Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
  • C04B20/02—Treatment

Definitions

• the present invention relates to a process for the accelerated carbonation of recycled concrete aggregates, as well as the implementation of this process in a process for the recovery of these aggregates and greenhouse gases emitted by an industrial installation, for example a cement plant.
• concrete is a mixture comprising, by mass, approximately: 80% inert mineral materials, i.e. aggregates (in different forms: gravel, chippings and sand), 15 % of a binder (essentially cement) and 5% water.
• Recycled concrete aggregates means concrete aggregates originating: from the demolition of works or buildings containing concrete elements, scrap production of concrete, as well as surplus site concrete.
• Recycled concrete aggregates are obtained by crushing and screening existing concrete which may be in the form of blocks and/or rubble. Recycled concrete aggregates are therefore composed of the old natural aggregate which is attached to the old cementitious paste.
• the following two types of fractions are distinguished:
• the waste materials based on concrete constitute an important raw material that the construction industry is currently seeking to efficiently conserve in order to manufacture new materials intended for construction, and this, according to an ecological virtuous circle.
• recycled concrete aggregates to constitute interesting substitutes for natural aggregates, it is essential that the concrete comprising recycled concrete aggregates has equivalent mechanical properties, or even better than those of the concrete obtained from aggregates. natural.
• recycled concrete aggregates have a higher porosity at the level of their microstructure which constitutes a technological obstacle to their use as substitutes for natural aggregates. Indeed, this high porosity generates greater water absorption; which reduces the mechanical properties of the resulting concrete.
• accelerated carbonation means a carbonation process implemented by a device (in particular a laboratory or industrial device) which therefore differs from natural carbonation as defined above. -below.
• the recycled concrete aggregates being partly composed of cementitious paste which therefore contains these hydrates formed during the hydration of the cement, it is these hydrates which have the capacity to carbonate when said recycled concrete aggregates are subjected to accelerated carbonation.
• application WO 2019/115722 A1 proposes a technical solution that meets this need, since it describes a method for manufacturing an additional cementitious material that can replace cement from exhaust gases.
• This process consists of bringing said recycled concrete aggregates stored in the form of a pile or in a silo into contact with the exhaust gas so as to obtain a carbonated material which is then deagglomerated to obtain said additional cementitious material.
• the inventors of the present invention have sought to optimize the parameters of the accelerated carbonation to make it more efficient so as to valorize recycled concrete aggregates to obtain directly, namely without an additional step such as a deagglomeration step described in patent application WO 2019/115722 A1, carbonated aggregates which are perfectly suitable as substitutes for natural aggregates.
• the inventors of the present invention have further sought to integrate their carbonation process accelerated in a process for the recovery of recycled concrete aggregate waste and greenhouse gas emissions, in particular gaseous emissions from the cement kiln for the manufacture of clinker.
• the first object of the invention is thus an accelerated carbonation process which is characterized in that it comprises at least the following steps: a) recycled concrete aggregates are available whose particle size is less than or equal to a value determined Vi which is between 1 mm and 6 mm, in other words a 0/Vi sand; b) a separation step is carried out on the 0/Vi sand by defining a particle size cut-off of a determined value V2 which is between 0.1 mm and 0.2 mm so as to obtain:
• dynamic carbonator means an accelerated carbonation device which is configured so that, during step c) of said method, the 2nd fraction is in motion within said accelerated carbonation device (for example by means of a lifting and dispersing device) and/or that said accelerated carbonation device is in motion.
• the dynamic carbonator comprises:
• the section has a generally cylindrical shape.
• the dynamic carbonator of step c) may consist of a rotary drum dryer (namely a device that is well known and used in many sectors of industry, including that of building materials) which has been adapted to the implementation of accelerated carbonation as described just above.
• the present invention can be implemented with a rotary drum dryer which has been adapted so as to obtain a dynamic carbonator having the technical characteristics described just above, as well as those described below.
• Examples of rotary drum dryers which can be used in the context of the present invention are in particular those of the TSM range marketed by the company Marini-Ermont or those with a jacket of the TTD range marketed by the company Allgaier.
• a gyratory crusher performing a crushing of concrete materials so as to obtain a particle size less than or equal to 20 mm.
• the recycled concrete materials thus obtained can be subjected to one or more screening steps until a 0/Vi sand is obtained. These screening steps are carried out in screening devices that are perfectly within the reach of those skilled in the art.
