Procal 2000 in Biomass Boiler Applications

Information Centre – Kittiwake Procal 2000 in Biomass Applications ©Kittiwake Procal Ltd Page 1 of 8  F:/Documents/Sales/Publicity/Procal/Information Centre Kittiwake Website Documents/Released/7-3241-01 The Procal 2000 in Biomass Boiler Applications Change Note: 7009344 Date: 27/09/12 Introduction “Biomass” is the term used to describe organic matter that is derived from plants that are produced by photosynthesis. Carbon dioxide (CO2) absorbed from the atmosphere and water absorbed through the plant roots are combined in the photosynthesis process to produce carbohydrates. When biomass is combusted in the presence of oxygen energy is released from the carbohydrates together with CO2 and water. The CO2 released to the atmosphere is available to produce further biomass in a cyclic process and energy produced from biomass is therefore considered to be carbon neutral. However, emissions from the use of fossil fuels arise during the commercial growth and transport of the biomass. In general plants are composed of approximately 75% carbohydrates and 25% lignin. The carbohydrate fraction consists of many sugar molecules linked together in long chains or polymers referred to as cellulose or hemi-cellulose. The lignin fraction consists of non-sugar type molecules that act as a glue holding together the cellulose fibres. Biomass that is used for fuel is sourced from forestry, agriculture, industry and waste operations. Sources of biomass include trees that can be replaced on a short time scale such as willow, poplar and eucalyptus and fuel crops that are specifically grown for use in electricity generation. Agricultural organic waste includes sewage sludge, manure and materials such as corn husks, rice hulls, peanut shells, grass clippings, and leaves. Industrial waste can also be utilised such as waste wood from the construction industry, sawdust from saw mills and fibrous waste from paper mills. Other sources of waste include grass cuttings and pruning remains from parks and gardens, wood from demolished structures, the organic fraction from municipal solid waste and bio degradable land-filled waste. An important property of the biomass is the moisture content. In combustion or thermo chemical processes that use biomass as a feedstock the energy content depends on the amount of moisture. Fresh woodchips and sawdust derived from forestry or sawmills can contain 40-60% moisture. The moisture content can be significantly reduced either by prolonged storage that allows natural evaporation to occur or by forced air drying. Emissions from Biomass Processes The Procal 2000 continuous emission system (CEMs) can effectively measure biomass process emissions. The Procal 2000 can monitor up to six gases including CO2, nitrogen oxides (NOx) and low level sulphur dioxide (SO2) emitted from the biomass process. The Procal 2000 can also measure water vapour and therefore report gas emissions on a wet or dry basis. Biomass emission levels depend on the type of feedstock and the technology that is used for electricity generation. Biomass has a lower sulphur and nitrogen content compared to coal and emissions of SO2 and NOx are lower than when coal is burnt alone. An advantage of biomass combustion is that the CO2 released is considered to be part of the natural carbon cycle allowing for some relaxation on emission measurements for this gas. Procal has over twenty five years’ experience in the field of continuous emissions Information Centre – Kittiwake Procal 2000 in Biomass Applications ©Kittiwake Procal Ltd Page 2 of 8  F:/Documents/Sales/Publicity/Procal/Information Centre Kittiwake Website Documents/Released/7-3241-01 The Procal 2000 in Biomass Boiler Applications Change Note: 7009344 Date: 27/09/12 monitoring with hundreds of applications helping plant operators to meet emission targets. The Procal 2000 when integrated into process control can also improve operational efficiency. Procal 2000 Approvals and Environmental Regulations affecting Biomass Processes The Procal 2000 is an approved analyser with approval from the United Kingdom Environmental Agency’s Monitoring Approval Scheme (MCERTS) and compliant to US EPA measurement standards. The Procal 2000 also has IEC and ATEX approval for use in hazardous areas. Procal as a company operates in accordance with the ISO 9001 2008 quality system. In 2008, the Climate Change Act came into law in the UK setting a target of reducing CO2 emissions by 80% (from 1990 levels) by the year 2050. In addition, EU Directive 2000/76/EC has committed member states to a 20% renewable energy target for 2020. Under a burden sharing agreement the UK has agreed to a target of 15% of all energy to come from renewable sources by 2020. Biomass fuels are therefore being encouraged in the UK so that these stringent targets can be met. However, in common with other combustion appliances, emissions from biomass boilers and combined heat and power (CHP) systems must be managed to maintain and minimise the impact on air quality. Regulations applicable to biomass boilers and CHP systems depend upon the size of the boiler (the rated thermal input MWTH) and the type of fuel burnt. Biomass fuels generally fall into three categories, depending on whether the fuel is classified as waste, and whether