DE102010061853A1 - Reducing tar content of combustible raw gases from biomass gasification, comprises e.g. supplying combustible raw gases over molded body of catalyst-oxygen carrier, and condensing tar components of combustible raw gases on surface of body - Google Patents

Abstract

Reducing the tar content of combustible raw gases from biomass gasification, comprises supplying the combustible raw gases over a molded body of catalyst-oxygen carrier, condensing the tar components of the combustible raw gases on the surface of the molded body and partially oxidizing the condensed tar components by oxygen supply to the molded body. An independent claim is also included for a system for reducing the tar content of raw gases of biomass gasification, comprising at least two reactors (R1, R2) filled with molded body of catalyst-oxygen carrier, where (a) the reactors respectively comprises a raw gas supply pipeline, a clean gas outlet, an air inlet- and an air outlet pipeline, (b) the gas pipelines are closable in a controlled manner y means of valves, (c) the reactors and the gas pipeline comprise a sensor for determining the gas composition, and (d) the reactors for reducing the tar content by means of the molded body and for the regeneration of used molded body are alternately loaded with raw gas or air.

Description

The invention relates to a method and a plant for purifying Brennrohgasen the biomass gasification, in particular for reducing the tar content in the raw fuel gas, the tars are partially reacted with oxygen and catalytically supported in carbon monoxide and hydrogen and the oxygen required for the partial oxidation directly from the system is won.

During the gasification of solid biomass, a combustion raw gas is produced which, depending on the type of biomass and the gasification conditions, has different concentrations of undesirable higher molecular weight hydrocarbons. Such designated as tar hydrocarbon mixtures are deposited before or in the engine and lead to high maintenance and repair costs or to limit the life of the equipment.

Due to incomplete gasification reactions and side reactions higher boiling hydrocarbons (tars), phenols and carbon are formed, which represent a further use of the gas - apart from the direct stationary combustion - serious interference components.

On the one hand, there is the possibility of reducing the tar content in the gasification gases by primary measures. Ie. Measures are carried out directly in the gasification process, which guarantee the lowest possible exit concentration of tar in the gas. The process can be controlled by the main main influencing variables temperature, gasification agent, pressure and residence time in connection with the apparatus technical execution. As another example of a primary measure, the use of catalytically active materials, especially in a fluidized bed, is possible.

For the production of a low-tar or fuel-free fuel gas, primary measures alone are not always sufficient. Physical and chemical methods are available as secondary measures for fuel gas treatment from biomass gasification plants.

Physical methods include gas scrubbing with aqueous media, gas scrubbing with organic media, deposition by means of a fixed bed filter, and wet electrostatic precipitation.

The chemical methods include cracking, hydrogenation, steam reforming and partial oxidation. All chemical methods can be supported with the use of a catalyst.

A number of processes with internal heating by partial oxidation of the tars are known from the prior art.

Known methods for the catalytic partial oxidation of hydrocarbons work with air as the oxidant or produced in air separation plants oxygen.

Main application of catalytic partial oxidation is the synthesis gas production from z. As methane, natural gas or liquid feeds.

