RU2729638C1 - Method for manufacturing fuel from solid municipal wastes - Google Patents

Abstract

FIELD: waste processing and disposal.SUBSTANCE: disclosed is a method of processing solid municipal wastes (SMW) into solid fuel (RDF fuel), involving receiving initial SMW, sorting them with screening of incombustible fractions, such as batteries, stones, construction materials wastes, scrap glass and ceramics, street estimates, food wastes, leaves, etc., extraction of secondary materials: paper, rags, plastics, including ferrous and non-ferrous metals, grinding of remaining wet combustible mass, its drying, further heating and thermoplastic extrusion, characterized by that the remaining combustible mass with moisture content of more than 15 % is pre-dehydrated in screw presses, roller presses, dryers or otherwise to moisture content of 5÷15 %, milled into fraction 5÷50 mm, heated to temperature of 180÷250 °C and subjected to thermoplastic extrusion to obtain fuel granules or briquettes, and waste water and gaseous products coming off during heating of combustible mass are subjected to purification from contained in them hydrogen halides.EFFECT: technical result consists in improvement of physical and mechanical strength of produced RDF fuel, increase of water absorption, in prevention of ingress of halogens into manufactured fuel, in reduction of power consumption of its production, as well as in improvement of environmental situation, including by reducing the volume of "tails" exported to SMW polygons.1 cl, 4 dwg

Description

The invention relates to the field of environmental protection, in particular to the processing of municipal solid waste (MSW) with the manufacture of solid fuel from a combustible component remaining after sorting the residues, the so-called "tails", currently sent for burial at the MSW landfills. The fuel manufactured in accordance with this invention can be used both independently in various power generating units and as an additive to the main process fuel in limestone kilns, kilns for high-temperature synthesis of cement clinker, blast furnaces, at thermal power plants, in other installations for the purpose of obtaining electric and thermal energy, as well as as a feedstock for obtaining pyrolysis gas.

Solid municipal waste is a mixture of substances and materials of complex morphological composition, which includes combustible materials (polymers, paper, cardboard, wood, rags), ferrous and non-ferrous metals, ballast non-combustible part (stones, waste of building materials, cullet and ceramics, street estimates, food waste, leaves, etc.), as well as highly toxic pollutants (mercury-containing lamps, batteries, rechargeable batteries, chlorine-containing materials).

The global trend in the field of municipal waste management is the complete rejection of landfill disposal of non-neutralized waste and an increase in the share of thermal utilization, followed by the use of the obtained thermal energy in industry. An important element in the system of thermal utilization of municipal waste is waste sorting, which involves screening out the ballast non-combustible part, highly toxic pollutants, extracting secondary materials from waste and making fuels suitable for environmentally safe use in various power generating units from sorting residues (“tails”).

Special requirements for MSW sorting are due to the complex morphological composition of municipal waste.

To assess the real value of the energy potential of "tails", the authors carried out a morphological analysis of the residual part of MSW after sorting at a waste sorting station in Lipetsk, which is currently sent for disposal at the MSW landfill. Morphological analysis showed the following fractional composition (wt.%): Polymeric materials - about 19%; cellulose-containing components - about 19%; textiles - 8.5%; wood - 1.5%; metal - 1%, as well as other unsorted waste - about 51%.

The composition of other unsorted waste contains the flammable components mentioned above, and may also contain halogen-containing plastics (PVC), food waste, cullet, ceramics, stones, street estimates, leaves, etc. Depending on the season, the moisture content of the “tails” may vary from 35% to 55%.

Figure 1 shows the morphological composition of briquetted MSW "tails" currently sent for disposal at the MSW landfill. The data obtained on the morphological composition of the "tailings" allow us to consider them as a resource for the production of solid fuel.

A significant number of technical solutions are known aimed at realizing the natural energy potential of MSW - solutions aimed at using MSW as an alternative fuel. The effectiveness of these solutions is due to the fact that as a result of the combustion of MSW, a significant and irreversible reduction in their volumes is carried out, as well as the fact that during the combustion of municipal waste a high yield of thermal energy is provided, which can be used for the needs of the national economy.

There is a known method of producing alternative fuel from solid municipal waste, including sorting waste with the release of combustible fractions with their subsequent grinding, as well as drying waste, characterized in that MSW is preliminarily prepared by dividing the main MSW stream into two fractions, small and large, and sorting coarse fraction with the release of secondary raw materials, in the process of which sorting "tails" are formed, from which the combustible fraction is separated during subsequent sorting, after crushing the combustible fraction, dried screening is added to it - the fine fraction isolated at the stage of MSW preparation, and they are mixed (patent RU 2681655, IPC С10L 5 | 48, 5/40 (2018/08)).

