DE102017123092A1 - Process for the purification of ground and surface water in the catchment area of coal mines using filter material such as biochar, which is produced by the known methods of pyrolysis or HTC - Google Patents

Abstract

The invention relates to a process for the purification of ground and surface waters in coal mines using biochar, which is used as a filter.

Description

The high iron and sulphate content is a late consequence of the decommissioning of opencast mines.

Years ago, the lignite excavators brought the minerals pyrite and marcasite to light when the groundwater was lowered. Upon contact with oxygen, they decomposed into iron hydroxide and sulfate. With the rising groundwater in the Bergbaufolgelandschaft now iron hydroxide and sulfate are flushed into the rivers and the open pit residual holes.

Exposure to acids, ferrous, sulphate, and, in addition, a number of heavy metals, such as arsenic and aluminum, is due to pyrite and marcasite weathering and its associated acidification.

Pyrite and marcasite are predominantly to be found as admixtures in the tertiary geological strata, which form the main part of the excavated masses in Lusatia, since predominantly only low-grade quaternary cover layers are formed. In the Central German area, too, the proportions of the tertiary strata in the roughage masses are increasing from south to north. Regardless of the particular tilting and dump areas are characterized in the Central German area by a strong tendency to acidification and as sulfate and iron source due to the inhomogeneous increase in the Abumummassen.

This phenomenon of acidification and hardening in coal mines will be counteracted by this invention.

According to the invention, the object is to find a method for the purification of groundwater and surface water using highly porous, produced by already known methods of pyrolysis or HTC filter material, wherein the application of biochar is carried out as a filter material.

The patent claim 1 is carried out as follows:
"Process for the purification of ground and surface water in coal mines using biochar, which is used as a filter, characterized in that between the inflow of groundwater and surface water filtering in the form of biochar is interposed and after saturation of the biochar an exchange this takes place and thus iron hydroxide is filtered with the biochar and non-polluted groundwater and surface water is forwarded as an underflow. "

The special physical properties of biochar, in particular its large and highly porous surface, cause the technical solution to the effect that the property of biochar is suitable as a filter material.

The extraction of biochar without land use takes place through the use of tree and shrub growth in the opencast mining holes, which are subject to the flooding process. This material is already recovered and can be used as biochar material. Further biomass production possibilities arise from the use of forest management material and stock rejuvenation in forest reclamation stocks, as well as agro-forestry material and from the herringbone material of rivers and other main receiving waters.

Furthermore, it is possible to activate the appropriate extraction of biochar from tree, shrub and grass clippings from private and municipal management. The required equipment is available. However, they should be decentralized plants in order to produce the biochar directly next to the resulting biomass.

The use of biochar for the purification of iron-hydroxide contaminated groundwater and surface water is new or not previously known. The problem of water pollution due to iron hydroxide and sulphate, which has existed for many years, can be remedied by the enormous filtering effect of biochar, if it is passed through as a filter by the groundwater and surface water.

The technological methods range from soil filters according to the principle of the diaphragm wall, as described in the patent claim 1, which is traversed by the groundwater, to filter systems in open waters. It is also possible to combine several processes, for example with drainage.

For the process application, a large amount of biochar is needed, which is prepared by the known methods of carbonization or pyrolysis.

• – Biomasseanfall,
• – standortnaher, dezentraler Anlagen der Carbonisierung aus der Biomasse und
• – Verwendung der Biokohle als Wasserfilter

wirken sich die Vorteile des komplexen Verfahrens auch auf die Ökonomie aus. Darüber hinaus gibt es zahlreiche, weitere Anwendungsmöglichkeiten für diese Biokohle. Ein Kohle-Wasser-Gemisch könnte als Alternative zu Kalkmilch in Grubenwasserreinigungsanlagen zum Einsatz kommen.In the production of a technological unit between

• - biomass attack,
• - Local, decentralized carbonization plants from biomass and
• - Use of biochar as a water filter

The benefits of the complex process also affect the economy. In addition, there are numerous other uses for this biochar. A coal-water mixture could used as an alternative to milk of lime in mine water treatment plants.

The contaminated biochar as filter material can subsequently be enriched in a composting process with plant nutrients. Thus, the entire carbon of the starting material would be permanently bound in the soil as CO ₂ sink and made a small contribution to climate change.

