KR100232406B1 - Use of alkaline earth metal hydroxides as a binder additive for refuse derived fuel - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to waste-extracted fuels (RDFs), and more particularly, to waste-extracted fuels prepared using alkaline earth metal hydroxide binders and methods for their preparation.

According to the present invention, the use of RDF pellets / hexahedrons with improved performance as a binder significantly reduces contaminants such as acid gases such as SO _X , NO _X , CO _2, and toxic substances such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls. A method is provided.

In the practice of the present invention, a particulate fuel containing one oxide and sulfur was introduced into a combustion section of a solid fuel combustion furnace. The composition of the particulate fuel was at least 10% of the densified RDF agglomerate containing alkaline earth metal hydroxide as a binder, based on calories.

Combustion conditions were formed inside the furnace and particulate fuel was combusted in the presence of oxides. Sufficient alkaline earth metal hydroxide was added to the RDF agglomerate / hexahedron to generate exhaust gas from the combustion unit. The exhaust gas was analyzed and the content of SO ₂ was based on the calorific value of the RDF agglomerate / hexahedron containing no alkaline earth metal hydroxide. At least 20% lower than the SO ₂ content of the same amount of fuel. The most preferred fuel composition is a mixture of sulfur-containing fuels with RDF agglomerates / hexahedrons with at least 20% of the alkaline earth metal hydroxide binder added on a caloric basis.

As another aspect of the present invention, the content of the polycyclic aromatic hydrocarbon of the exhaust gas generated in the combustion unit is the content of the polycyclic aromatic hydrocarbon of the fuel containing the same amount of RDF agglomerate / hexahedron containing no alkaline earth metal hydroxide on the basis of calories. More than 30% lower.

Another advantage of the present invention is that the content of polychlorinated biphenyls in the off-gas is at least 50% lower based on calorific value of RDF agglomerates / hexahedrons that do not contain alkaline earth metal hydroxides.

Description

Waste- Extracted Fuels Prepared Using Alkaline Earth Metal Hydroxide Binders and Methods for Making the Same

FIELD OF THE INVENTION The present invention relates to waste-extracted fuels (RDFs), and more particularly, to waste-extracted fuels prepared using alkaline earth metal hydroxide binders and methods for their preparation.

Fuel extracted from the waste (RDF) is a product produced in a solid waste treatment plant, where it is processed by commercial or industrial wastes before or after treatment, which significantly reduces the amount of waste that will actually fill the landfill. The calorific value of this waste extract fuel will be equal to or more than half the level of anthracite coal, and is expected to be used as the main fuel in coal-fired power plants or in combination with other hydrocarbon fuels, namely coal.

Conventional use practice is to produce waste extract fuels in the form of dense granules and store them as fuel for the combustion process. For example, according to US Pat. No. 4,561,860 to Gulley et al., The original waste is crushed and screened to remove fine or oversized material, and only medium-sized materials are sent to the air classifier, thereby reducing It suggests the process of separating light materials from heavier materials such as metal or glass.

Light material is sent to the dryer through a cutter and a high density machine, where the humidity is reduced by about 17%. The more dried material can then be mixed with coal dust to about 25-50 wt%. The mixture of coal and waste material enters the roller mill and the die screen passes through, resulting in a dense RDF product. However, the patent only discloses a process for producing a high density RDF product, and there is no mention of a binding additive.

The waste-derived fuel (RDF) of the present invention contains at least 5% by weight of a mixture of alkaline earth metal hydroxides in the form of granules used in the production of combustible mixtures. The fuel in pellet or cube form of the present invention containing alkaline earth metal hydroxide as a binder additive comprises at least 10% high density RDF pellets or cubes, and at least 20% sulfur-containing coal, on a thermal equivalent basis.

Combustion of high-density RDF pellets or mixtures of cubes and sulfur-containing coals results in the treatment of SO _2, NO _X , CO ₂ , polycyclic aromatic hydrocarbons and polychlorine from effluent gases from similar combustibles that do not contain alkaline earth metal hydroxides. It is effective to reduce the biphenyl content. Alkaline earth metal hydroxides used in the present invention are a mixture of calcium hydroxide and magnesium hydroxide of the same weight.

