CA2079508C - Method and apparatus for rendering waste substances harmless - Google Patents

Abstract

A method and apparatus are provided for the treatment of hydrocarbon-contaminated soil by chemical hydrolysis and/or oxidation of the hydrocarbons in the hydrocarbon-contaminated soil. The method includes conditioning lime with a particularly-specified fatty-acid activator. The conditioned lime is blended with physically-preconditioned, moist, hydrocarbon-contaminated soil, the degree of blending being at least near microscopic level. A charge of the blended lime/soil is conveyed to an enclosed reaction vessel, where hydration of the lime is carried out. The heat of the hydration reaction is retained within the vessel, so that hydrolysis of the fatty acid conditioner and/or hydrocarbon contaminants in the soil is effected. Air or oxygen-enriched air is substantially-simultaneously introduced into the reaction vessel together with steam and/or water as required by the chemical reactions, thereby to effect a flameless, intermediate-temperature oxidation of the hydrocarbons and their hydrolysed degradation products. Decontaminated soil product is discharged from the reaction vessel by passing the decontaminated soil product, in dry, dusty, hydrophobic form, through a treating zone where it is sprayed with a surfactant. The surfactant-treated solid is passed to a blender where it is mixed with sufficient water to provide a substantially dust-free decontaminated soil product.

Description

2079~08 This invention relates to a process and system for the treatment of hydrocarbon-contaminated soil.
For some time now, the art has been faced with the problem of the treatment of hydrocarbon-contaminated soils.
Such a problem relates to soil which may have been contaminated through intentional or accidental spills of petroleum oils, hydrocarbon solvents or other, semi-volatile or non-volatile organic materials. Such contaminants may extend over large tracts of land and may directly or indirectly, e.g. through subsequent contamination of an underlying aquifer, constitute an extreme threat to wildlife, vegetation or human health.
Conventional methods, e.g. land farming are not very suitable.
Another problem relates to oil well sumps. Oil well sumps are artificial pits used as dump sites for all kinds of liquid and viscous wastes. The physical consistency of the sump varies according to the random materials dumped.
Typically, however, in the absence of a water layer, the consistency is pasty. Inasmuch as sumps create traps for wild fowl, there is an increasing demand for elimination of sumps, especially those not being commercially used. In addition, they are unsightly. The traditional treatment has been to dump and mix dirt into the sump and thereby soak up sufficient of the oil until the dirt-sump material can be moved by conventional equipment. The mixture is then spread to dry. This treatment has not been acceptable because the mixture bleeds oil and chemicals. Over months 2Q79~

and years, this dirt-sump mixture oozes oil and becomes almost as objectionable as the original oil sump. This unsatisfactory type of treatment has called for an improved solution to the ecological problem of sump elimination.
The increasing use of hydrophobic substances, e.g.
oils and oily substances, as well as macromelecular substances, has created new problems which arise mainly out of the handling of these substances. Particularly, the use of old oil, heating oils, lubricating oils and diesel fuels often leads, either intentionally or through negligence, and often due to emergency situations, to dangerous contamination of the environment.
There are a number of methods for rendering harmless such oils or oily substances which, in a single phase or in multiple phase systems, entail an endangerment of the environment. For example, oil can be chemically reacted by being burned, for example, or biologically degraded. The combustion method used frequently in combatting oil damage results in considerable air pollution if the burning is performed in the open rather than in expensive combustion apparatus.
The use of adsorbents solves such problem only when the oil can be fixed with them in such a manner that it is chemically unaltered but is encapsulated or otherwise isolated or is accessible to biological degradation and no longer constitutes any danger to the environment. With the known adsorptive agents, e.g. activated charcoal, kieselguhr or bentonite, waste oil, for example, can be 2~9!~

adsorptively bound only with difficulty. Large amounts of oil may cement the adsorptive agent, especially in the case of high-viscosity oils, making further processing difficult.
It has furthermore been proposed in various ways to treat porous mineral substances with hydrophobic substances for the purpose of improving their adsorptive characteristics. In this manner hydrophobic waste substances can be preferentially bound, while the water is no longer primarily absorbed. In such adsorptive agents, such as hydrophobized pearlite, however, the absorptive capacity is greatly reduced, since the mineral starting material is partially sealed by surface treatment with hydrophobizing substances, so that the inner cavities are no longer accessible.
It is particularly important that the substances which are adsorptively bound by the known processes are so fixed on the adsorptive agent that they no longer constitute any danger to the environment.
In addition to the general, mainly unsatisfactory procedures for the problems of disposal of such wastes discussed above, the patent literature has purported to provide solutions to these problems. For example, one solution to the problem was said to be provided in U.S.
Patent No. 3,720,609, patented March 13, 1973 by C. L.
Smith et al. That patent provided a procedure whereby waste sludges containing small amounts of certain types of reactive materials were treated by adding, to such sludges, 2~P~9~

