DE102014006630B4 - Process for the safe disposal of power plant residues from thermal combustion of fossil fuels - Google Patents

Abstract

The invention relates to a method for the foreign waste disposal of power plant residues from thermal combustion of fossil fuels, being used as power plant residues ashes from a combustion of lignite. The invention has for its object to develop a method for the foreign waste disposal of power plant residues from thermal combustion of fossil fuels, which provides a safe, complete, fast and auslaugsichere possibility to store polluted power plant residues. This is inventively achieved in that a lime-rich lignite filter ash (BFA) with a free lime content of 8 to 10 M% additionally by an admixture of even lime-rich fluidized bed ash (WSA) with a share of 5 to 20 M% and a free lime content of 11 to 25 M-% is activated in a two-stage process such that the temperature-developing quenching reaction and the solidifying phase formation reactions are separated both temporally and spatially, wherein • in a first stage, the ash mixture depending on the present free lime content with mixing water in the order of 3 to 18 M% of the respective amount of ash is mixed, that with an optimal storage density of the ash particles, a complete filling of the remaining pore space is achieved, • the mixture is then stored and • mixed in a second stage by means of mixing so that the resulting mixture according to D Run the second stage, a water content of 1 to 25% by mass of the amount of ash depending on the present particle size distribution and a stabilizer is prepared, which ensures a quality-consistent installation consistency of the mix, the built-in water content of the mixture in a landfill space above the value of soil mechanical relevant Proctorgehaltes is set, and structure strengthening and -compacting reaction processes under the conditions of low-hydrothermal synthesis processes are created, the earth-moist introduced mixture after an additional compaction process when installed as landfill body in the form of monolithic microstructure bodies (monobody) is produced.

Description

The invention relates to a method for the foreign waste disposal of power plant residues from thermal combustion of fossil fuels, being used as power plant residues ashes from a combustion of lignite.

Modern lignite-fired power plants are only operated with flue gas desulphurisation plants (REA). If you want to achieve high levels of desulfurization, the use of a wet desulfurization is essential. The residues of such a power plant operation ultimately fall to a variety of ashes and solid and liquid residues of the flue gas desulfurization, which are to dispose of according to the legal provisions. Such disposals are costly for the power plant operator.

From the WO 88/02739 is a method for the disposal of pollutant-laden materials and a use of the product manufactured known, wherein the substance to be disposed directly with ash, optionally with the addition of water, while setting a water / ash ratio between 0.23 and 0.35 is mixed and the Mixture then fully hydrated at rest.

The DE 195 31 942 C2 describes a very similar process in which blast furnace sand is added to a mixture of filter ash and wet ash from lignite power plants to which are added as excitation filter ash, which are prehydrated with process water of a REA so that only their free lime is extinguished, using process water as a make-up REA becomes.

Also at the DE 44 29 781 C2 A method for the disposal of fly ash with high free lime content is described in which the fly ash is mixed with 10 to 25% water in order to extinguish the free lime sufficiently (at least one hour). The extinguished fly ash is then mixed in a second step again with 25% to 35% water and then transported away via a belt conveyor or chaff.

A very similar procedure describes the DE 101 09 903 A1 in which fly ash after a first mixing with water in a second step on the transport path at one or more places is moistened again with water, so that sets a moisture content of 15 to 35%.

A method for producing a substitute building material and for covering landfills describes the DE 10 2004 059 234 A1 , Here, ashes and waste are mixed in an intensive mixer until a pH of 10 to 11 sets and then compacted installed in a landfill.

The DE 196 32 518 B4 describes a system for treating CaO-containing material with water following a mixing device mixing the material, wherein the transport is guided on an upwardly open conveyor in a tunnel or under a hood and created by the hood together with the conveying means a reaction space is provided with at least one venting device in which a heat of reaction of 70 ° to 140 ° C is generated for the conveyed.

A similar plant will be in the DE 10 2007 056 905 A1 described in which waste materials are requested via a guided in a housing screw, the housing has a heating unit.

