CN110014580B

CN110014580B - Method and device for cleaning and recycling waste filter screen of plastic extruder

Info

Publication number: CN110014580B
Application number: CN201810959338.8A
Authority: CN
Inventors: 李必弘; 梅建国; 沈振邦
Original assignee: Hubei Kepuda Photoelectric Material Co ltd
Current assignee: Hubei Kepuda Photoelectric Material Co ltd
Priority date: 2018-08-22
Filing date: 2018-08-22
Publication date: 2021-08-31
Anticipated expiration: 2038-08-22
Also published as: CN110014580A

Abstract

The invention particularly relates to a method and a device for cleaning and recycling a waste filter screen of a plastic extruder. The method comprises the following steps: bundling a plurality of filter screens to be treated; placing the bundled filter screen in a closed cooking furnace, keeping the temperature at 350-500 ℃ under the action of a cracking catalyst, and cooking at high temperature for 16-20 h; cooling the cracked gas by cooling water at the temperature of 60-70 ℃, collecting the cooled liquid to obtain low-molecular polyethylene wax oil, and introducing the cooled cracked gas into a combustion furnace below a cooking furnace for combustion and utilization; and after the cooking furnace is cooled, the filter screen is taken out, cleaned and aired, and then the filter screen can be reused. The invention adopts the technology of combining the filter screen cooking furnace and the tail gas combustion utilization, and forms a stable recovery processing method for cleaning the filter screen by repeatedly searching the working conditions.

Description

Method and device for cleaning and recycling waste filter screen of plastic extruder

Technical Field

The invention relates to the field of plastic processing technology transformation, in particular to a method and a device for cleaning and recycling a waste filter screen of a plastic extruder.

Background

With the rapid development of the Chinese recycling economy industry, extrusion machinery required by plastic recycling processing is widely applied, an extruder using waste recycled plastics as a raw material is adopted, a stainless steel filter screen is required to be used on the extruder device, and the using amount of the filter screen is in direct proportion to impurities of the recycled plastics, so that the stainless steel filter screen replaced in the processing process is accumulated and more, most of enterprises at present are to recycle the filter screen, the generally adopted recycling scheme is to burn the filter screen in a furnace or heat (introduce air) to crack the waste plastics on the filter screen, the methods can generate larger smell and secondary pollution to a certain extent in the recycling process, and the filter screen recycled after being treated by the method can be recycled for 3-4 times due to high-temperature oxidation, and the service life is shorter. The technical center of the company obtains a new method and a new device for cleaning and recycling the waste filter screen of the plastic extruder through a plurality of tests and groping.

Disclosure of Invention

The invention aims to provide a novel method and a device for cleaning and recycling waste filter screens of a plastic extruder.

The technical purpose is realized by the following technical scheme:

the invention provides a method for cleaning and recycling a waste filter screen of a plastic extruder, which comprises the following steps:

(1) bundling a plurality of filter screens to be treated;

(2) placing the bundled filter screen in the step (1) in a closed cooking furnace, keeping the temperature at 350-500 ℃ under the action of a cracking catalyst, and cooking at high temperature for 16-20 h;

(3) cooling the cracked gas by cooling water at the temperature of 60-70 ℃, collecting the cooled liquid to obtain low-molecular polyethylene wax oil, and introducing the cooled cracked gas into a combustion furnace below a cooking furnace for combustion and utilization;

(4) and after the cooking furnace is cooled for more than 30 hours, taking out the filter screen, and cleaning and airing the filter screen for reuse.

Preferably, the filter screens in step (1) are bundled by a hydraulic bundling machine, wherein each bundle is 75-80 filter screens, and each bundle is 420-450mm high.

Wherein the cracking catalyst is an organic high molecular compound polyolefin.

Preferably, the cracking catalyst is paved at the bottom of the cooking stove, and the paving thickness is 40-60 mm.

Preferably, the cracked gas is cooled twice, the temperature of the cooling water in the first cooling is 60-70 ℃, and the temperature of the cooling water in the second cooling is 30-40 ℃.

