Online Reaction assignment help teacher needed in Melbourne

  • Melbourne, FL, USA
  • US$15/hour
  • Posted : Nov 28
  • Level : Bachelors/Undergraduate
  • Due Date : 06-12-2024
  • Requires : Part Time
  • Posted by : Neel (Student )
  • WhatsApp verified +1-**********
  • Gender Preference : None
  • Available online
  • Not available for home tutoring
  • Can not travel
  • Can communicate in : English, Hindi

I am trying to learn Aspen plus on my own and I have found a cery difficult problem that I am having trouble understanding and simulating. I wanted some help figuring out the issue and completing the problem from start to end as a lesson(s). Would you be able to help me? I can provide a breif overview of that I am working on:

It is desired to produce styrene based on a new process developed by R&D using a proprietary zeolite
catalyst in a packed bed reactor. The overall process shown in Figure 1 should be designed to produce
200,000 tonnes of styrene per year. Stoichiometric proportions of toluene and methanol are
independently preheated to a saturated vapor state (both @ 5.7 bar discharge pressure) using the reaction
heat from the reactor. The feed streams are mixed and then superheated as much as feasible (no closer
than 10 C approach) in an inter-changer prior to being sent through a fired heater where they are brought
up to the required reactor inlet temperature. The mixed feed is then passed through the catalytic reactor
where the following reactions take place:
Toluene + Methanol  Styrene + Water + Hydrogen
Toluene + Methanol  Ethylbenzene + Water

The reaction heat is recovered from the reactor effluent in the interchanger and vaporizers prior to the
product being condensed and cooled to 40oC with cooling tower water before being sent to the decanter
which operates at a pressure of 1.3 bar. From the decanter the gas is sent downstream and used for fuel
and the condensed phases are separated into an aqueous and an organic fraction. The aqueous phase
which contains significant methanol is sent to a downstream process for further purification. The organic
phase is sent to the separations section where first the unreacted toluene and methanol will be removed
and sent back to the front end of the process and the styrene and ethylbenzene are processed in a separate
column to purify the products.

It is your task to simulate the process with Aspen Plus and use the simulation results along with the data given in the problem statement and heuristics for process equipment where needed to develop
the capital costs, manufacturing costs and perform a profitability analysis for the process. You should initially focus on the front end of the process (up to and including the decanter) and determine the
optimum reactor inlet temperature based on the data in the table below.

Reactor Inlet Temperature (o C ********* 30
Conversion (mole of toluene reacted /mole of toluene fed ********* 735 0.750
Yield (mole of styrene produced /mole of toluene reacted ********* 745 0.645
Rate (g-mole toluene reacted /m3of catalyst - min *********

The procedure used to find the optimum temperature can be done as follows:
1) For each inlet temperature use excel to set up a table and calculate the # of moles of styrene
produced and ethyl benzene produced per mole of toluene fed.
2) Based on the selling prices for the products calculate / decide which temperature gives the
optimum revenue per mole of toluene fed.
3) Based on the temperature specification determine the required mass of toluene and methanol feed
(in tonnes / yr. and kmole / hr.) needed to produce the 200000 tonnes annually of styrene using a
mass balance assuming all the styrene produced can be recovered as part of the 200000 tonnes.
Note: Be sure to account for the 90% stream factor given in the specifications below (330 days of
operation per year) in your calculations).

Once you have fixed the front end of the process you need to design a two-column distillation train to purify the styrene and ethylbenzene.

Feed and Product Specifications:
 Impurities in the methanol and toluene feedstock are negligible.
 Methanol and Toluene are both in storage tanks at 25 oC and 1 atm.
 Both reactant feeds must be brought to pressure with an appropriate pump. Add 1.5 atm to the
required pressure at the pump to account for pressure losses in valves and piping throughout the
plant.
 Pumps efficiency can be assumed to be 80%.
 Assume a 90% stream factor (i.e. 330 days).
 Product pumps should be included for transport to storage. You may assume that a pressure rise of
1.25 atm is sufficient for this purpose.
 Storage should be provided for the products and reactants for 3 days.
Heat Exchanger and Heater Specifications:
 For gas side heat exchangers assume a 0.2 bar pressure drop.
 For liquid side heat exchangers assume a 0.4 bar pressure drop.
 For boiling and condensing heat exchangers assume a 0.1 bar pressure drop.
 For heat exchanger design use a temperature approach of 10 C. Defined as:
For heating: Hot inlet / Cold outlet
For cooling: Cold inlet / Hot outlet
 Cooling water can be assumed to be available at 30 C and 3 bar and should be cost as a utility.
 Refrigerated water can be assumed to be available at 5 C and 3 bar and should be cost as a utility.
 For the reboilers, steam should be assumed saturated at appropriate pressures and cost as a utility.
 For the fired heater, natural gas can be assumed as the fuel source and cost as a utility.
 Use appropriate overall heat transfer coefficients (see heuristics) for heat exchangers
Reactor and Catalyst Specifications:
 The reactor can be assumed to operate adiabatically.
 The pressure drop across the packed bed reactor can be assumed to be 0.5 bar.
 The zeolite catalyst has a cost of $2000 / metric ton with a 5-year life.
 The zeolite catalyst has a bulk density of 750 kg / m3.
Decanter Specifications:
 The decanter should be modeled as a 3-phase separator.
 The aqueous stream leaving the decanter can be ignored in terms of any additional design
requirements or costs.
 The vapor stream from the decanter is processed as fuel in a downstream process and can be
ignored in terms of revenue or cost.
 Size the decanter for 30 minutes liquid holdup and 60% full of total liquid.
Recovery Column Specifications:
 The recycle methanol and toluene sent back to the front end of the process is recovered from an
atmospheric distillation column.
 The recycle stream does not have to be simulated as being added back into the front end of the
process in the simulation although the design and cost of the reflux pump for the column and / or
booster pump should reflect this. Also account for the recovery by reducing the amount / cost of the
feed appropriately.
 Any nominal atmospheric distillation towers should operate with a condenser outlet pressure of 1.2
atm.
Purification Column Specifications:
 The ethyl-benzene byproduct should be at least 96% pure while the styrene needs to be 99.5% pure.
 For a vacuum column allow a 0.05 atm pressure drop between the top of the column and the
condenser outlet.
 To account for the operation of the purification column under vacuum modify the bare module
capital cost of the column based on the relationship: Actual Cost = (CBM) * (P)-0.9
Additional Column Specifications:
 Assume a 0.01 atm pressure drop per theoretical tray in the distillation towers.
 Do not exceed 150 C in any portion of a column with more than 50% styrene monomer to minimize
polymerization.
 Assume both columns are equipped with trays having a 70% efficiency.
 The tower reboilers and condensers duties are calculated with RADFRAC but should be modeled
and sized in a separate simulation file.
 Reflux pumps and drums need to be designed and sized for each of the columns. Using heuristics.
Simulation Specifications:
 Use the SRK method with Steam-NBS free water method for the front end of the plant.
 Use the NRTL-RK method with Steam-NBS free water method in the separations section including
the decanter.
 Use metcbar units for the Aspen simulation files.
 You should minimize utilities usage in your design by maximizing heat recovery where possible.