An extrusion granulation production process for a polypropylene device

Abstract

The present invention relates to an extrusion granulation production process for a polypropylene device. The output end of an extruder used is provided with a granulation template and a cutter for cutting granules. The output pipeline of the extruder is connected to a solid-liquid separator downstream. One side of the solid-liquid separator is connected to a dryer, and the bottom is connected to a granulation water tank. A main line cut-off valve V2 is provided on the output pipeline. A crossover line is connected to the output pipeline, which enables the granules produced by the cutter to be directly transported to the granulation water tank. A bypass cut-off valve V1 is provided on the crossover line. The main line cut-off valve V2, the bypass cut-off valve V1, and the extruder are all controlled by the same DCS interlocking system. The extruder is provided with a judgment system for judging whether the output material is qualified. When the judgment system judges that the material is unqualified, the DCS interlocking system controls the main line cut-off valve V2 to close and the bypass cut-off valve V1 to open. When the judgment system judges that the material is qualified, the DCS interlocking system controls the main line cut-off valve V2 to open and the bypass cut-off valve V1 to close.

Description

Technical Field

[0001] The invention relates to the technical field of polypropylene production, in particular to an extrusion granulation production process for a polypropylene device. Background Art

[0002] Polypropylene (PP) is a semi-crystalline thermoplastic with high impact resistance, strong mechanical properties, and resistance to corrosion from a variety of organic solvents and acids and alkalis. It is widely used in industry and is one of the most common polymer materials.

[0003] During the extrusion granulation process of a polypropylene plant, exemplified by the Spherizone polypropylene process, the extruder produces a certain amount of high-molecular-weight polymer particles, which are categorized as powder and pellets by size. Polypropylene powder and additives enter the mixer barrel, where they are mixed and melted at temperatures between 220°C and 250°C to form a mixed stream of resin and additives. Driven by the extruder screw, the mixture is pumped by a gear pump through a filter screen and die plate. The molten resin extruded from the die plate's forming orifice enters a water cooling tank, where it is cut into pellets by a high-speed cutting blade. After pelletizing, water cooling, and solidification, the pellets are transported to a centrifugal dryer. The dehydrated particles enter a vibrating screen, where they are screened and separated into large particles, normal particles, and fine foam.

[0004] However, irregular pellets frequently occur in polypropylene extrusion pelletizers during startup and normal production. This is primarily due to the outer tube failing to meet the definition in the SH / T 1541-2006 "Test Method for Appearance of Thermoplastics Granules," widely followed by the domestic industry. This refers to particles larger than 5 mm (including connected pellets) or smaller than 2 mm (including debris and granules) in any direction. Factors affecting the regularity of polypropylene pellets include pelletizer wear, insufficient blade straightness, insufficient verticality of the die plate and water chamber flange, and excessively high or low blade pads, extruder speed, and pelletizing water temperature. Once pellet irregularities occur, a large number of these irregularly shaped particles pass through the solid-liquid separator and dryer, enter the vibrating screen, and ultimately mix with other qualified products, impacting the quality of the final product shipped from the polypropylene plant.

[0005] At the same time, powders and pellets discharged from the production wastewater and flowing into the production wastewater network have particle sizes ranging from 88 to 3000 μm for powders and 3 to 4 mm for pellets. These powders and pellets have a specific gravity greater than water, are insoluble in water, and cannot be biodegraded. Currently, powders and pellets are typically separated from the extrusion granulation system by discharging them into a trench through the overflow pipe of equipment such as the extruder and pelletizing tank. A skimmer tank is located at the end of the trench, and a retaining wall is used to block polymer particles floating on the water surface. However, the particles are often easily carried out of the skimmer tank by the water flow, entering the underground production wastewater network and being dispersed throughout the network with the water flow. Once in the network, the polymer particles easily clog underground wellheads, water tank inlets and outlets, and equipment pipe openings, causing various problems in the daily maintenance and management of the equipment, as well as the recovery of the fallen materials.

[0006] In addition to polypropylene powder and pellets, wastewater discharged from polypropylene plants also contains small amounts of COD, BOD, petroleum, propylene glycol solution, and other substances. If these substances are not removed, the scooped material and wastewater pool will have strong odors, dirty waste materials, and poor quality wastewater, which does not meet environmental protection requirements. In addition, the scooped pellets will be of poor quality and unsuitable for sale. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an extrusion granulation production process for a polypropylene device which can monitor in real time whether the material discharged from the extruder is qualified, thereby timely recovering unqualified pellets and ensuring the quality of the product.