The invention also provides a device used for carrying out recovery processing of cleaning a filter screen of the plastic extruder by adopting the method, the device comprises a hydraulic binding machine, a cooking stove and a condensing device, the hydraulic binding machine is fixedly arranged in front of the cooking stove and the condensing device, a burner for supplying heat to the cooking stove is arranged below the cooking stove, a heat-insulating layer is arranged outside the cooking stove, a smoke channel is arranged between the cooking stove and the heat-insulating layer, a threaded ring is arranged in the smoke channel, a smoke outlet is arranged above the smoke channel, smoke is upwards discharged along the thread of the threaded ring and finally discharged from the smoke outlet, and the height of a smoke evacuation pipe is more than 15 m; be provided with feed inlet and gas outlet on the boiling furnace, what the feed inlet can be opened sets up with boiling furnace body is sealed (specifically for boiling furnace body top is through flange seal setting and can open as the feed inlet), the gas outlet sets up the top at the boiling furnace barrel, gas outlet and condensing equipment intercommunication, condensing equipment includes the condenser and connects the oil tank, connect the oil tank to be connected with condensing equipment's gas outlet, it is provided with the gas outlet to connect the oil tank top, the gas outlet that connects the oil tank is connected with the induced air pump, the gas outlet of induced air pump directly burns remaining gas through gas pipeline and combustor intercommunication.

Preferably, the number of the condensing devices is two, the condensing devices comprise a first condensing device and a second condensing device, and an air outlet of the first condensing device is communicated with the second condensing device through a pipeline.

Preferably, a pipeline of the condensing device connected with the air outlet of the cooking stove is provided with a thermometer and a pressure gauge.

Preferably, the condenser comprises a closed shell, a condensate pipe is arranged in the middle of the shell, gas buffer spaces are arranged above and below the shell, the gas buffer space above the shell is communicated with a gas outlet of the cooking stove, and the gas buffer space below the shell is communicated with the oil receiving tank.

During production, the catalyst is spread at the bottom of the cooking furnace, then the bundled filter screens are placed on a bracket in the cooking furnace (18000 filter screens are placed in each furnace), natural gas is adopted for combustion heat supply, generally, after the natural gas is used for combustion heat supply for 7-8 hours, the natural gas can be completely used for combustion heat supply for 9-12 hours by virtue of combustible gases such as alkane and the like generated after cracking, the temperature in the furnace body is kept at 350-500 ℃ in the cracking process, the gas temperature at a gas outlet is controlled at 200-300 ℃, and the combustion furnace is stoppedStopping heating and cracking after stopping combustion. The device can process 18000 filter screens each time, and consumes about 190-³The power consumption is about 120KWh, the water consumption is very small, the operation is safe, and the energy consumption is low. The device operates for 3 days (72 hours) in a period, wherein the charging is carried out for 8-9 hours, the heating operation of the boiling furnace is carried out for 16-20 hours, the natural cooling is carried out for 33-34 hours, and the screen unloading and furnace cleaning are carried out for 10 hours. The operation of washing, drying, collecting, bundling and carrying is performed alternately without affecting the operation period.

The polyethylene and impurities adhered to the filter screen are gasified and cracked after being heated and dry distilled in a closed space, high-temperature cracking products are converted into low-molecular petroleum gas and low-molecular polyethylene wax oil, and the low-molecular petroleum gas is introduced into the furnace to be combusted to replace natural gas energy, so that energy consumption is saved; the low molecular polyethylene wax oil is used as an auxiliary material for production, namely a lubricant, and can be recycled, so that new pollution can not be generated. The invention can recycle 180 ten thousand filter screens (basically matched with 6000 filter screens per day) in a year, the filter screens can be reused after being recycled, the direct cost can be saved by more than 80 ten thousand yuan per year, 200 tons of wastes are reduced, the environmental protection problem that a large amount of waste filter screens cannot be treated is solved, and the invention has very important significance for increasing income and reducing expenditure, environmental protection, energy saving and emission reduction and long-term development of enterprises.

The filter screen can be recycled for 7-8 times, which is increased by 3-4 times compared with the traditional direct oxidation combustion, and the expenditure cost of the stainless steel filter screen is saved by more than half compared with the traditional filter screen; the invention is safe, energy-saving and environment-friendly, solves the economic and technical problems that the waste filter screen of an enterprise can not be recycled, meets the requirements of environmental protection laws and regulations and the normal production and operation requirements of the enterprise, and has considerable economic and environment-friendly benefits.

Drawings

FIG. 1 is a schematic flow diagram of the present invention;

FIG. 2 is a schematic diagram of the structure of the apparatus of the present invention;

FIG. 3 is a schematic structural diagram of a condenser;

in the figure, 1 a burner, 2 a cooking stove, 3 a heat-insulating layer, 4 a first condensing device, 5 a second condensing device, 6 a condenser, 7 an oil receiving tank, 8 an induced draft pump, 9 a gas pipeline and 10 a pipeline.

