Scotland's Brick and Tile Manufacturing Industry

3/10/1881 – Glasgow Herald – Important improvements in burning fire bricks. A new application of heat regeneration.

During the last twenty years or so, and more especially since the Bessemer and Siemens processes of making steel came to be established as great manufacturing industries at home and abroad, the district of Glenboig, near Coatbridge, has acquired a great reputation for the character of the bricks and other goods from the millstone grit fine clay which has been so beautifully deposited in that particular portion of the Lanarkshire coalfield. For furnace construction, there is nothing to surpass a genuine Glenboig brick in respect of its fire resisting power, unless it is that peculiar product of south Wales manufacture known as the Dinas fire brick, which, however, is almost exclusively composed of silica and has but a limited range, of practical application. When some important improvements in burning fire bricks are completed it may confidently be expected that Glenboig manufacturers will rise still higher in reputation. Occasionally in recent years some of the manufacturers of fire bricks of this country have considered it desirable to adopt the heat regenerative system to the burning of such goods, but in no attempt that has been made, so far as we are aware, has any marked economical result been attained until within the last two or three weeks. The special case to which we are about to refer is that of Mr James Dunnachie, of the Glenboig Star Fire Brick Works, where there are manufactured goods of such remarkably refractory power as to be in, great demand for furnace construction. Having a raw material of such splendid utility as a fire-resisting medium, it was but natural that the gentleman whom we have named should exert every endeavour to turn it to the best possible account, both in the preparing and moulding stages of the manufacture and in the economical and perfect firing of the bricks after being prepared.

Having lately inspected the new firing arrangements at the Star Fire Brick Works, we give a brief sketch of the modus operandi pursued by Mr Duunachie and we would just remark in passing that the arrangements in question, which have long been worked out, were first brought into practical use in connection with the adoption of the Wilson, producer to supply the requisite gaseous fuel. It is not necessary that we should here describe that useful and valuable invention, but it is proper to state that this is the first occasion for it to be employed, in the successful burning of fire bricks. As at present developed, the arrangement adopted is a kiln consisting of two parallel stacks of brickwork, about 24 feet apart, and each containing five separate chambers, in each of which from 13,000 to 14,000 bricks can be fired at one “heat.” In order that the kiln may be capable of continuous regenerative firing the two sets of chambers are connected with each other at the two ends by means of underground flues, and in this way the ten chambers may be regarded as one continuous series – that number being required for completely carrying out the ideas of the inventor. The space between the two parallel stacks of brickwork is covered in by means of an iron roof, so that the operations of charging the green bricks and discharging the finished goods may be pursued in all kinds of weather. ‘There are, however, doors at both ends of the chambers. At the west end of the space just referred to there are erected two of Wilson’s gas producers of large proportions, for which the gaseous fuel is lead to the underground flues for working the separate chambers when charged with bricks to be fired. One great advantage of this system of heat regeneration in burning fire brick is that there is always a regenerator chamber in readiness for heating the air requisite for the combustion of the gaseous fuel. Of course, in commencing the process at the Star Fire Brick Works it was necessary to fire the first chamber in the usual way by means of specially erected coal furnaces, but as soon as it was fired off it was ready to become part of the future plan as the first regenerator chamber. At the time of our visit, the system was in successful operation with one set of five chambers, and the stack of brickwork containing the other five was in rapid progress. ‘The experience with the gas-fired kilns up to the present is that the firing operation can be thoroughly performed in from 1 to 24 hours, whereas in the best type of kilns used at the same works, employing coal as the fuel, the burning usually occupies from four to six 12-hour shifts. It is not considered a too sanguine expectation to suppose that, if desired, the time required for burning off a kiln chamber under the new order of things may eventually be reduced even to 12 hours.

