JP3246377U - Waste plastic continuous gasification and combustion equipment - Google Patents

Abstract

[Problem] To provide a compact continuous waste plastic gasification and combustion device that can directly pyrolyze and gasify used waste plastics containing different types of plastics or foreign matter without going through processes such as analysis, cleaning, sorting, blending adjustment, molding, etc., and burn them while controlling the amount of heat generated. [Solution] The waste plastic gasification and combustion device 1 is composed of a hopper 4 for supplying waste plastic materials, a combustion chamber 3a, a preheating burner installed inside the combustion chamber 3a, a screw cylinder 2b installed so as to penetrate the combustion chamber, a main exhaust pipe 5, a sub-exhaust pipe 6, and a residue discharge pipe 2e installed at the tip of the screw cylinder, and is equipped with a screw 2c inside the screw cylinder, a steam pipe 8a at the inlet of a dry distillation gas pipe connected to the heating part of the screw cylinder, a main damper 5a with an adjustable opening and closing degree inside the main exhaust pipe, and a sub-damper 6a with an adjustable opening and closing degree inside the sub-exhaust pipe. [Selected Figure] Figure 1

Description

The present invention relates to a compact device for gasifying and burning used waste plastics at high temperatures in an oxygen-free atmosphere.

Plastics are often used as a single component, but are also often combined with different types of plastics, such as in laminate films and PET bottle caps, or used in combination with other materials such as metals, such as in home appliances. Moreover, waste plastics that are discarded after use are generally mixtures of these materials or have dirt or other foreign matter attached to them.

In order to recycle waste plastics that contain a mixture of different types of plastics and foreign matter, complex processes such as sorting, crushing, pulverization, analysis, cleaning, sorting, blending adjustment, and molding are carried out. However, the present invention can process the plastics as long as they are crushed to a size that can be fed by a screw, and provides an apparatus that can pyrolyze and gasify them, and continuously burn them autonomously while controlling the temperature of the dry distillation gas.

It is also possible to utilize non-standard items that have been sorted for recycling but are difficult to separate and have no use, and are inevitably disposed of in landfills. This device is effective for treating used waste plastics, but it can also be used to treat new plastics, mixtures of new plastics and waste plastics, composites or mixtures of different materials such as metals, glass fibers, carbon fibers, cellulose, and other different materials, and plastics contaminated with other substances.

In addition, because waste plastics can be thermally decomposed in an oxygen-free atmosphere, valuable metals can be recovered without being oxidized. Because the device is compact, it can be moved to the site where waste plastics are generated and operated on-site. In that case, it becomes unnecessary to transport the waste plastics to a processing plant, which leads to further energy savings and reduction in carbon dioxide emissions.

Single-component plastic waste materials discharged as scraps from manufacturing plants and other sources are often reused as material recycling, but the thermal recycling method, in which plastic waste is reused as a heat source, is widely used as a method for recycling other used plastic waste.

A known method of thermally recycling used waste plastics is to turn them into pellet-shaped solid fuel and use them as such, as shown in Patent Document 1. Patent Document 1 describes a complex process for producing solid fuel, in which the composition and calorific value of the raw materials are analyzed when the raw materials are received, and then sorting, blending, molding, and other steps are carried out to adjust the composition and calorific value.

Furthermore, Patent Document 2 describes a complex waste gasification and combustion system that measures the CO concentration of pyrolysis gas to control the amount of waste material and the amount of auxiliary fuel supplied, thereby controlling the load on the device to a constant level.

The rotary kiln type pyrolysis apparatus described in Patent Documents 3 and 4 is large-scale and suitable for large-scale treatment but not for small-scale treatment. In addition, it is not suitable for on-site treatment by moving it to the waste generation site as needed.

As described above, conventional thermal recycling of waste plastic requires complex processes such as adjusting heat and removing foreign matter, and it has not become widespread due to high costs and other reasons, so a considerable amount of waste plastic is disposed of in landfills. In addition, even if it is sorted, unusable non-standard products are also disposed of in landfills.

Furthermore, when plastics are landfilled, they naturally deteriorate and turn into microplastics, which have a significant adverse effect on the living environment of living organisms, becoming a social problem.
Plastics that have washed up on coastlines and elsewhere and become brittle through natural deterioration are seen as a problematic source of microplastics, but because the device of the present invention is compact, it can be moved to the source of these plastics and processed on-site.

