RU2205797C1 - Oil-containing waste water treatment installation - Google Patents

Abstract

FIELD: waste water treatment. SUBSTANCE: installation has casing in the form of two interconnected settlers with thin-layer modules thus forming double-section settler containing, between sections, heater-equipped oil product collector. First section encloses stream energy-damping chamber. Thin-layer plates form manifold to distribute stream on the inlet. Cover is provided with oil and fat catcher attached to it. Second section has variable-height discharge threshold. Installation can be applied in shipbuilding, mechanical engineering, petrochemical and petroleum processing industries as well as in construction, transport, power engineering, and other areas. EFFECT: increased treatment efficiency with waste waters containing both low- and high-viscosity petroleum derivatives. 4 cl, 4 dwg

Description

 The invention relates to devices for the purification of oily wastewater and can be used in shipbuilding, engineering, food, petrochemical and oil refining industries, as well as in construction, transport, energy and other industries where the formation of effluents containing oil products and various organic substances.

 Due to the sharp increase in the number of enterprises engaged in the receipt, storage, wholesale and retail sale of petroleum products, the absence at most facilities (oil depots, petrol stations (gas stations), fuel and lubricant warehouses, fuel oil depots, etc.), equipped and efficiently operating collection systems and treatment of storm and emergency effluents, there is an increase in oil pollution. As a result, oil pollution is the most significant and widespread type of environmental pollution.

 Pollution of soil and groundwater in the territories of gas stations and other oil supply facilities is caused by leaks of oil products. The causes of leaks can be various defects: depressurization of tanks and other containers, malfunctions of technological equipment.

 Oil and petroleum products coming into direct contact with water pollute it, being in various states, the main of which are: free oil, unstabilized dispersions, stabilized dispersions, molecularly dissolved oil, enveloping solid inclusions. The state of oil in oily waters is crucial for choosing a method for treating these waters with a view to purifying them.

 The problem of purification of oily waters is especially acute on ships, railway and other types of transport.

 The main source of pollution of various liquids in ship systems is fuel. Water can be in the fuel in dissolved form, in a free state and in the form of a fuel-oil emulsion. The solubility of water depends on the chemical composition of the fuel. The highest solubility is observed in gasoline, less in diesel fuel and even less in fuel oil. Solubility increases with increasing temperature. Free water is usually at the bottom of the tanks. In light low-viscosity fuels, water quickly settles to the bottom. In heavier, highly viscous fuels, water can form water-fuel emulsions that do not decompose under the influence of temperature and gravitational forces. The stability of emulsions increases with increasing content of resinous and high molecular weight compounds, as well as sulfur compounds in the fuel. Fuel emulsions are coarse systems with a particle size of 1-100 microns or more. Organic and inorganic compounds are present in the fuel as mechanical impurities.

 The amount of oil contained in oily waters varies widely.

The average density of the mixture of petroleum products contained in the bilges of the engine rooms of ships is estimated at 0.85-0.97 g / cm ³ , i.e. slightly exceeds the average density of oil products used on ships (0.83-0.94 g / cm ³ ). The average content of solids in bilge waters is 0.006%, pH 5.9-7.1. The degree of dispersion of oil in them is different.

 A certain amount of mechanical impurities consisting of paint particles, nap from the crumbling vibration and rolling of insulation, various stuffing materials, corrosion products, and coked oil products enters and mixes with the oil-containing water in the bilge of the vessel. In addition, surfactants and organic inclusions (plankton, etc.) can fall into bilges.

 The treatment of oily wastewater is carried out, as a rule, in several stages, and the first stage is the cleaning of large mechanical impurities and the allocation of a lighter fraction - oil products. Finer cleaning is carried out in subsequent stages by filtration.

 For cleaning oil products, power purifiers of various designs are used, the principle of which is to separate the particles of pollution from oil products under the influence of an artificial force field or natural gravity. These are sedimentation tanks, centrifuges and centrifugal separators.

 Purification of oily water is carried out in separators of gravity, flotation, coalescing and centrifugal types.

 For cleaning oil products use filter cleaners of various types.

 Filtering oil products means passing oil products through screens, gaps between plates, wire cups, felt, felt or special porous filter elements.

 The main indicator of the quality of the filter is the filtering fineness provided by it, i.e. The minimum size of the detained particles of pollution. According to this indicator, all means of filtering petroleum products are divided into coarse filters and fine filters.

