RU2567861C1 - Production of combustible briquettes from solid household wastes sites - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention discloses production of combustible briquettes from solid household wastes and other organic wastes. Said process comprises the steps that follow. Solid wastes are classified to isolate combustible mass. Said isolated mass is subjected to grinding. Ground material is dried and heated to make the pellets thereof. Note here the initial solid household wastes are classified with isolation of combustible mass by hydromechanical process. Moisture content of the mass to be ground makes 40-55%. Said mass is heated to 550-1000°C. Power supply for production of combustible briquettes is covered completely by latent internal energy of combustible mass of said wastes. Gum condensate is used as a binder isolated from gaseous products of combustible mass thermal decomposition at 550-1000°C.

EFFECT: production of high-calorific, smokeless, non-polluting fuel to be used in whatever furnaces and at industrial plants.

4 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of environmental protection, to renewable energy sources, to utilities engaged in the disposal of municipal solid waste (MSW) and other organic waste.

Solid waste and other organic wastes covered by the invention include human waste products consisting of the following groups: paper and cardboard waste, food waste, textile waste, leather and rubber waste, polymer waste, inorganic waste (glass, concrete, ceramics, sand, soil, gravel, scrap of ferrous and non-ferrous metals).

MSW are characterized by significant phase and morphological heterogeneity:

physical water 15 ... 50% inorganic substance 12 ... 20% combustible mass (organic substance) 38 ... 65%

More than 100 patents of the Russian Federation issued over the past 20 years are known, in which various technical solutions are proposed, with varying degrees of efficiency, manufacturability, and environmental safety.

Among the known technical solutions, proposals that realize the natural energy potential are of the greatest interest. MSW, i.e. proposals for the use of solid waste as an alternative, non-traditional fuel. The effectiveness of this area, due to two fundamental circumstances: the combustion of solid waste provides the most significant and irreversible reduction in the volume of this product and the combustion of solid waste provides the output of thermal energy, measured from 2 to 3.5 Gcal per 1 ton.

If the average output of MSW per person per year is 0.35 tons, then in the Russian Federation approximately 50 million tons of MSW are formed annually, which is equivalent to 35 ... 38 million tons of coal.

Thus, the relevance of the present invention is obvious.

A known method of producing solid fuel (RU 21342881 C1), in particular from solid waste together with lime, limestone, dolomite, which is dried after molding. A disadvantage of the known fuel is that the MSW used in the fuel was not preliminarily subjected to heat treatment and contain various harmful compounds released during combustion. In addition, the mineral component of the proposed fuel (lime, limestone, dolomite) does not burn, reduces the calorific value of the fuel, increasing the amount of ash and slag.

A known method of processing waste, briquetted fuel, additive (RU 2109035 C1), in which solid waste is mixed with coal and fatty additives, for example with bleaching earth. The mass is granulated into fuel briquettes.

A known method and installation for the production of solid fuel from waste (RU 2334786 C2), in which solid fuel is proposed to be made from dry solid waste mixed with elastomeric or polymeric material when layered on a vehicle transporting fuel to the combustion site.

A known method of processing sorted household waste into fuel briquettes (RU 2492158 C1), including grinding solid waste, mixing the crushed material with water and binders, pressing briquettes at a pressure of 150 ... 200 kg / cm ² followed by drying at a temperature of 50 ... 60 ° C for 40 ... 90 minutes

A known method of producing solid fuel made from industrial and household waste (RU 2405027 C2), in which fuel briquettes are prepared from solid waste with the addition of lime, form round briquettes, dried. The resulting fuel has a calorie content of about 6000 kcal / kg.

All of the above technical solutions have the main drawback - the used solid waste did not undergo thermal preparation and contain a significant amount of harmful compounds released during combustion into the environment. This circumstance throughout the world is holding back the development of a method for the disposal of solid waste by direct burning in boiler furnaces.

Another disadvantage of the above analogues is the use of additional binder materials in the molding of fuel briquettes.

Common to all of these analogues are preliminary operations before use: mechanical sorting, grinding, and the use of high pressure in the form of extrusion or pressing when forming granules or briquettes.

