Patent Application
20150184090
The present specification relates to a hazardous, garbage, industrial waste treatment system and a novel method of gasification, treatment and or treating hazardous, medical waste.
Many types of hazardous wastes are generated every year. The wastes include organic materials, such as pesticides, polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), paints and solvents. Also, other wastes include inorganic material, such as the oxides of iron, zinc, aluminum, copper and magnesium and the salts of ferric chloride, ferrous chloride, aluminum chloride, etc.
Disposal of organic wastes in landfills and by incineration has become an increasingly difficult problem because of diminishing availability of disposal space, strengthened governmental regulations, and the growing public awareness of the impact of hazardous substance contamination upon the environment. Release of hazardous organic wastes to the environment can contaminate aft and water supplies thereby diminishing the quality of life in the affected populations.
Many patents are directed to waste incinerators and the following brief summary describes a representative number of such prior patents.
One of the most promising new methods is described in U.S. Pat. Nos. 4,574,714, 4,602,574, and 5,301,620 issued to Bach and Nagel. The method for destroying organic material, including toxic wastes, involves dissociation of the organic material to its atomic constituents in a molten metal and reformation of these atomic constituents into environmentally acceptable products, including hydrogen, carbon monoxide and/or carbon dioxide gases.
Various alternative ways of dealing with incineration have also been proposed: encapsulating in resin (U.S. Pat. No. 4,919,569), heating and encapsulating in heat activated plastic (U.S. Pat. No. 4,992,217), grinding waste and adding sterilizing fluid (U.S. Pat. Nos. 4,979,683; 5,035,367), crushing (U.S. Pat. No. 5,035,367) and irradiation (U.S. Pat. No. 5,035,858). However, incineration remains the major method of destroying medical and other waste.
Incineration of materials has several problems. Build up of slag on the furnace walls can clog outlets, and decrease efficiency. Various methods have been tried to solve these problems: adding metals with high melting points to reduce adherence of slag (U.S. Pat. No. 4,953,481), forcing air or mechanical means through ports to unclog them (U.S. Pat. Nos. 3,867,909; 3,900,011).
Likewise, various configurations of incinerators have been used. Many use grates (U.S. Pat. Nos. 4,006,693; 4,321,879; 4,430,948)—but grates may burn up, break, or become clogged. Caps over outlets and ports hinder cleanout and may break. Ports in the floor or sidewalls of many incinerators are subject to clogging with ash, melted plastic or slag which interferes with air flow and burning and requires shutdown of the unit to clean out the ports. Air tubes may be inserted into the chamber, but are usually rapidly destroyed by the corrosive action of acids in the wastes and by the intense heat.
Medical and biohazardous waste is often a special problem since it is usually non-homogeneous waste; i.e. it may include liquids and/or solids such as paper, plastic, fabric, biological tissues, metal, glass, and the like. Many incinerators do not fully burn such mixed composition waste.
The prior art reflects numerous attempts to process solid waste. Incineration through fluidized bed treatments systems is also well known. Characteristic of fluidized bed incinerators is Baston patent No. 4,352,332, issued Oct. 5, 1982.
Solid waste treatment is also shown in a fluidized bed environment in U.S. Pat. No. 3,776,150 issued Dec. 4, 1973. The latter device conveys solid waste through an auger system into a pair of separate fluidized beds. Baston patent No. 4,359,005, issued Nov. 16, 1982 also discloses a fluidized bed incineration of waste products, wherein a limestone bed is used to prevent phosphorus contamination.
Koyanagi patent No. 3,861,336 depicts an incinerator of the rotary kiln type. Refuse separation and sorting is seen in U.S. Pat. No. 3,650,396. Solid waste is transferred through a plurality of individual processing stages, including pulverization, fluidized bed reaction, and magnetic separation. Certain constituent byproducts are recovered.
U.S. Pat. No. 682,313 patented Sep. 10, 1901 by B. Zwillinger, provided an apparatus for carbonizing material. The apparatus included hollow internal walls, a chimney leading from one end of the flue, and a superheating-furnace discharging its waste gases into the opposite end of the flue, and means for passing gas through such superheating-furnace and into the carbonizing-chamber.
U.S. Pat. No. 1,747,816 patented Feb. 18, 1930 by W. H. Carrington, provided a garbage furnace comprising a fuel chamber and a combustion chamber for the garbage separated by a partition wall, a fuel grate in the fuel chamber, and a garbage grate at a higher level in the combustion chamber. The partition wall was provided with a port above the grates. A secondary grate was provided in such combustion chamber for guarding such port against obstruction.
U.S. Pat. No. 1,906,023 patented Apr. 25, 1933 by K. J. Tobin provided an incinerator appliance including a combustion chamber provided with a heat emitting source. A substantially-closed receptacle was mounted in the chamber above such heat source. The receptacle and the heat emitting source constituted the incinerator.
U.S. Pat. No. 2,196,343 patented Apr. 9, 1940 by D. J. Saltsman, provided an apparatus for distilling wood including a base, and a plurality of heating passageways therein. A fire chamber communicated with the heating passageways, so that heat could circulate therethrough. The apparatus included an outer insulated wall section, and an inner casing mounted on the base adjacent to the inner edge of the annular passageway and in spaced relation with the outer wall section.
A retort was disposed within the inner casing and was spaced from the inner surface thereof. A pipe carded off liquid from the retort. Means were provided for condensing vapours rising from the retort.
U.S. Pat. No. 2,812,291 patented Nov. 5, 1957 by C. H. Hughes, provided a broad oven including an elongated rectangular coking oven having a flat floor and capable of being sealed against air, and a heating flue system associated with such oven to supply heat. The heating system included a plurality of heating flues located directly under the floor of the oven, and side heating flues located in each side wall of the oven.
A heat exchanger unit was associated with such heating flues to transfer heat from outgoing hot burnt products of combustion to incoming air. A vaulted arch was disposed over the entire upper part of the oven, and a vaulted roof was located directly over such arch and spaced therefrom to provide a fume chamber.
