WO2009125004A2

WO2009125004A2 - Novel mineral gas adsorbers for biogas plants

Info

Publication number: WO2009125004A2
Application number: PCT/EP2009/054323
Authority: WO
Inventors: Joachim Schomburg; Christian Schultz; Marita Loeffler; Norbert Fritz Bernhard Rossow; Günter BIETZ
Original assignee: Durtec -- Ingenieur-, Beratungs- Und Laborgesellschaft Mbh; Prv -- Planungsbüro Rossow - Gesellschaft Für Versorgungstechnik Mbh
Priority date: 2008-04-09
Filing date: 2009-04-09
Publication date: 2009-10-15
Also published as: DE102008018698A1; EP2300154A2; WO2009125004A4; WO2009125004A3

Abstract

The invention relates to the use of naturally occurring and modified mineral adsorbers for purifying the crude gas in biogas plants and disposal stations from undesired or harmful accompanying substances, e.g. hydrogen sulfide and ammonia. The mineral adsorbers are characterized in that smectite-rich clays/bentonites containing at least 50 percent of three-layer silicates capable of swelling and/or halloysites containing at least 50 percent of halloysite can be used as agglomerates or granulates.

Description

NEW MINERAL GAS ADSORBER FOR BIOGAS

description

The invention relates to the use of various mineral Adsorber- materials, such as smektitreiche clays, bentonites and / or Hi ysite, in a filter module to remove harmful or interfering gas components from the raw gas, such as H ₂ S, NH ₃ , CO ₂ , NO _x and / or hydrocarbon compounds.

State of the art

The treatment and purification of the raw biogas by physical, chemical and / or biological sorption is state of the art. For a better methane yield and to minimize harmful gas constituents, mainly chemical additives and / or carbonaceous molecular sieves (activated carbon) are used for the treatment of the raw biogas.

The patents GB 692 804 A and GB 734 577 A prove the purification of biogas by means of pressure and temperature (physical parameters). [0004] Patent EP 0 628 339 B1 describes a process for the extraction of undesired substances from a biogas by means of chemical reactants. Other documents document the biogas purification of H ₂ S based on iron hydroxide (SU 814 414 Al, SU 768 440 A1, JP 54 100 975 AA).

Ammonia and hydrogen cyanides can be removed by means of formalin from the gas (Offenlegungsschrift DE 34 12 581 Al). By low concentrations of formaldehine in conjunction with metal salts, ammonia can also be bound from the gas (DE 34 12 581 A1).

The prior art is the inclusion of ammonium ions in acidic solutions (patent applications WO 93/006063 A1, GB 1 538 661 A). The state of the art is also the precipitation of sulfur from a gas by means of an iron (III) oxide mixture with the addition of air (Patent DE 1 050 013 C, US 2,641,526 A). For desulfurization and removal of COS (Kohlenoxidsulfi = carbonyl sulfide) usually impregnated carbonaceous molecular sieves are used. High costs for the purchase of carbonaceous molecular sieves as well as their disposal force manufacturers and users to a limited use. Primarily for fine purification of raw gases, carbonaceous molecular sieves are used.

The patent application EP 345 862 A2 describes the removal of H ₂ S from a gas mixture by means of potassium iodide impregnated activated carbon. Other patents, such as. For example, DE 25 07 672 C3 and US 4,075,282 A also document the removal of H ₂ S from a gas mixture.

The patent DE 25 07 672 C3 shows a solution for impregnating the activated carbon with potassium iodide.

Other documents document two-stage desulfurization processes for the removal of sulfur from a H ₂ S and water vapor-containing gas (EP 0 506 160 B1, DE 24 30 909 A1, EP 0 218 302). Metal oxide-rich catalysts (EP 0 215 317 A1) are used here.