materials capable of producing aluminum ions, lime and/or sulfate-bearing compounds to produce a composition containing sulfate ions, aluminum ions and equivalents thereof, and calcium ions and equivalents thereof. Over a period of time such compositions hardened by the formation of calcium sulfo-aluminate hydrates.
Another solution to the problem was said to be provided in U.S. Patent No. 4,028,240 patented June 7, 1977 by F. Marchak Jr. That patent provided a procedure whereby lime, preferably as calcium oxide, was mixed with the contents of sumps, e.g. oil well sumps. The calcium oxide reacted with the materials present and also dehydrated the contents of the sump, causing the sump contents to stiffen.
Yet another solution to this problem was said to be achieved in U.S. Patent No. 4,018,679 patented April 19, 1977 by F. Boelsing. That patent provided a method for rendering an oil waste material harmless by mixing an alkaline earth metal oxide with a surface active agent which delayed reaction between the alkaline earth metal oxide and water. The mixture was combined with oily material, e.g. a sludge or an oil-contaminated soil. The alkaline earth metal oxide charged with the waste material was reacted with approximately the stoichiometric amount of water to convert the alkaline earth metal oxide to the hydroxide. The alkaline earth metal oxide was preferably calcium oxide and advantageously it was also mixed with a hydrophobizing agent prior to mixture with the oily waste material.

In the patent to Boelsing described above, the composition used was preferably prepaled by blending lime with a solid fatty acid (in particular, a commercial grade of stearic acid commonly called stearin) by slowly adding the acid to coarse lime as it was subjected to the process of fine-grinding. The purpose of this operation was to render the lime hydrophobic, thereby delaying its hydration reaction with water and permitting it to be intimately mixed with cont~min~ted soil by mechanical means.Subsequent hydration then resulted in an extremely fine and uniform dispersion of the contaminants, hydrated lime and soil. In practice, however, the purpose of that invention was not always achieved to its optimum.
Nevertheless, the procedures outlined above did not provide a total answer to the problem of effective treatment of hydroc~bon-cont~min~ted soil.
Accordingly, an object of a principal aspect of the present invention is to provide a novel procedure and system for treating hydrocarbon cont~min~ed soils in a manner which will result in the substantially-complete destruction of the hydrocarbon and the fixation and stabilization of all noxious cont~min~nts.
The present invention, in one of its broadest aspects, provides a method for the treatment of hydrocarbon-cont~min~ted soil by chemical hydrolysis and/or oxidation of the hydrocarbons in the hydrocarbon-cont~min~ted soil, the method comprising: conditioning lime with a fatty acid activator, the fatty-acid activator comprising a liquid blend of a mixture of liquid fatty acids having from 6 to 12carbon atoms, and a mixture of glycerides of fatty-acids having from 8 to about 18 carbon atoms, thereby to provide conditioned lime; intimately blending the conditioned lime in a ratio of from 1-6 to 1-1 with physically-preconditioned, moist, hydrocarbon-contaminated soil, under conditions of high shear, the degree of blending being at least near microscopic level, thereby to provide blended conditioned lime/soil; conveying a charge of the blended conditioned lime/soil to an enclosed reaction vessel and carrying out hydration of the lime in the blended conditioned lime/soil charge; ret~ining the heat of the hydration reaction within the vessel, S whereby hydrolysis of the fatty acid conditioner and/or the hydrocarbon cont~min~nts in the soil is initiated; substantially simultaneously introducing air and/or oxygen-enriched air into the reaction vessel together with steam and/or water, thereby to effect a flameless, intermediate-te~l~pel~ture oxidation of the hydrocarbons and/or hydrolysed degradation products of the hydrocarbons, thereby to provide decontaminated soil product; discharging decont~min~tecl soil product from the reaction vessel by passing the decont~min~t~d soil product, in dry, dusty, hydrophobic form through a treating zone where it is sprayed with a surfactant, thereby to provide a surfactant-treated decont~min~ted soil solid; and passing the surfactant-treated decontaminated-soil solid to a blender where it is mixed with sufficient water, e.g., in an amount ranging from 5% to 25% based on the quantity of surfactant-treated decontaminated soil solid, thereby to provide a substantially dust-free decont~min~ted soil product.
By one variant thereof, the hydrocarbon cont~min~t~d soil is moist and has a maximum grain size less than 5 cm.
By another variant thereof, the liquid fatty-acid mixture comprises a preponderant amount of caprylic acid and capric acid, and the glycerides mixture is coconut oil, the composition of which comprises the glyceride of lauric acid, with appreciable amounts of the glycerides of capric, myristic, palmitic and oleic acids.

