KR100824815B1 - Plasma process for the removal of hydrocarbons contained in the sludge from petroleum storage tanks and for the treatment of residues containing hydrocarbons - Google Patents

Abstract

The present invention is excellently applied to remove toxic or harmful organic compounds, such as petroleum effluents or petroleum, oils, pesticides, herbicides and various hydrocarbon compounds, resulting from improper disposal or disposal, from various substances such as soil or sludge. Plasma method and apparatus, which may be used to remove hydrocarbon compounds contained in sludge formed at the bottom of a petroleum storage tank. Plasma methods of the present invention provided with the apparatus include removal of contaminants to less than 0.1% by weight of soil or sludge, compared to other methods used to treat similar materials; Continuous operation process; Contaminant recovery if desired; High energy efficiency of the process; And small amounts of processing gas. The plasma method utilizes a plasma system to supply sufficient energy to contaminated soil or sludge so that hydrocarbon compounds can evaporate, keeping the temperature of the process between 400 and 900 ° C. After leaving the plasma reactor, the evaporated compounds are collected in a condenser where the hydrocarbon compounds can be recovered in the form of liquid hydrocarbons (oil). Contaminated material is continuously fed into the reactor from one end, while clean material from which the contaminant has been removed is removed from the other end of the reactor. The atmospheric pressure in the plasma reactor is maintained at moderate or reduced pressure to prevent oxidation of the hydrocarbon compound. The apparatus of the present invention comprises a feed system, a fixed reactor, a rotating screw for transporting residue into the reactor, a plasma system, a tube for the removal of evaporated compounds, a condenser located outside the plasma reactor, and contaminants removed from the reactor. It consists of an outlet for removing clean material and a silo for collecting contaminants by removing contaminants.

Description

Plasma process for the removal of hydrocarbons contained in the sludge from petroleum storage tanks and for the treatment of residues containing hydrocarbons}

The present invention relates to a plasma method and apparatus suitable for the removal of hydrocarbon compounds from sludge formed at the bottom of a petroleum storage tank containing crude oil and significant amounts of inorganic solids and water. The method is applicable to the treatment of contaminated soils and sludges by removing toxic or harmful organic compounds such as petroleum oils, pesticides, herbicides and various hydrocarbon compounds resulting from the spillage or improper treatment of these substances.

Soils contaminated with petroleum or other types of oil are usually the result of an accidental spill or spill while maintaining an oil pipeline and are usually found or related to petrochemical plants and refining plants. It is common to find more than 25% by weight of petroleum or oil contaminated soil. Such petroleum or oil poses a serious threat to the environment by endangering animal or plant species, including humans. Soils, sludges and similar substances contaminated with other organic compounds, such as insecticides and herbicides, may also be included in this same category, in which case pollution levels may vary from tens of parts per million (ppm) to significant percentages. Since all of the above mentioned types of pollution pose significant risks to the environment, toxic or harmful organic compounds must be removed from the soil or sludge and disposed of properly.

Another source of hydrocarbon compounds is sludge formed in petroleum storage tanks containing not only water but also significant amounts of inorganic solids, which must be properly disposed of before returning to the natural environment. Briefly, the various kinds of organic compounds mentioned above, soil contaminants and those compounds present in different kinds of sludge will be referred to herein as hydrocarbon compounds.

There are several methods of treating the above-mentioned contaminated materials. The most commonly used methods include incineration and centrifugation. However, as described below, these methods present serious limitations, and the present invention provides a superior and suitable alternative method.

Incineration is a common method (see, eg, “Chemical Engineering Handbook”, edited by R. H. Perry e C. H. Chilton, McGraw-Hill Book Company, 5th edition, 1973, 9-35 and 9-36). In particular, for the treatment of substances contaminated with hydrocarbon compounds. The contaminated material is fed to a rotary furnace with a suitable heat resistant lining. Gas or oil burners are used to maintain the temperature of the furnace in the range 500 to 1000 ° C., where air must be present in the furnace, at which temperature oxygen from the air burns the hydrocarbon compound partially or completely. The water contained in the contaminated material evaporates and leaves the furnace with the combustion gases. Residues of this method should in principle be substances free of toxic or harmful organic compounds, but the problems associated with the incineration process are: a) large amounts of effluent gases that require treatment (the effluent gases are air taken out of the process, toxic organic compounds); Gas from burner, gas from burner and water vapor); b) poor energy efficiency (most of the heat from the oil / gas burners leaves the furnace with the off-gas, so the typical energy efficiency for the whole process is less than 20%); c) the inability to recover the initial organic material (the hydrocarbon compound burns out, which represents a significant loss).

