RU2525555C1 - Method to produce portland cement clinker - Google Patents

Abstract

FIELD: construction.SUBSTANCE: method includes heating of cement raw materials in cyclone heat exchangers, ignition in suspended condition in an incinerator, baking into a cement clinker in a rotary baking furnace and then cooling in a fridge with separation of gases produced in cyclone heat exchangers, in the incinerator and baking furnace and their removal via a fan, at the same time the annealed raw material from the incinerator with some gases is removed into a separate system with cyclones and a fan with partial discharge of annealed raw materials from the plant, at the same time discharge of annealed raw materials with some gases into the above separate system is carried out with content of sulphur oxides in gases in the amount of at least 2 vol. % with parallel return of the main part of annealed raw materials into the incinerator and/or baking furnace, besides, the above separate system is additionally equipped with a unit of oxidation of sulphur dioxide into sulphur trioxide and a unit of sulphuric acid production from sulphur trioxide, and fuel in the baking furnace is sulphury or high-sulphur hydrocarbon fuel.EFFECT: simultaneous production of a target product and sulphuric acid from raw materials with low sulphur content, reduced extent of alkaline and sulphuric clogging of plant equipment.5 cl, 1 dwg

Description

The invention relates to the building materials industry and can be used for the production of Portland cement clinker and sulfuric acid.

A known method of producing cement clinker according to the gypsum-sulfuric acid method with the simultaneous production of sulfuric acid from sulfur dioxide. In the known method, natural anhydrite-anhydrous calcium sulfate, as a carrier of CaO and SO ₃ , is partially replaced (by 5-80%) with waste containing calcium sulfite — CaSO ₃ generated during the desulfurization of flue gases, and with the feed mixture at the inlet to the rotary kiln roasting spray sulfuric acid waste in an amount providing a molar ratio of H ₂ SO ₄ : CaSO ₃ from 0.2 to 1.0. To implement the proposed method, it is recommended to use the waste generated during the desulfurization of flue gases with a content of 21-80% CaSO ₃ and 5-20% CaSO ₄ , and waste sulfuric acid with a content of 78-100% H ₂ SO ₄ (Pat. GDR No. 294009, MKI ⁵ C04B 7/48, C04B 7/04, claimed 20.11.89, published 14.09.91).

A known method of producing cement clinker and gases containing SO ₂ to produce sulfuric acid using the gypsum-sulfuric acid method, in which part of the natural anhydrite is replaced by industrial sulfite-containing wastes generated by desulfurization of flue gases by an absorption method and containing 35-80% CaSO ₃ and 5- 20% CaSO ₄ (Pat. GDR No. 289036, MKI ⁵ C04B 7/44, C04B 7/04, decl. 20.11.89, publ. 18.4.91).

The main disadvantage of the above methods is that sulfuric acid can only be obtained using raw materials with a high (over 10%) sulfur content - gypsum, phosphogypsum, other sulfates, sulfides and sulfites, suitable as raw materials for the production of clinker.

A known method of manufacturing a Portland cement clinker, adopted as a prototype, in which cement raw materials are preheated in a preheater (cyclone heat exchanger system), are calcined in suspension by hot gases in an annealing furnace (calciner), calcined in a cement clinker in a rotary kiln and then cooled in the fridge. A certain amount of calcined raw material with a high content of calcium oxide (CaO) is recovered through the calcination step by means of an additional gas separation cyclone and is obtained in pure form in a mixture with a small amount of alkali metal oxides. Gases are removed from the additional separation cyclone through a separate system containing a fan (Pat. RF No. 2387606 (FIG. 2), IPC C04D 7/36, F27B 7/20, op. 27.04.2010).

The known method is aimed at reducing alkaline clogging of the equipment of the installation and is not used to obtain simultaneously with cement clinker sulfuric acid.

