JPH11263642A - Double cylinder type firing furnace and firing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double cylinder type firing furnace for which waste plastics are usable as an inexpensive fuel, and a firing method. SOLUTION: The furnace body of this double cylinder type firing furnace for firing raw ores, such as limestone or a dolomite, consists of double cylinders packed with raw ores between the cylinders. A burner 9 for firing the raw ores is mounted at the outside cylinder of the double cylinders and eaves 3 forming a combustion space 4 by shielding the flow down of the raw ores is disposed above the burner. In such a case, the outside cylinder is provided with a blow port 15 for blowing the waste plastics into the combustion space. The firing method consists in blowing the waste plastics of an average grain size below 30 mm into the combustion space while maintaining the temp. of the space at a temp. of >=600 deg.C by using such furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-cylindrical firing furnace for firing lime, dolomite and the like using waste plastic as fuel, and a firing method using this furnace.

2. Description of the Related Art A double-cylindrical firing furnace is also called a Beckenbach furnace, and its structure is, as shown in FIG. 3 and FIG. . The outer cylinder 1 and the inner cylinder 2 are fixed by a plurality of bridges 3 having an arch-shaped or wedge-shaped cross section. Each bridge 3 serves as an eave to block the flow of the rough, and a space is formed below the eaves. It is a combustion chamber 4. The ore is supplied from the hopper 5 at the furnace top to the ore charging device 6
Is put between the outer cylinder 1 and the inner cylinder 2, descends, sequentially passes through the pre-tropical zone, the baking zone, and the cooling zone, accumulates in the hopper 7 at the furnace bottom, and is taken out by the product take-out device 8. Fuel such as heavy oil is burned in the combustion chamber 4 by a burner 9 attached to the outer cylinder 1. The combustion air is first sent to the recuperator 11 by the blower 10, where it is heated by exchanging heat with exhaust gas, and then used as primary air in each burner 9. The combustion gas passes through the calcination zone, rises to the pre-tropical zone, exchanges heat with the rough stone by the recuperator 11, and is then released by the exhaust gas fan 12. Cooling air is sent to the inner cylinder 2 by the inner cylinder cooling fan 13, and the high-temperature air cooled by the inner cylinder is
Used as the next air. The calcined product is cooled by the air sucked into the furnace, which has a negative pressure below the furnace, and the heated air and a part of the combustion gas from the lower combustion chamber are returned to the lower combustion chamber by the injector 14. Sent,
The inner cylinder 2 also functions as a passage for the circulating gas. In this furnace, the flow of gas with respect to the flow of limestone and the like is countercurrent in the cooling zone, and in the co-firing zone, the circulating gas and the combustion gas are co-current with the flow of limestone and the like. It is countercurrent in the tropics. Fuel for this double-cylindrical firing furnace is mainly heavy oil, and gas fuel and pulverized coal are also used.

SUMMARY OF THE INVENTION Waste plastic is a new fuel that has recently attracted attention, and is attractive in that it is less expensive than conventional heavy oil and gas. However, since solid waste plastics are not easily pulverized and costly, it is unsuitable to use them as fuel in a double-cylindrical firing furnace in the same manner as coal or petroleum coke. The present inventors have conducted various studies in order to develop a method of using this waste plastic as a fuel for a double cylindrical firing furnace. The difficulty of waste plastics as fuel for firing furnaces lies in the fact that solids, melting, and gasification change depending on the temperature and burn, and the change occurs in time depending on the size. For this reason, when continuously supplying waste plastics of a wide range of size groups, changes in the state of solidification, melting, and gasification are mixed, and the supply lines and injection nozzles are closed. Further, if the solid waste plastic blown into the packed bed is not melted or gasified smoothly, the solid waste plastic begins to accumulate in the space and does not permeate or diffuse into the rough stone, causing problems such as sooting. An object of the present invention is to solve such problems and to provide a double cylindrical firing furnace and a firing method that can use waste plastic as an inexpensive fuel.