The 1 shows a schematic representation of the method, wherein the extraction of the biomass material from the tree growth 6 for biochar production 5 is introduced. In addition, other biogenic residues can be carbonized. The biochar gets into a filter shaft 1 stored. This filter shaft 1 is between the groundwater 3 and the Tagebausee 4 arranged.

After saturation of the biochar with iron hydroxide, the biochar becomes 2 digested with the iron hydroxide and sulphate in a mechanical process and new unloaded biochar 2 brought in. This process is performed permanently as a process flow.

Due to the high filter properties of biochar 2 is achieved that the iron hydroxide and sulfate in the filtering process between groundwater 3 and the lake 4 and filtered out in the surface water of a running water.

In the open watercourse, however, a filter basket, which is adapted to the trench profile and also filled with biochar, is introduced. A minimal build-up, as overflow or bottom outlet, directs the ditch water through the filter. If necessary, this construction can be repeated cascade-like in the further trench course. Thus, untreated ground and surface water in the lake 4 or passed into the next receiving water.

In the 2 an embodiment is described where an accumulated upper run 14 Water loaded with iron hydroxide on a weir system made of a concrete profile 10 is accumulated and a dam 7 , preferably of wooden planks, over a biofilter 8th with included biochar 2 is directed. After flow of the biofilter 8th with the biochar 2 creates an underflow iron-free 12 , which then flows into appropriate waters or in standing and flowing waters. The dam 7 can be realized via a minijack with shutter panel and spindle lift. Larger trench widths require mass-produced dams 7 which also has a concrete profile 10 exhibit. As a filter basket, a wire basket for gabions 250 × 100 × 30 cm can be used, which is lined with water-permeable textile fleece, to prevent the washing out of the filter carbon. The basket can be completely replaced by a new one after saturation of the coal. This is the biofilter 8th , In order to apply the process to a greater extent, these filter baskets, adapted to local conditions in size, even on existing dams 7 be attached.

The 4 and 5 show here schematic representations, such as a concrete profile 10 is given in a weir plant and to a dam 7 from wooden planks is integrated in a terrain.

In the 4 is a plan view of a water defense plant with a concrete profile 10 shown where you can see a dam 7 from wooden planks and a biofilter 8th from biochar 2 from the accumulated upper course 14 to the lower reaches 12 is used.

From the 3 It can be seen that the same principle with a pent-up upper course 14 and an underflow 12 takes place, but here is the congested upper course 14 Groundwater that is forced through the dam 7 in the groundwater area in the biofilter 8th with the biochar 2 to flow. In the biochar 2 The water-polluted water is filtered, and an underflow is created 12 of groundwater, which is free of iron hydroxides.

By replacing the respective filter material of the biochar after saturation with the iron hydroxide, an iron hydroxide sludge is formed, which can be sustainably recycled further. Iron hydroxide (EHS) undergoes a thermal treatment and is ultimately used as a product and additive for road construction. In a first process step, the iron hydroxide is first dehydrated and dried. After drying, the material is subjected to thermal treatment at high temperatures, which can be achieved with biochar. The powdered material liquefies and becomes slag.

The production of biochar from biogenic waste materials via the pyrolysis process results in the so-called pyrocarbon, which results from a physico-chemical process at 350 to 600 ° C with low-oxygen combustion. Subsequently, it is named as biochar. In the hydrothermal carbonization, a carbon-rich, muddy mass is filtered at 20 bar and 250 ° C, dried and recovered as HTC coal. Both coals, collectively referred to as biochars, have approximately the same filter properties, which are subject to the claim.

LIST OF REFERENCE NUMBERS

1

filter shaft

2

biochar

3

groundwater

4

lake

5

Biokohleherstellung

6

forest cover

7

dam

8th

biofilter

10

concrete profile

12

underflow

14

accumulated upper reaches

Claims (1)

Process for the purification of ground and surface waters in coal mines using biochar, which is used as a filter, characterized in that between the inflow of groundwater and surface water, filtering in the form of biochar ( 2 ) and after saturation of the biochar ( 2 ) an exchange takes place and thus iron hydroxide with the biochar ( 2 ) and non-polluted ground and surface waters as underflow ( 12 ) is forwarded.

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