WO2008052951A2

WO2008052951A2 - Sand, shale and other silicon dioxide solid compounds as starting substances for providing silicon solid compounds, and corresponding processes for operating power stations

Info

Publication number: WO2008052951A2
Application number: PCT/EP2007/061574
Authority: WO
Inventors: Florian Krass
Original assignee: Sincono Ag
Priority date: 2006-10-29
Filing date: 2007-10-26
Publication date: 2008-05-08
Also published as: WO2008052951A3; EP2094816A2

Abstract

Process for providing silicon compounds from silicon dioxide compound, preferably from sand, having the following steps: a) introducing the silicon dioxide compound into a combustion zone, b) heating the combustion zone together with the silicon dioxide compound, c) conversion of silicon dioxide from the silicon dioxide compound into silicon (Si2), wherein a reducing agent is fed in order to remove the oxygen from the silicon dioxide, d) injecting a gaseous reaction partner in order to produce the silicon compound from the silicon (Si2).

Description

Sand, shale and other silica solid compounds as starting materials for providing silicon solid compounds and related methods of operating power plants

This application claims the priority of European application EP 06 022 578.6 entitled "Oily sands and shale and their mixtures as starting materials for binding or decomposing carbon dioxide and NOx, and for the preparation of crystalline silicon and hydrogen gas and for the production of silicon nitride, silicon carbide and silanes filed on 29.10.2006.

It is currently being researched and developed in a variety of directions to find a way to reduce anthropogenic CO ₂ emissions. Particularly in the context of energy production, which is often due to the burning of fossil fuels, such as coal or gas, but also in other combustion processes, for example in waste incineration, there is a great need for CO ₂ reduction. Hundreds of millions of tons of CO ₂ are released into the atmosphere through such processes every year. The combustion materials needed to generate heat typically produce CO ₂ . So far no one has come up with the idea sand (SiO ₂ ), shale and other silica-containing substances (eg oily sand, oily slate (SiO ₂ + [CO ₃ ] ² ), in bauxite or tar-containing sands or slates, and other mixtures existing sand) to use (heat) energy in power plant or power plant-like processes. This approach would be particularly advantageous if you could reduce or eliminate CO ₂ emissions. Furthermore, it would be ideal if products could be provided in such processes and power plants, which in turn could serve as "raw materials" for downstream processes or plants.

The stocks of sands and slates, and especially of oily sands (SiO ₂ ) and slates (SiO ₂ + [CO ₃ ] ² ) are enormous.

Sand is a naturally occurring, unconsolidated sedimentary rock and occurs in greater or lesser concentrations everywhere on the earth's surface. Much of the sand is quartz (silicon dioxide, SiO ₂ ).

The object of the present invention is to identify such possible raw materials and to describe their technical representation. The chemical considerations used in the process are characterized in that the SiO ₂ present in the sands and slates and other mixtures participates in a reaction (in a power plant process), wherein the SiO _{2 is} chemically modified in reaction into one or more silicon compounds.

Further embodiments of the invention are characterized by the following features / aspects:

1) From sand or other SiO ₂ mixtures, can be provided by burning or reaction together with liquid aluminum or hot aluminum dust silicon (Si). Simplified, the following reaction takes place: 5 "/ O ₂ + Al- → Si + Al ₂ O ₁₁

2) The heat released in an oven during the thermal reaction of the main process, e.g. using highly compressed water vapor to drive the turbine of a dynamo.

3) The most important ceramics used in technology Silicon nitride (Si ₃ N ₄ : with its diamond-like hardness) and silicon carbide (SiC: with its remarkable thermal conductivity) can be inexpensively and easily produced as raw materials.

4) If necessary, the crystalline silicon (e.g., as a powder at a suitable temperature) after ignition can be reacted directly with pure (cold) nitrogen (e.g., nitrogen from the ambient air) or with nitrogen radicals to form silicon nitride. This reaction is highly exothermic. The heat accumulating therefrom may be as e.g. in section 2) are used. For example, a nitrogen recovery process known from steel refining with propane gas (propane nitration) may be used.

