U.S. patent application number 10/416051 was filed with the patent office on 2004-03-18 for method and device for the production of concrete.
Invention is credited to Lindner, Erich, Reichel, Dieter, Tauchmann, Jens, Weichmann, Thomas.
Application Number | 20040050301 10/416051 |
Document ID | / |
Family ID | 7662062 |
Filed Date | 2004-03-18 |
United States Patent
Application |
20040050301 |
Kind Code |
A1 |
Lindner, Erich ; et
al. |
March 18, 2004 |
Method and device for the production of concrete
Abstract
The water necessary for the production of concrete is replaced
by a super-cooled, cooling transfer agent, comprising snow
crystals. The cooling transfer agent is produced by mixing water
with air and a cooling medium, such as liquid nitrogen, to give a
cold gas mixture. The cold gas mixture is sprayed in the form of a
cold gas stream. The snow crystals thus formed from the water are
brought to a low temperature, of, for example, below minus
30.degree. C. and added to the mixture of binding agents.
Inventors: |
Lindner, Erich; (Auerbach,
DE) ; Reichel, Dieter; (Neurnarkt, DE) ;
Tauchmann, Jens; (Berlin, DE) ; Weichmann,
Thomas; (Pilsach, DE) |
Correspondence
Address: |
Connelly Bove
Lodge & Hutz
PO Box 2207
Wilmington
DE
19899-2207
US
|
Family ID: |
7662062 |
Appl. No.: |
10/416051 |
Filed: |
October 8, 2003 |
PCT Filed: |
October 19, 2001 |
PCT NO: |
PCT/EP01/12100 |
Current U.S.
Class: |
106/638 ;
106/713 |
Current CPC
Class: |
C04B 22/0053 20130101;
F25C 3/04 20130101; F25C 2303/044 20130101; C04B 28/02 20130101;
A61P 25/00 20180101; C04B 40/0683 20130101; C04B 40/0028 20130101;
C04B 40/0028 20130101 |
Class at
Publication: |
106/638 ;
106/713 |
International
Class: |
C04B 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 3, 2000 |
DE |
10054563.7 |
Claims
1. A method to produce concrete, in which a binder, such as cement,
is mixed together with aggregates to form a binder mixture (Z) and
then fresh concrete is made by adding water to the binder mixture
(Z), characterized in that the water that is added to the binder
mixture (Z) is at least in part in the form of a cold transfer
agent (S) consisting of snow crystals.
2. The method according to claim 1, characterized in that, in order
to prepare the cold transfer agent (S), water is mixed together
with a propellant and a coolant to form a cold gas mixture, the
cold gas mixture is then sprayed in the form of a cold gas stream
into a spraying chamber (9), a process in which the water freezes
to form snow crystals.
3. The method according to claim 2, characterized in that the cold
gas stream is made to rotate when it is sprayed into the spraying
chamber (9).
4. The method according to claim 2 or 3, characterized in that,
prior to being added to the binder mixture (Z), the cold transfer
agent (S) is brought to a specified temperature of less than
-30.degree. C. [-22.degree. F.] in an after-cooling process.
5. The method according to one of claims 2 to 4, characterized in
that a cryogenic gas, for instance liquid nitrogen or liquid carbon
dioxide, is employed as the coolant for the cold gas mixture and/or
for the after-cooling of the cold transfer agent (S).
6. The method according to one of the preceding claims,
characterized in that nitrogen and/or air is employed as the
propellant for the cold gas mixture.
7. The method according to one of claims 2 to 6, characterized in
that the coolant is employed to transport the generated cold
transfer agent (S) to the binder mixture (Z).
8. A device to prepare concrete, comprising a mixing device (7) to
mix the water, the propellant and a coolant to form a cold gas
mixture, a spray nozzle (8) that is housed in a spraying chamber
(9) and that is flow-connected to the mixing device (7), said spray
nozzle (8) being used to spray the cold gas mixture so as to form a
cold transfer agent (S) that at least largely consists of snow
crystals, and a mixing chamber (2) in which the cold transfer agent
(S) generated in the spraying chamber (9) can be mixed together
with a binder mixture (Z).
9. The device according to claim 8, characterized in that the
spraying chamber (9) is linked to a cooling unit (11) for the
after-cooling of the cold transfer agent (S) generated in the
spraying chamber (9).
10. The device according to one of claims 8 or 9, characterized by
a control unit (12) that is effectively connected to the mixing
device (7) and/or to the mixing chamber (9), by means of which
control unit (12) the temperature and/or the composition of the
cold gas mixture and/or of the fresh concrete can be set.