 As the first stage to isolate the bulk of the oil, mechanical impurities and highly viscous inclusions are used: sedimentation tanks (gravitational) type; coalescing separators with a block of plates, which can be performed both flat and corrugated; coalescing filters. However, a significant drawback of these filters is the limited life of their elements. The desire to obtain good cleaning ability leads to the need to reduce the pores in the element, which in turn contributes to a more rapid increase in the resistance of the element in operation due to clogging of small pores, i.e. decrease in its resource.

 Of great importance on the quality of the separation plant, and especially with the settling and coalescing steps, is the choice of pumping agent.

 Known separation plant "Pematic" company "Salen and Vikander" (Sweden). This separator is available in three versions. The separator consists of three tanks mounted on the same foundation. A screw pump is installed on the same foundation. Cleaning in the separator is two-stage.

 Oil-containing water is first fed to a gravity-type separator (first stage), the separation of oil particles in which occurs mainly due to the difference in the density of water and oil product. The pump is installed after the separator, i.e., it is not in the first stage. Thus, the gravitational separator operates in a vacuum mode, which significantly increases its cleaning ability, because the dispersing effect of the pump on oil particles is excluded. The oil separated in the gravity separator is collected in its upper part and, as it is filled, is removed to the collection tank by the signal of the oil-water interface level sensor. Then partially purified water is supplied to the filter (second stage).

 A granular crystalline material treated with a chemical composition or other material is poured into the volume of the filtering tank. The company’s filters used polymer material made in the form of small "squirrel" wheels. Particles of oil that have not separated in the gravity separator are trapped on the surface of the filter material, and purified water is thrown overboard through the wash water tanks. The regeneration of the filter is carried out by back-flushing with purified bilge water enclosed in a flushing tank. Water is squeezed out of the washing tank by the pressure of compressed air into the filter, where it passes through the filter material at a higher rate than when cleaning oil-containing water. In this case, the oil is washed off from the surface of the filter and its regeneration. After each flushing, a certain amount of water with oil products is returned to the bilge well or bilge water collection tank. However, due to the coalescence of oil particles on the filter surface, their subsequent separation in a gravitational separator will be more efficient. The regeneration process is carried out periodically. The pneumatic and electronic valves that switch the operation of the unit from the cleaning mode to regeneration and vice versa are controlled through the control panel, supplied together with the unit (“Means for cleaning liquids on ships.” Reference edited by IA Ivanov, -L.: Shipbuilding , 1984).

 It is known to use a separator type SFC firm "Serep" (France). The separator is a single-case design, divided into two parts. One of them - the pre-treatment stage - is designed for gravitational separation of larger particles of oil. The other is a post-treatment filter located in the middle of the separator housing, designed to trap small drops of oil. The filter is filled with oleophilic material, patented by the company. The filling thickness of the filter material is 700 mm with a total filter height of 1000 mm. The company produces three modifications of the separator (ibid.). This design is more compact.

 A common drawback of plants containing gravity sumps, coalescing separators and filters are: accumulation of oil products in filter grains, lack of separation of solid particles from wastewater outside the coalescing chamber and, accordingly, clogging of coalescing material, regeneration time, impossibility to remove coarse oil droplets from plants, etc. .

 A known installation for purification of oil-containing wastewater, comprising a water inlet chamber with a submersible pump, a dirt trap with a dirt collector, a filter unit with sorption loading and a tank for purified water, which is serially connected between the filter block and the dirt trap, made in the form of a cylindrical chamber with a lid, the cylindrical part of which is divided by a vertical blank partition not reaching the lid, into two halves, one of which is made vertical cylindrical channels, and in the other half-rings are installed in a checkerboard pattern vertically, and above the conical part of the chamber a horizontal perforated partition is installed and the dirt trap is made in the form of a reverse truncated cone, to the smaller base of which there is a pipe located under the dirt collector with a ripper installed in it with the possibility of rotation (RF patent 2006474, BI 2, 1994).

 The disadvantages of this device include the presence of filters with sorption loading, which requires replacement or regeneration of the sorbent, and the design of the separator does not allow to separate high-viscosity oil products.

