DK179728B1

DK179728B1 - A system for pyroprocessing supplementary cementitious materials

Info

Publication number: DK179728B1
Application number: DKPA201770399A
Authority: DK
Inventors: L. Jepsen Ove; Simon Fortsch David; Hisham Omar
Original assignee: Flsmidth A/S
Priority date: 2017-05-29
Filing date: 2017-05-29
Publication date: 2019-04-23
Also published as: DK201770399A1

Abstract

A system for processing supplementary cementitious material such that the processed supplementary cementitious material can be used in concrete comprising a drier crusher for drying a raw material and for crushing the raw material to a size sufficient to be suspended in and conveyed in a gas stream; acombustor for generating fly ash containing hydrocarbons and clean bottom ash from a fuel material; an incinerator for accepting and heat-treating a material stream, the material stream comprised of the raw material from the drier crusher and the fly ash from the combustor; and a cooler for receiving and cooling the heat treated material stream from the incinerator.

Description

A SYSTEM FOR PYROPROCESSING SUPPLEMENTARY CEMENTITIOUS MATERIALS

FIELD OF THE INVENTION

This invention relates to a system for processing supplementary cementitious materials for the use in concrete.

BACKGROUND OF THE INVENTION

Typically, concrete is a mixture of portland cement, sand, coarse aggregate and water. The principal “cementitious” material in concrete is portland cement. Today, most concrete mixtures also contain supplementary cementitious materials (SCMs) that make up a portion of the “cementitious' material.

SCMs can be e.g. byproducts from other processes (e.g. slag), residues generated from combustion (e.g. ash), or synthetic (e.g. thermally activated clay). If processed efficiently SCMs can replace certain amounts of portland cement while maintaining the desired strength results. This reduces the amount of portland cement required in concrete and consequently reduce CO2 emissions.

Typical slag contains significant amounts of iron in the form of non-magnetic oxides that can cause premature wear of grinding elements used in the manufacture of cement. Ash materials contain impurities such as hydrocarbons that need to be removed prior to mixing with cement. A means for the effective disposal of uncrushed materials, e.g. rice husks / hulls is needed, especially in remote locations.

EP 2631222 A1 describes a gasification furnace 1, where waste and coal are turned into pyrolysis gas and bottom ash. The pyrolysis gas is sent to a calciner. The document further describes that char and ash can be blasted off a gas transport line 6 and that incombustible material is discharged from the bottom of the gasification furnace 1.

US 2016046525 A1 describes a reactor for carbonization, pyrolysis and/or combustion of fuel, which is difficult to ignite. The gas from the reactor enters the bottom of a calcinatory. The exhaust gas from the reactor burns in the calcinator and generates a substantially quantity of heat therein.

US 2007261618 A1 describes a combustion chamber which is directly connected to a calcinatory.

WO 0109548 A1 describes a compartment for incineration being directly connected to a calciner.

It will be clearly understood that any reference herein to background material or information, does not constitute an admission that any material, information, forms part of the common general knowledge in the art, or is otherwise admissible prior art.

OBJECT OF THE INVENTION

It is an object of the invention to overcome or at least alleviate one or more of the above problems and/or provide the consumer with a useful or commercial choice.

SUMMARY OF THE INVENTION

A system is provided for processing supplementary cementitious material such that the processed supplementary cementitious material can be used in concrete, the system comprises: a drier crusher for drying a raw material and for crushing the raw material to a size sufficient to be suspended in and conveyed in a gas stream; a combustor for generating fly ash containing hydrocarbons and clean bottom ash from a fuel material; an incinerator for accepting and heat treating a material stream, the material stream comprised of the raw material from the drier crusher and the fly ash from the combustor; a cooler for receiving and cooling the heat treated material stream from the incinerator; a means to maintain at least a portion of the cooler under reducing conditions; a separator for removing the magnetic metal oxides; wherein the material stream comprised of the raw material is comprised of slag comprising metals; wherein the incinerator is configured to oxidize the metals in the slag, and wherein the cooler and the means to maintain at least a portion of the cooler under reducing conditions are configured to transform non-magnetic metal oxides to magnetic metal oxides.

