RU2686560C1 - Solid wastes combustion method - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to means of processing solid materials by a firing method, and more specifically to a technology of an autothermal process of batch combustion of solid wastes in a vertical two-chamber furnace with successive separation of solid particles in the exit aerosol and neutralization of harmful gases in it by "wet" technology. Method comprises batch loading of recycled material on grate of vertical two-chamber furnace with central opening in separating arch, in which oxidising air is distributed in height, wherein waste gaseous combustion products are transitively cooled in a scrubber by transverse jet treatment with a reaction alkaline solution with subsequent final filtration to separate pure aerosol, which is forced into the exhaust pipe. At that, oxidising air is distributed in the following way: (3/5–3/4) under grate, (1/8–1/5) into central bore of arch and (1/8–1/5) into upper afterburning chamber, wherein the oxidising air, prior to treatment of waste gases in the scrubber, is removed from the jacket of the heat exchanger, where radiation energy is heated by means of heat transfer in counter-current with exhaust gaseous combustion products, then aerosol obtained after the scrubber, is fed for barbotage in a process alkaline solution with selection of a condensed phase, and before finishing filtration in a mist layer, which is formed by a sprayer in a receiver, the aerosol is cooled by means of a permeable heat-intensive filling from Raschig rings.

EFFECT: technical result is thinner cleaning of waste gases after combustion furnace, with optimization of distribution of hot oxidising air taken from heat exchanger, by furnace height and simplification of automatic process technical process of gas cleaning by various operations of wet technology.

1 cl, 3 dwg

Description

The invention relates to the technology of processing solid materials by the firing method, and more specifically, to a method of autothermal batch-burning process of solid waste in a vertical two-chamber furnace with sequential separation of solid particles in the exhaust aerosol and neutralization of harmful gases in it using the “wet” technology of chemical interaction with mixing the reaction alkaline solution.

The level of this technical field characterizes the method of burning solid waste in a vertical furnace, described in patent RU 2660966 C1, F23G 5/14, 2018, which includes batch loading of solid fragmented material on the combustion chamber grate, the flow of combustion gases into the afterburner through the central a window in the vault between them and removal of gas-aerosol products of combustion for filtration.

The method is characterized by the fact that the combustion of solid material is carried out in an atmosphere of excess oxygen in the structure of distributed oxidizing air distributed over the height of the furnace, in volume fractions: 1/4 under the grate, 1/2 into the central opening of the vault between the chambers, 1/8 across the nozzle of loading and 1/8 into the diffuser of the afterburner chamber, forming a positive oxygen balance of the combustion front in these technological zones of the vertical furnace.

The peculiarity of this method is that the bore of the central arch of the furnace is 9-13% of the cross section of its chambers, and the height of the nozzle is comparable to its two diameters, and the nozzle is equipped with two rows of distributed channels for supplying oxidizing air directed into the afterburner at an angle 30 °.

When the relative size of the flow area of the communication opening of the vault is less than 9%, the outgoing gas-air flow from the combustion chamber is clamped until the combustion process on the grate is completely attenuated.

When the relative size of the flow area of the communication opening of the furnace chambers is more than 13%, the required efficiency of mixing the laminar flow of combustion gases with locally supplied additional oxidizing air is not ensured, which requires a significant increase in the height of the furnace.

The ash is removed in trays under the grate, by means of screw conveyors, above which is placed a scraper associated with a cross feed mechanism.

The grate is made tubular with perforations and is connected to the system of distributed supply of oxidizing air.

At the outlet of the afterburning chamber, an emergency valve is mounted, made in the form of a hinged lid, which is connected via a lever with a manual actuator.

A portion of oxidizing air is forcibly supplied to the charge nozzle (across the load window in the combustion chamber) to form a gas-dynamic damper that prevents back emissions of combustion products.

The slope of the channels supplying oxidizing air to the central opening of the arch between the chambers of the furnace is fed at an angle of 30 ° to the longitudinal axis, accelerating the axial flow of the combustion gases of the combusted material into the afterburning chamber, thereby creating a vacuum under the vault, thereby providing injection of aerosol from the combustion chamber, as a result, gaseous products of combustion expanding in the diffuser of the afterburning chamber are actively mixed with the oxidizing air injected into it, which contributes to the complete oxidation of the products inside the furnace .

