RU2243946C1 - Method for production of gypsum binder - Google Patents

Abstract

FIELD: binder manufacturing, non-iron metallurgy, oil and gas industry, in particular gypsum binders.

SUBSTANCE: invention relates to manufacturing of gypsum binders in form of anhydrous plaster and estrich-gypsum by using elementary sulfur (optionally in liquid state) being process waste from melting of nonferrous-metal sulfide concentrates, as well as to production of packing for metal mining, oil and gas industry based on claimed binders. Gypsum binder is obtained by heat treatment of raw batch at elevated temperature (600-800⁰C for anhydrous plaster and 800-1100⁰C for estrich-gypsum) including oxidation of elementary sulfur S with oxygen blasting in presence of CaO carrier. Carrier for calcium oxide is preliminary treated by deep drying up to humidity of 0.3 % (preferably 0-0.5 %); mass ratio of sulfur, oxygen in blasting and CaO is 1.0:(1.5-3.0):(1.75-2.62). Materials from group including calcium oxide, hydrated lime, dolomite, dry hydrated lime, process waste with high calcium content, etc may be used as CaO carrier. Sodium sulfate and disulfate may be added in batch as curing catalyst. Process temperature may be decreased by dilution of oxygen blasting with excess air, or feeding of exhaust gas via cooling tubes, or introducing of packing components (e.g. dross, sand, chip) to batch.

EFFECT: gypsum binder of improved quality.

10 cl, 3 tbl

Description

The invention relates to the production of binders, non-ferrous metallurgy, gas and oil industry, in particular for the production of gypsum binders from elemental sulfur.

Currently, the use of elemental sulfur is very numerous. Over 50% of elemental sulfur is used for the production of sulfuric acid and oleum, about 25% - for the production of cellulose sulfite, 10-15% - in agriculture, the remaining amount of sulfur is used in the rubber industry, in the production of artificial fiber, explosives, in the organic synthesis industry , in medicine, etc. In recent years, new spheres of the use of elemental sulfur have been found, mainly in the construction industry (production of asphalt, concrete, highways, walls, floors, etc.).

A known method of producing high-calcined gypsum (estrich-gypsum), including the calcination of natural gypsum (CaSO ₄ · 2H ₂ O) at 800-1000 ° C followed by grinding [1, p. 70-73]

A known method of producing anhydrous calcium sulfate - anhydrite from natural gypsum, including calcining gypsum at 600-700 ° C, followed by grinding the calcination product together with additives - hardening catalysts (lime, sodium sulfate and sodium bisulfite mixed with iron or copper sulfate, etc.) [1, cf. 73-76].

The disadvantages of the known methods for producing anhydrite and estrich-gypsum are: 1) the need for extraction, transportation and grinding of natural gypsum; 2) the cost of a large amount of fuel for heating gypsum and its decomposition due to the fact that the process is endothermic.

By technical nature, the closest is the method of producing a gypsum binder at a temperature in the reaction zone of 120-150 ° C, including the oxidation of elemental sulfur by oxygen-containing blast in the presence of a carrier of calcium oxide, and limestone is used as a carrier of calcium oxide [2]. In the specified method, it is possible to introduce exhaust gases into the blast.

The disadvantages of this method are:

- obtaining a gypsum binder is carried out in a complex way by the interaction of SO ₂ (from the burning of elemental sulfur) with aqueous pulp with CaCO ₃ ;

- high costs of heat of evaporation of water and heating of water vapor to the temperature of interaction.

The objective of the present invention is the use of elemental sulfur - industrial waste - for the production of gypsum binders - anhydrite and estrich-gypsum.

This object is achieved by the fact that in the method of producing a gypsum binder by heat treatment of the initial mixture at an elevated process temperature, including the oxidation of elemental sulfur - S by supplying an oxygen-containing blast in the presence of a calcium oxide carrier - CaO, according to the invention, the calcium oxide carrier is preliminarily dried to moisture content it is 0-0.5%, the mass ratio in the charge S, oxygen in the blast is O ₂ and CaO is 1.0: (1.5-3.0) :( 1.75-2.62), and the temperature process support 600-1100 ° C.

At the same time, materials taken from the group consisting of calcium oxide, calcined lime, fluff, limestone, dolomite, high-calcium slag from ferrous metallurgy, industrial waste enriched with calcium oxide are used individually or jointly with each other as CaO support.

Elemental sulfur can be used in liquid form. The preferred embodiment, the moisture content in the CaO support is less than 0.3%.

Sodium sulfate and sodium bisulfate are introduced as materials containing hardening catalysts.

Upon receipt of anhydrite, the process temperature is maintained at 600-800 ° С, and for estrich-gypsum - 800-110 ° С.

The process temperature control in the claimed interval is carried out by diluting the blast with excess air, exhaust gases, using water pipes or introducing slag or crushed stone into the charge.

When using the claimed invention, the following technical result is obtained:

- provides rational utilization of industrial waste - elemental sulfur;

- the creation of a new substance is ensured;

- the process is exothermic (autogenous), i.e. does not require fuel;

- the method is accompanied by the release of a large amount of heat, which makes it possible to efficiently produce steam and / or its own cheap electricity.

