CO2 control system

1. CO2control system Lukasz Zwalinski –PH/DT 17.06.2010

2. Plant operation There will be one PCO with 3 option modes driven by allowance table Switch between modes is executed manually by the operator request. One PCO Alarm is blocked PCO is in run Order Push button to open sequencer panel PCO is in manual mode Current selected option mode L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

3. CO2PCO Safety position 0 T0 Start up request T1 Start up 1 T2 T0 Cool down request Cool down loop 2 T3 T0 Cool down accumulator request Cool down accumulator 3 T0 Plant operation In option mode Stand-By we can distinguish stepper with 4 steps associated 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) 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. L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

4. 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 except when in manual or forced mode. 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] L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

5. Dynamically calculated f(Rth) 0 ÷ 100 % Analog Digital Object High limit PC1104 Out High limit EH1104 PWM MV OutO 0÷100% SP Out Low limit Low limit 0% IF Out1 + Out2 > 0 Then EH1104 Active Else CV1105 Active PT1103 Acc. Tsp Psat(Tsp) 0% Analog Digital Object Out High limit High limit PC1105 CV1104 MV PWM OutO 0÷100% SP Out Low limit Low limit Dynamically calculated f(sub-cool) 0 ÷ -100 % Accumulator Control L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

6. Accumulator Control Sub cooling: Thermal resistance: subcool = Tsat(PT1103) – TT1110 calculated every 5s L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

7. Accumulator Control L.Zwalinski – PH/DTCO2 test stand control 17.06.2010

8. Logic L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

9. 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. L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

10. UNICOS user interface L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

11. Software preparation UNICOS project creation:1 –Exelspecyficationpreparation2 – PLC hardware configuration3 – PLC & PVSS instancegeneration4 – Processlogicprogramation5 – Codecompilation 6 –Loadingto PLC7 – Commisionig & operation Specyfication SCADA server Instance Generator SIEMENS PLC Logic Generator All generated files will be kept in Subversion Version Control (SVN) service. L.Zwalinski – PH/DTCO2 test stand control system17.06.2010

12. Tsat, Psat Enthaplpyserching method SMS/Mail … L.Zwalinski – PH/DTCO2 test stand control system17.06.2010