Method of intensification of the installation for production of nitric acid

FIELD: chemical industry; method of intensification of the installations for production of the non-concentrated nitric acid.

SUBSTANCE: the invention is pertaining to the method of intensification of the installations for production of the non-concentrated nitric acid and may be used for raising productivity of the installations for production of the non-concentrated nitric acid under pressure. The invention provides for creation of the excess pressure on the inlet of the air compressor by preliminary compression of the atmospheric air in the high-pressure fan. At that the heat of the compression process in the warm season of the year is withdrawn by the direct contact with the water at the inlet of the fan, and in the cold season the heat is used for heating, at that in full or partially excluding heating of the air in the preheater mounted to prevent the icing up of the guiding apparatuses of the air compressor. At the enterprises with the high degree of the air dusting or chemical pollution for the contact cooling of the air by water it is possible to use scrubbers-washers, which combine the functions of the air cooler and the purification device. The method is effective for the operating installations, in which as a result of the wear-out of the flow-through section of the air compressors and the gas turbines decreases not only productivity, but also the pressure in the system, and as the result of it the concentration of the nitric acid. The method allows to realize the intensification of the installations using already existed equipment due to the increased pressure in the system. Concentration of the nitric acid is not lowered, the degree of purification of the tailing gases is preserved, production cost and the specific consumption of the steam and the natural gas are reduced.

EFFECT: the invention allows to realize the intensification of the installations using already existed equipment, to reduce production cost and the specific consumption of the steam and the natural gas.

4 cl, 2 ex, 2 tbl, 2 dwg

 

The invention relates to the field of industrial production of non-concentrated nitric acid and can be used for intensification of existing facilities, in which nitric acid with a concentration of 55-65% HNO3produced by the method of oxidation of ammonia by oxygen under pressure and absorption of nitrogen oxides under the same or higher pressure.

The composition of these plants include native plant including an air compressor for compressing ambient air, nitrous supercharger to compress nitrous gases (in installations with higher pressure at the stage of absorption) and drive these compressors. Drive in modern installations include gas turbine for energy recovery of the compressed tail gas after absorption in combination with an electric motor or steam turbine.

In Russia and CIS countries the production of nitric acid is almost completely carried out on the units for energy-technological scheme, in which the engine unit is a gas turbine installation. In units of average power under uniform pressure (units of type UKL-7) gas turbine unit type GTT-3 includes an air compressor and a gas turbine with an estimated temperature of the tail gas 700°C. In large aggregates with two pressure type AK-72 gas turbine unit type GTT-12 VC is uchet air compressor, nitrous supercharger and a gas turbine with an estimated temperature of the tail gas 760°C. Heating the tail gas is the burning of natural gas. The motor in GTT-3 (10% of the total capacity of the drive), steam turbine (8%) GTT-12 project designed to run machine units, but in fact are constantly exploited as an additional drive.

The source of information

1. "The production of nitric acid in aggregates of large capacity". / Edited Olevsky V.M., M.: Chemistry, 1985, p.94-306.

2. Directory of apothica, M.: Chemistry, 1987, p.66-92.

Widely known for the installation of Western firms built on the basis of the schemes without the use of energy natural gas combustion. Accordingly, the drive machine units includes a gas turbine for energy recovery tail gas, heated to 300-500°With the warmth of nitrous gases by oxidation of ammonia, and the trailing engine - steam turbine or electric motor.

Performance installations for the production of nitric acid can be reduced during operation due to wear of machine units, and for technical reasons (for example, by reducing the degree of conversion of ammonia, wear heat-exchange equipment).

But the main reason for the poor performance of plants is always reduced the s air flow air compressor due to wear, pollution flowing part, reducing the number of turns. This refers to the machine units of any type, but in different degrees. Machine units, which ensures the constancy of the speed of the compressors (air and nitrous) at the expense of the electric motor great power more stable. Less stable machine with a steam turbine as the closing of the engine due to the lower speed when worn. The greatest instability different machine units with gas turbine drive, for example GTT-3 and GTT-12, in which the wear of the air compressor is added relatively fast, with the loss of efficiency, wear high-temperature gas turbines. It is particularly sensitive to the loss of efficiency of gas turbines gas turbine machine type GTT-12 in Assembly AK-72 with a low-powered steam turbine due to the fall speed of the air and nitrous compressor, which in addition to reducing the air flow, i.e. the plant productivity leads to a significant reduction of pressure in the absorption of nitrogen oxides and, consequently, reduce the effectiveness of the absorption column.

