GB2438262A

GB2438262A - Reagent for surface calcination of minerals and ashes

Info

Publication number: GB2438262A
Application number: GB0609574A
Authority: GB
Inventors: John William Carson
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-05-13
Filing date: 2006-05-13
Publication date: 2007-11-21
Also published as: GB0609574D0

Abstract

A pyrolytic reagent for use in the surface calcination of natural minerals and/or synthetic ashes comprised of three essential ingredients; industrial ethyl alcohol, water, and acid or alkali and/or salts. This pyrolytic reagent is used to coat particulate minerals and then ignited in a clamp and allowed to burn to completion. A low temperature surface calcination of the particulates ensues. The resulting modified minerals or ashes have reactive surfaces due to the thermo chemical effect of the pyrolytic reagent. Upon cooling such improved particulate products may be used as absorbents, aggregates, binders, catalysts, ceramics, fillers, fluxes, insulants, pigments, reactants, refractories and zeolites.

Description

IMPROVED MINERALS AND ASHES

The present invention relates to a process for improving natural or synthetic minerals, such as natural sands and furnace ashes.

This process for improving natural and synthetic minerals is based on the use of a range of novel pyrolytic reagents. The use of these pyrolytic reagents in conjunction with fine grain minerals improves the physical and chemical nature of these materials and makes them suitable for a range of industrial applications for which un treated minerals or ashes would not

be as suitable.

The extraction of fine grain minerals, typically from glacial and alluvial deposits and from river, estuarine and marine environments is practiced globally. The combustion of pulverised coal, anthracite, brown coal, lignite and peat is widely practiced for example in the industrial generation of electricity. A major by product from this combustion process is pulverised fuel ash. Other industrial furnace activities similarly generate by product ashes.

Whereas many natural minerals and synthetic ashes find commercial usage some are unsuitable and are considered to be waste materials. The present invention provides a process by which such waste or low value minerals and or ashes can be beneficiated so as to capture commercial usage.

The present invention provide a novel process for the further commercial utilisation of such fine grain natural and synthetic miherals. 2.

This novel process is a form of low temperature surface calcination wherein a pyrolytic reagent is burnt on the surface of the mineral grains.

The pyrolytic reagents are specifically formulated to provide chemicals which react with and bind to the surface of the mineral grains during the calcination process. The reagents also provide and function as the fuel needed for heat generation during the low temperature surface combustion process. This combustion of surface reacting ingredients plus fuel is specifically designed in respect of each natural or synthetic or blended fine grain mineral so as to achieve the desired improvement to the physical and chemical nature of the improved mineral or ash.

Conventionally, minerals are processed by high temperature calcinations, typically at temperatures over 1000 C. Such industries as cement, lime, and magnesia are all based on such processes carried out in rotary kilns. Such processes are inherently expensive both in terms of capital equipment and fuel. Such processes are also large producers of carbon dioxide, widely believed to be a damaging greenhouse gas.

High temperature rotary kilning may be necessary in processes wherein total calcination is needed. However, it has now been found that there are many potential industrial applications in which minerals need not be totally calcined at high temperature.

These potential industrial applications can be served by minerals which have been surface calcined at relatively low temperatures. 3.

Such low temperature surface calcinetion can be conducted in static piles and at temperatures below 1000 C. Such static low temperature surface calcination processes are lower in terms of capital cost, lower fuel consumption cost and lower in emissions of carbon dioxide. In the specific case where the chosen mineral is a carbonate this lower carbon dioxide emission is two fold because the surface calcination requires less fuel than the high temperature total calcination and, additionally, less carbon dioxide is displaced from the mineral. The improved minerals and ashes produced via the proposed process may therefore be seen as environmentally friendly.

It has now been discovered according to the present invention, that a wide range of both natural and synthetic minerals and blends of the same, in finely divided particulate form, may advantageously be calcined via this low temperature static surface calcination process, which is based on a range of novel fuel containing reactive reagents, that is pyrolytic reagents.

The invention described herein provides for the manufacture of this novel range of pyrolytic reagents and for the method by which they are used, in conjunction with fine grain minerals and ashes in this low temperature static surface calcination process.

