PROCEDURE FOR THE ENRICHMENT OF METHANE IN DUMP GAS AND FERMENTATION GAS
Biogas 1st Technical area The method can both the waste treatment, the treatment of refuse dumps (Include clean-up) and the energy technology are associated with. The method is one of the "enrichment process" ( engl. : "upgrading processes "), landfill gas or in the methane content. Biogas increase. At the same time it could also provide a method for the treatment of slag from Abfallverbrennunganlagen be seen ( MVASchlacke ). 2. State of the type Process for the separation of CO2, H2S and CH4 are based on physical principles or on the CO2 scrubbing currently to primarily H2S ( Chemisorbtlon , Physisorbtion ) and with liquids. The Druckwasserwäsche and Absorption process the domination of the statistics show: Technique CH cz DE DK FR GB IS IT NL 1 £1 5 1 3 6 1 5 (1) 4 1 1 1 18 > 15 > 32 PSA-Method MembranabsorptionDruckwasserwäsche SE S Selexol 1 1 1 1 1 3 1 4 > 5 1 ai (absorption) 7 5 3 (1) 4 1 1 2 8 26 > 58 Accumulated gas permeation Kryotechnik crude gas capacity Unknown sum [1,000 m3/hr] 0.83 0.04 0.35 1.29 n.b.n.b. n 1.35 9.71 6.75 20.3 Table 1. b.: Biogasaufbereitungsanlagen in Europe (source: TRETTER H., 2003, New Options use of biogas. Thesis at the Technical University, Institute for process engineering, environmental technology and Technical life sciences). The procedures are described in what follows, must be broad. Druckwasserwäsche ( DWW ) The solubility of NH3, H2S and C02 in water is significantly higher than that of CH,. This difference is used in the washing under pressure is effected-Method technically. In 6 and 12 bar in a CO2 is absorbed between pressures (substantially) physical process with water. The Druckwasserwäsche is currently the only method, which can carry out the separation without pre-purification of the gas (pre-cleaning: dewatering, separating H2S). But hS is-content of the crude gas also here a low condition. In most cases this condition is not given with biogas and landfill gas. (H2O, CO2 and H2S enriched with) is washing liquid The on many regenerated DWWVerfahren . The resulting gas stream is disposed of after a deodorization or emitted. Not regenerative DWW -Method need much water and are thus not resource-efficient. Pressure swing adsorption pressure swing adsorption, english "Pressure Swing adsorption", abbreviated "PSA" or "DWA", a method is, on the different sorption properties of the gases is based on high surface area materials. As materials are used predominantly zeolites and carbon molecular sieves (KMS). The entire treatment of the gas mixture consists of: • • H2S-• "conditioning" crude gas-compression removal: cooling, drying, separating water • pre-filter to protect the KMS • Methananreicherung to KMS-towers The first plant for the enrichment of methane from biogas Austrian, Pucking 17 June 2005 (Upper Austria) in opened is based on the PSA method. In producing methane from the biogas is Pucking into the Upper Austria The. Fed gas system. Absorption process are based on the mass transfer from the gas phase into a liquid Absorption process. By contact with the crude gas a washing liquid ("physisorption") or certain gas components are resolved by reaction with dissolved components of the washing liquid ("chemisorption") linked. "Absorption" is also often the vivid term instead of "gas scrubber" used. The simplest of all washing liquids is water. The corresponding technique has been already described further above ( DWW ) s. The for cleaning or. Enrichment of biogas suitable Absorption process before a regeneration see of the washing liquid, because otherwise the Chemikalienbedarf would be prohibitively expensive. In oilfield and synthetic chemistry a wider scope than find Absorption process in the biotechnology. Problematic the insert is partially of toxic chemicals, e.g. Monoethanolamine. Examples ( Firmenbezeichnungen ): Selexol -Method, COOAB -Method, MEAVerfahren . Membrane separation process is relatively new and (gas permeation, Membranabsorption ) The membrane technique still in development with respect to the separation efficiency and the life of the membranes. For Reinheitsansprüche must either multistage Method or Hybrid method currently high, i.e. the combination with other separation processes, are used. The membrane technique is based on the different diffusion and sorption properties of the gases. The basic characteristics of the gases in this respect is the effective diffusion coefficient in the separation membrane and the partition coefficient between gas phase and membrane material. Methane and nitrogen at the pressure side of the membrane are enriched therefore, CO2 and H2S the membranes preferably penetrate during. The necessary pressures can be 25 to 40 bar. Kryotechnik CO2 and methane at elevated pressure and very low temperatures