[0001] In respect of ground excavation for extraction of sand it is becoming of increasingly
greater importance from an environmental viewpoint to use the extracted sand in the
best possible manner.
[0002] Described in EP-A-0 319 070 is an installation in which, immediately after being
sucked up, the sand is separated into fractions and delivered in a particular desired
composition for different purposes, for instance for the concrete industry.
[0003] Such an installation has the problem that when sand or gravel is supplied in determined
compositions a quantity of granular material is left over. Such residue is transported
away by barge, whereafter this sand is used for instance as construction site filling.
[0004] US A-170677 teaches an apparatus for mixing materials, in particular materials involved
in the preparation of cement or the blending of gasoline, wherein a number of grinding
mechanisms for grinding down raw material are disclosed.
[0005] The present invention has for its object to provide a method with which the sand
can be separated into fractions at the extraction site and discharged as optimally
as possible in the desired composition while as little as possible is lost.
[0006] To this end the present invention provides a method for extracting and providing
a desired composition of granular material at an extraction site of the granular material,
comprising the steps of:
- sucking or scooping up of the granular material at the extraction site;
- separating the granular material into fractions of differing grain size classes according
to desired compositions to be obtained, at the extraction site;
- Supplying to the extraction site a fraction of said granular material insufficiently
available at the extraction location and adding said supplied fraction to the separated
fractions at the extraction site, said added granular material for improvement of
the properties of concrete obtainable from the desired compositions;
- and mixing the granular material from the differing grain size classes into a mixture
of granular material, at the extraction site, to provide a ready to use end mixture
whereby further processing steps therefor are substantially unnecessary, said mixture
being in a state suitable for transportation away from the extraction site.
[0007] When sand is extracted at a particular location, knowledge is available relating
to the composition of the already extracted sand, on the basis of which assessments
can be made with respect to the composition of the sand to be extracted in the near
future. If it is anticipated that a particular fraction will be extracted to an insufficient
extent - this depending on orders placed by end users - this fraction can be supplied
to the extraction location, for instance by barge or from bunkers.
[0008] Further advantages, features and details of the present invention will become apparent
in the light of the description of a preferred embodiment thereof wherein reference
is made to the annexed drawings, in which:
fig. 1 shows a perspective view of a preferred embodiment of an installation for performing
a method according to the present invention;
fig. 2 shows a diagram of the installation of fig. 1; and
fig. 3 is a diagram of a device for use in the installation of fig. 2 for determining
the content of dry substance in a particular fraction and/or mixture of the sand.
[0009] An installation 1 is provided with floater bodies 3, 4 and is displaceable (1') through
a lake area L already excavated by this installation 1. A barge B to which the extracted
sand of a determined specification is delivered can also be seen in fig. 1.
[0010] An installation 1 (fig. 2) comprises a suction pump 6 which sucks up and delivers
the sand to a separating means 7 wherein the granular material of a mean diameter
between 80 and 180 mm is discharged as gravel via arrow A to a barge S. Using a pump
8 the sand with a grain size smaller than 80 mm is added to separating means 9, 10,
11, 12, 13, 14, and 15, which are only designated schematically, where separation
takes place into fractions B, C, D, E, F and G.
[0011] These separating means 9-15 comprise dewatering means, float sand beds, cyclones
and the like for the purpose of separating the granular material into particular fractions
in effective manner. A similar installation is described in EP-A-0 319 070 of the
same applicant. In the present embodiment fractions B-G relate to grain sizes of respectively
8-80 mm, 4-8 mm, 2-4 mm, 0.5-2 mm, 250-500 µm, 100-250 µm. The fraction B is discharged
as gravel in a barge T - or in another embodiment - discharged as gravel in barge
S.
[0012] The fractions C-G are introduced in the composition desired by the end user after
they have been stored in the interim. Delivery of the mixture in desired composition
is indicated with line H. The feed conveyors (not shown) for the fractions C-G are
preferably each provided with devices for determining the quantity of each fraction
added to the mixture. A mixture H is well mixed in a mixer 16, details of which are
likewise described in EP-A-0 319 070, and delivered to a barge V. After mixing a sample
is taken in block 17 in order to check whether the desired composition of the mixture
has indeed been obtained and to control automatically or manually the feed of the
diverse fractions C-G. Further details hereof are likewise described in the above
cited European application.
[0013] In the installation according to the present invention it is possible to supply a
fraction K from a barge U if such an addition is desired in order to comply with the
orders of the end users, while it is thus avoided that extracted sand has to be discharged
as so-called filling sand whereof the composition is of less importance. As a result
of the supply of fraction K the extracted sand is utilized as optimally as possible.
[0014] It will be apparent that the planning with the use of a computer is of the greatest
importance in the above stated supply of a fraction or additive. In preference barges
requiring the same composition of the mixture are loaded directly one after another.
Further efficiency improvements are feasible by loading two barges with a different
mixture at substantially the same time.