There is no necessity, at this early stage of Mr Dunnachie’s operations, for giving any detailed account of the structure of his new kiln, and we, therefore, limit our remarks to a brief notice of the mode of employing the gas and air – the fuel and the supporter of combustion. Assuming, then, that No.1 chamber has been fired off, and that the effluent gases produced in the combustive process have passed through chamber No. 2, which is the next in the series, the contents of the latter are now in all probability at a bright red heat – the gas from the producers at a temperature of from 600 degs to 800 degs Fahrenheit – is turned on direct to No. 2. and so likewise is the highly heated air that is streaming through No. 1 – the regenerator chamber. These two currents are allowed to mix in the furnaces or burners beneath the floor of the chamber, and a magnificent glowing effect is soon evident. The underground flues are provided with valves that can be brought into action at a moment’s notice for turning on or turning off the gaseous current and regulating it according to the condition of the mass of bricks being operated on at the time. These valves are worked in the covered space formerly referred to, and at what may be termed the working front of the kiln. The quantity of air that passes from the regenerator chamber is regulated by means of dampers, which are also under the most complete control. At the end of from 18 to 24 hours, the firing is completed, and the particular chamber that has just been burned off becomes, in its turn, the regenerator for the next in the series, which by this time has doubtless already attained to a full red heat through the action of the heat of the effluent gases, but which heat is economised in the manner indicated. And in this way, the new system of using gaseous fuel in the fire brick manufacture may be fitly spoken of as one of continuous heat regeneration. The economy already attained as regards fuel is very significant, the saving of which is upwards of 60 per cent and there is every reason to expect that it will yet reach 75 per cent when the other five-chambers are brought into use. Besides the economy in fuel just stated, and the speed in burning, the special features of the new system of firing that have been aimed at and attained are the use of gaseous fuel, combined with the perfect diffusion of the heating current. Owing to the manner in which the gas and air flues are arranged in each chamber the most absolute perfection is attained in the admixture of the gas and hot air for the burning process before they are admitted into the kiln chamber proper. It is also worthy of mention that, if the front of the kiln should become too hot, cold air can be admitted at pleasure, and that it is possible to take off the effluent gases from any one chamber either at the top or bottom. Furthermore, the heat current may be conveyed directly to the next chamber in the series, so that there is practically no waste of heat at any stage of the process. From all the various circumstances which we have mentioned, we may (using the remark of a competing manufacturer of fire bricks) characterise Mr Dunnachie’s new system of burning bricks as being a revolution in the manufacture. So for as can be seen at present, there in abundant reason to believe that the same system of using gaseous fuel in continuous regenerative firing may be adopted with an equally marked economy in the manufacture of pottery ware and in other more or less similar industrial processes.

24/03/1885 – Continuous Regenerative Gas Kiln for Burning Fire bricks and Pottery etc. By Mr John Mayer, F.C.S. (see plate XVIII.) Received and Read 24th March 1885.

For fully twenty years the subject of firing by using fuel in the gaseous form, and on the principle of heat regeneration, has had a most intense attraction for me, partly on account of the scientific interest and beauty inherent in it, partly owing to its great importance in the industrial arts, and in no mean degree in consequence of it being made the theme of the last public discourse delivered in the Royal Institution, London, by the late Professor Faraday, which was the only occasion on which I had the great pleasure of listening to that distinguished chemist and physicist, and of seeing him perform many beautiful experiments with matchless skill and success. That was in the year 1862, while the Great International Exhibition of that year was being held in London; and on that occasion, the great experimental philosopher was surrounded by many of the most notable scientific men of this kingdom, of the Continent of Europe, and of the United States of America. The late Sir Wm. Siemens, who was then rapidly making his great reputation in physical and mechanical science, had quite recently got his regenerative system of gas-firing into successful operation at the famous glassworks of Messrs Chance Brothers, at Birmingham; and so greatly charmed was Faraday with the beauty of Siemens valuable invention that he made a special journey to the capital of the Midlands in order that he might look into the glass melting furnace with his own eyes and thereby be enabled to appreciate the merit of the invention in their true and full significance. It was upon that subject that “the old man eloquent” delivered his most memorable discourse, and during all the many years that have since elapsed the Siemens system of gas firing and heat regeneration has never in the least degree diminished in its scientific beauty and value, while as regards its importance in the industrial arts it has gone on from year to year attaining for itself a stronger and stronger position; indeed, so very marked is that the case that the system in question may be spoken of as one of the greatest industrial inventions of the present generation. Within those years there have been many and varied applications of gaseous firing and heat regeneration, according, both to the Siemens patents and to the patents of other inventors. It