LT6739B - Method of preparation of high strength gypsum binder - Google Patents

Abstract

The present invention relates to a process for the production of high strength gypsum binder using orthophosphoric acid waste, sulfur sludge and zeolite waste. More than twice the strength of gypsum stone specimens can be obtained by applying the present invention. In this invention, zeolite waste was used as an acid impurity absorber, and calcium oxide (calcium oxide reacts with acidic impurities to form water insoluble compounds) was used in the analogous invention. The experiments were carried out using milled to cement fines sulfur sludge as an activator and as an additive in gypsum binders to increase strength.

Description

FIELD OF THE INVENTION

The present invention relates to the production of a high-strength gypsum binder using orthophosphoric acid production waste, sulfur sludge and zeolite waste.

BACKGROUND OF THE INVENTION

Methods for obtaining gypsum binder using high heat consumption or very expensive binders are still known.

RU2601962 describes a method for obtaining a gypsum binder and a modified gypsum binder from technical gypsum - hemihydrate or dihydrate phosphogypsum. Also described is the preparation of a modified composite gypsum binder having a wide range of applications. The above-mentioned method of gypsum binder production is based on the heating of technical gypsum (hemihydrate or dihydrate phosphogypsum). It is performed in two stages. First stage: 85 + 5 ° C temperature, holding 40-60 min., 0.1 MPa, second stage: 160 + 5 ° C temperature, 30-60 min., Constant stirring. In this way, a material of increased strength is obtained.

RU2538556 describes a production method for obtaining a material with increased strength and water resistance. The binder consists of: dihydrate phosphogypsum - 77.0-87.5; silica component or diatomaceous earth of natural origin - 10.0-20.0; the zinc sterate is 2.5-3.0% by weight.

RU2522835 describes a process for the preparation of a homogeneous active bulk gypsum binder from phosphogypsum. This method consists of the following steps: drying the initial phosphogypsum using hot gas; neutralization of dried phosphogypsum by the addition of neutralizing agents; drying, cooling of neutralized material; crushing, mechanical, chemical and electrical activation. The result is a pure, ecological binder that uses little electricity to produce.

RU2200714 describes a method for obtaining a gypsum binder. This binder is obtained by treating carbonate sludge waste from thermal water treatment with sulfuric acid to pH 5-7. Simultaneously by mechanical activation and subsequent autoclaving.

LT4699 describes a process for the preparation of hemihydrate calcium sulphate as a gypsum binder, which can be carried out by neutralizing lime in a slurry and woven temperature (> 50 ° C) according to a predetermined pH curve to pH 8.5 - 9.5 phosphogypsum. The disadvantage of this method is that high heat consumption is required to maintain the temperature, pH meters are too inert, which complicates the raw material dosing operation, and pH meter sensors wear out very quickly in aggressive environments.

The closest method to the present invention is described in LT4698, in which phosphogypsum is added to an alkaline neutralizing agent consisting of Portland cement and SiCh micropowder - waste from the production of ferrosilicon, or magnesium hydroxide gel. The disadvantage of this method is that the Portland cement or magnesium hydroxide gel used is a very expensive binder, which increases the cost of the final product too much.

The physical invention improves the physical and mechanical properties of gypsum binders. It also consumes waste, does not pollute the environment, the starting materials cost nothing or have a symbolic price.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to the preparation of a high-strength gypsum binder using hemihydrate phosphogypsum as a waste from the production of orthophosphoric acid, sulfur sludge as an activator and zeolite waste. The obtained material can be used in the gypsum building materials industry, in the production of ceramics. By applying the said invention, unused waste is utilized, ecological problems are solved, and the properties of gypsum binders are improved. The present invention can be used for the production of gypsum building materials, for the production of gypsum dry mixes.

The invention describes a process for the preparation of a high-strength gypsum binder using orthophosphoric acid production waste, sulfur sludge and zeolite waste. With the implementation of the present invention, it is possible to obtain gypsum stone samples more than twice as strong. In this work, zeolite waste was used as an acid impurity absorbing material, and in a similar invention, calcium oxide was used (calcium oxide reacts with acidic impurities and water-insoluble compounds are formed). In this work, experiments were performed using ground to cement fineness sulfur sludge as an additive in gypsum binders to increase the strength. An analogous patent using this type of activator has not been found.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows the strong compression of hydrated phosphogypsum samples. The compressive strength values are compared with the compressive strength of the increased strength phosphogypsum samples. Phosphogypsum with sulfur sludge and zeolite performs strong compression of the samples. Labels: I - 5% (w / w) ground activator used and II - 10% ground activator used. * -Chosphogypsum control sample, without any additives.

fig. the microstructure (SEM) of hydrated phosphogypsum samples and enhanced phosphogypsum samples is presented. SEM photographs of hydrated specimens of high-strength gypsum binder. Notes: (a) without additives, (b) with 0,5% zeolite additive and 5% activator additive c) with 0,5% zeolite additive and 10% activator additive.