In some embodiments, the incinerator is configured to heat the fly ash containing hydrocarbons to a predetermined temperature such that hydrocarbons are burnt and the heat-treated material stream is produced.

In some embodiments, the system further comprises a second incinerator cyclone for collecting and further processing the heat-treated material stream from the incinerator.

In some embodiments, the system further comprises a filter for collecting and further processing the heat-treated material stream being collected by the second incinerator cyclone and for reintroducing the heat-treated material stream into the incinerator or for introducing the heat treat material stream into the cooler.

In some embodiments, the system further comprises a first incinerator cyclone for introducing the raw material from the drier crusher to the incinerator or for reintroducing the heat-treated material stream from the filter into the incinerator.

In an exemplary embodiment of the system, the system further comprises a means for removing the clean bottom ash from the combustor so that the clean bottom ash can be mixed with the material stream after the material stream passes through the cooler.

In an exemplary embodiment of the system, the system further comprises a drier crusher cyclone or a bag filter for collecting raw material from the drier crusher before the raw material is introduced into the incinerator.

In an exemplary embodiment of the system, the system further comprises means to maintain at least a portion of the cooler under oxygen depleted conditions.

In some embodiments the fuel material is comprised of rice husks, coal, pet coke tire-derived fuels (TDF), refuse-derived fuels (RDF).

Other details, objects, and advantages of the invention will become apparent as the following description of certain present exemplary embodiments thereof and certain present exemplary methods of practicing the same proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention, by way of example only, will be described with reference to the accompanying drawings in which:

Figure 1 shows an exemplary embodiment of a system for processing supplementary cementitious material for use in concrete.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1, raw material (feed) is directed to the drier crusher 14 where the raw material is crushed (e.g. to less than 5 mm) and preheated and dried (e.g. from an initial moisture content ranging from about 5% (wt) to about 35% to a moisture content of from about 0.25% to about 2.5%) by the hot gas from the first incinerator cyclone 12. Optionally, there can be a water spray stream directed into the drier crusher 14. The dried, crushed material is of a size suitable to be suspended and conveyed in a gas stream to e.g. the drier crusher cyclone 13 where it is separated from the gas stream. Any remaining fine dust is removed by a dust collector 15, e.g. which can be a bagfilter. After the dust collector 15 the gas is pulled by an optional ID fan 16 and exits the system via a stack. The fine dust from the dust collector 15 can be directed to an incinerator

9. Most of the dried, crushed material collected in the drier crusher cyclone 13 is directed to the incinerator 9, either directly or after passing through the first incinerator cyclone 12.

The incinerator 9 shown in Figure 1 can be e.g. an updraft calciner where the combustion air enters through a duct into the lower portion of the calciner. Water vapor and/or oxygen depleted gas and some vaporized fuel from inlet enter the calciner through a riser. Fuel can be directed into the incinerator 9 or the duct leading to the calciner through a single location or multiple locations. The number of fuel locations and the proportion of the fuel depend upon the properties of the fuel and the need to control the combustion in the incinerator 9. In some embodiments, the oil fume draft from a cooler 5 flows into the incinerator 9. In some embodiments, e.g. when the raw material is comprised of slag, the incinerator is configured to oxidize metals in the slag.

The combustor 8 shown in Figure 1 can be e.g. a fluid bed combustor. The combustor 8 can be fueled by fuel material e.g. rice husks, coal or pet coke. The combustion of the fuel material generates heat and produces ash, e.g. fly ash and bottom ash. The fly ash can be directed into the incinerator 9 for further processing and the bottom ash can be pulled out of the system via a chute means or the like 20. The bottom ash can then be removed and collected in e.g. a chute or bin via a conveyor and mixed with the material stream after is passes through the cooler 5 and or the magnetic separator 4.

The material stream, raw material from the drier crusher 14 and the fly ash from the combustor 8, is heat treated in the incinerator 9. The entrained heat-treated material is captured by a second incinerator cyclone 10 and can be directed to a cooler 5 for cooling the heat-treated material stream from the incinerator 9, which is depicted as a rotary cooler. Any remaining heat-treated material can be captured by a filter 11 and either (a) directed to the cooler 5 or (b) directed to the first incinerator cyclone 12 which can then be processed and added back into the incinerator 9.