Waste-extracted fuels of the invention, in particular waste-extracted fuels with binders, are in the form of pellets or cubes, which pellets or cubes are used in furnaces using solid fuels. In this specification, the terms "pellet" or "cube" are used interchangeably. The only difference is the shape of the finished high density product. In other words, the pellets are conical and the cubes are the same in all components or properties except that they are rectangular in cross section.

The addition of binders to the waste extract fuels produces more dense, high-strength RDF pellets. For example, US Pat. No. 4,405,331 to Blaustein et al. Discloses waste extraction fuel pellets using a binder fly ash system in addition to coal dust that can be selectively added to increase the calorie content of the fuel. Doing. More preferred wastes are solid cellulose materials such as paper or cards, or plastic materials such as styropol or soft plastics, and soft metal materials such as paper clips or staples and glass. Most preferably, the waste used in the treatment process is free of glass and metals. Suitable binders preferred here are corn starch, Portland cement, asphalt emulsion and lignin.

The RDF thus prepared is cylindrical, 3/4 inch in diameter and 3/4 inch in length, with a compressive strength of 30 psi and a humidity content of 10% by weight or less. The RDF pellets thus prepared have a calorific value of about 6000 BTUs per pound and are used as the primary or secondary fuel source. The patent does not mention the use of alkaline earth metal hydroxides as adhesive additives, or the preparation of mixed fuel pellets by mixing the above mentioned additives with coal powder. On the other hand, alkaline earth metal hydroxides are used as bonding additives to make RDF pellets or cubes by themselves or to be used with other solid fuels such as coal, for example.

US Patent No. 4,758,244 to Harvey et al. Discloses another method of raising the grade of coal. In this method, high density coal pellets with improved water content and improved calorie values are produced from lignite, which is deformed by shearing to form a wet plastic object, which is then extruded into pellets. Sodium carbonate is added to the aqueous phase to increase the strength of the densified product during plasticization. It also mentions the use of complex pellets consisting of coal dust and wet plastic mixtures.

The references cited above only describe the use of pellets in the form of compounds, made from coal strips and other waste products. In one reference discussing the addition of binders, there is no discussion of the use of alkaline earth metal hydroxides.

The use of alkaline earth metal hydroxides in the present invention has many advantages, and the method of the present invention overcomes the disadvantages of the prior art.

According to the present invention, RDF pellets / hexahedrons having improved performance as binders are used to greatly reduce contaminants such as acid gases such as SO _X , NO _X , and CO _2, and toxic substances such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls. A method for reducing is provided.

In the practice of the present invention, a particulate fuel containing one oxide and sulfur was put into a combustion section of a solid fuel combustion furnace. The composition of the particulate fuel was at least 10% of the densified RDF agglomerate containing alkaline earth metal hydroxide as a binder, based on calories.

Combustion conditions were formed inside the furnace and particulate fuel was combusted in the presence of oxides. Sufficient alkaline earth metal hydroxide was added to the RDF agglomerate / hexahedron to generate exhaust gas from the combustion unit. The exhaust gas was analyzed and the content of SO ₂ was based on the calorific value of the RDF agglomerate / hexahedron containing no alkaline earth metal hydroxide. At least 20% lower than the SO ₂ content of the same amount of fuel. The most preferred fuel composition is a mixture of sulfur-containing fuels with RDF agglomerates / hexahedrons with at least 20% of the alkaline earth metal hydroxide binder added on a caloric basis.

As another aspect of the present invention, the content of the polycyclic aromatic hydrocarbon of the exhaust gas generated in the combustion unit is the content of the polycyclic aromatic hydrocarbon of the fuel containing the same amount of RDF agglomerate / hexahedron containing no alkaline earth metal hydroxide on the basis of calories. More than 30% lower.

Another advantage of the present invention is that the content of polychlorinated biphenyls in the exhaust gas is at least 50% based on calorific value of RDF agglomerates / hexahedrons that do not contain alkaline earth metal hydroxides.

It is a mixture of calcium hydroxide and magnesium hydroxide suitable for RDF agglomerates / hexahedrons. The amount of calcium hydroxide / magnesium hydroxide mixture depends on the moisture contained in the RDF fluff, which is the raw material of the lump / hexahedron. The more moisture, the more calcium / magnesium hydroxide is needed. In many cases suitable amounts of calcium / magnesium hydroxide are 4-10% by weight. However, a feature of the present invention is that when mixing RDF lumps / hexahedrons with enhanced binders with coal having a very high sulfur content, lumps / hexahedrons containing at least 10% by weight of calcium / magnesium hydroxide can be used. have. The mass / hexahedron preferably contains 11-25% by weight of calcium / magnesium hydroxide, most preferably 12-20% by weight.