This contributes to saving fuel for waste transportation and the associated reduction in carbon dioxide emissions. Note that, unlike the direct incineration method shown in Patent Document 1, the device of the present invention gasifies and burns waste, so no soot is generated.
Furthermore, in the device of the present invention, plastics are pyrolyzed in an oxygen-free atmosphere, so even if metals are mixed in with the plastics, they are recovered without being oxidized.

Patent Document 5 describes a method for producing activated carbon by flash drying sludge and carbonizing it, in which the waste heat of the exhaust gas generated in the carbonization process is utilized as a heat source for the flash drying, and the flash-dried exhaust gas is introduced into an activated carbonization furnace to thermally decompose odorous components in the exhaust gas, thereby removing odors.
This is a method suitable for drying sludge with a high water content, but the drying process is not necessary for the pyrolysis and gasification of waste plastics, which has a lower water content than sludge and a higher calorific value, and it is necessary to prevent an excessive temperature rise in the combustion chamber due to the combustion of the dry distillation gas and to control the temperature of the combustion chamber. However, the method of Patent Document 5 does not mention temperature control of the combustion chamber using exhaust gas.

Patent Document 6 describes that in a carbonization furnace having multiple screw conveyors installed above and below, a connecting chute that sequentially drops and supplies sludge to the lower screw is made slightly larger than the outer jackets of the upper and lower screw conveyors to make it slidable, thereby making it possible to accommodate thermal expansion of the screw conveyors and the chute. It also describes that by arranging the connecting chute inside the carbonization furnace, adhesion of tar in the carbonization gas to the chute surface due to a drop in the temperature of the chute is prevented. Furthermore, it is shown that the carbonization gas generated by carbonization is supplied to a heating chamber surrounding the outside of the screw conveyor and used as a heat source.

As described above, Patent Documents 5 and 6 describe the use of the dry distillation gas generated in the carbonization process as a heat source for carbonization, but they make no mention of a system for controlling the temperature of the screw heating section in combination with water vapor in the thermal decomposition of waste plastics, which generate a large amount of heat.

In contrast, the present invention is a technology that controls the temperature of the screw heating part by adjusting the opening and closing degree of the damper of the main exhaust pipe and the damper of the sub-exhaust pipe of the carbonization furnace, the rotation speed of the screw, the amount of combustion air, and the amount of cooling air for the screw heating part using respective control motors while detecting the temperature of the dry distillation gas of waste plastics, which has a large calorific value, with a thermocouple, and is a technology with a different concept from the prior art documents.In addition, the method of using water vapor to exhaust air present in the screw heating part, to make the temperature of the screw heating part uniform, to increase the temperature rise rate, to isolate it from the outside air, and to exhaust pyrolysis residue from the tip of the screw is an original method not found in the prior art documents.

JP 2001-220590 A JP 2002-181320 A JP 2011-67800 A JP 2019-127578 A Patent Publication No. 3077802 Republished WO2004/092303

The problem that the present invention aims to solve is to provide a compact device that can directly pyrolyze and gasify used waste plastics containing different types of plastics or foreign matter, without going through processes such as analysis, blending adjustment, molding, etc., and can burn the resulting waste plastics while controlling the temperature of the dry distillation gas, and can recover valuable metals without oxidizing them.

The present invention has been made to solve the above problems, and is a waste plastic gasification and combustion device that includes a hopper, a preheating burner, a combustion chamber, a screw cylinder that penetrates the combustion chamber and has a screw inside, and an exhaust pipe that can be adjusted to open or close, and the carbonization gas that is vaporized from the heated part of the screw cylinder in an oxygen-free atmosphere while blocking air with water vapor is introduced into the connected carbonization gas pipe. The carbonization gas temperature is controlled to heat, melt, gasify, and combust waste plastics, and the pyrolysis residue is discharged from the tip of the screw cylinder.

In this gasification combustion device, the combustion chamber temperature is preheated to a predetermined temperature by a preheating burner, then the screw motor is rotated to supply waste plastic from a hopper, and while supplying steam into the dry distillation gas pipe connected to the screw cylinder heating section to block air, the combustion chamber temperature is preheated by the preheating burner until it reaches the thermal decomposition temperature (gasification temperature) of the waste plastic. After that, when the waste plastic decomposition gas (dry distillation gas) starts to burn in the combustion chamber, the preheating burner is stopped, and thereafter, the dry distillation gas temperature is controlled by adjusting the rotation speed of the screw motor, the opening and closing degree of the damper of the main exhaust pipe and the damper of the auxiliary exhaust pipe, the amount of combustion air, and the amount of cooling air for the screw heating section, to melt the waste plastic in the heating section inside the screw cylinder, and the dry distillation gas heated and melted in an oxygen-free environment is mixed with air at the outlet of the dry distillation gas pipe, and the mixed gas is completely combusted.