In addition, there remains an increased risk of sulfuric acid and alkaline clogging of the system cyclones - annealing furnace - a rotary kiln - a refrigerator, since sulfur oxides and alkali metal compounds formed in the kiln are subsequently sorbed by cement raw materials introduced into the gas stream, which also compounds of alkali metals are deposited with a further return of all of the above to the system cyclone heat exchangers - calcination furnace - rotary kiln - refrigerator.

The objective of the present invention is to obtain clinker from low-sulfur raw materials and, at the same time, sulfuric acid from sulfur, raw materials and fuels, control the degree of alkaline and sulfuric acid clogging of equipment when using a kiln of sulfur or high-sulfur hydrocarbons as a furnace.

This problem is solved in a method for producing Portland cement clinker, in which cement raw materials are preheated in cyclone heat exchangers, calcined in suspension in a calciner, calcined in a cement clinker in a rotary kiln, and then cooled in a refrigerator with the separation of gases generated in cyclone heat exchangers in calcinator and kiln and their removal through the fan, while the calcined raw material from the calciner with part of the gases is taken into a separate system with a cycle us and a fan with a partial terminal calcined raw materials from the plant according to the invention, removal of the calcined raw materials together with a part of the gases into the above separate system is carried out when the content of sulfur oxides in the gas in an amount of not less than 2 vol%. with the return of the main part of the calcined raw materials to the calciner and / or kiln, the above-mentioned separate system is additionally equipped with a unit for oxidizing sulfur dioxide into sulfur trioxide and a unit for producing sulfuric acid from sulfur trioxide, and sulfur or high sulfur is used as fuel in the kiln hydrocarbon fuel.

The temperature in the calciner is 700-950 ° C, and in the kiln -1450 ° C.

As a sulfur or high sulfur hydrocarbon fuel, it is advisable to use petroleum coke with a sulfur content of up to 10% of the mass.

The oxidation of sulfur dioxide (SO ₂ ) to sulfur trioxide (SO ₃ ) is carried out in a reactor using vanadium or platinum catalysts.

Sulfuric acid is obtained from sulfur trioxide (SO ₃ ) by absorption and / or condensation.

The removal of calcined raw materials together with part of the gases into the aforementioned separate system with a content of sulfur oxides in gases in an amount of at least 2% vol. into a separate system equipped with special units, it makes it possible to obtain sulfuric acid together with the target product - Portland cement clinker, and also to regulate the degree of acid clogging.

The use of sulfur coke with a sulfur content of up to 10% as a fuel in the kiln makes it possible to obtain additional amounts of sulfur oxides required to produce sulfuric acid when it is burned.

The drawing shows a schematic diagram of the manufacture of Portland cement clinker with the simultaneous production of sulfuric acid from low-sulfur raw materials, where 1 - crusher, 2 - silos for adjusting the composition, 3, 4, 5, 6 - cyclone heat exchangers, 7 - fan, 8 - calcination furnace (calciner ), 9 - a calcination furnace with lines 10 for supplying fuel and an oxidizing agent, 11 - a refrigerator, 12 - a line for outputting calcined raw materials from the installation, 13 - a line for returning calcined raw materials back to the calciner or a calcining furnace, 14, 15, 16 - cyclones - dust precipitators, 17 - f dust filter precipitator; 18 - a heat exchanger (recovery boiler), possibly together with a filter, 19 - a fan, 20 - a flue gas exhaust line, 21 - a reactor with a catalyst for producing sulfur trioxide, 22 - an absorber or condenser for producing sulfuric acid.

The method is as follows.

The initial low-sulfur raw material — limestone or other calcium-containing material with a sulfur content of 4%, together with clay is subjected to preliminary crushing and grinding of raw materials, followed by drying and heating in crusher 1 with simultaneous or subsequent crushing and grinding. Then the raw materials are sent in the form of fine powder - raw flour to reinforced concrete silos 2, where they are adjusted to its specified parameters and homogenized by mixing with compressed air.

