May, 1936] 229

JOINT MEETING OF THE LONDON SECTION WITH THELONDON SECTION OF THE INCORPORATED BREWERS' GUILD, HELD AT THE BRITISH INDUSTRIES HOUSE, MARBLE ARCH, LONDON, ON MONDAY, 7th DECEMBER, 1935

Mr. James Grant in the Chair

The following paper was read and discussed:—

CHEMICAL ENGINEERING IN THE BREWING INDUSTRY

By M. B. Donald, M.Sc., A.R.C.S., F.I.C., M.I.Chom.E.

The profession ofchemical engineering may which he is required to know.These are be said to have been founded by a former divided into four main groups, of which the alkali inspector, Mr. G. E. Davis, who was first, "Chemical Engineering Processes," or, the first secretary of the Society of Chemical more commonly, "Unit Processes," is the Industry in 1880 and who wrote the first most characteristic and important. These book on the subject in 1900. Some six years operations, which include leaching, heating, later the American Institute of Chemical pumping, grinding, filtering, evaporating, Engineers was founded but it was not until distilling, etc., are operations which occur in 1922 that a similar qualifying body was practically every type of works in which formed in England, its initiation being largely chemical changes occur. Since the publica due to the scarcity of men capable of tion of the physical and physico-chemical operating and maintaining munition plants theory underlying these operations by during the war. Walker, Lewis & McAdams, in 1923, in a book The Institution of Chemical Engineers entitled Principles of Chemical Engineering, define a chemical engineer as "a professional the literature on this subject has made vast man experienced in the design, construction strides. This book was based upon the course and operation of plant and works in which given at the Massachusetts Institute of matter is undergoing change of state or Technology, and covered entirely different composition." It will be seon that this ground to the earlier book by Davis, who definition embraces the art and practice of had confined his attention mainly to the brewing and can perhaps be best amplified practice of the profession. by considering firstly, theeducation necessary The second group is "Chemical Plant for a chemical engineer, and secondly, how Construction" and includes the properties of his training will fit him to deal with problems metals and their alloys and of non-metallic that arise in a brewery. materials with regard to both their construc Some universities provide a course leading tional and corrosion aspects. Students are to a batchelor's degree in chemical engineer expected to know the rules for thedesign ing, whereas others, including London, pro of plant from the point of view of strength. vide a graduate course with a diploma which The third group is headed "Factory Design can be taken by students who have already and Construction" and includes plant lay-out taken their degree in either chemistry or and construction and the generation of heat, engineering. Alternatively the Institution electricity and compressed air. The final of Chemical Engineers holds a qualifying group includes "Industrial Economics," or examination every year so that students the general principles of factory organisation who cannot attend the recognised courses and management. can still be admitted to Associate Member To apply the subject of chemical engineer ship on passing the examination and on ing to brewing it is necessary to be more having hadtwo years' experience in works of specific. An item of expenditure in breweries a kind approved of by the Institution. in which economies can often be effected is A pamphlet on " The Trainingof a Chemical that incurred in the boiler house and in the Engineer" was issued by the Institution in heating system in general. In many 1925 and this gives an outline of the subjects breweries the load on the boilers is very 230 DONALD: CHEMICAL ENGINEERING IN THE BREWING INDUSTRY [May, 1936 variable so that with coal firing it is prac with the least damage to the food and vita tically impossible to attain good combustion min content of the product and in this con of the fuel and to avoid smoke. A large nection the use of a coal-fired copper seems amount of heat often can bo lost up the rather like using a sledgehammer to drive in chimney owing to the necessity of using a a tintack. Only recently it was stated by large excess of air. The boiler load can be the Chief Sanitary Inspector of Edinburgh smoothed out by maintaining an unfircd but that the city air was being polluted by coal carefully lagged Lancashire boiler, containing fired coppers owing to the fact that they are water at the temperatures of the steam, on cooled down between successive boilings. the main steam line. This acts as an accumu Because of the low temperature of the fur lator, but, for more careful control, it is better nace, smoke emission is unavoidable even by to have a steam accumulator which is specially the most careful stoking. The relative designed to maintain the steam pressure advantages of coal and steam heating of constant. Much heat is often lost in the coppers is a subject of perennial discussion steam lines owing to inefficient or incorrect and the