 A known installation for the treatment of wastewater from oil products, including a housing with a preliminary sump placed in it, a thin-layer module of inclined corrugated shelves, a filter chamber with a coalescing charge, pipelines for the supply of waste water, drainage of oil products, sludge and purified water, a filter chamber with an adsorbent load and perforated manifold connecting both filter chambers and placed in their upper parts pipelines for the removal of petroleum products, equipped with regulatory It is not necessary to drain using screw-on cups, while the filter chambers are installed in the direction of the liquid behind the thin-layer module, the coalescing charge is made of granular hydrophobic material, for example polyamide or polyethylene, and the adsorbent charge is made of heat-resistant quartz fiber with high porosity, and the preliminary settler is equipped with a heating collector ( RF patent 2013375, BI 10, 1994).

 In practice, this design is close to the well-known installation of the company "General Electric", but a filter chamber with an adsorbing charge and a heating collector installed in the pre-sump have been added to it. This installation is not intended for the separation of wastewater containing highly viscous oil products, which will drastically reduce the life of the coalescing and adsorbing charge. The inclined arrangement of thin-layer corrugated elements reduces the efficiency of their work, and the placement of the heater in the preliminary sedimentation tank cannot significantly affect the viscosity of oil products.

 A known apparatus for the separation of two immiscible liquids (RF patent 2105592, BI 10, 1996), which is intended for the treatment of wastewater containing petroleum products. It consists of a casing made in the form of two communicating sections, one of which contains a nozzle for supplying the initial mixture, a pocket with an unloading threshold and a branch pipe for removing light fluid, and another pocket with a filter element installed in it and a unloading threshold with a branch pipe for draining heavy liquids moreover, in the first section there is a barrier with a flat horizontal surface, which is located below the level of the unloading threshold of the first section by a certain amount.

In addition to the disadvantage inherent in all devices containing filter elements, this apparatus has a number of disadvantages, namely:
- it is designed to separate a two-phase flow, waste water containing oil products, as a rule, this is a three-phase system;
- high viscosity oil products cannot be removed by gravity from the settling chamber; therefore, this design is applicable to light and medium viscosity oils;
- during the cleaning process, the resistance of the horizontal partition is not constant and it is necessary to change its position so that the mode remains stationary;
- the filter element installed in the second pocket has inherent known disadvantages - periodic replacement or regeneration.

 Closest to the proposed technical solution is a device for wastewater treatment, protected by RF patent 2163828, BI 7, 2001. It contains a housing, thin-layer elements, nozzles for withdrawing condensed product and clarified water, a collector for collecting clarified water, and the housing is made in in the form of two cylindrical sumps conjugated to each other at an angle of 60 degrees to the horizon, forming a two-section sump, as it were, and in each section of the thickening chamber, over which thin-layer elements are placed, each the thickening measure is associated with the cavity of the loading and unloading pipe, the discharge end of which is connected to a pipe for withdrawing condensed product, and the collector for collecting clarified water is connected to a clarified water collection chamber located above the thin-layer elements and a pipe for removing clarified water, while the ratio of the diameters of the loading discharge pipe and cylindrical sump is 1: 2-1: 3.

 The main disadvantage of the prototype is that with this design thin-layer elements are tilted at an angle of 60 degrees, which reduces the efficiency of their work, because the flow of wastewater moves towards the rising on the wall of each element of the oil film, preventing its ascent.

 In addition, with this device it is impossible to remove highly viscous petroleum products, because it does not provide such a node.

 The technical task of the invention is to provide a device capable of purifying to the required purity any wastewater containing both low- and high-viscosity oil products or mixtures thereof.

The known device has been amended, namely:
- sumps are installed vertically and parallel to each other, forming a two-section sump, and between the sections there is a collection of petroleum products, with a heater installed in the lower part;
- in the first section of the sump, an additional vertical partition is installed, forming with the outer wall of the housing a chamber for quenching the energy of the flow;
- coalescing plates of thin-layer elements are mounted vertically, forming a comb at the inlet of the flow into the first section of the settler for uniform distribution of the flow through the slotted channels;
- in the first section of the sump, in the accumulation zone of the separated light fraction, an oil separator is attached to the lid of the casing;
- unloading threshold into the chamber of clarified water is made with the possibility of changing its placement in height;
- an oil separator drive is installed on the housing cover.

 In addition, the wall of the first section of the sump associated with the collection of petroleum products is made slightly lower, forming a discharge threshold, and at the outlet of the condensation zones (sludge), pipes are installed to remove the condensed product (sludge).

 The oil separator contains a drum with movable coalescing disks mounted on it, scrapers located between the movable disks, the upper part of each of them pressed against the drum, and the lower part of the scrapers mounted on a common axis, which ensures their free sliding along the axis and eliminating jamming of the scrapers between the movable disks oil separator disks, and the plate forming the chute for transporting oil products to the accumulator is fixed only on two extreme scrapers equipped with shoulders. The rotation of the drum is carried out from a drive including an electric motor or hydraulic motor and transmission.

