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8/11/2019 Temperature Calculation Using Polynomial Eqn
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Estimating Temperatures in the primary reformer using K-Polynomials:
There are two major reactions taking place in the Primary reformer.
1. Reforming reaction : CH4 (g)+ H2O(g)CO(g)+ 3H2(g) (Equilibrium constantK1)
2.
Shift conversion : CO(g) + H2O(g)CO2 (g)+ H2 (g) (Equilibrium constantK2)
K1=()(
)
()()[P]2 and K2=
()()
()()[P]0
Where Pi is the partial pressure of component i and P is thetotal pressure.
From the Wet-Analysis of the outlet of primary reformer, we get the composition of the gas stream as :
Component Dry Analysis (mol%) Flow rates (Nm3
/hr) Wet Analysis (mol%)H2 66.51 59792.49 37.26
N2 0.82 737.18 0.46
CO 7.67 6895.33 4.3
CO2 10.86 9763.14 6.08
Ar 0.01 8.99 0.0056
CH4 14.13 12702.87 7.915
H2O 70585.76 44
Also, we know that,
Pi= xi * P where xi is the mole % of component i
Here, in the primary reformer, Ptotal= 33 kg/cm2 gauge.
And since the components in the outlet stream are in equilibrium, we take those compositions to calculate
the equilibrium partial pressures.
= 0.07195 x Ptotal
= 0.44 x Ptotal
= 0.043 x Ptotal
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= 0.0608 x Ptotal
= 0.3726 x ptotal
Kreforming= K1=()()
()()[P]2 =
()()
()()(
) = 74.87
And Kshift = K2=()()
()()[P]0 =
()()
()() = 1.197
K-Polynomials for calculating the Equilibrium Constant
K = exp (K1x InT + K2/T + K3 + T (K4+ T (K5+ K6x T)))
T = Temperature in Kelvin
Shift Reaction Ammonia Reforming Reaction
CO+H2OH2+CO2 3H2+N22NH3 CH4+ H2OCO+3H2
K1 -3.161655 x 10-1 -8.047466 8.611141
K2 5.016493 x 103 9.109037 x 103 -2.264800 x 104
K3 -4.104398 2.714340 x 101 -2.898262 x 101
K4
2.139622 x 10-3 4.730516 x 10-3 -4.980093 x 10-3
K5 -6.044361 x 10-7 -4.355303 x 10-7 3.977486 x 10-7
K6 7.582492 x 10-11 -6.422945 x 10-12 2.013355 x 10-11
Reforming reaction:
Given, K = (
( ( )))
lnK = K1lnT +
+ K3+ K4T + K5T
2+ K6T3
We have,
Kref= 74.87 ,
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And from the above table, for reforming reactions,
ln(74.87) = 8.611141lnT -
- 28.98262 - 0.004980093T + (3.977486x10-7)T2+ (2.013355 x 10-11)T3
Solving the above equation, we get,
Tref= 1039.037K = 766.0370C 7670C (as given in the data sheet)
Similarly, using the data given in the table for Shift reactions, we get,
Tshift= 766.7670C 767
0C
Thus, we can verify the operating values by theoretical methods.
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