Screening.docx

Screening Band Screen According to Ovivo, which develops highly technological water treatment solutions, the band screens are the most efficient means of removing suspended solids for primary wastewater applications from raw water intake and cooling water treatment. The fully automatic operation requires minimal operator intervention resulting in reduced operating costs.

Screen Capacity The screen capacity can be estimated using the equation 19-7 from Perry’s Chemical Engineer’s Handbook (7th edition), as shown below:

The unit capacity, Cu, can be estimated from the graph shown below:

The solids considered in this project were sand and gravel. From this information, the unit capacity can be estimated. Also, the square opening considered was 0.05 in to ensure that only minimal amount of the solids can pass through. The unit capacity obtained was 0.4 tons/h-ft2. The flowrate of the entering seawater was 195.66 tons/h. The open area factor can be determine using the equation:

Where a is equal to d for square openings. Thus,

2 0.25 𝐹𝑜𝑎 = 100 ( ) 0.25 + 0.25

𝐹𝑜𝑎 = 25 The slotted area factor can be obtained from the table shown below (Perry, 7th edition):

For square and rectangular openings, a value of less than 2 has to be used. In this project, 1.5 was used. Using this information, the area required for the screen can be estimated:

𝐴=

𝐴=

0.4 ∗ 𝐶𝑡 𝐶𝑢 𝑥 𝐹𝑜𝑎 𝑥 𝐹𝑠

0.4 ∗ 195.66 𝑡𝑜𝑛𝑠/ℎ 0.4 𝑡𝑜𝑛𝑠/ℎ − 𝑓𝑡 2 𝑥 25 𝑥 1.5 𝐴 = 5.22 𝑓𝑡 2

Active screen dimensions, 𝐴 = 𝐿𝑊 𝐿 = 1.5𝑊 𝐴 = 1.5𝑊 2 5.22 = 1.5𝑊 2 𝑊 = 1.86 𝑓𝑡

𝐿 = 2.80 𝑓𝑡