Spring 2017, 2016
FINAL PROJET DESCRIPTION
The simulation for the final project is that of a hydrogen plant. Currently the predominant method for manufacturing hydrogen is through “Steam-Methane” reforming process. In this process hydrocarbon is mixed with steam and reacted over reforming catalyst. The reaction mixture is heated to about 1500 F. Products of this reaction are H2, CH4, CO, CO2, and un-reacted H20. Reformed gases are then cooled to 660 F and sent to a High Temperature Shift (HTS) Reactor. In this reactor CO reacts with steam to make additional hydrogen and carbon dioxide. The HTS reactor effluent is cooled to about 100 F and sent to a Pressure Swing Adsorption Unit. In this unit about 80% of the hydrogen in the feed is separated to an essentially 100% pure hydrogen stream. The remaining gases, recovered at about 5 psig, are used as fuel gas and are burned in the reformer to provide most of the heat for the reforming reaction. Along with hydrogen, there is also high pressure steam that is generated. Part of this steam is used for the reaction and the rest is exported to other units in the facility.
Please use PSIG as the unit for pressure.
Please Name the Streams (DO NOT USE S1, S2, etc.)
Use SRK Thermo Package.
The library components for this simulation are: H2, CO, CO2, Methane, Water, Ethane, Propane, n-Butane, Oxygen, and Nitrogen.
There are three sets of reactions in this simulation. These are:
Psuedoref
C2H6+2H20----5H2+ 2C0
C3H8+3H20----7H2+3C0
C4H10+4H20--9H2+4CO
Reforming
CH4+ H20--- 3H2+C0
C0+H20------ H2+C02
Combustion
H2+1/2 02------H20
C0+1/2 02------C02
CH4+202------ C02+2H20
C2H6+7/2 02----2C02+3H20
C3H8+502-----3C02+4H20
Feed from the hydrogen plant comes from two sources. A propane rich stream from a De-Propanizer column, supplemented with Natural gas as needed to make40 MMSCFD (Million Standard Cubic per Day measured at 14.7 psia and 60 F) of hydrogen product.
The feed to theDe-Propanizer is 1100 moles/hr with the following composition and conditions:
Ethane 2 Mol%
Propane45 Mol%
n-Butane53 Mol%
Total100 Mol%
Temp100 F
Pressure310 psig
The De-Propanizer has a partial condenser (i.e. Top product is taken as vapor). It has 60 trays with a tray efficiency of 85 percent. The condenser pressure is 200 psig. Pressure drop through the condenser is 5 psi. Pressure drop per tray is 0.1 psi. Start with feed on stage number 4.
The column specifications are:
0.01 mole fraction of Butane in the top vapor product
0.02 mole fraction of Propane in the bottoms product
Use an Optimizer to find the optimum feed tray location (i.e. a feed tray location that results in minimum reboiler duty).
H2 Production
The feeds to the Hydrogen Plant are De-Propanizer overhead product along with Natural Gas.
Natural gas composition and conditions are as follows:
CH488 Mol%
Ethane 9 Mol%
Propane 3 Mol%
Total100
Temp60 F
Pressure300 psig
Start with 600 moles/hr of Natural gas.
Mix the Natural Gas with the De-Propanizer overhead vapor and compress the mixture to 450 psig. Compressor adiabatic efficiency is 75%.
Heat up the compressed gas to 700 F. Pressure drop through the heater is 20 psi.
Mix the heated gas with enough steam (steam conditions: 650 F and 650 psig) to achieve a Steam to Carbon Mole Ratio of 3.5(Use a Calculator routine for this purpose). Include all Carbon bearing components in the feed for this calculation.
Heat the hydrocarbon/steam mixture to 1000F. Pressure drop through the heater is 20 psi.
Feed the heated hydrocarbon/steam mixture to a Conversion Reactor. The reaction set for this reactor is the Psuedoref. Use Zero (0) reactor pressure drop. Specify 100% conversion of the hydrocarbon components for each of the reactions.
Feed the Conversion Reactor Effluent to a Gibbs Reactor. Set Reactor outlet at 1500 F. Specify a Reactor DP of 25 psi. The reaction set for this reactor is Reforming. Make sure to specify a Vapor Reaction Phase.
Cool the Reactor effluent to 660 F. Use a pressure drop of 10 psi for the cooler.
Feed the cooled gases to an Equilibrium Reactor. Specify the PROII built in Shift reaction for this reactor. Use 25 Fapproach to equilibrium and a 10 psi reactor pressure drop.
Cool the Reactor effluent to 100 F. Specify a pressure drop of 20 psi for the cooler.
Separate out the condensed water from the cooling step above in a flash drum. Specify a pressure drop of 1 psi for the Flash drum.