Detailed Description

For the purpose of promoting a clear understanding of the invention, reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings:

as shown in FIG. 1, the method for cleaning and recycling the waste filter screen of the plastic extruder provided by the invention comprises the following steps:

(1) bundling a plurality of filter screens to be treated;

(2) placing the bundled filter screen in the step (1) in a closed cooking furnace, and after a temperature rise stage (generally about 2 hours), keeping the temperature at 350-;

(4) and after the cooking furnace is cooled, the filter screen is taken out, cleaned and aired, and then the filter screen can be reused.

The method fully utilizes the chemical and physical characteristics and the cracking mechanism of the polyethylene plastic, heats, dissolves and cracks the residual polyethylene plastic on the filter screen under a closed condition, ensures that the cracked substance is low molecular olefin or alkane, avoids generating odor, toxic and harmful gases such as epoxy group, aromatic hydrocarbon, dioxin and the like through chemical reaction with oxygen in the air, utilizes the combustion energy of the cracked gas, saves resources and has a more environment-friendly treatment mode.

In the above processing steps, the filter screens in step (1) are bundled by a hydraulic bundling machine, each bundle of 75-80 filter screens is needed, the bundling pressure is 0.3-0.5MPa, wherein 0.4MPa is preferred, and at this time, each bundle is 420-450mm high. The bundling is to ensure that the bundling is tight, and also ensure that the amount of each bundle is not too much, namely the bundles are stacked too high, when the bundling is not tight enough, the cracked product is cooled to be polyethylene solid plastic (the purpose of tight bundling is to increase the energy of plastic falling off and increase the amount of cracked plastic); when the amount of binding per bundle is too large, the lysis treatment may be incomplete.

In the present invention, the cracking catalyst used is an organic high molecular compound polyolefin. In particular, in use, the cracking catalyst is paved on the bottom of the cooking stove, and the paving thickness is 40-60mm, wherein 50mm is preferred.

In the invention, the cracked gas is cooled twice, the temperature of cooling water in the first cooling is kept at 60-70 ℃, wherein the temperature can be preferably 65 ℃, the temperature of cooling water in the second cooling is 30-40 ℃, and preferably 35 ℃, and the recovery effect of the polyethylene paraffin is better after twice cooling. The applicant obtains the results of multiple experiments, and through two-stage cooling, when the first-stage cooling temperature is controlled to be 60-70 ℃, and the second-stage cooling temperature is controlled to be 30-40 ℃, the condensing device is not easy to block, the recovery rate of the polyethylene paraffin can reach 60%, and compared with the adoption of one-stage cooling, the recovery rate is respectively improved by 5%, 3% and 2% when the cooling temperatures are respectively controlled to be 60 ℃, 70 ℃ and 80 ℃.

In the present invention, 1 group of meshes (4) weighed 415g, the replaced meshes weighed 485-495g, and each group averaged 75g of waste plastics and impurities, of which about 20g was aluminum flake impurities and about 55g of pure waste plastics per group.

About 247500g (247.5kg) of waste plastics per furnace after 4500 sets of filter screens are processed, about 150kg of polyethylene wax oil is recovered per furnace by cracking, and the rest about 100kg of waste plastics become cracking gas to be burned again.

According to the data of 1kg of polyethylene combustion heat value 46000KJ, the coefficient is reduced to 1.57 of standard coal, the heat value of 100kg of waste plastics is recycled in each furnace, the standard coal is saved by 157kg, the standard coal is saved by 15.7 tons every year according to the estimation of 100 furnaces, and the secondary pollution caused by plastic incineration is reduced. In addition, the low molecular polyethylene wax oil is recycled by about 150 g/100 =15 tons every year, and most of the low molecular polyethylene wax oil can be used as a lubricant for processing reclaimed plastics or further processed into mineral oil to be continuously used in the recycling economy industry.

Comparative test

The treatment method is adopted to treat six groups of filter screens in the following table, except that the number and the height of each bundle of filter screens are different, the other groups of filter screens are treated according to an optimal mode, each furnace is used for treating 4500 groups of filter screens, each group of filter screens comprises 4 filter screens, and the total amount of polyethylene plastics stained on the filter screens in each furnace is = the total mass of the filter screens before treatment-the total mass of the filter screens after cleaning treatment; the amount of the polyethylene wax oil obtained after cracking is the total mass of the polyethylene wax oil received by the two oil receiving tanks; the recovery rate = amount of polyethylene wax oil obtained after cracking/amount of polyethylene plastic stained on the filter screen; the results of the treatment are shown in the table below:

TABLE-amount of polyethylene wax oil obtained in the different treatments

	Number of filter screens per bundle (sheet)	The pressure during binding is (MPa)	The total mass (Kg) of polyethylene plastic stained on the filter screen	Total mass (Kg) of polyethylene wax oil obtained after cracking	Recovery (%)
						Experiment set 1	72	0.3	244.3	130	53.2
Experiment group two	72	0.4	243.9	134.9	55.3
						Experiment group III	72	0.5	248.6	130.8	52.6
Experiment group four	80	0.3	245.6	147.9	60.2
						Experiment group five	80	0.4	241.3	148.3	61.3
Experimental group six	80	0.5	249.2	150.8	60.5
						Seven experimental group	92	0.3	247.3	140.2	56.7
Experimental group eight	92	0.4	242.5	129	53.2
						Nine experimental groups	92	0.5	244.1	132.1	54.1

As can be seen from the table above, only by ensuring the proper binding degree and the binding amount of each bundle, the environment-friendly recycling treatment of the polyethylene plastics can be realized, and the highest recycling efficiency can be ensured. Particularly, when the polyethylene plastic is subjected to high temperature, external force is needed for separating from the filter screen surface, the external force is heat, and polyethylene molecules are degraded and cracked into low-molecular compound gas in the process of separating from the filter screen surface.

The invention also provides a device used in the recovery treatment of cleaning the filter screen of the plastic extruder by using the method, as shown in figure 2, the device comprises a hydraulic binding machine, a cooking stove and a condensing device, the hydraulic binding machine is fixedly arranged in front of the cooking stove 2 and the condensing device, a burner 1 for supplying heat to the cooking stove 2 is arranged below the cooking stove 2, a heat-insulating layer 3 is arranged outside the cooking stove 2, a smoke channel is arranged between the cooking stove 2 and the heat-insulating layer 3, a threaded ring (not shown in the figure) is arranged in the smoke channel, a smoke outlet is arranged above the smoke channel, smoke upwards flows along the thread of the threaded ring and is finally discharged from the smoke outlet, the retention time of the smoke in the smoke channel is prolonged, the heating effect is good, and the heat utilization rate is high; the cooking stove 2 is provided with a feed inlet and an air outlet, the feed inlet can be opened and is hermetically arranged with the cooking stove 2 body, namely the feed inlet can be opened to place and take out the filter screen, and when the feed inlet is closed, the feed inlet and the cooking stove 2 have good sealing performance; the gas outlet sets up in the top of boiling furnace 2, and the gas outlet communicates with condensing equipment, and condensing equipment includes condenser 6 and connects oil tank 7, connects oil tank 7 top to be provided with the gas outlet, connects the gas outlet and the induced air pump 8 of oil tank 7 to be connected, and the gas outlet of induced air pump 8 passes through gas pipeline 9 and combustor intercommunication.

In this embodiment, the number of the condensing devices is two, and the condensing devices include a first condensing device 4 and a second condensing device 5, and the gas outlets of the first condensing device 4 and the second condensing device 5 are communicated through a pipeline, that is, the cracked gas is cooled in two stages.

In this embodiment, a thermometer and a pressure gauge are provided on a pipe connecting the condensing unit and the outlet of the cooking oven 2. In the practical application process, the size of the induced air pump can be adjusted according to data displayed by the thermometer and the pressure gauge, on one hand, the arrangement of the induced air pump can ensure that cracked gas is discharged in time and the cracking effect is ensured, on the other hand, the effect of stabilizing the pressure in the steaming and boiling furnace can be achieved, particularly, in the practical production application, except for the temperature rise stage, the value of the thermometer is stabilized at 200-300 ℃, and the value of the pressure gauge is less than 0.1 MPa.

In this embodiment, the condenser includes inclosed casing, and the centre of casing is provided with the condensate pipe, and the inside top of casing and below are gaseous buffering space, and the gaseous buffering space of top communicates with the gas outlet of cooking stove, and the gaseous buffering space of below communicates with and connects the oil tank. In practical application, the cracked gas can be increased instantly, and the buffer space is arranged to disperse uniformly and avoid poor pressure by using the cracked gas.

The process can generate net washing wastewater, waste gas, ash and polyethylene wax in the processing process.

a) Discharging the wastewater into a sedimentation tank for sedimentation treatment and then discharging;

b) the main fuel of the waste gas is natural gas and cracking waste gas in the furnace, the cracking gas is burnt at high temperature by oxygen enrichment of a blower at the bottom of the furnace, and the burning waste gas is mainly CO₂After being collected, the mixture is lifted to be discharged;

c) 25-30kg of ash slag is generated after each furnace is operated, the main components of the ash slag are carbon ash and aluminum ash, the ash slag is similar to soil, the RoHS limit is qualified through the detection of SGS company, the ash slag belongs to general solid waste, and the ash slag is collected and delivered to a small pool for sanitation disposal.

d) The byproduct polyethylene wax is returned to the production system and is recycled as a plastic lubricant.