As a prototype, a method of processing solid waste into fuel for high-temperature synthesis of cement clinker furnaces (RU 2479622 C1) was selected, including sorting the initial solid waste, grinding to a fraction of 50 ... 100 mm, drying to a residual moisture content of 5 ... 10%, secondary grinding to a fraction of 8 ... 10 mm, heating the crushed raw materials to a temperature of 160 ... 200 ° C, thermoplastic extrusion to obtain fuel granules.

The disadvantages of the prototype are the following:

- a complex, ineffective sorting process in the form of dry mechanical dispersion of the original solid waste;

- double grinding process, especially energy-intensive when grinding dry mass;

- low mass heating temperature (160 ... 200 ° C), which can only melt some thermoplastic polymers, the rest of MSW mass at a temperature of 160 ... 200 ° C does not change its state of aggregation, does not undergo degradation, which limits a more complete disclosure of potential energy possibilities;

- fuel pellets of the prototype have a relatively low calorific value (not higher than 5000 kcal / kg), smoke when burning, emitting harmful substances.

- the limited area of use of fuel briquettes is due to the need to use high temperatures to ensure environmental cleanliness when burning fuel briquettes.

The aim of the invention is the creation of a highly efficient method for producing fuel briquettes from solid waste and other organic waste, ensuring the production of high-calorie, smokeless, environmentally friendly granular fuel suitable for burning in any furnace devices with high and low combustion temperatures.

The goal is achieved in that the method of producing fuel briquettes from solid waste and other organic waste, including sorting the solid waste with the allocation of combustible mass, grinding the combustible mass extracted from the solid waste, drying the ground material, heating the ground material, forming granules from the ground material, is characterized in that the sorting initial solid waste with the release of combustible mass is carried out hydromechanically, the mass is subjected to grinding with a humidity of 40 ... 55%, the mass is heated in the temperature range 550 ... 1000 ° C, the energy supply for the production of fuel briquettes is made entirely due to the latent internal energy of the combustible solid waste mass; tar binder is used as a binder in the formation of briquettes.

The invention is illustrated by the following schemes.

The figure 1 presents the General technological scheme of production.

The figure 2 presents a diagram of the material balance of obtaining a coolant (gene gas) for pyrolysis of a drum retort.

The figure 3 presents a diagram of the material and thermal balances of the cooling unit of the gas mixture and the condensation of resins, water.

The figure 4 presents the General technological scheme for the production of fuel briquettes from solid waste of the present invention.

The positions in the diagrams indicate:

1. The hydraulic separation section;

2. The plot of cutting (grinding) of the combustible mass;

3. Tumble dryer;

4. Pyrolysis drum retort;

5. Remote gas generator;

6. Heat exchanger-condenser;

7. Refrigerator;

8. The mixer;

9. The extruder.

The process of obtaining fuel briquettes from solid waste and other organic waste proceeds in the following sequence.

MSW with natural moisture is fed to the hydraulic separation section 1, as a result of which organic and inorganic components are separated. Inorganic components are removed from the apparatus, metals are taken away, the rest is dried and crushed for further use as bulk material.

Organic substance (combustible mass) with a moisture content of 40 ... 55% is sent to the cutting (grinding) area 2. As a result of grinding, a uniform fractional composition and a decrease in humidity to 22 ... 25% are achieved. The resulting product is called - wet enriched unconventional fuel (ONT).

The grinding of the wet ONT is completed in the drying drum 3 with the heat carrier obtained by burning non-condensable gas (gaseous residue after the extraction of water and tar condensate from the pyrogen-generating gas).

Dry ONT is sent to the pyrolysis drum retort 4, where heat treatment occurs at 550 ... 1000 ° C. The solid coal residue of ONT pyrolysis is a semi-finished product of fuel briquettes.

Part of the solid coal residue is used in the remote gas generator 5, where the generator gas is obtained with a temperature of about 1000 ° C, which serves as a coolant in the pyrolysis drum retort 4.

A gas mixture consisting of pyrolysis gas and generator gas leaves the pyrolysis retort 4. The gas mixture passes through a heat exchanger-condenser 6, cooling, generating thermal (heat) energy.

