Drop-tube furnace rates

The volatility determination was part of a program to determine devolatilization kinetics fen petroleum coke. Samples of the petroleum coke were reacted in the drop tube furnace at ten )eratuies fiom 1000"C to 1700 C, in an argon atmosphere, to determine the rate of devolatilization. The procedure for calculating the kinetics was as follows ... 

The centerline gas velocity was approximated by doubling the bulk gas velocity. The bulk gas velocity was calculated as the volumetric gas flow rate divided by the cross sectional area of the tube inside the drop tube furnace. Stokes law was used to calculate the terminal velocity. At a temperature of 1700 C (3092°F). the calculated residence time for the coal particles was 186ms. The resulting devolatilization kinetics for petroleum coke are shown in Hgure 2.2. The devolatilization reactivity equations among various petroleum cokes will be reasonably consistent rather, the significant variability will come fi om the maximum volatile yield. 

Kajitani, S., Hara, S., and Matsuda, H. (2002) Gasification rate analysis of coal char with a pressurized drop tube furnace. Fuel, 81 (5), 539-546. 

The complete assembly for carrying out the catalytic decomposition of acids into ketones is shown in Fig. Ill, 72, 1. The main part of the apparatus consists of a device for dropping the acid at constant rate into a combustion tube containing the catalyst (manganous oxide deposited upon pumice) and heated electrically to about 350° the reaction products are condensed by a double surface condenser and coUected in a flask (which may be cooled in ice, if necessary) a glass bubbler at the end of the apparatus indicates the rate of decomposition (evolution of carbon dioxide). The furnace may be a commercial cylindrical furnace, about 70 cm. in length, but it is excellent practice, and certainly very much cheaper, to construct it from simple materials. 

The furnace is heated to 300-340° (Note 2), and 204 g. (195 cc., 2 moles) of tetrahydrofurfuryl alcohol (Note 3) is introduced from the dropping funnel at the rate of 50 cc. per hour. The product, collected in an Erlenmeyer flask which contains 30 g. of anhydrous potassium carbonate, consists of a light brown oil and a lower aqueous layer. When the reaction tube has drained, the lower aqueous layer is separated and discarded. The upper layer is fractionated through a short column, and a fraction boiling at 70-86° is collected. This consists of a mixture of water and dihydropyrane, most of which distils at 83-86°. The residue (25-35 g.) is mainly unchanged tetrahydrofurfuryl alcohol (Note 4). 

Now open the cocks on the absorption apparatus and the cock on the aspirator, and make sure that the previously determined rate of flow of the bubbles in the counter is maintained. A difference of 1-2 units in the number of bubbles passing in ten seconds has no detrimental effect. If necessary, restore the former rate of flow of the bubbles by lowering or raising the levelling tube of the aspirator. (Collect the water which drops from the aspirator during the analysis in a 500 c.c. measuring cylinder). Then place in position the copper-wire frame which conducts the heat from the furnace to the constricted part of the tube and to the side tube of the calcium chloride tube so that the metal touches the glass. Condensation of water in the side tubes is thus absolutely prevented. 

In an industrial facility, air is to be preheated before entering a furnace by geo-u thermal water at 120°C flowing through the tubes of a tube bank located in a S duct. Air enters the duct at 20°C and 1 atm v/ith a mean velocity of 4.5 m/s, H and flows over the tubes in normal direction. The outer diameter of the tubes is 1.5 cm, and the lubes are arranged in-line with longitudinal and transverse pilches of Sr = Sf = 5 cm. There are 6 rows in the flow direction with 10 tubes i in each row, as shown in Fig. 7-28. Determine the rate of heat transfer per unit 3 length of the tubes, and the pressure drop across the tube bank. 

Pybolysis Reactions. A pyrolysis apparatus consisting of a 30 mm. o.d. borosilicate glass tube filled with 75 ml. of 3 mm. borosilicate glass beads was heated to 435°C. in a tubular furnace. The sample to be pyrolyzed was introduced at a rate of two drops every 5 sec. in a stream of nitrogen (16 ml./min.). The effluent from the reactor was condensed and collected from a dry-ice cooled trap. 

The furnace is heated to 590° (Note 4), and after the air has been displaced 200 g. (216 ml., 2 moles) of ethyl acrylate (Note 5) is placed in the separatory funnel and admitted to the reaction tube at a rate of about 90 drops a minute (Note 3), so that the addition requires about 2 hours. At the end of the addition the contents of the receiver and the small amount of liquid in the traps are combined. The total weight of crude acrylic acid containing some ethyl acrylate is 126-136 g. 

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