GB2390363A - Method for the preparation of lime - Google Patents
Method for the preparation of lime Download PDFInfo
- Publication number
- GB2390363A GB2390363A GB0215008A GB0215008A GB2390363A GB 2390363 A GB2390363 A GB 2390363A GB 0215008 A GB0215008 A GB 0215008A GB 0215008 A GB0215008 A GB 0215008A GB 2390363 A GB2390363 A GB 2390363A
- Authority
- GB
- United Kingdom
- Prior art keywords
- lime
- limestone
- dielectric loss
- high dielectric
- gases
- 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.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 23
- 235000008733 Citrus aurantifolia Nutrition 0.000 title description 16
- 235000011941 Tilia x europaea Nutrition 0.000 title description 16
- 239000004571 lime Substances 0.000 title description 16
- 238000002360 preparation method Methods 0.000 title description 2
- 235000019738 Limestone Nutrition 0.000 claims abstract description 20
- 239000006028 limestone Substances 0.000 claims abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 15
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims abstract description 13
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 11
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910000019 calcium carbonate Inorganic materials 0.000 claims abstract description 9
- 239000010439 graphite Substances 0.000 claims abstract description 9
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 9
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 4
- 150000001298 alcohols Chemical class 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims description 12
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 4
- 235000010216 calcium carbonate Nutrition 0.000 abstract description 5
- 239000007789 gas Substances 0.000 description 20
- 239000000126 substance Substances 0.000 description 11
- 238000000354 decomposition reaction Methods 0.000 description 10
- 239000000292 calcium oxide Substances 0.000 description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 7
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 7
- 239000010703 silicon Substances 0.000 description 7
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- ILAHWRKJUDSMFH-UHFFFAOYSA-N boron tribromide Chemical compound BrB(Br)Br ILAHWRKJUDSMFH-UHFFFAOYSA-N 0.000 description 4
- 239000003153 chemical reaction reagent Substances 0.000 description 4
- 238000011109 contamination Methods 0.000 description 4
- 238000005334 plasma enhanced chemical vapour deposition Methods 0.000 description 4
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 230000005855 radiation Effects 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 238000009628 steelmaking Methods 0.000 description 4
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 239000003610 charcoal Substances 0.000 description 3
- 230000003750 conditioning effect Effects 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- HUAUNKAZQWMVFY-UHFFFAOYSA-M sodium;oxocalcium;hydroxide Chemical compound [OH-].[Na+].[Ca]=O HUAUNKAZQWMVFY-UHFFFAOYSA-M 0.000 description 3
- SYNPRNNJJLRHTI-UHFFFAOYSA-N 2-(hydroxymethyl)butane-1,4-diol Chemical compound OCCC(CO)CO SYNPRNNJJLRHTI-UHFFFAOYSA-N 0.000 description 2
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical class [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- YGYAWVDWMABLBF-UHFFFAOYSA-N Phosgene Chemical compound ClC(Cl)=O YGYAWVDWMABLBF-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- RBFQJDQYXXHULB-UHFFFAOYSA-N arsane Chemical compound [AsH3] RBFQJDQYXXHULB-UHFFFAOYSA-N 0.000 description 2
- 229950005499 carbon tetrachloride Drugs 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 2
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 2
- QKCGXXHCELUCKW-UHFFFAOYSA-N n-[4-[4-(dinaphthalen-2-ylamino)phenyl]phenyl]-n-naphthalen-2-ylnaphthalen-2-amine Chemical compound C1=CC=CC2=CC(N(C=3C=CC(=CC=3)C=3C=CC(=CC=3)N(C=3C=C4C=CC=CC4=CC=3)C=3C=C4C=CC=CC4=CC=3)C3=CC4=CC=CC=C4C=C3)=CC=C21 QKCGXXHCELUCKW-UHFFFAOYSA-N 0.000 description 2
- 238000001020 plasma etching Methods 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- WRECIMRULFAWHA-UHFFFAOYSA-N trimethyl borate Chemical compound COB(OC)OC WRECIMRULFAWHA-UHFFFAOYSA-N 0.000 description 2
- CYTQBVOFDCPGCX-UHFFFAOYSA-N trimethyl phosphite Chemical compound COP(OC)OC CYTQBVOFDCPGCX-UHFFFAOYSA-N 0.000 description 2
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- 229910015446 B(OCH3)3 Inorganic materials 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- XPDWGBQVDMORPB-UHFFFAOYSA-N Fluoroform Chemical compound FC(F)F XPDWGBQVDMORPB-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical class Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910000070 arsenic hydride Inorganic materials 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- -1 calcium oxide compound Chemical class 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- KYKAJFCTULSVSH-UHFFFAOYSA-N chloro(fluoro)methane Chemical compound F[C]Cl KYKAJFCTULSVSH-UHFFFAOYSA-N 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- BERDEBHAJNAUOM-UHFFFAOYSA-N copper(I) oxide Inorganic materials [Cu]O[Cu] BERDEBHAJNAUOM-UHFFFAOYSA-N 0.000 description 1