A plurality of ports was provided in such arch directly to connect the oven to the fume chamber. At least one burner and associated air port communicated with the fume chamber to produce burnt products of combustion. An outlet port was associated with such fume chamber for the withdrawal of gases and vapours and burnt products of combustion.
U.S. Pat. No. 580,594 patented Aug. 4, 1959 by M. A. Naulin, provided an incinerator wall construction. That wall construction included a substantially-channel-shaped metal outer wall member and a cementitious refractory liner. Such liner was formed by interlocking sections.
U.S. Pat. No. 2,959,140 patented Nov. 8, 1960 by H. Friedberg, provided a smokeless and odourless incinerator having walls forming a furnace chamber, and a casing surrounding such chamber on all sides and spaced outwardly therefrom. An opening was provided in the upper end of the casing for the introduction of the charge to be consumed.
A hollow combined burner shield and duct was disposed in the furnace chamber. An ash trap was also provided in the furnace chamber. Baffle means supported in the trap permitted only non-linear gaseous to flow through such baffle means.
A secondary combustion device was positioned at the flue connection near the top of the upwardly-extending burner shield and duct. A maze of ceramic material was provided through which products of combustion had to pass from the furnace chamber to the flue connection. A small opening was provided for supplying combustion air to the secondary combustion device.
U.S. Pat. No. 3,098,458 patented Jul. 23, 1963 by D. C. Lanty, Jr., provided a rotary refuse converter including the combination of a housing, a rotary converter extending longitudinally of the housing, burner means in the housing for heating the converter, means for rotating the converter, a fixed refuse inlet tube structure at one end of the converter, a fixed discharge receptacle and a charred refuse outlet tube at the other end of the converter, sealing means between the rotary converter and the discharge receptacle and sealing means between the rotary converter and the inlet tube structure to preclude escape of gases from the converter.
An outlet pipe for recovered combustible gases from the converter extended from the discharge receptacle to the burner means. Sealing means were provided for the refuse inlet tube, and for the charred refuse outlet tube. Valves in the outlet pipe selectively directed a portion of the recovered combustible gases to the burner.
Canadian Patent Number 805,446 patented Feb. 4, 1969 by P. W. Spencer, provided incinerators and methods for smokeless incineration. That incinerator included means defining a combustion chamber, and a charging door defining an access means to the combustion chamber, and means operatively connected to the combustion chamber to exhaust the waste gases.
Means were disposed above the charge of waste material for controlling the temperature of the portion of the charge on top of the burning portion of the pile of burning combustibles, the control means including a water spray nozzle extending into the chamber and above the burning charge of waste materials for modulating initial combustion of a new charge of waste combustibles.
Means were responsive to the opening of the door for activating the spray nozzle.
Means were provided for indicating when the temperature in the combustion chamber exceeded the distillation temperature of the combustibles.
Canadian Patent Number 688,561 patented Jun. 9, 1969 by F. A. Lee et al, provided a fired heater. That heater included a pair of refractory faced side walls oppositely disposed each relative the other and embracing a chamber therebetween. Heating means were operatively associated with each of the side walls for heating the refractory so that radiation was emitted therefrom. A tube was disposed in the chamber, and means were provided for circulating a process fluid through the tube.
Canadian Patent Number 879,446 patented Aug. 31, 1971 by M. E. P. Hill, provided an incinerator for the combustion of materials. The patented incinerator included a refractory-lined, substantially cylindrical combustion chamber having a flue outlet coupled to one end thereof. Means were provided for feeding combustible material into the chamber. Means were provided for introducing forced air into the chamber.
Means were provided for causing a stream of air to impinge upon the combustible material while entering the chamber. Means were also provided for controlling the flow of air into the chamber so that the rate of supply of air sufficed but did not substantially exceed that which was required for complete combustion of the combustible material within the combustion chamber.
U.S. Pat. No. 3,621,798 patented Nov. 23, 1971 by F. Pedersen, provided a furnace for the combustion and destruction of waste materials. The furnace had a combustion chamber and an adjustable heat source for supplying heat thereto.
The furnace also had a refractory lining with means thereon for receiving the heat source. The combustion chamber was provided, in the region of the heat source, with a particularly defined inner sheet metal mantle. The refractory lining was provided with passages for the supply of combustion air, and the mantle had slots therein in communication with the passages.
U.S. Pat. No. 4,230,451 patented Oct. 28, 1980 by M. Chambe, provided an apparatus for the thermal treatment of a mass of organic materials. That apparatus included a horizontally elongated tank having a generally cylindrical bottom and formed with an inner wall of thermally-conductive material spaced from an outer wall of thermally-insulating material. A roof was hermetically sealed to the tank, the roof was provided with a sealable opening through which the mass could be introduced into the chamber.
The tank was formed along the bottom thereof with a sealable outlet for discharging the thermally treated mass. A burner opened into the passage and sustained a flame adapted to generate hot air which traverses the passage along the inner wall to heat the mass. A duct was provided for feeding vapour evolved in the chamber to the burner and to supply the flame with the vapour. Temperature-sensing means responsive to the temperature in the chamber were provided for controlling the flame.
U.S. Pat. No. 4,289,079 patented Sep. 15, 1981 by G. K. Swistun, provided a sawdust burning furnace which included an inner shell, an outer shell disposed concentrically around the inner shell, a bottom member, a cover member, a lower horizontal channel interconnected therewith, and an exhaust aperture defined in the outer shell adapted for interconnection to a flue connector.
A firebox was disposed inside the inner shell and was provided with air intake means. A bleeder tube interconnected the firebox through the walls of the inner and outer shells to the outside of the outer shell, and has air vent means disposed between the inner and outer shells, and means to provide air to the bleeder tube.
U.S. Pat. No. 4,495,873 patented Jan. 9, 1985 by E. B. Blankenship, provided an incinerator for burning odour-forming materials. The incinerator was made up of an inner housing located within an outer housing and which had spaced-apart walls forming an interior space therebetween. The inner and outer housings had aligned upper openings with insulated closure members. A central chamber extended from the upper opening of the inner housing to a lower position for receiving material to be burned.
