Field of Invention

The present method belongs to treatment, recovery, decontamination, transformation, and elimination of solid, liquid, and gaseous constituents in waste and pollutants and in polluted soil and waters, including in- si tu soil and water treatment, wherein the treatment is facilitated by combusting fuels with oxidizers which do not form combustion gases.

Prior Art

The pertinent methods are facilitated by or rely on heat. Thermal waste treatment, including incineration, wet oxidation treatment of liquid waste and sludges with air or oxygen under pressure, various chemical, physical- chemical, and biological processes with heating are examples of such methods. These methods can be used for solid, liquid, and gaseous waste treatment in various reactor types and in-situ for soil, groundwater, or bodies of water. The treatment will result in conversions, immobilization, and transportation of waste and polluting constituents. Waste conversions include any chemical reaction or physical chemical action known to those skilled in the art and useful for such a treatment . Oxidation, reduction, fragmentation, polymerization and other reactions are few examples of such conversions. Immobilization includes chemical and physical chemical binding, such as in vitrification, producing alloys,

adsorption, ion exchange, etc. Transportation involves material transfer within the same phase, or between phases, or mechanical motion of material. Such material transport facilitates other treatment processes.

Combustion of carbonaceous fuels, and many variants of electrical heating are normally used for the above purposes. Disadvantages of the carbonaceous fuel combustion methods include the generation of large quantities of combustion gases which often need treatment, the low efficiency of heat utilization, and the complexity of apparatus and controls required. Disadvantages of electrical heating are the very high energy demand and low energy efficiency, the complex and heavy equipment required, and, consequently, the very high costs. Some modifications of electrical heating methods, for example, soil electromelting, cannot be used at temperatures lower than the soil's melting point to insure adequate electroconductance. Additionally, soil electromelting in- situ can be done only from the top down. It cannot be applied to a desired contaminated zone at a specified depth below the surface without melting the soil above. The maximum treatment depth in electromelting methods is limited to 7.5 m.

Summary of the Invention

The objectives of the present invention include but are not limited to the following: (1) to provide a thermal method of waste treatment that does not generate fuel combustion gases and eliminates or significantly reduces

formation of other gases, (2) to provide a simple, efficient, and inexpensive method of waste and pollution treatment, and (3) to provide a method allowing soil treatment in-situ at any location of the contaminated zone, or at any desired depth. Other advantages will become apparent from the ensuing description of invention and selected embodiments thereof.

These objectives are achieved by placing a combustible charge within the waste or pollution treatment zone (the treatment zone) , supplying an oxidizer to the charge, igniting and combusting the charge without formation of gaseous products, and using the heat of combustion for facilitating the required waste treatment by changing, immobilizing, and transporting constituents of the waste and pollution.

For example, metal charges can be combusted with either oxygen or metal oxides, or combination of both oxygen and metal oxides as oxidizers. When using oxygen as oxidizer, aluminum or iron are preferable combustible materials but other metals, Mg, Ca, Zn, Co, etc. are acceptable in particular systems. With metal oxides as oxidizers, thermite mixtures can be used. The most common thermite mixture is made of aluminum powder and iron oxides (Fe ₂ 0 ₃ ) , although numerous other thermite mixtures are known and can be used. In oxygen combustion of metals, metal oxides are formed. Thermite of aluminum powder and iron oxides produces aluminum oxide and metallic iron. Other metal-metal oxides result in other metal and metal oxide products. Both processes, metal

combustion with oxygen and thermite combustion, can have high combustion temperatures and large heat generation. Combustion gases are not formed when properly selected charges combust with these oxidizers. Accordingly, no heat is lost with the gases and a high heat efficiency is achieved.

Nonmetals, for example elemental silicon, or metal- nonmetal alloys, for example, ferrosilicon, can also be used as a fuel, and oxides of nonmetals can also be oxidizers. Such components are included in the fuel- oxidizer combinations of the present invention if they do not produce combustion gases. Therefore, mentioning of metals and metal oxides herein does not mean that nonmetals and oxides of nonmetals are excluded from the fuel-oxidizer types usable in this invention. On the contrary, particular applications may favor the use of nonmetals. Metal scrap can be used as combustible charges, and many metal oxide dusts, a waste generated in metallurgical industries, can be used as oxidizers.

