THE

AND

Edited by James H. Gardiner, F.C.S.

Established in the Year 1859

HYDROGEN PLANTS

MAXTED PROCESS.

PURITY 99'9 PER CENT AND OVER

directly and without purification.

LOW COST OF PRODUCTION COMPLETE ABSENCE OF CATALYST POISONS We also specialise in the conversion of existing Plants of the Intermittent type where bad results have hitherto been obtained, owing to impurities in the Hydrogen produced.

COMPLETE INSTALLATIONS for CATALYTIC HYDROGENATION OF OILS.

JOHN THOMPSON

(GAS DEVELOPMENTS) LIMITED

TETINGSHALL, WOLVERHAMPTON, ENG.

STILLS, CONDENSORS, JACKETTED PANS, MIXERS,

EVAPORATORS,

Manufactured to suit requirements

IN proceeding now to review the economic side of the matter, let us disclaim at once any intention of basing estimates upon the present values of chemical wood-pulp. These are about £35 to £45 per ton c.i.f. at British ports, according to quality, and undoubtedly represent temporary inflation. Any attempt to arrive at what may be the normal price of wood-pulp in this country when inflation has been worked off can only be a more or less intelligent appreciation of events, but considering that costs of production for labour, fuel, chemicals, machinery, freights, and wood are three to four times what they were in 1913, and that these advances are probably permanent, with wood still tending to rise, we shall not perhaps be far wrong in putting it at £28 per ton. If this is considered too high, the sequel will show that it is a figure permitting of considerable variation downwards. On similar grounds we would put the future normal price of mechanical wood-pulp-which is not cellulose at all, but only ground raw wood-at £16 per dry ton, Under the transport conditions I will describe later, bamboo can be delivered at manufacturing sites in Burma at a cost of 12s. 6d. to 15s. per dry ton, equivalent to from £1 11s. 3d, to £1 17s. 6d. per ton of unbleached pulp. Compare this with the like cost for wood-pulp, which is from £10 to £12.

Manufacturing charges, inclusive of liberal allowances for depreciation of plant and contingencies, will be under £10 per ton of pulp, so that the total cost on board steamer in Burma

ports will probably not exceed 12 per ton-about the cost of raw material alone in the case of

wood-pulp. In freights, of course, wood-pulp, being nearer has the advantage, though not proportionally to distance, since port and terminal charges, no inconsiderable proportion of the whole, are the same for any distance. At present, from Burma ports, they are about £6, but this is abnormal, and I am advised on good authority that the eventual normal figure will not exceed £4. The prospects, therefore, are that bamboo unbleached pulp can be delivered in this country at a cost not eceeding £16 to £18. Freights, again, are not entirely a matter of export in this country. There is a growing demand for India, China, Japan, and Australia, and to these countries freights would be in favour of bamboo-pulp and against wood-pulp. The economic position thus disclosed has an interesting relation to mechanical wood-pulp, for which we have assumed a future normal value of £16 per ton. I do not think it has ever been seriously suggested before that a chemically-prepared pulp could be

*From Journal of The Royal Society of Arts, June 24, 1921. (By permission).

brought within competition distance in cost with a mechanical one, but the figures given above do now suggest such a possibility, and it is not wholly a question of price. Mechanical pulp will not produce a useful paper by itself, and it adds nothing to the quality of a sheet. It is merely a convenient filler, make-weight, and reducer of cost, and must be held together by a considerable admixture of true cellulose. No paper-maker uses it because he loves it, but solely because he must to get his cost low enough, and he will willingly substitute for it a true cellulose if it does not cost him very much more, especially since he is well aware that such a substitution enables him more effectively to use fillers, which are cheaper even than mechanical pulp, such as that good old stand-by, China clay.

Few industries are more sensitve to transport conditions. Including the product, six tons has to be transported in and out of a factory for every ton of product where coal is available. If wood fuel is used, the total will be 8 tons. It does not necessarily follow that each of the primary materials required-which are bamboo, fuel, limestone, and imported soda-must be available under ideal transport conditions. It may be the case that some extraordinary advantage in one of them enables the manufacturer to raise his cost limit for another, but it is evident that next to the raw material, transport is the ruling factor. Its importance may be illustrated by my own recent experience. During the past eight years I have been asked to revise some sixteen propositions for establishment of factories. Of these, only three failed on account of defects in the raw material supply, nine had to be rejected on transport conditions, and only four satisfied all requirements. Judging from enquiries I receive, this phase of the question receives little attention, and a sufficient supply of raw material appears to be popularly regarded as a satisfactory foundation for the industry.