is the aim of this paper to describe another successful application of those two principles, almost at our own doors, as it were, and in a branch of the manufacturing industry in which there was great room for economising fuel and preventing the fouling of the atmosphere by the discharge of immense volumes of dense black smoke. The industry to which I refer is more especially the burning of fire bricks, though it may also be said to include all kind of goods that are made of clay; and the inventor of the system of kiln burning about to be described is Mr James Dunnachie, who has been intimately identified with the manufacture of that most refractory and heat-resisting, and now and most familiar article — a “Glenboig fire brick ” — for the last quarter of a century. Various persons, including Dr Siemens, had made attempts to produce a kiln for firing bricks on the heat regenerative principle, but in no case were any efforts in that direction attended with practical and commercially successful results until the matter was taken in hand by the proprietor of the Glenboig Star Fire clay Works, some four or five years since. One important factor for making kiln firing by regeneration a success was a means of providing a continuous supply of gaseous fuel, in a cheap and easy manner, and at that time such an appliance was ready to hand in the gas-producer which was brought under the notice of the members of this Institution some time ago by Mr F. J, Rowan. Without in any way detailing its construction or mode of action, I may pass on and simply state that such a gas generator, similarly to that of Siemens, produces gaseous fuel whose combustible constituents usually form well-nigh 40 per cent, of the whole, the non-combustible diluent being chiefly atmospheric nitrogen; and it may be well here to state that the chief combustible and calorific ingredient of producer gas is carbonic oxide. As regards the kind of fuel to be employed in the proposed new mode of burning fire-bricks, Mr Dunnachie had long had his mind made up, his desire on this point being to follow in the footsteps of Siemens; and as to the mode of practically using the gaseous fuel to the greatest advantage he also had his mind made up. Of course, it involved the adoption of the principle of heat regeneration, and in a way not only modified to suit the special circumstances of the case but so radically differing from the Siemens system of regeneration that the device adopted practically amounted to a new and important invention. Two producers were forthwith ordered, and in due course erected on a suitable spot within the works; and at the same time, Mr Dunnachie proceeded to erect a kiln embodying all the newest notions that seemed to accord with the most efficient method of developing the calorific powers contained in the gaseous fuel. Fully three years ago the first continuous regenerative gas kiln, as it was evolved from the brain of the inventor, was brought into full work, and it at once established itself as a very marked practical success. Since that time the system has been extended at the Star Works, and it has also been brought into use at the original Glenboig Works, and at the Cumbernauld Fire Clay Works — all the three establishments just named being now the property of one concern, the Glenboig Union Fire Clay Company (Limited). Of its applications elsewhere and of its prospective adoption in other directions, something may be said further on. As illustrated by the diagrams exhibited on the walls, and by the very excellent and instructive model placed on the table (the latter having been put at my service for this evening, prior to being sent to the International Exhibition of Inventions about to be held is London), it will be seen that the continuous regenerative gas-kiln under consideration is really a series — or, better still, two series— of separate kilns or firing-chambers which are well seen in the ground plan (Fig. 1, Plate XYIII.) That plan, taken along with Figs. 2, 8, 4 (Plate XYIII.), shows that there are two parallel masses of brickwork about 24 feet apart, each of which contains five separate firing chambers, which are all connected with each other in a series, by means of flues situated underneath the floors and in the walls of the individual chambers. These flues are for conveying the gaseous fuel from the gas-producer and the air which is to be used in its combustion wherever it is required. Situated opposite the middle of the 24-feet open space, and at a short distance outside, there are seen represented the two gas-producers with their overhead effluent tubes, and the latter are seen to terminate in a series of underground flues, which again terminate in the individual firing-chambers. There are likewise shown in Fig. 1, Plate XVIII., a number of other flues which terminate in two common underground passages by means of which the waste gases, after having done their regenerating work in the way of yielding up their surplus heat to the incoming air, pass into the chimney stack. It may here be mentioned that the stalk at the Star Works, and which is shown in the model, and its position indicated in the ground plan, is about 120 feet in height which (in addition to doing other work) is quite sufficient to produce a good draught. If a blower is used for the air, the chimney may be dispensed with, or one not so high may be employed. Still referring to Fig. 1, Plate XVIII., it may be observed that right over each individual gas flue leading to its respective firing-chamber, there is placed a valve for controlling and regulating the amount of gas passing into any chamber. Then, again, there are provided dampers for keeping the currents of entering air and effluent waste gas under the most perfect control. To an observer who sees this kiln in operation for the first time and can appreciate its merits, it would almost seem as if the ultimate effect of all the nicely harmonised arrangements were even more beautiful and scientifically perfect