Online detection and control of ammonia solution density (concentration)
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Online control instrument for ammonia concentration: online density meter (with temperature compensation), thermal resistor, and secondary display panel. A customer ordered an online density meter for ammonia use; the typical operating temperature is 30 degrees, and it is required that the mass percentage concentration of ammonia be maintained between 15% and 20%. At first, I designed a solution for the client: the real-time density values were fed into the secondary instrument; by referring to a table that provided the density values of ammonia solutions at 30 degrees, a linear range of concentration values around the control point was selected as the display range for the secondary instrument. The density values corresponding to this range were used as the output range for the on-line density meter. The secondary instrument then transmitted the concentration signals to the DCS system for control purposes. The customer stated that this plan is not feasible. For ammonia solutions of the same concentration, their density changes significantly with temperature; due to the large temperature differences between winter and summer, such control is inaccurate. Finally, the customer provides an empirical formula to convert the real-time density value into the standard density value at 20 degrees, thereby enabling control via ρ_std = K * (actual temperature – 20) + actual density. The specific approach is to input both the real-time density value with temperature compensation and the temperature signal into the secondary instrument, along with the relevant formula; this allows the instrument to display the real-time temperature, real-time density, and the standard density at 20 degrees. The instrument then outputs the standard density value to the DCS for control purposes. I wonder if my colleagues have any better methods.
Will such control be accurate? Can an ultrasonic ammonia concentration meter be used?
The concentration of a solution is related to many of its physical properties, such as density, conductivity, refractive index, and sound speed; therefore, in principle, the change in one of these physical properties can be used to indicate a change in concentration. Currently, ultrasonic concentration meters are commonly used to measure the concentration of ammonia solution. It utilizes the principle of sound speed. But it is relatively expensive, and its measurement accuracy can be affected by bubbles. Relatively speaking, the differential pressure principle offers better cost-performance. As long as the ammonia concentration is not too low, it can generally be determined using a differential pressure principle density meter.
Hello, I am working on a project and also need an instrument for measuring the density of ammonia solution in real time, with a pressure capacity of 8 atm. Is there any such instrument available? I need it urgently! Thank you
You can take a look at how the principle of refraction is used to detect the concentration of ammonia solution online; this technology is already well-established and widely used in China.