ES2748138T3 - Melting furnace for waste material - Google Patents

Abstract

Waste melting furnace (2) for drying, thermal decomposition, and waste melting, the furnace (2) comprising: a cylindrical main part (20) that extends vertically to form a space for containing waste and guiding waste from top to bottom; a melt tank part (22), attached to a lower end part of the main part (20) along a central axis (CL1) of the main part (20), for retaining melt generated from the waste; and a gas induction part (21), attached to an upper end part of the main part (20) along the central axis (CL1) of the main part (20), for collecting a gas generated from the waste and guiding the collected gas to an exhaust port (26); wherein an opening part (2a) for introducing the waste and carbon-based combustible material into the waste smelting furnace (2) is formed in an upper end part of the gas induction part (21); wherein the melt tank part (22) has a bottom part (22b) for forming a bed of the carbon-based fuel material; wherein the main part (20) has a conical part (24) having a gradually decreasing inner cross-sectional area to the bottom side; in which the conical part (24) vertically occupies the entire height of the main part (20) or the greatest height in all the parts that constitute the main part (20), so that the ratio between the height (H2) of the conical part (24) and the total height (H1) of the main part (20) is 50% or more; and in which an inner face of the conical part (24) forms an angle of inclination greater than 75° but less than 90° with a horizontal plane.

Description

DESCRIPTION

Melting furnace for waste material

Technical field

The present invention relates to a waste material melting furnace that dries, thermally decomposes, and melts waste.

Prior art

An example of the procedures for processing wastes, such as general and industrial wastes, is one that melts the wastes in an industrial furnace using a carbon-based fuel material, such as coke, as the source of fusion heat. Processing of waste by melting can reduce the volume of waste and also recycle burned ash and non-combustible waste, which until now have finally been disposed of as landfills, into slag and metals.

A procedure for melting waste is known which consists of burning the waste and then melting the burned ash and resulting non-combustible materials by heating. Attention has recently focused on a gasification and melting furnace that can burn and gasify combustible materials in waste and melt ash in the waste in a furnace. The gasification and melting furnace burns and gasifies the combustible materials in the waste by the heat of the combustion of a carbon-based combustible material and expels and melts the ashes and non-combustible materials left in the furnace by heating. That is, the gasification and melting furnace thermally decomposes the waste and melts the ash and non-combustible materials by heating.

As the gasification and melting furnace, shaft-type melting furnaces are known (see, for example, Patent Literatures 1 to 3). Each of the melting furnaces described in Patent Publications 1 to 3 comprises a cylindrical shaft part (straight cylindrical part), an inverted truncated cone part (conical part) and a bottom part of the furnace. The lower part of the oven is provided with a lower nozzle. A gas (combustion support gas) is inserted into the furnace to burn the carbon-based fuel material through the lower nozzle. This burns the carbon-based fuel material, which produces a high-temperature gas in the furnace, which rises. An exchange of heat occurs between the gas in the furnace and the waste, thus promoting drying and thermal decomposition of the waste. Ashes and non-combustible materials accumulate on the bottom side of the furnace along the inside face of the conical part, to be melted by the heat of combustion of the carbon-based fuel material. The melted mass is retained at the bottom of the oven and is removed from there.

In each of the melting furnaces described in Patent Literature 1 and 2, the inverted truncated cone portion is further provided with a top nozzle. Air enters the oven through the top nozzle. This favors the drying and thermal decomposition of the waste. Patent Literature 4 describes a waste melting furnace for drying, thermal decomposition and melting of waste, the furnace comprising a cylindrical main part which extends vertically so as to form a space for containing the waste. and guide waste from top to bottom; a melt deposit part, attached to a lower end part of the main part along a central axis of the main part, to retain the melt generated from the waste; and a gas induction part, attached to an upper end part of the main part along the central axis of the main part, to collect a gas generated from the waste and guide the collected gas to an exhaust port; wherein an opening part for introducing the waste and carbon-based fuel material into the waste melting furnace is constituted in an upper part of the gas induction part; wherein the melt tank part has a bottom part to form a bed of the carbon based fuel material; wherein the main part has a conical part having an inner cross section that gradually decreases to the bottom side; in which an inner face of the conical part forms a maximum angle of inclination of 80 ° with a horizontal plane.

Appointment list

Patent literature

Patent literature 1: Japanese patent application made available to the public No. H08-94036

Patent literature 2: Japanese patent application made available to the public No. 2011-89672

Patent literature 3: Japanese patent application made available to the public No. 2002-130632

Patent literature 4: JP 2011 012901 A

Description of the Invention

Technical problem

However, in each of the aforementioned gasification and melting furnaces, the rate of descent of the waste load is not uniform in the furnace, but tends to be lower near the furnace wall than in the central part of the furnace. oven. In the furnaces described in patent publications 1 to 3, the rate of descent of the load is low near the inside face of the inverted truncated cone part, in particular, whereby debris is likely to stop. In particular, debris is likely to be trapped at the boundary between the inside face of the shaft part and the inside face of the inverted truncated cone part. When such stagnation occurs, the gas in the furnace may not fully spread over a certain part, reducing the efficiency of heat exchange between waste and gas in the furnace.

Thermal decomposition can also occur locally in the part where the waste stops, thereby producing a gap. In the melting furnaces described in Patent Publications 1 and 2, local thermal decomposition is likely to occur, in particular near the top of the nozzle, since air is introduced into the inverted truncated conical part at through the top. When the space produced by local thermal decomposition forms a flow path for the gas in the furnace, the inlet gas can pass through the flow path and tends not to spread over other parts than the space (this phenomenon will be referred to later as "gas explosion"). This can further reduce the efficiency of heat exchange between waste and gas in the furnace.

Thermal decomposition debris produced when the space is formed can melt and adhere to the inside of the furnace. When such adhesion occurs, debris is more likely to stop. This can further reduce the efficiency of heat exchange between waste and gas in the furnace.

