Question

Q1)

Natural gas liquids (NGL) are recovered from wet natural gas by cooling, which results in condensation of the higher molecular weight components.

A raw natural gas has 92% methane, 4% ethane, 3% propane, 1% helium. NGL recovery condenses 89.4% of the propane and 5% of the ethane.

What fraction of the natural gas (by mole) is recovered as NGL?

Q2)

To ensure a slow rate of drying and thereby prevent cracking of a dried product, an inlet relative humidity of 68.8% at 75oF is specified for the air entering a dryer. Outside air is mixed with recycled air from the dryer exit to provide this inlet air at the required conditions. The air leaving the dryer has a relative humidity of 95% and temperature 70oF.

If the outside air has a dewpoint of 40oF, what PERCENTAGE of the air entering the dryer must come from the recycled air from the dryer exit to provide the desired moisture content in the air fed to the dryer?

Q3)

In the production of peanut oil from peanuts, ground peanut meal (38% oil and the balance insoluble solids) is mixed with a solvent (hexane) which dissolves essentially all of the oil in the meal.
The mixture then passes to a filter, in which the oil / hexane mixture is separated from the insoluble solids. The wet solids stream removed from the filter (filter cake) is 83% solids and 17% oil / hexane mixture.
The oil / hexane mixture from the filter is passed to a separator, which separates the hexane from the peanut oil.
If the purified hexane stream has a flow rate of 50 tonnes per hour and the purified oil stream has a flowrate of 12.6 tonnes per hour, how many tonnes per hour is the flowrate of the wet solids stream from the filter?

Answer 1

Answer-1 Let's take a basis of 100 moles of natural gas.

Thus, Number of moles of propane= 3 moles

Number of moles of ethane = 4 moles

Since NGL recovery condenses 89.4 % of the propane and 5 % of the ethane,

Number of moles of propane condensed= 89.4 % of 3 = 2.682 moles

Number of moles of ethane condensed= 5% of 4 = 0.2 moles

Thus, NGL as a fraction of natural gas =

Answer-3

Thus, the flow rate of oil/hexane mixture from the filter is,

Now, the liquid stream is 17% of the wet solids stream removed from the filter cake.

Hence, the flow rate of the wet solids stream can be found as,

Thus,