CN112760119A

CN112760119A - Waste plastic radiation thermal cracking process and system

Info

Publication number: CN112760119A
Application number: CN202110018521.XA
Authority: CN
Inventors: 李明泽
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-01-07
Filing date: 2021-01-07
Publication date: 2021-05-07

Abstract

The disclosure relates to the technical field of plastic cracking, and particularly provides a waste plastic radiation thermal cracking process and system. The process comprises a first-stage cracking and a second-stage cracking, wherein waste plastics are melted in the first-stage cracking and cracked into light oil, cracking gas and slag in the second-stage cracking, and the slag enters the first-stage cracking to be used as a waste plastics melting medium to be cooperatively melted with the waste plastics; the cracked gas generated by the second stage cracking is used as fuel for storage and later use, and the light oil is extracted and recovered. The cracking equipment mainly takes radiation cracking as a main principle, the heating pipe carries out radiation heating decomposition on the waste plastics, and high molecular weight organic matters are further decomposed into combustible gas with high combustion value after passing through the 800 ℃ high-temperature pipe, so that the gas yield is high. The invention solves a series of problems of high cost, environmental pollution and the like in the prior art that the waste plastic treatment is mainly a physical regeneration recovery, landfill and incineration power generation method.

Description

Waste plastic radiation thermal cracking process and system

Technical Field

The disclosure relates to the technical field of plastic cracking, and particularly provides a waste plastic radiation thermal cracking process and system.

Background

The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.

At present, with the development of industry, plastics are utilized more and more, so that the recycling of waste plastics becomes a big problem, and at present, the recycling of waste plastics mainly comprises a physical regeneration recycling method, landfill, incineration power generation and the like.

However, the physical recycling method has a high quality requirement for plastics, cannot contain impurities, and requires a large amount of pretreatment such as sorting, and thus the application range thereof is limited. In the case of landfill, limited cultivated land is occupied, and land resources are wasted seriously, and the landfill becomes a soft foundation and is difficult to reuse in the future. The incineration treatment utilizes macromolecular materials with high heat value, such as plastics, and has the characteristic of large heat productivity. However, burning waste plastics is easy to coke, has high requirements for devices such as a burning furnace, needs to establish a whole set of related supporting devices, and has very high cost.

Therefore, the inventor observes and analyzes the waste plastic treatment method in the prior art, and finds that the physical regeneration recovery, landfill and incineration power generation methods cannot well solve the problem of waste plastic recovery, and particularly have the problems of high cost, environmental pollution and the like.

Disclosure of Invention

The method aims to solve a series of problems of high cost, environmental pollution and the like in the prior art that the waste plastic treatment is mainly a physical regeneration recovery, landfill and incineration power generation method. The present disclosure uses a novel approach to radiation cracking for harmless treatment of waste plastics. Waste plastics are radiatively cracked into combustible gas with low pollution and high fuel value under proper temperature condition for boiler of factory. This way of recycling waste plastics is an important development in waste plastics processing.

In one or some embodiments of the present disclosure, a waste plastic radiation thermal cracking process is provided, which includes a first stage cracking and a second stage cracking, wherein waste plastics are melted in the first stage cracking and cracked into light oil, cracked gas and slag in the second stage cracking, and the slag enters the first stage cracking to be used as a waste plastic melting medium to be cooperatively melted with the waste plastics; and separating the oil-gas mixture generated by the second-stage cracking, storing the separated cracked gas as fuel for later use, and separating a small amount of water from the separated light oil and then extracting and recovering the separated light oil.

The amorphous radiation cracking process design of the invention mainly takes cracking high-quality combustible gas as a principle, the cracking equipment mainly takes radiation cracking as a main part, the heating pipe carries out radiation heating decomposition on the waste plastic, and simultaneously, high-molecular-weight organic matters are further decomposed into combustible gas with high combustion value after passing through the 800 ℃ high-temperature pipe, and the gas yield is high.

In one or some embodiments of the present disclosure, a system for implementing the above waste plastic radiation thermal cracking method is provided, which comprises a crusher, a mixer, a waste plastic thermal cracker and a dry bin connected in sequence.

One or some of the above technical solutions have the following advantages or beneficial effects:

1) the method has the advantages that the requirements for processing plastics in the prior art are high, only a single type of plastics can be processed, the plastics need to be strictly classified before processing, the requirements of various occasions cannot be met, the use cost is high, and therefore the method is difficult to popularize. The required corollary equipment is few, and the investment is relatively little.