The essence of the proposed method is as follows. Elemental sulfur - technogenic waste - is used for the production of gypsum binders - anhydrite and estrich-gypsum. This is achieved by burning (oxidizing) elemental sulfur in the presence of calcium oxide with the formation of CaSO ₄ . In this case, an exothermic reaction proceeds:

the change in enthalpy of which is Δ H ₂₉₈ = -188600 cal / g-at S. Thus, for 1 kg S _el the heat output by reaction (a) is 5893.7 kcal. In other words, burning 1 kg S in the presence of CaO in terms of heat generation exceeds the results of burning 1 kg of coke. The Gibbs energy of reaction (a) at 600-1000 ° C is (-131900) - (- 105800) cal / g-at S, respectively. This indicates the complete course of reaction (a) from left to right.

Elemental sulfur above was taken in the solid state. However, its use in liquid form is not excluded. In this case, some changes should be made to the above-mentioned thermotechnical indicators of the process.

The expenditure coefficients of the components can be set theoretically. So, the minimum consumption of components per 1 gram atom of elemental sulfur will be: oxygen - 1.5 mol, calcium oxide -1.0 mol. The maximum ratio S: CaO: O ₂ can be established on the basis of the excess coefficient, which is irrationally maintained above 3.0 for O ₂ and 1.5 for CaO. Then the molar ratio S: O ₂ : CaO can be taken equal to S: O ₂ : CaO = 1.0: (1.5-3.0) :( 1.0-1.5).

From here, the mass ratio of the components: S: O ₂ : CaO = 1.0: (1.5-3.0) :( 1.75-2.62) can be easily compiled.

The excess calcium oxide in the mixture is rational, since it can later be useful as a hardening catalyst.

As a carrier of calcium oxide (hereinafter CaO - carrier) individually or in mixture with each other, calcium oxide (CaO), calcined lime (~ 85% CaO), calcium carbonate (CaCO ₃ ), fluff / Ca (OH) can be used ₂ /, dolomite / Ca (Mg) CO ₃ /, various industrial wastes enriched with calcium oxide, natural mineral compounds enriched with calcium oxide, including those containing oxides and sulfates of alkaline-earth and alkali metals.

It should be noted that in order to avoid hemihydrite of calcium sulfate (CaSO ₄ · 0.5Н ₂ О) and gypsum (CaSO ₄ · 2Н ₂ О), it is advisable to introduce the CaO carrier in the process of obtaining the gypsum binder after its deep drying (moisture content in the CaO carrier : 0.0-0.5%).

Air, blast enriched with oxygen, and waste gases from metallurgical production, as well as mixtures thereof, can serve as an oxygen carrier.

Information confirming the possibility of implementing the method.

Of the CaO carriers listed above, calcium carbonate deserves the greatest attention, i.e. limestone. In this case, the elementary sulfur oxidation reaction is written as:

The change in the enthalpy of reaction (b) is Δ H ₂₉₈ = -146100 cal / g-at S or 4565.6 kcal / kg S, which is only 20-25% less heat when burning 1 kg of coke.

First of all, we performed calculations of material and thermal balances for reactions (a) and (b). The results of calculations by reaction (a) showed that even at a temperature of 1000 ° C there is a large excess of heat. In this regard, it becomes appropriate to combine the processes of obtaining CaO and oxidation of S _el . The foregoing can be achieved by oxidation of S _el in the presence of CaCO ₃ . To illustrate the truth of the above, Tables 1 and 2 show the material and thermal balances of S _el oxidation in the presence of calcium carbonate (limestone containing up to 93.0% CaCO ₃ ).

Table 1.
The material balance of the process of processing elemental sulfur in the presence of CaCO ₃ to produce estrich - gypsum. Received, kg Received, kg Sulfur Limestone Blowing CaSO ₄ CaO Gas Cepa s 100 100 - - Limestone in it: 355 - - - CaCO ₃ 330 - - - CaO 185 175 10 - CO ₂ 145 - - 145 O ₂ 170 150 twenty N 563 - 563 other 23 23 100 353 733 1186 448 10 728 1186 Table 2.
The heat balance of the production of estrich - gypsum from S _el and CaCO ₃ at 900 ° C (per 100 kg S _el. ) Heat Income Articles kcal % Heat consumption articles kcal % Combustion S _el (100 × 4565.6) 456560 99.7 Heat with CaSO ₄ and CaO (468 × 0.22 × 900) 92660 20,2 Heat with charge and
blowing 1440 0.3 Heat with oxygen (14 × 0.3529 × 900) 5560 1,2 Heat with nitrogen (450.4 × 0.3324 × 900) 134740 29.4 Heat with CO ₂ (73.8 × 0.526 × 900) 34940 7.6 Heat of decomposition CaCO ₃ (330 × 425) 140250 30.7 Heat loss 49850 10.9 458,000 100 458,000 100

In other words, the process of oxidation of elemental sulfur in the presence of CaCO ₃ with the production of estrich gypsum can be carried out autogenously in any metallurgical unit (without heating the air and the mixture). The foregoing is fully true for the anhydrite production option, since here the gas temperature is 200-300 ° C lower. A decrease in the process temperature can be achieved by increasing the consumption of the oxidizing gas (including by diluting it), overdosing the limestone, introducing some ingredients of the filling mixture into the charge (slag, crushed stone, sand, etc.), as well as by using known methods of cooling.

