only answer part 2 and 3 20 points) Convert the following process description in

Question

only answer part 2 and 3

20 points) Convert the following process description into a process flow diagram (labeled block flow diagram). A steelmaking dust treatment process consumes 200,000 metrictons (mt) peryear of dust, which contains 60% Feo, 30% ZnO, and 10% PbO. In the process, the steelmaking dust is mixed with coal dust (60,000 mt/y). The mixture is dried and sent to a circulating fluidized bed reactor (CFB), where the carbon and hydrogen in the coal reduce the metal oxides to produce crude direct reduced iron (DRI), hich contains mostly iron metal and an offgas stream that contains elemental zinc and lead vapors along with carbon monoxide, carbon dioxide, water vapor, and hydrogen gas The DRI is cooled, screened to separate out the unreacted coal which returns to the coal storage bin The screened DRI product contains 95% iron, 2.5% zinc, 1.2% lead, and minor impurities. Approximately 94,300 mt/y of the DRI product are shipped to an off-site steel mill for remelting in an electricarc furnace The CFB offgas passes through a cyclone to remove coarse particulate matter, which is returned to the CFB. The cyclone exit gas is air-cooled in an indirect heat exchanger. As the gas cools, the zinc and lead vapors react with carbon dioxide and waterto produce Zno, and Pbo dust. These oxides, along with any iron oxide fines that escaped collection in the cyclone, ae captured in a baghouse. The average analysis of the 82,700 mt/y of combined dust production is 5.5% FeO, 67.5% ZnO, and 21.0% PbO Some of the cleaned gas, which now consists of 50% nitrogen, 30% carbon monoxide, and 20% hydr turned to the CFB reactor. The rest of the gas is sent to a combustion chamber where it is ogen, is re oxidized with air to generate combustion gases. The hot combustion gases enter a boile generates steam that is used to drive a turbine to generate electricity for use in the plant. r, which 2. (10 points) Create a table; for the first column list the unit operations from the flow diagram for number one, for the second column indicate whether the unit operation is a reactive or a non-reactive process. 3. (70 points) Calculate and tabulate mass balances for iron, zinc, and lead. The table should indicate the mass balance closures (%) for these elements as well. Assume that the plant operates 24 h/day for 330 days/y Process Stream Steelmaking dust, mt/d Direct reduced iron, mt/d Baghouse product, mt/d Total, mt/d Mass Balance Closure, % Iron Zinc Lead

Explanation / Answer

Q2.

Q3

To calculate & tabulate Mass balances for Iron Zinc & lead.

Plant operates 24h/d for 330 days/yr.

i)

steelmaking dust 200,000 mt/yr of dust =200000/330 (mt/d)=606.060 mt/d of dust

FeO=0.6*606.060=363.636 mt/d

Mass of FeO =72 & Mass of Fe=56

therefore Fe content in FeO =363.636*56/72 =282.828 mt/d

Similarly Zinc

ZnO=0.3*606.060=181.818 mt/d

mass of ZnO =81.38 & mass of Zn =65.38

so mass of Zn in steelmaking dust =181.818*65.38/81.38=146.071 mt/d

similarly for lead

PbO in steelmaking dust = 0.1*606.060=60.606 mt/d

mass of PbO 223 g/mol & mass of Pb =207 g/mol

therefore mass of Pb in steelmaking dust = 60.606*207/223=56.257 mt/d

ii)

Direct reduced iron=94300mt/y =94300/330 mt/d=285.757 mt/d

contain 95% iron,2.5%Zn,1.2%Pb & impurities

Iron = 0.95*285.757=271.469 mt/d

Zn =0.025*285.757=7.143 mt/d

Pb=0.012*285.757=3.429 mt/d

iii) Baghouse product

combine dust prodution =82,700 mt/y = 250.606 mt/d

5.5% FeO , 67.5% ZnO & 21% PbO

Fe in combine dust = 0.055* 250.606*56/72=10.720 mt/d

Zn in combine dust = 0.675* 250.606*65.38/81.38=135.90 mt/d

Pb in combine dust = 0.21* 250.606*207/223=48.851 mt/d

so therefore

baghouse product = amount in feed - amount in DRI-Amount in combine dust product

Fe in baghouse product = 282.828-271.469-10.72=0.639 mt/d

Zn in baghouse product = 146.071 -7.143-135.90=3.028 mt/d

Pb in baghouse product = 56.257-3.429 -48.851=3.977 mt/d

closure %= mass in DRI /mass in feed *100

for Fe =271.469/282.828*100=95.98%

for Zn =7.143/146.071*100=4.89%

for Pb=3.429/56.257*100=6.09%

Sr.No. Unit Operation Type of process 1 Mixing non reactive 2 Drying non reactive 3 Reduction in CFB reactive 4 Screening non reactive 5 Recycling non reactive 6 Remelting non reactive 7 Separation non reactive 8 Cooling non reactive 9 Combustion reactive

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