In another aspect of the present invention, a method is provided for producing a densified RDF chunk / hexahedron. The same amount of particulate calcium hydroxide / magnesium hydroxide with an average particle size of less than 0.5 mm is added to an RDF fluff having a water content of about 10-50% by weight. Stir the mixture made by the addition of particulate calcium hydroxide / magnesium hydroxide to produce a product with evenly distributed calcium hydroxide / magnesium hydroxide in the raw material and having dense contact. This mixture is then passed through an injection or densification system, where the mixture is shaped into a lump or cube. The mixture of calcium hydroxide / magnesium hydroxide and fluff is densified at a temperature of 140-190 ° F. and the injection through time range is 2-10 seconds.

Garbage extraction fuel, as mentioned above, is primarily a solid waste product produced by recycling and processing of municipal solid waste and lesser, but usually landfill, commercial and industrial waste. Municipal waste consists mainly of cellulosic materials such as paper cardboard, wood and cut grass, food waste and plastics. Non-organic materials such as metal and glass also account for about 12-25% of municipal waste.

There are a variety of processing methods that make this product so that the extracted fuel can be finally reused. Usually, when solid waste arrives at the processing facility, large or dangerous substances such as electrical equipment, mattresses and car batteries are separated from the waste. The waste is then filtered, which removes fine organic matter. Then, manually recyclable items such as aluminum, glass, cardboard and rigid plastics are collected separately. The waste is broken up into small pieces, which are then passed through a magnetic separator to separate the ferrous metal and then to an air separator such as a cyclone or other suitable device. After being made into smaller pieces, a low density “fluff” is produced. The density of the raw materials is not very low, only a few pounds per cubic foot (ft ³⁾ can be used in suspension fired system. However, this raw material is usually compressed to form a solid mass or cube that has a density of about 20-40 pounds per cubic foot. At the end of the grinding process, the moisture of the raw material is about 10-40% by weight. The main constituents of the raw materials are of course fibrous materials and other organics and plastics.

When forming RDF chunks or cubes, binders may be used to increase the density and intergrity of the chunks or cubes. Unlike coal dust, which is relatively homogeneous in particle size and relatively constant in particle size, the RDF fluff is a heterogeneous mass of particles of low density and irregular shape, with a relatively wide particle size. Thus, if binders are used to form RDF agglomerates or cubes, they will usually take the form of hydraulically molded cements such as Portland cement or organic base materials such as lignin and corn starch.

In the present invention, alkaline earth metal hydroxide is used as a binder of densified RDF agglomerates or cubes. Suitable alkaline earth metal hydroxides are a mixture of calcium hydroxide / magnesium hydroxide and the use of calcium hydroxide / magnesium hydroxide mixtures used as binders in RDF agglomerates or cubes will be described in more detail later. However, other alkaline earth metal hydroxides containing calcium hydroxide / magnesium hydroxide, which are extracted from dodolite materials, can also be used as binders. Alkaline earth metal hydroxides, except calcium hydroxide / magnesium hydroxide, can theoretically be used as binders in the present invention, but those skilled in the art will realize that they cannot be used in reality for economic or other reasons.

When forming an improved mass or cube with a binder, several factors must be taken into account when determining the amount of calcium hydroxide / magnesium hydroxide added to the RDF fluff. As explained in more detail later, calcium hydroxide / magnesium hydroxide is preferably added to the RDF fluff in a finely ground, dry powder state if possible. As in some RDF applications, water is usually not intentionally added to the calcium hydroxide / magnesium hydroxide mixture, the fluff or the mixture of the hydroxide and the raw material in order to form a lump. Generally at least 5% by weight calcium hydroxide / magnesium hydroxide mixture will be used. That is, calcium hydroxide constituting 2½% of the weight and magnesium hydroxide constituting 2½% of the weight are added to an RDF fluff constituting 95% by weight. In general, as the water content of the RDF fluff increases, it is desirable to further add a calcium hydroxide / magnesium hydroxide mixture binder. Most RDF fluffs contain 20-30% by weight or more of water, with a moderate amount of 5% by weight calcium hydroxide / magnesium hydroxide mixture based on water alone. However, the moisture of some raw materials (fluff) increases to 40-50% by weight, in which case the content of calcium hydroxide / magnesium hydroxide should be 6-10% by weight or more.