After completion of the calculations, laboratory tests were performed on the oxidation of sulfur in the presence of CaO and CaCO ₃ .

The experiments fully confirmed the results of a theoretical analysis of reactions (a) and (b), the material and thermal balances of the oxidation process of S _el in the presence of calcium oxide and carbonate. These results can confirm: 1) the possibility of implementing the process of burning elemental sulfur in the presence of calcium oxide to obtain gypsum binders; 2) solutions to the problem.

The totality of theoretical analysis data, the results of experimental studies on the oxidation of S _el in the presence of calcium oxide, calculations of material and thermal balances are summarized in Table 3, the data of which indicate the influence of the molar (mass) ratio on the output of the gypsum binder.

The proposed method for producing gypsum binder by burning elemental sulfur in the presence of calcium oxide is especially applicable in the Far North for utilization of elemental sulfur produced from flue gases from kilns and smelters, as well as in all regions of Russia in which oil is extracted and / or processed and gas. In all regions, except for the direct use of gypsum binders for ordinary needs, the possibility of producing, based on gypsum binders, filling mixtures for filling the waste space in the mining, oil and gas industries is of great practical importance.

Table 3.
Examples of the method for producing gypsum binders by burning elemental sulfur in the presence of calcium oxide No. of examples The molar ratio of components Mass ratio of components The output of CaSO ₄ ,% S O ₂ CaO CaCO ₃ S O ₂ CaO CaCO ₃ 1 1,0 1,5 1,0 - 1,0 1,5 1.75 - 96.0 2 1,0 1,5 1,0 - 1,0 1,5 1.75 - 98.0 3 1,0 2.0 1,0 - 1,0 2.0 1.75 - 98.5 4 1,0 1,5 1,5 - 1,0 1,5 2.62 - 99.0 5 1,0 3.0 1,1 - 1,0 3.0 1.93 - 99.1 6 1,0 1.8 1,2 - 1,0 1.8 2.10 - 99.0 7 1,0 3.0 1,1 - 1,0 3.0 1.93 - 99.0 8 1,0 1,5 - 1,0 1,0 1,5 - 3,1 97.0 nine 1,0 1,5 - 1,5 1,0 1,5 - 4.4 99.0 10 1,0 2.0 - 1,2 1,0 2.0 - 3,7 99.1 eleven 1,0 3.0 - 1,1 1,0 3.0 - 3,7 99.1 12 1,0 3.0 - 1,1 1,0 3.0 - 3,7 99.1

SOURCES OF INFORMATION

1. Butt Yu.M., Technology of cement and other binders. M., 1956, p. 70-76.

2. Japanese Patent No. 07-237920, C 01 F 11/46, C 04 B 11/02, publ. September 12, 1995

Claims (10)

1. A method of producing a gypsum binder by heat treatment of the initial charge at an elevated process temperature, comprising oxidizing elemental sulfur (S) by supplying an oxygen-containing blast in the presence of a carrier of calcium oxide (CaO), characterized in that the carrier of calcium oxide is preliminarily dried to moisture content in it 0-0.5%, the mass ratio of S, oxygen in the blast of O ₂ and CaO is 1.0: (1.5-3.0) :( 1.75-2.62), and the process temperature is maintained at 600-1100 ° C. 2. The method according to claim 1, characterized in that, as a CaO carrier, materials are taken individually or together with each other, taken from the group consisting of calcium oxide, calcined lime, fluff, limestone, dolomite, high-calcium slag of ferrous metallurgy, industrial waste, enriched with calcium oxide. 3. The method according to claim 1 or 2, characterized in that the carrier CaO is preliminarily subjected to deep drying to a moisture content of less than 0.3%. 4. The method according to claim 1, characterized in that the elemental sulfur is used in a liquid state. 5. The method according to claim 1, or 2, or 4, characterized in that the materials containing hardening catalysts are introduced into the initial charge. 6. The method according to claim 5, characterized in that as the materials containing hardening catalysts, sodium sulfate and sodium bisulfate are introduced. 7. The method according to claim 1, characterized in that upon receipt of the anhydrite, the temperature is maintained at 600-800 ° C, and that of estrich-gypsum is 800-1100 ° C. 8. The method according to claim 1 or 7, characterized in that the process temperature is reduced by diluting the blast with excess air or introducing exhaust gases. 9. The method according to claim 8, characterized in that the process temperature is reduced by means of cooling pipes. 10. The method according to claim 8, characterized in that the process temperature is reduced by introducing into the mixture the ingredients that are part of the filling mixture, taken from the group of slag, sand, gravel.