When the efficiency of the heat exchange between the waste and the gas in the furnace decreases, the carbon-based fuel material is consumed in greater quantity to compensate for this. Since carbon-based fuel material is derived from fossil fuels in general, increased consumption of carbon-based fuel material is undesirable from the point of view of environmental protection. Therefore, an object of the present invention is a waste melting furnace that can reduce the consumption of carbon-based combustible materials.

Solution to the problem

The above problem is solved by a waste material melting furnace according to the features of the independent claim of the present invention.

Burning a carbon-based fuel material in a lower part of this waste melting furnace produces a high-temperature gas in the furnace, which rises. The debris descends against the upward flow of gas in the furnace. In this process, a heat exchange occurs between the gas in the oven and the waste, thus favoring the drying and thermal decomposition of the waste. The gases produced by the thermal decomposition of the waste are concentrated in the gas induction part and are discharged from there. The ash and non-combustible materials that remain in the furnace accumulate on the underside of the furnace along the inside face of the conical part and are melted by the heat of combustion of the carbon-based combustible material. The melt is retained in the melt tank part and is removed from it.

Here, the conical part occupies the highest height in all the parts that make up the main part. Therefore, the inner face of the conical part forms an angle of inclination with the horizontal plane greater than in the case where the non-conical straight barrel part occupies the greatest height. This allows debris near the inside of the taper to be gently guided down. Furthermore, even when the conical part is attached to the underside of the straight cylindrical part, the inner face of the conical part tilts moderately relative to the inner face of the straight cylindrical part, whereby debris tends not to stop at the top end of the conical part. If the conical part occupies the highest height, the top end part of the conical part is on the top side of the main part. The waste reduces its volume by drying and thermally decomposing as it descends through the main part. Volume reduction is also done on top of the main part. When the upper end part of the conical part is located on the upper side of the main part, the cross-sectional area of the main part becomes smaller from the upper side towards the lower part, in accordance with the reduction of volume that also unfolds on the upper side of the main part. This prevents gaps from forming and prevents gas explosions from occurring. This allows to improve the efficiency of the heat exchange between the waste and the gas in the furnace above the case in which the straight barrel part occupies the highest height. Therefore, the consumption of carbon-based combustible materials can be reduced.

In this case, the fact that the interior volume of the main part is less than in the case where the straight part of the barrel occupies the highest height does not negatively affect the efficiency in waste processing.

This is because the efficiency of the heat exchange between the waste and the gas in the furnace improves as mentioned above, so that the volume of the waste is reduced efficiently.

The inner face of the conical part forms an angle of inclination that exceeds 75 °, but less than 90 °, with the horizontal plane. This more safely prevents debris from stagnating. Therefore, the efficiency of the heat exchange between the waste and the gas in the furnace can be further improved.

The main part may have a drying region to dry the debris and a thermal decomposition region, located below the drying region, to thermally decompose the debris while, in the conical part, a boundary may be located between the drying regions and thermal decomposition. In this case, the upper end part of the conical part is in the drying region. The reduction in waste volume mentioned above also occurs within the drying region. When the upper end portion of the conical portion is located in the drying region, the cross sectional area of the main portion becomes smaller from the interior of the drying region downward, in accordance with the reduction in volume that it also proceeds within the drying region. This can more safely prevent gaps from occurring.

The melt tank part can be provided with a lower nozzle to introduce an oxygen enriched gas into the furnace, the conical part can be provided with an upper nozzle to introduce air into the furnace, and in the oven drying region it can have at least one upper nozzle. In this case, introducing the oxygen enriched gas into the furnace through the lower nozzle can maintain the combustion of the carbon-based fuel material. Supplying air to the furnace also from the top of the nozzle can promote drying and thermal decomposition of waste. Here, at least one upper nozzle is arranged in the drying region. This further favors drying of the waste in the drying region. Since the upper end part of the conical part is located in the drying region as mentioned above, the debris in the drying region descends along the conical part. The waste further reduces its volume as drying is favored, making it easier to lower the load along the conical part. The waste that has reduced its volume, by favoring its drying, accumulates in the center by the conical part, thus preventing the formation of spaces. Therefore, the fact that the upper end part of the conical part is located in the drying region cooperates with the fact that the drying region is provided with the upper nozzle, which favors the drying of waste. at the same time that space is prevented from forming.

The upper nozzle in the drying region may be located closer to a lower end part of the drying region between the lower end part of the drying region and the upper end part of the conical part. This can more safely prevent gaps from occurring.

Advantageous effects of the invention

The waste melting furnace according to the present invention can reduce the consumption of carbon-based combustible materials.

Brief description of the drawings

Figure 1 is a schematic view of a waste processing system using the waste melting furnace according to the present invention;

Figure 2 is a vertical sectional view illustrating the waste melting furnace in Figure 1;

Figure 3 is a diagram schematically illustrating the drying, thermal decomposition and melting regions in the waste melting furnace;

Figure 4 is a set of diagrams illustrating examples and a comparative example;

Figure 5 is a graph illustrating daily changes in differential pressure in the furnace;

Figure 6 is a graph illustrating daily changes in gas temperature at the top of the furnace;

Figure 7 is a set of graphs illustrating changes in the temperature of the central furnace gas over time;

Figure 8 is a graph illustrating measurement results of the amount of processed waste, coke ratio, differential pressure in the furnace, and gas temperature in the upper part of the furnace;

Figure 9 is a set of diagrams illustrating furnace gas flow distributions and furnace differential pressure in the furnace height direction;

Figure 10 is a graph representing measurement results of the heat exchange temperature in the furnace and the coke ratio;

Figure 11 is a graph showing measurement results of moisture drying capacity by volume and coke ratio;

Figure 12 is a graph showing measurement results of the heat transfer efficiency and gas flow rate in the furnace; Y

Figure 13 is a graph representing measurement results of the time in which the gas burst occurs and the coke ratio.

