A process system for the manufacture of ethylene glycol is shown in Figure Q1. Ethylene oxide...

  

 

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A process system for the manufacture of ethylene glycol is shown in Figure Q1. Ethylene oxide (CaH.O) is produced in the reactor by the following main reaction of catalytic oxidation of ethylene (C2H«): (6)O'HO- (6)o (6)"H) An undesired competing side reaction is the combustion of ethylene to CO2. CaHa(g) + 302(g)- 2CO2 (g) + 2H:O(g) The reactor product is fed to a separation system where water is added to convert ethylene oxide to ethylene glycol. CH,O(g) + H20(1)CaHO2(1) recycle: n, purge: n. water: n. ethylene: net oxygen: 10 kmol/h T 350°C T= 380 °C Separation System Preheater Reactor Q=? ethylene glycol product: neg n, - molar flow rate of x, kmol/h Figure Q1 (a) Produce a process material balance for the production of ethylene glycol based on an oxygen feed rate of 10 kmol h-1. Calculate the molar flowrates of each component in each stream. The following conditions apply: • All oxygen reacts, 90% goes to ethylene oxide, the rest to CO2 and H20. • Ethylene and oxygen feeds are pure. • 20% excess ethylene is fed to the process to ensure process safety. • No reaction of ethylene oxide with water takes place in the reactor. • All the water and ethylene oxide entering the separator is converted to • ethylene glycol. • Gases do not dissolve in ethylene glycol and the separation is assumed to • be ideal, i.e. ethylene glycol, is pure. • There is no water in the recycle, purge and product streams. 1% of gas stream is purged. Assume the combined stream consisting of the two fresh feeds and the recycle enters the reactor at 350°C, the reactor effluent is at a temperature of 380°c and that there are no heat losses. Using the data below, calculate how much heat has to be removed or supplied to the reactor to maintain the 380°C temperature. (b) [9 marks) Heat of formation for Cp in kJ mol K1 kJ mol 52.28 -52.6 Heat capacity coefficients Temperature units a 4.245 x 10 4.037 x 102 2.9253 x 10-2 3.682 x 102 3.333 x 10 8.852 x 10 1.392 x 104 9.242 x 105 3.141 x 105 9.353 x 10 ethylene ethylene oxide Tin °C for Cp = a + bT 0.0 охудеn carbon dioxide -393.5 -241.83 water (c) How would you control the reactor temperature? [1 mark] A process system for the manufacture of ethylene glycol is shown in Figure Q1. Ethylene oxide (CaH.O) is produced in the reactor by the following main reaction of catalytic oxidation of ethylene (C2H«): (6)O'HO- (6)o (6)"H) An undesired competing side reaction is the combustion of ethylene to CO2. CaHa(g) + 302(g)- 2CO2 (g) + 2H:O(g) The reactor product is fed to a separation system where water is added to convert ethylene oxide to ethylene glycol. CH,O(g) + H20(1)CaHO2(1) recycle: n, purge: n. water: n. ethylene: net oxygen: 10 kmol/h T 350°C T= 380 °C Separation System Preheater Reactor Q=? ethylene glycol product: neg n, - molar flow rate of x, kmol/h Figure Q1 (a) Produce a process material balance for the production of ethylene glycol based on an oxygen feed rate of 10 kmol h-1. Calculate the molar flowrates of each component in each stream. The following conditions apply: • All oxygen reacts, 90% goes to ethylene oxide, the rest to CO2 and H20. • Ethylene and oxygen feeds are pure. • 20% excess ethylene is fed to the process to ensure process safety. • No reaction of ethylene oxide with water takes place in the reactor. • All the water and ethylene oxide entering the separator is converted to • ethylene glycol. • Gases do not dissolve in ethylene glycol and the separation is assumed to • be ideal, i.e. ethylene glycol, is pure. • There is no water in the recycle, purge and product streams. 1% of gas stream is purged. Assume the combined stream consisting of the two fresh feeds and the recycle enters the reactor at 350°C, the reactor effluent is at a temperature of 380°c and that there are no heat losses. Using the data below, calculate how much heat has to be removed or supplied to the reactor to maintain the 380°C temperature. (b) [9 marks) Heat of formation for Cp in kJ mol K1 kJ mol 52.28 -52.6 Heat capacity coefficients Temperature units a 4.245 x 10 4.037 x 102 2.9253 x 10-2 3.682 x 102 3.333 x 10 8.852 x 10 1.392 x 104 9.242 x 105 3.141 x 105 9.353 x 10 ethylene ethylene oxide Tin °C for Cp = a + bT 0.0 охудеn carbon dioxide -393.5 -241.83 water (c) How would you control the reactor temperature? [1 mark]