[0008] The technical solution adopted by the present invention to solve the above technical problems is:

[0009] An extrusion granulation production process for a polypropylene device, comprising: an extruder output end equipped with a granulation die plate and a cutter for cutting pellets; an output pipeline of the extruder connected downstream to a solid-liquid separator; a dryer connected on one side of the solid-liquid separator and a pelletizing water tank connected on the bottom; a main line shut-off valve V2 provided on the output pipeline; and a crossover line connected to the output pipeline that allows pellets produced by the cutter to be directly transported to the pelletizing water tank; a bypass shut-off valve V1 provided on the crossover line;

[0010] The main line shut-off valve V2, the bypass shut-off valve V1 and the extruder are all controlled by the same DCS interlocking system. The extruder is provided with a judgment system for judging whether the output material is qualified or not. When the judgment system judges that the material is unqualified, the DCS interlocking system controls the main line shut-off valve V2 to close and the bypass shut-off valve V1 to open. When the judgment system judges that the material is qualified, the DCS interlocking system controls the main line shut-off valve V2 to open and the bypass shut-off valve V1 to close.

[0011] In the present invention, the judgment system determines whether the material is qualified based on the relationship curve between the extruder's inlet air pressure and the cutter speed and / or the pressure parameter changes on the pelletizing die plate. The two judgment methods are arranged in parallel. That is, if either method determines that the material may be unqualified, the DCS interlocking system will issue a signal that the material is unqualified.

[0012] Preferably, the judgment system judges whether the material is qualified or not by the relationship curve between the extruder feed air pressure and the cutter speed. On the premise that the extruder produces products with qualified appearance in the early stage, according to the actual production situation, the control function relationship is calibrated as follows:

[0013] f1=q-0.355n+0.797,

[0014] in,

[0015] f1——feed air pressure, MPag,

[0016] q——feed rate, t / h,

[0017] n——cutter speed, r / min,

[0018] The control system records the data of f1, q, n, and counts them every 1 second within 60 seconds, and the corresponding statistics are the data set F={f 1m |m=1,2,3……59,60},Q={q m |m=1,2,3……59,60}, N={n m |m=1,2,3……59,60},

[0019] Let f 1m '= q m -0.355n m +0.797, F={f 1m '-f 1m | m=1,2,3……59,60}, whose variables obey X~N(μ,σ 2 ), if the mathematical expectation μ>14, or the variance σ 2 If the value is >0.45, it is considered that there is a large deviation in the production conditions and there is a risk of producing unqualified pellets. At this time, the DCS interlocking system opens the cross-line shut-off valve V1, closes the main line shut-off valve V2, and issues an alarm.

[0020] Preferably, a pressure sensor is provided on the granulation template, which is composed of a combination of multiple piezoresistive sensors and is electrically connected to the DCS interlocking system to detect the distributed pressure at various locations on the surface of the granulation template in real time;

[0021] Each piezoresistive sensor is numbered independently, and its number is recorded in the data set W={w|w=1,2,3,...n}. At the same time, the pressure returned by each piezoresistive sensor is recorded as the corresponding data set T={t w |w=1,2,3,...n}; if the standard deviation of the data set T is higher than 0.24, the data is marked as 1, otherwise the data is marked as 0; the piezoresistive sensor records data every 1 second, and the sum of the data within 1 minute is If the number of sets If the pressure is >12, it is considered that the pressure between the cutter and the granulation template is uneven, and there is a risk of waste. At this time, the DCS interlocking system opens the cross-line shut-off valve V1, closes the main line shut-off valve V2, and sounds an alarm.

[0022] In the present invention, the upper side of the pelletizing water tank is connected to the pelletizing material processing equipment through an overflow pipe, and the bottom of the pelletizing water tank is connected to the pelletizing water pipe at the extruder outlet through a pelletizing water pump and a heat exchanger.