Feed the cooled gases to a Stream Calculator. This operation is to represent a Pressure Swing Adsorption (PSA) unit used for hydrogen purification. In this unit 80% of the hydrogen in the feed to the PSA unit is recovered as 100% pure hydrogen (i.e. Hydrogen Product) at 105F and a pressure 10 psi less than the feed pressure. The remaining components are recovered in a second stream (i.e.Purge Gas) at 5 psig and same temperature as feed gas (100 F).
At this point use a controller to vary the Natural Gas Feed so that the Hydrogen Product stream is 40 MMSCFD (Million Standard Cubic Feet per Day). (Standard conditions are 14.7 psia and 60 F – Hint 1 Mole of ideal gas is 379.48 SCF)
Hydrogen product is to be delivered to another facility at 330 psig (minimum pressure) through a 900 ft (equivalent length) schedule 40 pipe line. What minimum size standard diameter pipe is required?
One Credit Stop Here (Go to Deliverables)
Two and Three Credits ( Continue)
Next task is to figure out how much fuel gas will need to be combusted to supply the heat for the reforming reaction. Start with 400 moles/hr of Natural Gas and mix it with PSA purge gas. Name the mixture Fuel Gas.
Start with 17,000moles/hr of air (79 Mol% N2, 21 Mol% O2 at 0 psig and 60 F) and mix it with the fuel gases. Feed the mixture to a Conversion Reactor and use the reaction set Combustion. Use a controller to adjust the combustion air flow so that percent oxygen in the reaction product (i.e. Flue Gas) is 5 Mol%.
Cool the flue gas to 1800 F in cooler with 0 psig pressure drop. Use another controller to adjust the Natural Gas flow used as fuel gas so that the duty from the cooling of the flue gas matches the duty required by the Reforming Reactor.
At this point we will be in a position to calculate how much steam we can generate and export from the heat available in the process. LNGHX module can be used for this purpose. Steam is generated from Boiler Feed water delivered to the Plant at 220 F and 800 psig.
The Hot Streams are:
Flue Gas Cooled from 1800 F to 350 F.
Reformer Reactor Effluent cooled to Shift Reactor Inlet Temperature
High Temperature Shift Reactor Effluent cooled to T? (this will be calculated by the program)
Cold Streams are:
Compressed Hydrogen Plant hydrocarbon feed gas heated to 700 F at 430psig.
Reaction steam/hydrocarbon feed to Reformer heated to 1000 F and 410 psig.
Steam condensate from cooling of HTS reactor effluent heated from 100 F and 345 psig to 200 F and 335 psig
BFW at 220 F and 800 psig heated to 650 F and 650 psig to make the steam used in the reaction plus steam available for export.
As an initial estimate use a BFW rate of 300,000 lb/hr. Use a controller and vary the BFW rate so that the Minimum Temperature Approach for the LNGH is 45 F.
Split the Steam make into two streams. One stream will have the same rate as the steam fed to the Reformer. The Other Stream is steam available for export.
Deliverables:
One Credit
1- Print out copy of input keyword file and the summary file of results (Stream component molar flow rates)
2- Prepare a Table showing the amount of feed and utilities needed to make 40 MMSCFD of hydrogen:
1)De-Propanizer Overhead Vapor, moles/hr
2)De-Propanizer Optimum Feed Tray Location
3)Natural gas used as feed, moles/hr
4)Minimum standard pipe diameter required for transferring the hydrogen product
5)Compressor Horsepower (HorsePower)
6)Required Cooling water flow rate ( gallons per minute) to De-Propanizer OVD Condenser ( Cooling water supply 75 F & 80 Psig , Cooling water outlet temperature is 95 F)
7)Required Steam flow ( Lb/hr) to De-Propanizer Reboiler (50 psig steam saturated steam fully condensing in the reboiler at 50 psig).
8)Required Diameter of De-Propanizer Trays based on close to 80% flood factor for Valve Trays. Report required column diameters for above feed tray section (Rectifying Section) and feed tray and below section (Stripping Section) based on column diameters in 6 inch increments.
Two Credits
1- Print out copy of input keyword file and the summary file of results (Stream component molar flow rates)
2- Prepare a Table showing the amount of feed and utilities needed to make 40 MMSCFD of hydrogen:
1)De-Propanizer Overhead Vapor, moles/hr
2)De-Depropanizer Optimum Feed Tray Location
3)Natural gas used as feed, moles/hr
4)Minimum standard pipe diameter required for transferring the hydrogen product
5)Compressor Horsepower (Horse Power)
6)Required Cooling water flow rate ( gallons per minute) to De-Propanizer OVD Condenser ( Cooling water supply 75 F & 80 Psig , Cooling water outlet temperature 95 F)
7)Required Steam flow( Lb/hr) to De-Propanizer Reboiler (50 psig steam saturated steam fully condensing in the reboiler at 50 psig).
8)Natural gas used as fuel, moles/hr
9)Export Steam make, lb/hr
10)Cooling water rate in gallons per minute needed to cool the Shift Reactor Effluent from temperature T? leaving the LNGHX Module to 100 F. Cooling water supply temperature is 75 F. Supply Pressure is 80 psig . Cooling water temperature rise is 20 F. Allowable pressure drop on the cooling water side is 20 psi.