In installations of the type UKL-7 with the machine GTT-3, which supports a constant speed by an electric motor, wear an air compressor and gas turbine leads to decreased production HNO3not only because of the direct reduction of the feed in the spirit, but because of the need to increase the proportion of compressed air directed past the technology of the gas turbine.

The technical problem to be solved by the present invention is directed, is to achieve a substantial increase in productivity plants nitric acid is not less than 8-15% (depending on the type of units) without expensive upgrades or replacement of engine units on existing process equipment by simultaneously increase the air flow and pressure. The invention can be used in the construction of new plants, but its main purpose is to intensify existing units type UKL-7 and AK-72 gas turbine engine assemblies.

The essence of the invention is to provide a positive air pressure at the inlet of the air compressor machine unit (instead of vacuum) by pre-compression of air in the high-pressure fan and cooling by direct contact with water.

The novelty of the method according to the invention lies in the creation of excess pressure at the inlet of the air compressor and the air temperature decreases after the preliminary compression in the high-pressure fan direct contact of air with the water.

According to the present invention the pressure on the inlet air is tion of the compressor is limited by admissible pressure in the apparatus installation nitric acid, which intensifies. Ceteris paribus (the speed of the shaft of the compressor, the air temperature at the inlet, polytropic efficiency, etc.) air pressure after compression is approximately directly proportional to the density of air at the inlet. Technological equipment is usually calculated on the maximum air pressure that can be achieved in air compressor in the cold season, when the density of air at the inlet of the maximum.

The standard conditions for the calculation of machine units type GTT-3 and GTT-12 in terms of suction air compressor:

- nominal temperature +20°C

- in winter - 5°C (including heating at a lower temperature to prevent icing of the guide vane),

- barometric pressure of 745 mm Hg (99,3 kPa),

the vacuum in the suction pipe 500 mm VST (0,49 kPa), i.e. the absolute pressure at the inlet 98,81 kPa.

This means that in winter the maximum air density, and hence the maximum rated air pressure (273+20)/(273-5)=1,0932 times higher than the nominal. Accordingly, the allowable absolute pressure in the suction pipe at a nominal temperature of +20°will be 98,81×1,0932=108,02 kPa, which is achieved by pre-compression of air at 11-11,5 kPa. Accordingly, the performance of an air compressor due to the factor air density Mack the distribution panel is minimal can be increased by (108,02-98.81)× 100/98,81=9.3 per cent. For machine units with gas turbine drive type GTT-12, the speed of which depends on the wear of the drive, the performance of the air compressor increases to a greater extent. This is because the compression of air and the specific energy consumption in air compressor does not depend on the air density, while the energy output in a gas turbine is increased by increasing the degree of expansion, which leads to an increase in the number of revolutions. Table 1 presents the results of computational studies of the current machine GTT-12 in one of the installations AK-72 after many years of operation with the use of actual indicators of air flow, the number of revolutions of the shaft of the air compressor and nitrous supercharger, the pressure and temperature of gases in the system path.

When installing the high pressure fan pressure 11-11,5 kPa at the inlet of the air compressor creates overpressure 0.09 kgf/cm2above the original.

On the basis of such excess pressure, the calculations (table 1) different modes of increasing the air supply of the existing GTT-12. The original mode, option 0, reflects the actual performance to intensify. They served as baseline data for the program computational study of the effect of the pressure at the inlet of the air compressor. Var is the ants 1-5 apply to the GTT-12 to repair nitrous supercharger, 6-7 - after repair.

As can be seen from the calculation results, after increasing the pressure on the suction intensification (air supply) is 12% without changing the power consumption from steam drive (option # 3), and after repair No. 4 (with reduction of steam consumption in back-pressure steam turbine from 41 to 24 t/h (option # 6), the pressure at the stage of oxidation of ammonia increased from 3.9 to 4,51-4.47 kgf/cm2at the stage of absorption from 9.2 to 10,42 and 10,38 kgf/cm2i.e. on - 1,2 bar; shaft rpm OK > > > 4860 up to 4960 rpm.

The pressure increase at the stage of oxidation of ammonia by 15%at the stage of absorption by 13% allows intensification on the same manufacturing equipment.

In mode No. 8 with no reduction in load of the steam turbine can be obtained increases the production of nitric acid ˜19%.

Abbreviations in table 1:

OK - axial air compressor;

NN - nitrous supercharger;

TVD - high pressure turbine.

For installations UKL-7 gas turbine engine Assembly type GTT-3 the ratio between the increase in air pressure at the inlet of the air compressor and increase production of nitric acid retains its disproportionate, but to a lesser extent due to the constancy of the speed provided by the motor.

