Note: Descriptions are shown in the official language in which they were submitted.
CA 03049835 2019-07-10
Description
Method for Protecting/Purifying Water by Recharging Iron-Containing Sewage
into Stratum
Destroyed by Coal Mining
I. Technical Field
The present invention relates to a water resource protection and purification
method, in particular to
a method for protecting/purifying water by recharging iron-containing sewage
into the coal mining
damaged stratum, which is applicable to the field of aquifer restoration and
water resource protection
in stratum of mining areas.
Background Art
The underground coal mining may result in displacement and damage of the
overlying strata, and
thereby result in formation of mining fractures in the overlying strata; the
mining fractures formed in
the overlying strata provide channels for the loss of regional water resource,
and become geological
sources of ecological environment damages. Therefore, how to control the
development of water
flowing fractures in the mining overlying strata and seal the water resource
loss channels in the
underground aquifer to improve and protect the ecological environment in the
coal mining area is a
major technical challenge encountered in most coal mining areas.
On the other hand. a large amount of sewage is produced in the daily life and
industrial production of
the residents in the coal mining area and peripheral towns, and the sewage
usually contains excessive
iron component. Therefore, iron removal becomes a necessary procedure for
artificial purification of
the sewage. A matured iron removal method is to transport the iron-containing
sewage centrally to a
sewage treatment plant, and drive the iron component in the sewage to form
Fe(OH)3 through
chemical reactions and flocculate and precipitate, by adding chemical agents,
through aeration,
oxidation reaction, precipitation and filtration processes, etc., so as to
accomplish iron removal from
the sewage finally.
Inspired by that idea, the inventor has conceived: if the above-mentioned iron
removal process of
iron-containing sewage can be applied to fractures in rock mass damaged by
mining, the Fe(OH)3
flocculated precipitate formed through the iron removal process can
effectively plug the mining
fractures, so that the water loss channels in the aquifer in the formation can
be effectively isolated,
the iron component in the iron-containing sewage can be effectively removed,
the iron-containing
sewage can be effectively purified, and thereby a purpose of realizing water-
saving coal mining and
natural purification of sewage in the coal mining area can be achieved.
Therefore, it is necessary to
carry out the special design of a method for protecting/purifying water by
recharging iron-containing
sewage into the coal mining damaged stratum on the basis of the development
range and distribution
characteristics of water flowing fractures in the mining overlying strata.
Contents of the Invention
Object of the invention: to overcome the drawbacks in the prior art, the
present invention provides a
method for protecting/purifying water by recharging iron-containing sewage
into a coal mining
damaged stratum, in which iron-containing sewage and oxygen-containing
water/weak alkaline water
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are recharged through borehole in the ground surface to the aquifer in the
coal mining damaged strata,
the mining fractures are plugged by means of Fe(OH)3 flocculated precipitate
generated through an
oxidation reaction of the iron component in the iron-containing sewage. and
thereby water loss
channels of the aquifer in the stratum are isolated, the iron component in the
iron-containing sewage
is effectively reduced, and finally effects of protecting the underground
water resources in the coal
mining areas and removing iron component from the iron-containing sewage and
purifying the iron-
containing sewage are attained.
Technical scheme: to attain the object described above, the technical scheme
employed in the present
invention is as follows:
the invention discloses a method for protecting/purifying water by recharging
iron-containing sewage
into a coal mining damaged stratum, in which iron-containing sewage recharging
boreholes and
oxygen-containing water/weak alkaline water recharging boreholes are
constructed in the ground
surface corresponding to the boundary and the central part of a mining area
according to the
developing characteristics and distribution range of water flowing fractures
in the mining overlying
strata; mining fractures are effectively plugged with a Fe(OH)3 flocculated
precipitate generated
through an oxidation reaction between iron component in the iron-containing
sewage and oxygen-
containing water/weak alkaline water; the generated Fe(OH)3 flocculate can
gradually precipitate
within a certain range near the bottom holes of the recharging boreholes to
form an iron active filter
membrane, which acts as catalyst on the oxidation reaction of ferric (or
ferrous) ions, and an iron
removal effect is effectively guaranteed; at the same time, the gushing water
resource at a low-lying
terrain area of an underground goaf is subjected to an iron component test; if
the iron component still
exceeds the standard, the underground gushing water is transported through a
pipeline to a relatively
high terrain area and is recharged to aquifer in the stratum again through an
underground upward
inclined construction borehole for further oxidation reaction and iron
removal; if the iron component
of the underground gushing water does not exceed the standard, the underground
gushing water is
directly transported to other mining areas or ground surface for reuse.