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- KRFJLUBVMFXRPN-UHFFFAOYSA-N cuprous oxide Chemical compound [O-2].[Cu+].[Cu+] KRFJLUBVMFXRPN-UHFFFAOYSA-N 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- ZOCHARZZJNPSEU-UHFFFAOYSA-N diboron Chemical compound B#B ZOCHARZZJNPSEU-UHFFFAOYSA-N 0.000 description 1
- MROCJMGDEKINLD-UHFFFAOYSA-N dichlorosilane Chemical compound Cl[SiH2]Cl MROCJMGDEKINLD-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005670 electromagnetic radiation Effects 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- GHDIQXYAVDNRPK-UHFFFAOYSA-N fluoroform;tetrafluorosilane Chemical compound FC(F)F.F[Si](F)(F)F GHDIQXYAVDNRPK-UHFFFAOYSA-N 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/02—Oxides or hydroxides
- C01F11/04—Oxides or hydroxides by thermal decomposition
- C01F11/06—Oxides or hydroxides by thermal decomposition of carbonates
-
- 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
- C04B2/00—Lime, magnesia or dolomite
- C04B2/02—Lime
-
- 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
- C04B2/00—Lime, magnesia or dolomite
- C04B2/10—Preheating, burning calcining or cooling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Treating Waste Gases (AREA)
Abstract
A method of converting limestone (CaCO3) to lime (CaO) using microwave energy. The limestone may be heated with a material of high dielectric loss distributed therein. Such material may be water, ethylene glycol, alcohols, SiC, graphite and/or alumina, and may be present naturally in the limestone.
Description
- 1 - 2390363
METHODS AND APPARATUS FOR THE PREPARATION OF LIME
This invention relates to the conversion of hazardous gaseous effluents by chemical reactions into safer solid or gaseous products in which the chemical reagents used are solids, hence reducing the risk of carry-over contamination from the gas conditioning equipment. The solid chemical reagents used are easier and safer to handle than liquid reagents. The solid reagents lend themselves readily to encapsulation in exchangeable cartridges.
The gaseous effluents can be the gases that come from etching of semiconductor devices or from PECVD (Plasma Enhanced Chemical Vapour Deposition) on to semi-conductor materials; similar gases and vapours are used in several stages of manufacture in the semi-conductor manufacturing process. The effluent gases (and vapours) from reactive ion etching and plasma etching include chlorine, silicon tetrachloride, copper chloride (CuCI), aluminium chlorides (ie. AICI3), silicon tetrafluoride trifluoromethane (CHF3), carbonyl fluoride (COF2), carbonyl chloride (COCI2), nitrogen trifluoride (NF3), boron bichloride (BCI3), boron tribromide (BBr3), hydrogen chloride (HCI), carbon tetra-chloride (CCI4), chloro-fluoro carbon gases and others. Additional gases and vapours that are sometimes found in the effluent of PECVD operations include silane (Sand), dichlorosilane (SiCI2H2), tetraethylorthosilicate (Si(OC22Hs)4), diborane (B2H6), trimethyl borate (B(OCH3)3), phosphine (PH3), trimethylphosphite (P(OCH3)3), arsine (AsH3) and others.
The current practice is to allow these gases/vapours to enter an exhaust duct to be transported to a wet scrubber positioned at the exhaust end of the lines. This method is occasionally supplemented by local placement of scrubbers. For etching these may be either:
- 2 a) Of the activated charcoal type to trap the acid gases. This method can trap up to 15% of its charcoal weight of Cl2. The product is charcoal with the effluent gases trapped but not converted to safer products and some of these effluent gases will be liberated if the charcoal is burnt.
b) Of the wet type; there are several designs of wet scrubber, most using either a Venturi stage or a packed tower or a combination of both. These designs have been used for larger applications: when placed local to the source of the contamination they present the danger of contamination of the process chamber with their aqueous solutions of caustic type media. The contamination can result from a back streaming type of mechanism or from a massive suckback.
c) The chemical filter type utilising a combination of adsorption and chemical adsorption. These are expensive and do not have a good capacity per unit volume. PECVD scrubbers can be as above but often have a Burn box gas conditioning unit introduced locally. These units burn the effluent gases to form their oxides and water vapour. They suffer from blockage problems and there are normally large volumes of oxides to contend with.
