The subject of the invention consists of the method of obtaining ternary chemical compounds based on iron oxide and copper oxide used in the processes of chemical oxygen transport in chemical looping fuels combustion or gasification.

Requirements related to carbon dioxide and nitrogen oxides emission reduction cause a significant intensification of research on the application of chemical looping combustion and gasification processes. The application of solid oxygen carriers in processes of chemical looping combustion or gasification enables carrying out the process with the use of pure oxygen, which transfer proceeds due to a permanently circulating bed of an oxygen carrier obtained on the basis of metal oxides. Because of the application of chemical looping combustion or gasification there is no nitrogen in the flue gas, contrary to conventional methods of energy generation from fossil fuels; this results in the lack of nitrogen oxides emission, substantially facilitates carbon dioxide capture and considerably reduces the flue gas volume.

Many possible oxygen carriers are known, including various compositions of copper, cobalt, manganese, iron or nickel oxides used as active materials and aluminium oxide, titanium oxide, zirconium oxide, silicon oxide, zirconium-stabilised yttrium used as an inert material. Inert materials are added at the amount from a few to a few dozen wt.% in relation to the active material, due to which the oxide carriers life is extended, inter alia via the reduction of their abrasion.

The chemical looping was initially used for the process of gaseous fuels combustion; later on it was expanded onto solid fuels combustion (including biomass and coal).

The paper "Characterisation of oxygen carriers for chemical looping combustion" published during the Seventh International Conference in Vancouver, Canada in 2004 shows that the use of oxygen carriers consisting of one active and one inert component is known. While the known methods of oxygen carriers obtaining for chemical looping are based on one-stage process of calcination most often not exceeding the period of 6 hours. French patent description No FR 2 923 035 presents a preparation, which is an oxygen carrier consisting of one active and one inert oxide. This preparation contains from 5 to 20% of graphite; moreover, the process of calcination is performed in one stage at a temperature between 650 and 1050 °C during 3 to 9 hours.

Patent application No P-389853 and additional patent P-391770 present a method for producing ternary chemical compounds based on iron oxide and manganese oxide used in the processes of chemical oxygen transport for chemical looping fuels combustion or gasification. The method of obtaining ternary chemical compounds based on iron oxide and manganese oxide, consisting in mixing the initial components, calcination of the mixture at a high temperature, acc. to the invention is characterised by the fact that powdered graphite at the amount of 1 to 25 wt.% in relation to the initial mixture is added to the initial components in the form of Fe ₂ 03 and Mn0 ₂ and an inert material, used in proportions resulting from a general chemical formula∑ (¾e203 + Ϊ Μηθ2 + -Zinert material) = 100 wt.%, where X and Y are within the ranges l≤x<99, l≤y<99 and the inert material is used at the amount supplementing to 100 wt.%, and the whole is subject to at least one-stage calcination in an oxidising atmosphere at a temperature of 600 - 1500 °C during 3 to 24 hours.

The invention is aimed at the method of obtaining ternary chemical compounds based on iron oxide and copper oxide, useful for the process of oxygen transport in chemical looping, of more favourable reactivity parameters and primarily of improved oxygen transport capacity and of lower agglomeration tendency.

The method of obtaining ternary chemical compounds based on iron oxide and reactive oxide carriers as well as inert materials and carbon carriers, consisting in mixing the initial components, calcination of the mixture at a high temperature, acc. to the invention is characterised by the fact that powdered carbon carrier at the amount of 1 to 25 wt.% in relation to the initial mix is added to the initial components in the form of Fe ₂ 03 and CuO and an inert material, used in proportions resulting from a general chemical formula∑ (¾e203 + F _Cu o + -Zinert material) = 100 wt.%), where X and Y are within the ranges l≤x<99, l≤y<99 and the inert material is used at the amount supplementing to 100 wt.%, and the whole after blending is subject to at least one-stage calcination in an oxidising or inert atmosphere at a temperature of 400 - 1100 °C during 3 to 24 hours. What is favourable, the input components with a carbon carrier are subject to at least two-stage calcination in an oxidising or inert atmosphere at the temperature of 850 °C during 24 hours.

What is favourable, the inert material consists of sepiolite and/or bentonite and/or kaolin and/or Zr0 ₂ and/or Ti0 ₂ and/or A1 ₂ 0 ₃ and/or Si0 ₂ or any mixture of them.

What is favourable, X assumes values of 20, 30, 40, 60 wt.% and Y assumes values of 60, 50, 40, 20 wt.%.