In summary, the present invention is a thermal method for facilitating waste and pollution treatment by changing, immobilizing, or transporting constituents in at least one waste or pollution treatment zone, comprising steps of placing a combustible charge in the treatment or pollution zone and providing an oxidizer to the combustible charge; igniting and combusting the placed combustible charge with the oxidizer without forming gases from combusting the placed combustible charge; and releasing the heat from combusting the placed combustible

charge and facilitating treatment of the waste and pollution by changing, immobilizing, or evacuating the waste and pollutants.

The waste or pollution treatment zone (treatment zone) can be a polluted soil treated in-si tu, a reactor or a section of a reactor for processing solid material, a reactor for processing liquid material, a reactor for processing gaseous material, or combinations thereof. Batch and continuous reactors, and pressurized and nonpressurized reactors can be used. The treatment can include thermal treatment methods, wet oxidation methods, wet reduction methods, chemical methods, physical-chemical methods, biological methods, mechanical-effects methods, in-si tu soil treatment methods, and combinations thereof. Selected in-si tu and in-reactor treatment methods are described separately in the subsequent sections.

Multiple combustible charges can be placed in the waste or pollution treatment zone in the configuration selected from the group comprising positioning charges along a line, a wall, a block, an encirclement, a grid, a continuous area, and an envelope. Such positioning of combustible charges can be beneficial for waste treatment in reactors because it can increase the heat transfer over the reactor volume. For in-si tu soil treatment, additional advantage is in forming molten barriers to the flow of groundwater and pollutants and in confining the pollution within the encirclements and envelopes.

In- Si tu Soil Treatment

The combustible charges can be placed in the contaminated soil area to be treated by using vertical, inclined, or horizontal boreholes, excavations, hydraulic punch holes, or other means. The charges can be positioned at any depth in a borehole, well or excavation under structures, roads, and waterways. Single or multiple combustible charges in each well or in multiple wells can be used. The charges can be covered and confined in pressurized volumes to hold a pressure and to facilitate outward dissipation and filtration of gases, vapors and liquids, or water solutions of reagents or other additives near the charges.

The volume of soil enveloped by an imaginary boundary within which the desired operational conditions (for example, temperature) are established upon combustion of the substrate charge is called herein the zone of influence. The radius of this zone is the radius of influence. Besides temperature, other conditions, may also be operable in determining the zone of influence. Such conditions will be discussed later. The radius of influence has a dynamic nature. Due to the outward heat transfer from the center of the zone, the radius where a desired temperature (or other conditions) is established changes in time. Accordingly, a conditional radius of influence, for example, established as a preset time after combustion, can be used. This time can be determined based on technical considerations (e.g., nature of soil and pollutants) and economic considerations.

Depending on temperature regimes within the treatment zone the heat treatment can be conducted as follows: (1) vaporization of the media to be extracted from the waste or soil (100 °C for water or other specific temperatures for various organics) , (2) contaminant pyrolysis (250 °C to 400 °C, depending on the organics) , (3) high temperature combustion of pollutants (600 0°C to 1000 °C) , (4) waste-contaminant or soil-contaminant vitrification (usually, greater than 1000 °C) . Waste vitrification can be improved by providing sand, glass, and other means for creating glass-like or rock-like vitrified mass. In the vaporization mode, the vaporized matter is evacuated, collected, and may be treated, for example, at a wellhead or at an exit port of a combustion apparatus . Separate collection wells for vaporization gases can be provided. The carboneous residue of the pyrolyzed matter will stay in the treated soil as harmless materials, while carbon dioxide, water vapor, hydrogen and other gaseous products will be either confined in the soil, or discharged and treated, if needed, at the surface. The high temperature combustion occurs in the presence of an oxidizer provided for the incineration of pollutants. This oxidizer is delivered to the reactor or a soil stratum in the treatment zone and can be the same or different from the oxidizer used to combust the charge. Incineration products are mainly carbon dioxide and water vapor. Sufficiently complete destruction of organics occurs in the high temperature combustion and in many cases the gaseous products can be discharged to the atmosphere. If needed, gases can be treated by chemical means. For example, they can be brought in contact with alkalies to