[0023] Preferably, the pellet processing equipment comprises:

[0024] An electrochemical device for removing suspended oil, dispersed oil, emulsified oil and propylene glycol from wastewater from a polypropylene plant; the electrochemical device is provided with a waste oil discharge port at the top and a sludge outlet at the bottom;

[0025] A buffer tank is located downstream of the electrochemical facility, with an inlet on the top for inputting liquid treated by the electrochemical facility for further oil-water separation, a waste oil discharge port on the top, a sludge outlet at the bottom, and an output port for discharging wastewater with particles at the lower part;

[0026] The particle separation pool is arranged downstream of the buffer tank. The first side is provided with an inlet arranged lower than the output port of the buffer tank so that sewage can flow into the particle separation pool by gravity. The second side is provided with an outlet arranged lower than the inlet so that sewage can flow out by gravity. The particle separation pool is provided with a particle separation basket arranged near the inlet for blocking and storing particulate matter therein.

[0027] The main problems of the existing drainage system containing polymer particles are as follows: (1) When receiving the drainage containing polymer particles from the production equipment, the skimming tank cannot intercept all the polymer particles, and a part of the polymer particles inevitably enter the underground pipe network of the production sewage. After the polymer particles enter the pipe network, they are carried to various places in the pipe network with the water flow, and their positions are scattered, making it difficult to clean and collect them; (2) At present, the technology for separating powder and granular materials from wastewater at home and abroad usually adopts mechanical fishing abroad and manual fishing with net bags in China, both of which are ineffective and easy to miss. The present invention first uses electrochemical facilities to separate oil and remove the floating, dispersed oil, emulsified oil and propylene glycol in the wastewater of the polypropylene device, and then uses gravity to make the sewage pass through the particle separation tank to collect the powder and granular materials in the sewage, effectively recover the powder and granular materials, and avoid the particles from entering the downstream and causing adverse effects. The recovered granular materials are placed in the particle separation basket for easy removal, and the operation is simple and convenient.

[0028] Preferably, the electrochemical facility includes a first part and a second part arranged adjacent to each other, a partition extending downward from the top is provided in the first part, a gap is formed between the bottom of the partition and the inner bottom wall of the first part for the sewage after oil separation to enter the second part, and a dirty oil discharge port is provided at the top of the first part; the sewage inlet of the electrochemical facility is connected to the side of the first part, and the sewage outlet is connected to the side of the second part.

[0029] Preferably, the system further comprises a waste oil collection tank, which is located above the electrochemical device and the buffer tank. The waste oil inlet of the waste oil collection tank is connected to each waste oil discharge port through a pipeline. The waste oil collection tank is provided with a channel for conveying the settled wastewater to the wastewater inlet of the electrochemical device, and a sludge outlet for discharging the settled sludge.

[0030] It also includes a homogenizing tank connected to the upstream of the electrochemical facility, the top of the homogenizing tank is used to input wastewater from the polypropylene device, the lower outlet of the homogenizing tank is connected to the sewage outlet of the electrochemical facility, and the bottom of the homogenizing tank is provided with a sludge outlet;

[0031] It also includes a wet sludge tank and a sludge thickening tank. The top of the wet sludge tank is provided with a sludge inlet connected to each sludge outlet. The outlet of the wet sludge tank is connected to the inlet of the sludge thickening tank. The top of the sludge thickening tank is provided with a pipeline for sending the obtained supernatant to the oil inlet of the oil collection tank.

[0032] Preferably, the bottom wall of the particle separation pool is higher than the second side near the first side, thereby forming a support platform on the first side, the particle separation basket is placed on the support platform and the top is open corresponding to the inlet pipe of the particle separation pool, and the second side is concave to form a water accumulation area, and the outlet of the particle separation pool is connected to the water accumulation area.

[0033] Compared with the prior art, the advantages of the present invention are as follows: the present invention is provided with a main line shut-off valve V2 and a cross-line including a bypass shut-off valve V1 on the output pipeline, and the extruder is provided with a judgment system for judging whether the output material is qualified or not. When the judgment system judges that the material is unqualified, the DCS interlocking system controls the main line shut-off valve V2 to close and the bypass shut-off valve V1 to open. When the judgment system judges that the material is qualified, the DCS interlocking system controls the main line shut-off valve V2 to open and the bypass shut-off valve V1 to close, thereby being able to monitor in real time whether the extruder discharge is qualified and to promptly recycle unqualified pellets, which not only ensures the quality of the product but also facilitates more effective processing and recycling of the pellets according to their characteristics, thereby avoiding pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0035] Figure 2 Schematic diagram of the positional relationship between the granulation die plate and the cutter of the extruder in an embodiment of the present invention;