• the residence time in the dynamic carbonator of the 2nd fraction can be between 15 minutes and 12 hours. In an advantageous embodiment of the invention, this residence time is one hour.
• the relative humidity within the dynamic carbonator is advantageously between 50% and 100%.
• recycled concrete aggregates are upgraded to carbonated recycled concrete aggregates which are, as explained above, perfectly suitable as substitutes for natural aggregates to be used in concrete formulations;
• the 1st fraction in other words the 0/V2 sand, of particle size less than V2 (namely the fines), V2 being between 0.1 mm and 0.2 mm, is used in the manufacture of a clinker.
• V2 the fines
• These fines are particularly suitable, as it is a carbon-free material that avoids the decarbonation of natural limestone.
• the process for recovering recycled concrete aggregates and industrial gaseous discharges makes it possible to recover not only the 2nd fraction of particle size between V2 and V1 to obtain recycled concrete aggregates carbonated at the resulting from accelerated carbonation which are perfectly suitable as substitutes for natural aggregates to be used in concrete formulations, but also the 1st fraction with a grain size less than V2 which is a decarbonated material very suitable in the formulation of clinker .
• FIG. 1 Figure 1 is a schematic representation of an installation implementing the process for recovering recycled concrete aggregates and industrial gaseous discharges according to the invention.
• Figure 2 is a histogram of the percentage of carbon dioxide capture obtained from 5 experimental samples comprising sands of different grain sizes.
• FIG 1 is shown schematically an installation 1 which implements the process for recovering recycled concrete aggregates and industrial gaseous discharges according to the invention.
• a truck 2 delivers to the installation 1 a sand of recycled concrete aggregates with a particle size less than or equal to 2 mm (in other words a 0/2 sand). This 0/2 sand is transported to a silo 3 thanks to a 1st transport system 4.
• Installation 1 has an annual recovery capacity of 15,000 tonnes of 0/2 sand. To do this, it is continuously supplied with 0/2 sand, at a rate of approximately 2 tonnes/hour.
• the silo 3 comprises at its base an extraction system 5 which is configured for:
• the defillerization loop 6 is broken down into a dynamic separator 7 and a flash drying system 8.
• the defillerization loop 6 is configured for:
• the adjustment of the dynamic separator 7 makes it possible to define a particle size cut-off of a determined value V2 which is between 0.1 mm and 0.2 mm.
• V2 value has been set at 0.15 mm.
• the 1st fraction represents, in mass percentages, approximately 20% (i.e. 0.4 tonnes/hour) and the 2nd fraction 80% (i.e. 1.6 tonnes/ hour).
• the 1 st fraction thus obtained and which is therefore dry is then routed using a 2 nd pneumatic conveying system 9 to a kiln 10 of a cement works for the manufacture of clinker.
• the fines of the 0/2 sand fraction are upgraded in the kiln 10 of a cement plant as a decarbonated material very suitable in the formulation of clinkers.
• the 2nd fraction (which is therefore also dry) is humidified so that its humidity level is 4% before its introduction at the level of the 1st open end 12 of a dynamic carbonator 11 which comprises besides a 2nd open end 13.
• Said 1st and 2nd open ends 12, 13 are separated by a rotary section 31 which has a generally cylindrical shape with a length of 6.5 m and a diameter of 1.3 Mr.
• the humidification of the 2nd fraction can be carried out with an injection rod not shown in FIG. 1. Thanks to the rotation of the rotary section 31 of the dynamic carbonator 11 at a speed of 1.5 revolutions/minute, 2nd fraction advances from the 1st end 12 to the 2nd end 13 of said dynamic carbonator 11. This thus allows the mixing of the bed of material consisting of the 2 nd fraction and its advancement within the rotary section 31 of the dynamic carbonator 11 .
• the rotary section 31 also has a downward inclination of 2 which is oriented in the direction of advancement of the 2 nd fraction within said rotary section 31 .
• the residence time of the 2nd fraction in the dynamic carbonator 11 is approximately one hour.
• This gas stream is at a temperature of 55° C. and has a flow rate of 2000 m 3 /h.
• the relative humidity within the dynamic carbonator 11 is 75%.
• the 2 nd fraction is thus swept by the gaseous flow which circulates against the current of the progress of the 2 nd fraction within the rotary section 31 of the dynamic carbonator 11 .
• the rotary section 31 is equipped at its internal surface with a device for lifting and dispersing the 2nd fraction (not shown in the figure). figure 1 ).
• a gas stream at a flow rate of 6000 m 3 /hour is taken from the outlet 14 of a kiln 15 for producing clinker from a cement plant.
• the composition of this gas stream in volume percentages, is as follows: 23% carbon dioxide, 5% oxygen, 65% dinitrogen and 7% water vapour.
• the temperature of this gas stream is 350°C.
• This gas flow is conveyed with a 3 rd conveying system 29 to a cooling device which consists of an atomization system 16 comprising nozzles for atomizing air and water so as to be cooled to a temperature of 150°C.
• this gas stream is conveyed with a 4 th conveying system 30 to a bag filter 17 to be dedusted.
• This gas stream is then routed with a 5th routing system 18 to an intersection point 19 from which:
• the gases remaining at the end of the accelerated carbonation and the gases used in the defillerization loop 6 are collected at the outlet 24 of the dynamic separator 7 to be dedusted, then routed through a 9th system of routing 32 to a cement kiln 33 to be reintroduced into the gases of said kiln 33.
• the gas flow rate supplying the dynamic carbonator 11 is in excess of the maximum potential for capturing carbon dioxide by the recycled concrete aggregates.
• the installation 1 contributes to the recovery of part of the gaseous discharges from the cement kiln 15 . In fact, 470 kg of carbon dioxide are emitted per tonne of cement produced.
• the accelerated carbonation installation 1 as described which is capable of carbonateting 15,000 tonnes/year of sand 0/2, contributes to a reduction of the order of 0, 08% of carbon dioxide emissions from this cement plant.
• the major advantage of installation 1 lies in the recovery of recycled concrete aggregates into carbonated recycled concrete aggregates which are perfectly suitable as substitutes for natural aggregates to be used in concrete formulations.
• the recycled concrete aggregates obtained at the end of the accelerated carbonation are evacuated at the 2nd end 13 of the dynamic carbonator 11 to be transported, via an endless screw 27 to an elevator at buckets 29, then introduced into a storage silo 26 via a connecting sheath 25.
• the recycled concrete aggregates are transported via an endless screw 27 to a truck 28 to be transported outside the installation 1.
• the mass of each of the samples was 500 g.
• the 5 samples were subjected to accelerated carbonation for a period of one hour in a dynamic carbonator consisting of a sealed laboratory mortar mixer equipped with a gas circulation system, as well as a a heating system.
• the conditions were as follows:
• the gas stream was a mixture of 25% vol. carbon dioxide, 70% vol. of nitrogen, 4.7% vol. of oxygen, 0.3% vol. nitrogen dioxide and 500 ppm sulfur dioxide at a temperature of 55°C;
• the carbon dioxide capture percentage of each of the 5 samples was determined with a carbonate bomb by carrying out an attack with hydrochloric acid on each of the samples 1 to 5 before and after the accelerated carbonation and by measuring the pressure induced by the release of carbon dioxide resulting from this acid attack. “Percentage of carbon dioxide capture of a sample” means the ratio of the mass of carbon dioxide captured by said sample to the mass of said sample.
• Table 1 below details the carbon dioxide capture percentage for each of the 5 samples.
• Figure 2 is a histogram of the carbon dioxide capture percentages of samples 1 to 5. In view of Table 1 and Figure 2, it is noted that with identical conditions of accelerated carbonation:
• the gas stream was a mixture of 3% vol. of carbon dioxide and 97% vol. air at a temperature of 20°C;
• the carbon dioxide capture percentage for sample no. 1 was 2.8% and that of sample no. 4 was 3.6%.
• Sample n°6 contained 0/4 sand obtained after crushing concrete aggregates recycled from the demolition of a building. This 0/4 sand was subjected to a separation step consisting of sieving by air jet according to standard NF EN 993-10 with a particle size cut-off of 0.15 mm so as to obtain sample no. a mass of 500 g which contained sand 0.15/4.
• Samples 6 and 7 were subjected to accelerated carbonation for a period of one hour in the same laboratory mortar mixer as that of the previous series of experiments, under the same accelerated carbonation conditions. than those of the 1st series of experiments.
• the carbonated sample n°2' was obtained from a 2nd sand 0/2 different, in terms of its physico-chemical properties, from that used for the 1st series of experiments, because obtained after crushing recycled concrete aggregates from the demolition of a building of different origin.
• This 2nd 0/2 sand was also subjected to a separation step which consisted of sieving by air jet according to standard NF EN 993-10 with the 0.1 mm particle size cut-off so as to obtain a sample no. 2' containing a 0.1/2 sand fraction.
• Sample no. 2' was subjected to accelerated carbonation under the same conditions as those of sample no. 2 and which are described in the 1st series of experiments so as to obtain sample no. °2' carbonated.
• Concrete no. 2 was prepared with the same composition of sands and natural aggregates as concrete no. 1, except that 30% of the mass of natural sands was replaced by sand from the sample. n°2' carbonated.
• the compressive strength of concretes Nos. 1 to 3 was measured according to standard NF EN 12390-3 on test specimens of dimension 11 ⁇ 2.2 cm after 7 and 28 days of wet curing at 20° C.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Processing Of Solid Wastes (AREA)
• Treating Waste Gases (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=78649380

Family Applications (1)

Country Status (7)

Families Citing this family (2)

Family Cites Families (1)

• 2021
  • 2021-08-02 FR FR2108401A patent/FR3125815A1/fr active Pending
• 2022
  • 2022-08-01 MX MX2024001621A patent/MX2024001621A/es unknown
  • 2022-08-01 EP EP22760763.7A patent/EP4380906A1/de active Pending
  • 2022-08-01 BR BR112024001992A patent/BR112024001992A2/pt unknown
  • 2022-08-01 CN CN202280054146.7A patent/CN117813271A/zh active Pending
  • 2022-08-01 WO PCT/FR2022/051534 patent/WO2023012424A1/fr active Application Filing
  • 2022-08-01 CA CA3225877A patent/CA3225877A1/fr active Pending

Also Published As

Similar Documents

Legal Events