JPH031253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metallothermal process for the simultaneous production of calcium and cement.

As is already known, magnesium and calcium are generally produced by electrolyzing melts of their salts.

Salts (generally chlorides) are electrolyzed at approximately 700-900°C. The disadvantage of this method is that it requires very pure starting materials, completely free of water, and such materials can only be produced by complex and long procedures that require a lot of effort and energy.

Dolomite ( _CaCO3・
Several attempts have been made to mass-produce magnesium and calcium from MgCO ₃ ) and limestone (CaCO ₃ ), respectively. According to these methods, dolomite or limestone is first calcined and the resulting calcined product (CaO.MgO or CaO)
is subjected to metal heating reduction. Applying silicon as a reducing agent, calcined dolomite yields magnesium according to the equation 2(CaO.MgO) + Si = 2CaO.SiO ₂ + 2Mg, whereas calcined lime yields magnesium according to the equation 4CaO + Si = 2CaO.SiO ₂ + 2Ca. It produces calcium.

When aluminum is used as a reducing agent in a metal heating process, magnesium or calcium is formed according to the formula 3(CaO.MgO)+2Al= _{3CaO.Al2O3 +} 3Mg6CaO+ _2Al = _3CaO.Al2O3 +3Ca.

Until now, such methods have not been able to compete with electrolytic methods. This is because they produced an extremely large amount of unnecessary slag in addition to the desired product. According to theoretical calculations, 3.6 tons of slag with a composition of 2CaO.SiO ₂ is formed when producing 1 ton of magnesium by heating with silicon, whereas 1 ton of magnesium is produced using heating with aluminum. to
3.72 tons of slag with a composition of 3CaO.Al ₂ O ₃ is produced. In the production of calcium, along with 1 ton of the necessary product
2CaO.SiO ₂ 2.14t or 3CaO.Al ₂ O ₃ 2.24t is formed.

The present invention solves the above-mentioned drawbacks of the method of producing calcium by heating with silicon or heating with aluminum, and provides an easy-to-implement, economical, large-scale production method for producing calcium by metal heating of two types of alkaline earth metals. The purpose is to solve this problem by providing a production method.

Next time, when producing magnesium from calcined dolomite or calcium from calcined lime, use an appropriate amount of a reducing agent containing silicon and aluminum in a Si:Al weight ratio of 3:1 to 2:1. When you do
It has been found that cement can be obtained as a useful by-product in addition to the two metals. This method uses 600-800 parts by weight of calcined dolomite or 700-1000 parts of calcined lime.
Apply 100-200 parts by weight of reducing agent to convert parts by weight. When trying to produce magnesium, 600 to 800 parts by weight of calcined dolomite to 200 parts by weight of calcined lime.
Add less than 100 parts by weight of reducing agent to this mixture.
This can also be done by reducing with 200 parts by weight.

Therefore, the present invention applies a reducing agent containing silicon and aluminum in the weight ratios specified above, and the heating process with silicon or the aluminum process, provided that the ratio of reducing agent to starting material is maintained within the above limits. This method is based on the recognition that cement is produced as a by-product instead of useless slag. As is clear from the above ratios, the mixture of starting material and reducing agent contains a relatively large amount of calcium oxide. As mentioned above, special advantages arise from the additional addition of calcium oxide to the calcined dolomite before the metal thermal reduction in the production of magnesium. These facts are in stark contrast to previous efforts to keep the calcium oxide proportion to a minimum in order to reduce the amount of slag. According to the invention, however, it is essential that the mixture is treated with a relatively high calcium oxide content. This is because this ensures the formation of cement outside the slag as a by-product.

According to a further variant of the invention, reducing agents containing calcium are also applied. This is also in contrast to previous efforts. The meaning of the presence of calcium can be easily understood based on the following equation.

5(CaO.MgO)+Ca+2Si=2( _3CaO.SiO2 )+5Mg This equation shows that calcium also participates in the reduction of calcined dolomite as a reducing agent. Of course, in the case of calcined lime treatment, calcium has no reducing effect, but merely increases production.
The reason for using a calcium-containing reducing agent in the treatment of calcined lime is that it is one of the most practically applicable reducing agents.
This is because CaSi alloy is the most easily available. The calcium contained in this reducing agent increases the yield of the desired product.