What is favourable, powdered graphite is the carbon carrier.

What is favourable, 10 wt.% of powdered graphite are added to the mix.

What is favourable, powdered active carbon, peat, hard and brown coal, graphite, anthracite, petroleum coke, pitch-derived carbon materials, fullerene or any mixture of them are the carbon carrier.

What is favourable, the inert material consists of inorganic heat-resistant minerals or their mixture.

What is favourable, bentonite or sepiolite or kaolin or any mixture of them is the inert material.

What is favourable, once the process of high-temperature calcination is completed the process of controlled cooling at a temperature decrease rate from 1 °C/minute to 1000 °C/minute is carried out.

What is favourable, the input components consist of chemical compounds containing iron and copper, from which iron and copper oxides are obtained as a result of calcination in an oxidising or inert atmosphere.

The basic merit of the invention is the fact that from metal oxides due to the mechanical mixing and calcination of the oxide materials are obtained, which are oxygen carriers featuring better capacity of oxygen transport, more favourable parameters of reactivity with fuel (in the combustion/gasification reaction) and with oxygen from the air (at the stage of carrier regeneration) as compared with the solutions known from the state of the art. Using the method of the invention an oxygen transfer capacity at the amount of 4 - 20 wt.% was obtained as well as the melting point in a reducing atmosphere above 1300 °C.

This was achieved because of using two active components and one inert component, which are the basic components of the oxygen carrier. The use of such system enabled primarily the obtaining of more perfect oxide materials by increasing their reactivity with fuel (in the combustion/gasification reaction) and increasing their life due to reducing their abrasion and weakening their tendency to agglomerate.

The obtained oxide materials are used as solid oxygen carriers in chemical looping processes.

The obtained oxide materials may be used for fuels conversion in chemical looping, inter alia in the process of combustion and gasification of: gaseous fuels, including e.g. hydrocarbon fuels, natural gas; hydrocarbon liquid fuels; solid fuels, e.g. hard coal, lignite, plastic waste, biomass and biodegradable waste; and may be intended as a structural material of membranes applicable in 0 ₂ separation from N ₂ in the temperature range of 400 - 1500 °C; and applicable in processes of solid and liquid fuels conversion by partial oxidation in membrane reactors.

Moreover, they enable carrying out thermochemical reactions in lower temperature ranges. In general, complex oxygen carriers feature a better reactivity.

The method of manufacturing acc. to the invention is simple in the practical application and gives repeatable results, enables obtaining oxygen carriers for chemical looping purposes with a possibility of free mixing of active and inert components of the input products, which is not ensured by other methods, e.g. impregnation, because in this respect they are very limited by the amount of active component fed, frequently up to the amount of ca. 20 wt.%.

Appropriate calcination, with adequately chosen calcination time and temperature, enables increasing the oxide product life due to reducing its abrasion and favourable weakening its tendency to agglomerate and increasing the homogeneity of the end product obtained. Thereby this has a favourable impact on the costs of fuels combustion or gasification processes, which are reduced due to their increased reactivity and life. In addition, the use of inorganic heat-resistant minerals and chemical compounds containing iron and/or copper ensured the improvement to the economic efficiency. The graphite addition to the blend caused that during calcination at the temperature of 850 °C in the air atmosphere it is subject to oxidation to carbon dioxide, which release results in an increase in: the specific surface, the conversion and the reaction rate.

The selection of components' proportions is related to the obtaining of valuable, for chemical looping, oxides properties taking into account the reduction of their production costs.

The method acc. to the invention has been described in non-restrictive examples of implementation.

The following components have been used as raw materials to obtain oxygen carriers: Fe ₂ 0 ₃ (purity > 99%), CuO (purity > 99%), bentonite, sepiolite, A1 ₂ 0 ₃ (purity > 99.7%), Ti0 ₂ (purity 99%), Zr0 ₂ (purity 99%), Si0 ₂ (purity 99%), synthetic graphite.

Example 1

The method of obtaining ternary chemical compounds consists in mixing 60 g of Fe ₂ 0 ₃ , 20 g of CuO, 20 g of sepiolite and 10 g of graphite. The components were rubbed with distilled water till obtaining the grain size below 100 μιη. After drying the blend was calcined. The calcination was carried out during 24 hours at the temperature of 850 °C. Then the blend obtained was milled again and calcined at the temperature of 850 °C during 24 hours. As a result, a sample was obtained of composition of 60 wt.%> of Fe ₂ 0 ₃ , 20 wt.% of CuO, 20 wt.% of sepiolite.