By another variant thereof, the intimate blending is provided by an apparatus capable of imparting sufficient shear and mixing action, the apparatus being a concrete mixer or a pug mill; but preferably, a pug mill.
By still another variant thereof, the enclosed reaction vessel is subjected to continuous feeding of the blended lime/soil charge, whereby the blended lime/soil charge moves through the reaction vessel. By a variation thereof, the direction of flow of the introduced air is co-current to the direction of flow of the blendedlime/soil charge through the reaction vessel. By another variation thereof, the introduced air flows from the point of introduction into the reaction vessel to the point of discharge from the reaction vessel.
By still another variant thereof, the enclosed reaction vessel is subjected to batchwise feeding of the blended lime/soil charge, the charge being retained in the reaction vessel for a predetermined period of time, of from 10 minutes to 45 minutes which is ade~uate for completion of all hydration, hydrolysis and oxidation reaction.
By a further variant thereof, the surfactant comprises commercial soaps, industrial soaps or detergents, each at a concentration ranging from 30% to 80% by weight. By a variation thereof, the surfactant comprises an aqueous solution of sodium hydroxide, e.g., from 5% to 10% by weight.
In more general terms, the process includes conditioning lime with a fatty acid activator and then intimately blending the conditioned lime at a ratio ranging from 1:6 to 1 :1 with the mass of physically-preconditioned cont~min~t~cl soil having a maximum grain size of less than approximately 5 cm under conditions of high shear.
The conditions of high shear should be similar to those obtained with the aid of a concrete mixer, e.g. the one known by the trade-mark NIKKO MIXERTM, a product of Nikko Co., Ltd. in Tokyo, Japan. The degree of intimate blending must be at least near microscopic level. A charge of the blended lime/soil blend is conveyed to an enclosed reaction vessel and hydration of the lime is carried out. The heat of the hydMtion reaction is retained within the vessel, whereby hydrolysis of the fatty acid conditioner and/or hydrocarbon cont~min~nts in the soil is initiated. Substantially simultaneously, air or oxygen-enriched air is introduced into the reaction vessel together with water in an amount required to satisfy the stoichiometry of the hydrolysis reaction, and/or steam additionally to maintain the t~ el~ture of thereacting mixture, thereby to effect a flameless, intermediate-telllpel~ture oxidation of the hydrocarbon or the hydrolysed degradation products of the hydrocarbon.
Decont~min~ted soil product is discharged from the reaction vessel by passing the soil product, in dry, dusty hydrophobic form, through a treating zone where it is sprayed with a surfactant. The surfactant-treated solid is passed to a blender where it is mixed with sufficient water, ranging from 5 % to 25 % based on the quantity of treated solid, to provide a substantially dust-free product.
By variants of this method, the fatty-acid activator may comprise one of the following: a liquid blend of a first mixture of liquid fatty acids having from 6 to 12 carbon atoms; and a second mixture of glycerides of fatty acids having from 8 to 18 carbon atoms, e.g., where the first liquid lui~lule may comprise a preponderant amount of caprylic acid and capric acid; or may comprise a preponderant amount of caprylic acid and capric acid. Preferably, the liquid mixture may comprise caproic acid, caprylic acid, capric acid and lauric acid. Still more preferably, the liquid mixture may comprise 1% caproic acid, 55% caprylic acid, 42% capric acid and 2%
lauric acid. The mixture may comprise coconut oil, babassu oil or palm kernal oil.

The coconut oil may comprise the glyceride of lauric acid, with appreciable amounts of the glycerides of capric, myristic, palmitic and oleic acids; or where the general composition of fatty acids in the coconut oil may comprise caprylic, 8.0, capric, 7.0, lauric, 48.0, myristic, 17.5, palmitic, 8.2, stearic 2.0, oleic, 6.0, and linoleic, 2.5;
or the composition of fatty acids in the coconut oil may comprise lauric acid, 47%, myristic acid, 19%, palmitic acid 9%, oleic acid, 7 %, stearic acid, <3%, and other (lower molecular weight fatty acids) > 15 %; or the babassu oil may comprise caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid and oleic acid; or where the palm kernel oil may comprise caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid and linoleic acid.
The ratio of the first mixture to the second mixture (by weight) is generally 90:10 to 65:35, and preferably is 73:27.
The present invention, in another of its broad aspects, provides three alternative improvements in the method for the treatment of hydrocarbon-contaminated soil by chemical hydrolysis and/or oxidation of the hydrocarbons in the hydrocarbon-contaminated soil, including subjecting a blend of conditioned lime and hydrocarbon-cont~min~ted soil to a hydrolysis reaction in an enclosed reaction vessel to provide a decont~min~ted soil product. One improvement comprises introducing air or oxygen-enriched air into the reaction vessel together with steam and/or water in an amount required to initiate, sustain and complete the hydrolysis/oxidationreaction, thereby to effect a flameless, intermediate-temperature oxidation of the hydrocarbon to their totally degraded products. A second improvement comprises discharging decont~min~tPd soil product, from the reaction vessel by passing the soil , ~ product, in dry, dusty hydrophobic form through a treating zone where it is sprayed /~

