In the hydrotreating process, the entering feedstock is mixed with hydrogen and heated to - oC. The oil combined with the hydrogen then enters a reactor loaded with a catalyst which promotes several reactions:. The hydrogen sulphide created from hydrotreating is a toxic gas that needs further treatment.
The usual process involves two steps:. Solvent extraction, using a solution of diethanolamine DEA dissolved in water, is applied to separate the hydrogen sulphide gas from the process stream. The hydrocarbon gas stream containing the hydrogen sulphide is bubbled through a solution of diethanolamine solution DEA under high pressure, such that the hydrogen sulphide gas dissolves in the DEA.
The DEA and hydrogen mixture is the heated at a low pressure and the dissolved hydrogen sulphide is released as a concentrated gas stream which is sent to another plant for conversion into sulphur. As the reaction products are cooled the sulphur drops out of the reaction vessel in a molten state. Sulphur can be stored and shipped in either a molten or solid state.
Air, water and land can all be affected by refinery operations. Refineries are well aware of their responsibility to the community and employ a variety of processes to safeguard the environment.
The processes described below are those used by the Shell refinery at Geelong in Victoria, but all refineries employ similar techniques in managing the environmental aspects of refining.
Sulphur enters the refinery in crude oil feed. Gippsland and most other Australian crude oils have a low sulphur content but other crude's may contain up to 5 per cent sulphur. To deal with this refineries incorporate a sulphur recovery unit which operates on the principles described above. Many of the products used in a refinery produce hydrocarbon vapours. The escape of vapours to atmosphere are prevented by various means. Floating roofs are installed in tanks to prevent evaporation and so that there is no space for vapour to gather in the tanks.
Where floating roofs cannot be used, the vapours from the tanks are collected in a vapour recovery system and absorbed back into the product stream. In addition, pumps and valves are routinely checked for vapour emissions and repaired if a leakage is found.
Smoke is formed when the burning mixture contains insufficient oxygen or is not sufficiently mixed. Modern furnace control systems prevent this from happening during normal operation.
Smells are the most difficult emission to control and the easiest to detect. Refinery smells are generally associated with compounds containing sulphur, where even tiny losses are sufficient to cause a noticeable odour.
The majority of the water discharged from the refinery has been used for cooling the various process streams. The cooling water does not actually come into contact with the process material and so has very little contamination. The cooling water passes through large "interceptors" which separate any oil from minute leaks etc.
The cooling water system at Geelong Refinery is a once-through system with no recirculation. Rainwater falling on the refinery site must be treated before discharge to ensure no oily material washed off process equipment leaves the refinery. This is done first by passing the water through smaller "plant oil catchers", which each treat rainwater from separate areas on the site, and then all the streams pass to large "interceptors" similar to those used for cooling water.
This unit cleans the water by using a flocculation agent to collect any remaining particles or oil droplets and floating the resulting flock to the surface with millions of tiny air bubbles. At the surface the flock is skimmed off and the clean water discharged.
Process water has actually come into contact with the process streams and so can contain significant contamination. This water is treated in the "sour water treater" where the contaminants mostly ammonia and hydrogen sulphide are removed and then recovered or destroyed in a downstream plant. The process water, when treated in this way, can be reused in parts of the refinery and discharged through the process area rainwater treatment system and the DAF unit.
Any treated process water that is not reused is discharged as Trade Waste to the sewerage system. This trade waste also includes the effluent from the refinery sewage treatment plant and a portion of treated water from the DAF unit. As most refineries import and export many feed materials and products by ship, the refinery and harbour authorities are prepared for spillage from the ship or pier. In the event of such a spill, equipment is always on standby at the refinery and it is supported by the facilities of the Australian Marine Oil Spill Centre at Geelong, Victoria.
Within the refinery, all hydrocarbon wastes are recycled through the refinery slops system. This system consists of a network of collection pipes and a series of dewatering tanks.
The recovered hydrocarbon is reprocessed through the distillation units. Wastes that cannot be reprocessed are either recycled to manufacturers e. Waste movements within the refinery require a "Process liquid, Sludge and Solid waste disposal permit".
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Keyword Search Enter a list of keywords and press Enter to submit your search query. This fuel oil is neither volatile nor likely to form emulsions, and is relatively non-persistent in the environment.
This fuel oil has a low volatility and moderate flash point, and is fairly persistent in the environment. Preheating may be necessary in cold climates, and this fuel oil is difficult, if not impossible, to disperse.
This fuel oil may be heavier than water, is not likely to dissolve, is difficult or impossible to disperse, and is likely to form tar balls, lumps, and emulsions. It has a low volatility and moderate flash point. Lubricating Oil , a medium-weight material that flows easily and is easily dispersed if treated promptly.
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