Description of embodiments

Hereinafter, preferred embodiments of the present invention will be explained in detail with reference to the drawings. In the drawings, the same constituents or those having the same functions will be referred to with the same signs while omitting their overlapping descriptions.

As illustrated in Figure 1, a waste processing system 1 is a system for processing general and industrial waste and comprises a waste melting furnace 2, a granulation pit 5, a combustion chamber 6, a heater 61 , a cooling tower 62, a bag filter 63, a catalytic reaction tower 64, and a chimney 65. In a reducing atmosphere, the waste melting furnace 2 decomposes thermally and gasifies combustible materials in the waste and melts the ash and non-combustible materials. As will be explained later, gases generated from the waste are discharged from the top of the waste melting furnace 2, while melts generated from the waste are discharged from the bottom of the waste melting furnace. waste 2.

The granulation pit 5 granulates, cools, and collects the melt discharged from the waste melting furnace 2. The granulation pit 5 comprises a casing to retain cooling water and a scraper conveyor (not shown) to extract the cooled granulated products and cooled inside the housing. The combustion chamber 6 and the heater 61 are connected to the upper part of the waste melting furnace 2 through an exhaust duct, to collect the thermal energy from the exhaust gases of the waste melting furnace 2. The tower Cooling unit 62, bag filter 63, and catalytic reaction tower 64 are connected to the downstream side of heater 61, to detoxify exhaust gases. Chimney 65 discharges the detoxified exhaust gases.

The waste melting furnace 2 is formed of a refractory material and the like, examples of which include bricks, SiC, and alumina. The waste melting furnace 2 comprises a vertically extending cylindrical main part 20 centered on a vertical axis CL1, a gas induction part 21 attached to the upper side of the main part 20, and a melting tank part 22 attached to the bottom side of the main part 20. The main part 20 forms a space to contain the waste and guides them from top to bottom. The gas induction part 21 collects the gases generated from the debris within the main part 20 and guides the collected gases towards the exhaust duct. The melt tank part 22 retains the melt generated from the debris within the main part 20.

The main part 20 is constituted by a straight cylindrical part 23 having a fixed inner cross-sectional area and a conical part 24, attached to the underside of the straight cylindrical part 23, which has an inner cross-sectional area which gradually decreases towards down. The straight cylindrical part 23 has a cylindrical inner face 23a, while the conical part 24 has an inner face 24a of an inverted truncated cone. The inner diameter of the upper end part of the conical part 24 is equal to that of the straight cylindrical part 23.

The height H2 of the conical part 24 is greater than the height H3 of the straight cylindrical part 23 (see Figure 3). That is, the conical part 24 occupies the highest height in all the parts that make up the main part 20. Therefore, the inner face 24a of the conical part 24 forms an angle of inclination 0 with a greater horizontal plane than in the case wherein the straight barrel portion 23 occupies the greatest height. The tilt angle 0 is greater than 75 ° but less than 90 °. More preferably, it is at least 80 ° but less than 90 °.

The inside diameter and height of the main part 20 are determined according to the volumes required for a drying region 70 and a thermal decomposition region 71 which will be explained later, for example. The volume required for drying region 70 is a volume in which the total amount of moisture contained in the waste deposited in the waste melting furnace 2 per hour (i.e., amount of inlet moisture) can be dried, assuming that the amount of moisture that dries per hour is between 50 and 150 kg / m3 h, for example. The volume required for thermal decomposition region 71 is a volume in which the amount of carbon contained in the waste and the coke that is deposited in the waste melting furnace 2 per hour can be gasified, assuming that the amount of gasification by hour is between 50 and 150 kg / m3 h, for example.

The fusion reservoir part 22 has a cylindrical side wall part 22a centered on the axis CL1 and a bottom part 22b which closes the bottom end part of the side wall part 22a. The upper end part of the side wall part 22a is connected to the lower end part of the conical part 24. The inner diameter of the part of side wall 22a is equal to that of the bottom end part of the conical part 24. At the bottom end part of the side wall part 22a a casting hole 27 has been formed to discharge the melt retained in the tank part part of melting 22. The casting hole 27 is provided with an opening and closing mechanism (not shown) through which the melt is discharged intermittently. A melting channel 28 is provided outside the casting hole 27 extending obliquely downward from the side wall portion 22a. The melting channel 28 sends the melt to the granulation pit 5.

The gas induction part 21 has a cylindrical shape centered on the axis CL1. The bottom end part of the gas induction part 21 is connected to the top end part of the straight barrel part 23 of the main part 20. The inside diameter of the bottom end part of the gas induction part 21 is equal than that of the straight barrel part 23. The vertical middle part of the gas induction part 21 protrudes radially. Therefore, the gas induction part 21 has an internal face 21a that protrudes radially compared to the internal face 23a of the straight cylindrical part 23. The upper end part of the gas induction part 21 is narrower than the bottom end and constitutes an opening in part 2a of the waste smelting furnace 2.

An inner cylinder 25 is inserted in the opening part 2a. The inner cylinder 25 has a cylindrical shape centered on the CL1 axis and introduces the waste and a carbon-based fuel material into the waste melting furnace 2. The bottom end part of the inner cylinder 25 is located higher than that of the gas induction part 21. The upper part of the gas induction part 21 is provided with an exhaust port 26. The exhaust port 26 discharges gases generated from the debris within the main part 20. The exhaust port 26 is connected to the combustion chamber 6 through the exhaust duct.

