# 7.39: Untitled Page 184

## Chapter 7

dioxide in the synthesis gas must be removed before the gas is used as feed for an ammonia converter. This process is illustrated in Figure 7.16, and the product gas in Stream #3 is required to contain hydrogen and nitrogen in a 3

to 1 molar

ratio. In this problem you are asked to determine the ratio of e th molar flow rate

of the flue gas to the molar flow rate of the water gas, i.e., M

/ M , that is

1

2

required in order to meet the specification that ( y

)  3( y

) .

H2 3

N2 3

/ M  0 . 467

1

2

Figure 7.16. Synthesis gas reactor

7‐17. A process yields 10,000 ft3 per day of a mixture of hydrogen chloride ( HCl ) and air. The volume fraction of hydrogen chloride ( HCl ) is 0.062, the temperature of the mixture is 550°F, and the total pressure is represented by 29.2

inches of mercury. Calculate the mass of limestone per day required to neutralize the hydrogen chloride ( HCl ) if the mass fraction of calcium carbonate ( CaCO ) in the limestone is 0.92. Determine the cubic feet of as g liberated

r

pe

3

day at 70°

F if the partial pressure of carbon dioxide ( CO )

is 1.8 inches of

2  Material Balances for Complex Systems

345

ercury.

m

Assume that the reaction between HCl and CaCO to form CaCl , 3

2

CO , H O goes to completion.

2

2

7‐18. Carbon is burned with air with all the

carbon being oxidized to CO

.

2

Calculate the flue gas composition when the

percent of excess air is 0, 50, and

100. The percent

of excess air is defined as:

 molar flow 

mol

ar t

ra e of

rate of oxygen

 consump

tion of oxygen 

percent of

entering

owin

g to reaction

 

 100

excess air 

 molar rate of

consumption of oxygen

 owing to reaction 

Take the composition of air to be 79% nitrogen and 21% oxygen. Assume that no NOX is formed.

7‐19. A waste gas from a petrochemical plant contains 5% HCN with the remainder being nitrogen. The waste gas is burned in a furnace with ess

exc

air

to make sure the HCN is completely removed. The

combustion process

is

illustrated

in Figure 7.19. Assume that the percen

t excess air is 100%

and

Figure 7.19. Combustion of hydr

ogen cyanide  346