Applied similarity criteria in the scale-up from existing to large MSF desalination plants
✍ Scribed by D. Barba; S. Arazzini; G. Migliorini
- Publisher
- Elsevier Science
- Year
- 1984
- Tongue
- English
- Weight
- 738 KB
- Volume
- 49
- Category
- Article
- ISSN
- 0011-9164
No coin nor oath required. For personal study only.
✦ Synopsis
The trend of building large desalination water stations with a large number of parallel units of 5-6 migd each is critically exammed. The opportunity to increase unit size to 12-13 migd for cross tube and to 20-25 nngd for long tube geometry has been discussed previously [l] . In this paper optlrnal sizes analyzed for cross tube and for long tube geometry are 12 migd and 18 migd respectively, and the snnilarity criteria, that can be used for design purposes startmg from the behavior of two reference industrial plants (5 migd cross tube and 8 migd long tube respectively), are illustrated.
The scale-up from existing units is based on the similarity of evaporator parameters: brine specific flow rate, flashdown, Froude number at entrance of the stages, dimensionless vapor velocity at the brme release surface, dimensionless vapor velocity through the demisters, two phases flow parameters at the cross-section below the distillate channel (only for cross tube geometry), dimensionless stage length defined as the ratio between actual and critical length.
The designs of new large units, characterized by process and geometrical features similar to the reference plants based on these profiles, allows the same water purity and performance ratio for the new capacities.
An economic analysis on a standard 6 mrgd unit shows that the mvestment cost/m3/d is is about 20% lower for 12 migd cross tube and 30% lower for 18 migd long tube plants. A ARP ND' -temperature drop or flashdown between stages for New Design and Reference Plant respectively, 'C x -water latent heat of vaporization, kcal/kg EC -discharge orifice coefficient PL -brme viscosity, centipoise VT -turbulent kmematic viscosity of brine, m2/h Pv, PL -vapor and brme density respectively, kg/m2 u -superficial tension of brme, dme/cm $ -constant of Baker's parameter defined by Eq. (12)