According to the prediction of 18000 pieces/time of recovered filter screen, the required energy consumption and material consumption is about 0.06 yuan/piece, the personnel wages are about 0.23 yuan/piece, the equipment depreciation and maintenance and the like are calculated according to 0.1 yuan/piece, the total cost of 1 piece of recovery treatment is 0.39 yuan, the annual recovery utilization of 180 ten thousand pieces is calculated, and the annual running total cost of the invention is 70.2 ten thousand yuan. If a disposable filter screen is adopted, the cost is more than 190 ten thousand yuan, so that the following steps are required: the direct investment of the project is removed, and the operation benefit of the project is that the direct economic benefit of saving material consumption and spending more than 80 ten thousand yuan (190-38-70.2 =81.8 ten thousand yuan) is very considerable.

It should be understood that the above description is only a preferred embodiment of the present invention and that any modifications and equivalents within the spirit and scope of the present invention are included in the scope of the appended claims.

Claims

1. The method for cleaning and recovering the waste filter screen of the plastic extruder is characterized by comprising the following steps:

(1) bundling a plurality of filter screens to be treated together, namely bundling the filter screens with residual polyethylene plastics by a hydraulic bundling machine, wherein each bundle of the filter screens is 75-80, and each bundle of the filter screens is 420-450mm high;

(2) spreading the cracking catalyst on the bottom of a cooking furnace, wherein the spreading thickness is 40-60mm, placing the bundled filter screen in the step (1) in a closed cooking furnace, keeping the temperature at 350 ℃ and 500 ℃ under the action of the cracking catalyst, and cooking at high temperature for 16-20h, wherein the cracking catalyst is an organic high molecular compound polyolefin;

(3) cooling the cracked gas twice, wherein the temperature of cooling water in the first cooling is 60-70 ℃, the temperature of cooling water in the second cooling is 30-40 ℃, collecting the cooled liquid to obtain low-molecular polyethylene wax oil, and introducing the cooled cracked gas into a combustion furnace below a cooking furnace for combustion utilization;

and after the cooking furnace is cooled, the filter screen is taken out, cleaned and aired, and then the filter screen can be reused.

2. The device for cleaning and recycling the waste filter screen of the plastic extruder according to the method of claim 1, which comprises a hydraulic binding machine, a cooking stove and a condensing device, wherein the hydraulic binding machine is fixedly arranged in front of the cooking stove and the condensing device, a burner for supplying heat to the cooking stove is arranged below the cooking stove, an insulating layer is arranged outside the cooking stove, a smoke channel is arranged between the cooking stove and the insulating layer, a threaded ring is arranged in the smoke channel, a smoke outlet is arranged above the smoke channel, and smoke upwards flows along the thread of the threaded ring and finally is discharged from the smoke outlet; be provided with feed inlet and gas outlet on the boiling furnace, what the feed inlet can be opened sets up with boiling furnace body is sealed, and the gas outlet setting is in the top of boiling furnace, gas outlet and condensing equipment intercommunication, and condensing equipment includes the condenser and connects the oil tank, connects the oil tank to be connected with condensing equipment's gas outlet, connects the oil tank top to be provided with the gas outlet, connects the gas outlet and the induced air pump of oil tank to be connected, and the gas outlet of induced air pump passes through gas pipeline and combustor intercommunication.

3. The device for cleaning and recycling the waste filter screen of the plastic extruder as claimed in claim 2, wherein the number of the condensing devices is two, and the two condensing devices comprise a first condensing device and a second condensing device, and the air outlet of the first condensing device is communicated with the second condensing device through a pipeline.

4. The apparatus for cleaning and recycling the waste filter screen of the plastic extruder as claimed in claim 2, wherein a temperature gauge and a pressure gauge are provided on a pipe connecting the condensing unit and the gas outlet of the cooking oven.

5. The device for cleaning and recycling the waste filter screen of the plastic extruder as claimed in claim 2, wherein the condenser comprises a closed shell, a condensate pipe is arranged in the middle of the shell, gas buffer spaces are arranged above and below the inside of the shell, the gas buffer space above is communicated with the gas outlet of the cooking furnace, and the gas buffer space below is communicated with the oil receiving tank.