Porous element / diffuser

01

Choose the media grade and alloy

Mott says its sintered porous metal spargers introduce gas through thousands of tiny pores, producing bubbles that Mott describes as much smaller and more plentiful than from drilled pipe and increasing the gas–liquid contact area so less time and gas are needed to dissolve the gas; it claims up to 300% better gas absorption in tanks than drilled pipes. [1] Its design guide gives the example that, for equal gas volumes, 1 mm bubbles have 6.35 times the contact surface of 6.35 mm (1/4 in) bubbles, while noting actual bubble size depends on the liquid and conditions. [2]

The guide recommends Media Grade 2 for general gas sparging, Media Grade 10 for steam sparging and Media Grade 40 for agitation, with other grades on request. Standard porous media is 316L stainless steel, with corrosion resistance and temperature capability up to 750 °F, and standard hardware is 316 stainless; 304L, 347 and 430 stainless, Inconel 600, Monel 400, Nickel 200, Hastelloy C276, C22 and X, and Alloy 20 are available on special order. [2]

Mott also offers in-line spargers installed in the flow path, sparger assemblies with replaceable elements for bioreactors, and multi-element assemblies for large tanks. [1]

GKN Sinter Metals Filters, another porous-metal maker, lists sparging, aeration and carbonisation among the uses of its SIKA sintered elements. It makes seamless elements up to 1,500 mm long and 320 mm outside diameter, assembling larger ones by welding, and joins porous parts to solid fittings by sinter bonding to avoid weld seams. Its material table covers stainless grades such as 304L and 316L, nickel alloys, titanium and bronze, with maximum temperatures that differ between reducing and oxidising atmospheres — for 89/11 bronze, 300 °C reducing and 250 °C oxidising. Its SIKA-R…AS membrane version adds a 200 µm active layer with grades down to 0.1 µm absolute, which GKN says gives up to four times the flow of conventional sintered cartridges. [3]

Editorial note: a sparger runs in gas–liquid service, which can be hot and wet, so ask for the temperature limit of the chosen alloy in your actual atmosphere (reducing or oxidising) rather than a single catalogue figure. [3]

Give the supplier the gas and flow (SCFM or Nm³/h), liquid, temperature and pressure at the sparger, tank or pipe size and liquid flow, agitation and agitator tip speed, required dissolution or bubble behaviour, chemistry and cleaning, connection type, materials and sanitary needs.

02

Size the element by gas exit velocity

Mott's guide sizes spargers by superficial gas exit velocity from the porous surface in feet per minute, calculated from actual cubic feet per minute per square foot of sparger area at the liquid pressure and temperature at the sparger, not the gas supply pressure. The procedure converts the required SCFM to ACFM using liquid pressure (head in feet × 0.433 × specific gravity, plus any head-space pressure) and temperature, selects an exit velocity, and divides ACFM by that velocity to get the sparger area. [2]

Its exit velocity chart gives 5–10 FPM design and 25 FPM maximum for unagitated tanks; for agitated tanks it gives 25 FPM design (50 FPM maximum) at agitator tip speeds of 1–5 ft/s, 25 FPM design (100 FPM maximum) at 5–10 ft/s and 50 FPM design (150 FPM maximum) above 10 ft/s, where tip speed = agitator diameter (in) × rpm ÷ 229. Lower exit velocities give smaller bubbles, and reinforced or supported elements should be used in agitated vessels. Intrusive pipeline spargers are sized from gas exit velocity in relation to liquid velocity in the annulus. [2]

Editorial calculation: 5–10 FPM is about 0.025–0.051 m/s and 25 FPM about 0.13 m/s; 750 °F is about 399 °C. [2]

03

Find porous element and diffuser manufacturers

The companies in the manufacturer list below show this product on their own websites. Confirm the legal seller, factory and scope for your order.

Ask any supplier for media grade and pore rating, porosity, element dimensions and surface area, alloy, maximum temperature and differential pressure, flow versus pressure-drop data, connection types, reinforcement for agitated service, cleaning method and lead time.

04

Keep the gas flux per cm² low enough to hold bubbles small

Poral, a maker of sintered porous metal elements, publishes bubble-size data for its stainless-steel elements used as static diffusers in tanks. For grades 03 to 10, average bubble size rises from 0.4 to 1.4 mm as gas flux increases up to 3 L/h per cm² of porous surface, then settles at about 1.4 mm whatever the grade. For grades 15 to 40, bubbles reach millimetre size quickly and settle at about 1.4 mm above 2 L/h/cm². Poral says coalescence could explain this ceiling. [4]

Its standard isostatic tubes, 316L by default with 304L, Inconel 600, Monel 400 or Hastelloy on request, are listed from 14 to 100 mm outside diameter and 250 to 1,000 mm long (table). EN 10204 3.1 reports can include a permeability test to EN ISO 4022 and a bubble-point test to EN ISO 4003, which measures the pressure that pushes the first bubble through the widest pore with the element in ethanol. [4]

Editorial calculation: an IS 30.600 tube with 565 cm² of porous area stays at or below 3 L/h/cm² up to about 1,695 L/h (565 × 3), about 1.7 m³/h of gas; above that, Poral's data show bubble size no longer falls with a finer grade. [4]

05

Trace what each part does

This is a functional reference built from the sources cited; it is not one maker's specification.

06

Fill the specification fields with values for your order

A sparger quotation needs values for your process. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the gas, liquid and vessel data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Gas: [type; SCFM or Nm³/h]
Liquid: [type; temperature; pressure at sparger]
Vessel: [tank; pipeline; size; liquid flow]
Agitation: [none; tip speed]
Media: [grade]
Material: [316L; other alloy]
Connection: [NPT; weld; sanitary]

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