DE19531942A1 - Cement-free hydraulic setting building material prodn. - Google Patents

Abstract

Prodn. of a cement-free hydraulically setting dump construction material and of systems for dumped material consolidation and immobilisation from a mixt. of filter ash and wet ash from brown coal-fired power stations, with addn. of smelter sand, comprises: (a) hydration of the active constituents of the starting material, which is initiated, accelerated and/or controlled by addn. of the requisite activator, in the form of part of the filter ash which has been intentionally moistened and pre-hydrated by process water from a flue gas desulphurisation unit, so that only the free lime is slaked; and (b) using flue gas desulphurisation process water as (part of) the added water.

Description

The invention relates to a method for producing hydraulically hardening landfill building materials and systems for Landfill consolidation and immobilization from residues of lignite-fired power plants.

Modern lignite-fired power plants are only included Flue gas desulfurization plants operated. If you want high Achieve desulfurization levels is the use of a Wet desulfurization is essential. As residues of one Power plant operations ultimately fall various ashes as well as solid and liquid Residues of the flue gas desulfurization, which accordingly must be disposed of in accordance with the statutory provisions. The Disposal is very costly for the Power plant operators.

There is a solution to this problem various suggestions.

A method for producing a binder is known and its use, the desulfurization product first mixed with fly ash in such an amount will that in the subsequent oxidation and Calcination process its content of free and at the same time lime released completely with water reactive aluminates and silicates bound, then ground the multiphase mixture formed and finally with the ground multi-phase mixture Hut sand is mixed (DE-OS 38 21 657).

This process is very complex to handle. Of the mentioned oxidation and calcination process runs at approx. From 1000 ° C. The grinding of the mixture requires in addition to the heat treatment, another apparatus Expenditure.

According to this procedure, a special clinker is made first Fly ash and a desulfurization product at temperatures over 700 ° C (see claim 4) produced, the fine  ground and together with ground slag sand into one Finished product is mixed. In thermal synthesis arise in the above Special clinker new minerals (cf. Claim 1), which from the Portland cement clinker (z. B. C₂S and C₁₂A₇) or from the clinker for sulfoaluminate cements (e.g. C₃A₃Cs) have been known in cement chemistry for years and be produced by the cement industry.

The binding properties of the product so produced are based on the properties of thermal Synthesis of minerals. The above Patent specification does not talk about recycling wet ash and REA water.

Making one quickly after starting with water the solidifying hydraulic binder describes the DE-OS 38 43 625. In this process Calcium-Alphahy Drat sand blended in. The calcium sulfate alpha halfhy drat represents the rapid setting component, the In contrast, blastfurnace slag is in the long-term range reacting latent hydraulic component. The emerging Dihydrate works as a sulfate stimulator for the Slag sand.

The aim of this process is the production of a water resistant gypsum binder. As a disadvantage of the process is the use of an already treated and therefore costly product from the gypsum or REA gypsum finishing can be seen. The high quality and expensive Sulfate binder - calcium sulfate alpha hemihydrate - is essential component or main component of the End product (see page 1 of the description). A Recycling of filter ash, wet ash and REA water not addressed.  

A method for the disposal of is also known pollutant-laden substances and a use of the manufactured product according to WO 88/02739, the to disposal material immediately with ash, if necessary under Add water, setting a water / ash ratio mixed between 0.23 and 0.35 and the Then mix completely hydra in retirement tized. Here z. B. the fly ash of a coal power plant kes with the waste product from the flue gas desulfurization plant (50 mass% fly ash and 50 mass% calcium sulfate / sulfite mixture) and the waste water from the same flue gas sulfurization plant intimately mixed.

This process is limited to using ashes at least latent hydraulic properties (see page 3 and Claim 1). Such ashes have their own setting property ten, d. i.e., is capable of adding an exciter (latent hydraulic ash) or without additional stimulators (hydraulic ash) under water. Other Abbin demechanisms, e.g. B. gypsum or lime-like, can not be referred to as (latent) hydraulic. The water/ The ash ratio is above all very limited adjustable and is always below 0.35.