The oxygen carriers obtained in this way feature:

- high oxygen transport capacity of 19.03% at the temperature of 950 °C (Table 1),

- specific surface BET of 7.4 m ² /g and mean value of pores diameter equal to 8.8 nm,

- low abrasion index, AI = 3.5%,

- good regeneration capacity (Fig. 1),

- repeatability of results,

- the fact that the optimum range of preparation action falls within the temperature range of 400 - 1300 °C, where the application of mineral in the form of sepiolite has especially favourable impact on increasing the oxygen transport capacity at lower temperatures in relation to commonly used inert materials, e.g. in the form of A1 ₂ 0 ₃ (Table 1), - high thermal resistance; the melting point in a reducing atmosphere amounted to 1440 °C,

- low tendency to agglomerate, because 90% of the material produced was a fraction < 616 μιη and 50% was a fraction < 237 μιη,

- short oxidation and reduction time, where 80% of fraction is oxidised during 2.46 minutes, reduced during 8.56 minutes for hydrogen and oxidised during 4.3 minutes after previous reduction with carbon (Table 2),

- higher and hence more favourable oxygen transport capacity as compared to adequate binary oxygen carrier (Fig. 8),

- more favourable kinetics of the combustion reaction e.g. of carbon than in the case of using adequate binary oxygen carrier (Fig. 8), where the reaction of coal combustion in oxygen released from the oxygen carrier structures, with the applied 20%> CuO addition, proceeds approx. 1.7 times faster,

- 100% regeneration capacity after the reaction of gaseous and solid fuels combustion, e.g. hydrogen and coal (Fig. 4, Fig. 8)

- using coal as fuel no problems of oxygen carrier deactivation with soot was observed,

- application of a system, at least ternary, as compared with conventionally used binary, had a favourable impact on increasing the fuel combustion reaction rate (Fig. 8)

Example 2

The method of obtaining ternary chemical compounds consists in mixing 60 g of Fe ₂ 0 ₃ , 20 g of CuO, 20 g of bentonite and 10 g of graphite. After the components mixing the blend was twice calcined during 24 hours, where the calcination temperature amounted to 1050 °C. As a result, a sample was obtained of chemical composition 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% of CuO, 20 wt.% of bentonite.

The oxygen carriers obtained feature:

- high oxygen transport capacity of 18.61% at the temperature of 950 °C (Table 1),

- higher and hence more favourable oxygen transport capacity as compared to adequate binary oxygen carrier (Fig. 7.), - more favourable kinetics of the combustion reaction e.g. of coal than in the case of using adequate binary oxygen carrier (Fig. 7), where the reaction of coal combustion in oxygen released from the oxygen carrier structures, with the applied 20% CuO addition, proceeds approx. 1.2 times faster,

- specific surface BET of 1.4 m ² /g and mean value of pores diameter equal to 7.2 nm,

- short oxidation and reduction time, where 80% of fraction is oxidised during 2.6 minutes, reduced during 7.88 minutes for hydrogen and oxidised during 3.88 minutes after previous reduction with carbon (Table 2),

- 100% regeneration capacity after the reaction of gaseous and solid fuels combustion, e.g. hydrogen and coal (Fig. 4., Fig. 7),

- high thermal resistance; where the melting point in a reducing atmosphere amounted to 1430 °C,

- the scope of the compound use is optimal in the temperature range of 400 - 1300 °C,

- low tendency to agglomerate, where 90% of the material produced was a fraction < 642 μιη and 50% was a fraction < 200 μιη,

- repeatability of results.

These advantages have been confirmed by product analyses, including investigations of: thermogravimetry coupled with a quadrupole mass spectrometer, X- ray diffraction on powder specimens, melting points, abrasion tests using a fluidised bed reactor, grain size distribution measurements, BET specific surface and pore size distribution measurements.

The manufacture methods specified guarantee that the conversion of substrates used ranges from 80 to 100%.

The oxygen transport capacity, as a characteristic parameter of an oxygen carrier, is defined as the mass difference between oxidised and reduced form of solid oxygen carrier. In practice it stands for the amount of oxygen released by the carrier from its structure and transferred to the fuel.

To determine the oxygen transport capacity of the obtained solid oxygen carriers (Table 1) based on transition metals cyclic tests in oxidising (synthetic air) and reducing (3% hydrogen, hard coal from Janina colliery featuring favourable physicochemical parameters) conditions were carried out by means of coupled TG-MS technique using a Netzsch STA 409 PC Luxx thermobalance coupled with an Aeolos QMS 403C quadrupole mass spectrometer, where the mass spectrometry was used to control substrates and to identify the flue gases.