2) The prior art adopts the intermittent feeding mode more, and waste plastic can only once add when handling, and the time of adding plastics each time will wait before the reaction thoroughly after, leads to the treatment effeciency not high to all cool off and reheat at every turn, greatly wasted the energy, in addition can lead to partial cracked gas to escape from the reactor at the time of adding at every turn, cause the pollution to the environment. This results in low reaction efficiency, low throughput, and low practicality. This is disclosed regard the slag charge as the medium, has improved plastics and to the absorbing capacity of heat in the radiation process, and utilizes the high temperature flue gas that the pyrolysis process produced to carry out preliminary preheating to plastics, plastics continuous feed can, and the reaction waste residue continues to utilize as the medium, realizes the complete utilization of plastics. The problems of incomplete reaction and low utilization rate of plastics are solved.

3) In the prior art, plastic is directly placed in a reactor for heating, a carrier is not adopted, so that waste plastic is unevenly heated, the plastic is easily melted and then directly adhered to the wall of the reactor, and the plastic is directly coked and carbonized, so that the cracking efficiency is reduced, the product is changed, the oil yield is low, and the reactor is damaged. The method can prevent the plastic from forming a molten state in the waste plastic thermal cracking machine by using the high-temperature slag as a medium.

4) The process and the system are designed according to the basic principle of thermal cracking and the practical application of waste plastic radiation thermal cracking, the system can recycle various waste plastics without being classified in advance, the recycled products are mainly combustible gas and then liquid hydrocarbons and solid products, and the combustible gas can be directly used as fuel. Waste plastics produced by paper mills consisting of: 42% of Polyethylene (PE), 35% of polyeneine, 18% of polystyrene, 2% of contained chloride and 5% of other components, and due to the fact that oxidative cracking is not carried out, dioxin cannot be generated, and combustible gas is purified and belongs to clean energy.

5) The thermal cracking method is adopted, no catalyst is used, the treatment cost is reduced, and the method is favorable for popularization. There are a number of disadvantages to using a catalyst: 1. most of the catalyst is rare metal or metal compound, and the use cost is high; 2. the catalyst is easy to lose effectiveness, and the catalyst is often rapidly deactivated due to high temperature and high pressure and the generation of certain solid products in the reaction process. This is also a feature of the coke deposition process, resulting in the need to continually add catalyst to maintain catalysis, and some catalysts are themselves expensive, resulting in excessive costs for thermal cracking. 3. During the use of the catalyst, the catalyst is mixed with the products (such as coke, ash, slag and the like) generated by the reaction. It is difficult to separate the catalyst from the product, resulting in the inability to recycle the catalyst. In addition, the mixing of the catalyst is not favorable for the utilization of the residual solid phase. Therefore, the catalytic cracking is too costly to promote and use. Compared with catalytic cracking, the thermal cracking method can reduce the cost and is beneficial to popularization.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the disclosure and, together with the description, serve to explain the disclosure and not to limit the disclosure.

FIG. 1 is a schematic view of a waste plastic radiation thermal cracking system according to example 2.

Wherein: 1. a crusher; 2. a mixer; 3. a waste plastic thermal cracker; 31. high-temperature flue gas; 32. high-temperature slag charge; 33. slag meeting the standard; 34. mixing oil gas; 4. a dry bin; 5. an oil-gas separation device; 51. an oil-water separation device.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

The method aims to solve a series of problems of high cost, environmental pollution and the like in the prior art that the waste plastic treatment is mainly a physical regeneration recovery, landfill and incineration power generation method.

Preferably, the waste plastics are subjected to preliminary sorting prior to the two-stage cracking: the iron wire and stone are sorted out and the waste plastics are crushed into small particles.

Preferably, the small waste plastic particles and slag are mixed and preheated and then subjected to first-stage cracking;

preferably, part of pyrolysis gas generated by pyrolysis is used for mixing and preheating the waste plastic particles and the slag.

Preferably, the first stage cracking comprises the following specific steps: the mixture of waste plastics and slag charge with residual heat is continuously rotated, part of easily cracked plastics are directly thermally cracked into gas, most of other waste plastics are melted,

preferably, the gas generated by the first stage cracking is used for preheating the mixture of the waste plastic granules and the slag charge.

Preferably, the second stage cracking comprises the following specific steps: and (3) performing radiation combustion on the molten plastic after the first-stage cracking, cracking high molecular components in the waste plastic into light oil and combustible gas, carbonizing the residual waste plastic to form slag, and introducing the slag into the first-stage cracking.