Mineral molecular sieves are usually used only for cleaning special gases such. B. for emission control. Here, mainly synthetic zeolites are used, which are also doped. These are aluminosilicates, which are composed of crystalline AlO ₄ and SiO ₄ ^-1 tetrahedra and have defined pore sizes of between 0.3 and 1 nm depending on the grade. Their modification is easy due to the ease of exchange for metal cations. The adsorption properties of the mineral molecular sieves are based on the large internal surface area, on the high electrostatic adsorption forces and on the molecular sieve effect. They are particularly suitable for drying gases and have selective release properties.

In the petroleum industry doped synthetic zeolites are used as catalysts for the adsorption of NO _x and CO. Preference is given to a zeolite of the type 5 A, which was also doped with calcium (DE 38 05 734 Al). The patent US 3,702,886 A describes the preparation of this zeolite. Exhaust gases are purified from NO _x and CO using a silicic acid-rich zeolite, which was prepared on a synthetic basis (US Patent 4019 879, EP 0 003 818 Al). In another method, CO2 and H ₂ O from the contaminated air by means of zeolite X and LSX, which were agglomerated with binder, adsorbed (EP 1 218 099 Bl). Synthetically produced powdered silica gels or silica gels were used for the adsorption of gases and vapors as early as the 1950s (Patent DE 883 743 B, DE 877 445 B).

To stabilize the fermentation process in biogas plants modified zeolite to activate the degradation of the fermentation substrate, or to improve the environment conditions, to reduce the ammonia and / or F ^ S content, to optimize cell division and to reduce the time to digestion Fermentation substrate added in the fermenter (Patent AT 413 209 B, EP 1 577 269 Al). According to the action goal of the natural zeolite is modified, for. B. doped with potassium to increase the ion exchange capacity to H and NH4 ⁺ ions or with enzymes to improve cell division, etc. .. With a degree of fineness <100 microns, the modified zeolite is added to the fermentation substrate.

Bentonites are due to their properties, such as swellability, the possibility of ion exchange and because of their thixotropic ability in the most diverse

Fields used.

Bentonites, which are used for the purification of the raw gas, are not known.

Test approaches with bentonite for the immobilization of toxic substances during the fermentation achieved only limited success, an increase in the gas yield with shorter digestion time could not be observed (EP 1 577 269 Al).

To improve the fermentation and the increase of the methane content in the gas and solids such as zeolites or silicates are added (JP 60014995 AA).

Halloysite have hitherto been used only for hydrogen storage (US 7425232).

In biogas plants, mineral adsorbers for purifying the raw biogas are currently not used.

Object of the invention

Development of mineral adsorbers for a safe, durable, cost-effective and effective (fine) purification of the raw gas from unwanted or harmful accompanying substances. fen, such as As H ₂ S and NH ₃ , to protect against damage to the conversion systems (eg., Combustion engines, fuel cells) and to ensure the gas quality.

Solution of the task

The object has been solved according to the features of the claims. In accordance with the invention, selected natural mineral products with good adsorption properties have been produced as granules to ensure good gas flow due to their large internal surface area and / or porosity.

Surprisingly, it has been found that smektitreiche clays, bentonites and halloysite bind particularly well hydrogen sulfide and ammonia from the raw gas. The proportion of these harmful gas constituents in the product gas can be permanently reduced to below 20 ppm. The examples given show that the product gas is almost free of H ₂ S and NH ₃ . Specific clay mineral raw material examples are:

> Bentonite from MiIo s, Greece

> Bavarian Bentonite, room Landshut

> Ton Friedland / Mecklenburg-Vorpommern> Halloysite from New Zealand

According to the invention naturally occurring and modified phyllosilicates with three-layer structure consisting of two tetrahedral layers, which are electrostatically connected via cations with an octahedron intermediate layer and z. B. property-determining mineral in smektitreichen clays or bentonites are related.

For the adsorption of harmful gas components swellable three-layer silicates are used which have a high specific surface area (100-800 m ² / g) and a high cation exchange capacity (> 50 meq / 100g) and thus are capable of undesirable Tie gas components or give it back on thermal reactivation.

To ensure good gas permeability agglomerated three-layer silicates are used with uniform grain structure in the particle sizes 0.1 -5 mm, preferably in grain sizes 1-5 mm, whereby the grain shape can vary. The grain structure should be as free as possible of grain fractions <0.1 mm.

