The in situ moist unit weight of a soil is 17.3 kN/m^3 and the moisture content is 16%. The specific gravity of soil solids is 2
.72. This soil is to be excavated and transported to a construction site for use in a compacted fill. If the specification calls for the soil to be compacted to a minimum dry unit weight of 18.1 kN/m^3 at the same moisture content of 16%. 1) How many cubic meters of soil from the excavation site are needed to produce 2000 m^3 of compacted fill? 2) How many 20 ton truckloads are needed to transport the excavated soil?
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Answer:
Explanation:
Hello,
a. On the attached document, you can see a brief scheme of the process. Thus, to know the degrees of freedom, we state the following unknowns:
- and
: extent of the reactions (2).
- ,
,
,
and
: Molar flows at the second stream (5).
On the other hand, we've got the following equations:
- : oxygen mole balance.
- : methane mole balance.
- : water mole balance.
- : formaldehyde mole balance.
- : carbon dioxide mole balance.
Thus, the degrees of freedom are:
It means that we need two additional equations or data to solve the problem.
b. Here, the two missing data are given. For the fractional conversion of methane, we define:
And for the fractional yield of formaldehyde we can set it in terms of methane as the reagents are equimolar:
In such a way, one realizes that the output formaldehyde's molar flow is:
Which is equal to the first reaction extent , therefore, one computes the second one from the fractional conversion of methane as:
Now, one computes the rest of the output flows via:
-
-
-
-
-
The total output molar flow is:
Therefore the output stream composition turns out into:
Best regards.
Answer:
Explanation:
the solution is well stated