lO 2079508 with a surfactant. A third improvement comprises discharging decont~min~t~ soil product from the reaction vessel by passing the soil product, in dry, dusty hydrophobic form through a treating zone where it is sprayed with a surfactant; and blending the surfactant treated soil with sufficient water in an amount ranging from 5 % to 25 % based on the quantity of treated solid to provide a substantially dust-free product.
The present invention, in still another of its broad aspects provides a system for the treatment of hydrocarbon-cont~min~ted soil by chemical hydrolysis and/oroxidation of the hydrocarbons in the hydrocarbon-cont~min~t~l soil. The system comprises means for finely-dividing the hydrocarbon-contaminated soil; a storagehopper; means for feeding the finely-divided, hydrocarbon-cont~min~ted soil to the storage hopper; a blender; means for feeding finely-divided, hydloc~l.on-conta-min~ed soil from the storage hopper to the blender; a conditioned lime storage vessel; means for feeding activated lime from the activated lime storage vessel to the blender; means for feeding conditioned lime from the conditioned lime storage vessel to the blender, the conditioned lime comprising lime and a fatty acid activator, the fatty-acid activator comprising a liquid blend of a mixture of liquid fatty acids having from 6 to 12 carbon atoms, and a mixture of glycerides of fatty-acids having from 8 to 18 carbon atoms, the blender being adapted intimately to blend the conditioned lime in a ratio of from 1-6 to 1-l with physically-preconditioned, moist, hydrocarbon-contaminated soil, under conditions of high shear, the degree of blending being at least near microscopic level, thereby to provide blended conditioned lime/soil; an enclosed inclined reaction vessel, the enclosed, inclined reaction vessel including a lower inlet, a bottom line, for admitting air or oxygen-enriched gas, an upper line for ~dmitting steam or water, an upper discharge means within the reaction vessel for moving a solid material charge from the inlet to the discharge, and an upper surfactant admitting line at the discharge, whereby the enclosed inclined reaction vessel is adapted to enable effecting hydrolysis of the fatty acid conditioner and/or the S hydrocarbon cont~min~nts in the soil, while ret~ining the heat of the hydration reaction within the vessel, whereby to carry out a flameless, intermediate-lelllpel~ture oxidation of the hydrocarbons and/or hydrolysed degradation products of the hydrocarbons, thereby to provide decont~min~ted soil product; discharge means from the blender for feeding a charge of the blended conditioned lime/soil directly to the lower inlet of the enclosed, inclined reaction vessel; a treating/blending vessel having means for moving a solid charge from an intake end to a discharge end and also having an upper water inlet line; discharge means from the enclosed, inclined reaction vessel for discharging a finely-divided decont~min~ted soil product, in dry, dusty, hydrophobic form directly to the intake end of the treating/blending vessel through a spray of surfactant, thereby to provide a surfactant-treated decont~min~ted soil solid; a discharge tower; and discharge means from the keating/blending vessel for discharging surfactant-treated decont~min~tçd soil solid from the treating/blending vessel directly to a central intake of the discharge tower, where the surfactant-treated decontaminated soil solid is adapted to be mixed with sufficient water, thereby to provide a substantially dust-free decon~min~ted soil product.
In one variant of the system of this aspect of the present invention, the means for finely dividing hydrocarbon-cont~min~ted soil is a jaw crusher or a roll crusher.
In another variant of the system of this aspect of the present invention, the means for feeding the finely divided hydrocarbon-contaminated soil from the storage hopper to the blender comprises a screw conveyor within the storage hopper and an upwardly inclined belt conveyor leading from the storage hopper.
In yet another variant of the system of this aspect of the present invention, the discharge means from the blender comprises a rotating blade blender/screw conveyor.
In still another variant of the system of this aspect of the present invention, the upper discharge means within the enclosed, inclined reaction vessel comprises an inclined screw conveyor.
In a still further variant of the system of this aspect of the present invention, the treating/blending vessel is a pug mill including a rotating blade blender/screw conveyor.
In still another variant of the system of this aspect of the present invention, the discharge tower includes a fan for discharge of excess air to an emissions cleanup system and to maintain a negative pressure in the reactor.
In more general terms des~ ive of the present invention, lime is mixed with the following fatty acids and glycerides. The mixture of liquid saturated fatty acids consists mainly of 55% caprylic acid and 42% capric acid by weight, and most preferably consists of 1% caproic acid, 55% caprylic acid, 42% capric acid, and 2%
lauric acid. The plerelred mixture of glycerides is coconut oil. Other mixtures of glycerides include babassu oil and palm kernel oil. In particular, the ratio of liquid saturated fatty acids to glycerides is 90:10 to 65:35, with the optimum ratio being 73:27.
In providing the conditioned lime, the amount of the hydrophobizing composition is selected to be sufficient fully to coat the finely divided lime particles.
In practice therefore, this would range from 0.5% to 2.5% by weight, with the A