suggestion made that fire heating lagging and the chemical engineer is trained imparted a flavour of caramelisation, could to be able to calculate the optimum thickness easily be arranged by less drastic means. of lagging for any particular case. Other In any case it would appear that copper is subsidiary factors, such as water softening, an unsuitable metal to use for this purpose are important and call for expert technical because, owing to its high conductivity, it supervision, especially now that so many spreads the heat. For this reason copper is unproven electrical methods are being put preferred to stainless steel in jam making, on the market more by good salesmanship which has the opposite tendency of localising than by properly substantiated results. the heat and giving hot spots. The grinding of malt and its relation to The chief objects of boiling in the copper the efficiency of extraction in the malt tun appear to be:— would assume an importance if it were not (1) To sterilise the wort. This is said to for the fact that ample water is available occur after 15 minutes. for leaching owing to the weak extract (2) To coagulate certain proteins by heat. required. Economic grinding can only be This apparently requires a temperature of obtained if the crushed material is removed 180° F. as fast as possible after its initial crushing, (3) To extract the tannin and aroma from otherwise much of the power is consumed in the hops. converting the product into small unstable (4) To remove or modify the malty smell briquettes. The normal size reduction for and flavour of the wort. most materials should be not more than three None of these reasons accounts for the to one. The speed of revolution of the rolls extensive boiling usually given to the wort, therefore should be about three times that so that either reasons are incomplete or of the rolls of the previous stage. Tn deter alternatively the boiling is carried on too mining the speed of revolution, it is generally long. Colour is given to the latter reason by found necessary with semi-plastic materials the statement that "beer made in an iron to apply the crushing force as suddenly as square back with a steam coil, which only possible because they are then more liable succeeded in keeping up a semblance of a to crack than to squeeze. Too high a speed boil, for often not more than 80 minutes, however will bring increased friction on the was not inferior to that made in a fire heated bearings and increase the power consumption. copper, and equal to that made in steam The correct design of a copper is an interest- heated coppers." It would appear rather as ing problem although difficult in practico if the brewer was trying to do too many because it is not easy to obtain a clear things at the same time. The removal of conception of what happens when a wort is the smell from the wort requires an open boiled. It is impossible to make a good vessel with efficient agitation to expose design until the optimum time and tempera plenty of surface, whereas the extraction of ture for each of the factors is known. In the full aroma of the hops requires the most food industries to-day, demands are reverse process. made on the ingenuity of the chemical on- The correct filtration of the hopped wort gineer to carry out some heating operation in the hop back is another point which calls May, 1936] donald: chemical engineering in the brewing industry 231 for comment. The proper removal of the and vitamin B content of foods run parallel solids at this stage is necessary becauso of to each other. Brewer's yeast is one of the the resulting coating of the yeast cells and chief sources of vitamin B. also of the possibility of a harsh flavour being Great improvements have been made in transmitted to the beer. Hop backs do not recent years in the design of plant for cooling appear to be designed as very efficient filters; of the wort before fermentation by substitu possibly a Monel metal screen with a precoat ting enclosed plate heat oxhangers for the of filter aid might produce a clearer wort. older type of falling film coolers with exposed In the fermenting vessel, the correct design surfaces. The newer typo takes up less of the attemperator coils is a small but space, although this point is not always of interesting problem. Weighton (Trans. Inst. importance in a brewery. These plate heat Naval Architects, 1906), showed that the most exchangers require pumps to force the liquids suitable surface section ratio for pipes was through them at a high velocity, but the about 2,900, which means that, for a circular cost can bo offset to some extent by that pipe, the ratio of the length to the diameter of the fan required for forcing sterilised air should bo about 700. The length of a pipe into the rooms containing the falling film can be decreased by making a pipe of the cooler. Possibly the best method of judging same cross section but oval in form. The their performance is to balance the freedom total area of the tube is determined by the from bacterial contamination resulting from heat transmission from the cooling water to their use against the loss of prestige conse the wort and in this the metal