Process Description

The objective of the SPM-600 Unit Operations of Chemical Processing Simulation is to blend the two paraffins hexane (C6) and heptane (C7) to a specific product composition by pumping them into a mix tank.

The mixture is then pumped from the bottom of the mix tank through a countercurrent tube and shell type heat exchanger where the temperature of the process fluid is raised. The mixture is then separated into its constituent components in a flash tank by virtue of the difference in the boiling point temperatures of hexane (C6) and heptane (C7). The separated products are then sent to other units for further processing.

Click here to view schematic display A
Click here to view schematic display B
Click here to view schematic display C
Click here to view schematic display D
Click here to view schematic display E

Approximately 140 GPM of 100 WT % hexane and 160 GPM of 100 WT % heptane are to be blended in the mix tank. The hexane is supplied at 68 Deg F and the heptane is supplied at 100 Deg F. A total of approximately 300 GPM of product mixture at 46 WT % hexane and a temperature of 85 Deg F is to be produced. The process fluid is then to be heated from 85 Deg F to 390 Deg F in the heat exchanger.

Hot ThermOil at 500 Deg F is provided to accomplish this task. The mixture is then to be separated into its constituent components in the flash tank. A total of approximately 420 ACFM of hexane rich vapor at 80 PSIG and 319 Deg F is to be produced. A total of approximately 220 GPM of heptane rich liquid at 80 PSIG and 319 Deg F is to be produced.

The unit consists of a hexane flow loop, a heptane flow loop, a mix tank (T-301), a mixture flow loop, a countercurrent tube and shell type heat exchanger (E-401), a flash tank (T-501), an overhead vapor line, and a bottoms liquid line.

The hexane feed flow loop has two supply block valves (HV-201 and HV-202) in parallel and two pumps (P-201 and P-202) in parallel. The heptane feed flow loop has two supply block valves (HV-203 and HV-204) in parallel and two pumps (P-203 and P-204) in parallel.

Each of the primary pumps (P-201 and P-203) are rated at 25 horsepower. Spare pumps (P-202 and P-204) are provided with the same ratings as the primary pumps.

The hexane flow loop is modulated by a flow control valve (V-201) with linear flow characteristics. The heptane flow loop is modulated by a flow control valve (V-202) with equal percentage flow characteristics. Each of the flow loops (valves, piping, and pumps) have been designed to supply a maximum of approximately 500 GPM of fluid.

The mix tank (T-301) is a cylindrical tank 4 feet in diameter by 12 feet in height. The mix tank has a total capacity of 150 cubic feet or 1128 gallons of fluid. At design conditions the mix tank provides approximately 2 minutes of holdup running half full.

The mixture flow loop is modulated by a flow control valve (V-401) with parabolic characteristics. A mixture pump (P-301) rated at 25 horsepower is required to pump the fluid through the heat exchanger to the flash tank (T-501). A spare pump (P-302) is provided with the same rating as the primary pump. The mixture line (valves, piping, and pumps) is sized to provide a maximum of approximately 500 GPM of fluid.

The process fluid passes through the heat exchanger (E-401) on the shell side while the hot ThermOil passes through on the tube side.

The ThermOil flow loop is modulated by a temperature control valve (V-406) with linear flow characteristics. The ThermOil flow loop (valves and piping) has been designed to supply a maximum of approximately 1000 GPM of fluid.

The flash tank (T-501) is a cylindrical tank 4 feet in diameter by 12 feet in height. The flash tank has a total capacity of 150 cubic feet or 1128 gallons of fluid. At design conditions the flash tank provides approximately 2 minutes of holdup running half full.

Block valves with bypasses are provided for both the vapor (HV-501 and HV-502) and liquid (HV-503 and HV-504) lines.

The overhead vapor line is modulated by a pressure control valve (V-501) with quick opening flow characteristics. The bottoms liquid line is modulated by a level control valve with linear flow characteristics. The unit (valves, piping, and vessel) has been designed to process a maximum of approximately 500 GPM of feed. Sufficient pre-heating capacity is provided to accomplish this task.

The hexane feed flow loop is outfitted with upstream and downstream pressure indicators (PI-201 and PI-203). Pump discharge pressure (PI-202) is also provided. Flow is controlled by flow controller FIC-201. A composition analyzer measures weight percent hexane and heptane (AI-301 and AI-302 respectively). Feed temperature is measured by TI-401.

The heptane feed flow loop is outfitted with upstream and downstream pressure indicators (PI-204 and PI-206). Pump discharge pressure (PI-205) is also provided. Flow is controlled by flow controller FIC-202. A composition analyzer measures weight percent hexane and heptane (AI-303 and AI-304 respectively). Feed temperature is measured by TI-402.

