Testing service for bag filters of power generation units

Bag Filter Performance Testing Service for Power Generation Units – Validating Emission Control Efficiency and Compliance for Brazilian Thermal Power Plants

As an ISO/IEC 17025 accredited independent testing laboratory, we offer comprehensive bag filter performance testing services for power generation units across Brazil's thermoelectric, biomass, and co‑generation facilities. Bag filters (fabric filters) are critical components of flue gas cleaning systems, removing particulate matter and ensuring compliance with stringent environmental emission limits set by IBAMA (Brazilian Institute of Environment and Renewable Natural Resources) and state environmental agencies, as well as operational reliability standards required by ANEEL (National Electric Energy Agency). Our test protocols evaluate filtration efficiency, pressure drop, bag integrity, emissions concentration, and dust loading capacity using standardised methods. All procedures are aligned with ABNT NBR standards, EPA Method 5 (Particulate matter from stationary sources), EPA Method 17 (In‑stack particulate matter), ISO 11057 (Air quality – Test method for filtration characterisation of cleanable filter media), VDI 3926 (Standard test method for filter media), ASTM D6830 (Standard test method for characterizing the pressure drop and filtration performance of a filter medium), and ABNT NBR ISO 14168 (Emission measurement). Our inspection reports are recognised by IBAMA for environmental compliance auditing, by ANEEL for operational licensing, by INMETRO for product certification, and by Brazilian power utilities and EPC contractors for supplier qualification, maintenance planning, and emissions guarantee verification.

Types of Bag Filters and Components We Regularly Test

Our testing facilities and field‑service capabilities cover a broad range of bag filter media and assemblies used in power generation applications. Typical test articles include:

• Needle‑felt filter bags – polyester, polypropylene, acrylic, and aramid (Nomex®‑type) media
• Woven and non‑woven glass fibre bags – for high‑temperature (up to 260 °C) applications
• PTFE (Teflon®‑type) membrane‑coated bags – for surface filtration and low emissions
• PPS (polyphenylene sulfide) bags – for acidic flue gas environments
• P84® (polyimide) and Ryton®‑type bags – for high‑temperature and aggressive chemical conditions
• Stainless steel and metal fibre bags – for high‑temperature and abrasive applications
• Bag cages (support structures) – galvanised, epoxy‑coated, or stainless steel
• Cleaning systems and pulse‑jet valves – for filter regeneration performance

Filtration Efficiency and Particle Removal Performance – Collecting and Analysing Particulate Matter

• In‑stack particulate matter sampling and measurement (EPA Method 5 / EPA Method 17 / ABNT NBR 13274) – We perform isokinetic sampling at the inlet and outlet of the bag filter system using a calibrated probe and sample train. The particulate matter is collected on a glass fibre filter, dried and weighed to determine the total particulate concentration (mg/Nm³). The sampling duration is typically 1‑2 hours, with at least three replicate runs per test condition. The removal efficiency is calculated as Efficiency (%) = [(C_in – C_out) / C_in] × 100. For Brazilian thermoelectric plants, a removal efficiency of ≥ 99.9 % (with outlet concentration ≤ 50 mg/Nm³ for solid fuels, and ≤ 20 mg/Nm³ for liquid/gaseous fuels) is typically required under CONAMA Resolution No. 382/2006 and subsequent updates.
• PM2.5 and PM10 fraction measurement (EPA Method 201A / ISO 23210) – For environmental impact assessments, we also size‑segregate the particulate matter using a cascade impactor (cyclone or ELPI) to determine the PM10 and PM2.5 fractions. The emission of fine particles is a key parameter for Brazilian licensing in urban and sensitive areas.
• Filtration efficiency vs. particle size – fractional efficiency test (ISO 11057 / VDI 3926 adapted) – In the laboratory, we test filter media samples using a test rig with a defined dust aerosol (e.g., SAE Fine or ISO 12103‑1 A2 test dust). The upstream and downstream particle concentrations are measured using an optical particle counter (OPC) or scanning mobility particle sizer (SMPS), and the fractional efficiency is reported for each particle size (0.3‑10 µm). This generates the characteristic efficiency curve, which is essential for assessing the filter’s performance against Brazilian emission limits.
• Mass emission rate and opacity correlation – We measure the opacity (in % light obscuration) using an in‑stack opacity meter (per EPA Method 9) and correlate it with the measured dust concentration (mg/Nm³). This provides a real‑time indication of filter performance, which is particularly useful for Brazilian operators monitoring daily compliance.

