Condensers surface

Surface condensers, as the name implies, provide a suitable heat transfer surface for condensing to occur. Consequently, cooling water and process fluids remain completely separated. However, the heat transfer surface is subject to fouling, corrosion, and plugging. Surface condensers are generally more expensive than direct contact condensers, but offer many advantages which frequently make them the most economical choice. Advantages include  

When water is used as a coolant, shell-and-tube units may be installed horizontally or vertically. Condensing may occur either on the tube side or the shell side. For air-cooled and eveporative-cooled condensers, the process elmost always is condensed inside horizontal tubes, although air-cooled units may be vertical or inclined. 

Steam used to drive a turbine can be extracted at an intermediate pressure for further use of the low-pressure steam. Rarely is the steam vented to the atmosphere, as this wastes steam and the condensate is also lost. Many turbines exhaust steam under vacuum to a surface condenser. The lower the pressure in the surface condenser, the greater the amount of work that can be extracted from each pound of steam (see Chap. 24, Steam Turbines). 

Discounting the presence of air leaks, the temperature inside the surface condenser determines the pressure of the steam exhausting from the turbine. This pressure is the vapor pressure of water at the surface condenser outlet temperature. 

The original steam condensers were barometric condensers, which were used to increase the efficiency of the steam-driven reciprocating beam engines by a factor of 10. The barometric condenser was invented by James Watt (the steam engine was invented by Thomas Newcomen). Exhaust steam is mixed directly with cold water. As this creates a vacuum, the barometric condenser must be elevated about 30 ft above grade. The mixed condensate and cooling water drains through a pipe called a barometric leg—hence the name barometric condenser. 

The surface condenser is an improvement on the barometric condenser, because it permits recovery of clean steam condensate. Other than this factor, the old-fashioned barometric condenser is more efficient than the more modern surface condenser. 

The shell-side pressure drop of the surface condenser is quite low. The vapor outlet flow consists of air drawn into the system through leaks, COj, and a small amount of uncondensed steam. The weight flow of vapor from the top of the condenser is 1 percent or less than the flow of condensate from the bottom of the condenser. 

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Now filter the ether through a fluted filter-paper directly into a 100 ml. distilling-flask, and then equip the latter with a 100° thermometer and a double-surface condenser to the end of the latter attach a receiver with a rubber delivery-tube precisely as before. Place the flask cautiously in a water-bath, the contents of which have previously been heated to about 60° at some distance from the apparatus arrange the depth of the flask in the water-bath so that the ether distils slowly over. Collect the fraction boiling between 34-39°. Yield, 25 g. (35 ml.). Not more than a verv small residue of etlianol should remain in the flask. 

Figs. II, 13, 7 and II, 13, 8 depict various set-ups which involve tlio refluxing of a liquid the Liebig condenser may, of course, be replaced by a double-surface condenser. In Fig. II, 13, 7 a calcium chloride guard protects the contents of the flask from ingress of moisture. The... 

Attention is directed to the fact that ether is highly inflammable and also extremely volatile (b.p. 35°), and great care should be taken that there is no naked flame in the vicinity of the liquid (see Section 11,14). Under no circumstances should ether be distilled over a bare flame, but always from a steam bath or an electrically-heated water bath (Fig.//, 5,1), and with a highly efficient double surface condenser. In the author s laboratory a special lead-covered bench is set aside for distillations with ether and other inflammable solvents. The author s ether still consists of an electrically-heated water bath (Fig. 11, 5, 1), fitted with the usual concentric copper rings two 10-inch double surface condensers (Davies type) are suitably supported on stands with heavy iron bases, and a bent adaptor is fitted to the second condenser furthermost from the water bath. The flask containing the ethereal solution is supported on the water bath, a short fractionating column or a simple bent still head is fitted into the neck of the flask, and the stUl head is connected to the condensers by a cork the recovered ether is collected in a vessel of appropriate size. 

Mg. 11, 56, 17 (Davies types) and Fig. 11, 56, 18 (double coil type) are examples of efficient double surface condensers. Fig. 11, 56, 19 depicts a screw type of condenser (Friedrich pattern) the jacket is usually 10, 15 or 25 cm. long and the cone and sockets are fil9 or 24 this highly efficient condenser is employed for both reflux and for downward distillation. 

Simple distillation. The assembly shown in Fig. II, 60, 1 is of general utihty for very volatile liquids the Liebig s condenser may be replaced by a double surface condenser. 

Fit the central neck of a 1-litre three-necked flask with an efficient double surface condenser and close the two side necks with corks (1). Place 52 g. (59-5 ml.) of ethyl n-valerate (Section 111,104) and 800 ml. of super-diy ethyl alcohol (Section 11,47, 5) (2) in the flask. Add 95 g. of clean sodium in small pieces through one of the apertures at such... 

Place a mixture of 114 g. (140 ml.) of methyl -amyl ketone (2-hepta-none) (1), 300 ml. of rectified spirit (95 per cent, ethyl alcohol) and 100 ml. of water (2) in a 1500 ml. three-necked fiask or in a 1500 ml. round-bottomed fiask provided with a two-way addition tube (Fig. 11,13, 9). Attach an efficient double surface condenser to the fiask and close the... 

Fit a 500 ml. round-bottomed flask with a dropping funnel and a double surface condenser alternatively, the flask may be provided with a two-way addition tube (Fig. II, 13, 9) and the dropping funnel and condenser inserted into the latter. Place 37 g. (46 ml.) of iso-butyl alcohol (b.p. 106-108°) and 40 g. (41 ml.) of pure pyridine in the flask and 119 g. (73 ml.) of redistilled thionyl chloride in the dropping funnel. Insert a cotton wool or calcium chloride guard tube into the mouth of the funnel. Introduce the thionyl chloride during 3-4 hours a white solid... 

