RU2296723C2 - Power-saving method of utilization of the calcium sulfates - the phosphogypsum and the sediments of the sewage disposal plants with production of the cement clinker and the sulfur dioxide gas for production of the sulfuric acid - Google Patents

Abstract

FIELD: chemical industry; power-saving methods of production of the cement clinker and the sulfur dioxide gas from calcium sulfates and the sediments of the sewage disposal plants.

SUBSTANCE: the invention is pertaining to the method of production of the calcium sulfate and the sulfur dioxide gas for production of the sulfuric acid from the gypsum or the phosphogypsum burnt together with the argillaceous materials in the rotating furnaces or in the fluidized layer furnaces. The power-saving method of utilization of calcium sulfates - the phosphogypsum and the sediments of the sewage disposal plants provides for the biological purification of the sewage with production of the cement clinker and the sulfur dioxide gas - the raw material for production of the sulfuric acid. The indicated utilization is conducted by sintering of the calcium sulfates - the phosphogypsum with the sediment of the sewage system aeration stations of the biological purification of the sewage at the temperature of 850°C-1450°C. The technical result of the invention is the utilization of the phosphogypsum and the wastes of the biological purification of the cities and the industrial complexes sewage, that solves the ecological problem of the accumulation and storage of million tons of the substances contaminating the environment and causing alienation of the agricultural lands, the possibility to use the wastes of the biological purification in the production of the phosphoric fertilizers, reduction of the power input and the sharp reduction of the financial expenditure on production of the cement clinker and the sulfur dioxide gas.

EFFECT: the invention ensures utilization of the phosphogypsum and the wastes of the biological purification of the cities and the industrial complexes sewage, solution of the ecological problem of the accumulation and storage of million tons of the substances contaminating the environment and causing alienation of the agricultural lands, the possibility to use the wastes of the biological purification in the production of the phosphoric fertilizers, reduction of the power inputs and the sharp reduction of the financial expenditure on production of the cement clinker and the sulfur dioxide gas.

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Description

The method of utilizing calcium sulfates and sludge from treatment plants to produce cement clinker and sulfur dioxide for producing sulfuric acid, proposed as a patent for the invention, relates to the technology for producing cement clinker and sulfur dioxide for producing sulfuric acid from gypsum or phosphogypsum, fired with clay materials in rotary kilns or fluidized bed furnaces (1 ÷ 17).

Gypsum and clay were probably used for the production of cementitious material even during the construction of the Egyptian pyramids, but the production of cement clinker and sulfur dioxide suitable for the production of sulfuric acid was started at the beginning of the twentieth century with the implementation of the processes of Müller and Kühne (Pat. No. 1069191, 1913. Pat. No. 5049198, 1991. Pat. No. 4503018, 1985. Pat. No. 4608238, 1986. Pat. No. 12061993, 1970. Pat. No. 1285864, 1971. Pat. No. 3865602, 1975). These technologies are currently used in Austria, England, Germany, France, Poland, South Africa. In the eighties of the last century, the Soviet Union conducted experimental work on the development of technology for the production of calcium oxide and sulfur dioxide from phosphogypsum at the NIUIF experimental base.

The Mueller and Küchnet process is carried out sequentially in several stages, which include the desulfurization of calcium sulfates at a temperature of 900 ° C ÷ 1200 ° C; sintering of calcium oxide with clay materials at a temperature of 1450 ° C with the formation of clinker C ₃ S, C ₂ S and other calcium compounds with aluminum and iron. The processes of desulfurization and mineral formation are carried out in accordance with the reactions:

In total, this reaction is expressed as follows:

and

The desulfurization reaction takes place in the atmosphere of the flue gases in the furnace, which rise from its lower to upper part. The reaction is endothermic and for its implementation requires 36.0% more energy than the decarbonization reaction of limestone in the production of cement clinker in the classical way. The high energy intensity of the process is one of the problems in the implementation of the Muller-Küchnet process, which is solved by applying the process of the proposed method.

The processes of interaction of calcium sulfate with the carbon component of the technological mass

pass respectively with the release and absorption of heat (-36.3 kcal / mol; +82.4 kcal / mol; -46.1 kcal / mol).

Processes occur in an oxidizing atmosphere.

with the release of heat (-105.6 kcal / mol)

with heat (-151.3 kcal / mol) and

with the release of heat (-94.052 kcal / mol) and they occur at a temperature of 750 ÷ 800 ° C.

Reaction

at a temperature of 1200 ° C it takes 1.5 hours.

