Automatic control and regulation of the air separation process - diploma

Contents

INTRODUCTION

1 PROCESS DESCRIPTION WITH SUMMARY OF PROCESS EQUIPMENT

1.1 Process Description

1.2 Summary of process equipment

2 OBJECT RESEARCH AND DEVELOPMENT OF CONTROL SYSTEM

2.1 Basic Properties of the Control Object -------------------------------------------------------------------------------------------------

2.2 Defining performance indicators and management objectives

2.3 Selection of adjustable parameters and channels for adjustment

influences-----------------------------------------------------------------------------------------------------

2.4 Selection of monitored and signaled parameters

2.5 Selection of measures for protection and blocking ---------------------------------------------------

2.6 Control Object Survey ---------------------------------------------------------------------------------------------------------------------

3 CONSTRUCTION AND CALCULATION OF AUTOMATIC CONTROL SYSTEMS AND INDIVIDUAL COMPONENTS

3.1 Description of control system operation

3.2 Selection of automation tools

3.3 Microprocessor Controller Description

3.4 Calculation of regulator (valve)

4 DEVELOPMENT OF SIGNALLING AND PROTECTION SCHEMES

5 DESIGN OF CONTROL BOARDS AND PANELS

5.1 Purpose, design of boards

5.2 Wiring of panels and panels

5.3 Grounding of boards and panels

5.4 Controller Installation Procedure

5.5 Rules for Installation of Automation Devices and Equipment

5.6 Arrangement and installation of boards

6 INSTALLATION OF AUTOMATION EQUIPMENT

6.1 Safety Rules for Installation of Primary Devices

6.2 Installation of instruments and equipment

6.3 Installation of automation equipment. Alignment Plan

7 PATENT STUDY

8 FEASIBILITY STUDY

8.1 Calculation of annual economic effect

8.2 Calculation of production cost

8.3 Material Cost Calculation

8.4 Calculation of Energy and Electricity Costs

8.5 Calculation of wages of the main workers

8.6 Cost of production

8.7 Calculation of economic efficiency indicators of technical solution -------------

9 SAFETY OF LIFE

9.1 Analysis of Hazardous Production Factors

9.2 Analysis of Harmful Production Factors ---------------------------------------------------------------------------

9.3 Production sanitation

9.4 Safety precautions during operation

9.5 Protection against static electricity and electric shock

9.6 Classification of rooms by fire and explosion hazard

9.7 Fire safety of laboratory, site, department

9.8 Atmospheric emissions

9.9 Wastewater -----------------------------------------------------------------------------------------

9.10 Water supply and sewerage ---------------------------------------------------------------------

9.11 Labor protection -------------------------------------------------------------------------------------------

CONCLUSION

LITERATURE AND REGULATORY DOCUMENTS

APPLICATION

Introduction

Due to the large volumes of production and the requirements for the quality of products, the issue of production automation is acute.

Managing the production process requires many complex tasks. Therefore, the main functions of the management system were previously entrusted to a person.

But the development of the theory and technique of automatic control, based on modern electronics, led to the creation of automatic control devices. As they improve, more complex management functions are transferred to them, resulting in a higher level of automation of production processes.

Automation of production - a process in which control and control functions previously performed by a person are transferred to instruments and automatic systems. Automation of production is the basis for the development of modern industry.

This diploma project deals with the automation of the process of obtaining pure argon

The process of producing pure argon is three successive production steps. Each step is a rectification process, wherein in the production of crude and technical argon, the main product is distillate, and in the production of pure argon, the main product is bottoms. Argon is an inert gas and therefore there is an urgent need to install equipment and carry out measures to ensure fire and safety explosions, in this project automatic control of the safety of the production process is carried out.

The purpose of my diploma project was to modernize the automation system, that is, to create a new system using modern microprocessor tools on the basis of existing automation tools. The technical solutions adopted in the project are based on the latest achievements of science and technology in the field of automation of chemical production.

Based on economic feasibility, the complete replacement of automation tools and devices is inefficient and not profitable. The implementation of the complete replacement of the entire control and control base will take an unacceptably long time and large investments, while the instrumentation and control services are tasked with installing and commissioning old and new instrumentation and control equipment as soon as possible, replacing mentally and physically obsolete instruments.

