A presentation to SEIMA. Activated carbon, the world s most powerful adsorbent

Transcription

1 A presentation to SEIMA For: Saskatoon November 30, 2011 and Regina December 2011 Activated carbon, the world s most powerful adsorbent Stanley R. Shewchuk Saskatchewan Research Council and Adjunct Professor, Dept. of Chem. and Biological Eng., University of Saskatchewan Ajay K. Dalai Professor of Chemical Engineering, Dept. of Chem. and Biological Eng., University of Saskatchewan Ramin Azargohar Postdoctoral fellow, Dept. of Chem. and Biological Eng., University of Saskatchewan

2 What is activated carbon? Activated carbon is pure elemental carbon based material produced from a series of raw carbon items such as: Wood Coal Peat Nut shells etc.

3 Activated Carbon Aerosols

4 Activation Refers to the development of the property of adsorption on the raw carbon product Activated Carbon (AC) is produced either by: 1) Physical activation 2) Chemical activation

5 Activated carbon aerosols can be used to improve both air and water quality environmental needs: 1) Systems are available to remove metals, organics, solids in municipal water treatment facilities with filters etc. 2) Odor removal utilizing carbon filtration. 3) Trace chemical species for in-stack emission control into the atmospheric environment

6 Activated Carbon material can be impregnated with various specious such as; sulfur, chloride, iodine, bromine etc. to increase its adsorptive capacities. Activated carbons are used in the food, pharmaceutical and other similar industries to improve consumer product. Activated carbons function as a catalyst in many of these above applications primarily due to its extremely large surface area i.e. one gram of AC has a surface area of approximately 500 m 2.

7 Applications for activated carbon aerosols at the Saskatchewan Research Council (SRC) and the University of Saskatchewan over the past decade have been mainly along the lines of aerosol design and construction for the specific atmospheric regulated priority issue of mercury in the environment.

8 SRC, The University of Saskatchewan and SaskPower have worked together for many years to design an activated carbon aerosol that will capture in-stack elemental mercury on its surface microporosity features in a cost effective manner. Once these atoms are trapped on the aerosol surface, they are removed from the emission stream by a filtration process.

9 The current Environmental Issue The current environmental issue of today is elemental mercury atoms within the GLOBAL ATMOSPHERIC ENVIRONMENT. These atoms are being emitted into the global atmosphere from various anthropogenic sources with the result that they are methylating the water systems of planet earth. Essentially a series of medical disorders in human beings over the past several decades have been attributed to methyl mercury in fish tissues.

10 Basic Principles of In-stack Elemental Mercury Capture with Activated Carbon sorbent control aerosols surface microporosity ~10 Angstroms mesoporosity Å S Hg Under oppropriate conditions Hg reacts with S to form HgS on the aerosol surface. Surface functional group sulfur chemistry bind to the activated carbon aerosol surface. 30 to 60 micron particle diameter macroporosity >100 Å

11 Basic principles of in-stack elemental mercury capture with activated carbon sorbent control aerosols Under appropriate conditions Hg reacts with S to form HgS on the aerosol surface. Surface functional group sulfur chemistry binds to the activated carbon aerosol surface. Aerosol surface microporosity is in the order of Angstrom. The aerosol particle is in the order of 10 s of Microns. Note: 1 micron = 1*10-6 meters 1 Angstrom = 1*10-10 meters The wavelength of light is 5000 Angstroms.

12 Scientists have discovered that at the microphysical level (Skodras et al, 2007) that the pollutant mercury molecule is being captured on the micropores (~ 10 Å) of the activated carbon aerosols. Essentially, The mercury atoms move from AC mesoporosity to microporosity. Ref.: Skodras G. et al, Role of activated carbon structural properties and surface chemistry on mercury adsorption, Science Direct 210 (2007)

13 Activated carbon adsorption for Hg o capture Micropores are active sites for sulfur and Hg capture. Micropore size is smaller than 10 Å. Mesopore size are between Å. The Hg atom size is ~ 1 Å. Therefore, we have collected in the order of 100 atoms in each micropore.

14 A new application for activated carbon aerosols is in the Environmental Issue of Global Warming. Carbon is entering the global atmosphere these days, as carbon dioxide (CO 2 ) from industrial streams. It then mixes globally. This global mixture is largely unbalanced within the global atmosphere.

15 As CO 2 has gradually built up in the earth atmosphere over the decades, it is beginning to interfere with the sun s radiation balance of planet earth. This is causing a gradual rise in the mean annual temperature of planet earth known as the Global Warming.

16 Fig. 1: Atmospheric Carbon Dioxide measured in Mauna Lao, Hawaii

17 Fig. 2: Global Temperature Anomaly The curve shows seasonal variations in atmospheric CO 2 flactuations based on biological activity in the Northern Hemisphere and a regularly yearly increase the annual temperature Source:

18 Fig. 3: A reconstructed Global Atmospheric Temperature profile And the next question is: What is on the horizon for the next millenium?

19 As a result, a current research area is that the Chemical Engineering scientists of the world are now focusing upon is designing activated carbon aerosols specifically for the capture of CO 2 emision products from anthropogenic sources of the world. The current approach is to work with the Activated Carbon aerosols surface microporosity characteristics to capture a CO 2 driven acid/base chemical mix on the aerosol s surface.

20 At the scale of the aerosol microporosity, we have: Microporosity of the activated carbon surface The CO 2 molecule captured on the aerosols surface.

21 The advantages of activated carbon aerosols designed for CO 2 capture are: Low pressure highly efficient collected CO 2 capture. Captures other trace constituents such as; mercury and arsenic. Has a high CO 2 /N 2 discrimination ratio. Known to be reversible for the activated carbon aerosol.

22 As this new activated carbon aerosol research develops, the Chemical Engineers of the world are finding a new way of : Fighting Carbon with Carbon

23 Finally as a result Activated Carbon, particularly in it aerosol form, is being used as a focal point in Saskatchewan and indeed for the entire world, as dealing with issues that are global in environmental perspective with the University of Saskatchewan and SRC being at the leading edge of this research activity.

24 Thank you for Your attention and are there Any questions?