RU2552259C2 - Method of processing of domestic and industrial wastes to furnace fuel and hydrocarbon substance and device to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to disposal of solid domestic wastes, organic domestic and industrial wastes, low-grade solid fuels, in particular, peat and coal stock. Proposed method comprises grinding and separation of wastes, their decomposition at combined effects of thermal and electromagnetic fields with ingress of oxygen, production of carbon substance and hydrocarbon fraction as furnace fuel and cleaning of exit flue gases. This process and device allow the increase in yield of target products and 95-98% increase in degree of disposal.

EFFECT: production of 35-45 wt % of carbon substance and up to 10 wt % of black oil fraction.

2 cl, 5 dwg

Description

FIELD OF THE INVENTION

The invention relates primarily to technologies for the disposal of municipal solid waste (MSW), urban waste, waste from the polymer, food, woodworking, petrochemical industries, as well as partial processing of substandard stocks of peat and coal raw materials. The invention allows the organic components of these wastes to be involved as a technogenic source of fuel materials in the fuel and energy complex. The proposed technology can be used in utilities, as well as in oil refining and coke chemistry enterprises to produce carbon carbonate (coke), coke oven gas and gas oil resins, which in quality meet the standard technical standards of the Russian Federation.

State of the art

A known method of disposal of solid household, industrial and polymeric waste by pre-drying it, feeding it into the pyrolysis chamber, burning it with separation into a solid residue and a gaseous component, which are then subjected to high-temperature processing in a slag metal bath of a melting furnace (RF patent N 2135896, class F23G 5 / 027 dated 12/28/1998). The technical implementation of the method requires significant capital and operating costs, consumables and resources with a high market value, characterized by extremely low economic efficiency in terms of obtaining target products.

A known method of processing municipal solid waste (MSW) by pyrolysis and subsequent utilization of the energy of pyrolysis gases (RF patent N 2254518, CL F23G 5/24, F23G 5/027 from 10.23.2003). The method includes loading solid waste and a loose inert coolant into a vertical shaft furnace, initiating the pyrolysis process by supplying a hot steam-water mixture, obtaining a low-pressure pyrolysis gas and burning it with utilization of the heat of combustion. The method provides a high degree of waste disposal. However, energy efficiency and practical implementation of the proposed method remains at a relatively low level due to the characteristics of the composition and quality of solid waste.

A known microwave oven is mainly for heating liquid and bulk materials (RF patent N 7646, class F27D 11/12 of 03/20/1996), containing a heating chamber, at least one waveguide and a channel of transverse section for supplying material, while the channel for material feed is installed in the waveguide and between the dielectric partitions and the heating chamber. The most significant drawback of this prototype is the inability to reach high temperatures (above 500 ° C) and to carry out high-temperature processing of carbon materials for a long time, since the proposed material of the dielectric partitions of the waveguides (fluoroplast) undergoes thermal degradation at temperatures above 350 ° C. Also, the effect of thermal expansions (extensions) of the metal parts of the microwave oven structure on the dielectric partitions is not taken into account, because at high temperature pressures (the temperature difference between the heated substance in the chamber and the ambient air in the microwave activation zone), a significant change in the physical and mechanical properties of the metal and the mechanical pressure of hard steel parts on brittle fluoroplastic (or ceramic) partitions increases.

The closest analogue (prototype of the proposed invention) is a device for processing organic components of waste and car tires into motor fuel using microwave radiation (Yatsun A.V. Gaseous products of pyrolysis of car tires under the influence of microwave frequencies / A.V. Yatsun, P. N. Konovalov, NP Konovalov // Chemistry of solid fuel. - 2008. - No. 3. - p. 70-75). The proposed method is highly energy efficient due to the influence of the microwave field on the physicochemical pyrolysis reactions of organic substances. The main disadvantage of this method is the low productivity of the retort reactor, the selectivity of the process due to the different dielectric constant of the waste components and, as a result, the limited use for the disposal of multicomponent composition due to the lack of suitable stages of grinding and separation, significant losses of electromagnetic radiation into the environment, revealed during operation of the device.