1 process description with summary of process equipment

1.1 Process Description

Due to its chemical inertia, argon is widely used in many industries. These include:

1) electric arc welding of aluminium, magnesium, titanium, copper and their alloys, as well as various types of stainless steels;

2) manufacture of lighting lamps, pulse light sources and electronic devices;

3) electric arc cutting of non-ferrous metals in a protective argon-hydrocarbon atmosphere;

4) smelting and processing of non-ferrous metals, in particular titanium, copper, sodium, magnesium, uranium, zirconium and tungsten, as well as high-quality steels;

5) purging of liquid steels to remove gas impurities [2].

The pure argon production process consists of three successive production steps:

1) extraction of raw argon from air;

2) purification of raw argon from oxygen, i.e. production of technical argon;

3) purification of technical argon from nitrogen, i.e. production of pure argon [see drawing BR 05 2203011].

Vapour argon fraction taken from the middle of the upper column of the KfA21 air separation unit (hereinafter simply referred to as separation unit) with 88% oxygen content; 0.7% nitrogen is supplied to the bottom of the raw argon column (item 1). To remove heat from the top of the raw argon column (item 1) and condense the vapors formed in it, liquid nitrogen is supplied to the condenser of the raw argon column (item 4) from the outlet of the separation unit with a temperature of minus 1900C. After the condenser of the raw argon column (item 4), partially evaporated nitrogen enters the evaporator of the separation unit.

In the raw argon column (item 1), the vaporous argon fraction is separated into crude argon with a 0.5% oxygen content; 2.3% nitrogen and liquid oxygen fraction containing 91.5% oxygen, which then, after passing through the hydraulic seal, returns to the upper column of the separation unit [2].

From the top of the raw argon column (position 1), vaporised raw argon enters the condenser of the raw argon column (position 4), where it condenses. At the outlet of the condenser of the raw argon column (position 4), liquid raw argon is divided into two streams. One part of it through the hydraulic seal

is supplied for reflux to the top of the raw argon column (item 1).

The other part of the liquid raw argon enters the heat exchanger (item 10), where it is heated to a temperature of minus 1830C and, turning into a vapor-gas mixture, enters the middle part of the technical argo column (item 2). To heat the raw argon, the bottom liquid from the bottom column of the separation unit with a temperature of minus 1700 C. After heating the raw argon, the bottom liquid from the heat exchanger (10) enters the top of the upper column of the separation unit.

In the technical argon column (item 2), vaporised raw argon is divided into technical argon with a content of 0.0002% oxygen and a discarded liquid fraction consisting of 50% oxygen and 50% argon.

The waste liquid fraction at the outlet of the bottom of the AR column (item 2) is divided into two streams. One part of it enters the technical argon column preheater (item 7), evaporates in it and rotates back to the technical argon column cube (item 2).

The other portion of the waste liquid fraction enters the heat exchanger (item 12) and evaporates to the lower portion of the raw argon column (item 1). To evaporate the waste liquid fraction, circulating nitrogen gas is supplied to the heat exchanger of the technical argon column (item 7) and heat exchanger (item 12) after the circulating heat exchanger of the separation unit with temperature minus 1700C, after which partially condensed circulating nitrogen is supplied to the upper column of the separation unit.

From the top of the technical argon column (item 2), vapour technical argon enters the condenser of the technical argon column (item 5), where it is condensed. At the outlet of the condenser of the technical argon column (item 5), liquid technical argon is divided into two streams. Part of it is supplied through the hydraulic seal for reflux to the upper part of the technical argon column (item 2).

The other part of the liquid technical argon enters the heat exchanger (item 11), where it is heated to a temperature of minus 1840C and, turning into a vapor-gas mixture, enters the middle part of the pure argon column (item 3), where the final purification of argon from nitrogen takes place.

To heat technical argon, the bottom liquid from the bottom column of the separation unit with a temperature of minus 1700C enters the heat exchanger (item 11). After heating the technical argon, the liquid bottoms from the heat exchanger (item 11) are fed to the top of the overhead column of the separation unit.

To remove heat from the top of the technical argon column (item 2) and condense the vapors formed in it, liquid nitrogen is supplied to the condenser of the technical argon column (item 5) from the outlet of the separation unit with a temperature of minus 1900C. After the condenser of the technical argon column (item 5), partially evaporated nitrogen enters the evaporator of the separation unit.