Next, a homogeneous, finely ground mixture is preheated to 600-800 ° C in cyclone heat exchangers 3, 4, 5, 6, followed by calcination in calciner 8, where the raw material mixture is heated to 700-1000 ° C, undergoing dehydration and decarbonization.

Then, the resulting raw material mixture is calcined in a cement clinker in a kiln 9 at temperatures up to 1450 ° C, to which sulfur coke with a sulfur content of about 4% and air are fed from the other end in countercurrent through line 10. The resulting clinker is then cooled in the refrigerator 11. In this case, in the furnace 9 at the temperature of up to 1450 ° C, sulfur oxides, mainly SO ₂ and, partially, SO _{3 are formed} .

Sulfur oxides together with flue gases are removed from the kiln 9 to calciner 8 and cyclone heat exchangers 3, 4, 5, 6, where they bind to Ca, Na, K oxides with the formation of the corresponding sulfates and sulfites and are deposited on the starting raw materials. Since Na and K oxides can be sublimated at temperatures above 1350 ° C, they are also taken out from the kiln 9 to calciner 8 and cyclone heat exchangers 3, 4, 5, 6 together with flue gases, where they settle onto raw materials and then return to kiln. Further, the flue gases are blown off by the fan 7 to the flue gas exhaust line 20. Thus, only a small amount of sulfur is present in the flue gases from its total amount supplied with the fuel and, in part, with the feed. The rest, most of the sulfur and its compounds, as well as alkali metal compounds, are not removed from the system by cyclone heat exchangers 3, 4, 5, 6 — calciner 8 — rotary kiln 9, and again through calciner 8 enter the rotary kiln 9, adding to the amount of sulfur and alkali metals, which again comes with sulfur coke through line 10 and with the feedstock through cyclonic heat exchangers 3, 4, 5, 6 (internal circuit). Thus, the accumulation of sulfur and alkali metal compounds in the system of cyclone heat exchangers 3, 4, 5, 6 - calciner 8 - rotary kiln 9.

In the gases leaving the cyclone heat exchangers 3, 4, 5, 6 and blown by the fan 7 along line 20, sulfur oxides are practically absent; carbon dioxide, oxygen, and nitrogen are present here.

After accumulation of at least 2% vol. sulfur oxides, which occurs on the approximately 5-20th circle of sulfur circulation in the internal circuit when using sulfur coke with a sulfur content of about 4 wt% as fuel, exhaust flue gases from calciner 8 into a separate system containing cyclones 14, 15 , 16 with a line 13 for returning deposited dust of calcined raw material particles to the calciner 8 and a line 12 for outputting a part of deposited dust for alkalized calcined raw material particles from the installation, a filter precipitator 17, a cooler 18 and a fan 19, a reactor with a catalyst 21 and a condenser or abs ber of sulfuric acid 22. The main stream of flue gases containing no sulfur oxides is withdrawn via line 20. The gas stream blown from the calciner or kiln is freed of solid particles of precipitated dust in cyclones 14, 15, 16, which are then sent back to the kiln system furnace 9 - calciner 8 - cyclone heat exchangers 3, 4, 5, 6 along the return line 13, partially precipitated dust is removed from the installation via line 12, thus regulating the degree of alkaline clogging. The gases blown away by the fan 19 of a separate system are sent through a filter to the reactor 21 to carry out the oxidation of SO ₂ to SO ₃ on a vanadium or platinum catalyst. Next, the oxidation product enters the condenser or absorber 22 to produce sulfuric acid.

The removal of the calcined raw materials together with the gases into a separate system from the calciner or the kiln allows you to mainly control the amount of sulfur oxides and, in addition, alkalis (through the output of the calcined material from the unit via line 12), which are accumulated in the system by cyclone heat exchangers 3, 4 , 5, 6 - calciner 8 - rotary kiln 9, thereby controlling the degree of clogging downward, which allows accumulating a sufficient amount of SO ₂ to oxidize it to SO ₃ on a platinum or vanadium catalyst.