Disclosure of invention

The objective of the present invention is to increase productivity, practical yield of heating oil and carbon substance, increasing energy efficiency and simplifying the hardware design of the process. To solve these problems, the creation of a combined electromagnetic (microwave) and heat field in the working environment (recyclable organic waste components) without air for solid household waste or in an inert environment (nitrogen, water vapor) for some special easily oxidized production waste is used.

The essence of the method of waste disposal is as follows. With regard to unsorted municipal solid waste, the preparatory stage is the grinding of waste up to 95% content of particle size class 1 ... 10 mm, the extraction of ballast (inorganic) components consisting of metal fractions, glass, construction waste, estimate, screening, in a pneumatic separator under pressure a separating agent (in particular, air). Since inorganic components have a solid phase density of more than 1200 kg / m ³ , they are deposited in a high-pressure stream of a separating agent (for example, air, exhaust flue gases, water vapor), and lighter (less than 1200 kg / m ³ ) organic components ( polymers, synthetics, textiles, woody plant residues, food waste, paper, cardboard, etc.) are carried out by the flow of a separating agent into a receiving hopper-distributor. Then, in a special chamber sectional furnace, physicochemical decomposition of the extracted organic components is carried out under the influence of heat treatment of 430-1000 ° C without oxygen access together with the activation of 2.5 GHz electromagnetic microwave radiation. The radiation power and fuel consumption for creating the temperature are determined depending on the performance and composition of the solid waste. The process is carried out in semi-continuous mode for 12 hours, the structure of the process is grouped by the following stages:

1) 20 ... 100 ° C - heating of solid waste;

2) 100 ... 200 ° C - drying of solid waste, melting of polymer components;

3) 200 ... 400 ° C - the primary decomposition of polymer components, wood-vegetable, food and paper-cardboard fractions;

4) 400 ... 700 ° C - physico-chemical decomposition of solid waste with the formation of resins and gas phase;

5) 700 ... 1000 ° C - calcination of the products of the decomposition of solid waste with the receipt of a carbon substance (carbonization).

Upon reaching 1000 ° C, the MSW is isothermally aged, as a result of which the vapor-gas phase is released and a carbon residue (carbon substance) is formed, which is 70-90% consisting of technically pure carbon. The practical yield of carbon substance depends on the composition of solid waste and averages 35 ... 45% of the initial mass of solid waste with a design humidity of 20%. After the carbon substance is unloaded from the furnace, it is quenched with inert gases in order to cool the carbon to temperatures below its autoignition temperature (below 200 ° C). Inert gases (a mixture of air and water vapor) take on the heat of the carbon substance and are sent to the recovery boiler to generate water vapor for the distillation unit. After utilizing the generated heat, the cooled gases are returned to quench the carbon.

The low-pressure vapor-gas phase formed in the process of solidification of solid waste is sent to the scrubber for washing, where it is in contact with the washing water, which ensures the condensation of the vapor of liquid hydrocarbons (resins), the products of the decomposition of solid waste contained in the initial gas-vapor phase. Non-condensed low-pressure gases, containing mainly acetylene, ethylene, methane, ammonia, hydrogen, carbon oxides (II) and (IV), etc., are removed from the scrubber for drying in an adsorbent layer (mainly silica gel), and then sent to afterburning in a carbonization furnace as a fuel.

The condensed fraction of hydrocarbons (resins) is sent to the distillation column apparatus, where the resins are heated in the evaporators with water vapor generated in the carbon quenching unit. Rectification is carried out under vacuum (200 ... 400 mm water column), due to which boiling points are reduced and water is distilled off from the hydrocarbon fraction. The dehydrated hydrocarbon fraction is an analogue substitute for heating oil with a boiling point of 100 ... 250 ° C, its practical yield is on average 10% of the total mass of initial solid waste with an estimated humidity of 20%. It can be distilled to narrower fractions (100 ... 140 ° C with an aromatic hydrocarbon content> 80% and an OC octane number of 60-65, 140 ... 180 ° C with an aromatic hydrocarbon content> 50%, 180 ... 250 ° C with a predominant olefin content and paraffins), however, the need for this stage is determined by technical and economic criteria, since the yield of a narrow hydrocarbon fraction of 100 ... 140 ° C is not more than 2-3% (mass.) from the total mass of the initial solid waste and is not always economically feasible .