Specifically, the method comprises the following steps:
a. determining a coal mining area where the aquifer in the stratum is
damaged by mining according
to the height of a water flowing fractured zone in the overlying strata and
the geological borehole
column; if there is aquifer within the range of the height of the water
flowing fractured zone, the
water flowing fractured zone in the corresponding area has communicated with
the aquifer, and
the corresponding recharging boreholes need to be arranged; if there is no
aquifer within the
range of the height of the water flowing fractured zone, no construction of
recharging borehole
is required.
Preferably, the height of the water flowing fractured zone may be detected
with a field measuring
method such as a drilling fluid loss method, or may be judged with a
theoretical calculation
method such as "a prediction method for the height of water flowing fractured
zone based on key
stratum locations".
b. constructing iron-containing sewage recharging boreho les and oxygen-
containing water/weak
alkaline water recharging boreholes in the ground surface corresponding to the
mining area where
the water flowing fractured zone communicates with the aquifer in the stratum.
Preferably, the iron-containing sewage recharging boreholes are arranged near
the outer side of
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the boundary of the mining area and in the central part of the mining area,
wherein the boreholes
arranged near the outer side of the boundary of the mining area shall be
located outside lateral
development boundary of the water flowing fractured zone, at 30-40m distance
from the
boundary of the mining area.
Preferably, the oxygen-containing water/weak alkaline water recharging
boreholes are arranged
near the inner side of the boundary of the mining area, at 10-20m distance to
the mining boundary.
Preferably, when the strike and dip size of the mining area is greater than
1.000m, the iron-
containing sewage recharging boreholes and the oxygen-containing water/weak
alkaline water
recharging boreholes may be arranged in groups along the strike or the dip at
1,000m interval.
Preferably, the construction method of the iron-containing sewage recharging
boreholes and the
oxygen-containing water/weak alkaline water recharging boreholes in the ground
surface is as
follows: during drilling construction, the boreholes is drilled with a
diameter of 120-140mm, and
drilled to a certain depth below the top interface of the aquifer that
communicates with the water
flowing fractured zone, the distance between the bottom hole of the borehole
and the top interface
of the aquifer that communicates with the water flowing fractured zone is not
less than 0.3-0.5
times of the thickness of the aquifer that communicates with the water flowing
fractured zone. A
casing is adopted for protecting the borehole within a range from the ground
surface to 10m
below the top interface of the aquifer that communicates with the water
flowing fractured zone,
and a perforated casing is adopted for protecting the borehole in the aquifer
that communicates
with the water flowing fractured zone. After the borehole is constructed, a
closed cover plate
connected with a water pipeline is covered on the opening of the borehole.
c.
arranging a drainage pipeline at a low-lying terrain area corresponding to an
underground goaf.
testing the iron component in the goaf drainage water, and determining whether
to recharge the
goaf drainage water or directly reuse the goaf drainage water according to the
content of iron
component in the goaf drainage water. The specific steps are as follows:
If the iron component in the goaf drainage water still exceeds the values
specified in relevant
national standards. the goaf drainage water is transported to a relatively
high terrain area of the
mining area through a pipeline, and is recharged again to the aquifer that
communicates with the
water flowing fractured zone through recharging boreholes constructed upwardly
in a nearby
roadway for further iron removal and purification.
If the iron component in the goaf drainage water is lower than the values
specified in relevant
national standards, it is directly transported to other underground mining
areas or ground surface
through a pipeline for reuse.
Preferably; the bottom hole location of the underground constructed recharging
borehole reaches
at about 5m above the bottom interface of the aquifer that communicates with
the water flowing
fractured zone, the horizontal distance of the bottom hole location to the
mining boundary is 10-
20m. and at the inner side of the mining boundary. A casing is adopted for
protecting the
recharging borehole in a section that is not damaged by mining fractures, and
a perforated casing
is adopted for protecting the recharging borehole within the range of the
water flowing fractured
zone.
In the present invention, on the basis of the development and distribution
characteristics of water
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flowing fractures in the mining overlying strata, the Fe(OH)3 flocculated
precipitate generated
through an oxidation reaction of iron component in iron-containing sewage is
fully utilized to
plug the water flowing fractures, so that the water loss channels in the
aquifer in the stratum are
isolated, and the iron component in the iron-containing sewage is effectively
reduced, and
thereby effects of in-situ protection of the aquifer in the stratum in the
coal mining area and iron
removal and purification of the iron-containing sewage are attained, and
protection and efficient
utilization of water resources during coal mining is guaranteed in the mining
area. In addition,
the method provided in the present invention is reliable and highly practical.
