Storage Requirements

C4 streams contain butane isomers with vapor pressures requiring storage at 100-250 psig depending on composition and temperature. The vessel maintains liquid inventory between supply and demand while handling vapor formation from pressure drops, temperature swings, and agitation during transfers. Vapor recovery prevents atmospheric losses and captures valuable product.

Regasification Function

Some operations need C4 as vapor rather than liquid. Internal heating coils or external vaporizers convert stored liquid to gas phase for alkylation feed, petrochemical processes, or fuel blending. Controls manage vaporization rate matching downstream demand while maintaining safe operating pressure and temperature.

Vessel Construction

Horizontal or vertical pressure vessel with vapor space sized for flash gas accumulation, liquid outlet to pumps or vaporizer, vapor outlet to compression or recovery, internal heating coils where vaporization required, spray nozzles for rapid mixing, and temperature monitoring throughout. Material selection handles C4 composition including olefins when present.

Operating Pressure

Design pressure 16-25 bar contains C4 vapor pressure across operating temperature range -10°C to 50°C. Higher pressures suit refrigerated storage reducing vapor losses. Relief valves protect against fire exposure, overfilling, and blocked outlets per API standards.

Material Selection

Carbon steel construction per ASME Section VIII works for most C4 service. Stainless steel where trace contaminants cause corrosion. Welding procedures prevent hydrogen cracking in butadiene-containing streams. External coating protects against atmospheric corrosion.

Applications

Refinery C4 storage between FCC and alkylation units, gas plant butane product tanks, petrochemical C4 feed surge vessels, LPG fractionation intermediate storage, and olefin plant C4 raffinate tanks. Capacities from 100 to 5,000 m³ serve diverse facility scales.

Vapor Handling

Vapor recovery compressors return flash gas to process rather than flaring. Compression ratios account for C4 vapor pressure and downstream system pressure. Alternatively, vapor routes to fuel gas after composition verification. Level and pressure controls coordinate liquid and vapor flows.

Temperature Control

Insulation reduces solar heat gain minimizing vapor generation. Active cooling using refrigeration or water spray lowers pressure during high ambient temperatures. Heating prevents wax formation when heavy C4 streams approach pour point during cold weather.

Safety Systems

High-pressure alarms and shutdown prevent overpressure beyond relief valve capacity. High-level protection stops incoming flow before overflow. Gas detection monitors C4 leaks around vessel and piping. Grounding eliminates static discharge risks during transfers.

Construction Standards

Fabrication per ASME Section VIII Division 1 with radiographic examination and hydrostatic testing. Foundation design accounts for seismic loads, wind forces, and liquid weight. Documentation includes stress analysis, relief calculations, and materials traceability.

ERGIL C4 storage vessels handle butane-rich streams with proper pressure containment and vapor recovery supporting refinery and petrochemical operations.