The melt tank part 22 is provided with lower nozzles 40 to supply oxygen enriched air (hereinafter referred to as "oxygen enriched gas") into the furnace. Oxygen enrichment is intended to improve oxygen concentration. The lower nozzles 40 are disposed at a plurality of circumferentially aligned locations of the side wall portion 22a. In a preferred example of their arrangement, the bottom nozzles 40 are arranged at eight locations that are aligned circumferentially at 45 ° intervals. The anterior end portion of each lower nozzle 40 may or may not project toward the melt reservoir 22 portion.

The conical part 24 is provided with upper nozzles 30, 31, 32, 33 to supply air to the furnace. The upper nozzles 30, 31, 32, 33 are aligned from top to bottom. The number of stages of the upper nozzles that are vertically aligned is not limited to 4, but may be less than or greater than 4. Each of the respective groups of upper nozzles 30, 31, 32, 33 are arranged in a plurality of locations They are of circumferential alignment of the conical part 24. In a preferred example of their arrangement, each set of the upper nozzles 30, 31, 32, 33 is arranged in four locations that are aligned circumferentially at 90 ° intervals. The anterior end part of each of the upper nozzles 30, 31, 32, 33 may or may not project towards the conical part 24.

A blower 42 is connected to the upper nozzles 30, 31, 32, 33 and the lower nozzles 40. The flow passages from the blower 42 to the upper nozzle assemblies 30, 31, 32, 33 and lower nozzles 40 are provided with flow regulating valves 30a, 31a, 32a, 33a, 40a, respectively. An oxygen generator 41 for enriching the air with oxygen is also connected to the flow path from the flow regulating valve 40a to the lower nozzles 40.

As illustrated in Figure 2, the waste melting furnace 2 is provided with thermometers T1 to T5 to measure the temperatures in the furnace. The thermometer T1 is arranged in the upper part of the gas introduction part 21. The thermometer T5 is embedded in the refractory material that constitutes the lower part 22b of the part of the fusion tank 22. The thermometers T2, T3, T4 are aligned from top to bottom between thermometers T1, T5. The waste melting furnace 2 is also provided with a plurality of manometers for measuring pressures in the furnace. The pressure gauge P1 is arranged at the top of the gas induction part 21. The pressure gauges P2, P3, P4 are arranged at the top, middle and bottom of the conical part 24, respectively.

The operations of the waste melting furnace 2 will now be explained in detail. First, before placing the waste, a carbon-based fuel material is introduced into the furnace 2 through the inner cylinder 25. An example of the material carbon-based fuel is coke. Coke can be partially or totally replaced by biomass carbides such as wood. The coke accumulated at the bottom 22b in the waste melting furnace 2 is ignited by a burner (not shown) or the like. This forms a so-called coke bed 81 on the bottom of the furnace.

Next, a mixture of coke and waste is introduced into the waste melting furnace 2 through the inner cylinder 25 and fills the main part 20. The type of waste is not particularly limited, but may be any of the general and industrial waste. This can process crusher dust (ASR), excavation waste, burned ash, and the like separately or in mixtures with or without combustible waste. Dry distilled waste can also be placed. Limestone and the like can be added to waste as an alkalinity regulator in addition to coke.

In this state, the oxygen enriched gas is supplied to the furnace through the lower nozzles 40. In a preferred example for establishing the burst pressure of the oxygen enriched gas, it is established within the range of 5 to 25 kPa. Combustible gases such as LNG can be mixed with the oxygen enriched gas that is supplied to the furnace through lower nozzles 40. Air is supplied to the furnace through upper nozzles 30, 31, 32, 33. In one example Preferred for setting air jet pressure, this is set within the range of 5 to 25 kPa.

On the bottom side 22b of the waste melting furnace 2, the oxygen enriched gas supplied from the lower nozzles 40 keeps the coke burning, producing a high temperature gas in the furnace, which rises. The air supplied from the upper nozzles 30, 31, 32, 33 partially burns the debris in the conical part 24, thus producing a gas in the high temperature furnace, which rises. The wastes are guided to the main part 20 and descend against upward flows of the gases in the furnace. In this process, a heat exchange occurs between the waste and the gases in the furnace, thus favoring the drying and thermal decomposition of the waste. The gases produced by the thermal decomposition of the waste concentrate in the gas induction part 21 are guided upwards to be discharged through the exhaust port 26. The discharged gases are sent to the combustion chamber 6 through the exhaust duct .

Thermal decomposition wastes (carbides), together with ash and non-combustible materials, accumulate on the bottom side 22b of the waste melting furnace 2 along the inner face 24a of the conical part 2, thus forming a layer of carbide particles (the so-called carbon layer) 82 in the coke bed 81. The carbon layer 82 functions as a layer of resistance to ventilation and regulates the flows of oxygen-enriched gas supplied from the Lower nozzles 40. This prevents local explosion of the oxygen enriched air supplied from the lower nozzles 40.

The dry distilled fuel product (fixed carbon) in the thermal decomposition residue is burned with coke. Coke flue gas and dry distilled fuel product reaches the highest temperature in a region near the upper end of the coke bed 81. Ash and non-combustible materials melt in this region. The melt enters the melt tank part 22 through the interstices of the coke bed, to retain it. In this way, the retained melt is intermittently removed from hole 27. The melt removed from hole 27 is granulated and cooled in granulation pit 5, to be collected as slag and metals. Subsequently, the furnace is filled with the mixture of coke and waste, and the waste melting process continues.

Here, as the waste melting process continues, the drying region 70 is formed at the top within the waste melting furnace 2. The drying region 70 primarily performs drying and preheating of the waste. Thermal decomposition region 71 is formed below drying region 70. Thermal decomposition region 71 primarily performs thermal decomposition and gasification of combustible components in dry waste. Under the thermal decomposition region 71 a melting region 72 is formed. The melting region 72 mainly performs the melting of ash and non-combustible materials (see Figure 3). As mentioned above, the upper end part of the conical part 24 is higher than in the case where the straight barrel part 23 occupies the highest height, thus reaching the drying region 70, whereby the limit between the drying region 70 and the thermal decomposition region 71 is located in the conical part 24.