The desulfurization process is one of the most complicated in the current technology and requires special apparatus to accelerate this process for its implementation. In particular, for this purpose, the floating grate of the sintering machine is also used, and to reduce the length of the rotary kiln, sintering machines with an electric furnace and apparatuses with electric discharge are used.

The proposed technology eliminates many of the shortcomings of the current technology for the production of cement clinker and sulfuric acid from calcium sulfates and clay materials. It does not require the use of carbon or mineral additives for the formation of cement clinker, it does not require special measures to reduce the length of the furnace or expand the sintering zone, providing a high level of heat transfer in the thickness of the process mixture by combustion of organic compounds from the sludge of treatment plants. The ash from the sludge from sewage treatment plants serves as a guarantee of the formation of a stable structure in the cake and melt of cement clinker with a guaranteed level of 9.0% sulfur dioxide, which enters the contact sulfuric acid contact production line. The use of treatment facilities in the process of burning sludge contributes to a sharp reduction in fuel consumption for the entire process. In this way, the problem of large cities and industrial regions is solved, and the environmental problem of the disposal of sludge from the treatment facilities of biological wastewater treatment plants is solved. The technology proposed for implementation is changing the paradigm of the process for the disposal of sewage sludge. The problem of the utilization of sewage sludge on an industrial scale consisted not only in the absence of sludge disposal technology, but also in the irretrievable loss of organic substances, which, if rationally collected and obtained, could be used as fertilizers to increase soil fertility. Sulfur gas generated in the process can be converted to sulfuric acid. Sulfuric acid allows the processing of phosphate raw materials to obtain phosphoric, polyphosphoric acid and, on their basis, a whole spectrum of phosphoric mineral fertilizers, indispensable for increasing soil fertility. Thus, the proposed technology for the disposal of sludge from sewage treatment plants allows not only to obtain the most valuable building materials in the form of cement clinker and sulfur dioxide suitable for producing sulfuric acid, but also opens a seemingly deadlock in the problem of using sewage from sewage treatment plants for agricultural purposes.

In the proposed energy-saving method for the disposal of calcium sulfates - phosphogypsum and sludge from biological wastewater treatment plants to produce cement clinker and sulfur dioxide - raw materials for the production of sulfuric acid, this disposal is carried out by sintering calcium sulfates - phosphogypsum with sludge from wastewater treatment plants at biological wastewater treatment plants at temperature 850 ° С-1450 ° С.

The technical result is achieved by using, in the Muller-Küchne process, instead of clay material and mineral additives, sludge from treatment plants of aeration stations, biological wastewater treatment plants, by sintering a technological mixture of gypsum or dihydrate, phosphogypsum hemihydrate with clay material from sludge from treatment plants in rotary kilns of modern cement plants.

The chemical composition of raw materials and their consumption rates for the production of 1000 kg of cement clinker are shown in Table No. 1, Table No. 2.

The standard consumables required for the production of 1000 kg of cement clinker in processes using anhydrite, hemihydrate and calcium sulfate dihydrate to obtain 9.0% SO ₂ , the basic physico-chemical data and the estimated values of the processes are shown in Tables No. 3, No. 4, No. 5.

The data in Tables No. 3, No. 4, No. 5 show that the processes of processing anhydrite, hemihydrate and calcium sulfate dihydrate (phosphogypsum) are close to the above equations with the formation in the gas phase (reduced to normal conditions) of SO ₂ in a concentration close to 5.0% -9.0% , and in the solid phase of cement clinker C ₃ S; C ₂ S.

Drying the exhaust gas with sulfuric acid allows you to raise the concentration of SO ₂ to 17.9%, which is enough for the contact process of processing SO ₂ in SO ₃ and the subsequent production of sulfuric acid of any concentration up to oleum.

A laboratory experiment established the possibility of obtaining 98.0% sulfuric acid and cement clinker with standard technological parameters. Physico-technical and mechanical data of samples obtained from calcium sulfate anhydrite, calcium sulfate hemihydrate and calcium sulfate dihydrate are shown in table No. 6.