The device of the present invention can be effectively used to process not only used waste plastics, but also new plastics, mixtures of new plastics and used waste plastics, composite materials with non-combustible materials such as metals, embrittled plastic products caused by natural deterioration such as washed up on the coast, etc. In addition, since the device is compact, it is also suitable for on-site processing such as on the coast, riverbanks, event venues, plastic molding factories, etc. In such cases, it becomes unnecessary to transport the waste plastics to the processing plant, which can further save energy and reduce carbon dioxide emissions.

In the treatment of chlorine-containing plastics such as polyvinyl chloride and polyvinylidene chloride, there is little risk of dioxin generation due to oxygen-free, high-temperature pyrolysis. However, in order to prevent dioxin generation during the temperature drop of the combustion exhaust gas, it is effective to provide an alkaline liquid scrubber for rapid cooling and chlorine absorption.

Furthermore, the combustion heat generated by the device of the present invention can be utilized for a variety of applications, such as small-scale thermal power generation and hot air drying.

It should be noted that the description of the first embodiment is merely an example of a basic embodiment, and it is of course possible to modify and implement the embodiment in accordance with the actual situation.

The waste plastic gasification and combustion apparatus of the present invention is a compact device that can directly pyrolyze and gasify used waste plastics containing different types of plastics or foreign matter by controlling the temperature of the dry distillation gas, without performing analysis, cleaning, sorting, blending, etc.

1 is a structural schematic diagram of one embodiment of a waste plastic continuous gasification and combustion device according to the present invention. FIG. FIG. 2 is a schematic diagram showing a state in which a preheating burner is used in the waste plastic continuous gasification and combustion apparatus of FIG. FIG. 2 is a schematic diagram of the combustion state of plastic pyrolysis gas in the waste plastic continuous gasification and combustion apparatus of FIG. 1 and its control system. FIG. 2 is a schematic perspective view of the external appearance of the waste plastic continuous gasification and combustion apparatus of FIG. 1.

An embodiment of the continuous waste plastic gasification and combustion apparatus according to the present invention will be described with reference to the drawings. The following description is merely one embodiment of the present invention, and in practice, the present invention can be implemented in various applications and modified forms.

The configuration of the device is as follows.
The structure of the device of the present invention is as shown in FIG. 1. The waste plastic gasification and combustion device of the present invention is composed of a hopper 4, a preheating burner 11, a combustion chamber 3a, a screw cylinder 2b having a screw 2c inside and installed so as to penetrate the combustion chamber 3a, a main exhaust pipe 5 and a sub-exhaust pipe 6 equipped with dampers 5a and 6a whose opening and closing degree can be adjusted, a residue discharge pipe 2e, a steam pipe 8a which supplies steam to the inlet of the dry distillation gas pipe connected to the heating part 2g of the screw cylinder 2b, and cooling water pipes 10a and 10b provided on both sides of the outside of the heating part 2g of the screw 2c.
The hopper 4 is a hopper for supplying waste plastic to be treated. Not only waste plastic, but also new plastic and a mixture of new plastic and waste plastic can be treated.
The screw 2c sends the plastic supplied from the supply port to the heating portion 2g of the screw cylinder 2b, where the supplied plastic is melted and thermally decomposed.
As shown in Fig. 2, the preheating burner 11 of the apparatus of the present invention preheats and thermally decomposes the plastics sent by the screw 2c to the heating section 2g in the screw cylinder 2b when the apparatus starts to operate, and is stopped when thermal decomposition becomes steady. Once the thermal decomposition of the plastics becomes steady, the preheating burner 11 is no longer used and may be removed. In this case, the preheating burner insertion port 11a after the preheating burner 11 is removed is blocked with a blocking material 11b such as a firebrick. This state is shown in Fig. 3.
As shown in Fig. 3, the carbonization gas generated by the thermal decomposition of plastics in the heating portion 2g in the screw cylinder 2b is combusted at the outlet of the carbonization gas pipe 3 in the combustion chamber 3a together with air supplied from the combustion air pipe 7. The combustion exhaust gas generated in the combustion chamber 3a is discharged from the main exhaust pipe 5 and the sub-exhaust pipe 6.
Steam is supplied from a steam pipe 8a to the inlet of the carbonization gas pipe connected to the screw heating part 2g in the screw cylinder 2b. This steam expels air from the screw heating part, blocks the outside air, and has the effect of making the temperature of the screw heating part 2g uniform and increasing the temperature rise rate.
Moreover, the steam supplied from the steam pipe 8b at the tip has the function of facilitating the discharge of the thermal decomposition residue and also blocks the outside air.
The steam used in the steam pipes 8a and 8b can also be produced in an energy-saving manner by utilizing the combustion heat generated by the dry distillation gas.
Residues such as foreign matter that have not been thermally decomposed in the screw cylinder 2b are discharged from a residue discharge pipe 2e.
As shown in FIG. 2, the temperature of the carbonization gas is detected by a thermocouple 9 while the opening and closing degree of the damper 5a of the main exhaust pipe 5 and the damper 6a of the auxiliary exhaust pipe 6 and the rotation speed of the screw motor 2a are adjusted by the respective control motors 13a, 13b, 13c, 13d, and 13e to control the carbonization gas temperature to a constant value by a PLC control 13f, so there is no need to adjust the calorific value of the plastic being supplied.
The external appearance of the device of the present invention is compact, as shown in FIG.