Centrifugation to separate liquids from solids is also a common operation (for example, "Chemical Engineering Handbook", edited by RH Perry e CH Chilton, McGraw-Hill Book Company, 5th edition, 1973, 19-87 and 19 -Page 98). Centrifugation is used to treat soil or sludge contaminated with hydrocarbon compounds (for example, US Pat. No. 6149345-A, PE Atkins, “Centrifuges, Vacuum Sources, Vents, Fractional Distillers (FS) and Filled Amounts). Relief of hydrocarbon compounds-contaminated soil or groundwater by means of a device comprising a detector, wherein the separated liquid is fed to the FS via a low shear pump ". In this application contaminated materials containing varying amounts of hydrocarbon compounds and water are fed to a rotating vessel called a centrifuge, where the liquid hydrocarbon compounds and water are separated from the solids contained in the contaminated soil or sludge by centrifugal force. As a result of this process, ideally, soil or sludge free of hydrocarbon compounds and water should be obtained and such organic liquid should be recovered. The problems associated with the centrifugation method are the inability to completely remove the hydrocarbon compound and that the soil or sludge after treatment still typically contains at least 5% by weight of organic contaminants.

The use of thermal plasma is a well-known method used to treat hospital waste and industrial residues, and to recover aluminum from foundry waste (dust) and the like. In this regard, R.N. See Szente (AIP Cinference Proc., N.345, p. 487, 1995). Thermal plasma is obtained by using an electric arc to heat a normal gas to a temperature of around 20,000 ° C. The device for generating thermal plasma is a plasma torch, which can have different forms, such as tubular metal electrodes or graphite electrodes. In any case, an electric arc is maintained between the electrodes to heat the gas. In this temperature range, the gas is partially ionized and called plasma, which is different from the outlet gas and can be used when high temperatures are required for the process or when ionized forms are required for certain chemical reactions or physical deformation of the material. Can be. The usual method of generating thermal plasma is obtained from a direct current power source as opposed to the alternating current used in metallurgical arc furnaces. A given residue will require a particular type of plasma system and reactor. Plasma methods for residues usually require a process temperature of about 1,500 ° C. in order to melt the inorganic compounds contained in the residues and also oxidize the organic compounds to generate carbon monoxide or carbon dioxide and water vapor.

In connection with the present invention, the following research data on the thermal plasma treatment of aluminum tailings, G. Dube, JP Huni, W. Stevens, S. Lavoie, "Recovering Non-Ferrous Metals from Tailings Using Plasma Tailings Process," United States Patent 4,960,460 should be mentioned in particular, which has some similarities to the method of the present invention in terms of operating conditions and heat transfer mechanism. In order to dispose of the aluminum tailings, once the material is fed into the rotary reactor, the door of the reactor is closed. Within the reactor, a graphite electrode is used in which a direct current electric arc collision occurs between the plasma torch or the electrodes in order to supply the energy necessary for the process while maintaining a controlled air pressure. Plasma torch or graphite electrodes are usually located in the center of the reactor. The method consists essentially of melting aluminum out of the tailings at a temperature of about 700 ° C. under a non-oxidizing atmosphere to avoid oxidation of the metal recovered. Water should not be present in the aluminum tailings as it can be oxidized or reduced from molten aluminum to hydrogen, causing an explosion. The method is carried out in batch form. Once the aluminum contained in the tailings is melted, the reactor is opened and the liquid metal is poured into the mold. Other compounds, mainly aluminum oxide, are removed from the reactor and filled with another charge. This method works well for treating aluminum tailings but is used for other types of residues in that it is essentially a batch process, does not provide off-gas, and hardly any material melts at 700 ° C for the desired separation. There is no bar.

It is an object of the present invention to treat soil and / or sludge contaminated with various hydrocarbon compounds, toxic or harmful compounds such as petroleum, oil and / or pesticides and herbicides and similar organic compounds, or to form at the bottom of a petroleum storage tank. A method for removing hydrocarbon compounds contained in sludge and a suitable apparatus thereof are provided to overcome the problems of the conventional methods that have been used in the industry.

More specifically, an object of the present invention is a plasma method and a suitable apparatus for treating soil and / or sludge contaminated with hydrocarbon compounds, due to its technical characteristics, compared to other known methods for the treatment of similar substances. It is to provide a plasma method and apparatus that provides the following advantages:

a) removal of less than 0.1% by weight of soil or sludge contaminants;

b) continuous operation process;

c) recovery of contaminants, if desired;

d) high energy efficiency of the process; And

e) small or small amounts of treatment gas.