Agglomerates / granules of naturally occurring or modified smectite-rich clays / bentonites with a montmorillonite content of> 50%, better with a proportion of> 75%, are suitable according to the invention.

According to the invention, naturally occurring halloysites (7 Å or 10 Å type) which are produced by mechanical preparation in granular form (0.1-5 mm) are used. Due to their considerable nanopore volume (up to 30%), these cause the described cleaning effects in the gas treatment. The Halloysitanteil should amount to at least 50%.

Compared to customary cleaning processes according to the present state of the art - ^■ except for filtration with activated charcoal ^"■ the use according to the invention of smectite-rich clays and bentonites produces a qualitatively better product gas which contains almost no or only very small amounts of hydrogen sulphide and ammonia, and thus ideally suited for energy conversion in conversion plants.

Mineral filters with smektitreichen clays, bentonites and / or halloys achieve in comparison with carbon filters the same cleaning performance in terms of reducing harmful gas components in the product gas, such as H ₂ S, NH ₃ , CO ₂ and N ₂ .

The use of zeolites, better known as molecular sieves, for exhaust gas purification is common practice. Due to their large porosity and the associated high internal surface area (up to 1000 m ² / g) zeolites have a high and specific ion exchange, adsorption and hydration ability. Experiments with granulated naturally occurring zeolites as adsorbers for biogas purification were in their purification performance behind the smektitreichen clays / bentonites and halloysites back.

Economically speaking, the mineral adsorber according to the invention to be preferred to the activated carbon over. Activated carbon is expensive due to the high energy input in the production in purchasing and also dispose after reaching an insufficient reactivity as hazardous waste (additional costs). In the mineral adsorbers are naturally occurring raw materials, which can also be produced with much less effort than filter material for gas purification. Their disposal is unproblematic (no hazardous waste), reuse z. B. as mineral fertilizer should be given priority.

By using mineral adsorber material procurement costs can be reduced to less than 20% compared to activated carbon.

In the gas contained undesirable impurities such. As hydrogen sulfide and ammonia have a significant influence on the plant operation, the wear or the missions.

By eliminating or greatly reducing these impurities in the product gas gas systems and especially conversion systems can be operated more economically and environmental pollution can be reduced. Maintenance costs are reduced and the service life of the conversion plants increases.

The inventive use of mineral adsorbers, such as bentonites, smektitreiche clays and / or halloysite has an impact on a better use of energy from biogas and landfill gas. Especially in low calorific gases with a methane content <40%, hydrogen sulphide contents negatively influence the gas quality, elimination or strong reduction of these contents counteracts this.

The invention thus also relates to the use of smectite-rich clays and / or bentonites and / or natural halloysites for a safe, durable and cost-effective purification of the raw gas of unwanted or harmful accompanying components, such as H ₂ S and NH ₃ , to protect against damage to the conversion equipment of gas treatment plants, preferably biogas and landfill gas plants and to secure / stabilize the gas quality. The mineral products in gasgängiger form can be used as agglomerates and granules with a grain diameter> 0, 1 mm, preferably in the fraction 1-5 mm.

It is also possible to use the mineral adsorber components, such as smectite-rich clays, bentonites and halloysites in filter systems varying in order and mixture, as well as individual components and to realize a vote on the organic input materials and the plant technology requirements. The filter module is preferably arranged after the raw gas drying and can be variably dimensioned with mineral gas adsorbers according to requirements and technical requirements.

[0045] In addition, the activated carbon granules which have hitherto been used traditionally can also be packaged components in the mineral gas adsorber systems.

The agglomerates / granules of smectite-rich clays and bentonites contain> 50% swellable three-layer silicates, which may possibly also be chemically modified. The granules of the natural Hello ysite contain> 50% of the mineral Hi ysit (7 Ä or 10 Ä - type) and may possibly also be chemically modified. [0048] It is also possible to dehydrate the agglomerates, granules, crushing the grains of the mineral products, if necessary, by thermal treatment partially, preferably in the temperature range up to 200 ⁰ C.

