Off-gas Treatment Technology (Part I)

Introduction Air polution /off-gas ‘The increase, or even decrease of any atmospheric constituent from the value that would have existed without human activity’ Or “The presence of substances in the ambient atmosphere, resulting from the activity of man from natural processes, causing adverse effects to man and the environment” (Weber).

Introduction Negative impacts of off-gas/air polution: Climate change Green house gasses effects Acid rain Corrosion to iron or building  due to acir rain Ozon layer depletion Bad odour Respiratory diseases to human etc PREVENTION & TREATMENT OF OFF-GASS  CRITICALLY IMPORTANT

Introduction Alternatives solution to avoid off-gas emission, include: To select or substitute any process input with zero gas emission To carry out any process activities that can reduce the generation of gas emission To change or substitute any process that resulted gas emission with zero gas emission process To eliminate or reduce any contaminants present in off-gas/gas stream

Classification of Off-gas Treatment Technology If any prevention options of gas emission  FAILED OFF-GAS TREATMENT IS NEEDED  TO REDUCE OR ELIMINATE POLLUTANTS ERLU PENGOLAHAN LIMBAH GAS A number of technologies have been widely applied for removal of pollutants from off-gas or gas emission streams. However, the application of these technologies to off-gases from site remediation may be quite limited.

Klasifikasi Teknologi Pengolahan Limbah Gas Treatment technologies for off-gas treatment are categorized into four groups: Biological – Use of living organisms that consume or metabolize chemicals in the off-gas Adsorption – A process separating contaminants using a medium or matrix Thermal – An oxidation process in which the temperature is increased to destroy vapor-phase contaminants; for this report, internal combustion engine (ICE) is included as a thermal technology Emerging technologies – Including photocatalytic and non-thermal plasma treatment, which destroy contaminants using ultraviolet (UV) light and electrical energy, respectively

Classification of Off-gas Treatment Technology The comparison between two technologies

Classification of Off-gas Treatment Technology Factors influence off-gas treatment technology efectiveness and costs, include: Volatile Organic Carbon (VOCs) concentration VOCs type presence of halogenated VOCs presence of catalyst poisons particulate loading moisture content gas flow rate ambient temperature

Biofiltration BASIC PRINCIPLES Vapor-phase organic contaminants are passed through a bed of porous media and sorb to the media surface where they are degraded by microorganisms in the media Biofiltration has been widely applied for VOC destruction in Europe, Japan, and the United States Biofiltration is a low-cost and highly effective air pollution control (APC) technology

Biofiltration The aim is of using this technologi is to eliminate and reduce any pollutan present in gas streams Specific strains of bacteria may be introduced into the filter and optimal conditions provided to preferentially degrade specific compounds. Biofiltration is used primarily to treat nonhalogenated VOCs and fuel hydrocarbons. Halogenated VOCs also can be treated, but the process may be less effective. Biofilters have been successfully used to control odors from compost piles

Biofiltration Advantages: Filter media does not require regeneration, and the required bed length is greatly reduced. These features reduce capital and operating expenses Under proper conditions, biofilters can remove virtually all selected contaminants to harmless products The biofilter provides several advantages over conventional activated carbon adsorbers, thus, the contaminants are destroyed not just separated, as with granulated activated carbon (GAC) technologies Bio-regeneration keeps the maximum adsorption capacity available constantly; thus, the mass transfer zone remains stationary and relatively short.

Biofiltration Limitations: The rate of influent air flow is constrained by the size of the biofilter. Fugitive fungi may be a problem. Low temperatures may slow or stop removal unless the biofilter is climate-controlled. Compounds that are recalcitrant to biodegradation will not be converted to harmless products. Biofiltration is highly dependent upon the biodegradability of the contaminants

Biofiltration Selection and use of media influence the design of biofilter For biofilter to functioned efficiently, media should be able provide omptimum environment for microorganisme to grow, and to maintain the porosity to allow air flow easily A good filter material should have a: high porosity Moisture capacity holding Nutritions content Low decomposition Example of filter media include soil, wood chips, compost, ect.

Biofiltration

Biofiltration Example of biofilter construction and placement http://www.extension.umn.edu/agriculture/manure-management-and-air-quality/air-quality/biofilter-design-information/

Membrane Separation This technology uses the prinsipal of Diffusion and transport of organic vapors through a nonporous gas separation membrane. The aim is treatment of off-gasses Advantages : 95% removal efficiency, with the remaining poplished through carbon adsorption Limitations : Inability to handle fouling constituents in soil, Inability to handle fluctuations in VOC concentrations, Membranes are sensitive to moisture The targeted contaminants are VOCs, carbon tetrachloride, and chloroform in gas streams

Pemisah membran (membrane separation)

Membrane Separation Classification of membrane process Important factors for selection of membrane include membrane material, type and the membrane’s porosity size Classification of membrane process Porous membrane Gas diffusion: The rates of gas diffusion depend on the pore sizes and the molecular weights. We may have molecular, transition, and Knudsen diffusion regions depending on the relative sizes of pore and gas molecule. Microfiltration (MF): This refers to membranes that have pore diameters from 0.1 to 10 μm. It is used to filter suspended particulates, bacteria or large colloids from solution. Ultrafiltration (UF): This refers to membranes having pore diameters in the range 20-1000 Å . It can be used to filter dissolved macromolecules, such as proteins and polymers, from solution. Reverse osmosis (RO): The membrane pores are in the range of 5-20 Å in diameter, which are within the range of the thermal motion of the polymer chains. Dialysis

Membrane Separation 2. Tight (nonporous, or dense) membrane The permeants are sorbed into the membrane material under the influence of their thermodynamic potential and pass it as a result of a driving force exerted: Gradient of vapor pressure  pervaporation (feed is liquid) and vapor permeation (feed is vapor) Pressure gradient  gas permeation (feed & permeant are gases) and reverse osmosis (feed & permeant are liquids) Temperature gradient  thermoosmosis Concentration gradient  dialysis (osmosis, liquid permeation) and pertraction Gradient in electric potential  electrodialysis (ion-selective membrane)

Membrane Separation   Knudsen diffusion membranes – have low selectivities, resulting in inefficient separation Molecular-sieve membrane/ ultramicroporous membran – They have a continuous network of passages connecting the upstream and downstream faces of the membrane. Thus can be used for gas separation, but depend on the size of porous. In solution-diffusion membrane - gas dissolves in the membrane material and diffuses from high concentration to low concentration. Certain gases permeate the membrane, whereas others do not, resulting in a separation

Membrane Separation Ion transport membrane Are made of a ceramic material that ionizes under pressure and temperature. The oxygen molecules are separated from the gas when they form ionic bonds with the ionized membrane material. The ion transport membrane separates oxygen using less energy since it requires no external electrical source

Membrane Separation

Application example Example schematic aplication of the pilot-scale biofilter used to treat restaurant emissions (Andersson-Chan, 2006)

Application example (Socool et al., 2003)

Application example Schematic of gas membrane separation incorporated photobioreactor on CO 2 enrichment process in microalgae cultivation (Syukri et al., 2011)