January 26, 1917. THE COLLIERY GUARDIAN. 179 THE RECTIFICATIOM OF BENZOL* By W. Newton Drew. : The writer has been connected with a carbonising plant, the Rockingham Chemical Works, at which benzol has been rectified-since 1883. The by-product coke oven has superseded the .fireclay retort, and the details of absorbing the aromatic compounds from the gas with oil, and distilling crude benzol from this oil have changed.-" The methods of washing the crude benzol and distilling the same for rectified products are, however,- very,much, the same as formerly. Nearly all by-product oven, installations nowadays recover their benzol, toluol, etc., in the form of 65 per cent, crude benzol—that is, benzol which when distilled in the labor- atory will give-65 per cent, as a distillate under 120 degs. Cent.' ■ ' • ■ / In former days, this crude benzol was transferred at once to the washer, and thence to the rectifying still, whence 90 per cent, benzol, 50/90s benzol, toluol, and naphtha were produced. The modern practice is, how- ever, to distil, this unwashed crude benzol in a still of simple construction, and to separate an unwashed benzol fraction, an unwashed toluol fraction, and an unwashed naphtha fraction,. the residue being run into a pan, where the naphthalene solidifies out on cooling. The benzol fraction will be the first distillate up. to the point at which the product at the delivery gives its first drop at about ,105 degs. Cent., and the toluol fraction the second distillate up'to the point at which the delivery product gives its first drop at about 124 degs. Cent. These three partly-rectified unwashed fractions are accumulated in separate tanks, and are in due course blown or pumped separately to the w’asher, where , the material is agitated with acid and then with caustic soda. The washer may hold from 1,200 to 2,500 gals., and is,.usually a vessel of steel, lead-lined, or of cast iron, with a conical bottom, and a mechanically-driven vertical shaft. To this shaft is attached a spiral blade working in a wide tube,, or some other contrivance for •continually raising the acid and benzol up. the centre of the washer, and allowing the same to descend near ths walls, whereby an intimate mixing is obtained. From 5 to 8 per cent, by volume of strong acid (D.O.V.) is employed, the percentage' varying with the nature of the charge!'(that is, whether benzol, toluol, or naphtha),- the quality of the same, the efficiency of the washer, and the purity of the product desired. If benzene boil- ing within 0’5 deg., or toluene boiling within 0*8 deg., is required, a more thorough washing is necessary, but this paper deals only with the commercial rectified product. ■As an example, in one case 1,200 gals, of benzol are agitated for one hour with 4 per cent, of acid, settled for one- hour, and then run oft; 3 per cent, of acid is then added and agitated for hoars, settled for two 'hours, and.run off; 25 per cent, of water is added, and, after a brief agitation, is allowed to settle for three- quarters of an hour, and run off; then 4 per cent, of caustic soda of a specific gravity of 1’1 is added, agitated for .20 minutes, settled for.half an hour, and run off; finally, a little water is added, agitated, and run off.after two hours. A patent has recently been taken out by M.essrs. Simon Carves and Moss, whereby the whole routine of the washer is obviated. In the new process, the vapours from the crude benzol still before condensation are con- ducted first through acid, and then through caustic soda. This system, if successful, would be an immense, gain, but the writer has no knowledge as to whether it has proved commercially satisfactory. Mr. M. Wynter Blyth has devised a method for the continuous washing of crude benzol, whereby the liquid falls down a series of long vertical tubes, and is treated in succession with the right proportions of. acid, water, alkali, and water, and is continuously delivered in a washed condition. By washing, the crude material is freed from thiophene, pyridine, and various other impurities, and loses from 8 to 12 per cent, of its volume. It has now become washed crude benzol, toluol, or naphtha, light brown in-colour, and is ready for rectification. . The stills for treating the unwashed crude and the washed crude are usually similar, except that the latter have a more elaborate fractionating apparatus, whereby the compounds of different boiling points are more com- pletely separated at the cost of more time and more steam. The still for rectifying washed products may have a capacity of 3,000 Jo 5,000 gals. This still, if used in the preliminary distillation of crude benzol, would have fewer trays in the fractionating column and no dephlegmator, the vapour pipe from the top of the column going direct to the condenser. The design of the trays in.the column is almost precisely as in,the column of an ammonia still. The dephlegmator is a cylindrical vessel, in }yhich the vapour is cooled to a particular temperature, and from which any condensed liquid passes back into the fractionating column. The vapours pass from the dephlegmator to the condenser, or sometimes to two condensers in series, and the con- densed liquid, which should not be much higher in tem- perature than the atmosphere, is received in the separator. Here any water produced by the condensa- tion of steam is removed, and the finished product passes on to one of the receiving tanks. A useful device for indicating the rate at which the. still is working consists of a graduated glass cylinder, with an open top, and having a small aperture in the side near the bottom. The whole is enclosed in an outer glass cylinder, completely sealed at the top. and the bottom except for an exit pipe leading to the separator. The condensed benzol is discharged in a jet