DETAILED DESCRIPTION OF THE INVENTION

The method of obtaining is realized as follows:

The main raw material for the gypsum binder is fresh hemihydrate phosphogypsum taken from a carousel filter and dried at 100 ° C. The average chemical composition of phosphogypsum in% by weight is given in Table 1.

Oxidic composition of phosphogypsum.

Name CaO so ₃ SiO ₂ Fe ₂ O ₃ AI ₂ O ₃ F MgO p ₂ o ₅ total p ₂ o ₅ soluble in water H ₂ O Phosphogypsum 38.60 53.48 0.37 0.03 0.13 0.14 0.04 0.82 0.40 5.99

We used the following for the tests:

AB Orlen Lietuva zeolite waste, which is dominated by zeolite Y. Its specific surface area according to the Blaine method was S = 294.2 m ² / kg. The average elemental composition of zeolite waste in% by weight is given in Table 2.

elemental composition of zeolite waste,% by weight

Name Si Al 0 C Na Mg Ti S Fe Cu Zeolite waste 13.15 17.8 62.93 2.92 0.18 0.55 0.66 0.2 0.78 0.84

Activator ground to cement fineness. Specifically, sulfur sludge is used as said activator.

The invention is illustrated by the following examples:

Example:

Table Reinforced gypsum binders,% by weight

Sample serial no Composition,% Phosphogypsum Zeolite performs Activator I 95 0 5 94.5 0.5 5 92 3 5 90 5 5

table. PH values of high-strength gypsum binder when 5% of activator is used

Amount of zeolite waste 0% 0.5% 3% 5% pH at 5% activator 4.7 5.76 6.28 6.95

Example:

Table Reinforced gypsum binders,% by weight

Sample serial no. Composition,% Phosphogypsum Zeolite performs Activator II 90 0 10 89.5 0.5 10 87 3 10 85 5 10

table. Phosphogypsum samples with activator additive and zeolite perform pH values when 10% of activator is used

Amount of zeolite waste 0% 0.5% 3% 5% pH at 10% activator 4.7 5.65 5.91 6.07

The optimal amount of zeolite required for the sorption of acidic impurities is 5%. Phosphogypsum samples with 5% activator samples had a pH of 6.95 and 10% pH = 6.07, respectively.

First, the mixture of phosphogypsum, zeolite waste, and sulfur slurry was weighed according to the data in Tables 3 and 5 and homogenized in a homogenizer for 30 min to a homogeneous composition. Water was added to the mixture to a normal dough consistency. The resulting binder dough is poured into molds. After 2 hours, the samples are formed and dried first in air and then in a dryer at 50 ° C to constant weight. Such products can already be used for construction purposes.

Based on the results of the studies presented in Figure 1, we can state that the compressive strength of the dry samples increased from 11 MPa without additives to 22 MPa with 0.5% zeolite and 10% ground activator additives. By using the optimal amount of zeolite currant, the compressive strength of the dry samples is further increased and at the same time the pH becomes close to neutral.

Based on SEM photographs (Fig. 2), it is stated that the structure of the high-strength gypsum binder is significantly reduced by the use of the activator. The more ground the activated activator powder is added, the finer the resulting microstructure.

Claims (3)

DEFINITION OF THE INVENTION 1. A process for the preparation of a gypsum binder, characterized in that said substance is obtained by mixing phosphogypsum 85-90% by weight, zeolite waste 0.5-5% by weight and sulfur sludge 5-10% by weight, the resulting mixture is homogenized, poured into molds and dried at 50 ° C. 2. A process for the preparation of a gypsum binder according to claim 1, characterized in that the optimum amount of zeolite used is 5% by weight. 3. A process for the preparation of a gypsum binder according to claims 1 and 2, characterized in that the pH of the sample is in the range from 6.07 to 6.95.