The operation of the device is as follows.
In the waste plastic continuous gasification and combustion device 1 of the present invention, waste plastic is supplied from the hopper 4 into the screw cylinder 2b by rotating the screw motor 2a, and while supplying steam from the steam pipe 8a to the inlet of the dry distillation gas pipe connected to the screw cylinder 2b to block air, the combustion chamber 3a is preheated using the preheating burner 11 until the temperature reaches the thermal decomposition temperature (gasification temperature) of the waste plastic.
Thereafter, when the carbonization gas generated by the thermal decomposition of the waste plastics in the combustion chamber 3a starts to burn, the preheating burner 11 is stopped, and thereafter, while the temperature of the carbonization gas is detected by the thermocouple 9, the opening and closing degree of the damper 5a of the main exhaust pipe 5 and the damper 6a of the sub-exhaust pipe 6 and the rotation speed of the screw motor 2a are adjusted by the respective control motors 13a, 13b, 13c, 13d, and 13e to control the carbonization gas temperature and to control a good combustion state in the combustion chamber 3a. After the preheating burner 11 is stopped, it may be removed to prevent damage due to heat, but it may also be left installed.
In the device of the present invention, once operation has stabilized, the materials to be treated are heated, melted, and pyrolyzed using the combustion heat of the distillation gas generated by the thermal decomposition of waste plastics, making it possible to operate in an energy independent manner and economical.

A specific example of the operation is as follows.
Used polypropylene food trays partially laminated with aluminum wheels and contaminated with food were crushed and fed into the hopper 4 of the waste plastic continuous gasification and combustion apparatus having the structure shown in FIG.
The damper 5a of the main exhaust pipe 5 of the waste plastic continuous gasification and combustion apparatus was set to a closed state, and the damper 6a of the sub-exhaust pipe 6 was set to an open state.
Next, the preheating burner 11 was attached to the preheating burner insertion port 11a, and the preheating burner 11 was ignited. This state is shown diagrammatically in FIG.
Thereafter, the screw motor 2a was started, and when the raw material to be processed reached approximately 1/3 of the heated portion 2g in the screw cylinder 2b, the screw motor 2a was temporarily stopped.
Thereafter, when the temperature indicated by the thermocouple 9 exceeded 100° C., circulation of cooling water was started through the screw cooling water pipes 10 a and 10 b.
Next, when the temperature indicated by the thermocouple 9 exceeded 250° C., a small amount of steam was discharged from the steam pipes 8 a and 8 b and a small amount of combustion air was discharged from the combustion air pipe 7 .
Thereafter, when a flame started to emerge from the dry distillation gas pipe 3, the amount of air in the combustion air pipe 7 was adjusted to obtain a good combustion state.
Thereafter, the flame of the preheating burner 11 was gradually reduced in size in accordance with the flame amount of the dry distillation gas pipe 3. Thereafter, when the temperature indicated by the thermocouple 9 reached 470° C., the screw motor 2a was started.
Thereafter, when the temperature indicated by the thermocouple 9 reached 540° C., the preheating burner 11 was removed, and a firebrick as a preheating burner insertion port clogging material 11b was inserted into the preheating burner insertion port 11a. This state is shown diagrammatically in FIG. 3.
Next, the main damper 5a was opened when the temperature indicated by the thermocouple 9 was 570°C, and the opening and closing degree was adjusted so that the temperature indicated by the thermocouple 9 was 580°C or less.
Furthermore, if the temperature indicated by the thermocouple 9 exceeded 580° C., the secondary damper 6 a was closed to discharge cooling air.
Although almost no pyrolysis residue was generated, the gate valve 2f of the residue discharge pipe 2e was opened at an appropriate timing to discharge the residue. At this time, steam was discharged from the tip side steam pipe 8b in order to shut off the outside air and forcibly discharge the residue.
The aluminum foil was present in the discharged residue without being oxidized.