it falls under the Waste Incineration Directive (WID): • ‘Virgin’ fuels – e.g. fuels derived from fresh timber • Waste or waste derived fuels, exempt from WID – e.g. agriculture residues • Waste or waste derived fuels, covered by WID – e.g. treated wood waste. The WID aims to minimise the effect on health of emissions to air, land and water from the incineration of hazardous and non-hazardous waste. The directive controls the category and quantity of waste used in incineration processes and describes sampling and measurement procedures. Emission limit values (ELVs) for pollutants such as hydrogen chloride, hydrogen fluoride, heavy metals, SOx, NOx, dioxins and furans are set by the WID. Permit conditions are based on the use of Best Available Techniques (BAT), which have to be adopted by installations where appropriate to prevent the occurrence of unnecessary pollution. Emissions from large combustion plants (>50MW thermal input capacity), irrespective of the fuel used, are regulated under the large combustion plant directive (LCPD). This directive controls emissions of NOx, SO2, and particulate matter to air. The Procal 2000 CEM system is an in-situ analyser that allows for easy installation in many waste incineration and large combustion plant applications. The Procal 2000 is therefore well suited to flue gas measurement on both direct fired and co-fired biomass boilers that fall within both the WID and LCPD regulations. The in-situ Information Centre – Kittiwake Procal 2000 in Biomass Applications ©Kittiwake Procal Ltd Page 3 of 8  F:/Documents/Sales/Publicity/Procal/Information Centre Kittiwake Website Documents/Released/7-3241-01 The Procal 2000 in Biomass Boiler Applications Change Note: 7009344 Date: 27/09/12 design uses the reflective beam principle to directly measure process gas that enters the in-situ measuring cell through permanent sintered panels that prevent the ingress of particulate matter. The in-situ design of the Procal 2000 removes the need for separate gas filtering or sample conditioning equipment that is common with extractive systems. The Procal 2000 offers high reliability, high availability and low maintenance, achieving an uptime of over 98%. In 2008 Environmental Permitting Regulations (EPR) replaced Pollution Prevention & Control (PPC) regulations in England and Wales. Most installations (known as Part A1) are regulated by the Environment Agency, with a lesser number of smaller installations (known as Part A2) regulated by local authorities. Some smaller installations (Part B) are regulated by local authorities for emissions to air only. In Scotland all installations are regulated by the Scottish Environmental Protection Agency (SEPA). In Northern Ireland all Part A and Part B installations are regulated by the Northern Ireland Environment Agency (NIEA) for emissions to air. The Clean Air Act (1993) which is regulated by local authorities is the primary UK regulatory legislation for smaller biomass burning facilities that fall outside the PPC system. Table 1. Regulations for biomass boilers used for the generation of electricity and heat. Fuel Type Plant Capacity Applicable Regulations Regulator Biomass fuels e.g. coppice willow <20MWTH 20-50MWTH >50MWTH Clean Air Act LA-PPC (Part B PPC) EPR (PartA1), PPC Part A Sc/NI LCPD also applies Local Auth. Local Auth., SEPA/NIEA Environment Agency, SEPA/NIEA Waste or waste derived biomass exempt from WID <0.4MWTH & <50kg/hr 0.4 to 3MWTH <50-1000Kg/hr >3MWTH and or 1000kg/hr >50MWTH Clean Air Act LA-PPC (Part B PPC) EPR (PartA1), PPC, Part A Sc/NI EPR (PartA1), PPC Part A Sc/NI LCPD also applies Local Auth., SEPA Local Auth.,SEPA/NIEA Environment Agency, SEPA/NIEA Environment Agency, SEPA/NIEA Waste or waste derived biomass to which WID applies <3MWTH >3MWTH WID applies LA-PPC (Part2A) WID applies PPC (Part A)Local Auth., SEPA/NIEA Environment Agency/SEPA/NIEA In the UK anaerobic digestion facilities are regulated under the Environmental Permitting regime 2010 (SI2010 No. 675). This requires operators to obtain permits for some facilities and register an exemption where smaller scale operations are Information Centre – Kittiwake Procal 2000 in Biomass Applications ©Kittiwake Procal Ltd Page 4 of 8  F:/Documents/Sales/Publicity/Procal/Information Centre Kittiwake Website Documents/Released/7-3241-01 The Procal 2000 in Biomass Boiler Applications Change Note: 7009344 Date: 27/09/12 concerned. Landfill operators are required to monitor, for example, methane emissions through the cap of a landfill as an integral part of demonstrating compliance with regulations such as the EU Landfill Directive (1999/31/EC) and the IPPC directive (96/61/EC). In the US, the EPA regulates biomass fired boilers under the National Emission Standards for Hazardous Air Pollutants (NESHAP 40 CFR Part 63). To minimise emissions operators must implement Maximum Achievable Control Technology (MACT) standards. MACT standards require procedures provided by the boiler manufacturer to be adhered to, for example, when starting-up and shutting-down the boiler. The number of shut-down and start-up events have to be minimised as these events are associated with peak emissions. In addition, an initial performance test of the boiler is required so that operating parameters can be established. The performance