As shown in Figure 1, a small amount of reducing agent 6, e.g. fuel oil, can be added into the cooler to create local reducing conditions, i.e., an oxygen depleted or low (from about 0% to about 5% by volume) oxygen environment and either CO and/or volatized hydrocarbons, near the material during at least the initial part of the cooling process. Downstream from the cooler area in which the small amount of reducing agent 6 was added, a water sprayer 3 can be utilized to spray water onto the material to contribute to cooling the material. The cooler and the reducing agent 6 / water sprayer 3 are designed such that at least a portion of the cooler 5 is under reducing conditions so that non-magnetic metal oxides in the material are transformed to metal oxides.

As shown in Figure 1, cooled material from the cooler 5 is directed to a separator 4, e.g. a magnetic separator, which can remove e.g. magnetic metal oxides from the slag. The processed SCM material can then be used in concrete.

Such a system is advantageous in that the reduction of e.g. iron from the slag extends the wear life for the grinding elements used in the manufacture of cement; the removal of hydrocarbons from the ash eliminates the possibility of the ash being classified as a hazardous waste so that it can be used in cement; the combustion of the fuel material, e.g. rice husks, generates heat and produces ash with desired properties which upgrades the concrete product; and activating various types of SCMs using an incinerator, e.g. a flash calciner, provides higher cement strength development allowing for higher rates of activated SCM substitution to the finished cement and at a lower fuel consumption than with traditional systems.

It is to be understood that the form of this invention as shown is merely a preferred embodiment. Various changes may be made in the function and arrangement of parts; equivalent means may be substituted for those illustrated and described; and certain features may be used independently from others without departing from the spirit and scope of the invention as defined in the following claims.

Claims

REQUIREMENTS

A system for processing supplementary cementitious material so that the processed supplementary cementitious material can be used in concrete, comprising:

a drying crusher (14) for drying a raw material and for crushing the raw material to a size sufficient to be suspended in and conveyed in a gas stream; a combustion chamber (8) for generating fly ash containing hydrocarbons and pure bottom ash from a fuel material;

an incinerator (9) for receiving and heat treating a stream of material, the stream of material comprising the raw material from the dryer (14) and the fly ash from the combustion chamber (8);

a cooling device (5) for receiving and cooling the heat-treated material stream from the incinerator (9);

a means (6) for maintaining at least a part of the cooling device under reducing conditions;

a separator (4) for removing the magnetic metal oxides;

wherein the material flow comprising the raw material further comprises slag comprising metals;

wherein the incinerator (9) is configured to oxidize the metals in the slag; and wherein the cooling device (5) and the means (6) for maintaining at least a part of the cooling device under reducing conditions are configured to convert non-magnetic metal oxides into magnetic metal oxides.

The system of claim 1, wherein the incinerator (9) is configured to heat the fly ash containing hydrocarbons to a predetermined temperature so that hydrocarbons are burned and the heat treated stream of material is produced.

The system of claim 2, further comprising a second incinerator cyclone (10) for collecting and further processing the heat treated material stream from the incinerator (9).

The system of claim 3, further comprising a filter (11) for (a) collecting and further processing the heat treated material stream collected by the second incinerator cyclone (10) and for (b) reintroducing the heat treated material stream into the incinerator (9) or for introducing the heat-treated material stream into the cooling device (5).

The system of claim 4, further comprising a first incinerator cyclone (12) for introducing the raw material from the dryer (14) to the incinerator (9) or for re-introducing the heat-treated material stream from the filter (11) into the incinerator (9).

The system of claim 1, further comprising means (20) for removing and collecting the clean bottom ash from the combustion chamber (8) so that the clean bottom ash can be mixed with the material stream after the material stream passes through the cooling device (5).

The system of claim 1, further comprising a dryer crusher cyclone (13) or a bag filter (15) for collecting raw material from the dryer (14) before the raw material is introduced into the incinerator (9).

The system of claim 1, further comprising means (3) for maintaining at least a portion of the refrigeration device under oxygen-poor conditions.

The system of claim 1, wherein the fuel material comprises rice husks, coal, petroleum coke, RDF or TDF.