Dynamics Quick Guide Beta

DYNAMIC SIMULATION COURSE 2013

By: Eng. Ahmed Deyab Fares

Mobile: 002-01227549943 - Email: [email protected]

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DYNAMICS

QUICK GUIDE

2013

Beta


[email protected] – [email protected]




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NGL FEED (St. State Case)

A stream of NGL at 15oC, 380 kPa and with a Std Ideal Liq Vol Flow of

200 m3/hr and the following composition:

Component Mole Fraction Component Mole Fraction

Ethane 0.01 i-Pentane 0.05

Propane 0.43 n-Pentane 0.04

i-Butane 0.07 n-Hexane 0.28

n-Butane 0.12

Is fed to a Valve (pressure drop =70 kPa) and then sent to a Separator.

The Liquid product from the separator is then fed to a Pump (delta P =

1900 kPa) with adiabatic efficiency of 75% and then flashed down

through a Valve (∆P=70 kPa). The valve outlet is then sent to the tube

side of a Shell and Tube Heat Exchanger, where it exchanged heat with

a shell inlet stream named (Shell In), the shell out stream named (Shell-

out) have the following information:

Temperature Pressure Std Ideal Liq Vol Flow

155 oC 1100 kPa 55 m

3/hr

Component Mole Fraction Component Mole Fraction

Ethane 0 i-pentane 0.11

Propane 0 n-pentane 0.11

i-butane 0 n-hexane 0.75

n-butane 0.03

The ∆P for both shell & tube sides=70 kPa, and UA = 8000 kJ/C-h. The

tube side outlet is then sent to a heater in order to meet the column feed

temperature (50oC) the ∆P inside the heater is 70 kPa.

Calculate:

- The pressure of the Column Feed Stream

- The molar flowrate of the Column Feed Stream




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Transitioning From St. State to Dynamics

1) Equipment Sizing

Vessel Heater Heat Exchanger Shell Tube

Volume 85 m3 33 m

3 9 m

3 33 m

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2) Enable pressure flow equations not

pressure drop

3) Enable stream pressure specifications on

ALL BOUNDRY STREAMS

• F= Fn(Cv, P1, P2) Valves

• F= K√ρ∆P Heat Transfer Equipment

• Characteristic Curve (Q vs H & Q vs Efficiency) Rotary Equipment

• dp/dt=Fn (V, F, T) Vessels




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Adding PID controllers in Aspen HYSYS

PID Controllers

• Process Variable - the "measured" variable. This is usually the variable that

you want to control, i.e. pressure, temperature, liquid level, etc.

• Output Target Object - the "adjusted" variable. This is what the

controller can change in order to control the process variable. This is most

often a valve.

• Action - the action of the controller can be chosen as Reverse or Direct. The

OP of a Direct action controller will rise as the PV rises above the SP.

Likewise; the OP will fall if the PV falls below the SP. Conversely, the OP of a

Reverse action controller will fall if the PV rises above the SP, and rise if the

PV falls below the SP.

• Mode - the mode of the controller can be chosen as: Off, Man. (manual),

Auto (automatic), or Tune. In Manual mode, the user can set the OP; in

Automatic mode, the user can set the SP.

• SP - the setpoint of the controller. This is the "goal" value. The controller

will always strive to have the process variable meet this value.

• PV - an abbreviation for the Process Variable.

• OP - an abbreviation for the Output Variable.

• Kc - the controller gain.

• Ti - the integral time of the controller.

• Td - the derivative time of the controller.

• PV Minimum - should be set to the minimum value that the PV could reach

during the simulation.

• PV Maximum - should be set to the maximum value that the PV could

reach during the simulation. It is used with PV minimum to determine the

"span" of the controller.

Note that not every variable must be set for each controller. The value for each cell

will depend on the controller’s situation.




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NGL Controllers

Separator

Feed Controller

Separator

Pressure Controller

Connections

Controller Name NGL-FC Flare-PC

Process Variable Source To Sep, Mass Flow Separator, Vessel Pressure

Output Target Object VLV-100 VLV-102

Parameters

Action Reverse Direct

PV Minimum 0 kg/h 135 kPa

PV Maximum 250 000 kg/h 415 kPa

Mode Auto Auto

SP 1.169 e+5 kg/h 310 kPa

Kc 0.1 2.0

TI 0.2 minutes 2.0 Minutes

Separator

Level Controller

Column Feed

Temperature Controller

Connections

Controller Name Separator-LC Heater-TC

Process Variable Source Separator, Liquid Percent Level ColFeed, Temperature

Output Target Object VLV-101 Heater-Q (0 2.0 ـــــــe7 kJ/hr)

Parameters

Action Direct Reverse

PV Minimum 0% 15°C

PV Maximum 100% 80°C

Mode Auto Auto

SP 50% 50°C

Kc 2.0 5

TI 10 Minutes 20 Minutes

Add a strip chart to monitor the change of the vessel pressure

with time around the Set Point (SP)




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Depropanizer

The heated stream from the NGL Feed steady state case is fed to the 12th

tray of a depropanizer (distillation column) which consists of 24 stages, a

full reflux condenser and Kettle reboiler. The pressures inside the

condenser and reboiler are 1925 and 2070 kPa respectively. Column

reflux ratio is 2.

The second specification for the distillation column is a 0.95 mole

fraction of both ethane and propane comes out of the condenser stage.

You may need to install valves to the 2 column products

Column Sizing:

Condenser Reboiler

Volume 10 m3 20 m

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For the Tray Section, specify the following values on the Tray Sections

page of the Rating tab.