When forming binder-added RDF lumps or cubes, the calcium hydroxide / magnesium hydroxide mixture and the RDF raw material (to ensure that the calcium hydroxide / magnesium hydroxide mixture is evenly mixed with the fluff and that the fluff is in good contact with the calcium hydroxide / magnesium hydroxide mixture) It is important to mix the fluff together. The calcium hydroxide / magnesium hydroxide mixture should be ground to an average particle size of less than 0.5 mm. In order to prevent excessive dust generation during the manufacturing process, the particle size of the calcium hydroxide / magnesium hydroxide mixture should normally be at least 0.04 mm (number obtained by 400 US sheaves). When preparing a mixture between calcium hydroxide / magnesium hydroxide and raw materials, both batch mixing and continuous mixing can be used, but in practice, a continuous mixing method is preferable. For example, a well separated calcium hydroxide / magnesium hydroxide mixture can be gravity fed into a screw-type conveyor about 30-45 ° inclined from a metered hopper. As the fluff and calcium hydroxide / magnesium hydroxide mixtures ride up the conveyor, mechanical mixing and rotational motion ensures an even distribution of the calcium / magnesium hydroxide mixture throughout the fluff.

At the top of the conveyor the mixture is fed into a hopper of a lump or hexahedron maker, which may be of the general type with a roller machine installed in a rotating die screen, as disclosed in the above patent publications of Gulley et al. The way in which the mixture of raw materials and calcium hydroxide / magnesium hydroxide is passed through the discharge die by a die screen or other suitable device is very important in giving the desired properties to the mass or cube.

Factors affecting the characteristics of agglomerates or cubes include the length of the injection channel (the wall thickness of the die screen, as disclosed in Gulley et al.), The injection diameter (the diameter of the injection passage within the die screen), and the injection temperature ( Temperature at which the mixture of raw materials and calcium hydroxide / magnesium hydroxide passes through the die screen). Usually, if the injection temperature is high, the transit time is long, or the injection diameter is too small, the injection machine will become clogged. However, biased to the other extreme, if the injection temperature is too low, the injection time is too short, or the injection diameter is too large, the mass or cube will not have the desired density and the integrity will be relatively poor. If possible, maintaining an injection diameter of ½-1 inch and an injection diameter of ¾ inch is assumed to produce optimal results.

Suitable injection temperatures are preferably 140-190 ° F, most preferably 150-170 ° F. The passage time is preferably 2-10 seconds, most preferably 3-5 seconds.

Increasing the amount of calcium / magnesium hydroxide mixture usually increases the density of the RDF mass or cube added with the binder until the amount of calcium / magnesium hydroxide mixture is 10-11% by weight. If more than this amount is added, the molded article is less dense. Therefore, considering only the effect of the binder, the upper limit of addition of calcium / magnesium hydroxide mixture is 10-11%.

However, as will be explained below, higher amounts of calcium / magnesium hydroxide mixtures in certain applications are effective in reducing the amount of undesirable or toxic emissions.

The existing use of RDF fuels, such as in power plants, is to use RDF agglomerates or cubes with particulate coal as fuel in furnaces that burn solid fuels. Pollutants emitted from these furnaces include acid gases, SO _X and NO _X , which cause so-called “acid ratios” and polycyclic aromatic hydrocarbons (PAH _S ) and polychlorinated biphenyls (PCB _S ).

RDF- when burning coal mixture, SO _X emission (mainly sulfur dioxide containing some sulfur trioxide) are mainly produced from coal. In this regard, the amount of sulfur contained in the RDF chunks and cubes is relatively low, with the content of ¼% and rarely exceeding ½%. The sulfur content of coal is usually significantly higher than this, above 2½%. Therefore, emission of SO _X is can be expected to mainly the case of the sulfur contained in the coal because RDF- coal mixture, increasing the amount of RDF lumps or cubes reduce the discharge of SO _X.