of which the quent on, and tho actual cost of dealing with, tube is made plays but a small part. The "returns." chief resistance to the transfer of heat The filtration of beer is generally carried resides in the very thin film of almost station out in pulp filters, and the use of filter presses ary fluid which adheres firmly to any solid- using filter aids does not appear to have been liquid interface and whose thickness decreasos in much favour. This appears to be due to as the velocity of the fluid past the surface two main causes. In tho first place, ordinary increases. Since most fluids are bad conduc unpurified kieselguhr has been used and this tors of heat a high velocity is found to have has given an unpleasant flavour to the beer. a marked effect on the heat transference and In the second place, the filters have not always consequently the area of cooling surface been designed to give good cleaning facilities. necessary to remove a given amount of heat. Neither of these problems is insoluble and Since the wort cannot be stirred and is in fact this method is used widely in the moving very slowly, it would probably be United States for Lager beers. An advantage found that the addition of a fin running along of using a filter aid is that it enables the the tube (instead of around it as in ordinary capacity of a filter press to bo increased, filmed tube heaters) would bo advantageous sometimes as much as fivefold, and that is of in that it would increase the area of heat course of great importance when the plant transference on the side where it was least, is required to meet a sudden demand. This and it would also be capable of easy cleaning. very rigorous filtration of the beer to obtain The problem of the design of collectors a crystal clear product is not beneficial to for the carbon dioxide evolved during fer the consumer as it may remove any traces mentation consists of having a gas governor of vitamins. Examination of such beers which will draw off the gas at the same rate have shown them to be practically free of at which it is being produced, and to compress vitamin B. Patents have been taken out for this gas without excessive generation of heat rupturing the yeast cells and liberating the so as to avoid altering the flavour of the beer vitamin, which can then be put back into the after carbonation. The handling and treat beer. Probably this will give rise to un ment of solid carbon dioxide has recently wanted flavours unless care is taken that the been discussed by Cosbie (this Journ., 1932, vitamin containing solution is treated to 427). The view was expressed some years remove such flavours. ago that it was difficult to see how copper The chemical engineer should have an could betaken up by the yeast from the bottom important part to play in a brewery, especially of the fermenting vessel, and in this connec when due consideration is given to the other tion it is interesting to note that recent aspects of his training such as economics, research has shown that the copper content plant design and layout. The intensive 232 donald: chemical engineering in the brewing industry [May, 1936 analytical training which a chemist receives coagulation of proteins would, if adopted, may result in a rather introspective and result in unstable beer, for under such condi reserved character, which is not well suited tions he doubted if the spores carried forward for the handling of the human side of a works from the mash tun would be destroyed. The and is apt to make him overlook some of the reference to the breaking up of yeast cells was broader issues. On the other hand the of interest for possibly some other means of engineer who is liable to be engaged mainly preparing yeast as a saleable by-product on maintenance and repair work often de would be more remunerative than the present velops the opposite characteristics and does price of waste yeast. not stop sufficiently to pause and consider Dr. R. Seligman said he wished to draw the why and wherefore of the work which he attention to one respect in which the British is doing. His reference book becomes more chemical engineer differed from his colleague and more thumbed and his brain gets less in America. In America the man who and less of that exercise which is so necessary operated the plant was a chemical engineer, for proper development. In the training of as stated in the description given by the a chemical engineer it is necessary to apply Institute of Chemical Engineers, but here the a corrective in each case before a student chemical engineer did not as a rule operate finishes his course. The chemists are en the plant, otherwise brewers would all be couraged to widen their horizon by workshop chemical engineers, since they all operated training, and by the habit of making suitable their plants. He thought the author had approximations, to arrive at the decisions overlooked the physical effects of boiling in that are necessary for the proper economic the copper, and in that connection he sug management of men and plant. The en gested that the proposal to use mechanical gineers are required to extend their chemical means to do what at present was done by