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PROJECT OVERVIEW. Objective: make 3000 metric tons of liquid ammonia per dayTwo options for SuperPro simulationSingle-pressure processDual-pressure processCompare and contrastEconomics (capital and operational)Environmental (emissions and solid/liquid)Determine the most profitable process. K
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1. SUPERPRO-BASED AMMONIA PLANT RETROFIT REACTOR OPTIMIZATION THROUGH ASPEN ASSISTANCE
NORTH CAROLINA STATE UNIVERSITY
DEPARTMENT OF CHEMICAL ENGINEERING
SPRING 2004
R. BARNHILL
E. FABRICIUS
A. HERRMANN
D. JONES
2. PROJECT OVERVIEW Objective: make 3000 metric tons of liquid ammonia per day
Two options for SuperPro simulation
Single-pressure process
Dual-pressure process
Compare and contrast
Economics (capital and operational)
Environmental (emissions and solid/liquid)
Determine the most profitable process
3. KINETICS SUPPLIED Equation:
Constants:
K1 = k01exp(-E1/RT)
K2 = k02exp(-E2/RT)
K01 = 1.78954*104 kgmol/m3-hr-atm1.5
K02 = 2.5714*1016 kgmol-atm0.5/m3-hr
E1 = 20,800 kcal/kgmol
E2 = 47,400 kcal/kgmol
4. CHALLENGES WITH SUPERPRO Rate equation proves to be incompatible with given data
SuperPro only accepts simplified kinetics
However, SuperPro offers extent of reaction option
5. ASPEN THEORY Supply SuperPro with extent of reaction
Optimize through analysis of critical parameters that affect the rate of reaction
Advantages
Basic Aspen simulation with one piece of equipment
Aspen supports supplied kinetics
Disadvantages
Basic knowledge of Aspen required
Iterative process between two simulation systems
6. ASPEN SIMULATION: STEP 1 Setup Aspen to run ammonia reaction with supplied kinetics
7. ASPEN SIMULATION: STEP 2 Run simulations varying critical parameters
Temperature
Pressure
Reactor Size
Composition of inlet stream
Study the relationship between the different parameters of the reaction
Plotting the information and studying trends works well
8. ASPEN SIMULATION: STEP 3 Simulate the reactor at an “initial composition” obtained
Record SuperPro required Data
Temperature
Pressure
Reactor Size
Extent of Reaction
9. SUPERPRO SIMULATION: STEP 1 Plug the results from Aspen reactor simulation into SuperPro simulation (shown on next two slides)
Conduct mass and energy balances
10. SUPERPRO SIMULATION: STEP 1a Set Aspen operating temperature of the reactor
11. SUPERPRO SIMULATION: STEP 1b Set the extent of reaction that agrees with the Aspen data
12. SUPERPRO SIMULATION: STEP 2 Study the effects that the new outlet stream (from the reactor) has on the inlet stream
Take new inlet stream data and plug back into Aspen and re-run the simulations
This step is the final step in the cycle between Aspen and SuperPro – this cycle is to be repeated several times until optimal results are obtained
13. SUMMARY AND KEY POINTS Iterations between Aspen and SuperPro require the use of multiple sets of data
Keep accurate records
Optimize the system based on costs
Cost of pressurizing the feed stream
Cost of compressors
Energy cost of the compressors
Cost of cooling the reactor to the optimal temperature
Cost of the reactor (size dependent)