Industrial-scale Pyrolysis Processes

The manufacture of the highly pure ketene required for ketenization and acetylation reactions is based on the pyrolysis of diketene, a method which has been employed in industrial manufacture. Conversion of diketene to monomeric ketene is accompHshed on an industrial scale by passing diketene vapor through a tube heated to 350—600°C. Thus, a convenient and technically feasible process for producing ketene uncontaminated by methane, other hydrocarbons, and carbon oxides, is available. Based on the feasibiHty of this process, diketene can be considered a more stable form of the unstable ketene. 

A series of industry-scale processes for recovery of liquid fuel from waste plastics have been developed and applied in countries such as the United States, Japan, Germany and England. Some of the processes, such as the Veba process, the BP process, the Fuji process and the Hunan University process have been applied widely and successfully in industry. Some typical pyrolysis processes are listed in Table 28.6. 

Various types of ceramic fibers, coatings, and moldings from precursor polymers are produced and commercialized on an industrial scale. The properties of ceramics are correlated with the microstructure formed in the thermal decomposition process. Detailed information about polymer pyrolysis is now required to control the qualities of the ceramics obtained. 

Industry Interest. One of Canada s leading solar and biomass conversion equipment companies, Petro-Sun International Inc. became interested in scaling up the Universite Laval/universite de Sherbrooke vacuum pyrolysis process on a cost-shared basis. Special Note. As of January 1988, Petro-Sun International Inc. was forced into receivership for reasons unrelated to their activities in biomass pyrolysis. The Universite Laval is seeking alternative industrial partners. Another company, Ensyn Engineering Ltd., was established, and proposed a cost-shared, scaled-up development of the University of Western Ontario ultrapyrolysis. Similarly, there has been a number of industrial expressions of interest in the University of Waterloo flash pyrolysis. 

While pyrolysis of coal plays an important role in the production of blast furnace coke on a large industrial scale (approximately 600 Mt of coal/year), it is of minor importance for biomass today. Around 50 Mio.t charcoal are used especially in South America as blast furnace coke. However, modem iron smelting processes would allow for substitution of coke by secondary reduction media and fuels produced from biomass and organic waste. Nonmetallurgical production of carbon is estimated at 18 Mt/year, approximately 600 000 t/year being used as adsorbent with its diverse applications. The latter is prepared mainly from coke, charcoal, and coconut shell coke. 

Catalysts (mostly zeohtes) have been employed in order to improve the conditions of the pyrolysis to yield more useful products and lower the operation temperatures. Nevertheless, the produced oils require further processing in order to meet standard fuel qualities [10]. Various problems such as blockages caused by the production of unwanted products such as coke, waxes, and organic acids have been encountered. Another problematic issue is the thermal conductivity ofplastics, which is low. Values as low as 0.17 and 0.33 Wm have been reported for the thermal conductivity of polypropylene (PP) and polyethylene (PE), respectively [11, 12]. Although most of these problems have been overcome one way or another and some industrial-scale units are operational in the world today, in general, the scale of production is too small to make these processes economically viable. Political and enviromnental pressure obliges the continuation of such endeavors [13]. 

Fuel industry is of increasing importance because of the rapidly growing energy needs worldwide. Many processes in fuel industry, e.g. fluidized catalytic cracking (FCC) [1], pyrolysis and hydrogenation of heavy oils [2], Fischer-Tropsch (FT) synthesis [3,4], methanol and dimethyl ether (DME) synthesis [5,6], are all carried out in multiphase reactors. The reactors for these processes are very large in scale. Unfortunately, they are complicated in design and their scale-up is very difflcult. Therefore, more and more attention has been paid to this field. The above mentioned chemical reactors, in which we are especially involved like deep catalytic pyrolysis and one-step synthesis of dimethyl ether, are focused on in this paper. 

---