Description
[0001] The invention relates to a method and to a device for the
production of concrete.
[0002] In order to avoid the formation of cracks and the occurrence
of stresses in the construction of large concrete elements such as
bridge abutments, concrete dams, pylons and the like, it is common
practice to employ cooled fresh concrete for these structures. With
this technique, the heat released during the hydration of the
cement can be better compensated for and dissipated more evenly,
thus avoiding stress differences in the concrete. Moreover,
processing uncooled fresh concrete at outdoor temperatures above
25.degree. C. [77.degree. F.] is problematic because, at such high
outdoor temperatures, the resultant peak temperature of the
concrete while it is setting lies above 60.degree. C. [140.degree.
F.], and this can lead to losses in strength. Cooling prevents this
limit from being exceeded.
[0003] In order to produce cooled fresh concrete, it is a known
technique to cool the already freshly mixed concrete to the desired
temperature by adding chip ice or liquid nitrogen in the stationary
or mobile mixer or in the rotary drum of a concrete-mix truck. A
summarizing overview of the known cooling methods can be found in
the articles titled "Kuhlen von Frischbeton mit flussigem
Stickstoff" [Cooling fresh concrete with liquid nitrogen] by W.
Trappman and W. Duesberg in the German publication "gas aktuell",
25 (1983), page 15, and "Frischbeton mit flussigem Stickstoff"
[Fresh concrete with liquid nitrogen] by D. Rebhan in the German
publication "Betonwerk+Fertigteil-Technik", issue 8,1981, page
507.
[0004] When ice is employed as the coolant, there is a risk of
inhomogeneities caused by water pockets in the concrete.
Furthermore, the cooling effect is extremely limited since cooling
chip ice to temperatures T<0.degree. C. [32.degree. F.] can only
be achieved with a great deal of effort, and this is not
economically warranted in most cases. Moreover, chip ice does not
dissolve well and it prolongs the mixing times, an aspect that
considerably reduces the production output, particularly in the
case of mixers.
[0005] A drawback of cooling by means of cryogenic nitrogen
(LN.sub.2) is the fact that this method is not very efficient since
relatively large amounts of LN.sub.2 have to be fed into the batch
in question within a short period of time in order to achieve the
desired cooling effect. The poor efficiency of this cooling method
lies in the fact that primarily only the evaporation heat of the
liquid nitrogen can be utilized and that the surface area available
for the heat exchange is limited. The fast evaporation of the
nitrogen causes large volumes of gas to be released within the
shortest of times, and this can lead to local explosions and
ejections from the mixer. Besides, owing to localized critical
sub-cooling, the fresh concrete can suffer frost damage.
[0006] JP 61201681 A1 suggests adding a liquefied gas, such as
nitrogen or carbon dioxide, in order to cool down the starting
materials prior to adding cement and water. This method, however,
can only be employed with certain restrictions since the cooled
medium has to be kept insulated against heat and moisture.
Moreover, substances with a high moisture content cannot be cooled
to temperatures below 0.degree. C. [32.degree. F.].
[0007] Therefore, the objective of the present invention is to put
forward a method as well as a device for the production of concrete
which avoid the disadvantages of the prior-art cooling methods and
which particularly allow a cost-effective use of the coolant while
concurrently providing a high cooling output.
[0008] This objective is achieved, on the one hand, by means of a
method having the features cited in Patent claim 1 and, on the
other hand, by means of a device having the features cited in
Patent claim 8.
[0009] Thus, with the method according to the invention, either
some or all of the water added to the binder mixture consisting of
a binder, such as cement, and of aggregates, such as gravel, sand,
fly ash and the like, is in the form of a previously prepared cold
transfer agent made up of snow crystals.
[0010] The term "snow crystals" as employed throughout the text is
to be understood as particles of frozen water that are generated in
a cold atmosphere.
[0011] In comparison to chip ice, such snow crystals entail the
advantage that they have a larger surface area while at the same
time having a lower specific weight. As a result, the process heat
generated during the setting phase is transferred much faster than
with chip ice. Moreover, inhomogeneities due to water pockets can
be largely avoided.
[0012] In a preferred method for generating snow or ice crystals, a
cold gas is made from water, a propellant as well as a coolant and
this gas is then sprayed in the form of a cold gas stream into a
spraying chamber. This cold gas stream is at a temperature that is
clearly below the freezing temperature of water. The water present
in the cold gas stream freezes to form crystals that are
subsequently admixed with a binder mixture in order to produce
fresh concrete. The size, temperature and surface characteristics
of the crystals are decisively determined by the composition of the
cold gas and by the temperature of the cold gas stream. The
production of crystals at temperatures well below 0.degree. C.
