Note: Descriptions are shown in the official language in which they were submitted.
METHOD AND DEVICE FOR AUTOMATED OPERATION OF A PLANT FOR STORING
BULK MATERIAL
The invention relates to a method for operating a plant for storing bulk
material, for
example a plant for material transloading of bulk material or a material
extraction plant
used in strip mining, with storage operation of excavated material
respectively bulk
material mined in the material extraction plant.
The present invention also relates to a computer program, to a machine-
readable data
medium for storing the computer program and to a device by means of which the
method
according to the invention can be carried out.
During stockyard holding in a material transloading site for bulk material,
for example a
material transloading site of a shipping port or a material mining site, the
materials are
temporarily stored in so-called stockpiles. These stockpiles consist of mounds
of for
example ore, lignite, raw material for cement production, or salts, for
example potash
(potassium carbonate) or the like. During the stockyard holding respectively
storage of
bulk material, physical influences on the respectively stored material, due to
the storage,
are often taken into account insufficiently or even not at all.
WO 2009/075945 Al discloses a method for simulating a material reservoir, for
example
an oil or gas deposit for oil or gas production. A reservoir model is in this
case generated,
the generated model being partitioned into various domains, each domain of
which
corresponds to an efficient partition for a particular part of the model.
During the method,
the simulation of the reservoir is divided into a plurality of processing
elements and a
multiplicity of processing elements are processed in parallel on the basis of
the partitions.
In the three-dimensional reservoir model, for example, the operation of an oil
and/or gas
reservoir having one or more vertical boreholes is simulated. The model is
divided by a
grid network into a plurality of nodes, and the nodes of the model may have
different
sizes.
From JP 2017 138166 A is a monitoring system for a coal stockpile, various
types of coal
being stored while grouped together.
1
Date Recue/Date Received 2024-02-08
CN 104 634 815 B discloses a method for simulating the spontaneous ignition of
a coal
stockpile.
DE 10 2015 104229 Al discloses a system and a method for operating a stockpile
with a
three-dimensional stockpile model.
Peuker Urs: "Analyse und Strategien zum Verringern von Anbackungen bei der
Lagerung
von Mehrstoffsystemen insbesondere Glasgemenge in Rohstoffsilo" [Analysis and
strategies for the reduction of caking during the storage of multi-material
systems, in
particular quantities of glass in a raw materials silo], 12.12.2016, pages 1-
116,
XP0557793396 discloses a final report of a project for analyzing and
developing
strategies for reducing caking during the storage of multi-material systems,
in particular
quantities of glass in raw materials silos.
The invention is based on the concept, in a plant of the type in question here
for storing
bulk material, for example a plant for material transloading of bulk material
(so-called
"material transloading site" for transloading of bulk material in a material
extraction plant
operated in strip mining, to control the storage operation of material stored
there on the
calculation basis of a computer-assisted stockyard model respectively
stockpile model, in
a way which is material-friendly and as automated as possible.
It is specifically not material-friendly for the bulk material to have to be
broken up again
during storage because of hardening or caking before being removed.
It should be emphasized that the invention may also be used in so-called
"blending bed"
plants in which different materials and/or different material qualities of a
material and/or
materials having different material states are (temporarily) stored in a
blending bed in
order to mix them together. In such an application scenario, in addition to
the material
state, the digital stockpile model may also describe which material
respectively which
material quality is present at a particular position in the stockpile. This
also makes it
possible to predict the precise degree of blending of material to be stored
after mixing has
been carried out.
The invention is based on the discovery that for the stockyard holding in a
material
transloading site for bulk material, for example a stockyard for the
transloading of
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materials arranged in a shipping port or a material mining site, under
particular physical
influencing factors superficial hardening and/or caking of the stored material
may take
place to a greater extent. Such influencing factors are, for example, the
mechanical
pressure on the material due to storage, the material temperature due to
external and/or
internal influences, the air humidity respectively material moisture content
due to external
and/or internal influences, and/or the storage time. Said material
modifications due to
storage may for example occur with materials respectively raw materials, for
example iron
ore, lignite, raw material for cement production, for example limestone,
limestone/marl/clay mixtures, gypsum or clay, and potassium carbonate,
granular sulfur,
fertilizer, or the like. In addition to the material moisture content, other
material-dependent
physical respectively chemical influencing factors that are relevant for
hardening and/or
caking of the material may also be taken into account, for example the lime
content in the
case of limestone.
