The term environment can be described as follows: The conditions, circumstances and influences under which an organism or system exists. It may be affected or described by physical, chemical and biological features, both natural and man-made. The environment is commonly used to refer to the circumstances in which man lives. Environmental issues are mainly concentrated on air pollution and nuisance, especially in the area downwind of the refinery. Generally nuisance that is experienced is that of stench and soot.
Pollution can be described as the introduction by man into the environment of substances or energy liable to cause hazards to human health, harm to living resources and ecological systems, damage to structures and amenity, or interference with legitimate uses of the environment.
Air pollution by the refinery is caused through chimneys (smoke and soot), flares (flames, smoke and soot), drains and vents.
At times in a process, unwanted material has to be removed, which may be done by draining or ventilating. This procedure should not result in release of stench causing material, but at times this will happen, causing nuisance downwind.
Flares are safety devices. When the pressure in plant equipment becomes too high, gas is released to the flare system and burned. To avoid smoke and soot, steam is injected. If however in an emergency situation a very large quantity of gas is released, the amount of steam available is not sufficient, and the flame will produce soot. This may also happen during starts and stops of plants.
Chimneys are to route combustion gases from furnaces and boilers into the atmosphere. In the refinery generally 3 types of fuel are used: gas, fuel and asphalt (pitch).
– Gas comes from the crude oil, or is produced during chemical processes. The gas is cleaned and sent to the refinery gas system. Gas is a clean fuel.
– Asphalt is a product with a very high viscosity (semi solid at normal temperatures), it is the lowest cost product of the refinery, and it contains a high amount of sulfur and ash. The sulfur burns to sulfur dioxide whilst the ash produces the fine particles (generally grayish). The asphalt is circulated over the refinery at a temperature of around 300 degrees Celsius to maintain a suitable viscosity, where furnaces and boilers take their share and the remainder is sent back to a heating system. By using steam a better combustion is achieved, and the amount of soot is reduced.
– Fuel is asphalt mixed with diluent, so the product is less viscous. Fuel is a commercial product which is sold as fuel for ships and power stations. In the refinery it is used during startup and stop of operations of the plants and in case of emergency. Fuel has a fair amount of sulfur and ash.
After years of operation oil from leakages, both from tanks or equipment, has leaked into the soil and may seep into the sea. The Solid Waste Management Unit (SWMU) processes this oily waste into oil (reprocessed), water and sludge.
In the various processes, cooling water is used for cooling and this may contain oil. Also by leakages of equipment, oil may end up in water and cause pollution. This water flows back to the Schottegat through so called “cooling water channels”. Oil catchers are used to separate oil from water. The oil is reprocessed and water is sent to the Schottegat. Also there is a sour water stripper to clean process water from toxic substances before sending it to the Schottegat.