than the original conception of the inventor could have been. It is perhaps scarcely necessary to give a detailed series of dimensions bearing upon the construction of one of these regenerative gas kilns but a few such data may be mentioned. The extreme length of each mass of brickwork containing five firing-chambers is 69 feet; the length, height, and width of the chambers internally are, respectively, 17 feet, 11 feet, and 10 feet; and the internal capacity of each chamber is equal to about 13,000 or 14,000 bricks — the number varying according to their size and shape. Such experience as has now been gained at Glenboig shows that it is possible by means of a set of ten chambers arranged according to the plans in the diagrams to fire 800,000 bricks per month. By reference to Fig. 2, Plate XVIII., which shows the end elevation of one complete kiln, or set of ten firing chambers, it will be seen that the open 24-feet space, is covered in by means of a light iron roof, so that it is possible to carry on all the operations of charging and drawing, “steaming” and heating-up, regenerating, firing, and cooling-down, etc., in any kind of weather. It may also be noticed that over the space just referred to and over the two series of firing- chambers there is a floor, formed partly of wood and partly of iron, which is used as a drying stove, and on which the moulders pursue their business of brick-making so long as there is any room for doing so. This floor is admirably suited for drying purposes, as most of the waste heat that escapes from the kilns by radiation into the air is here utilised in this way. A brief account of the way in which these firing chambers are employed in continuous series may now be given. Let us assume that two of the chambers have been burned off, say, Nos. 1 & 2 on the ground plan. The current of gas from the gas producers, at a temperature of from 600 degrees to 800 degrees Fahrenheit, is turned on to No. 3 chamber, which, up to the present, may be regarded as being a green kiln, one in which no distinct combustion of gas has yet taken place. The stream of air necessary for the burning of the current of gas, now directed into No.3 chamber, is made to pass through the mass of finished brick in what we may call the burned off kilns. Such kilns are the very best regenerators that it is possible to conceive of, one of extraordinary efficiency, and a green kiln properly so-called, is the most natural recipient and store-room of what would, under other circumstances, be waste heat. But the term waste heating connection with the Glenboig regenerative gas kiln is almost, if not quite, a misnomer, as there is practically no heat allowed to escape into the atmosphere without doing its allotted work, such as regenerating and steaming within the kilns, drying green bricks above them, or producing an ascensioned current in the chimney stack. It may be taken as a sort of fixed rule in the working of these kilns that the working chamber — that is to say, the one on ”full fire” — always has one or two, and sometimes even as many as three, burned off chambers in its rear in the series and a green chamber on the other side. In its passage through the regenerator, the stream of air is soon raised to a brilliant steel melting heat and that is by and by imparted to the mass of bricks in the chamber which is now passing through the stage of full firing — an operation that is accomplished in from 24 to 86 hours. But while the last-named operation is in progress the next chamber in the series, No. 4, is in its turn made the recipient of the heat which is carried over by the effluent gases from the chambers where the producer gas is actually undergoing combustion; and in this way, its contained bricks may become not only dried to perfection but even heated up to redness, which is more or less bright on the side next to No. 3 chamber, though of a dull red on the opposite side. When bricks are stacked in any of these firing chambers, even though apparently dry, they always contain a certain amount of moisture which has to be driven off in the stage called ” steaming ” prior to that of full firing. In the ordinary course of things, the next chamber in the series. No. 5, is at this time the “steaming ” chamber, and that operation may be effected by passing hot air into it from, say, No. 4 chamber, or it may be done by means of a jet of gas direct from the producer, so as thereby not to interfere with the kilns or chambers that are on full fire. The vapour as it is dispelled from the green bricks makes its escape by means of a number of openings in the roof, one of which is indicated at E in Fig. 3. These openings are only used when a chamber is undergoing  “steaming” or being cooled down for drawing 3 when full firing or regeneration is in progress they are made as close as possible. Hitherto I have omitted to state how the gas and air find admission into and egress from the individual firing chambers, ten in all, and in two series of five each. The gas valves indicated on the ground plan, and in vertical section in Fig. 2, can be used at pleasure to admit gas to any chamber by means of the underground flues, shown by dotted lines in Figs. 1 and 2, and in the section at A. in Fig. 8. By means of the same valves, the admission of gas may be entirely cut off, or the amount of the current may be adjusted with the greatest nicety to meet the circumstances of the case. The gas passes from the flue into the burner, marked B in Fig. 4, and it ascends into the chamber by a series of openings immediately in front of the dividing wall of brickwork. What has just been called the burner is really a space of about 18 inches that is left between the partition wall and the mass of bricks to be fired when the latter are being charged. It extends all the way from side to side of the firing chamber. The air required for the combustion of the gas, and which is brought in a highly heated condition from the regenerator, passes through the floor of the kiln