Refrigerant circuit is inventoried with refrigerant. The Oil Reclaimer has been inventoried with oil and oil has been circulated through the Oil Separator to remove dirt and debris. The Net Gas In has been pressured and is flowing through the circuit.
The Refrigerant Compressor is controlled by the Distributed Control System DCS and a PLC. The PLC control circuit is designed to ensure the compressor is unloaded prior to start-up.
1. Check level in Oil Separator # 1. Initial inventory of the Oil Separator # 1 should be 152-229 mm below the top of the level glass.
2. Check oil level in Oil Reclaimer. The oil level should be such that the electrical heater element is immersed in oil and oil level should be above level switch setting. 3. Ensure the Oil Heaters Y-01/02 are energised. The heaters are designed to turn on
only when the oil temperature is less than the designed setpoint and when the compressor is not running.
4. Line out cooling water to lube oil coolers S04 A/B and refrigerant condenser S05. 5. Line out refrigerant circuit and check that all block valves are open or in normal
operating position.
6. Check that PDV-018 is set to obtain a 3.5 Kg/Cm2 differential between the lube oil pump discharge pressure and the Oil Separator # 1 operating pressure. This will ensure a 4.5 Kg/Cm2 differential between the oil header pressure and Refrigerant Compressor discharge pressure.
7. Set the Refrigerant Receiver/Economiser pressure PV-038 to design pressure. This will ensure that there is sufficient driving force between the Refrigerant
Receiver/Economiser and the Combined Vapor-Liquid Chiller, during low load conditions when the suction port and Economiser port are at the same pressure. 8. Ensure that the compressor is unloaded prior to start-up. If the Compressor is
started in loaded condition then the motor will draw a higher starting torque and can get damaged.
9. Start Net Gas In circulation. Ensure the 12” bypass valve is open.
DO NOT CUT IN NET GAS FLOW UNLESS H2O IS < 35 MOL PPM.
Gradually open the valves located at battery limits Tie points # 1 and 2 for the net gas in and pressure up the circuit.
Lean Oil: Establish a liquid level in the Absorber V01. Temporarily start the lean oil pump, P01 A/B, in order to establish a liquid level in the Absorber.
10.Ensure that the refrigerant for the Combined Vapor-Liquid Chiller is on level control, LIC-002. Initially keep a low setting of LIC-002. Gradually increase the level setpoint to the desired operating level. A high level can lead to entrained liquid carry over to the Compressor.
11. Set capacity switch to auto.
12.Ensure the Compressor is 10% loaded. This is the minimum loading of the compressor.
13.The starting of the Compressor consists of a sequence of events when the start button is pushed. The first task is to clear all the trips and permissive. Next the sequence will start with the starting of the lube oil motor. As soon as the lube oil pressure is build up the compressor motor should start. Once the Compressor motor starts, valves open or close automatically.
14.Check the temperature of the Rich Gas stream (TIC-009) and Lean oil Stream (TIC- 011). Set TIC-009 and TIC 011 in automatic at approximately 5 oC higher than the refrigerant in the Combined Vapor-Liquid Chiller. The signal resulting from TIC-011
being set at 5 oC higher than the refrigerant temperature, will start closing the slide valve, thereby increasing the mass flow rate of refrigerant pushed through the Compressor. This will increase the current drawn to the motor. An override activated by the motor current draw is provided to regulate the time it takes the slide valve to close to avoid drawing too much current. This ensures the capacity of the compressor is gradually increased and subsequently the process temperature is decreased.
15.If the suction pressure decreases below 0.35 Kg/Cm2 and the refrigerant compressor shuts down, decrease the temperature of TIC-011 approximately 2-4 oC, thereby increasing the load and suction pressure of the refrigerant compressor.
16.Gradually decrease the temperature of TIC-009 to approximately 5 oC. hold the lean oil temperature TIC-011 constant and start the lean oil pump. Set the lean oil rate at 50% of design flow. Gradually increase the lean oil rate to design.
17.Hold the net gas into the Absorber temperature constant, 5 oC, and gradually increase the Rich Gas In flow to design by closing the bypass.
18.Before the Rich Gas In and Lean Oil In temperature can be decreased to design, ensure that the circuit is dried out.
6.0
START UP
6.1 General
For subsequent start-ups, the procedure as described in the initial start up procedure is to be followed except the following:
a) Evacuation of Air, Nitrogen and Water removal will not be required.
b) No need to inventory the refrigerant since it is already available in the system.
The following procedure is to be followed for subsequent startups:
6.2 Notification to Other Departments
a) Inform concerned intra plant department i.e. Mech. / Electrical / Instrument / Laboratory / etc. prior to startup so that they will be ready for action.
b) Inform concerned inter plant department i.e. off site, utility, CES, Central Lab., safety and fire prevention, refinery units, etc. prior to startup so that they will be ready for action.
c) Notify the operators of the other process units in the aromatic complex of the intended Recovery Plus startup.
d) Plant supervisor and other operating units in the complex which are related with the unit should be informed well in advance about the exact time of start up by proper communication media, preferably in writing.
e) Tank farm/Refinery Control Room should be informed as startup of Recovery Plus will require Tank farm/Refinery to supply the necessary raw materials.
6.3 Utilities Startup
Inform Utility department about the Startup and also the approximate quantity that will be required. Cooling Water Supply / Return headers and Nitrogen headers are to be charged and made ready for consumption by different users. Electrical power should be available and charged up.
6.4 Outline Of Initial Startup
The initial startup of the HNUU section can be divided into the following steps: Compressor start-up