BP01 Hyper Compressor Fouling Prevention
Most common location where thermal fouling occurs in the hyper compressor.
Between 1st stage discharge and intercooler inlet. Recycle carryover will foul the exchangers themselves, in some reactors this will be more common than the thermal polymerization (e.g. HCC).
Name 2 safety devices that safely relieves decompositions.
Dump valves & rupture discs.
Define SADT.
Self Accelerating Decomposition Temperature, storage temperature when a peroxide will undergo self-accelerating decomposition in one week.
This type of actuator typically provides the fastest response (~200ms to 1s).
Hydraulic actuator
This flammability threshold must never be exceeded inside the silo atmosphere.
Lower explosion limit (LEL)
What are the preferred 1st and 2nd stage discharge temperatures?
1st stage: 80 degC
2nd stage: 55-75 degC
This pressure target must be acheived during tubular reactor depressurization within 10 seconds.
< 1000 bar
Name 3 ingredients that may result in an adiabatic compression.
Air
Fuel
Ignition source
This value failure mode is commonly used to prevent unnecessary shutdowns when loss of function is tolerable.
Fail last
The "safe to pack" ethylene concentration in pellets is defined at this level.
15 wtppm
Low concentrations of this component leads to formation of very high molecular weight polymer and increased fouling.
Modifiers
This detection method, using temperature with voting logic is used to trigger decomposition interlocks in reactors.
Temperature high-high detection with 2ooN voting
When multiple peroxides are stored together, temperature limits must be based on this criterion.
Lowest control and emergency temperature of all stored peroxides (keeping in mind minimum storage temperature of some peroxides)
This ultimate protection action is triggered during decomposition or extreme pressure conditions.
Emergency venting (reactor depressurization)
The undesirable silo filling practice that leads to poor purge distribution and explosive pockets.
Poly Alkylene Glycol (PAG) oils
Explain why HPS decompositions deserve additional attention.
When in large volumes in the poly system, may result in very violent reactions of explosive nature (aerial decomposition) causing significant damage (due to overpressure).
Highly Flammable peroxide that has the similar ignition energy to ethylene.
Di-tert-butyl peroxide (DTBP)
The voting logic provides redundancy for safety-critical systems while retaining responsiveness.
Redundant voting (2oo3 or 2ooN)
After complete silo filling, this is the recommended degassing time for LDPE with pellet cooling water at 40degC.
10 hours
This type of radical formed during chain transfer with propylene is relatively stable and reduces reinitiation rates.
Allyl radicals
These devices must be used exclusively in HPS system for overpressure protection.
Rupture discs
In peroxide unloading system design, name 2 risks that must be mitigated.
Air/nitrogen ingress
Thermal decomposition
Excessive mechanical work
This key design principle balances safety and operability when choosing between fail action and fail no-acion.
Defining the "safe state" of the system considering both hazard prevention and nuisance trips
Upon loss of purge air, this immediate action must be taken to prevent hazardous conditions.
Stop silo filling immediately and purge with nitrogen.