test must be repeated every 3 years. An initial analysis of the fuel used must also be undertaken followed by monthly fuel analysis for each type of fuel used in the combustion. Site-specific testing and monitoring plans must also be developed and followed. An important requirement is the installation of Continuous Emission Monitoring systems (CEMs) to record emissions and demonstrate compliance with operating limits. CEM systems must be subject to performance evaluations including a relative accuracy test audit (RATA). A tune up of the boiler based on emissions data and fuel analysis is also required every 2 years. The US Clean Air Act (1963), which is regulated by the EPA, requires large municipal waste landfill sites to collect and combust land fill gas. Controlling emissions from landfill involves drilling collection wells and routing the gas to a suitable energy recovery system or combustion device. Anaerobic digestion is less common in the US as installations have high capital costs and are generally not commercially viable for power production applications. Regulations covering biogas combustion devices apply such as 40CFR Part 89 for internal combustion non-road engines. Biomass Technologies for Power Generation Electricity can be generated in direct-firing applications where biomass feedstock is burnt in a boiler to create steam that drives a turbine. In co-firing applications fossil fuels such as coal are burnt together with biomass. To enable co-firing the power plant must be modified to accommodate the biomass which can then make up to 20% of the fuel. The biomass feedstock is blended either initially with coal before combustion through a blended delivery system, or inside the boiler through a separate feed system, a process that requires more extensive plant retro-fitting. Biomass can reduce SO2 emissions as the feedstock normally has lower sulphur content than coal. The Procal 2000 is capable of measuring SO2 with a minimum range of 0-100ppm. Information Centre – Kittiwake Procal 2000 in Biomass Applications ©Kittiwake Procal Ltd Page 5 of 8  F:/Documents/Sales/Publicity/Procal/Information Centre Kittiwake Website Documents/Released/7-3241-01 The Procal 2000 in Biomass Boiler Applications Change Note: 7009344 Date: 27/09/12 Table 2 – Procal 2000 typical ranges required for a Biomass boiler Measured Gas Range Carbon Monoxide (CO) 0-2000ppm Carbon Dioxide (CO2) 0-15% Nitric Oxide (NO) 0-800ppm Nitrogen Dioxide (NO2) 0-300ppm Sulphur Dioxide (SO2) 0-300ppm Water Vapour (H2O) 0-30% Biomass can fully substitute for fossil fuels if an existing fossil fuel plant is repowered. Repowering requires substantial modification but can allow an existing facility to continue operating when it may otherwise struggle to meet new environmental regulations when burning the fossil fuel for which it was originally designed. Combined heat and power (CHP) facilities allow fuel to be burnt to produce both electricity and useful heat. A CHP plant allows biomass to be combusted to produce steam to power a steam turbine generator. The turbine exhaust can be utilised on site for further electricity generation or directly for either district heating or for industrial process heaters. CHP plants generating both electricity and heat have efficiencies that are in the region of 75 to 90%. Synthesis gas (syngas) can also be produced from biomass using a gasification process in which the feedstock is processed in a hot, oxygen-starved environment. The syngas produced is composed mostly of carbon monoxide and hydrogen. Installations of this type, known as biomass integrated gasification combined cycle plants (BIGCC), are a developing technology with a potential efficiency of up to 60%. A BIGCC plant is shown in figure 1. Waste heat is used to dry the biomass that is then transferred to the gasifier which converts the biomass into a combustible fuel gas.   Information Centre – Kittiwake Procal 2000 in Biomass Applications ©Kittiwake Procal Ltd Page 6 of 8  F:/Documents/Sales/Publicity/Procal/Information Centre Kittiwake Website Documents/Released/7-3241-01 The Procal 2000 in Biomass Boiler Applications Change Note: 7009344 Date: 27/09/12 Figure 1. Low Pressure Indirect BIGCC Schematic  Most of the biomass can be gasified by in-direct heating (using hot sand). Un-gasified solid carbon referred to as char is separated from the gas together with the sand using a cyclone. The char and sand are transferred to a char combustor where air is introduced to burn the char and re-heat the sand. In practice carbon conversion in the gasifier may be sufficiently high that the char combustor is not necessary. The heat produced by the gasifier provides pre-heating for the biomass dryer. A second gasification stage known as a tar cracker may be incorporated. The tar cracker uses a catalyst to reduce the content of heavy hydrogen products (tars) that form part of the gas produced in the first reactor. The removal of the tars prevents downstream tar condensation. The synthesis gas contains particulates that are removed in a low temperature cleaning process that involves quenching the gas with water and removing the particulates in a series of cyclone vessels. However, the gas turbines downstream of the gasifier require the gas at high temperature and pressure therefore as