immediately on the other side of the partition wall, by means of a series of slits in the brickwork, into another flue, shown at F in the same Fig. Along this part of the dividing wall, there are numerous small apertures for the exit of the air from the flue into the firing chambers. The hot air and gas meet in numerous streams at or near the floor level of the chamber, the resultant effect being most thorough combustion, followed by intense heat which is eventually raised to that required in steel-melting. Great sheets of flame pass upwards through the space above the so-called burner, and which space may fittingly be termed a heat-radiating chamber or space — much of the value of the Qlenboig kiln being doubtless due to the great amount of radiation which proceeds from the wall forming the permanent portion of the burning chamber. Then, again, the arched crown of the kilo also forms a most valuable heat-radiating surface. And here it may be well to mention that the space between the arched roof of the kiln and the mass of bricks being fired goes on increasing up to the stage of full firing, owing to the shrinkage or contraction in the bricks to the extent of about one-twelfth of their bulk. With the formation of such a large space above the mass of bricks, the radiant heat has an opportunity of exerting its full measure of effect. The flames and highly-heated gases in their upward passage swirl over the top and through amongst the bricks, the effluent or so-called waste gases eventually finding their way to the floor of the chamber on the opposite or exit side, where there are numerous slits through which the gases pass down into the flue marked C in Fig. 4, and from which they may proceed either into the next chamber of the series or direct to the chimney, as may be desired. By means of the gas valves already spoken of, and movable dampers working in the flues marked F, the gas and air to be admitted into any chamber are under the most perfect control, as they may be decreased or diminished in quantity at will, and maybe so proportioned as to give any quality of flame required. At D, in Fig. 4, there is shown another flue about halfway up in the dividing wall. This may be used to draw air from one chamber to another at a higher level, thus effectually exhausting the heat of the burned off kiln and, at the same time, shifting the intensity of the heat nearer to the back part of the burning kiln or chamber. When it is required, the same flue (D) may also be used to admit cold air (by a simple arrangement of dampers) in sufficient quantity to mellow or tone down the intense heat of the front, and permit of the back part of the kiln being hard burned without injuring the front bricks. Up to the present, the description of the mode of working the Glenboig gas kiln has scarcely dealt with more than one series of chambers, forming half of the complete kiln, but those of the other series may be regarded as having been in the various stages of cooling-down, drawing, re-filling, &c. As will be seen by again referring to Fig. 1, Plate XYIII., there are underground passages or fines which give communication between the respective end chambers — No. 5 with No. 6, and No. 10 with No. 1. In this way, the two sets of chambers are made quite continuous, so that practically there is a circle in which neither terminal nor commencing chamber occurs. In devising and working out his gas kiln to be a practical success, Mr Dunnachie freely admits that he has followed the lines of Siemens and Hoffman, neither of whom was successful in producing a kiln that should be fired with gas, worked on the heat-regenerative principle, and be continuous in its action. The former tried his hand most anxiously in the direction indicated, but he failed in his efforts, and departed from the idea, under the belief that it could not be realised. His kiln had not the means of keeping up the heat of the regenerator chamber to the high point necessary for completing the full-firing operation. A nice white heat is needed to finish off the burning, thereby requiring a high heat in the regenerator which is amply provided by Mr Dunnachie’s method. One of the chief causes of failure on the part of every person who attempted to bum bricks by the use of gas before the Glenboig kiln was brought to a practical success, was a want of the proper distribution of gas and air throughout the burning chamber, as also a proper admixture of the gas and hot air at every point. At one place the bricks would be roasted, while at another they would be under-burned; in the Glenboig kiln, on the other hand, there is no burning in streaks of hard and soft bricks, as there is an even distribution of heat throughout the whole mass of the bricks under fire. The Hoffman kiln is continuous in its action and is worked on the principle of heat regeneration, but the fuel used in it is small coal, which requires to be fed in from the top. No doubt, the kiln in question is very serviceable where the bricks can be burned by employing a moderate heat; but it would not serve for burning refractory fire bricks, which require a high melting heat. One disadvantage attending the use of the Hoffman kiln is the tendency which certain earthy constituents of the coal have to form fusible silicates with the clay, many of the bricks being wasted in the burning operation by being fluxed. That difficulty never arises where gaseous fuel is used. Owing to the fact that the Glenboig kiln is under such perfect control, it may be advantageously employed in burning the most refractory fire bricks, even ganister bricks, and down to common red bricks. While speaking of the fluxing of bricks by the use of solid fuel in ordinary kilns, it may be stated that the walls themselves also suffer seriously from the same cause, whereas the kiln under consideration seems scarcely to suffer at all from tear and wear. In addition to the extensive adoption of this new kiln at the Glenboig Company’s own works, progress has been or is being, made