Table number 1 Raw material components and their chemical composition ^*) Raw Material Components The chemical composition of the raw materials, wt.% CaO SiO ₂ CO ₂ SO ₃ Al ₂ About ₃ Fe ₂ About ₃ MgO W p.p.p. ∑% Anhydrite CaSO ₄ 41.17 - - 58.82 - • - - 58.82 99.99 CaSO ₄ * 2H ₂ O dihydrate 31.0 0.079 - 46.08 0.42 0.3 1.2 20.9 67.0 99.9 CaSO ₄ * 0.5H ₂ O hemihydrate 38.62 0.12 0.8 55.17 0.36 0.2 1.6 6.21 61.38 one hundred Sewage sludge ash 9.3 46.6
(68.24) - - 12.0 9.4 1.06 - - 78.36 Clinker 63.0 22.0 - - 6.0 3.0 1.5 - - 95.5 Apatite phosphogypsum CaSO ₄ * 2H ₂ O 31.8 0.79 - 44.6 0.42 0.33 - 19.6 K ₂ O = 0.06
Na ₂ O = 0.06 P ₂ O _5total = 0.87
P ₂ O _5total = 0.3 Phosphogypsum Karatau CaSO ₄ * 2Н ₂ О 3.2 - - 46.5 0.5 0.2 - 17.5 P ₂ O _5total = 1.6
P ₂ O _5total = 0.3 *)
The specific gravity of phosphogypsum: 2.2-2.4 g / cm ³
Refractive Index: Ng = 1.530; Np = l.52
Specific surface: 3800 cm ² / g
Solubility: 0.2-0.22%
Bulk mass
uncompressed: 0.49 g / cm ³ -0.72 g / cm ³
compacted: 0.67 g / cm ³ -0.93 g / cm ³
at W = 20.1% and 43.5%; slope angle is 53 °

Table number 2 Consumption rates of raw materials for the production of 1000 kg of cement clinker and 1287 kg of sulfuric acid, depending on the composition of sulfate raw materials Raw materials and derivatives Consumption rates of raw materials for production methods of Portland cement clinker with calcium sulfates, kg Anhydrite CaSO ₄ CaSO ₄ * 0.5H ₂ O hemihydrate CaSO ₄ * 2H ₂ O dihydrate one 2 3 four Anhydrite CaSO ₄ 1787.4 - - CaSO ₄ * 0.5H ₂ O hemihydrate - 1905.7 - CaSO ₄ * 2H ₂ O dihydrate - - 2260.6 Residue after calcination 736 736 736 Sewage treatment plants 3971.6 3971.6 3971.6 Sludge water from sewage treatment plants 2819.9 2819.9 2819.9 Dry sludge from treatment facilities 1151.8 1151.8 1151.8 Sewage sludge ash 564.4 564.4 564.4 The moisture content of the sewage treatment plant,% 71.0 / 20 71.0 / 20 71.0 / 20 The humidity of the technological mixture,% 48.964 50.2 53 Protein content, kg 587.4 587.4 587.4 The carbon content in protein, kg 323.1 323.1 323.1 The amount of O ₂ required for the oxidation of protein in the sediment of treatment facilities, kg 430.8 430.8 430.8 The amount of CO formed during the combustion of protein, kg 753.8 753.8 753.8 The amount of air required for burning protein, l / m ³ 1584404.6 / 1584.4 1584404.6 / 1584.4 1584404.6 / 1584.4

The standard consumables required for the production of 1000 kg of cement clinker 3CaOSiO ₂ in the process

with the receipt of 9.0% SO ₂ and basic physical and chemical data.

Table number 3 No. p / p Raw materials and derivatives Consumption rates Dimension Value one 2 3 four one Calcium Anhydrite CaSO ₄ / CaO kg / kg 1787.43 / 736 2 Sediment consumption kg 3971.6396 3 Sludge water from sewage treatment plants kg 2819.8696 four Dry sludge from treatment facilities kg 1151.77 5 Sewage sludge ash kg 564.37 6 Process Humidity % 48,964 7 Sludge % 71.0 8 The protein content in dry sediment kg 587.4027 9 The carbon content in the protein mass of dry sediment kg 323,071 10 The amount of O ₂ required for oxidation of carbon kg 430.76 eleven The amount of CO formed by the direct combustion of carbon kg 753.83 12 O ₂ content in air % 21.0 13 O ₂ content in air gram 6.09 fourteen The amount of air needed to oxidize carbon l / m ³ 1584404.5E77 / 1584.4 fifteen The amount of oxygen required to burn carbon sludge m ³ 332.724 16 The amount and volume of CO ₂ generated in the process kg / m ³ 578.286 / 294 (294400 * 145 L) 17 The amount and volume of SO ₂ generated in the process kg / m ³ 841.1435 / 294.4 (294400 * 225 L) eighteen Calorific value of dry sediment kcal / kg
Kj / kg 2640-4500
11000-18750 19 Heat of vaporization kcal / mol
KJ / mol 10.519
43.99 twenty Liquid fuel consumption for clinker formation kg 115 21 Calorific value of liquid fuel kcal / kg
Kj / kg 10000-11000
41800-45980 22 Fuel cost $ / kg 0.3 23 Clinker Enterprise Performance tons of clinker / year 730000 24 The amount of heat required to remove water from the process pulp kcal / 2819.8696
KJ / 2819.8696 1647960.52
6882330.405 25 The volume of water vapor removed in the process m ³ 3509.17105 26 The amount of heat released during the combustion of dry sludge kcal / 1151.77 5182965 27 The amount of heat released into the system kcal / kJ 3535065 28 Fuel consumption kg / ton
clinker 115 29th The amount of SO ₂ generated in the production of 1 ton of clinker m ³ / ton of clinker
kg / ton clinker 841.14 / 294.339 thirty The amount of SO ₃ m ³ / ton of clinker
kg / ton clinker 1051.425 / 294.339 31 The amount of H ₂ SO kg / ton
clinker 1287.99 32 The amount of heat released into the system during fuel combustion kcal kj 1265000 5287700