Among the upper nozzles 30, 31, 32, 33, the upper nozzles 30, arranged in the uppermost stage, are located in the drying region 70. The upper nozzles 30 are located closer to the bottom end of the region dryer 70 between the lower end of the drying region 70 and the upper end of the conical part 24.

A larger space is formed between the waste pieces in the drying region 70 than in the thermal decomposition region 71, whereby the residues in the drying region 70 are easier to move than in the thermal decomposition region 71. Therefore, if the upper part of the nozzles 30 of the drying region 70 produces an excessive explosion, the formation of escape routes for the gases in the furnace can be favored. Therefore, it is preferable that the explosion of the upper nozzles 30 is 50 Nm3 / h or less per location. It is not always necessary for the drying region 70 to be provided with the upper nozzles 30. Two or more stages of the four-stage upper nozzles 30, 31, 32, 33 may be arranged within the drying region 70.

The parts in the oven that are in the drying region 70, the thermal decomposition region 71 and the melting region 72 can be conceived according to the oven temperatures, for example. For example, a part that shows an oven temperature between 350 and 600 ° C is the drying region, a part that shows an oven temperature between 600 and 1200 ° C is the thermal decomposition region, and a Part that shows an oven temperature between 1200 and 1800 ° C is the melting region. In this embodiment, thermometers T1 to T5 are arranged within the waste melting furnace 2 from its top to the bottom. The extent of the drying region 70, the thermal decomposition region 71, and the melting region 72 can be taken approximately according to the respective temperatures measured by the thermometers.

The position of the boundary between the drying region 70 and the thermal decomposition region 71 can also be taken according to the differential pressures in the furnace. In drying region 70, the waste reduces its volume by losing moisture as it dries. In the thermal decomposition region, the waste forms carbide particles when thermally decomposing, in order to further reduce its volume, thus thickening. Therefore, there is a difference of about 0.5 kPa / m, for example, between the differential pressure in the drying region and that in the thermal decomposition region. Here, the differential pressure is what increases the pressure caused by a 1m drop. Therefore, taking a part in which the differential pressure increases by approximately 0.5 kPa / m compared to that of the upper region, the boundary between the drying region 70 and the thermal decomposition region 71 can be approximately determined. The respective differential pressures in the individual parts within the furnace can be approximated by the pressure gauges P1 to P4 arranged within the furnace. For example, when the differential pressure near the mean pressure gauge P3 is higher than in the upper region by about 0.5 kPa / m, the proximity of the mean pressure gauge P3 is taken as the boundary between the drying region 70 and the thermal decomposition region 71.

That is, the thermal decomposition region 71 of the waste is a region located lower than the part where the differential pressure has fully increased to 0.5 kPa / m or more within the drying region 70. Here, the differential pressure refers at the differential pressure at the time that the operation of the furnace is relatively stable, while excluding the differential pressure at the time of the gas burst and the like.

In the waste melting furnace 2 explained above, the conical part 24 occupies the highest height in all the parts constituting the main part 20. Therefore, the inner face 24a of the conical part 24 forms an angle of inclination with the horizontal plane greater than in the case where the non-conical straight barrel part 23 occupies the greatest height. As a consequence, the debris in the vicinity of the inner face 24a of the conical part 24 is gently guided downwards. In addition, the inner face 24a of the conical portion 24 slopes moderately with respect to the inner face 23a of the straight cylindrical portion 23, making it difficult for the waste to stop at the top of the end of the conical portion 24. If the portion Conical 24 occupies the highest height, the upper end portion of conical portion 24 being on the upper side of main portion 20. The waste reduces its volume by drying and thermal decomposition as it descends through main portion 20. The volume reduction also occurs on the upper side of the main part 20. If the upper end part of the conical part 24 is located on the upper side of the main part 20, the cross-sectional area of the main part 20 becomes smaller from the upper side to the lower side, in accordance with the volume reduction that also occurs on the upper side of the main part 20. This prevents fo They close spaces and prevent gas bursting. This allows the efficiency in the heat exchange between the waste and the gases in the furnace to be improved more than in the case where the straight barrel part 23 occupies the highest height. Therefore, the consumption of coke can be reduced.

In this case, the fact that the interior volume of the main part 20 is less than in the case where the straight barrel part 23 occupies the highest height does not adversely affect the efficiency in the processing of waste. This is because the efficiency in the heat exchange between the waste and the gases in the furnace is improved, as mentioned above, so that the waste reduces its volume efficiently.

The inner face 24a of the conical part 24 forms an angle of inclination greater than 75 °, but less than 90 °, with the horizontal plane. This more safely prevents waste from stagnating. Therefore, the efficiency in the heat exchange between the waste and the gas in the furnace can be further improved.

The boundary between the drying region 70 and the thermal decomposition region 71 is located in the conical part 24. As a consequence, the upper end of the conical part 24 is located in the drying region 70. The reduction in volume of the aforementioned debris also proceeds within drying region 70. When the upper end portion of conical portion 24 is located in drying region 70, the cross-sectional area of main portion 20 becomes smaller from within drying region 70 through bottom side in accordance with the volume reduction that also occurs within the drying region 70. This can more safely prevent gaps from occurring.

The upper nozzles 30 are located in the drying region 70. This further favors drying of the debris in the drying region 70. Since the upper end of the conical part 24 is located in the drying region 70 such as mentioned above, the drying region 70 descends along the conical portion 24. The waste further reduces its volume as drying is promoted, whereby the load decreases along the conical portion. 24 is softer. The waste that has reduced its volume by favoring its drying accumulates in the center by the conical part 24, so that the formation of spaces is prevented. Therefore, the fact that the upper end part of the conical part 24 is located in the drying region 70 cooperates with the fact that the drying region 70 is provided with the upper nozzles 30, allowing to favor the drying of waste while preventing the formation of gaps.