207950~

optimum amount being 1.0~. The size of the finely divided lime is generally within the range of minus lO mesh to sub-micron sizes, preferably minus 100 to sub-micron sizes.
The preferred method of providing the conditioned lime comprises feeding the S above-described hydrophobizing agent to a spray nozzle, and spraying such hydro-phobizing agent into a rising air stream carrying fine lime particles. The pressure gradient across the spray nozzles should be 10 to 30 psig. The velocity of upward flow of air is within the range 50 to 100 ft/sec.
By the present invention, in its various aspects, a novel procedure and system are provided to the treatment of hydrocarbon-cont~min~ed soil through effective L~ "//
A

2(~7~8 taminants. In the first step of the procedure, lime (CaO) is conditioned with a suitable fatty acid activator. An appropriate quantity of the conditioned lime, ranging, based on the mass of soil, from 15% to 100% as dictated by the quantity of moisture in the feed, the nature of the soil and the type and quantity of the hydrocarbons present and determined through laboratory testing, is intimately blended with physically-preconditioned, moist, hydrocarbon-contaminated soil, which may or may not be further con-taminated with noxious heavy metals. While a wide varietyof devices capable of imparting the requisite shear and mixing action to the ingredients are commercially available, it is imperative that the degree of dispersion achieved be at the near microscopic level. This provides a blended soil charge.
The blend is, then, transferred to a reaction vessel in either continuous or batchwise fashion. If it is fed in a continuous fashion, the blended soil charge moves slowly through the reactor; if it is fed batchwise, the blended soil charge is retained for a predetermined period of time which may range from 10 minutes to 45 minutes and is adquate for completion of all hydration, hydrolysis and oxidation reactions. In either procedure, the reactor design is such that the heat generated during the hydration ~5 of the lime in accordance with the reaction:
CaO + H2O >ca(OH) 2 is contained within the blended soil charge, thereby causing the temperature to rise to a level at which 2~7~ 8 hydrolysis of the activator and, possibly certain of the hydrocarbon contaminants, is initiated.
Air, or oxygen enriched air, combined with water and/or steam where required by the chemical processes, is also introduced to the reactor to effect a flameless, intermediate temperature oxidation of the original hydrocarbons or the hydrolyzed degradation products of such hydrocarbons. The air or oxygen enriched air flow rate must be sufficiently high to provide an excess of 50% to 100% of the stoichoimetric oxygen requirements of the oxidation reactions while being limited to a level which will minimize the heat removal from the reaction mixture.
These conflicting requirements may be accommodated through adjustments in the quantity of steam supplied to the reactor and the degree of oxygen enrichment of the air.
The oxidation reactions may be represented generically as:

CxHyOz + ~2 > C~2 + H20 In the continuous method embodiment, the direction of flow of the air and the solid charge in the reactor is co-current. This ensures that any vaporized hydrocarbons, orincompletely hydrolyzed/oxidized hydrocarbon degradation products, are carried from the region of high concentration obtaining near the blended feed influent port to a region of low concentration and higher temperature nearer the exit, thereby providing an enhanced opportunity for further reaction.
The decontaminated soil product, which is normally very dry, dusty and extremely hydrophobic, leaves the 2~95~

reactor and passes through a spray of surfactant en route to another blender te.g. a conventional pug mill) where it is mixed with a sufficient quantity of water to permit dust-free transfer to the final disposal site and/or compaction into a dense, stable monolith which, upon curing, provides virtually permanent encapsulation of any inorganic or surviving, trace organic residues.
The surfactant or wetting agent may be any of a number of commercially available long chain organic molecules, e.g. industrial or domestic soaps and detergents. However, it is preferable that this agent be a solution of approximately 5% sodium hydroxide in water which is sprayed onto the dry reactor effluent in sufficient volume to ensure the desired water-wetting and compaction qualities of the final product from the process. The actual quantity will be determined by the nature of the soil, the quantity of lime employed, etc. and will range from 1% to 10% of the weight of the process product.
The lime conditioning agent comprises a liquid blend of certain liquid saturated fatty acids (coconut oil, or babassu oil or palm kernel oil) and certain glycerides of fatty acids. The resulting blend is a liquid at room temperature, thereby allowing it to be very easily and uniformly combined with the fine-ground lime. This procedure is accomplished with the aid of a spray nozzle which introduces the hydrophobizing agent into a rising air stream carrying the fine lime particles.

