CS257571B1 - Method of ammonium hydroxylamine disulphanate's aqueous solution production - Google Patents

Abstract

Process for the preparation of an aqueous solution of hydroxylaminedisulfonate ammonium at a concentration of 300 to 550 kg / m3 produced from ammonium nitrite solutions ammonium bisulfite and gaseous oxide sulphurous, with both the reaction and reaction solutions the blend contains minor components by operation technology controlled by a digital controller with selected pH control algorithms between 2.5 and 5.0 and the redox potential of which values in millvolts correspond to concentration ammonium nitrite in the range of 0 to 5 kg / m 3 and hydrogen ammonium sulfite in the range of 0 to 5 kg / m 3 in the output current consisting of the regulator The pH and the redox regulator are operated independently wearing, the pH regulator controls the amount of input raw materials and regulator redox their ratio, taking the redox regulator adjusts the input ratio solutions according to the redox setpoint, if deviations from the desired pH value value ranging from +10 to -10 relative percent.

Description

The present invention relates to a process for the production of ammonium hydroxylaminedisulfonate (hereinafter HAD) controlled by digital control of pH and redox potential.

HAD production is based on three basic components:

and - sulfur dioxide (g) SO ₂ b - ammonium nitrite (aq) NH 4 NO ₂ (hereinafter DA) c - ammonium hydrogen sulfite (aq) NH 4 HSO 4 (hereinafter B1)

The HAD solution is obtained by reacting the three components in the aqueous phase. Hydrolysis of this solution produces hydroxylamine sulfate (HAS).

The main reactions proceed according to the following stoichiometric equations:

NH ₄ NO ₂ + NH ₄ HSO ₃ = (nh ₄ ) ₂ (hunt (sat ₃ ) ₂ ) (1) (NH ₄ ) ₂ (HON (SO ₃ ) ₂ ) + SO ₂ + H ₂ O = NH ₄ (H ₂ NO ₂ SO ₃ ) + NH ₄ HSO ₃ (2) NH ₄ (H ₂ NO ₂ SO ₃ ) = NH ₄ (nasal ₃₎ + H ₂ O (3) NH ₄ (nasal ₃₎ + NH ₄ HSO ₃ = HON (SO ₃ NH _{4) 2} HAD (4)

In the industrial production of the HAD solution, DA solutions containing ammonium hydrogen carbonate (hereinafter KUA) and ammonium carbonate (hereinafter UA) and solution B1 containing also ammonium sulphite (hereinafter SU) are first mixed together to form a so-called nitroso mixture (hereinafter NiS) - see equation (1). This NiS, whose pH varies between 7 and 9, is fed to a HAD production column, where the pH is immediately lowered to about 3 to 5 due to SO ₂ (g) being fed, see reactions 2-4.

A disadvantage of the present process is that the DA and B1 solutions contain carbonate and sulphite ions in addition to the principal components. These ions gradually produce the desired hydrogen sulfite ions in the course of the main reactions, but their gradual formation in the reaction mixture affects the kinetics of the main reactions and hence the yield of HAD and consequently HAS.

Since the production process is controlled so that the concentrations of DA and B1 are close to zero at the exit of the HAD production column, there is an excess of DA at the inlet of the column. Excess DA, caused by the formation of part B1 only during the production of HAD, results in the formation of undesirable compounds which reduce the yield. It is known from the literature that the end product of these side reactions is sulfuric acid, nitric oxide and nitrogen. Nitric oxide also functions as a carrier of air oxygen and thus as a catalyst for the oxidation of sulphite ions to sulphate ions.

The content of carbonate ions in the DA solution cannot be significantly reduced in the present production process as it constitutes the safety alkalinity of the solution. Also, undesirable SU content in solution B1 cannot be eliminated yet.

In order to suppress unwanted side reactions, it is currently necessary to operate at temperatures close to 273 K, which places an energy demand on machine cooling. The yields are 90% based on DA.