Pressure Drop, Cleanability and Regeneration Performance – Energy and Maintenance Optimisation

• Pressure drop measurement across the bag filter (ISO 11057 / ASTM D6830) – Using calibrated differential pressure transducers (accuracy ±1 Pa), we measure the pressure drop (ΔP) across the filter bag (from the dirty side to the clean side) at various air‑to‑cloth ratios (typically 0.5‑2.0 m/min for pulse‑jet systems). The initial pressure drop (clean bag) and the pressure drop at the end of the filtration cycle (before cleaning) are recorded. The average pressure drop and the rate of pressure rise (Pa/h) are calculated. An excessive pressure drop (> 2,500 Pa for pulse‑jet baghouses) indicates blinding or excessive dust loading, which increases fan energy consumption and may require cleaning optimisation.
• Cleaning efficiency – pulse‑jet performance test (VDI 3926 / ISO 11057) – We operate the pulse‑jet cleaning system (or simulate it on the test rig) and measure the residual pressure drop after cleaning. The cleaning efficiency is calculated as Cleaning Efficiency (%) = [(ΔP before cleaning – ΔP after cleaning) / (ΔP before cleaning – ΔP clean bag)] × 100. A cleaning efficiency of less than 80 % indicates that the cleaning parameters (pressure, duration, pulse valve timing) need adjustment, or that the bag has become permanently blinded – a common issue in Brazilian biomass‑fired plants with high organic dust content.
• Dust loading capacity (g/m²) – accelerated life test (ISO 11057 / VDI 3926) – Using a test rig with a constant dust feed rate, we run the filter medium through repeated filtration and cleaning cycles until the pressure drop reaches 1,500 Pa (or the specified terminal ΔP). The accumulated dust mass per unit area (g/m²) at that point is reported as the dust loading capacity. This parameter is critical for predicting the bag life and the required cleaning frequency in Brazilian power plants.
• Effect of temperature and humidity on pressure drop – We perform the filtration test at three different flue gas temperatures (e.g., 80 °C, 120 °C, and 180 °C) and at two relative humidity levels (dry and 50 % RH) to assess the effect on pressure drop and cleaning performance. The results are reported as temperature and humidity correction factors, which are useful for Brazilian operators with variable ambient conditions.

Bag Integrity and Durability – Mechanical Strength, Abrasion and Chemical Resistance

• Tensile strength of filter fabric (ASTM D5034 / ISO 13934‑1) – We cut specimens from the filter bag material (both new and used bags) and perform a tensile test (grab method) in both the warp and weft directions. The maximum force (in N) and the elongation at break are reported. A reduction in tensile strength of more than 30 % from the new bag value indicates significant degradation – either thermal, chemical, or mechanical – which may lead to premature bag failure.
• Puncture and tear resistance (ASTM D4833 / ISO 13937‑2) – We measure the tear strength (by Elmendorf method) and puncture resistance (using a ball burst or nail penetration test) on samples of the filter fabric. A tear resistance below 50 N is considered insufficient for bag filters subjected to high‑velocity particle impacts, such as those in Brazilian coal‑ and biomass‑fired boilers.
• Abrasion resistance (ASTM D4966 / ISO 12947‑2 – Martindale method adapted) – We subject the filter fabric to a standard abrasive (e.g., wool felt or emery paper) for a specified number of cycles (typically 1,000, 2,000, 5,000) and measure the weight loss and any visible fibre breakage. The abrasion resistance is rated on a 0‑5 scale (0 = severe wear, 5 = no wear). For Brazilian plants burning abrasive ashes (e.g., bagasse or eucalyptus biomass), an abrasion rating of ≥ 3 after 5,000 cycles is required.
• Chemical resistance – acid and alkali immersion test (ISO 175 / ASTM D543 adapted) – We immerse filter fabric samples in representative flue gas condensates (e.g., 5 % H₂SO₄, 5 % HCl, or 5 % NaOH) at 60 °C for 72 hours. After immersion, we measure the tensile strength retention and any change in fabric weight. A tensile strength retention below 70 % indicates significant chemical degradation, which is a common problem for polyester bags in Brazilian coal‑fired plants with high sulfur content.