A treatment plant for the treatment and utilization of fly ash from power plants, in particular fly ash from electrostatic precipitators, wet separators, etc. describes the DE 20 2006 003 458 U1 ,

The DD 291 015 A5 describes a method for the treatment of calcareous fly ash, the entire ash is pre-moistened with a defined water claim, after a three-minute reaction time completely or partially dispersed in a gas stream and classified and the fine grain fraction of about 20 +/- 5 microns is subjected to a repeated Ablöschreaktion so that a powdery product is formed.

• 1. Es findet eine Dispergierung des Gemisches aus zwei Filteraschen oder deren Komponenten mit einem hohen Wasseranteil statt.
• 2. Es findet keine Zwischenlagerung der Dispersion statt (Reaktionszeit).
• 3. Das Verfahren ist schwer nacharbeitbar und kompliziert handhabbar.

In the DE 4103 412 C2 describes a process for producing a composition which is hydratable to a building and / or sealing material using filter ash, wherein the filter ash is stirred with the addition of water and the mass is processed into the building and / or sealant, for mixtures of at least two Filter ashes and / or filter ash components, which have different Körnungsbänder, the respective water claim for the production of the respective mixing ratio corresponding dispersion is determined, and that the filter ash and / or Filteraschekomponenten in a mixing ratio, which is outside the mix of W / A value or a Relative maximum of the curve of the W / A value in the range of a relative minimum of the W / A value or a region with a relatively small A / W change, is mixed and stirred to a dispersion. This method has several disadvantages:

• 1. There is a dispersion of the mixture of two filter bags or their components with a high water content instead.
• 2. There is no intermediate storage of the dispersion (reaction time).
• 3. The process is difficult to reproduce and complicated to handle.

The DE 10 2004 051 A1 describes a process for producing a landfill binder for the immobilization and solidification of waste containing heavy metals in a landfill, wherein the respective solubility or concentration of the phase former and determined solid SO ₃ , uses these results for the calculation of the substance proportions and the determined proportions to a mixture with a water content of 2 to 40 M% mixed and applied as a layer on a landfill surface, compacted and formed as a self-supporting layer with a high proportion of a finely crystalline, silicon-containing ettringite. After a premixing of the mixture and a water addition of 20 to 40% by mass, the mixture can be mixed according to claim 2, in which context no further statements are made throughout the document. The process is basically carried out in one stage. A possible remixing is coupled to a high water demand of 20 to 40 M%. There is no intermediate storage of the mixture.

• • die Ablöschung von kalkhaltigen BFA ist oft zeitaufwendig und kostenintensiv
• • derartige Aschen neigen unter Wassereinwirkung zu heftigen hydraulischen Reaktionen mit massiven Wärmeentwicklungen und anschließenden Treiben, sodass in der Regel keine auslaugsichere Lagerung möglich ist
• • die Zugabe von Zusatzmitteln, wie Hüttensand, REA-Gips, REA-Prozesswässern, Klärschlamm etc. macht eine Ablöschung noch schwieriger und die Reaktionen noch komplexer
• • es liegen in der Regel dann Festkörper vor, die aufgrund der unkontrollierten Volumenzunahme der Asche nach Wasserkontakt eine heftige Riss- und Bruchbildung aufweisen, so dass entweder ein trockenes, abgelöschtes Schüttgut mit hohen Restkalkgehalten oder ein zerstörter Festkörper (ebenfalls mit unreagierten Freikalk-Anteilen) vorliegt

All known methods for depositing ash have the following disadvantages:

• • the deletion of calcareous BFA is often time consuming and costly
• • Such ashes tend to violent hydraulic reactions when exposed to water with massive heat and subsequent drift, so that usually no auslaugsichere storage is possible
• • the addition of additives such as blastfurnace slag, REA gypsum, REA process water, sewage sludge, etc. makes extinguishing even more difficult and the reactions even more complex
• • there are then usually solid, which have due to the uncontrolled increase in volume of ash after contact with water a violent cracking and breakage, so that either a dry, extinguished bulk material with high lime content or a destroyed solid (also with unreacted free lime content) present

The invention has for its object to develop a method for the foreign waste disposal of power plant residues from thermal combustion of fossil fuels, which provides a safe, complete, fast and auslaugsichere possibility to store polluted power plant residues.

