co2 progress and issues on the control system lukasz zwalinski – ph/dt 13.04.2010

CO2progress and issues on the

control system

Lukasz Zwalinski – PH/DT13.04.2010

There will be one PCO with 3 option modes driven by allowance table

Plant operation

L.Zwalinski – PH/DT CO2 test stand control system 12.04.2010

Stop Stand-By Run

Stop x 1 x

Stand-By 1 x 1

Run 1 1 x

Switch between modes is executed manually by the operator request.

Stop (Option Mode 1)All devices are in safety position.

Stand-By (Option Mode 2)Operator can safely move system from “warm” environmental conditions to the state where accumulator is cooled down.

Run (Option Mode 3)Run is defined as an option in which plant is fully operated and tested structure can be entered with certain inlet enthalpy.

PCO is in run OrderOne PCO Alarm is blocked

Push button to open sequencer panel

PCO is in manual mode

Current selected option mode

Plant operation

In option mode Stand-By we can distinguish stepper with 4 steps associated

2

Start up1

CO2 PCO

T2

Cool down loop

Safety position

3

0

Cool down accumulator

T3

T0

T0

T0

Start up request

Cool down request

Cool down accumulator request

T1

T0

Safety position – It is preparation step before plant start up. Before first operation accumulator will be filled up to 75% of volume. This step in P-h diagram Fig.3 is somewhere along 220C isotherm in the 2-phase region. Pump inlet temperature will be 220C. Pump head and system pressure will be about 60 Bar. In this step all objects are switched off.Start up – accumulator is heated up to 270C and the system pressure increase to the corresponding saturation pressure 67 bar. In the first stage of plant operation set-point selection has to be done manually by the operator. When this condition is fulfilled, loop should be filled with liquid and then pump might be manually switched on. The liquid level in accumulator will decrease.Cool down loop – once liquid circulation is achieved chiller might be switched on. Accumulator is still kept at high pressure and the condenser will sub-cool the liquid. This is important to assure that CO2 is out of the 2-phase region flowing sub-cooled liquid in to the pump.

Cool down accumulator – starting the accumulator cooling spiral will drop the pressure and the liquid temperature to the desired set point. The vapor in the accumulator will condense; therefore the liquid level will start to increase.

Transition conditions:

T0 = Not Run Order OR Not Option Mode Stand-by

T1 = Run Order & Option Mode Stand-by

T2 = Run Order & Option Mode Stand-by & liq. circulation is achieved Pump ON & FT1901 > 0.0

T3 = Run Order & Option Mode Stand-by & TT1110 – 30C < TTsat(calculated from PT1104)


PCO alarms

PCO alarms:

Start interlock: all requests are blocked when ON, prevents the object from starting

SI1 – NOT Option Mode Selected; [0s delay] Temporary Stop interlock: sends OFF request to the object when ON (Resetting does not require the intervention of the operator If Run-order

was active before interlock appear then after the elimination of interlock source Run-order becomes active automatically)

TS1 – NOT 24V PS01 Status OK; [0s delay] Full Stop interlock: sends OFF request to the object & waits acknowledge when ON (Restarting requires the elimination of the interlock and the

operator attending to do it. If Run-order was active before interlock appear then after the elimination of interlock source Run- order rest deactivated)

Run-order – indicate that the object start is requested and there is no interlock.

FS1 – NOT (Process Stop Button OK AND Process Stop OK); [0s delay] FS2 – Chiller Pressure Switch Low = 1 OR Pressure Switch High = 1 [0s delay] FS3 – Pump Thermal Switch TS1101 [5s delay]


Accumulator Control

PT1103

Acc. Tsp

PC1104MV

SP

EH1104Out High limit

Out Low limit Low limit

High limit

0%

Dynamically calculated f(Rth)0 ÷ 100 %

PC1105

Out Low limit

Out High limitMV

SP

Psat(Tsp)

