efficiency (Tubine) Molecular mass of Sodium Chloride (g/mol) 165% 155 % 58.5

Explanation / Answer

given data -

permeate side flow rate = Vp = 800 m3/day

applied pressure = Pap = 65 bar = 65 x105 Pa

pressure drop on premeate side = 2 bar = 2 x 105 Pa

pressure on permeate side = Pp = 65 - 2 = 63 x 105 Pa

Recovery feactor = Vp/Vf = 0.35

so Vf = Vp/0.35 = 800/0.35 = 2285.714 m3/day

(1) Retention (Ro) = Vf - Vp = 2285.714 - 800 = 1485.714 m3/day

(2) Energy required-

Here we calculate that what amount of work required to transfer liquid on the permeate side .

so, work = Pap* Vf - Pp* Vp

= 65 * 2285.714 * 105 - 63*800 * 105 Pa-m3/day  

= 98171.42857 x 105 Pa - m3/day = 27.2698 x 105 Pa-m3/sec

As, pump eficiency is 65%,

so required amount of energy = 27.2698 x 105 / 0.65 = 41.954 x 105 Pa-m3/sec (J/sec)

(3) Now in order to recover energy from permeate side, we connect a turbine which is 55% efficient.

so, recovered energy = 63 x105 x 800 x 0.55/(3600 ) J/sec = 7.7 x 105 J/sec

(4) calculation of effective energy consumed-

Effective energy consumed = energy supplied at feed - energy recovered from permeate side

= 65 x 105 x 2285.714 /(0.65 x 3600) - 7.7 x 105

= (63.492 - 7.7 ) x 105

= 55.792 x 105 J/sec

I hope you can understand the solution

Thank you!!!

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