Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/04—Treating liquids
  • G21F9/06—Processing
  • G21F9/16—Processing by fixation in stable solid media

Definitions

• the present invention relates to the field of disposal of inorganic and organic waste including chemical waste and low-level and medium-level nuclear waste and, more particularly, to the field of disposal of waste via microencap- sulation or solidification. Still more particularly, the present invention relates to the field of disposal of waste by reacting the waste with a chemical reagent and a pozzolanic material to form solids suitable for safe storage or disposal.
• the chemical reagent includes a retarder, such as glycerine or other viscosity-altering reagent or mixture containing them, and an accelerator.
• Another method used in the past for the disposal of waste has been chemical treatment.
• One disadvantage of such treatment is that it is not effective because most of the compounds present in waste, and especially hazardous waste, do not react chemically with other compounds to form non- hazardous compounds. Furthermore, even if the conversion to harmless compounds is possible, such process is uneconomical.
• Incineration has also been used in the past as means for the disposal of waste. Incineration, however, is not effective in most applications. Furthermore, incineration processes result in the formation of other undesirable chemicals in the form of ash or gases emitted to the environment. Furthermore, incineration is a very costly process that requires highly sophisticated incineration equipment and requires the transportation of the waste to special locations for the incineration to be performed.
• Another method that has been used in the past for disposal of waste has been the process of solidifying the waste by mixing it with sawdust, various pozzolanic materials and polymeric substances.
• One disadvantage of such methods is their inability to adequately solidify liquid or sludge-type waste.
• Another disadvantage is that several pozzolanic materials used in the past have not been shown to be effective because of their physical or chemical properties. Attempts, for example, in the past to solidify waste with Portland cement produced a solid product which was very permeable, porous, subject to leaching and deficient in mechanical strength.
• the present invention overcomes the deficiencies of the prior methods by providing a unique chemical reagent and a unique process wherein such chemical reagent is mixed with the waste and highly active pozzolanic material to produce a solid product that is non-toxic, safe, strong, smaller in volume than the resultant waste products of previously used solidification processes, easily transportable and easily disposable in landfill or in readily available natural disposal sites such as salt domes and the like. Furthermore, the present invention discloses a chemical reagent and a process utilizing that reagent wherein a pozzolanic waste material is used effectively to dispose of other waste, thus simultaneously disposing of two wastes. The production of the chemical reagent and its application are very simple and economical.
• Inorganic and organic waste including chemical and low-level and medium-level nuclear waste is solidified by mixing such waste with a chemical reagent and a pozzolanic material.
• the chemical reagent includes a retarder, which could be glycerine or other viscosity-altering reagents, and an accelerator, namely calcium chloride.
• the retarder prevents a flash set of the pozzolanic material and slows the setting process, whereas the accelerator promotes the solidification activity.
• the retarder further acts as a lubricant and improves the viscosity.
• the pozzolanic material may _be not only pozzolanic material specifically manufactured for cementing operations, such as Portland cement, but also waste material produced in several industrial applications such as fly ash, kiln dust, and steel or lead baghouee dust.
• the solid waste material formed may be thereafter stored or disposed in natural storage places without affecting or harming the environment.
• a chemical roagent has been developed having unique properties for the solidification of organic and inorganic waste, such as chemical waste, and low-level and medium-level nuclear wastes and the safe disposal thereof.
• the chemical reagent is mixed with the waste and the pozzolanic material to form a solid waste material. It is essential that the mixing and related steps be carried out simultaneously or in a particular sequence, hereinafter described, to accomplish the desired results.
• the chemical reagent is primarily composed of a retarder and an aqueous solution of an accelerator compound.
• the retarder is glycerine, a well-known compound readily available in the market, or another viscosity altering reagent.
• the retarder may also be glycerine in combination with other viscosity-altering reagents.
• Other retarders can be used alone or in combination depending on their availability, economics and the properties of the waste.
• the glycerine is a suitable retarder and could be used alone or with other retarders in different compositions in the various applications in accordance with the present invention, it is preferred that glycerine be used in most applications because of its superior retarding and lubricating properties.