in the way of adopting it elsewhere, the interest excited in regard to it being very great, as is evidenced by the fact that almost all the leading firebrick manufacturers of the kingdom have either visited the works themselves or have sent responsible representatives to inspect the new kiln in operation. It is in use at Garnkirk burning fire clay goods. At Tamworth, it is being used for the well known Staffordshire blue bricks, and in this case, there are some facts of very special interest, as they show how the kiln can be adapted to new circumstances. The raw coal is distilled or carbonised in ordinary gas retorts, and the by-products are collected and subsequently treated separately, while the gas which is obtained is used in firing the brick kiln. It is got without the use of a separate producer, and as it contains no air it has probably five times the calorific or fuel efficiency of ordinary producer gas. The residual coke that is drawn from the retorts is a good marketable commodity. As evidence of the confidence which the proprietor of the Tamworth Coke Works has in the efficiency and economy of the Glenboig gas kiln, it may be stated that he has recently completed negotiations for the erection of another complete kiln of ten chambers. In another kiln of the same sort erected at Sheffield, Messrs Lowood & Co. are successfully firing their famous ganister bricks. Messrs Henry Sharp, Jones and Co., of Poole, in Dorsetshire, are now erecting a set of ten chambers for firing sewerage pipes. Not only is the kiln in this instance identical with that first erected at the Star Fire Brick Works, but it has, in addition, an arrangement for the economical introduction of the common salt required for glazing the pipes. A kiln such as we are speaking of was erected some time ago at the Rutherglen Pottery, the proprietor of which declined to accede to the suggestion of the patentee to construct a muffle within each chamber so that the ware in course of being fired might be completely protected from the direct action of the flame and heated gases passing through the chamber. As might have been expected, the ware, coated with its delicate glazes, did not ‘stand fire’ under such conditions, and the use of the kiln for firing pottery was suspended; but as Mr Dunnachie is confident of the ultimate success of the kiln for firing either earthenware or porcelain when his valuable suggestion as to the adoption of a muffle is acceded to, he does not regard the Rutherglen example of his invention as having been ‘put on the shelf’ in perpetuity, but simply as being in abeyance in the meantime. The peculiar adaptability of the Glenboig kiln is abundantly shown by the great range of firing temperatures that may be got in it, extending from that which suffices for the Tamworth blue bricks, which is far below that required for burning fire-bricks, up to that which is needed for Sheffield ganister bricks — being almost as great an extreme in the other direction. As an invention in connection with sanitary improvement in industrial districts, the Glenboig gas kiln ought to take a very high place; indeed, with smoke-prevention advocates, it has already gained such a position, from the fact that its general adoption in brick-making and pottery districts would reduce to a minimum smoke nuisance in many places that have acquired an unenviable notoriety for polluting the atmosphere. There is no breach of confidence in saying that the Duke of Sutherland, Lord Whamcliffe, Sir Thomas Brassey, M.P., and many other persons of greater or less eminence, and who have large industrial interests at stake, are now giving attention to the Glenboig gas kiln, on account, in some measure, of its intimate connection with the prevention of smoke. There are many directions in which the use of this kiln is attended with economical results. Some of these have already been incidentally mentioned or alluded to, yet still, one more may be adduced; it is in the kind of coal from which the required gaseous fuel may be obtained, for even the commonest or least valuable slack or dross amply suffices as the source of the gas. Furthermore, if we tab weight for weight, a very much less quantity of it is needed when compared with what is necessary to do the same amount of work in an ordinary coal-fired kiln, in which, by the way, good round coal at a high price has often to be used. It will serve a good purpose if I now lay before the members of the Institution one or two most reliable facts bearing on the relative fuel-economy of this kiln. At the request of the Directors of the Glenboig Union Fire Clay Company, the managers of the several works recently made careful observations, and without any collusion with each other, in regard to the consumption of coal for firing purposes, over a period of some six or seven weeks, with the different kinds of kilns in use. The data obtained from the separate reports of the managers show that the average cost of fuel used by the Newcastle kiln was 8s 2d per 1000 bricks burned; that the cost of fuel used in the hopper kiln, invented by Mr Dunnachie about twenty years ago, was an average of 6s 6d per 1000 bricks; and that the average cost of the fuel used in the form of gas, in what has already been called the Glenboig kiln, did not exceed 2s 9d per 1000 bricks burned. Mr Frederick Siemens, who was long and intimately association with his distinguished brother, the late Sir William Siemens, in connection with heat regenerative furnaces, etc., has become so profoundly impressed with the merits of this gas kiln that negotiations are in progress between his firm and the patentee, with the view of the former undertaking its introduction into various industrial district at home and abroad, in conjunction with the newest form of Siemens gas producer, which is doubtless well known to many of the members referring with a little more detail to the producer, it may be said that a jet of steam is introduced into the generator chamber in order to give the