Logistics center of the hottest polymer industry

2022-09-21
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Logistics center of polymer industry

ordinary polymer manufacturers are constantly expanding their scale. The capacity of polymer storage, transportation, packaging and shipping must keep pace with this development, and the importance of economically operating logistics centers has become greater

Figure 1 Logistics centers of different polymers

when designing logistics centers, the key considerations are the respective requirements of operators and the methods used for product transportation. Regional differences have to be considered here. Pellets are transported from the manufacturer to the processor in "bulk", that is, in the form of no packaging, especially in Europe and North America. This trend is also gradually taking shape in South America and China

the reason for the increased importance of bulk transportation is the cost savings in packaging materials, packaging equipment, and the handling and recycling of packaging materials. These packaging costs account for about 6% of the product sales value, and the use of bulk packaging can be reduced to less than 2%. Bulk logistics is more economical for plastic processing manufacturers with an annual consumption of more than 100 tons. In Europe, polymers transported in bulk are stored in silos, sometimes with hundreds of silos. In North America, they are stored in railway cars with a loading capacity of about 100 tons

storage capacity requirements

modern manufacturers can manufacture polymers of various levels, and the general production cycle is days. The average storage capacity corresponds to the production cycle. For example, the average production capacity is about one month, or 10% of the annual production capacity. More than half of this quantity has to be stored in silos for bulk transportation. The number of silos required should exceed 50% of the number of polymer grades to provide sufficient containers for ordinary grade polymers. Large modern manufacturers need silos. Today, the production scale of general factories is about 250000 tons/year, and the best silo size is m3. For factories with a production capacity of 350000 tons/year in the future, the silo size will be increased to about 750 m3. Products not transported in bulk will be bagged. For the warehouse with two floors and pallet stacking, its storage capacity is required to reach 1 ton/m2

layout of warehouse and bagging machine

in addition to the static load and cost factors related to the foundation, the need to fill many trucks at the same time determines the layout of the warehouse. As a general reference, it can be assumed that each row of warehouses provides 20000 tons of environmental protection, which is still its biggest advantage, and the loading capacity of tons/year. Figure 2 shows a group of silos that load pellets into trucks, with a load of 120000 tons per year. The truck was driven directly to the gate of the warehouse silo. When leaving the site, the truck driver got the shipping bill after weighing the vehicle at the gate. With this system, the whole loading operation can be completed in less than an hour. When planning the silo yard, we must consider the later capacity improvement according to the arrangement of transmission equipment and silo space requirements

this warehouse for bulk transportation should be located between the extruder and the bagging equipment. Products not loaded into trucks are pneumatically transferred to bagging equipment. In addition, a granular cleaning and panning device is added at the silo of the bagging warehouse. In bagging equipment, pellets are generally loaded into 25kg bags by the packer, with an average capacity of T/h

conveying system

most of the pellets come out of the extruder and are transferred to the mixing, storage and bagging warehouse through the pneumatic conveying system. The advantages of pneumatic transmission are flexible line selection, easy installation and operation. The disadvantage is that fine powder is inevitably produced on the transmission line. The amount of fine powder produced depends largely on the type of polymer and the transmission method used. A basic choice must be made between the two delivery systems, that is, dilute state and dense state

in the dilute state transfer, because the transfer gas speed is high, the particles collide and generate more powder. It will also form long polymer spikes, which will hinder the downstream processing steps. In dense state transmission, because the gas velocity used is slow, the particle friction is significantly less

it is assumed that the amount of fine powder produced in the dilute state transmission is 300ppm/industrialized utilization of new technology. Finally, the amount of fine powder produced in the dense state transmission is 40 ppm/100M less than 100m according to the requirements of the other party. The dilution state transfer system without subsequent panzers (particle cleaners) can only be used in the case of extremely short transfer distance to meet the powder limit of 100ppm. On the other hand, dense state transmission will exceed this limit only when the transmission distance exceeds 250m. Because of this, the distance below 250 meters is most suitable for dense conveying system, which flows through the whole conveying path from extruder to bagging. Because the new large-scale factory makes the transmission distance of more than 250 meters necessary, granular cleaners will be required for the two transmission modes

for economic reasons, the best combination of dilute state and dense state transmission is needed to minimize the investment cost and improve the operational reliability when the product level changes and the production capacity is different. Moreover, the capacity limit of a single transmission system must also be considered. The advantage of high-pressure dilution state transmission is to reduce the pipe diameter and gas volume

principle of logistics center

from the above discussion, it can be seen that the diluted state transmission with subsequent panzers is suitable for long-distance transmission, while the dense state transmission is suitable for short-distance transmission from classification point to bagging warehouse. The combination of the two is a very suitable solution in terms of product quality and investment cost. Figure 3 shows a basic principle of this type. In order to minimize the distance from the elutriator to the silo, the classifier is best placed in the center of the depot. However, it is more economical to combine the elutriator into the stair structure at one end of the storage yard. If the conveying distance is too long, the silo of the mixing warehouse can be placed on the extruder and reinforced in time at the midpoint between the extruder and the warehouse yard, and the same is true for a platform

Figure 1 shows such a principle. The background is the depot for storage and loading. A sorter is added to the stair structure. Dense state transfer is used for allocation. The pellets can be transferred from the storage warehouse to the bagging and storage place. Before entering the bagging silo, the pellets are cleaned in another elutriator. The area shown in the figure is part of a logistics center, which processes nearly onemillion tons of polymers from four different plants every year

in Europe, service providers manage many logistics centers, usually from upstream industries. Because it is required to load and bag at the same time, a two-story concept has emerged. The storage silo is built above the middle bagging floor, and the loading is carried out below the bagging floor. Mobile bagging machines that move on rails or air cushions are used for bagging. The truck can be filled by feeding the hose from the bagging floor to the truck. This principle (as shown in Figure 4) has low space requirements and high flexibility. In particular, it can be bagged and loaded into trucks or containers at "actual timing". If there is enough storage capacity in the silo, the size of the bag warehouse can be reduced. Depending on the contact with the production plant, the warehouse silo can be filled through dense state transmission or dilution state transmission with subsequent panzers. Film blowing equipment can be incorporated into the warehouse concept where there is no sealing film to continuously produce packaging bags

conclusion

the requirements for granular material transportation and storage in each factory are different, and the selection of the design of the whole logistics center is determined. Only by closely contacting with expert companies and developing an appropriate concept can we correctly consider the customer's operating requirements and processes. Good design and engineering can reduce operating costs or increase the number of products handled by each employee by up to 30%

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