An upper chamber holding a heat activated odour reducing catalyst surrounded the upper portion of the central chamber.
A gas collection chamber surrounded the upper chamber and an exhaust blower was provided for drawing gas from the central chamber to the interior space by way of the heat activated odour reducing catalyst and the collection chamber. A heater was provided for preheating the heat activated odour reducing catalyst.
A second exhaust blower was provided for drawing gas from the interior space to the atmosphere. A main heater was located within the lower portion of the central chamber for burning the material deposited therein. An air inlet extended through the wall of the inner housing to the central chamber and a blower was provided for drawing air from the interior space into the central chamber. Air ducts extended into the interior space for providing air to support combustion and for cooling purposes.
Canadian Patent Number 1,205,683 patented Jun. 10, 1986 by E. H. Benedick, provided a vertical flow incinerator having regenerative heat exchange. That thermal recovery incinerator included a plurality of adjacent, substantially-vertical gas-processing sections, each of which included heat exchange means and a cover for the section with apertures formed therein. A high temperature combustion chamber was disposed above the sections, and was in gas-flow communication therewith through the apertures.
U.S. Pat. No. 4,688,495 patented Aug. 25, 1987 by T. R. Galloway, provided a hazardous waste reactor system. The hazardous waste disposal system included a hollow high temperature cylindrical core defining a central reaction zone, a shell about the core and defining an annular space thereabout communicating with the reaction zone interior, and means for heating the core.
Means directed a carrier gas in a flow through the annular space for preheating the gas and then through the reaction zone. Means were provided for continuously-inserting hazardous waste into the reaction zone and means were provided for removing reaction product from a bottom end of the reaction zone.
Many patents have also issued which were directed to methods and apparatus for the thermal decomposition of stable chemicals. Among these patents are the following:
U.S. Pat. No. 4,140,066 patented Feb. 20, 1979 by H. Rathjen et al, provided a process for the thermal decomposition of polychlorinated organic compounds, e.g., polychlorinated phenyls and biphenyls (PCB's). The process comprised heat treating the polychlorinated organic compounds in a flame, in a particularly-defined high-turbulence, combustion chamber.
Canadian Patent Number 1,164,631 patented Apr. 3, 1984 by O. D. Jorden, provided a system and apparatus for the continuous destruction and removal of polychlorinated biphenyls from fluids. That system included a mixing chamber, an agitator in the mixing chamber, a pump for feeding the fluid containing polychlorinated biphenyl into the mixing chamber, a heater for raising the temperature of the fluid to a predetermined temperature, and an injector for feeding a predetermined quantity of a reagent.
A reaction chamber was operatively-connected to the mixing chamber for receiving the fluid containing the polychlorinated biphenyl and reagent from the mixing chamber. A separator separated the products of reaction between the polychlorinated biphenyl and reagent from the fluid leaving the reaction chamber. A degasser was provided for removing certain gases contained in the fluid and products of reaction leaving the separator means.
Canadian Patent Number 1,166,654 patented May 1, 1984 by G. Evans, provided an apparatus for PCB disposal. The apparatus included a substantially air-tight assembly which included at least one internal combustion engine for burning of a mixture of PCB liquids, fuel and air, and means for processing exhaust gases therefrom. Such means included either at least one gas scrubber supplied with water, and at least one gas scrubber supplied with fuel, or at least one adsorber tower with packing material which was adapted for the passage of gases and which was suitable for adsorption of organic contaminants.
Canadian Patent Number 1,169,883 patented Jun. 26, 1984 by O. L. Norman, provided a method for destruction of polyhalogenated biphenyls. The method included the steps of reacting the polyhalogenated biphenyls at a high temperature in a solution in an inert liquid with a dispersion of sodium in a hydrocarbon oil.
U.S. Pat. No. 4,479,443 patented Oct. 30, 1984 by I. Faldt et al, provided an apparatus for thermal decomposition of stable compounds. The apparatus included a plasma generator for producing a high temperature plasma, means for feeding hazardous waste to and through the plasma generator, means for feeding sufficient oxidizing agents to the hazardous waste to permit the complete decomposition of the hazardous waste to stable products, and means for controlling the temperature of the plasma and the flow of hazardous waste through the plasma generator.
Canadian Patent Number 1,225,775 patented Aug. 18, 1987 by W. C. Meenan, provided a method for treating polychlorinated biphenyl contaminated sludge. The method included the steps of heating the material by exposure to hot gas in a heating means thereby separating the polychlorinated biphenyls from the material, and then conveying the separated polychlorinated biphenyls out of the heating means for further treatment.
Canadian Patent Number 1,230,616 patented Dec. 22, 1987 by Y. Kilamira, provided an apparatus for rendering polychlorinated biphenyl toxic free. The apparatus included a combustion furnace, a combustion vessel disposed in the combustion furnace, and a grid in the combustion vessel which divided the interior thereof into an upper and lower section.
A PCB tank communicated with the lower section of the combustion vessel, for filling the combustion vessel. A burner and a fan were movable so as to be selectively placed in a position in opposition to an opening of the combustion furnace. A gas treatment tank communicated with the combustion furnace via an exhaust duct.
Molten metal reactors may be used to treat a wide variety of waste materials including wastes which include halogenated hydrocarbons, biomedical waste, and radioactive wastes. Molten metal reactors utilize a bath of molten reactant metal which may include aluminum, magnesium, and/or lithium, for example, along with other metals. The atmosphere above the bath is preferably purged of oxygen. When waste material is placed in contact with the molten reactant metal, the metal reacts with the organic molecules in the waste material to strip halogen atoms and form metal salts.
The reaction also liberates carbon along with other elements such as hydrogen and nitrogen. Carbon, hydrogen, nitrogen, and some metal salts may be removed from the molten metal reactor in a gaseous form. Metals which may be included in the waste material, or are liberated from the waste material, may alloy with the bath. Other reaction products or liberated materials collect at the surface or bottom of the bath and may be removed by suitable means.