As mentioned above, a substance containing silicon and aluminum in a weight ratio of 3:1 to 2:1 is applied as the reducing agent. The total silicon and aluminum content of the reducing agent is
It may vary between 50 and 100%. This means that simple mixtures or alloys of silicon and aluminum containing the two metals in the above weight ratios can be used as reducing agents in the process of the invention. However, reducing agents containing other substances besides aluminum and silicon can be used as well. As mentioned above, reducing agents containing calcium are also preferred.
The calcium content of such reducing agents may be up to 30% by weight, and they generally contain 1 to 30% by weight of calcium. The reducing agents used in practice are generally iron-containing alloys or mixtures of these alloys.
The iron content of the reducing agent may be up to 25% by weight. The reducing agent generally contains 0.1 to 25% iron by weight. Silicoaluminum, ferrosilicon, as reducing agent
Suitable alloys of calcium silicon, calcium silicoaluminum, and calcium ferrosilicoaluminum can be used. in this case,
The silicon to aluminum ratio, the total silicon and aluminum content, and the calcium and iron content are such that they meet the above requirements. Of course, a single alloy having an appropriate composition can also be used as is.

The reduction itself is carried out in accordance with known methods using equipment used for heating with silicon and heating with aluminum.
At a temperature of 1300-1600℃ and a pressure lower than 10mmHg,
This is continued until the generation of calcium vapor stops.

Mixtures of starting materials are powders and briquettes
It is in a state of Suitable lumps are generally 500 ~
It can be formed at a pressure of 2000 Kib/cm ² (226.8 to 907 tons/cm ² ). The nodules, either as such or after optionally curing and/or preheating, are filled into a refractory chamber maintained at 1300-1600° C. in a furnace filled with an inert protective gas. The furnace is closed, the internal pressure is reduced to less than 10 mmHg, and heating is continued to heat the nodule to 1300-1600°C to allow the metal heating reaction to take place. The calcium vapor formed is collected in the furnace condenser. There, calcium precipitates in crystalline form. At the end of the process, the temperature of the condenser further decreases as no calcium vapor precipitates in the condenser.

Depending on the composition of the starting material and reducing agent mixture, furnace size, temperature, and other factors, the reduction is generally between 4 and 12
Complete in time.

At the end of the reaction, the furnace is refilled with inert protective gas and the formed cement clinker is removed from the refractory chamber, while the crystalline calcium is removed from the condenser. The process can then be started again. Preferably, the furnace is operated in a cyclical manner.

Preferably, argon is used as the protective gas.

The cement clinker taken out from the refractory of the furnace contains 20-25% by weight of SiO ₂ and 6-12% by weight of Al ₂ O ₃
and 62-69% by weight CaO, optionally up to 2% by weight MgO and/or 6% by weight iron.
The composition of this product corresponds to that of Portland cement. It can be used as a binder in the construction industry.

The most important advantages of the new method according to the invention are:
The objective is to provide an economical method for mass production of calcium. Using the method of the present invention, the disadvantages of conventional silicon heating methods and aluminum heating methods, such as the generation of large amounts of unnecessary slag and further environmental protection problems, can be completely avoided. This is because all the products formed by the new method can be used.

The method of the invention is easy to implement and does not require special technical operations or special equipment. The process can be carried out in equipment commonly used in silicon and aluminum heating processes, provided that pressures below 10 mm Hg and temperatures between 1300 and 1600 DEG C. are maintained therein.

The present invention will be explained in detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 814 parts by weight of calcined lime were mixed with 70% by weight of silicon and 30 parts by weight.
Mixed with 100 parts by weight of reducing agent containing % aluminum by weight. The mixture was ground into a powder and the powder was made into pellets. The small lumps were heated to 1500℃ and 10 ^-3 mm.
It was heated in a fireproof room until the generation of calcium vapor stopped under the pressure of Hg. This method produced 258 parts by weight of calcium as the main product and 64.5 parts by weight as a by-product.
CaO, 23.6 wt% _SiO2 , 11.4 wt% _{Al2O3 ,}
and 656 parts by weight of cement containing 0.5% by weight of MgO were obtained.