The plasma method and apparatus of the present invention and the details thereof are as described below.

The plasma method developed by the present inventors utilizes a plasma system to provide sufficient energy for contaminated soil or sludge so that hydrocarbon compounds can evaporate. The normal operating temperature of the proposed plasma process is between 400 and 900 ° C. so that all hydrocarbon compounds contained in the material to be treated can be evaporated. After leaving the plasma reactor, the evaporated compound is collected in a condenser where the hydrocarbon compound can be recovered in the form of liquid hydrocarbons (oil) when treating petroleum or oil contaminated soil / sludge. Water contained in contaminated material is also evaporated during the process and collected in the condenser. Contaminated soil or sludge is continuously fed into the reactor from one end of the reactor, while oil-free soil or residue is removed from the other end of the reactor. The air pressure in the plasma reactor is maintained at a non-oxidizing pressure, i.e., in a neutral or reducing atmosphere, which prevents oxidation of the hydrocarbon compound and evaporates the hydrocarbon compound in the reactor to cool outside the plasma reactor. To recover later.

Compared with the usual incineration method, the main advantages of using a plasma system to treat the above mentioned residues are as follows. That is, a) high energy efficiency, which means that the plasma jet is at a much higher temperature than the flame generated by the oil or gas burners used in the incineration process (typically 15,000 ° C for plasma ejection, and the oil Or 2,000 ° C. for gas flames), the heat transfer depending on the energy source and the temperature of the material being heated is significantly higher in the plasma method, substantially increasing the energy efficiency of the plasma method. Compared to the energy efficiency of approximately 20% of ordinary gas or oil burners, the plasma method usually yields an efficiency of at least 80%. b) Recovery of hydrocarbon contaminants is possible, which may be an important process benefit, especially if the soil or sludge contains more than 10% by weight hydrocarbon compounds. c) The volume of effluent gas to be treated is significantly lower, which is comparable to the volume of gas produced when burning oil or gas in the burner, and the plasma torch can be operated with a small amount of gas and also consists of evaporated organic compounds. This is because the outflow gas by the plasma method can be easily cooled to obtain a negligible amount of exhaust gas. Compared with the centrifugation method, the main advantage of using the plasma method to treat the above-mentioned residues is the complete removal of contaminants from the soil and sludge, which is 5% by weight of the hydrocarbon compound remaining after the centrifugation method. And advantageously compared.

The proposed method, together with the apparatus, has the following differences and advantages in treating contaminated soil or sludge compared to conventional plasma methods used to treat aluminum tailings. a) In the method and apparatus of the present invention, contaminants are continuously supplied and clean substances from which the contaminants have been removed are continuously removed, but this is not possible with the conventional aluminum tailing method. b) In the process of the present invention contaminants evaporate and leave the reactor continuously in gaseous form, but in the case of aluminum tailings the contaminants remain in the reactor until the batch cycle ends. c) In the process of the present invention the gas can be cooled immediately upon leaving the reactor to recover hydrocarbon compounds from contaminated material. d) The aluminum tailing plasma process produces a small amount of gas, which is neither normally removed nor subsequently processed from the reactor interior during the process.

A description of the apparatus used in the above-described method for treating soil or sludge contaminated with hydrocarbon compounds using thermal plasma will be provided below with reference to the accompanying drawings.

Figure 1 is a block diagram illustrating the main steps of constructing the method of the present invention.

Continuous feeding of residue into the A-stop (non-rotating) reactor;

Heating the residue to a temperature of 400 to 900 ° C. under a non-oxidizing atmosphere using a B-plasma system;

C- initial evaporation of water and hydrocarbon compounds present in the residue and subsequent removal of the resulting gas;

Cooling of the effluent steam in a vessel (condenser) located outside of the D-reactor, or burning of steam to generate energy;

Removal of solids free of E- hydrocarbon compounds.

2 is a side view of the device proposed for carrying out the developed method, and FIG. 3 is a front view of the device shown in FIG. 2. Reference numerals in the figures have been used to identify different devices.

The apparatus comprises a supply system (1), a fixed (non-rotating) reactor (2), an internal mechanism, a rotating screw (3) for transporting the residue into the reactor, and a graphite electrode holding a direct current electric arc (5). It consists of an internal mechanism, such as a plasma system (4). At the same end of the feed system there is a tube 6 or other means for removal of the evaporated compound. The evaporated compound is passed through a condenser 7 located outside the plasma reactor. A normal fan or blower is used to remove the effluent gas from the reactor and pass it to the condenser. The hydrocarbon-free material is removed by gravity through the outlet (8), the inlet valve (9) or similar device prevents air from entering the reactor, and the clean material, free of contaminants, enters the silo (10). Is collected.

