RU2716652C1 - Smw disposal furnace - Google Patents

Abstract

FIELD: waste processing and disposal.

SUBSTANCE: invention relates to devices for recycling solid municipal wastes (SMW), in particular, in heat treatment of garbage, domestic and industrial wastes. SMW disposal furnace comprises a housing accommodating two chambers, top and bottom, separated by a fixed grate and interconnected by at least one recirculation path, primary air supply pipe, connected to housing by means of recirculation stroke, afterburning chamber connected to housing by means of at least one gas channel, and an exhaust fan connected to the afterburner chamber, wherein at least one circulation path is connected to the lower chamber and with the possibility of directing the gas flow coming out of it at a tangent to the inner surface of the lower chamber. Furnace additionally includes heat exchanger connected with afterburner chamber and exhauster.

EFFECT: improvement of ecological indices, reduction of total value of heat losses with chemical and mechanical underburn at output from furnace up to 10 %, absence of necessity to introduce additional fuel sources during SMW disposal.

1 cl, 1 dwg

Description

Technical field

The invention relates to a device for the disposal of municipal solid waste (MSW), in particular, in the thermal processing of garbage, household and industrial waste.

State of the art

Currently, there are a large number of devices for the disposal of MSW.

So, in the prior art, a furnace is known (RU 2559103 C2, 08/10/2015) D1) with a fixed grate and a movable layer of fuel with an inclined combustion mirror for burning agropellets, including a furnace of a water tube or fire tube boiler and a cast-iron grate.

The disadvantage of the furnace presented in D1 is the lack of the possibility of utilizing heterogeneous fuel (for example, MSW of natural moisture) and the formation of a large amount of emissions of combustion products into the atmosphere.

Also known in the prior art is a pyrolysis thermogasochemical installation for the disposal of municipal solid waste (RU 2428629 C1, 09/10/2011), including a combustion chamber with grate, connected to the primary air supply channel, a thermogaschemical reactor made in the form of a housing with a cylindrical retort placed in it, equipped with a sealed lid and the output of the pyrolysis products, and the secondary air supply chamber. The installation is equipped with a collector, a filtering unit, the input of which is connected in the upper part of the thermogas chemical reactor body above the cylindrical retort, and the outlet is connected to the secondary air supply chamber and the atmosphere by means of a gas duct that ensures the circulation of exhaust gases. The combustion chamber and the secondary air supply chamber are placed in a separate housing, separated by a curved partition, and the chamber cavities are made in communication with the cavity of the thermogas chemical reactor body, flow swirls are fixed along the inner side surface of the thermogas chemical reactor housing.

The disadvantage of the device presented in D2 is the design complexity and the need to use an additional significant source of heat energy in terms of power consumption.

Disclosure of Invention

The task to which the claimed invention is directed is to develop a furnace for the disposal of MSW, which will eliminate the disadvantages of the prior art.

The technical result of the claimed invention is aimed at providing the following features:

- improvement of environmental indicators, due to the fact that: the amount of СО emissions is reduced, not exceeding 40 PPM, СО ₂ to 8%, NOх, not exceeding 30 PPM, SO ₃ to 10 PPM, etc., the exhaust gas contains from 9 to 16% oxygen;

- reduction of the total value of heat loss with chemical and mechanical burning at the exit of the furnace to 10%.

- the absence of the need to introduce additional fuel sources in the process of MSW disposal, with the possibility of achieving a thermal voltage of the combustion chamber of 0.2 MW / m ³ , due to the disposal of MSW.

The specified technical result, to which the claimed technical solution is directed, is achieved due to the fact that the furnace for utilization of municipal solid waste (MSW) contains a housing, inside which there are two chambers - the upper and lower, separated by a fixed grate and connected at least in one recirculation stroke, a primary air supply pipe connected to the housing by means of a recirculation stroke, an afterburner connected to the housing by at least one a gas channel, and a smoke exhauster associated with the afterburner, wherein at least one recirculation stroke is connected to the lower chamber and with the possibility of directing the outgoing gas flow tangentially to the inner surface of the lower chamber.

The furnace further includes a heat exchanger connected to the afterburner and the exhaust fan.

The housing is equipped with a hatch for loading solid municipal waste.

Brief description of the drawing.

The drawing shows a General diagram of the furnace for disposal of MSW.

