SU1490071A1 - Method of controlling weak nitric acid production - Google Patents

Abstract

The invention relates to the control of the production of non-concentrated nitric acid and can be used in the mineral fertilizer industry and in the chemical industry. The aim of the invention is to reduce the specific consumption of ammonia. The method involves correction of mathematical model coefficients by measured temperatures in the contact apparatus, air flow into the mixer and its pre-heater inlet temperature, calculation of ammonia conversion from measured flow values and ammonia temperature, air humidity, pressure in the contact apparatus, ambient temperature and corrected coefficients of the mathematical model, the calculation of the degree of oxidation of nitrous gas based on measured values of consumption and temperature of ammonia, humidity ear pressure in the contact apparatus and steam at the outlet of the recovery boiler, ambient temperatures, feed water at the inlet of the recovery boiler and the air at the heater inlet, calculation and setting the optimum values of air flow and its temperature at the outlet of the heater according to the measured temperature value in the contact the apparatus, the calculated values of the degree of ammonia conversion and the degree of oxidation of the nitrous gas, and the specified boundary values of the temperature in the contact apparatus and the degree of oxidation of the nitrous gases. 2 Il.

Description

This invention relates to managing the production of weak nitric acid and can be used in the mineral fertilizer industry and in the chemical industry.

The aim of the invention is to reduce the specific consumption of ammonia.

Figure 1 is a schematic diagram of the implementation of the proposed control method; Fig. 2 is a diagram of the interconnection of blocks included in the computing device.

The implementation scheme (FIG.) Contains an ammonia and air mixer 1, an ammonia oxidation contact apparatus 2, a waste heat boiler 3, an oxidizer 4, an air preheater 5, ammonia and air flow sensors 6 and 7, and ammonia 8 contact temperature sensors 8-11

apparatus, air after n to put

a superheater, pressure sensors 12 and 13 in the contact apparatus and steam after the waste heat boiler, actuators 14 and 15 for changing the flow rate of nitrous gas by the heater preheater and air into the mixer, air humidity sensor 16, control device 17, computing device 18, sensor 19 feedwater temperatures, channels 20 and 21 of entering technological limits and ambient temperatures

The interconnection scheme of the functional blocks 22-24 of modeling, optimization and adaptation included in the VU18 computing device and their connection with sensors of measured parameters of the nitric acid production process is shown in Fig.2. The interaction of these blocks sets the keys 25-28.

Vj

Measured parameters used only when adapting the coefficients of the model of the contact apparatus: bg - sensor 7; Tr - sensor 10; , d - sensor 9 "

The method is carried out as follows.

The signals from the sensors 6,8,11,12,13, 16,19 and channel 21 entering the computing device 18 correspond to the group A of the input variables of the simulation function block. From channel 20 the values of the restrictions on the allowed maximum temperature of the contact device arrive at the computing device and the minimum degree of oxidation of nitrous gases after the air preheater.

The equations implemented by the fuctional blocks of the auxiliary device 18 are as follows. Shred 2 modeling

In the drawings, the following are accepted., T-p

Ok

designations: TL, oi- limits

 Chok

the values of the parameters — the temperature in the contact apparatus and the degree of oxidation of the nitrous gas behind the air heater; , T are the calculated values of the air flow rate in the mixer and its temperature; G, - optimal values of G, T,

f

6

6T

OSKD, (Lo1s 5 to L - calculated values of the degree of conversion of ammonia, the degree of oxidation behind the air heater in the contact apparatus; A, B, C are groups of parameters, and

    RP "

 i

„KftKA„ KChN

--and n

BT

T.Tj; with

VD;

I d, bg, t 5, - measured values of the temperature of the contact apparatus, the flow rate of air into the mixer and its temperature

The connection of blocks 22-24 with sensors (FIG. 1) is as follows. The components of vector A are measured by sensors: G sensor 6; TD, sensor 8; sensor 1 1; EE / - sensor 16; RCD - sensor 12; RP - sensor 13; Tdd - sensor

nineteen;

m RC - N

I (H

 OK

 - and

.CB

- input 21

Technological limitations used only when optimizing:

-KA

oi

R

input 20.