The use of catalytic partial oxidation as a possibility of tar reduction in combustion raw gases from biomass gasification and the results of experimental investigations have been widely published: (a) Jönsson, O .: Thermal Cracking of Tars and Hydrocarbons by Addition of Steam and Oxygen in the Cracking Zon ;. In: Overend, RP; Milne, TA; Mudge, LK (ed.), Fundamentals of Thermochemical Biomass Conversation. London and New York: ElsevieR 1985 p. 733 ff ; (B) Jensen, PA, Larsen, E., Jorgensen, KH: Tar Reduction by Partial Oxidation. 9th European Bioenergy Conference Copenhagen 1996 p. 1371 ff ; (C) Brandt, P .; Henriksen, U .: Decomposition of tar in pyrolysis gas by partial oxidation and thermal cracking. 10th European Conference and Technology Exhibition Biomass for Energy and Industry. Wuerzburg 8-11 June 1998. p. 1616 ff ; (D) Draelants, DJ, Zhao, H., Baron, GV: Preparation of catalytic filters by the urea method and its application for benzene cracking in H2S-containing biomass gasification gas. Industrial & Engineering Chemistry Research 40 (15); 3309-3316; 2001 ; (E) Institute for Energy and Environmental Technology e. V; FEM Research Institute for Precious Metals and Metal Chemistry: Catalytic oxidation of hydrocarbons using noble metal catalysts based on coated metal shavings. AiF project. 2004 ; (F) Wang, CG; Wang, TJ; Ma, LL; Gao, Y .; Chuang Zhi Wu, CZ: Partial oxidation reforming of biomass fuel gas over nickel-based monolithic catalyst with naphthalene as model compound. Korean Journal of Chemical Engineering 25 (738-743). 2008 ,

From the use of air as an oxidizing agent resulting from the relatively high proportion of nitrogen supplied on the one dilution of the fuel gas (calorific value) and on the other cooling effects in the overall system, which by an internal heating on the partial combustion of the gas components carbon monoxide and hydrogen or by external heating in the form of z. B. electrical energy must be balanced to thus to ensure the temperatures required for the partial oxidation in the system.

The use of oxygen-enriched air or pure oxygen increases the energy and technological effort in the overall plant concept.

Out JP 2008-238012 is a method for tea reduction from gases of biomass gasification known. Here, the hot Brennrohgas is passed at over 850 ° C via a perovskite catalyst. Although the decomposition of tar constituents in the hot combustible gas, including the reduction of sulfur-containing gases, is called for, the catalyst will tend to promote the chemical conversion of energetically more readily available gas constituents, e.g. For example, the oxidation of CO as the selective reduction of tar load. This procedure also leads to the reduction of the calorific value of the fuel gas by complete oxidation of gas components and increasing the CO ₂ content.

In DE 198 36 824 A1 A method and apparatus for converting a hydrocarbon-containing stream by partial oxidation is described. Target is a stream containing hydrocarbons, eg. As natural gas to convert into a synthesis gas. The oxygen required for the partial oxidation is generated by means of air separation with cryogenic distillation. The oxygen is in liquid form with a purity of 95% and must be compressed for use in the partial oxidation to 36 bar and vaporized in a heat exchanger in the heat exchange with air at a compressor pressure of 70 bar.

The oxidant is in most applications centered at one point fed to the process, usually at the entrance of the raw combustion gas. With this process, the disadvantage arises that the chemical reactions in the system can not be influenced, since the oxygen then reacts with the corresponding components depending on the prevailing temperature. Since in Brennrohgas in addition to the hydrocarbons, other combustible components are present, the various fuel gas constituents react with the oxygen according to the equilibrium position of the corresponding reactions, so that there are undesirable reactions between z. B. the carbon monoxide and oxygen leads to carbon dioxide.

The object of the present invention is to provide a method and a plant for the economic reduction of the tar load in Brennrohgasen the biomass gasification. The tar-reduced gases are to be used energetically and have a calorific value which corresponds at least to that of the tar-rich combustible natural gas.

According to the invention the object is achieved by a method for reducing the tar content of Brennrohgasen the biomass gasification, in which the raw gas is passed over shaped bodies of catalyst oxygen carriers that condense the Teerbestandteile of Brennrohgases on the surface of the moldings and the condensed tar constituents by oxygen release of the moldings partially oxidize.

The moldings are formed from catalyst-oxygen carrier materials which are functionally capable of incorporating and expanding oxygen under defined operating conditions. Thus, the catalytic activity of the material used and the oxygen supply for the partial oxidation of hydrocarbons are coupled together.

With the use of shaped bodies of catalyst-oxygen carrier materials, the oxygen required for the partial oxidation is selectively provided under in-situ conditions in the tar reduction reactor.