Further details and advantages of the invention will be described below with reference to exemplary embodiments.

Detailed description

The invention will now be described by way of example. A first example relates to the application of the invention in a power plant operation to "burn" sand there with nitrogen to use heat for power generation in this new form of energy production.This new type of power plant approach reduces or eliminates the CO ₂ produced to date Output.

According to the invention, a series of deliberate chemical reactions is involved in which new chemical compounds (called products) are formed from the starting materials (also called reactants or reactants). The Reactions of the invention described at the beginning as the main process are designed such that a nitrogen-based "combustion" of SiO ₂ takes place.

As a starting material used in a first embodiment, for example, sand (which may be offset, for example, with mineral oil as the primary energy supplier), or slate. These starting materials are fed to a reaction chamber, for example in the form of an afterburner or a combustion chamber. In this chamber, a reducing agent is injected or introduced and the chamber together with the silicon dioxide compound is brought to high temperatures (preferably it is about temperatures higher than 1000 ⁰ C, preferably about 1350 ⁰ C). As a result, oxygen is split off from the silicon dioxide and there is highly reactive silicon. By blowing in or introducing a gaseous reactant (for example nitrogen or carbon dioxide), a silicon compound can be produced from the silicon. The conversion to a silicon compound is typically exothermic to highly exothermic, meaning that heat is released. This heat can, as in other known power plant processes, be used for energy production or conversion into electrical or mechanical energy.

In a preferred embodiment, CO _{2 is} blown into this chamber as a gaseous reactant. This CO ₂ can be, for example, the CO ₂ - exhaust gas, which is obtained in the energy production from fossil fuels in large quantities and so far escapes into the atmosphere in many cases. In addition, the chamber (ambient) air is supplied. Instead of the ambient air, or in addition to the ambient air, steam or hypercritical H ₂ O at over 407 ° C can be supplied to the process. The silicon in the combustion chamber reacts with the CO ₂ to silicon carbide (SiC). This reaction is slightly exothermic.

Furthermore or alternatively, the injection of nitrogen at another point in the process, or the combustion chamber provided.

In addition, a kind of catalyst as a reducing agent or Reduction partner used. Particularly suitable is aluminum (liquid or powdery). Under suitable environmental conditions, a reduction takes place in the chamber, which can be represented greatly simplified as follows:

SiO ₂ ^red > Si

This means that the quartz content present in the sand or shale is converted into crystalline silicon.

The used mineral oil of the sands can take over the role of the primary energy supplier and is then decomposed in the inventive process itself pyrolytic at temperatures above 1000 degrees Celsius largely in hydrogen (H ₂ ) and a graphite-like mass. Thus, the hydrogen is removed during the course of the reactions of the hydrocarbon chain of the mineral oil. For example, hydrogen can be diverted to natural gas piping systems or stored in hydrogen tanks.

In a further embodiment, the invention in connection with a pyrolysis of the company Pyromex AG, Switzerland, applied. However, the present invention can also be used as a supplement or alternative to the so-called oxyfuel process. Thus, for example, by means of the present invention, an energy cascade heat recovery can be carried out according to the following approach. In a modification of the oxyfuel process, heat is generated with the addition of aluminum, preferably of liquid aluminum, and with the addition of nitrogen (N ₂ ) (analogous to the known Wacker accident). If necessary, the nitrogen coupling to silicon is preferably the pure nitrogen atmosphere from the ambient air achieved by (known from the propane nitration) combustion of the oxygen content of the air with propane gas.

According to the invention, preference is given to using aluminum (Al) as reducing agent or reducing partner. Economic extraction of aluminum is currently possible only from bauxite. Bauxite contains about 60 percent alumina (Al ₂ O ₃ ), about 30 percent iron oxide (Fe ₂ O ₃ ), silicon oxide (SiO ₂ ) and Water. That is, the bauxite is typically always contaminated with the iron oxide (Fe ₂ O ₃ ) and the silicon oxide (SiO ₂ ). Bauxite can therefore be used as fuel or fuel in a power plant according to the invention, or bauxite can be added in a further step to sand or shale.