[32.degree. F.] is likewise possible without any problems. In
particular, at temperatures below -30.degree. C. [-22.degree. F.],
the crystals formed exhibit especially good transport properties
since, at these temperatures, microscopic domains of liquid water
that could cause the snow crystals to adhere to each other are no
longer present on the surface of the snow crystals. Therefore, the
cooling action of the coolant is utilized to a far greater extent
than in conventional cooling methods.
[0013] Advantageously, the cold gas stream is made to rotate. This
lengthens the stream path in the stream chamber, thus achieving
greater homogeneity of the crystals formed.
[0014] In order to quickly reach the target temperature of the
fresh concrete, the cold transfer agent generated in the spraying
chamber is subjected to an after-cooling procedure. When a suitable
coolant is selected, for instance, liquid nitrogen, snow crystal
temperatures as low as -190.degree. C. [-310.degree. F.] can be
generated. A cryogenic gas is the preferred coolant for the
production of the cold gas as well as for the after-cooling
procedure. In this context, the use of liquid nitrogen or liquid
carbon dioxide is particularly recommended from an environmental
and cost standpoint.
[0015] Gaseous nitrogen is advantageously employed as the
propellant for the production of the cold gas or of the cold gas
stream. The use of nitrogen--which is itself hardly
water-soluble--prevents oxygen from dissolving in the water.
[0016] The liquid coolant used preferably also serves to transport
the cold transfer agent from the spraying chamber to the binder
mixture. Thus, the cold transfer agent can be discharged virtually
without compressing, clumping or altering the crystal structure of
the snow or ice crystals.
[0017] The device according to the invention as cited in claim 8
comprises a mixing device in which water, a propellant, for
instance, nitrogen, and a coolant, for example, liquid nitrogen,
are mixed together to form a cold gas, said mixing device being
flow-connected to a spraying device housed in the spraying chamber.
When the cold gas is sprayed, its water content forms snow or ice
crystals in the spraying chamber. The spraying of the cold gas into
the spraying chamber gives rise to an inert and sub-cooled
atmosphere therein and this promotes the formation of snow crystals
having a large surface area and low specific weight. The cold
transfer agent generated in the spraying chamber is fed to a mixing
chamber, where it can be mixed together with a binder mixture to
form fresh concrete.
[0018] Advantageously, the spraying chamber is associated with a
cooling unit with which the snow created in the spraying chamber
can be further cooled to a specified temperature. By choosing a
suitable coolant in the cooling unit, temperatures of -30.degree.
C. to -190.degree. C. [-22.degree. F. to -310.degree. F.] can be
attained.
[0019] In an advantageous embodiment of the invention, the mixing
device for generating the cold gas and/or the mixing chamber for
making the fresh concrete are connected to a control unit by means
of which the composition of the cold gas and/or of the fresh
concrete can be set in accordance with a specified program. Aside
from the geometry of the spraying nozzle, it is the composition of
the cold gas that decisively determines the consistency and
temperature of the generated cold transfer agent. The feed is
regulated by suitable valves on the mixing device or mixing chamber
that are operated by the control unit.
[0020] The drawing will serve to explain an embodiment of the
invention in greater detail below.
[0021] The single drawing (FIG. 1) schematically shows the mode of
operation of a device according to the invention for the production
of fresh concrete.
[0022] The device 1 has a conventional mixing chamber 2 which
receives the aggregates needed for the production of fresh concrete
such as sand, gravel, fly ash as well as cement, and these are
mixed to form a binder mixture Z. The mixing chamber can be, for
instance, a mobile or stationary mixing installation. Instead of
the water in liquid form employed in common production methods, a
sub-cooled cold transfer agent S is added to the binder mixture in
the mixing chamber 2; the preparation of said cold transfer agent
will be described below.
[0023] In order to prepare the cold transfer agent S, water as well
as gaseous and liquid nitrogen are fed in via the appertaining
lines 4, 5, 6, then thoroughly mixed in a mixing segment 7 to form
a cold gas mixture, and subsequently conveyed to a spray nozzle 8
situated in a spraying chamber 9. Instead of having a mixing
segment of a certain length, the lines 4, 5, 6 can also open up
directly into the spraying nozzle 8, which is then configured as a
three-component nozzle for this purpose. Moreover, the invention is
not limited to liquid nitrogen as the coolant for the production of
the cold gas mixture, but rather, other known coolants, especially
other liquefied gases, can also be employed for this purpose.
