Material Balance - Recovery of L Serine L - Serine is a nonessential amino acid,

Question

Material Balance - Recovery of L Serine

L - Serine is a nonessential amino acid, but can be a useful constituent of a healthy diet and is often provided in intravenous feeding solutions for recovering patients. L serine has a molecular weight of 105, is produced by fermentation, and is recovered and purified by crystallization at 10degree C. Yield from the crystallization process is enhanced by the addition of methanol, which reduces serine solubility. An aqueous serine solution containing 40.0 wt% serine and 60.0 wt% water is added along with methanol to a batch crystallize that is allowed to equilibrate at 10degree C. The resulting crystals are recovered by filtration; liquid passing through the filter is known as filtrate, and the recovered crystals may be assumed in this problem to be free of adhering filtrate. The crystals contain a mole of water for every mole of serine and are known as a monohydrate. The crystal mass recovered in a particular laboratory run is 500.0 g, and the filtrate is determined to be 0.400 wt% serine, 58.8 wt% water and 40.8 wt% methanol. Determine the number of unknowns and independent mass balances that may be written for the crystallization operation. There are independent mass balances that may be written for the crystallization operation. Determine the ratio of the mass of methanol added per unit mass of feed. The ratio of the mass of methanol added per unit mass of feed is The laboratory process is to be scaled to produce 750.0 kg/hr of serine monohydrate. Determine the required feed rates (kg/hr) of aqueous L - serine solution and of methanol. The feed rate of aqueous L serine solution is kg/hr. The feed rate of methanol is kg/hr.

Explanation / Answer

Let F be feed rate of lserine and water

X be feed rate of methanol

Z be rate of filterate

BASIS: 500 g of serinemonohydrate crystal and 1 hour ooperatiion

Serine mol wt=105 total hydrate wt= 102+18=123

Therfore mass % of serine = 85.36%

And of water= 14.64%

Writing overall balance ,

F+X=Z+500

writing mass balances for Lserine,water and methanol respectively

0.4F=0.04Z+0.8536(500),

0.6F=0.588(Z)+0.1464(500),

X=0.408Z

3 UNKNOWNS and 3 EQUATIONS

F=1067g

X=231.336g

Z=567g

Ratio of mass of methanol to mass of feed = 231.336/1067=0.2168

Basis:750kg of crystallate

For 500 g of crystallate 1067 g of feed is req

For 750 kg of crystallate 1600.5 kg of feed is req

And 0.2168*1600.5=346.98 kg of methanol

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