Wastewater treatment of oil refineries and enterprises Wastewater from an oil refinery is formed as a result of oil refining production processes and at each of these stages wastewater is formed with its own specific composition and sometimes the presence of specific components (which, in particular, are determined by the chemical composition of the initial crude oil). Let's list the most frequent effluents of an oil refinery:
- Water after desalination of oil, including from electric desalination plants (ELOS).
- Condensate of atmospheric and vacuum distillation.
- "Acidic" condensates of catalytic cracking and hydrocracking.
- Wastewater from an oil refinery after pyrolysis.
- Sulphurous-alkaline effluents of a high concentration oil refinery resulting from the processing of sulphurous oil and the purification of petroleum products with alkalis.
Wastewater from an oil refinery, in addition to oil and petroleum products themselves, contains a number of specific components, for example, phenols, naphthenic acids, sulfides and hydrogen sulfide, mercaptans, organic acids and aldehydes, ammonium ions. The effluents of the refinery after desalination are characterized by high salinity, in particular, chloride content up to 15 g /l and, accordingly, have high corrosion activity. Washing wastewater from an oil refinery is formed after washing barrels, closed production sites, and draining and filling overpasses. The effluents of an oil refinery are very polluted, which are formed during the cleaning and washing of tanks of a tanker, which are produced in the case of receiving a higher-quality product than previously transported, as well as during periodic cleaning of tanks from sediments (rust, other solid residues). Sewage sludge from an oil refinery is formed from food storage tanks. Surface wastewater of an oil refinery is the wastewater of an oil refinery that is formed during the melting of snow and precipitation. The volumes of surface wastewater from an oil refinery are calculated using appropriate techniques. Here we have indicated the main types of wastewater from an oil refinery that are formed in the refining processes. However, a large amount of wastewater from an oil refinery may be generated that is not directly related to oil refining. The composition of such effluents of an oil refinery is determined mainly by commercial petroleum products used at this enterprise and their physico-chemical properties, the main pollutants may be fuels for various purposes (gasoline, ligroins, gas oils, kerosene, diesel fuel, etc.), various lubricants, fuel oils, etc.
Characteristics of the composition of wastewater from an oil refinery The effluents of an oil refinery have their own specifics with regard to their composition and the behavior of petroleum products in the aquatic environment, which ultimately determines the methods of wastewater treatment of an oil refinery. The main features determining the behavior of petroleum products in water are their lower density compared to the density of water (gasoline 0.70—0.76, diesel fuel 0.8—0.9, jet fuel 0.8—0.85, fuel oil 0.94—1.0 g/cm3) and low solubility. The latter for light fractions of oil (gasoline) in water does not exceed 20-30 mg / l, for kerosene 70-90 mg / l, and for heavy fractions it is practically zero. Petroleum products, once in the water, are mostly in a coarse (droplet) state and, due to their lower density, are easily released onto the surface of the water, forming a floating film or layer. Another, smaller part of petroleum products may end up in a finely dispersed state, forming an oil-in-water emulsion. It is generally believed that a true emulsion is formed with colloidal droplet sizes of petroleum products (approximately 0.1 microns). But in the effluents of an oil refinery, persistent emulsions are also observed with large droplet sizes. The stability of the emulsion is due to surface tension, kinetic stability of particles, their low concentration, suspended particles present in the wastewater of an oil refinery can act as stabilizers of emulsions. The technology of wastewater treatment of an oil refinery The capacity of the refinery's wastewater treatment plant is not limited. A promising and modern scheme for effective wastewater treatment of an oil refinery, compiled taking into account the latest advances in technology and technology.
