Method and apparatus for treating hydrocarbon-contaminated water

Abstract

Methods and apparatus for purifying water (particularly bilge water) contaminated with hydrocarbons and / or mineral oils, which can also be implemented on ships. The method includes a series of treatment cycles of water with a hydrophobic adsorbent material and a series of desorption cycles of hydrocarbons and oils by flushing with a liquefied gas to regenerate the adsorbent material. Hydrocarbons and oils are separated from the liquefied gas by evaporation, and the liquefied gas is then condensed and provided in liquefied form for a new regeneration cycle of the adsorbent material.

Description

Technical Field

[0001] This invention relates to a method and apparatus for treating water contaminated by hydrocarbons, mineral oils, etc. Background Technology

[0002] There are many instances of water pollution caused by hydrocarbons: in the industrial sector, hydrocarbons and mineral oils used in production processes come into contact with process water; and in the civil sector, hydrocarbons and / or oils are accidentally leaked or spilled into domestic water, or more simply, water generated from cleaning surfaces contaminated with hydrocarbons and oils.

[0003] Therefore, reusing this water in the industrial sector, introducing it into urban main roads or waterways, or purifying polluted ocean surfaces can all reduce pollution loads and comply with current regulations.

[0004] Examples of water contaminated with hydrocarbons, mineral oils, etc., include runoff from port areas (such as docks and surrounding areas). These areas are subject to traffic, which can cause leaks of fuel, lubricants, etc., which are then washed away by rainwater or water used to clean these areas. This water contaminated with hydrocarbons, mineral oils, etc., is collected in tanks or storage containers and must be treated before being released into the environment.

[0005] Another example of hydrocarbon-contaminated water is the drainage of sludge produced from oil wells. This water actually contains hydrocarbons and must be treated before being released into the environment. In the case of offshore wells, the water is effectively released into the sea.

[0006] The specific case of water contaminated with hydrocarbons is bilge water.

[0007] The bilge is a section located below the hull of a ship and is designed to collect leaks and various liquid discharges, such as lubricants, engine oil, residual wash water and other waste liquids, as well as liquids from regular maintenance activities performed on board.

[0008] Because current regulations prohibit the discharge of polluting liquids into the sea, water contaminated with hydrocarbons and other pollutants collected in the bilge must be discharged in port through special pipes and pumps connected to the sewer system, or treated on board to reduce the pollution load below the prescribed limits.

[0009] Therefore, it is known that bilge water treatment systems can be placed on ships, particularly for separating hydrocarbon residues and mineral oils to reduce their content to a level that allows bilge water to be discharged into the sea without harming the marine environment.

[0010] US 2009 / 0090473 A1 describes a complex system for treating bilge water that includes the evaporation of such water.

[0011] WO 2018 / 0177795 A1 discloses a treatment and regeneration system for extracting organic solutes from water using a filter media, which is then regenerated by a displacement fluid. The organic solutes are then separated from the displacement fluid, which can be reused. Although mentioned among possible filter media, activated carbon is described as difficult to regenerate and reuse because it requires very high treatment temperatures (T ~ 900°C) or must be discarded and replaced with fresh material. Backwashing or backflushing the filter media with a solvent is mentioned to regenerate granular filter media other than activated carbon.

[0012] Smathers C. et al., “Removing Dispersed and Dissolved Hydrocarbons from Water Using Adsorption Media Systems with Multiple Regeneration Processes”; Society of Petroleum Engineers-192355-MS; April 23, 2018, disclosed a method for removing hydrocarbon contaminants from water using a material named “Osorb”.

[0013] Therefore, there is a need to provide a system for treating water contaminated with hydrocarbons and lubricating oils, which allows for the elimination or reduction of the drawbacks of known systems.

[0014] Therefore, the object of the present invention is to provide a method and apparatus for treating water contaminated with hydrocarbons and lubricating oils, which represent an improvement over currently available systems, particularly in their efficiency in removing hydrocarbon residues and mineral oils from bilge water, and can be manufactured in a sufficiently compact size so that they can be placed and managed on ships that are not particularly large and on offshore platforms. Summary of the Invention

[0015] One aspect of the present invention includes a method for treating water contaminated with hydrocarbons and / or mineral oils, the method comprising the steps of:

[0016] a) Passing the water contaminated with hydrocarbons and / or oil through a hydrophobic material that has the ability to adsorb the hydrocarbons and / or oil, thereby obtaining the adsorption of the hydrocarbons and / or oil in the adsorbent material;