by condensation of C02 can (8a 50 bar, -110 to -150oC) are separated. Documented in the literature is a single pilot plant Only. This technique is extremely energieaufwändig . Using waste products for the absorption of CO2 (absorption in the fixed bed reactor) In European Patent EP 0669900 mi in claim 12 is referred to as the "use waste incineration residues as an absorbent material for removing CO2...". Concerning the separation of CO2 from biogas or The procedure is. Landfill gas but not discussed in more detail and a Ha generated- hälltiges , for the little suitable gas Venwertung of methane, as fresh or classified MVA-slag is used directly. Final remark-State of the type Druckwasserwäsche , pressure swing adsorption and higher investment costs and cause much higher energy than the liquid-Absorption process hereinafter represented invention. None of these method of reducing the leachability of MVA-slag ökobonus concerning has a on. 3. three tasks are simultaneously solved by the invention task Technical: 1. energy-saving enrichment of methane gas in landfill gas or biogas and Low cost. With ageing ChU content can be observed on many landfills a decrease in the. In the recovery of the gas-e.g. in gas engines-is called for, however, a minimum methane content. In order to achieve this, the methane content is included in gas lift. Also for the feeding into the gas system is a purification, enrichment of methane and increase the calorific value (or of the WobbeIndex ) of the gas required. 2. separating l-l2S from the landfill gas or biogas. 3. reduction in slag from waste incineration plants and Pb (MVA-Schlacke) the leachability of AI. The risks to the reduced leachability Schutzgut groundwater, this reduction in the in the case of the deposit, but also with regard to recovery of the MVA-slag in road building. 4 . 1st Process for the enrichment of methane in landfill gas Claims, biogas or mixtures thereof and for simultaneously separating CO2 and H2S from these gases using waste incineration slag, MVASchlacke , while reducing the Ausiaugbarkeit of metals and metalloids, particularly AI and Pb, in MVA-slag, by the MVASchlacke with landfill gas, biogas or a mixture of these gases is brought into contact, cheracterised in that the MVA-slag, has been taken from the classified Schlackebad after the grate furnace of waste, and at least two days (hydrated) is introduced in the wet state, mounted, before passing into a static reactor and with the landfill gas, the biogas is brought into contact or mixture thereof. 2. method according to any one of the preceding claims, characterized in that the MVA-slag to particle sizes is classified under 20 cm, preferably by sieving to a particle size under 6 to 2 cm. 3. method according to one of the preceding claims, characterized in that the storage in the wet state (hydration), preferably at between 12 and 35 mass % on WassergehaltenFeuchtsubstanz takes place, whereby a clear reduction in the entry of hydrogen (H2) into the recoverable methane gas is achieved. 4. method according to one of the preceding claims, characterized in that the storage of particulate or non-particulate (hydration) in the wet state in MVA slag Mietenform ( Dreiecksmieten , flat heaps or Trapezmieten ) takes place, preferably with Mietenhöhen over 90 cm and preferably using a Geotextile for covering. 5. method according to one of the preceding claims, characterized in that the duration of storage while wet 4. claims 1. method for the enrichment of methane in landfill gas, biogas or mixtures thereof and for simultaneously separating CO2 and H2S from these gases using waste incineration slag, [...] , while reducing the [...] of metals and metalloids, particularly AI and Pb, in MVA-slag, by the [...] with landfill gas, biogas or a mixture of these gases is brought into contact, cheracterised in that the MVA-slag, has been taken from the classified cinder bath after the grate furnace of waste, and at least two days (hydrated) is introduced in the wet state, mounted, before passing into a static reactor and with the landfill gas, the biogas is brought into contact or mixture thereof. 2. method according to any one of the preceding claims, characterized in that the MVA-slag to particle sizes is classified under 20 cm, preferably by sieving to a particle size under 6 to 2 cm. 3. method according to one of the preceding claims, characterized in that the storage in the wet state (hydration), preferably at between 12 and 35 mass % on water contentsdamp substance takes place, whereby a clear reduction in the entry of hydrogen (H2) into the recoverable methane gas is achieved. 4. method according to one of the preceding claims, characterized in that the storage of particulate or non-particulate (hydration) in the wet state in MVA slag rent form (triangle rents , flat heaps or trapezoid rents) takes place, preferably with [...] over 90 cm and preferably using a Geotextile for covering. 