[0015] Installation 1 is further provided with means 20 for adding a fraction of extremely
small grain size. This is of relevance for particular applications, especially in
the concrete industry and more especially for improving properties of concrete. As
indicated with arrow L, a portion of the fraction E is carried via a collecting tank
21 and a conveyor 22 to a grinding device 23, in the present case a ball mill. Via
tank 24 and pump 25 the ground fraction is separated in a first cyclone 26. Via collecting
tank 27 and pump 28 the small fraction is carried from the first cyclone 26 to a second
cyclone 29, wherein a second separation takes place until a fraction is obtained at
M with a grain size smaller than 125 µm. This fraction M is placed in a collecting
tank 30 in which this fraction M is kept continually in motion using a stirring means
31. Using a special pump 32, such as for instance that in use as concrete pump, this
fraction of extremely small diameter is carried from the tank 30 to a pre-mixer 33
where the fraction M is mixed together with the fraction G and added to the mixture
H.
[0016] Shown in fig. 3 is a device 41 with which the amount of moisture in each fraction
or the mixture, and therefore the amount of dry substance, can be measured, which
is of course of the greatest importance for end users. The thickness T of a layer
of granular material 40 transported on a conveyor 38 is measured using a radiation
source 39, for instance for gamma radiation, and a detector 34 for this radiation,
and generated to a recording device 35. Using a microwave transmitter 36 and a microwave
receiver 37 a measure for the moisture present between transmitter 36 and receiver
37 is also generated to the recording device 35, whereafter the dry substance content
is calculated by the recording device 35 using calibration factors stored therein.
[0017] Finally, each conveyor for each fraction is preferably provided with both a weighing
device for determining the quantity of sand per fraction and a moisture content meter.
1. A method for extracting and providing a desired composition of granular material at
an extraction site of the granular material, comprising the following steps of:
- sucking or scooping up of the granular material at the extraction site;
- separating the granular material into fractions of differing grain size classes
according to desired compositions to be obtained, at the extraction site;
- supplying to the extraction site a fraction of said granular materials insufficiently
available at the extraction location and adding said supplied fraction to the separated
fractions at the extraction site, said added granular material for improvement of
the properties of concrete obtainable from the desired compositions;
- and mixing the granular material from the differing grain size classes into a mixture
of granular material, at the extraction site, to provide a ready to use end mixture
whereby further processing steps therefor are substantially unnecessary, said mixture
being in a state suitable for transportation away from the extraction site.
2. Method according to claim 1 comprising the further step of adding one or more additives
to the mixture at the extraction site, said additives for improving the utility of
the separated fractions in concrete to be made from the desired compositions.
1. Verfahren zum Fördern und Bereitstellen einer gewünschten Zusammensetzung an körnigem
Material an einem Förderort des körnigen Materials, das die folgenden Schritte umfaßt:
- Aufsaugen oder Aufhäufen des körnigen Materials am Förderort;
- Trennen des körnigen Materials in Fraktionen unterschiedlicher Korngrößenklassen
entsprechend zu erzielender, gewünschter Zusammensetzungen, am Förderort;
- Zuführen zum Förderort einer Fraktion des körnigen Materials, das am Förderort nicht
ausreichend verfügbar ist und Zusetzen der zugeführten Fraktion zu den getrennten
Fraktionen am Förderort, wobei das zugesetzte, körnige Material der Verbesserung der
Eigenschaften des aus den gewünschten Zusammensetzungen erhaltbaren Betons dient;
- und Mischen des körnigen Materials aus den unterschiedlichen Korngrößenklassen in
ein Gemisch körnigen Materials am Förderort, um ein gebrauchsfertiges Endgemisch vorzusehen,
wobei weitere Verarbeitungsschritte hierfür im wesentlichen nicht notwendig sind und
das Gemisch in einem Zustand ist, in dem es für einen Wegtransport von dem Förderort
geeignet ist.
2. Verfahren nach Anspruch 1, desweiteren mit dem Schritt des Zusetztens eines oder mehrerer
Zusätze zu dem Gemisch am Förderort, wobei die Zusätze zur Verbesserung der Brauchbarkeit
der getrennten Fraktionen im Beton aus den gewünschten Zusammensetzungen hergestellt
werden.
1. Procédé pou extraire et délivrer une composition désirée de matériau granulaire sur
un site d'extraction du matériau granulaire, comprenant les étapes consistant à :
aspirer ou pelleter le matériau granulaire sur le site d'extraction ;
séparer le matériau granulaire en des fractions de différentes classes de taille de
grains en fonction des compositions souhaitées à obtenir, sur le site d'extraction
;
délivrer au site d'extraction une fraction dudit matériau granulaire insuffisamment
disponible sur le site d'extraction et ajouter ladite fraction délivrée aux fractions
séparées sur le site d'extraction, ledit matériau granulaire ajouté étant destiné
à améliorer les propriétés d'un béton pouvant être obtenu à partir des compositions
souhaitées ;
et mélanger le matériau granulaire provenant des différentes classes de taille de
grains en un mélange de matériau granulaire, sur le site d'extraction, pour fournir
un mélange final facile d'emploi, d'autres étapes de traitement étant donc superflues,
ledit mélange étant dans un état convenant à son transport depuis le site d'extraction.
2. Procédé selon la revendication 1, comprenant l'étape supplémentaire consistant à ajouter
un ou plusieurs additifs au mélange sur le site d'extraction, lesdits additifs étant
destinés à améliorer l'utilité des fractions séparées dans du béton devant être fabriqué
à partir des compositions désirées.