[0017] b) At the end of step a), a liquefied gas capable of dissolving the hydrocarbons and / or oils is passed through the hydrophobic material, thereby obtaining the desorption of the hydrocarbons and oils from the adsorbent material;

[0018] c) Transferring the liquefied gas containing the hydrocarbons and / or oils to an evaporation chamber, where the liquefied gas evaporates, thereby releasing the hydrocarbons and oils; and

[0019] d) Draw the evaporated gas from the evaporation chamber, compress and cool it to condense it and obtain the liquefied gas;

[0020] The characteristic feature is that the liquefied gas in step b) is a halogenated hydrocarbon belonging to the hydrofluoroolefin category, which is fed at a temperature of 30 to 50°C and a pressure of 5 to 10 bar.

[0021] Another aspect of the invention includes an apparatus for carrying out the method for treating water contaminated with hydrocarbons and / or oil as described above, the apparatus comprising:

[0022] A. A treatment chamber suitable for containing absorbent material for hydrocarbons and mineral oils, the chamber being hydraulically connected to the storage tank for water contaminated with hydrocarbons and / or oils;

[0023] B. An evaporation chamber for the solvent liquid, which is hydraulically connected to the processing chamber;

[0024] C. A component for compressing, cooling, and condensing gases, connected to the evaporation chamber and the processing chamber;

[0025] D. A storage tank for liquefied gases, hydraulically connected to the compression, cooling, and condensation components, the tank being hydraulically connected to the processing chamber; and

[0026] E. A series of valves for managing the flow of the water and the liquefied gas.

[0027] According to embodiments of the present invention, the method and apparatus for treating water contaminated with hydrocarbons and / or mineral oils are particularly advantageous for treating bilge water.

[0028] In an embodiment of such an apparatus of the invention, a treatment chamber suitable for containing hydrocarbon and / or mineral oil absorbent material is hydraulically connected to a storage tank of water contaminated with hydrocarbons and / or oil, which may be directly in the bilge of a ship. Attached Figure Description

[0029] The present invention is described in detail below, wherein:

[0030] - Figure 1 A non-limiting embodiment of both the method according to the invention and the apparatus for carrying out the method is schematically depicted; and

[0031] - Figure 2 The shape of the adsorbent material according to an embodiment of the present invention is shown. Detailed Implementation

[0032] In its most general aspect, the present invention relates to methods and apparatus for treating water contaminated with hydrocarbons and / or mineral oils.

[0033] The water that can be advantageously treated using the methods and apparatus of the present invention is, in particular, bilge water. Therefore, the following description specifically refers to the treatment of bilge water containing hydrocarbons, oils, greases, and other hydrophobic organic contaminants to purify such water and allow its discharge into the sea, followed by analysis to verify that the residual levels of the contaminants comply with current regulations. Furthermore, it is apparent that, after appropriate compatibility checks, the hydrocarbons and oils separated from the water can be advantageously reused as fuel in marine engines.

[0034] However, the treatment of bilge water is merely a non-limiting example of the types of water that can be treated using the methods and apparatus according to the invention.

[0035] In the maritime field, the term "bill water" refers to water that is essentially a mixture of water and oil, originating from leaks in shipboard equipment (machinery and piping), including equipment used to manage fuel and lubricants, including its purification equipment.

[0036] In this specification, the term "vessel" means any vessel of any size, provided that it has sufficient and suitable space to accommodate the apparatus for carrying out the treatment method.

[0037] The method of the present invention comprises a series of steps that can be repeated cyclically until the minimum contaminant content achievable by the method itself is reached. This allows for the use of a device with a relatively compact size, making it suitable for placement on a ship, although the same device can be advantageously placed on land, such as in a port area.

[0038] Step a)

[0039] In the first step a) of the method according to the invention, bilge water is drawn directly from the bilge of the ship or from a bilge water storage tank located on the ship itself (in Figure 1 (Uniformly represented by 4) is taken out and sent to the processing room 6.

[0040] According to the present invention, the term "processing chamber" refers to a containing space for adsorbing hydrophobic materials, which may consist of a single chamber or multiple chambers connected in series or parallel, all of which contain adsorbed hydrophobic materials.

[0041] The total volume Q1 of the processing chamber (single chamber or multiple interconnected chambers) is filled with adsorbed hydrophobic material.

[0042] In the treatment chamber, bilge water flows through a hydrophobic material 10 that adsorbs hydrocarbons and oils, which are then absorbed by the material. Due to the hydrophobic nature of the adsorbent material, water is not absorbed but flows through it and is released with little or no hydrocarbon and oil contaminants.