• the retarder prevents "flash" set and slows the setting and solidification of the pozzolanic material when mixed with water and waste. It is believed the retarder coats the particles of waste to slow solidification. The retardation of the solidification permits sufficient time to uniformly mix the pozzolanic material and waste to achieve a uniform encapsulation and bonding of the waste in the resultant waste product. Further, the slower set-up time produces a greater mechanical strength in the resultant waste product.
• the retarder further acts as a lubricant. As a lubricant, the retarder provides a lower viscosity and thus friction reducing properties to facilitate the mixing of the chemical reagent, the wastes and the pozzolanic material in the manner hereinafter described.
• the preferred accelerator compound is calcium chloride (CaC1 2 ) which promotes the setting process of the pozzolanic material.
• the chemical reagent may also include other solvents that remain neutral during the solidification process in question.
• the chemical reagent is prepared by mixing an aqueous solution of calcium chloride with the retarder by well-known mixing techniques.
• the amount of calcium chloride present in the aqueous solution that serves as the start-up material for the chemical reagent may range from 15 percent by weight to saturation.
• the amount of retarder used in the chemical reagent depends on the retarding and viscosity properties desired, and on the properties of the waste being treated. If, for example, a longer set-up time is desired, the amount of retarder is increased whereby the reaulting waste product is harder and stronger. In a typical application, the amount of retarder may range from 0.01 to 15 parts of retarder per 100 parts of reagent chemical in undiluted form.
• the chemical reagent is a non-toxic, homogeneous solution that retains its homogeneity and stability for a long time.
• the reagent could be easily stored at temperatures ranging from -40°C to 35°C and above. Because the retarder and accelerator compounds are inexpensive and because the mixing process is simple, the chemical reagent is also inexpensive.
• pozzolanic materials including fly ash produced in coal-fired power stations, including Class C type fly ash known for its high calcium content, and Class F type fly ash characterized by its high silica and aluminum oxides content; cement kiln dust; lime kiln dust characterized by a high calcium content; steel or lead baghouse dust; silica fume dust from'the refractory industry; gypsum; and Portland cement.
• the majority of the pozzolanic material listed herein could be characterized as waste material.
• waste pozzolanic material is a unique feature of the present invention in that it utilizes pozzolanic wastes to dispose of other wastes, including chemical and low-level and medium-level radio- .
• pozzolanic material used to practice the present invention would depend on the availability of such material in the particular location, the price of such material, the needs of the entity generating the waste, and the guidelines of the regulatory authorities. In certain. areas of the United States of America for example, where fly ash is available in large quantities, fly ash would be used. In special circumstances the nature of the waste to be treated may require the use of pozzolanic materials with higher calcium content such as Portland cement or lime kiln dust to perform the cementation process.
• the utilization of the chemical reagent described herein enables one to use- a pozzolanic material having a large reactive surface, whereby the pozzolanic material reacts more readily with the waste and forms a resultant waste product which has a large density and small pores.
• the pozzolanic material used has small, uniform powder particulate components with a high content of calcium and other cementation elements.
• Fly ash for example, is a pozzolanic material that is composed of very small, spherical, uniform particles. Accordingly, fly ash possesses a superior ability to absorb, react with, or entrap the constituents of hazardous waste. Fly ash, however, tends to set-up very quickly when mixed with water and wasta.
• fly ash includes a relatively small amount of calcium, a material that contributes to the mechanical strength and bonding forces of the resultant waste product. Therefore, fly ash alone would not produce a solid waste-containing compound with great mechanical strength.
• the use of the present chemical reagent compensates for such deficiencies by providing calcium to enhance the mechanical strength of the resultant waste solid and the retarder to prevent the flash setting of the fly ash when it is mixed with water and the waste.
• One very important aspect of the process disclosed by the present invention is the requirement that the mixing, blending and related steps be carried out simultaneously or in a specific sequence in order to obtain optimum results.
• the sequence of the steps depends on whether the organic or inorganic waste to be treated is a liquid or a solid waste. It should be understood that the term "solid waste” as used in the specifications and in the claims shall mean waste that includes less than about 15 percent of liquid in free form. Furthermore, “liquid waste” as used herein shall mean waste that includes more than about 15 percent of liquid in free form. If the waste is a liquid waste as defined herein, it is essential that the liquid waste be mixed first with the chemical reagent in a conventional mixer suitable for such mixing for a sufficient time to obtain a uniform distribution of the chemical reagent in the liquid waste.
