Vent stack

The autoclave is not the only component of an LDPE plant which may be exposed to a decomposition. Local hot spots in a secondary compressor may initiate a decomposition reaction consequendy it is necessary to protect these units from serious overpressure by pressure relieving devices and to release the products of the decomposition reactions safely. The problem of the aerial decomposition referred to eadier has been largely overcome by rapidly quenching the decomposition products as they enter the vent stack. 

Finish removers are manufactured in open or closed ketdes. Closed ketdes are preferred because they prevent solvent loss and exposure to personnel. To reduce air emissions from the solvents, condensers are employed on vent stacks. Mild steel or black iron ketdes are used for neutral or basic removers stainless steel (316 or 317) or reinforced polyethylene ketdes are used for acidic removers. The ketdes are heated to increase dispersion of paraffin waxes and aid in the mixing of other ingredients. Electric or air driven motors drive either sweeping blade or propeller mixers that give sufficient lift to rotate and mix the Hquid. Dispenser-type mixers are used to manufacture thick and viscous removers. Ketde, fittings, mixer, and fill equipment must be fabricated with materials resistant to the chemicals in remover formulas. 

Atmospheric corrosion. Air-cooled heat exchangers should not be located where corrosive vapors and fumes from vent stacks will pass through them. 

After the tank was repaired, the vent stack was replaced by a flarestack. 

These recommendations apply to vent stacks as well as flarestacks. 

To prevent leaks of carbon monoxide and hydrogen from the glands of a number of compressors getting into the atmosphere of the compressor house, they were sucked away by a fan and discharged through a small vent stack. Air leaked into the duct because there was a poor seal between the duct and the compressor. The mixture of air and gas was ignited by lightning. 

Why were they not followed Perhaps because it was not obvious that recommendations made after an explosion on a large flarestack applied to a small vent stack. 

There are, however, two cases in which flame arrestors in vent stacks are justified ... 

The common theme of many of these items is that blowdown lines and flare and vent stacks should be kept simple because they are part of the pressure relief system. Avoid flame arrestors, molecular seals, water seals, and U-bends. Avoid steam, which brings with it laist and scale and may freeze. 

Personnel changes Flares and vent stacks Fire protection systems ... 

Disposal provision of effective vent stacks to disperse material vented from pressure relief devices or use vent scrubbers. 

NFPA requirements state that if equipment or process vessels, columns of tanks are suitably constructed of substantial steel construction adequately grounded, and do not give off flammable vapors, no other mechanism of lighting protection is required. This is also true of flares, vent stacks and metal chimneys by nature of their construction and grounding facilities. 

Fire prevention may include providing degassing boots/vent stacks to the top of risers where flammable combustible vapors can be entrained in the water system, i.e. water pressure lower than process pressure. Combustible gas detection at the top ofthe vent stacks can be used to detect flammable material presence in cooling tower. However, the hostile environment and difficult to access location makes the detection challenging to maintain. 

Finish removers are manufactured in open or closed kettles. Closed kettles are preferred because they prevent solvent loss and exposure to personnel. To reduce air emissions from the solvents, condensers are employed on vent stacks. 

This particular design is most effective in reducing SRV discharge noise to safe levels and equally effective in reducing noise from superheater vent stacks, process waste gas stacks and other sources discharging steam, air or gases into the atmosphere (Figure 8.3). 

There is a single vent stack in the plant. The stack gases are treated in a benzene scrubber to remove benzene vapours prior to incineration or other means of treatment290. 

The investigating team recommended both hardware and procedural changes. They recommended that the vent stacks on each tank be increased from 6 inches (15 cm) in diameter... 

Open vent stack drain valve, then close. 

Open pump cool down and purge trailer vent stack for 2 minutes. 

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