5. method according to one of the preceding claims, characterized in that the duration of storage while wet (hydration) preferably between 14 and 28 days. 6. method according to one of the preceding claims, characterized in that the classified, hydrated MVA-slag before mixing with the landfill gas, the biogas is brought into contact or mixture thereof, in the static reactor with inert gas, in particular N2, Rinse, 20 and 30 minutes and wherein the duration of the flushing preferably between 4 and 10 m3 inert gas per ton slag preferably between the inert gas flowing (based on damp substance), respectively. 7. method according to one of the preceding claims, characterized in that the static reactor for contact between [...] and biogas, landfill gas or a mixture thereof cyclically charged, purged with inert gas is emptied and used for the reaction. 8. method according to one of the preceding claims, characterized in that the gas exchange rate , CO2 and H2S in which is received by the MVA-slag, 0.2 to 3.0 m3 crude gas/ton slag/hr, preferably 0.5 to 1.2 m3 supplied raw gas/ton slag/hr is. 9. method according to one of the preceding claims, characterized in that additionally with a recirculation pump (5) from biogas, landfill gas, or a mixture thereof raw gas (1), the temperature and the water vapour in the static reactor (4) are distributed evenly, wherein by the recirculation pump (5) generated is greater than the the static reactor volume flow (4) supplied raw gas-volumetric flow. 10. method according to claim 8, characterized in that by the recirculation pump (5) 10-to 30 times the volume flow of the generated volume flow the raw gas (1) is. 11. method according to claim 8 or 9, characterized in that the reaction in the static reactor (4) in an initial method step without switching on the circulating pump (5) expires and after reaching an elevated concentration of 50% by volume in the recovered CH4 methane-enriched gas from preferably at least (6) the recirculation pump (5) for a second filter-is turned on. 5. description of the invention is represented in Figure 2. the new procedure The sequence reacts carbon dioxide (CO2) and thus can bind MVA-slag alkaline. The landfill gas or.
Biogas (raw gas) is passed (static reactor) in a closed system (e.g., sinter) MVA-slag over classified. The enriched gas has a much higher methane content on. By this treatment the MVA-slag leachability is reduced at the same time the "critical" metals lead and aluminium (Pb, AI) substantially.
In the case of studies have been achieved (75 to 90 kg MVA-slag) technical school yardstickmaximum concentrations to 99% by volume of CH4 in the clean gas. The [...] -receiving the MVA-slag is 36.7 kg/tonne [...] 19.2 to classified slag (results from the year 2006, slag from two different MVA-installations, not published). H2S by the slag is received.
The crude gas can for example consist of:
• Landfill gas: "producer gas" Low [...] -content is also so-called suitable • biogas from the anaerobic waste treatment • biogas from the anaerobic wastewater treatment (sewage gas) • mixtures of the gases mentioned reference putrid towers • biogas from: "biogas" is defined differently in the literature the term, "biogas" is not associated with the concept wherein sometimes landfill gas. Therefore are quoted in the claims and in the summary both biogas and landfill gas.
The waste incineration slag from the incineration residual materials (MVA-Schlacke) that part is the inorganic, rust heating installations for municipal waste in (domestic waste, etc. commercial waste [...]) is not transported with the exhaust gas from the burner, but remains on the grate through the grate (rust release , predominant proportion by mass of the residual materials) or can fall (rust passage , less mass fraction). In almost all MVA-installations (incinerators) MVA is cooled-slag, consisting of rust passagerust release and, in a water bath, which is referred to as " cinder bath ".
The classifying the MVA-slag is taken from the cinder bath , can take place in a simple way by screening. If for depositing metals (e.g. transferring magnet , eddy current separator) additionally aggregates are used, then primarily for the purpose of recycling of metals.
Before the screening the arrangement may be necessary a a coarse barred window, if this is not an integral part of the discharge system of the MVA-Plant.
Grain sizes between < 2 cm and < 20 cm are for the purpose of the new method the enrichment of methane (preferably: < 6 cm to < 2 cm) suitable. The duff (2a 6 cm) round in the region of the optimum hole sizes is from 85 to 95 mass %. The non-recoverable (15% by mass to .5 ca) must be disposed of [...] (e.g. deposition).