[0036] Figure 3 for Figure 1 Schematic diagram of the structure of medium-grained material processing equipment;

[0037] Figure 4 for Figure 3 Schematic diagram of the structure of the septum granule pool;

[0038] Figure 5 for Figure 4 Top view of . DETAILED DESCRIPTION

[0039] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0040] like Figure 1 、 2 As shown, the extrusion granulation production process of the polypropylene device of this embodiment adopts an extruder output end provided with a granulation template and a cutter for cutting the produced pellets. The downstream of the output pipeline of the extruder is connected to a solid-liquid separator. One side of the solid-liquid separator is connected to a dryer, and the bottom is connected to a pelletizing water tank. The output pipeline is provided with a main line shut-off valve V2. The output pipeline is connected to a crossover line that allows the pellets produced by the cutter to be directly transported to the pelletizing water tank. The crossover line is provided with a bypass shut-off valve V1.

[0041] The main line shut-off valve V2, the bypass shut-off valve V1, and the extruder are all controlled by the same DCS interlocking system. The extruder is equipped with a judgment system to determine whether the output material is qualified or not. When the judgment system determines that the material is unqualified, the DCS interlocking system controls the main line shut-off valve V2 to close and the bypass shut-off valve V1 to open. When the judgment system determines that the material is qualified, the DCS interlocking system controls the main line shut-off valve V2 to open and the bypass shut-off valve V1 to close.

[0042] In this embodiment, the judgment system determines whether the material is qualified based on the relationship curve between the extruder's air pressure and the cutter speed, as well as the pressure parameter changes on the pelletizing die plate. These two judgment methods are set up in parallel. That is, if either method determines that the material may be unqualified, the DCS interlocking system will issue a signal that the material is unqualified.

[0043] When judging whether the material is qualified or not by the relationship curve between the extruder feed air pressure and the cutter speed, under the premise that the extruder produces products with qualified appearance in the early stage, according to the actual production situation, the control function relationship is calibrated as follows:

[0044] f1=q-0.355n+0.797,

[0045] in,

[0046] f1——feed air pressure, MPag,

[0047] q——feed rate, t / h,

[0048] n——cutter speed, r / min,

[0049] The control system records the data of f1, q, n, and counts them every 1 second within 60 seconds, and the corresponding statistics are the data set F={f 1m |m=1,2,3……59,60},Q={q m |m=1,2,3……59,60}, N={n m |m=1,2,3……59,60},

[0050] Let f 1m '= q m -0.355n m +0.797, F={f 1m '-f 1m | m=1,2,3……59,60}, whose variables obey X~N(μ,σ 2 ), if the mathematical expectation μ>14, or the variance σ 2If the value is >0.45, it is considered that there is a large deviation in the production conditions and there is a risk of producing unqualified pellets. At this time, the DCS interlocking system opens the cross-line shut-off valve V1, closes the main line shut-off valve V2, and issues an alarm.

[0051] When judging whether the material is qualified or not by the change of pressure parameters on the granulation template, a pressure sensor is set on the granulation template. The pressure sensor is composed of a combination of multiple piezoresistive sensors and is connected to the DCS interlocking system electrical signal to detect the distributed pressure at various locations on the granulation template surface in real time;

[0052] Each piezoresistive sensor is numbered independently, and its number is recorded in the data set W={w|w=1,2,3,...n}. At the same time, the pressure returned by each piezoresistive sensor is recorded as the corresponding data set T={t w |w=1,2,3,...n}; if the standard deviation of the data set T is higher than 0.24, the data is marked as 1, otherwise the data is marked as 0; the piezoresistive sensor records data every 1 second, and the sum of the data within 1 minute is If the number of sets If the pressure is >12, it is considered that the pressure between the cutter and the granulation template is uneven, and there is a risk of waste. At this time, the DCS interlocking system opens the cross-line shut-off valve V1, closes the main line shut-off valve V2, and sounds an alarm.

[0053] In this embodiment, the upper side of the pelletizing water tank is connected to the pelletizing material processing equipment through an overflow pipe, and the bottom of the pelletizing water tank is connected to the pelletizing water pipe at the outlet of the extruder through a pelletizing water pump and a heat exchanger.

[0054] like Figure 3 As shown in Figure 5, the pellet processing equipment of this embodiment includes:

[0055] Electrochemical facility 01 is used to remove suspended oil, dispersed oil, emulsified oil, and propylene glycol from wastewater from the polypropylene unit. The top of electrochemical facility 01 is equipped with a waste oil discharge port and a sludge outlet at the bottom.