Al ₂ O ₃ can not be chemically reduced due to the extremely high lattice energy. Technically, the production of aluminum is possible, but by the fused salt electrolysis (cryolite-alumina method) of aluminum oxide Al ₂ O _3. The Al ₂ O ₃ is obtained, for example, by the Bayer process. In the cryolite-alumina process, the alumina is melted with cryolite (salt: Na ₃ [AIF ₆ ]) and electrolyzed. In order not to work at high melting temperature of the alumina of 2000 ⁰ C, the alumina is dissolved in a melt of cryolite. In the procedure lies thus the working temperature is only with 940 to 980 ⁰ C.

In fused-salt electrolysis, liquid aluminum is produced at the cathode and oxygen at the anode. Carbon blacks (graphite) are used as anodes. These anodes burn off due to the oxygen produced and must be renewed continuously.

It is considered to be a major drawback of the cryolite-clay process that it is very energy-consuming because of the high binding energy of the aluminum. A problem for the environment is the partial formation and emission of fluorine.

In the method according to the invention, the bauxite can be added to the process in order to achieve cooling of the process. With the bauxite you can get the excess heat energy in the system under control. This is analogous to the process where iron scrap is fed to a molten iron in a blast furnace for cooling, when the molten iron is too hot.

Alternatively, cryolite can be used if the procedure threatens to get out of control (see Wacker accident), so as to reduce the temperature in the system in the sense of emergency cooling. Just like silicon carbide (SiC), silicon nitride (SΪ3N ₄ ) is a wear-resistant material that can or will be used on highly stressed parts in mechanical engineering, turbine construction, chemical apparatus, engine construction.

Further details on the described chemical processes and energy processes can be found on the following pages.

Quartz sand can be exothermically converted into silicon and aluminum oxide with liquid aluminum according to the textbook Holleman- Wiberg:

(ex

Silicon burns with nitrogen to silicon nitride at 1350 ⁰ C. The reaction is again exothermic

(Exothermic)

Silicon reacts with carbon slightly exothermic to silicon carbide.

(Exothermic)

On the other hand, silicon carbide can be obtained endothermically directly from sand and carbon at around 2000 ^° C.

(Endothermic)

To from the by-product bauxite resp. Alumina Al ₂ O ₃ again recover aluminum, electrolyzed liquid Al ₂ O ₃ (melting point 2045 ⁰ C) without Kryolithzugabe to aluminum and oxygen. The reaction is highly endothermic and is used to cool the exothermic reactions. 2 Al ₂ O ₃ (I) -> 4 Al (I) + 3 O ₂ (g) Δ H = +1676.8 kJ / mol

(Endothermic)

According to a further embodiment of the invention, a thermite reaction (redox reaction) is used in which aluminum is used as a reducing agent to reduce iron (III) oxide to iron.

Fe ₂ O ₃ + 2 Al -> 2 Fe + Al ₂ O ₃

The reaction products are alumina and elemental iron. The reaction is very exothermic and there is a great deal of heat. The firing process is a highly exothermic reaction and it produces up to 2500 ⁰ C. The aluminum and the iron (III) oxide is therefore liquid due to the temperatures reached.

By means of such a thermite reaction, the reduction of the silicon dioxide to silicon can be initiated or maintained (aluminothermic reduction of silicon dioxide). The silica also becomes liquid. Since burning thermite does not require external oxygen, the reaction can not be stifled and continue to burn in any environment. That Nitrogen can be added at the same time without stopping the reaction and thus producing silicon nitride.

To aid in the conversion of silica to silicon and the conversion ("combustion") to silicon carbide or silicon nitride, from time to time the thermite reaction may be initiated by, for example, introducing aluminum and the ferric oxide.

