Best Available Techniques in Pyrolysis and Anaerobic Digestion EBIMUN interregional meeting Tartu (Estonia) 29-30th September 2011 Julio Fierro 1
Introduction: Pyrolysis The process of pyrolysis consists in a descomposition of the material by means of temperature, in total absence of oxygen Gas fraction Light hydrocarbons (mainly C1 C4), CO, CO 2, H 2 and little amounts of SO 2 Liquid fraction Complex mixture of organic compunds between 5 and 20 carbons with a very high proportion of aromatics Solid fraction: BIOCHAR Carbon residue (80-90% carbon) mix of products coming from the degradation of biomass components. 2
Rapid Thermal Process (RTP) Technology 3
Rapid Thermal Process (RTP) Technology Characteristics of the process It is used to convert non-food-based feedstock into pyrolysis oil. This oil can then be used in the generation of electricity and for the production of process heat. Development is underway to upgrade pyrolysis oil into green gasoline, green diesel and green jet fuel. Biomass is heated rapidly by contact with hot sand, the biomass is first vaporized and then rapidly cooled. (The process occurs in less than two seconds). Typically yielding 65wt% to 75wt% pyrolysis oil. 4
Rapid Thermal Process (RTP) Technology Achieved environmental benefits When pyrolysis oil replaces fossil fuels to produce heat or steam, life cycle greenhouse gas emissions are reduced by 70-88% depending on the biomass transport distance. The SOx emissions from burning pyrolysis oil are similar to natural gas 5
Dinamotive`s Fast Pyrolysis 6
Dinamotive`s Fast Pyrolysis Characteristics of the process Feedstock is fed into a bubbling fluid-bed reactor heated to 450-500 C in absence of oxygen. Lower temperature than conventional pyrolysis and therefore higher overall energy conversion efficiency. Resulting gases pass into a cyclone where solid particles (char) are extracted. The gases enter a quench tower where they are quickly cooled using pyrolysis oil (Bio Oil) already made in the process As the non-condensable gases are used as energy to run the process, no waste is produced. Uncondensed gases are burned and supply 75% of energy needed by the pyrolysis process Products of the process: Pyrolysis oil (60-75% by weight), char (15-20wt%) and non-condensable gases (10-20wt%) 7
Dinamotive`s Fast Pyrolysis Achieved environmental benefits As the non-condensable gases are used as energy to run the process, no waste is produced. The uncondensed gases are burned and supply 75% of energy needed by the pyrolysis process 8
Pyrolysis Reactor for bio-char production 9
Pyrolysis Reactor for bio-char production Characteristics of the process Designed to treat woody residues from pruning and other agroresidues. Biochar is the principal desired product, in order to use it as soil amendment. The reactor consist in a easy transport unit designed to move to the place where the biomass is. Once the plant reaches the working temperature, it runs with the pyrolysis gases generated (no auxiliary fuel needed). 10
Pyrolysis Reactor for bio-char production Achieved environmental benefits Transporting the reactor where the residues are, better than carrying low density biomass, reduces the GHGs emissions. Bio-char on soil is a carbon capture technique, due to its stability. Pyrolysis plant at Instituto de Recursos Naturales (IRENA). University of León (Spain) 11
Pyrolysis with microwaves Characteristics of the process The feedstock is heated by microwaves. Microwave heating can be controlled instantly and the power applied can be accurately regulated. Heating rates are higher than on the traditional pyrolysis. Flexibility in operation to favors the production of gas, liquids or solids 12
Pyrolysis with microwaves Achieved environmental benefits More energy efficiet than conventional phyrolysis Reduced CO2 emissions due to the decrease of the energy consumtion. 13
The Carbo-V process Characteristics of the process Three phase process: First a Low temperature pyrolysis with a gassification agent A high temperature gasification Endothermic entrained flow gasification 14
Characteristics of the process Three phase process: The Carbo-V process First a Low temperature pyrolysis with a gassification agent A high temperature gasification Endothermic entrained flow gasification Focused on the production of chemical raw materials 15
Best Alvailable Techniques in Anaerobic Digestion EBIMUN interregional meeting Tartu (Estonia) 29-30th September 2011 16
Introduction Anaerobic digestion of organic matter has been reported as a widely used technology in the efficient treatment of organic waste and the simultaneous production of a renewable energy source through the use of biogas 17
Batch-dry anaerobic digestion Characteristics of the process Digestion of solid wastes (>30% TS), like manure and household wastes. Three-step treatment with aerobic-anaerobic-aerobic phases for the production of biogas and quality compost, treating either farm or municipal wastes The aim of the aerobic phases is the stabilization and sanitation of the substrate in order to obtain a product valuable as compost Substrate is a solid-like material which remains inside the reactor during the process without being stirred or mixed. 18