The products of fuel combustion (flue gases) formed during the operation of the furnace are sent to a two-stage gas treatment. The first gas treatment stage (thermocatalytic stage) consists in passing uncooled flue gases (temperature over 700 ° C) through a fluidized bed of catalyst (calcined mullite-siliceous fiber with copper-cobalt promoters) to capture highly toxic oxides of organochlorine and fluorine compounds (such as dioxins, , benzapyrenes, biphenyls, mercaptans). In the process of tarring and contamination, the catalyst with the neutralized substances (hazard class IV-V) is sent for regeneration (re-firing) or disposal (disposal).

The second stage of gas purification (chemisorption) is intended for the collective removal of toxic components NH ₃ , H ₂ S, oxides N _x O _y , S _x O _y , CO, CO ₂ from flue gases in bubble scrubbers in which they interact with a chemisorbent - aqueous solution alkali NaOH (concentration of 15 wt%) and urea (concentration of 10 wt%), as a result of the chemical neutralization of nitrogen oxides, sulfur, carbon and physical absorption of nitrogen and hydrogen sulfide to obtain a suspension of ammonium sulfate (NH ₄ ) ₂ SO ₄ and sodium carbonate Na ₂ CO ₃ as final merchandise product. A chemisorbent is prepared in a homogenizer reactor, to which water, urea in crystalline form and a concentrated aqueous NaOH solution are preliminarily fed. During chemisorption, flue gases are cooled from 400 ° C to 80 ... 120 ° C.

Then, at the exit from the scrubbers, post-treatment of the cleaned flue gases in centrifugal separators and / or bag filters is carried out in order to remove moisture and dispersed particles, after which the flue gases are driven off by smoke exhausters through the chimney and emitted into the atmosphere.

The spent chemisorbent in the process of gas purification takes the heat of the flue gases and heats up to 80 ... 90 ° C, then it is cooled with recycled water to 30 ° C in heat exchangers. After the heat exchange step, the chemisorbent stream is separated in a divider. One part of the flow is returned for chemisorption, the other part is sent for vacuum crystallization (separation of crystalline ammonium sulfate from the suspension as a commercial product) into a shell-and-tube apparatus with a steam heater and a separation zone. The dehydration of crystals of ammonium sulfate by filtration through a semipermeable membrane is provided.

Brief Description of the Drawings

Figure 1 - Schematic diagram of the processing of household and industrial waste into heating oil and carbon substance:

B1-2 - smoke exhaust (gas blower), H1-4 - centrifugal pumps, E1-3 - storage silos, D - rotary knife crusher, Ps-pneumatic separator, FR1 - bag filter, Pg - recovery boiler (steam generator), T1-4 - heat exchangers, K1-3 - distillation columns, A - adsorber, TKR - thermocatalytic reactor, AB - vacuum crystallizer, KB - barometric condenser, VN - vacuum pump, NF - suction filter, V31-28 - shut-off valve , KN1-3 - check valve, KSh1-30 - control ball valve, KO1-2 -condensate drain. Lines and streams: T7 - heating steam, T8-condensate, B4 - recycled water (supply), B5 - recycled water (return), 1 - MSW size 5 ... 2000 mm, 2 - MSW size 1 ... 10 mm, 3 - air, 4 - light fraction (<1200 kg / m ³ ), 5 - fuel, 6 - flue gases, 7 - combined-gas phase, 8 - non-condensed gases, 9 - water-tar emulsion, 10 - bottom residue, 11 - heating oil 12 - flushing water, 13 - chemisorbent, 14 - purified flue gases, 15 - dissolved ammonium sulfate, 16 - dried flue gases, 17 - dehydrated ammonium sulfate, 18 - unreacted chemisorbent, 19 - steam with ect.