The production of silicon carbide and silicon nitride from oily sand is described below by way of example. However, this is a specific embodiment of the invention. Production of silicon carbide and silicon nitride from oil sand

1 . Introduction and "formula ^" for Oelsand

The ceramic materials silicon nitride Si ₃ N ₄ and silicon carbide SiC can be obtained from an oil sand containing around 30% by weight of crude oil via a multi-stage process. In order to be able to deal with the chemically very complex mixture of various hydrocarbon compounds, which is known as petroleum, stoichiometrically sensible, is representative of the petroleum formula C ₁₀ H ₂₂ , which actually stands for decane, used. Sand a substance which is exactly described with the Formed SiO ₂ stands with the contained oil in a weight ratio of 70% to 30%. The oil sand is thus described by the formula SiO ₂ + C ₁₀ H ₂₂ in a rough approximation, wherein SiO _{2 has} a molecular weight of 60 g / mol and decane has a molecular weight of 142 g / mol. If one takes up 100 g of oil sand, then there are 70 g of SiO ₂ and 30 g of "decane" or petroleum. If the amounts of SiO ₂ and "decane" contained in it are calculated, SiO _{2 is obtained} :

And for petroleum:

Number of moles multiplied both by 5, one obtains 5.833 mol of SiO ₂ and for C ₁₀ H ₂₂

1,056 mol, which makes up about 6 moles of SiO ₂ per mole of C ₁₀ H ₂₂ . For oil sand, therefore, the formula 6 SiO ₂ + "I" C ₁₀ H ₂₂ can be used to a good approximation.

2. Synthesis path

The representation of silicon nitride Si ₃ N ₄ from oil sand is as follows: First, the oil sand is heated together with Dichlonnethao CH ₁ Oj in a säuhstofflreicn atmosphere at 1000 ⁰ C. In this case, silicon changes the bond and forms silizimimetrachiodd according to equation (I);

In a wide step, the obtained SiuziumchSorid is hydrogenated at room temperature with Lithiumaiuminiumhycϊrid hydrogenated J. 1 J. according to equation (II),

Finally, the resulting MonostLm StH _{f is} burnt in pure nitrogen, equation (UI):

In order to obtain silicon carbide SiC, one could find instead of the energetically very expensive high temperature reaction (equation IV), which takes place at 2000 ° C, also a more energetically favorable reaction path.

It starts again from silicon tetrachloride SiCI ₄ , which is obtained from equation (I), and converts it with graphite or methane:

Or:

3. Stoichiometric calculations

If 1 kg of oil sand is assumed, this contains 700 g of silicon dioxide and 300 g of "decane." Converted into the molar amounts, for silicon dioxide n = 1, 1.16 mol and for "decane" n * 2.1, 1 mol is obtained. I) the following relative molecular weights apply to the compounds:

Since the amount of silicon tetrachloride SiCl _{4 is} the same due to the same stoichiometric factor, 1 kg of oil sand results in an amount of SiCl ₄ of:

Because of the double amount of CO compared to SiO ₂ , a mass of CO results from:

Due to a 10-fold increase in methane Cl U compared to ^" Dtx'atT, a mass is converted

TH _t from:

Because of the half ϊstofϊmenge of Hj compared to Sif K results in a mass of H2 from:

Since in case of U ii), all sttchmmerri pakloron equals one k, it holds

This is:

Since equation (III) is still the initial amount of silica of 11.67 mol instructive, and the amount of substance of S ₃ N ₄ compared to that of SiH _{4 is} one third, applies here:

The amount of substance of N ₂ is 4/3 compared to that of SiH ₄ : from this is calculated for nitrogen a mass of:

Converted to the volume, these correspond to 435.5 g N ₂ with a molar volume of 22.4 liters: V = 348.4 liters N ₂ .

Even with NH ₃ , the amount of substance is 4/3 compared to that of SiH ₄ :

Converted to the volume, these correspond to 264.4gNH ₃ at a molar volume of

22.4 liters in turn: V = 348.4 liters NH ₃ .