The residence time in the filter module can vary depending on the flow rate of the raw gas and on the loading of the raw gas with harmful components, wherein preferably a residual charge of H ₂ S and NH ₃ of less than 20 ppm is maintained.

New and old plants without previous crude gas treatment can be easily equipped with a filter module with Mineraladsorberfüllung according to claim 10 to 12 in order to improve the reliability and system efficiency. After loading with the interfering components from the raw gas, the mineral adsorber components can be utilized as soil improvers in agriculture, forestry and horticulture or, if appropriate, can be used again in the filter system after thermal reactivation (temperatures up to about 450 ^° C.).

The use according to the invention of mineral adsorbers, such as smectite-rich clays / bentonites / halloysites, offers a better utilization of low-calorific gases with a methane content <40%, in particular the landfill gas.

embodiments

Embodiment 1 "Fine purification of the raw gas with granulated smectite-rich clay (1 -5 mm)"

Under practical conditions, a representative 500 kW biogas plant with pre-desulfurization and gas drying was used directly on the state-of-the-art The biogas in the bypass system is branched off in front of the engine of the cogeneration unit and passed and analyzed via the specially developed filter module. The filter module was designed according to the principle of a multi-chamber daylighter and consists of 3 floor feeders with 3 chambers, which can be filled depending on the requirements and needs with a wide variety of adsorbent materials. Each chamber has a volume of 5.301 dm ³ . Easy access and handling of the chambers also makes it easy to replace adsorber materials. By means of a gas pump, the gas flow is conducted evenly over all filter columns. Coupled to a measuring device SR2-BIO of Hermann Sewerin GmbH, the gas composition is recorded after passing through the filter unit.

For a test run over 6 weeks, the columns 1 and 2 were filled with granulated clay and for direct comparison of practice, the column 3 with activated carbon. Measurements of the gas components methane, carbon dioxide, oxygen, ammonia and hydrogen sulphide on the product gas (after passing through the filter module) and on the raw gas (adjacent to the bypass) were performed on a weekly basis and are listed in Table 1. The listing of the measurement results for oxygen and ammonia (constant measured value = zero) was neglected.

Tab.1: Gas-fine cleaning with smectite-rich toner adsorber measurements

1) smectite-rich clay agglomerate (1 -5 mm) ² ^ smectite-rich clay agglomerate (1 -5 mm) 3 ⁾ activated carbon AIR SKP 30/15 4 ^ Raw gas adjacent to the bypass

Based on the test run 1, the granulated clay contained in column 1 was observed over a longer period of time. Figure 1 shows the measured values for hydrogen sulfide in the product (after flowing through the Tonadsorbers) and raw gas in the weekly rhythm.

FIG. 1 shows the results for smectite-rich clay in the long-term test.

Embodiment 2

"Fine purification of the raw gas with granulated helium ysit (1 -5 mm)"

Under real-life conditions, the large-scale test was carried out on a representative state-of-the-art 600 kW biogas plant with pre-desulfurization and gas drying after successful testing in the prototype (structure and procedure see Example 1). As a filter body, the installed activated carbon filter was used to fine-clean the biogas with a capacity of approx. 1,000 liters.

The structure of the large filter and the procedure for fine purification of the biogas correspond to the prior art. For the experiment, the activated charcoal charge was replaced by about 800 kg of granular halloysite. To remove the harmful biogas components (hydrogen sulfide, ammonia), the biogas was passed through the mineral helical filter before entering the CHP (engines) (average throughput 260 m ³ / h).

Over a period of 10 weeks, the experiment was carried out under real-world conditions. The measurements regarding the gas components methane, carbon dioxide, oxygen, ammonia and hydrogen sulphide on the raw gas were carried out before entry and on the product gas after discharge from the mineral filter at weekly intervals (T ab.2). The values were measured with a measuring device SR2-BIO from Hermann Sewerin GmbH. The listing of the measurement results for oxygen and ammonia (constant measured value = zero) was neglected.