• eine kalkreiche Braunkohlenfilterasche (BFA) mit einem Freikalkgehalt von 8 bis 10 M-% zusätzlich durch eine Beimischung von noch kalkreicheren Wirbelschichtaschen (WSA) mit einem Anteil von 5 bis 20 M-% und einem Freikalkgehalt von 11 bis 25 M-% in einem zweistufigen Verfahren derart aktiviert wird, dass die temperaturentwickelnde Löschungsreaktion und die verfestigende Phasenbildungsreaktionen sowohl zeitlich als auch räumlich voneinander getrennt werden, wobei
• • in einer ersten Stufe das Aschegemisch je nach vorliegendem Freikalkgehalt mit Anmachwasser in einer Größenordnung von 3 bis 18 M-% der jeweiligen Aschemenge vermischt wird, dass bei einer optimalen Lagerungsdichte der Aschepartikel eine vollständige Ausfüllung des verbleibenden Porenraumes erreicht wird,
• • wobei das Gemisch anschließend zwischengelagert wird und
• • in einer zweiten Stufe mittels Nachmischung so gemischt wird, dass das entstehende Gemisch nach Durchlaufen der zweiten Stufe einen Wassergehalt von 1 bis 25 Ma-% der Aschemenge in Abhängigkeit von der vorliegenden Korngrößenverteilung aufweist und ein Stabilisat hergestellt wird, welches eine qualitätsgerechte Einbaukonsistenz des Mischgutes sicherstellt, wobei der Einbauwassergehalt des Gemisches in einen Deponieraum über dem Wert des bodenmechanisch relevanten Proctorgehaltes eingestellt wird, und gefügeverfestigende sowie -verdichtende Reaktionsprozesse unter den Bedingungen niedrig-hydrothermaler Syntheseprozesse geschaffen werden, wobei das erdfeucht eingebrachte Gemisch nach einem zusätzlichen Verdichtungsvorgang beim Einbau als Deponiekörper in Form monolithischer Gefügekörper (Monokörper) hergestellt wird.

This is inventively achieved in that

• a lime-rich lignite filter ash (BFA) with a free lime content of 8 to 10 M% additionally by an admixture of even lime-rich fluidized bed ash (WSA) with a share of 5 to 20 M% and a free lime content of 11 to 25 M% in a two-stage Method is activated so that the temperature-developing quenching reaction and the solidifying phase formation reactions are separated both temporally and spatially, wherein
• In a first stage, the ash mixture, depending on the free lime content present, is mixed with mixing water of the order of 3 to 18% by weight of the respective amount of ash so that complete filling of the remaining pore space is achieved with an optimum storage density of the ash particles;
• • wherein the mixture is then stored and
• Is mixed in a second stage by means of subsequent mixing so that the resulting mixture after passing through the second stage has a water content of 1 to 25% by mass of the amount of ash depending on the present particle size distribution and a stabilizer is prepared, which is a quality-consistent installation consistency of the mix ensures, wherein the built-in water content of the mixture is set in a landfill space above the value of soil mechanically relevant Proctorgehaltes, and fabric strengthening and compression reaction processes under the conditions of low-hydrothermal synthesis processes are created, the earth-moist introduced mixture after an additional compression process when installed as landfill body in Form monolithic microstructure body (monobody) is produced.

The free lime represents the main component of the reactive portion of the ash and is therefore due to its compared to the other components very high hydraulic reactivity and the associated phenomena (heat development, volume increase) determining the initial reaction behavior of the ash in contact with water.

• • des Freikalks
• • des Tricalciumaluminats und
• • des Yeelimits,

wobei keine der Reaktionen vollständig verläuft. Mit nur sehr minimalen oder keinen Reaktionserscheinungen gehen alle übrigen reaktiven Komponenten (Anhydrit, Brownmillerit, Periklas und Ascheglas) aus diesem Prozess hervor. Damit laufen in der ersten Verfahrensstufe bevorzugt jene Reaktionen ab, die die höchste Wärmefreisetzung aufsetzen. In diesem erfindungsgemäß ersten Prozess, wirken, bedingt durch die hohe Hydratationswärmeentwicklung, zwei konkurrierende Prozesse:

• a. die steigende Löslichkeit und zunehmende Reaktionsgeschwindigkeit des Freikalks,
• b. die beschleunigte Verdampfung des zum Freikalklöschen notwendigen freien Wassers im Reaktions-Gemisch

mit steigenden Temperaturen.The reactions which take place during the first stage of the process during ripening are essentially limited to the reaction:

• • the free lime
• • tricalcium aluminate and
• • the Yeelimit,

where none of the reactions is complete. With very minimal or no Reaction phenomena are apparent from all other reactive components (anhydrite, brownmillerite, periclase and ash glass) from this process. Thus, in the first stage of the process, preferably those reactions take place which produce the highest heat release. In this first process according to the invention, due to the high heat of hydration, two competing processes act:

• a. the increasing solubility and increasing reaction rate of the free lime,
• b. the accelerated evaporation of the free water necessary for free water in the reaction mixture

with rising temperatures.

• • trockenes, abgelöschtes Schüttgut mit hohen Restfreikalkgehalten oder
• • zerstörter Festkörper (ebenfalls mit unreagierten Freikalk-Anteilen) vor.

Since the reaction a. is also dependent on other chemically and physically influenced states of the free lime (firing temperature, grain size, chemical composition or purity), the time required for a complete free-lime conversion is usually longer than that for the evaporation of the water in the mixture, that is the extinguished ash material is dry despite excess water (based on the stoichiometrically necessary for the quenching reaction water requirement) before the free lime is completely hydrated. Although a greater excess of water reduces the temperature development in the ash-water mixture, but also changes the conditions of formation for the ongoing Hydratphasenkristallisation and consistency and thus pore ratios of the material. The consequence would be rapid, strongly solidifying reactions (ettringite formation), which, accelerated by the elevated temperatures, lead to a stone-like hardening of the material and are desired in this form only at the time when the ash-water mixture through the entire process and has been disposed of in the intended form. These reactions would also be complete before the free-lime is completely hydrated. All other possible reactions due to the still available water practically ran off in a solid, which would react to the associated increase in volume with cracking and fracturing. As a result of both reaction processes, the ash would be at a single addition of water, depending on the amount of water added either as

• • dry, quenched bulk material with high residual free chalk content or
• • destroyed solid (also with unreacted free lime content).

In the context of elaborate series of experiments, it has surprisingly been found that a high free-lime quench occurs within the scope of the two-stage process according to the invention if the temperature-developing quenching reaction and the solidifying phase-forming reaction were separated in time and space from each other in the first stage. To ensure this, it is necessary to store the moistened, reacting ash in a system, which ensures a longer residence time and thus contact time of the mixing water with the free lime. The second stage of the process must ensure a quality-consistent installation consistency of the mixed material in accordance with the desired material technology properties of the solidified end product (stabilizer).

• • dem Einbauwassergehalt
• • der Einbautemperatur
• • den Umgebungseinflüssen
• • den Hydratationswärmeentwicklungen

innerhalb des Stabilisatkörpers bestimmt, wobei aufgrund seiner Dimension von einer ausgesprochenen Konstanz langzeitwirkender mechanischer und thermischer Einflüsse auszugehen ist.As a result of the procedural separation of the quenching and solidification process, the structure-forming hydration reactions essentially shift to the period after final mixing of the mixed material. At this time, the material must have all the features that enable it to cure to a long-term stable product with the required performance properties. The reaction mechanisms at this stage are mainly due to temperature and pressure conditions resulting from:

• • the built-in water content
• • the installation temperature
• • the environment
• • the hydration heat developments

determined within the Stabilisatkörpers, which is due to its dimension of a pronounced constancy of long-term mechanical and thermal influences is assumed.

The ash-water mixture according to the invention is a chemically active, dynamic, time-varying system whose sealing and strength properties are constantly improving as time progresses, since the hardening processes are accompanied by the progressive formation of new crystalline or amorphous phases resulting from those described with reference to FIG these phases excrete saturated pore solutions, perform. The soil mechanical properties are completely lost with increasing age in favor of a concrete-like consolidation and compaction. At the time when the ash-water mixture has the best performance properties as a stabilizer, it is available as a rigid solid-state system whose deformation behavior is exclusively elastic.

