CHAPTER 7 (PART 4) Dr Mohd Azmier Ahmad Tel:

Example 7.21: Consider a packed bed of solid particles with screen size of 0.2 mm packed in a solid volume fraction of The height of bed is 50 cm. The sphericity of particles is Air is flowing through the bed with a velocity of 0.05 m/s. The density of air is 1.2 kg/m 3 and its viscosity is 1.8x10 -5 Pa.s. Density of solid is 6000 kg/m 3. Determine wether the bed is fludized or not. Solution Use Ergun equation (Eq. 22):

Example 7.22: A partial oxidation is carried out by passing 0.15 m/s air with containing 1 mol% hydrocarbon through 40-mm ID 2 m height vertical tubes packed with 1 mm catalyst pellets. The air enters the bed from the bottom at 200 o C & 2 atm. The density of the catalyst pellets is 960 kg/m 3 and their sphericity is The reactor operates at 200 o C. The air viscosity and density are 2.6x10 -5 Pa.s & 1.54 kg/m 3, respectively. Assume voidage of packed bed = 0.4; i) Calculate outlet pressure from the packed bed. ii) Calculate air flowrate that just enough to fluidize the solids. iii) Calculate velocity required to expand the fluidize bed by 20%. Given : Φ s ε 3 mf = 1/14 Solution i. Eq. (21);

ii) Calculate air flowrate that just enough to fluidize the solids Use Eq. 18 Use Eq. 21 at MF

iii) Calculate velocity required to expand the bed by 20%. Use Eq. 18 Use Eq. 21 at MF Use Eq. 20 at MF

WORK IN PAIR 6 Consider a packed bed of solid particles with screen size of 0.38 mm packed in a solid volume fraction of The height of bed is 50 cm. The sphericity of particles is Air is flowing through the bed with a velocity of 0.2 m/s. The density of air is 1.2 kg/m 3 and its viscosity is 1.8x10 -5 Pa.s. Density of solid is 4500 kg/m 3. Determine wether the bed is fludized or not.

WORK IN PAIR 7 A partial oxidation is carried out by passing 0.22 m/s air with containing 1 mol% hydrocarbon through 40-mm ID 2 m height vertical tubes packed with 1 mm catalyst pellets. The air enters the bed from the bottom at 200 o C & 2 atm. The density of the catalyst pellets is 1200 kg/m 3 and their sphericity is The reactor operates at 200 o C. The air viscosity and density are 2.6x10 -5 Pa.s & 1.54 kg/m 3, respectively. Assume voidage of packed bed = 0.45; i) Calculate outlet pressure from the packed bed. ii) Calculate air flowrate that just enough to fluidize the solids. iii) Calculate velocity required to expand the fluidize bed by 30%. Given : Φ s ε 3 mf = 1/14