NO _X emissions (nitrous oxide and nitrogen dioxide) is caused by the nitrogen compound, and nitrogen molecules in the air with the coal and RDF chunks / cubes. Nitrogen-containing compounds are found in both coal and RDF agglomerates / hexahedrons, and the nitrogen content of coal is usually higher.

NO _x produced by nitrogen molecules in the air is directly related to the combustion temperature, and the higher the temperature, the more nitrogen is produced. If such a circumstance, when increasing the content of the RDF in the coal mixture -RDF, SO _X, of course is expected to reduce NO _X emissions FIG.

Polycyclic aromatic hydrocarbons (PAH) released during the combustion of solid fuels usually contain compounds containing 2-7 aromatic rings in the condensed ring structure. Polycyclic aromatic compounds such as benzo-a-pyrene and methylcholanthrene are carcinogenic, and other naphthalenes and anthracene are not carcinogenic. Polycyclic aromatic hydrocarbons in the combustion products, measured in the experiments described below include naphthalene, acenaphtylene, benzo-a-anthracene, chrysine, acenathrene, benzoafluoranthene, flu Orene, benzo-k-fluorandene, phenanthrene, benzo-a-prene, anthracene, dibenzo-a, h-anthracin, fluoranthene, benzo-g, h, i-perylene, prelene, and Indendo-1,2,3, c, d-prene and the like. Polycyclic aromatic compounds are produced during the incomplete combustion of hydrocarbons during the combustion process and thus may be due to the use of coal or RDF lumps / hexahedrons.

The chemical formula of polychlorinated biphenyl is as follows:

C ₁₂ H _m CI _n

In this formula, the sum of m and n is 10 and n is 1 or more. It is produced from the corresponding product in the fuel of the PCB in the combustion emissions and is the product of burning hydrocarbons in the presence of chlorine from various extractions.

Not just the SO ₂ emissions, NO _X, HCI and CO ₂ emissions, and polycyclic aromatic hydrocarbons and poly according to the features of the present invention to reduce the discharge of chlorinated biphenyl, calcium hydroxide / hydroxide as a binder in the process of manufacturing a high-density RDF chunks / cubes Use a magnesium mixture. The first experiments conducted in connection with the present invention revealed that the calcium / magnesium mixture binder has the effect of inhibiting contaminants only for coal-RDF mixtures containing 10% RDF fuel on a caloric basis.

Here, unless otherwise indicated, the relative amounts of RDF chunks / hexahedrons are based on calories. Thus, if there are RDF chunks / hexahedrons with 7,000 BTU calories per pound and coal with 11,000 BTU calories per pound, a mixture containing 10% RDF and 90% coal by calories is about 15 It will contain% RDF and about 85% coal.

In particular, the first findings of the above experiments were that the binder inhibited SO ₂ in a mixture containing 10% by weight of RDF fuel and 90% by weight of coal, but was not effective when the RDF content was raised to 20%. The effectiveness of the binder to inhibit the NO _X content is difficult to determine. Some tests have shown inhibitory effects for fuels mixed with 10% and 20% RDF fuel, but have no practical effect in other tests.

Regarding the content of polycyclic aromatic hydrocarbons, the test results show that the RDF / coal mixture containing 10% by weight of RDF is excellent at first, but when the RDF content is raised to 20% by weight, the binder rather than the amount of PAH is released. It has been shown to increase.

However, subsequent analyzes of these results show that calcium hydroxide / hydroxide is used to reduce undesirable contaminant content, especially when 20% and 30% RDF is used on a caloric basis, and even up to 50%. It has been found that there is an effect of a magnesium mixture binder. The SO ₂ content could be significantly reduced by using a binder with a high RDF fuel mixture, and NO _x was not reduced, but the binder had no adverse effect. However, PAH and PCB contents were significantly reduced by using binders in mixtures containing large amounts of RDF.

In the experiments of the present invention, a total of 300 tonnes of RDF agglomerate was burned in a furnace of a boiler together with high sulfur coal as fuel, and among the five boilers for supplying heavy equipment for Argonne National Laboretory, Argonne, Illinois. It was one. The boiler's nominal capacity was 170,000 tonnes of steam per hour with a saturation gauge pressure of 200 psig.