 The design of the installation for the treatment of oily wastewater is illustrated by drawings.

 Figure 1 - General view of the installation without the front wall of the housing.

 Figure 2 is a left view with cutouts in the upper and lower parts of the housing.

 FIG. 3 - layout and design of the oil separator scraper.

 FIG. 4 is a top view of the oil separator.

 In FIG. 1 shows a casing 1, an inlet pipe 2, an additional vertical partition 3, forming, together with the outer wall of the casing, a flow energy quenching chamber, a first section of a sump 24 with vertical coalescing plates installed in it, forming a comb 4 (more clearly seen in Fig. 2), an oil separator containing movable disks 5 mounted on the drum 6, scrapers 7 mounted between the movable disks 5, a first discharge threshold 8, a collection of oil products 16, a second section of the settler 24 with the vertical installed therein parallel coalescing plates 9, the second unloading threshold 10, installed with the possibility of changing its height on the partition 11, the pipe 13 for the output of clarified water, the chamber of clarified water 14, formed between the outer wall of the second section of the settler by the walls of the housing 1, pipes 15, 19, 20 for the outlet of the condensed product (sludge) from the condensation zones 12, 18 and the quenching chamber, a pipe 17 for removing oil products from the collection, a housing cover 21, an oil separator drive including an engine 22 and a gear 23, an oil product heater 25 ( ur. 2), a chute for collecting highly viscous oil product 26 (FIGS. 3 and 4), a common axis 27 for attaching scrapers to the oil separator (ibid.).

 Installation works as follows. Oil-containing wastewater enters the casing 1 at a speed of 1-2 m / s through the pipe 2 into the flow quenching chamber formed by the outer wall of the casing 1 and an additional vertical partition 3 inserted into the first section of the settler 24. The flow at the entrance to this chamber expands and reduces speed. Due to this, the largest mechanical impurities settle in the lower part of the flow quenching chamber, and the main waste water stream containing oil products in the form of large droplets of oil or a finely dispersed emulsion enters the first section of the sump 24, in which there is a thin-layer module.

 The thin-layer module is made of separate vertical parallel-located coalescing plates that form gap channels between themselves. The upper edges of the plates protruding above the partition 3, form a comb 4 (figure 2), playing the role of a uniform flow distributor for individual slotted channels. As a result of the fact that the stream enters the upper part of the first section of the sump, and leaves in the opposite diagonal angle, a condensation zone 18 is formed in the sump, in which sludge and sludge accumulate. When an oil-containing stream passes through slotted channels, a natural coalescence process occurs, i.e. enlargement of oil product droplets and due to the difference in the density of water and oil, they float to the surface in the upper settling zone of the first section of the settler, which plays the role of a reservoir of the oil product layer.

 In addition, coalescing plates capture small drops of oil products, while the droplets adhering to the surface of the plates merge and coarsen, forming a continuous film, which rises up to the same zone under the action of the Poiseuille effect. So, as the outer wall of the first section of the sump 24 is made slightly lower than the walls of the housing 1, as a result, the first discharge threshold 8 is formed, through which low-viscosity oil products flow into the oil collection 16. However, high-viscosity oil products cannot flow by gravity to this collection 16, therefore To remove them, use an oil separator attached to the cover 21 of the unit body 1 so that the movable disks 5 mounted on the drum 6 are immersed in the oil storage zone.

 In practice, other mounting options for the oil separator in the accumulation zone of oil products are possible. The drum rotation drive in this example includes a motor 22 and a gear 23 connecting the motor shaft to the oil separator shaft (Fig. 2). It is possible to use a hydraulic motor or other drive device instead of an electric motor. The rotation of the drum is carried out in such a way that the oncoming film of a highly viscous oil product is attacked by the descending half of the disks 5. Under these conditions, the bulk of the oil product is pressed against the moving disks, wetting their surface and forming a well-held film on it. This film is removed from their surface by scrapers 7 installed between the movable disks, and by gravity through the groove 26 (Fig.3) flows into the collection of petroleum products 16.

