RU2186021C2 - System controlling process of hydroxylaminesulfate winning - Google Patents

Abstract

FIELD: production of synthetic fibers and polyamide resins. SUBSTANCE: invention refers to automatization of technological processes of synthesis of hydroxylaminesulfate from nitrogen oxide with catalytic oxidation of ammonia. System controlling process makes it feasible to raise accuracy of control over ratio of key flows and temperature in contact apparatuses and reactors with allowance for restrictions for technological parameters. It increases conversion of reagents and safety of process which in the long run improves qualitative indices and raises productivity of plant employed in process. EFFECT: improved qualitative indices and raised productivity of plant. 1 dwg, 1 tbl

Description

 The present invention relates to the field of automation of technological processes for the synthesis of hydroxylamine sulfate from nitric oxide during the catalytic oxidation of ammonia and can be used to produce caprolactam in the production of synthetic fibers and polyamide resins.

 A known method of producing hydroxylamine sulfate by catalytic reduction of nitric oxide. In this case, a mixture of gaseous ammonia, water vapor and oxygen is supplied to the contact apparatus, where ammonia is oxidized on platinum-rhodium networks and then the mixture is fed to another contact apparatus, where a small amount of hydrogen is added. Then the formed nitric oxide with hydrogen is fed into the synthesis reactor, filled with a suspension of the catalyst in sulfuric acid. The resulting product is taken through a filter to a finished product warehouse. The synthesis of hydroxylamine is carried out by regulating a given ratio of components (ammonia - oxygen; ammonia - steam; nitric oxide - hydrogen) at a given temperature and pressure. The reaction heat generated is used to produce water vapor using a recovery boiler [Caprolactam Production / Ed. IN AND. Ovchinnikova and V.P. Rushinsky. M .: Chemistry, 1977, pp. 136-143].

 The disadvantage of this method of producing hydroxylamine is the low accuracy of the regulation of process parameters.

 Closest to the proposed invention is a device (system) for controlling the contact oxidation process in the production of nitric acid, contained control loops (sensor - regulator - valve) of ammonia, air (oxygen) consumption, temperature sensors of the oxidation process; temperature and pressure sensors for ammonia and the environment. The device is implemented using microprocessor technology (microcomputers), in which there are blocks for calculating the ammonia-air ratio, blocks for input and output of information for process control, and blocks for issuing control actions to the valve. Depending on the temperature of ammonia, the temperature of the oxidation process is adjusted and the temperature correction unit is turned off depending on the ammonia-air ratio [RF Patent 2114056, IPC 6 C 01 B 21/38, G 05 D 27/00 of 06/23/96. Bull. 18, 1998].

 The disadvantages of the device are the limited scope (can not be used in other industries), insufficiently high accuracy of regulation of process parameters and, as a result, deterioration of the quality of the target product, since the regulation does not take into account restrictions on the ratio of parameters, which also reduces the safety of the process.

 The aim of the invention is to expand the scope and increase the accuracy of regulation of parameters.

 This goal is achieved by the fact that the known control system for the process of producing hydroxylamine sulfate, carried out in series connected mixers, contact devices and reactors, containing control loops (sensor - regulator - valve) of the flow of ammonia and oxygen into the mixer, oxidation temperature sensors in contact devices, control loops temperature in reactors with water, a unit for calculating the ratio of the flow rates "ammonia - oxygen" implemented in a microcomputer connected to the inputs and outputs of the decree sensors and regulators, additionally contains circuits for regulating the flow of steam into the first mixer, circuits for regulating the flow of hydrogen into the second and third mixer, a sensor for controlling the flow of nitric oxide into the reactor, shut-off valves installed on gas pipelines of ammonia, oxygen, steam, hydrogen, nitric oxide, blocks for calculating the ratios of ammonia-steam, ammonia-hydrogen, nitric oxide-hydrogen, a control unit for temperature limits in contact devices and reactors, while the outputs of the flow sensors for steam, hydrogen, nitric oxide, Temperature microcomputer connected to the inputs, the outputs of which are connected to the inputs of ammonia flow controllers, oxygen, hydrogen and water input to slam pipelines ammonia, oxygen, steam, hydrogen, nitrogen oxide. In addition, the units for calculating the ratios of ammonia – vapor, ammonia – hydrogen, nitric oxide – hydrogen, and temperature limit control units in contact devices and reactors are implemented in a modular form in a microcomputer.