The aim of the process is after complete hydrauli shear hardening of solid or deposited Breaking / grinding as binding material or as a filter layer e.g. B. can be used in landfills or soils.

The invention has for its object from the water a flue gas desulphurization plant (REA water), the ashes a coal-fired power plant and, if applicable, blast furnace sand To develop special building material that is an elution-proof Immobilization of all existing pollutants sufficient compressive strength without the addition of cement guaranteed and hydraulically hardened under water as well is stable when stored in water.  

This is achieved in that the invention Hydration of the active ingredients in the raw materials initiated by supplied necessary stimulators and / or is accelerated and / or controlled, being a stimulator Part of the flue gas desulfurization process water system (REA) specifically humidified and pre-hydrated Filter ash in which only the free lime (CaO) is extinguished was used and that as mixing water or as Part of the mixing water REA process water is used.

The proportion of the ash mixture from brown coal filter ash and wet ash on the total mixture should at least 50% by mass and the maximum proportion of slag sand 50 mass%. The water-solids ratio should do not exceed 0.5. The wet ash can completely or partially by one or more silicate (s) or clayey silicate (s), by Fluidized bed ash, foundry sand, tempered or untempered mining material, recycled concrete and Brick grit, clay or concrete or a mixture of the mentioned substances are replaced.

The brown coal filter ash (s) can also completely or partially from a mixture Hard coal and / or lignite fluidized bed ash be replaced. It is also possible to use sulfate and calcareous lignite filter ash and / or FGD gypsum and / or α-, β-gypsum or anhydrite from REA gypsum and / or non-ash residues from industrial processes and / or sulfates, clinker, water glass or soda too use. Instead of REA process water is also normal Tap water possible as mixing water. As lignite Filter ashes are preferably mixed ashes of various types which flue gas purification levels are considered while in shape of the aggregate preferably a wet ash in the Band width up to 2 mm grain size is used. Of the Slag sand is used as a hydraulic binder.  

It is a finely ground latent hydraulic fabric (preferably 2500-4000 cm² / g) Substance in the form with the addition of exciters (CaO, sulfate) of REA water can also set under water.

It is between water / solids and water / filter ash ratio distinguished, the Wasser- or REA-What water / filter ash ratio is always greater than 0.35.

After extensive trials, it was surprisingly found that a targeted and controlled deletion of the Free lime content of filter ash by moistening and Pre-hydration using process water Flue gas desulfurization system for the initiation of almost complete hydration of the active ingredients of the Leads. This allows hydration speed up or slow down. As the mixing water of the Ash mixture and the slag sand also comes REA process water for use. The hardening of the prepared mixture is shrinkage free under lighter Swelling. The swelling depends on the proportion of brought in hut sand. This increases the Immobilization effect of the pollutants and the Resistance to leaching.

The present results show that even with addition from 2.5 to 3.5 mass% of slag sand to one Lignite filter ash / REA / water mixture in one REA water / filter ash ratio of approx. 0.5-0.8 with a strength of 3-5 N / mm² after 7 days in water tion is to be expected. An extremely high level of integration of REA water (W / A ratio of 3.5) is e.g. B. at a Addition of 12.5% by mass of slag sand reached.  