[0043] In an implementation of the treatment method, the bilge water flows continuously through the adsorbent material, wherein the same water undergoes a series of passes and is recycled to the same chamber and the same adsorbent material 10 after being discharged from treatment chamber 6, until the desired level of purification is achieved, for example, until a residual content of hydrocarbons and oils of no more than 5 ppm is obtained.

[0044] For example, water recirculation can be achieved by using pump E1 inserted into recirculation loop 7, which is equipped with three-way valves V1, V2 and V3.

[0045] In one embodiment, the hydrophobic adsorbent material comprises expanded particles obtained from siliceous rock and treated with a hydrophobic polymer to retain the typical ability of siliceous rock to absorb hydrocarbons and mineral oils, but to become water-repellent due to the hydrophobic properties acquired through the treatment with the hydrophobic polymer. Therefore, water flows through the material 10 without being absorbed. These properties make the material 10 suitable for use in step a) of the method of the present invention.

[0046] The adsorbent material advantageously used for this purpose is manufactured by Airbank Srl and sold under the trade name H2OILSORB.

[0047] In another embodiment, the hydrophobic adsorbent material is advantageously mixed with activated carbon.

[0048] In another embodiment, the adsorbent is activated carbon.

[0049] Step b)

[0050] In the second step b), the liquefied gas is fed into the processing chamber 6 and flows through the hydrophobic material 10, which has absorbed hydrocarbons and oils. The liquefied gas has a dissolving capacity for hydrocarbons and oils; therefore, due to the stripping effect exerted by the flow of the liquefied gas, the hydrocarbons and oils are also desorbed from the material 10 and dissolved in the liquefied gas.

[0051] The amount of liquefied gas flowing through the hydrophobic material in the filling chamber (volume Q1) is defined by volume Q2. Both volumes Q1 and Q2 are expressed in liters.

[0052] According to one aspect of the invention, the ratio Q2 / Q1 is 4 to 3, preferably 3.8 to 3.2, and more preferably about 3.5. The liquefied gas is a halogenated hydrocarbon belonging to the hydrofluoroolefin (HFO) class commonly used for refrigeration, which is gaseous at ambient temperature and pressure. Preferably, HFO is gaseous even at temperatures ranging from -5 to -15°C and pressures from 1 to 4 bar.

[0053] HFO is introduced into the processing chamber 6 in liquefied form at a temperature of 30 to 50°C, preferably 35 to 40°C, and a pressure of 5 to 10 bar, preferably 6 to 8 bar.

[0054] In embodiments of the method of the present invention, HFO is trans-1,3,3,3-tetrafluoropropylene, usually represented by the abbreviation ASHRAE R1234ze.

[0055] In another embodiment of the method of the present invention, HFO is trans-2,3,3,3-tetrafluoropropylene, usually represented by the abbreviation HFO-1234yf, and has the molecular formula CH2=CFCF3.

[0056] At the end of step b), the adsorbent material is regenerated and can be used for a new bilge water treatment cycle.

[0057] In one embodiment of the method of the present invention, the adsorbent material 10 is stacked in a cylindrical shape in the processing chamber, such as... Figure 2 As shown. Preferably, the processing chamber (or each single chamber if there is more than one chamber) also has a cylindrical shape.

[0058] According to the preferred aspects, such as Figure 2 As shown, the cylindrical adsorbent material has an axial internal channel 30 through which liquefied hydrofluoroolefins are fed, causing them to flow from the internal channel through the adsorbent material to the outside of the adsorbent material. Surprisingly, this flow path allows for the minimization of the amount of liquefied gas required to dissolve the adsorbed hydrocarbons and oils.

[0059] Step c)

[0060] In the third step c), the liquefied gas containing hydrocarbons and oils is transferred to the evaporation chamber 3, where the liquefied gas is evaporated to release the hydrocarbons and oils dissolved or entrained therein.

[0061] Evaporation is achieved by expanding the liquefied gas due to suction applied by compressor 8 (which is located downstream of evaporation chamber 3). Hydrocarbons are collected in evaporation chamber 3 and can subsequently be removed from it.

[0062] The gas temperature in the evaporation chamber is preferably -5 to -15°C, more preferably -2 to -9°C.

[0063] The pressure in the evaporation chamber is preferably 1 to 4 bar, more preferably 1.5 to 3.5 bar.

[0064] Step d)

[0065] In step d), the gas evaporated in the evaporator 3 is drawn off and transferred to the condenser 5. This drawing is performed by connecting the evaporator 3 to the suction side of the compressor 8. The compression and cooling of the gas causes it to condense, thus producing liquefied gas.

