Pyrolysis continued reactor

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 %). 

Beside continuous horizontal kilns, numerous other methods for dry pyrolysis of urea have been described, eg, use of stirred batch or continuous reactors, ribbon mixers, ball mills, etc (109), heated metal surfaces such as moving belts, screws, rotating dmms, etc (110), molten tin or its alloys (111), dielectric heating (112), and fluidized beds (with performed urea cyanurate) (113). AH of these modifications yield impure CA. 

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. 

This reaction has been studied using batch reactors, perfectly stirred continuous reactors, tubular continuous reactors, BENSON type reactors, wall-less reactors and shock tubes. The reaction has been carried out at temperatures between 700 and 1300 K, at pressures of 0.1 Pa to 10 Pa and at reaction times of 10 s to 10 s. The effects of the nature and of the area of the reactor walls as well as those of various additives have also been studied. The diversity of the studies carried out by a dozen teams throughout the world, the particularly widespread range of operating conditions (600 K for the temperature, which represents 11 orders of magnitude for the rate of initiation, 8 orders of magnitude for the pressure and reaction duration) make the pyrolysis of neopentane into a model radical reaction. 

Continuous Reactions As a reaction vessel for a unimolecular reaction such as an ester pyrolysis, one thinks first of a pyrolysis tube, which is the simplest sort of continuous reactor. There are certain advantages to running bimolecular laboratory reactions in a similar manner Reaction times can be shorter, yields are higher (especially when heat-sensitive substances are involved), and less solvent is required. For large scale operations such as the first reactions in a long multistep synthesis, continuous reactors are worth considering. Two reactions are used to illustrate the technique. In the first, reactants are added from the top the volatile product distills out, and the nonvolatile product collects at the bottom. In the second, the nonvolatile reactant is added from the top and the volatile reactant from the side the products collect as before. 

Titanium disulfide can also be made by pyrolysis of titanium trisulfide at 550°C. A continuous process based on the reaction between titanium tetrachloride vapor and dry, oxygen-free hydrogen sulfide has been developed at pilot scale (173). The preheated reactants ate fed iato a tubular reactor at approximately 500°C. The product particles comprise orthogonally intersecting hexagonal plates or plate segments and have a relatively high surface area (>4 /g), quite different from the flat platelets produced from the reaction between titanium metal and sulfur vapor. The powder, reported to be stable to... 

Industrial Engineering Chemistry Research 37, No.6, June 1998, p.2316-22 DEVELOPMENT OF A CONTINUOUS ROTATING CONE REACTOR PILOT PLANT FOR THE PYROLYSIS OF POLYETHENE AND POLYPROPENE... 

A pilot plant for the high temperature pyrolysis of polymers to recycle plastic waste to valuable products based on rotating cone reactor (RCR) technology. The RCR used in this pilot plant, the continuous RCR was an improved version of the bench-scale RCR previously used for the pyrolysis of biomass, PE and PP. 9 refs. 

Continuous production of fullerenes was possible by pyrolysis of acetylene vapor in a radio-frequency induction heated cylinder of glassy polymeric carbon having multiple holes through which the gas mixture passes [44]. Fullerene production is seen at temperatures not exceeding 1500 K. The yield of fullerenes, however, generated by this method is less than 1%. A more efficient synthesis (up to 4.1% yield) was carried out in an inductively coupled radio-frequency thermal plasma reactor [45]. 

To illustrate the concepts of determining, non-determining and negligible processes, the mechanism of the pyrolysis of neopentane will be discussed briefly here. Neopentane pyrolysis has been chosen because it has been studied by various techniques batch reactor [105— 108], continuous flow stirred tank reactor [74, 109], tubular reactor [110], very low pressure pyrolysis [111], wall-less reactor [112, 113], non-quasi-stationary state pyrolysis [114, 115], single pulse shock tube [93, 116] amongst others, and over a large range of temperature, from... 

D. P. Serrano, J. Aguado, J. M. Escola, and E. Garagorri, Conversion of low density polyethylene into petrochemical feedstocks using a continuous screw kiln reactor, J. Anal. Appl. Pyrolysis, 58-59, 789 (2001). 

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