RU2795903C1 - Device for controlling concentration of nitric acid - Google Patents

Abstract

FIELD: chemical and metallurgical production.

SUBSTANCE: devices for measuring the concentration of nitric acid solutions in chemical and metallurgical production in the manufacture of fuel compositions. Invention can be used in particular in the technology of nuclear fuel production and radioactive waste processing. The device for monitoring the concentration of nitric acid contains two hydrostatic tubes connected to each other and fixed in a flange located at different levels in a solution of nitric acid, a temperature transducer fixed in the same flange, a differential pressure gauge with two measuring chambers, each of which is connected to one of the hydrostatic tubes, digital millivoltmeter, air preparation unit. In this case, the device additionally contains a temperature compensation unit, the temperature converter is placed in a sealed case, and a power supply unit is built into the digital millivoltmeter to supply electrical power to the differential pressure gauge.

EFFECT: increase of efficiency of the technological process, increase of the measurement accuracy and expansion of measurement range, as well as enabling the ability to display the results in units of concentration on the digital display of the millivoltmeter.

5 cl, 2 dwg

Description

FIELD OF TECHNOLOGY

The invention relates to devices for measuring the concentration of nitric acid solutions in chemical and metallurgical production in the manufacture of fuel compositions and, in particular, can be used in the technology of nuclear fuel production and radioactive waste processing.

BACKGROUND OF THE INVENTION

To ensure safe and high-quality extraction of uranyl nitrate with a solution of tributyl phosphate (TBP) at the radioactive waste processing site, it is necessary to use nitric acid solutions of a strictly specified concentration for use in the process of dissolving initial nuclear materials in it. In this regard, it became necessary to control the concentration of nitric acid supplied to the dissolution operation.

The preparation of nitric acid, a given concentration, occurs by diluting 98% of the acid. Currently, sampling is done manually through a sampling system into a portable container and the actual value of the concentration of the prepared nitric acid solution is determined the next day in the express laboratory and is approximate, due to the impossibility of accurate determination in solutions with a concentration of nitric acid over 40% according to existing methodology. To quickly obtain information on the concentration of the prepared acid and, if necessary, to adjust the concentration of the solution, it became necessary to install a device for measuring concentration with a measurement range of (40-70)% mass fraction at the dilution operation of 98% nitric acid.

There is a known method for determining the density of a liquid, which consists in blowing air in two cycles through a long and short measuring tubes placed in the test liquid, in regulating the pressure in the compensator, measuring the pressure difference in the compensator and measuring tubes, followed by determining the density. In the first cycle, air is blown through the compensator and the short tube, the pressure is adjusted so that the pressure drop between the compensator and the short tube becomes zero. In the second cycle, air is blown through the compensator and a long tube, the pressure difference between them is measured and the density of the liquid is judged from it. (SU 1434330 A1, published 10/30/1988)

The disadvantages of this method are the additional operations of air purge measuring tubes, the lack of a device for calculating the concentration of nitric acid.

A device for measuring the density of a liquid is known, which contains a bubbling sensor consisting of two tubes of different heights, an air flow sensor, two compensation vessels and a differential pressure gauge. Bubble tubes are excluded from the compensation vessels, the lower parts of the vessels are connected directly to the measuring chambers of the differential pressure gauge. The air pressure from the bubble tubes of the working sensor is supplied to the upper parts of the compensation vessels. The tubes connecting the compensation vessels with the inputs of the differential pressure gauge are interconnected through an equalizing valve (RU 2418287, pub. 05/10/2011).

The disadvantages of this device are the complexity of the design, the lack of a temperature compensation circuit and a means of displaying in units of measurement of the concentration of nitric acid.

The closest analogue of the invention is a nitric acid concentration meter (KKA-70M), designed for continuous measurement of the mass fraction of nitric acid in aqueous solutions. The concentrator consists of two hydrostatic tubes placed on a rod immersed in the working medium, a thermoelectric converter placed on the same rod, a pressure measuring transducer, a temperature transducer, an air preparation unit consisting of a pressure regulator and two air flow regulators, a power supply unit and programmable controller (No. 40811-09, State Register of Measuring Instruments).

The disadvantages of the device are a narrow range and a large measurement error, as well as the use of an expensive controller, signal input and output units for signal processing. Also, the disadvantage is the design of the temperature transducer immersed in a solution of nitric acid, which is not protected from corrosion.

DISCLOSURE OF THE INVENTION

The objective of the invention is to create a device for online control of the concentration of a solution of nitric acid in the process, allowing you to simultaneously determine the temperature of the solution of nitric acid and adjust the concentration of this solution depending on its temperature.

The technical result of the invention is: increasing the efficiency of the technological process, increasing the measurement accuracy and expanding the measurement range, as well as providing the ability to display the results in units of concentration on the digital display of the millivoltmeter.

The technical result is achieved by a device for controlling the concentration of nitric acid, which contains located at different levels in a solution of nitric acid, two hydrostatic tubes connected to each other and fixed in a flange, a temperature transducer fixed in the same flange, a differential pressure gauge with two measuring chambers, each of which connected to one of the hydrostatic tubes, a digital millivoltmeter, an air preparation unit. The device contains a temperature compensation unit. The temperature transducer is placed in a sealed case, and a power supply unit is built into the digital millivoltmeter to supply electrical power to the differential pressure gauge.