2~g5~

The chief constituents of coconut oil are the glyceride of lauric acid, with appreciable amounts of the glycerides of capric, myristic, palmitic and oleic acids.
The general composition of fatty acids in coconut oil is as follows: caprylic, 8.0; capric, 7.0; lauric, 48.0;
myristic, 17.5; palmitic, 8.2; stearic, 2.0; oleic, 6.0 and linoleic, 2.5.
In one preferred coconut oil, the approximate composition of the fatty acids is as follows: lauric acid, 47%; myristic acid, 19%; palmitic acid, 9%; oleic acid, 7%;
stearic acid, <3% and other (lower molecular weight fatty acids), >15%.
The approximate composition of fatty acids in babassu oil is as follows: caprylic, 6.5; capric, 2.7; lauric, 45.8; myristic, 19.9; palmitic, 6.9; and oleic, 18.1.
The approximate composition of fatty acids in palm kernel oil is as follows: caprylic, 3.0; capric, 3.0;
lauric, 52.0; myristic, 15.0; palmitic, 7.5; stearic, 2.5;
oleic, 16.0; and linoleic, 1Ø
A preferred liquid fatty acid mixture is that known by the trademark INDUSTRENE 365TM of Hunko Products Division;
National Dairy Products Corporation. A preferred coconut oil is that known by the trademark VICTORY 76TM of Bareco Division; Petrolite Corp.
The most efficacious composition of the conditioning agent blend should be:
1. 73% INDUSTRENE 365TM- and 2. 27% VICTORY 76TM-2Q79~8 The desired characteristic of the conditioning agent is that it virtually inhibit the lime hydration until the lime is mechanically blended with the contaminated soil with the aid of vigorous stirring, then allowed to remain undisturbed, at which time the reaction should occur at a high rate as indicated by a rapid and extensive rise in temperature. This behaviour is seen to be optimum when the concentration of the conditioning agent in the treated lime is within the range of 0.5% and 2.5%, with the optimum performance noted at approximately 1.0%. It is possible that other blends of oil and fatty acids would perform equally well. For example, blends of liquid fatty acids with babassu oil or with palm kernel oil may be useful.
The conditioning agent also acts as an activator/initiator in a method for rendering waste substances harmless.
In the novel method of the present invention, as will be described in greater detail hereinafter, at some point during the lime hydration reaction, the conditioning agent begins to react with the lime. Coupled with the destruction of the lime is the release of sufficient heat to raise the temperature of the mass significantly above 100~C, the boiling point of water. Temperatures in excess of 150~C may be achieved. At this temperature, hydration, which clearly involves water as a reactant, must soon cease and hydrolysis of the agent takes place. In mixtures of fatty acid activated lime and hydrocarbon contaminated soil, temperatures in excess of 400~C have been observed.

207!9~

This behaviour of the agent as an activator/initiator contributes to the chemical destruction of the hydrocarbon contaminants originally present in the waste soil and is an important mechanism in the operation of the above-described novel method.
In the accompanying drawing, the single Figure is a schematic process flowsheet of the method and system of one embodiment of this invention.
The contaminated soil is removed from the area of contaminants and is fed, by a front-loader 10 either to a jaw crusher 11 or a roll crusher 12 to a hopper 13 provided with a conveyor system 14. Conveyor system 14 feeds an inclined ramp portion 15 leading to a hopper 16 provided with a feed rate control screw soil feeder 17, driven by means (not shown) in the direction shown by the arrow.
Screw soil feeder 17 feeds soil to a second weigh-type conveyor system 18 where the soil is fed through a blender hopper 19 to a blender 20 provided with suitable means 20a for blending.
The lime is activated in the manner previously described in the activity apparatus 21 shown. Lime is stored in a lime storage vessel 22 where it is fed from a rotary valve 23 at the bottom of the lime storage vessel 22, and is carried by air, supplied through line 24, mixed with conditioned fatty acid composition (as previously described) in line 25 to combined inlet line 26 to activated lime storage and feed apparatus 21. Air is exhausted through vent 27. The conditioned lime is 2079~S

discharged via outlet 28 through the blender hopper 19 to the blender 20. From the blender 20, the blended lime/soil charge is fed to an inclined reactor 48 provided with an upwardly feeding screw conveyor 29 rotated by motor means (not shown) in the direction shown. Oxidizing air together with water and/or steam as determined by the stoichoimetry and thermal requirements of the chemical reactions is fed co-currently to the flow of the charge through air inlet 30 to the inclined reactor 48.
At the exit 31 from the inclined reactor 48, the decontaminated soil is sprayed with a suitable wetting agent as previously described through spray nozzle 32 and is fed to a pug mill 33. At the pug mill 33, the decontaminated soil is wetted with water through inlet 34, and is discharged by horizontal screw conveyor 36, rotated by motor means (not shown) in the direction shown to the outlet 37 of a discharge tower 38 to a suitable truck 39.
The discharge tower 38 includes an internal fan 40 which forces air outwardly to 41 to a cleanup zone (not shown) and maintains a slight negative pressure in the reactor of approximately 1 cm to 3 cm water vacuum to minimize fugitive emissions.
The decontaminated soil may be fed to a compaction zone (not shown) and/or to landfill.