In the pure argon column (item 3), the vaporous technical argon is separated into pure argon with a content of 0.0002% oxygen and 0.002% nitrogen and a discarded nitrogen fraction with a content of 80% nitrogen and 20% argon. From the top of the pure argon column (position 3), the vaporised nitrogen drop fraction enters the condenser of the pure argon column (position 6), where it is condensed.

At the outlet of the condenser of the pure argon column (item 6), the liquid nitrogen waste fraction is divided into two streams. One part of it passes through the hydraulic seal for reflux to the top of the pure argon column (item 3). The other part of liquid nitrogen waste fraction enters the upper part of the upper column of the separation unit .

To remove heat from the top of the pure argon column (item 3) and condense the vapors formed in it, liquid nitrogen is supplied to the condenser of the pure argon column (item 6) from the outlet of the separation unit with a temperature of minus 1900C.

After the condenser of the pure argon column (item 6), partially evaporated nitrogen enters the evaporator of the separation unit. The liquid pure argon at the outlet of the bottom of the pure argon column (position 3) is divided into two streams.

One part of it enters the heater of the pure argon column (position 8), evaporates in it and returns back to the cube of the pure argon column (position 3). Another part of the liquid pure argon enters the pure argon collector (position 9), which is necessary to maintain the balance in the pure argon column (position 3) in the liquid phase.

To evaporate the liquid pure argon, the bottom liquid from the bottom column of the separation unit with a temperature of minus 1700C is supplied to the preheater of the pure argon column (item 8), after which the bottom liquid is supplied to the upper part of the upper column of the separation unit.

In the pure argon collector (item 9), vaporous pure argon is separated from liquid pure argon. From the pure argon collector (position 9), the vaporous pure argon is returned back to the cube of the pure argon column (position 3).

Liquid pure argon from the pure argon collector (item 9) enters the heat exchanger (item 13), where it is cooled to minus 1830C.

After that, pure argon enters the liquid argon storage tank of the separation unit and is then drained to the consumer.

To cool pure argon, liquid nitrogen is supplied to the heat exchanger (item 13) from the outlet of the separation unit with a temperature of minus 190 С. After the heat exchanger (item 13), partially evaporated nitrogen is supplied to the evaporator of the separation unit .

Basic properties of the management object.

The properties of the object must be taken into account when compiling the automation diagram, selecting the adjustment and determining the optimal values ​ ​ of the regulator settings. Proper consideration of the properties of the object allows you to create a management system that has higher indicators of the quality of the transition process. The main properties of the control object are self-alignment, capacity and lag.

Self-leveling of an object characterizes its stability. Self-alignment is the property of a stable object to be independently set to an equilibrium state after changing its input value. In self-leveling objects, a stepwise change in the input value leads to a change in the output value with a rate gradually decreasing to zero, which is associated with the presence of an internal, negative level bond.

The greater the degree of self-alignment, the less the deviation of the output value from the original position.

Object capacity is a property inherent in all dynamic objects. It characterizes their inertia.

The larger the capacity, the lower the rate of change of the output value of the object, and vice versa.

The delay of an object is expressed in that its output value begins to change not immediately after the perturbation, but only after a certain period of time, called the lag time.

All real objects have a delay, since the change in the flows of substances or heat propagates in objects at a final speed and it takes time to travel the signal from the place of perturbation to the place where the change in the output value is recorded.

Use the following methods to define object properties:

- analytical;

- experimental;

- experimental-analytical.

In the work, an experimental method is used, consisting in determining the characteristics of a real object by placing an experiment on it. The method is quite simple, has little labor, allows you to accurately determine the properties of the object.

2.2 Defining performance indicators and management objectives

The main indicator of the efficiency of this process is the purity of the resulting argon at the outlet of the pure argon column (position 3) [See drawing of DP 04 VAE 15.01].

In other words, the main performance indicator in this case is the percentage of nitrogen and oxygen in the pure argon at the outlet of the pure argon column (position 3). The purpose of this process is to maintain the percentages of nitrogen and oxygen in pure argon at predetermined values. Nitrogen content in pure argon shall not exceed 0.0005%. Oxygen content in pure argon must be not more than 0.005%. The process of producing pure argon should occur at the highest intensity and economy of the process, in addition, the process should be safe and accident-free.

