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Solar thermal process for cement production
  • Solar Thermal Electrochemical Production STEP process at George Washington University in Ashburn, Virginia.

    They say it is also zero carbon emission process. Scientists also add that the STEP process could be extended beyond cement
    production to other applications that convert limestone to lime, such as
    purifying iron and aluminum; producing glass, paper, sugar, and
    agriculture; cleaning smoke stacks; softening water; and removing
    phosphates from sewage.Main paper behind a paywall I believe OSE is firmly for solar thermal solutions.

    From Physorg

    "As the scientists explain, 60-70% of CO2 emissions during cement production occurs during the conversion of into lime. This conversion involves decarbonation, or removing the carbon atom and two oxygen atoms in limestone (CaCO3) to obtain lime (CaO) with CO2 as the . The remainder of the emissions comes from , such as coal, to heat the kiln reactors that produce the heat required for this decarbonation process.

    The STEP process addresses both issues, starting by replacing the fossil fuel
    with solar thermal energy. The solar heat is not only applied directly
    to melt the limestone, it also provides heat to assist in the
    electrolysis of the limestone. In electrolysis, a current applied to the
    limestone changes the chemical reaction so that instead of separating
    into lime and CO2, the limestone separates into lime and some
    other combination of carbon and oxygen atoms, depending on the
    temperature of the reaction. When electrolyzed below 800°C, the molten
    limestone forms lime, C, and O2. When electrolyzed above 800°C, the product is lime, CO, and ½O2.

    “Electrolysis changes the product of the reaction of the limestone as
    it is converted to lime,” coauthor Stuart Licht, a chemistry professor
    at George Washington University, told “Rather than
    producing carbon dioxide, it reduces the carbon dioxide (adds electrons)
    and produces only oxygen and graphite (which can be readily stored as
    solid carbon) or CO for fuels, plastics or pharmaceuticals. This is
    accomplished at low energy and high throughput.”

    When separated, the carbon and no longer pose the threat to the atmosphere that they do as CO2.
    As Licht explained, the carbon monoxide byproduct in the higher
    temperature reaction can be used in other industries, such as to produce
    fuels, purify nickel, and form plastics and other hydrocarbons. Plus,
    the carbon monoxide is produced significantly below market value by this
    solar thermal electrolytic process. The main product, lime, doesn't
    react with the other byproducts, but instead forms a slurry at the
    bottom of the vessel where it can easily be removed.

    “This study presents a low-energy, entirely new synthetic route to
    form CaO without any carbon dioxide emission, and is based on unexpected
    solubility behavior in molten salts,” Licht said. “This synthesis can
    be accomplished without solar energy, and without our new STEP process,
    but is particularly attractive when combined with this new solar
    process. Alternatively, the new synthesis could be used by industry to
    produce cement using any non-solar renewable or nuclear energy without
    any CO2 release, or greatly decrease CO2 if
    were used to drive the new cement production (in the latter, worst-case
    scenario, the products are lime, graphite and oxygen; there is still no
    CO2 product, but CO2 would be used in the energy to drive the process).”

  • 2 Comments sorted by
  • wow, amazing!!!!
  • There is great explanation why cement could be replaced in some parts of building homes by hemp/lime combination:

    Producing lime takes less energy (i think 600 degrees)

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