[0056] Buffer tank 02 is located downstream of electrochemical facility 01. It has an inlet on the top for the liquid treated by electrochemical facility 01 for further oil-water separation. It also has a waste oil outlet on the top, a sludge outlet on the bottom, and an outlet on the lower side for the discharge of wastewater with particles.

[0057] The particle separation pool 03 is arranged downstream of the buffer tank 02. The first side is provided with an inlet arranged lower than the output port of the buffer tank 02 so that sewage can flow into the particle separation pool by gravity. The second side is provided with an outlet arranged lower than the inlet so that sewage can flow out by gravity. The particle separation pool 03 is provided with a particle separation basket 031 arranged near the inlet for blocking and storing particulate matter.

[0058] The electrochemical facility 01 includes a first part 011 and a second part 012 arranged adjacent to each other. A partition 013 extending downward from the top is provided in the first part 011. A gap is formed between the bottom of the partition 013 and the inner bottom wall of the first part 011 for the sewage after oil separation to enter the second part 012. A waste oil discharge port is provided at the top of the first part 011; the sewage inlet of the electrochemical facility 01 is connected to the side of the first part 011, and the sewage outlet is connected to the side of the second part 012.

[0059] This embodiment also includes a waste oil collection tank 04, located above the electrochemical facility 01 and buffer tank 02. The waste oil inlet of waste oil collection tank 04 is connected to the various waste oil discharge ports via pipes. Waste oil collection tank 04 is equipped with a channel for conveying settled wastewater to the wastewater inlet of the electrochemical facility 01, and a sludge outlet for discharging settled sludge. This embodiment also includes a homogenization tank 05, connected upstream of the electrochemical facility 01. The top of homogenization tank 05 is used to input wastewater from the polypropylene plant. The bottom outlet of homogenization tank 05 is connected to the wastewater outlet of the electrochemical facility 01. A sludge outlet is provided at the bottom of homogenization tank 05.

[0060] This embodiment also includes a wet sludge tank 06 and a sludge thickening tank 07. The top of the wet sludge tank 06 is provided with a sludge inlet connected to each sludge outlet. The outlet of the wet sludge tank 06 is connected to the inlet of the sludge thickening tank 07. The top of the sludge thickening tank 07 is provided with a pipeline for sending the obtained supernatant to the waste oil inlet of the waste oil collection tank 04.

[0061] In this embodiment, the bottom wall of the particle separation pool 03 is higher than the second side near the first side, so that a support platform 032 is formed on the first side. The particle separation basket 031 is placed on the support platform 032 and the top is open corresponding to the inlet pipe 001 of the particle separation pool 03. The second side is concave to form a water accumulation area 033, and the outlet 002 of the particle separation pool 03 is connected to the water accumulation area 033.

[0062] Filter holes are provided on the side walls of the particle isolation pool 03. A cover plate 034 is provided at the top opening of the particle isolation pool 03, offset from the side of the inlet pipe. The cover plate 034 is detachably provided on the top of the particle isolation pool 03. A ladder 035 is provided on the inner wall of the particle isolation pool 03, extending downward from the top opening to facilitate internal maintenance.

[0063] like Figure 3 As shown, when the recycling system of this embodiment treats sewage:

[0064] (1) After the wastewater from the polypropylene unit (temperature 30-95°C, polypropylene powder and pellets 10-100 ppm, propylene glycol 10-20 mg / L, petroleum 30 mg / L, SS 100 mg / L) enters the homogenizing tank 05, it is pumped into the electrochemical facility 01, where most of the floating, dispersed and emulsified oils and propylene glycol are removed through oil separation and electrocoagulation. The electrochemical facility 01 uses 380V AC, a current density of 500-600A / ㎡, and the electrode plates are made of nickel-plated titanium. The electrolysis time is 60 minutes. The electrochemical facility is divided into two parts: the first part is the oil separator and the second part is the reaction tank. The upstream water first enters the oil separator and then enters the reaction tank. Sodium chloride is added to the water to keep the conductivity of the wastewater at 40-80 μS / cm. To remove propylene glycol, hydrogen peroxide is added to the electrochemical facility 01 to oxidize propylene glycol to produce malonic acid, which is then neutralized by adding sodium hydroxide to the buffer tank 02.