Normative consumables and calculated values during the implementation of the process

and basic physical and chemical data.

Table number 4 No. p / p Raw materials and derivatives Consumption rates Dimension Value one 2 3 four one Calcium sulfate hemihydrate CaSO ₄ * 6Н ₂ О Kg 1905.714 2 The amount of water in the hemihydrate of calcium sulfate CaSO ₄ * 0.5Н ₂ O Kg 118.285696 3 The residue after calcining CaO Kg 736 four The amount of SO ₃ Kg 1051.4284 5 Sewage treatment plants Kg 3971.6396 6 Sludge water from sewage treatment plants Kg 2819.8696 7 System water Kg 2938.1553 8 Dry sludge from treatment facilities Kg 1151.77 9 Sewage sludge ash Kg 564.37 10 Sludge % 71.0 eleven Process Humidity % 47.97 12 Process weight Kg 5877.3536 13 The protein content in dry sediment Kg 587.4027 fourteen The carbon content in the protein mass of dry sediment Kg 323.071 fifteen The amount of O ₂ required for oxidation of carbon Kg 430.76 16 The amount of CO generated during the combustion of carbon in the sediment protein Kg 753.83 17 Carbon content in protein % 55 eighteen The amount of O ₂ required for oxidation of carbon %
kg / m ³ 5.88 433 / 303.1 19 The amount and volume of carbon C in protein mass Kg 324.75 twenty The amount of CO generated during the combustion of protein %
kg / m ³ 11.76
757.75 / 606.2 21 The amount of SO ₂ formed in the process %
kg / m ³ 6.06
841.14 / 294.399 22 The amount of N ₂ About in the hemihydrate of calcium sulfate CaSO ₄ * 0.5H ₂ O kg / m ³ 118.2856 23 Sum of Н ₂ О from CaSO ₄ * 0.5Н ₂ O and precipitate in the system %
kg / m ³ 70.93
2938.1553 / 3656.37 24 Gas phase volume m ³ 5154.433 25 With _CO2 %
kg / m ³ 5.7115
578.2856 / 294.397

Normative consumables and calculated values during the implementation of the process

and basic physical and chemical data.

Table number 5 No. p / p Raw materials and derivatives Consumption rates Dimension Value one 2 3 four one Calcium sulfate dihydrate CaSO ₄ * 2Н ₂ O kg 2260.57 2 Amount of water in calcium sulfate dihydrate CaSO ₄ * 2Н ₂ O kg 473.14 3 The residue after calcining CaO kg 736 four The amount of SO ₃ kg 1051.4284 5 Sewage treatment plants kg 3971.6396 6 Sludge water from sewage treatment plants kg 2819.8696 7 Dry sludge from treatment facilities kg 1151.77 8 Sewage sludge ash kg 564.37 9 Sludge % 71.0 10 Process Humidity % 52.8385 eleven System water kg 3293.0096 12 Process weight kg 6232.2096 13 The protein content in dry sediment kg 587.4027 fourteen The carbon content in the protein mass of dry sediment kg 323.071 fifteen The amount of O ₂ required for oxidation of carbon %
kg 5.25
430.76 / 301.532 16 The amount of CO generated during the combustion of carbon in the sediment protein %
kg / m ³ 13.128
753.83 / 17 Carbon content in protein % 55 eighteen The amount of carbon C in protein mass kg 324.75 19 The amount of SO ₂ formed in the process %
kg / m ³ 5.13
841.14 / 294.39 twenty The amount of H ₂ O in the technological mixture and in the volume of the gas phase %
kg / m ³ 71.37 3293.012 / 4097.97 21 The amount of CO ₂ in the system %
kg / m ³ 5.13
578.28 / 294.397