11)Required Diameter of De-Propanizer Trays based close to 80% flood factor for Valve Trays. Report required column diameters for above feed tray section (Rectifying Section) and feed tray and below section (Stripping Section) based on column diameters in 6 inch increments
12)Size the Shift Effluent Water Cooler (Determine number of tubes required and exchanger surface area) using the following information:
- Cooling Water on Tube Side
- Specify Shell Outlet Temperature to be 100 F
- Tube OD 1 inch
- Tube Thickness 14 BWG
- Tube Length 18 ft
- Tube Pitch 1.25 inch Square Pitch
- Baffle Cut 20 % of Diameter
- Baffle spacing 10 inches
- Material Carbon Steel
- Number of Tube Passes 4(Starting Point). Consider changing the number of Tube passes to the limit of the cooling water side maximum allowable pressure drop of 20 psi. State the rationale on the final selection of Number of Tube passes.
- Exchanger Tube AES
- Shell side and Tube side fouling factors , 0.001 each side
- Shell Diameter 39 Inches
- Print copy of the Exchanger Data Sheet from PROII Output file
Three Credits
1- Print out copy of input keyword file and the summary file of results (Stream component molar flow rates)
2- Prepare a Table showing the amount of feed and utilities needed to make 40 MMSCFD of hydrogen:
1)De-Propanizer Overhead Vapor, moles/hr
2)De-Depropanizer Optimum Feed Tray Location
3)Natural gas used as feed, moles/hr
4)Minimum standard pipe diameter required for transferring the hydrogen product
5)Compressor Horsepower (Horse Power)
6)Required Cooling water flow rate ( gallons per minute) to De-Propanizer OVD Condenser ( Cooling water supply 75 F & 80 Psig , Cooling water outlet temperature 95 F)
7)Required Steam flow( Lb/hr) to De-Propanizer Reboiler (50 psig steam saturated steam fully condensing in the reboiler at 50 psig).
8)Natural gas used as fuel, moles/hr
9)Export Steam make, lb/hr
10)Cooling water rate in gallons per minute needed to cool the Shift Reactor Effluent from temperature T? leaving the LNGHX Module to 100 F. Cooling water supply temperature is 75 F. Supply Pressure is 80 psig . Cooling water temperature rise is 20 F. Allowable pressure drop on the cooling water side is 20 psi.
11)Required Diameter of De-Propanizer Trays based close to 80% flood factor for Valve Trays. Report required column diameters for above feed tray section (Rectifying Section) and feed tray and below section (Stripping Section) based on column diameters in 6 inch increments
12)Size the Shift Effluent Water Cooler (Determine number of tubes required and exchanger surface area) using the following information:
- Cooling Water on Tube Side
- Specify Shell Outlet Temperature to be 100 F
- Tube OD 1 inch
- Tube Thickness 14 BWG
- Tube Length 18 ft
- Tube Pitch 1.25 inch Square Pitch
- Baffle Cut 20 % of Diameter
- Baffle spacing 10 inches
- Material Carbon Steel
- Number of Tube Passes 4(Starting Point). Consider change the number of Tube passes to the limit of the cooling water side maximum allowable pressure drop of 20 psi. State the rationale on the final selection Number of Tube passes.
- Exchanger Tube AES
- Shell side and Tube side fouling factors , 0.001 each side
- Shell Diameter 39 Inches
- Print copy of the Exchanger Data Sheet from PROII Output file
13)You have received information from a High Temperature Shift catalyst vendor regarding their new higher actively catalyst. The vendor states that with the new catalyst the reactor inlet temperature can be lowered from 660 F to 550 F and that the approach to equilibrium for the shift reaction is reduced from 25 F to 15 F. Since the new catalyst results in a lower concentration of carbon monoxide at the reactor outlet, an additional benefit provided by the new catalyst is 0.5% better hydrogen recovery in the PSA unit ( i.e. hydrogen recovery increases from 80% to 80.5%).
- Assuming a Natural Gas Price of $3 per 1000 SCF ( Standard Cubic Feet measured at 60 F and 14.7 psia – Hint 1 mole of ideal gas is 379.48 SCF) ) , and a value of 650 psig Export Steam of $4 per 1000 lb, determine if there are any annual savings, dollars/year, resulting from switching to the new catalyst? Prepare a Table as follows:
Base Case / New Catalyst / Delta (New- Base) / Savings ( Loss) $/Year
Natural Gas Feed, Moles/hr
Natural Gas Fuel, Moles/hr
Export Steam, Lb/hr
Total Savings ( Loss) $/Yeas
14)Write a brief report on the following”
- Production of hydrogen through other means and use of Hydrogen in Industry
- Description on how a Pressure Swing Adsorption (PSA) Unit works
Final Report will be collected on May 18 at the Start of Class at 5 PM
1