The upper nozzles 30 are located closer to the lower end of the drying region 70 between the lower end of the drying region 70 and the upper end of the conical part 24. This can separate the upper nozzles 30 located in the drying region 70 from the boundary between the straight cylindrical part 23 and the conical part 24 and, more securely, prevents gaps from occurring.

Furthermore, the waste melting furnace 2 prevents thermal decomposition waste from adhering and therefore the workload at the time of maintenance of the waste melting furnace 2 can be drastically reduced since the spaces are restricted , the waste melting furnace 2 can operate stably. If a gap occurs and then it increases, the differential pressure in the furnace will decrease. If the growing space is filled with a load displacement, the differential pressure in the furnace increases dramatically. Preventing gaps suppresses such fluctuations in the differential pressure in the furnace, allowing the waste smelting furnace to operate stably.

In the waste melting furnace 2, the inner diameter of the thermal decomposition region 71 is smaller than in the conventional furnace compared to the case where the straight barrel part 23 occupies the greatest height. Consequently, the carbon layer can be increased in thickness, thereby ensuring sufficient differential pressure in the furnace. This also helps stabilize the operation of the waste melting furnace 2.

Although a preferred embodiment of the present invention has been explained above, the present invention is not necessarily limited to the above-mentioned embodiment, but can be modified in various ways within the scope without departing from the essence thereof. For example, the main part 20 may be constituted by the conical part 24 alone without the straight barrel part 23. That is, the conical part 24 can occupy the total height H1 of the main part 20.

Hereinafter, examples of the present invention, which do not restrict the present invention, and a comparative example will be illustrated.

(1) Example 1

As Example 1, a waste melting furnace 2A schematically illustrated in Figure 4 (a) was prepared. The waste melting furnace 2A corresponds to the waste melting furnace 2 of the aforementioned embodiment. The ratio between the height H2 of the conical part 24 and the height tota1H1 of the main part 20 is 95%. The inner face 24a of the conical part 24 forms an inclination angle 0 of 80 ° with the horizontal plane. In the waste melting furnace 2A, the aforementioned thermometers T2 are arranged at four locations that are aligned circumferentially at 90 ° intervals.

(2) Example 2

As Example 2, a waste melting furnace 2B illustrated schematically in Figure 4 (b) was prepared. The waste melting furnace 2B corresponds to the waste melting furnace 2 of the aforementioned embodiment. The ratio of the height H2 of the conical part 24 to the height tota1H1 of the main part 20 is 50%. The inner face 24a of the conical part 24 forms an inclination angle 0 of 75 ° with the horizontal plane. The inside diameter of the straight barrel part 23, the inside diameter of the bottom end part of the conical part 24, and the total height H1 of the main part 20 in the waste melting furnace 2B are equal to those of the waste melting 2A.

(3) Comparative Example 1

As Comparative Example 1, a waste melting furnace 2C illustrated schematically in Figure 4 (c) was prepared. The waste melting furnace 2C differs from the waste melting furnace 2 mentioned above in the following points. The straight barrel part 23 occupies the highest height in all the parts constituting the main part 20. The ratio between the height H2 of the conical part 24 and the height tota1H1 of the main part 20 is 35%. Among the upper nozzles 30, 31, 32, 33, the uppermost 30 are omitted. All the upper nozzles 31, 32, 33 are located in the thermal decomposition region 71. The inner face 24a of the conical part 24 forms a tilt angle 0 of 70 ° with the horizontal plane.

The inside diameter of the straight cylindrical part 23, the inside diameter of the bottom end part of the conical part 24 and the total height H1 of the main part 20 in the waste melting furnace 2C are equal to those of the waste 2A. The aforementioned thermometers T2 are arranged at four locations that are aligned circumferentially at 90 ° intervals also in the waste melting furnace 2C.

(4) Comparative evaluation of differential pressure in the furnace, gas temperature in an upper part of the furnace and gas temperature in an intermediate part of the furnace

The waste melting furnaces 2A, 2B, 2C of Examples 1 and 2 and Comparative Example 1 were operated in the same time period and their differential pressures in the furnace were measured. As for the furnaces 2A, 2C of Example 1 and Comparative Example 1, the gas temperature in the upper part of the furnace and the gas temperature in an intermediate part of the furnace were measured. To evaluate only the effects of shapes of the main part 20 while using Comparative Example 1 having no upper nozzles 30 as the comparison subject, no air was supplied from the upper nozzles 30 in Examples 1 and 2.

The differential pressure in the furnace in this test example is the difference between the value detected by manometer P4 arranged at the bottom of conical part 24 and the value detected by manometer P1 arranged at the top of induction part gas temperature 21. The gas temperature in the upper part of the furnace is the value detected by the thermometer T1 arranged in the upper part of the gas induction part 21. The temperature of the gas in the middle of the furnace is the value measured by the T2 thermometer.

Figure 5 is a graph illustrating daily changes in differential pressure in the furnace. In Comparative Example 1, as indicated by a polygonal line L1 in Figure 5, the differential pressure in the furnace was low during the period from the first day to the third day, falling below the lower limit LL of a range suitable for operate the oven. From these results it is speculated that the gas explosion occurred during the period between the first day and the third day in the waste melting furnace 2C, thus reducing the differential pressure in the furnace.

The gas burst appears to be caused by stagnation of the debris near the inner face 24a of the conical portion 24 in the debris melting furnace 2C (see hatched portions in Fig. 4 (c)). Stagnant waste, if it exists, can be thermally decomposed locally by air from the upper nozzles 31, 32, 33, for example, to generate spaces, which can grow, thus forming flow pathways for gases in the furnace (this phenomenon it is likely to occur in particular near the boundary between the inner face 23a of the straight barrel portion 23 and the inner face 24a of the conical portion 24).