Compared with the
prior art, the present invention has the following advantages:
(1) Utilizing the precipitate generated in the iron removal and purification
process of iron-
containing sewage to plug the water flowing fractures in the overlying strata
not only is
scientific and reliable, has very low engineering workload, but also can
effectively mitigate
the degree of water loss from the aquifer, and purify the iron-containing
sewage at a low cost;
(2) The present invention can adapt to the determination of water protection
and purification
methods for recharging iron-containing sewage into the coal mining damaged
stratum under
different mining conditions, and can provide a guarantee for coordinated
development of
coal mining and water resource protection in regions where the iron-containing
sewage is
abundant but the water resources are in short in China. In addition, the
method provided in
the present invention is simple to use and highly practical.
IV. Description of Drawings
Fig. 1 is a plan view of the layout of the recharging boreholes of the present
invention;
Fig. 2 is a sectional view A-A of the layout of the recharging boreholes of
the present invention;
Fig. 3 is a sectional view B-B of the layout of the recharging boreholes of
the present invention;
Fig. 4 is a sectional view of the recharging boreholes of the present
invention;
Fig. 5 is a schematic diagram of the drilling column ZI and the development
height of the water
flowing fractured zone at a mining face 22301 in a certain coal mine in the
actual application process
of the present invention;
Fig. 6 is a plan view of the layout of the recharging boreholes at a mining
face 22301 in a certain coal
mine in the actual application process of the present invention.
In the figures: 1 - iron-containing sewage recharging borehole; 2 - oxygen-
containing water/weak
alkaline water recharging borehole; 3 ¨ underground constructed recharging
borehole; 4 - casing; 5 -
perforated casing; 6 - Fe(OH)3 active filter membrane.
V. Embodiments
Hereunder the present invention will be further detailed in embodiments, with
reference to the
accompanying drawings. It should be appreciated that those embodiments are
provided only for
describing the present invention, and shall not be deemed as constituting any
limitation to the scope
of the present invention. After reading the present invention, various
equivalent modifications to the
present invention made by those skilled in the art shall be deemed as falling
into the scope as defined
by the attached claims of the present application.
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As shown in Figs. 1-4, in the method for protecting/purifying water by
recharging iron-containing
sewage into a coal mining damaged stratum in the present invention, iron-
containing sewage
recharging boreholes 1 and oxygen-containing water/weak alkaline water
recharging boreholes 2 are
constructed in the ground surface corresponding to the boundary and the
central part of a mining area
according to the developing characteristics and distribution range of water
flowing fractures in the
mining overlying strata; mining fractures are effectively plugged with a
Fe(OH)3 flocculated
precipitate generated through an oxidation reaction between iron component in
the iron-containing
sewage and oxygen-containing water/weak alkaline water; the generated Fe(OH)3
flocculate can
gradually precipitate within a certain range near the bottom holes of the
recharging boreholes to form
an iron active filter membrane 6, a catalyst effect is achieved on the
oxidation reaction of ferric (or
ferrous) ions, and an iron removal effect is effectively guaranteed; at the
same time, the gushing water
resource at a low-lying terrain area of an underground goaf is subjected to an
iron component test; if
the iron component still exceeds the standard, the underground gushing water
is transported through
a pipeline to a relatively high terrain area and is recharged again to the
aquifer that communicates
with the water flowing fractured zone through an underground upward inclined
construction
recharging borehole 3 for further oxidation reaction and iron removal; if the
iron component of the
underground gushing water does not exceed the standard, the underground
gushing water is directly
transported to other mining areas or the ground surface for reuse.
Specifically, the method comprises
the following steps:
a. determining a coal mining area where the aquifer in the stratum is damaged
by mining according
to the height of a water flowing fractured zone in the overlying strata and
the geological borehole
column; if there is aquifer within the range of the height of the water
flowing fractured zone, the water
flowing fractured zone in the corresponding area has communicated with the
aquifer, and the
corresponding recharging boreholes need to be arranged; if there is no aquifer
within the range of the
height of the water flowing fractured zone, no construction of recharging
borehole is required;
The height of the water flowing fractured zone may be detected with a field
measuring method such
as a drilling fluid loss method, or may be judged with a theoretical
calculation method such as "a
prediction method for the height of water flowing fractured zone based on key
stratum locations".
b. constructing iron-containing sewage recharging boreholes and oxygen-
containing water/weak
alkaline water recharging boreholes in the ground surface corresponding to the
mining area where the
water flowing fractured zone communicates with the aquifer.
The iron-containing sewage recharging boreholes are arranged near the outer
side of the boundary of
the mining area and in the central part of the mining area, wherein the
boreholes arranged near the
outer side of the boundary of the mining area shall be located outside lateral
development boundary
of the water flowing fractured zone, at 30-40m distance from the boundary of
the mining area.
