RU2079778C1 - Method for thermal processing solid garbage and industrial waste - Google Patents

Abstract

FIELD: waste processing. SUBSTANCE: solid garbage is loaded together with solid carbon-bearing or gases to the melt slag bath blown with the mixture of oxygen and diluting gas, that is free of nitrogen. The processing is carried out at rarefaction in the top portion of gas plenum of 10 - 20 Pa. Carbon-graphite industry waste or bio-gas from solid garbage disposal sites is used as carbon-bearing fuel. Carbon dioxide or steam may be used as diluting gas. EFFECT: waste utilization. 3 cl, 1 tbl

Description

 The invention relates to methods for thermal processing of waste and can be used in housing and communal services, chemical industry, energy, agriculture.

 There is a method of thermal processing of solid household waste by loading them into a molten slag bath, sparged with a mixture of air and oxygen with a content of the latter of 30-60% (AS USSR N 1783234, class F 23 C 5/00, 1991).

 The disadvantage of this method is the high content of harmful substances in the exhaust gas gases of nitrogen oxides and dioxides due to the purge of the melt with an air-oxygen mixture containing a large amount of nitrogen (40-70%).

 The closest in technical essence is the method of thermal processing of solid waste, including loading these waste together with carbon-containing fuel into a molten slag bath and purging with oxygen-containing gas with a certain blast intensity, while the carbon content of the waste and fuel loaded into the slag withstands 2-25 % and, as it increases, they additionally load metal oxides and scrap metal (A.S. USSR N 1315738, class F 23 C 5/00, 1987).

 The disadvantages of this method are: a high content of nitrogen oxides and dioxides in the exhaust gases (due to blowing the melt with an air-oxygen mixture), as well as sulfur dioxide (when using natural gas or coal containing sulfur as an additional fuel). In addition, the addition of coal to the charge being loaded is not economically beneficial for many regions of the country (remoteness of coal deposits, and consequently, high transportation costs and losses during transshipment and transportation).

 The purpose of the invention is the waste-free disposal of solid household and industrial waste with improved environmental and economic indicators with maximum isolation of the processing process. Moreover, reduction or elimination of the negative impact of these factors is carried out at the initial stage of the waste processing process.

 The technical result that can be obtained by using the invention is to increase the environmental efficiency of the process by reducing the content of nitrogen and sulfur oxides in the exhaust gases, reducing operating costs during the melting of waste by replacing natural fuels with carbon-containing waste, and increasing the complexity of the use of waste by involving the process of products of their processing (carbon dioxide, water vapor).

 The technical result is achieved by the fact that in the known method for the thermal processing of municipal solid waste, including loading them together with carbon-containing fuel into a molten slag bath, purged with a mixture of oxygen with a diluent gas, according to the proposed solution, carbon-containing solid waste or gases are used as fuel, the melt is blown a mixture of oxygen with a diluent gas that does not contain nitrogen, and the processing process is carried out with a vacuum in the upper part of the gas working volume + 10-20 Pa. Waste from the carbon industry and electrode production or biogas from solid domestic waste landfills is used as carbon-containing fuel, and carbon dioxide or water vapor is used as a diluent gas.

 In addition, industrial solid waste containing non-ferrous metals is added to solid household waste loaded into a molten slag bath.

 These distinguishing features are dictated by the following.

 Solid domestic waste in its composition (combustible components - carbon, hydrogen) provides melting (processing) due to its own calorific value with the corresponding enrichment of oxygen in the blast (i.e., autogenous mode is achieved). When industrial wastes are added to solid household bins that do not have a calorific value but contain non-ferrous and other metals (they are trimmed from the point of view of both utilization and increasing the process efficiency by extracting valuable metals into a marketable product), the processing process requires the introduction in the melting unit (in the bath of slag melt) of additional fuel (gas, solid or liquid).

Studies show that the main oxides of nitrogen and sulfur are formed from gas agents (blast) and fuel (natural gas content up to 1% H ₂ S, coal and fuel oil up to 3% S and more), and from the forms of these elements in the waste itself the emission of NO _x and SO ₂ oxides into the gas phase is less pronounced. Therefore, the elimination of the causes (factors) of pollution of exhaust gases emanating from the blast of additional fuel and air leaks into the working volume of the smelting unit should be considered a more appropriate direction in improving environmental performance in this regard (reducing harmful emissions).

