CS239261B1 - Production method of mixed plaster binding agents - Google Patents

Abstract

Process for the production of mixed plasterucan binders containing 94.99 to 5 S gypsum binder, 5 to 94.99% of pozzolanic substances and 0.01 to 10% of others admixtures, e.g. suspensions, eg from chemical formulations and lime and / or limestone desulfurization methods of flue gases that contain one from the main constituents calcium sulfate dihydrate, it sprays into the stream of hot waste gases, eg flue gases, in drying equipment dispersion type. Suitable facilities are e.g., spray or fluid dryers and a range of suitable drying media temperatures it is limited to 120 and 580 ° C. The agglomerates are further mills in conventional devices 0 to 10% residue on 0.2 mm mesh.

Description

The invention relates to the production of mixed gypsum binders. Known processes for the production of mixed gypsum binders are generally based on the joint grinding of gypsum, prepared in the conventional manner, mostly from natural gypsum, CaSO4 · ZH2O dihydrate and pozzolanic active substances of natural or artificial origin.

Despite the increasing efforts to utilize even the so-called waste gypsum from chemical production, wet lime and / or limestone desulphurisation processes, etc., a considerable part of them remains unused for various reasons.

One of the main reasons is, in addition to the inadequate purity and often unsatisfactory morphology of the dihydrate crystals, that the mentioned gypsum waste falls off in the form of sludge, whose subsequent processing is difficult and especially energy intensive.

Conventional gypsum production processes also have some disadvantages. High-quality types of gypsum are produced by the most low-cost, discontinuous methods requiring the use of 1 energy.

The burning of gypsum in rotary kilns makes it possible to increase the volumes of the product produced, but its quality is considerably lower due to the difficult controllable gypsum dehydration process, when in addition to the required CaSO4 hemihydrate. 1/21 ^ 0 results in less suitable, so-called beta-modification of hemihydrate, but also undesirable forms of anhydrite, the main disadvantage being the impossibility to observe suitable reaction conditions for dehydration, ie mainly to maintain homogeneous temperature distribution in particles of processed material and associated partial pressures H. 0 (g).

These disadvantages are largely eliminated by the process according to the invention, in which the waste slurry from wet lime and / or limestone desulphurisation methods and / or from various chemical processes containing calcium sulphate dihydrate CaSO ₄ .2H ₂ O is one of the main solids. and further spraying, for example, alkali metal and alkaline earth metal carbonates, hydrated oxides, chlorides, sulfites and silicates into a stream of hot gases, e.g. flue gases or flue gases, in dispersion-type drying apparatuses.

The range of suitable drying medium temperatures is relatively wide at about 120 to 580 ° C.

In such devices, in particular for drying agglomerates, drying the slurry dihydrate CaSO ₄ .2H ₂ O, dehydrating the dihydrate to the alpha- and beta-hemihydrate time0 ₄ .l / _{2 H2} 0, and drying the slurry of the hemihydrate.

When fly ash particles are present in the hot waste gases used in the process, they are transferred to the product both by entrapment on drying agglomerates by direct impact and also by mixing the dry agglomerates with the fly ash collected in the drying apparatus.

It is also possible to subsequently mix the solids collected in the separator with a stream of solid cleaners exiting the drying apparatus. The product is thus enriched with another active component of the mixed binder - pozzolanic particle.

Conventional gypsum production processes are known to be sensitive to relatively precise adherence to reaction conditions, particularly temperatures. When carrying out the process according to the invention, the risk of non-compliance with the optimum reaction conditions is considerably reduced since, due to the relatively high water vapor partial pressure inside the drying agglomerates, flue gases of relatively high temperature can be used without exceeding the stability limits of the hemihydrate.

The range of suitable temperatures of the drying agglomerates is limited to 60 to 200 ° C. Said reaction conditions provide a gypsum binder of maximum achievable quality. By appropriately selecting the ratio of gypsum binder to pozzolanic admixtures, a wide range of commercially desired binders of this kind can be covered.

