Client Project Title Location Project No. Document No. 20.0
: : : : : Inner Mongolia China Coal Mengda New Energy Chemical Co., Ltd. 500 KTA Engineering Plastic Project PP Plant Ordos City, Inner Mongolia Autonomous Region 1115120 1115120-00-IA343-1 Rev.: 0 17 of 22 REACTOR C-4301 PROPYLENE FEED CONTROL (CONTROL LOOP
DIAGRAM SHEET 23)反应器 C-4301 丙烯进料控制 （控制回路图表，表23）
FRC-5230-4 control room mounted flow controller to regulate quantity of hydrocarbon liquid returned to the reaction system for dewpoint control. The rest of the stream is returned to the degassing pot, C-5257, through LV-5230-1.
HS-5230-4: Control room handswitch to select either FY-4001-1 or FY-4301-27 to control flow from E-5230.
AIC-4301-44 controls the ratio of propylene concentration to ethylene concentration in the reactor cycle gas by adjusting the setpoint of propylene flow controller FRC- 4301-27.
AY-4301-44 divides the propylene concentration (from AI-4301-15) by the ethylene concentration (from AI-4301-16) to provide the ratio signal to controller AIC-4301-44.
FIC-4301-27 records and controls the flow of propylene to the reactor. The controller receives a setpoint from the propylene/ethylene concentration ratio controller, ARC-4301-44. During a reactor kill, Logic 43-1 overrides the flow controller and closes the control valve. Refer to Logic 43-1 for details. FY-4301-27 sums the flow signals from FI-4301-27 and FI-5230-4 and provides a total flow signal to FIC-4301-27.
21.0
REACTOR C-4301 ETHYLENE FEED CONTROL (CONTROL LOOP DIAGRAM SHEET 24)
Reactor pressure recorder PRC-4301-30 provides a signal to a summer, PY-4301- 46A, which converts gauge to absolute pressure and then to a multiplier, PY-4301- 46B, which multiplies the reactor pressure signal with a ethylene concentration signal from the cycle gas analyzer. This multiplier then provides the setpoint for the ethylene partial pressure controller, PIC-4301-46. The ethylene partial pressure controller provides a setpoint to FRC-4301-2 for ethylene flow control.
The analyzer signal to PY-4301-46B may require filtering to avoid abrupt signal changes to the controller. Filter time constant should be adjustable from 0 to 1.0 hours.
Client Project Title Location Project No. Document No.
: : : : : Inner Mongolia China Coal Mengda New Energy Chemical Co., Ltd. 500 KTA Engineering Plastic Project PP Plant Ordos City, Inner Mongolia Autonomous Region 1115120 1115120-00-IA343-1 Rev.: 0 18 of 22 FRC-4301-2 Measures and controls the flow ethylene to the Reactor. FRC-4301-2 receives a setpoint from the ethylene partial pressure controller, PIC-4301-46. During a reactor kill, Logic 43-1 overrides the controller and closes the control valve. Refer to Logic 43-1 for details.
22.0
REACTOR C-4301 HYDROGEN FEED CONTROL (CONTROL LOOP DIAGRAM SHEET 25)
AIC-4301-45 controls the ratio of hydrogen concentration to ethylene concentration in the reactor cycle gas by adjusting the setpoint of the selected hydrogen flow
controller FRC-4301-3A or FRC-4301-3B or FRC-4301-3C.
AY-4301-45 divides the hydrogen concentration (from AI-4301-17) by the ethylene concentration (from AI-4301-16) to provide the ratio signal to controller AIC-4301-45.
FRC-4301-3A/B/C measures and controls the flow of hydrogen to the reactor. The flow controller receives its input from hydrogen/ethylene concentration ratio controller AIC-4301-45. During a reactor kill, logic 43-1 overrides the controller FRC-4301-
3A/B and forces valves FV-4301-3 A/B closed. Refer to logic 43-1 for details. HS- 4301-3B is used to select the appropriate control system.
23.0
PURGE HEADER ETHYLENE/LIGHTS RECYCLE FEED CONTROL (CONTROL LOOP DIAGRAM SHEET 26)
PDICAL-4301-31 measures and controls the pressure differential between the ethylene purge header and the cycle gas compressor suction piping. A low differential pressure alarm sounds in the control room. During a Type 2 reactor kill, Kill Logic 43-1 overrides the pressure differential controller and after a time delay closes PDV-4301-31A and PDV-4301-31B. Refer to Logic 43-1 for details.