gas a slight push though it is stated that experience gained in some recent cases, shows that such a device is not actually necessary. In it ‘clinkering’ is reduced to a minimum, if it is not practically altogether met; and as no stoppage is required for cleaning operations, one generator will suffice for a kiln of ten chambers, whereas, up to the present, two producers have always been considered necessary. In conclusion, I may be permitted to say a few words in regard to the relationship which this gas kiln bears to the Thomas-Gilchrist or basic process of making steel, a process which will doubtless soon bulk largely in this part of the kingdom. After having undertaken the sole manufacture in Scotland of the basic bricks for lining the steel converters, Mr Dunnachie found that an enormous expense would attend the firing of such bricks if raw coal had to be used as the fuel, as they would need quite a steel-melting heat; and it may almost be said that the necessities of the case led to the construction of the continuous regenerative gas kiln treated of in this paper, which is almost the first formal communication that I have had the honour and pleasure of making to the Institution. In inviting discussion on the paper, The President said he was sure all present had listened with pleasure to the interesting and instructive communication. Mr K Kemp had really great pleasure in listening to the paper on what appeared to be a really efficient invention. At the beginning of the paper, it was stated that the kiln practically utilised all the heat that was in the gas, but that there was still sufficient escaping to give draught enough to pull the waste gas up the chimney. Perhaps Mr Mayer could tell them what temperature there was in the chimney to cause that draught, as it must be a percentage of the total beat. Mr Mayer replied, that the chimney at Glenboig was used for other kilns besides the regenerative kiln. Not only did it do the work of that kiln, but also of some of the other kilns in the works, so that the heat in it was not due to the former entirely. He was not aware whether the temperature in the chimney had been tested, but as Mr Dunnachie’s son had had three years’ training in a laboratory in the City, and was devoting some attention to the production of a really serviceable pyrometer, something would doubtless be done in that direction by-and-by. One main point, he repeated, was that practically there was no waste heat. Mr Kemp said from the explanation given it was apparent that the draught in the chimney was kept up by other fires, and not by the escaping gases from the regenerative kiln. Mr Mayer rejoined that the chimney had certainly to do other work. The President recollected well the Hoffmann kiln for burning bricks, which had been erected at Belfast a good many years ago, and which he had frequent opportunities of visiting. The economy of heat in that kiln was remarkable, so much so, in fact, that it became necessary rather to throw away a little more of the heat purposely because the chimney was too cold almost, and the moisture evaporating out of the warmer damp bricks condensed upon the cooler ones, and so the economy was carried a little too far. Probably Mr Mayer had something to tell them on that subject in regard to this new kiln. Mr Mayer said that the arrangements for getting rid of the escaping vapour in the steaming process were very perfect. The chamber in which the steaming operation was carried on was actually cut off from all the others. The vapour escaped through the crown of the chamber by some fifteen openings, and special means were taken to increase the activity of the current from the chamber during the steaming stage. Mr S. G. G. Copestake noticed that in the model shown the crown was semi-circular and in the drawings on the wall somewhat flatter He wished to know whether or not the shape had anything to do with, the effectiveness of the kiln. Mr Mayer said Mr David Johnston, who was to some extent responsible for the diagrams, might be able to answer that question. Mr Johnston explained that Fig. 1 was merely a ground plan, but that there was a longitudinal section in Fig. 4, Plate XVIII. Mr Copestake was anxious to find out if there was anything special in the shape of the arch. Mr Mayer did not think there was any essential element in the shape of the arch. Mr Kemp thought the half-circle was better suited than the other form for the purpose in view. Mr Johnston wished it to be understood that in the diagrams he had merely followed lithographed drawings, given in the patentee’s ‘blue book.” Mr Kemp was of the opinion that the model showed the ordinary arch. Mr Mayer believed that the model might show a more recent method than the diagrams and that the semi-circular arch might give better results than the flatter one. Mr James M. Gale observed that there was less lateral thrust in the semi-circular than in the other form of an arch. Mr Geo. Russell asked if men worked in the drying stove at a place indicated by him. It appeared to be a hot place, especially in summer, with furnaces below, and its roof of iron. Mr Mayer replied in the affirmative, explaining that he had referred to it as the moulding floor. The discussion of this paper was resumed on 28th April 1885. On the call of the Chairman, Mr F. W. Dick said he had not been able to be present at the last meeting to hear the paper read, nor had he been able to find time to peruse it since; but he knew something of Mr Dunnachie’s plans. Of course, anything which utilised heat, instead of allowing it to radiate into space, must be good. On the whole, he thought the plan an excellent one, but he would prefer to say nothing more at present, as he was ignorant of the contents of the paper. Mr Henry Dyer simply wished to remark that as Mr Mayer’s paper was descriptive of an invention, which seemed to be correct in principle and successful in practice, there was not much to be said about it in the way of discussion. The chief duty incumbent