Figure 2 - Schematic longitudinal section of the furnace chamber: 1 - lower base plate, 2 - support, 3 - upper foundation plate, 4 - axis of the discharge feeder screw, 5 - disk shutter, 6 - carbonization chamber (furnace section), 7 - screw axis loading feeder, 8 - loading feeder, 9 - fuel line, 10 - burner, 11 - combustion zone, 12 - microwave radiation waveguide, 13 - flue gas collector, 14 - common loading distributor, 15 - coke oven gas collector, 16 - discharge feeder, 17 - microwave generator, 18 - feed hopper, 19 - gas blower, 20 - pla belt conveyor, 21 - receiving hopper.

Figure 3 - Schematic cross section of the furnace chamber: 1 - lower foundation plate, 2 - support, 3 - upper foundation plate, 4 - axis of the discharge feeder screw, 5 - disk shutter, 6 - carbonization chamber (furnace section), 7 - axis loading feeder screw, 8 - loading feeder, 9 - fuel line, 10 - burner, 11 - combustion zone, 12 - microwave radiation waveguide, 13 - flue gas collector, 14 - common loading distributor, 15 - coke oven gas collector, 16 - discharge feeder, 17 - microwave generator, 18 - feed hopper, 19 - gas blower, 20 - pl stinchaty conveyor 21 - receiving hopper.

Figure 4 - General top view of the furnace battery:

1 - lower foundation plate, 2 - support, 3 - upper foundation plate, 4 - axis of the discharge feeder screw, 5 - disk shutter, 6 - carbonization chamber (furnace section), 7 - axis of the loading feeder screw, 8 - loading feeder, 9 - fuel line, 10 - burner, 11 - combustion zone, 12 - microwave radiation waveguide, 13 - flue gas collector, 14 - common loading feeder-distributor, 15 - coke oven gas collector, 16 - unloading feeder, 17 - microwave generator , 18 - feed hopper, 19 - gas blower, 20 - plate conveyor, 21 - receiving hopper.

5 is a schematic view of the furnace battery device (isometry).

The implementation of the invention

Figure 1 presents a schematic diagram of a technological process for the disposal of domestic and industrial waste by processing organic components into heating oil and carbon substance. Installation for implementing the process works as follows.

I grind municipal solid waste in a rotary knife crusher D to a particle size of 1 ... 10 mm in one or two stages. The crushed product is loaded into an intermediate storage hopper E3 and, via pneumatic conveying, the air pressure supplied by the B1 blower is sent to the ps air separator for separation into heavy ballast (inorganic) and light (organic) fractions. The ballast fraction is removed from the pneumatic separator by a conveyor belt through a lock gate. The light fraction (organic solid waste components) from the confuser zone of the pneumatic separator is sent to the drive of the PC carbonization furnace.

The scheme of the carbonization furnace is shown in Fig.2-5. The carbonization furnace consists of at least one furnace chamber 6, separated by heating walls 110 mm thick (made of fireclay shaped bricks). The bottom zone of the chamber is laid out on the upper foundation plate 3 of heat-resistant concrete. The upper base plate is installed on the supporting reinforced concrete blocks 2, which, in turn, are installed on the lower base plate 1 (on the strip foundation).

The heating of the furnace chambers is carried out by burning gaseous fuel in the burners 10 in accordance with three modes:

1) starting mode I - 100% natural gas + cold air (excess coefficient 1.1);

2) transition mode II - a mixture of 50% (vol.) Natural gas + 50% (vol.) Coke oven gas + cold air (excess ratio 1.1);

3) main mode III - from 50% (vol.) Natural gas + 50% (vol.) Coke oven gas + hot air (excess coefficient of 1.5).