 The combination of additional devices in combination with the known ones gives the control system new properties that increase the accuracy of controlling the ratio of the initial flows and temperature of the process of ammonia oxidation and the synthesis of hydroxylamine sulfate, and taking into account restrictions on the process parameters increase its safety and expand the scope of the system for similar plants.

 The essence of the invention is illustrated in the drawing, which shows a schematic diagram of a process control system for the production of hydroxylamine sulfate (HAC) by direct catalytic synthesis from hydrogen and nitric oxide, obtained by oxidation of ammonia, followed by recovery of excess oxygen with hydrogen and vapor condensation from the gas mixture.

 Conventionally shown one production line (out of five working).

 The system includes apparatuses 1-7, where 1, 3, 5 are ejector mixers; 2, 4 - contact apparatuses filled with a catalyst, where ammonia is oxidized and nitric oxide is formed, 6 - a hydroxylamine sulfate synthesis reactor filled with a suspension of catalyst and sulfuric acid; 7 - filter cleaning hydroxylamine sulfate.

The control system of devices 1-7 includes:
- ammonia flow control loop, 8-10 (sensor 8, regulator 9, control valve 10),
- oxygen flow control loop 11-13,
- steam flow control loop 14-16;
- shut-off valves 17, 18, 19, installed respectively on the gas pipeline of ammonia, oxygen and steam in front of the mixer 1;
- a hydrogen flow control loop 20-22 and a shut-off valve 23 mounted on a gas line in front of the mixer 3;
- temperature control sensors 24, 25, installed respectively in the middle part and at the output of the contact apparatus 2,
- a hydrogen flow control circuit 26-28 and a shut-off valve 29 mounted on the gas line in front of the mixer 5;
- a temperature control sensor 30 installed at the output of the contact apparatus 4;
- a nitric oxide flow sensor 31 and a shut-off valve 32 mounted on a gas pipeline in front of the mixer 5.

 The control system also includes a temperature control loop 33-35 (sensor 33, controller 34, control valve 35) in the reactor 6 with water. The process is controlled by a microcomputer 36, which is connected by electric communication lines ("input - output") with the inputs of the sensors 8, 11, 14, 20, 24, 25, 26, 30, 31, 33, and to control the outputs of the microcomputer 36 are connected to the inputs regulators 9, 12, 15, 21, 27, 39 and with inputs of shut-off valves 17, 18, 19, 23, 29, 32. (Inputs - outputs of electrical connections "computers - sensors, regulators" are conventionally shown on the diagram in one line) In addition In addition, the functions of monitoring temperature limitations and calculation units for the ratios “ammonia - oxygen”, “ammonia - steam”, “ammonia - hydrogen”, “nitric oxide - hydrogen” implemented as modules in microcomputer 36.

 The study of the synthesis of hydroxylamine sulfate showed that the quality of the resulting product is affected by the accuracy of maintaining the ammonia-oxygen ratio, taking into account the limitations, so when you go beyond the lower set limit, the amount of nitric oxide decreases, and when you go beyond the upper set limit, an excess of oxygen is formed, which increases the concentration of nitric acid (as a by-product) and leads to the formation of an explosive mixture. Maintaining the accuracy of the specified ratio “nitric oxide - hydrogen” is necessary so that the activity and selectivity of the catalyst in the hydroxylamine sulfate synthesis reactor is maintained at the required level, which affects the reaction rate between nitric oxide and hydrogen, and side reactions are accordingly reduced. In addition, it is necessary to take into account restrictions on the limiting ratios of flow rates and temperature, since this affects the safety of the process, it is necessary to take into account the sequence of shutdowns of flows supplied to the devices, and on the other hand, take into account that too frequent shutdowns of devices lead to an excessive consumption of energy resources and reducing the performance of the installation of hydroxylamine sulfate.

 Process control is as follows.