laboratory experience so as to instil into it intensive boiling should be borne in mind. a spirit of adventure and not drudgery. Most brewers he believed, would agree that Naturally it is not always possible to obtain in the cooling of wort there wore other things a true balance in the short space of one aca to be considered than a mere exchange of demic year, and the ideal would be to have heat. He did not think that the application the students for the whole of their academic of the knowledge of heat exchange to attem- career instead of a post-graduate course. perating would be very fruitful. In connection with the corrosion of copper Discussion by yeast, reference had been been made to Mr. W. J. Watktns said that he had had the relation between copper and vitamin B. no experience of steam accumulators, and he A. C. Chapman, in his researches on the effect would like to ask the author if there was any of copper on yeast drew attention to the fact use for them in a brewery in view of the fact that minute quantities of copper were often that most of the steam was used for heating stimulating, whereas subsequent doses were and not for power. Was not an accumulator toxic. Was it not probable that the first a means of obtaining an extra supply of what small quantities were necessary for the de must be saturated steam at a low pressure? velopment of the vitamins, whereas further He had been able to effect considerable coal quantities were toxic? economies by installing steam flow meters. He believed that the steam accumulator He required information as to what the boilers had little value unless in connection with the were doing, and it was difficult to calculate generation of power by steam. The accumu from water meters, because water was de lator was most useful where pass-out turbines rived from several points including the loop were used and the exhaust steam could be system from steam coppers. Results with accumulated until required. steam flow meters taught him how to ration Mr. A. J. C. Cosbie said in view of the steam in such a manner that he was now able author's remarks about boiler-house control, to get a more even load upon the boilers it would be of interest to hear his opinion on throughout the day. In these times brewers the subject of mechanical stoking. Further, were not allowed to waste fuel, and he was with regard to the question of water softening, inclined to question the author's theoretical had the author any experience of a system of considerations about boiling. The alloca water treatment involving the use of very tion of certain periods for sterilising and small currents at low voltage? It was May, 1936] donald: chemical engineering in the brewing industry 233 claimed for that process that unlimited get his wort up from the hop back on to the quantities of water could bo treated at a cooler in a short time, and over his coolers negligible cost per annum. It was supposed in an hour, or in 1£ hours at the most. that the carbonate crystals wore caused to Many suggestions had been made, but change from one crystal system to another he had not come across one which would under the influence of tho electric current. effect a sufficiently speedy filtration to enable Mr. J. H. Jeacock said he had been in a brewer to carry out bis work in the limited terested in the remarks about water softening time available. as he had hoard that the electrical method was With most C02 plants it was difficult to supposed to be effective in keeping the scale prevent oil being transmitted to the gas from formation under control. the compressor, and if the CO2 was used for Dr. Oliver said he thought that, taking carbonating beers the matter became serious. into consideration all the various factors The minutest trace of oil in gas would involved, the brewer nowadays conducted destroy the head of a beer, and he had such parts of his process, as grinding, and come across many instances where head re extracting tho mash, with a high degree of tention trouble had been caused by oil. efficiency, and, of the various subjects that Mr. M. B. Donald said in reply that his the author had discussed, the greatest criti paper was designed to submit the views of cism could be made on the matter of layout. an onlooker and he was grateful to those To some extent that was understandable speakers who had appreciated the spirit in because many breweries developed on a site which he had had to address them. that was limited, and expediency had to take precedence over technical efficiency. Accumulators had been installed in a num Mr. H. Heron said the author had raised ber of breweries on the continent and it was many points that had been agitating the only one of their functions to maintain better minds of brewers and brewers' engineers for operating conditions for prime movers genera years past, and he had made some useful ting power. Most modern works now pro suggestions, especially as regards boiling. duced steam at a slightly higher pressure and, He believed the controversy between steam by passing it through a back pressure steam and fire boiling had been more or less settled engine, supplied themselves with what elec by the introduction of