Air pollution suppression equipment consisting of a multicyclone, lime spray dry absorber, and fiber filter baghouse connected in series to the boiler furnace was installed. The discharge from the furnace first enters the multicyclone system, where particulates are removed and then the spray dryer is operated. When the exhaust gas comes into contact with the lime slurry in the spray dryer, sulfur dioxide is absorbed and the exhaust gas is cooled. According to the design specification of the spray drying absorber, more than 78.3% of the sulfur dioxide in the off-gas is separated. Some of the dry products resulting from this operation, namely the lime particles which have not reacted with coal ash, sulfite and calcium sulfate, fall to the bottom of the absorption chamber.

The exhaust gas cooled in the spray drying absorber is then sent to a bag house module where residual coal ash and particulates are removed. Emission samples were taken manually at three points during the experiment. Point 1 is in the combustion section where the temperature is approximately 1200 ° F, point 2 is the point where the temperature between the multicyclone and the spray dryer module is about 320 ° F, and point 3 passes through all the contaminating equipment and then the temperature is approx. It was a chimney that was 170 ° F.

The RDF chunks / hexahedrons used in the experiment were purchased from two manufacturers and these were labeled as Company A and Company B, respectively. RDF agglomerates / hexahedrons used included agglomerates or cubes containing no binder and chunks or cubes containing 4% and 8% by weight of a calcium / magnesium hydroxide binder. These agglomerates / hexahedrons were mixed in coals with high sulfur content at 10, 20, 30 and 50 weight percent based on calories. The coal used in the experiment is a high-sulfur content Kentycky coal with a sulfur content of 2.7% by weight upon receipt of coal (about 6.3% moisture) and 2.88% by weight sulfur when dried. The average calorific value of coal was 11,200 BTUs per pound based on quantity.

As described above, in the present specification, the term "lump" and the term "hexahedron" are interchangeably used with one another. The only difference between the two words is the form of the densified RDF product, and all other features and characteristics are the same.

The sulfur content of the RDF fuel mass / hexahedron was about 1/4% by weight. The calorie of A's product was about 7500 BTU per pound and the calorie of B's product was about 7000 BTU per pound. In general, A's products were more homogeneous and more robust than B's. In addition, A company's actual content of the binder was closer to the nominal binder content than that of B company. In the experimental report, the use of coal-RDF mixture or coal was classified into 12 items using only coal and increasing the RDF content.

During the experiment, the contents of SO ₂ , NO _X , polycyclic aromatic hydrocarbons, and polychlorinated biphenyls of samples collected at points 2 and 3 were analyzed.

As will be appreciated by those skilled in the art, the sample taken at point 2 more accurately reflects the amount of contaminants in the exhaust gas of the combustion section than the sample taken at point 3. In this regard, treatment of flue gas in a multicyclone module that filters only particulate matter has no practical effect on the content of SO ₂ , NO _X , CO ₂ or HCI in the exhaust gas. It is estimated that polychlorinated biphenyls and polyaromatic hydrocarbons remain in the vapor phase at the time they pass through the multicyclone module, so that only a small fraction of them are removed from the first effluent filtration module. Only when the temperature of the exhaust gas drops below 300 ° F, these substances condense and absorb and become particulates.

Therefore, the experimental results were evaluated under the assumption that the actual filtered amount in the multicyclone module among the polyaromatic hydrocarbon and the polychloride biphenyl was less than 10-20%.

Acid gas generated from combustion of the effluent gas was collected using an Anderson Model 300 gas rod collector and ion chromatographic-analyzed using a Dionex Model 20101 ion chromatograph. The trapping reagents used in the samples are mostly 2% by weight sodium hydroxide solution and 2% by weight aqueous sodium hydroxide solution, and 4% by weight potassium permanganate. In some cases other reagents were used, as shown in Table 1. The 2% sodium hydroxide solution was considered to yield the most accurate results in the collection of HCI, and the 2% sodium hydroxide and 4% potassium permanganate solutions were considered to be most effective for the collection of SO ₂ and NO _X. The effect of these two reagents is shown in the comparative sample taken for about 3 hours as described in Table 1.

The use of calcium and magnesium sodium binders in accordance with the present invention can reduce carbon dioxide emissions. Look at coal-RDF pellets or cubes containing 4% calcium hydroxide / magnesium hydroxide, and compare them with the corresponding fuels containing the same RDF pellets or cubes at the corresponding temperatures without the binder in the pellets in the combustion zone. The spilled gas resulted in a reduction of carbon dioxide of more than 5%. Coal RDF pellets or cubes containing 8% by weight calcium hydroxide / magnesium hydroxide binder showed a corresponding reduction in carbon dioxide of at least 20% by volume.