The implementation of the invention

The combustion chamber for MSW disposal shown in the figure is a housing (1), inside of which there are two chambers - the upper (2) and lower (3), separated by a fixed grate (4). The upper (2) and lower (3) chambers are interconnected by at least one recirculation stroke (5). To supply primary air to the furnace, when it starts, to achieve operating temperature, a primary air supply pipe (6) is used, which is connected to the casing by means of a recirculation stroke. Subsequently, in the process of utilizing MSW, the pipe (6) is blocked and air does not enter through it.

The furnace is made of heat-resistant steel (for example, 18XH10T).

At least one recirculation stroke (5) is connected to the lower (3) chamber in such a way that the gas stream exiting from it exits tangentially to the inner surface of the lower (3) chamber to form a vortex upward flow. At least one gas channel (7) connected to the afterburner chamber (8) is installed in the lower part of the lower (3) chamber. In the afterburner (8), the afterburning of gaseous combustion products occurs. To create a forced draft in the claimed design uses a smoke exhaust (9) connected to the afterburner (8), through at least one gas channel (7). On the gas exhaust path, which is at least one gas channel (7), there is a carbon monoxide concentration sensor connected to the smoke exhaust control unit (exhaust gas discharge speed) (not shown in the figure).

 To remove the generated heat, the furnace may additionally contain a heat exchanger (10) connected to the afterburner (8) and a smoke exhauster (9).

To load MSW into the furnace, a hatch (11) is provided in the housing (1). The hatch (11) is connected to the body (1) by means of hinges.

The body (1) of the furnace and the recirculation stroke (5) are thermally insulated, while standard mulite heat-insulating materials can be used as insulation.

The theory of combustion processes includes the issues of gas dynamics of jets and flows, the kinetics of very different chemical reactions associated with elevated temperatures in the reaction region, heat transfer with the surfaces of the furnace and channels, etc. The multiplicity of factors makes the optimization of the design of furnaces a very difficult task not only in theory, but also in practice, even for specialists.

The claimed furnace is designed for the disposal of MSW. The main criterion for disposal is to minimize emissions of harmful substances into the atmosphere. Further, the criterion of the efficiency of the furnace is assumed to be high heat stress in the furnace and a decrease in the amount of ash insoluble in water resulting from the disposal of water.

One of the main problems in the design of the furnace was that with a large thickness of the utilized MSW layer and a large temperature difference in the MSW layer located on the grate, a wide range of thermochemical and catalytic reactions are observed, ranging from oxidation and gasification to hydrothermal carbonization. Therefore, the design is based on the layered principle of utilization in an upward vortex flow of recirculation gases.

The furnace works as follows. First, the furnace is heated to a temperature of 800 ° C (for example, using a gas burner, plasma torch, coal, firewood, etc.) Next, the MSW is loaded on top of the stationary grate (4). Warming up MSW leads to the release of combustible gases (gasification). Gases rise up, heat up the MSW layers located above, which fill the upper (2) part of the furnace. Next, the gases through the recirculation paths (5) under the influence of the pressure difference created by the smoke exhaust (9) are thrown tangentially into the lower (3) chamber of the formation of the vortex upward flow. The rising vortex stream forms along the perimeter an upward flow of high temperature gases and a downward flow of gases of lower temperature in the center of the lower (3) chamber of the formation of the vortex flow. The low-temperature gas stream is drawn in by the exhaust fan into the afterburner (8) and then sent to the chimney (12) through the exhaust fan (9). When the content of carbon monoxide in the flue gas is more than 80 PPM, the control unit increases the speed of the flue gas by increasing the frequency of the electric supply of the exhaust fan to reduce the concentration of monoxide to 20 PPM units.

During gasification of solid fuel, up to 80% of the organic part of the fuel passes into the gas phase. Due to insensitivity to the quality of raw materials and the presence of ballasts (mineral impurities and moisture), the declared furnace has great prospects for processing low-grade fuels (including MSW). In addition, the resulting gaseous fuel during combustion emits significantly less harmful substances than in direct combustion of solid fuel.

The set of processes occurring during gasification is given below:

C + O ₂ → CO ₂ + 408.9 kJ / mol

C + ½O ₂ → CO + 123.2 kJ / mol

C + CO ₂ → 2CO - 161.5 kJ / mol

C + H ₂ O → CO + H ₂ - 136.9 kJ / mol

CO + H ₂ O → CO ₂ + H ₂ + 42.8 kJ / mol

Gases obtained during gasification through recirculation are used as fuel directly in the furnace volume to maintain heat balance and intensify gasification processes.

In the process of gas recirculation in the lower fuel layer, located directly on the fixed grate (4), carbonization reactions occur. Stages of artificial carbonization include the destruction of non-aromatic molecules; cyclization - the formation of more stable aromatic molecules with side chains, which in turn are destroyed or cyclized; condensation to form polycyclic aromatic systems; and further dehydrogenation and condensation of polycyclic systems.