Moreover, a different multi-nozzle system can also be used instead
of a three-component nozzle.
[0024] By means of the spraying nozzle 8, the cold gas mixture is
emitted in the form of a cold gas stream aimed at the interior of
the spraying chamber 9, whereby the cold gas stream is made to
rotate around its own axis in order to lengthen the stream path.
The feeding of the cold gas stream causes a sub-cooled atmosphere
to form inside the spraying chamber 9 already after a short time.
The water contained in the cold gas stream freezes and precipitates
inside the spraying chamber 9 in the form of snow crystals, i.e.
the cold transfer agent S. The cold, inert atmosphere inside the
spraying chamber 9 promotes the formation of crystals having a
large surface area and a low specific weight. In this context, the
size, consistency and temperature of the crystals are especially
determined by the mixing ratio of gaseous and liquid nitrogen as
well as water in the cold gas mixture.
[0025] In the embodiment presented, the snow crystals formed in the
spraying chamber 9 are fed into an after-cooling unit 10, where the
cold transfer agent S is cooled down further. The after-cooling
unit 10 consists of a cooling chamber 11 for the material to be
cooled, which is in thermal contact with a cold transfer agent 12.
Within the scope of the invention, it is likewise possible to
directly employ the spraying chamber 9 with the liquid nitrogen
that has been fed into it as the cooling chamber 11 of the
after-cooling unit 10 and/or to also use liquid nitrogen from the
cold gas stream as a transport medium for the snow crystals. If the
after-cooling unit 10 is operated with liquid nitrogen as the cold
transfer agent 12, then temperatures as low as -190.degree. C.
[-310.degree. F.] can be reached. The snow crystals can be
transported very well at temperatures below -30.degree. C.
[-22.degree. F.], for instance, -40.degree. C. [-40.degree. F.].
The cold transfer agent S thus cooled is conveyed to the mixing
chamber 2, where it is admixed with aggregates and with cement in a
known manner to form fresh concrete.
[0026] The large surface area of the snow crystals of the cold
transfer agent S allows an effective and fast absorption of the
process heat generated during the setting process of the cement. By
varying the temperature and the amount of cold transfer agent S
employed, fresh concrete temperatures as low as 0.degree. C.
[32.degree. F.] can be reached.
[0027] An electronic control unit 13 allows the production of the
cold transfer agent S or of the fresh concrete according to a
specified program. The electronic control unit 13 is connected to
actuatable valves 14, 15, 16, for instance, solenoid valves, in the
lines 4, 5, 6, by means of which the mixing ratio and/or the
appertaining pressure in lines 4, 5, 6 can be set. A control line
17 serves to regulate the temperature in the after-cooling unit 10.
The feed line 18 for the cold transfer agent S to the mixing
chamber 2 is likewise fitted with a solenoid valve 19 that can be
actuated by the control unit 13. In this manner, the temperature,
consistency and amount of the cold transfer agent S fed to the
binder mixture Z can all be precisely and reliably set and, for
example, selected in such a way that the fresh concrete made has a
certain temperature, for instance, 0.degree. C. [32.degree. F.]. In
order to maintain the specified temperature for the duration of the
production of a batch of concrete, the temperature of the fresh
concrete, which is continuously or regularly measured with an
appropriate measuring device, is utilized as the manipulated
variable to which the value is constantly regulated by setting the
temperature of the added cold transfer agent S.
[0028] The method according to the invention makes it possible to
convert the feed water into cold transfer agent S within a few
minutes. Due to the large surface area of the snow crystals, the
transfer of cold during the after-cooling procedure is very
effective, so that this procedure, too, only takes a few
minutes.
List of Reference Numerals and Letters
[0029] 1 device
[0030] 2 mixing chamber
[0031] 3 -
[0032] 4 line
[0033] 5 line
[0034] 6 line
[0035] 7 mixing segment
[0036] 8 spraying nozzle
[0037] 9 spraying chamber
[0038] 10 after-cooling unit
[0039] 11 cooling chamber
[0040] 12 cold transfer agent
[0041] 13 electronic control unit
[0042] 14 valve
[0043] 15 valve
[0044] 16 valve
[0045] 17 control line
[0046] 18 feed line
[0047] 19 solenoid valve
[0048] S cold transfer agent
[0049] Z binder mixture
* * * * *