bind acid gases, such as chlorides, sulfites, carbonates. Other reagents can be used as needed for binding specific pollutants in the waste combustion gases . Physical or physical chemical gas treatment means, for example, gas cooling for condensing the target gaseous or vaporized constituents, can also be used. These gas treatment means are known to those skilled in art. In case of vitrification, the destruction of organics may occur as a complete oxidation with an ample oxidizer supply, or as a reduction and/or pyrolysis with deficient oxidant supply. Mineral constituents of waste or soil and the contaminants, including the radioactive nuclides, will be vitrified into a consolidated rocklike or glass-like material. Accordingly, the remaining contaminants are immobilized in the vitrified material. This material is virtually unleachable, and the treated waste or the treated soil are impermeable to water. Vitrified soil also has an increased bearing capacity as compared to the loose soil.

The borehole space above the combustible substrate may be plugged. In case of moist or wet soil and a sufficient supply of oxidizer, wet oxidation conditions, or, at appropriate temperature and pressure, supercritical oxidation conditions can be created in the treatment zone. All solid, liquid, and gaseous products of these reactions are expected to be harmless and may be retained in the soil or allowed to gradually diffuse within the soil and to the atmosphere. In dry soils, water or steam may be injected to the combustion zone to facilitate the supercritical oxidation. To address the formation of

chlorides or hydrogen chloride, alkalies can be added, for example, as a water solution to the treatment zone. Wet or supercritical oxidations may be complemented with the addition of reagents, for example, hydrogen peroxide. Reducing conditions helpful for dehalogenation of organics may be enhanced by addition of a reducing substance, for example, methane, propane, or hydrogen, or other gaseous, solid or liquid fuel to the treatment zone. The destruction of organics can be further improved by cycling the oxidizing and reducing conditions in the combustion and treatment zones. Such cycling can be achieved by intermittent increase and decrease in supply of oxidizer and corresponding decrease and increase in supply of reducing substances.

In cases of treating water saturated soil layers, water can be initially displaced near the combustible substrate with compressed oxygen, air, nitrogen, water vapor, or other gases. After that, the water will be pushed outward from the combustion front by the vapors generated from the heating of the moisture at this zone. Water present in the soil or added to the treatment zone can form steam that can be used to vaporize organic pollutants and carry them to the surface for treatment or utilization.

To accelerate the heat propagation within the zone of influence in the soil, the melted material can be dispersed by fracturing the surrounding soil and forcing the molten body to flow into the fractures and outward from the melted core. Accordingly, the heat is spread out

faster than by a simple heat transfer in the soil. One way to produce soil fracturing can be by injecting water into the molten body thus blasting and rupturing the soil around the molten mass and creating an elevated pressure which propels the molten material in the ruptures.

In treatment of polluted groundwater strata, the method can be further improved by providing metals in the melt and dispersing the melted metal into slugs, pieces, and particles in the described ruptures in the soil. The dispersed metal will react with organics (a reaction known as zero metal reduction of organics) and with many heavy metals (a process known as cementation) thus eliminating many organic and metal containing pollutants or rendering them immobile, and/or nontoxic. This process modification can be further improved by providing two metals in the melt so that bimetal particles will be formed and dispersed by blasting into the soil ruptures. The process can be even further improved by providing a reagent for inducing a cementation driven migrational process on the surface of the metal pieces dispersed into the soil ruptures. The reagent (s) include salts of noble metals or other noble species, indifferent ions, and active anions. The physical chemical processes at the metal surfaces in reactions with organics and heavy metal salts are described in the US Patent No. 5,348,629 and in papers: Boris M. Khudenko "Mathematical Models of Cementation Processes", Proceedings of the Environmental Engineering Div., Am. Soc. of Civil Eng., 113: 681-701 (1987), and Boris M. Khudenko "Feasibility Evaluation of a Novel