Further, in the confuser of the afterburning chamber, the gas-air mixture is braked and additional mixing is caused due to the turbulence of turbulent flows formed after the arch between the chambers of the furnace.

The hinged lid on the outlet pipe of the afterburner chamber in the open position serves to create thrust when the furnace is ignited, and in operation it acts as an emergency valve that automatically releases pressure to the atmosphere.

However, as practice has shown, the following disadvantages are inherent in the described method of burning.

In the distributed supply of oxidizing air, the ratio of its volumes at the technological levels of the furnace is not optimized, in particular, a double gas dynamic shutter is created in the central opening of the roof, which locks the exhaust gaseous combustion products in the combustion chamber, where the pressure and temperature rise, which requires additional capital investments to reduce them .

The consumption of generated gaseous combustion products in the combustion chamber is also significantly reduced from the forced length of the central opening of the vault due to the need to accommodate two rows of inclined air channels, with a markedly insufficient cross-section for complete combustion and high-temperature oxidative pyrolysis, which reduces the overall performance of the process.

In addition, as a result of imbalance in the combustion chamber of gas-dynamic processes, arches and a crust of sintered and melted fragments are formed in the material burned on the tubular grate; for eccentric agitators and a drive scraper, which periodically remove ash and slag in a tray with a screw conveyor, are mechanically destroyed.

More perfect is the combustion method described in patent RU 2392544 C1, F23G 5/14, 2010, which, by its technical essence and the number of matching signs, is chosen as the closest analogue to the one proposed.

In the known method, high-performance autothermal combustion of various solid and viscous materials with high-quality oxidation of combustion products in a vertical two-chamber furnace and continuous stepwise filtration of exhaust gases in a compact installation, safe and environmentally friendly in operation, are ensured.

Waste incineration is carried out in a vertical furnace, in which the distribution is applied to the oxidizing air under the grate, into the central opening of the vault between the combustion chambers and afterburning and to the cut-off of the loading window.

Afterburner has a horizontal pipe connection with a parallel installed transit scrubber for wet scrubbing of waste gases, which is carried out with a jet transverse flow of the reaction solution, after which the aerosol is mechanically filtered and forcibly supplied by an exhaust fan to the traction pipe for release into the atmosphere.

The outgoing aerosol filtering device consists of two parallel streams connected through gate valves with an injection fan, each of which has a cascade of replaceable cassettes of gas-permeable material mounted, which are put into operation in series when the second is technically re-equipped.

The scrubber uses a supply tank of a working fluid closed with a central nozzle mounted on the discharge pipe.

The disadvantages of the known method of burning solid and liquid waste are incomplete oxidation of gaseous products of combustion and poor cleaning of exhaust gases from solid impurities in the scrubber and mechanical filters of replaceable cassettes, which complicate the technological maintenance and increase the capital cost of production.

In addition, the volume distribution of oxidizing air over the structural elements of the furnace is not optimized, in particular, in the central opening of the roof, an aerodynamic shutter is formed due to an overabundance of two-stage annular air supply, which prevents the free passage of the combustion gases that are locked in the combustion chamber, destabilizing the gas-dynamic combustion process , and in the afterburning chamber they break through with acceleration, where the oxidation process of the exhaust gaseous products, which are removed from ovens.

At the same time, the efficiency of chemical combustion reactions is slowed down due to the loss of thermal energy in the furnace to heat the incoming cold masses of oxidizing air.

The technical problem addressed by the present invention is a finer purification of flue gases after the combustion furnace, while optimizing the distribution of hot oxidizing air drawn from the heat exchanger along the furnace height and simplifying the automatic process process of efficient gas cleaning with various wet technology operations.

The required technical result is achieved by the fact that in a known method of burning solid waste containing batch loading of recyclable material on the grate of a vertical two-chamber furnace with a central hole in the separating roof, which is distributed over the height, oxidizing air is fed, while the exhaust gaseous products of combustion are transit-cooled in a scrubber cross-jet treatment by reaction alkaline solution followed by final filtration to separate the pure aerosol, forcibly injected into the exhaust pipe according to the invention, the oxidizing air heated is distributed distributed over the height of the furnace in volume fractions: (3/5-3 / 4) under the grate, (1 / 8-1 / 5) into the central opening of the roof and (1 / 8- 1/5) in the upper afterburning chamber, while the oxidizing air, before processing the exhaust gases in the scrubber, is removed from the heat exchanger jacket, where the radiation energy is heated by heat transfer in countercurrent by the exhaust gaseous products of combustion, then the aerosol obtained after the scrubber is fed to sparging process alkali ohm solution with selection of the condensed phase, and before the final filtration layer mist generated in the receiver spreerom aerosol cooled by the heat capacity permeable filling of Raschig rings.

