DE3149804A1 - Process for producing gypsum fibre board - Google Patents

Abstract

In the production of gypsum fibre board by a wet process, the offcuts and the waste are suspended in water and held at an elevated temperature, preferably above 80 DEG . In this way, the hydration is delayed, so that all the waste material can be slowly and uniformly recycled into the process.

Description

"Process for the production of gypsum fiber boards"

The invention relates to a method for producing plasterboard, suspended in water in the case of the waste material before the plaster of paris sets and the Suspension is reused in the manufacture of the starting material.

In the manufacture of gypsum fiber boards in the winding process, what More particularly, the invention relates to a suspension of plaster of paris and paper fibers dehydrated in water on a circulating felt belt by passing through the felt belt from below water is sucked through. This is how a fleece is created. The fleece is placed on a winding roller wound, and after the intended thickness has been reached, the is wound on the winding roller formed jacket loosened and cut to the plate size. The resulting Cut off is immediately resuspended in water in the manner mentioned above and mixed with the starting materials of the process.

This is not possible with other waste material, namely the committee, i.e. faulty production. Overall, the amount of scrap that occurs could be accommodated in the starting material will.

However, rejects arise irregularly and in different ways Amounts. The reuse of the scrap material would then be for the moment too much. However, it cannot be stretched because the plaster of paris has meanwhile become hydrated and the resulting dihydrate crystals in the starting material nucleation form. The hardening acceleration caused by this inoculation leaves nothing satisfactory control of the process and is otherwise within the scope of Procedure not acceptable.

The invention is based on the object, the scope for reuse of waste material to enlarge.

According to the invention is for this purpose in a method of the opening designated type provided the suspension of the waste material at a temperature to hold above 500 C.

In this case, the hydration occurs completely or approximately in the suspension to a standstill. This allows the waste material regardless of the time of its Occurrence solely with regard to a uniform or at least not too high To treat metered addition to the starting material of the process and, at least in the Within the framework of the requirement to accept any storage times. In order to you also get a sufficient buffer to distribute the scrap over time and put back in the proceedings.

If so the temperature of the suspension of the starting materials on the If felt belt increases e.g. from approx. 220 to approx. 350, this results in further advantages. The viscosity of the water drops, suction and drainage are accelerated and increases the performance of the system. The increase in production speed at the same time allows expensive retardants to be saved, with which one can reduce the hardening process of the plaster of paris it adapts the drainage speed.

Already at the production of the starting material for the process can the higher temperature level can be used: If you use the relatively thin, e.g. a suspension of the waste material containing 80% by weight of water instead of water the Preparation of the paper fiber production in the so-called pulper, so the higher temperature facilitates and accelerates the digestion of the processed here Waste paper.

As a rule, the method according to the invention will be used Include all waste material, scrap and scrap, in the process.

The temperature of the suspension should be around 80 in most cases up to 950 C, although a useful delay in hydration has already occurred 500 C occurs and therefore depending on the circumstances it can also suffice with this Temperature or e.g. 60 or 70 C. To get the desired Having temperature one can use for the suspension of the waste material that is yes, together with a quantity of water it contains, is at a lower temperature, Use water at a higher temperature, if possible.

In order not to use more energy for heating than necessary, will the concentration of the waste material in the suspension is set as high as possible. It will range between 10 and 30 tonnes by weight, preferably 20 to 25 tonnes by weight.

The procedure is suitable for most plasters and in particular for hemihydrate plasters, the specific surface of which is not in aqueous suspension or only comparatively little increased.

In the following, the invention is numerical on the basis of test results explained and documented.

Test series 1 A stucco plaster of paris, as used for the production of plasterboard is used, was suspended in 10 times the amount of water and 0 held at 90 with stirring. Samples were taken after various times, and in these the crystal water of the gypsum was used as a measure of the hydration certainly.

In a parallel experiment, 10 z of raw plaster of paris was added to the suspension.

The results can be found in the table below: Holding time of the suspension crystal water ion% in with addition min h of 10 6 Raw plaster . ..... ~ ~~~. . .. 0 5.3 10 5.55 25 5.5 45 5.4 7-5 in 5.45 90 1.5 5.35 5.4 7.2 2 5.45 7.1 3.25 5.35 7.1 4.5 5.5 9.2 5.5 5.7 11.9 6.5 5.55 10.5 As can be seen from the table, the degree of hydration in the samples without addition remained unchanged for 6 hours. The addition of raw plaster of paris, although an extremely effective vaccination, did not result in any further hydration for more than 3 hours. (The mean value of 7.1 for the period from 1.5 to 3.25 hours compared to 5.4 without addition does not mean any progress in hydration, but is explained by the water of crystallization of the added raw gypsum.) Test series 2 From one roughly as in the previous series 1, but with fresh offcuts from a gypsum fiberboard production and held (at 85 to 900C) suspension, samples were taken after various times and used to make a conventional, delayed starting mixture for the production of gypsum fiber boards in an amount of 10% each.

For this purpose, parallel tests with a suspension kept at 23 ° C. were carried out carried out. Further parallel attempts were made with a plaster of paris fiber Mixture without the usual addition of retarders.

The setting time of the gypsum-fiber mixtures thus produced was determined.

The results are compiled in the following table: t Holding time 0 Setting time in min the suspension at 85-90 C holding temperature at 23 0C holding temperature in min temperature of the sus- pension pension without without Retarder retarder 0 25 16 26 15 10 26 15 5 5 25 23 8 2 1 40 27 13 1 1 60 27 12 1 - 80 23 7 1 As the table shows, the use of a suspension kept at 85-900C to make the gypsum-fiber mixture, which is usually provided with a retarder, does not shorten the setting time. The comparative example with the suspension kept at 230 ° C., on the other hand, shows a rapid shortening due to the inoculation effect.

Claims (4)

Claims 10 method for producing gypsum fiber boards, suspended in water in the case of the waste material before the plaster of paris sets and the Suspension is reused in the manufacture of the starting material, thereby characterized in that the suspension is kept at a temperature above 500.degree will. 2. The method according to claim 1, characterized in that committee is reused in the aforementioned manner. 3. The method according to claim 1 or 2, characterized in that the Suspension is kept at a temperature of 80 to 950 C. 4. The method according to any one of claims 1 - 3, characterized in, that the suspension should preferably have a solids content of 10 to 30 wt 20 to 25 wt.