Method for Destruction of Organics", Water Science and

Technology, Vol. 25, Kyoto, pp. 1873-1881 (1991) . The teaching of these articles is incorporated herein by reference. Single metal can be provided, for example, in reactions with thermites which always result in a metal in the molten products. In cases of metal combustion with oxygen, an excess metal can be provided. This metal excess will be melted but will not be combusted due to the controllable supply of oxygen. Bimetal can also be produced using thermites by either adding a metal which is not reacting in the thermite mixture, e. g. copper in aluminum-iron oxide mixture, or by using an excess of a reacting metal. For example, excess aluminum in aluminum- iron oxide mixture will result in a melt containing metallic aluminum and metallic iron. Bimetal can also be formed in the metal combustion process by adding a second metal to the charge, or by combusting an alloy. In either case, excess of both metals must be provided and metals will be only partially combusted. Addition of a noble metal salt or several salts, for example, a copper salt, to the combustible charge, of to the water used for blasting can be used.

The method can be further improved by adding reagents and/or microbial inoculum to the water at the well bottom, or by putting a water solution with reagents and inoculum in the well, placing a combustible charge above the water solution and separated from it by a layer of insulator, and plugging the well from the charge up, combusting the charge and producing melted body, adding a water slug to the melt and producing a blast in the confined bottom section of the well, whereby the soil around the well

bottom is fractured and the solution of reagents and/or inoculum is pushed in the soil around the well, wherein the reagents and inoculum are used for treatment of pollution. Such a pollution can be associated with the groundwater, or the soil, or both.

In-Reactor Treatment

Thermal treatment methods such as vaporization, pyrolysis, high temperature combustion, vitrification, and combinations thereof can be facilitated by using fuel combustion that does not produce combustion gases. For example, combustion products will be reduced in pyrolysis thus making product utilization easier. Chemical treatment assisted by this combustion can be conducted with reagents added to treatment zone, and/or reagents generated while combusting the combustible charge, or combination thereof. In one process modification, as previously described, the reagents generated in the combustion process and added to the treatment zone can be zero valence (sacrificial) metals, bimetals, noble metal ions, indifferent ions, active anions, and combinations thereof. Further, water, oxidizing or reducing agents, and pH-control means can be added to the waste or pollution treatment zone. The biological treatment processes, for example, anaerobic digestion, can be assisted by combustion that does not produce combustion gases. The mechanical-effects treatment steps can include the following: 1) the generation of water vapor and corresponding pressure elevation in the treatment zone, 2) increasing gas pressure via heating by combusting the combustible charge, 3) blasting the products of combusting

of the combustible charge in the waste or pollution treatment zone and 4) fracturing the material in and around the treatment zone and depositing reagents and other materials facilitating treatment in the fractures.

A wet (or supercritical) oxidation process with heating by a combustible charge placed in the pressurized reactor is significantly simpler than conventional wet oxidation processes. The use of solid or liquid oxidants, for example, magnesium peroxide or hydrogen peroxide solution, further simplifies the wet oxidation process by eliminating the need in oxygen storage, supply, and control systems. Similarly to wet oxidation, wet (or supercritical) reduction can be used. The required heat or part of this heat can be provided by a combustion charge that does not produce gases in a pressurized reactor. Wet reduction can be achieved with addition of reductants (carbonaceous material, hydrogen, or sacrificial metals) . In wet reduction with aluminum-iron oxide thermite charge, metallic iron is produced.

Metallic iron will react with many heavy metals and reduce them. It will also react with organics and transform them into harmless constituents, especially at elevated temperatures . The process can be further improved by using a couple formed by iron and a more electropositive metal, such as copper. The matter transformation can be even further improved by using migrational electrochemical processes with sacrificial metals, noble species, for example, ions of copper, indifferent ions (potassium, sodium) , and active anions (chlorides, sulfates) in the

solution or suspension being treated (see already cited US Patent No. 5,348,629) .

Small amounts of waste can be treated in a disposable reactor-container filled with waste and fitted with a combustible charge that does not produce combustion gases. If needed, such containers can be provided with means for treatment or absorption of the gases generated from the waste treatment. The container-reactor can be used for a single combustion operation, or it can be refitted with new combustion charges till the entire usable volume of the container is depleted. The treated material and the container can be disposed together, or the container can be reused. The apparatuses for carrying out present method are very simple because there is no need in complex exhaust gas treatment systems, or in complex electric power supplies and power conversion systems.