In addition to the purely physical elution reduction due to the increasing structure density, these new phases are, due to their specific chemistry, causally responsible for the pollutant immobilization capacity of the ash stabilizer in the true sense of a crystal chemical fixation. Prerequisite for a sufficient reduction of porosity in the course The solidification is the greatest possible water saturation of the pore space, since the condensing (and solidifying) hydrate phase formation processes proceed exclusively in the aqueous phase. It has been found that all remaining at the time of installation end air pores are retained even after curing of the mixture to a solid (stabilizer) in full and can only be reactivated by subsequent water supply. For this reason, a water content is required to achieve maximum material properties, which completely fills the remaining pore space with optimum storage density of the ash particles after installation or compression. The pore space must be sufficient to absorb all crystallizations and the associated crystallization pressures without stress and expansion. For this purpose, it is necessary that the built-in water content is above the value of the soil mechanically relevant Proctorgehaltes. By transferring the system into a constrained state by applying appropriately sized loads, crack formation can be counteracted. The ballast must be completed within 24 hours and has to reach twice the height of the mounting position to be weighted. A 1 m high layer installed in a 25 x 25 m grid must be covered with a height of 2 m so that 1,000 t of ash are installed in the first layer and then covered with approx. 2,000 t of ash. The known soil mechanical relations between initial degree of compaction and structure tightness is not transferable to hydraulically responsive systems. High densities of the built-ash-water-fresh mixture under any circumstances pull high leaks and thus low water permeability of the stabilizer necessarily after. The reactions taking place during this period only have a compressive effect, as long as the newly formed structures crystallize inwards, ie close the pore spaces. If this room is no longer available, they only act expansively to the outside, joint-loosening and contrary to the original compaction during installation. Although a very high degree of compaction for strongly reacting systems primarily reduces the available pore space, it subsequently leads, in the course of the reaction, to a considerably greater secondary expansion of the microstructure, that is to say undesired drifting.

It has been found that the ash stabilizer to be produced is considered to be an artificially created solid which combines the properties of a geogenic diagenetically solidified sedimentary rock with those of a technogenously produced cement mortar.

Due to the pollutant-immobilizing properties of the hydraulic bond strengthening and compacting reaction processes, the entire ash body acts as a pollutant leakage barrier. The central ash body and possibly separately applied ash layers (landfill base, lid seal) form a materially identical system in which the circulating or flowing solutions are chemically in equilibrium with the surrounding ash material - a concentration gradient of pollutants within the ash body according to the invention does not exist - so that for the Material discharge from this system only the Eigenelutionsverhalten the ash stabilizer is relevant.

The ash body according to the invention is therefore to be regarded in its entirety as a monolithic microstructure.

Due to the material identity of the landfill body to be produced and sublayers to be applied separately, similar exothermic hydration processes take place in both areas, which are comparable to heat-releasing setting and hardening processes in the cement or concrete sector. The amount and course of the temperatures that occur essentially determine the chemical character of the reaction processes taking place and the stability of the hydration products formed.

In the case of the stabilizer to be prepared according to the invention, a long-term effect of temperatures in the range of> 80 ° C., preferably 80 to 100 ° C., is to be assumed almost in the entire material. The temperatures then slowly go back inside the ash body. The microstructure-strengthening and compacting reaction processes thus proceed under conditions of low-hydrothermal synthesis processes. The high heat storage capacity and the good insulation properties of the ash stabilizer and the pronounced long-term effect of some phase formation processes cause a long-term stability of the given environmental conditions, so that even retrograde cooling processes will take place in periods which in themselves have a quasi-static (isothermal) equilibrium with regard to the thermodynamics of chemical reactions represents.

The ash body is therefore to be regarded as a monolithic overall system also from the perspective of physical effects.

Advantages of the invention:

• • Outlet-safe, long-term stable disposal of power plant residues possible
• • no additional landfill measures (sole, cover) necessary, except for the special installation of the material
• • For the first time, single-gapped monobodies made of different ashes in the form of a concrete-like block
• • Activator enables a fast hydraulic and yet manageable reaction
• • very low permeabilities (eluent ability)
• • Degradation of the free CaO contained in the ashes through the first reaction time between mixing stages 1 and 2
• • Production of a self-hardening installation material
• • complete integration of the added process / mixing water

embodiment

Reference to an embodiment, the invention will be explained in more detail below.

