CN-121989383-A - Energy-saving system and process for physical regeneration process of waste PET bottle flakes and/or polyester materials

CN121989383ACN 121989383 ACN121989383 ACN 121989383ACN-121989383-A

Abstract

The invention discloses an energy-saving system and a process for a physical regeneration process of waste PET bottle flakes and/or polyester materials. The invention reduces the dry gas-solid ratio to <3 on the premise of not increasing pretreatment steps such as pre-crystallization, effectively utilizes the waste heat of solid-phase tackifying cooling, and reduces the drying comprehensive energy consumption to below 20% of the fluidized bed process while comparing the drying quality with the fluidized bed (the water content is < 0.05%). The invention solves the problems of overhigh energy consumption, insufficient drying effect of the fixed bed process, complex process flow, energy consumption superposition and the like of the existing fluidized bed process, realizes unification of deep drying and ultralow energy consumption, and has good industrial application prospect.

Inventors

ZHAO LI
LI CHUANG
BI YANG
MA LU
WANG YONGHENG
ZHAO MINGXIU
WANG NA
LING SHAN

Assignees

大连海新工程技术有限公司

Dates

Publication Date: 20260508
Application Date: 20260403

Claims (10)

1. An energy-saving system for the physical regeneration process of waste PET bottle flakes and/or polyester materials comprises a first pneumatic conveying system (2), a screw melt extrusion granulating system (3), a second pneumatic conveying system (4), a solid-phase tackifying system (5), a slicing cooling bin (6) and a packaging machine (7) which are sequentially connected, and is characterized by further comprising a dryer (1) and a hot air circulation recycling system, wherein a discharge hole is arranged at the bottom of the dryer (1) and is connected with an inlet of the first pneumatic conveying system (2); a stirrer (1-1) is arranged in the dryer (1); the hot air circulation recovery system comprises a main fan (9), an auxiliary air heater (10), a dust remover (11), an energy-saving heat exchanger (12) and a first air inlet filter (8); The bottom of the slice cooling bin (6) is provided with a cooling air inlet which is communicated with the outlet of the first air inlet filter (8), a top hot air outlet of the slice cooling bin (6) is communicated with the inlet of the main fan (9), the outlet of the main fan (9) is communicated with the bottom air inlet of the dryer (1) through the auxiliary air heater (10), the top exhaust outlet of the dryer (1) is communicated with the inlet of the dust remover (11), the outlet of the dust remover (11) is communicated with the first medium inlet of the energy-saving heat exchanger (12), and the first medium outlet of the energy-saving heat exchanger (12) is discharged to a blow-down pipe.
2. The energy-saving system according to claim 1, wherein the stirrer (1-1) comprises a stirrer variable frequency motor (1-12), a stirring shaft in driving connection with the stirrer variable frequency motor (1-12) and a stirring paddle (1-13) arranged on the stirring shaft, the dryer (1) is further provided with a manual regulating valve (1-11) of the stirrer variable frequency motor electrically connected with the stirrer variable frequency motor (1-12), the stirring paddle (1-13) is provided with a plurality of layers of paddles, the number of layers is 5-10, each layer of paddles comprises 1-4 paddles uniformly distributed in the horizontal direction, and the paddles between adjacent layers are staggered in the horizontal projection.
3. The energy saving system according to claim 1, characterized in that the hot air recycling system further comprises a second air intake filter (13), the outlet of the second air intake filter (13) is communicated with the second medium inlet of the energy saving heat exchanger (12), and the second medium outlet of the energy saving heat exchanger (12) is connected to a pipeline between the hot air outlet of the slice cooling bin (6) and the main fan (9).
4. Energy saving system according to claim 2, characterized in that the stirrer variable frequency motor (1-12) is configured to 1 to 10 revolutions per minute, preferably 1 to 5 revolutions per minute.
5. The energy-saving system according to claim 2, further comprising a control system, wherein the main fan (9) is a variable frequency fan, and the variable frequency fan is connected with the control system to control the ratio of the air inlet flow rate of the dryer (1) to the bottle chip handling capacity within the range of 2 to 3.
6. The energy-saving system according to claim 5, characterized in that a thermometer (15) and a flowmeter (14) are arranged on a pipeline connecting the main fan (9) and the dryer (1), signal output ends of the thermometer (15) and the flowmeter (14) are connected with the control system, and control output ends of the control system are respectively connected with a frequency converter of the main fan (9), a power controller of the auxiliary air heater (10) and a blow-down valve arranged on a blow-down pipeline.
7. The energy saving system according to claim 1, wherein a first air inlet regulating valve (8-1) is arranged on an outlet pipeline of the first air inlet filter (8), a second air inlet regulating valve (13-1) is arranged on an outlet pipeline of the second air inlet filter (13), and a fan motor variable frequency controller (9-1) is arranged on an outlet pipeline of the main fan (9).
8. A physical recycling and energy saving process for waste PET bottle flakes realized by adopting the system of any one of claims 1 to 7, which is characterized by comprising the following steps: And (3) conveying the PET bottle flakes into a dryer (1) for drying, wherein hot air required in the drying process is at least partially derived from waste heat recovered in the slicing cooling process after solid-phase tackifying, tail gas discharged from the dryer (1) is used for preheating supplementary fresh air after waste heat recovery, and the preheated fresh air is mixed with the recovered waste heat and recycled.
9. The energy-saving process according to claim 8, wherein the drying process specifically comprises the steps of conveying PET bottle flakes into a dryer (1), heating and drying the PET bottle flakes by hot air from bottom to top under the turning of a stirrer (1-1), drying until the water content is lower than 0.05%, wherein the drying temperature is 140-150 ℃, and the gas-solid ratio of the drying process is controlled within a range of 2-3.
10. The energy saving process according to claim 8 or 9, characterized in that the waste heat recovery specifically comprises: hot air recovered in the slicing and cooling process after solid phase tackifying is taken as a main heat source to be sent into a dryer (1); The high-temperature tail gas discharged from the dryer (1) is dedusted by a deduster (11) and then sent to an energy-saving heat exchanger (12), heat exchange is carried out on the high-temperature tail gas and fresh air supplemented by a second air inlet filter (13), the preheated fresh air is mixed into the main heat source, and mixed hot air is formed and then sent to the dryer (1) for recycling.