The rate of combusting the charge that does not produce combustion gases can be dynamically controlled by the rate of oxygen supply. The process temperature and pressure can be controlled by selecting combustion charge materials and mass during the design stage, and by sensing temperature, pressure and process specific parameters known to those skilled in the art for controllably interrupting, varying, or restarting the supply of oxygen and/or other gases, additives and reagents. Other controls can include oxidation-reduction potentials, pH, and other process specific parameters. These parameters can also be controlled by additions of various reagents and varying fuel to oxidizer ratio.

Brief Description of the Drawings

Fig. 1 is a vertical cross-section of a borehole in a system for thermal treatment of soil . Fig. 2 is a cross-section of an alternative configuration of a borehole in a system for thermal treatment of soil .

Fig. 3 is a cross-section of a block of a combustible substrate.

Fig. 4 is a view along lines A-A in Fig. 3. Fig. 5 is a plan view of the wall arrangement of boreholes.

Fig. 6 is a plan view of the grid arrangement of boreholes.

Fig. 7 is a plan view of the block arrangement of boreholes.

Fig. 8 is a plan view of the area arrangement of boreholes .

Detailed Description of Embodiments

Fig.l illustrates a system for treatment of contaminated soil comprising a contaminated soil zone 1, a borehole 2 in the soil layer 50, an optional well casing 3, a block of a combustible substrate 4, a pipe 5 attached to the block 4 for oxidizer supply, fittings 6, 7, and 8 attached to pipe 5 for connecting the source of oxidizer, for example, oxygen, and optional supply of combustible gases, nitrogen, water, or steam, an ignition means 9, for example, an electrical igniter, wires 10 and 11, clamp 12, ignition power source 13, and a switch 14 constituting with the pipe 5 and ignition means 9 the ignition circuit,

an optional plugging material 15, such as soil, sand, concrete, or other material placed above the combustible substrate 4. A single block, or charge, of the combustible substrate or several stacked blocks can be used.

Fig. 2 illustrates a modification of the borehole system given in Fig. 1, in which many elements are the same and their description is not repeated. In the system of Fig. 2, the plug 15 is not used, and means 16, for example, a metal dome, is provided for the exhaust gas collection. Means 16 is tightly attached to the pipe 5 using a fitting 18, and secured to the ground surface using a barrier 19 anchored into the ground. A fitting 17 is provided in the gas collection dome 16 for evacuating the collected gas to a gas treatment unit.

Figs. 3 and 4 present one possible design of the combustible block 4. It comprises a cylindrical body 20, a top plate 21 tightly secured to the body 20, and a fitting 23 attached to the top plate 20 and intended for connecting pipe 5 for oxidizer (and other gases) supply. The internal space in the body 20 is densely packed with generally linear strands of wire made of combustible substrates. The generally longitudinal holes spaces between the wires provide passages for the gases fed into the block. Ignition means 9 shown in Figs. 1 and 2 is secured under the block 4. Combustible blocks can be arranged serially within the borehole and combusted sequentially using one or more igniters.

Combustible blocks holding thermite charges can be constructed of a variety of materials and in a variety of shapes. The charge can also be divided into sections that will be combusted sequentially. Sections can be separated from each other by layers of a mineral insulation material to delay the ignition of each consecutive section. Optionally, oxygen supply, and supply of other gases, neutral or reducing, to the thermite charges can be provided.

Metal charges combusted with oxygen and thermite mixtures can be combined.

Referring now to Figs. 1, 3, and 4 the system is operated as follows. Borehole 2 is made (optionally fitted with casing 3) , blocks 4 with ignition means 9, wires 10 and 11, clamp 12, and switch 14 are installed, plugging material 15 is optionally put in the top of the borehole 2, sources of oxidizer, and optionally, combustible gas, water or steam, or nitrogen are connected via lines 6, 7 and 8 to the pipe 5, the ignition power source is connected to wires 10 and 11. Switch 14 is turned to ignite the ignition means, the oxidizer is supplied and blocks 4 are ignited. The oxidizer flows through the line 6, pipe 5, and through the longitudinal spaces inside the block 4 to the bottom of the block 4 resulting in combustion from the bottom up.