Chemical exhaust gas conditioning unit operating in two main sections and an optional third section were described in our prior POT Application No. GB 89/00600 assigned to the present Applicants. In these units, the effluent gases pass first through a section in which the active chemical components is elemental silicon.
Second, through a section in which the active component is lime, or soda lime (calcium oxide or calcium hydroxide). Third, and optionally, through a section in which the active components are lime and copper oxides (CuO or Cu2O). These sections can be housed in a single container (Figure 1) or compartmentalized in different containers (Figure 2) so that the gases can flow from one to the next.
- 3 - Alternatively the sections can be combined, the silicon mixed with the lime/soda lime in a single reactor.
Broadly stated, the invention of our prior Application consisted of apparatus for treatment of exhaust gases, comprising means for exposing the gases to silicon, or a silicon rich alloy or substance, and means for then exposing the gases to calcium oxide or a calcium oxide compound or calcium oxide containing material, or a soda lime containing medium.
A preferred embodiment of the prior Application comprised a first (silicon) stage, and a second (calcium oxide) stage arranged in sequence and conveniently a single gas treatment chamber having in series silicon and calcium oxide containing zones.
However, there are problems associated with the production of the calcium oxide.
Historically and generally, limestone (CaCO3) is heated to produce lime or calcium oxide (CaO). The decomposition of limestone is an endothermic process and both limestone and lime are very poor conductors of heat. As such, there are difficulties in achieving an even heating of the limestone and achieve a consistent quality of lime. If limestone is heated above 800 C, the decomposition commences and higher temperatures result in a faster decomposition. However, at high temperatures, a recrystallization process may be initiated at the surface of the lime which will reduce the porosity sand the reactivity of the lime product (both essential for the invention).
Traditionally, large quantities of limestone are used in large steelmaking furnaces and the high temperatures therein cause the production of lime. Generally, the time of the "burn" in the furnace is such that the degree of decomposition is of the order of ninety percent; this ensures that the decomposition is incomplete and that the continuing emission of carbon dioxide (CO2) from the decomposition reaction eliminates or at least reduces the onset of recrystallization.
However, the availability of lime from steel making facilities is continually reducing due to the closure of certain plants and the adoption of alternative steel making techniques. The invention is concerned with a new process for the production of lime which surprisingly overcomes such problems in the prior methods (large furnaces to control the decomposition process) and in the increasing unavailability of lime from steel making furnaces.
In accordance with the invention, there is provided a method of converting limestone (CaC03) to lime (CaO) using microwave energy.
Microwave is a form of electromagnetic radiation having a frequency of between 300MHz and 300GHz (wavelength of about 1 m to 1 mm) which generally causes molecular rotation and hence heating of the substance on which the radiation impinges. In its broadest embodiments, the limestone is heated by the impingement of the microwave radiation on to its surface(s).
However the use of microwave radiation energy for heating commonly requires the presence of a material which can ensure the transformation of the electromagnetic energy in to heat. The magnitude of this effect is dependent on the dielectric properties (dielectric loss factor in particular) of the material and allows the selectivity of target specific molecules and deposition of the energy throughout the whole volume of the substance to be heated.
Examples of the many materials having a high dielectric loss factor are water, ethylene glycol, alcohols, silicon carbide, graphite and alumina. Limestone would not generally be regarded as such a material.
- 5 In preferred embodiments of the invention, therefore there is provided a method of heating the limestone with a material of high dielectric loss distributed therein, thereby allowing the microwave energy to couple to the substance and localised heating area to be created. The limestone is thereby heated to above its decomposition temperature and the lime produced. Alternatively, the limestone may be held in a container made of a high dielectric loss material, for example sodium carbide, graphite or alumina.
It has further surprisingly been found that a coupling of the limestone/lime to the microwaves improves dramatically with higher temperatures, and it is therefore possible for the decomposition to continue even if the materials having a high dielectric loss are removed from the heating process.