The following is a calculated example of the implementation of the proposed method for the manufacture of Portland cement clinker with the simultaneous production of sulfuric acid.

Suppose that with a raw mixture (CaCO ₃ with clay with a sulfur content of 0.44% wt.) For the production of clinker, 11 g of SO ₃ per 1 kg of clinker is added.

Alkali metal oxides also enter the rotary kiln together with raw flour: 10 g K ₂ O per 1 kg of clinker and 2 g Na ₂ O per 1 kg of clinker, which, like sulfur oxides, participate in the internal circuit in a rotary kiln with cyclone heat exchangers.

In terms of 100 g of fuel (petroleum coke / clinker ratio = 1/5) with raw materials, 5.5 g of SO ₃ or 2.2 g of sulfur will enter the clinker production process with the raw mixture.

In terms of 100 g of fuel (petroleum coke / clinker ratio = 1/5) with raw materials, about 5 g of K ₂ O and 1 g of Na ₂ O will go into the production of clinker with the raw mix.

As fuel for the kiln, 100 g of petroleum coke with a calorific value of 34903 kJ / kg, containing 89% wt., Carbon, 4% wt., Hydrogen, 4% wt., Sulfur, the rest is ash, nitrogen, oxygen. The fuel: clinker ratio is 1: 5.

Then we have 89 g of carbon, 4 g of hydrogen and 4 g of sulfur in 100 g of fuel, and the total amount of sulfur in the process will be 6.2 g.

It is known that the proton mass is 1.673 × 10 ^-24 g, the neutron mass is 1.675 × 10 ^-24 g, the electron mass is 9.109 × 10 ^-28 g, excluding the mass defect:

- atomic mass of carbon 12 amu or 20.0934 x 10 ^-24 g;

- the atomic mass of hydrogen is 1 amu or 1.674 x 10 ^-24 g;

- atomic mass of sulfur 32 amu or 53.5825 × 10 ^-24 g.

Then in 6.2 g of sulfur there will be 0.1157 × 10 ²⁴ sulfur atoms, in 89 g of carbon there will be 4.4293 × 10 ²⁴ carbon atoms, and in 4 g of hydrogen there will be 2.3895 × 10 ²⁴ hydrogen atoms.

Thus, when 100 g of petroleum coke is burned in a stoichiometric amount of oxygen during clinker burning, 4.4293 × 10 ²⁴ molecules of CO ₂ , 1.1947 × 10 ²⁴ molecules of H ₂ O and 0.1157 × 10 ²⁴ molecules of SO ₂ , or all molecules 5.7397 × 10 ²⁴ .

Thus, the concentration of SO ₂ in flue gases excluding nitrogen will be about 2.01% vol. (mol.), the concentration of CO ₂ will be 77.17% vol. (mol.), the concentration of H ₂ O will be 20.82% vol. (mol.). In this case, 5.14235 × 10 ²⁴ oxygen molecules are consumed.

During air oxidation, along with atmospheric oxygen, about 20 × 10 ²⁴ nitrogen molecules and oxygen molecules will come to further oxidize SO ₂ to SO ₃ on the catalyst.

In total, after burning fuel, taking into account air nitrogen, there will be about 25.7397 × 10 ²⁴ gas molecules in flue gases.

Then, when burning fuel in a stoichiometric amount of air, the concentration of SO ₂ in flue gases will be about 0.45% vol.

Taking into account alkali metal oxides, the material balance is obtained as follows:

- the atomic mass of oxygen is 16 amu or 26.784 x 10 ^-24 g;

- atomic mass of potassium 39 amu or 65.286 x 10 ^-24 g;

- atomic mass of sodium 23 amu or 38.502 × 10 ^-24 g.

Then the molecular weight of potassium oxide will be 94 amu or 157.356 × 10 ^-24 g, the molecular weight of sodium oxide will be 62 amu or 103.788 × 10 ^-24 g. In 5 grams of K ₂ O there will be 0.0318 × 10 ²⁴ molecules of potassium oxide.