While combusting the blocks 4, solid metal oxides are formed and heat is liberated. This heat is spent for at least a partial melting and for heating soil next to the

borehole. The border of the zone of influence is marked by numeral 49. Simultaneously with the melting and heating within the zone of influence, moisture and volatile constituents in the soil will be vaporized and several chemical transformations as previously described may occur.

The described system can be used in dry and in water saturated soil. In the latter case, at least part of the borehole should be plugged with a material allowing a pressurization of a volume under the block of combustible substrate. Oxygen, air, or nitrogen, under pressure is pumped into block 4 for displacing water in the zone next to the ignition means and the combustible charge. Upon igniting the combustible block, water will be further displaced by the steam formed in the space around the combustion zone.

Under operating conditions, some gases may be formed in the thermal transformations of inorganic and organic constituents of the soil. These include, mainly, steam from water vaporization, and carbon dioxide and water vapor from organic and inorganic transformations. These gases do not need interception, collection or treatment.

If a thermite mixture is the substrate, the block 4 can be a canister with a thermite mixture. In such a case, oxygen supply is optional. The thermite is ignited by the ignition means 9, heat is liberated and soil treatment is effected. All other features are the same as

in the case of the metal substrate-oxygen system and are not repeated.

Referring now to Figs. 2, 3, and 4, the system is operated as follows. In cases when the volatile organic or inorganic constituents are formed in the thermal reactions in the soil, for example, hydrochloric acid, they may flow between the walls of the borehole 2, or the casing 3, from the borehole and into the collection dome 16, and further through the fitting 17 to a gas treatment unit. A special gas collection well placed in an appropriate location can also be provided. Optionally, steam can be formed at the combustion zone using either underground or added water as described above. The steam can vaporize organic pollutants and carry them to the wellhead for treatment or utilization.

Alternatively, there are possibilities of intercepting volatile constituents in the borehole, for example, by neutralizing hydrochloric acid using lime or other alkaline material placed above the combustion block 4 in the borehole.

Referring now to Figs. 5 through 8, there are shown several possible layouts of boreholes that may be used to fulfill the particular needs of the site. Fig. 5 is a wall configuration. This configuration may be used as a cut off wall for stopping a flow of groundwater. Fig. 7 is a block configuration, which possibly can be used to improve the bearing capacity of the soil. In such a case, substantial melting and solidification are required. Fig.

6 is a grid configuration that can be used for confining the soil pollutant from spreading with the groundwater flow. Fig. 8 is an area type layout that should be used in case of a complete cleanup of the polluted site. Optionally, tridimensional positioning of charges can be used. For example, charges can be placed at lower and upper boundaries of the area to be treated. The charges can form a tridimensional envelop surrounding the volume to be treated. Other encirclements can also be used. More than one charge may be placed in a single borehole at different distances from the borehole's mouth. The order of firing in cases of wall, block, grid, and area configurations should be established to reduce heat dissipation and losses. The mass of combustible substrate and oxygen, or the thermite mixtures required, will be least in case of simultaneous firing of all boreholes. However, this may be not always practicable. Then, a section by section firing should be performed saving the heat of the previous firings in the zones of the sequential firings.

Thermal treatment of water saturated soil can be advantageously combined with the pumping and treating the groundwater. For example, the contaminated area is circled by an impermeable wall or a grid of walls made by the described method thus providing an encirclement. Groundwater is pumped from the inner area of the wall, or from multiple areas. This water is treated and discharged beyond the contaminated site. Dried, or largely dried, the area is now treated using the area layout of the boreholes (Fig. 8) thus rendering the soil clean.

A computational analysis of the present system for in-si tu soil treatment showed that the system is technically and economically feasible and advantageous over the prior art. The basic embodiments described herein are examples of possible systems using in-si tu combustion of charges producing no fuel combustion gases during soil treatment. Other embodiments describe cases with very small generation of gases to be released from boreholes. Yet other embodiments exemplify several versions of in-reactor waste treatment. Various other modifications are also possible. It will therefore be understood by those skilled in the art that the particular embodiments of the invention here presented are by way of illustration only, and are not meant to be restrictive in any way; therefore, numerous changes and modifications may be made, and the full use of equivalents resorted to, without departing from the spirit or scope of the invention as outlined in the appended claims.