Question

Coal containing 21% ash is completely combusted, and the ash is 100% removed in a water contact scrubber. If 10,000 kg of coal is burned per hour with a scrubber flow rate of 1.0 m3/min, the weight percentage of the ash in the water/ash stream leaving the scrubber is most nearly:_______.

a. 3.4
b. 14.3
c. 25.9
d. 67.7

Answer 1

Weight Percentage of Ash = 3.4

Step-by-step explanation:

Given - Coal containing 21% ash is completely combusted, and the ash is 100% removed in a water contact scrubber. If 10,000 kg of coal is burned per hour with a scrubber flow rate of 1.0 m3/min.

To find - the weight percentage of the ash in the water/ash stream leaving the scrubber is most nearly ?

Solution -

Given that,

Coal Burned Rate = 10,000 kg/hr

=
`(10,000)/(60 min) * 1 hr *(kg)/(hr)`

= 166.6666 kg/min

⇒Coal Burned Rate = 166.6666 kg/min

Now,

Given that,

Ash content in coal = 21 %

⇒Ash in (coal that burned) = 166.6666 ×
`(21)/(100)` kg/min

= 34.9999 ≈ 35 kg/min

⇒Ash in (coal that burned) = 35 kg/min

Now,

We know,

Density of water = 1000 kg/m³

Now,

Water flow Rate =
`1(m^(3) )/(min) * density`

= 1000 kg/min

⇒Water flow Rate = 1000 kg/min

Now,

Total Mass flow Rate of (Water + Ash stream) = ( 1000 + 35) kg/min

= 1035 kg/min

⇒Total Mass flow Rate of (Water + Ash stream) = 1035 kg/min

So,

Weight Percentage of Ash = (Weight of Ash ÷ Total weight of Stream) × 100

= (35 ÷ 1035) × 100

= 3.38 ≈ 3.4

∴ we get

Weight Percentage of Ash = 3.4