PDIC-4301-31 is used to control the flow of ethylene or lights recycle to the purge header.
PY-4301-31A The switch should have both AUTO and MANUAL capabilities.
Client Project Title Location Project No. Document No.
: : : : : Inner Mongolia China Coal Mengda New Energy Chemical Co., Ltd. 500 KTA Engineering Plastic Project PP Plant Ordos City, Inner Mongolia Autonomous Region 1115120 1115120-00-IA343-1 Rev.: 0 19 of 22
In AUTO, the switch will automatically select Lights Recycle if the ethylene purge header to reactor pressure differential is low. Operator to have option to RESET the switch to Ethylene.
In MANUAL, the operator will have option to choose either Lights Recycle or Ethylene for the purge header.
PY-4301-31B Receives signal from PY-4301-31A and switches output from PDIC- 4301-31 to either PDV-4301-31A (Ethylene) or PDV-4301-31B (Lights Recycle).
PDV-4301-31A and PDV-4301-31B The unselected valve goes to its fail position.
24.0
REACTOR C-4301 PURGE CONTROLLER (CONTROL LOOP DIAGRAM SHEET 27)
FIC-4301-6 measures and controls the cycle gas vent. FY-4301-6 is a selector which selects the highest output signal from either PICA-4301-38 or FIC-4301-6 to control the valve. This allows PIC-4301-38 to open the vent in case a process upset results in high reactor pressure. For FIC-4301-6 the setpoint is provided by the operator to prevent the build up of inerts in the reactor. The vented stream flows to the Product Receiver through FV-4301-6. Product Receiver PA3H-5013-5 or the Kill System Logic overrides FIC-4301-6 and closes FV-4301-6. Refer to Logic 43-1 for additional details.
Total reactor pressure is controlled by maintaining the reactor inerts level. A controller PIC-4301-38 is provided to avoid reactor overpressure. The high pressure setpoint is set higher than the normal reactor pressure controller, PICA-4301-30. When reactor pressure exceeds the high pressure setpoint, PIC-4301-38 sends a signal to high signal selector FY-4301-6 which selects the highest output signal from either PIC-4301-38 or FIC-4301-6 to control the vent to Product Receiver.
The reactor pressure controller annunciates an alarm in the control room when the pressure exceeds 2.17 MPag. See Loop No. 4301-30 for details.
Client Project Title Location Project No. Document No.
: : : : : Inner Mongolia China Coal Mengda New Energy Chemical Co., Ltd. 500 KTA Engineering Plastic Project PP Plant Ordos City, Inner Mongolia Autonomous Region 1115120 1115120-00-IA343-1 Rev.: 0 20 of 22 This controller PIC-4301-38 is not a standard PIC type but a proportional only. The output is zero when the process variable (PV) is equal to the set point and is 100% when the process variable (PV) is 0.10 MPag above the set point. In between, the performance is linear.
PAH-4301-38 prevents overpressure in the reactor by opening FV-4301-6. Refer to Logic 43-1 for additional details.
25.0
RECYCLE LIGHTS FEED TO REACTOR C-4301 (CONTROL LOOP DIAGRAM SHEET 28)
Reactor pressure controller PIC-4301-30 measures and controls the pressure of the Reactor.
PIC-4301-30 sends a signal to the lights recycle flow controller FIC-4301-64. Adjustable output limits are required to restrict the adjustment of the various controllers receiving a setpoint. When in auto PIC-4301-30 receives a signal from the reactor pressure transmitter PT-4301-30.
FRC-4301-64 controls and records the flow of lights feed to the reactor. The lights flow can be used to control the total reactor pressure by maintaining the reactor inerts level. In this case FRC-4301-64 receives its setpoint from the reactor pressure controller, PRC-4301-30.
26.0
DEPRESSURISATION TRANSFER TANKS C-4311 AND C-4321 (CONTROL LOOP DIAGRAM SHEET 29)
PDIA-5014-1 Provides control room display of the pressure drop across the Product Receiver Filter. High differential pressure switches are required. The signal from PDIA- 5014-1 is one of two inputs to PDY-4311-2JJ low selector and PDY-4321-2JJ low selectors.
