5.4

What is the primary goal during the start-up phase of a distillation unit?

• Ensure steady-state operation.

• Increase temperature rapidly.

• Maintain constant reflux ratio.

• Stop feed flow intermittently.

• Operate without monitoring pressure.

During the start-up of a catalytic cracker, why is it essential to preheat the catalyst bed?

• To achieve the required reaction temperature.

• To cool down the system.

• To remove contaminants.

• To increase feedstock viscosity.

• To promote rapid shutdown.

Why is inert gas used during the initial phase of starting oil refining equipment?

• To prevent explosion due to residual hydrocarbons.

• To increase oxygen concentration.

• To accelerate reaction rates.

• To reduce feedstock flow rate.

• To enhance fouling of heat exchangers.

What is the correct sequence for starting a hydrotreater?

• Purging → Catalyst activation → Feed introduction.

• Feed introduction → Purging → Cooling.

• Heating → Feedstock mixing → Shutdown.

• Cooling → Product collection → Catalyst regeneration.

• Steam purging → Cooling → Final adjustment.

What is the critical parameter to monitor during the start-up of a thermal cracking unit?

• Furnace temperature.

• Product storage capacity.

• Maintenance schedule.

• Laboratory test results.

• Feed temperature.

What is the first step in shutting down a distillation column?

• Stop the feed flow.

• Turn off the reboiler.

• Disconnect utility lines.

• Isolate the reflux drum.

• Drain the column contents.

In a gas compressor system, what should be done to prevent backflow during shutdown?

• Close the discharge valve immediately.

• Open the suction valve completely.

• Increase compressor speed briefly.

• Shut down without adjusting valves.

• Flush the system with water.

Why is gradual cooling important during the shutdown of reactors?

• To prevent thermal shock to equipment.

• To increase production output.

• To avoid fouling of pipelines.

• To facilitate rapid catalyst removal.

• To reduce monitoring requirements.

Which gas is commonly used for purging reactors during shutdown?

• Nitrogen.

• Oxygen.

• Hydrogen.

• Chlorine.

• Methane.

What is the most common reason for a controlled shutdown of oil refining units?

• Equipment maintenance.

• Increasing feedstock supply.

• Decreasing product demand.

• Eliminating byproducts.

• Optimizing plant layout.