Installation mass-flow sensors

Flow Low mass flow indicated. Mass flow error. Transmitter zero shift. Measurement is high. Measurement error. Liquid droplets in gas. Static pressure change in gas. Free water in fluid. Pulsation in flow. Non-standard pipe runs. Install demister upstream heat gas upstream of sensor. Add pressure recording pen. Mount transmitter above taps. Add process pulsation damper. Estimate limits of error. 

In hot-wire probe designs, the cooling effect of the flowing process gas stream is detected, as was already discussed in connection with anemometers (see Figure 3.50). A major limitation of the hot-wire-type mass flowmeters is that they do not detect the mass flow across the full cross section of the pipe, but do so only at the tip of the sensor. Therefore, if the sensor is installed in a nonrepresentative location, the resulting reading will be in error. 

One of the earliest methods of mass flow determination was to install two separate sensors one to measure the volumetric flow, and the other to detect the density of the flowing stream. On the basis of these two inputs, a microprocessor-based transmitter can measure mass flow. A further improvement occurred when the density and volumetric flow sensors were combined in a single package (Figure 3.75). These units are composed of either a Doppler ultrasonic flowmeter or a magnetic flowmeter and a gamma radiation-... 

Different feedstocks and/or solvents require different solvent to feed ratios. Each packing has a specific flooding point These two effects can lead to a great difference in mass flow. Because of this, pressures and temperatures should be controlled automatically. The flow must be measured exactly, preferably with a mass flow meter, but automatic flow control is not suitable for a multi-purpose plant The valves which are used for pressure and temperature control should be installed so that they can be replaced easily or adapted to new conditions. A very important requirement for the continuous operation of the plant is liquid level indication and control in the extractor and regenerator. Therefore the plant is equipped with capacitive level sensors which are part of a control circuit. The suitability of these sensors for measuring the level of oily products, vitamins and some type of hydrocarbons in supercritical systems have been tested in the lab previously. 

Flow. Nonintrusive sensors that can be maintained at the process temperature are ideally suited to measure the flow rate of feed and product streams. Magnetic flow meters are suitable and inexpensive choice for aqueous streams. Organic streams with low dielectric constants require a vibrating tube mass flow meter to satisfy these criteria. Although commonly installed, flow meters that operate by inducing a pressure drop proportional to the flow rate present restrictions for solids accumulation that may alter the calibration. An alternative approach is to monitor the rotational speed of a positive displacement pump. Accuracy of this method is subject to wear and tolerances in the pump. 

Therefore, a range of on-line sensors will be installed to measure for instance temperatures (including those along the absorber and stripper), pressures, liquid and gas flows, gas composition and absorber and stripper solvent levels. Solvent sample points will be included for solvent extraction to facilitate detailed off-line composition analysis. The rich stream shall be equipped with a coriflow mass flow meter that is able to measure solvent density. Since the solvent density increases with CO2 loading, this means that one obtains an indication of die loading real-time. 

Figure 2.48 Injector back pressure regulation. 1. Carrier gas inlet filter, 2. mass flow regulator, 3. electronic pressure sensor, 4. septum purge regulator, 5. solenoid valve, 6. electronic pressure control valve and 7. injector with column installed.

---