Wednesday, June 19, 2013

Ye cannae break the laws of physics, Solvay Process and Calera concrete

Many an inventor has thought he or she found the chemical version of a perpetual motion machine, where by-products are incorporated into new useful end-products.

The laws of thermodynamics tell us that energy flows down hill towards heat, so lots of energy would be needed to revert a product of a chemical process back up the thermodynamic hill to its starting materials. For unregulated industries it has been expedient (basically cheaper) to go with the flow of thermodynamics and let slag, waste heaps and pollution accumulate at the bottom of the hill, sometimes literally as well as figuratively. On that thermodynamic down-hill roll, a myriad variety of products can branch off.

Figuratively, the process is like an old pinball machine;  energy pushes the molecules up initially,  and as they roll down the thermodynamic slope,  they can be nudged to end in a particular slot.

Calera plans to take waste carbon dioxide (CO2) and incorporate it into concrete in what we might characterize as a novel slot in the thermodynamic pinball machine.

CO2 sequestration is the advertised outcome, but Calera's flow chart tells something more. For one, it will use salt, in addition to the CO2 laden materials.  For another, it will have sodium hydroxide (NaOH) as one of its products.

Sodium hydroxide has a huge history in my hometown of Syracuse, New York.

It was an important product of the Solvay Process, an industry that had followed the salt industry.   The Solvay Process uses brine (water and salt (NaCl)), limestone (largely CaCO3), and energy (initially from coal) to produce soda ash, which is largely sodium carbonate. But - they had by-products, which they cleverly found slots for.

Solvay Process, the collection of Solvay-named companies, eventually became Allied Chemical, which subsequently combined with Honeywell, and took the name Honeywell, except for spinning off LCP Chemical, which had the effect of distancing Allied from a large part of its mercury pollution. The chemical products also evolved to include a long list, among them sodium hydroxide, baking soda, chlorine, and components for making plastics.

One of the big questions being raised about the Calera process is, can it scale up to stow away the enormous amounts of CO2 being generated by the burning of fossil fuel.  People are wishing for a Big Fix for the dilemma of a huge dependence on fossil fuel and the ill effects of its use.

As much as I'd like Calera to succeed in making low-CO2 concrete and sequestering some CO2, the warning signs are there.  Salt in, sodium hydroxide out.
Scale that part of the Calera process up to a global scale, and I foresee issues, even if the CO2 sequestration works technically.

No comments:

Post a Comment