It has been found that the highest yields are obtained while keeping the redox potential of the solution at a level that corresponds to zero concentrations of DA and B1 in the reaction mixture at the outlet. Furthermore, it has been shown that the yield of the reaction strongly influences the excess of SO ₂ in the water phase, continuous measurement is ensured by a pH meter. Long-term operation has shown that administration a relationship of input components, i.e. DA and Bl _SO2 favorably affects yield of the process. Conventional analog control does not guarantee sufficient accuracy and sensitivity of control interventions at any variations in production, which is reflected in the fact that it takes a relatively long time to remove the control deviation.

The proposed procedure is based on the observation that fitting the regulator can be production technology HAD control automatically both the pH of the solution indicating the excess S0 ₂ and the redox potential, indicating the excess DA or Bl, and two values, both pH and redox , independently.

The regulated system consists of two basic control loops. The first, simple, stabilizes the level in the column by draining the product. A PI controller is used. The second loop is more complex. It stabilizes the pH of the solution at the outlet of the column at the setpoint by controlling the setpoints of the DA feed. The PID controller is used.

The flow reference value B1 is derived from the flow rate value DA of the linear dependence. The constant of this coupling is calculated by another PID controller whose input parameter is the redox potential measured at the same location as the pH. This regulator corrects the ratio constant of both flow rates only if the measured pH is close to the setpoint.

The flow rates DA and B1 are stabilized at the calculated setpoint by the PI regulators.

The number of control loops depends on the wiring of the devices. The above description corresponds to HAD production control in one column. The control system of the digital controller can be operated with the same results even with extended technological connection of apparatuses.

The advantage of using a digital controller is that the controller's arithmetic allows very fine control interventions, even at one-second intervals. The PID controller controls the redox potential continuously, only at a narrow pH value (even in hundredths of a pH) so that the optimum ratio of reactants is maintained.

Example 1

Classical analog pH control and HAD redox potential

258 kg / h UA, 630 kg / h kUA, 3,601 kg / h DA, 186 kg / h SU, 3,682 kg / h B1 were fed into the system. S0 ₂ delivery not measured. 4 180 kg / h of HAS were produced. The yield of HAS on consumed DA was 90.6% when hydrolyzing HAD to HAS in 100% yield. Setpoint pH 4.6, redox relative value 0 mV.

Example 2 *

Classical analog redox control, pH controlled by a digital controller

258 kg / h UA, 638 kg / h kUA, 3,601 kg / h DA, 186 kg / h SU, 3,682 kg / h B1 were introduced into the system. SO ₂ delivery not measured. 4,217 kg / h of HAS were produced. The yield of HAS on consumed DA was 91.4% when hydrolyzing HAD to HAS with 100% yield. Setpoint pI 4.6, redox relative value 0 mV.

He did

Redox potential and pH controlled by a digital controller

258 kg / h of UA, 638 kg / h of kUA, 3,601 kg / h of DA, 186 kg / h of SU, 3,682 kg / h of B1 were fed into the system. SO ₂ delivery not measured. It was produced 4,259 kg / h HAS. The yield of HAS on consumed DA was 92.3% when hydrolyzing HAD to HAS with 100% yield. Setpoint pH 4.6, redox relative value 0 mV.

Claims (1)

OBJECT OF THE INVENTION A process for the manufacture of an aqueous solution of 300-550 kg / m ammonium hydroxylamisulphonulfonate produced from solutions of ammonium nitrite, ammonium hydrogen sulfite and sulfur dioxide gas, wherein both the feed solutions and the reaction mixture contain by-technology components controlled by a digital controller with selected pH control algorithms. in the range of 2.5 to 5.0 and a redox potential whose values in millivolts correspond to a concentration of ammonium nitrite in the range of 0 to 5 kg / m and ammonium bisulphite in the range of 0 to 5 kg / m in the output stream, The pH and the redox controller are operated independently of each other, the pH controller controls the amount of feedstock and the redox controller their ratio, and the redox controller adjusts the ratio of the inlet solutions to the redox setpoint when the deviations from the pH setpoint do not exceed +10 to -10 relative h percent.