The disadvantage of this method is the need to divide the main stream into two fractions, small and large, which complicates the technological process, as well as the fact that batteries (batteries, accumulators) may be present in the separated fine fraction, up to 30 mm.

There is a known method for the production of solid fuel made from industrial and domestic waste, which consists in the fact that at the first stage, industrial and domestic waste is sorted into three groups: the first group contains large metal objects, cords and hazardous substances that are removed from the total mass of the original objects for the manufacture of solid fuel and subsequently disposed of; the second group contains large-sized industrial and household waste; the third group contains waste that is less than 150 mm in overall dimensions; at the second stage, the first stage of processing industrial and household waste is carried out to reduce their overall dimensions to less than 150 mm, while the waste of the second group is placed in a screw crusher; at the third stage, the second stage of processing industrial and household waste is carried out, during which the waste of the second and third groups is fed into a horizontal splitting unit to reduce their volume; at the fourth stage, lime is added to the waste obtained in the horizontal breaking unit, then round briquettes are formed at high pressure and temperature, the resulting round briquettes are dried to form the final product with a diameter of 15-30 mm, a length of 30-150 mm, a caloric value of over 6000 kcal / kg and a combustion temperature over 1100 ° C. (patent RU 2405027, IPC C10L 5/48, 5/46 (2006.01)).

The disadvantage of this method is the absence of a stage for extracting secondary materials from waste: paper, rags, plastic, glass, ferrous and non-ferrous metals, used in the future for the needs of the national economy, as well as the use of waste of the second and third groups sorted from the total mass for the manufacture of solid fuel. may contain metal objects, glass, other inert materials with overall dimensions less than 150 mm, which increase the ash content in the combustion products of the produced fuel, reduce the heat of combustion of the fuel, and also significantly complicate the combustion process and the operation of furnaces.

A known method of manufacturing fuel briquettes from solid domestic waste (MSW) and other organic waste, including sorting solid waste with the release of a combustible mass, grinding the combustible mass separated from solid waste, drying the crushed material, heating the crushed material, forming granules from crushed material, characterized in that sorting of the initial solid waste with the release of combustible mass is carried out by a hydromechanical method, the mass with a moisture content of 40 ... 55% is crushed, the mass is heated in the temperature range 550 ... 1000 ° C, the energy supply for the production of fuel briquettes is completely due to the hidden internal energy of the combustible mass of solid waste, as binder when forming briquettes, resinous condensate is used, isolated from gaseous products of thermal decomposition of a combustible mass heated to a temperature of 550 ... 1000 ° C (patent RU 2567861, IPC C10L 5/46, 5/00, 5/40 (2006.01)).

The disadvantages of this method are as follows:

- leaching of salts of heavy metals and other toxic substances from waste, and, as a consequence, saturation of the liquid used in hydraulic separation with salts of heavy metals and other toxic substances, which will lead to contamination of pure components of waste - waste paper, polymers, wood, etc .;

- the need for subsequent thorough cleaning of the fluid used for hydraulic cleaning;

- reduced heat of combustion of fuel due to the presence of excess moisture in the components (since hydraulic separation is used);

- complex hardware design of the process. as a binder in the formation of briquettes, resinous condensate is used, isolated from gaseous products of thermal decomposition of a combustible mass heated to a temperature of 550-1000 ° C, which is obtained by pyrolysis (patent RU 2567861, Fig. 1, position 4 of the general technological scheme for the production of fuel briquettes) ;

- since the hydraulic separation is carried out indoors, the air in the room is saturated with moisture and harmful vapors, which is dangerous for the service personnel;

- insufficient use of the energy component of municipal solid waste, because for the manufacture of fuel, only the combustible mass of solid municipal waste (MSW) is used, which remains after pyrolysis and distillation of volatile components from the combustible component of the waste at temperatures above 550 ÷ 1000 ° C.

The authors studied the yield of volatile components and coal residue during the pyrolysis of the combustible component of the residual MSW after sorting with varying temperatures with a step of 100 (50) ° С and an exposure time of 30 min.

Figure 2 shows the results of the pyrolysis studies carried out by the authors for the components of the "tails" of MSW output depending on the temperature: a) - volatile; b) - carbonaceous residue.

As can be seen from the results, the polymer components of MSW are almost completely degraded already at a temperature of 500 ° C and do not leave a carbonaceous residue, while cellulose-containing fractions continue to pyrolyze at higher temperatures, and only at temperatures above 700 ° C the yield of gas and carbonaceous residue becomes constant ...