Gaseous fuel is supplied from the external gas pipeline 9 through a mixer and an air heater to the burners 10 located in the hearth of the furnace between the chamber walls. Heat is transferred from burning gas through the walls. The number of burners per furnace section is at least 2 (excluding pilot burners and flame control devices). On the upper side, the combustion zone 11 is limited by overlapping from a refractory reinforced concrete slab into which openings (chimneys) are mounted for the removal of flue gases into the gas collector 13. There are also penetrations for pipes in the roof of the furnace chambers and gas collectors 15, designed to remove the gaseous charge formed during thermal decomposition volatile products, hereinafter referred to as coke oven gas.

The raw material charge is loaded from the common loading feeder 8 by screws 7 through the lock fittings in the arch of the furnace chambers. The vault of the chamber is made of refractory plates installed conically. The feeder housing and screw are made of heat-resistant steel. A disk lock 5 with a pneumatic actuator is installed in the loading gateway, blocking the chamber after it is loaded with raw materials.

The assembly of the unloading of the finished carbon substance from the chamber is similarly arranged. At the end of the carbonation period, the lower shutter is opened and the discharge screw 4 is rotated. Carbon substance is removed from the furnace chambers to a common discharge feeder 20. The total discharge feeder is a plate conveyor in a sealed enclosure. At the same time, cooled and purified inert gases are supplied to the case by gas blower 19 to extinguish (cool) the carbon substance. The cooled product enters the receiving bunker-pit 21. The gas medium that has taken the heat of the carbon substance is cleaned of dust and soot in a cyclone, then it enters the recovery boiler to generate water vapor (not shown in Figs. 2, 3, 4, 5) where it cools and returns back to the quenching cycle.

All feeders are equipped with electric drives with frequency converters. Electric motors are installed on special racks from the outside of the case of screw mechanisms.

The thickness of the overall lining of the furnace made of lightweight concrete type ALAKS-1.6 is 170 mm. On the outside of the lining, a metal supporting frame is installed from small and large I-beam support posts connected to each other by stiffeners (equal-angle corners). The support posts are attached to the lower foundation plate by anchor bolts, to the lining - by means of metal pins and power springs that transmit vibrations and deformation of the furnace walls (including thermal expansion).

The frame is equipped with stairs and platforms for servicing peepers, pipes and gas collectors.

At least one box with a microwave radiation system 17 is installed on the sides of the lining on the platforms. A microwave generator is installed in the metal box, to which a waveguide fitting with a radio-permeable membrane is connected. If there are 4 or more sections in the furnace, microwave generators are installed parallel to each other and communicated by waveguides 12 with absorption chambers of residual radiation (closed tanks filled with water). The waveguide is a circular tube permeable, made of quartz glass or artificial mica, mica, etc., mounted through the walls and furnace chambers. The pipe gaps between the piers in the combustion zone are coated on the outside with stainless steel (pipe sections of a round profile with a thickness of 10 mm). This is done to minimize the propagation of microwave waves into the combustion zone and to prevent thermal destruction of the dielectric waveguide.

The vapor-gas phase released during the decomposition of MSW in the carbonization furnace (see Fig. 1) is sent by natural convection through a gas collector to water washing into a K1 scrubber, which is a distillation column with bubbled trays or a mass transfer nozzle (depending on the ratio of steam and liquids). Condensed liquid is pumped by pump Н3 to distillation column K2 with an integrated evaporator T1, into which water vapor with an overpressure of 6 ... 7 atm is sent. As a result of distillation under vacuum, steam of washing water comes out as a distillate, which is cooled in a heat exchanger T2 and partially fed as a reflux to a column K2 for irrigation. The dehydrated hydrocarbon fraction with a boiling point of 100 ... 250 ° C leaves the T1 evaporator and flows under the influence of gravitational forces into the T3 heat exchanger-cooler, is cooled to 40 ° C and sent to the warehouse.