through an orifice, anj rises in the graduated inner glass cylinder to a definite level, which varies with the rate of work- ing of the still, and is easy to read.. _____________ * From a paper read before the Midland Institute of Mining, Civil and Mechanical Engineers. The writer can commend the running of a benzol still- as being both interesting and instructive. Speaking roughly, the charge of, say, 4,000 gals, of washed crude benzol contains 0'25 per cent, of carbon bisulphide (CS2), boiling at 58degs. Cent.; 82*75 per cent, of benzene (CfiHfi)y boiling at 81degs. Cent.; and 17 per cent, of toluene (C7H8), boiling at 111 degs. Cent. The washed crude benzol fraction will test 86 per cent, at 100 degs.,.the washed crude toluol fraction 95 per cent, at 120degs., and the washed crude naphtha fraction 70 per cent, at 160 degs. Cent. A sample should always be tested by "the standard "War Office method before the bulk is distilled. If a charge of this washed crude benzol be taken, and steam introduced into the coils of the still, the liquid will boil, and the vapour rising at first will consist of some carbon bisulphide, much benzene, and a trace of toluene. The toluene and some of the benzene are condensed in the fractionating •column, and continuously return to the still, scrubbing out of the vapours which may rise .through them any mechanically-carried particles of liquid. The vapour .which leaves the top of the fractionating column is therefore benzene rich in carbon bisulphide. In the dephlegmator this vapour is cooled to such a point that the benzene in it is partly condensed, and passes back as liquid to the base of the column. The vapour passes on, is liquefied in the condenser, and should be rich in carbon bisulphide and other low boiling impurities. This distillate, which amounts to 3- per cent, of the charge, is usually run into a separate receiver. After a time, the temperature at the top of the fractionating column will rise, and benzene becomes the sole compound delivered in the separator. The product is then turned into a fresh receiver, for 90 per cent, benzol, and the distillation continues with little change for a consider- able time. Ninety per cent, benzol is, however, in these war times, superseded by standard benzol—that .is, benzol giving 95 per cent, below 90degs. Cent.; and for this the still is not run so far. Ninety per cent, benzol, contains approximately 84 per cent, of benzene, 15 per cent, of toluene, 'and 1 per cent, of xylene. Standard benzol contains about 96 per cent, of benzene and 4 per cent, of toluene. In running a still for standard benzol, the operator must be guided largely by his laboratory test with a sample of the charge, which will show him what quantity of final products he ought to obtain. He will from time to time test a sample from the separator, and later on he. will take a “bulk” sample from the receiving tank (after mixing thoroughly), and decide, whether the time has come for the still to deliver into a fresh receiving tank. The still must not at any time be run so fast that it does not fractionate properly, and when a “ change over ” to another receiver is approaching, it should be run very steadily. After changing the still from making “ standard benzol,” it' is usual to make an “ intermediate ” benzol- toluol fraction, and then to run for 90 per cent, toluol; or the distillation may be stopped, and the charge “topped up” with the washed “once run” toluol fraction referred to previously. In the course of running for toluol, wet steam will be required, in addition to the dry steam. Ninety per cent, toluol is not so easy to make as standard benzol. Solvent naphtha is gener- ally made in a simple form of still, and requires “ wet ” (that is, direct) steam to bring it over. Sometimes the still is run for naphtha, under a vacuum. No one recti- fying plant employs the same system as another of collecting intermediates and residues from distillations, nor of “ cutting ” fractions in distillation; but the final products are usually standard benzol, 90 per cent, toluol, and solvent naphtha, and these products should be obtained with as little re-distillation as possible.' The laboratory tests of products generally produced are as follow : 1st drop. 90 per c. at 95 per cent, at degs. Cent. degs. Cent. degs. Cent. Standard benzol... 80 ... — ... 90 Commercial toluol 90 per cent..... 102 ... 120 ... — Solvent naphtha... 133 ... 156 ... (contains 4% per cent, of toluol). In the distillation of both washed crude benzol and unwashed crude benzol, “ topping up ” is frequently’ made use of—that is, in the latter still, after the benzol fraction has come off completely, the distillation is stopped, and the residue allowed to cool down somewhat in the still; then a fresh supply of crude unwashed benzol is added, and the still run for benzol as before. This “ topping up ” is repeated until the still is nearly full of residue, and the still is then run for the toluol and naphtha fractions. This method is the easiest way of ensuring that the still shall work on as full charges as possible, and consequently with the minimum of starting, stopping, and changing over. The accompanying table embodies records taken in the rectification of a charge of washed crude benzol. In 'this case there was no preliminary fractionation before washing, and the distillation is a continuous one through the whole series, and therefore very instructive. Observations were taken every two hours during the 52 hours of the operation. . The charge was 4,640 gals., and the production as follows :— Analysis. £ .Eq'S.2 <--------------■*-------> Gals. First runnings* . 2^8 .. Pc. P c. . 1’8 ... 97 0 ... P.c. 1'2 ... Pc. Standar benzol*...... 2,391 .. . — ... 95’0 ... 5'0 ... — Intermediate 212 .. . — ... 56 0 ... 