A known method for the production of solid fuel from waste for directing said fuel to an incineration plant, including: providing the first component, which is a dry fraction extracted from municipal solid waste, in a crushed form, providing at least one second component in a crushed form, selected made of elastomeric and thermoplastic polymer material, or mixtures thereof, separate dosing and supply of the first component and at least one second component to the continuous conveyor so that the components form overlapping layers, loading the components thus collected into at least one temporary storage with the formation of solid fuel from waste, dosing and supply of the thus obtained solid fuel from waste to the incineration plant (patent RU 2334786, IPC C10L 5/46. 5/48, (2006.01)).

The disadvantages of this method is the need for at least two components for the manufacture of solid fuel - a dry fraction of municipal waste and a crushed fraction of a thermoplastic polymer material, which are mixed before shipment of solid fuel to an incineration plant and, as a consequence of the presence of a storage area for the dry fraction of municipal waste, and at least one storage area for dry comminuted thermoplastic polymeric material. The storage of such dry crushed materials imposes special requirements for compliance with the rules and regulations of the fire regime. In addition, the morphological analysis of secondary materials remaining after extraction from solid municipal (municipal) waste, carried out by the authors, showed that about 19% of polymeric materials are already present in these residues (wt%).

The closest analogue of the proposed technical solution is a method of processing solid household waste into fuel for furnaces of high-temperature synthesis of cement clinker (patent RU 2479622 IPC С10L 5/46, 5/08). The method includes sorting the original solid waste with screening out non-combustible fractions and extracting secondary materials, crushing the remaining mass to a fraction of 50-100 mm, drying it to a moisture content of 5-10%, additional crushing to a fraction of 8-10 mm, heating the crushed mass to a temperature of 160 ÷ 200 ° C, thermoplastic extrusion of the heated mass to obtain fuel pellets, which are cooled down from the extruder and sent as fuel to cement plants for subsequent combustion in furnaces of high-temperature synthesis of cement clinker. This method is taken as a prototype.

The disadvantages of the prototype are:

- double grinding process, especially energy-intensive when grinding dry mass, increasing capital and operating costs;

- low temperature of heating the mass, heating of the crushed mass to a temperature of 160 ÷ 200 ° C does not provide the release of hydrogen chloride from polyvinyl chloride stabilized by special additives. When pure polyvinyl chloride (PVC) is heated above 140 ° C, its destruction occurs, accompanied by the release of hydrogen chloride. To increase the thermal stability of polymeric products made of polyvinyl chloride, stabilizers are added to it that increase the temperature threshold of destruction (E. V. Kuznetsov, I. P. Prokhorova, D. A. Fayzullina Album of technological schemes for the production of polymers and plastics based on them, M., " Chemistry ", 1976, 108s.). The presence of chlorine-containing compounds in the manufactured fuel leads to the release of dioxins and dibenzofurans (PCDDs and PCDFs) into the environment as a result of their recombination in flue gases upon cooling in the temperature range 400–200 ° C;

- high viscosity of molten polymer components in the crushed mass when heated to 160 ÷ 200 ° C.

The task to be solved by the claimed invention is to reduce the cost of manufacturing and improve the quality of fuel, ensure the possibility of using it both independently in various power units and as an additive to the main process fuel, as well as as a feedstock for producing pyrolysis gas. The method makes it possible to extract halogens, hydrogen halides from halogen-containing PVC plastics and other materials and substances at the stage of fuel production and to prevent them from entering the final product (manufactured fuel).

The technical result of the proposed technical solution consists in:

- reducing the number of technological operations in the manufacture of fuel;

- extraction of halogens, hydrogen halides from PVC plastics and other materials and substances from the original mass at the stage of its heating before thermoplastic extrusion;

- reducing the loads during thermoplastic extrusion by increasing the heating temperature of the initial mass and bringing the polymer components contained in the original mass into a more plastic state;

- increasing the physical and mechanical strength of the resulting fuel

due to more complete impregnation of the fuel components with the molten polymer component contained in the original mass;

- exclusion of water absorption due to the encapsulation of granules of the molten polymer component in the process of their manufacture;

- preventing the possibility of rotting and spontaneous combustion;

- reducing costs for storage and transportation;

- reducing the energy intensity of fuel production;

- improving the environmental situation, including reducing the volume of solid waste disposed of at landfills.