 The wastewater freed from oil products from the outlet of the first section of the settler 24 enters from the bottom to the inlet of the second section of the settler 24, which also houses a thin-layer module 9, consisting of vertically parallel coalescing plates forming slotted channels. In these slotted channels, denser solid particles are separated from the water. This is because, due to the parabolic distribution of velocities in the slotted channels, the upward flow forces the denser particles toward the plates forming the walls of the slotted channels (Poiseuille effect). By displacing solid particles to the surfaces of the coalescing plates, the flow carries them out due to the diagonal direction of movement to the stagnant zone 12, where these particles slowly settle in the form of sludge or sludge, and are removed from the installation as they accumulate. The clarified water through the second discharge threshold 10, configured to change its height relative to the partition 11, enters the clarified water chamber 14, formed by the outer wall of the second section of the sump 24 and the walls of the housing 1, from which it is removed by the nozzle 13. Condensed products (solid particles, sludge, sludge) are removed from the condensation zones 12, 18 and the quenching chamber of the flow energy through the nozzles 15.19 and 20, respectively.

The removal of petroleum products from the reservoir 16 is carried out as they accumulate through the pipe 17, but in order to reduce the viscosity of high-viscosity petroleum products, a heater 25 is installed in the lower part of the petroleum reservoir 16 (Fig. 2). The heating temperature depends on the properties of high viscosity oil and is in the range of 50-80 ^o C.

 For a better understanding of the design of the assembly of transportation of collected oil products in FIG. 3 shows an assembly diagram of scrapers 7 on a common axis 27.

 From FIG. 3 and 4, we can judge, more clearly, about the design of the common trough formed by a solid plate 26, mounted only on two extreme scrapers equipped with collars (not shown in the drawing). The installation of scrapers on a common axis allows them to acquire the ability to move along a common axis and thereby avoid jamming them with adjacent moving disks, as each scraper spontaneously takes the desired position.

 The base of the common groove (plate 26) covers all the gaps between the scrapers and eliminates the possibility of oil getting back into the first section of the settler 24. The fastening of the plate 26 on the extreme scrapers allows the others to move freely along axis 27.

Thus, the proposed technical solution has several advantages compared with the technical solutions used for the same purposes, namely:
- structurally, there are no separators with coalescing loading and with filtering with adsorption loading, requiring periodic replacement and regeneration;
- coalescing plates are arranged vertically, are not contaminated by particles of separated impurities, i.e. the plate block is self-cleaning;
- allows you to simultaneously purify waste water from low and high viscosity oil products, and their extraction is at least 95-98%;
- the degree of water purification is carried out up to 3-5 ppm, which, according to European standards, allows their discharge into natural water bodies.

 Currently, design documentation has been developed and the proposed installation for the treatment of oily wastewater is being manufactured. The installation is scheduled for the end of the current year or in the first quarter of 2002.

Claims (4)

 1. Installation for the purification of oily wastewater, comprising a housing equipped with nozzles for introducing oily wastewater and the withdrawal of clarified water, as well as nozzles for removing petroleum products and condensed product, moreover, the housing is made in the form of a two-section sump with a thin-layer module placed in each section containing parallel coalescing plates, under which thickening zones are formed, a chamber for clarified water, characterized in that the sections of the sump are installed vertically and parallel to each other to each other, a collection of petroleum products is placed between them, an additional vertical partition is installed in the first section of the sump, forming a flow energy quenching chamber with the outer wall of the casing, thin-layer modules are made of separate vertical coalescing plates, forming a comb, which distributes the input stream over the slots, with the upper edges in the first section of the sump thin-layer module, in the first section of the sump in the accumulation zone of the separated oil products installed oil separator equipped with a drive, the bottom of the oil collector is mounted heater, wherein the clarified water chamber wall adjacent to the second section of the settler, is adapted to change its height.  2. Installation according to claim 1, characterized in that the wall of the first section of the sump adjacent to the collection of petroleum products is made in height below the walls of the housing, forming the first threshold overflow.  3. Installation according to claim 1 or 2, characterized in that at the outlet of the additionally formed condensation zones, nozzles for removing sludge are installed.  4. Installation according to any one of claims 1 to 3, characterized in that said oil separator comprises a drum with movable coalescing disks mounted on it, rotating by means of a drive and a transmission connecting the drum shaft to the motor shaft, as well as scrapers located between the movable disks, moreover, the upper part of each of the scrapers is pressed against the drum, and the lower part of the scrapers is mounted on a common axis with the possibility of longitudinal movement, and the plate forming the chute for transporting oil products to the accumulator is fixed and on the two outer scrapers fitted with collars.

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