Raw gas - measured directly in front of input filter module;

2) product gas - measured directly after output filter module;

Tab.2: Fine gas cleaning with granular Halloysite - measurement results

definitions

Smectite-rich clays and bentonites

The term "smectite" is included in the nomenclature developed by the Welttonmineralassoziations and is common in Anglo-Saxon usage.

It translates to all swellable three-layer silicates (eg montmorillonite, nontronite, beidellite, muscovite-montmorillonite exchange storage minerals).

modified phyllosilicates Modified three-layer silicates means z. B. a sodium occupancy of the swellable Dreischichtsilikate by soda activation or H-occupancy of the swellable Dreischichtsilikate by acid activation with HCl or H ₂ SO ₄ .

halloysite

Roll-shaped bilayer silicates of the kaolinite mineral group, which are present as a 7 Ä or 10 Ä type, depending on the state of hydration. The average diameter of the helium ysit nanotube is about 30 nm.

Claims

claims

1. Mineral gas adsorber for the purification of raw biogas, characterized in that it is an effective component for removing harmful or interfering gas constituents from the raw biogas a) naturally occurring phyllosilicates with three-layer structure and / or b) naturally occurring halloysite and / or c) modified phyllosilicates with three-layer structure and / or included.

2. Mineral gas adsorber according to claim 1, characterized in that it is the smectite-rich clays and bentonites in the naturally occurring phyllosilicates with three-layer structure.

3. Mineral gas adsorber according to claim 1, characterized in that the modified layered silicates having a three-layer structure are smectite-rich clays and bentonites which have been acid-activated or soda-activated.

4. Mineral gas adsorber according to one of claims 1 to 3, characterized in that it is agglomerated three-layer silicates with uniform grain structure in the particle sizes 0.1 -5 mm, preferably in the particle sizes 1-5 mm, is.

5. Mineral gas adsorber according to one of claims 1 to 4, characterized in that it is crushed grains or granules whose specific surface area (100-800 m ² / g) and whose cation exchange capacity is> 50 meq / 100g.

6. Mineral gas adsorber according to one of claims 1 to 5, characterized in that it is agglomerates / granules of naturally occurring or modified smektitreich clay / bentonites with a Montmorillonit- share of> 50%, preferably with a share of> 75% is acting.

7. Mineral gas adsorber according to claim 1, characterized in that it is naturally occurring Hello ysite type 7 Ä or 10 Ä.

8. Mineral gas adsorber according to claim 7, characterized in that they are in granular form (0.1 -5 mm) and have a Nanoporenvolumens to 30%, wherein the proportion of the mineral Halloysite is> 5%.

9. Mineral gas adsorber according to one of claims 1 to 5, characterized in that they additionally contain activated carbon as an effective component for the removal of harmful or interfering gas constituents from the raw biogas.

10. filters containing at least one mineral gas adsorber according to one of claims 1 to 9.

11. Filter according to claim 10, characterized in that they can be combined in a modular manner.

12. Filter module according to claim 10, characterized in that it is a single or multi-chamber floor filter, which preferably each consist of three floor filters with 3 chambers each.

13. A method for removing harmful or interfering gas components from raw biogas, characterized in that the raw biogas is diverted after pre-desulfurization and without or with gas drying immediately before the engine of the CHP and passed through the filter according to any one of claims 10 to 12.

14. The method according to claim 13, characterized in that the smektitreiche clays, Bentonite and Hello ysite are used in the filter modules both varying in order and mixture and as individual components.

15. The method according to claim 13 or 14, characterized in that the agglomerates, granules, Brechkörner the active component were partially hydrated by thermal treatment, preferably in the temperature range up to 200 ⁰ C.

16. Use of the mineral gas adsorber according to one of claims 1 to 9 or the filter according to claims 10 to 12 for protection against damage to conversion devices of gas treatment plants.

17. Use according to claim 17 for protection against damage to biogas and / or landfill gas systems and for securing / stabilizing the gas quality.