Distinctive features of the proposed technical solution ensured the complete combustion of solid materials in the autothermal mode to the final products and the efficiency of cleaning the exhaust gaseous products of combustion by wet technology to environmental standards and requirements, with concomitant stepwise low-temperature cooling before emission into the atmosphere.

The proposed method is characterized by the following advantages:

- optimal distribution of hot oxidizing air in the characteristic zones of the vertical furnace for maximum efficiency and full combustion of the starting solid materials to the final oxidation products;

- heating the oxidizing air supplied to the furnace contributes to raising the temperature of a more productive process of burning solid materials, while utilization of the heat of combustion waste products to preheat the air reduces energy consumption inside the furnace, which creates a rise in temperature and burning rate;

- heat utilization is carried out automatically in the heat exchanger during the oncoming movement of hot exhaust gaseous products of combustion and oxidizing air through the separating wall of the transporting coil;

- additional (after scrubber) cooling of gas-aerosol products of combustion by sparging combined with physical selection of the condensed phase of the aerosol — solid particles not burnt in the furnace, in the form of settling slurry, markedly reduced the temperature of the aerosol fed to the final filtration column;

- additional cooling through heat transfer of a moving aerosol with surface contact through the permeable filtering barrier of heat-intensive Raschig rings allows effectively reducing the temperature of the aerosol at the entrance to the column of finishing treatment;

- the subsequent interaction of the aerosol with a curtain of mist from the technological alkaline solution formed by the sprayer in the receiver ensures the generality of the wet technology without breaking the flow of cleaning and cooling of the aerosol at the exit of the final treatment column to a temperature of 130-150 ° C, in order to avoid dropping on the drive of the exhaust pump, delivering clean aerosol to the traction pipe for dispersion into the atmosphere.

The proposed fractional distribution of hot (250-300 ° C) oxidizing air is justified by the fact that:

- (3/5-3 / 4) of the volume supplied under the grate, activates and stabilizes the combustion of the source solid material in an atmosphere of excess oxygen;

- (1.8-1 / 5) of the volume supplied to the central opening of the roof counter at an angle to the axis, creates a gas valve, inhibiting the release of gaseous combustion products from the lower combustion chamber of the furnace for 2s, which ensures the efficiency of chemical interaction of thermal decomposition products in an excess atmosphere oxygen;

- (1.8-1 / 5) volume supplied to the afterburning chamber of a vertical furnace, it is necessary, by definition, to obtain at the outlet the final oxidation products.

The oxidizing air is preheated by the utilized heat energy of the combustion gases exhausting from the furnace, due to convective heat transfer through the walls of the heat exchanger jacket, and is carried out before treatment in a scrubber.

The post-spray irrigation of gas-aerosol combustion products with a working alkaline solution, additional cooling by bubbling, ensures the selection of the condensed phase precipitated in the bubbler and the accumulation of purified aerosol to drain to the final filtration column.

After sparging, the aerosol is efficiently cooled by contact over the developed surface of the heat-intensive Raschig rings moistened with the working fluid.

The final filtration of the exhaust aerosol in the mist layer from the working solution, which is transversely dispersible with the sprayer into the receiver, provides washing and sedimentation of residual solid particles, as well as cooling the aerosol to a temperature that prevents dropping on the drive of the exhaust pump that feeds it into the traction pipe.

Consequently, each essential feature is necessary, and their combination in a stable relationship is sufficient to achieve a novelty of quality that is not inherent to features in disunity, that is, the required technical result is achieved not by the sum of effects, but by a new supereffect of the sum of features.

The invention is illustrated in the drawing, which is purely illustrative purpose and does not limit the scope of the claims set of essential features of the formula.