As a result of cooling the gas mixture in the heat exchanger-condenser 6 to 30 ... 40 ° C, the pairs of resins and water contained in the gas mixture are condensed and removed from the apparatus. The non-condensable gas remaining after condensate extraction is burned, the resulting coolant is used in the drying drum 3 for drying wet ONT.

The cooled solid coal residue from the refrigerator 7 is sent to the mixer 8, where it is mixed with a resinous substance. After homogenization, the resulting press mass is passed through an extruder 9, in which briquetting takes place to obtain fuel briquettes.

The figure 1 presents the General technological scheme for the production of fuel briquettes from MSW of the present invention.

The rationale for the novelty of the claimed technological operations in the proposed invention

Hydraulic sorting of solid waste is carried out in a fluid stream moving at a certain speed in horizontal directions. Since the components of solid waste are characterized by different densities: combustible mass (organic) - 1300 ... 1400 kg / m ³ , inorganic (glass, concrete, ceramics) - 2400 ... 2500 kg / m ³ , metals (2700 ... 8000 kg / m ³ ), then from the horizontal liquid flow (density ≈1000 kg / m ³ ) the components of solid waste fall out at different distances. Only the hydraulic method for the separation of solid waste provides the highest purity of selection of organic (combustible) components. The presence of inorganic inclusions in the combustible mass after hydraulic sorting does not exceed 2% (as a rule, fine sand particles).

“Wet” solid waste sorting processes compare favorably with “dry” ones, firstly, because they proceed with minimal dusting, and secondly, acutely smelling nitrogen decay products dissolve in a liquid substance, which characterizes the hydraulic sorting process as environmentally friendly.

Water-saturated cutting of flammable mass

Cutting a combustible mass selected from solid waste in a water-saturated state (W = 40 ... 55%) requires 20 ... 25% less electric energy, while the wear of the cutting elements is reduced and, accordingly, the working life of the equipment increases.

Mass heating up to 550 ... 1000 ° C

The prototype claims the heating of the combustible mass to 160 ... 200 ° C. This temperature allows melt only certain types of thermoplastics (polyethylene, polystyrene, polypropylene, etc.), the bulk of the components: paper, food, wood, textiles, etc. remain in their original unstructured state of aggregation, i.e. After heating to 160 ... 200 ° C, the morphological composition of the combustible mass remains unchanged, extremely heterogeneous, and when burning, there is abundant evolution and uncontrolled jumps in flame temperatures.

Another happens when the combustible mass is heated to 550 ... 1000 ° C in the absence of an oxidizing agent (oxygen).

In the indicated temperature range, thermal decomposition (pyrolysis) of organics occurs with the release of volatile substances (pyrolysis gas) and solid coal residue. The amount of thermal decomposition products depends on the pyrolysis temperature. The higher the temperature, the lower the yield of solid coal residue and, conversely, the higher the yield of volatiles. In this case, the composition and calorific value of the decay products depend on the pyrolysis temperature.

Let us illustrate by the example of pyrolysis of wood at various temperatures.

At a pyrolysis temperature of 550 ° C, complete carbonization of the mass is achieved, while ensuring the highest yield of solid coal residue in the range 550 ... 1000 ° C. A decrease in the pyrolysis temperature (less than 550 ° C) is accompanied by an increase in the uncarbonized, initial mass of the substance. An increase in temperature above 550 ° C is accompanied by an increase in the fraction of carbon with a simultaneous decrease in the fraction of hydrogen and oxygen to zero.

The selected temperature range in the present invention 550 ... 1000 ° C is justified by the fact that the lower limit guarantees the absence of uncarbonized substance in the product, and the upper limit ensures the production of pure coal in the solid residue, which is especially valuable when using a solid residue to produce synthesis gas.

The coolant for the implementation of solid waste pyrolysis.

A feature of pyrolysis is the heating of organic matter in the absence of an oxidizing agent (oxygen). The less oxygen enters the pyrolysis retort, the more efficient the process, the cleaner the pyrolysis gas.

Usually used hermetic, isolated from the environment retorts. In this case, the thermal energy for activation of the pyrolysis process is transmitted through the walls of the retort by thermal conductivity. This method of heat transfer is extremely inefficient, therefore, it is applicable only for low power pyrolysis production.

