PROCESS FLOW ANALYSIS RESOLVES FILTER CHANGE OUT ISSUES AT STEEL PLANT

Challenge

Our customer makes steel wires, rolls and sections of different shapes, sizes and specifications, using process gas to reduce iron ores into iron pellets for introduction into an arc furnace. An important by-product of the reduction process is the exhaust process gas from the DRP reactor. The gas passes through different rehabilitation units to remove heat, solid and liquid contaminants before being introduced to a gas compressor which recycles the gas to the reactor at the correct pressure.

The concentration of solid and liquid contaminants in the recycled gas stream can severely damage the downstream compressor and lead to off-spec gas and rapid deposition on the compressor’s internals, resulting in frequent emergency shutdowns. The customer was experiencing higher change out frequencies on its existing filtration system and wished to monitor the size and quantity of solid and liquid contaminants, so that an optimal filtration solution could be proposed and evaluated.

Solution

Celeros Flow Technology mobilised its innovative Gas Filtration Test Skid at the customer’s site to perform the analysis of the process gas without interrupting production. Tests were run over five days to determine:
• Solid contaminants quantity represented as concentration of total suspended solid contaminants in mg/l.
• Verify the quality of contaminant as particle size distribution.
• Liquid contaminants by concentration of free liquids by measurement of free liquid volume.

The samples were examined at Celeros Flow Technology’s laboratory in Killarney, Ireland along with local laboratories to determine the actual process gas conditions. The analysis determined that the current filters provide an initial removal efficiency of 93-95% at 50μm: but there were significant volumes of particulates in the range of 2μm - 40μm present in the flow. These finer particles, when combined with the high residual liquid concentrations present, are likely to form a slurry on surfaces downstream which could affect the filter element structure, process pipework, valves, and the internal compressor surface/blades.

Permeability tests also highlighted that the flow permeability of the 50μm filter is reduced by 2025% due to liquid saturation of the media. The wetting of the filter media occurs very quickly, so the differential pressure starting point is higher than that for a dry gas application.

Outcomes

Based on these results, Celeros Flow Technology recommended a reconfiguration of the existing filter to 98% @ 100μm. This will reduce the element differential pressure significantly and improve the operating lifetime. A finer filtration system downstream was also recommended to achieve the customer’s optimum requirement of 5-10μm whilst still improving the operational lifetime overall.