Table 2 shows the average carbon dioxide content of the gas collected at position 2 during the experiment. The dates set out in Table 2 are for 10, 20, 30% RDF pellets or cubic carbon mixtures for 0.4 and 8% by weight calcium hydroxide / magnesium hydroxide binder pesticides. The default value of carbon burned without any RDF pellets or cubes is about 9.1%.

As noted earlier, the properties of RDF in source A are generally more uniform than those in source B. In addition, the analysis for Source A shows that it is much closer to the calcium hydroxide / magnesium hydroxide pesticide as its name suggests. In addition, the density of Source A gradually increased with increasing calcium hydroxide / magnesium hydroxide content. The average density of the source A-free binder is a 42.0lb / ft was ^3, 4% of calcium hydroxide / average density of the source A with a binder of magnesium hydroxide was 43.3lb / ft ^3, 8% with a source of calcium hydroxide / magnesium hydroxide binder A The average density was 45.7 lb / ft ³ . Source B, on the other hand, did not show this correlation. The average density of the absence of binder, 4% calcium hydroxide / magnesium hydroxide and 8% calcium hydroxide / magnesium hydroxide was 26.8, 25.6 and 26.8 lb / ft ^3, respectively.

Looking at the data reported above, the contents of SO ₂ and NO _X decrease with increasing RDF content in the fuel mixture. The calcium hydroxide / magnesium hydroxide from this will showing a clear effect of reducing the SO _X amount. This effect can be clearly seen when reducing the data for 80% coal and 20% RDF mixtures using pellets or lumps in Source B. When going binder is transferred in a state of 4% and 8% calcium hydroxide / magnesium hydroxide-free binder, a tremendous decrease in the SO _X during discharge can be observed in both the 10% and 30% RDF pellets or cubes.

Regarding NO _x emissions, a reduction can be seen for 90% coal, 10% RDF mixtures. When using the binder containing more than 10% of pellets or cubes, the release of NO _X can be found to be increased by some data. However, it appears to be to decrease the data based on the source B, I binding at the fuel with a higher content of RDF is even less effective in reducing the emission of NO _X, that is also adversely affected.

Since the initial source of chlorine is the plastic content of the RDF, the HCI content increases with increasing RDF pellets or cube content. The binder appears to have a minor effect on the content of HCI up to approximately 30%.

Data for 10% and 30% RDF mixtures for a single coal show that calcium hydroxide / magnesium hydroxide reduces PCB and PAH emissions when considering only data for Source A. Position 2 data for a mixture of 80% coal and 20% RDF pellets or cubes shows that the PAH content decreases rapidly when transferring to 4% binder in the absence of binder, and PAH content even when transferring from 4% to 8% binder. This decreasing, data release at 80% calcium hydroxide / magnesium hydroxide is also showing much more commission than mixtures without binder.

It would be desirable to limit the amount of calcium hydroxide / magnesium hydroxide binder to 10% by weight since the use of the calcium / magnesium hydroxide binder will ultimately add to the content of ash that will remain. However, a binder content of more than 10% may be used, which is advantageous when RDF pellets or cubes are mixed with a relatively high sulfur content.

In this regard, coal used for combustion in power plant furnaces often shows 3-4% of sulfur and sometimes up to 6-7% of sulfur. In this case, RDF pellets or cubes containing at least 11% calcium hydroxide / magnesium can be burned together with the atomized coal as co-fuel, resulting in a reduction of sulfur dioxide due to sulfur in the coal. Up to 25% calcium hydroxide / magnesium hydroxide binder can also be used. The ideal amount of calcium hydroxide / magnesium hydroxide used with this high sulfur content is 12-20% by weight.

At the Idaho National Institute of Engineering (INEL), a follow-up experiment was conducted in a fluidized bottom combustion chamber that embodies the results obtained from the Argonne National Laboratory experiment, not reported herein. High-density RDFs with binders tested at INEL were tested at the Argonne National Laboratory, except that a 1⁄4 inch concentrated RDF was produced in section 1 by a cube device that formed the RDF into a square shape. Same as the one. The binder consists of a calcium hydroxide / magnesium hydroxide mixture of 1 1/2 the weight of calcium hydroxide and 1 1/2 of magnesium hydroxide. Approximately 50 tonnes of concentrated RDF cubes were burned with varying percentages of the bottom bituminous coal. It was confirmed that the shape of the concentrated RDF (cylindrical or square) did not affect the experimental results.