• the resultant mixture comprising the liquid waste and the uniformly distributed chemical reagent, is blended or mixed with the pozzolanic powder material for sufficient time to obtain complete and uniform mixing. Following such mixing, the mixture is allowed to solidify to form waste solids. It may be desirable to pour the mixture into casting containers or molds to form the waste solids in predetermined shapes, such as blocks, for ultimate disposal.
• the process for a liquid waste be performed in.a continuous mixer.
• the continuous mode may be carried out by utilizing well-known mixing and blending equipment.
• the mixing of the liquid waste with the chemical reagent may be carried out in a blending pump or in an in-line blender and the mixing of the resultant mixture and the fly ash may be carried out in a screw-type or a ribbon-type blender.
• a batch mode may be utilized, particularly when only a relatively small amount of waste requires solidification.
• the process may be carried out in a central batch-type mixer.
• the waste to be treated is a solid waste as defined hereinabove, it is first mixed with the powder pozzolanic material until a uniform mixture is obtained.
• water is added to the chemical reagent to bring the chemical reagent to an optimum water content which is required for the treatment of the solid waste in question.
• various slump ratings may be desired depending upon the type of waste and its disposal, it is generally preferred that sufficient water be added to the solid waste to permit the resultant compound to be poured prior to solidification.
• the chemical reagent is added to the uniform mixture comprising solid waste .and pozzolanic material and mixed therewith for a sufficient period of time to obtain a uniform mixture.
• the resultant mixture is allowed to solidify to form waste solids.
• the treatment of solid waste may also be carried out effectively by carrying out the aforementioned steps simultaneously.
• the treatment of the solid waste may be carried out in either a batch or a continuous mode by utilizing well-known devices that are comparable to the devices used in the solidification of the liquid waste previously described.
• preparatory ateps are taken to prepare the waste prior to its mixing with the chemical reagent and the pozzolanic material to enhance the reactive interaction of the compounds and to obtain a better final solid waste product.
• One preparatory step. is the neutralization of the waste, whether acidic or basic, by well-known neutralizing agents such as sodium, lime, etc. to obtain a preferred pH.
• Another preparatory step which is more applicable to solid waste and to liquid waste that contains solids is the grinding of the solid components of the waste to increase the surface area of the solids contained in the waste and to decrease the size of the solid material in the waste whereby better mixing with the pozzolanic material its achieved.
• Another preparatory step applicable in the treatment of solid waste containing liquid involves the drying of the solid waste prior to its mixing with the chemical reagent and pozzolanic material.
• the drying and the grinding of the waste may be carried out in well-known devices such as a rotary drier and grinder.
• the process of the present invention may be utilized to treat a wide variety of organic and inorganic wastes, including chemical and low and medium-level nuclear waste, which are produced by industrial processes and other applications including, but not limited to, aromatic heavy oils and tars, creosote sludges tars, tank bottoms; petroleum heavy oils, tars and sludges; petrochemical heavy oils and tars and all by-products and tank residues including polymers; halogenated organic sludges containing PC B s, dioxins and other chlorinated solvent manufacturing tank bottoms; pesticide/herbicide sludges including arsenic; organic and inorganic sludges and wastes including leaded tank bottom cleanings; inorganic sludges, electroplating and metal finishing sludges and waste, chrome zinc, etc; contaminated soils, PCB and dioxin contaminated oil, tainted dirt and soils; waste gases adsorbed or entraped in solids or
• the process used is the same as the process for solidifying liquid wastes. It is preferred, however, to use a pozzolanic material of steel or lead baghouse dust containing high lead content to provide lead screening for the radiation emitting nuclear wastes.
• the amount of chemical reagent and pozzolanic material utilized to treat various wastes depends on the kind of waste being treated and the particular requirements of the process.
• the amount of chemical reagent ranges from 16.3 to 130.5 milliliters of chemical reagent per kilogram of waste material being treated and the amount of pozzolanic material ranges from 94 grams to two (2) kilograms of pozzolanic materials per kilogram of waste material.