In addition to the function of providing oxygen, the oxygen carrier has the task of serving as carrier material for the catalytically active component. The catalytically active component brings about the reduction of the activation energy required for the reactions of the partial oxidation of the tars, so that the temperatures in the reaction system can be substantially lower than in the process without using a catalyst.

Perovskites or perovskite compounds of the type ABO _3-δ with A = La, Ba, Sr and / or Ca are preferred as catalyst-oxygen carrier materials; B = Ti, Cr, Mn, Fe, Co, Ni, Al, Zr, Nb, Al, Sn and / or Ce). Perovskites or the perwoskite compounds are good oxidation catalysts and thermally very stable. To reduce the activation energy, these materials contain a catalytically active component.

Particular preference is given to using perovskite compounds as the oxygen storage material, selected from Ca _0.5 Sr _0.5 Fe _0.2 Mn _0.8 O _3-δ ; Ca _0.5 Sr _0.5 Fe _0.5 Mn _0.5 O _3-δ ; Sr ₃ Fe ₂ O _{6 + δ} ; Sr _2.25 Ca _0.75 Fe ₂ O _{6 + δ} , Sr _1.5 Ca _1.5 Fe ₂ O _{6 + δ} ; Sr _0.75 Ca _2.25 Fe ₂ O _{6 + δ} or Ca ₃ Fe ₂ O _{6 + δ} .

The catalytic active component is a metallic component, e.g. As Ni or Co, or a metal oxide compound selected from LaCoO _3-δ , LaFeO _3-δ , LaMnO _3-δ , La _0.8 Sr _0.2 FeO _3-δ or NiO.

Advantageously, the shaped bodies are kept at a temperature of 200 to 250 ° C. before the partial oxidation.

According to an advantageous embodiment, the method for purifying Brennrohgasen from the biomass gasification using at least two reactors, which are filled with shaped bodies of catalyst oxygen carriers, out so that the reactors several times mutually to the partial oxidation of condensed tar constituents of the Rohrohgases means of the moldings, by passing the raw combustion gas over the moldings, and to regenerate or reoxidize spent moldings by passing air or oxygen-enriched air over the spent moldings.

Advantageously, the fuel raw gas is passed over the moldings of the first reactor such that the tar constituents of the raw combustion gas condense on the surface of the moldings and partially oxidize the condensed tar constituents by releasing oxygen from the moldings. Before the oxygen of the shaped bodies of the first reactor has been used up, the stream of raw fuel gas is passed via the shaped bodies of the further reactor for the condensation and partial oxidation of the condensed tar constituents.

The spent moldings of the first reactor are regenerated by supplying air for renewed admission with raw combustion gas, so that before consuming the oxygen of the shaped body of the second reactor, the Brennrohgasstrom can be passed through the regenerated moldings of the first reactor and regenerated by air supply the spent moldings of the second reactor become.

Advantageously, bulk reactors are used as reactors. In these reactors are shaped bodies of catalyst oxygen carriers, which are reduced or reoxidized (regenerated) depending on the operating cycle.

For technical application, the catalyst-oxygen carrier system can be constructed of different moldings, D. h. from uniformly shaped bodies (eg honeycombs), but also from divergent shapes. In this case, the highest possible density of shaped bodies is provided in the bed together with a large active surface area for the physical and chemical processes characteristic in the system.

The process according to the invention consists of the sub-processes reduction process and reoxidation process. Both processes take place alternately in one of the reactors.

The reduction process is the actual sub-process of raw gas tannification. The reoxidation process serves to regenerate the catalyst-oxygen carrier materials of the moldings.

Before the initial start-up, the catalyst oxygen carrier shaped bodies are in the oxygen-loaded state in the reactors and are preheated to a temperature of: 200 to 250 ° C.