The proposed method for processing solid municipal waste into fuel for various power generating units includes:

- Reception and sorting of initial MSW with screening of non-combustible fractions, such as batteries, stones, building materials waste, cullet and ceramics, street estimates, food waste, leaves, etc. and MSW components containing toxic substances;

- extraction of secondary materials: paper, rags, polymeric materials (plastic), including ferrous and non-ferrous metals;

- dehydration of the remaining mass with a moisture content of more than 15% in screw presses, roller presses, dryers, or in another way to a moisture content of 5 ÷ 15%;

- crushing the dewatered mass to a fraction of 5 ÷ 50 mm;

- heating the crushed mass to a temperature of 180-250 ° C with the removal of water vapor and the resulting gaseous substances, followed by neutralization of the halogens and hydrogen halides contained therein, by known methods;

- thermoplastic extrusion of the heated mass to obtain fuel pellets or briquettes.

The combination of these essential features makes it possible to obtain the specified technical result.

According to the studies carried out by the authors of the morphological and component composition of MSW "tails" (see Table 1 of Fig. 1), they contain an insignificant amount of food waste, but polymer fractions account for more than 30% of the MSW dry weight. This circumstance makes it possible to use them as a binder after heating the initial mass during thermoplastic extrusion. Figure 3 shows samples of briquettes obtained by thermoplastic extrusion in accordance with the proposed technical solution.

According to the conclusion of FSUE "VNIIM im. Mendeleev ”(St. Petersburg), the arithmetic mean value of the specific combustion energy of fuel samples manufactured in accordance with the proposed technical solution was 30709 kJ / kg (measurement protocol No. 2414-22.05.2012 / Alternative Polymer Fuel -Q-19), which is combustion energy is comparable to the specific energy of combustion of coal.

Figure 1 shows table 1 - the morphological composition of MSW after the sorting line of the Lipetsk waste sorting plant (CJSC EcoProm-Lipetsk) in terms of dry matter; figure 2 shows the graphs of the dependence of the yield of volatiles (a) and carbonaceous residue (b) on temperature during pyrolysis of the components of "tails" of MSW, figure 3 - photographs of samples of fuel briquettes obtained from MSW in the experiment; Fig. 4 shows a technological diagram of the installation.

The method of processing MSW into fuel is carried out as follows. After the delivery of solid municipal waste to the sites, the accumulators of the waste sorting stations (factories), large-sized waste is preliminarily removed from them with further crushing in crushers. Plastic bags with MSW are destroyed (cut, torn), screening of MSW is performed on drum or other separators, screens with screening out of batteries, waste of building materials, stones, cullet, ceramics, sand and other fine waste. Further sorting of MSW is carried out with the maximum extraction of secondary materials from them, including ferrous and non-ferrous metals. Ferrous metals are extracted by magnetic separation, non-ferrous metals are extracted - using an alternating magnetic field or by crushing with subsequent pneumatic vibration separation. An increase in the extraction of metal fractions leads to a decrease in the toxicity of the residue.

The remaining mass of MSW waste - "tails" (in this case, raw materials) are dumped onto a conveyor and fed to a screw or roller press, or to a dryer (1), for dehydration to a moisture content in the mass of 5 ÷ 15%. Further, the mass is loaded into a shredder type crusher (2) and crushed to a fraction of 5 ÷ 50 mm. After the crusher, the crushed raw material enters the raw material heater (3) to remove the remaining moisture from it and heat it to a temperature of 180 ÷ 250 ° C. The water vapor effluent during heating and the resulting gaseous substances contaminated with halogens and hydrogen halides are purified or neutralized by known methods. The heated mass enters a screw-type pellet press (4), or another type, where it is used to produce fuel pellets or briquettes by thermoplastic extrusion.

The proposed method of manufacturing from MSW fuel for power units can be implemented on the standard equipment of the waste sorting station, supplemented with the equipment necessary for its implementation.

Claims (1)

A method of processing solid municipal waste (MSW) into solid fuel (RDF fuel), including the reception of the initial MSW, their sorting with screening out non-combustible fractions such as batteries, stones, building materials waste, cullet and ceramics, street estimates, food waste, leaves, etc. etc., extraction of secondary materials: paper, rags, plastic, including ferrous and non-ferrous metals, crushing of the remaining wet combustible mass, drying it, further heating and thermoplastic extrusion, characterized in that the remaining combustible mass with a moisture content of more than 15% is preliminarily dehydrated into screw presses, roller presses, dryers, or in any other way to a moisture content of 5 ÷ 15%, crushed to a fraction of 5 ÷ 50 mm, heated to a temperature of 180 ÷ 250 ° C and subjected to thermoplastic extrusion to obtain fuel pellets or briquettes, and the effluent when heated with fuel masses of water vapor and gaseous products are purified from the hydrogen halides contained therein.

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