According to a first aspect of the method proposed according to the invention,
a digital
stockpile model is compiled for a respective storage region, respectively a
corresponding
stockpile. On the basis of this model, the probability of the occurrence of
physical states
determined empirically in advance, for example by preliminary tests or
simulation
calculations, that may arise during the storage of the respectively stored
material is
calculated. These states are then used as process variables in the automation
of the
storage operation, in order to effectively avoid said undesired physical
storage states by
suitable storage operation respectively corresponding countermeasures.
It should in this case be noted that said storage region is referred to in the
relevant
literature as a stockpile, arranged in a stockyard, which represents a storage
site for a
bulk material in question here. In the case of a material extraction plant in
question here,
a stockyard is, for example, mainly produced respectively fed by material
conveyor
apparatuses.
According to the invention, a stockpile of the type in question here is
decomposed into a
multiplicity of smaller volume elements. These volume elements are preferably
elements
that are symmetrical in all three spatial directions, for example cubic volume
elements, so
that the calculation of the physical forces acting on an individual volume
element,
respectively the calculation of a corresponding physical state of such a
volume element,
is simplified considerably. During the calculation of a current stockpile
model, the
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influences of neighboring elements arranged above it and laterally are
respectively taken
into account for a predetermined volume element. In this case, the number of
nearest
neighboring elements may optionally be increased in order to improve the
accuracy of the
model calculation. In test calculations, it has been found that horizontally
taking into
account only nearest neighbors, and vertically taking into account as many as
possible of
the volume elements arranged above the volume element considered delivers
sufficiently
precise results.
According to another aspect of the proposed method, the pressure, preferably
isostatic
pressure, prevailing locally respectively on average and the temperature
existing on
average in the respective volume element are taken into account in the
calculation of said
volume elements, in order to calculate from these factors how probable
hardening of the
material of the respectively considered volume element is and/or how probable
caking of
the material of this volume element with the material of one of the
neighboring elements
is. This is preferably based on data determined empirically in advance for the
hardening
and/or caking behavior of different materials. The data thus determined in
advance
comprise, for example, the hardening respectively caking probability (in %) as
a function
of the pressure prevailing at the interface between two volume elements and
the
temperature, specifically as a function of the respective material.
According to another aspect of the proposed method, the storage time of the
respective
material which has already elapsed is additionally taken into account in the
calculation of
said volume elements of the stockpile model. In this way, time-dependent
effects can be
taken into account more precisely for the hardening and/or caking behavior of
the
respective material.
According to another aspect of the proposed method, spatial data, required for
the
calculation of the stockpile model, of a currently existing material mound are
combined
respectively compared with topographical surface data recorded by sensors, and
adaptation of the stockpile model to the current material mound is optionally
carried out
by means of the comparison. The determination by sensors of such surface data
may in
this case be carried out contactlessly by means of conventional camera systems
or by
laser technology, radar technology, optically, or by means of autonomously
acting aerial
or ground drones. The physical data likewise required for the calculation of
the stockpile
model, for example current temperatures on the surfaces respectively in the
outer regions
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of a material mound, may likewise preferably be recorded contactlessly by
sensors, for
example by means of infrared thermometers known per se (so-called pyrometers)
or by
means of thermal imaging cameras known per se.
According to yet another aspect of the proposed method, the results of the
calculation of
a currently applicable stockpile model, for example in the case of stockyard
holding with a
machine controller for operating a corresponding transport respectively
conveyor
technology (for example belt loaders) for bulk material, may be supplied in
real time to a
programmable logic controller (PLC). In this way, significant automation of
the operation
of a stockyard of the type in question here may be achieved.
The device likewise proposed according to the invention is configured to
operate a
stockyard controller of the type in question here or a material extraction
plant equipped
with stockyard holding, in particular a storage region provided there
respectively a
corresponding stockpile, by means of the proposed method in a substantially
automated
but nevertheless material-friendly way.