Molten metal reactors require a heating arrangement to heat the reactant metal to a molten state and then maintain the reactant metal in a molten state at a pre-determined temperature as waste material is added to the bath. U.S. Pat. No. 5,000,101, U.S. Pat. No. 6,195,382, to Wagner shows a molten metal reactor having an induction heater for heating the reactant metal. U.S. Pat. No. 5,271,341 to Wagner discloses a two-chamber molten metal reactor having a hydrocarbon-fired heater in one of the chambers. This two-chamber arrangement allows the reactant metal to be heated with hydrocarbon-fired burners while maintaining a separate area in which reaction products may collect for removal.
Tyrer (in U.S. Pat. No. 1,803,221) and Nixon (in U.K. Patent 1,187,782) describe in general terms two-zone gasifier processes that have the potential to produce a high-purity hydrogen-rich gas by introducing the hydrocarbon feed below the surface of the molten iron, thereby minimizing the production of cracked products. However, by operating at atmospheric pressure, these molten—metal gasifier processes produce hydrogen-rich and carbon monoxide-rich gases at atmospheric pressure, when in fact most industrial processes require that such gases be available at higher pressures, such as 5 to 100 atmospheres absolute or higher. Thus, when using such processes, it is necessary to compress the gases prior to industrial use, which is very expensive.
Molten metal, especially molten iron, baths are well known and widely used as gasifiers. The light temperatures in such baths rapidly decompose, by thermal action, a variety of solid, liquid and gaseous feeds into hydrogen and/or carbon oxides. Such processes are well known, e.g., U.S. Pat. Nos. 4,574,714 and 4,602,574 to Bach teach a molten iron gasifier. Another, and preferred, molten metal reactor is disclosed in U.S. Pat. No. 5,435,814, MOLTEN METAL DECOMPOSITION APPARATUS, Charles B. Miller and Donald P. Malone.
U.S. Pat. No. 4,062,657 issued to Knuppel et al. is directed to a process and an apparatus for gasifying sulphur-bearing coal in a molten iron bath. Reportedly, hot liquid slag is transferred from the iron bath to a second vessel in which the slag is desulfurized by contact with an oxygen containing gas, and then returned to the iron bath for reuse.
An article by L. Meszaros and G. Schobel in British Chemical Engineering, January 1971, Volume 16, No. 1 describes a molten-bed reactor having a molten lead bath which facilitates the simultaneous oxidation and decarboxylation of furfurol to produce furan. Furfurol and air were reportedly bubbled through molten lead in stoichiometric ratio from a common furfurol-air inlet system and, alliteratively, from a separate furfurol inlet and air inlet system. The article states that the method is useful for the partial oxidation of hydrocarbons, alcohols, aldehydes, and for the decomposition of natural gas and gasoline.
U.S. Pat. No. 4,406,666, issued to Paschen et al., is directed to a device for the gasification of carbon-containing material in a molten metal bath process to obtain the continuous production of a gas composed of carbon monoxide and hydrogen. The '666 Patent states that gaseous carbon materials as well as gases containing oxygen can be introduced into the reactor below the surface of the molten metal bath. The molten metal reportedly consists of molten iron, silicon, chromium, copper, or lead.
A method for converting carbon-containing feed, such as municipal garbage or a hydrocarbon gas, to carbon dioxide is described in U.S. Pat. No. 5,177,304 issued to Nagel. The carbon-containing feed and oxygen are introduced to a molten metal bath having immiscible first and second molten metal phases. The '304 Patent states that the feed is converted to atomic carbon in the bath, with the first metal phase oxidizing atomic carbon to carbon monoxide and the second metal phase oxidizing carbon monoxide to carbon dioxide. Heat released by exothermic reactions within the molten bath can reportedly be transferred out of the molten system to power generating means, such as a steam turbine.
Hydrocarbon-fired heaters are desirable for many molten metal reactor applications. However, other applications for molten metal reactors cannot accommodate heating using hydrocarbon-fired burners. For example, a molten metal reactor may be highly desirable for treating biomedical wastes and other wastes generated aboard a ship. However, a sufficient hydrocarbon supply may not be readily available aboard the ship to provide the required heating.
Induction heaters are well-suited for fixed plants which have access to a suitable electric power supply. However, the electromagnetic field produced by induction heaters may limit the temperatures at which the molten metal reactor could be operated. This temperature limitation arose from the fact that portions of the electromagnetic field extended beyond the molten reactant metal and passed through the reactor vessel and related equipment.
The electromagnetic field generates heat in these metallic structural elements as well as in the reactant metal. Therefore, structural elements associated with the molten metal reactor had to be comprised of metals which maintained strength at high temperatures. Operating temperatures still had to be kept low enough to maintain the structural integrity of structural elements associated with the molten metal reactor.
The temperature limitations associated with prior molten metal reactors also effectively limited the types of wastes which could be treated. For example, although wastes which included transuranic elements (all elements having an atomic number greater than uranium), could be treated in prior molten metal reactors, the treatment was slowed by the temperature of the molten metal bath. In prior art molten metal reactors, the molten metal temperature was insufficient to cause transuranic metals to go to a molten state.
Thus, transuranic metals dissolved relatively slowly in prior art molten metal reactors, and the transuranic elements alloyed with the reactant metals only after this relatively slow dissolution process
According to an exemplary embodiment of the present specification, industrial waste treatment system is disclosed which comprises a refractory-lined crucible vessel for holding a melt (molten metal) and a inlet tubular conduit for directing the flow of a stream of industrial waste material or feed such as carbonaceous feedstock to be dropped into contact with the said melt disposed within the refractory-lined crucible, an outlet exhaust conduit for directing the flow of exhaust gases evolving from the melt to a gas treatment unit (in a second vessel) for reducing the Sulphur and particulate content of said exhaust gases.
