CHEMRAWN-XVII and ICCDU-IX Conference on Greenhouse Gases Kingston, Ontario, July 8-12, 2007 The Pidgeon Process for Magnesium Production: Dolomite Calcination and MgO Silicothermic Reduction: Fuel Savings and CO2 Emission Avoidance : CHEMRAWN-XVII and ICCDU-IX Conference on Greenhouse Gases Kingston, Ontario, July 8-12, 2007 The Pidgeon Process for Magnesium Production: Dolomite Calcination and MgO Silicothermic Reduction: Fuel Savings and CO2 Emission Avoidance M. Halmann1 and A. Steinfeld 2 1Weizmann Institute of Science, Department of Environmental Sciences and Energy Research, Rehovot, Israel 2ETH, Department of Mechanical and Process Engineering, Zurich, and Paul Scherrer Institute, Villigen, Switzerland
Industrial Production of Magnesium: Industrial Production of Magnesium Silicothermic Reduction of Calcined Dolomite, CaMg(CO3)2, Pioneered by Loyd M. Pidgeon in Canada during World War II.
Afterwards replaced by the
2. Electrochemical Reduction of Fused Magnesium Chloride, derived from Brine Lakes, such as the Dead Sea, or from Seawater – mainly in the U.S.A., Russia, Canada, and Israel.
Strong Revival of the Pidgeon Process since about 20 Years. About 73% of World Primary Magnesium Production now in China : Strong Revival of the Pidgeon Process since about 20 Years. About 73% of World Primary Magnesium Production now in China Advantages of Pidgeon Process-
Abundant Occurrence of Raw Materials:
Dolomite, Coal, Silica (sand), Iron Oxide (hematite).
Formation of High Purity Magnesium (99.97%).
Relative Simplicity of the Process.
Drawbacks of Pidgeon Process –
Severe Environmental Pollution (dust, toxic gases).
High Fuel Consumption.
Heavy CO2 Emissions.
World Primary Magnesium Production – about 726,000 Ton/year (in 2006): World Primary Magnesium Production – about 726,000 Ton/year (in 2006) Of these produced in:
China: 526,000 Ton
Canada: 50,000 Ton
Russia: 50,000 Ton
U.S.A. 43,000 Ton
Israel: 28,000 Ton
Kazakhstan: 20,000 Ton
U.S.Geological Survey, 2007
www.intlmag.org
The Three Steps of the Pidgeon Process: The Three Steps of the Pidgeon Process Calcination of Dolomite,
CaMg(CO3)2 = CaO + MgO + 2CO2
Ferrosilicon Alloy Production ,
Fe2O3 + 4SiO2 + 11C = 2(Fe)Si2 + 11CO
Silicothermic Reduction of MgO by Ferrosilicon,
2MgO + 2CaO + (Fe)Si = 2Mg(g) + Ca2SiO4(s) + Fe
Toguri and Pidgeon, Can. J. Chem., 40, 1769 (1962)
Energy Consumption and Greenhouse Gas Emissions in the Industrial Pidgeon Process From Ramakrishnan and Koltun, Resources, Conservation & Recycling, 42, 49 (2004) : Energy Consumption and Greenhouse Gas Emissions in the Industrial Pidgeon Process From Ramakrishnan and Koltun, Resources, Conservation & Recycling, 42, 49 (2004)
Purpose of Present Study: Purpose of Present Study To identify Potential Fuel Savings and
CO2 Emission Avoidance in the three
Steps of the Pidgeon Process
by
1. Applying Concentrated Solar Energy.
2. Co-production of Syngas Converted to Methanol.
THERMOCHEMICAL CALCULATIONS : THERMOCHEMICAL CALCULATIONS
The 1st Step of the Pidgeon Process: The 1st Step of the Pidgeon Process Calcination of Dolomite,
at ~1300o C,
CaMg(CO3)2 = CaO + MgO + 2CO2
Highly Endothermic Reaction.
CO2 Released both from the Reaction,
and from Fuel Burned for Process Heat.