The solution according to the invention thus has the following advantages on:

• - All types of ash can be used. Also pozzolanic ashes that are only added by adding Reaction partners (lime, cement, slag sand) hydraulically set, are suitable according to this procedure.
• - Use wet ash, which as an inert or z. T. inert substance simultaneously the roles of the fine aggregate in the system as well as the water storage. At the same time, the wet ash serves as a water supplier for the later slow hydration of the slag sand and part of the ashes.
• - REA water of seizure quality is used as water.
• - Coarse filter ash can also be used (below 2000 cm² / g) in addition to the wet ash with a naturally occurring as well used with sand or pebble-like grain structure will.
• - The individual components do not all have to be from the start be mixed.
• - High integration of REA water in the mixture.
• - Minimal leachability of sulfate and chloride.
• - Resistance to space when stored in water.
• - Sufficient final compressive strength of the hardening mixture from 2-10 N / mm².
• - Permeability coefficient (k value) less than 10-7 m / s.
• - economically competitive landfill building material.  
• - Building material handling of the fresh mass (Mixing / pumping units, compressibility, solidification).

Using two exemplary embodiments, the Invention will be explained in more detail.

example 1

According to the invention, a mixture of 50% (m / m) was obtained Lusatian lignite filter ash (BFA) and 50% (m / m) ground blast furnace sand (HüS) with the addition of REA water produced.

The REA water / BFA mass ratio was 3.5. This The brown coal wet ash was mixed into the mixture. The Mass ratio o. G. BFA / HüS binder for wet ash was 1 to 3. The mixtures composed in this way based on prisms produced on DIN 1164 were 1 day at 20 ° C / 95% relative humidity stored. Further storage the samples took place underwater at 20 ° C.

The samples with a slag sand content of the solid mixture of 12.5% (m / m) have proven to be water-resistant and reached after 7 or 28 days as described above The following strengths:

Example 2

According to the invention, a mixture of 95% (m / m) was obtained Lusatian lignite filter ash (BFA) and 5% (m / m) ground blast furnace sand (HüS) with the addition of REA water produced.

The REA water / BFA mass ratio was 0.82. This The brown coal wet ash was mixed into the mixture. The Mass ratio o. G. BFA / HüS binder for wet ash was 1 to 1. The mixtures composed in this way based on prisms produced on DIN 1164 were 1 day at 20 ° C / 95% relative humidity stored. Further storage the samples took place underwater at 20 ° C.

The samples with a slag sand content of the solid mixture of 2.5% (m / m) have proven to be water resistant and reached after 7 or 28 days as described above The following strengths:

Claims (8)

1. A process for the production of cement-free hydraulically hardening landfill building materials and systems for landfill consolidation and immobilization from an ash mixture of filter ash and wet ash from lignite-fired power plants with the addition of blast furnace sand, characterized in that the hydration of the active constituents of the starting materials is initiated by supplied necessary stimulators and / or accelerated and / or controlled, part of the filter ash specifically moistened and pre-hydrated by process water from a flue gas desulphurization system (REA), in which only the free lime (CaO) was extinguished, used as the exciter and as mixing water or as part of the mixing water REA process water is used. 2. The method according to claim 1, characterized in that the wet ash completely or partially by one or several silicate or clayey-silicate substances is replaced. 3. The method according to claim 1 and 2, characterized in that that all or part of the wet ash Fluidized bed ash from stone and / or brown coal power plants cen, foundry sand, annealed or untempered bergema material, building rubble and recycled concrete breakage - in particular the fraction <5 mm - and brick chips or by a Mixture of the above Substances to be replaced. 4. The method according to claim 1 to 3, characterized in that that the wet ash is wholly or partly by clay and / or concrete is replaced. 5. The method according to claim 1 to 4, characterized in that that the ash mixture from lignite filter ash is complete  dig or partially through a mixture of hard coal vortices layer pockets and / or lignite fluidised layer layers is set. 6. The method according to claim 1 to 5, characterized in that that the stimulator completely or partially by sulfate and calcareous lignite filter ash and / or through REA gypsum and / or by β-, α-gypsum or anhydrite REA gypsum is replaced. 7. The method according to claim 1 to 6, characterized in that that the stimulator is completely or partially by non-ash residues from industrial processes or replaced by sulfates, clinker, water glass or soda becomes. 8. The method according to claim 1 to 7, characterized in that that the mixing water does not contain any REA process water.