• the amount of pozzolanic material required decreases as the amount of suspended solids in the liquid waste increases. It is preferred that, before a waste is treated, laboratory tests be carried out with the particular waste to determine the optimum amounts of pozzolanic material and chemical reagent required.
• the chemical reagent, the pozzolanic material and the waste are crosslinked and bonded in the solidification process which changes the physical and chemical properties of the waste.
• the process reduces the coefficient of permeability, and the matrix plasticity index of the waste while it increases the mechanical internal strength into a load bearing mass upon solidification.
• the process provides a microencap- sulation that surrounds and seals the portion of the matrix that is not chemically incorporated into the reaction, whereby the' ingredients become microencapaulated in the interstices formed by the particles of pozzolanic material and virtually impermeable and essentially free of leaching.
• the reactions between the several components are thoroughly distributed over the particulate surfaces throughout the mass of the waste.
• waste material takes an active role in the process and functions as a chemical reagent on its own and further contributes to the physical hardening and reduction of permeability and leaching characteristics.
• the volume of the resultant waste product is smaller than the volume of the resultant product of the solidification processes previously used in the prior art.
• the solids formed by the present process may be safely transported, and stored at various sites, such as landfills.
• One particular place for storing such waste solids is salt caverns that are located throughout the United States. Such storage may be accomplished by direct placement of the solids into the disposal site or by pumping the waste slurry prior to solidification down into a salt cavern where it is allowed to solidify by permanent storage.
• One-hundred (100) grams of baghouse steel dust was blended with 15 grams of Portland cement.
• seven (7) parts of water (12.85 grams) were added to one (1) part of chemical reagent (2.65 grams) containing 0.03 grams of glycerine, 0.03 grams of polyethylene glycol, and 2.59 grams of 39 percent calcium chloride solution in water to form 15.5 grams of diluted chemical reagent.
• the chemical reagent was then added to a separately-formed blend of baghouse steel dust and Portland cement. The resultant mixture was allowed to solidify.
• Example II The procedure of Example II was repeated utilizing fifty (50) grams of Class "C” fly ash instead of 15 grams of Portland cement.
• diluted chemical reagent 17.5 grams was formed by adding two (2) parts of water (9.5 grams) to one (1) part of chemical reagent (8.0 grams) containing 0.11 grams of glycerine, 0.11 grams of polyethylene glycol, and 7.78 grams of 39 percent calcium chloride solution in water. Following, the diluted chemical reagent was mixed with one hundred (100) grams of wet soil. The resultant mixture was mixed with fifty .(50) grams of Class C fly ash. The resultant mixture was allowed to solidify.
• Example VI The procedure of Example VI was repeated using five (5) grams of the same chemical reagent.
• Example VIII The procedure of Example VIII was repeated using five (5) grams of the same chemical reagent.
• Example X The procedure of Example X was repeated utilizing the same waste with 15 percent by weight of solids.
• Example X The procedure of Example X was repeated utilizing five (5) grams of chemical reagent.
• Example XI The procedure of Example XI was repeated utilizing five (5) grams of the same chemical reagent.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Processing Of Solid Wastes (AREA)

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Citations (4)

• 1987
  • 1987-07-07 CA CA000541526A patent/CA1280449C/en not_active Expired - Lifetime
  • 1987-07-07 ES ES87401702T patent/ES2052592T3/es not_active Expired - Lifetime
  • 1987-07-07 ZA ZA874912A patent/ZA874912B/xx unknown
  • 1987-07-07 AT AT87401702T patent/ATE81563T1/de not_active IP Right Cessation
  • 1987-07-07 EP EP87401702A patent/EP0258088B1/de not_active Expired - Lifetime
  • 1987-07-07 DE DE8787401702T patent/DE3782218T2/de not_active Expired - Fee Related
  • 1987-07-08 MX MX007248A patent/MX170108B/es unknown
  • 1987-07-08 CN CN87105717A patent/CN1011931B/zh not_active Expired
  • 1987-07-20 WO PCT/FR1987/000266 patent/WO1989000752A1/fr unknown
• 1993
  • 1993-01-14 GR GR930400050T patent/GR3006795T3/el unknown

Patent Citations (4)

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