Master of DonNTU - Dar'ya Lytvynova

Theme of master's work: "Substantiation of industrial enterprises sewage control system extraction photometer structure"

Actuality of the Theme

Industrial sewage is at the first place concerning its volume and damage that it causes.

Content of heavy metals in water affects the natural processes in it greatly. The metal that needs on-line inspection is Ńr⁺⁶ contained in sewage of galvanizing shops of machine-building, aircraft and automobile plants, enterprises of chemical and tanning industry flowing to water reservoirs.

Concentration of Cr⁺⁶ in polluted and low-polluted river waters varies from several tenths mg/dm³ to several mg/dm³. Because of high toxicity the content of Ńr⁺⁶ in water reservoirs is normalized and should not exceed maximum permissible concentration equal to 0,05 mg/dm³. One of the compulsory conditions of control of content of Ńr⁺⁶ natural waters is immediacy of its determination since the storage of samples is impossible because of Ńr⁺⁶ convert to Ńr⁺³ in anaerobic conditions.

Objective and Tasks of the Work

Objective of the work – to develop a design of a device for on-line control of ions of chrome (Cr⁺⁶) in sewage of industrial enterprises in the area of water discharge.

Tasks of the work – analysis of methods and tools for measurement of chrome concentration in sewage; choice of a measuring method on the basis of which the device will be developed; evaluation of the level of influence of affecting factors (đÍ and temperature) on measurement of chromium ions (Cr⁺⁶) concentration in sewage; development of mathematical model of optical measuring channel. Solving of these tasks is the basis for design of the extraction photometer structural scheme of the control system of industrial enterprises sewage.

Idea of the Work

To determine the level of concentration of chromium ions (Cr⁺⁶) the extraction and photometric method was chosen with the level of concentration of chromium ions (Cr⁺⁶) being determined by colouring power of coloured compounds. Suspension was chosen as an extract and because of this the transmitted flow quickly attenuates that is why the reflected flow depending on wave length of the radiation source and concentration of chromium ions.

Scientific Novelty of the Work

The mathematic model describes the measuring tool, influence of affecting factors on measuring process and allows to asses metrological characteristics of the measuring tool.

Practical Value

Taking into account the mathematic model the structural scheme of the measuring tool is developed. The mathematical model provides for account of influencing factors and high accuracy of the working measuring tool.

General Working Material

To define chromium ions (Cr⁺⁶) concentration the extraction and photometric method is applied with the quantity of the substance defined by colouring power of coloured compounds. The defined metal ion is transferred to the coloured compound with the help of the reagent and then the colouring power of its solution is measured.

Suspension was chosen as an extract and because of this the transmitted flow quickly attenuates that is why the reflected flow depending on wave length of the radiation source and concentration of chromium ions.

Since the radiant is frequency dependent and the absorption spectrum is limited the light emitting diode (LED) with the wave length α=540 nm is chosen as the radiation source that complies with the maximum of the absorption spectrum and provides for method selectivity. The selectivity function can be increased by adding a supplementary optical filter at the wave length α=540 nm with the pass band of 25 ± 10 nm.

The photometer is the device for the channel of the automatized measuring system of sewage control (such systems are serviced once in 2 weeks) where the chrome ions (Cr⁺⁶) are measured. The channels for measurement of other values can also be present. For example the level of pH (the account of such factor allows to decrease error from 6-7% to 3-4%) affects measurement of Cr⁺⁶. To record and optimize the pH level at measurement of concentration of chromium ions (Cr⁺⁶) it is expedient to add the required (dosed) quantity of acid Í₂SO₄ to the sample. The temperature affects measurement of pH. Thus it is important to measure the level of pH and temperature. As a result we have a multi-channel system consisting at least of three measuring channels: pH, temperature and concentration of chrome ions (Cr⁺⁶).

Connection of chrome ions (Cr⁺⁶) concentration with the parameters affecting its measurement can be presented in the form of a system (1).

where Ccr – chrome concentration;

Ô – reflected flow;

pH – pH level;

CH₂ – hydrogen concentration;

T – temperature value.

To provide for the method of extraction the system of samples preparation is necessary to provide for the extract addition to the working dish by periodically dosing it. It is necessary to provide the most favourable conditions for formation of a coloured compound, that is, to stabilize the temperature, fluid, extract and time consumption. Determination of concentration takes place after the time interval equal to eightfold restitution of the fluid of the dish (3-5 ml³). Sample size – not more than 50 ml.

It is supposed to take measurements with a one-hour interval.

As a result the construction diagram of measurement of automated system of sewage control having 3 measurement channels was made:

- temperature measurement channel;

- pH measurement channel;

- chrome ions (Cr⁺⁶) concentration measurement channel.

The aforementioned construction diagram is presented on figure 1.

Figure 1 – Construction diagram of measurement of automated system of sewage control.

To realize the fulfilled method the luminous flux (radiant flux) is created a part of which passes through the dish with the previously prepared coloured fluid and a part is reflected and transformed to an electric signal. The possibility of processing of a received signal and results of control of the object for their future analysis. The whole system is supplied with power.

Obtained and Planned Results

Obtained results:

- characteristics of chrome (Cr⁺⁶) are investigated;

- methods of measurement of concentration of chrome ions (Cr⁺⁶) in sewage are analysed;

- tools for measurement of concentration of chrome ions (Cr⁺⁶) in sewage are analysed;

- construction diagram of measurement of automated system of sewage control is made.

To date the mathematical model of the optical channel of measurement of chrome concentration (Cr⁺⁶) is being developed.

Planned result – the structural diagram of the developed device is made on the basis of the designed mathematical model.

At the moment of preparation of the present abstract the master's work is still in development stage. Completion and defense of the work is scheduled for December 2007.

Dar'ya Lytvynova

Beginning