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have newly provided a waste plastic injection port in the fuel chamber and reduced the average particle diameter of the waste plastic to 30 mm or less. The temperature of the combustion space to 60
By blowing while maintaining the temperature at 0 ° C. or higher, the waste plastic was successfully burned smoothly. That is, in the present invention, the furnace main body is formed of a double cylinder in which the ore is filled between the cylinders, and a burner for firing the ore is attached to the outer cylinder of the double cylinder, and the flow of the ore flows down above the burner. In a firing furnace provided with an eave that blocks and forms a combustion space,
A double-cylindrical firing furnace for firing a rough stone such as lime or dolomite, wherein a blow port for blowing waste plastic into the combustion space is provided in an outer cylinder; The present invention relates to a firing method characterized by blowing waste plastic having an average particle size of 30 mm or less while maintaining the temperature of a combustion space at 600 ° C. or more using a furnace. In the above-mentioned firing furnace, when the upper and lower combustion chambers and the ore around the combustion chamber are heated by the auxiliary burner and reach 600 ° C. or higher, the solid waste plastic is preferably applied to the frame of the auxiliary burner, Is sprayed so as to evenly distribute the surface of the deposit. In this process, the small solid waste plastics come into contact with the high-temperature gas and melt and gasify and burn.
The large-particle waste plastic traces and lands on the gemstone sedimentary surface, which in turn melts and gasifies and infiltrates the gemstone bed with co-current or countercurrent combustion air as the gem falls. , Diffuses and completely burns in the gap.

BEST MODE FOR CARRYING OUT THE INVENTION The waste plastic inlet has an inner diameter of about 10 to 100 mm, preferably about 30 to 50 mm depending on the number of bridges, and the installation site is a bottom surface of a space formed by a bridge as an eaves, that is, a bridge. It is determined that the waste plastic particles can be blown over the entire upper surface of the limestone flowing from the lower edge toward the center with a repose angle.
Since waste plastic is usually blown with gas, often air, as carrier gas, many installation sites are possible by changing the blowing pressure and angle. However, it is preferable to provide the waste plastic above the normal fuel burner used as an auxiliary burner so that the waste plastic passes through the flame of the normal fuel burner and falls on the surface of limestone. It is also preferable to use the blowing port as a nozzle and swing it up and down or left and right. Limestone fired in the furnace of the present invention has an average particle size of about 10 to 100 mm, usually about 40 to 60 mm, and a repose angle of about 35 to 45 °. The waste plastic may be anything that burns, for example, polyethylene, polypropylene, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, polyvinyl chloride, polyvinylidene chloride,
Used paper or a mixture of two or more of these. If the waste plastic is too large, not only is it difficult to inject but also it takes time to ignite, so the upper limit of the appropriate particle size is about 30 mm, preferably 20 mm or less. Although there is no particular lower limit, it is usually 3 mm or more. The ignition time of the waste plastic varies depending on the type and particle size of the waste plastic. In the case of a plastic having good flammability such as polyethylene, polypropylene, polystyrene, ABS, etc., the ambient temperature is 6 ° C.
At 00 ° C, the particle size is about 50 seconds for 10 mm, and 10 for 20 mm.
It is about 0 second, about 180 seconds with a particle size of 30 mm. When the ambient temperature is 800 ° C., the particle size is about 5 seconds at a particle size of 10 mm, about 10 seconds at a particle size of 20 mm, and about 20 seconds at a particle size of 30 mm. Polyethylene terephthalate, polyvinyl chloride, polyvinylidene chloride, etc., which are inferior to the above plastics, have a particle diameter of 20 mm at 800 ° C. for about 20 seconds, and a particle diameter of 3
It is about 35 seconds at 0 mm. A high temperature field was an essential condition (about 600 ° C. or higher) for combustion of the waste plastic injected into the furnace, and no waste plastic was burned at 500 ° C. Therefore, at the start-up of the furnace, the temperature of the combustion chamber is first raised to 600 ° C. using fuel such as heavy oil, pulverized coal, pulverized coke, kerosene, and LPG. After that, the injection of waste plastic is started, but during operation, heavy oil, pulverized coal, pulverized coke, and kerosene are intermittently or continuously as necessary so that the combustion chamber can be constantly maintained at 600 ° C. or higher, preferably 1300 ° C. or higher. , LPG. The supply amount of the waste plastic is within a range in which the waste plastic is deposited in each combustion chamber and does not cause the clogging of the gap between the limestones, the generation of soot, and the like. One measure is that the amount of charge per second does not fill the space in the combustion chamber. Waste plastic can be blown into the inner cylinder as well as the combustion chamber. Injection into the inner cylinder penetrates through the lower combustion chamber and the inner cylinder wall, inserts a water-cooled / air-cooled jacketed injection pipe, and directs its tip downward. The waste plastic is injected into the inner cylinder when the temperature distribution in the entire furnace reaches a stable state (equilibrium state). The auxiliary burner which raises the circulating gas temperature always keeps the temperature of the combustion chamber at 60
The temperature is monitored so as to be 0 ° C. or higher, and the intermittent or continuous operation is performed with the petroleum fuel being kept to a minimum as the waste plastic is injected.