In the case of large tonnage processing of solid waste, a more efficient method of heat transfer is required. The most effective method of heat transfer is convection in the execution of drawing gaseous heat carrier through the MSW layer, somewhat inferior to convection - radiant heat transfer - in the execution of drawing gaseous heat carrier over the MSW layer. However, in both cases, there are limitations associated with the temperature of the gaseous coolant. If the pyrolysis temperature of solid waste is 550 ... .600 ° C (the most favorable for obtaining a coal residue), then the temperature of the gaseous coolant should not exceed 1000 ° C.

It is possible to obtain a gaseous coolant devoid of free oxygen in two ways (using a part of the solid coal residue): either provide complete combustion of a part of the coal residue, which ensures the absence of free oxygen in the combustion products, or gasify a part of the solid coal residue with the generation of gas. In the first case, the temperature of the combustion products of the solid coal residue is up to 1500 ° C; therefore, before feeding into the pyrolysis retort, the temperature of the combustion products must be reduced to the required 1000 ° C. Typically, in technical processes, “hot” combustion products are cooled by mixing with cold air. Less commonly used is the installation method on the path between the furnace and the pyrolysis retort of the heat exchanger, which reduces the temperature of the coolant from 1500 ° C to 1000 ° C by heating the heating water. The first method of cooling is unacceptable due to the appearance of oxygen in the coolant. The latter method is quite attractive, but technically not very convenient (high metal consumption of the heat exchanger, increased consumption of solid coal residue, which is a commercial product of the process).

A more technically and economically advantageous method is to obtain a coolant for the pyrolysis retort in the form of an air generator gas consisting of CO, H ₂ O, N ₂ and a certain amount of CO ₂ . The temperature at the outlet of the gas generator is about 1000 ° C, i.e. exactly what is required. In addition, the CO contained in the gene gas enriches the pyrolysis gas, increasing its calorific value.

Binders for obtaining fuel briquettes from carbonized solid waste

Preservation by the briquettes of solid waste of the form and mechanical strength after molding (extrusion) is ensured by the content of the adhesive substance in the briquettes. In some cases, it is peat, in others lime, in the prototype is a melt of thermoplastics. However, the pyrolysis gas leaving the pyrolysis retort always contains 10 ... 12% of the total gas mass of a pair of resinous substances, which, when the pyrolysis gas is cooled, condenses into a viscous liquid, which is proposed to be used as a binder. When the pyrolysis gas is cooled, water precipitates along with the resinous substance, the remaining non-condensable gas has sufficient calorific value so that heat after oxidative afterburning can be used, for example, for drying solid waste before pyrolysis.

An example of the practical use of the invention

Initial data

In a city with a population of 600 thousand people there is an annual output of solid waste in the amount of: 600,000 × 0.35 = 210,000 tons (0.35 is the average output of solid waste per year per person).

The average humidity of solid waste is 40%, the content of inorganic substances is 16%.

As a result of hydromechanical enrichment of 210 thousand tons, 127 thousand tons of enriched unconventional fuel (ONT) with a moisture content of 22% and an inorganic content of 5% were obtained.

ONT phase composition:

The morphological composition of the combustible mass (absolutely dry matter):

The chemical composition of 92.7 thousand tons of combustible mass, together with 6.3 thousand tons of inorganics, which forms a “dry” ONT:

Based on the chemical composition of the combustible mass, we calculate the higher calorific value of the combustible mass according to Mendeleev’s formula:

Further calculations were performed for the ONT hourly output if the production operation mode is 360 days a year, in three shifts, 8640 hours. Hourly productivity:

Phase composition of “wet” ONT hourly productivity:

Process stages

The first stage of heat treatment of solid waste is drying.

As a result of drying and returning 3235 kg of water, the phase composition of the “dry” ONT:

Drying is carried out in a rotating drying drum 3 by heating non-condensable gas with combustion products (see below).

The second stage of heat treatment of solid waste is pyrolysis.

As a result of pyrolysis, the combustible mass decomposes into two products: pyrolysis gas (47.8%); solid coal residue (52.2%).

