Rotary kiln reactors pyrolysis

The Veba Oel pyrolysis processes was originally designed for the upgrading of heavy oil hydrogenation residues (such as coal and petroleum residues). The pyrolysis process uses a rotary kiln reactor with spheres and crossform bodies to prevent coke deposition. The kilns used in this process were operational until 1964. However, it was found that these kilns had three disadvantages [8] ... 

Li et al. [16] also stndied the influence of pyrolysis temperature on the pyrolysis products derived from solid waste in a rotary kiln reactor. They used an externally heated laboratory-scale rotary kiln pyrolyser (Figure 19.8). The length of the rotary kiln was 0.45 m with an internal diameter of 0.205 m. Kiln rotation speed can be adjusted from 0.5 to 10 rpm. The raw materials used in this study were polyethylene (PE), wood and waste tyres. The results obtained by Li et al. [16] reiterated that as the reaction temperature profile changes so does the product yield (Figure 19.9). 

As described previously pyrolysis is a process that thermally degrades organic waste at high temperatures in absence of air and oxygen. This process can be carried out in a rotary kiln reactor or in a fluidized bed. In a rotary kiln process the feed material is conveyed through a rotating drum (i.e. reactor) and is then pyrolysed in the hot atmosphere into gas and solid residues. The residence time of the reaction is dependent on the rotating... 

The most popular type of gasification furnace in Europe is the vertical shaft gasifier, used in the Andco-Torrax, Saarberg Fernvarme and Pyrogas process. Pyrolysis processes are often conducted in an indirectly heated rotary kiln reactor, e.g. in the Kiener, GMU or Krauss-Maffei process. Fluidized bed reactors are used at the universities of Hamburg, Eindhoven and Brussels and thus seem more popular in academic than in industrial spheres. 

Conrad process—American Plastics Council Variable residence time and pyrolysis temperatures, rotary kiln reactor, CaO for HCl capture Feedstock for steam crackers giving higher amount of monomers, 86% naphta grade products 381a... 

The majority of the cyanuric acid produced commercially is made via pyrolysis of urea [57-13-6] (mp 135°C) primarily employing either directiy or indirectly fired stainless steel rotary kilns. Small amounts of CA are produced by pyrolysis of urea in stirred batch or continuous reactors, over molten tin, or in sulfolane. The feed to the kilns can be either urea soHd, melt, or aqueous solution. Since conversion of urea to CA is endothermic and goes through a plastic stage, heat and mass transport are important process considerations. The kiln operates under slight vacuum. Air is drawn into the kiln to avoid explosive concentrations of ammonia (15—27 mol %). 

Different types of reactors are utilized for a wide variety of pyrolysis applications, including processing of waste plastics. The worldwide waste plastic pyrolysis systems utilize the fixed-bed designs of vertical shaft reactors and dual fluidized-bed, rotary kiln and multiple hearth reactor systems. The type of reactor used is chiefly based on material to be pyrolyzed and expected products from the pyrolysis. Stainless steel shaking type batch autoclave and stainless steel micro tubular reactors have also been used extensively [14]. Fluidized-bed reactors have been extensively used in producing raw petrochemicals from the pyrolysis of waste plastics [22, 24]. 

The majority of the scientific literatnre devoted to pyrolysis of plastics is focused on the development of equipment or processes having recycling as their ultimate goal. Many of these have been introdnced in previous chapters and include studies using fluidized beds [61-77], cycled-sphere reactors [78, 79], fixed-bed reactors [80, 81], rotary kilns [82], screw reactors [83] and rotating cone reactors [84]. In all these studies the chemical analysis of the pyrolysis prodncts has been an important goal in order to asses the behavionr of the pyrolysis of plastics. 

The dehydrochlorinated molten polymer in the molten polymer vessel is qnantitatively fed into the pyrolysis reactor (Figure 26.11), which is of rotary kiln type. It has a hot air jacket and ceramic balls inside to prevent coking problems, as shown on the Fignre 26.12. Thermal degradation is at 400°C and 5 kPa overpressure. 

A limitation of vacuum pyrolysis technology is heat transfer. Previous studies have shown that the rate of heat transfer is essentially the rate limiting step for pyrolysis reactions [2]. Conventional pyrolysis reactors such as multiple hearth furnaces, rotary kilns and screw type reactors exhibit overall heat transfer coefficients ranging from 10 to 60 [3], depending on the type of feedstock handled. The low thermal... 

Pyrolysis can be used for the thermal decomposition of waste materials that are predominantly organic in nature, e.g. scrap tyres, scrap cables, waste plastics, shredder wastes, and acid sludge. Rotary kilns are particularly suitable as universally applicable pyrolysis units for continuous operation. Highly aromatic pyrolysis oils for use as chemical raw materials are obtained at reactor temperatures of about 700 °G. Such pyrolysis oils could form the basis for the production of aromatics such as benzene, naphthalene, and their homologues, thermoplastic hydrocarbon resins and precursors of industrial carbon, when the proven processes for the refining of coal tar and crude benzene are applied. 

Several pyrolysis processes using reactors such as a fluidized bed (3 ), a shaft furnace, an extruder and a rotary kiln have also been studied in Japan. Pyrolysis using a rotary kiln has been studied since 1973 (U ). A pilot plant test was finished in 1976, and an actual plant with a capacity of 7,000 ton per year has been constructed at Sumitomo Cement Co., Ltd. in AK0 City, Hyogo Prefecture, in 1979 (l) The plant will recover fuel oil and carbon black from the scrap tires. 

The pyrolysis is complicated by the fact that plastics show poor thermal conductivity, while the degradation of macromolecules requires considerable amounts of energy. The pyrolysis of mixed plastic wastes and used tires has been studied in melting vessels, blast furnaces, autoclaves, tube reactors, rotary kilns, cooking chambers, and fluidized bed reactors [17,18]. 

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