Presented by : Calgon Carbon Corporation, Pittsburgh PA. Stephanie Carr Principal Applications Engineer

Transcription

1 November 24, 2014

2 Presented by : Calgon Carbon Corporation, Pittsburgh PA Stephanie Carr Principal Applications Engineer What is Activated Carbon/How it works Siloxane Removal with Activated Carbon Sulfur/H2S Removal with Activated Carbon

3 Drinking water Home water Waste water treatment Pharmaceutical intermediates Sweeteners Glycerine Acids/Citric acid Beverages/Beer Landfill Leachate

4 Structure of Activated Carbon AC is 99% graphite Carbon is the base element of graphite Graphite is used in everything from pencil lead to lubricants to fighter jets AC is a crude form of graphite Like a deck of well used playing cards Imperfections result in porosity and greater surface area Million-fold range in pore sizes in an AC granule From visible cracks/crevices down to molecular scale pores (macro, meso, and micro pores) AC is the original nanotechnology Only the smallest 5-fold range of pores adsorb Some pores transport and some adsorb Highways and parking lots Graphitic plate structure

5 Granular Activated Carbon CARBON GRANULE FLOWING WATER BULK DIFFUSION FILM DIFFUSION PORE DIFFUSION CARBON GRANULE SURFACE DIFFUSION

6 BITUMINOUS COAL WOOD COCONUT SHELL LIGNITE SUB- BITUMINOUS PEAT PETROLEUM

7 INLET HEADSPACE SATURATED OUTLET MASS TRANSFER ZONE VIRGIN

8 Saturation Pressure The closer to saturation pressure, the more strongly adsorbed Concentration Wt% loading increases as inlet concentration increases Relative Humidity (RH) RH above 50% interferes with adsorption efficiency lower adsorption capacity Temperature Higher temperatures result in lower wt% loading

9 Vapor Adsorption/Physical Adsorption capacity on activated carbon for vapor phase organics depends on : o Species type and concentration o Temperature o Pressure o Relative humidity (RH) Chemisorption : a constant weight % capacity for a species depending on the amount of impregnant present on the activated carbon Can get High Levels of % removal with a properly designed system

10 Siloxanes are: silicone+oxygen+methane Siloxanes are used in household and commercial products such as cosmetics, toiletries, paints, cleaning products, clothes, health-care products, etc. Siloxanes find their way into solid waste Siloxanes volatilize into landfill and digester gases SiO2 forms during combustion SiO2 causes plugging to catalyst, fouling in combustion turbines, reciprocating engines and burners

11 Hexamethylcyclotrisiloxane C 12 H 18 O 3 Si 3 D 3 Octamethylcyclotetrasiloxane C 8 H 24 O 4 Si 4 D 4 Decamethylcyclopentasiloxane C 10 H 30 O 5 Si 5 D 5 Dodecamethylcyclohexasiloxane C 12 H 36 O 6 Si 6 D 6 Hexamethyldisiloxane C 6 H 18 SiO L 2 Octamethyltrisiloxane C 8 H 24 Si 3 O 2 L 3 Decamethyltetrasiloxane C 10 H 30 Si 4 O 3 L 4 Dodecamethylpentasiloxane C 12 H 36 Si 5 O 4 L 5

12 Siloxanes Can Be Removed with Activated Carbon -Typical siloxane concentration <5 ppmv total Coal based 4 mm pellet vapor activated carbon used Single adsorber or lead/lag arrangement, non regenerable in situ Vessel size depends on flow, operating pressure and carbon usage Carbon usage rate can be estimated by carbon supplier/computer adsorption programs Stainless Steel Adsorber Construction

13

14

15 Spent carbon from siloxane removal projects can be thermally reactivated in a regional reactivation center, for reuse in same or other industrial applications Usually the spent carbon is classified as RCRA non hazardous, but decision is by the generator Carbon can be changed out usually via vacuum service and fresh carbon refilled from bags or super saks

16 Coal based carbon for adsorption of organic sulfur, mercaptans ( R-SH), disulfides and COS For H2S removal : Selection of the activated carbon is a function of the gas stream - is oxygen present or not? H2S removal is typically by Chemisorption or Catalytic reaction ( if O2 present) Usually a CuO impregnation can be on the coal or coconut based activated carbon / for chemisorption of the H2S with or without O2 present

17 Activated Carbon usually used for H2S <50 ppmv For higher H2S concentrations other technologies would be used, ie iron sponge Activated carbon is a polishing media

18