Example 2 814 parts by weight of calcined lime, 52% by weight of silicon, 22
It was mixed with 135 parts by weight of a reducing agent containing % aluminum and 26% calcium by weight. The mixture was pulverized, the resulting powder was formed into pellets, and the pellets were heated in a refractory chamber at 1600° C. and a pressure of 10 ⁻¹ mmHg until calcium vapor evolution ceased. This method produces 294 parts by weight of calcium as the main product and 66.7% by weight of CaO, 22.8% by weight of SiO ₂ as by-products,
650 parts by weight of cement containing 9.9% by weight Al ₂ O ₃ and 0.6% by weight MgO was produced.

Example 3 814 parts by weight of calcined lime, 57% by weight of silicon, 24 parts by weight of calcined lime
It was mixed with 123 parts by weight of a reducing agent containing % aluminum and 19% iron by weight. The mixture was ground into a powder, the resulting powder was formed into pellets, and the pellets were heated in a refractory chamber at 1450° C. and a pressure of 10 ⁻⁴ mmHg until calcium vapor evolution ceased. In this method, the main products are 254 parts by weight of calcium and
64.8 wt% CaO, 22.7 wt% _SiO2 , 8.5 wt%
of Al ₂ O ₃ , 0.3% by weight MgO and 3.7% by weight iron resulting in 680 parts by weight of cement.

Example 4 814 parts by weight of calcined lime, 44.3% by weight of silicon,
It was mixed with 158 parts by weight of a reducing agent containing 19.0% by weight aluminum, 22.2% by weight calcium and 14.5% by weight iron. The mixture was ground into a powder, the resulting powder was made into small pieces, and the small pieces were heated at 1550°C.
Heated in a fireproof chamber at a pressure of 10 ^-3 mmHg. This method produces 298 parts by weight of calcium as the main product, 62.9% by weight of CaO, 23.5% by weight of SiO ₂ as by-products,
675 parts by weight of cement containing 9.6% by weight Al ₂ O ₃ , 0.7% by weight MgO and 3.3% by weight iron were produced.

Claims (1)

[Claims] 1. In a method for simultaneously producing calcium and cement from calcined lime, calcined lime is mixed with silicon and aluminum at a pressure lower than 10 mmHg and at a temperature of 1300 to 1600°C in a ratio of Si:Al of 3:1 to Reduction is carried out using a reducing agent contained in a weight ratio of 2:1, in which the total amount of silicon and aluminum accounts for 50-100% by weight, and 100-200 parts by weight of the reducing agent is added to 700-1000 parts by weight of calcined lime.
A method for simultaneously producing calcium and cement, characterized in that they are used based on parts by weight. 2. Process according to claim 1, characterized in that a reducing agent containing up to 25% by weight of iron is applied. 3. Process according to claim 1, characterized in that a reducing agent containing up to 30% by weight of calcium is applied. 4 Silicon and aluminum metals in a ratio of 3:1 to 2:1
2. The method according to item 1, characterized in that a mixture or alloy of silicon and aluminum containing a weight ratio of . 5. Contains silicon and aluminum in a total amount of 50-100% by weight, up to 30% by weight calcium, and 25% by weight
2. Process according to claim 1, characterized in that an iron-containing alloy or alloy mixture is applied as reducing agent. 6 characterized in that silicoaluminum, silicoaluminum calcium and/or ferrosilicoaluminum calcium or mixtures thereof or mixtures of any of the former alloys with ferrosilicon and/or calcium silicon are applied as reducing agents. The method according to item 5 above. 7. Place the mixture of starting material powders and nodules and the reducing agent in a condensing furnace heated to 1300-1600°C in the presence of an inert protective gas, maintaining the furnace temperature within the above range. , after the evolution of calcium vapor has ceased, the reduction is carried out in a circular operation by filling the furnace with an inert protective gas, removing the cement clinker from the furnace, removing the crystalline calcium from the condenser, and starting the above process again. The method according to item 1 above, characterized in that: 8. Process according to claim 7, characterized in that argon is applied as inert protective gas.