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Lactam preheating

A technical peculiarity of PE technology is the 2-step preheating of caprolactam before feeding into the prepolymerisation. For this beside of a primary energy in its own preheater there is energy originated from the cooling of the melt to be used and released in the post-condensator.  By this way it saves about 30% of the cost for the required heating of caprolactam. The subsequent heating of caprolactam to starting reaction temperature in the second heater ensures that the reaction starts immediately once the caprolactam are fed into the prepolymerisator. Likewise the required additives will be dosed immediately by the mixing device patented by PE when caprolactam is heated to the starting reaction temperature after feeding into prepolymerisator. This brings a high level of operational safety and a precise and controllable control over the process and the composition of the raw materials for the reaction. 

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The closed driving mode of pre-polymerisator under the partial pressure of the water content adapting exactly for the product parameter speeds up the reaction of ring opening of the monomer caprolactam and guarantees a 100% implementation of all additives. Here the additives are used especially economically and cost effectively. Through a special design of reactor installation it ensures that there is a uniform velocity across the entire cross-section in the course of the reaction. The proven and widely applied design of PE reactors permits the realization of reactors with a capacity of over 400 Tons per day. The customer-tailored plant design in conjunction with the melt dryer combines perfectly the pre-polymerization with the post-condensation together so as to ensure the narrow distribution of the parameter of the polymer.

The post-condensation of PE is driven up to a high viscosity range without vacuum. Thus it is ensured that there is no danger of oxidation of the product. The separation of deaerated water in the post-condensator will be taken place through a special bubble cap tray column whereby an effective removal of water and volatile impurities of caprolactam from product components is fulfilled. By using this bubble cap tray column the system reacts self- regulatively and dynamically according to the changes in throughput, as opposed to a packed column controlled complicatedly in technically process demanding.

All reaction steps have been designed so that reaction equilibrium is always accomplished at the outlet of the reactor and therefore a stable and uniform product quality even with brief interruption of production can be guaranteed.

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PE has developed modern process for the introduction of additives in different process sections in the past few years and  put into use successfully. So the feeding of hydrous and anhydrous additives takes place immediately prior to the dosing of the raw material in the reaction process in the pre-polymerisator. The raw material caprolactam is thus only reactive with the entry into the pre-polymerisator, which will not generate any operational risks in the event of unexpected interruptions of production process and the adjustment of additive composition could be fulfilled in a very short time without increased costs by transitional products.  

The required additives are dosed into the main input stream through a static mixing device patented by PE.

Furthermore, the addition of anhydrous additives happens at the outlet of the polymer melt from the post condensator through a specially designed static mixer without affecting the quality of the products. Therefore it is possible to reach a uniform quality for special applications (light-stable, temperature-resistant, pigmented polymer). The mixer drives purely static and thus ensures a very even distribution of additives in the melt without particular technical and technological risks.

Another innovative way to modify the polymer offered by PE is at the end of the drying process. For this purpose, PE has developed a modern process for dosing of additives. This technology is required to present a possibility for further processing of film materials with other polyamide products.  

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This single- or multistage extraction and the design of installations, developed by PE, guarantee that the monomer content in the end product is less than 0.3% and the proportion of cyclic oligomers lesser than 0.05%. These values are essential for the further processing of the product for e.g. high-performance textile and films granulates. Either under the pressure or non-pressure the extraction process is application-dependent. Transportation of granulates is very efficient and low-abrasion by injectors. 

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The drying process developed by PE corresponds basically to the current world standard and has been optimized by PE at the aspects of energy efficiency and throughput maximization. One special feature is the cooling of the product at the outlet of the drying by means of indirect water cooling. This granulate cooling through a tube bundle operated by cooling water can avoid the changing of the dew point as compared to the direct nitrogen cooling of granulates as well as ensure a particular  narrow distribution of dwell time through a special design even in the event of a large throughput. By this way it is also ensured that the adjusted residual water content of end product could be kept always controlled and stable. Requesting a high viscosity of the end product, it is then optional that the solid state post-polymerization will be integrated in the drying process. 

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The technology PE used in the lactam recovery system is an environmental friendly process and can be operated through the solutions developed by PE, for example, without distillation. The extract containing water is concentrated with a 3-stage system with forced circulation evaporation. The extract concentrate containing dimer and oligomer is fed back to the polymerization main process after the patented hydrolysation process, consisting of 2 reaction stages. The hydrolysation reactors will be exactly adjusted to the respective application according to the product requirements. This exclusive procedure offered by PE is internationally protected by patents and provides guarantee of a 100% usage of caprolactam without a demonstrably negative impact on the quality of the product as well as for the high performance polyamide. 

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Green Process

The world exclusive recovery process, patented by PE, of extract containing water from extraction process comprises the evaporation which is designed particularly for the special conditions of polyamide product and the subsequent hydrolysation process. In this special adjusted recovery procedure it is not essential to take a clean with e.g. acidic or alkaline substances, which represents a high environmental impact as a result and requires significantly higher specific energy consumption, similar to other recovery plants offered for producing polyamide. In the technology applied by PE generates neither contamination nor deposits in the apparatus or equipment, as well no wastes or residues must be disposed or further handled with cost intensive.  Feeding the recovered extract concentrate into the main process enables to reduce considerably the consumption of caprolactam compared to conventional technique. The quality of polymer produced by this PE process does not differ demonstrably from such one made with 100% caprolactam and will be deemed as a real green process for the production of polyamide worldwide. 

The revamping of present plants is a specificity which can be offered by PE on the basis of a accurate and scientifical analysis of each plant. PE has developed special solutions for the modernization of present inefficient plant or for adjustment of end product quality in the current plant according to the requirement of the current market so as to integrate modularly and individually all above-mentioned modern and efficient technological solutions. So after implementation of such revamping the economy of material and energy efficiency and thus the profitability of existing plants can be significantly improved with relative small investments.