EP0397649A1 - Method for improving the concrete-technical properties of fly ash - Google Patents

Method for improving the concrete-technical properties of fly ash

Info

Publication number
EP0397649A1
EP0397649A1 EP88907697A EP88907697A EP0397649A1 EP 0397649 A1 EP0397649 A1 EP 0397649A1 EP 88907697 A EP88907697 A EP 88907697A EP 88907697 A EP88907697 A EP 88907697A EP 0397649 A1 EP0397649 A1 EP 0397649A1
Authority
EP
European Patent Office
Prior art keywords
ash
fractions
weight
additive
concrete
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP88907697A
Other languages
German (de)
French (fr)
Inventor
Aino Heikkinen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fescon Oy
Original Assignee
Fescon Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fescon Oy filed Critical Fescon Oy
Publication of EP0397649A1 publication Critical patent/EP0397649A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04Waste materials; Refuse
    • C04B18/06Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
    • C04B18/08Flue dust, i.e. fly ash
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02WCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00Technologies for solid waste management
    • Y02W30/50Reuse, recycling or recovery technologies
    • Y02W30/91Use of waste materials as fillers for mortars or concrete

Definitions

  • the present invention concerns a method for improving the properties of fly ash produced in the burn ⁇ ing of solid fuels, so as to make the ash better suitable for an additive for concrete.
  • the fly ash is usually re ⁇ moved from the flue gases of a combustion plant by means of electric filters or other suitable filter and separa ⁇ tion apparatuses.
  • the ash separated in this way, in par ⁇ ticular the ash produced on combustion of coal, has been used as an additive for concrete, partly to substitute for the binder material in concrete.
  • the fly ash also includes fractions that reduce the effect of the ad ⁇ vantageous • fractions when used in concrete and may even suppress said effects completely.
  • a particular problem has been the variation of the proportion of the harmful frac ⁇ tions in relation to the advantageous fractions, which va ⁇ riation results, e.g., from the operating conditions of the combustion plant. The variations may be considerable even within one combustion plant, but in particular ashes obtained from different combustion plants cause inpredict- able problems when they are used for concrete products to ⁇ gether.
  • a coarse fraction of the ash is separated from the ashes so that in the ash to be recovered, at the maximum, approximately 50 % of the weight of the ashes consist of a fraction that is retained on a screen of 45 ⁇ m, and the recovered ash is divided into at least two fractions of different grades of coarse ⁇ ness, to which Na- or Ca-lignosulphonate is added at the rate of about 0.1 to 2.5 % of the weight of the ash so that the total quantity of the addition is distributed among the ash fractions of different grades of coarseness substantially at a weight ratio proportional to their average particle sizes.
  • the fol ⁇ lowing procedure has proved the simplest one.
  • a coarse fraction is removed from the flue gas prior to the electric filtration so that the ash separated at the electric filters yields a screening result, wherein the
  • the method of the invention has proved partic ⁇ ularly suitable for the treatment of fly ash produced on combustion of coal, but it is also suitable for the treat ⁇ ment of ash produced on combustion of peat as well as on combustion of bituminous shale, when the ash is processed so as to make it suitable for an additive for concrete.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Civil Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)
  • Solid Fuels And Fuel-Associated Substances (AREA)

Abstract

Procédé permettant d'améliorer les propriétés techniques des cendres volantes utilisées dans le béton et produites lors de la combustion de combustibles solides puis séparées des gaz de fumée. Selon la présente invention, les cendres volantes subissent une extraction de la fraction grossière, de sorte qu'elles contiennent, au maximum, environ 50 % en poids d'une fraction qui subsiste sur un tamis de 45 mum. Les cendres restantes sont divisées en au moins deux fractions de différents degrés de grossièreté, auxquelles on ajoute du lignosulfonate de Na ou Ca à raison d'environ 0,1 à 2,5 % en poids, après quoi le dosage est réparti parmi les différentes fractions selon un rapport en poids sensiblement proportionnel à leurs granulométries moyennes. Ce procédé est particulièrement approprié pour être utilisé dans le cadre de la filtration électrique de gaz de fumée, auquel cas l'additif peut être ajouté au flux de gaz de fumée après élimination de la fraction grossière en amont des filtres électriques.Process for improving the technical properties of fly ash used in concrete and produced during the combustion of solid fuels and then separated from the flue gases. According to the present invention, the fly ash undergoes an extraction of the coarse fraction, so that they contain, at most, approximately 50% by weight of a fraction which remains on a sieve of 45 mm. The remaining ash is divided into at least two fractions of different degrees of coarseness, to which is added Na or Ca lignosulfonate in an amount of about 0.1 to 2.5% by weight, after which the dosage is divided among the different fractions according to a weight ratio substantially proportional to their average particle sizes. This process is particularly suitable for use in the context of the electrical filtration of flue gases, in which case the additive can be added to the flue gas flow after removal of the coarse fraction upstream of the electric filters.