The basis of the present invention is the recognition that, for many industrial processes the complete calcination of minerals is un-necessary. All that is required for many such minerals in many such industrial processes is the thermal creation of a reactive surface layer on the granular material. If a reactive surface layer is provided, by low temperature static surface calcination, then reactions, such as particle to particle bonding, for which such minerals are used in industrial processes, will proceed satisfactorily. 4.

These bonding processes are, by nature, surface to surface phenomenon, in which the cores of the particulates play no part. It is therefore no advantage to completely calcine such minerals for such applications, Indeed, it is an economic and ecological disadvantage to totally calcine such minerals for such purposes.

This recognition forms the basis of this ecologically and commercially advantageous approach to the improvement of minerals and ashes.

The novel pyrolytic reagent defined in the present invention is a composition of matter produced when three essential material ingredients are blended together. These three essential ingredients will be defined in the following paragraphs: The first essential material is a fuel. This may be in the form of either a finely divided solid or a liquid. However a liquid fuel is advantageous. Moreover a water soluble or water miscible liquid fuel has been found to be advantageous in the present invention. Examples of water soluble fuels which can be used include organic chemicals such as: alcohols, aldehydes, ketones, esters and ethers. Alternatively, a water miscible fuel such as petrol with appropriate miscibilising additives can be used. The preferred fuel is industrial ethyl alcohol also known as blo-ethanol.

The second essential material is water. This may be present in the fuel, or may be added as a separate ingredient to the mixture, or may be used to pre dissolve the third essential ingredient of the reagent mixture. 5.

The third essential material is a water soluble chemical, which may be an acid, alkali or salt or a combination of acid or alkali with a salt. Examples of this third essential material include acids such as hydrochloric; sulphuric and phosphoric. Examples of alkalis include the following, sodium hydroxide, sodium carbonate, ammonium hydroxide, potassium hydroxide. Examples of salts that can be used include ammonium phosphates, magnesium chloride, sodium silicate and transition metal salts such as titanium tetra chloride, sodium dichromate, potassium permanganate, ferrous sulphate, cobalt sulphate and zinc nitrate.

In addition to these three essential materials the novel reagent may contain other materials that serve the purpose of modifying the fuel, such as miscibilising agents, combustion control agents and oxidising accelerants. Also in addition to the three essential materials the novel reagent may contain other materials that serve the purpose of modifying the water, such as surface active agents, foaming agents and sequestering agents. As further additions to the three essential materials the novel reagents may also contain other materials that serve the purpose of modifying the water soluble chemicals, such as secondary binders, set modifiers, fluxes, reaction accelerants, colour modifiers, surface modifiers and catalysts.

The novel pyrolytic reagent is the result of blending the three essential materials together. The pyrolytic reagent may therefore typically be defined as an alcohol in water solution containing acids or alkalis and or salts. The pyrolytic reagent may be blended prior to use or blended at the time of use and even at the location of use. Conventional techniques are used to blend the novel reagent and to ensure that solubilisation and or dispersion is maximised.

It is a feature of the present invention that the pyrolytic reagent contains a fuel which is intimately dispersed throughout the reagent. 6.

Similarly it is a feature of the present invention that the pyrolytic reagent contains a soluble chemical that is intimately dispersed throughout the reagent. This allows for complete distribution of the various components of the pyrolytic reagent over the entire surface area of the mineral grains, to be calcined. This in turn facilitates optimum and even combustion, calcination and production of activated surfaces, of and on, the mineral grains.

The method by which the novel reagent is applied and used will now be described in the following paragraphs: The pyrolytic reagent will usually be a liquid but alternatively can be a slurry or a damp powder or a dry solid, or two separate components there of. This pyrolytic reagent is intended to be applied to mineral grains. These grains may be natural mineral sand or a synthetic mineral ash or several such substances blended together. The particle sizes of such minerals may vary. However the process based on the novel reagent, defined herein, will work on a wide range of particle sizes. Usually, the particle sizes of such minerals lie in the ranges typically associated with gravels, sands, silts, muds, clay and dusts. Thus any mineral particulate within the range 10mm to 0.0001 mm can be treated in this way.

The process by which such mineral grains are treated is essentially a surface coating process.