Slide10: CO2 Dolomite MgO CaO
Slide11: H2 H2O CO2 MgO CO CH4
Slide12: H2 CO C(gr) MgO
The 2nd Step of the Pidgeon Process: The 2nd Step of the Pidgeon Process Ferrosilicon Alloy Production
by Electric Arc through Mixture of
Hematite, Quartz Sand, and Coal.
Extremely Endothermic Reaction;
Emits Toxic CO.
Literature Reported Reaction:
Fe2O3 + 4SiO2 + 11C = 2(Fe)Si2 + 11CO
Slide14: CO FeSi C(gr) SiO2 SiC SiO
Slide15: H2 CO FeSi C(gr)
Equilibrium Composition vs. Temperature for the System Fe2O3 + 4SiO2 + 11CH4 at 1 bar: Equilibrium Composition vs. Temperature for the System Fe2O3 + 4SiO2 + 11CH4 at 1 bar
At 19000 K the Calculated Equilibrium Reaction is
Fe2O3 + 4SiO2 + 11CH4 =
2FeSi + 22H2 + 10CO + SiC + SiO
Slide17: CO H2 FeSi C(gr) SiO2
Thermogravimetric Experiment: Thermogravimetric Experiment Purpose of experiment:
To test if for Ferrosilicon Production, the Customary Internal Heating by an Electric Arc could be Replaced by External Heating, potentially with Concentrated Solar Energy. Expected Reaction from Literature:
Fe2O3 + 4SiO2 + 11C = 2(Fe)Si2 + 11CO
A mixture of hematite, quartz sand and active carbon
was heated under constant Ar flow in a high-temperature thermogravimeter.
Evolved gases measured by gas chromatography.
Solid products analyzed by X-ray diffraction.
Frei, Halmann and Steinfeld, unpublished
From Calculated Equilibrium: Fe2O3 + 4SiO2 + 11C = 2FeSi(s) + SiC(s) + 10CO(g) + SiO(g) : From Calculated Equilibrium: Fe2O3 + 4SiO2 + 11C = 2FeSi(s) + SiC(s) + 10CO(g) + SiO(g)
Calculated weight loss by release of gaseous CO and SiO: 61%
Observed weight loss: 59%
XRD of the Solid Product of the Reaction Fe2O3 + 4SiO2 + 11C = 2FeSi + SiC + 10CO + SiO Identified FeSi and SiC: XRD of the Solid Product of the Reaction Fe2O3 + 4SiO2 + 11C = 2FeSi + SiC + 10CO + SiO Identified FeSi and SiC
The Products of Ferrosilicon Production: The Products of Ferrosilicon Production According to the Literature:
Fe2O3 + 4SiO2 + 11C = 2(Fe)Si2 + 11CO
At 20000 K, the Equilibrium Products are:
Fe2O3 + 4SiO2 + 11C =
2FeSi + 10CO + SiC + SiO
Confirmed by above Experiments
The 3rd Step of the Pidgeon Process: The 3rd Step of the Pidgeon Process
Silicothermic Reduction of MgO by Ferrosilicon,
at ~1200-1500oC under Vacuum.
Highly Endothermic Reaction,
2MgO + 2CaO + (Fe)Si =
2Mg(g) + Ca2SiO4(s) + Fe
Products: Gaseous Mg and
Slag of Dicalcium Silicate.
Slide24: Mg(g) Ca2SiO4(s) MgO(s)
Potential Fuel Savings and CO2 Emission Avoidance in a Solar Pidgeon Process Combined with Conversion of Syngas (if formed) to Methanol – vs. Conventional Processes.: Potential Fuel Savings and CO2 Emission Avoidance in a Solar Pidgeon Process Combined with Conversion of Syngas (if formed) to Methanol – vs. Conventional Processes.
Conclusions: Conclusions Considerable Fuel Savings and CO2 Emission Avoidance Predicted by using Concentrated Solar Energy for Process Heat in all Three Steps of the Pidgeon Process for Mg Production.
For Dolomite Calcination, and for Ferrosilicon Production, Additional Fuel Saving and CO2 Emission Avoidance Possible by using CH4 or C + H2O as Reductant, resulting in Co-Production of Magnesium and Syngas.