For equation (V), finally, the initial amount of substance of 1 1, 67 mol for

Silicon tetrachloride:

Thus: m (SiC) =

CHi) =

On the volume speak these 186.7gCH ₄ at a molar volume of

22.4 liters: V = 261.3 liters CH ₄ ,

If a ton scale is used, the g lbs can be calculated by kg. kg by ton and liters by m ^J ! without ιfaκs the irish value changes ir ^ cndwus. For equation (I) the following thermodynamic quantities apply:

For, the value is calculated as follows:

Equation (I) is thus an endothermic reaction at room temperature, since

For ΔS, the following value is obtained:

The entropy is increased so that equation (I) is favored at least by the driving force of entropy, presumably reacting towards the product side. To answer this question conclusively, the free enthalpy change ΔG has to be calculated, where the formula

For temperature T, the standardized 291 Kelvin are used. Thus, amounts

At room temperature the free enthalpy is positive, which indicates that

Reaction (I) at this temperature, cntlergonically, re

not voluntary. Ultimately, the driving force of entropy does not suffice to shift the reaction towards the product side, since the endothermic contribution of the heat of reaction counteracts this too much.

How does the increase in prices affect you?

and uu us

1300K) and

about the change in heat capacity is isobaric

Conditions calculated

For equation (II) the following thermodinamic quantities apply:

Equation (II) is thus an exothermic reaction since

For the value of the entropy change can not be determined because the Entropieangabe for LiAlH ₄ not found wound [2]. 1 By contrast, this reaction in the Lehrbuch der Anorgische Chemie by Hollemann-Wiberg [1] is spontaneous, resp. described exergonic running, which provides the indication that must be.

For oleoation (IU), the following thcπnodytiamic quantities apply:

Equation (III) is thus an exothermic reaction

For, the following value is obtained:

that is, the reaction never leads an entropieaboali.

At room temperature, the free enthalpy

thus negative, which means that the reaction (III) at this temperature is exergonic, ie completely spontaneous, resp., entirely voluntary without external compulsion. However, because of the activation energy needed to break up the N ₂ molecule, an ignition temperature of about 900 K must still be selected to initiate the reaction, and then the reaction will continue on its own. For equation (V) the following thermodynamic quantities apply:

g (V) is thus an endothermic reaction at room temperature, since

takes place

With

= -

The reaction is both endothermal at room temperature

as well as endergonic oi

The reaction can therefore take place at 1300 Kelvin.

For equation (VI), the following thermodynamic quantities apply:

Equation (IV) is thus an endothermic reaction at room temperature, since

It can therefore not run off at room temperature. What does it look like at a temperature of 1300 Kelvin?

AG (1300K) +378.5 kJ / mol, the reaction remains unchanged at 1300 K endergonic.

This last reaction demonstrates in a demonstrative way that not every equilibrium can be shifted to the other ropes with a temperature increase, occasionally everything remains the same and the proposed reaction path must be discarded. At least this happens in this reaction.

5. Summary

The synthetic route described in Chapter 2 can be carried out with the proposed reaction equations if the corresponding thermodynamically favorable temperatures are observed, reaction (VI) being the exception because it can not take place at any of the calculated temperatures. This distinguishes a clear synthetic route for the preparation of silicon nitride Si ₃ N ₄ and silicon carbide SiC, which will be described again below, supplementing the necessary operating temperatures. First, the oil sand is heated to 1300 Kelvin (1000 ° C) together with dichloromethane CH ₂ Cl ₂ in an oxygen-free atmosphere. In this case, silicon changes the binding partner and forms silicon tetrachloride according to equation (I):

In a broad text, the resulting succinic chloride is hydrogenated at room temperature with alJthiumalutniniumh> drid [I], according to equation (II),

Schlϊesslich w ill the resulting Munosilan SiJ i ₄ combusted in pure nitrogen "öleichung (Hi U wherein the / tiiyiemperatur \ ^ ay of JUΓ Λufbrcchung of Stick & totTmpleköls benörigten Aktivicrungsencrgie peeling / ungjjweise 60Λ K higher than the room temperature

ItttISS '

In order to obtain silicon carbide Sic, it starts again from silicon tetrachloride SiCl ₄ , which is obtained from equation (I) and converts it with methane at 1300 K:

Instead of the monosiktis obtained in equation Cl), it is also possible to obtain higher silyl chlorides by polymerization reactions of SiClj and also higher silanes by the subsequent hydrogenation with LiAlH *, as shown by the following reaction equations:

Higher silanes (from Si ₇ H ₁₆ ) have the advantage that they are no longer self-igniting and can be burned much more controlled than SiH ₄ . Accordingly, combustion with pure nitrogen is preferred when higher silanes arrive at this reaction.