Any conventional surface coating process can be used. Appropriate surface coating processes include dip coating, slurrying, coating, pasting, slip spraying, paint spraying and wet milling. Alternatively a mixture of the mineral and novel reagent can be agglomerated via granulation, pelletisation or bricketting. Additionally, two or more part reagents may be added to mineral particutates by any two or more of the above coating processes applied sequentially. In this way two or more part pyrolytic reagents may be applied. 7.

The coated mineral may, in many cases, be used without further processing that is in a moist state. Alternatively, when some specific fuels are used, a draining stage may be applied. Once the particles of the mineral are adequately coated with the pyrolytic reagent they are ready for the surface calcination stage.

The surface calcination of minerals coated with the novel reagent will now be described in the following paragraphs: It is a feature of the present invention that the minerals coated as described with pyrolytic reagent are to be ignited. The purpose of igniting the coated minerals is to effect surface calcination and, when so required, to modify the physico-chemical nature of the particulate surface through reaction between the mineral surface and the chemicals contained in the pyrolytic reagent. Ignition of the coated mineral causes surface calcination because of the burning of the fuel, contained in the pyrolytic reagent, on the surface of the mineral particulates.

The coated mineral may be contained in many different styles of furnace for the ignition and calcination stages. Examples include, rotary kilns, tunnel kilns, fluidised bed calciners and sinter-stand furnaces. However, for the purpose described in the present invention we have found that static calcinations is advantageous. The preferred structure used to contain the coated mineral during the ignition and calcination stages is a clamp. In this context a clamp is a simple open topped refractory brick built rectangular walled structure standing on a refractory brick base or floor. Such structures are well understood in the manufacture of stock bricks. 8.

Ignition can conveniently be achieved by any conventional means such as a flame lance or a blow torch. It is a feature of this approach, to the ignition and calcination of mineral particulates, that a stable steady and non-explosive burn is achieved.

The surface calcined modified mineral product obtained via the ignition and calcination process described above will now be defined, in its cooled state, in the following paragraphs: Upon cooling the calcined mineral in the clamp may be removed mechanically by any convenient conventional means. The product is then ready for sale and use.

The product is a surface modified mineral. The surface layer will have been modified by the calcination and may have been further modified by reaction with the chemical components of the pyrolytic reagent.

The product may be of a free flowing particulate nature or it may be a partially or totally sintered solid. The physical nature of the product can be determined in advance by the formulation of the pyrolytic reagent.

Essentially, according to the current invention, the modified mineral product is not completely calcined. This incompleteness of calcine is manifest in a core of unchanged mineral within the particulate nature of the product. It follows that the product may be either an un-sintered material or a sintered material but not a melt or glass. 9.

I have researched the formulation and use of a wide range of pyrolytic reagents in conjunction with a wide range of minerals. The results of my research will now be defined, in general terms, in the following paragraphs: My research has shown that versions of the pyrolytic reagent can be used to effect surface calcination and physico-chemical surface change on most commonly available natural and synthetic minerals.

I have shown that the use of pyrolytic reagents containing acids will react with calcarious minerals and or ashes to provide products wherein the particulate surfaces carry chemically bound substances derived from the anion of the acid. I have shown that the use of pyrolytic reagents containing alkalis will react with siliceous minerals or ashes to provide products wherein the particulate surfaces carry chemically bound substances derived from the cation of the alkali. I have shown that the use of pyrolytic reagents containing inorganic salts will react with various minerals or ashes to provide products wherein the particulate surfaces carry chemically bonded thermal derivatives of the salt. I have also shown that mixtures of acids, alkalis and salts used in conjunction with blends of minerals produce complex surface coated products which may be defined as combinations of the above reactions.

A representative range of novel pyrolytic reagent formulations and resulting surface modified minerals will now be described in the following paragraphs: The following initial formulation is independent of the chemical used in the specific pyrolytic reagent and also independent of the mineral to which the formula is applied: 10.

Fuel 30kg to 80Kg per 100Kg of ready to use pyrolytic reagent.

Water 1 Kg to 40Kg per 100Kg of ready to use pyrolytic reagent.

Chemical 5Kg to 70Kg per 100Kg of ready to use pyrolytic reagent.

Within the above ranges, the following are examples of preferred novel reagents: The first specific version of the pyrolytic reagent is designed for use with calcarious sands: Bio-ethanol 60Kg.

Water 10Kg.