54 0 ... — Commercial tr luolf... 638 .. . —- 8'0 76'0 ... 160 Solvent naphth a J 419 .. . — 11’0 ... 89’0 ... — Creosote 755 .. . _ . . — ■ — Lo«s 47 . —- ... — — — . * By Government test. First drop, 80° Cent. ; 97 per cent. at 90° Cent, f By Government test. I By retort test. First drop, 123° Cent.; 90 per cent, at 160° Cent. Mr. E. J. Adderley (Wm. Cory and Son) has been elected, for the fifth time in succession, chairman of the Humber Coal Exporters and Shippers Association, and Mr. James Turner (D. M. Stevenson and Co.)., for the second year, vice-chairman, This distillation was made early in 1915. Not more than 5 per cent, of toluol is now permissible in,solvent naphtha, and the writer’s firm now make it .with the first drop at 133 degs. Cent. Mr. J. A. Wilson, of Staveley, recently, stated at a meeting of the Coke Oven Managers’ Association that 70 to 72 per cent, of the crude benzol treated .should be recovered as rectified products. It is important that the pressure of. the steam should be constant, preferably not less than 75 lb. The more elaborate the fractionating apparatus is, the more steam will be required, and naturally also the toluol, and naphtha will require more steam than the benzol. The writer has been recently informed that in rectification about 281b. of steam are required per gallon of unwashed crude benzol. This figure includes pump- ing, etc. All pipes used in conveying benzol should be properly earthed. There seems no doubt that an electric poten- tial is created by the rapid passage of benzol through a narrow pipe. In conclusion, the writer may be allowed some general reflections on the industry, speaking as one originally trained to mining. The colliery manager is, as is well known, expected to be a mining, an elec- trical, and a mechanical engineer, to deal with condi- tions of labour, to comply with and to fill up innumer- able regulations and forms, etc. To expect from him anything beyond a general knowledge of by-product chemistry would be unjust. The by-product installa- tions of each district should be linked up in some asso- ciation or associations outside the coal and coke indus- tries. One such association is that of the.Coke Oven Managers, which has already done excellent work for the industry and the nation. The recently-formed Association of British Chemical Manufacturers should be made' representative of the by-product industry, but probably a local association for the by-product plants of the Midland counties would be of more immediate ser- vice. For example, consider the products just dealt with. As Is W’ell known, benzol and toluol are both explosive bases, and every gallon is needed now for the Allied cause. What will happen after the war? A certain amount of these products will be required for dyes, but 40,000,000 gals, per annum, let us say, of benzol will have to be sold as a motor spirit. This benzol must be of standard quality as regards the dis- tillation test, purity, and dryness. It must be obtain- able everywhere in standard 2-gal. tins at a standard price. What has been done to prepare for this market by the producers as a body as yet? Nothing whatever. As far as the writer knows, if the war were to stop to-morrow, the industry (including the gas companies) would have no organisation whatever, and would be at the .mercy of the highly-organised petrol combinations, which have hitherto succeeded in selling an inferior fuel at a higher price. NATIONALISATION OF NUNES. At the annual conference of the Labour Party, meeting in the Albert Hall. Manchester, on Wednesday, Mr. R. Smillie, president of the Miners’ Federation of Grat Britain, moved :—(i.) That in the opinion of this Conference the time has come when this country should no Ion o'er be dependent for its coal supply on a small number of capitalist colliery proprietors, coal merchants and dealers, among whom there is an increasing tendency to combinations and price-arrangements, by which the consumer is ma^e to pay a quite unnecessary price for coal; and that the Government should at once take over all coal and other mines, work them as a national enterprise, and appropriate to the nation all rents andwayhaves ; (ii.) that in organising the nation’s coal supply on the basis of production for use instead of production for profit, due arrangements should.be made for the participation in the management, both local and central, of the employees of all grades ; (iii.) that the Government coal department might undertake the supply for export and shipping, the local authorities and all industrial consumers of any magnitude; delivering the coal for domestic consumption to any railway station at fixed price, as unalterable and as uniform as that of the postage stamp, for retailing and delivery at a fixed additional charge just covering cost. Mr. Smillie said the Miners’ Federation for many years had given the question of national ownership-of mines very careful consideration at conference after conference. Thev did not think that the living condi- tions of their class ought to be decided by capitalist combinations and bargaining on the market. They did not think that the public in the shape of the consumers of coal should be left to the tender mercies of the exploiter to make fortunes out of. Yet that had been how the coal trade had been treated up to the present time. Miners considered that under nationalisation the wages of the miners would be more stable. The miners did not wish the mines to be nationalised to ph’e tlu m in a more favourable position as wage-earners. In many places the highest qualification for a mine manager was not that he might produce the coal safely but that he made the largest profit. They believed it. would save many lives if the coal mines were State-owned and worked.. The resolution was carried unanimously.