EXAMPLE In the firing furnace shown in FIGS. 3 and 4, a suspension type furnace in which a cylinder was suspended was used. Each combustion chamber 9 was provided with a waste plastic inlet 15 shown in FIGS. The waste plastic inlet 15 is a nozzle having an inner diameter of 40 mmφ, and blows the waste plastic into the combustion chamber 4 with compressed air. Waste plastic has an average particle size of 10mm
Was used. The firing conditions and results are shown in the table below.

[Table 1]

According to the present invention, it is possible to completely burn waste plastic even in the packed bed, and by uniformly distributing waste plastic to the surface of the deposited limestone at the lower part of the combustion chamber, the product can be manufactured in a conventional manner. Similar quality is ensured. As a result, fuel efficiency can be significantly reduced by injecting solid waste plastic.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state in which a waste plastic injection port is provided in a combustion chamber of a double cylindrical lime burning furnace.

FIG. 2 is a cross-sectional view in a direction perpendicular to FIG.

FIG. 3 is a sectional view showing the structure of an example of a double cylindrical lime burning furnace.

FIG. 4 is a perspective view showing a main part of the firing furnace with a part cut away.

[Description of Signs] 1 ... Outer cylinder 2 ... Inner cylinder 3 ... Bridge (eave) 4 ... Combustion chamber 5 ... Hopper 6 ... Rough stone input device 7 ... Hopper 8 ... Product unloading device 9 ... Burner 10 Blower 11 Recaperator 12 Waste gas fan 13 Inner tube cooling fan 14 Injector 15 Waste plastic inlet

Continuing on the front page (72) Inventor Susumu Isozaki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Takuya Kadowaki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Disruption Otani 3-21-6, Highland, Yokosuka, Kanagawa (72) Inventor Toshio Katata 2272-14, Fukaya, Ayase-shi, Kanagawa (72) Mitsuo Tani Central, Oyama-shi, Tochigi 1-314, Machimachi (72) Masahiro Nakada, Inventor 8-2, Hachigicho, Kuzuu-cho, Anso-gun, Tochigi Prefecture (72) Inventor Hiroyasu Ito 1089-6, Horimecho, Sano-shi, Sano-city, Tochigi Prefecture

Claims (2)

[Claims] 1. A furnace body comprising a double cylinder filled with a rough between cylinders, a burner for firing the rough is mounted on an outer cylinder of the double cylinder, and a flow of the rough is blocked above the burner. In a firing furnace provided with an eave that forms a combustion space,
A double-cylindrical firing furnace for firing rough stones such as lime or dolomite, wherein an outlet for blowing waste plastic into the combustion space is provided in an outer cylinder. 2. A sintering method, characterized in that waste plastic having an average particle size of 30 mm or less is blown into the double cylindrical sintering furnace according to claim 1 while maintaining the temperature of the combustion space at 600 ° C. or higher.