- gaseous ammonia is fed into the mixer 1 and, using the control loop 8-10, the specified flow rate is stabilized, for example, according to PI - the control law. Ammonia consumption is a leading quantity,
- gaseous oxygen is supplied to the mixer 1 depending on the amount of ammonia and, according to the sensors 8, 11, the consumption of ammonia (G ^A ) and the oxygen consumption (G ^K ) determine the current value of the ratio "ammonia - oxygen" (C ^to _tech ) and when it deviates from a given value (C ^k _ass ) adjusts the oxygen flow into the mixer 1, for example, according to the PI control law.

где К1 и К2 - константы.

where K1 and K2 are constants.

The value of ΔG ^k (control action) is worked out using the regulator 12 and valve 13 on the oxygen supply line, to bring the current ratio of ammonia to oxygen to a predetermined value,
- compare the current ratio of "ammonia - oxygen" with limitations
C ^k _min ≤ C ^to _tech ≤ C ^k _max (2)
where With ^k _min - the minimum value of the ratio "ammonia - oxygen";
C ^k _max - the maximum value of the ratio "ammonia - oxygen".

When C ^k _{tech exceeded} the limit values, they sent from the microcomputer 36 to the shut-off valves 17, 18 a command to stop the flow of ammonia and oxygen to the mixer 1,
- 1 steam is supplied depending on the amount of ammonia into the mixer and, according to the information from sensors 8, 14, the flow rates of ammonia (G ^A ) and steam (G ^P ) determine the current ammonia-steam ratio (C ^P _tech ) and when it deviates from the set value (With ^P _ass ) and adjust the flow of steam into the mixer 1, for example, according to the PI law of regulation.

где К3, К4 - константы,
Величину ΔG^п (управляющее воздействие) отрабатывают с помощью регулятора 15 и клапана 16 для приведения текущего соотношения "аммиак - пар" к заданному значению
- сравнивают текущее соотношение "аммиак - пар" с ограничениями:
С^П _min≤С^П _тек≤С^П _max (4)
где С^П _min, С^П _max - соответственно минимальные и максимальные значения соотношения "аммиак - пар".

where K3, K4 are constants,
The value of ΔG ^p (control action) is worked out with the help of the regulator 15 and valve 16 to bring the current ratio of ammonia-steam to a predetermined value
- compare the current ratio of "ammonia - steam" with limitations:
C ^P _min ≤ C ^P _tech ≤ C ^P _max (4)
where C ^P _min , C ^P _max - respectively, the minimum and maximum values of the ratio of ammonia - steam.

где К5, К6 - константы.When C ^P _{tech goes} beyond the limit values, it is sent from the microcomputer 36 to the shut-off valves 17 and 19 to shut off the ammonia supply and partially the steam supply (to ensure the safety of the process, the valves 16 and 19 on the pair are closed at 40% of the maximum value);
- after mixing the streams, the gas-vapor mixture is fed into the contact apparatus 2, where the catalytic oxidation of ammonia takes place with the release of heat, which is removed to produce steam (boilers are conventionally not shown in the diagram);
- according to the information of sensors 24, 25, the temperature in the middle (T ^cf ) and lower (T ⁿ ) parts of the contact apparatus 2 is controlled, and when it exceeds a predetermined value (T ^cf _ass , T ⁿ _ass ) when
T ^av ≥T ^av _ass (5) and T ⁿ ≥T ⁿ _ass (6),
command from the microcomputer 36 to the shut-off valves 17 and 18 to stop the flow of ammonia and oxygen;
- the nitrous gases formed in the contact apparatus 2 are supplied to the mixer 3, where hydrogen is also supplied depending on the amount of ammonia, and according to the information of the sensors 8 and 20, the flow rates of ammonia (G ^A ) and hydrogen (G ^B ) determine the current ammonia-hydrogen ratio ( G ^In _tech ) and when it deviates from the set value (With ^B _ass ) adjust the flow of hydrogen into the mixer 3, for example, according to PI - the law of regulation

where K5, K6 are constants.

The value of ΔG ⁱⁿ (control action) is worked out using the controller 21 and valve 22 to bring the current ratio of ammonia to hydrogen to a predetermined value,
- compare the current ratio of "ammonia - hydrogen" with limitations
C ^V _min ≥ C ^V _tech ≥ C ^V _max (8)
where C ^B _min , C ^B _max - respectively, the minimum and maximum values of the ratio "ammonia - hydrogen".