Table number 6 Physico-technical and mechanical data obtained as a result of testing samples of cement clinker produced by sintering a mixture of calcium sulfates and sludge from treatment plants at a temperature of 1450 ° C Sample Number Specific surface cm ² / g Normal density,% Spreadability, mm Setting time, hours Strength in bending and compression in age, MPa / day Start end 3 7 28 one 2700 25.4 110 3 ³⁰ 540 1.9 / 9.8 3.6 / 29.3 4.8 / 38.9 2 2720 26.1 115 3 ²⁰ 550 2.25 / 12.8 4.9 / 32.0 5.8 / 41.5 3 2690 24.8 112 3 ²⁵ 545 2.3 / 12.3 3.6 / 31.1 5.3 / 40.2 four 2750 25.2 110 3 ¹⁰ 540 2.41 / 12.5 3.5 / 29.0 5.4 / 40.9 5 2750 26.2 115 3 ³⁰ 550 2.1 / 11.8 3.8 / 29.4 5.2 / 40.5 6 2710 24.5 120 3 ²⁴ 545 2.8 / 12.4 3.9 / 30.5 5.3 / 39.8 7 2720 25.3 115 3 ²⁵ 545 2.5 / 12.8 4.8 / 32.0 5.7 / 41.2 8 2725 26.3 112 3 ³⁰ 550 2.9 / 13.0 4.1 / 32.0 5.1 / 39.4 9 2705 25.5 118 3 ²⁵ 555 2.85 / 12.9 4.0 / 31.9 5.0 / 40.0 10 2708 25.2 120 3 ²⁰ 545 2.9 / 12.9 3.6 / 29.5 4.9 / 40.5 *)
The physical density of the samples, g / cm ³ , varies in the density range 3.1. The bulk density in a loose and compacted state averages 1.15 g / cm ³ and 1.5 g / cm ³
**) For samples 1-3, mixtures from Table 1 were used. No. 2 with anhydrite as phosphogypsum; for samples 4-6, mixtures with hemihydrate as phosphogypsum; for samples 7-10, mixtures with dihydrate as phosphogypsum.

List of scientific, technical and patent literature used in a patent search for an invention: ENERGY-SAVING METHOD FOR DISPOSAL OF CALCIUM-PHOSPHOGYPES SULFATES AND SEDIMENTS OF CLEANING FACILITIES WITH PRODUCING CEMENT CLINKER AND SULFUR GAS FOR No. Author Title Edition one Venua M. Technological schemes of cement production M., "Building Materials", 1980 2 Gorchakov G.I. Construction Materials M., 1986 3 Cement and its application No. 1 2004 four Taylor, Hal F. Cement chemistry M., "World", 1996 5 Goldstein L.Ya. Cement production through industrial waste disposal L., "Stroyizdat", 1985 6 Shevtsov A.M. Patent of Russia No. 2065845 1996 7 Shevtsov A.M. Patent of Russia No. 2074134 1997 8 Butt Yu.M., Volkonsky B.V., Egorov G.B. Cement Handbook L, 1980 9 Verdiyan M.A., Bobrov D.A., Verdiyan A.M. Scientific Foundations of Cement Technology M, 2000 10 Structure and performance of cements London, New York, 1983 eleven My Moscow. Magazine of metropolitan life No. 7 2004 12 F.won Schlippenbach Pat. US No. 1069191, 1913. 1913 13 R.S. Ribas Pat. US No. 5049198, 1991. 1991 fourteen S.A. Gardner, T.E. Ban Pat. US No. 4503018, 1985. 1985 fifteen E.K. Wilson, S.J. Spigolon Pat. U.S. No. 4,608,238, 1986. 1986 16 Pat. UK No. 1206193, 1970. 1970 17 H. Stich, W. Binder et al. Pat. US No. 3865602, 1975 1975

* Sources Nos. 12-17 describe the Mueller-Küchnet process.

Claims (1)

An energy-saving method for the disposal of calcium sulfates - phosphogypsum and sludge from biological wastewater treatment plants to produce cement clinker and sulfur dioxide - raw materials for the production of sulfuric acid, characterized in that this utilization is carried out by sintering calcium sulfates - phosphogypsum with sludge from wastewater treatment plants of biological wastewater treatment plants water at a temperature of 850-1450 ° C.