For better thermal control it is common to make catalytic reactors that have many tubes packed with catalysts inside a larger shell (just like a shell and tube heat exchanger). Consider one tube inside such a reactor that is 2.5 m long with an inside diameter of 0.025 m. The catalyst is alumina spheres with a diameter of 0.003 m. The particle density is 1300 kg/m3 and the bed void fraction is 0.38. Compute the pressure drop seen for a superficial mass flux of 4684 kg/m2hr. The feed is methane at a pressure of 5 bar and 400 K. At these conditions the density of the gas is 0.15 mol/dm-3 and the viscosity is 1.429 x 10-5 Pa s.

Respuesta :

Answer:

the  pressure drop  is 0.21159 atm

Explanation:

Given that:

length of the reactor L = 2.5 m

inside diameter of the reactor d= 0.025 m

diameter of alumina sphere [tex]dp[/tex]= 0.003 m

particle density  = 1300 kg/m³

the bed void fraction [tex]\in =[/tex]  0.38

superficial mass flux m = 4684 kg/m²hr

The Feed is  methane with pressure P = 5 bar and temperature T = 400 K

Density of the methane gas [tex]\rho[/tex] = 0.15 mol/dm ⁻³

viscosity of methane gas [tex]\mu[/tex] = 1.429  x 10⁻⁵ Pas

The objective is to determine the pressure drop.

Let first convert the Density of the methane gas from 0.15 mol/dm ⁻³  to kg/m³

SO; we have :

Density =  0.15 mol/dm ⁻³  

Molar mass of methane gas (CH₄) = (12 + (1×4) ) = 16 mol

Density =  [tex]0.1 5 *\dfrac{16}{0.1^3}[/tex]

Density =  2400

Density [tex]\rho_f[/tex] =  2.4 kg/m³

Density = mass /volume

Thus;

Volume = mass/density

Volume of the methane gas =  4684 kg/m²hr / 2.4 kg/m³

Volume of the methane gas = 1951.666 m/hr

To m/sec; we have :

Volume of the methane gas = 1951.666 * 1/3600 m/sec = 0.542130 m/sec

[tex]Re = \dfrac{dV \rho}{\mu}[/tex]

[tex]Re = \dfrac{0.025*0.5421430*2.4}{1.429*10^5}[/tex]

[tex]Re=2276.317705[/tex]

For Re > 1000

[tex]\dfrac{\Delta P}{L}=\dfrac{1.75 \rho_f(1- \in)v_o}{\phi_sdp \in^3}[/tex]

[tex]\dfrac{\Delta P}{2.5}=\dfrac{(1.75 *2.4)(1- 0.38)*0.542130}{1*0.003 (0.38)^3}[/tex]

[tex]\Delta P=8575.755212*2.5[/tex]

[tex]\Delta = 21439.38803 \ Pa[/tex]

To atm ; we have

[tex]\Delta P = \dfrac{21439.38803 }{101325}[/tex]

[tex]\Delta P =0.2115903087 \ atm[/tex]

ΔP  ≅  0.21159 atm

Thus; the  pressure drop  is 0.21159 atm