UTILISATION POTENTIAL OF GASIFICATION CARBON RESIDUE

Transcription

1 1 UTILISATION POTENTIAL OF GASIFICATION CARBON RESIDUE Sari Kilpimaa, Ulla Lassi, Toivo Kuokkanen

2 2 CONTENT Background Aim of the work Chemical activation Physical activation Adsorption batch tests Optimisation of ph Optimisation of concentration Effect of adsorption time Determination of adsorption rates Conclusions

3 3 BACKGROUND HighBio2 project University of Oulu is mostly working within the work packages WP3 and WP4 An important objective of the WP3 is the utilisation of carbon residue formed in wood gasification Figure 1. A schematic presentation of the route to produce biofuels and chemicals from biomass-based syngas.

4 AIM OF THE WORK 1/2 4 Figure 2. Development process for utilisation of carbon residue formed in wood gasification process. Reference: Kilpimaa, Lassi, Kuokkanen (2013) Chemical and Physical Activation of Gasification Carbon Residue: Adsorption Studies, HighBio2 project publication

5 5 AIM OF THE WORK 2/2 Activated carbon can be produced from a variety of raw materials such as coal Preparation: physical or chemical activation The aim is to chemically or physically modify carbon residue formed in wood gasification process and use it as an adsorbent. Reference samples: activated carbon and carbon residue without pretreatment Figure 3. Dried, crushed and sieved carbon residue Figure 4. Commercial activated carbon

6 6 CHEMICAL ACTIVATION Wet impregnation method Carbon residue pre-treatment Drying at 110 o C Washing with 1 N solution of HCl : H 2 SO 4 Washing with distilled water, dried, crushed and sieved to achieve particles < 150 µm Chemical activation Mixing 5 min with 0.1 M HCl, 0.1 M H 2 SO 4, 5 M ZnCl 2, 5 M KOH, HCl or HNO 3, L/S 10 (w/w) Drying, activating at 500 o C for 1 hour Washing sequentially with 0.5 M HCl, hot distilled water and distilled water Drying, crushing and sieving (< 150 µm)

7 SPECIFIC SURFACE AREAS OF CHEMICALLY ACTIVATED CARBON RESIDUE 7 Chemical activating agent Specific surface area of sample [m 2 g -1 ] 0.1 M HCl M H 2 SO M ZnCl M KOH 117 HCl 171 HNO Unactivated carbon residue 14.4 Reference: Kilpimaa, Runtti, Kangas, Lassi, Kuokkanen (2013) Removal of phosphate and nitrate over a modified carbon residue from biomass gasification, submitted

8 8 OPTIMISATION OF PARAMETERS Next step in chemical activation was to examine optimal Liquid-to-solid ratio (L/S 4-10) Concentration of impregnation solution (2-5 M) Contact time (10 min 6 h) The best chemical activation result was obtained by using 5 M ZnCl 2, L/S 10 and contact time 1 hour

9 9 PHYSICAL ACTIVATION Physical activation was carried out in a vertical furnace, where 1 g of gasification carbon residue was placed in the reactor tube The oven was continuously heated at a rate 10 o Cmin -1 to the target temperature under N 2 atmosphere. The activating agent was fed by the selected flow rate at activation temperature. N 2 was used also during the cooling stages Figure 6. Furnace and reactor used for physical activation

10 10 CONDITIONS DURING PHYSICAL ACTIVATION Physical activation was carried out by using two different activation agents, CO and CO 2 Temperatures 600 o C and 800 o Cweretested and duration varied between 1-3 h In addition, reference samples were prepared by thermal treatment in N 2 flow without activating agent

11 ADSORPTION BATCH TESTS FOR PHOSPHATE / NITRATE REMOVAL OVER CHEMICALLY ACTIVATED CARBON RESIDUE 11 Laboratory experiments were carried out in order to examine effect of ph (4-8), initial solution concentration ( mg L -1 ) and adsorption time (1 min 24 h) Solution and adsorbent was mixed and ph was adjusted by adding 0.1 M NaOH or HCl Adsorbent dose 5 g L -1 Adsorption time 24 h Samples were filtered through 0.45 µm filter, phosphate /nitrate concentration was analysed by ion chromatography

12 12 RATES OF ADSORPTION The kinetics of phosphate and nitrate adsorption on different adsorbent s surface was studied by using pseudo-first-order and pseudo-second-order kinetic models Pseudo-first-order rate expression: q e and q t are the amounts of phosphates or nitrates adsorbed (mg g -1 ) at equilibrium (here the point is at 1440 minutes) and at time t. The pseudo-first-order rate constant is marked as k f Pseudo-second-order process which can be expressed in a linear form: k s is the rate constant of pseudo-second-order kinetics Equation (1) Equation (2)

13 ADSORPTION BATCH TESTS FOR PHOSPHATE AND NITRATE REMOVAL OVER PHYSICALLY ACTIVATED CARBON RESIDUE 13 Laboratory experiments were carried out in order to examine effect of ph (4-8), initial solution concentration ( mg L -1 ) and adsorption time (1 min 24 h) Solution and adsorbent was mixed and ph was adjusted by adding 0.1 M NaOH or HCl Adsorbent dose 5 g L -1 Adsorption time 24 h Samples were filtered through 0.45 µm filter, phosphate /nitrate concentration was analysed by ion chromatography

14 14 CONCLUSIONS Chemical and physical activation increases specific surface area of gasification carbon residue Highest specific surface area was obtained by using 5 M ZnCl 2 CO 2 as activating agent Chemically and physically activated carbon residue removes phosphate better than commercial activated carbon

15 15 PUBLICATIONS Kilpimaa, Kuokkanen, Lassi (2013) Characterization and Utilization Potential of Wood Ash from Combustion Process and Carbon Residue from Gasification Process, Bioresources. 8(1), Kilpimaa, Kuokkanen, Lassi (2011) Physical and chemical properties of wood ash from burning and gasification processes, The Journal of Solid Waste Technology and Management, Proceedings in ICSW 2011: Kilpimaa, Runtti, Lassi, Kuokkanen (2012) Chemical activation of gasification carbon residue for phosphate removal, Porous Media and its applications in Science, Engineering and Industry, AIP Conference Proceedings 2012: Characterisation Modification and utilisation application Kilpimaa, Runtti, Kangas, Lassi, Kuokkanen (2013) Removal of phosphate and nitrate over a modified carbon residue from biomass gasification, submitted. Kilpimaa, Runtti, Kangas, Lassi, Kuokkanen Preparation of novel carbon adsorbent from biomass gasification by physical activation for the removal of phosphate and nitrate, manuscript. Runtti, Kilpimaa, Kangas, Lassi, Kuokkanen, Rämö (2013) Activated carbon residue from biomass gasification as an adsorbent for iron(ii), copper(ii) and nickel(ii) ions submitted. Runtti, Kilpimaa, Kangas, Lassi, Kuokkanen, Rämö Adsorption of sulphates from mine waters over modified carbon residues, manuscript.

16 16 Thank you for your attention! Researcher Sari Kilpimaa, M.Sc. (Chem.) University of Oulu Department of Chemistry