upon them on that occasion was to thank Mr Mayer for his excellent paper and to congratulate Mr Dunnachie on his marked success. Perhaps he might be allowed to suggest that a few simple experiments should be made with the oven to ascertain if it was working under the conditions of maximum efficiency. These were first, that there should be little or no external radiation; second, that the combustible gases should be consumed; and third, that the temperature of the chimney should be just sufficiently high to carry off the waste gases. In the oven described he thought that the chimney served for other purposes so that it might be somewhat difficult to carry out some of the experiments, but he had no doubt that Mr Dunnachie would be able to ascertain the actual efficiency of his invention. In concluding, Mr Mayer had remarked that this was the first paper he had read before the Institution; but for his own part he hoped, now that the author had made a start, he would give other papers of the same class, especially as the Transactions of the Institution in the past had been somewhat deficient in papers relating to applied chemistry and metallurgy. Of course, they knew that Mr Mayer had paid special attention to these subjects, and he would confer a great boon upon the members by supplying them with particulars of recent advances in these departments especially in the industries connected with Glasgow and neighbourhood. The Chairman (Mr C. C. Lindsay, Vice-President) said he had not the pleasure of hearing Mr Mayer read his paper, neither had he read it in the transactions, but it was a class of paper — bearing upon the economical use of fuel — which he would like to see more of. He was not acquainted with the burning of fire bricks and pottery as described, but he had some experience of steelmaking with gaseous fuel, and it seemed to him that Mr Dunnachie had been very successful so far in his work. He hoped Mr Mayer would, as Mr Dyer had suggested, give more papers of a similar class in the future. Mr Mater said with regard to the remarks made in the discussion, it was Mr Kemp, he thought, who referred to the chimney at the Glenboig Works doing more than the work of the simple kiln or set of ten chambers to which it was specially attached. In regard to that, Mr Dunnachie had informed him that some of the kilns which had been erected in England were doing work only into one chimney stalk, and that each chimney stalk was doing the work of only one set of chambers so that doubtless some specific details might be got in the course of the next few months as to the results in one or more of those instances. He had no doubt Mr Dunnachie would be quite willing to receive a Committee of experts from the Institution and make preparations for them carrying out certain observations, if that should, in the opinion of the Council, be deemed desirable. As Mr Dyer seemed to be much interested in the subject dealt with in the paper, he (Mr Mayer) suggested that that gentleman might act on that Committee. The question had been raised by Mr George Russell about the rather hot quarters that the brick-moulders and their attendants would have, working in the drying stove, shown in Fig. 2, cross-section. But it must be remembered, however, that the drying stove was some 60 or 70 feet long, and extended not only over the open space between the two rows of firing chambers but over those two rows of firing chambers themselves so that while a drying stove, it could also be fitly employed as a moulding room, for the ten chambers were not all equally hot. The brick-moulder could, therefore, moving his moulding table about at pleasure, always have a cool place to work in, even in the height of summer. Then, lastly, with reference to the point raised by Mr Copestake about the arches of the kiln being flat rather than semi-circular. It would be remembered that the arches were flat in one of the diagrams shown at the last meeting and semi-circular in the model, which was now in the Inventions Exhibition in London. In the plans, as originally drawn out the arches were semi-circular, but the diagram was copied from the patent specification drawings where they were given flat by mistake by the patent agent without the knowledge of the patentee or inventor. The arches were, therefore, semi-circular from the first, thus securing what Mr Gale desiderated— the utmost strength possible. Personally, he could assure them that some of the chambers he had seen lately had borne the test of age and experience without giving way in the slightest particular. In his opinion, they had great durability and power of resisting wear and tear. The suggestion Mr Dyer had thrown out would, he hoped, be acted upon so that the Committee might report to the next Session of the Institution what had been done. Mr Dyer thought Mr Mayer had mistaken its meaning. He did not propose that the Institution should appoint a Committee, because if they once commenced that they would have plenty of work to do. It was Mr Dunnachie’s business, he thought, to make a few simple experiments, and give the results to the Institution. Of course, there was nothing wrong in such a proposal, but there were other important matters that equally required investigation at their hands, and if the Council took up such things they would have more than enough to do. The Chairman asked Mr Mayer if he had anything further to say in view of Mr Dyer’s remarks. Mr Mayer replied that he had nothing to say beyond this, but he was quite willing to bring up a report in the shape of results. tested as far as he was able to test them, and that he would do his best to collect information on the subject in question from those persons whom he had referred to in the paper as using the regenerative gas kiln. The Chairman said he had much pleasure in proposing a hearty vote of thanks to Mr Mayer ‘for his’ paper. ***************************************

Below  – Sept 1899 – British Clay Worker.

Below – Oct 1899 – British Clay Worker.