In existing methods for processing waste in a bubbled slag bath (including in Vanyukov PV furnaces), the melt is purged everywhere with an air-oxygen mixture, while the regulation and fixing of the value of the degree of enrichment of the blast with oxygen necessary for the process is carried out by increasing or decreasing the air flow as diluent gas. The presence of a high nitrogen content in the supplied air at normal temperatures of the process 1250-1450 ^o C leads to the formation of harmful substances of nitrogen oxides in the exhaust process gases, the purification of which requires large capital and operating costs and is not always effective. Replacing air with gases or vapors that do not contain nitrogen (for example, carbon dioxide, water vapor) can solve this problem at the stage of waste melting (in the head of the process). The rarefaction in the gas working volume (i.e., the free space above the slag melt bath) of the melting unit (usually the PV furnaces operate when the vacuum is up to -30-50 Pa or more) acts in the same direction: the lower the vacuum, the less the ambient air leaks (nitrogen) into the furnace space with high temperatures and, therefore, there is less possibility of pollution of the exhaust gases with nitrogen oxides.

In turn, the presence of nitrogen and sulfur in the feed materials leads to a corresponding pollution of the exhaust gases with nitrogen and sulfur oxides. Replacing coal containing sulfur with cleaner carbon impurities (carbon-graphite and electrode industry) eliminates the possibility of sulfur dioxide formation, and, therefore, there is no need for corresponding expensive treatment of waste gases. Biogas from solid waste landfills also contains a small amount of sulfur (up to 0.3% H ₂ S, while in natural gas up to 1% H ₂ S), and, therefore, its use as an additional fuel reduces flue gas pollution by sulfur dioxide substances.

In addition to the environmental effect considered, the proposed solution leads to an increase in the efficiency of the processing process, since practically waste products are used in the process: carbon dioxide (CO ₂ ), which is usually released into the atmosphere with exhaust (flue) gases (there are currently a number of technologies for producing CO ₂ of these gases to the integrated use of raw materials), steam generated during cooling caisson elements melting furnace and cooling the flue gases in the heat recovery boiler (typically using for heating purposes, less often for electricity production and other purposes), coal and graphite waste and electrode production (the level of reuse of the latter at the country's electrode plants is about 70%, the rest is stored and accumulated), landfill biogas released during anaerobic methane decomposition organic part and having a high calorific value (usually lost in the atmosphere, in addition, polluting the environment). It should be especially noted that the listed products can be as close as possible to waste processing plants according to the proposed method (electronic plants are located in various regions of the country: Center, South, Ural, Siberia) or can be practically combined with the sites of these plants (carbon dioxide, water vapor biogas). It also increases the efficiency of waste processing.

 Examples of the method.

The method was tested on a semi-industrial installation of smelting in a liquid bath (Vanyukov furnace) of the Ryazan experimental metallurgical plant (ROEMZ) of the Gintsvetmet Institute. Solid household waste of chemical composition, 4-6 silica, 0.3-0.6 calcium oxide were subjected to processing; 2-3 alumina, 0.2-0.4 copper, 2.1-2.4 iron, 0.1-0.2 sulfur, 18-20 carbon, 2.0-2.5 hydrogen, 14-16 oxygen , 0.3-0.6 nitrogen, humidity 35-55% calorific value Q $\genfrac{}{}{0ex}{}{\text{n}}{\text{R}}$ = 5-7 MJ / kg (1200-1700 kcal / kg and industrial waste copper cake of the Moselectrofolg plant, 5-10 copper, 0.1 nickel, 0.1 iron, the rest is gypsum, humidity 50-60% and cake varied between 1: (0.1-1.0).

Example 1. A mixture of solid waste containing 4.62 silica, 0.52 calcium oxide, 2.1 alumina, 0.32 copper, 2.31 iron, 0.2 sulfur, 19.2 carbon, 2.34 hydrogen, 15 3 oxygen, 0.5 nitrogen, Q $\genfrac{}{}{0ex}{}{\text{y}}{\text{R}}$ = 6.27 MJ / kg (1550 kcal / kg) and a cake containing 8 copper, 0.1 nickel, 0.1 iron, with a humidity (average) of 51.7%, was loaded into a molten slag bath, purged with process oxygen (100% O ₂ ). The ratio of solid waste and cake 1: 0.4. The vacuum in the working volume is 10-13 Pa. Additional fuel is a natural gas of the composition, 93.2 CH ₄ , 0.7C ₂ H ₆ ; 0.6 C ₃ H ₈ , 0.6 CH ₄ H ₁₀ , 0.5 C _m H _n , 4.4 nitrogen, up to 1.0 hydrogen sulfide, calorific value - Q $\genfrac{}{}{0ex}{}{\text{y}}{\text{R}}$ = 35.5 MJ / m ³ (8500 kcal / m ³ ). The exhaust gases contained, mg / m ³ : (1-2) • 10 ^-2 sulfur dioxide, (0.6-1.0) • 10 ^-2 nitric oxide, (0.5-0.8) • 10 ^{- 2} nitrogen dioxide.