Type of trays Valve tray

Tray Spacing 600 mm

Diameter 3.7 m

Weir Height 60 mm

Flow Paths 2

Foaming Factor 0.85

Tray Volume [m3] …………………..

Rating (dynamics) DP …………………..

Stage 12 Pressure …………………..




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Depropanizer Column Controllers

Condenser

Pressure Controller

Condenser

Level Controller

Connections

Controller Name Cond-PC Cond-LC

Process Variable Source Condenser, Vessel Pressure

Condenser, Liquid Percent

Level

Output Target Object VLV-103 Reflux Stream (0 3000 ـــ)

Parameters

Action Direct Direct

PV Minimum 1725 kPa 0%

PV Maximum 2070 kPa 100%

Mode Auto Auto

SP 1925 kPa 50%

Kc 2.0 2.0

TI 2.0 Minutes 10 Minutes

Reboiler

Level Controller

Tray 23

Temperature Controller

Connections

Controller Name Reb-LC Tray 23-TC

Process Variable Source Reboiler, Liquid Percent Level Main TS, Stage Temp., Stage

23

Output Target Object VLV-104 Q Reb (0 1.0 ـــــــe8 kJ/hr)

Parameters

Action Direct Reverse

PV Minimum 0% 100°C

PV Maximum 100% 200°C

Mode Auto Auto

SP 50% 140°C

Kc 2.0 5

TI 10 Minutes 20 Minutes




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Exercise:

Change the Output Variable for the Condenser-LC to Cond-Q, from

Reflux. Make sure that you choose reasonable values for the maximum

and minimum cooling duty. Change the molar flow specification for the

Reflux stream to 1620 kgmole/h (3560 lbmole/hr).

Does this control strategy provide better control over the De-

Propanizer?




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Tank Filling

Feed stream consists of 0.8 H2O, 0.04 O2, and 0.16 N2 (Mole fractions) @

25°C and 3 bar-g, and a flow rate of 4000 Kg/hr, enters a Tank

(Volume= 3 m3, Liquid Volume Percent 0%)

Fluid pkg: Peng Robinson

Feed and both products stream Valves spec:

Pressure drop for all valves = 100 kPa

VLV-100 VLV-101 VLV-102

CV (Conductance): 70 50 50

- Control the tank liquid percent level and the feed mass flow

Controllers:

LIC FIC

SP 50% 4000 kg/hr

Kc 0.5 0.5

Ti (Minutes) 5 1

PV Min 0% 0 Kg/hr

PV Max 100% 9000 Kg/hr

- Run the integrator for 180 min. with acceleration of 0.5

- Create a strip chart to monitor the filling of the tank with the

controller setpoint.




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Refrigerated Gas Plant A feed stream is fed to a valve (delta P= 70 kPa) before entering an inlet separator,

which removes the free liquids (both water and other more dense liquids). Overhead

gas from the inlet Separator is fed to the tube side of a shell & tube heat exchanger,

the tube side outlet (-10 oC) is then sent to a Chiller where it is cooled to -20oC,

which will be modeled simply as a Cooler (Pressure Drop=35 kPa). The cold stream is

then separated in a low-temperature separator (LTS). Overhead gas from the LTS is

fed to the shell side of the shell & tube heat exchanger where it is heated with the

inlet separator vapor to meet Sales Gas Specifications.

Feed Stream:

Temperature Pressure Molar Flow Rate

0C 6200 kPa 1440 kgmole/h

Composit ion:

Mole% Component Mole% Component

0.0068 i-Butane 0.0066 N2

0.0101 n-Butane 0.0003 H2S

0.0028 i-Pentane 0.0003 CO2

0.0027 n-Pentane 0.7576 Methane

0.0006 n-Hexane 0.1709 Ethane

0.0000 H2O 0.0413 Propane

Use Peng Robinson (PR) Equation of State

Shell & Tube Heat Exchanger Parameters:

- Build a steady state case and convert it to dynamics (make the necessary

changes).

- Enter a vessel volume of 2 m3 (70 ft3) for both separators

- Set up the following PID controllers.

1- Control the level of the inlet separator with the following parameters:




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2- Control the pressure of the LTS (Low Temp Separator) by manipulating the valve on the Sales Gas stream (Shell Side outlet stream) with the following parameters:

- Run the case in the dynamics mode




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Control Loop Exercise 1- For the following heat exchanger, draw a feedback control loop

It is desired to control the Exit stream temperature, T2, at a certain set point, SP.

2- For the following heat exchanger, draw a feedback control loop.

It is desired to control the liquid level inside the tank, H, at certain set

point, SP.

3- For the following column, draw a feedback control loop

It is desired to control column's bottom temperature, T, at certain set point, SP.




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Expanding the overhead system 1- Add a Splitter (TEE)

2- Add the Relief Valve (Orifice Area = 1300 mm2)

3- Add the Air Cooler (delta P =70 kPa)

4- Add the Accumulator

5- Add the Vapour Product Valve (delta P =70 kPa)

6- Add the Pump (Pump Speed = 85 rpm)

Curve Speed = 60 rpm

Flow (USGPM) Head (ft) % Efficiency

0 275 0

100 260 42

200 235 60

300 190 66

400 150 70

500 140 75

600 100 69

700 70 65

800 40 60

7- Add a Reflux Valve (delta P =70 kPa)




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Controllers:

- Accumulator Pressure Controller

- Accumulator Level Controller




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Dynamics Quick Guide Beta