Owing to the corrosive action of bromine upon corks j-jg 7, l. and rubber stoppers, ground glass joints are recommended in this preparation. The apparatus, depicted in Fig. Ill, 37, 1, is particularly convenient for the preparation of bromides from alcohols. A double surface condenser is fitted into D and a round-bottomed flask is fitted on to the ground glass joint at C R is a three-way stopcock f which permits the removal of the contents of A without disconnecting the apparatus. For preparations of moderate size, A has a capacity of 60 or 100 ml. and a 250 or 500 ml. flask is attached at C. 

Place 92 5 g. (114 5 ml.) of n-butyl alcohol and 8 55 g. of purified red phosphorus (Section 11,50,5) in a 500 ml. round-bottomed flask (attached at C) and 100 g. (32 ml.) of bromine in A. Pass a stream of cold water through the condenser F and through the double surface condenser fitted at D the condenser F prevents the volatilisation of the alcohol from the... 

Alternatively, place the mixture of alcohol and red phosphorus in a 500 ml. three-necked flask fitted with a mechanical stirrer, dropping funnel and double surface condenser. Heat the phosphorus - alcohol mixture to about 250°, and add the bromine whilst stirring vigorously. Work up the reaction product as above. 

In a 1-litre three-necked flask, mounted on a steam bath and provided respectively with a separatory funnel, mechanical stirrer and double surface condenser, place 165 g. of bromoform (96 per cent.). Add 10 ml. of a solution of sodium arsenite made by dissolving 77 g. of A.R. arsenious oxide and 148 g. of A.R. sodium hydroxide in 475 ml. of water. Warm the mixture gently to start the reaction, and introduce the remainder of the sodium arsenite solution during 30-45 minutes at such a rate that the mixture refluxes gently. Subsequently heat the flask on the steam bath for 3-4 hours. Steam distil the reaction mixture (Fig. 11, 41, 1) and separate the lower layer of methylene bromide (79 g.). Extract the aqueous layer with about 100 ml. of ether a further 3 g. of methylene bromide is obtained. Dry with 3-4 g. of anhydrous calcium chloride, and distil from a Claisen flask with fractionating side arm. The methylene bromide boils constantly at 96-97° and is almost colourless. 

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. 

To obtain a maximum yield of the acid it is necessary to hydrolyse the by-product, iaoamyl iaovalerate this is most economically effected with methyl alcoholic sodium hydroxide. Place a mixture of 20 g. of sodium hydroxide pellets, 25 ml. of water and 225 ml. of methyl alcohol in a 500 ml. round-bottomed flask fitted with a reflux (double surface) condenser, warm until the sodium hydroxide dissolves, add the ester layer and reflux the mixture for a period of 15 minutes. Rearrange the flask for distillation (Fig. II, 13, 3) and distil off the methyl alcohol until the residue becomes pasty. Then add about 200 ml. of water and continue the distfllation until the temperature reaches 98-100°. Pour the residue in the flask, consisting of an aqueous solution of sodium iaovalerate, into a 600 ml. beaker and add sufficient water to dissolve any solid which separates. Add slowly, with stirring, a solution of 15 ml. of concentrated sulphuric acid in 50 ml. of water, and extract the hberated acid with 25 ml. of carbon tetrachloride. Combine this extract with extract (A), dry with a httle anhydrous magnesium or calcium sulphate, and distil off the carbon tetrachloride (Fig. II, 13, 4 150 ml. distiUing or Claisen flask), and then distil the residue. Collect the wovaleric acid 172-176°. The yield is 56 g. 

Place 100 g. (105 ml.) of n-butyl cyanide (Section 111,113) and a solution of 92 g. of pure sodium hydroxide in 260 ml. of water in a 1500 ml. round-bottomed flask, attach a double surface condenser, and reflux... 

Ethyl bromoacetate (1). Fit a large modified Dean and Stark apparatus provided with a stopcock at the lower end (a convenient size is shown in Fig. Ill, 126, 1) to the 1-htre flask containing the crude bromoacetic acid of the previous preparation and attach a double surface condenser to the upper end. Mix the acid with 155 ml. of absolute ethyl alcohol, 240 ml. of sodium-dried benzene and 1 ml. of concentrated sulphuric acid. Heat the flask on a water bath water, benzene and alcohol will collect in the special apparatus and separate into two layers, the lower layer consisting of approximately 50 per cent, alcohol. Run ofi the lower layer (ca. 75 ml.), which includes all the water formed in the... 

Fit a 1-litre three-necked flask with two double surface condensers and a glycerine-scaled stirrer (Fig. II, 7, 10). Place 25 g. (29 ml.) of mesityl oxide (Section 111,79), 50 ml. of dioxan and a cold (10°) solution... 

Allyl cyanide. Into a 1 5 litre three-necked flask (1), provided with a mercury-sealed stirrer and two long double surface condensers, place 293 g. (210 ml.) of freshly-distilled allyl bromide, b.p. 70-71° (Section III, 35) and 226 g. of dry cuprous cyanide (Section 11,50,3, Method 1), Remove the mercury-sealed stirrer and replace it by a tightly fitting... 

Place 56 g. of clean sodium, cut into small pieces, in a 500 ml. round-bottomed flask fitted with two 25 or 30 cm. double surface condensers in series. Weigh out 136 g. (72 ml.) of freshly distilled allyl iodide, b.p. 99-101° (Section 111,39). Introduce about one quarter of the aUyl iodide through the condensers. Warm the flask gently until the sodium commences to melt and immediately remove the flame. A vigorous reaction sets in and a liquid refluxes in the condensers. Add... 

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