The principle of an analytical salt content analyzer

The salt content analyzer is a new generation product that uses microcoulometry analysis technology and computer-controlled microcoulometry titration to determine salt content. It has the characteristics of stable performance, easy operation, good repeatability of analysis data, and easy installation.

It can be used for the determination of salt content in heavy oil, residual oil, refineries, oil fields, various industrial water and discharge water, and is also suitable for the determination of inorganic chloride ions in various samples mentioned above.

The salt content analyzer is a closed-loop negative feedback system designed using the principle of micro Coulomb titration, consisting of a Coulomb amplifier, a titration cell, and a suitable electrolyte in a zero equilibrium working mode.

The data collection and processing are controlled by a microcontroller and connected to a computer through serial communication to achieve automatic control.

The reference electrode in the titration cell supplies a constant reference potential and forms an indicator electrode pair with the measuring electrode to generate a voltage signal. This signal is connected in reverse series with a given bias applied and added to the input of the Coulomb amplifier.

When the two voltage values are equal, the amplifier input is zero and the output is also zero. There is no current passing between the electrolytic electrode pairs, and the instrument display shows a smooth baseline. When the sample is injected into the titration cell through a syringe, the titrant Ag+in the electrolyte is consumed.

The change in titrant concentration causes a change in the potential of the indicator electrode pair in the titration cell. The change in its value is sent to a microcomputer-controlled microcoulometry amplifier, which is amplified and added to the electrolytic electrode pair (anode and cathode). The titrant ion Ag+is electrogenerated on the anode to supplement the consumed titrant Ag+.

The above process continues with the consumption of the titration ion Ag+until no substance that consumes the titration ion enters and sufficient titration ions have been electrogenerated, so that the value of the indicator electrode pair is equal to the given bias value again, and the instrument returns to equilibrium.

During the process of consuming and supplementing the titration ion Ag+, the sample content can be calculated by measuring the amount of electricity generated by the titrant and processing the data according to Faraday's law.

Crude oil is heated in the presence of polar solvents, and the salt is extracted with water. After centrifugation and separation, the extraction solution is injected into a titration cell containing a certain concentration of titrant using a syringe. The following reaction occurs between Cl - in the sample and Ag+in the electrolyte:

The result of Ag++Cl -- → AgCl causes a change in Ag+concentration. The measurement reference electrode pair senses this change and sends the potential difference caused by this change to the micro Coulomb amplifier, which outputs a corresponding voltage applied to the working electrode pair;

Electrolytic anode electrogenerated titrant Ag+is used to supplement the consumed Ag+until the concentration of the titrant returns to its original concentration. The required amount of electricity for supplementing the consumed Ag+is measured, and the sample salt content can be obtained according to Faraday's law.