Reheaters

Freezing point NF M 07-048 ISO 3013 ASTM D 2386 Temperature of disappearance of cloud on reheating... 

After preliminary shop tests on different mockups (e.g. superheater and reheater headers and steamline pipe sections), since 1996 AEBIL systems have been installed and are at work on several power plant components. In particular, three different components have been monitored throughout 1997 (monitoring still under way at the time being) ... 

Place 5 mi. of ethyl acetate in a 100 ml. round-bottomed flask, and add about 50 ml. of 10% sodium hydroxide solution, together with some fragments of ungiazed porcelain. Fit the flask with a reflux water-condenser, and boil the mixture gently over a wire gauze for 30 minutes. Now disconnect the condenser, and fit it by means of a bent delivery-tube (or knee-tube ) to the flask for direct distillation (Fig. 59, or Fig. 23(0), p. 45). Reheat the liquid, and collect the first 10 ml. of distillate, which will consist of a dilute aqueous solution of ethanol. Confirm the presence of ethanol by the iodoform test Test 3, p. 336). 

When the addition of the bromobenzene is complete and the ether is boiling gently, reheat the flask on the water-bath for a further 15 minutes to ensure completion of the reaction the solution will now be slightly dark in colour, and only a trace of metallic magnesium should remain. 

Now remove the flask from the water-bath, and slowly add a solution of 5 ml. (5-2 g.) of dry ethyl benzoate in 15 ml. of anhydrous ether down the condenser in small quantities at a time, mixing the contents of the flask thoroughly between each addition. When the boiling of the ether again subsides, return the flask to the water-bath and reheat for a further 15 minutes. Then cool the mixture in ice-water, and carefully pour off the ethereal solution into a mixture of about 60 ml. of dilute sulphuric acid. and 100 g. of crushed ice contained in a flask of about 500 ml. capacity fitted for stearn-distillation, taking care to leave behind any unchanged magnesium. 

Note, (i) Care should be taken to distinguish between a residue of carbon which may be very difficult to bum off completely, and a really non-volatile residue due to the presence of a metallic derivative. Thus for instance starch leaves a hard black residue of carbon which can best be burned away by moistening with a saturated solution of ammonium nitrate and then reheating. 

Use the procedure given under 2 for p-bromophenacyl esters. If the ester does not crystallise out on coofing, reheat the reaction mixture, and add small portions of hot water to the point of incipient cloudiness and allow to cool. 

In some inlet devices, the volatile sample materials are first separated from entrained hydrogen gas or air by condensing them in a coolant bath. Subsequently, when all of the volatile sample components have been condensed and the hydrogen or air has been swept away, the sample is reheated and sent to the plasma flame. 

Dehumidification. Dehumidification may be accompHshed in several ways (see Drying). Moderate changes in humidity can be made by exposing the air stream to a surface whose temperature is below the dew point of the air. The air is cooled and releases a portion of its moisture. Closed cycle air conditioning systems normally effect dehumidification also. The cooled air may require reheating to attain the desired dry-bulb temperature if there is insufficient sensible load in the space. 

The double-bubble process may be used to produce biaxiaHy oriented film, primarily polypropylene. In this process the first bubble formation is similar to the conventional blown film, except that the bubble is not coUapsed. Rather it is reheated to the orientation temperature and blown and drawn further in a second stage. It is then coUapsed, sUt, and wound. This process is generally limited to a final film thickness of less than 24 p.m. 

Attempts have been made to perform thermal retorting ia a gas barrier flexible pouch or tray. The retort pouch, under development for many years, has a higher surface-to-volume ratio than a can and employs a heat seal rather than a mechanical closure. Similarly, plastic retort trays have higher surface-to-volume ratios and are usually heat seal closed. Plastic cans iatended for microwave reheating are composed of bodies fabricated from multilayer plastic including a high oxygen barrier material, plus double-seam aluminum closures. 

Thermoforming includes the extmsion of sheets, thicker than 0.25 mm, followed by forming a reheated sheet in an open-face mold by pressure, vacuum, or both. Sheet of less than 0.25 mm thick is therm oformed in-line, and filled and sealed with contents such as processed meats, cheeses, and pastas. 

Hot product char carries heat into the entrained bed to obtain the high heat-transfer rates required. Feed coal must be dried and pulverized. A portion of the char recovered from the reactor product stream is cooled and discharged as product. The remainder is reheated to 650—870°C in a char heater blown with air. Gases from the reactor are cooled and scmbbed free of product tar. Hydrogen sulfide is removed from the gas, and a portion is recycled to serve as the entrainment medium. 

An example of a modem, tangentially fired, supercritical, lignite-fuel furnace is shown in Figure 5. This unit, at maximum continuous ratings, supplies 2450 metric tons pet hour superheat steam at 26.6 MPa (3850 psi) and 544°C, and 2160 t/h reheat steam at 5.32 MPa (772 psi) and 541°C. These ate the values at the superheater and reheater oudet, respectively. Supercritical fluid-pressure installations ate, however, only rarely needed. Most power plants operate at subcritical pressures in the range of 12.4—19.3 MPa (1800—2800 psi). 

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