2.3 Selection of adjustable parameters and channels for control actions

The process of producing pure argon is three successive production steps. Each step is a rectification process, wherein in the production of crude and technical argon, the main product is distillate, and in the production of pure argon, the main product is bottoms. Therefore, it makes sense to look first at the typical rectification process and then draw conclusions, refinements and additions for each stage.

The main parameters characterizing the rectification process are distillate and bottoms compositions. Existing domestic devices do not have sufficient accuracy and speed. The composition of the distillate and the bottoms cannot be controlled with sufficient accuracy, since the distillation column is a multi-capacitive object with distributed parameters, and therefore with a large lag. Therefore, it is necessary first of all to eliminate the main external disturbances and stabilize indirect parameters characterizing the composition of products. The main disturbances of the process are related to the change in the parameters of the flows at the input and output of the process. This is primarily: the flow rate, composition and initial temperature of the initial mixture, the flow rate of coolant to heat exchangers, the flow rate of reflux, distillate and bottoms, the flow rate of coolant to the condenser.

Consider the effect of the above factors on the operation of the column. Suppose the feed is not supplied to the column in sufficient quantity. This results in a decrease in the content of the low boiling component in the distillate. With an excess of the initial mixture, the heat supplied to the evaporator is not enough for evaporation. The content of the low boiling component in the bottoms is increased. Therefore, in order for the column to work economically and give a clean product, the load of the column must be stabilized. In this case, the flow rate of the feed depends on the previous process, therefore, the change in column load should be considered as a strong disturbance. Reducing the content of the low boiling component in the feed leads to a reduction in the heat consumption for evaporating the low boiling component. The temperature in the column rises and the specified accuracy is not achieved. This disturbing effect cannot be eliminated before entering the control object. If the feed mixture is not introduced into the column at boiling point, it must be heated to this temperature by vapors rising from below. As a result, the temperature of the pores decreases and the process of mass exchange between the liquid and steam phases is disrupted. Vapour condensation is more intense, while part of the low-boiling component enters the bottom residue, the distillate extraction decreases. In the rectification process scheme, there is a heat exchanger for heating the initial mixture, which allows stabilizing the temperature of the initial mixture, thereby eliminating one of the disturbing effects to the object. In turn, this stabilization will eliminate disturbing effects along the coolant flow line.

The flow rate of coolant to the column bottom heat exchanger depends on the column vapor velocity, which determines the intensity and economy of the process. Therefore, the optimal mode of the column will occur at a speed slightly lower than at the beginning of the flooding. At constant load, the coolant supply could be stabilized. This is best done at the introduction of coolant into the column cube.

The purity of the distillate depends on the supply of reflux to the column. Increasing the reflux number increases the purity of the distillate but reduces the economy of the process. Therefore, it is best to control the reflux supply by the temperature at the top of the column.

Changes in distillate and bottoms flow rates cause thermal and material imbalances in the column. Distillate and bottoms flow rates shall be adjusted in accordance with changes in the amount and composition of the feed. In order that the distillate flow rate depends only on the parameters of the initial mixture, it is necessary to stabilize the flow rate of the coolant supplied to the condenser.

The change in the flow rate and composition of the feed mixture are the main disturbing factors. Consider the possibility of adjusting the mode parameters characterizing the composition of distillate and bottoms.

The composition of the vapor and liquid phases depends on the temperature and pressure in the column. If the pressure is stabilized, then the relationship between temperature and composition will be unambiguous. Consider the possibility of stabilizing the pressure in the column. Fluctuations in the flow rate and composition of the feed mixture and reflux flow rate are disturbing factors causing the pressure change in the column. All these disturbances occur, so the pressure must be stabilized. This can be done by changing the flow rate of the vapors discharged from the column to the condenser or by changing the flow rate of the coolant supplied to the condenser. The first option is unsuccessful, since in this case the condenser will operate at variable pressure. The second option is most suitable, but it should be borne in mind that the capacitor has a significant delay. Stabilizing the pressure at the top of the column greatly simplifies the task of maintaining the distillate composition. It is not necessary to stabilize the pressure in the bottom of the column, since the column has self-leveling over this para-meter. Thus, it is necessary to stabilize the pressure at the top of the column, then the composition of the distillate and the bottoms will depend only on the temperature .

