Making air, pollution free

In an interview, Shrish Patel, PhD Researcher at Orlov Materials Lab of Stony Brook University with Chemical Today Magazine talks about the ways in which air pollutants can be minimized in the cement industry.

Removing air pollutants.

The current research is to understand the interaction of nitrogen dioxide and sulfur dioxide with crushed demolished concrete. These interactions facilitate adsorption and conversion of these oxides on the concrete surfaces. Such removal of air pollutants can be affected by several parameters, such as age, cement content, type of aggregate used, the source of demolished concrete, chemical composition, porosity. Relating these parameters to mechanisms of removal is an important part of our project.

Concrete interaction and elimination of sulphur and nitrogen oxides.

The calcium hydroxide in the concrete reacts with nitrogen dioxide to form calcium nitrate and calcium nitrite.

                  2Ca(OH)2 + 4(NO)2 → Ca(NO3)2 + Ca(NO2)2 + 2H2O

Moreover, calcium nitrite will further decompose to calcium nitrate in the following manner

                  3Ca(NO2)2 + 2H2O→ Ca(NO3)2 + 4NO + 2Ca(OH)2

The possible reaction of calcium hydroxide and sulfur dioxide is

                  Ca(OH)2 + SO2 → CaSO3.½ H2O + ½ H2O

Use of waste concrete to minimize air pollution.

Currently, the main technique employed in cement industry to mitigate NOx emission is a selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). SCR uses ammonia and a catalyst to selectively reduce NOX emissions from exhaust gases. A much more popular approach is SNCR, which applies ammonia injection technique in the flue-gas at an appropriate temperature. The efficiency of this process varies from 25 to 85 percent.

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