In one non-limiting example of the present specification, the molten metal comprises the following melt composition:
(with 4 proximate readings):
In one aspect of the above embodiment, a slag-oxide layer formed subsequently during the operation of the present specification is periodically drained and removed from the refractory-lined vessel.
A typical reference composition of the molten slag layer is exemplified as follows:
In another non-limiting aspect of the present specification, industrial waste is first loaded onto a compactor unit/train, compacted into a dense, compacted paste-form and pumped by means of an auger drive through a conduit that is adapted to direct the compacted waste into contact with a molten metal disposed within a refractory-lined treatment vessel (first reactor). A lance device positioned above the surface of the molten metal ejects an air jet to cause contact with the molten metal to cause partial oxidation of the molten metal and to form a slag layer thereon. Evolving gases are directed via one or more exhaust gas passageway to a second reactor where additional heat is supplied to further reduce dioxins otherwise not treated in the first reactor.
In one mode of the present specification, at least a jet of air in ejected from a lance device positioned above the molten metal and molten slag-oxide layer in the manner as follows:
a) ejecting at least one primary jet of air from a lance positioned above the molten metal into the molten metal to react with impurities therein and to form a layer of molten slag;
b) continuing to eject the primary jet of air from the lance and thereby causing the primary jet of air to pass through the slag layer into the molten metal;
c) ejecting a plurality of secondary jets of air from the lance, the secondary jet of air travelling for a distance separately from the primary jet of air; and
d) entraining the secondary jets of air into the primary jet of air upstream of the entry of the primary jet of air into the volume of the molten metal.
The said primary jet of air is desirably ejected from the lance in both step (a) and step (b) of the method according to the specification at an axial velocity that is supersonic. In both these steps, a supersonic velocity in the range of Mach1.5 to Mach 3 may be used.
In order to achieve entrainment of each secondary air jet at a suitable intermediate location of its associated primary jet, the longitudinal axis of each secondary jet diverges from the longitudinal axis of its associated primary jet in the direction of travel at an angle of up to 45°.
The preferred angle of divergence of each secondary air jet from its associated primary air jet is in the range of 5° to 25° depending on the absolute velocity of the second air jet and its velocity relative to the first air jet. Particularly preferred angles of divergence are in the range of 10° to 20′.
The reactor vessel 101 contains a molten metal layer 107 and a molten slag-oxyde layer 108 which floats on top of the molten metal layer 107.
The gasifier comprises injection tubes 105, 106 for injecting air jets into the molten slag-oxyde layer 108 and through the slag-oxyde layer into the molten metal layer 107. Furthermore, an overhead lance 116 is provided in the cover 102 and feed conduits 109, 110 are provided in a bottom wall of the reactor vessel 101. In other embodiments, further feed conduits may be provided in side walls of the reactor vessel 101. The overhead lance provides an example of a tubular conduit according to the specification.
The injection tubes 105, 106 are connected to an air reservoir 111 via a compressor 112. The overhead lance 116 is connected to a reservoir 113 of a feed fuel via a feeder pump 114. A tilting mechanism 115 is provided for tilting the first reactor vessel 101 at a tilt angle alpha. In one embodiment, the tilt angle can be adjusted between 0 and 60 degrees.
Tables 1-5 are exemplary operation design parameters that may be used with the waste treatment system. However, other operations and/or configurations may be realized. Tables 6-7 includes the bill of materials which may be varied.
It should be noted that sodium hydroxide is an optional additive and may not be applied depending on waste composition, operating condition and melt temperature.
In another embodiment of the present specification, sodium oxide and or CaCO3 is deployed by admixing a pre-determined amount to the industrial waste prior to being pumped into contact with the molten slag-oxide layer in the first vessel of the present specification to control the basicity of the slag-oxide layer during the treatment of the waste material.
Depending on the moisture present in the industrial waste, sodium oxide admixed into the waste will undergo a limited reaction as follows:
Na2O+H2O→2NaOH
The composition of slag varies with the type of melting process used and the type of iron or steel being melted in the first vessel, additional oxides or nonmetallic compounds are formed when molten metal is treated with industrial waste material that changes the chemistry of the system, and because these oxides and nonmetallics are not soluble in iron, they float in the liquid metal as an emulsion, and eventually these nonmetallics coalesce into the molten slag-oxide layer on the top surface of the molten metal.
In carrying out the present specification, it is possible to use a readily castable, water-free refractory material for the working liner, comprising 60% Al 2 O 3, 38% SiO 2, and 2% TiO 2.
In one configuration of the present specification, the lance device (positioned above the molten metal), and or parts of the first vessel adapted to contain the molten metal can be made from alumina refractory containing at least 88 wt. % alumina and being non-porous with a porosity of up to 20%. The terms non-porous and substantially non-porous are used herein to describe a refractory with a porosity of up to 20%.
In one non-limiting sample, the refractory composition and specifications are herein disclosed:
It is noted above in Table 2 that the waste streams need not be separated and can be directed as a waste mixture thus making waste treatment significantly more cost effective.
In one configuration of the present specification, the refractory-lined vessel is configured to hold between 1 to 15 metric tons of melt, and the refractory-lined vessel further operable to be adapted onto a skid-mount rail.
The present specification may be mounted on a trailer truck and the first vessel configured to be held in a 20-foot or 40-foot freight container unit (shipping TEU), and be adapted such that the trailer is divided into two sections, each section having means for connection with the respective ends of the skid members and each section having means for raising one end of the trailer into the connection means at the required level for travel, and each section having adjustable stabilizing equipment for maintaining the tanks in position on the trailer as it is transported.
In another configuration the refractory-lined vessel is configured to hold between 500 Kg to 1.5 tons of molten metal (melt).
In another non-limiting aspect of the present specification, industrial waste is first compacted prior to being pumped into the flow conduit tubular apparatus that directs the compacted industrial waste into contact with the molten metal, the compaction is further operated by means of a compaction power unit.