The production of silicon carbide and silicon nitride from oily sand is described below by way of example with reference to a further exemplary embodiment. However, this is a specific embodiment of the invention. 1) combustion of oil sand:

To capture oil sand approximately stoichiometrically, with the chemically manageable formula

worked

The following thermodynamic quantities apply to equation (I) or (II):

reduced:

For ΔH the value is calculated as follows:

Equation (i) is thus a clearly exothermic reaction at room temperature, since

2) Reduction of silica with aluminum:

For equation (III), the following thermodynamic quantities apply:

Equation (II) is thus an exothermic reaction at 25 °

3) combustion of silicon with nitrogen:

For equation (IV), the following thermodynamic quantities apply:

Equation (III) is thus a 25 ° C exothermic reaction there

4) Reduction of alumina (bauxite) to aluminum:

For equation (V), the following thermodynamic quantities apply:

Equation (IVj is thus a very strongly endothermic reaction at room temperature, since

5} Energy balances for the cycle for m * s at 25 ° C (298 K):

HM thus remains an exothermic heat exchanger at room temperature in the course of room temperature

5'384 IcJ left.

The production of silicon carbide and silicon nitride may also be combined as follows. This elemental silicon, which is produced in a reduction process (eg by adding aluminum to silicon dioxide) used. A portion of the silicon may be used to bind carbon dioxide resulting, for example, from heating the silica solids. This bonding process produces silicon carbide and CO ₂ silicon carbide in a slightly exothermic process. The rest of the silicon can be reacted with nitrogen gas as a reactant to silicon nitride. This process is highly exothermic.

Part of the heat energy generated in these exothermic processes can be used to prepare the reductant. For example, the energy can be used to make aluminum (with heat and / or power) from alumina. The processes are preferably spatially separated.

The inventive processes are characterized by the fact that they are in can advantageously be used to combine the different substances that are formed so that ALON (a lighter and more transparent material) can be produced. The powdery materials are mixed and heated to produce ALON.

Claims

claims:

A method of providing silicon solid compounds from silica solid compounds, preferably sand, comprising the steps of: a) introducing the silica solid compound into a firing zone, b) heating the firing zone together with the silica solid compound, c) converting silica from the silica solid compound into silicon (Si ₂ d) injecting a gaseous reactant to produce the silicon solid compound from the silicon (Si ₂ ); e) employing a portion of the heat energy released upon production of the silicon solid compound; to provide the reducing agent in a reduction process.

2. The method of claim 1, wherein the silicon compound is silicon nitride (Si ₃ N ₄ ) and nitrogen, preferably nitrogen radicals, in step d) serve as a gaseous reactant.

3. The method of claim 1, wherein the silicon compound is silicon carbide and gaseous CO ₂ , in step d) serves as a gaseous reactant.

4. The method of claim 1, 2 or 3, wherein in step c) liquid or powdered aluminum is supplied as a reducing agent.

5. The method according to claim 4, wherein in a previous or simultaneous running step, the liquid or powdered aluminum from bauxite or Al ₂ O _{3 is} provided.

6. The method of claim 2, wherein atomic oxygen is used to radicalize the nitrogen.

7. The method of claim 2, wherein the reaction to form the silicon nitride (Si ₃ IM ₄ ) is highly exothermic and the resulting waste heat is used to generate electricity.

8. The method of claim 7, wherein the resulting waste heat in an adjacent zone for melting of Al ₂ O ₃ (eg from bauxite) is used.

9. The method according to any one of the preceding claims, wherein various endothermic and exothermic reactions are thermally coupled.

10. The method according to any one of the preceding claims 1 to 9, wherein one or more of the steps are carried out in a pyrolysis furnace.

11. The method of claim 10, wherein the pyrolysis furnace is provided with a high temperature resistant coating.