Claims (22)

1. A method for the treatment of hydrocarbon-contaminated soil by at least one of chemical hydrolysis and oxidation of said hydrocarbons in said hydrocarbon-contaminated soil, said method comprising:
1) conditioning lime with a fatty acid activator, said fatty-acid activator comprising a liquid blend of a) a mixture of liquid fatty acids having from 6 to 12 carbon atoms, and b) a mixture of glycerides of fatty-acids having from 8 to about 18 carbon atoms, thereby to provide conditioned lime;

2) intimately blending said conditioned lime in a ratio of from 1-6 to 1-1 with physically-preconditioned, moist, hydrocarbon-contaminated soil, under conditions of high shear, the degree of blending being at least near microscopic level, thereby to provide blended conditioned lime/soil;

3) conveying a charge of said blended conditioned lime/soil to an enclosed reaction vessel and carrying out hydration of said lime in said blended conditioned lime/soil charge;

4) retaining the heat of said hydration reaction within said vessel, whereby hydrolysis of at least one of said fatty acid conditioner and said hydrocarbon contaminants in said soil is initiated;

5) Substantially simultaneously introducing at least one of air and oxygen-enriched air into said reaction vessel together with at least one of steam and water, thereby to effect a flameless, intermediate-temperature oxidation of at least one of said hydrocarbons and hydrolysed degradation products of said hydrocarbons, thereby to provide decontaminated soil product;

6) discharging decontaminated soil product from said reaction vessel by passing said decontaminated soil product, in dry, dusty, hydrophobic form through a treating zone where it is sprayed with a surfactant, thereby to provide a surfactant-treated decontaminated soil solid;
and 7) passing said surfactant-treated decontaminated-soil solid to a blender where it is mixed with sufficient water, in an amount ranging from 5 %
go 25% based on the quantity of surfactant-treated decontaminated soil solid, thereby to provide a substantially dust-free product.
2. The method of claim 1 wherein said hydrocarbon-contaminated soil is moist and has a maximum grain size less than 5 cm.
3. The method of claim 1 wherein said liquid fatty-acid mixture a) comprises a preponderant amount of caprylic acid and capric acid; and wherein said glycerides mixture b) is coconut oil, the composition of which comprises: the glyceride of lauric acid, with appreciable amounts of the glycerides of capric, myristic, palmitic and oleic acids.
4. The method of claim 1 wherein said intimate blending is provided by an apparatus capable of imparting sufficient shear and mixing action, said apparatus being selected from the group consisting of a concrete mixer and a pug mill.
5. The method of claim 4 wherein said blender comprises a pug mill.

6. The method of claim 1 wherein said enclosed reaction vessel is subjected to continuous feeding of said blended lime/soil charge, whereby said blended lime/soil charge moves through said reaction vessel.

7. The method of claim 6 wherein the direction of flow of said introduced air is co-current to the direction of flow of said blended lime/soil charge through said reaction vessel.

8. The method of claim 6 wherein said introduced air flows from the point of introduction into the reaction vessel to the point of discharge from the reaction vessel.

9. The method of claim 1 wherein said enclosed reaction vessel is subjected to batchwise feeding of said blended lime/soil charge, said charge being retained in said reaction vessel for a predetermined period of time, of from 10 minutes to 45 minutes which is adequate for completion of all hydration, hydrolysis and oxidation reaction.

10. The method of claim 1 wherein said surfactant comprises at least one of commercial soaps, industrial soaps and detergents, each at a concentration ranging from 30% to 80% by weight.

11. The method of claim 10 wherein said surfactant comprises an aqueous solution of sodium hydroxide.

12. The method of claim 11 wherein the concentration of said sodium hydroxide is from 5% to 10% by weight.

13. In a method for the treatment of hydrocarbon-contaminated soil by at least one of chemical hydrolysis and oxidation of said hydrocarbons in said hydrocarbon-contaminated soil, including subjecting a blend of conditioned lime and hydrocarbon-contaminated soil to a hydration reaction in an enclosed reaction vessel, said conditioned lime comprising an intimate blend of lime and fatty-acid activator, said fatty-acid activator comprising a liquid blend of a) a mixture of liquid fatty-acids having from 6 to 12 carbon atoms, and b) a mixture of glycerides of fatty acids having from 8 to 18 carbon atoms, thereby to provide said conditioned lime, thereby to provide said conditioned lime, thereby to provide a decontaminated soil product, the improvement comprising: introducing air or oxygen-enriched air into said reaction vessel together with steam or water in an amount required to initiate, sustain and complete said hydrolysis and oxidation reactions, thereby to effect a flameless, intermediate-temperature, oxidation of said hydrocarbon and hydrolysed degradation products of said hydrocarbon.

14. In a method for the treatment of hydrocarbon-contaminated soil by at least one of chemical hydrolysis and oxidation of said hydrocarbons in said hydrocarbon-contaminated soil, including subjecting a blend of conditioned lime, and hydrocarbon-contaminated soil to a hydration reaction in an enclosed reaction vessel, said conditioned lime comprising an intimate blend of lime and a fatty-acid activator, said fatty-acid activator comprising a liquid blend of a) a mixture of liquid fatty acids having from 6 to 12 carbon atoms, and b) a mixture of glycerides of fatty acids having from 8 to 18 carbon atoms, thereby to provide said conditional lime, thereby to provide a decontaminated soil product, the improvement comprising: discharging said decontaminated soil product from said reaction vessel by passing said decontaminated soil product, in dry, dusty hydrophobic form through a treating zone where it is sprayed with a surfactant.

