VISCOSITY MEASUREMENT - Phosphorous Pentasulfide

SUMMARY

Viscosity-to-composition relationships determine whether a product is within specification for use as raw material for fertilizer and pesticide products. Continuous Model 1810 VISCOLINER. measurement with the customer’s distributed control system has proven useful in reduced production of scrap (e.g., matchheads and hazardous waste). The process VISCOLINER® measurement has proven reliable; in one case it “proved an error in the lab viscosity method.”

INSTALLATION

HPHT, transducer mounts flush on a jacketed tank below the liquid level using an ANSI flange to a stud pad. There is a non-active, tapered sensor extension on the process side to improve sensor strength and have the active sensor clear the tank wall. There are two RTDs to monitor fluid temperature and transducer coil block temperature. Cold nitrogen continuously purges both the coil block area and the water cooling jacket of the transducer to maintain coil temperature at 150°C (NOTE: coils are rated to 230°C). The VISCOLINER® transmitter can be in the control room up to 1000’ from the transducer.

OPERATION

The instrument measures nominal viscosity as the power required to hold a constant amplitude of torsion oscillation. Output to the DCS is continuous and linear. In-process precision better than ±1% of viscosity reading is required for sensitivity in the composition relationship. In one case, 200 seconds of signal time average is required to hold signals to within ±1%. Temperature compensation using ASTM method D341 corrects for viscosity change due to temperature fluctuation. Density compensation is based upon fluid temperature measurement and the customer’s density=temperature function. Compensations are numerical methods programmed into the UVEPROM of the VISCOLINER®. Operation requires liquid contact to avoid precipitation of contaminants onto the sensor during gas phase contact. Shut down requires the sensor to withstand the weight of solid material. Liquid phase clean up is not possible due to spontaneous combustion in air.

TEST

Customers have laboratory capillary method viscosity data and correlations to percent phosphorus content. Temperature measurement and compensation maintain the composition relation. Capillary method reports cP ÷ g/cm3 and process method reports cP · g/cm3. One customer reports better results by VISCOLINER® method due to operator error and the need to replace worn parts in the lab method.

TYPICAL OPERATING CONDITIONS

Temperature: 350°C to 380°C

Pressure: ATM to 150 psig

Viscosity: 50 to 350 cP x g/cm3

VISCOLINER® SPECIFICATION

Temperature: -40°F to 500°F

Pressure: Ambient to 5000 psig

Viscosity: 0.1 to 1,000,000 cP

Materials of Construction: 316SS 5/12/2005

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