It should be noted that during storage, during the controlled (hydration) of the slag or after direct introduction of aging not aged or incompletely hydrated slag in the static reactor hydrogen gas is produced (ha). This is primarily due to the reaction of metallic aluminum in the alkaline medium:
Al-oxidation: AI + 3H2O + OH " = 1.5 Hz + [(OH) 4 AI]-This the amount of combustible gas is possible to win, which is in the process, increases. In some countries, however, may complicate the recovery of the enriched gas a high Hz-content. G31 when fed in the gas system provides for-Directive [...] Between, for example, a 4% by volume before Hz-maximum content of.
In addition is made in the presence of higher Hz-content of the gas-but only whereby the relevant security measures-increased risk of explosion in the case of the handling and abuse. 4-2 is-to from this point of view, a " • • • • I week prior to carbonation (aging, hydration) of the slag storage wet advantageously, because within 2 to 4 weeks (14 to 28 d) most Al-oxidation proceeds. The minimum time for the hydration two days. In a duration of the hydration of a few days is still considerable [...] in static reactor to be expected.
For a full use of the responsiveness of water must be provided from MVA-slag, so that the hydration of CaO can take place:
Hydration: CaO + H2O = (OH) 2 can proceed hydration of CaO Ca The, by passing the wet slag a few days to weeks in the form of triangular, supports [...] flat heaps. The preferred height for an optimum course of the hydration and CO2 taken to avoid premature reaction with atmospheric is more than 90 cm.
The water content for the hydration and for the subsequent reaction with landfill gas or. Biogas in static reactor should preferably 12 to 35 mass % FS (based on damp substance), respectively. Slag from the cinder bath of MVA-installations these provisos (referenced as " [...] slag" denotes) almost always met.
This storage or. Aging, the "storage (hydration) in the wet state" in the claims is referred to, react with water also further high temperature phases of MVA-slag. Educated mineral new phases 26, e.g. calcite, goethite (OH) 3 (FeOOH) or amorphous AI, are stable in the long term and reduce the leachability of high temperature phases to water than the metals by buffering or sorption.
During the hydration (= storage) and also during an optional intermediate storage of fresh MVA-slag should be noted:
• Accumulations of H2-gas are not reliably to prevent • The MVA-slag is to dry up, but also not be excessively wet. Some basic on a fixed face under a geotextile is e.g. the storage (flow) or under roof.
•Leachate is to detect and derive to avoid or, if they require it.
The appropriateness of the order of the process steps (= storage)-> feed of the reactor is screening-> hydration technical school yardstick safeguarded by scale tests. In the new proceedings before the enrichment of methane is also, in principle, possible following series: hydration (classification) (= storage)-> screening > feed of the reactor. In Figure 2 by dotted arrows This possibility is displayed. Whether and where they are in the process chain recoverable metals are separated is only a minor detail.
After the classification and storage In wet state the classified, in a static reactor [...] MVA is introduced-slag. The static reactor is a correspondingly dimensioned concrete or [...] In the simplest case, can be emptied and charged by means of a shovel loader.
The following technical claims are provided to the reactor:
• Gastight • rustproof closable • temperature-steadily to 100oC (landfill gas) and MVA-slag to biogas gas distribution horizon or slots for the introduction of the gas or • gas distribution layer • Mechanically robust, especially road bottom and for the "dead volume" feed/emptying [...] suitable walls • Low Central, therefore almost completely filled in the closed state, the dead volume is less than 3% of the reactor volume The method preferably contains a cyclic feed, flushing, [...] (= reaction, enrichment of CH4) and carry out the emptying of the static reactor. The duration of the overall process cycle is [...] days 1a.
After filling with particulate, hydrated MVA-slag takes place a flush of the static reactor with inert gas, e.g. technically pure Nj. 30 minutes is preferably between 20 and flushing The duration of, and preferably between 4 and 10 m3 inert gas/ton slag the inert gas flowing through. Afterwards the static reactor can be charged with raw gas (biogas, landfill gas).
The main reaction and thus in the new method the receptacle is of static reactor In CO2, called carbonation, as it tends to carbonates, particularly calcite and microcrystalline CaC03 be formed:
Carbonation : (OH) 2 + CO2 = H2O Note CaOa + Ca: side reactions forming other carbonates Through the alkalinity of the MVA-slag referenced hydrogen sulfide (H2S) from the landfill gas or. Biogas Removing.