When C ^B _{tech exceeded} the limit values, a command was sent from the microcomputer 36 to the shut-off valve 28 to stop the supply of hydrogen. After mixing hydrogen and nitrous gases, the mixture is fed into contact apparatus 4 (afterburning reactor), where nitric oxide is formed. The temperature at the outlet of apparatus 4 is controlled by a sensor 30.

 The resulting nitric oxide is fed into the mixer 5, the flow rate of which is controlled by the sensor 31 and, depending on its amount, hydrogen is also supplied there.

где К7 и К8 - константы.According to the information of the sensors 31 and 26, the flow rates of nitric oxide (G ^O ) and hydrogen (G ^B ) determine the current ratio (C ^O _tech ) "nitric oxide - hydrogen, and when it deviates from the set value (C ^O _back ), the flow rate of hydrogen (ΔG $\genfrac{}{}{0ex}{}{\text{2}}{\text{in}}$ ) to the mixer 5, for example, according to PI - the law of regulation

where K7 and K8 are constants.

ΔG $\genfrac{}{}{0ex}{}{\text{2}}{\text{in}}$ work out using the regulator 27 and valve 28 to bring the current ratio of nitric oxide to hydrogen to a predetermined value,
- compare the current ratio of "nitric oxide - hydrogen" with limitations
C ^O _min ≤C ^O _tech ≤C ^O _max (10)
where C ^O _min and C ^O _max - respectively, the minimum and maximum values of the ratio "nitric oxide - hydrogen".

When C ^O _{max exceeds} the limit values, a command is sent from the microcomputer 36 to the shut-off valves 32.28 to stop the flow of nitric oxide and hydrogen into the mixer 5.

After mixing the streams in the mixer 5, the gas mixture is fed to the hydroxylamine synthesis reactor 6 (one of the reactors connected in series is conventionally shown), where, with constant stirring in the presence of a catalyst and sulfuric acid, a GAS is formed. The set temperature (T ^r _back ) is maintained using the control loop 33-35 and microcomputer 36, for example, according to PI - the law of regulation of water supply (to the internal and external coils of the reactor 6).

 The resulting GAS solution is passed through a filter 7 and then fed to the production of caprolactam.

 Thus, maintaining a given ratio of the initial flows “ammonia - oxygen”, “ammonia - steam”, “ammonia - hydrogen”, “nitric oxide - hydrogen”, taking into account the limitation on the maximum permissible values and temperature of the process, we achieve a more complete use of reagents in the process , and in a timely manner and in a given sequence, acting on the shut-off and control valves, we increase the safety of the process, which ultimately increases the productivity of the installation.

 An experimental verification of the system’s operation in an industrial installation carried out in the 4th quarter of 1999 in the direct synthesis synthesis hydroamino sulphate production shop at ZAO Kuibyshevazot in Togliatti showed the system’s efficiency. The following is a numerical example of the system and a comparative test table.

Example
Initial data:
1. the specified flow rate of ammonia G ^A = 1000 kg / h;
2. The ratio of "ammonia - oxygen" in the mixer 1
C ^to _back = 1: 1.35 - set value;
C ^to _min = 1: 1.46 - the minimum value;
C ^to _max = 1: 1.27 is the maximum value.

3. The ratio of "ammonia vapor"
With ⁿ _ass = 1: 4.7 - set value;
With ^p _min = 1: 5.5 - the minimum value;
With ^p _max = 1: 4,5 - the maximum value.

4. The value of the temperature in the apparatus 2
- the maximum value in the middle part of the apparatus 2 T ^max _cp = 1050 ^o С,
- the maximum value in the lower part of the apparatus 2 T ^max _n = 350 ^o With
5. The ratio of "ammonia - hydrogen" in the mixer 3
C ^{in the} _back = 1: 0.3 - the set value;
C ⁱⁿ _min = 1: 0.25 - the minimum value;
C ⁱⁿ _max = 1: 0.35 is the maximum value.

6. The ratio of nitric oxide - hydrogen
With ^about _back = 1: 1.77 - set value;
With ^about _min = 1: 1,80 - the minimum value;
With ^about _max = 1: 1.75 - the maximum value.