According to a first aspect, the proposed device comprises sensors for
preferably
contactless recording of topographical data of the respective stockpile, in
particular the
current surface data thereof, and/or for recording physical data of the
respective
stockpile, in particular the temperature data thereof. The device additionally
comprises a
data processing unit by means of which a current stockpile model is calculated
on the
basis of the surface data and/or physical data recorded by sensors. The
results of the
calculations by means of the stockpile model are supplied by the device to a
control unit
of the respective stockpile plant respectively material extraction plant.
According to another aspect of the proposed device, the data processing unit
is
configured to calculate current physical and/or chemical state variables of
the stockpile by
means of the digital stockpile model and the data recorded by sensors, to
calculate
current physical respectively chemical states of the materials stored in the
stockpile by
means of the calculated state variables, and to make a prediction of possible
material
modifications of the stored material by means of the calculated physical
respectively
chemical states, respectively to provide a corresponding prediction data.
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According to another aspect of the proposed device, the control unit is
configured to
calculate one or more suitable measures for preventing material modifications
respectively material degradation by means of the prediction data delivered by
the data
processing unit, and to supply the countermeasure data calculated in this way
for
example to a PLC controller or machine controller for the stocking, by means
of which the
countermeasures can be carried out during the stocking.
According to yet another aspect of the proposed device, the control unit is
configured to
carry out at least one suitable measure by means of predetermined possible
measures,
suitable countermeasures being determined in advance by means of test runs for
particular physical respectively chemical states.
The invention may be used particularly in the area of, for example, material
transloading
sites provided at shipping ports for the transloading of bulk material (for
example ore,
coal, lignite, fertilizer, or salts such as potassium carbonate) and in the
area of
corresponding material extraction of such a bulk material, for example in a
mine plant
operated in strip mining or in a storage device for bulk materials of cement
production,
with the advantages described herein. The method and the device may, however,
also be
used correspondingly in stockyards provided for other purposes, for example in
stockyards for the storage of stone/natural stone material.
The computer program according to the invention is configured to carry out
each step of
the method, in particular when it runs on a control apparatus for controlling
the stocking of
a storage region respectively stockyard of the type in question here. It makes
it possible,
in particular, to implement the method according to the invention on an
electronic control
apparatus, for example a PLC control apparatus, without having to carry out
structural
modifications on the control apparatus. For this purpose, the machine-readable
data
medium on which the computer program according to the invention is stored is
provided.
By installing the computer program according to the invention onto a device,
respectively
a corresponding electronic control apparatus, the device according to the
invention is
obtained, which is configured to operate respectively control a stockyard
control system
of the type in question here respectively a corresponding store respectively
temporary
store for bulk material respectively excavated material of a material
extraction plant by
means of the method according to the invention.
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Further advantages and configurations of the invention may be found in the
description
and the appended drawings. In the drawings, elements respectively features
that are
identical or functionally equivalent are provided with the same references.
It is to be understood that the features mentioned above and those to be
explained below
may be used not only in the combination respectively specified but also in
other
combinations or separately, without departing from the scope of the present
invention.
Figure 1 schematically shows a digital stockpile model to
illustrate the method
according to the invention and the device.
Figure 2 shows a first exemplary embodiment of the method
according to the
invention for calculating a physical stockpile model by means of a
schematic representation of a local arrangement of volume elements.
Figure 3 shows a second exemplary embodiment of the method
according to the
invention respectively the device by means of a combined flowchart/block
diagram.
The stockpile model shown in Figure 1 relates to the temporary storage of
potassium
carbonate (so-called "potash") in a stockpile. During the storage of potassium
carbonate,
caking and/or hardening of the material takes place under particular physical
influencing
factors such as pressure, temperature, air humidity and/or storage time. This
or a similar
effect may under certain circumstances also be observed with other materials.
Caked material has, for example, the following disadvantageous effects:
- a reduction of the material quality and therefore loss of
revenue for the material
owner;
- greater wear of reloading machines due to tooth abrasion;
- a reduction of the efficiency of the stockyard device and
therefore revenue losses
due to delayed removal and through further working steps required, in order to
regrind the caked material.
