Pyrolysis optimum

A report on the continuous flash pyrolysis of biomass at atmospheric pressure to produce Hquids iadicates that pyrolysis temperatures must be optimized to maximize Hquid yields (36). It has been found that a sharp maximum ia the Hquid yields vs temperature curves exist and that the yields drop off sharply on both sides of this maximum. Pure ceUulose has been found to have an optimum temperature for Hquids at 500°C, while the wheat straw and wood species tested have optimum temperatures at 600°C and 500°C, respectively. Organic Hquid yields were of the order of 65 wt % of the dry biomass fed, but contained relatively large quantities of organic acids. 

The results of research into the fluidised bed pyrolysis of plastic wastes are reported, with reference to determining the optimum process conditions for the process with respect to the reactor behaviour. The study investigates the effects of process variables such as bed temperature, polymer feed rate, bed hold-up, fluidising velocity, and size of inert material. Findings illustrate the importance of the knowledge of the hydrodynamics of the fluidised bed and of the interactions between bed and polymer particles in the design and operation of the reactor. 15 refs. 

The purpose of the study was to determine the optimum conditions of operation of pyrolysis equipment by the combined solution of equations relating to the technological and economic analysis of the process. The material considered was poly(methyl methacrylate) one of the most popular types of plastic waste. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. 

Optimum operating conditions of the pyrolysis unit by joint solution of equations of teehnological and eeonomic analysis of the proeess. PMMA, one of the most popular types of plasties waste, was chosen as the example. Stages of teehnologieal analysis of industrial chemical processes are presented. 7 refs. Translation of Plast.Massy, No.6, 1995, p.37... 

Figure 11.1 shows the pyrogram of lead white pigmented linseed oil paint obtained at 610 °C with a Curie-point pyrolyser, with on-line methylation using 2.5% methanolic TMAH. The pyrolyser was a Curie-point pyrolysis system FOM 5-LX, specifically developed at FOM Amolf Institute (Amsterdam, the Netherlands), to reduce cold spots to a minimum. This means that the sample can be flushed before pyrolysis in a cold zone, and it also ensures optimum pressure condition within the pyrolysis chamber, thus guaranteeing an efficient transport to the GC injection system [12]. 

The two most convenient procedures for preparing ketene are the present one and the pyrolysis of acetone over a hot wire. The latter procedure can give ketene at a faster rate (0.45 mole per hr. versus 0.2 mole per hr.), but it takes considerable adjustment to get optimum conditions, and trouble is sometimes caused by the wire getting coated with carbon. Furthermore, because the efl ciency of a given wire coil varies with time, passing throu a maximum, frequent calibration of the apparatus is necessary. The present method is more reliable and is the method of choice, when diketene is available. 

Both the COED process and Garrett Flash Pyrolysis have been "proved" in small demonstration plants and subject to tests designed to establish optimum operating conditions for a particular feed coal, both are claimed to be ready for commercial use. 

Significant amounts of CH4 and C2H2 are also formed but will be ignored for the purposes of this example. The ethane is diluted with steam and passed through a tubular furnace. Steam is used for reasons very similar to those in the case of ethylbenzene pyrolysis (Section 1.3.2., Example 1.1) in particular it reduces the amounts of undesired byproducts. The economic optimum proportion of steam is, however, rather less than in the case of ethylbenzene. We will suppose that the reaction is to be carried out in an isothermal tubular reactor which will be maintained at 900°C. Ethane will be supplied to the reactor at a rate of 20 tonne/h it will be diluted with steam in the ratio 0.3 mole steam 1 mole ethane. The required fractional conversion of ethane is 0.6 (the conversion per pass is relatively low to reduce byproduct formation unconverted ethane is separated and recycled). The operating pressure is 1.4 bar total, and will be assumed constant, i.e. the pressure drop through the reactor will be neglected. 

A Systems Approach to Optimum Pyrolysis Reactor Design... 

Pyrolysis is the thermal decomposition occurring in the absence of oxygen. It is always the first step in combustion and gasification processes where it is followed by total or partial oxidation of primary products. Lower process temperature and longer vapour residence times favour the production of charcoal. High temperature and longer residence time increase the biomass conversion to gas, and moderate temperature and short vapour residence time are optimum for producing liquids. 

As stated previously, optimal temperatures and residence times are needed for maximal bio-oil production, which could be achieved in so-called fast or flash pyrolysis, when the residence time of the pyrolysis vapors and the optimal temperature are 0.1-2 s and between 400°C and 650°C, respectively [12, 13], with the optimum being usually approximately 500°C [14], Reactors where the optimal pyrolysis conditions can be achieved include the following [11, 13, 15, 16] ... 

Pyrolysis reactions of mononuclear carbonyls and low-nuclearity cluster compounds have been used extensively in the syntheses of HNCC of osmium (54, 72,80,95,108), ruthenium (18,20,29), and, more recently, rhenium (2-4). The reactions have been carried out either in inert solvents or, to facilitate the ejection of CO or other volatile ligands, in the solid state under vacuum. Condensation processes under pyrolytic conditions are rarely specific and, as such, lead to the formation of a wide range of products. In order to obtain optimum yields of a particular HNCC, the reaction conditions must be carefully screened. Solution reactions offer advantages such as the ability to monitor the progress of the reaction using IR spectroscopy. As they often give... 

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