Furthermore, it has been found that certain naturally occurring substances which, whilst comprising predominantly calcium carbonate, also contain either silicon carbide and/or graphite. As noted above, these forms of limestone will self-couple directly to the microwave energy by virtue of the presence of these other substances and heating will occur. It has also been shown, however, that the carbon dioxide produced as a byproduct of the decomposition of calcium carbonate reacts with the graphite to form carbon monoxide and this causes removal of at least some of the graphite. For a better understanding of the invention, reference will now be made, by way of exemplification only, to the accompanying drawing which shows a schematic cross section through a microwave heating apparatus in which the method of the invention can be performed.
There is shown in the drawing, an apparatus generally indicated at 1 for heating limestone (CaC03) in accordance with the method of the invention.
- 6 -,
The apparatus comprises a double wall container 2 having an outer wall 3 and an inner wall 4. Four individual microwave sources in the form of magnetrons 5, 6, 7, 8 are positioned between the walls 3, 4 and secured to the inner wall 4 and arranged such that microwave radiation can be directed in to the interior of the container 2.
Means (not shown) are provided to hold a crucible 9 made of graphite centrally in the container 2. A fan or ventilator 10 is provided at the base of the container 2 between the wall 3, 4 therefore to ensure good circulation of heat.
An infra red (JR) temperature sensor 11 operated by a temperature controller 12 is provided for sensing temperatures in the container 2 through a window 13 in the top 14 by being secured to a top plate 15 which is itself attached to the top 14 by means of security contacts 16.
In use of he apparatus 1, calcium carbonate 17 was placed in the crucible 9 and heating tests were conducted with an overall input power of 6kW, a microwave output of 4kW, a microwave frequency (preferred overall) of 2. 45GHz and a maximum temperature achieved of 1500 C.
The quality of the lime produced showed a marked improvement over that produced by traditional methods and rendered it very suitable for use in the silicon/calcium oxide abatement devices described above.
In comparison with prior furnaces heated by gas (or whatever), the microwave method of the invention was shown to exhibit the following advantages 1. Fast and volumetric heating. The heat is dissipated from the centre of the substance to the walls in a short time.
2. Environmental friendly atmosphere. The surface of the furnace does not become hot, generally being at room temperature.
- 7 3. A continuous operation is not necessary. It can be switched on off at any time. 4. The price and cost of the operation are more economic.
Claims (5)
1. A method of converting limestone (CaC03) to lime (CaO) using microwave energy.
2. A method according to Claim 1 comprising heating the limestone with a
material of high dielectric loss distributed therein.
3. A method according to Claim 1 or Claim 2 in which the high dielectric loss material is one or more of water, ethylene glycol, alcohols, silicon carbide, graphite and alumina.
4. A method according to any preceding claim in which the high dielectric loss material is present naturally in the calcium carbonate.
5. A method according to Claim 4 in which the high dielectric loss material is silicon carbide and/or graphite.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0215008A GB2390363B (en) | 2002-06-28 | 2002-06-28 | Methods and apparatus for the preparation of lime |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0215008A GB2390363B (en) | 2002-06-28 | 2002-06-28 | Methods and apparatus for the preparation of lime |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0215008D0 GB0215008D0 (en) | 2002-08-07 |
| GB2390363A true GB2390363A (en) | 2004-01-07 |
| GB2390363B GB2390363B (en) | 2006-06-07 |
Family
ID=9939492
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0215008A Expired - Fee Related GB2390363B (en) | 2002-06-28 | 2002-06-28 | Methods and apparatus for the preparation of lime |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2390363B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104310809A (en) * | 2014-10-22 | 2015-01-28 | 张土山 | Sandwich-structure lime burning device |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5378319A (en) * | 1993-05-07 | 1995-01-03 | Tran Industrial Research Inc. | Lime mud calcining using dielectric hysteresis heating |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6259512A (en) * | 1985-09-10 | 1987-03-16 | Todaka Sekkai Kako Kk | Production unit for carbonic acid gas |
-
2002
- 2002-06-28 GB GB0215008A patent/GB2390363B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5378319A (en) * | 1993-05-07 | 1995-01-03 | Tran Industrial Research Inc. | Lime mud calcining using dielectric hysteresis heating |
| US5525783A (en) * | 1993-05-07 | 1996-06-11 | Tran Industrial Research Inc. | Microwave heating device for lime and calcining |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104310809A (en) * | 2014-10-22 | 2015-01-28 | 张土山 | Sandwich-structure lime burning device |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2390363B (en) | 2006-06-07 |
| GB0215008D0 (en) | 2002-08-07 |
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Effective date: 20070628 |