[0066] Therefore, at the end of step d), liquefied gas can be used to regenerate the adsorbent material after new treatment of other bilge water contaminated with hydrocarbons and oil.

[0067] Steps a), b), c), and d) are repeated the required number of cycles to ensure maximum efficiency in removing hydrocarbons and oils from the bilge water. This method allows for the acquisition of bilge water that is no longer contaminated and can thus be reused on board the ship, for example, as wash water, and the extraction of hydrocarbons and oils, which can also be used on board, for example, as combustibles or fuels, depending on their properties. The apparatus according to the invention comprises a bilge water treatment chamber 6 suitable for containing material 10 for absorbing hydrocarbons and mineral oils, which is hydraulically connected, for example, via pipe 19, to the ship's bilge or bilge water storage tank (in... Figure 1 (This is uniformly represented by 4). An electric pump E1 is present in the recirculation line 7 connected to the pipe 19 to allow treated bilge water taken from the bottom of chamber 6 to be pumped to the inlet of the chamber itself and flow through the adsorbent material 10 again.

[0068] A series of three-way solenoid valves V1, V2, V3, and V4 allow for the management of the recirculation loop and the discharge of liquefied gas from chamber 6.

[0069] Processing chamber 6 is connected to the bottom of evaporation chamber 3 via pipe 21. As described above, since the evaporation chamber is connected to the suction side of compressor 8 via pipe 23, it is suitable for evaporating liquefied gas. Downstream of evaporation chamber 3 and upstream of compressor 8, there is filter 17, which is suitable for retaining any hydrocarbon and oil residues still present in the gas exiting the evaporation chamber.

[0070] A condenser 5 is located downstream of the compressor 8, which cools and condenses the fluid, restoring the liquefied gas introduced into the processing chamber 6.

[0071] The device also includes a liquefied gas storage tank 2, which is hydraulically connected to the compressor 8. A three-way valve 9 allows liquefied gas to be fed into the tank 2 or directly into the processing chamber 6 via a pipe 12 equipped with valve V1. The liquefied gas tank 2 is connected to the processing chamber 6 via a pipe 13 equipped with valve 15.

[0072] The processing chamber 6 is connected to a vacuum pump 25, such as a two-stage rotary oil pump, which functions to extract non-condensable gases, consisting mainly of oxygen, nitrogen and water vapor, from the liquefied gas inlet chamber 6 to prevent contamination of the chamber.

[0073] Programmable Logic Controllers (PLCs) allow for the automated management of various system components.

[0074] Regarding the treatment chamber 6, in an embodiment not shown, it may consist of several chambers connected in series or in parallel, each containing adsorbent material.

[0075] Therefore, the method and apparatus according to the invention involve alternating between treating contaminated bilge water using adsorbent materials and regenerating the adsorbent materials using suitable halogenated hydrocarbons (particularly those belonging to the hydrofluoroolefin (HFO) category).

[0076] Furthermore, the evaporation and condensation cycle of liquefied gases allows for the possible reuse of the obtained hydrocarbons and oils.

[0077] Currently, hydrofluoroolefins are used as refrigerants and have the following advantages:

[0078] 1) They are not toxic or harmful;

[0079] 2) They have low environmental impact (ODP = 0; GWP = 7);

[0080] 3) They are gaseous at room temperature and pressure, and can be easily removed from the solid matrix composed of hydrophobic adsorbent materials and from the recovered contaminants (oil and hydrocarbons) at the end of the treatment.

[0081] 4) They are non-toxic and non-flammable or weakly flammable.

[0082] 5) The amount of hydrofluoroolefins used to regenerate the adsorbent is very limited and on the same order of magnitude as the amount of adsorbent material used, thereby facilitating the subsequent recovery of the fluid at the end of the treatment process and also appropriately utilizing the liquid-to-gas transition and vice versa.

[0083] As can be seen from step b) above, it has been found that the method according to the invention allows for the regeneration of the adsorbent material at temperatures of 30 to 50°C and pressures of 5 to 10 bar. These are relatively low temperature and pressure values, making the method both cost-effective and efficient.

[0084] Furthermore, the amount of liquefied gas Q2 used to regenerate the adsorbent material of volume Q1 is limited because the ratio Q2 / Q1 is not greater than 4.

[0085] The aforementioned characteristics allow for the implementation of this method in a relatively compact device, making it suitable for installation on ships. The possibility of manufacturing a relatively compact device is also advantageous for installation in port areas (where available space is limited), or in any other suitable location, or on offshore platforms.