Description

Energy-saving system and process for physical regeneration process of waste PET bottle flakes and/or polyester materials Technical Field The invention relates to the field of high polymer material recovery and processing, in particular to an energy-saving system and a process for a physical recycling process of waste PET (polyethylene terephthalate) bottle chips and/or polyester materials, which are particularly suitable for the physical recycling process of the waste PET bottle chips. Background Polyethylene terephthalate (PET) is widely used in the fields of bottle chips, fibers, etc. due to its excellent properties. Along with the development of society and the improvement of living standard of people, the use amount of PET bottles is continuously enlarged, and the recycling of waste PET bottles is imperative. The recycling of the waste PET bottles is divided into chemical recycling and physical recycling, the chemical recycling process is complex, the energy consumption is high, the actual application is not much, and the recycling of the waste PET bottles in the current stage is mainly physical recycling. The physical regeneration flow is as follows: sorting, cleaning, crushing, sorting, drying, melt extrusion granulation and solid phase tackifying of waste PET bottles; Wherein, drying is a key pre-process, and if water exists in the melting process of PET, hydrolysis reaction can occur, so that the viscosity of the polymer is reduced, the higher the water content is, the larger the viscosity reduction is, and the quality of the reclaimed materials is seriously affected. In order to minimize the viscosity drop, the PET bottle flakes need to be dried before melt extrusion granulation, so that the moisture in the bottle flakes is minimized. At present, two main processes exist for drying PET bottle flakes in industry, one is a fluidized bed drying process and the other is a fixed bed drying process. The fluidized bed drying process uses high-flow hot air with the gas-solid ratio of 5-7 times as a drying medium, and the bottle flakes are kept in a fluidized state all the time in the drying process by continuous blowing of the high-flow hot air. The large flow rate of the drying air results in high exhaust temperature and a large heat loss. Meanwhile, as the drying air flow is large, the drying fan has high power and high power consumption. The fluidized bed drying process has large comprehensive energy consumption. In addition, the fluidized bed layer thickness has a certain limit, in order to ensure that the bottle flakes have enough drying residence time, the fluidized bed area must be large enough, and the fluidized bed equipment is relatively large in volume, so that the equipment investment is large. The fluidized bed equipment has complex structure and high processing difficulty, and if equipment processing or later-stage equipment operation and maintenance control are not good, the bottle flakes have fluidization dead angles, and the non-fluidized bottle flakes stay for a long time and can be oxidized, so that the product quality is influenced. The fixed bed drying process uses hot air with the gas-solid ratio of 3-4 times as a drying medium, the hot air enters from the bottom of the drying tower and passes through the bottle slice bed layer in the drying tower from bottom to top, and the bottle slices are heated and moisture is taken away, so that the purpose of drying the bottle slices is achieved. However, the softening point of the PET bottle flakes is low (80 ℃), and the temperature of hot air cannot exceed the softening point of the PET bottle flakes, otherwise the PET bottle flakes can adhere and agglomerate to block equipment. This limits the drying effect and the moisture content of the bottle flakes after drying is >0.1%. High water content in downstream processes can lead to increased levels of viscosity degradation of the bottle flakes, which can have adverse effects, and even be unacceptable in certain processes. In a word, the existing fluidized bed and fixed bed drying processes and the derived composite processes such as 'pre-crystallization and high-temperature drying', respectively put the regeneration production of PET bottle flakes into the dilemma of 'high quality and high consumption', 'low quality and low consumption', and 'high quality and high consumption and high complexity', and respectively have the inherent defects of complex and expensive equipment, limited drying effect or lengthy and repeated heating process. The technical stiffness is broken through, an industrial solution which can realize deep drying, ultra-low energy consumption, stable operation and controllable cost is developed, and the industrial solution becomes a key bottleneck for improving competitiveness and sustainable development in the field of physical regeneration of waste PET. Disclosure of Invention Aiming at the problems, the invention discloses an energy-saving system and a process thereof for t