In a previous paragraph I made a statement to the effect that India and Burma could produce ten million tons per annum under possible manufacturing conditions-possible, that is, with a normal value of £28 per ton in England-but the areas included in such a survey are naturally capable of being divided into best and secondbest, and the best are probably not more than a fifth of the whole. They are to be found chiefly in the coastal belt of Burma and North-Eastern Bengal and Assam, with a smaller area in SouthWest India. I have myself explored a considerable area of the coastal region of Burma, where the transport conditions are nearly ideal-numerous rivers, many of them tidal to 100 miles from the sea, and with good rafting water above that intersected with creeks and connecting channels, and down which bamboo, felled upon their banks, can be floated to the manufacturing sites on deep water, or within easy reach of ports and anchorages by the aid of lighters. If wood fuel is not available-and it frequently is-coal from Calcutta or oil from Rangoon can be had, and limestone, also by water, exists at several places on the mainland or islands close to the coast. The only foreign import required carrying a high freight cost is the small amount represented by 15 to 20 per cent of the total soda consumption. There is one peculiar feature of bamboo as to

which a warning should be issued, viz., the extraordinary phenomenon it exhibits of cyclical gregarious seeding and death. A few species do follow the usual rule of grasses in annual seeding, and a few others seed sporadically, but most of the important ones flower in cycles of long period and gregariously, and each species has its own length of cycle. It goes on reproducing itself by shoots thrown up from the root year after year for 20, 40, or 60 years, until, feeling old age approaching, it throws all its remaining energies into producing an enormous crop of seed, and then dies. The new generation, although ultimately destined to produce culms which may be 120ft. in length, and 6in. in diameter at the butt, throws up a first crop of diminutive stems, perhaps 18in. high and less than a fin. thick. Next year brings a crop somewhat larger, and so on, increasing year by year in strict proportion to the growing power of the plant to produce starch and store it in its roots, until, after from four to ten yearsthe period varying with species, soil, and climate

it is again throwing up its full-sized culms. Note also, as a striking example of Nature's silent dynamic, that these stems which, as I have said, may be 120ft. by 6in., are produced of full height and diameter in four months. It is one of the few plants which you can literally see grow. Its branch and leaf system are developed in its second season, and it is then fully matured.

It will be clear from this that a factory planted in a district without some enquiry having been made as to the seeding cycle, might find itself suddenly bereft of supplies for a prolonged period. There are two methods of insuring against this; first, the next seeding period may be known to be at such a date that supplies can be depended upon for a period long enough to secure an ample return on capital invested in the undertaking, and, second, the presence in the area of an alternative species which, as is invariably the case, does not flower at the same period. It is satisfactory to be able to add that most of the important species have seeded within recent years, or are now in process of doing so, as if Nature had anticipated the demands we are about to make.

The crisis now threatening the paper industry, and, it may be added, the large and increasing family of industries based on cellulose, of which artificial silk and celluloid are types, is no unprecedented experience. It is historic and oft repeated. Beginning with the failure of rag to provide for a continually increasing demand, the trade during the last 100 years has passed in succession through the phases represented by the utilisation of textile wastes, straw, esparto, and wood, each in turn hailed as salvation, and each in turn failing to cope with the requirements or finding a better market. It remains a fundamental axiom of the industry that it is a "picker-up of unconsidered trifles." As the interests of other manufactures in a material increase so in proportion that of the paper-maker decreases. They can all pay more for it than he can. I have been trying for 25 years in various parts of the world to find a solution for this recurring trouble. As the final considered result of that experience, I venture to express the belief that no permanent solution of it can be found, except in the vast stores of annual

-and I lay much stress on the annual-products of the forests and waste places of tropical and sub-tropical regions. Enormous in their volume, frequently co-existing with splendid transport and manufacturing facilities, continuous and rapid in their natural reproduction and easily converted by modern methods, they provide a field of enterprise of which we may well hesitate to prophesy the expansion and wholly fail to see the end. And remembering recent experience when found ourselves almost wholly dependent upon foreign supplies, may we be pardoned for uttering a little pæan of congratulation that such areas are within the Empire?

DISCUSSION.

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Mr. SINDALL then contributed the following observations: Mr. Raitt, in his address, shows that with regard to the preparatory treatment of bamboo for ultimate conversion into paper, two rival schools are in existence, which he describes as the "crushers" and the "chippers." The argument on behalf of the crushing school has been exhaustively presented, and it would, therefore, be interesting to know the line of argument adopted by the "chippers," so-called.

In this case, the stems of bamboo are passed through a special slab-wood chipping machine, which cuts the bamboo into small chips similar to those obtained by the treatment of slabwood. It is stated that such a process gives a much greater capacity in the digester, with a closer and better packing of the material. The digester is more easily and quickly filled, and owing to the closer packing of the material, less liquor is required. This, in its turn, means the use of a stronger liquor, and ultimately a much smaller quantity would need to be evaporated for the recovery of the soda. Messrs. Boving & Co., who have de veloped this system, state that they are able to fill a digester of a capacity of six tons by blowing in the chips in about half-an-hour. Experiments were made by them in Sweden on a large scale, some 20 tons of bamboo having been utilised for the purpose, and it has been proved that the product obtained is perfectly satisfactory.