Claims

1. A method for treating water contaminated with hydrocarbons and / or mineral oils to remove said hydrocarbons and / or mineral oils, characterized in that... Includes the following steps: a) Passing the water through a hydrophobic adsorption material that has the ability to adsorb the hydrocarbons and / or oils, thereby achieving the absorption of the hydrocarbons and / or oils in the adsorption material; b) At the end of step a), a liquefied gas capable of dissolving the hydrocarbons and / or oils is passed through the hydrophobic material, thereby obtaining the desorption of the hydrocarbons and oils from the adsorbent material; c) The liquefied gas containing the hydrocarbon and / or oil is transferred to an evaporation chamber, where the liquefied gas evaporates, thereby releasing the hydrocarbon and oil; and d) Draw the evaporated gas from the evaporation chamber, compress and cool it to condense it, and regenerate the liquefied gas; The liquefied gas in step b) is a halogenated hydrocarbon belonging to the hydrofluoroolefin category, which is fed at a temperature of 30 to 50°C and a pressure of 5 to 10 bar.

2. The method according to claim 1, characterized in that... The hydrophobic adsorbent material is composed of expanded particles obtained from siliceous rock and treated with a hydrophobic polymer.

3. The method according to one or more of the preceding claims, characterized in that... The liquefied gas in step b) is a halogenated hydrocarbon belonging to the hydrofluoroolefin (HFO) category, selected from trans-1,3,3,3-tetrafluoropropylene and trans-2,3,3,3-tetrafluoropropylene.

4. The method according to one or more of the preceding claims, characterized in that... The liquefied gas in step b) is in gaseous form at a temperature range of -5 to -15°C and a pressure of 1 to 4 bar.

5. The method according to claim 4, characterized in that... The liquefied gas in step b) is in liquefied form at a temperature of 35 to 40°C and a pressure of 6 to 8 bar.

6. The method according to one or more of the preceding claims, characterized in that, The liquefied gas evaporates in the evaporation chamber due to the suction applied by the compressor located downstream of the evaporation chamber.

7. The method according to one or more of the preceding claims, characterized in that, In step c), the temperature of the gas in the evaporation chamber is -5 to -15°C, preferably -2 to -9°C.

8. The method according to one or more of the preceding claims, characterized in that, In step c), the pressure in the evaporation chamber is 1 to 4 bar, preferably 1.5 to 3.5 bar.

9. The method according to any one of claims 1 and 3-8, characterized in that, The adsorbent material is activated carbon.

10. The method according to any one of claims 1-9, characterized in that, The adsorbent material is contained in a processing chamber having a cylindrical shape, and the adsorbent material also has a cylindrical shape and forms an axial internal channel.

11. The method according to claim 10, characterized in that, The liquefied gas, which belongs to the hydrofluoroolefin category, is fed into the axial internal channel and flows from the inside of the adsorbent material to the outside.

12. The method according to any one of claims 1-11, wherein the adsorbent material occupies a volume Q1 of the processing chamber and the liquefied gas flowing through the adsorbent material in step b) has a volume Q2, characterized in that, The ratio Q2 / Q1 is 4 to 3, preferably 3.8 to 3.2, and more preferably about 3.

5.

13. Apparatus for carrying out a method for treating water contaminated with hydrocarbons and / or oil, comprising: A. A treatment chamber (6) suitable for containing absorbent material (10) of hydrocarbons and mineral oils, the chamber being hydraulically connected to the storage tank (4) of water contaminated with hydrocarbons and / or oils; B. An evaporation chamber (3) for the solvent liquid, which is hydraulically connected to the processing chamber (6); C. A component for gas compression (8), cooling and condensation (5), which is connected to the evaporation chamber (3) and the processing chamber (6); D. A storage tank (2) for liquefied gas, hydraulically connected to the compression (8), cooling and condensation components (5), the tank (2) being hydraulically connected to the processing chamber (6); and E. A series of valves for managing the flow of the water and the liquefied gas.

14. The apparatus according to claim 13, characterized in that, It includes a water recirculation loop (7), which includes an electric pump (E1) and a series of three-way solenoid valves V1, V2, V3, V4 for managing the bilge water recirculation.

15. The apparatus according to claim 13 or 14, characterized in that, The processing chamber (6) is connected to a vacuum pump (25) for extracting non-condensable gases.

16. The apparatus according to one or more of claims 13 to 15, characterized in that, The storage tank (4) is the hull of the ship.

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