The phase composition of the decay products of "dry" ONT (11465 kg):

The chemical composition of pyrolysis gas:

The chemical composition of the solid coal residue:

The calorific value of the pyrolysis gas according to the formula of Mendeleev:

The calorific value of the solid coal residue according to the formula of Mendeleev:

The pyrolysis of ONT is carried out in a rotating pyrolysis drum retort 4 by heating with an oxygen-free heat carrier - generator gas, which is obtained in a remote generator, where the working fluid is part of the solid coal residue.

The consumption of solid coal residue to obtain a coolant (generator gas) is taken from the calculation of the heat balance of the pyrolysis retort. The need for pyrolysis activation energy consists of: the energy of heating ONT to temperatures (550 ... 600 ° C), the entrainment of heat with pyrolysis gas and solid coal residue, heat loss to the environment.

Common articles of the heat balance are: the heat of exothermic reactions of organic decomposition and the heat of “dry” ONT with a temperature of about 100 ° C.

The activation energy for the pyrolysis of “dry” ONT (11465 kg / h) is approximately 600,000 kcal / h.

The “dry” ONT in the pyrolysis retort is heated by an air generator gas with a temperature of about 1000 ° C, obtained from a solid coal residue in a remote gas generator.

The figure 2 shows a diagram of the material balance of obtaining the coolant (gene gas) for the pyrolysis retort.

The coolant (generator gas), carrying out the pyrolysis of ONT, is mixed with the pyrolysis gas to obtain a gas mixture (5480 + 1430 = 6910 kg). From the pyrolysis drum retort 4 leaves the mixture of the following chemical composition:

The calorific value of the gas mixture is determined by the periodic formula:

The heat content of the gas mixture at a temperature of 500 ° C-i _gs = 1036500 kcal.

Passing the gas mixture through the heat exchanger-cooler 6 with decreasing temperature to 30 ° C leads to the condensation of resinous substances (560 kg) and water (400 kg).

The figure 3 presents a diagram of the material and thermal balances of the cooling unit of the gas mixture and the condensation of resins, water.

The calorific value of non-condensable gas, determined by the periodic formula, is equal to:

A resinous substance of 560 kg is used as a binder for solid coal residue during the extrusion of fuel granules (instead of melt thermoplastics in the prototype).

The amount of solid coal residue minus 200 kg / h spent on the preparation of the coolant - generator gas is 5785 kg / h.

The flaking to the solid coal residue of 560 kg / hr of resinous substance gives 6345 kg / hr of molding material, which in the extruder 9 is formed in the form of fuel briquettes, characterized by the following properties:

The figure 4 presents the General technological scheme for the production of fuel briquettes from solid waste of the present invention.

Basic technological equipment

- Hydraulic separator for separating inorganic components of solid waste from organic with obtaining enriched unconventional fuel (ONT).

- A drying drum for dehydration of ONT.

- Pyrolysis, drum retort for separation of “dry” ONT into a gaseous substance (pyrolysis gas) and solid coal residue.

- A portable gas generator for the preparation of a coolant for the pyrolysis of ONT.

- A heat exchanger-condenser for separating the gas substance that leaves the pyrolysis retort into a resin substance, water condensate and non-condensable gas.

- Homogenizing mixer for the preparation of the press mass from solid coal residue and tar condensate.

- Extruder for molding fuel briquettes.

Thus, using the technical solution “Method for the production of fuel briquettes from solid waste and other organic waste” as an example, it is shown that with the full disposal of solid waste in a city with a population of 600 thousand people, 210 thousand tons of solid waste per year will be processed into the following products:

Claims (1)

A method of manufacturing fuel briquettes from solid household waste (MSW) and other organic waste, including sorting the MSW with the release of combustible mass, grinding the combustible material extracted from the MSW, drying the crushed material, heating the crushed material, forming granules from the crushed material, characterized in that the sorting initial solid waste with the release of combustible mass is carried out hydromechanically, the mass is subjected to grinding with a moisture content of 40 ... 55%, the mass is heated in the temperature range 550 1000 ° C, energy production of fuel briquettes produced entirely by the latent internal energy combustible mass TBT, as a binder when forming the briquettes used resinous condensate derived from the gaseous products of thermal decomposition of the combustible mass heated to a temperature of 550 ... 1000 ° C.

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