The measuring chambers of the differential pressure gauge are connected to the hydrostatic tubes by means of connecting tubes. The hermetic case, in which the temperature transducer is placed, is a tube made of corrosion-resistant material, plugged from below. The air preparation unit contains a reducer for stabilizing the air pressure and two regulators for supplying air to the hydrostatic tubes. The temperature compensation unit is a voltage divider with a reference electrical signal from a differential pressure gauge, on one side of which there is a temperature transducer, and on the other, a variable resistance for balancing the circuit.

LIST OF DRAWINGS

The invention is illustrated by drawings.

The figure 1 shows the general scheme of the device.

The figure 2 shows the electrical circuit of the temperature compensation.

IMPLEMENTATION OF THE INVENTION

The device for monitoring the concentration of nitric acid is based on the measurement of air pressure drop. In a container with a solution of nitric acid 1, through the connecting flange 14, interconnected hydrostatic tubes 2 and 3, fixed in the flange 14, were installed at different levels. 12. The hydrostatic tube 2 is connected to the measuring chamber 17 of the differential pressure gauge 5, and the hydrostatic tube 3 is connected to the measuring chamber 18 of the differential pressure gauge 5. Through the connecting tubes 15, 16 and the measuring chambers 17, 18 of the differential pressure gauge 5, the tubes are purged with air coming from the block preparation 6, consisting of a reducer for stabilizing air pressure 7 and two air flow regulators 8 and 9. When passing air of the same and given flow rate through each of the two hydrostatic tubes, a pressure drop Δh occurs due to the difference in the depth of immersion of the hydrostatic tubes. The air pressure in hydrostatic tube 3 (positive) is higher than the air pressure in hydrostatic tube 2 (negative). The hydrostatic pressure drop ΔP is a linear function of the acid solution density ρ. The calculation of the concentration of nitric acid is carried out in accordance with the algorithm specified in the digital millivoltmeter with the corresponding functions embedded in it according to the formula:

where: ΔP - pressure drop across hydrostatic tubes, Pa;

Δh is the difference between the immersion depths of the hydrostatic tubes (sensor base);

g - free fall acceleration, g=9.81 m/s ² ;

ρ is the density of the nitric acid solution at a temperature of 20°C, kg/m ³ .

The base of the measuring sensor is the difference Δh, which is a constant value determined by the sensor design and selected based on the range of change in the density of nitric acid, corresponding to the selected concentration measurement range. The differential pressure is measured by a differential pressure gauge 5 and converted by it into a standard electrical signal that corresponds to the selected measurement range of the mass fraction of nitric acid.

To bring the density of nitric acid to 20 ° C, an electric temperature compensation unit 13 (Fig. 2) is used with a temperature converter 12 included in the output circuit 11 of the differential pressure gauge 5 and placed in the tube 4 together with the hydrostatic tubes 2, 3 in the area of formation of the hydrostatic pressure drop. pressure and immersed in a solution of nitric acid.

The electrical temperature compensation unit 13 uses a voltage divider circuit with a built-in temperature converter 12 (Rt).

An electrical signal of 4-20 mA from the differential pressure gauge 5 passes through the voltage divider. When the temperature changes, the density of the solution changes and the output current from the differential pressure gauge changes accordingly, but the voltage from the temperature compensation unit applied to the input of the millivoltmeter 10 remains the same due to a change in the resistance of the temperature converter . To balance the circuit and bring the density of nitric acid to 20 ° C, a variable resistance R3 is used. The digital millivoltmeter has a built-in power supply to supply electrical power to the differential pressure gauge.

The digital indicator of the millivoltmeter 10 displays the result of measuring the mass fraction of nitric acid in solutions as a percentage.

Thus, as a result of the use of this device, the accuracy has been increased and the measurement range has been expanded, the need for sampling and chemical analysis has been eliminated, and the efficiency of the technological process has been increased.

Claims (5)

1. A device for controlling the concentration of nitric acid, containing located at different levels in a solution of nitric acid, two hydrostatic tubes connected to each other and fixed in a flange, a temperature transducer fixed in the same flange, a differential pressure gauge with two measuring chambers, each of which is connected to one of the hydrostatic tubes, a digital millivoltmeter, an air preparation unit, characterized in that the device contains a temperature compensation unit, the temperature converter is placed in a sealed case, and a power supply unit is built into the digital millivoltmeter to supply electrical power to the differential pressure gauge. 2. The device according to claim 1, characterized in that the measuring chambers of the differential pressure gauge are connected to the hydrostatic tubes by means of connecting tubes. 3. The device according to claim 1, characterized in that the hermetic case, in which the temperature transducer is placed, is a tube made of corrosion-resistant material, plugged from below. 4. The device according to claim 1, characterized in that the air preparation unit contains a reducer for stabilizing the air pressure and two regulators for supplying air to the hydrostatic tubes. 5. The device according to claim 1, characterized in that the temperature compensation unit is a voltage divider with a reference electrical signal from a differential pressure gauge, on one side of which there is a temperature transducer, and on the other, a variable resistance for balancing the circuit.

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