The drawing shows:

in fig. 1 is a flow chart for solid waste incineration;

in fig. 2.1 - vertical oven with loading mechanism;

in fig. 2.2 - section for cooling the exhaust gases and aerosol purification with its final filtration.

The proposed method is implemented in the installation (Fig. 1), which includes mounted in interconnection sequentially: a device 1 batch load packaged waste stacked in a tilting container 2, a floodgate receiver 3, bounded below by a gate valve 4, controlled from the limit switch 5.

The receiver 3 oblique nozzle 6 communicates with the loading window 7 of the combustion chamber 8, which through the central opening 9 of the roof 10 is connected to the afterburning chamber 11, collectively forming a vertical furnace for burning solid and viscous materials connected by a discharge pipe 12 to the parallel processing of the outgoing gaseous combustion products in the composition of sequentially mounted heat exchanger 14, scrubber 15 with nozzle 16 and replaceable bubbler 17.

To the outlet of the heat exchanger 14 is connected to the duct 18 connected to the system 19 of the forced distributed supply of hot oxidizing air to the vertical furnace (the pump is conventionally not shown) by means of the dampers 20 and 21.

The bubbler 17 by pipe 22 in the upper part communicates with the lower part of the filtering column 23 (absorber), where the gas-and moisture-permeable filling 24 of Rashiga heat-generating rings is placed below, and the spray irrigator 26 of the ascending aerosol supplied from the bubbler 17 is mounted at the top of the receiver 25.

The receiver 25 of the filtration column 23 by the pipe 27 through the bellows 28, which damps the mechanical vibrations, communicates with an exhaust pump 29, which supplies a clean, cooled aerosol to the traction pipe 30.

The locking receiver 3 of the vertical furnace (Fig. 2.1) is adjoined by the loading mechanism 1 of a portion of waste packaged in a container bag, which is placed in a container 2 mounted on platform 31.

Platform 31 is mounted with rollers 32 in rail guides 33, the profile of which provides for tilting of container 2 in the upper loading position.

The receiver 3 is made in the form of a gateway with a supporting gate valve 4, made in the form of a rack-lined with refractory, kinematically connected with the drive gear 34.

The vertical furnace is equipped with a distributed supply system 19 (pump conventionally not shown) of the oxidizing air by levels: under the grate 35 through the gas distribution grid 36, into the central hole 9 of the roof 10 through nozzles 37 of the annular collector 38 and through nozzles 39 of the annular collector 40 located in the converger 41 of the chamber 11 afterburner.

Under the grate 35, the ash collection tray 42 is fixed, which is removed from it by a screw conveyor 43.

The diffuser 44 of the post-combustion chamber 11 communicates with a straight-through pipe 45, equipped with a hinged lid 46, which serves as an emergency pressure valve. By the handle 47, the cover 46 is opened manually when the furnace is ignited, to create thrust.

A tangential lined switching pipeline 12 is combined with a nozzle 45 with a parallel mounted column 13 (FIG. 2.2) for complex processing of gaseous products of combustion from a vertical furnace as part of successively mounted interconnecting heat exchanger 14, scrubber 15 with nozzle 16 and bubbler 17.

The heat exchanger 14 is made according to the scheme pipe 48 in the pipe 49, in the jacket of which (between pipes 48, 49) a spiral tray 50 is fixed for circulation of forced air blown through a cascade of through pipes 51 overlapping the internal pipe 48 through which the exhaust gaseous products of combustion are longitudinally displaced , contact cooled by heat transfer, heating the process air, which is discharged through the duct 18.

The lower part of the heat exchanger 14, to its pipe 48, is adjacent to the air supply duct 18 by the pump 52 of heated air, with a temperature of 250-300 ° C to the system 19 (Fig. 1 and 2.1) of the distribution over the levels of the vertical furnace (in fractions of volume): 3 / 5-3 / 4 under the grate 35, 1 / 8-1 / 5 into the central hole 9 of the arch 10 and 1 / 8-1 / 5 into the confuser 41 of the after-burning chamber 11.

A coaxial scrubber 15 is connected to the pipe 48 (FIG. 2.2) of the heat exchanger 14, containing an axial nozzle 16 of a transverse jet supply of the working solution for chemical interaction with the outgoing gaseous products in the stream from the heat exchanger 14.