The process of chemical looping was simulated this way using a thermogravimetric analysis. What's more, the reactivity tests were carried out versus temperature.

For example, Fig. 1 gives results of cyclical thermogravimetric examinations for a sample of 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% of CuO, 20 wt.% of sepiolite, performed versus temperature from the range of 700 - 950 °C.

Table 1 presents the oxygen transport capacity versus the composition and temperature for selected ternary oxygen carriers based on iron and copper oxide. Table 2 includes examples of estimated, at the temperature of 950 °C, both regeneration and reduction periods for oxygen carrier examples.

Table 1. Oxygen transport capacity versus the chemical composition of solid oxygen carriers

Oxygen carrier Temperature (°C)

700 800 900 950

Oxygen transport capacity (wt.%>)

60 wt.% of Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.% Si0 ₂ 15.40 15.45 18.21 18.52

60 wt.% Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.% A1 ₂ 0 ₃ 15.25 14.28 18.46 19.31

60 wt.% of Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.% Ti0 ₂ 16.54 16.44 19.25 19.94

60 wt.% Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.% sepiolite 16.19 16.13 18.59 19.03

60 wt.% Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.% bentonite 16.96 17.09 18.94 18.61 Table 2. Time necessary to reach preset conversion at the temperature of 950°C

Conversion Regeneration time Reduction time

(%) (min) (min)

Fe ₂ 0 ₃ - Cu0 / Sepiolite

50 2.07 4.02

80 2.46 8.56

100 4.7 19.88

Fe ₂ 0 ₃ - CuO / Si0 ₂

50 2.14 5.00

80 2.81 10.45

100 4.79 22.71

Fe ₂ 0 ₃ - CuO / Al ₂ 0 ₃

50 2.11 5.00

80 2.79 9.54

100 5.0 22.66

Fe ₂ 0 ₃ - CuO / Bentonite

50 1.92 3.87

80 2.6 7.88

100 4.18 19.49

Fe ₂ 0 ₃ - CuO / Ti0 ₂

50 1.87 4.73

80 2.54 11.66

100 4.15 25

Example 3

The method of obtaining ternary chemical compounds consists in mixing 60 g of Fe ₂ 03, 20 g of CuO, 20 g of Ti0 ₂ and 10 g of graphite. The components were rubbed with distilled water till obtaining the grain size below 100 μιη. After drying the blend was calcined. The calcination was carried out during 20 hours at the temperature of 850°C. Then the blend obtained was milled again with 10 g of graphite and calcined at the temperature of 850°C during 24 hours. As a result, a sample was obtained of composition of 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% of CuO, 20 wt.% of Ti0 ₂ .

The oxygen carriers obtained in this way feature:

- high oxygen transport capacity of 19.94% (at the temperature of 950 °C),

- higher and hence more favourable oxygen transport capacity as compared to adequate binary oxygen carrier (Fig. 10), - more favourable kinetics of the fuel combustion reaction e.g. of coal than in the case of using adequate binary oxygen carrier (Fig. 10), where the reaction of coal combustion using oxygen released from oxygen carrier structures, with the applied addition of 20% of CuO proceeds slightly faster,

- specific surface BET of 0.4 m ² /g and mean value of pores diameter equal to 6.2 nm,

- good capacity of regeneration,

- repeatability of results,

- the fact that the optimum range of preparation action falls within the temperature range of 600 - 1350 °C,

- high thermal resistance; the melting point in a reducing atmosphere amounted to:

1440 °C,

- low agglomeration tendency, because 90% of the material produced was a fraction < 772 μιη and 50%> was a fraction < 212 μιη,

- short oxidation and reduction time, where 80% of fraction is oxidised during 2.54 minute, reduced during 11.66 minutes for hydrogen and oxidised during 4.02 minutes after previous reduction with carbon (Table 2),

- 100%) regeneration capacity after the combustion reaction of gaseous fuels (e.g. hydrogen) (Fig. 4) and of solid fuels (e.g. coal) (Fig. 10)

Example 4

The method of obtaining ternary chemical compounds consists in mixing 60 g of Fe ₂ 03, 20 g of CuO, 20 g of AI ₂ O ₃ and 10 g of graphite. The components were rubbed with distilled water till obtaining the grain size below 100 μιη. After drying the blend was calcined. The calcination was carried out during 8 hours at the temperature of 850 °C. Next the blend obtained was milled again with 10 g of graphite and calcined at the temperature of 850 °C during 24 hours. Then the blend obtained was milled again with 10 g of graphite and calcined at the temperature of 850 °C during 24 hours. As a result, a sample was obtained of composition of 60 wt.%> of Fe ₂ 03, 20 wt.%> of CuO, 20 wt.%> ofAl ₂ 0 ₃ .

