Development system, pyrolysis technology

Three recycling news items are very briefly reported upon a Canadian-developed pyrolysis technology that converts plastics scrap into alpha-olefins, a scrap-plastics-to-monomers system under construction in Scotland, and statistical forecasts on chemical recycling in Germany for 1996. 

Figure 1 shows a computational framework, representing many years of Braun s research and development efforts in pyrolysis technology. Input to the system is a data base including pilot, commercial and literature sources. The data form the basis of a pyrolysis reactor model consistent with both theoretical and practical considerations. Modern computational techniques are used in the identification of model parameters. The model is then incorporated into a computer system capable of handling a wide range of industrial problems. Some of the applications are reactor design, economic and flexibility studies and process optimization and control. 

Pyrolysis of tyres is a feasible, yet technically difficult operation. The handling of the remnants of the steel carcass, the carbon black, the zinc oxide, as well as the tendency to repolymerize of the major products are serious stumbling blocks. Various rubber pyrolysis technologies have been developed, using, e.g. fluid bed, rotary kiln (Sumitomo Cement), molten salts, or cross-flow shaft systems (WSL/Foster Wheeler). 

The 1973 petroleum crisis intensified research on coal liquefaction and conversion processes. The technology developed in this field was later harnessed in chemical recycling of plastics. Mastral et al. [32], for example, employed two different batch reaction systems (tubing bomb reactors and magnetically stirred autoclave) and a continuous reactor (swept fixed bed reactor). Chemical recycling techniques such as pyrolysis [28, 33-38] or coliquefaction with coal [39, 40] convert plastic wastes into hydrocarbons that are valuable industrial raw materials. 

The pyrolysis section of the system has a capacity of 600 t/d wet bagasse, which corresponds to the typical capacity of wood pyrolysis plants that are foreseen by the process technology developers and that have been analyzed in previous technical economic studies. ... 

On the basis of these circumstances, the need for a better solid waste disposal system has stimulated a great deal of interest in the application of pyrolysis to solid wastes instead of the traditional incineration system in our country. Since the Agency of Industrial Science Technology, MITI had launched the national project on development of technology and system of resource recovery from refuse in 1973, more than a dozen processes of PTGL are being developed at the national level, municipal level, and the level of private companies as shown in Table I. 

Resource Recovery Process System Developed by National Project. Phase I of the national project was carried out from 1973 to 1976 for developing the feasible technology and systems of resource recovery from solid wastes, and the demonstration plant (100 tons/day) for the material - reclamation system in phase II is under construction. The pyrolysis processes which have been developed in phase I of the national project are as follows ... 

Bio-Electrics, Incorporated, has developed the Electrofrac Detoxification System to treat hazardous contaminants in soil. The system, which was developed from gasification research, uses electrodes placed in soil to heat the site. There are potential applications of this technology for removal of volatile organic compounds (VOCs), pyrolysis of non-VOCs, treatment of organic residues, and in situ vitrification of soils and asbestos. There have been bench-scale tests of the technology for remediation applications. 

TerraTherm Environmental Services, Inc., a subsidiary of Shell Technology Ventures, Inc., has developed the in situ thermal desorption (ISTD) thermal blanket technology to treat or remove volatile and semivolatile contaminants from near-surface soils and pavements. The contaminant removal is accomplished by heating the soil in sim (without excavation) to desorb and treat contaminants. In addition to evaporation and volatilization, contaminants are removed by several mechanisms, including steam distillation, pyrolysis, oxidation, and other chemical reactions. Vaporized contaminants are drawn to the surface by vacuum, collected beneath an impermeable sheet, and routed to a vapor treatment system where contaminants are thermally oxidized or adsorbed. 

Originally, extractive distillation was limited to two-component problems. However, recent developments in solvent technology enabled applications of this hybrid separation in multicomponent systems as well. An example of such application is the BTX process of the GTC Technology Corp., shown in Figure 6, in which extractive distillation replaced the conventional liquid-liquid extraction to separate aromatics from catalytic reformate or pyrolysis gasoline. This led to a ca. 25% lower capital cost and a ca. 15% decrease in energy consumption (170). Some other examples of existing and potential applications of the extractive distillations are listed in Table 6. 

The pyrolysis of tires based on rotary kiln technology started quite early in the 1970s. A field-scale rotary kiln at Rocky Flats is documented in [5]. Very new developments can be found in [6]. The rotary kiln developed by Faulkner has several distinct heating zones independent from each other. The system consists of a rotary feed cylinder that includes a screw-Uke flight extending from the inner wall of the feed cylinder. As the feed cylinder rotates, the flight directs the supply of vehicle tire pieces into the infeed end of the pyrolysis section. The temperature levels of the kiln zones decrease from a maximum of 800°C to 500°C at the end of the kiln. A separation of char and scrap steel... 

X HE USE OF CHEMICAL APPROACHES to improve the processing, properties, and performance of advanced ceramic materials is a rapidly growing area of research and development. One approach involves the preparation of organometallic polymer precursors and their controlled pyrolysis to ceramic materials. This chapter will review the preparation and application of silicon-, carbon-, and nitrogen-containing polymer systems. However, the discussion is not exhaustive the focus is on systems with historical significance or that demonstrate key technological advances. 

Several processes have been developed [41-43] to overcome the technological drawbacks of plastics incineration cited above. These include continuous rotary-kiln processes a process for glass-reinforced PET a combined system for wood fiber and PET to provide steam to power equipment and a fluidized system for pyrolysis, in combination with silver recovery from photographic film. Incineration of photographic film raises the additional problem of the formation of toxic halogenated compounds due to the presence of silver halides. 

Chapter 6 describes the concept of hybrid mass spectrometric system with ion attachment technique as ionization method. A combined (hypemated) MS represents time-of-flight (TOP), ion trap quadmpole, ion mobility spectroscopy, ion cyclotron resonance (ICR) or aerosol MS, while descriptions of specially designed inlet system include chromatographic introduction (inlets), and various pyrolysis probes for evolved gas analysis. Some applications of each technology are presented, together with representative and/or illustrative examples. In addition, development of portable lAMS is provided along with explanations and spectral applications. 

Synthetic routes derived from molecular and non-molecular precursors have expedited the development of technologically important 2- and 3- dimensional materials. Such approaches have often proved superior to conventional ceramic techniques in that high purity bulk samples or thin films can be prepared at lower temperatures much more rapidly. Predominant among the precursor methods are those based on decomposition reactions. These either involve gaseous species, such as those used in chemical vapor deposition (CVD), or solids. Examples include the pyrolysis of the gas-phase precursor [(CH3)2A1(NH2)]3 to produce aluminum nitride (i) and the thermal decomposition of solid state carbonate precursors of calcium and manganese (Cai j,Mn C03, 0 < x < 1) to produce several of the known ternary compounds in the Ca-Mn-O system (2). Single-displacement reactions are also common as precursor methods. These approaches usually involve gas-phase reactions and are also used in CVD techniques. Examples here include the formation oi... 

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