Anadi

Evaluation of Thermal Processes for CCA Wood Disposal in Existing Facilities: 

Evaluation of Thermal Processes for CCA Wood Disposal in Existing Facilities Anadi Misra1, Brajesh Dubey1, Chang-Yu Wu1, Timothy Townsend1, Helena Solo-Gabriele2 1University of Florida 2University of Miami 2005 TAG Meeting

Overview: 

Overview Background Methodology Task 1: Inventory of Combustion Facilities Task 2: Survey of Arsenic air pollution control technologies Task 3: Screening of potential materials for minimizing leaching Results and Discussions Summary and Future Work

Background: CCA Wood: 

Background: CCA Wood Currently not considered hazardous under Resource Conservation & Recovery Act (RCRA) which monitors hazardous waste Disposed alongside other wood waste in Construction & Demolition (C & D) debris landfill ~ 60% is burned to produce energy

Background: Problems with incineration of CCA Wood: 

Background: Problems with incineration of CCA Wood Heavy Metal Emissions from combustion Leaching of Heavy Metals from Ash into Groundwater National Physical Lab: www.npl.co.uk Rain Ground Water Contaminated Soil

Proposed Solution: 

Proposed Solution Use mineral sorbents (e.g. lime) for Preventing emission of metals Preventing leaching of metals from incinerator ash Many sorbents have good capture efficiency with respect to metal emissions ( Venkatesh et al, 1996, Kenjiro et al, 2004)  so we have focused on the leaching behavior of CCA metals on interaction with sorbents Activated Carbon Injection :www.epa.gov

Methodology: 

Methodology Task 1: Inventory of Existing Major Wood-Fired Capable Facilities Task 2: Survey of Available Arsenic Air Pollution Control Technologies Task 3: Screening of Potential Materials for Preventing Heavy Metal Leaching from Incineration Product

Task 1: Inventory of Combustion Facilities in Florida: 

Task 1: Inventory of Combustion Facilities in Florida

Task 1: Inventory of Combustion Facilities in Florida (cont.): 

Task 1: Inventory of Combustion Facilities in Florida (cont.) Back

Task 2: Arsenic Pollution Control Technologies: 

Task 2: Arsenic Pollution Control Technologies Reduction in emissions Co-incineration along with dilution Low temperature pyrolysis Capture of emissions Combination of filters and scrubbers Sorbent injection combined with filtration Pyrolysis Furnace Econ Systems: www.econ.co.at Baghouse www.midstatecontracting.com Back

Task 3: Screening of Potential Materials for Preventing Heavy Metal Leaching from Incineration Product : 

Task 3: Screening of Potential Materials for Preventing Heavy Metal Leaching from Incineration Product Evaluate Potential mineral sorbents in combustion environments Analysis of Ash by Toxicity Characteristic Leaching Procedure (TCLP) for leaching properties X-Ray Diffraction (XRD) to identify the crystalline composition

List of Sorbents Used in Experiments: 

List of Sorbents Used in Experiments *Approximate molecular formula based on % composition. Varies according to mineral composition

Experimental Procedure: 

Experimental Procedure Prepared a spike sample of CCA metals having same concentration as that of CCA Type C chemical (47.5% CrO3, 18.5% CuO & 34% As2O5) Heated sorbent and spike sample at 700oC, 900oC & 1100oC for 30 minutes Analysis of the residue TCLP Leaching tests Speciation characterization by XRD

Results: Arsenic Retention in Residue: 

Results: Arsenic Retention in Residue Ca(OH)2 , Cement and Mg(OH)2 show over 98% retention for As at both temperatures Alumina & Diatomaceous Earth show over 80% retention at 900oC

Results: Arsenic Leaching from Residue: 

Results: Arsenic Leaching from Residue Cement, Ca(OH)2 and Mg(OH)2 leach less than 5 mg/l of arsenic in both cases All other sorbents exceed the TC limit for leaching

Results: Chromium Retention in Residue: 

Results: Chromium Retention in Residue Alumina, Silica, Kaolin & Diatomaceous Earth show over 90% retention for Cr at both temperatures Attapulgite Clay shows higher Cr retention at 900oC Ca(OH)2 and Cement show negligible retention

Results: Chromium Leaching from Residue: 

Results: Chromium Leaching from Residue Alumina and Silica leach less than 5 mg/l of Cr at both temperatures Kaolin leaches less than 5 mg/l of Cr at 900oC All other sorbents exceed the TC limit at both temperatures

Results: Copper Retention in Residue: 

Results: Copper Retention in Residue All sorbents except silica and attapulgite clay show ~80% or greater retention at both temperatures Cement, Ca(OH)2 , Mg(OH)2 show over 98% retention at both temperatures and Kaolin at 900oC

Major XRD Results: 

Major XRD Results The major metal-mineral compounds formed in spike samples are Cu3(AsO4)2 , Ca3(AsO4)2 CuHAsO4, CaCrO4 etc., when Cement and Ca(OH)2 are used CuCr2O4, ,when Alumina and Silica are used Cu has high affinity for forming compounds

Summary: 

Summary Cement, Ca(OH)2 & Mg(OH)2 are good at retaining and preventing leaching of As & Cu Alumina & Silica are good at retaining and preventing leaching of Cr The variation in metal-metal and metal-mineral compounds being formed could be the major reason for different retention capabilities. Understanding their interaction will provide solution to the challenging issue of CCA wood disposal.

How can we utilize this study for effective control of heavy metals during combustion of CCA wood?: 

How can we utilize this study for effective control of heavy metals during combustion of CCA wood? A possible strategy involving Cement, Ca-based sorbents to chemically adsorb arsenic in air stream Alumina, Silica to retain chromium in feed Potentially viable option for disposal: Cement kiln Coal-fired power plants equipped with SO2 scrubbers Steel mills Provide alumina/silica Provide Ca-based sorbent Cr in feed As in gas phase

Acknowledgements: 

Acknowledgements Financial Support by Florida Center for Solid and Hazardous Waste Management Grant# 00050891 Major Analytical Instrumentation Center, Department of Material Science and Engineering, UF Particle Engineering Research Center, UF Officials at Florida Department of Environmental Protection (FDEP) Mr. Henry Gotsch, Florida Rock Industries Inc. Sang-Rin Lee, Clarkson University

Slide22: 

Thank You

Slide23: 

http://combustcca.ees.ufl.edu