The oxygen carriers obtained in this way feature:

- high oxygen transport capacity of 19.31% (at the temperature of 950 °C), - higher and hence more favourable oxygen transport capacity as compared to adequate binary oxygen carrier (Fig. 6),

- more favourable kinetics of the combustion reaction e.g. of coal than in the case of using adequate binary oxygen carrier (Fig. 6) where the reaction of coal combustion with the applied 20% addition of CuO proceeds approx. 1.7 times faster,

- specific surface BET of 0.5 m ² /g and mean value of pores diameter equal to 6.3 nm,

- good regeneration capacity (Fig. 2.),

- repeatability of results,

- the fact that the optimum range of the preparation action falls within the temperature range of 600 - 1600 °C,

- high thermal resistance; the melting point in a reducing atmosphere amounted to: > 1650 °C,

- low agglomeration tendency, because 90% of the material produced was a fraction < 608 μιη and 50%> was a fraction < 189 μιη,

- short oxidation and reduction time, where 80%> of fraction is oxidised during 2.79 minutes, reduced during 9.54 minutes for hydrogen and oxidised during 4.64 minutes after previous reduction with carbon,

- 100% capacity of regeneration, after the combustion reaction of hydrogen (Fig. 4) and coal, no problem of deactivation with soot was observed (Fig. 6).

The following graphs present the obtained results of examinations, of which:

Fig. 1 - Results of cyclic thermogravimetric examinations 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% CuO, 20%) wt.%) of sepiolite, using hydrogen as the fuel,

Fig. 2 - Results of cyclic thermogravimetric examinations 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.%) of A1 ₂ 0 ₃ , using hydrogen as the fuel,

Fig. 3 - Results of cyclic thermogravimetric examinations 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.%) of Si0 ₂ , using hydrogen as the fuel,

Fig. 4 - Oxidation ability (regeneration) of examples of oxygen carriers based on iron oxide and copper oxide, Fig. 5 - Reduction ability of examples of oxygen carriers based on iron oxide and copper oxide, depending on the inert material used,

Fig. 6 - Results of thermogravimetric examinations of coal combustion in oxygen released from oxygen carriers of the following composition: 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.% of AI ₂ O ₃ and 80 wt.% of Fe ₂ 0 ₃ , 20 wt.% of A1 ₂ 0 ₃ ,

Fig. 7 - Results of thermogravimetric examinations of coal combustion in oxygen released from oxygen carriers of the following compositions: 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% of CuO, 20 wt.% of bentonite and 80 wt.% of Fe ₂ 0 ₃ , 20 wt.% of bentonite,

Fig. 8 - Results of thermogravimetric examinations of coal combustion in oxygen released from oxygen carriers of the following compositions: 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% of CuO, 20 wt.% of sepiolite and 80 wt.% of Fe ₂ 0 ₃ , 20 wt.% of sepiolite,

Fig. 9 - Results of thermogravimetric examinations of coal combustion in oxygen released from oxygen carriers of the following compositions: 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% CuO, 20 wt.% of Si0 ₂ and 80 wt.% of Fe ₂ 0 ₃ , 20 wt.% of Si0 ₂ ,

Fig. 10 - Results of thermogravimetric examinations of coal combustion in oxygen released from oxygen carriers of the following compositions: 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% of CuO, 20 wt.% of Ti0 ₂ and 80 wt.% of Fe ₂ 0 ₃ , 20 wt.% of Ti0 ₂ ,

Marking:

Symbols + used in Fig. 1-3. and Fig. 6-10 stand for temperature.

Dash lines were used to mark the reaction rate, where the black colour was used for a ternary system and grey for a binary oxygen carrier. In turn, solid lines mean a change of mass versus temperature or time, where the grey colour was used for a binary system, e.g. 80 wt.%), 20 wt.%) of Ti0 ₂ , and the black colour for a ternary system, e.g. samples of the composition: 60 wt.% of Fe ₂ 0 ₃ , 20 wt.% of CuO, 20 wt.% of Ti0 ₂ .