How to find a suitable flow meter for molten sulfur?

Accurate Measurement of Molten Sulfur Flow: Coriolis Mass Flow Meters

In some industries like chemicals, fertilizers, and refining, accurately measuring tough fluids like molten sulfur flow is vital for process stability, safety, and efficiency. Molten sulfur has unique challenges: high temperatures (130-155°C / 266-311°F), potential corrosiveness (H₂S, acid), and rapid solidification if cooled. Coriolis Mass Flow Meters (CMF) are currently the best flow measurement solution due to their ability to measure mass flow directly and withstand these demanding conditions.

Molten sulfur flow measurement is a tough job

Why Coriolis flow meter works for molten Sulfur

1. Direct Mass Flow Measurement of liquid sulfur: Molten sulfur's density changes with temperature (~1800 kg/m³). Traditional volume flow meters (vortex flow meter, magmeter ) need extra instrument sensors to calculate mass flow, adding complexity and error near sulfur's phase change point. Coriolis meters output mass flow directly, eliminating this error source – ideal for tightly controlled sulfur temperatures (normal ~145°C). accuracy: ≤ ±0.5% of reading, repeatability ≤ 0.05%.

Direct liquid sulfur mass flow measurement and indication

2. Not affected by Fluid Changes: Coriolis meters are insensitive to viscosity, pressure, and temperature variations within range. Low sulfur viscosity (normal ~8 cP, range 7-10 cP) doesn't impact accuracy of Coriolis meter , ensuring reliable flow measurement.

3. Handles Impurities fluids by Coriolis flow meter: Industrial molten sulfur contains solids (≤0.5% wt - carbon, ash), dissolved H₂S gas (≤700 ppm), and moisture (≤0.8% wt). Coriolis meters tolerate minor two-phase flow (solids/gas, gas contain less than 5% ) better than many alternatives, such as oval gear flow meters, oval gear flow meters can be get stuck by impurities of liquid. Maintaining performance within these specified limits. Coriolis flow meter has the suitability for "solid or two-phase mixed fluid".

Coriolis meters handle impure molten sulfur flow measurement

Coriolis meters easily handle impure molten sulfur flow measurement

Critical Engineering Selection to choose correct molten sulfur flow sensor

1. Flow sensor Material Selection (Corrosion Resistance is important)

- Flow meter Wetted Parts (Tube, Connections): Must resist corrosion from molten sulfur and impurities (H₂S, acids). Some buyer mandates NACE MR0175/ISO 15156 compliance (resistance to Sulfide Stress Cracking - SSC). Coriolis flow meter is with stainless steel 316L material which can be used for sulfur measurement.

- Common Options:

• 316L Stainless Steel (SS316L):Coriolis flow meter from silverinstruments.com specifies this for housing and wetted parts. 316L stainless steel offers good general corrosion resistance and fair chloride resistance. It's the cost-effective, widely used solution for conditions within molten sulfur specs (H₂S≤700ppm, acidity≤0.02% wt H₂SO4, ≤155°C, ≤150 psig / ~10.3 bar).

stainless steel 316L wet parts of coriois flow meter

Wet parts of coriois flow meter is stainless steel 316L which is suitable for sulfur

M	Tube Material
M1	316L
M2	Hastelloy alloy C-276
M4	Hastelloy alloy B3
M5	Alloy20（N08020）
M6	Titanium (ASTM B265)
M7	Tantalum (ASTM B708)
M8	C4 steel ASTM A600T12004
M9	Copper-nickel alloy
M10	Nickel-based alloy

• Hastelloy Alloys (C-276/B3): Silver Automation instruments have options with hastelloy alloys , Provide superior corrosion resistance for harsher conditions (higher impurities, stronger acids, extreme T/P). Use if 316L is insufficient for liquid sulfur, considering the significant cost increase. Select based on corrosion assessment.

2. Steam Heating Jacket for Coriolis flow meter

Why it's mandatory to have insulation jacket for molten sulfur?

Sulfur solidifies at ~115°C. Solidification inside the flow sensor or pipes causes blockages and can damage the mass flow sensor tubes. Steam jacketing is absolutely required.

• Design & Selection: Uniform Heating: Jacket covers the entire sensor body;
• Adequate Steam Supply: sulfur required steam (T=147°C / ~297°F & P=64 psia / ~4.4 bar). Steam parameters must maintain sulfur temperature well above
•solidification (typically ≥130-135°C), accounting for ambient heat loss. Steam temp (147°C) > process temp (145°C) is sound design.
• Robust Construction: Jacket material (e.g., carbon steel, SS304) is compatible and withstands steam. Welds/connections are leak-proof.

silverinstruments.com uses steam or hot oil jacket on 1/2” process pipe as below picture shows：

How steam jacket mass flow meter looks

3. High temperature flow meter

Coriolis flow sensor can measure high-temperature liquids, with a maximum liquid temperature of up to 350 degrees Celsius, which is crucial for high-temperature non curing molten sulfur. When designing a high-temperature Coriolis flowmeter, we chose a split electronic flow transmitter to protect the electronic transmitter from being burned out by high temperatures.

High temperature flow meter for molten sulfur

- Key Technical Specifications Points：

•Flow Meter Flow range for molten sulfur

DN	Flow Range
1.5	0~4 kg/h
3	0~40 kg/h
6	0~100 kg/h
8	0~200kg/h
10	0~0.5 T/h
15	0~1.0 T/h
20	0~3.0 T/h
25	0~10 T/h
40	0~20 T/h
50	0~30 T/h
65	0~50 T/h
80	0~100 T/h
100	0~150 T/h
125	0~200 T/h
150	0~400 T/h
200	0~500 T/h

•Pressure rating : Coriolis flow meter can max stand 100Mpa pressure,
•Temperature rating, Corolis flow meter flow sensor can withstand below temperature range.

T	Temperature
T1	(-50~150℃)
T2	(-50~250℃)
T3	(-50~350℃)
T4	(-200~150℃)

•Material selection: we have several types flow meter wet parts material options. Normally 316L stainless steel is enough for sulfur application.

2. Installation:

- No upstream/downstream straight pipe runs needed (major advantage for Coriolis meter, which is pretty good when no inlet and outlet sections required for the flow meter).

- Ensure tubes are always full of molten sulfur.

- Install steam jacket piping correctly, insulate it, and include steam traps.

3. Signals & Power: Use 24VDC loop power or 220V AC power supply. Output 4-20mA + HART + Modbus integrate easily with DCS/PLC for monitoring, totalizing mass flow, density, temperature measuring and data logging.

4. Environment: Users can select flow transmitter suitable for ambient temperature (-29 to +65°C / -20 to 149°F), ingress protection (IP67), and area classification (Unclassified per datasheet, but meter supports ATEX certification if needed).

For challenging molten sulfur flow measurement, Coriolis Mass Flow Meters deliver a reliable, accurate, low-maintenance solution. Their core strengths – direct mass flow measurement, density and temperature measurement, high accuracy, insensitivity to fluid changes – combined with careful material selection (e.g., NACE-certified 316L) and essential steam jacketing, provide engineers with precise control. This makes CMFs the critical flow instrument for safe, efficient, long time and economical operation. Always rigorously match process conditions to the flow meter specifications during selection.