According to the specific embodiments of the present invention described above, those skilled in the art will be able to recognize that various changes and modifications can be made within the scope of the present invention.

According to the present invention, RDF pellets / hexahedrons having improved performance as binders are used to greatly reduce contaminants such as acid gases such as SO _X , NO _X , and CO _2, and toxic substances such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls. A method for reducing is provided.

In the practice of the present invention, a particulate fuel containing one oxide and sulfur was introduced into a combustion section of a solid fuel combustion furnace. The composition of the particulate fuel was at least 10% of the densified RDF agglomerate containing alkaline earth metal hydroxide as a binder, based on calories.

Combustion conditions were formed inside the furnace and particulate fuel was combusted in the presence of oxides. Sufficient alkaline earth metal hydroxide was added to the RDF agglomerate / hexahedron to generate exhaust gas from the combustion unit. The exhaust gas was analyzed and the content of SO ₂ was based on the calorific value of the RDF agglomerate / hexahedron containing no alkaline earth metal hydroxide. At least 20% lower than the SO ₂ content of the same amount of fuel. The most preferred fuel composition is a mixture of sulfur-containing fuels with RDF agglomerates / hexahedrons with at least 20% of the alkaline earth metal hydroxide binder added on a caloric basis.

As another aspect of the present invention, the content of the polycyclic aromatic hydrocarbon of the exhaust gas generated in the combustion unit is the content of the polycyclic aromatic hydrocarbon of the fuel containing the same amount of RDF agglomerate / hexahedron containing no alkaline earth metal hydroxide on the basis of calories. More than 30% lower.

Another advantage of the present invention is that the content of polychlorinated biphenyls in the exhaust gas is at least 50% based on calorific value of RDF agglomerates / hexahedrons that do not contain alkaline earth metal hydroxides.

Claims (8)

(a) 5 to 25% by weight of a binder binder and from 75 to 95% by weight of combustible components comprising cellulose and plastics derived from waste, in a form of 10 to 50% of dense pellets or cubes based on a heat equivalent Fuel raw materials; And (b) a mixture of coal particles having a thermal equivalent of 50 to 90% of sulfur content of 1% by weight or more, wherein the hydroxide binder is a mixture of calcium hydroxide and magnesium hydroxide in the same weight ratio. (a) adding at least 5% hydroxide binder having an average particle size of 0.5 mm or less to raw materials derived from waste having a water content of 10 to 40% by weight; (b) stirring the mixture of step (a) to provide a mixture in which the hydroxide binder and the waste-derived raw material are in uniform contact; (c) transferring the mixture of step (b) to an extruder and extruding it through a die; And (d) extruding the mixture raw material for a residence time of 2 to 10 seconds at a temperature of 140 to 190 ° F, wherein the hydroxide binder is a mixture of calcium hydroxide and magnesium hydroxide of the same weight. Way. 3. The method of claim 2 wherein the extrusion diameter is 0.75 inches in the case of the particles and 1/1/4 × 1/1/4 inch in the case of cubes. The method according to claim 2, wherein the residence time for shaping the particles or cubes is 3 to 5 seconds. The method of claim 2 or 4, wherein the extrusion temperature is 150 to 170 ° F. (a) 65 to 50% by weight of sulfur, based on the total weight of the mixed fuel, which is derived from household waste, commercial waste or industrial solid waste comprising cellulose and plastics with a moisture content of 10-40% by weight. 90% by weight of combustible raw materials; And (b) 5 to 25 wt% of a hydroxide binder with a particle size of 0.04 to 0.5 mm, based on the total weight of the mixed fuel, wherein the hydroxide binder is mechanically mixed with the same weight of calcium hydroxide and magnesium hydroxide. And mixed fuel densified in a biologically stable form. 7. The mixed fuel according to claim 6, wherein the calorific value is 7,000 BTU / lb or more. 7. The mixed fuel according to claim 6, wherein the calorific value is 7,500 BTU / lb or more.