Showing:

1 - temporal correlation between temperature evolution and phase degradation

2 - Influence of the WSA admixture on the reaction rate and the maximum temperature reached in the quenching test

In the course of extensive and long-term investigations, it was found that the reaction behavior of lignite filter ash can be added by admixing calcareous components in the form of fluidized bed ash in order to greatly improve and influence the reaction behavior of the filter ash in the quenching and maturing process. This makes it possible to specifically counteract difficulties in the process of a two-stage treatment of filter ash, which are caused by the greatly delayed reaction behavior of the filter ash.

Fluidized bed ash (WSA) often has a high free lime content, which reacts in contrast to the free lime of the filter ash within a short time after addition of water with release of heat. However, since fluidized-bed ash has large amounts of non-reactive components as a result of its formation, higher addition amounts are required in order to achieve a desired thermal effect.

Since a calcareous absorber medium for desulfurization is added directly to the combustion chamber in fluidized bed plants, WSA are a mixture of ash, desulfurization product and residual additives. As a result, the WSA always have high levels of free lime and sulfur (SO ₃ ); In addition, the free lime of the WSA is hydraulically very reactive due to the comparatively low combustion temperatures. In contrast to the filter ash, the WSA have small amounts of Al ₂ O ₃ and SiO ₂ .

The significantly higher free lime content (between 11 and 25% by mass, depending on the source of the WSA) compared to the BFA (about 8% by mass) increases the lime content in the BFA-WSA mixture.

The admixture of WSA in proportions of 5 to 25% by mass results in an acceleration of the quenching reaction and an increase in the temperature maximum achieved for the BFA investigated. The amount and type of WSA influence the reactivity of the filter ashes to different degrees.

The water permeability of the stabilizer must satisfy a value of <5 × 10 ^-9 m / s.