The raw combustion gas has a temperature of more than 500 ° C at the entrance to the first reactor. Due to the relative relatively cold surface of the shaped bodies, the tar fed with the combustion gas stream condenses and settles on the surface of the shaped bodies. The combustion raw gas is constantly in the overflow of the moldings with them by convective heat transfer mechanisms in exchange, D. h. the continuously flowing combustion raw gas releases its physical energy on the way through the system to the moldings and instationarily heats them away from the combustion gas inlet in the direction of the burner gas outlet. As a result of the condensation of the tar, a proportion of the chemical energy of the raw combustion gas is also released to the shaped bodies.

After the moldings have been heated to about 300 ° C., the physical process of oxygen expansion from the solids system of the moldings begins, initially with a low intensity.

The oxygen entering the surface of the molds now selectively reacts with the tar condensate at the same place and carbon monoxide and hydrogen (partial oxidation) are produced from the hydrocarbons with the oxygen. Since in addition to the oxygen, a catalytically active component is additionally integrated in the solid system of the shaped body, the reactions also begin even at the relatively low temperatures of 300 ° C. The products are discharged through the condensate layer in the gas phase and so discharged with the fuel gas from the process. In this process phase, the ratio of oxygen supply to oxygen demand for the partial oxidation of tars is first «1, D. h. only a small part of the condensed tar is converted into carbon monoxide and hydrogen.

As the process progresses, the temperature of the catalyst-oxygen carrier moldings continues to increase, and the intensity of oxygen evolution increases, which is associated with an increasing oxygen mass flow. The ratio of oxygen supply to oxygen demand for the partial conversion of the tars increases and approaches a value of 1. In parallel, the tar conversion rate through the partial oxidation increases until a Balance between oxygenation and tar condensation sets.

The oxygen concentration in the catalyst-oxygen carrier material steadily decreases during the reduction process. There is an exponential dependence between the temperature increase and the oxygen expansion rate.

Since the heating of the catalyst-oxygen carrier molded body is dependent on the direction of flow of the raw combustion gas, the shaped bodies are reduced differently in the direction of flow. The layers at Brennrohgaseintritt heat up quickly, so that the oxygen expansion intensity in the flow direction is smaller.

In order to optimally utilize the amount of oxygen stored in the catalyst-oxygen carrier moldings in the process of fuel gas tinning, at least one change of direction in the fuel gas flow takes place during one cycle. With the change of direction of Brennrohgasdurchströmung the operating time of the moldings can be significantly increased.

With a continuous CO concentration measurement in the clean gas the process of the Entteerung can be supervised. In the case of partial oxidation of the tar with the oxygen provided from the solids, the CO content must increase from the crude to the pure gas since a reaction product is CO. If the concentration remains almost constant, that is an indicator that the oxygen in the system is no longer available in sufficient quantities for the conversion of tars into CO and H ₂ .

Upon reaching a target value of the oxygen storage amount in the catalyst-oxygen carrier material of the molded body, the flow through the first reactor is stopped and the raw combustion gas is passed immediately through the other reactor. The reduction process of the catalyst-oxygen carrier material and the deaeration of the raw combustion gas start anew.

It is advantageous for the change of the flow-through reactor that sufficient oxygen is still present in the catalyst-oxygen carrier material of the molded body to partially convert the residual condensate remaining on the surface of the solid-state system into carbon monoxide and hydrogen. The reaction products of this process phase can now be added to the clean gas of the other reactor.

The first reactor is followed by the sub-process of reoxidation (regeneration). For the reoxidation, air is conveyed through the spent moldings by means of a blower. At the outlet of the first reactor, the oxygen content of the lean air is measured with a probe. The value of the oxygen content in the exiting air stream is a measure of the oxygen uptake in the catalyst-oxygen carrier system of the moldings. By changing this parameter, the state of loading of the catalyst-oxygen carrier system with oxygen is displayed. When the oxygen content increases, the air flow is interrupted. The reactor thus generated is maintained at a temperature of about 200 to 250 ° C until the next use in the reduction process.