15. In a method for the treatment of hydrocarbon-contaminated soil by at least one of chemical hydrolysis and oxidation of said hydrocarbons in said hydrocarbon-contaminated soil, including subjecting a blend of conditioned lime, and hydrocarbon-contaminated soil to a hydration reaction in an enclosed reaction vessel, said condition lime comprising an intimate blend of lime and a fatty-acid activator, said fatty-acid activator comprising a liquid blend of a) a mixture of liquid fatty acids having from 6 to 12 carbon atoms, and b) a mixture of glycerides of fatty-acids having from 8 to 18 carbon atoms, thereby to provide conditioned lime, thereby to provide a decontaminated soil product, the improvement comprising: discharging said decontaminated soil product from said reaction vessel by passing said decontaminated soil product, in dry, dusty hydrophobic form through a treating zone where it is sprayed with a surfactant, thereby to provide surfactant-treated decontaminated soil product; and blending said surfactant-treated decontaminated soil product with sufficient water, in an amount ranging from 5 % to 25 % based on the quantity of said surfactant-treated decontaminated soil product to provide a substantially dust-free product.

16. A system for the treatment of hydrocarbon-contaminated soil by chemical hydrolysis and/or oxidation of said hydrocarbons in said hydrocarbon-contaminated soil, comprising:
a) means for finely-dividing said hydrocarbon-contaminated soil;
b) a storage hopper;
c) means for feeding said finely-divided, hydrocarbon-contaminated soil to said storage hopper;
d) a blender;

e) means for feeding finely-divided, hydrocarbon-contaminated soil from said storage hopper to said blender;
f) a conditioned lime storage vessel;
g) means for feeding conditioned lime from said conditioned lime storage vessel to said blender, said conditioned lime comprising lime and a fatty acid activator, said fatty-acid activator comprising a liquid blend of a) a mixture of liquid fatty acids having from 6 to 12 carbon atoms, and b) a mixture of glycerides of fatty-acids having from 8 to 18 carbon atoms, said blender being adapted intimately to blend said conditioned lime in a ratio of from 1-6 to 1-1 with physically-preconditioned, moist, hydrocarbon-contaminated soil, under conditions of high shear, the degree of blending being at least near microscopic level, thereby to provide blended conditioned lime/soil;
h) an enclosed inclined reaction vessel, said enclosed, inclined reaction vessel including a lower inlet, a bottom line, for admitting air or oxygen-enriched gas, an upper line for admitting steam or water, an upper discharge means within said reaction vessel for moving a solid material charge from said inlet to said discharge, and an upper surfactant admitting line at said discharge, whereby said enclosed inclined reaction vessel is adapted to enable effecting hydrolysis of at least one of said fatty acid conditioner and said hydrocarbon contaminants in said soil, while retaining the heat of said hydration reaction within said vessel, whereby to carry out a flameless, intermediate-temperature oxidation of at least one of said hydrocarbons and hydrolysed degradation products of said hydrocarbons, thereby to provide decontaminated soil product;

i) discharge means from said blender for feeding a charge of said blended conditioned lime/soil directly to said lower inlet of said enclosed, inclined reaction vessel;
j) a treating/blending vessel having means for moving a solid charge from an intake end to a discharge end and also having an upper water inlet line;
k) discharge means from said enclosed, inclined reaction vessel for discharging a finely-divided said decontaminated soil product, in dry, dusty, hydrophobic form directly to the intake and of said treating/blending vessel through a spray of surfactant, thereby to provide a surfactant-treated decontaminated soil solid;
l) a discharge tower; and m) discharge means from said treating/blending vessel for discharging surfactant-treated decontaminated soil solid from said treating/blending vessel directly to a central intake of said discharge tower, where said surfactant-treated decontaminated soil solid is adapted to be mixed with sufficient water, thereby to provide a substantially dust-free decontaminated soil product.

17. The system of claim 16 wherein said means for finely dividing said hydrocarbon-contaminated soil comprises a jaw crusher or a roll crusher.

18. The system of claim 16 wherein said means for feeding said finely divided hydrocarbon-contaminated soil from said storage hopper to said blender comprises a screw conveyor within said storage hopper and an upwardly inclined belt conveyor leading from said storage hopper.

19. The system of claim 16 wherein said upper discharge means within said enclosed, inclined reaction vessel comprises an inclined screw conveyor.

20. The system of claim 16 wherein said discharge means from said blender comprises a rotating blade blender/screw conveyor.

21. The system of claim 16 wherein said treating/blending vessel comprises a pug mill including a rotating blade blender/screw conveyor.

22. The system of claim 16 wherein said discharge tower includes a fan for discharge of excess air to an emissions cleanup system and to maintain a negative pressure in the reactor.