US2135542A - Utilization of colliery shale and other waste bituminous shales in the manufacture of cementitious products - Google Patents

Description

vulllllu VII UNITED STATES PATENT OFFICE UTILIZATION OF COLLIERY SHALE AND OTHER WASTE BITUMINOUS SHALES IN THE MANUFACTURE OF CEMENTITIOUS PRODUCTS Norman Victor Sydney Knibbs, Westwood, New

Continental Investment Syndicate Limited,

London, England No Drawing. No. 72,591.

3 Claims.

This invention relates to moulded building blocks, artificial stone, paving slabs, moulded pipes and posts and like products which are produced by moulding or otherwise shaping cementitious materials derived from admixtures of lime and argillaceous and/or siliceous materials.

In the mining of coal there is generally produced a considerable quantity of shale or other argillaceous substance which ordinarily is valueless and is discarded, forming the dumps that are to be seen at nearly all collieries. In some few instances this shale has been found suitable for brick-making by the usual process and some other minor uses have been found for small quantities of it, but ordinarily it is'valueless and is an expense to dump. Furthermore, because of the combustible it contains the heaps of shale generally take fire and slowly burn, with attendant disadvantages of smoke nuisance, et

cetera. In the same way, a low grade oil shaletoo poor to use in the retorts--is sometimes produced when mining oil shales of higher quality.

By experiment we have found that the colliery or oil shales are often suitable for making blocks of high quality by the processes described in our pending application Serial No. 62,298, for not only do these shales .ordinarily contain suflicient combustible material to calcine themselves and to produce from limestone, chalk or other form of calcium carbonate, the lime required for our processes, but they also ordinarily contain sumcient sulphur in the form of pyrites or otherwise, to produce in burning with limestone suflicient calcium sulphate to enable the special advantages of steam-hardening according to our processes to be obtained or at any rate to contribute materially to this result.

According to the present invention, a moulded or otherwise formed article is made by steamhardenin g underpressure 'a cementitious matermtmduceaihmeksawn manner by calcinipg the shale with limestone, chalk or other form of calcium carbonate, the combustible of the shale at least contributing to that necessary for effecting calcination of the shale-lime mixture, crushing and/or grinding the mixture, and adding water. With previously proposed processes the wet mass was merely moulded or otherwise formed into the required article without being subjected to steam-hardening.

The steam-hardening of the shale-lime mixture which characterizes the present invention is preferably performed in autoclaves at a pressure of about lbs. per square inch.

We have found that when a cementitious ma- Application April 3, 1936, Serial In Great Britain August 8, 1935 terial such as that above mentioned is subjected to the action of steam under pressure, any deleterious sulp lriggs -that s 0 say sulp ides liable to oxidize and cause expansion on subsequent exposure-are hydrolyzed and the sulphur 5 evolved as'hydrogeh' siflphide. The steam-hardening process therefore turns a faulty material into a sound one. It will be appreciated-that where the term shale is used in the following description, it is intended to imply colliery shale or other argillaceous wastes from mining coal, bituminous shale, low grade oil shale, and similar combustible containing waste argillaceous or siliceous products.

Although it is preferred that the shale used in the production of the cementitious material should contain combustible sufficient to effect calcination not only of itself but also of the calcium carbonate of the shale-lime mixture, we wish it to be understood that the invention also extends to cases in which coal or other fuel is added to supplement the combustible matter in the shale. In the following description, which may be said to be a preferred embodiment, it will be assumed that the combustible of the selected shale efiects calcination of the shale-lime mixture. Moreover, although limestone may generally be the most convenient form of calcium carbonate, any other form of calcium carona e w 0 may be available can be used.

The proportion of shale to limestone that is used will depend upon the amount of combustible matter in the shale and upon the use to which the mixture is put. We have found that some shales we have tried will calcine about their own 35 weight of limestone in addition to themselves, while others will not calcine nearly as much limestone. A suitable plant for the calcination of the mixture is a short shaft kiln, similar to a short lime kiln, and the height required will vary with 40 the size of the shale and limestone used. We have found that ordinarily it is preferable but not essential to have the shale and limestone of roughly the same size.

For crushing and'grinding the mixture any suitable machines may be used, such as a jawcrusher, followed by a tube mill. Hydration if required may be carried out by known methods.

The ground mixture contains silica and 50 alumina, combined or free, and free liine, and it is therefore a potential source of calcium silicates and alumiiiates. me-roen'crmxtme after mixiiig withm and after the lime has hydrated will harden to produce a mass of high 55 strength when it is subjected to the action of s sai nundeuxa s s- To effect hydration of the lime, ii. required, water is added equivalent to between 33% and of the weight of lime in the mixture, which is then put into bunkers and left to stand till hydration has been completed whereaiter further water is added to the mass which is then passed to the moulds or like shaping devices.

For use in steam-hardened blocks or other articles, the mixture may be ground to a fineness of passing a sieve of meshes to the linear inch. Generally, the optimum lime content is about 20 to 25 per cent. by weight of the calcined mixture and the shale and limestone are therefore mixed in a proportion to produce this calcined mixture.

The mixture after grinding and with or without hydration of the lime may be used instead of Portland or other cement to produce building blocks, moulded or otherwise formed articles such as posts, pipes, asbestos-cement sheets, et cetera, decorative mouldings, et cetera, the moulded or formed articles being finished by steam hardening. The mixture may be used instead of lime in sand-lime bricks, in which case the mixture ordinarily is ground to a lesser degree of fineness than that previously mentioned. Aluminium dust or other gas-generating agent may be added to the mixture to produce porous blocks and like articles.

In the production of building blocks and like moulded articles according to the present invention, it is preferable that the general processes as described in our pending application, Serial No. 62,298, should be used. It may be observed that this application deals with the efiects of an inclusion with the mixture of a compound of an oxy-acid of sulphur, and in this connection it may be mentioned that colliery shale and like materials ordinarily contain sulphides which on calcination produce sulphur oxides, but if the shale is calcined by itself a greater part of the oxide compounds is lost, and it is only when the mixture is calcined that the oxides are absorbed by the lime and thus retained to form calcium sulphate.

For asbestos-cement products the requisite quantity ofgan be added to the mixture while in a similar way,"s'a'nd gravel, crushed stone or other aggregate or mixtures of aggregates may be added.

What we claim then is:-

1. A method of making a cementitious product that comprises mixing fuel-containing shale with calcium carbonate, utilizing the fuel contained in the shale to at least partly calcine the shale and the calcium carbonate to produce quicklime, dividing the calcined mixture into smaller parts, adding water, shaping to the re-' quired form, hydrating the quicklime, and applying steam under pressure to harden.

2. A method of making a cementitious product that comprises mixing fuel-containing and sulphur-containing shale with calcium carbonate, utilizing the fuel contained in the shale to at least partly calcine the shale and the calcium carbonate to produce quicklime and to produce calcium sulphate by the reaction of the sulphur with the calcium carbonate, dividing the calcined mixture into smaller parts, adding water, shaping to the required form, hydrating the quicklime, and applying steam under pressure to harden.

3. A method of making a cementitious product that comprises mixing fuel-containing shale with calcium carbonate, utilizing the fuel contained in the shale to at least partly calcine the shale and the calcium carbonate to produce quicklime, adding a gas-generating agent to the mass to render it cel1ular. djviding the calcined mixture into smaller parts, adding water, shaping to the required form, hydrating the quicklime, and applying steam under pressure to harden.

NORMAN VICTOR SYDNEY KNIIBBS. ALFRED PE'I'I'ER PEI-IRSON.