The Green Island Cement Company and the growth of the cement industry in Hong Kong, 1932

IDJ has sent the following newspaper article which mainly focuses on the Green Island Cement Company in Hong Kong and outlines its production of cement in 1932.

HF: I have retyped the article to improve clarity and searches on the website.

Thanks to SCT for proofreading the retyped version of the original article.

The Green Island Cement Company first started the manufacture of cement in 1889, and increased its capacity ten years later by the installation of kilns and machinery at Hok Un in Kowloon. In 1905 the earliest type of Rotary kilns were installed at Hok Un, and, since that date, cement has been manufactured in these Rotary kilns on the dry process.

In 1931, however, the Green Island Cement Co.’s factory was completely remodelled by the introduction of new machinery for grinding and burning on the wet process. The new factory is up-to-date in every respect, and is equipped with the most modern plant of its kind in the world.

RAW MATERIALS

The chief raw materials for the manufacture of Portland cement are limestone and clay. Limestone is obtained from a number of sources and landed in junks at the works’ wharf. Here it is transferred to an aerial ropeway, which, in turn, deposits the stone upon the storage ground.

The clay or mud used is dug locally and landed at the works in the Company’s clay barges. A 2½ ton grab capacity limestone digger, working on a caterpillar track, loads the limestone from the storage piles into trucks, which are, in turn, hauled to the crushers. The limestone is crushed from pieces as large as 2 feet cube down to ¾ inch size and under by means of these crushers. 

Grinding

The crushed limestone and clay are fed together into what is known as a compound hull and tube mill, 40 feet long by 6 feet 6 inches in diameter. These mills are about half full of steel balls and revolve at the rate of 25 revolutions per minute. There are three of these grinding mills coupled to 375 h.p. motors.

Slurry

The resulting raw material comes out in the form of slurry, which should contain approximately 76½ per cent of calcium carbonate. The exact determination of the quantity of calcium carbonate in the slurry and its fine adjustment is carried out by the works’ Chemist. When the slurry contains the proper proportion of materials, it is pumped to the feed end of two Rotary kilns. These kilns are each 254 feet long and slowly revolve at a speed of about 1 revolution per minute. They are set on a slope, and, at the bottom end, powdered coal is blown in, which ignites in the firing zone. The hot gases travelling up the kiln, as they meet the down coming slurry, drive off the water and carbon dioxide, and finally sinter the calcarious and argillacceous materials into cement clinker. The temperature at which this operation takes place is 2,700° fahr.

Making the Cement

All that now remains is the storage of this clinker and its grinding into cement. For this purpose a large clinker store is furnished, together with the necessary feeding and extracting conveyors, and the clinker is taken to the cement mill house. In this house are three 36 feet by 6 feet 6 inches diameter compound ball and tube mills, as before about half full of steel balls, and revolving at the rate of 23 revolutions per minute. Into these mills the clinker is fed, together with a small portion of gypsum. The gypsum is required to regulate the setting time of the cement, which, without its addition, would be too rapid to work. The cement for ordinary purposes is ground in these mills to such a fineness that 95 per cent of the cement passes through a sieve having 32,400 holes to the square inch.

Storage and Bagging

Finally the cement is stored in eight reinforced concrete silos about 95 feet high, which contains 2,000 tons of cement each. From the silos it is extracted by means of conveyors and transported to the bagging plant. Here automatic bag filling and barrel filling machinery is installed and cement is delivered from the packing house to the godown or direct for export.

The Dust Problem

Throughout the works the greatest care has been taken with the elimination of dust. Elaborate dust collecting plants are installed in the cement mill and packing plant, where, otherwise, a quantity of dust would be dissipated into the atmosphere. Ordinarily speaking, the gases from the kilns contain a percentage of dust. In order to prevent this reaching the atmosphere, an electrical dust precipitation plant has been installed, which deposits approximately 97 per cent of the dust which is contained in the gases. When it is realised that the total dust contained in these gases only amounts to approximately 5 per cent of the weight of raw material used, it will be observed that when the gases have passed through the precipitator, and 97 per cent of this 5 per cent has been deposited, very little dust escapes into the atmosphere.

British Machinery

The machinery installed in the new plant is entirely British, and is, in the main, manufactured by Vickers Armstrongs Ltd., of Barrow-in-Furness. Vickers Armstrongs’ representative responsible for the proper working of the machinery is Mr. W.G.A. Turner, Assoc. M. Inst. C.E. who has been present throughout the erection. The Consulting Engineer, who designed the plant, and its arrangements on site, is Mr. Henry Pooley Jun., B.Sc., Assoc.M.Inst.C,E., A.M.I.Mech.E., M.I.Struct.E.,F.G.S.

160,000 Tons Annually

The cement manufactured by the Company is of the highest quality and equal to any cement produced in Great Britain or elsewhere. The cement is largely used locally and exported to the Straits Settlements and elsewhere. At the present time cement is being manufactured at Hok Un at the rate of something in the neighbourhood of 160,000 tons per annum.

Source: Hong Kong Sunday Herald 10th January 1932.

This article was first posted on 22nd January 2022.

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