The reactors with the moldings are in the process alternately in the cycle of reoxidation or reduction. In the cycle of reoxidation, ambient air is introduced into the reactor, the oxygen is enriched in the moldings and oxygen-poor air leaves the reactor.

The relatively low temperature of the molded body leads to overflowing with raw fuel gas for condensation of the tar constituents of the raw combustion gas. The condensed tar separates on the surface of the moldings.

In the cycle of reduction tarry rich raw gas is introduced into the reactor, the tar is partially chemically reacted with oxygen in carbon monoxide and hydrogen, the moldings impoverished by continuous reduction stepwise to oxygen and low tar or tarerfreie Brennrohgas leaves the reactor.

Oxygen _expansion preferably proceeds at low oxygen partial _{pressures of the} gas phase surrounding the solid (p _{O2 gas} " _{O2 solid} ) and high system temperatures. On the one hand, with the "hot" raw fuel gas, heat is continuously supplied in the form of physical energy to the process and thus also to the catalyst-oxygen carrier system. is the temperature of the solid bed increases continuously and the process of oxygen expansion is terminated when the oxygen partial pressure in the solid is less than the oxygen partial pressure of the gas atmosphere.

The oxygen exiting the catalyst-oxygen carrier system is consumed by the presence of the tar condensate on the solid surface directly with the chemical reaction of partial oxidation, so that no increase in the oxygen partial pressure occurs in the gas atmosphere.

Oxygen removal is completed when the oxygen in the solid of the moldings is used up. During operation, the oxygen capacity is controlled and the reduction process ends when a setpoint is reached.

The process of reoxidation or regeneration of spent moldings is an exothermic process, ie. Oxygen production generates heat. The temperature of the regenerated moldings at the end of the reoxidation process is about 230 to 250 ° C.

Oxygen incorporation occurs increasingly at low oxygen partial pressures and low temperatures in the solid phase. Due to the enrichment of the oxygen in the solid phase and the exothermic nature of the reoxidation of the catalyst, the process automatically stops when the limit parameters are reached. The operation is controlled by means of the oxygen content in the reoxidation medium.

The temperature of the moldings at the end of the reoxidation process is kept at this value by the in-process heat utilization from the biomass gasification process or from the exhaust gases of the combustion raw gas burnt in a combustion chamber in the startup state of the overall system.

The inventive method is based on a chemical method for Brennrohgasbehandlung, the partial oxidation, wherein the oxygen is obtained directly from the applied moldings. Due to the special process parameters, in particular operating temperatures of the solid and gaseous phase, the hydrocarbons condense on the surface of the catalyst-oxygen carrier materials of the moldings. The reaction of partial oxidation takes place under these conditions in the condensed phase and undesired reactions of carbon monoxide and hydrogen in the gas phase are excluded. This makes it possible to provide a tarry or low-tar fuel gas with a calorific value of at least that of the tar-rich combustible gas.

The invention also includes a plant for reducing the tar content of Brennrohgasen the biomass gasification, comprising at least two reactors, which are filled with moldings of catalyst oxygen carriers, wherein the reactors each have a Brennrohgaszuleitung, a Brennreingasableitung and a supply air and air outlet line and the gas lines Valves are controlled shut off, reactors and gas lines having sensors for determining the gas composition, wherein the reactors for reducing the tar content by means of the moldings and for the regeneration of spent moldings are alternately acted upon with raw fuel gas or air.

For gas production, a suction fan is advantageously used.

Perovskites or perovskite compounds of the type ABO _3-d with A = La, Ba, Sr and / or Ca are preferred as catalyst oxygen carriers; B = Ti, Cr, Mn, Fe, Co, Ni, Al, Zr, Nb, Al, Sn and / or Ce). Perovskites are good oxidation catalysts and very stable thermally.