The method of the present invention can be understood as follows according to this figure. The material containing the hydrocarbon compound is fed into a plasma reactor, heated to a temperature of about 700 ° C., and the water present in the hydrocarbon compound and the residue is evaporated. When treating soil or sludge contaminated with petroleum, oil or similar hydrocarbon compounds, the outlet gas is passed through a condenser to recover valuable hydrocarbon compounds. The contaminated material is gradually free of organic contaminants as it passes through the reactor and becomes very clean once it reaches the outlet chute to be removed from the reactor.

The proposed device for treating soil / sludge contaminated with organic material has some basic differences with respect to the above-mentioned device used for treating aluminum tailings, among which the following are particularly notable.

a) The device of the present invention is a fixed container comprising a conveying device that moves to transport material into the reactor, whereas the device used to treat aluminum tailings consists of a rotating container having no movable parts in the reactor; b) The apparatus of the present invention comprises a continuous feeding device for contaminated material and another device for continuously removing clean material, but the aluminum tailings device is a batch process; c) The apparatus of the present invention comprises an exhaust pipe and condenser for the effluent gas and / or a gas cleaning system, whereas the apparatus for treating aluminum tailings has no device for the removal and treatment of gases during operation.

It is evident that many details of the invention can be modified within the scope, method and scope of the claims. For example, it is disclosed herein that the conveying system consists of a rotating screw, but this is only one of the possible forms of operation. An alternative may be a vibrating conveyor. Similarly, a device having a plasma system at one end of a fixed vessel as a suitable device for carrying out the method has been disclosed, but one or more plasma torches or a pair of graphite electrodes may be installed to provide the required process energy. will be.

Typical of the device of the present invention was made to develop the method of the present invention. Contaminated soil containing 5 to 90% by weight of petroleum or oil was fed into a plasma reactor similar to that described above. The temperature in the plasma reactor was maintained at approximately 700 ° C. using direct current electric arc bombardment between the graphite electrodes disposed at one end of the reactor, and the contaminated material was fed to the opposite end of the reactor as described above. The contaminant-free material was removed from the reactor and the effluent gas passed through the condenser and released into the atmosphere. The materials were analyzed before and after the start of the process, respectively. Analyzes in an independent analytical laboratory (Laboratorio Bauer-Abbo S / C Ltda, R. Aquininos, SP, Brazil, email: bauer@falcaobauer.com.br) show the relationship between the initial composition and the content of organic pollutants in the soil. Without, the contaminants removed after the plasma method contained less than 0.05% of organic compounds, which are believed to be free of contaminants. The hydrocarbon compound was recovered from the test in a condenser outside the reactor and could be reused for another application.

Claims (6)

Using a plasma torch to transfer heat to contaminants consisting of soil contaminated with hydrocarbon compounds or residues containing hydrocarbon compounds, and placing the plasma torch at the opposite end of the reactor to which the contaminants are supplied; Continuously feeding the contaminant to one end of the reactor; Maintain the reactor in a non-oxidizing atmosphere while treating the contaminants in the reactor; Continuously heating the contaminant in a temperature range of 400 to 900 ° C. while the contaminant moves from one end of the reactor to the opposite end of the reactor in which the plasma torch is placed; Continuously removing the treated material from the opposite end of the reactor; A method of treating soil-contaminated soils or residues containing hydrocarbon compounds, consisting of continuously cooling hydrocarbon compound vapors outside the reactor to recover them as oils and simultaneously cooling water vapor to water. The hydrocarbon compound is continuously evaporated to produce an organic compound vapor, and the water originally present in the contaminant is also evaporated; The hydrocarbon compound vapor is continuously removed from one end of the reactor that is identical to one end of the reactor to which the pollutant was supplied; A negligible amount of gas is treated since the outlet gas consisting of the steams produced above is cooled outside the reactor to form oil and water, Wherein said treated material that is continuously removed contains a negligible amount of hydrocarbon compound, wherein the soil or hydrocarbon compound contaminated with a hydrocarbon compound. 2. The method of claim 1, wherein the plasma torch consists of graphite electrodes with an electric arc held therebetween. The method of claim 1, wherein at least one plasma torch is provided inside the reactor. delete delete delete

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