Description

Method for improving the concrete-technical properties of fly ash
The present invention concerns a method for improving the properties of fly ash produced in the burn¬ ing of solid fuels, so as to make the ash better suitable for an additive for concrete. The fly ash is usually re¬ moved from the flue gases of a combustion plant by means of electric filters or other suitable filter and separa¬ tion apparatuses. The ash separated in this way, in par¬ ticular the ash produced on combustion of coal, has been used as an additive for concrete, partly to substitute for the binder material in concrete.
It has, however, proved problematic to bring out the favourable properties of the ash, as the fly ash also includes fractions that reduce the effect of the ad¬ vantageousfractions when used in concrete and may even suppress said effects completely. A particular problem has been the variation of the proportion of the harmful frac¬ tions in relation to the advantageous fractions, which va¬ riation results, e.g., from the operating conditions of the combustion plant. The variations may be considerable even within one combustion plant, but in particular ashes obtained from different combustion plants cause inpredict- able problems when they are used for concrete products to¬ gether.
As is well known, attempts have been made to eliminate these problems by means of various treatments of the ash, such as by fractioning the ashes by screening, cyclone separation, flotation, and magnetic methods.
Thereat, it has, however, been necessary to re¬ move most of the ashes (from the recovered ashes, the pro¬ portion of powder that passes through a 45 \_m screen is about 99 per cent) to achieve usable concrete-technical properties with the remaining fraction. This results in high costs of the ashes in the form of separation work and large-scale separation equipment, and correspondingly in low proportion of the usable ash of the total quantity of ashes, whereby the profitability and even the quantity of available usable ash have imposed restrictions on rational utilization of the ashes.
By means of the operation of the present inven¬ tion, a substantial improvement has been provided for said problems.
According to the invention, it has been dis¬ covered that it is sufficient if a coarse fraction of the ash is separated from the ashes so that in the ash to be recovered, at the maximum, approximately 50 % of the weight of the ashes consist of a fraction that is retained on a screen of 45 μm, and the recovered ash is divided into at least two fractions of different grades of coarse¬ ness, to which Na- or Ca-lignosulphonate is added at the rate of about 0.1 to 2.5 % of the weight of the ash so that the total quantity of the addition is distributed among the ash fractions of different grades of coarseness substantially at a weight ratio proportional to their average particle sizes.
In particular in respect of the amounts of addi¬ tion of lignosulphonate, surprising results have been ob¬ tained in so far as the results aimed at were obtained with quite a small quantity of additive, which said result is obviously attributable to a "pickling effect" produced by the additive on the ash particles in the method of the invention.
In the application of the additive, it is pos¬ sible to use two alternative procedures, depending on the construction of the flue gas cleaning equipment of the combustion plant.
In connection with electric filtration, the fol¬ lowing procedure has proved the simplest one. A coarse fraction is removed from the flue gas prior to the electric filtration so that the ash separated at the electric filters yields a screening result, wherein the
The figure has been drafted on the basis of. standard concrete tests, wherein the aim has been a 28-day compression strenght of about 60 MN/m^.
The method of the invention has proved partic¬ ularly suitable for the treatment of fly ash produced on combustion of coal, but it is also suitable for the treat¬ ment of ash produced on combustion of peat as well as on combustion of bituminous shale, when the ash is processed so as to make it suitable for an additive for concrete.

Claims

WHAT IS CLAIMED IS:
1. Method for improving the concrete-technical properties of fly ash produced in the burning of solid fuel and separated from the flue gases, c h a r ¬ a c t e r i z e d in that a coarse fraction of the ash is separated from the ashes so that, in the ash to be re¬ covered, at the maximum, approximately 50 % of the weight of the ashes consist of a fraction that is retained on a screen of 45 μm, that the recovered ash is divided into at least two fractions of different grades of coarseness, and that Na- or Ca-lignosulphonate is added to the re¬ covered ash fractions at the rate of about 0.1 to 2.5 % of the weight of the ash so that the overall quantity of the additive is distributed among the ash fractions of diffe¬ rent grades of coarseness substantially at a weight ratio proportional to their average particle sizes.
2. Method as claimed in claim 1, c h a r ¬ a c t e r i z e d in that the quantity of additive ad¬ ministered to the ash is 0.1 to 1 %, advantageously 0.1 to 0.5 % of the weight of the ash.
3. Method as claimed in claim 1 or 2, c h a r ¬ a c t e r i z e d in-that the additive is added to frac¬ tions formed in connection with the separation of the ash.
4. Method as claimed in claim 1 or 2, c h a r ¬ a c t e r i z e d in that the additive is added to the flue gas flow after the separation of the coarse ash frac¬ tion, so as to be separated in subsequent separation sta¬ ges along with the ash fractions.
EP88907697A 1987-08-31 1988-08-31 Method for improving the concrete-technical properties of fly ash Withdrawn EP0397649A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI873768A FI873768A (en) 1987-08-31 1987-08-31 FOERFARANDE FOER ATT FOERBAETTRA DE BETONGTEKNISKA EGENSKAPERNA HOS FLYGASKA FRAON STENKOLSFOERBRAENNING.
FI873768 1987-08-31

Publications (1)

Publication Number Publication Date
EP0397649A1 true EP0397649A1 (en) 1990-11-22

Family

ID=8524971

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88907697A Withdrawn EP0397649A1 (en) 1987-08-31 1988-08-31 Method for improving the concrete-technical properties of fly ash

Country Status (4)

Country Link
EP (1) EP0397649A1 (en)
DK (1) DK51290D0 (en)
FI (1) FI873768A (en)
WO (1) WO1989001917A1 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL1016972C2 (en) * 2000-12-22 2002-06-25 Duos B V Screening method for separating fine particles, especially fly ash, using screen with bed of fine particles on top

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1165897A (en) * 1965-10-05 1969-10-01 John Mchenry Pellet-Hardening Method
DE3411010A1 (en) * 1983-03-26 1984-09-27 Herbert Keller GmbH & Co, 4600 Dortmund Use of flue dust as additive for concrete

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8901917A1 *

Also Published As

Publication number Publication date
WO1989001917A1 (en) 1989-03-09
FI873768A0 (en) 1987-08-31
DK51290A (en) 1990-02-27
DK51290D0 (en) 1990-02-27
FI873768A (en) 1989-03-01

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