[0065] (2) The effluent from the electrochemical facility 01 enters the buffer tank 02, where the floating, dispersed and emulsified oil that was not completely treated in the previous stage is treated.

[0066] (3) Mechanical filtration to recover polypropylene pellets from wastewater. After the water is discharged from the buffer tank 02, the production wastewater containing polypropylene pellets is connected to the particle separation tank 03 by gravity through a pipe. There is a height difference between the water inlet pipe and the water outlet pipe in the particle separation tank 03. The water flows by gravity through the particle separation basket 031 and flows into the downstream pipe network. The particle separation basket 031 is placed at the bottom of the particle separation tank 03. The polypropylene pellets carried in the water flow are intercepted by the particle separation basket 031. The staff confirms the full state of the particle separation basket 031 through the observation hole of the cover. During the production drainage interval, the staff opens the cover, lifts the particle separation basket 031, and collects the intercepted polypropylene pellets and powder particles.

[0067] (4) After the water is discharged from the particle separation tank 03, the sewage is pumped to the sewage treatment plant for subsequent treatment.

[0068] (5) During the treatment process, a certain amount of sludge and waste oil will be generated. Sludge is mainly generated during the backwashing of the electrochemical facility 01 and the discharge of the buffer tank 02. Considering the harmless and resource-based treatment of sludge, the sludge is first collected in the wet sludge pool 06 for storage, and then pumped to the sludge thickening pool 07 for concentration and solid-liquid separation, and the supernatant is returned to the waste oil collection pool 04. The effluent from the thickening pool is sent to the sludge dehydration unit for dehydration. The concentrated sludge at the bottom of the waste oil collection pool 04 is pressurized and transported back to the wet sludge pool. After dehydration and volume reduction, it is sent to an off-site treatment facility for harmless and resource-based treatment. Waste oil is mainly generated during the backwashing of the electrochemical facility 01 and the discharge of the buffer tank 02. The waste oil has a high water content. After being pumped to the waste oil collection pool for natural sedimentation and separation, the upper waste oil is pumped to the oil recovery system for system recovery, and the middle wastewater is sent to the downstream sewage treatment plant for subsequent treatment.

Claims

1. An extrusion granulation production process for a polypropylene device, wherein the output end of the extruder is provided with a granulation template and a cutter for cutting the produced pellets, the output pipeline of the extruder is connected downstream to a solid-liquid separator, one side of the solid-liquid separator is connected to a dryer, and the bottom is connected to a pelletizing water tank, characterized in that: The output pipeline is provided with a main line shut-off valve V2, and the output pipeline is connected to a crossover line that enables the pellets produced by the cutter to be directly transported to the pelletizing water tank, and the crossover line is provided with a bypass shut-off valve V1; The main shut-off valve V2, the bypass shut-off valve V1, and the extruder are all controlled by the same DCS interlocking system. The extruder is provided with a judgment system for judging whether the output material is qualified or not. When the judgment system judges that the material is unqualified, the DCS interlocking system controls the main shut-off valve V2 to close and the bypass shut-off valve V1 to open. When the judgment system judges that the material is qualified, the DCS interlocking system controls the main shut-off valve V2 to open and the bypass shut-off valve V1 to close. The judgment system judges whether the material is qualified or not through the relationship curve between the extruder feed air pressure and the cutter speed and / or the pressure parameter change on the granulation template; When the judgment system judges whether the material is qualified or not by the relationship curve between the extruder feed air pressure and the cutter speed, under the premise that the extruder produces products with qualified appearance in the early stage, according to the actual production situation, the control function relationship is calibrated as follows: f1=q-0.355n+0.797, in, f1——feed air pressure, MPag, q——feed rate, t / h, n——cutter speed, r / min, The control system records the data of f1, q, n, and counts them every 1 second within 60 seconds, and the corresponding statistics are the data set F={f 1m |m=1,2,3……59,60},Q={q m |m=1,2,3……59,60}, N={n m |m=1,2,3……59,60}, Let f 1m '= q m -0.355n m +0.797, F={f 1m '-f 1m | m=1,2,3……59,60}, whose variables obey X~N(μ,σ 2 ), if the mathematical expectation μ>14, or the variance σ 2 If the value is >0.45, it is considered that there is a large deviation in the production conditions and there is a risk of producing substandard pellets. At this time, the DCS interlocking system opens the cross-line shut-off valve V1, closes the main line shut-off valve V2, and issues an alarm. When the judgment system judges whether the material is qualified or not by the change of the pressure parameter on the granulation template, a pressure sensor is set on the granulation template. The pressure sensor is composed of a combination of multiple piezoresistive sensors and is connected to the DCS interlocking system electrical signal to detect the distributed pressure at various locations on the surface of the granulation template in real time; Each piezoresistive sensor is numbered independently, and its number is recorded in the data set W={w|w=1,2,3,...n}. At the same time, the pressure returned by each piezoresistive sensor is recorded as the corresponding data set T={t w |w=1,2,3,...n}; if the standard deviation of the data set T is higher than 0.24, the data is marked as 1, otherwise the data is marked as 0; the piezoresistive sensor records data every 1 second, and the sum of the data within 1 minute is , if the number of sets If the pressure is >12, it is considered that the pressure between the cutter and the granulation template is uneven, and there is a risk of waste. At this time, the DCS interlocking system opens the cross-line shut-off valve V1, closes the main line shut-off valve V2, and sounds an alarm.