Example 2. Melted a mixture of solid waste and cake of approximately the same composition as in example 1, the ratio of these wastes 1: 0.2. Purging the melt with a mixture of oxygen and carbon dioxide while enriching the blast with -70% O ₂ . Depression - 10 Pa. Additional fuel electrode fragments containing 98% carbon, Q $\genfrac{}{}{0ex}{}{\text{y}}{\text{R}}$ = 34.3 MJ / kg (8200 kcal / kg). The exhaust gases contained, mg / m ³ : (0.3-0.5) • 10 ^-2 nitric oxide, (0.4-0.6) • 10 ^-2 nitric oxide, (0.3-0.6 ) • 10 ^-2 nitrogen dioxide.

Example 3. The composition of the waste mixture and their ratio are the same as in example 2. The mode of operation with melt blowing with a mixture of oxygen and water vapor during blast enrichment to 70-80% O ₂ . Vacuum up to -10 Pa. Additional fuel fragments of the electrodes (as in example 2). In exhaust gases, mg / m ³ : (0.3-0.4) • 10 ^-2 sulfur dioxide, (0.3-0.5) • 10 ^-2 nitric oxide, (0.3-0.5) • 10 ^-2 nitrogen dioxide.

Example 4. The composition of the waste mixture and their ratio are the same as in example 1. The mode of operation with the melt blowing technological oxygen with air containing a significantly reduced amount of nitrogen (from 20% to 0 with pure oxygen). Vacuum -10 Pa. Additional fuel biogas of the MSW landfill composition, 56.6 CH ₄ , 37.7 CO ₂ , 0.5 H ₂ , 0.4 CO, 0.31 hydrogen sulfide, alkanes 2.16, alkenes 1.49, Q $\genfrac{}{}{0ex}{}{\text{y}}{\text{R}}$ = 22.1 MJ / m ³ (5278 kcal / m ³ ). In exhaust gases, mg / m ³ : (0.7-1.5) • 10 ^-2 sulfur dioxide, (0.6-1.0) • 10 ^-2 nitric oxide, (0.6-1.0) • 10 ^-2 nitric oxide.

 The test results and design and experimental studies of a number of regime options are shown in the table.

As can be seen from the table and description of the implementation of the method, the best results in ecology (purity of exhaust gases from oxides of nitrogen and sulfur) were obtained in experiments N 7-11, i.e., in the absence or minimum in the blast and additional fuel of nitrogen and sulfur (using pure oxygen, CO ₂ and water vapor mixed with blast oxygen, a fragment of electrodes and biogas as additional fuel) and with a vacuum in the working volume within + 10-20 Pa (see experiments N 3, 4, 5). Moreover, the remaining harmful microimpurities (anthracenes, pyrenes, etc.) almost do not change under all the studied technological conditions (experiments in the table). Under certain technological conditions, the operation of the melting unit was noted: rarefaction (pressure) +20 Pa leads to the knocking out of furnace gases into the workshop (experiment No. 6), at the same time, a large vacuum (-30-50 Pa), ensuring a normal state in this regard at the same time worsens the composition of the exhaust gases (for nitrogen oxides, experiments N 1, 2), the use of pure oxygen (100% O ₂ ) or highly enriched blast for blasting leads to overheating of the molten bath (excess heat - experiments N 7, 11), although In principle, there is the possibility of additional processing eytralnyh thermally promotohodov.

The proposed method of thermal processing of waste:
provides high environmental cleanliness of the processing process;
reduces operating costs during melting;
increases the completeness of waste management.

In addition, the method has the advantages of:
practically non-waste production is achieved and the most closed cycle of waste disposal is organized;
the possibility of involving in the processing of a wide variety of industrial (including waste) waste with a high efficiency of their use increases.

Claims (3)

 1. The method of thermal processing of solid household and industrial wastes, including loading them together with fuel into a molten slag bath, purged with a mixture of oxygen with a diluent gas, characterized in that carbon-containing solid waste or biogas from solid domestic waste landfills is used as fuel as a diluent gas, carbon, hydrogen, oxygen-containing gases having a minimum content or not containing impurities of nitrogen and its compounds, while the processing process is carried out during rarefaction in erhney working part of the gas volume of 10 20 Pa.  2. The method according to p. 1, characterized in that the fuel used is waste from the carbon industry and electrode production.  3. The method according to p. 1, characterized in that carbon dioxide or water vapor is used as a diluent gas.

Images