Preferably, the process is a continuous feed process.

Preferably, the method also comprises the step of carrying out water-oil separation on the cracked gas and the light oil.

Preferably, a high-temperature flue gas conveying pipeline is arranged between the waste plastic thermal cracking machine and the mixer.

Preferably, a high-temperature slag conveying pipeline is arranged between the waste plastic thermal cracking machine and the mixer.

Preferably, the waste plastic thermal cracking machine is also connected with a separation and recovery device.

Preferably, the light oil and the pyrolysis gas are separated in a separation and recovery device, specifically, the separation and recovery device comprises an oil-gas separation device and an oil-water separation device, the light oil and the pyrolysis gas are separated in the oil-gas separation device, however, the separated light oil contains a small amount of water, so that the light oil and the water are separated by the oil-water separation device, the light oil is recovered and reused, and the water is discharged.

Preferably, the crusher is a two-stage crushing and tearing machine

Preferably, the entire mixer is filled with waste plastic to be processed, and the mixer is sealed.

Preferably, the mixer is of a jacket structure, and the waste plastics are heated by high-temperature flue gas through the interlayer.

Example 1

The embodiment provides a waste plastic radiation thermal cracking process, which comprises the following steps,

1) preparing: preliminary sorting of waste plastics: iron wires and particle stones larger than 100mmm are sorted out and stored separately, and after iron is removed from waste plastics through strong magnetism, the waste plastics are sent into a crusher 1 to be torn and crushed into materials smaller than 30 mm. Is conveyed to the mixer 2 by a conveyor, in the mixer 2, the waste plastics are fully mixed with the high-temperature slag 32 provided by the waste plastics thermal cracker 3, and the mixture of the two carries the residual heat of the high-temperature flue gas 31. The high-temperature flue gas 31 is flue gas generated in the waste plastic thermal cracking machine 3, namely flue gas generated in the waste plastic thermal cracking process, has high temperature, and is suitable for being used as a preheating heat source. Specifically, the waste plastic thermal cracking machine 3 can feed the high-temperature slag 32 into the mixer 2 through a quantitative feeding device, control the amount of the high-temperature slag 32 during feeding, and specifically adjust the amount of the high-temperature slag 32 according to the amount of different waste plastics.

2) First-stage cracking: the mixture of waste plastics with waste heat and the high-temperature slag 32 is fed into a waste plastic thermal cracking machine 3, the waste plastics are melted, part of easily cracked plastics are directly thermally cracked into gas, most of other waste plastics are continuously updated on the surface under the action of rotation, the temperature is gradually increased under the action of thermal radiation, the melting is more complete, and the high-temperature slag 32 is continuously turned over to be fully contacted with the crushed waste plastics in the waste plastic thermal cracking machine 3. And because in the first stage of cracking, the waste plastics are mixed with the high-temperature slag 32, the high-temperature slag 32 is used as a medium, the waste plastics can be prevented from forming a molten state in the waste plastics thermal cracking machine 3, and simultaneously the waste plastics are heated by using the waste heat in the second stage of cracking, so that the plastics shrink, reduce the volume and heat up, the moisture in the plastics is evaporated, and the basic temperature is provided for the second stage of cracking reaction. Isolating oxygen in the whole process of the first-stage cracking, and starting the second-stage cracking after the waste gas purification treatment.

Specifically, the first stage cracking and the second stage cracking can be realized by means of device separation, that is, the waste plastic thermal cracking machine 3 is divided into a first stage cracking unit and a second stage cracking unit, and the two units are separated from each other to realize two cracking separations. Or the two cracking sections are not separated, and the reaction condition is controlled to understand, namely the first section cracking temperature is low, air is isolated, and the second section cracking temperature is correspondingly increased.

In the first stage of cracking, the temperature in the furnace is maintained to be more than 550 ℃, waste plastics enter the furnace to be rapidly heated and cracked, and experimental operation proves that the gas yield of plastic cracking is positively correlated with the heating speed.

3) Second stage cracking, in which the waste plastics melted in the first stage cracking are subjected to second stage cracking, in which high molecular components in the waste plastics are cracked into light oil and combustible gas, and the remaining waste plastics are carbonized. Namely, the surface of the waste plastic is continuously updated under the action of continuous rotation, and the temperature is gradually increased to generate mixed oil gas 34 and standard slag 33 (mainly carbonized plastic).

