THE FILTRATION OF HIGH TEMPERATURE, HIGH PRESSURE SYNGAS FROM
Andy Bevis (pages 202-212)
The filtration of high temperature and high pressure syngas, derived from the gasification of coal or petroleum coke, can be performed with metallic filter elements. This is a demanding filtration duty owing to the nature of the corrosive gas composition, which is significantly accelerated by the chemistry of the char contaminant retained by the filter media. There are additional demands on the system due to the quantity of char present, which can be measured in excess of 10% by mass of the gas throughput, therefore challenging the individual filter system with loads as high as 10,000 kg/hr. The filter elements are pulse-jet cleaned in-situ with previously filtered and modified (recycled) syngas, at pressures in excess of 100 bar. This presents another design and operational challenge which needs to be correctly controlled and delivered.
The paper seeks to provide an overview of the presence of filtration in gasification when specifically applied in the high temperature part of the process and where the operation is generally at a high pressure.
A NEW TEST SYSTEM FOR THE IN-LINE MONITORING OF AUTOCLAVE EXHAUST TREATMENT: A STUDY OF UNCERTAINTY
Carsten Grumbach and Peter Czermak (pages 213-222)
The development of test systems to monitor the filtration of exhaust gases from laboratory autoclaves is driven by emerging laboratory safety regulations. The water intrusion test is suitable for this purpose, and therefore the test was adapted to account for the risks inherent in the filter systems used for the treatment of exhaust gas. To validate the test principle, the uncertainty of calibration and measurement was investigated using two commercial test gauges (Palltronic®Flowstar XC, Sartocheck 4). The calibration data revealed a good fit (R² = 0.988) over a measurement range of 0.0-3.0 mg/mL, confirming the stability of the test system. The uncertainty of the new test system corresponds to other measurement gauges in a range of ± 0.01 (for low flow rates) to ± 0.05 (for high flow rates). These data highlight the potential of our device for the development of reliable test systems for small plants, with adjusted costs for design, integration and qualification.
CHALLENGE TESTING – CURRENT TECHNOLOGIES AND FUTURE PROSPECTS
Keith Brocklehurst, Andrew Hassall, Graham Rideal and Abi Stewart (pages 222-226)
Unlike test sieves, which have plain weaves and can be measured optically, complex 3D weaves of twilled construction do not allow light to pass and so cannot be measured optically. The apertures then have to be estimated by air flow rate studies (Porometry) or challenged by a wide distribution of particles such that those passing are measured to determine the cut point of the filter (Challenge Test). Historically, various sands such as Arizona test dusts have been used, but their irregular shapes mean that it is difficult to obtain an unambiguous measurement of aperture size. Using glass microspheres has partially solved the problem, but a small percentage of misshapes in the product can seriously overestimate the aperture size when the particle is expressed as the equivalent spherical diameter.
When an Image Analyser is used for particle measurement, it is now possible to electronically filter non-spherical particles from the size/shape distribution and thus provide much more accurate measurements of the aperture sizes. The method has been validated using plain weaves down to 20 µm, where optical measurements have been used to confirm the data, and then extended to complex twilled meshes down to 5 µm. At this size there are no other methods available to obtain unambiguous, NIST traceable results.
METAL FILTER CLOTH AND NEW DEVELOPMENTS IN HIGH PERFORMANCE WOVEN WIRE MEDIA
Haver &Boecker, Germany (pages 227-230)
This technical note describes some recent developments in MINIMESH® metal filter media and the manner in which testing can be used to validate their performance.
THE APPLICATION OF AEROSOL SPECTROMETERS IN FILTER TESTING STANDARDS
Stephen N. Smith (pages 230-240)
This paper discusses the use of aerosol spectrometers over traditional aerosol photometers when applied to filter testing in ISO 12500-1:2007 ‘Filters for compressed air – Test methods – Part 1: Oil aerosols’. It highlights the limitations of making measurements with traditional photometers in such an application and the importance of using the correct substance properties for refractive index and density to enable the accurate computation of the resulting mass concentration in the sampled air stream. Example test data obtained from isobaric sampling upstream and downstream of a coalescing filter is also given to provide an insight into temporal changes to coalescing filter performance due to oil saturation over time. Thus, having the ability to ascertain changes in filter performance over time provides the researcher with the potential to better understand what impact design changes or operating conditions might have on coalescing filter performance.