2. The extrusion granulation production process of the polypropylene device according to claim 1, characterized in that: The upper side of the pelletizing water tank is connected to the pelletizing material processing equipment through an overflow pipe, and the bottom of the pelletizing water tank is connected to the pelletizing water pipeline at the outlet of the extruder through a pelletizing water pump and a heat exchanger.

3. The extrusion granulation production process of the polypropylene device according to claim 2, characterized in that: The pellet processing equipment includes An electrochemical facility for removing floating oil, dispersed oil, emulsified oil and propylene glycol from wastewater from a polypropylene plant; the electrochemical facility is provided with a waste oil discharge port at the top and a sludge outlet at the bottom; A buffer tank is located downstream of the electrochemical facility, with an inlet on the top for inputting liquid treated by the electrochemical facility for further oil-water separation, a waste oil discharge port on the top, a sludge outlet at the bottom, and an output port on the lower side for discharging wastewater with particles; The particle separation pool is arranged downstream of the buffer tank. The first side is provided with an inlet arranged lower than the output port of the buffer tank so that sewage can flow into the particle separation pool by gravity. The second side is provided with an outlet arranged lower than the inlet so that sewage can flow out by gravity. The particle separation pool is provided with a particle separation basket arranged near the inlet for blocking and storing particulate matter therein.

4. The extrusion granulation production process of the polypropylene device according to claim 3, characterized in that: The electrochemical facility includes a first part and a second part arranged adjacent to each other. A partition extending downward from the top is provided in the first part. A gap is formed between the bottom of the partition and the inner bottom wall of the first part for the sewage after oil separation to enter the second part. A dirty oil discharge port is provided at the top of the first part; the sewage inlet of the electrochemical facility is connected to the side of the first part, and the sewage outlet is connected to the side of the second part.

5. The extrusion granulation production process of the polypropylene device according to claim 4, characterized in that: The system also includes a waste oil collection tank, which is located above the electrochemical facility and the buffer tank. The waste oil inlet of the waste oil collection tank is connected to each waste oil discharge port through a pipeline. The waste oil collection tank is provided with a channel for conveying the settled wastewater to the wastewater inlet of the electrochemical facility and a sludge outlet for discharging the settled sludge. It also includes a homogenizing tank connected to the upstream of the electrochemical facility, the top of the homogenizing tank is used to input wastewater from the polypropylene device, the lower outlet of the homogenizing tank is connected to the sewage outlet of the electrochemical facility, and the bottom of the homogenizing tank is provided with a sludge outlet; It also includes a wet sludge tank and a sludge thickening tank. The top of the wet sludge tank is provided with a sludge inlet connected to each sludge outlet. The outlet of the wet sludge tank is connected to the inlet of the sludge thickening tank. The top of the sludge thickening tank is provided with a pipeline for sending the obtained supernatant to the oil inlet of the oil collection tank.

6. The extrusion granulation production process of the polypropylene device according to claim 3, characterized in that: The bottom wall of the particle separation pool is higher than the second side near the first side, thereby forming a support platform on the first side. The particle separation basket is placed on the support platform with the open top corresponding to the inlet pipe of the particle separation pool. The second side is concave to form a water accumulation area, and the outlet of the particle separation pool is connected to the water accumulation area.

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