Block valves V-201, V-202, V-203, and V-204 can be opened and closed with switches HV-201, HV-202, HV-203, and HV-204 respectively.

Primary feed pumps P-201 and P-203 can be turned on and off with the switches HS-201 and HS-203 respectively. Spare feed pumps P-202 and P-204 can be turned on and off with the switches HS-202 and HS-204 respectively.

Mix tank level is maintained by level controller LIC-301. Mixture composition is measured by AI-305 (WT % C6) and AIC-306 (WT % C7). Mixture temperature is indicated by TI-403.

Mixture pumps P-301 and P-302 can be turned on and off with the switches HS-301 and HS-302 respectively. Pump suction (PI-301) and pump discharge (PI-302) pressure indicators are provided. Mixture flow is controlled by flow controller FIC-401.

The process outlet of the heat exchanger is outfitted with a temperature indicator (TIC-406).

The ThermOil loop is also outfitted with inlet and outlet temperature indicators (TI-404 and TI-405). ThermOil flow is modulated by temperature controller TIC-406. TIC-406 controls the outlet temperature of the process loop.

Block valves (HV-401 and HV-402) are provided for the ThermOil flow loop.

The overhead vapor line is outfitted with a composition analyzer that measures weight percent hexane and heptane (AI-501 and AI-502 respectively). Flash Tank pressure is regulated by pressure controller PIC-501. Vapor rate is measured by FI-501. Vapor flow can be blocked in by block valves HV-501 and HV-502. Downstream pressure is measured by PI-502.

The bottoms liquid line is outfitted with a composition analyzer that measures weight percent hexane and heptane (AI-503 and AI-504 respectively). Flash Tank level is controlled by level controller LIC-501. Liquid rate is measured by FI-502. Tank temperature and tank bottom pressure are measured by TI-501 and PI-503 respectively. Liquid flow can be blocked in by block valves HV-503 and HV-504. Downstream pressure is measured by PI-504.

The feed flow controllers' outputs may be modulated manually by the operator to achieve the desired flow rates, or the flow controllers (FIC-201 and FIC-202) may be placed in automatic with their appropriate setpoints entered by the operator. In this manner, flow rates may be specified, with no further adjustments required by the operator.

The feed flow controllers' setpoints may be modulated manually by the operator to achieve the desired product composition, or the composition controller (AIC-306) may be cascaded to the heptane flow controller (FIC-202) in a master-slave arrangement. In this manner, hexane flow rate and product composition may be specified, with no further adjustments required by the operator.

The mix tank level may be maintained manually by modulating the mixture flow controller's (FIC-401) setpoint, or the mix tank level controller (LIC-301) may be cascaded to the mixture flow controller (FIC-401) in a master-slave arrangement. In this manor, mix tank level may be specified, with no further adjustments required by the operator.

The heat exchanger's outlet process fluid temperature may be maintained manually by modulating the position of temperature control valve V-406 (TIC-406 controller output), or the temperature controller (TIC-406) may be placed in automatic. In this manor, the operator may specify the desired temperature by entering the correct setpoint. No further adjustments would be required.

The flash tank pressure may be regulated manually by modulating the pressure control valve (PIC-501 controller output), or the pressure controller (PIC-501) may be placed in automatic. In this manner, flash tank pressure may be specified (PIC-501 setpoint), with no further adjustments required by the operator.

The flash tank level may be maintained manually by modulating the level control valve (LIC-501 controller output), or the level controller (LIC-501) may be placed in automatic. In this manor, flash tank level may be specified (LIC-501 setpoint), with no further adjustments required by the operator.

All faults can be failed high or low to any degree with any of 8 fault function generators (step change, square wave, staircase, stairs, ramp, sawtooth, slope, or sine wave). Faults can be programmed to start and/or stop at various times during a simulation exercise.

You may create a virtually unlimited number of scenarios and training exercises by programming the faults described in the previous section. You can then establish performance standards for each one of those exercises. Simtronics provides a number of exercises with established performance standards for each process simulation. The objective, time to complete the exercise, cause, effect, solution, and procedure for each exercise is documented. You may modify these procedures to more closely reflect your particular process plant operating procedures.

• Exercise 1: Design
• Exercise 2: Cold Start
• Exercise 3: Power Failure - All Pumps Stop
• Exercise 4: FC201 Faulty Transmitter
• Exercise 5: Pump P-301 Fails
• Exercise 6: Thermoil Block Valve V-401 Ramps Closed
• Exercise 7: Pressure Transmitter PC501 Fails Low