The flue gases of the carbonization furnace are pumped out by a B2 exhaust fan to a TCR thermocatalytic reactor with a fluidized bed of catalyst for the first gas treatment stage. In the K3 scrubber, the second stage of gas purification (chemisorption) takes place, where a chemisorbent prepared in a H2 homogenizer tank is supplied with a chemical pump H2. The purified and cooled flue gases are emitted into the atmosphere through the separator FR1, a smoke exhaust fan (or high-pressure fan) B1 and a chimney Tr. The spent chemisorbent solution is sent to the AB vacuum crystallizer, which is a shell-and-tube apparatus with a steam heater and a separation zone. In this apparatus, under the action of heating with water vapor (steam pressure 5–7 atm) and evacuation (up to 0.5 atm), part of the solvent is removed in the barometric condenser BK and crystals of ammonium sulfate and sodium carbonate are formed, which are the final gas purification products. The suspension of crystals by gravity is removed to the capacitive suction filters for dehydration. The filtrate containing dissolved particles of unreacted chemisorbent is cooled in a T4 heat exchanger and returned to the SC column for recycling.

Technical result

This method of processing household and industrial wastes and its proposed hardware design can increase the yields of targeted commercial products, thereby increasing the depth of utilization to 95-98%. Also, this method is characterized by relatively low energy consumption (due to the absence of the problem of slag formation and melting of ballast inorganic components of the waste), approximately 1.5-2 times lower in comparison with the known methods of disposal.

The proposed device can improve energy efficiency (by 25 ... 30% compared with known analogues) and productivity (up to 60%) of the decomposition and carbonization of both carbon-containing organic waste and low-grade fuels in comparison with known analogues. The device carries out joint thermal degradation, pyrolysis by convective heat transfer and thermolysis of substances by absorbing the energy of an electromagnetic wave, thereby increasing the thermal efficiency, which can reach 92%, and the rate of coking (carbonization) of products (up to 250 mm depending on thermophysical properties and porosity of the material). In addition, the nodes of loading and unloading of raw materials can reduce operating costs, minimize the use of auxiliary transport infrastructure and labor-intensive mechanisms.

Claims (2)

1. A method of processing household and industrial wastes into furnace fuel and a carbon substance, including grinding waste, extracting ballast (inorganic) components in a high-pressure stream of a separating agent, physicochemical decomposition of organic components under the influence of heat treatment with activation by electromagnetic microwave radiation, rectification hydrocarbon fractions (resins), drying and afterburning of low-pressure gases, passing flue gases through the catalyst bed, removing toxic components in bubble scrubbers, post-treatment of flue gases, cooling of spent chemisorbent, vacuum crystallization and dehydration of crystals of ammonium sulfate, characterized in that the grinding is carried out to 95% content of the particle size class 1 ... 10 mm, the heat treatment temperature is 430-1000 ° C together with the activation of 2.5 GHz electromagnetic microwave radiation, the low-pressure vapor-gas phase is sent to the scrubber for washing and condensing the vapors of liquid hydrocarbons (resins), non-condensed bottom onapornye gases discharged from the scrubber to a drying adsorbent bed then is sent to afterburning in the carbonization furnace as fuel and generated during operation of the furnace flue gases are fed to two-stage gas cleaning (step catalytic thermal and chemisorption) with additional purification. 2. A device for processing household and industrial wastes into furnace fuel and a carbon substance, including a waste shredder, a sectional carbonization chamber furnace for the physicochemical decomposition of organic components under the influence of heat treatment with activation by electromagnetic microwave radiation, column apparatus for the rectification of hydrocarbon fractions ( resin), a scrubber for drying and subsequent afterburning of low-pressure gases in the furnace, characterized in that an organic separator is provided gas and ballast (inorganic) components in the high-pressure flow of the separating agent, a fluidized catalyst bed for passing and neutralizing the furnace flue gases, bubble scrubbers for removing toxic components and post-treatment of flue gases, heat exchangers for cooling spent chemisorbent, a shell-and-tube apparatus for vacuum crystallization, a filter with a semipermeable membrane for the dehydration of crystals of ammonium sulfate.

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