Wire-Mesh Reactors

Wire-mesh reactors can apply rapid heating (100-10 K/s) to small amoimts of particles ( 1 g). Therefore, a flat layer of coal particles is placed between two layers of wire-mesh that can be heated by electric current The pressure ranges from 10 to 100 bar and high-resolution data for temperature versus time can be gained. A carrier or reaction gas is forced through the wire-mesh, passing the particles and even gas distribution over the sample is accomplished [60,75]. 

The main purpose of investigations is to study the volatile matter yield and composition as well as the structure of a char produced during rapid heating. 

The measurement of gasification rates with several reactants is also possible [59]. 

The conditions in wire-mesh reactors fit better to entrained-flow systems and the gathered data are used for modeling the release of volatile matter, that is, the impacting flame formation. Although a small-scale and inexpensive method, investigations using wire-mesh reactors remain a more academic subject compare to TGA, which has been broadly used in industry. 

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Various laboratory reactors have been described in the literature [3, 11-13]. The most simple one is the packed bed tubular reactor where an amount of catalyst is held between plugs of quartz wool or wire mesh screens which the reactants pass through, preferably in plug flow . For low conversions this reactor is operated in the differential mode, for high conversions over the catalyst bed in the integral mode. By recirculation of the reactor exit flow one can approach a well mixed reactor system, the continuous flow stirred tank reactor (CSTR). This can be done either externally or internally [11, 12]. Without inlet and outlet feed, this reactor becomes a batch reactor, where the composition changes as a function of time (transient operation), in contrast with the steady state operation of the continuous flow reactors. 

A small modification of the above design, in which the catalyst in the form of granules or pellets is placed in an annular basket made of wire mesh fitted close to the reactor wall, has also been examined. The use of such an annular basket-type reactor has been reported by Tajbl et al. (1967), Relyea and Perlmutter (1968), and Lakshmanan and Rouleau (1970). The basic features of this reactor are the same as the ones described above. The reactor has been used to carry out high-pressure, high-temperature catalytic methanation of mixtures of carbon monoxide/hydrogen and carbon dioxide/hydrogen. 

Catalysts may be porous pellets, usually cylindrical or spherical in shape, ranging from 0.16 to 1.27 cm (Vm to Vi in) in diameter. Small sizes are recommended, but the pressure drop through the reactor increases. Among other shapes are honeycombs, ribbons, and wire mesh. Since catalysis is a surface phenomenon, a physical property of these particles is that the internal pore surface is nearly infinitely greater than the outside surface. 

This study was primarily focused on the volatility of tars that were prepared under conditions that minimize the extent of secondary reactions. Tars were produced using a fast pyrolysis technique (heating rate greater than 5 °C/sec). About 2 or 3 grams of sample on a wire mesh holder was pushed into the pre-heated tubular pyrolysis reactor. The sample temperature was measured by a thermocouple and the holder was pulled out from the heated region after the sample reached desired temperature. The final temperature was selected based on thermogravinietrig experiments at heating rate of 20 °C /min for each material studied and arc shown in Table 1. The inert gas (N ) flow was 300 ml/min at room temperature. That corresponds to the gas phase tar maximum... 

A gravimetric reactor was used in these experiments which consisted of an upflow vertical stainless steel reactor with catalyat contained in a gold wire mesh basket suspended from an overhead electronic balance. Isolation of the balance chamber is maintained by a downflow purge of an inert gas which exits with product gases above the catalyst basket. Experimental details of this unit have been given previously (ref. 1). 

Ten untreated oil shale samples were simultaneously pyrolyzed in a segmented reactor constructed of stainless steel (Figure 2). Approximately 12 g of shale was weighed into each 6-inch high individual sample vessel with stainless steel frit bottom. The vessels were placed into the 10 compartments of the reactor resting on a wire mesh so as to be positioned near the center of the furnace. The lid with 3 thermocouples and a gas inlet was bolted into place with a Viton 0-ring seal (the top... 

Platinum and silver gauze are used in ammonia and methanol oxidation to nitric oxide and formaldehyde, respectively. The gauze consists of fine wire mesh of O.Smm diameter, supported as layers within the reactor. Activation that pits" the metal wire is necessary to enhance the active surface area. ... 

In a typical test the wire mesh basket is initially in an upper, cooled portion of the reactor in which a downward, inert gas flow is maintained. During this time the desired temperature and pressure conditions are established in a lower, heated portion of the reactor in the presence of a flowing gas. A test is initiated by lowering the basket into the heated reaction zone, a procedure which takes 5-6 sec. Theoretical computation shows that about 2 min are needed for the sample to achieve reactor temperature as measured by several thermocouples surrounding the basket in the reaction zone. This computation is reasonably corroborated by various kinetic indications and by the behavior of the thermocouples in re-attaining their preset temperatures. The sample is kept in the heated portion of the reactor for the specified time while its weight is continuously recorded. The test is terminated by raising the basket back to the upper, cooled portion of the reactor. 

The 116-N-8 hazardous and mixed waste storage area Is a concrete-paved less-than-90-day waste container storage pad. The pad is curbed and surrounded by a wire mesh fence. The pad is 18 m by 46 m (60 ft by 152 ft) in size. It is located inside the double-fenced reactor area at the southern corner of the fence. The pad is covered by a roof and walled on two sides. 

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