Top-heating device

The most important manufacturing components are casting mould, top heating device, lifting platform, and stopping fixture for the glass strand. 

The casting mould is covered with the so-called top heating device with which it is preheated to approximately 1000 °C before casting. 

Top heating device Casting mould Scraper conveyor... 

After the transport vehicle is fixed on the centrifuge with the filled casting mould, the top heating device is raised a few centimetres above the casting mould. The centrifuge is set into rotation (5.6 revolutions per minute). The paraboloid-shaped upper side of the meniscus is generated by the centrifugal force. 

Fig. 4.25. Schematic representation of the structure of the spinning process with top heating device and cooling cover...

Conventional flame techniques present problems when dealing with either small or solid samples and in order to overcome these problems the electrothermal atomization technique was developed. Electrothermal, or flameless, atomizers are electrically heated devices which produce an atomic vapour (Figure 2.36). One type of cuvette consists of a graphite tube which has a small injection port drilled in the top surface. The tube is held between electrodes, which supply the current for heating and are also water-cooled to return the tube rapidly to an ambient temperature after atomization. 

Recent converter hardware development has concentrated on flame heated devices for terrestrial topping cycle applications. Significant progress has been made with chemical vapor deposited silicon carbide as the oxidation protection hot shell. Flame heated converters have now been operated by Thermo Electron Corporation with emitter temperatures over 1700 K for 7000+ hours ( ). 

The apparatus consists of a heating device (A) and a solvent reservoir and extract flask (B), which will be a round-bottomed flask if a heating mantle is used, or a flat-bottomed Florence flask if a hot plate is used to supply the heat. The heating mantle s temperature is controlled by a variable transformer (C). An extraction chamber (D) is placed on top of B and contains a porous paper extraction thimble (E), Figure 10-11. Porous ceramic extraction thimbles are also available. The sample (F) is placed inside of the thimble and covered with a small amount of glass wool (G) to spread out the extraction solvent and reduce channeling during the extraction. A condenser, usually an Allihn type (H), is connected to the top of the extraction chamber. 

We use a reactor with a cold inner surface, cylindrical and vertical. The gas inlet is at the top with a heating device in the middle, and the outflow of the gas at the bottom. 

A glass MSR was used to perform the dehydration of ethanol. The microchan-nel of size 200 X 80 pm deep X 30 mm (in a Z shaped configuration) was produced by photohthographic etching [71]. A sulfated zirconia catalyst immobihzed over the surface of the top cover block. In addition, a NiCr wire was immobilized in the reactor cover as a heating device. At a reaction temperature of 155 °C and a flow rate of 3 plmin the main products were 68% ethylene, 16% ethane, and 15% methane. A further increase of the residence time resulted in a reaction progress beyond dehydration to almost complete cracking of the ethanol to methane. 

It is good practice to unplug all heaters when not in use as some older heaters have malfunctioned in the off position or when the thermostat safety cutoff failed. These have resulted in fires in unattended laboratories (See Incident 7.3.1.3 and Figure 7.3.1.4). It is prudent to only operate these devices when you are present. Do not leave heating devices on overnight. Do not use heaters with plastic components on top of hot plates and do not use plastic water baths with immersion heaters - use metal water baths. Covering baths may prevent evaporation. 

Equip a 500 ml. three necked flask with a reflux condenser, a mercury-sealed mechanical stirrer and separator funnel, and support it on a water bath. Attach an absorption device (Fig. II, 8, 1, c) to the top of the condenser (1). Place 134 g. (152 ml.) of A.R, benzene and 127 g. of iodine in the flask, and heat the water bath to about 50° add 92 ml. of fuming nitric acid, sp. gr. 1-50, slowly from the separatory funnel during 30 minutes. Oxides of nitrogen are evolved in quantity. The temperature rises slowly without the application of heat until the mixture boils gently. When all the nitric acid has been introduced, reflux the mixture gently for 15 minutes. If iodine is still present, add more nitric acid to the warm solution until the purple colour (due to iodine) changes to brownish-red. 

In a 1 litre round-bottomed flask provided with an efficient double surface condenser, place 40 g. (39 ml.) of aniline, 50 g. (40 ml.) of carbon sulphide CAUTION inflammable) (1), and 50 g. (63-5 ml.) of absolute ethyl alcohol (2). Set up the apparatus in the fume cupboard or attach an absorption device to the top of the condenser (see Fig. 11, 8, 1) to absorb the hydrogen sulphide which is evolved. Heat upon an electrically-heated water bath or upon a steam bath for 8 hours or until the contents of the flask sohdify. When the reaction is complete, arrange the condenser for downward distillation (Fig. 11, 13, 3), and remove the excess of carbon disulphide and alcohol (CA UTION inflammable there must be no flame near the receiver). Shake the residue in the flask with excess of dilute hydrochloric acid (1 10) to remove any aniline present, filter at the pump, wash with water, and drain well. Dry in the steam oven. The yield of crude product, which is quite satisfactory for the preparation of phenyl iao-thiocyanute (Section IV.95), is 40-45 g. Recrystalhse the crude thiocarbanihde by dissolving it, under reflux, in boiling rectified spirit (filter through a hot water funnel if the solution is not clear), and add hot water until the solution just becomes cloudy and allow to cool. Pure sj/m.-diphenylthiourea separates in colourless needles, m.p, 154°,... 

Fig. 2. Rigid foam laminating line 1, material tank 2, agitator 3, metering pump 4, heat exchanger 5, bottom facet toU 6, bottom facet alignment device 7, top facet toU 8, top facet alignment device 9, mixing head 10, traverse assembly 11, top nip toU 12, bottom nip toU 13, take-up conveyor top belt with adjustable height 14, take-up conveyor bottom belt 15, curing oven 16, laminate 17, side-trim saws 18, cutoff saw (traversing) 19, laminated-panel stack...

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