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According to the stockpile model represented in an isometric top view in
Figure 1, the
respective stockyard of the type in question is converted into a digital
stockyard model by
subdividing it in the present exemplary embodiment into cubic digital volume
regions
respectively volume bodies. The size of these regions determines the
resolution of the
digital model and may be varied according to requirements.
Each of the volume regions may be assigned different physical respectively
chemical
state variables (parameters). These factors may be:
- the instantaneous (average) pressure prevailing in the volume region;
- the time when the material in question was stored in the
volume region, in order to
calculate the storage period which has elapsed since then;
- the external temperature in the vicinity of the stockpile at the time when
the
material in question was stored;
- the air humidity prevailing in the vicinity of the
stockpile at the time when the
material in question was stored;
- said pressure in a volume region, specifically multiplied by the storage
period
which has elapsed since said time of storage, in order to obtain a time-
dependent
pressure characteristic;
- the nature of the material in question;
- quality information relating to the material in question, for example the
chemical
composition and purity or the physical fineness of the material particles;
- and other influencing factors respectively influencing quantities for the
storage of
the material in question, for example its caking probability, specifically as
a
function of said state variables.
In the stockpile model represented in Figure 1, there are the following values
of
aforementioned state variables in the volume regions 100 shown here:
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- time when the material in question was stored:
2019.04.10 / 12:35:24
- storage period so far: 56:20:54 h
- instantaneous average pressure: 10 000 N
- type of material: potash
- material quality: xyz
- caking probability: 50%
In the present example of potash said values give a (non-negligible) caking
risk for the
eight volume regions respectively volume elements 105 shaded in light gray, a
caking
probability of < 30% for the four volume regions 110 shaded in medium gray,
and a
caking probability of > 90% for the four volume regions 115 shaded in dark
gray.
The digital stockpile model therefore existing according to Figure 1 is
compiled in the
present exemplary embodiment by means of image-recording sensors, for example
laser,
radar, photogrammetric sensors, or the like, which are preferably arranged on
a (belt)
loader and/or on a reloading apparatus of the respective stocking device.
When the material is stored, the parameters available at this time, in the
present
exemplary embodiment the material stored, the storing time, the air humidity
prevailing on
storage, etc. are assigned to the volume region respectively filled at this
time. On the
basis of these state variables respectively parameters, a material-specific
algorithm
calculates the probability of states of the material in the respective, here
cubic, volume
regions in the present exemplary embodiment according to the following
relation:
_ _
Material state(t) = iwi * tvi * Xi * (t ¨ ti)}
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i=1 j=0
in which the quantity t indicates the time of the material state, the quantity
X, indicates a
material-related state variable Xi, the quantity w, indicates a weighting
factor for the state
variable X1, the quantity v, indicates a weighting factor for time dependency
of the state
variable X1, and the quantity T1 indicates the number of previous respectively
historical time
steps which have been considered for the state variable X.
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Example of the State Calculation:
The example is based on the material respectively storage material potassium
carbonate
(potash), which is assumed to cake by 90% after a storage time of x hours at a
pressure
y. The algorithm above is formed respectively adapted on the basis of
corresponding
preliminary tests and/or the physical respectively chemical relationships
thereby obtained.
The algorithm therefore makes it possible to evaluate probabilities
respectively prediction
of storage-related states of the type in question here, for example said
caking states,
which the material takes on in said volume regions.
The plant controller may then be configured respectively programmed on the
basis of the
probabilities respectively predictions calculated in this way so that the
probability that a
particular undesired (storage-related) material state will occur is reduced.
Possible measures during the operation of a storage device of the type in
question here
in order to reduce the occurrence probabilities of particular material states
may be:
- prompt removal of material i.e. corresponding reduction of
the storage time;
- less stockpiling of material and therefore a lower height of a stockpile at
critical
points, so that the pressure on respectively in a described volume element is
reduced;
- storing new material only at correspondingly noncritical
points, likewise in order to
reduce said pressure.