• – Die mitteldeutsche BFA kann durch Zumischung von WSA im Bereich von 5 bis 20 Ma-% in ihrem Reaktionsverhalten verbessert werden.
• – Die höhere Reaktivität der WSA führt im Ablöschprozess des Aschegemisches zu einer Anhebung des Temperaturniveaus und zu einem beschleunigten Ablauf der Löschreaktion.
• – Das Ausmaß der Reaktionsbeschleunigung und Temperaturanhebung steigt mit zunehmendem WSA-Anteil im Gemisch.
• – Trotz höherer Ausgangsgehalte durch Zumischung von WSA verbleiben im Aschegemisch nach Abschluss des Ablösch- und Reifeprozesses keine höheren Restfreikalkgehalte.
• – Die Zumischung der WSA hat keinen negativen Einfluss auf die Ausbildung der Stabilisatfestigkeit und führt in nahezu allen Fällen zu gleichen bis höheren Druckfestigkeitswerten im Vergleich zum reinen BFA-Stabilisat ohne WSA-Zumischung.
• – In Bezug auf die Wasserdurchlässigkeit des Stabilisats bewegen sich die Werte der WSA-haltigen Versuchsserien im Bereich bzw. unterhalb jener des reinen BFA-Stabilisats.
• – Das Auslaugverhalten des Stabilisats wird durch die Zumischung von WSA in seiner Charakteristik nicht verändert. Bestimmend für den Umfang der Stofffreisetzungen sind die Qualität der BFA und die thermischen Lagerungsbedingungen entscheidend.
• – Die Wasserlagerungsbeständigkeit der Stabilisate zeigt eine stark ausgeprägte Abhängigkeit von der Menge an zugemischter WSA. Während bis zu einem WSA-Anteil von 15 Ma-% WSA-Zumischung keine Beeinträchtigung in der Beständigkeit erkennbar wird, zeigen die Stabilisate mit 25 Ma-% WSA-Zumischung starke Quellerscheinungen bis hin zum vollständigem Zerfall. Dieses Verhalten ist abhängig von der jeweiligen Herkunft der WSA.
• – Großtechnische Versuche zur Einbautechnologie haben gezeigt, dass ein lagenweiser Verschub des abgekippten Asche-Wasser-Gemisches mittels Planierraupe notwendig und ausreichend ist, um in Form eines terrassenförmig angelegten, die Überdeckung des eingebauten Materials gewährleistenden Aschenkörpers die materialtechnischen Anforderungen erfüllen.
• – Die Verfestigung des Asche-Wasser-Gemisches zu einem gesteinsähnlichen Festkörper (Stabilisat) führt neben der Freisetzung von erheblicher Wärmemengen in Verbindung mit den adiabatischen Eigenschaften großvolumiger Körper im Gefügeverband eines Großkörpers zu langzeitwirkenden hydrothermalen Temperaturbedingungen.
• – Die Temperaturverläufe insgesamt sind unabhängig von Messanordnung und Materialdimension durch zwei getrennte exotherme Effekte gekennzeichnet:
• – Der Erste, im Zeitintervall von 0 bis 24 Std. angesiedelt, läuft parallel mit dem vollständigen Umsatz der reaktiven Komponenten Anhydrit und Yeelenit unter intensiver Bildung von Ettringit.
• – Der Zweite, wesentlich beschleunigter verlaufende Effekt zwischen 24 und 60 Std. ist phasenanalytisch mit weiterer Ettringitbildung und Abbaureaktionen am Freikalk und Brownmillerit verbunden. Es wurde nachgewiesen, dass sich die Ettringitbildungen in beiden Temperatur-Phasen chemisch und hinsichtlich ihrer Korngröße erheblich voneinander unterschieden, so dass sie zwei unterschiedlichen Reaktionsmechanismen zugeordnet werden können.
• – Die Expansion selbst verläuft im Aschekörper nicht isotop, sie ist abhängig von den Auflastverhältnissen. Tieferliegende Bereiche des Monoblocks zeigen aufgrund größerer Materialzwängungen eine geringere Ausdehnung als an der Materialoberfläche.
• – Der Reaktionsmechanismus ist als eine Art Langzeit-in-situ-Hydrothermalsynthese zu charakterisieren, die zum einen neue Temperatur, Druck- und damit Stabilitätsverhältnisse für bereits existierende Strukturen schafft (hier: Ettringit), und zum anderen für Strukturen mit breiterem Stabilitätsbereich (hier: CASH- und CSH-Phasen) eine starke Beschleunigung der Kristallisationsvorgänge bewirkt.

The following conclusions can be derived from the investigations on the quenching behavior of Central German filter ash in a mixture with proportionally added WSA:

• - The Central German BFA can be improved by adding WSA in the range of 5 to 20% by mass in their reaction behavior.
• - The higher reactivity of the WSA leads in the quenching process of the ash mixture to an increase in the temperature level and to an accelerated execution of the quenching reaction.
• - The extent of reaction acceleration and temperature increase increases with increasing WSA content in the mixture.
• - Despite higher starting contents due to the admixture of WSA, no higher residual free-lime content remains in the ash mixture after completion of the quenching and maturing process.
• - The admixture of the WSA has no negative influence on the formation of the stabilizing strength and leads in almost all cases to equal to higher compressive strength values in comparison to the pure BFA stabilizer without WSA admixture.
• - With regard to the water permeability of the stabilizer, the values of the WSA-containing test series are within or below that of the pure BFA stabilizer.
• - The leaching behavior of the stabilizer is not changed by the admixture of WSA in its characteristics. The quality of the BFA and the thermal storage conditions are decisive for the extent of the release of the substances.
• - The water storage stability of the stabilizers shows a strong dependence on the amount of admixed WSA. While up to a WSA content of 15% by weight WSA admixture no impairment in the resistance is evident, the stabilizers with 25% by mass WSA admixture show strong swelling phenomena up to complete disintegration. This behavior depends on the origin of the WSA.
• - Large-scale experiments on installation technology have shown that a positional shift of the dumped ash-water mixture by means of bulldozer is necessary and sufficient to meet in the form of a terraced, the coverage of the built-in material ensuring ash body material requirements.
• - The solidification of the ash-water mixture to a rock-like solid (stabilizer) leads in addition to the release of significant amounts of heat in conjunction with the adiabatic properties of large-volume body in the structural union of a large body to long-term hydrothermal temperature conditions.
• The overall temperature profiles are characterized by two separate exothermic effects, independent of the measuring arrangement and material dimension:
• - The first, located in the time interval of 0 to 24 hours, runs parallel with the complete conversion of the reactive components anhydrite and yeelenite with intensive formation of ettringite.
• - The second, significantly accelerated running effect between 24 and 60 hours is phase-associated with further ettringite formation and degradation reactions on free lime and brownmillerite. It has been demonstrated that the ettringite formations in both temperature phases are chemically and significantly different in their grain size so that they can be assigned to two different reaction mechanisms.
• - The expansion itself is not isotope in the ash body, it depends on the Auflastverhältnissen. Lower-lying areas of the monoblock show a smaller expansion than at the material surface due to larger material constraints.
• - The reaction mechanism is to be characterized as a kind of long-term in situ hydrothermal synthesis, which creates a new temperature, pressure and thus stability conditions for already existing structures (here: ettringite), and for structures with a broader stability range (here: CASH and CSH phases) causes a strong acceleration of the crystallization processes.