7. The set temperature values in the reactor 6
T ^p _ass = 42 ^o With
T ^p _max = 45 ^o With
1. Serve in the mixer 1 a predetermined amount of ammonia G ^A = 1000 kg / h, using a control loop 8-10.

2. For a given ratio of "ammonia - oxygen" C ^to _back = 1: 1.35, oxygen is supplied in an amount of G ^to = 1350 kg / h, which is processed by the control circuit 11-13.

3. For a given ratio of "ammonia - steam" With ^p _ass = 1: 1.41 steam is supplied in an amount of G ^p = 4700 kg / h, which is worked out by the control loop 14-16.

4. According to the information of the sensor 24, the temperature in the middle part of the apparatus 2 T ^tech _media = 940 ^o C is controlled and according to the information of the sensor 25 in the lower part of the apparatus 2 T ^tech _lower = 295 ^o C.

5. For a given ratio of ammonia - hydrogen With ^{In the} _ass = 1: 0.3 serves hydrogen in an amount of 300 kg / h, which is worked out using a control loop 20-22.

6. The obtained nitric oxide (with a temperature of T ⁴ = 380 ^o C according to the information of the sensor 30) in quantity according to the information of the sensor 31 G ^О = 6300 kg / h is fed to the mixer 5, where also for a given ratio nitric oxide - hydrogen C ^О _back = 1: 1.77 serves hydrogen in an amount of 11151 kg / h, which is worked out using a control loop 26-28.

7. Stabilize the temperature in the reactor 6 T ^r _ass = 42 ^o With the use of the control loop 33-35 water supply. The resulting hydroxylamine sulfate is passed through a filter 7 and sent to the finished goods warehouse.

 The ratios ammonia - oxygen, ammonia - steam, ammonia - hydrogen, nitric oxide - hydrogen, as well as temperatures in apparatuses 2, 4, 6 are within the specified limits, therefore, the commands for the shut-off valves 17, 18, 19, 23, 29, 32, respectively on the supply of oxygen, ammonia, steam, hydrogen to block the flow with the microcomputer 36 is not served.

 The table shows the improvement in performance of the production of hydroxylamine sulfate, the effect will be 1.5 million rubles per year. The introduction of a process control system for the production of hydroxylamine sulfate is scheduled for the 1st quarter of 2000 in the workshop of Kuibyshevazot CJSC (Togliatti).

Claims (1)

 The control system for the process of producing hydroxylamine sulfate, which includes an oxygen and ammonia mixer and an ammonia oxidation contact device in series, the control circuits are a sensor, a regulator, an ammonia and oxygen flow valve, an ammonia oxidation temperature sensor, a microcomputer connected to the inputs of ammonia, oxygen and temperature control and the inputs of the regulators of the flow of ammonia and oxygen, characterized in that it further comprises a mixer of ammonia and hydrogen oxide, on-line nitric oxide apparatus, nitrogen and hydrogen oxide mixer, hydroxylamine sulfate synthesis reactor and hydroxylamine sulfate purification filter connected in series by gas pipelines, steam flow control circuits in an oxygen and ammonia mixer, hydrogen flow control circuits in ammonia and nitrogen oxide mixers, outlet temperature sensors contact apparatus for the oxidation of ammonia and nitrogen, a nitric oxide flow sensor at the inlet of a nitrogen and hydrogen oxide mixer, a temperature control loop in the reactor synt for hydroxylamine sulfate, shut-off valves installed on gas pipelines supplying ammonia, oxygen, steam to the mixer of oxygen and ammonia, supplying hydrogen to the mixer of ammonia and hydrogen and supplying nitric oxide and hydrogen to the mixer of nitric oxide and hydrogen, while the outputs of the sensors for the flow of steam, hydrogen , nitric oxide, the temperature at the outlet of the contact apparatus for the oxidation of ammonia and nitrogen and in the reactor for the synthesis of hydroxylamine sulfate are connected to the inputs of the microcomputer, the outputs of which are connected to the inputs of the regulators of the flow of steam, hydrogen, water and shut-off valve inputs for supplying ammonia, oxygen and steam to the oxygen and ammonia mixer, supplying hydrogen to the ammonia and hydrogen mixer, and supplying nitric oxide and hydrogen to the nitrogen and hydrogen oxide mixer.

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