To reduce the activation energy, these materials contain a catalytically active component.

Particular preference is given to using perovskite compounds as the oxygen storage material, selected from Ca _0.5 Sr _0.5 Fe _0.2 Mn _0.8 O _3-δ ; Ca _0.5 Sr _0.5 Fe _0.5 Mn _0.5 O _3-δ ; Sr ₃ Fe ₂ O _{6 + δ} ; Sr _2.25 Ca _0.75 Fe ₂ O _{6 + δ} , Sr _1.5 Ca _1.5 Fe ₂ O _{6 + δ} ; Sr _0.75 Ca _2.25 Fe ₂ O _{6 + δ} or Ca ₃ Fe ₂ O _{6 + δ} .

The catalytic active component is a metallic component, e.g. As Ni or Co, or a metal oxide compound selected from LaCoO _3-δ , LaFeO _3-δ , LaMnO _3-δ , La _0.8 Sr _0.2 FeO _3-δ or NiO.

The plant also contains a device for temperature control of the moldings to a temperature of 200 to 250 ° and a device for raw gas reversal.

embodiments

Based 1 an embodiment of the invention will be explained in more detail. 1 shows a scheme of a plant for the purification of fuel gases from biomass gasification.

Two bulk material reactors R1 and R2 each have a Brennrohgaszuleitung and a Brennreingasabgang on. The bulk material reactors are furthermore each connected to a supply air line and an air discharge line. All lines can be shut off via valves. Valve control is via an in 1 not shown process control station. Reactors R1 and R2 as well as gas lines are equipped with gas sensors that communicate with the process control station.

The raw and clean gases are extracted with an induced draft fan integrated into the overall system.

Both reactors R1 and R2 are filled with mini-honeycomb bodies of a perovskite designated "CSFM 5555" (Ca _0.5 Sr _0.5 Fe _0.5 Mn _0.5 O _3-δ ). The mini honeycomb bodies have nickel as the catalytically active component.

The mini honeycomb bodies have an oxygen storage capacity of 4.5 liters per kg. With the geometric dimensions of the reactor - DurchmesserR 250 mm and 500 mm dump height - and a bulk density of "CSFM 5555" of about 1000 kg / m ³ results for the reactors R1 and R2 after the cycle of regeneration (reoxidation) a stored amount of oxygen of 110 liters.

The plant after 1 is operated as follows:
Prior to initial startup, in both reactors R1 and R2, the minibody bodies are in the oxygen-loaded state (regenerated state) and are warmed to about 250 ° C.

In the steady-state operating state of the gasification plant whose Brennrohgas is first fed via the Brennrohgaszuleitung reactor R1 the mini honeycomb bodies. The gases are conveyed using the induced draft fan integrated in the overall system. The volumetric flow of crude gas is 35 m ³ _iN / h and, in addition to the tar constituents, has the gas components CO, CO ₂ , H ₂ , CH ₄ , H ₂ O and N ₂ in the following concentrations: CO 18 vol.% CO ₂ 9 vol.% H ₂ 8 vol.% CH ₄ 2 vol.% H ₂ O 8 vol.% N ₂ 55 vol.%

The reactor R2 remains initially untouched. The raw combustion gas has a temperature of about 600 ° C at the inlet to the reactor R1. Due to the relative relatively cold surface of the mini honeycomb body of about 250 ° C, the tar fed with the Brennrohgasstrom condenses and settles on the surface of the mini honeycomb body. The raw combustion gas is constantly in exchange when flowing over the mini honeycomb body with this by convective heat transfer mechanisms, D. h. the continuously flowing with approx. 600 ° C combustion raw gas releases its physical energy on the way through the system to the solid and heats this instationary of Brennrohgaseintritt towards Brennreingasaustritt. As a result of the condensation of the tar, a certain proportion of the chemical energy of the raw combustion gas is also released to the mini honeycomb bodies.