Consider the effect of column temperature on process quality. The decrease in temperature reduces the productivity of the column and part of the low boiling component enters the bottoms. An increase in the temperature in the column leads to an increase in the content of the high boiling component in the distillate. At constant pressure, the temperature in the column depends on the parameters of the initial mixture, on the amount of reflux and coolant supplied to the column bottom heat exchanger. The temperature at the top of the column can be stabilized by changing the reflux flow to the column and in the bottom of the column by changing the coolant flow to the column bottom heat exchanger. Since the fractionation column is an object with interconnected parameters, when simultaneous temperature control is applied in the upper and lower parts of the column, the regulators will be connected through the process, which can lead to an oscillating mode of operation. Therefore, the temperature should be controlled in one part of the column. Since the temperature at the bottom of the column depends on the flow rate of steam supplied to the column bottom heat exchanger and the parameters of the feed mixture (stroke and temperature) that are stabilized, the temperature at the bottom of the column will be less susceptible to changes and it is necessary to adjust the temperature at the top of the column. The control action is introduced by changing the reflux flow rate. At the same time, the temperature sensor should be installed on the control plate, where the temperature of the tour changes most greatly when changing the compositions of distillate and bottoms.

To maintain the material balance of the column, it is necessary to stabilize the liquid level in the cube by changing the bottoms flow rate and the distillate level in the condenser by changing the distillate flow rate.

All of the above is true for the steps of producing technical argon and pure argon. However, due to the fact that the raw argon production stage is intended to enrich the argon fraction, the control system of this part of the process will have a "lightweight" appearance. It will control only the temperature and pressure at the top of the column, as well as the reflux level in the condenser.

So, to achieve the control goals, I choose the following automatic control systems:

1) the pressure at the top of the raw argon column (item 1) by changing the liquid nitrogen flow rate to the raw argon column condenser (item 4);

2) pressure at the top of the technical argon column (item 2) by changing the flow rate of liquid nitrogen to the condenser of the technical argon column (item 5);

3) the pressure at the top of the pure argon column (item 3) by changing the liquid nitrogen flow rate to the pure argon column condenser (item 6);

4) the temperature on the control tray in the raw argon column (item 1) by changing the reflux flow rate from the condenser of the raw argon column (item 4);

5) the temperature on the control tray in the technical argon column (item 2) by changing the reflux flow from the condenser of the technical argon column (item 5);

6) the temperature on the control tray in the pure argon column (item 3) by changing the reflux flow rate from the condenser of the pure argon column (item 6);

7) raw argon temperature at the inlet to the technical argon column (item 2) by changing the flow rate of bottom liquid from the bottom column of the separation unit to the heat exchanger (item 10);

8) the temperature of technical argon at the inlet to the pure argon column (item 3) by changing the flow rate of bottom liquid from the bottom column of the separation unit to the heat exchanger (item 14);

9) nitrogen gas flow to heat exchanger (item 8);

10) the temperature of pure argon at the outlet of the heat exchanger, item 13) by changing the flow rate of liquid nitrogen to the heat exchanger (item 13);

11) flow rate of nitrogen gas to heat exchangers (items 7.12);

12) the liquid level in the condenser of the crude argon column (item 4) by changing the liquid nitrogen flow rate to the condenser of the crude argon column (item 4);

13) the level of liquid in the condenser of the technical argon column (item 5) by changing the flow rate of liquid nitrogen to the condenser of the technical argon column (item 5);

14) the liquid level in the condenser of the pure argon column by changing the liquid nitrogen flow rate to the condenser of the pure argon column (item 6);

15) the level of liquid in the bottom of the technical argon column (item 2) by changing the flow rate of bottom liquid at the outlet of the heat exchanger (item 12);

16) the level of liquid in the bottom of the pure argon column (item 3) by changing the flow rate of bottom liquid at the inlet to the argon collector (item 9);

17) the level of liquid pure argon in the argon collector (item 9) by changing the flow rate of liquid pure argon at the outlet of the heat exchanger (item 13).