The oxygen-containing water/weak alkaline water recharging boreholes are
arranged near the inner
side of the mining boundary, at 10-20m distance to the mining boundary.
When the strike and dip size of the mining area is greater than 1,000m, the
iron-containing sewage
recharging boreholes and the oxygen-containing water/weak alkaline water
recharging boreholes may
be arranged in groups along the strike or the dip at 1,000m interval.
The construction method of the iron-containing sewage recharging boreholes and
the oxygen-
containing water/weak alkaline water recharging boreholes in the ground
surface is as follows: during
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drilling construction, the boreholes is drilled with a diameter of 120-140mm,
and drilled to a certain
depth below the top interface of the aquifer that communicates with the water
flowing fractured zone,
the distance between the bottom hole of the borehole and the top interface of
the aquifer that
communicates with the water flowing fractured zone is not less than 0.3-0.5
times of the thickness of
the aquifer. A casing 4 is adopted for protecting the borehole within a range
from the ground surface
to 10m below the top interface of the aquifer that communicates with the water
flowing fractured
zone, and a perforated casing 5 is adopted for protecting the borehole in the
aquifer that communicates
with the water flowing fractured zone. After the borehole is constructed, a
closed cover plate
connected with a water supply pipeline is covered on the opening of the
borehole.
c. arranging a drainage pipeline at a low-lying terrain area corresponding to
an underground goaf,
testing the iron component in the goaf drainage water, and determining whether
to recharge the goaf
drainage water or directly reuse the goaf drainage water according to the
content of iron component
in the goaf drainage water. The specific steps are as follows:
If the iron component in the goaf drainage water still exceeds the values
specified in relevant national
standards, the goaf drainage water is transported to a relatively high-lying
terrain area of the mining
area through a pipeline, and is recharged again to the aquifer that
communicates with the water
flowing fractured zone through recharging boreholes constructed upwardly in a
nearby roadway for
further iron removal and purification.
If the iron component in the goaf drainage water is lower than the values
specified in relevant national
standards, it is directly transported to other underground mining areas or
ground surface through a
pipeline for reuse.
The bottom hole location of the underground constructed recharging borehole
reaches about 5m
above the bottom interface of the aquifer that communicates with the water
flowing fractured zone,
the horizontal distance of the bottom hole location to the mining boundary is
10-20m, and at the inner
side of the mining boundary. A casing is adopted for protecting the recharging
borehole in a section
that is not damaged by mining fractures, and a perforated casing is adopted
for protecting the
recharging borehole within the range of the water flowing fractured zone.
Please see Fig. 5, which is a schematic diagram of the drilling column Z1 and
development height of
the water flowing fractured zone in a mining area at a mining face 22301 in a
certain coal mine in the
actual application process. It can be seen from the figure, the water flowing
fractured zone in the
overlying strata resulted from the mining at the mining face 22301 has
communicated with aquifer in
the stratum. Therefore, it is necessary to construct boreholes in the ground
surface in the mining area
at the mining face to recharge iron-containing sewage and oxygen-containing
water/weak alkaline
water.
As shown in Fig. 6, in view that the advance length of the mining face 22301
in the strike is relatively
longer (about 4,000m), thus, recharging boreholes are arranged at 1,000m
interval along the advance
direction in the strike near the mining boundary at the two sides of the
mining face; besides, iron-
containing sewage recharging boreholes are also arranged correspondingly in
the central part of the
mining face along the dip between the two groups of recharging boreholes.
According to the
occurrence of the rock formation exposed by the borehole Z1, the depth of the
bottom hole of the
recharging borehole is 60m, which has entered the aquifer by 41.54m (0.3-0.5
times of the thickness
of the aquifer).
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On the basis of the development and distribution characteristics of water
flowing fractures in the
mining overlying strata, the present invention fully utilizes the Fe(OH)3
flocculated precipitate
generated through the oxidation reaction of iron component in iron-containing
sewage to plug the
water flowing fractures, so that the water loss channels in the aquifer in the
stratum is isolated and
the iron component in the iron-containing sewage is effectively reduced, and
thereby effects of in-
situ protection of the aquifer in the stratum in the coal mining area and iron
removal and purification
of the iron-containing sewage are attained, and can provide guarantee for the
protection and efficient
utilization of water resources during mining in the mining area.
While the present invention is described above in some preferred embodiments,
it should be noted
that those skilled in the art can make various improvements and modifications
without departing from
the principle of the present invention, and those improvements and
modifications should be deemed
as falling in the scope of protection of the present invention.
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