In the case of a content of 95% of pozzolanic substances, a usable binder can be obtained.

Since most of the substances which may be considered as impurities in the practice of the present invention are pozzolanic active substances, the utility value of the resulting binders increases further.

Another possibility to improve the quality of the mixed binders prepared by the process according to the invention is to increase the hydraulic activity by means of successive additions of so-called activators, e.g. Ca / OH / ₂ and the like added to the mixture before further processing.

The mixture containing 94.99 to 5% of gypsum binder, 5 to 94.99% of pozzolanic substances and 0.01 to 10% of other admixtures, e.g. 10% of the residue on 0,2 mm sieves.

The process according to the invention can advantageously be used for the production of mixed gypsum pozzolanic binders, both in devices specially built for this purpose and in particular in devices forming part of flue gas desulphurisation systems from boilers fired with solid, liquid and gaseous fuels, respectively. desulphurisation equipment of other waste gases.

An embodiment of the process of the invention is illustrated by the following examples.

Example 1

Suspension from wet limestone scrubbing desulphurisation equipment, thickened dry solids content of 36% by weight. and the solid phase composition of 15% Smeral brown coal fly ash, 8,5% CaCO-j.ZHjO was dried in a spray dryer with an output of about 100 kg.h ^{-1 of} dry matter by a stream of warm exhaust air at a temperature of 200 ° C at _b = 52, Low: 14 ° C.

The volumetric air flow rate through the device was about 3200 Nm ³ .h ^-1 , the average air outlet temperature was about n ° c and the product was about 95 ° c. The resulting product was ground in a ball mill to a fineness of 6.5% residue on sieves of 0.2 mm without further additives.

The binder thus prepared was mixed with water to a mortar mixture with a water coefficient of 0.87, from which the test specimens according to ISO were prepared. After solidification, the bodies were tested for compressive strength, which after 24 hours averaged 32.4 MPa.

Example 2

2.5% (w / w) was added to the binder stock prepared as described in Example 1 prior to grinding. CaO and 0.4 wt. Na 2 SO 4. This mixture was ground in a ball mill to a fineness of 7.3% residue on a 0.2 mm sieve.

The binder thus prepared was separated with water into a mortar mixture with a water coefficient of 0.72, from which ISO test specimens were prepared, whose compressive strength after 24 hours was an average of 45.1 MPa.

Example 3

The slurry from the flue gas desulfurization desulphurisation test apparatus with a solid phase composition of 58% Smeral brown coal fly ash, 2% CaCO3 and 40% CaSO4 H2O was adjusted as described in Example 1 and ground in a ball mill to a fineness of 6.6 % residue on sieve 0,2 mm.

The binder thus prepared was separated with water into a mortar mixture with a water coefficient of 0.77, from which ISO test specimens were prepared whose compressive strength after 24 hours was an average of 11.4 MPa.

Claims (3)

BACKGROUND OF THE INVENTION A process for the production of mixed gypsum binder compositions comprising 94.99 to 5% of gypsum binder, 5 to 94.99% of pozzolanic substances and 0.01 to 10% of other impurities, for example activators, characterized in that the waste slurries, for example from chemical or from wet lime- and / or limestone desulfurization processes, containing CaSO4 as the main solid component. is sprayed into a stream of flue gases or other flue gases at a temperature of 120 to 580 ° C in dispersion-type drying machines, the temperature of the drying agglomerates being maintained in the range 60 to 200 ° C and said agglomerates discharged from the above mentioned equipment are further milled in conventional equipment to a fineness of not more than 10% of the residue on sieves 0,2 mm. Method according to claim 1, characterized in that the pozzolanic substances are part of the suspension injected into the drying apparatuses and / or are additionally added to the agglomerates before their dosing into the milling apparatuses. 3. The process according to claim 1, wherein the other ingredients, for example activators, are added to the mixture before it is metered into the milling equipment. Severography, n. P., MOST Price 2,40 Kčs