The scrubber 15 is fixed to the support 53 and connected to the receiving central pipe 54 of the replaceable bubbler 17, at the end of which a perforated nozzle 55 is fixed for the jet distribution of gases neutralized in the scrubber 15 in the working bubbler 17 solution, above which fluid level 54 is fixed on the pipe 54.

The bubbler 17 in the upper part is equipped with a switching pipe 22 with a column 23 of wet cleaning of the aerosol flowing from below.

At the bottom, the column 23 is filled with Raschig rings, which multiply the contact surface of interaction with the sprayed working fluid from the sprayer 26 placed in the receiver 25.

In the interaction of the ascending aerosol with the working fluid in countercurrent, its solid phase is washed off into the sump 57, and the gas component rises and fills the receiver 25, which functions as a shut-off chamber with increased aerodynamic drag.

The receiver 25 is connected by a pipe 27 through the bellows 28 with an exhaust pump 29. which is equipped with a traction pipe 30.

In the combustion chamber 8 of the vertical furnace (Fig. 1 and 2.1), a hatch is made, closed by a door 58 for manual turning, if necessary, of arches of sintered ash material.

Proposed in the invention method is carried out in the described flow installation as follows.

Before work on waste disposal, the vertical furnace is manually fired, for which the hinged cover 46 of the vertical nozzle 45 is opened by the handle 47, in order to provide traction.

Through the hatch with the door 58 open, the combustible material is placed on the grate 35 and it is ignited - the ignition material ignites, after which the door 58 of the hatch is closed to raise the temperature in the combustion chamber 8. Then the lid 46 covers the volume of the furnace, which, when burned, of the melting material, enters the autothermal mode.

Next is the automatic batch loading recyclable material.

Briquetted waste material, packaged in tare bags, portionwise placed in a container 2 mounted on the platform 31 of the loading device 1, which rises to its highest position, where it is tilted under the action of the profile of the guide rails 33 of contact with the rollers 32.

In this case, the signal of the limit switch 5 of the track control system triggers the actuator 34, which moves the gate valve 4 to the open position of the inclined nozzle 6.

A portion of the Packed material falls out of the container 2 and through the pipe 6 is moved into the chamber 8 of the vertical furnace, where it is placed on the grate 35.

Next, the gate valve 4 is reversed by the engine 34 to the initial closed position, and the container 2 on the platform 26 returns to the bottom of the device 1.

The loaded portion of the material is ignited and burns under the action of the ignition temperature, at an average temperature in the combustion chamber 8 of 1150 ° C in an atmosphere of excess oxygen, which is supplied from the system 19 to the gas distribution grid 36 under the grate 35.

The gaseous products of combustion of the material are inhibited by the vault 10 and are retained in the combustion chamber 8 for 2 s, ensuring the completeness of the chemical reactions of the combustion process.

In the central opening 9 of the roof 10, the combustion gases are mixed with the oxidizing air transversely supplied from the oppositely inclined 30 ° to the longitudinal axis of the nozzles 37 of the annular manifold 38, which improves the dispersion conditions.

At the same time in the collector 38 oxidizing air into the system 19 is taken from the heat exchanger 14, where it is heated by the exhaust gaseous products of burning to a temperature of 250-300 ° C, which saves part of the thermal energy in the combustion chamber 8, which is used for its intended purpose.

From the central hole 9 of the roof 10, the gas-air mixture laminar expires, expanding and braking, into the diffuser 41 of the afterburner chamber 11, where additional (excess) oxidizing air is injected from the distributed nozzles 39 of the ring collector 40, creating a positive oxygen balance for complete oxidation of the structural components of the aerosol and afterburning of condensed particles in the volume of chamber 11 at an average temperature of 1250 ° С, where the process of combustion and oxidation to the final products is completed.

In the confuser 44 of the afterburning chamber 11, the gaseous products of combustion are accelerated and enter the horizontal lined nozzle 12 for further processing for cooling, neutralization and separation.

During the volume burning of fragmented material on the grate 35, ash residue is generated, which wakes up through the grid 36 into the collection tray 42, from where the screw conveyor 43 is removed to the receiving container for recycling.

The optimized autothermal process of burning solid fragmented material in a two-chamber modified furnace by the proposed method eliminates the sintering of parts of the material and the formation of arches.