On the contrary, as indicated by the polygonal line L2 of figure 5, the differential pressure in the furnace in Example 1 exceeded the lower limit LL of the desirable range to operate the furnace, while its daily displacement width was small. As indicated by a polygonal line L3 in figure 5, the differential pressure in the furnace in Example 2 was less than in Example 1, but it exceeded the lower limit LL, while its daily displacement width was small. From these results, it is speculated that the gas explosion is eliminated in Examples 1 and 2.

Figure 6 is a graph illustrating daily changes in gas temperature at the top of the furnace. As indicated by a polygonal line L4 in Figure 6, the gas temperature at the top of the furnace in Comparative Example 1 is elevated during the period from the first day to the third day and differs greatly from that of the fourth day and beyond . The temperature during the period from the first day to the third day exceeds the upper limit ML of a desirable range for operating the oven. From these results it is seen that the gas explosion occurred during the period between the first day and the third day in Comparative Example 1, thus raising the temperature of the gas in the upper part of the furnace.

On the contrary, as indicated by the polygonal line L5 of figure 6, the gas temperature in the upper part of the furnace in Example 1 was less than the upper limit ML of the desirable range to operate the furnace, while its width of daily commute was small. From these results it is speculated that the gas explosion is prevented from occurring in Example 1.

Figure 7 illustrates the results of measuring the gas temperature of the central furnace. Figure 7 is a set of graphs illustrating changes in the temperature of the gas in the oven medium over time. As Figure 7 (a) indicates, a large temperature fluctuation over time was observed in each of the four T2 thermometers in Comparative Example 1. The time intervals when the temperature fluctuated vary between thermometers. From these results it is speculated that the gas explosions occurred one after another at different locations at different time intervals within the furnace in Comparative Example 1. Conversely, as indicated in Figure 7 (b), No large temperature fluctuation was observed in any of the four T2 thermometers in Example 1. From these results it is speculated that the fact that the gas explosion occurs is much more restricted than in the melting furnace. Waste 2C from Comparative Example 1.

From the above results it is appreciated that the present invention can prevent the gas explosion from occurring. In particular, due to the fact that the ratio between the height H2 of the conical part 24 and the height tota1H1 of the main part 20 is 50% or more in Example 2, it is substantially observed that the occurrence of gas explosion if the condition is met that the conical part occupies the highest height in all the parts that make up the main part 20.

The operation stopped after one month, and the interior of each furnace was inspected. The results showed that adherent substances made from molten thermal decomposition residues were formed on the inside of the waste melting furnace 2C of Comparative Example 1. On the contrary, no adhered substances made from molten thermal decomposition wastes were observed on the face Inside the waste melting furnace 2A of Example 1.

(5) Comparative evaluation of the coke ratio

The waste melting furnaces 2A, 2C of Example 1 and Comparative Example 1 were operated for about one week in the same time period, and their coke ratios were compared to each other. To evaluate only the effects of the shapes of the main part 20 while using Comparative Example 1 having no upper nozzles 30 as the comparison subject, no air was supplied from the upper nozzles 30 in Examples 1 and 2.

Figure 8 is a graph illustrating measurement results of the amount of waste processed, the coke ratio, the differential pressure in the furnace, and the temperature of the gas in the upper furnace. The coke ratio, the differential pressure in the furnace and the gas temperature in the upper part of the furnace are indicated by the differences with the measurement results of Comparative Example 1 which serves as a reference. The coke ratio (kg / TR) is a value obtained by dividing the quantity (kg) of coke introduced into the melting furnace by the total amount (t) of waste processed in the melting furnace. As illustrated in Figure 8, the coke ratio was lower in Example 1 by approximately 12.7 kg / TR than in Comparative Example 1 in a short-term test of approximately one week. From these results it is appreciated that the present invention can reduce the consumption of carbon-based fuel materials.

According to the results of Figure 8, the gas temperature in the upper part of the furnace in Example 1 is lower by approximately 100 ° C than in Comparative Example 1. The differential pressure in the furnace in Example 1 is higher by about 1.5 kPa than in Comparative Example 1. From these results it is speculated that the stagnation of the waste and the appearance of gas explosions are suppressed in the waste melting furnace 2A. This appears to contribute greatly to reducing the consumption of carbon-based fuel materials.

(6) Comparative evaluation of drying capacity

The waste melting furnaces 2A, 2C of Example 1 and Comparative Example 1 were operated in the same time period and their drying capabilities were compared to each other. As parameters related to drying capacities, its furnace gas flow rates (surface velocities), furnace differential pressures, coke ratios, furnace heat exchange temperatures, volume moisture drying capacities, and efficiencies Heat transfer rates were measured during operation and compared. The objective of this evaluation is to verify the effects obtained when the lower end part of the drying region 70 is located in the conical part 24, while the drying region 70 is provided with the upper nozzles 30. Therefore, the Air was supplied from the top nozzles 30 in Example 1.

Figure 9 (a) is a graph illustrating the gas flow distributions (surface velocity) in the furnace in the direction of furnace height. Curves L6, L7 illustrate gas flow rates in the furnace in Example 1 and Comparative Example 1, respectively. Reference lines b1, b2, b3, b4 indicate where the nozzles are located upper 30, 31, 32, 33, respectively. Figure 9 (b) is a graph depicting a differential pressure distribution in the furnace in the direction of furnace height. Reference lines a1, a2, a3, a4, a5 indicate where the manometers used to measure the differential pressures in the furnace are located. The manometers used here differ from the manometers P1, P2, P3, P4 mentioned above. Points F1, F2, F3, F4 indicate the differential pressure between the reference lines a2, a1, the differential pressure between the reference lines a3, a2, the differential pressure between the reference lines a4, a3, and the differential pressure between reference lines a5, a4, respectively. Figures 9 (a) and 9 (b) are represented with their ordinates indicating the height of the oven, while the scale of each ordinate is in accordance with the height in the sectional view of the oven illustrated in Figure 9 (c) .