Bag Cleaning and Leak Detection – Identifying Failures and Optimising Maintenance

• Visual bag inspection (on‑site or in‑laboratory) – ABNT NBR 14132 adapted – We inspect the internal and external surfaces of each bag for tears, holes, excessive dust adhesion, creases, or discolouration. The bags are rated using a 0‑5 condition scale (0 = new, 5 = end of life). We also measure the bag length and diameter to check for any shrinkage or stretching, which would affect the sealing and the cleaning performance.
• Spark and leak detection – using fluorescent powder or tracer gas (VDI 3926 / EPA Method 27) – We inject a fluorescent tracer powder (e.g., zinc sulfide) upstream of the baghouse and then use an ultraviolet (UV) lamp to inspect the clean side for any leaks. The number and location of leaks are recorded, and the corresponding bag(s) or seals are identified for replacement. This is a routine maintenance tool for Brazilian plants aiming to reduce emissions and avoid fines.
• Flow distribution and dust loading pattern analysis – by differential pressure and thermography – We use a portable manometer to measure the pressure drop at individual bag rows or compartments to identify areas with high dust loading or gas maldistribution. We also use infrared thermography to detect any hot spots (indicating bag fires or chemical exothermic reactions) or cold spots (indicating air in‑leakage). The results are presented as a “bag health map” for the entire baghouse.
• Residual dust analysis – particle size and composition (by laser diffraction and EDX/SEM) – We collect dust samples from the bag surface and from the hopper, and analyse the particle size distribution (by laser diffraction, ISO 13320) and the elemental composition (by SEM‑EDX). This data is essential for diagnosing the source of the dust (e.g., boiler carry‑over, mechanical wear, or chemical reaction products) and for selecting more appropriate bag materials for Brazilian plants.

Emissions Monitoring and Compliance Reporting – Real‑Time and Periodic Validation

• Continuous emission monitoring system (CEMS) validation – EPA Method 2 / ABNT NBR 14472 – We compare the readings of the plant’s CEMS (opacity, dust concentration, temperature, flow) with our reference measurement (manual sampling with a calibrated filter system). The relative accuracy (RA) and the bias are calculated. An RA of less than 20 % (or the specified acceptance criterion) is required for CEMS certification under Brazilian environmental regulations.
• Opacity and visible emissions evaluation (EPA Method 9) – We perform a visible emissions evaluation by a trained observer (certified by the local environmental agency) for a specified period (typically 3 hours, with readings every 15 seconds). The average opacity and the number of exceedances (e.g., > 20 % opacity) are reported. This is a statutory requirement for Brazilian power plants to avoid operational restrictions.
• Dioxins and furans – screening test (EPA Method 23 / ISO 17873 adapted) – For plants burning chlorine‑containing fuels (e.g., biomass with salt, or certain types of municipal solid waste), we sample the flue gas and analyse it for PCDD/PCDF dioxins and furans using a GC‑MS/MS. The concentration (in ng TEQ/Nm³) is compared to the limit set by CONAMA Resolution No. 316/2002 (0.1 ng TEQ/Nm³ for new sources, 0.5 ng TEQ/Nm³ for existing sources). Although dioxin formation is not directly controlled by the bag filter, the filter’s efficiency in capturing fine particles (which adsorb dioxins) is a key parameter.
• Mercury and trace metal emissions – EPA Method 29 / ASTM D6784 – For coal‑fired plants, we sample and analyse the flue gas for mercury (Hg), cadmium (Cd), lead (Pb), and other trace metals. The concentration is compared to the limits set by CONAMA Resolution No. 313/2002 (for mercury: 5 µg/Nm³ for existing sources, and a future limit of 1 µg/Nm³). The performance of the bag filter in capturing these sub‑micron metals is critical, and we correlate the total metal concentration with the particulate removal efficiency.

Report Acceptance & Compliance with Brazilian Environmental and Power Sector Regulations

All bag filter tests described above are conducted under our ISO/IEC 17025:2017 accreditation, using calibrated sampling trains, pressure transducers, opacimeters, and analytical instruments traceable to INMETRO and international reference standards. Our final test reports include: a comprehensive description of the filter system and test conditions, raw and calculated emissions data (particulate concentration, efficiency, PM fractions), pressure drop and cleaning performance data, bag integrity and durability test results, photographic and microscopic evidence of bag condition, and a clear conformity statement against the applicable environmental limit (e.g., CONAMA resolution) and operational acceptance criteria. We also provide an expanded uncertainty (k=2) for all key quantitative measurements. These reports are widely accepted by IBAMA for environmental licence renewals and compliance auditing, by ANEEL for operational safety and energy efficiency assessments, by INMETRO for product certification of filtration equipment, and by Brazilian thermoelectric plant operators, EPC contractors, and environmental consultants for performance validation, maintenance optimisation, and regulatory reporting. Bilingual (Portuguese/English) versions are available to facilitate submissions to regulatory agencies and to support your engineering, environmental and procurement teams. With our rigorous and comprehensive bag filter testing service, you can confidently verify your emission control performance, minimise environmental liability, and ensure the reliable operation of your power generation units in compliance with Brazil's evolving environmental standards.