NL8005401A - METHOD FOR MAKING FOAMED GLASS PREPARATIONS. - Google Patents

Description

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Method for making foamed glass articles.

The invention relates to a process for making foamed glass articles by digesting naturally occurring weathering products wet-drying, drying and grinding the reaction mass, granulating as well as foaming the granulate at temperatures above 70 ° C.

Such processes are known, for example, from British Patent Specification 1,407,515. As a naturally occurring weathering product, a relatively rare but easily accessible clay, namely so-called bentonite clay, is used. The clay is stirred at room temperature with a digestion agent such as boric acid, potassium hydroxide and sodium acetate and granulated at the end of the reaction while the resulting granulate is foamed at temperatures above 700 ° C.

The already known process may indeed be carried out with the special bentonite clay mentioned therewith, but not with products that are difficult to digest, such as, for example, sludge and sludge materials. However, it is precisely the generation of these materials that is economically interesting because these products have not yet found use.

Further methods for preparing foamed glasses are described in DE-P's 1,154, .732, 1,671,266 and 2,151,232. However, these known methods are also based on other starting materials, while these methods cannot simply be affected by the processing of sludge and sludge materials either.

The object of the invention is now to provide an economically feasible method for the most inexpensive production of molded products of foamed glass. For the preparation of this objective it is proposed to use sludge or sludge as a natural processing product and this with a commercial water undiluted solution -2- (40-42 ° C and additional free alkali metal hydroxide in a ratio based on the solid of 1: 1 to 1: 6 as well as to be mixed with blowing agents and to be reacted at temperatures of 40-100 ° C. After the reaction has been completed, a thick liquid slurry is obtained, which is dried, ground, granulated in accordance with the known methods. and foamed.

The grounding method is. economically very favorable because of the. said starting materials can be assumed which are under easily feasible operating conditions. can be unlocked with relatively cheap further chemicals.

The boundaries with regard to the composition of the stated starting materials, namely sludge and sludge materials, are fluid. Even at the winning places they can still change within certain limits. Higher contents of sand materials or stones are not advantageous for the economic implementation of the method, because they must first be separated by flotation or sieving. Therefore, starting products will be used without these components if possible. The mentioned sludge and sludge materials may, depending on the location, contain more or less high contents of SiC2, CaO, Α ^ Ο. ^, Fe2 ° 3 'MgO, MnO and other metal oxides, as well as carbonates and sulphates, organic components and bound water. Sludge and sludge materials, in particular, have an unusually high organic material content, which greatly inhibits work-up and foaming by the known methods. According to the proposed method, it is possible to work up these products if the water glass content as well as the free NaOH content remain within the indicated limits. In this case, it is essential to increase the oxygen-releasing blowing agent content so that all of the organic matter can burn. Red sludge is preferably used as the oxygen-releasing blowing agent.

As a water glass solution, solutions with a high solids content are used in the digestion, so that as little water as possible has to be evaporated during drying. greatly favored by the added NaOH. The digestion time can vary, usually it is sufficient to stir the hot solution for 30-60 min until a creamy, viscous consistency is reached. Drying can be carried out with the aid of the known drying devices. It has proved advantageous to use a belt dryer.

The conversion product, which is still bound at about 200 ° C, dried, is converted as much as possible to the fineness of. cement made. The finer the grinding, the better the granulation according to the known techniques, for example on a granulating tray. In general, water serves as granulating liquid, to which binders, for example adhesives, can also be added.

In order to reduce the tendency for the granulate to stick together when foaming the granulate, the still moist granulate granules are coated with well-adhering release agents, for example cement, plaster and the like. It is recommended to dry the granulate at about 200 ° C before foaming. This makes the green granulate suitable for storage and transport, so that foaming devices can also be operated in a decentralized manner.

Depending on the different melting and foaming temperatures determined by the preparation instructions, the furnace is chosen for the foaming, a circulating flow furnace or a rotary furnace being preferred for preparing a granulate. Long furnaces are suitable for the production of plates 30 in molds, which must be followed by a cooling section of the correct dimensions. The molds can be filled with green granulate or with the ground product obtained after digestion. Also for the production of a foamed glass granulate, it is recommended to include a rotating cooling tube after the foaming in order to avoid cooling cracks in the foamed glass granulate. Thanks to their light weight, the cooled granules become a major advantage o η Λ K /. Λ * -4- transported to storage silos via suction or compressed air via a cyclone separator.

The method described is explained in more detail below with reference to an example: 5 In a steam-heated stirring vessel, 60 kg were dredged in the Rijnmond area, very carbon-rich wet sludge, together with 20 kg of soda water glass of 40-42 ° Be, 2 5 kg of sodium hydroxide and 14 kg of red sludge are reacted with each other for 35 min at a temperature of 70 ° C until a creamy consistency is reached. After. drying at 180 ° C and subsequent fine grinding, the milled product was granulated using water or a granule tray.

The wet granulate granules were coated in a very thin cement layer drum dryer during drying and then foamed at 1100 ° C in a CS oven (circulating flow oven) to a granulate of foamed glass 3 with a bulk density of 180 kg / m.

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Claims (3)

2- Process according to claim 1, characterized in that to the mass of alkali metal silicate in an amount of 5-45 wt.% And Na 2 O (in the form of alkali metal hydroxide) is added in an amount of 0.5-10 wt.% , based on the total mass of solids. Method according to claim 1 or 2, 20, characterized in that water glass solutions with. a high solids content and a Na 2 O: S ± O 2 ratio of 1: 2 to 1: 4 are used. 4. Method according to one or more of the preceding claims, characterized in that to the mass of oxygen-releasing blowing agents, for example red sludge, are added in amounts of at most 20% by weight. 80 05 40 1