In 1 g of Na ₂ O will be 0.0096 × 10 ²⁴ molecules of sodium oxide.

Total alkali metal oxides will be 0.0414 × 10 ²⁴ molecules.

Since 0.1157 × 10 ²⁴ sulfur molecules (atoms) are supplied with fuel and raw materials in terms of 100 g of sulfur dioxide, and, given that one sulfur molecule in the composition of sulfur dioxide or trioxide reacts with one molecule of Na ₂ oxide O or K ₂ O and the resulting substances are excreted in solid form, then, after sulfur is bound by alkali metal oxides, 0.0743 × 10 ²⁴ molecules of sulfur oxides, or 0.29% vol., Remain in the flue gas, given that water, nitrogen and carbon dioxide are removed with flue gases, then the concentration of sulfur oxides on the 20th circle of internal circulation will be 5.78% vol. or 1.486 × 10 ²⁴ molecules and 1.1947 × 10 ²⁴ water molecules, which results in a 124% oleum. Since it is possible to deduce from the system only the number of sulfur atoms that enter it - 0.1157 × 10 ²⁴ molecules (atoms) of sulfur or 0.0743 × 10 ²⁴ molecules of sulfur oxides after they are combined with alkali oxides (20th part) , and, accordingly, 0.06 × 10 ²⁴ water molecules (20th part), we will additionally receive 11.76 g of 124% oleum from 0.0143 × 10 ²⁴ SO ₃ molecules (1.92 g) and 0.06 × 10 ²⁴ molecules of H ₂ SO ₄ , (9.8 g).

In total, we obtain 0.5 kg of clinker and 11.76 g of 124% oleum.

The example shows that, taking into account the presence of alkali metal oxides in the feedstock, the accumulation of sulfur oxides in flue gases in an amount sufficient to implement the oxidation of sulfur dioxide (SO ₂ ) to sulfur trioxide (SO ₃ ) on the catalyst will occur, for example, at 20- m circulation circle of sulfur, its oxides and alkali metal oxides in the internal circuit in a rotary kiln with cyclone heat exchangers.

Thus, the present invention allows to obtain simultaneously with the target product - Portland cement clinker sulfuric acid (oleum) from raw materials with low sulfur content using sulfur or high sulfur petroleum coke as fuel, as well as adjust the degree of alkaline and sulfuric acid blockage of the plant equipment.

Claims (5)

1. A method of obtaining a Portland cement clinker in which cement raw materials are preheated in cyclone heat exchangers, calcined in suspension in a calciner, calcined in a cement clinker in a rotary kiln and then cooled in a refrigerator with the separation of gases generated in cyclone heat exchangers in a calciner and kilns and their removal through the fan, while the calcined raw material from the calciner with part of the gases is diverted to a separate system with cyclones and a fan from part the initial conclusion of the calcined raw materials from the installation, characterized in that the removal of the calcined raw materials with part of the gases into the aforementioned separate system is carried out at a sulfur oxide content of at least 2% vol. with the return of the main part of the calcined raw materials to the calciner and / or kiln, the above-mentioned separate system is additionally equipped with a unit for oxidizing sulfur dioxide into sulfur trioxide and a unit for producing sulfuric acid from sulfur trioxide, and sulfur or high sulfur is used as fuel in the kiln hydrocarbon fuel. 2. The production method according to claim 1, characterized in that the temperature in the calciner is 700-950 ° C, and in the kiln - 1450 ° C. 3. The production method according to claim 1, characterized in that petroleum coke with a sulfur content of up to 10% wt. Is used as sulfur or high-sulfur hydrocarbon fuel. 4. The production method according to claim 1, characterized in that the oxidation of sulfur dioxide (SO ₂ ) to sulfur trioxide (SO ₃ ) is carried out in a reactor using vanadium or platinum catalysts. 5. The production method according to claim 1, characterized in that sulfuric acid is obtained from sulfur trioxide by absorption and / or condensation.

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