Figure 2 shows a schematic representation of a local arrangement of described
volume
elements, specifically for the sake of simplicity only five contiguous volume
elements 200
- 220. By means of this representation, a first exemplary embodiment of the
method
according to the invention for calculating a physical stockpile model of the
type in
question here by means of a said algorithm will be described.
The pressure gradient Api,2, shown only for the two volume elements 200, 205,
in the
vertical direction of the arrangement shown is substantially determined by the
pressure
exertion due to gravity of the upper volume element 200 on the volume element
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underneath. The pressure gradient between the two lower volume elements 205,
210 is
then given correspondingly, although the total pressure load of the two volume
elements
200, 205 on the volume element 210 underneath needs to be taken into account.
The temperature gradient AT1,2, likewise shown only for the two volume
elements 200,
205, in the vertical direction of the arrangement shown is substantially
determined by
external influences such as solar radiation and the ground temperature as well
as the
temperature difference AT 225 resulting therefrom over the stockpile height
(in the y
direction 230). The temperature gradient between the two lower volume elements
205,
210 is then given correspondingly.
The average pressures and average temperatures prevailing in the three volume
elements 200 - 210 may be derived from said pressure and temperature
gradients. From
these data, the storage-related physical respectively chemical material
modifications may
be determined specifically for the material respectively present. In the
present exemplary
embodiment, this determination is carried out by means of data obtained in
test runs for
the respective material, which are provided for example in the form of
(electronic) tables
or databases.
The pressure gradient Api,3, shown only for the two volume elements 205, 215,
in the
horizontal direction of the arrangement shown is substantially determined by
horizontal
pressure loading components between horizontally neighboring volume elements,
which
are caused by the lateral movement of individual material particles that is
possible during
the pouring of granular material.
The temperature gradient AT1,3, likewise shown only for the two volume
elements 205,
215, in the horizontal direction of the arrangement shown is substantially
determined by
the temperature profile along the stockpile, specifically in the present
example along the x
direction 235 shown.
A second exemplary embodiment of the method according to the invention,
respectively
the device, is represented in Figure 3 by means of a combined block
diagram/flowchart.
In block respectively step 305, a data processing unit 300 calculates a
described digital
stockpile model on the basis of current physical and/or chemical data recorded
by
sensors 310. In the present exemplary embodiment, these data comprise
geometrical
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data respectively corresponding surface data of a stockpiling question,
temperature data
recorded by sensors in the vicinity of the stockpile in question and/or inside
the stockpile,
as well as material-specific data relating to the material instantaneously
stored in the
stockpile. A current respectively instantaneously valid stockpile model is
calculated by
means of these data 305.
The data processing unit 300 calculates 315 current physical and/or chemical
state
variables of the stockpile by means of the digital stockpile model 305 and the
data 310
recorded by sensors. By means of these calculated state variables, current
physical
respectively chemical states of the materials stored in the stockpile are
calculated 320
and a prediction of possible material modifications of the stored material is
made 325 by
means of the physical respectively chemical states calculated in this way,
respectively
corresponding prediction data, are provided 330. For the prediction, the
probability of the
occurrence of physical states that may arise during the storage of the
respectively stored
material may in this case be calculated 325, 330.
The prediction data provided in this way 330 are supplied to a control unit
335 of the
respective stockyard plant respectively material extraction plant. By means of
the present
prediction data 330, in the present exemplary embodiment one or more suitable
countermeasures for preventing a material modifications are calculated 340 in
the control
unit 335 and the data thereby obtained are supplied 350 in the present case to
a PLC
controller 350, by means of which the calculated 340 countermeasures are
carried out
during the stockpile operation of the storage device of the type in question
here.
It should be noted that the calculation of the suitable countermeasure(s) in
the present
exemplary embodiment is carried out by means of a predetermined catalog
respectively a
corresponding selection 345 of possible countermeasures, countermeasures
suitable for
the particular physical respectively chemical states being determined in
advance by
means of test measurements respectively test runs.
It should furthermore be noted that a method as described above and a device
as
described above may, for example, be used in the case of a temporary material
store
provided in a material extraction plant (ore mining, coal mining, potash
mining, etc.) or
material transloading site provided in a shipping port for the transloading of
corresponding
bulk material.
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