KC-4311-2JJ (KC-4321-2JJ) is the ramp function controller. The slope of this ramp is determined and set during commissioning; one typically ends up with full opening taking about 50 seconds when operating without the crosstie valve (KV-4311-2FF) in operation. PDY-4311-2JJ (PDY-4321-2JJ) is a low selector.
Client Project Title Location Project No. Document No.
: : : : : Inner Mongolia China Coal Mengda New Energy Chemical Co., Ltd. 500 KTA Engineering Plastic Project PP Plant Ordos City, Inner Mongolia Autonomous Region 1115120 1115120-00-IA343-1 Rev.: 0 21 of 22 Transfer Tank depressurization valve (Valve-“JJ”) is opened by Logic 43-5 (43-12) to vent the Transfer Tank from 2.08 to 0.172 MPag approximately 10 times per hour. The Transfer Tank is vented to the Product Receiver/Product Receiver Filter, C-5013/Y-5014. Valve-“JJ” gets it output from a low signal selector (PDY-4311-2JJ, PDY-4321-2JJ). This signal selector has two inputs. One is from a DCS ramp function (KC-4311-2JJ, KC-4321-2JJ). The output from the BPCS (which tells Valve-“JJ” to open) is what turns the ramp on. If the BPCS output is \The other input to the low selector is PDICA-5014-1. This is a controller that uses the Product Receiver Filter DP as its process variable. This controller is normally on automatic with a setpoint of 200 mm H20. Because the DP is normally low, the output is normally 100%. If the filters become gradually plugged the PIC drops back the opening of the valve.
27.0
DEMIWATER TO PROPANE PURGE RATIO CONTROLLER (CONTROL LOOP DIAGRAM SHEET 30)
FRC-5260-2 Control room mounted flow recording controller to regulate quantity of propane purged from the system. The controller also provides a setpoint to the water injection pump flow ratio controller (FFICA-5275-1).
FV-5260-2 is closed by TAH-5275-3 located downstream of propane/water mixing. To prevent plugging potential, the output signal from FRC-5260-2 should have a low limit so that a minimum flow rate always passes through FV-5260-2. There should be a solenoid valve in the pneumatic tubing between the positioner and the actuator such that the high temperature interlock de-energizes the solenoid, removing air from the actuator, and closing FV-5260-2 completely, independent of the signal from FRC-5260-2.
FFICA-5275-1 To control, indicate and alarm in control room water flow injected into propane purge stream by varying capacity of metering pump G-5275. The ratio controller receives flow signal from propane flow controller FRC-5260-2. The signal from FFICA-5275-1 adjusts metering pump G-5275 through
transducer FZ-5275-1. Low-low flow alarm is interlocked to shutdown pump G-5275. See Logic 52-3 for details.
Client Project Title Location Project No. Document No.
: : : : : Inner Mongolia China Coal Mengda New Energy Chemical Co., Ltd. 500 KTA Engineering Plastic Project PP Plant Ordos City, Inner Mongolia Autonomous Region 1115120 1115120-00-IA343-1 Rev.: 0 22 of 22 28.0
FLUIDZED BED LEVEL AND WEIGHT OF REACTOR C-4001 AND C-4301 (CONTROL LOOP DIAGRAM SHEET 31)
Compare with fluidzed bed level LT-4001-35 and its setpoint. The bed level controller signal is input into the PDS logic to initiate operation of the product discharge system when the bed level exceeds the setpoint. Refer to Logic 41-1 for details. Normal operating setpoint is 610 mm below the expanded section. Alarm setpoint is 610 mm above the bottom of the expanded section.
Compare with fluidzed bed weight WT-4001-33 and its setpoint. The bed weight controller signal is input into the PDS logic to initiate operation of the product discharge system when the bed weight exceeds the setpoint. Refer to Logic 41-1 for details. The bed weight control setpoint is to be operator adjustable.
Compare with fluidzed bed level LT-4301-35 and its setpoint. The bed level controller signal is input into the PDS logic to initiate operation of the product discharge system when the bed level exceeds the setpoint. Refer to Logic 44-1 for details. Normal operating setpoint is 610 mm below the expanded section. Alarm setpoint is 1000 mm above the bottom of the expanded section.
Compare with fluidzed bed weight WT-4301-33 and its setpoint. The bed weight controller signal is input into the PDS logic to initiate operation of the product discharge system when the bed weight exceeds the setpoint. Refer to Logic 44-1 for details. The bed weight control setpoint is to be operator adjustable.