Sintered metal filter

One of the problems with early hydride systems was decrepitation of the alloy. Each time the metal hydride storage tank was recharged the particles would break down and eventually the particles became so small that they began to pass through the 5-p.m sintered metal filter which kept the hydride inside the tank. Addition of 0.5% manganese, which caused the decrepitation process to cease once the particles reached a size of about 10 p.m, solved this problem. 

Figure 4-77B. Porous sintered metal filter elements. By permission, Pall Process Filtration Co.

After the activation period, the reactor temperature was decreased to 453 K, synthesis gas (H2 CO = 2 1) was introduced to the reactor, and the pressure was increased to 2.03 MPa (20.7 atm). The reactor temperature was increased to 493 K at a rate of 1 K/min, and the space velocity was maintained at 5 SL/h/gcat. The reaction products were continuously removed from the vapor space of the reactor and passed through two traps, a warm trap maintained at 373 K and a cold trap held at 273 K. The uncondensed vapor stream was reduced to atmospheric pressure through a letdown valve. The gas flow was measured using a wet test meter and analyzed by an online GC. The accumulated reactor liquid products were removed every 24 h by passing through a 2 pm sintered metal filter located below the liquid level in the CSTR. The conversions of CO and H2 were obtained by gas chromatography (GC) analysis (micro-GC equipped with thermal conductivity detectors) of the reactor exit gas mixture. The reaction products were collected in three traps maintained at different temperatures a hot trap (200°C), a warm trap (100°C), and a cold trap (0°C). The products were separated into different fractions (rewax, wax, oil, and aqueous) for quantification. However, the oil and wax fractions were mixed prior to GC analysis. 

Dust Separation It is usually necessary to recover the solids carried by the gas leaving the disengaging space or freeboard of the fluidized bed. Generally, cyclones are used to remove the major portion of these solids (see Gas-Solids Separation ). However, in a few cases, usually on small-scale units, filters are employed without the use of cyclones to reduce the loading of solids in the gas. For high-temperature usage, either porous ceramic or sintered metal filters have been employed. Multiple units must be provided so that one unit can be blown back with clean gas while one or more are filtering. 

Another option to improve TSS performance is use of a sintered metal filter. This technology has typically been applied only as a fourth stage application on the TSS underflow. Pall has commercialized this barrier filter on the entire FCC flue gas on one commercial unit. 

Most analyzer sampling systems require a filter with at least one wire mesh strainer (100 mesh or finer) to remove larger particles that might cause plugging. Available filter materials include cellulose, which should only be considered if it does not absorb the components of interest. Sintered metallic filters can remove particles as fine as 2 ym, cellulose filters can remove down to 3 /on, and ceramic or porous metallic elements can trap particles of 13 ym or larger. When the solids content is high, two filters can be installed in parallel with isolation valves on each. Motorized self-cleaning filters are also available for such services. 

Particle removal at high temperatures is possible with ceramic or sintered metal filters as has been demonstrated in the VSmamo biomass gasification plant. Filter blinding (reaction of tars in the filter pores) has occasionally been found to be a problem when testing high temperature filters. This phenomenon is, however, not reproducible nor understood ... 

Learn to understand and predict blinding of high temperature ceramic/sintered metal filters ... 

Off-gas from the calcination process was passed through sintered-metal filters located in the upper section of the calcination vessel. The process off-gas was then cooled in the offgas condenser where most of the N09 released in the denitration process was recovered as nitric acid and collected in the condensate tank. Uncondensed vapors were passed successively through the de-entrainer, the off-gas preheater, the HEPA filter, and then vented to the off-gas system. 

The principal process instrumentation included (1) thermocouples to monitor the temperature at various locations (2) a flow controller to measure the air flow rate to the calciner and (3) differential-pressure transmitters to monitor the pressure drop across the distributor plate, the fluidized-bed and the sintered-metal filters. 

Offgas treatment is extensive and involves use of sintered metal filters, quench systems, venturi scrubbers, a condenser, a mist eliminator, an offgas heater, parallel HEPA filters, a carbon filter for radioactive iodine removal, a baghouse, and a selective catalytic reduction unit a packed tower scrubber system is used as a backup. 

Circulation of the SCO2 is driven by a magnetically coupled gear pump. Micropump Model 183HP-346, specially modified by the manufacturer for operation up to 5000 psi. A 40-pm filter (FI) is installed upstream of the pump, and a 2- um sintered metal filter is located downstream to prevent solids from entering the sample valve. A safety rupture disk (PSE), rated at 4300 psi, protects... 

A one-liter continuous stirred tank reactor (CSTR) was used in this study. A sintered metal filter was installed to remove the wax samples from the catalyst slurry. The wax sample was extracted through the internal filter and collected in the hot trap held at... 

The process was commercialized in 1976. A vanadium catalyst with Geldard group A/C characteristics is used. The catalyst is circulated between a reactor operating at 400°C and a reoxidizer operating at 427°C. The reactor operating pressure is not reported but is expected to be 1 to 2 atmosphere. Catalyst losses are kept to a minimum by the use of sintered metal filters (Fig. 18). 

The use of an integral fill tank, located at the lowest point in the system to permit charging the loop with metal through a pipe "dip leg completely immersed in the metal, is recommended. The application of gas pressure on the fill tank will transfer the metal slowly into the loop. By charging the metal from the bottom, into a previously evacuated system, gas entrainment will be minimized. A sintered metallic filter should be used to remove oxide and other scum from the metal while filling the loop. This filter should always be located outside the fill tank, since this will facilitate removal of the filter when it becomes clogged and will prevent cracking of the pores if the contents of the fill tank freeze. 

Sintered metal filters become increasingly more competitive from pore sizes of about 100 pm downwards. At the finer end, however, spherical metal particles of the order of 5 to 10 pm diameter are expensive to produce and costly to classify although they have been produced down to 1 pm in size. Some typical porous metal elements are shown in Figure 3.54. 

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