Advantages of the wastewater treatment plant of the oil refinery JSC "Engineering Center "Barents Region": Compactness and small footprint of the refinery wastewater treatment plant with the highest quality of wastewater treatment of the refinery; Easy installation (the refinery's wastewater treatment plant is supplied in large factory-ready units); The small collection area of oil-containing flotation sludge in the process of wastewater treatment of an oil refinery, with the possibility of supplying highly polluted wastewater from an oil refinery and the rectangular geometry of the main part of the height of the wastewater treatment plant of an oil refinery, make it possible to place installations on the street; The possibility of a closed design of the wastewater treatment plant of an oil refinery with rotating covers with a nozzle for gas extraction during the wastewater treatment of an oil refinery; The ability of the refinery's wastewater treatment plant to operate in a nitrogen environment; The absence of the need to erect a separate building of explosive and fire-hazardous categories with complex engineering systems for the installation of wastewater treatment of an oil refinery, which allows significant savings on the implementation of the wastewater treatment project of an oil refinery as a whole; The maximum possible use of existing communications, networks, and facilities for the installation of wastewater treatment at an oil refinery; The introduction of new wastewater treatment plants of an oil refinery and the reconstruction of old wastewater treatment facilities of an oil refinery without stopping the wastewater treatment process of an oil refinery, reducing the wastewater treatment capacity of an oil refinery, or temporarily deteriorating the existing level of wastewater treatment of an oil refinery for the period of preparation, installation and start-up; The maximum possible use of the hydraulic profile of the existing wastewater treatment facilities of the refinery, i.e., if possible, the exclusion of new additional pumping for the new wastewater treatment plant of the refinery; Reduction of energy costs through the use of modern innovative high-efficiency equipment for the wastewater treatment plant of an oil refinery, controls and regulation; Reduction of capital costs for wastewater treatment of an oil refinery, abandonment of the construction of new buildings; Reduction of capital costs through the use of thoughtful technological solutions and the use of innovative, patented equipment for the wastewater treatment plant of an oil refinery; The possibility of adapting the wastewater treatment plant of an oil refinery to the size of existing channels, reservoirs and structures; Reduction of installation time due to the use of equipment for the wastewater treatment plant of an oil refinery supplied in assembled or block form. To achieve the specified requirements for the quality of purified water, it is proposed to use a wastewater treatment plant of an oil refinery based on the pressure flotation method.
The pressure flotation method for wastewater treatment of an oil refinery is one of the most versatile, compact and short-term methods of water conditioning and sediment compaction. Pressure flotation provides a high degree of purification from suspended solids of different nature, BOD, petroleum products, surfactants, fats and other undesirable impurities, a high concentration of flotation sludge in the process of wastewater treatment of an oil refinery. The wastewater treatment plant of an oil refinery based on the pressure flotation method is in many cases the foundation for the creation of closed water use systems. The core of wastewater treatment of an oil refinery based on the pressure flotation method is the saturation of a part of clarified water with air at a pressure of 4-6 atm. and its mixing with purified water in a flotation plant. Subsequent decompression, directly in the body of the flotation device, leads to the formation of micro-bubbles of air (20-50 microns in size), which adhere to the particles of pollution and float to the surface of the wastewater treatment plant of the refinery, forming a flotation sludge. The flotation sludge from the refinery's wastewater treatment plant is collected from the entire surface into the center of the flotation device by a special collector. The dissolution of gas in water during the wastewater treatment process of an oil refinery occurs in air saturation plants. In the process of wastewater treatment at an oil refinery, part of the clarified water on the flotation device is taken away by a recirculation pump and supplied to the water saturation units with air at a pressure of ~ 5.5 atm. The special design of the water saturation unit with air makes it possible to achieve effective dissolution of gas in water in the wastewater treatment plant of an oil refinery. After the water is saturated with air, the gas-saturated (saturated) water passes through a pressure reducing valve, where pressure loss occurs from 5.5 atm. up to the pressure in the supply pipeline of the refinery's wastewater treatment plant. At the same time, a huge number of microbubbles are released from the saturated water to purify the effluents of the refinery. The purified water is supplied with an air-water mixture from a saturator for wastewater treatment of an oil refinery. This water enters the central part of the refinery's wastewater treatment plant. From the central distribution column, the mixture is distributed throughout the entire volume of the refinery's wastewater treatment plant. In the process of cleaning the effluents of an oil refinery, intensive separation of pollutants occurs. Pollutants entrained by air bubbles rise to the surface of the water and form a stable layer of flotation sludge after wastewater treatment of an oil refinery. A carriage rotates along the rail of the cylindrical part of the wastewater treatment plant of the refinery, on which a spiral collector is installed. Rotating, the spiral collector scoops up the flotation sludge and dumps it into the central pipe to exit the wastewater treatment plant of the refinery. After cleaning the effluents of the refinery, the flotation sludge exits the flotation device by gravity. Pollution-free water is collected in the annular channel of the refinery's wastewater treatment plant, fixed to the inner surface in the middle part of the cylindrical body. After cleaning the wastewater of the refinery, the water flows out of the flotation device by gravity through an adjustable overflow mounted on the outer wall of the flotation device. The settled impurities are removed from the wastewater treatment plant of the refinery under the action of hydrostatic pressure using clamping valves in the lower part of the flotation device. The installation has a very reliable and easily configurable flotation sludge removal system during the wastewater treatment of an oil refinery. The water level in the bathtub of the refinery's wastewater treatment plant is regulated. The flotation device has a spiral collection of flotation sludge to remove the maximum amount of sludge during the wastewater treatment of an oil refinery. The speed of the collector of the wastewater treatment plant of the refinery is regulated through the frequency converter of the motor depending on the amount of flotation sludge. This makes it possible to maintain a high concentration of the flotation sludge removed from the wastewater treatment plant of the refinery.