Basic Operation and Safety Considerations
Terminal Vapor Combustor Flares
The MRW terminal flare systems and vapor combustors operate following these basic steps.
The operation is fully automatic, including safety shutdowns. The operators will proceed as normal.
- Signal to Start the Flare System - A truck, barge, or rail car pulls up to the loading rack. The loading terminal sends a signal at some point to the flare system to initiate startup. This can be automatically achieved by the simple presence of a truck, tank car, or barge, by the opening of a gate, or by an operator pressing a button at the loading rack.
- Purge Cycle - In the case of an "enclosed" combustor, the flare system will start a purge cycle to push any remaining hydrocarbons out the stack.
- Pilot Ignition - Once the combustor has been purged, the pilot will automatically ignite. Ignition of the pilot indicates that the flare is "ready". A signal is sent back to the loading rack and the pump will begin filling up the truck, barge, rail car, storage tank, etc as it normally would.
- Vapor Displaced to Flare - Vapor is then displaced to the flare. In most cases, the system can withstand some pressure. The pressure is usually enough to push the vapors to the flare. In the case where inadequate pressure exists a blower can be used to push the vapors to the flare. Before reaching the flare, the vapors pass through valves, a detonation arrestor, and eventually through the MRW anti-flashback burners and into the combustion chamber (or flare tip in the case of an open flare) of the vapor combustor flare system.
- Operation and Temperature Control- Assist air is provided by a blower and temperature is maintained via electric or pneumatic actuated dampers. The flare system will usually maintain a temperature of 1600F to 1800F during normal operation. Once loading is completed the system will remain in "ready" operation for a fixed period of time to accommodate other sequential loading cycles if necessary. This is done to avoid unnecessary startup and shutdown of the flare system. This saves time, fuel, and electricity.
- Shutdown Mode - Usually, after the predetermined fixed time has elapsed and no other loading cycles have started this signals the flare to shutdown. The flare system will automatically shut the valves, distinguish the pilot, fully open the air dampers and shutdown the blower. However, some terminals may require the presence of a constant pilot.
- Safety Shutdowns - Please see "Safety Shutdowns" below.
Safety Considerations for Vapor Combustors and Terminal Flare Systems
MRW terminal vapor combustion systems adhere to strict safety standards. MRW does not sacrifice safety in any
element of our designs in order to cut costs. Because most terminal emissions are in the explosive limits, safety
is of the utmost importance. Also, the flow rate and composition of the mixture of vapors vary during a loading cycle. Pressure drop is also prevalent.
The following safety precautions should be evaluated, monitored and corrected:
MRW designs all of our vapor control combustion systems with the following minimum safety features:
- Flashback Protection, Monitoring, and Shutdown
- Loss of Pilot
- Other Ignition Source(s) Location to Flare and Loading Rack
- Safety Shut Downs
- Interface with Loading Rack
- Anti-Flashback Burners or Flare Tips - To discourage flashback into the flare header at low loading rates.
- Detonation Arrestor - To prevent flashback upstream of the flare system. It is important to utilize an arrestor made for "detonations" due to explosive vapors, long pipe runs, and multiple pipe bends. A standard flame arrestor should not be used.
- Enrichment System - To ensure the waste gas vapor is always above the upper explosive limit (UEL) inside the flare header. This also contributes to a smoothly operating system with varying compositions and loading rates.
Safety Shutdowns - Control System
MRW vapor combustor systems are designed for numerous safety and shutdown precautions.
Our systems will detect and shutdown if the following situations occur.
In the unlikely event a safety shutdown occurs, the system must be manually checked and the problem must be
fixed before the system can be started again.
- High liquid level
- High temperature on detonation arrestor
- Loss of pilot
- Excessive high stack temperature
- Loss of permissive signal from loading rack
- Manual shutdown by operator