The device of the present invention is a simple device that performs thermal recycling of plastics and can be used in many industrial applications that require a heat source, such as boilers, air conditioners, etc.
Furthermore, in the processing of home appliances, electronic devices, electronic circuit boards, etc., rare metals and the like are recovered as pyrolysis residue without being oxidized, so they can also be used to recover valuable resources.

1 Furnace body 1a Shelf 2a Screw motor 2b Screw cylinder 2c Screw 2d Cylinder cooling pipe 2e Residue discharge pipe 2f Gate valve 2g Screw heating part 3 Dry distillation gas pipe 3a Combustion chamber 4 Hopper 5 Main exhaust pipe 5a Main damper 6 Auxiliary exhaust pipe 6a Auxiliary damper 7 Combustion air pipe 8a Supply side steam pipe 8b Tip side steam pipe 8b Electric couple 9 Hopper side cooling water pipe 10a Screw tip side cooling water pipe 11 Preheating burner 11a Preheating burner insertion port 11b Preheating burner insertion port plug 12 Screw heating part cooling air pipe 13a Main damper opening degree control motor 13b Auxiliary damper opening degree control motor 13c Screw rotation speed control inverter 13d Screw temperature control cooling air inverter 13e Combustion flame control combustion air inverter

Claims (5)

The device is equipped with a hopper for supplying waste plastic materials, a preheating burner, a combustion chamber, a screw cylinder with a screw inside that is installed so as to penetrate the combustion chamber, a distillation gas pipe that supplies the distillation gas generated when the waste plastic is thermally decomposed inside the screw cylinder heated by the heat of the combustion chamber to the combustion chamber, a combustion air pipe that supplies combustion air to the distillation gas pipe, a steam pipe that supplies steam to the distillation gas pipe inlet connected to the screw cylinder heating section, dampers whose opening and closing degree can be adjusted that are installed on each of the main exhaust pipe and auxiliary exhaust pipe, and a residue discharge pipe at the tip of the screw. 2. A continuous waste plastic gasification and combustion device as described in claim 1, in which the temperature of the screw heating part is controlled by adjusting the opening and closing degree of the damper of the main exhaust pipe and the damper of the sub-exhaust pipe, the rotation speed of the screw, and the amount of combustion air and the amount of cooling air for the screw heating part using respective control motors while detecting the temperature of the dry distillation gas with a thermocouple. 3. The continuous gasification and combustion apparatus for waste plastics according to claim 1 or 2, which requires an external heat source such as a preheating burner at the start of operation, but enables continuous operation using only the waste plastics without requiring external heat in a steady state. 4. A continuous waste plastic gasification and combustion apparatus according to claims 1, 2 or 3, which processes new plastics, mixtures of new plastics and waste plastics, and mixtures or composite materials of plastics and metals, glass fibers, carbon fibers, cellulose or other heterogeneous materials. 5. A continuous gasification system for waste plastics as described in claims 1, 2, 3 and 4, in which the temperature of the combustion chamber is preheated to a predetermined temperature with a preheating burner, then the screw is rotated to supply waste plastics from a hopper into the inside of the screw cylinder, and water vapor is supplied to the inlet of the dry distillation gas pipe connected to the heating section of the screw cylinder to block air. After preheating with the preheating burner, when the combustion of the pyrolysis gas of the waste plastics begins in the combustion chamber, the preheating burner is stopped, and thereafter, without requiring heat from outside, the temperature of the dry distillation gas is detected with a thermocouple, and the opening and closing degree of the damper of the main exhaust pipe and the damper of the auxiliary exhaust pipe, the rotation speed of the screw, the amount of combustion air, and the amount of cooling air for the heating part of the screw are adjusted with the respective control motors to continuously maintain a stable combustion state.