As curves L6, L7 in Figure 9 (a) illustrate, the gas flow rate in the furnace is higher in Example 1 than in Comparative Example 1. From this, it is speculated that Example 1 improves efficiency. in the heat exchange between the gas in the oven and the waste and improves the drying capacity. Furthermore, as mentioned above, Example 1 prevents the gas explosion from occurring and stabilizes the gas flow in the furnace. Therefore, it is assumed that the fact that the gas flow in the furnace is higher and the fact that the gas flow in the furnace stabilizes cooperate with each other to further improve the efficiency of heat exchange between the gas in the oven and waste.

In Comparative Example 1, the gas explosion occurred frequently during operation, thereby raising the temperature of the gas at the top of the furnace, thus forcing the explosion to stop from the upper nozzles 31. The result also appears in the flow data of figure 9. In contrast, Example 1 prevented a gas explosion from occurring, thus allowing a stable and constant explosion from the upper nozzles 31.

Figure 10 is a graph showing the results of measuring the furnace heat exchange temperature (° C) and the coke ratio (kg / TR). In the graphs, the black circles indicate the measurement results of Example 1, while the white triangles indicate the measurement results of Comparative Example 1. The heat exchange temperature in the oven is calculated using the following expression:

Furnace heat exchange temperature = Furnace combustion temperature 1000 ° C (assumed) -temperature at the top of the furnace (actual value).

As indicated in figure 10, Example 1 showed a higher heat exchange temperature and a lower coke ratio than Comparative Example 1. That is, it is observed that Example 1 favors the drying of the waste in Comparison with Comparative Example 1.

Figure 11 is a graph showing measurement results of moisture drying capacity by volume (Mcal / (m3 h)) and coke ratio (kg / TR). In the graphs, black circles indicate the measurement results of Example 1, while white triangles indicate measurement results of Comparative Example 1. The moisture drying capacity by volume is calculated by the following expression:

Moisture drying capacity by volume = [amount of input waste (t / h) x moisture in waste (%) x latent heat of evaporation of humidity (Mcal / t)] / volume of the drying region (m3).

Figure 12 is a graph showing measurement results of the heat transfer efficiency (Mcal / (m3 h ° C)) and the gas flow in the furnace (surface velocity) (Bm / s). In the graphs, black circles indicate the measurement results of Example 1, while white triangles indicate the measurement results of Comparative Example 1. The heat transfer efficiency is calculated using the following expression:

Heat transfer efficiency = heat transfer area x heat transfer coefficient.

The furnace gas flow indicates the flow at the height of the upper nozzles 30. As illustrated in Figures 11 and 12, it is observed that Example 1 has a drying capacity that is approximately 2.5 times greater than that of the Example Comparative 1. According to the heat transfer area and the heat transfer coefficient, the 2.5-fold improvement in drying capacity is produced by a roughly 1.7-fold improvement due to stabilization of the flow of gas in the oven and approximately a 1.5-fold improvement due to the increased gas flow rate in the oven.

(7) Comparative evaluation of whether or not there are superior nozzles 30

While operating the waste melting furnace 2A of Example 1, the times when the gas burst occurred were compared between the respective cases in which air was supplied from the upper nozzles 30 and in those which were not. Figure 13 is a graph that represents the results of the measurement of the time in which it occurred gas burst and coke ratio. In the table, black circles indicate the measurement results in the case that air was supplied from the upper nozzles 30, while white triangles indicate the measurement results in the case that no air was supplied from the upper nozzles 30 .

As Figure 13 illustrates, when air was not supplied from the top nozzles 30, the gas burst time fluctuated greatly, and there were cases where the burst occurred over a long period of time. The white triangles also indicate a tendency to increase the proportion of coke under the influence of the long-term outburst when the latter occurs.

In contrast, when air is supplied from the upper nozzles 30, the gas exhaust time fluctuated less and was shorter overall. From these results it is observed that supplying air from the upper nozzles 30 prevents a gas explosion from occurring and reduces the consumption of carbon-based combustible materials.

Industrial applicability

The present invention can be used to process general and industrial waste.

List of reference signs

2 ... waste smelting furnace; 20 ... main part; 21 ... gas induction part; 22 ... part of the fusion deposit; 24 ... conical part; 24a ... inner face; 26 ... escape port; 30, 31, 32, 33 ... upper nozzle; 40 ... lower nozzle; 70 ... drying region; 71 ... thermal decomposition region; 72 ... fusion region; CL1 ... axis

Claims (1)

1. Waste melting furnace (2) for drying, thermal decomposition, and waste melting, the furnace (2) comprising: a cylindrical main part (20) that extends vertically to form a space to contain the waste and guide the waste from top to bottom; a fusion reservoir part (22), attached to a lower end part of the main part (20) along a central axis (CL1) of the main part (20), to retain melt generated from the waste; Y a gas induction part (21), attached to an upper end part of the main part (20) along the central axis (CL1) of the main part (20), to collect a gas generated from the waste and guiding the collected gas to an exhaust port (26); wherein an opening part (2a) for introducing the waste and carbon-based fuel material into the waste melting furnace (2) is constituted in an upper end part of the gas induction part (21); wherein the melt tank portion (22) has a bottom portion (22b) to form a bed of carbon-based fuel material; wherein the main part (20) has a conical part (24) that has an interior cross-sectional area that gradually decreases to the underside; in which the conical part (24) occupies vertically the entire height of the main part (20) or the highest height in all the parts that constitute the main part (20), so that the relationship between the height (H2) of the conical part (24) and the total height (H1) of the main part (20) is 50% or more; Y wherein an inner face of the conical part (24) forms an angle of inclination greater than 75 ° but less than 90 ° with a horizontal plane.