CV1104

Low limit

High limit

Dynamically calculated f(sub-cool)0 ÷ -100 %

0%

OutO

OutO

IF Out1 + Out2 > 0 Then EH1104 ActiveElse CV1105 Active

Analog Digital Object

Analog Digital Object

PWM

0÷100%PWM

0÷100%


Accumulator Control

calculated every 5s

Thermal resistance:

thth

ththnew RR

OutHOutHRROutHOutH

minmax

)(*max minmaxmin

CO2_B158_PC1104minRth 50 mK/W

CO2_B158_PC1104maxRth 75 mK/W

CO2_B158_ PC1104OutHmin 25 %

CO2_B158_ PC1104OutHmax

100 %

subcool = Tsat(PT1103) – TT1110

Sub cooling:

LH

Lnew subcoolsubcool

OutLOutLsubcoolsubcoolOutLOutL

)(* minmax

min

CO2_B158_PC1401scH 5 K

CO2_B158_PC1401scL 3 K

CO2_B158_ PC1401OutLmin -10 %

CO2_B158_ PC1401OutLmax -100 %

Power

TAccuTR satheater

th

_


Accumulator Control

Power

TAccuTR satheater

th

_


Logic

STOPStand-By

RunSafty

positionStart-up Cool down loop

Cool down accumulator

EH1101 Pump oil bath OFF OFF Reg TT1101 SP= Reg TT1101 SP= Reg TT1101 SP= Reg TT1101 SP=

EH1102 Dumper OFF OFF Reg TT1102 SP = Reg TT1102 SP = Reg TT1102 SP = Reg TT1102 SP =

EH1104 Accumulator OFF OFFReg PT1103

SP=27CReg PT1103

SP=27CReg PT1103 Reg PT1103

EH1301 Chiller OFF OFF OFF ON ON ON

EH1903 after supply/return HX OFF OFF OFF OFF OFF

IF TT1103 -20C ≤ Tsat(PT1105)

Positon request = (hrequested - h3) * Øm

CV1105 OFF OFF OFF OFF Reg PT1103 SP= Reg PT1103 SP=

Pump OFF OFF OFF

IF TT1110 – 3C < TTsat(calculated

from PT1104) THEN ON

IF TT1110 – 3C < TTsat(calculated

from PT1104) THEN ON

IF TT1110 – 3C < TTsat(calculated from PT1104) THEN ON

Chiller OFF OFF OFF Chiller = ON Chiller = ON Chiller = ON


Enthalpy control

Øm = Qexperimet / (h5 - h4)

Qheater = (hrequested - h3) * Øm

It is not possible directly control the enthalpy in a PID loop.

The enthalpy can be derived from measured pressure and temperature only when the state point is present in the liquid phase which means that measured temperature should be at least 20C lower than calculated Tsat . Because the enthalpy of point 3 and 3’ (Fig.3) can be in the 2-phase area calculation procedure have to use previous measurements from state point 2 (Fig3.). The PLC is calculating enthalpy from measured temperature TT1103 and pressure PT1105 and it’s on only if TT1103 -20C ≤ Tsat(PT1105) is true.


PT to H conversion

50

100

150

200

250

300

0 10 20 30 40 50 60 70 80

Pressure (bar)

En

thalp

y (

kJ/k

g)

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20

25

UNICOS user interface


Software preparation

SCADA server

Logic Generator

Instance Generator

Specyfication

SIEMENS PLC

UNICOS project creation:

1 – Exel specyfication preparation

2 – PLC hardware configuration

3 – PLC & PVSS instance generation

4 – Process logic programation (98%)

5 – Code compilation

6 – Loading to PLC

7 – Commisionig & operation

All generated files will be kept in Subversion Version Control (SVN) service.


Log-in account to PC and PVSS


More topics to discus:

• common login to PC

• login to PVSS and privileges

• enthalpy search method (are there any formulas to calculate enthalpy form

measured temperature and pressure or only NIST tables)

co2 progress and issues on the control system lukasz zwalinski – ph/dt 13.04.2010

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