the gas has been cooled during the cleaning process it must be re-heated and re-pressurised. The cooling of the gas during the cleaning phase and the fuel gas recompression systems reduce the efficiency of the process by up to 10%. The hot exhaust of the gas turbine can be recovered using a heat recovery steam generator for additional electricity production. An alternative BIGCC technology (see figure 2. below) uses hot gas filtration that allows the process to be operated at higher efficiencies and also generates less waste water. A fluidised bed reactor operating at atmospheric pressure uses air to partially oxidise the biomass material. In this configuration, the gas exiting the gasifier is only slightly cooled and then cleaned at elevated temperature using a CHAR COMBUSTOR Procal 2000 Catalyst Fines Hot gas Cyclone for Ash Cyclones Sand & Char Sand BiomasDryer GASIFIERDry Biomass Dryer Exhaust Gas Tar Cracker Blower Heat recovery & Gas clean up Information Centre – Kittiwake Procal 2000 in Biomass Applications ©Kittiwake Procal Ltd Page 7 of 8  F:/Documents/Sales/Publicity/Procal/Information Centre Kittiwake Website Documents/Released/7-3241-01 The Procal 2000 in Biomass Boiler Applications Change Note: 7009344 Date: 27/09/12 ceramic or sintered metal filter. After recompression (which in this configuration is more efficient) the gas is passed to the gas turbine combustor. Both particulate and nitric oxide (NOx) emissions can be significantly reduced in comparison with coal-based electricity generation processes. The gas filtration technique is considered to be the technologically more advanced choice for new dedicated biomass plants. Figure 2. High Pressure BIGCC Schematic   In routine use the Procal 2000 provides continuous measurement with no operator intervention. Data measured with the Procal 2000 can be displayed on a Microsoft Windows-based system or a standalone unit, such as the Procal 1000 Analyser Control Unit. This unit can display gas concentrations, sample conditions, diagnostic data and trends, along with data from other sources, allowing for a single CEMS data hub. Landfill Gas Land fill gas (LFG) is created as solid waste decomposes in a landfill. The land fill gas is composed of approximately 50% methane and 50% carbon dioxide with a small amount of volatile organic compounds (VOCs). Instead of allowing the gas to escape into the air it is preferable to capture the gas and convert it for use as a fuel. LFG is extracted from landfills using a series of wells that allow the gas to be conveyed to a central point where it can be processed and treated. The gas can be flared to reduce otherwise harmful emissions, used directly as a replacement for non-renewable fossil fuels such as coal in electricity generation, upgraded or processed into an alternative vehicle fuel. LFG projects capture between 60-90% of the methane, a potent greenhouse gas, which would otherwise be emitted from the landfill. CO2 emissions from municipal solid waste (MSW) landfills are not considered to contribute to global climate change as the carbon in the form of CO2 would normally be emitted as a result of the natural Stack Dryer Procal 2000 AshBiomasFluidised Bed Gasifier Dry Biomass Dryer Exhaust Gas Clean Fuel GasCeramic Candle Filter Gas Turbine Re-compression Information Centre – Kittiwake Procal 2000 in Biomass Applications ©Kittiwake Procal Ltd Page 8 of 8  F:/Documents/Sales/Publicity/Procal/Information Centre Kittiwake Website Documents/Released/7-3241-01 The Procal 2000 in Biomass Boiler Applications Change Note: 7009344 Date: 27/09/12 decomposition of the organic waste materials outside the landfill environment. During combustion landfill gas produces nitrogen oxide and CO2 emissions as well as trace amounts of toxic materials. The amount of these emissions can vary widely, depending on the waste from which the landfill gas was created. Electricity can be generated from LFG using a variety of different technologies, including internal combustion engines, turbines, and fuel cells. Microturbine technology is also used at smaller landfills and in niche applications. Technologies such as Stirling and organic Rankine cycle engines are in development. Indirectly, by offsetting the use of non–renewable resources power plant emissions of CO2 are reduced. Criteria pollutants such as sulphur dioxide, particulate matter and trace hazardous air pollutants are also reduced. Anaerobic Digestion Anaerobic digestion consists of a series of processes that involve the breakdown of bio-degradable material by micro-organisms in the absence of oxygen. A product known as Biogas, which is principally composed of methane and carbon dioxide, is generated. Carbon dioxide and other contaminants can be removed from the biogas to produce a bio-methane with the same specification as natural gas for injection into the gas network. Compressed bio-methane can also be used as a direct substitute for compressed natural gas as a transport fuel. Biogas constitutes a sizeable and renewable form of energy that is currently the focus of much interest in the European Union. When used as part of an integrated waste management system anaerobic digestion reduces the emission of landfill gas into the atmosphere and produces a valuable organic fertilizer in addition to the biogas.