Once the minipods are heated to a temperature of 300 ° C, the physical process of oxygen evolution from the solids system of the minipods begins, initially at a low intensity.

The oxygen entering the surface of the minipods now selectively reacts with the tar condensate at the same place and carbon monoxide and hydrogen (partial oxidation) are produced from the hydrocarbons with the oxygen. Since the minipods additionally contain nickel as the catalytically active component, the reactions start even at the relatively low temperatures of 300.degree. The products are discharged through the condensate layer in the gas phase and are discharged with the entteerten Brennrohgas as Brennreingas from the reactor R1. In this process phase is the ratio. oxygen supply to oxygen demand for the partial oxidation of the tars first «1, D. h. it only becomes one. small part of the condensed tar converted into carbon monoxide and hydrogen.

In the further course of the process, the temperature of the mini honeycomb body increases further and the intensity of the oxygen expansion increases, which is associated with an increasing oxygen mass flow. The ratio of oxygen supply to oxygen demand for the partial conversion of the tars increases and approaches a value of 1. At the same time, the tar conversion rate through the partial oxidation increases until a balance between oxygen evolution and tar condensation occurs.

The oxygen concentration in the mini honeycomb bodies of the reactor R1 decreases steadily during the reduction process. There is an exponential dependence between the temperature increase and the oxygen expansion rate.

Since the heating of the mini honeycomb body is dependent on the direction of flow of the fuel gas, the solids system of the mini honeycomb body is reduced differently in the direction of flow. The layers at the fuel gas inlet heat up quickly, so that the oxygen expansion intensity in the flow direction is smaller.

In order to optimally utilize the amount of oxygen stored in the mini honeycomb bodies in the process of fuel gas tinning, at least one change of direction in the fuel gas flow takes place during one cycle. In the o. G. Oxygen storage capacity of the bed used in the reactors R1 and R2 results in a maximum operating time for one cycle without the reversal of the flow direction of 20 minutes. With the change of direction of the fuel gas flow, this operating time can be significantly increased.

With a continuous CO concentration measurement in the clean gas, the process of Entteerung is monitored.

Upon reaching a target value of the oxygen storage amount in the mini honeycomb bodies, the flow through the reactor R1 is stopped and the raw fuel gas is passed immediately through reactor R2.

Decisive for the change of the flow-through reactor is that in the mini honeycomb bodies in reactor R1 still enough oxygen is present to partially convert the remaining on the surface of the solid residue condensate in carbon monoxide and hydrogen. The reaction products of this process phase can now be added to the Brennreingas from reactor R2.

For the reactor R1, the sub-process of reoxidation (regeneration) follows. For the reoxidation, air is conveyed via the catalyst-oxygen carrier system by means of a blower. At the outlet of the reactor R1, the oxygen content of the lean air is measured with a probe. The value of oxygen content in the exiting air stream is a measure of oxygen uptake in the catalyst-oxygen carrier system. By changing this parameter, the state of loading of the catalyst-oxygen carrier system with oxygen is displayed. When the oxygen content increases, the air flow is interrupted. The reactor R1 is maintained until the next use in the reduction process at a constant temperature of about 230 to 250 ° C.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2008-238012 [0014]
• DE 19836824 A1 [0015]