A power unit of this aspect is of the type which moves a compaction head along between the ends of a refuse container for packing the refuse and for removing the compacted refuse from the refuse container. The power unit is attached to the interior of the refuse container and to the compaction head.
The power unit of this aspect comprises a housing provided with a chamber therein. A first piston of a given transverse dimension is positioned within the chamber. Attached to the first piston and coaxial therewith are spaced-apart coaxial cylinders. A second piston which has a smaller transverse dimension than the first piston is also within the chamber and is coaxial with the first cylinder and is between the cylinders which are attached to the first piston.
Fluid is introduced through a main passage of the housing for operation of the pistons. A valve mechanism is located within the main passage. The fluid is conducted into the main passage and then through an auxiliary passage into a space between the cylinders which are attached to the first piston, for movement of the second piston or smaller piston, for initial operation of the power unit and for initial movement of a compaction head which is attached to the power unit. Fluid which moves the first piston or smaller piston is of a given initial pressure. This fluid of the given pressure moves the smaller piston until this fluid pressure is unable to move the smaller piston farther.
Then the pressure of fluid flowing into the main passage increases. This increase in fluid pressure causes valve operation in the main passage which closes the auxiliary passage and closes fluid between the main passage and to the smaller piston. Thus, fluid which has moved the smaller piston is trapped within the chamber of the housing. The valve operation within the main passage almost simultaneously opens a second auxiliary passage for flow of fluid to the first piston or larger piston. The larger piston then moves, and applies increased pressure upon the fluid which is trapped within the chamber and which is engaging the smaller piston. Thus, increased pressure is applied to the smaller piston for additional movement of the compaction head.
In another non-limiting aspect of the present specification, industrial waste material is loaded into a common hopper unit prior to compaction in a mechanically integrated train wherein the waste processing system according to the specification utilizes as a base a commercially available horizontal axis ram type comparatively low silhouette refuse compactor unit having means to couple releasable with large refuse transport containers.
Upon this compactor unit base in tandem relationship are a fixed hopper bin having a bottom outlet opening which registers with an opening in the underlying compactor unit ahead of the horizontal ram thereof; and a vertically swingable dumping bin which is raised to a steep angle above the compactor unit base to feed large volumes of waste by gravity action into the fixed hopper bin. The side walls of the hopper and dumping bins at one side of the apparatus are cut downwardly to allow side loading of refuse by front end loaders and the like when the dumping bin is in a level position on the compactor unit base. The dumping bin is raised and lowered by power cylinder means on opposite sides of the compactor unit base.
In another non-limiting aspect of the present specification, a load cell device is configured to read and record the mass weight of the industrial waste material and transmits the recorded data signal to a remote processor for calculating the quantity of CaCO3 to be admixed during the stage of waste compaction so as to adjust and control the chemical composition of the molten slag layer that is formed during operation of the molten metal disposed in the first reaction vessel.
In another non-limiting aspect of the present specification, a remote processor calculates the quantity of CaCO3 to be admixed into the industrial waste based on the function of the total mass weight of the molten metal in the first reactor vessel, the mass weight of the industrial waste material loaded into the hopper unit, or a combination thereof.
Based on a iron melt, substantially molten at a temperature of between 1100 to 1300 degrees C, the reaction dynamics are as follows:
FeO(l)+C(s)→Fe(l)+CO(g)
Moisture contained within the waste material is reacted in accordance with the following reaction chemistry:
Fe(l)+H2O(l)→FeO(l)+H2(g)
Various slag-oxide chemistry are as follows (where cast iron 3-4.5% carbon is utilized):
CaCO3→CaO+CO2
MgO.Al2O3(l)→Mg(l)+2Al(l)+4O
Mg(s)+CO(g)→MgO(l)+C(l)
In some cast irons the silicon and manganese levels present in its solid phase may range from Si 1.5 to 2.0% wt and Mn from 0.5 to 1.0%, and while energy fuel expenditure for such cast iron charge materials are lower during reactor start-up, the formation of the molten iron bath and in combination with the stirring action of the oxidizer gas will cause formation of SiO and MnO in the slag layer right above the molten iron bath surface, contributing to limited but severe erosion of the refractory lining in the reactor.
The heat of reaction (ΔH), or enthalpy, determines the energy cost of the process. If the reaction is exothermic (ΔH is negative), then heat is given off by the reaction, and the process will be partially self-heating. If the reaction is endothermic (ΔH is positive), then the reaction absorbs heat, which will have to be supplied to the process. The Gibbs free energy (ΔG) of a reaction is a measure of the thermodynamic driving force that makes a reaction occur. A negative value for ΔG indicates that a reaction can proceed spontaneously without external inputs, while a positive value indicates that it will not. The equation for Gibbs free energy is:
ΔG=ΔH−TΔS
where ΔH is the enthalpy change in the reaction, T is absolute temperature, and ΔS is the entropy change in the reaction. The enthalpy change (ΔH) is a measure of the actual energy that is liberated when the reaction occurs (the “heat of reaction”). If it is negative, then the reaction gives off energy, while if it is positive the reaction requires energy. The entropy change (ΔS) is a measure of the change in the possibilities for disorder in the products compared to the reactants.
An Ellingham diagram is a plot of ΔG versus temperature. Since ΔH and ΔS are essentially constant with temperature unless a phase change occurs, the free energy versus temperature plot can be drawn as a series of straight lines, where ΔS is the slope and ΔH is the y-intercept. The slope of the line changes when any of the materials involved melt or vaporize. (note that free energy of formation is negative for most metal oxides).
The position of the line for a given reaction on the Ellingham diagram shows the stability of the oxide as a function of temperature. Reactions closer to the top of the diagram are the most “noble” metals (for example, gold and platinum), and their oxides are unstable and easily reduced. As we move down toward the bottom of the diagram, the metals become progressively more reactive and their oxides become harder to reduce.