This firm have given considerable attention to the question of economy in the production of esparto and bamboo pulp, and are at the present moment engaged in the erection of a large esparto plant in Scotland, based in the most modern practice of pulp treatment and the methods being introduced are certainly worthy of close attention on the part of paper-makers. The system as devised introduces many ingenious methods for economy in fuel and labour. The material is cut into small pieces, cleaned and dusted, and then blown into the digesters. The requisite amount of caustic soda is run into the digester, and the cooking proceeds by a new system of circulation. In present practice the material is cooked by blowing live steam into the mixture, with the result that the consequent condensation of the steam increases the volume of the liquor to be evaporated for the recovery of soda. In the new system the liquor is passed through the grass in the digester through an outside circulating system heated by highpressure steam in such a manner that the steam condensed is drawn off separately and utilised for heating washing water or cooking liquor. The volume of liquor in the digester in this case is not increased and a definite saving is thus effected.

It is proposed to utilise this condensed steam for heating up the cooking liquor so that the pulp is at once supplied with hot liquor and this again means economy in steam.

When the pulp is sufficiently cooked, the pressure in the boilers is utilised to discharge or blow out the boiled grass direct to the washing tanks or diffusers. This method is substituted for the present system of allowing the steam to blow out into the air or into water. The practical result is that the black liquor containing all the non-fibrous organic compounds present in the original esparto has a density of something approximating 14° to 16° Twaddle as opposed to 6° or 8° Twaddle.

The clean pulp is flushed out of the diffusers by water, and passed over screens and sand traps similar to those employed for the production of wood pulp.

The whole process is continuous, requiring very little attention, and appears to be a great advance on the present system.

The same plant can be used and has been carefully designed for the treatment of bamboo. It appears that the knots in bamboo offer no difficulty, and certainly results obtained on such a large scale as that involved in the treatment of 20 tons should afford sufficient evidence as to the value of the method designed by them.

The most important development, however, in connection with esparto, bamboo, and similar materials such as Indian grasses, is the treatment of the black liquor obtained during the process of digestion. When these materials are treated with caustic soda, some 45 per cent to 50 per cent of the original matter is dissolved and the liquor is then highly loaded with organic matter.

In the earlier days of paper making this liquor was discharged into open streams and rivers of the neighbourhood, but owing to the action taken by local authorities it became necessary to devise some method of dealing with this black liquor, the discharge into streams and rivers being forbidden. A method was found in a process by means of which the liquor was evaporated to a thick consistency, in which condition the mass would catch fire and could be burnt, the organic matter in solution acting as fuel for a more or less complete incineration. The organic soda compounds were thus converted into crude carbonate of soda, in which form, after boiling with a definite proportion of lime, it was re-converted into caustic soda. The methods of evaporation, economy of washing water and scientific control of the several stages of treatment were gradually improved, and the recovery process, at first regarded as the outcome of a mere whim the part of obnoxious local authorities, soon revealed itself as an important factor in reducing costs of production.

on

Of recent years, considerable attention has been given to a more scientific method of recovery in the hopes of obtaining more valuable bye-products than combustible matter. Rinman's process for the conversion of the soluble organic constituents into definite bye-products of commercial utility, already well established for wood pulps in Sweden, has now been applied in these recent experiments with bamboo, and an estimate of byeproducts available from a standard bamboo pulp mill having a capacity of 10,000 tons air-dry pulp per year (using 22,000 raw material) is as follows:

This

Rinman's process is carried out on the following lines. The black liquor already suitably concentrated to the required density is mixed with a small proportion of caustic soda liquor and a carefully calculated quantity of quick lime. mixture when showing a density of about 40° Beaume is kept at a high temperature in proper storage tanks. The mixture is fed as required into a number of iron trays to the depth of about 2 cm. These trays fit into square shaped wagons, four of which are at one time pushed into the distillation furnace, which is perfectly airtight when closed up ready for the operation of distilling. The temperature of the oven is gradually increased to 200° C., the heat for this process being obtained by burning gases which are given off during the distillation process, any extra heat being obtained from a gas generator using coke. At 200° C. the excess moisture is driven off.

The temperature is raised to 300° C., and at this stage the bye-products given off are mainly crude methyl alcohol and hydrogen gas. These products are drawn off in a suitable manner. At an increased temperature of 400° C., the byeproducts obtained are acetone and light oils.

The whole operation of distilling occupies about 18 hours. The furnace is then cooled and the wagons drawn out of the apparatus, the contents of each trunk being tipped into water and causticised with lime. The lime mud, which is necessarily contaminated with the carbon left from the distillation process, is dried in a rotary furnace and ultimately burnt at a high temperature in another rotary furnace heated from the gas generator already described. By this means the lime mud is reconverted into quick lime which can be utilised over again in the process of causticising the crude carbonate of soda obtained from the distillation furnace.

If the Rinman process proves commercially practicable on a large scale as applied to esparto and bamboo, then the prospects for cheap bamboo pulp seem bright. The quantity of bye-products obtained as shown in the above table amount to nearly 10 per cent calculated on the original raw bamboo. At present the story reads like a fairy tale, but the fact remains that mills are being erected in Great Britain having all these new applications in view for the treatment of esparto and grasses and its application to bamboo is stated to be merely a matter of adaptation.

Mr. E. F. HEYERDAHL, of Christiania, said that last year he investigated the sulphate process and made trials with different materials. He had had a long experience in the treatment of coniferous woods, and he had also been to South Africa,