Batch-dry anaerobic digestion Achieved environmental benefits Neither additional water nor wastewater takes part in the process. Digestate is a solid product more easily handled for fertilization and reclamation purposes than liquid digestates. The solid digestate is a valuable compost product. Applicability Available for farms with more than 107 livestock units or 228 livestock units if compost can t be sold Batch-dry anaerobic systems can be implemented in small and medium farms where the management of biowaste is expensive (like insolated or poorly communicated places). If compost trade and demand is well developed, feasibility of the system will be clearer. 19
Plug-flow reactor Characteristics of the process Plug flow reactors are used in the treatment of wastes with high solid content 10-12% TS. Long narrow tank (typically 5:1 ratio) with a gas tight cover to capture the biogas, and a heating system. It is usually built below ground level Unmixed system that works on a semi-continuous mode by regularly receiving untreated wastes in one side of the reactor, and ejecting digested waste out at the end of the digester. Low maintenance and operational costs due to its simplicity. The heating system is the only mechanical components of the digester. 20
Plug-flow reactor Achieved environmental benefits Suitable for difficult feedstock that can t be treated in any other digester (CSTR, UASB, anaerobic filter, etc.) Secure sanitation. The risk of discharge un-decomposed substrate (shortcuts between inlet and outlet) is lower than in other digesters. Due to its simplicity, plug flow reactors are wide used in developing countries, particularly India, Nepal, China and Vietnam, providing a cheap source of fuel, and reducing diseases caused by the use of untreated manure as fertilizer. Cross-media effects Lower performance than other digesters like CSTR or UASB (growth based system). High retention times, thus bigger reactors are needed. 21
Description Continuously Stirred Tank Reactor (CSTR) The CSTR reactors are the most common low rate digesters for large scale application. Feed is introduced to a constantly stirred tank to ensure complete mixing of the reactor content. At the same time an effluent flow is removed from the reactor. CSTR reactor is continuously stirred so there aren t any concentration or temperature gradient. Stirring also improves contact between anaerobic microorganisms and feedstock The main characteristic of the CSTR reactor is that solids and liquid retention times on the reactor are equal. Feeds between 3-10% TS. Biogas production 1-1,45 m 3 m -3 d -1. HRT 15-25 days 22
Continuously Stirred Tank Reactor (CSTR) Achieved environmental benefits Better performance than other low rate digesters such plug-flow or covered lagoons. Due to the mixing system, a CSTR reactor can decrease the hydraulic retention time of the waste from months to between 10 and 20 days, increasing the biogas production over 10-fold. It is possible to treat a wide type of different wastes like slurries, swine, etc., making possible to mix different wastes to improve the biogas production (codigestion). 23
Continuously Stirred Tank Reactor (CSTR) Cross-media effects Lower performance than other digesters like UASB or anaerobic filter (nongrowth based system). For the same organic load bigger reactors are needed. Short-circuiting. Fractions of undigested stock can reach the outflow. More sensitive to shook loads, as inhibitors spreads immediately in reactor than plug-flow. With heterogeneous wastes or large digesters, complete mixing it is difficult to attempt. 24
Description Upflow anaerobic sludge blanket (UASB) It is a high rate anaerobic reactor designed for the treatment of wastewater. The sludge bed is a layer of biomass settled at the bottom of the reactor. The sludge blanket is a suspension of sludge particles mixed with biogas and wastewater. Wastewater is distributed into the tank at appropriately spaced inlets, passing upwards through the sludge bed. 25
Upflow anaerobic sludge blanket (UASB) Achieved environmental benefits High biogas production with high methane content (about 0.15 to 0.35 Nm 3 /kg COD destroyed). It supports high organic loads. HTR 4 20 hours. Stirring system is not necessary due to the action of the influent and biogas bubbles. (Lower energy consumption). Less amount of digested sludge is generated. Main application on industrial wastewaters with high organic content and low solids. 26
Upflow anaerobic sludge blanket (UASB) Cross-media effects Requires skilled staff for construction, operation and maintenance (control of feeding pump and influent organic load). Only suitable for treatment of wastewaters with low solid content. Long start-up phase Not resistant to shock loading. Treatment may be unstable with variable hydraulic and organic loads Insufficient pathogen removal without appropriate post-treatment Constant source of electricity and water flow is required Not adapted for cold regions 27