When using carbon as a reducing agent, there will be a minimum ratio of CO to CO2 that will be able to reduce a given oxide. The main reactions within the molten iron agent are similar to that of the common gasification reactions that occur in today's conventional processes, namely the partial oxidation of carbon expressed as follows:
C(s)+0.502(g)→CO(g)
C(s)+H2O(g)→CO(g)+H2(g)
C(s)+CO2(g)→2CO(g)
H2O→0.5O2+H2
Typical composition of the exhaust gas produced may be as follows:
Herein, “.sub.” denotes a subscript notation which refers to the numbers following the “.sub.”-Symbol. Within the context of this specification, chemical sum formulae may be written with or without subscript. For example, “O2” is equivalent to “O.sub.2”. Similarly, “.sup.” refers to a superscript. In another embodiment, the molten metal is inductively heated in the vessel to at least 1300 degrees C, and industrial waste material is pumped via a tubular conduit into contact with the slag oxide layer that is formed on the top surface of the molten metal.
In another non-limiting aspect of the present specification the molten metal is inductively heated and further exothermically oxidized to a temperature in the range of between 1400-1500 degrees C, and between 0.5% to 10.7% mass weight of the industrial waste is admixed with CaCO3 (CaCO.sub.3) to control the basicity of the molten slag layer that forms on the top surface of the molten metal in the first reactor vessel.
The vessel is refractory-lined and may be made up of the following refractory material having the chemical composition:
Periodically, the chemical composition of the molten metal or molten slag-oxide layer would be monitored by using a measuring lance device to be inserted into the molten metal which comprises an expendable body, a protected first thermocouple mounted on one end of said lance, a receptacle chamber for receiving the molten metal, a protected second thermocouple mounted inside said chamber, and a path for the molten metal leading to said chamber, characterized in that an opening through which air can be discharged is provided in a part of a protecting tube for the second thermocouple, said part not positioned in said receptacle chamber.
According to the example of
The temperature of the molten steel can be measured by a thermocouple 2′ provided at the tip end of lance body 10. The molten steel enters deoxidation chamber 1′ through a path or mouth 9 thereof, where the steel comes into contact with a deoxidation agent 14 such as Al, Ti, etc. which has previously been placed in chamber 1′. The molten steel thus deoxidized enters receptacle chamber 1 through an outlet 15 where the solidification temperature of the molten steel is measured by another thermocouple 2 to determine the amount of carbon in the steel.
The lance which has thus received the molten steel is withdrawn from the bath, and the steel in the receptacle chamber 1 can be measured with respect to its composition such as Mn, S, P, etc. by the use of a Count VAC analyzer.
As deoxidation chamber 1′ is made of steel as above, there is hardly any adverse effect which would otherwise have been encountered by the through melting loss of a part of the deoxidation chamber 1′ such as a corner of the mouth 9, the outlet 15 and the like.
As for receptacle chamber 1, there is hardly any occurrence when a part thereof melts into the molten steel, since the temperature of the molten steel is somewhat lowered as it is passed from the deoxidation chamber, and also there is no corner part or notch contacting the molten steel in this case.
In the practice of this specification, a spray nozzle can be provided in the upper part of the connector.
In
A spray nozzle 19 is provided at the sub-lance 18 in the upper part of the connector 16. When the lance is in operation, a gas such as oxygen, nitrogen and the like is sprayed to cool lead wires 13 and the connector 16, while water vapor or tar, etc. in the holder 17 and the sub-lance 18 can be purged from a hole 20.
In
In a first aspect, the present specification discloses a method for operating a waste treatment system for treating a feed, such as an industrial waste material, by contacting the feed into a molten metal in a first vessel, wherein the first vessel contains a volume of the molten metal.
A jet of air is ejected from a lance positioned above the molten metal into the molten metal to react with the molten metal to form a layer of molten slag-oxide. The jet of air is continued to be injected from the lance at least until the jet of air passes through the molten slag-oxide layer into the molten metal.
The feed is pumped from a tubular conduit positioned above the molten slag-oxide layer to cause contact between the feed and the molten slag-oxide layer, wherein the feed is selected from coal, coal-liquid slurry, biomass, waste-derived material, crude oil, tar sands, shale-derived material, or a combination thereof.
The molten metal bath material has the following composition:
Exhaust gases evolving from the molten metal and molten slag-oxide layer are directed to a second vessel to treat the exhaust gases to a pre-determined proximate gas molar composition.
A product syngas flowing from the molten metal is directed by one or more gas passage conduit configured in operational communication with the second vessel and with a powerplant for electric power generation, a first chemical catalytic reactor to chemically reform product syngas into a pre-determined hydrocarbon product, a second chemical catalytic reactor to chemically reform product syngas into anhydrous ammonia product, a third chemical catalytic reactor to chemically reform product syngas into methanol product, or a combination thereof.
Experiments have shown that the abovementioned composition of the molten metal bath leads to a high efficiency of syngas production for the abovementioned types of feed materials. This efficiency is further enhanced by blowing air through the slag layer into the molten metal and thereby increasing the amount of metal in the slag layer. According to the present specification, the injection of air may be made even more effective by using a Laval nozzle, also known as “convergent-divergent nozzle”, to produce a supersonic air jet and by using a first and second jet of air which are inclined to each other, thereby entraining the second jet of air into the first jet of air. In one embodiment, the air speed is controlled by a processor, for example adjusting an air pressure or a shape of a Laval nozzle.
In a second aspect, the present specification discloses a device for operating a waste treatment system for treating a feed, such as industrial waste material, by bringing the feed into a molten metal in a first vessel, wherein the first vessel contains a volume of the molten metal.
The device comprises ejection means, such as an ejection nozzle, for ejecting at least one jet of air from a lance positioned above the molten metal into the molten metal to react with the molten metal to form a layer of molten slag-oxide and for continuing to eject at least one jet of air from the lance and thereby causing at least one jet of air to pass through from the molten slag-oxide layer into the molten metal.
Furthermore, the device comprises a tubular conduit for connection to a feeder pump and for causing a contact between the feed and the molten slag-oxide layer, the tubular conduit being positioned above the vessel.