• – Druckfestigkeit – 10 N/mm²
• – Wasserdurchlässigkeit – 5 × 10^–9 n/s
• – Elutionswerte
• • Sulfat – 500 mg/l
• • Chlorid – 95 mg/l
• • Calcium – 600 mg/l.

The monobody to be prepared from stabilizer achieves the following minimum values:

• - Compressive strength - 10 N / mm ²
• - water permeability - 5 × 10 ^-9 n / s
• - elution values
• • Sulfate - 500 mg / l
• • chloride - 95 mg / l
• • Calcium - 600 mg / l.

Claims (7)

Process for the safe disposal of power plant residues from thermal combustion of fossil fuels, using ash from incineration of lignite as power plant residues, characterized in that a lime-rich lignite filter ash (BFA) with a free lime content of 8 to 10 M% additionally by an admixture of even lime-rich fluidized bed ash (WSA) with a share of 5 to 20 M% and a free lime content of 11 to 25 M% in a two-stage Method is activated so that the temperature-developing quenching reaction and the solidifying phase formation reactions are separated both temporally and spatially, wherein In a first stage, the ash mixture, depending on the free lime content present, is mixed with mixing water of the order of 3 to 18% by weight of the respective amount of ash so that complete filling of the remaining pore space is achieved with an optimum storage density of the ash particles; • wherein the mixture is then stored and Is mixed in a second stage by means of subsequent mixing so that the resulting mixture after passing through the second stage has a water content of 1 to 25% by mass of the amount of ash depending on the present particle size distribution and a stabilizer is prepared which a quality-consistent installation consistency of the mix ensuring that the incorporation water content of the mixture in a landfill space is set above the value of the soil mechanically relevant Proctor content, and bond-strengthening and -compacting reaction processes are created under the conditions of low-hydrothermal synthesis processes, wherein the earth-moist introduced mixture after an additional compression process during installation as a landfill body in the form of monolithic microstructure body (monobody) is produced. A method according to claim 1, characterized in that the monobody is prepared so that after 180 days at least a compressive strength of 10 N / mm ² and / or a water permeability (kf value) of <5 × 10 ^-10 m / s and / or elution values for sulphate of 500 mg / l and / or for chloride of 95 mg / l and / or for calcium of 600 mg / l and a water storage resistance is achieved. A method according to claim 1 and 2, characterized in that the stabilized stabilization with heat so hydraulically that the Abbindereaktionen proceed in a temperature range of> 80 ° C, preferably from 80 ° C to 100 ° C, without cracking. A method according to claim 1 to 3, characterized in that the available installation volume is minimally filled by a minimized addition of process water / mixing water. A method according to claim 1 to 4, characterized in that REA water is used as mixing water. A method according to claim 1 to 5, characterized in that in the first stage of the BFA depending on the particular free lime content mixing water in the order of 3 to 15% by mass of the respective amount of ash is added. A method according to claim 1 to 6, characterized in that the mix is mixed in the first as well as the second stage so that in each case a residence time of 1.5 to 2 minutes is achieved.

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