Phosphoric acid [industrial concentrate grade). 30Kg.

The resulting modified mineral can be used as a phosphatically bonded reactant filler.

The second version of the pyrolytic reagent is designed to be used with silicacious ashes: Bio-ethanol 60Kg.

Water 10Kg.

Sodium carbonate 30Kg.

The resulting modified mineral can be used as a fluxing additive in brick making.

This third version of the pyrolytic reagent is designed to be used with flint fines: Bio-ethanol 90Kg.

Water 9Kg.

Cobalt sulphate 1 Kg.

The resulting modified mineral can be used as a blue pigmented aggregate.

The above relative proportions may be varied. 11.

However, sufficient bio-ethanol or other suitable fuel must be present in the pyrolytic reagent to ignite and burn in a controlled manner, when coated on the chosen mineral.

In broad terms I may describe my invention in three parts: A novel composition of matter which is a pyrolytic reagent for use in the surface calcination of minerals, based on: Bio-ethanol.

Water.

Acids, alkalis and or salts.

A novel process, that is a method of manufacture, for low temperature surface calcined mineral and or ashes based on the use of the pyrolytic reagent in the following stages: Coating particulate minerals with the reagent.

Placement of the coated particulates in a clamp.

Igniting the coated particulates.

Surface calcining and/or surface modifying the particulates.

Allowing the modified mineral to cool.

A range of novel products, which may be derived from usage of the pyrolytic reagent in conjunction with the above manufacturing process, are as follows: Speciality minerals.

Bonding aggregates. 12.

Lightweight aggregates.

Fluxed minerals.

Pigmented minerals.

Reactive minerals.

Zeolitic minerals.

Refractory materials.

Ceramic materials.

Cementitjous materials.

The advantages of the present invention will now be defined in the following paragraphs: The pyrolytic reagent is economic in use, being based on relatively inexpensive raw materials.

It may also be seen as being environmentally friendly. It is also simple to formulate, easy to store and convenient in use.

The calcination process achieved through the use of the pyrolytic reagent is versatile, it can be applied to a wide range of available natural minerals, synthetic ashes and blends of the same.

It can also be applied to a wide range of particulate sizes.

The manufacturing approach based on the use of the pyrolytic reagent via the above calcination process is inherently low capital cost, in comparison to kiln calcinations.

The surface calcinations which the manufacturing process effects are advantageous in terms of thermal efficiency in achieving the desired level of surface reactivity. 13.

Surface calcinations may also be regarded as environmentally friendly being a lower carbon dioxide generator than conventional calcinations.

Taken together the above advantages constitute a significant improvement in the process by which minerals are conventionally calcined.

The reader's attention is directed to all papers and documents which are filled concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and/or steps are mutually exclusive.

Each feature disclosed in this specification [including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the detail of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings], or to any one or more novel combination of the steps of any method or process so disclosed. 14.

Claims

CLAIMS

1. A pyrolytic reagent for the surface calcinations of mineral particulates comprising in combination: a) A water soluble or water miscible fuel.

b) Water.

c) Acids or alkalis and/or salts.

2. A pyrolytic reagent for the surface calcinations of mineral particulates, according to claim 1, wherein the proportions by weight percentage of the components to each other are: a) Water soluble or miscible fuel 30% to 80%.

b) Water I % to 40%.

c) Acids or alkalis and/or salts 5% to 70%.

3. A pyrolytic reagent for the surface calcinations of mineral particulates, according to claims I and 2, wherein the water soluble fuel is bio-ethanol, that is industrial ethyl alcohol.

4. A pyrolytic reagent for mineral particulates according to claims I and 2, wherein the acid is phosphoric acid.

5. A pyrolytic reagent for mineral particulates according to claims to I and 2, wherein the alkali is sodium carbonate.

6. A pyrolytic reagent for mineral particulates according to claims I and 2, wherein the salt is a transition metal salt.

7. A method or process by which improved mineral particulates can be made via calcinations of minerals or ashes together with a pyrolytic reagent according to any preceding claim.

8. A pyrolytic reagent for the surface calcinations of mineral particulates substantially as described herein.

9. A method of producing improved mineral particulate products substantially as described herein.

10. A range of calcined synthetic mineral products substantially as described herein.