If necessary, the turning of the burning material is produced manually through the hatch in the chamber 8 with its door 58 open.

Upon subsequent loading of a portion of the material, when the bag falls on the grate 35, mechanical crushing of burning elements, which serve as distributed sources of local ignition, occurs, ensuring the continuity of the combustion process.

In the heat exchanger 14 adjacent to the nozzle 12, while the gaseous products of combustion move along the inner pipe 48, an active heat removal takes place on the contact surfaces of the streamlined nozzles 51 through which external air is blown, supplied by the pump 52 through the spiral tray 50 in the jacket 48-49. At the same time, the convective heat transfer from the pipe 48 to the external pipe 49 of radiation is carried out through the spiral tray 50, which heats up the oxidizing air supplied by the pipeline 18 to the system 19 to the temperature of 250-300 ° C.

Exhaust gaseous products of combustion from the heat exchanger 14 enter the adjacent scrubber 15, where their flow is dissected by transverse jets of the reaction alkaline solution from the nozzle 16, which are mixed and interact, resulting in chemically binding gases and radicals, when the temperature of aero-hydrosol is reduced to 650-700 ° C.

The reacted chemical neutralization products come from the scrubber 15 through pipe 54 to bubbler 17, where they are ejected through the perforations of the central nozzle 55 into the working solution, turbulizing it and forming cavitation bubbles, resulting in flotation and foam formation, during separation of fractions: gases fill the free volume of the upper part of the bubbler 17, and the solid phase deposited on the conical chipper 56, where the conglomeration of solid particles occurs, in the form of sludge slides and falls on the inclined bottom of the bubbler 17 and rolls enters.

The sparger from the bubbler 17 with a temperature of 400-450 ° C through the pipe 22 enters the lower part of the parallel installed purification column 23 by wet technology, filled with Raschig rings, repeatedly developing contact surface interaction with the ascending aerosol, as a result of which the temperature of the latter decreases to 200-250 ° s

Next, the aerosol is inhibited in the receiver 25, where it interacts with a mist of droplets of the process solution dispersed by the sprayer 26, thus ensuring a high efficiency of purification of the aerosol from solids, unreacted fragments of active gases and radicals that are bound, neutralized and collected in the sump 57, and the pure aerosol with a temperature of 130-150 ° C through the pipeline 27 is removed by an exhaust fan 29 into the traction pipe 30, through which it naturally rises to a height, where it is emitted into the atmosphere.

Experimental verification of the combustion method in the proposed sequence of technological operations in the structural elements of an industrial plant as a whole confirmed the efficiency of batch combustion of various solid and viscous materials for household, industrial and medical waste with high quality exhaust gas cleaning, which allows us to recommend the method according to the invention for practical use.

Comparison of the proposed technical solution with the closest analogues of the prior art did not reveal an identical match of the set of essential features of the invention.

The proposed differences in the method of incineration of solid waste, which do not directly follow from the statement of the technical problem, are not obvious to a specialist in the technology of autothermal furnaces.

The implementation of the method according to the invention is possible in an industrial plant integrated process stream.

From the above, we can conclude that the invention complies with the conditions of patentability.

Claims (1)

The method of incineration of solid waste containing batch loading of recyclable material on the grate of a vertical two-chamber furnace with a central opening in the separating roof, which is distributed over the height of oxidizing air, while the exhaust gaseous combustion products are transiently cooled in a scrubber due to cross-jet treatment of the reaction alkaline solution subsequent final filtration to separate the pure aerosol forcedly forced into the exhaust pipe, characterized in that it oxidizes in Zdukh heated distributed distributed over the height of the furnace in volume fractions: (3/5-3 / 4) under the grate, (1 / 8-1 / 5) into the central opening of the arch and (1 / 8-1 / 5) into the upper afterburning chamber, At the same time, the oxidizing air is removed from the heat exchanger jacket, before heat treatment of waste gases, where radiation energy is heated by heat transfer in a countercurrent by exhaust gaseous combustion products, then the aerosol obtained after the scrubber is fed to sparging in process alkaline solution with condensed phase selection, and before finishing f In a mist layer formed by a sprayer in a receiver, the aerosol is cooled by means of permeable heat-intensive filling from Raschig rings.

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