Secondary reactions include the formation of a mixture of various pasty hydrocarbons with a low specific hydrogen content in the molecules of the compounds.

In the process of gasification, reactions of synthesis of heavier molecules from low molecular weight unsaturated hydrocarbons take place. Basically, these are reactions of the formation of aromatic, condensed aromatic hydrocarbons.

The process of hydrogenation of CO with the formation of hydrocarbons is thermodynamically advantageous. If we compare the values of free energies (∆G °), we can see that the reactions that occur with the formation of water are the most advantageous.

3 H ₂ + 1 CO = H ₂ O + CH ₄ ΔG ° = –94 kJ / mol

2 H ₂ + 1 CO = H ₂ O + 1/3 (C ₂ H ₆ ) ΔG ° = –31 kJ / mol

2 H ₂ + 1 CO = CH ₃ OH ΔG ° = +21 kJ / mol

4 H ₂ + 2 CO = CH ₃ CH ₂ OH + H ₂ O ΔG ° = –27 kJ / mol

3 H ₂ + 1 CO ₂ = CH ₃ OH + H ₂ O ΔG ° = +3 kJ / mol

H ₂ O + 1 CO ⇄ H ₂ + CO ₂ ΔG ° = –28 kJ / mol

The reaction mechanism, despite decades of study, is still unclear in detail. Despite the thermal transformations taking place at elevated temperatures, all hydrogenation reactions are catalytic.

The catalysts for the hydrogenation process are the following metals and compounds:

- metals of group VIII (Fe, Co, Ni, Pd, Pt) and group I (Cu, Ag) of the periodic system of elements.

The chamber and grate are made of stainless steel (for example, 18XH10T), which contains, in addition to iron, 9% nickel - which solves the problem of the presence of a catalyst in the furnace.

In addition to the above, hydrocarbon formation processes can take place in the furnace. The thermodynamic laws of the process of hydrocarbon formation can be summarized as follows:

1. The formation of CO and H ₂ hydrocarbons of any molecular weight, type and structure is possible.

2. The probability of hydrocarbon formation decreases in the series: methane - hydrocarbons of a linear or branched structure with the general formula C _n H _{2n + 2.} The likelihood of the formation of normal alkanes decreases, while normal alkenes with the general formula C _n H _2n increase with increasing chain length.

It follows from the foregoing that, despite a wide range of reactions taking place, a sufficiently effective parameter to control the recycling process is to control the content of carbon monoxide in the exhaust gases.

It was experimentally found that a sufficient method for controlling the process is the rate of removal of exhaust gases by means of a smoke exhaust (9). The experiments showed that an increase in the content of CO in flue gases accompanies the deterioration of almost all the main indicators of the process. Lowering the pressure in the chamber (which follows an increase in the flue gas flow rate) leads to an increase in the process temperature and an increase in the carbonization and gasification rates and a decrease in the CO content in the flue gases. This is achieved by increasing the frequency of the alternating current supplying the exhaust fan (9). Frequency control is carried out by means of a signal coming from the gas analyzer through the control unit.

When MSW was loaded into a working furnace (heated to 800 ° С) in a volume of 1 m3, 0.2 MW of heat was released on the heat exchanger. The measurements were carried out by fixing the velocity of the coolant pumping through the heat exchanger and the temperature difference at the outlet of the heat exchanger and the inlet of the heat exchanger after the radiator, which dissipated the heat power.

When adjusting the operation mode of the furnace with a volume of 0.5 m3, by changing the gas velocity, the following values were obtained for the composition of the flue gases: СО up to 4 PPM, СО ₂ up to 7%, NOх up to 6 PPM, SO ₃ up to 6 PPM. The oxygen content in the flue gas during the disposal of tires recorded in the range of 9-16%.

Claims (7)

1. A furnace for the disposal of municipal solid waste, including a housing inside which there are two chambers - the upper and lower, separated by a fixed grate and connected by at least one recirculation stroke, the primary air supply pipe connected to the housing by means of a recirculation stroke, a afterburner connected to the housing via at least one gas channel, and smoke exhaust associated with the afterburner, wherein at least one recirculation stroke is connected to the lower chamber and with the possibility of directing the gas flow emerging from it along the tangent to the inner surface of the lower chamber. 2. The furnace according to claim 1, which further includes a heat exchanger connected to the afterburner and the exhaust fan.

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