The MVA-slag acts as a sink for CO2, which is attached permanently and non-polluting in the form of calcium carbonate. The calcium carbonate acts as a pH buffer (in landfills) subsequently scrubbing of heavy metals and AI counter to the long-term. The pH-value in the eluate is significantly less [...] MVA-slag from (pH: about 7 to 10, 5, often about 8.5) than in the eluate (pH: 12.0 to 12.7 usually) fresh slag-samples. This the leachability is reduced (AI, cu, Zn, Pb) amphoteric elements. Particularly clearly the reduction is the "critical" elements leachability of the for the evaluation of the environmental compatibility and Pb AI (2a 3 orders of magnitude less AI and Pb in the eluate in comparison with fresh, [...] MVA-slag).
The carbonation extend side reactions in the reactor 26 and the overall exothermic inorganic entering, are therefore heat freely. All reactions are accelerated by the temperature increase in the static reactor, in particular also the hydration remaining residual amounts and CaO.
Temperatures between 50 and 850C are no adverse influence on the in the material to be expected and carbonating process.
The gas exchange in the reactor is characterized by the gas exchange number u (m3 supplied raw gas/ton slag/hr). The following range is the duration of reaction is about between gas exchange number conditions for the 50 hr 15 and is.
If the capacity of the sized, hydrated MVA-slag for H2S [...] and is exhausted, the slag is exchanged. The [...] in the crude gas a suitable criterion clean gas and in the ratio between the end of the reaction is for. Generally Cancel 6 is the reaction is, when this ratio includes [...] 1.5.
Process variants according to claim 9, claim 10 and claim 11 are represented in a sketch, (see Figure 1) represents the the principle of these process variants: The inclusion of C02 can also by the means for circulating gas in the static reactor (4) be accelerated and intensified. The means for circulating gas will be continuously by means of a recirculation pump (5) carried out. The conveying capacity of the recirculation pump (5) greater than the delivery rate of the raw gas-pump is to (3) be. The optimal 10:1 to 30:1 mechanical handling capacities a ratio (volume flows) is the guidance of the circulation effected by the more even distribution of the still reactive C02. The further over the reactor cross, a distribution of steam and to a small extent also a minimization of the temperature gradient (temperature differences between center and edge zones) prevailing in the reactor.
technical school yardstick scale tests have shown that a discontinuous means for circulating gas is not appropriate, as it tends to produce a reduced pressure in the reactor repeatedly (4) can arise is not appropriate for a simple and cost-effective implementation of the carbonation. Continuous means for circulating gas, e.g. with the 10bis 30-volume flow times, based on the volume flow of the supplied crude gas, however has the disadvantage that initially the [...] content is not as strong as with variants without cycling increases. Since this is not initially Low [...] gas formed can be recycled, [...] can of about 2% (based on the total mass of CH4 profitable) occur. Falls taken to process variant with circulation decides, a start of the reaction without cycling is therefore recommended. [...] Only when the in the clean gas (6) well above the 50% by volume is-preferably via border content necessary for recovery CK, -is therefore turned on in the process variant according to claim 11 the recirculation pump (5). Here CH4-loss may be significantly below the 0.5% pressed (apart from the inevitable loss during removal of material from the static reactor). The [...] can here increased after switching on of the recirculation pump by Unique in the short term, in the short term higher raw gas-supply that is, temporary increase in the delivery rate of the raw gas-pump (3) are compensated. A knowledge is therefore in this case also a corresponding dimensioning of the intermediate store (2) for the crude gas (1) or any intermediate store for the clean gas (not shown).
Process variants with circulation also allow for the cooling of the process gas (7). This cooling is generally not be necessary. With NCAR variability of the composition of refuse or to regional consideration.
[...] possible future change in the composition of waste and is the possibility within the framework of the process gas and a means for circulating a cooling control of the temperature in the reactor but not exclude attendant. Cooling leads to condensate, (approximately pH = 5 to pH = 6) which due to its pH value (that is, in the pipe) can be expected to be only indirectly initiated.
The back-pressure set up by the slag-fixed bed reactor is only a few mbar In static. The method applies (or only minimum) overflow vacuum to no. Therefore the explosion protection is simpler than for existing method (e.g. Membrane process-> high pressures " costlier Explosion protection).
The clean gas (6) is approximately vapour-saturated. For CH4 enriched gas in the gas system or with the feed of the for transportation to an aggregate for the conversion into energy of the gas is in most cases a dewatering of the pure gas (6) be necessary. This dewatering can be carried out with the after State of the kind available devices. 6. Figures Two Figures, see continuation pages.