The second section of cracking device can be arranged by a plurality of layers of heat pipes, and the cracked oil and the macromolecular organic matters pass through the 800-900 ℃ high-temperature radiation cracking pipe in the evaporation process to be further cracked into combustible gas with low molecular weight and high combustion value, so that the gas yield is further improved.

The mixed oil gas 34 enters the oil-gas separation device 5 to realize separation and recovery, namely the mixed oil gas 34 is separated into light oil and cracked gas in the oil-gas separation device 5, wherein the light oil contains a small amount of water, the quality of the light oil is low, the light oil and the small amount of water are separated in the oil-water separation device 51, the light oil is recycled, and the water is discharged.

4) And introducing the separated pyrolysis gas into a paper mill gas boiler to provide fuel for papermaking.

Example 2

The present embodiment provides a waste plastic radiant thermal cracking system capable of realizing the waste plastic radiant thermal cracking process described in embodiment 1.

Comprises a crusher 1, a mixer 2, a waste plastic thermal cracking machine 3 and a dry material bin 4 which are connected in sequence. The connection mode is carried out according to the process sequence, namely, waste plastics are crushed firstly, then mixed with medium high-temperature slag 32 in a mixer and preheated, then the mixture enters a waste plastic cracking machine for two-stage cracking, and finally the residual slag 33 reaching the standard enters a dry material bin 4. Specifically, the crusher 1 is a two-stage crushing and tearing machine. The mixer 2 is of a jacket structure, and the waste plastics are heated by high-temperature flue gas through the interlayer.

A high-temperature slag conveying pipeline is arranged between the waste plastic thermal cracking machine 3 and the mixer 2. So that the high-temperature slag can be used as a medium for the first-stage cracking. A high-temperature flue gas conveying pipeline is arranged between the waste plastic thermal cracking machine 3 and the mixer 2, and the waste plastic and the high-temperature slag 32 are heated by the high-temperature flue gas to have certain heat.

The waste plastic thermal cracking machine 3 is also connected with an oil-gas separation device 5. And storing the obtained pyrolysis gas and light oil.

The light oil and the pyrolysis gas are separated in the oil-gas separation device 5. Light oil and water are separated in the oil-water separating device 51.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, therefore, the present invention is not limited by the appended claims.

Claims

1. A radiation thermal cracking process for waste plastics is characterized by comprising a first-stage cracking step and a second-stage cracking step, wherein waste plastics are melted in the first-stage cracking step and are cracked into light oil, cracking gas and slag charge in the second-stage cracking step, and the slag charge enters the first-stage cracking step to be used as a waste plastics melting medium to be cooperatively melted with the waste plastics; and separating the oil-gas mixture generated by the second-stage cracking, storing the separated cracked gas as fuel for later use, and separating a small amount of water from the separated light oil and then extracting and recovering the separated light oil.

2. The waste plastic radiation thermal cracking process of claim 1, wherein the waste plastics are preliminarily sorted prior to the two-stage cracking: the iron wire and stone are sorted out and the waste plastics are crushed into small particles.

3. The waste plastic radiation thermal cracking process of claim 2, wherein the first stage cracking is carried out after the small waste plastic particles are mixed with the slag and preheated;

4. The waste plastic radiation thermal cracking process of claim 3, wherein the first stage cracking comprises the following steps: the mixture of waste plastics and slag charge with residual heat is continuously rotated, part of easily cracked plastics are directly thermally cracked into gas, most of other waste plastics are melted,

5. The waste plastic radiation thermal cracking process of claim 1, wherein the second stage cracking comprises the following steps: and (3) performing radiation combustion on the molten plastic after the first-stage cracking, cracking high molecular components in the waste plastic into light oil and combustible gas, carbonizing the residual waste plastic to form slag, and introducing the slag into the first-stage cracking.

6. The waste plastic radiative pyrolysis process of claim 1, wherein the process is a continuous feed process.

7. The waste plastic radiation thermal cracking process of claim 1, further comprising the step of water-oil separating the cracked gas and light oil.

8. A system for carrying out the waste plastic radiation thermal cracking method of any one of claims 1 to 7, comprising a crusher, a mixer, a waste plastic thermal cracker and a dry bin, connected in this order.

9. The system for radiation thermal cracking of waste plastics according to claim 8, wherein there is a high-temperature flue gas transfer line between the waste plastic thermal cracker and the mixer;

10. The system for radiation thermal cracking of waste plastics according to claim 8, wherein the waste plastic thermal cracker is further connected to a separation recovery unit;

preferably, the light oil and the pyrolysis gas are separated in a separation and recovery device.