Cited non-patent literature

• Jönsson, O .: Thermal Cracking of Tars and Hydrocarbons by Addition of Steam and Oxygen in the Cracking Zon ;. In: Overend, RP; Milne, TA; Mudge, LK (ed.), Fundamentals of Thermochemical Biomass Conversation. London and New York: ElsevieR 1985 p. 733 et seq. [0011]
• Jensen, PA, Larsen, E., Jorgensen, KH: Tar Reduction by Partial Oxidation. 9th European Bioenergy Conference Copenhagen 1996 p. 1371 ff [0011]
• Brandt, P .; Henriksen, U .: Decomposition of tar in pyrolysis gas by partial oxidation and thermal cracking. 10th European Conference and Technology Exhibition Biomass for Energy and Industry. Wuerzburg 8-11 June 1998 p. 1616 ff [0011]
• Draelants, DJ, Zhao, H., Baron, GV: Preparation of catalytic filters by the urea method and its application for benzene cracking in H2S-containing biomass gasification gas. Industrial & Engineering Chemistry Research 40 (15); 3309-3316; 2001 [0011]
• Institute for Energy and Environmental Technology e. V; FEM Research Institute for Precious Metals and Metal Chemistry: Catalytic oxidation of hydrocarbons using noble metal catalysts based on coated metal shavings. AiF project. 2004 [0011]
• Wang, CG; Wang, TJ; Ma, LL; Gao, Y .; Chuang Zhi Wu, CZ: Partial oxidation reforming of biomass fuel gas over nickel-based monolithic catalyst with naphthalene as model compound. Korean Journal of Chemical Engineering 25 (738-743). 2008 [0011]

Claims (10)

A method for reducing the tar content of Brennrohgasen from the biomass gasification, the Brennrohgas is passed over shaped bodies of catalyst oxygen carriers, that the tar constituents of the Brennrohgases condense on the surface of the moldings and partially oxidize the condensed Teerbestandteile by oxygen release of the moldings. A method according to claim 1, characterized in that perovskites or perovskite compounds of the type ABO _3-δ with A = La, Ba, Sr and / or Ca as catalyst-oxygen carrier; B = Ti, Cr, Mn, Fe, Co, Ni, Al, Zr, Nb, Al, Sn and / or Ce can be used with a catalytically active component. The method of claim 1 or 2, characterized in that using at least two reactors, which are filled with shaped bodies of catalyst oxygen carriers, the reactors are used repeatedly alternately for the partial oxidation of condensed tar constituents of the raw gas by means of the shaped body by the raw gas via the Molded body is passed, and for the regeneration or reoxidation of spent moldings by air or oxygen-enriched air is passed over the spent moldings. Method according to one of claims 1 to 3, characterized in that that the raw combustion gas is passed over the moldings of the first reactor, that the tar constituents of the raw combustion gas condense on the surface of the moldings and partially oxidize the condensed Teerbestandteile by oxygen release of the moldings, that the Brennrohgasstrom is passed over the moldings of the other reactor for condensation and partial oxidation of the condensed Teerbestandteile before the oxygen of the moldings of the first reactor is used up and that the spent catalyst-oxygen carrier moldings of the first reactor by air supply for a re-application of raw gas be regenerated. Method according to one of claims 1 to 4, characterized in that takes place during the partial oxidation of the raw combustion gases at least one change of direction in the Brennrohgasdurchströmung. Method according to one of claims 1 to 5, characterized in that the change of the flowed through with raw material gas reactor takes place when the moldings can still deliver sufficient oxygen for the partial oxidation of the condensed on the moldings tar components. Plant for reducing the tar content of raw gases of biomass gasification, comprising at least two reactors, which are filled with shaped bodies of catalyst oxygen carriers, wherein the reactors each have a Rohgaszuleitung, a clean gas discharge and a Zuluft- and air outlet line and the gas lines are shut off controlled by valves, wherein reactors and gas lines have sensors for determining the gas composition, wherein the reactors for reducing the tar content by means of the shaped bodies as well as for the regeneration of spent moldings can be acted upon alternately with raw gas or air. Plant according to claim 7, characterized in that the shaped bodies perovskites or perovskite compounds of the type ABO _3-δ with A = La, Ba, Sr and / or Ca; B = Ti, Cr, Mn, Fe, Co, Ni, Al, Zr, Nb, Al, Sn and / or Ce and a catalytically active component. Plant according to claim 7 or 8, characterized in that the reactors have a device for temperature control of the molded body. Installation according to one of claims 7 to 9, characterized in that the reactors have a device for raw gas reversal.

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