The American Concrete Institute Wants You to Prevent Hydrogen Formation in Your Concrete.

[NNadir]

I came across this fun paper this evening: Silica Fume Formation in Different Gas Atmospheres Vegar Andersen, Kristian Etienne Einarsrud, Azam Rasouli, and Gabriella Tranell Industrial & Engineering Chemistry Research 2023 62 (10), 4246-4259.

It contains the following introductory text, which I personally found amusing:

During carbothermal production of metallurgical-grade silicon in submerged arc furnaces (SAF), a significant amount of fine SiO2 particles, called silica fume, are formed along with silicon in the reduction process. Silica fume is formed in a semiclosed furnace hood, where the process gas meets excessive amounts of air to ensure complete combustion and sufficiently low temperatures for the off-gas system. The silicon yield describes how much silica fume is formed and determines how much carbon the process needs, which is expressed as R1. (1)

Initially a waste product, silica fume is today used as an important addition to concrete, refractory materials, and a range of other products and hence is considered an important byproduct of the silicon production process. (2) The added fine silica fume, usually with a specific surface area (SSA) around 20 m2/g, acts as a pozzolan in concrete and adds strength, decreases thermal expansion, and increases corrosion resistance in the concrete product. The purity of the silica fume is important for the end-product application. Elemental silicon is an impurity that should be limited in silica fume due to safety. Silicon can react with pore water in the concrete and slowly evolve hydrogen or hydrogen sulfide, according to R2 or R3. This could lead to dangerous H2 or H2S concentrations if it occurs in closed-off concrete installations with limited air circulation. A review of the effects of silica fume in concrete can be found in the guide by the American Concrete Institute. (3)

Carbothermal reduction of silica leads to emissions of CO2 through combustion of the CO formed in R1. Carbon capture (CC) may be an option for reducing the footprint of silicon production, either by sequestration (CCS) or utilizing the captured CO2 for purposes that displace the use of other fossil materials (CCU). There are several ways CCU/S can be implemented, and an extensive review of the subject has been done by Gür. (4) A common way of classifying CC is by pre-combustion capture, oxyfuel combustion, or post-combustion capture. Pre-combustion capture, which is the method of capturing CO2 from the fuel before combustion, is not an option for silicon production as solid carbon is needed for the reduction process of SiO2 into Si. For CC through oxy-fuel combustion, air is replaced with O2 under combustion, avoiding diluting N2 and giving an off-gas with a very high concentration of CO2. This could be an option for silicon production but requires closing of the furnace. Previous attempts at closing the furnace have been done by Elkem in 1981 (5) and by Dow in the 1990s, (6,7) with a motivation of improving the process and producing a sellable combustion gas, consisting mainly of CO and some H2. These efforts showed a wide range of challenges that needed to be solved to make a closed furnace process viable. One of these challenges was maintaining the product quality of the silica fume.

Reference 3 is this one:

American Concrete Institute. In Guide for the Use of Silica Fume in Concrete: 234R-06; Fidjestol, P., Ed.; American Concrete Institute: Farmington Hills, Mich, 2006.

That, by the way folks, is the way silicon for all those swell solar cells that are going to cover vast areas of future industrialized wilderness, like say, the grasslands I recently noted here, in the solar "renewable energy" nirvana that's been the subject of so much soothsaying for so many decades but seems not to have arrived after all that talk and money: By heating to high temperatures in the presence of carbon, ultimately yielding CO2.

Good luck maintaining the temperatures of the arc furnaces with variable energy in the predicted "100% renewable energy" nirvana, folks, telling the furnace operators to only show up for work when the wind is blowing and the sun is shining.

As for the carbon dioxide: Don't worry. Be happy. You can always sequester the stuff, right?

As for any hydrogen that may form interstitially in concrete, you can always mine it by drilling holes in the concrete to get hydrogen to power ferries in San Francisco Bay.

Future generations cannot possibly be bad enough to deserve what we are about to give them.

[cachukis]

1. It would seem to me that our technological advances present

unwitting complications.

Introducing foxes to mitigate the rabbit population works for a while.

Ghandi was very opposed to antibiotics as they protected one from choosing a healthy alternative.

Psychologically we seek solutions to our problems.

Many of us have lived much longer because of technology.

My children believe we will escape calamity technologically. It is their experience.

You read these papers with expertise and your findings are chilling.

We are on the cusp of dynamic environmental intrusions to our sense of normal.

The rich are building bunkers.

The monied cannot stop moneying

My carbon footprint is relatively small.

Does it matter to anyone but a few of us?

Or are we overreacting and should go with the flow because ultimately we are in that flow?