Moreover, the device comprises one or more gas passage conduits configured in operational communication with the first vessel. The gas passage conduits comprise a first gas passage conduit for directing exhaust gases evolving from the molten metal and molten slag-oxide layer to a second vessel to treat the exhaust gases to a pre-determined proximate gas molar composition. Furthermore, the one or more gas passage conduits comprise a second gas passage conduit for directing syngas from the first vessel to a syngas consumer. The first and the second gas passage conduit may also be identical.
For example, the syngas consumer may be provided by a powerplant for electric power generation, a first chemical catalytic reactor to chemically reform product syngas into a pre-determined hydrocarbon product, a second chemical catalytic reactor to chemically reform product syngas into anhydrous ammonia product, a third chemical catalytic reactor to chemically reform product syngas into methanol product, or a combination thereof. According to one embodiment, the second vessel is located within the syngas consumer. According to a further embodiment, the second vessel is located between the first vessel and the syngas consumer.
A device according to the current specification is capable of generating a high yield of syngas by providing a high metal content in the slag layer and thereby an effective heat transfer to the feed. In particular, the metal content in the slag layer is increased by providing suitable ejection means for blowing air through the slag layer into the molten metal.
Experiments on direct-contact heat exchange between molten metal and water for steam production were conducted. These experiments involved the injection of water into molten lead-bismuth eutectic for heat transfer measurements. Based on the initial results of the experiments, the effects of the water flow rate and the molten metal superheat temperature difference between molten metal and saturated water on the volumetric heat transfer coefficient were discussed. Molten lead-bismuth was chosen to obtain text data. The experiments were performed with lead to demonstrate feasibility of steam production from water injection in dense metal without molten metal contamination with the carbon feedstock first. However, it is believed that the steam production also works with molten iron.
The molten metal-slag experiments that are mentioned below were conducted in the Republic of Singapore detailing some of the reaction dynamics related a further embodiment of the present specification. A steam production according to the further embodiment may be used in combination with a gasification method or with a gasification apparatus according to any of the other embodiments.
A total of 32 tests including shakedowns were conducted. It was found that the plugging of the injection nozzle due to the back flow and freezing of the molten metal in the injector could be reduced by mixing the water injection with an argon flow to. A run typically consisted of transient cooldown of the molten metal with intermittent, short-duration quasi steady states.
Data for three selected quasi steady states are used to estimate the volumetric heat transfer coefficient. These data show axial temperature profiles through the liquid metal in the test section. It is seen that the molten metal temperature is remarkably uniform and constant throughout the liquid metal-water mixing zone. We believe that the molten metal surface corresponds to the height at which the temperatures deviated significantly from the uniform distribution.
Based on the above observation of the data, the volumetric heat transfer coefficient for the molten metal water mixture. Uv, was estimated from the expression
Uv=m.sub.W(cPTsub+hfg)/VT Eq. (1)
wherein m.sub.W is the water injection rate, Tsub is the degree of subcooling of the injected water. Cp and hfg are the specific heat and the heat of vaporization of water, respectively, V the volume of the molten metal-water mixture, and T is the temperature difference between the molten metal and saturated water.
The estimate of equation (1) does not include possible superheating of the steam produced, so it is considered to give a lower estimate of the volumetric heat transfer coefficient. The estimates of Uv along with the test conditions for the three quasi steady states selected are summarized in Table 1. The average void fraction of the molten metal water/steam mixture (alpha) was estimated by
(alpha)=(z−z0)/z Eq. (2)
where z is the height or the molten metal-water mixing zone and of the collapsed height (i.e metal only) both being measured from the water injection point.
Experimental Apparatus: The experimental apparatus consists of a test section and associated components.
Water is pumped from a supply tank to the injector through a set of filters The filters were reused from a previous project WATERMUSIC. The water flow rate is metered by valves and measured by flow meters with ranges of 14 to 100 ml/min and 50 to ml/min. There is also an argon supply to the injector, the purpose being to have flow through the injector while molten metal is being transferred to the test section from the melt vessel. Without this argon flow, metal could flow down into the injector and plug it. Accordingly, the present specification discloses a water injector for a gasifier having a supply means for an inert gas, such as argon, and a step of injecting water onto molten metal through an injector and injecting an inert gas into the injector.
When metal has been transferred from the melt vessel to the test section, an air supply into the containment vessel is turned on to freeze metal in the transfer tube and prevent inadvertent transfer back to the melt vessel.
Finally, a pump is provided that would remove any water that condensed inside the containment vessel. However, this should not happen since the steam is exhausted into a condenser outside of the containment vessel.
Test Procedure: Lead alloy (lead-bismuth, melting point.=125° C.) that has previously been loaded into the melt vessel is heated to a temperature sufficiently above the melting point for the lead alloy to flow easily. Once this temperature is reached, lead alloy starts to flow under gravity from the melt vessel into the test section.
During the transfer, a flow of argon gas through the injector is maintained to prevent backflow of molten metal into the injection port. Once transfer is complete, as indicated by level probes in the test section, the air supply to the containment vessel is turned on and the heater on the transfer tube is turned off. This enables a metal plug to form and prevents molten lead alloy from back into the vessel. The molten metal in the test section now be further heated.
Once water flow is established, the argon flow is gradually reduced to zero. Heat transfer measurements are made using the thermocouples in the molten metal, and by measuring the power output of the test section heaters.
While various embodiments of the specification have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the specification. Furthermore, while various dimensions are described in the specification and/or figures, these dimensions are exemplary values. It is contemplated that larger or smaller dimensions may be employed within the scope of the specification. Accordingly, the subject matter of the present specification is not to be restricted except in light of the attached claims and their equivalents.
The embodiments can also be described with the following lists of elements being organized into items. The respective combinations of features which are disclosed in the item list are regarded as independent subject matter, respectively, that can also be combined with other features of the application.
Carbon in the range of 3.3 to 3.97 mass weight percent
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/IB2012/052893 | Jun 2012 | IB | international |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2013/054736 | 6/10/2013 | WO | 00 |