25

o6 ,, f, (A, B, C) f, (G,

PX,. fb. &);

Td, ES.

0

Ka, ok

 n

t

 Ka

2 s

TH

f2 (A, C, fb, b) f, {G «, Td.-Ze,

pmmm I

  - BOX -6PP H p. , fi, B);

f j (A, C, B) f, (Gd, T,%, RCD,

Lb h

V lb.b);

five

at

Gg, Ta- matched parameters during optimization

G

 V

t „6t -v

input parameters for adaptation

five

0

Block 23 optimization

"W T, (.oi ,,, t

 M, (si

Ka

1 oi7J;

 Ka

. - Chg,.

t-ka

gr

 Ka

OK .1

).

Block 24

 C (T

adaptations

l

Ky

Ky

BT

T.);

wg - tue

50

TB

AT

The position of the keys 25-28 establishing the interconnection between the blocks is the following: О - adaptation mode; 1 - mode when tasks of optimization and adaptation are solved; 2 - optimization mode.

In the computing device 18 in accordance with the described interactions

The optimization and modeling function blocks are used to select the flow rate 0 and the temperature T6 of the air supplied to the mixer. The found values 0 and Td are fed from the device 18 to the regulating device 17, where the error P and T are determined with their measured (current) values received from sensors 7 and 10, the error signal is processed by actuators IA and 15. Changing any of the parameters of group A of the input variables of the modeling unit (input values of temperature limits contact apparatus and the degree of oxidation of nitrous gas after the air preheater, values kozffitsientov contactor model received from the functional block adaptation) is indicative of the need to re Retenu optimization problem.

Entering the computational device 18 from sensors 7, 10 and 9, the measured flow rates and air temperature into the mixer, the temperatures of the contact device are used by the adaptation unit to adjust the values of the coefficients of the model of the contact device when the mismatch between the measured and calculated values of the temperature of the contact device exceeds the specified level

Using the proposed method allows to reduce the specific consumption of ammonia by 1%.

Claims (1)

Invention Formula Method for controlling the production of weak nitric acid, including regulation of the air temperature at the outlet of the preheater by varying the flow rate of nitrous gases through the bypass of the preheater, controlling the air supply to the mixer of the contact apparatus and measuring the flow rate of ammonia 0 0 five five into the mixer of the contact apparatus, the temperature in the contact apparatus and the vapor pressure at the outlet of the recovery boiler, characterized in that, in order to reduce the specific consumption of ammonia, the temperatures of the external environment, the ammonia at the inlet of the mixer, the air at the inlet of the preheater, feed water are measured the inlet of the boiler, the pressure in the contact apparatus and the air humidity at the inlet of the heater, set the boundary values of the temperature in the contact apparatus and the degree of oxidation of the nitrous gas, according to the measured values the temperature in the contact apparatus, the air flow rate into the mixer and its outlet temperature of the preheater, corrected the coefficients of the mathematical model of production using measured values of the flow rate and temperature of ammonia, air humidity, pressure in the contact apparatus, ambient temperature and corrected coefficient of the mathematical model for various the values of air flow and its temperature at the outlet of the preheater calculate the degree of conversion of ammonia and the temperature in the contact apparatus, by measuring The values of flow rate and temperature of ammonia a, airflow, pressures in the contact apparatus and steam at the outlet of the recovery boiler, ambient temperatures, feed water at the inlet of the recovery heat exchanger and inlet air under the preheater and corrected coefficients of the mathematical model calculate the degree oxidation of nitrous gas, according to calculated values of the degree of ammonia conversion, The g temperatures in the contact apparatus and the degree of oxidation of the nitrous gas and the given boundary values of the temperature in the contact apparatus and the degree of oxidation of the nitrous gases calculate and determine the optimal values of air flow and its temperature at the outlet of the preheater. 0 five T and -  H cl ovc U Sh and Ka & tue to