Plastics Feedstocks

However, more recently, ethylene production in China has been on the rise. For example, in 2003, China s output of ethylene increased by 15%, to 3.44 million tonnes, according to the State Statistical Bureau. Ethylene consumption in the same period rose by 14%, to 3.45 million tonnes. Output of purified terephthalic acid - a key raw material in the production of many petrochemical derivatives and plastics - rose by 10%, to reach 1.47 million tonnes, while the production of benzene increased 16%, to 1.16 million tonnes. 

China s two major state-owned companies - China Petrochemical Group Corp (Sinopec Beijing www.sinopec.com) and China National Petroleum Corp (CNPC Beijing www.cnpc.com.cn) - still dominate the production of feedstock ethylene and many petrochemical intermediates and downstream products, and their combined capacity accounts for more than 90% of the country s total output. However, increasingly, Sinopec and CNPC have been partnering with many of the world s leading chemical companies to build world-class petrochemical complexes. 

56 Plastics China Technologies, Markets and Growth Strategies to 2008 

---

A new application oF triboeleetrie separation involves the separation oF PVC From PET and other plasties. Recent developments in pre-eharging technology permit PVC to assume a strong negative charge and be removed cFFieientlv From properly protected mixed plastic Feedstocks (Fig, 19-62),... 

A 20ft-high mini plant has been built at BP s refinery at Grangemouth, near Edinburgh, as an experiment by several leading European petrochemical companies to address the difficult issue of plastic recycling. The 7501/ y pilot plant accepts mixed plastics ground into pieces a maximum of 2cm across and passes them over hot sand which converts them into a gas. This is distilled back into plastic feedstock which can be fed back into the petroehemical plant to make fresh plastic. This process eould be replieated at many small plants, located at ehemieal works or even beside municipal waste tips. 

BASF has delayed a decision on whether to press ahead with a DM300 million investment in a plastics feedstock recycling unit at Ludwigshafen. The decision to go ahead depends on the winning of a contract from DKR, a new recycling company for plastics packaging waste. The article supplies full details. 

The composition of the plastic feedstock for pyrolysis processes has a direct bearing on the quality of the resultant fuel products, especially flash point, cetane index, low-temperature properties and heteroatom content (e.g. sulphur, chlorine and nitrogen). 

It has been demonstrated that oil recovered from PVC-containing plastic feedstock can be used as a fuel. Cost is the main obstacle since it requires a large amount of slaked lime to neutralize the HCl gas that is produced by the thermal cracking. Table 15.1 shows the effect that slaked lime has on reducing the chlorine content of fuel oil derived from the pyrolysis of PE (55 wt%), PP (28 wt%) and PS (17 wt%) at a decomposition temperature of 420°C. 

Plastic feedstock specifications are extremely important in order to obtain satisfactory and consistent fuel quality (see Table 15.2). A rigid incoming feedstock specification (IFS) ensures that limits are placed on critical contaminants. The critical contamination is based around the so-called hetero-atoms . These are listed below in order of priority ... 

Table 15.2 Properties of fuel produced by pyrolysis of various plastic feedstocks. (Reproduced by permission of Masataka Tsukada)...

Figure 15.4 A schematic of a typical continuous stirred tank pyrolysis process. Legend 1 pyrolysis vessel with internal agitator 2 catalyst chamber 3 plastic feedstock hopper 4 char auger to remove solid residue 5 agitator drive motor 6 lower temperature sensor 7 upper temperature sensor 8 burner for furnace 9 feed auger for plastic feedstock 10 condenser cooling jacket 11 condenser 12 oil recovery tank (adapted from Saito, K. and Nanba, M., United States Patent 4,584,421 (1986) Method for thermal decomposition of plastic scraps and apparatus for disposal of plastic scraps )...

Nickel silicate and ferrous silicate are the preferred catalysts in the Smuda process. The Smuda catalyst is a layered silicate clay framework with ordered nickel (or iron) atoms inside. The catalyst is charged at 10 wt% ratio of the plastic feedstock. The catalysts are based on layered silicates with Lewis acid activity [24]. Catalytic cracking results in very little noncondensable gas (<1%) and minimal carbonaceous char. The hfe of the Smuda catalyst is approximately 1 month [24]. 

Due to the sensitivity of the catalyst, the Smuda process requires that the plastic feedstock be pre-processed and cleaned by mechanical processing (i.e. other than washing). In this way dirt, food impurities, etc. can be removed before they deactivate the catalyst [24]. 

The biggest difference between this process and the others lies in the reactor, which was originally a fixed-bed reactor. A sand fluidized-bed reactor has been adopted for the BP process, which can guarantee a uniform temperature in the reactor due to the uniform particle size and fluidized nature of sand. In traditional processes, because of the poor heat transfer properties of plastics, a uniform temperature is difficult to achieve in the plastics feedstocks so a long reaction time was always required. On the other hand, after waste plastics are heated and melted, they usually adhere to the surface of reactors owing to their poor flow characteristics. The BP process has successfully solved all these problems, and a continuous production of liquid oil is achieved. 

Co-extrusion processing using thermoplastic binder systems for ceramic bodies has been described by Van Hoy [Hoy 98]. The major binder component used in this study was ethylene vinyl acetate, and methoxypoly-ethylene glycol was used as a plasticizer. Feedstocks of alumina, a piezoelectric ceramic powder and carbon black were repeatedly co-extruded to form an array of fine M -shaped structures. With this method the size of the alumina M shapes could be reduced by a factor of 915. In this example the use of solvent-based binders would have been problematical because of drying of the feedstocks and extrudates during the co-extrusion process and during handling. 

In the future, feedstock recycling of mixed plastics to synthesis gas, petrochemical feedstocks, coal and coke replacements, and monomers has the potential to complement mechanical recycling processes at a significant scale worldwide. Many of the plastic feedstock recycling processes appear to be technically feasible and robust enough to warrant further development. Much more needs to be understood about infrastructure requirements, feedstock quality requirements, processing, and economics. 

Some spontaneous processes take place over geological time scales—the formation of petroleum used for plastics feedstocks,... 

Process energy, fossil, GJ/t plastic Feedstock energy, fossil, GJ/t plastic Total fossil energy, GJ/t plastic Fossil CO2 from process energy, kg/t plastic CO2 absorption, plant growth, kg/t plastic NetC02, kg/t PLA ... 

Suitable waste plastics feedstocks are single contaminated polymers with high selectivity to monomers or commingled waste plastics. Some mixed polymer waste streams and their estimated volume, (US 1993 statistics), amenable to recovery/recycling by thermolytic processes are shown in Table [1]. 

---