up-to-date steam tricity they required and then used the low heating plant. When fire heating was pre pressure steam for heating purposes. A cer ferred to steam heating, it was because with tain amount of balancing could be accom the latter a brewer thought he had got a plished by the use of a steam meter to ration boil, but it was really getting nothing of steam requirements during the day but it tho sort. Ho had in fact seen coppers was not generally possible to ensure a con heated by steam coils, which never reached stant load on tho boilers by those means. a temperature of more than 200° F. He An accumulator automatically ensured would like to enlighten the author, as to smoothing of the load and would thus secure the reason why a brewer boiled his copper more economical operation of the boilers for so long a time. Firstly, brewers wort and enable them to take higher loads. It could not bo sterilised in half an hour, or also contributed to more continuous working even under an hour, owing to tho presence in the brewery. of spores. Secondly, as had been shown by The process for extracting vitamin B from Dr. Walker, resins could not be extracted yeast involved the use of a colloid mill. A from a hop under 45 minutes. Then again, rotor, whose speed was from 1,000 to 20,000 brewers got an excellent agitation if they revs, per minute, was separated from the had a fountain in their copper, but he was stator by a gap of some two to ten thousandths afraid that if they carried out the suggestion of an in. through which the material was of the author, the hops would be broken up passed. Tho shearing action thus produced to such an extent that they would fail to ruptured the cell walls and released tho obtain efficient hop back filtration, and aqueous extract of the vitamin B complex. would have difficulty in separating the hops The extract ought to command a good price from the wort. Most brewers had come to for medicinal purposes although it should the conclusion that the hop bed was the most have a greater ultimate value to the brewers efficient filter they had. A brewer had to if it were added at least in part to the beer. 234 DONALD: CHEMICAL ENGINEERING IN THE BREWING INDUSTRY [May, 1936

In reply to Dr. Seligman, the majority crystal structure would not affect the soap of chemical engineering students operated requirements of water for washing purposes. plants in various industries and he believed Tho reason he did not touch on the question that a chemical engineering training would of layout of breweries was because few be a valuable asset to a brewer. The question breweries were now being built and it was of the application of knowledge of heat very difficult to alter an old arrangement transmission to attemperating might not except in minor details. produce very marked results but it provided Mr. Heron had raised a number of pertinent an excellent opportunity to introduce the points, amongst which were that it took general effect of streamline surface films, the 45 minutes to extract all the resins from the study of which was so important in many hops and that excessive agitation would give branches of chemical engineering. bad hop-back filtration. The answer would Mechanical stoking was advantageous be appear to be that a compromise was necessary cause it converted firing into a continuous and to employ such agitation as would reduce operation and thereby gave increased effi the time of resin extraction comparable with ciency. The volatile products from the coal a reasonable time of filtration. Alternatively were gradually distilled into an oxidising tho time of filtration could be reduced by the atmosphere and that diminished the smoke use of suitable filter aids. The speed of trouble. With hand firing the volatile filtration was determined not only by the products were evolved immediately after resistance of the cake but also by the surface firing, and, if the air supply was increased area employed, and whether pressure or to cope with them, then it moant that too vacuum was used to assist the pressure head much air was being introduced during the re due to the liquor. mainder of the period with consequent lack It should not be difficult to prevent oil of efficiency. being carried forward from a C02 compressor With regard to electrical water softeners, providing that a correct grade of lubricating a large amount of recent research had oil was employed and a simple catch-all of so far failed to confirm the claims made the silencer type, with a trap to remove for those methods and it would be very liquids, was placed after the compressor. dangerous to install them in a high pressure For this purpose the compressor usually boiler plant. Assuming that the crystals of worked at a very slow speed. calcium carbonate did change their structure, Filter aids, similar to highly purified then the solution of the problem of water kie8elguhr, could now be obtained with softening was no nearer its goal because it various pore sizes and it would seem merely was the calcium sulphate which gave rise to a matter of selecting the right type to avoid the troublesome scale. Also a change in removing the valuable colloids from the beer.