Table 2 shows the results of calculation of the s research machines GTT-3 in the installation of nitric acid UKL-7 under uniform pressure on the stages of the oxidation of ammonia and absorption.

The original mode, version 0.1, reflects the actual performance to the intensification of the machine GTT-3M working in the installation of UKL-7 in the region with a temperate climate and a barometric pressure of 745 mm Hg

Version 1.1 - mode after intensification with the installation of the fan to pre-compress the air to 11-11,5 kPa and a load of the motor (motorgenerator PHASE-800) with low power consumption.

Options 0.2, 1.2 job related GTT-3M in the region with a hot climate in summer (up to 35°C) and low barometric pressure (Central Asia, Caucasus).

Computational studies were conducted on the basis of the performance of existing machines in the installations.

Baseline to install 1 in temperate climates correspond to develop 14 t/h MNG. HNO3for installation 2 in the Central Asia development 12 t/h MNG. HNO3.

After the intensification under other equal conditions for the installation of 1 production is increased to 15.3 t/h (˜9,0%), in units of 2 to 13.8 t/h (˜15,0%).

Abbreviations in table 2:

OS - axial compressor;

TSN - centrifugal supercharger air compressor;

GT - gas turbine;

PHASE-800 - reversible motor comprising GTT-3M (M - upgraded).

Pre-compression of air to 11-11,5 kPa in the fan increases its temperature at 10-12�B0; With that somewhat offsets the increase in its density. The air must be cooled to a reference temperature +20°C. the known method of cooling through the wall will need a refrigerant with a temperature of +5°C.

To remove the heating of the air during compression is required to take 12500-18700 kcal per 1 t HNO3that is equivalent to the evaporation 42-60 kg of liquid ammonia.

The power consumption for the refrigeration potential of +5°in modern ammonia-refrigerating machines will be at least 5-6 kWh per 1 ton of HNO3.

Significant capital costs for construction of the ammonia refrigeration plant and air cooler, while cooling air is required 5-8 months of the year.

Therefore, according to the present invention, the cooling air produced by direct contact with water, i.e. evaporative cooling.

For removal 12500-18700 kcal required to vaporize 21,7-26 kg of water per 1 ton of HNO3(for installations AK-72 at the intensification of 12% - ˜1215 kg/h, for UKL-7 at the intensification of 9% - ˜420 kg/h).

When evaporative cooling is the degree of cooling affects the relative humidity of the atmospheric air.

As the calculations show, for air with an initial temperature of +20°and when the initial relative humidity <65% evaporative cooling can cool the air before initial replication of the th temperature +20° C, at a relative humidity of 70% to 21°C, at a relative humidity of 90% to 23°C.

But in those days than cooling through the wall of the contact cooling is not lost. Niedokladnie air 1-3°With contact cooling is compensated by a lower hydraulic losses due to the exclusion of the heat exchanger.

Contact cooling water is especially effective from the point of view of energy consumption, if it is carried out by injection of water through the nozzle with a fine spray on the suction side of the fan, when the compression process in the fan approaching isothermal.

In certain cases, for example when operating plants in hot and dry climates (a significant part of Russia, Central Asia), can be used for pre-cooling the air in the scrubber, as in these areas during the hot season, the air has a low relative humidity, but are often contaminated with dust from dust storms. When you install a scrubber to fan air temperature decreases at the inlet, the water spray drift and evaporation in fan during compression of the air contributes to a decrease in air temperature at the inlet of the air compressor, and reduces the energy consumption for air compression.

Contact cooling slightly increases the water vapor content in the air, but the e is more of 0.4-0.5% by volume.

Consequently, compared with the cooling of the compressed air through the wall of the reduced performance of the air compressor by 0.45%, and the heat load of the condenser on nitrous gases is increased by 2%.

These negative side contact of the cooling air is negligible compared with the benefits in relation to cooling through the wall, especially since the cooling air is required only in the warmer months (when the air temperature is +10°it may not be).

The implementation of the invention may be illustrated by examples 1 and 2.

Example 1, figure 1. Intensification of units of type AK-72 and UKL-7.

The newly installed fan 1 performance 230-240 thousand nm3/h - 15-20% above nominal performance air compressor GTT-12; pressure fan 11-11,5 kPa.

On the suction side of the fan through a nozzle 2 is supplied 1-1,25 m3/h steam condensate or demineralized water.

At ambient temperature +20°C, relative humidity of 60-65% and the heat of compression evaporation of water temperature on the discharge of the fan is maintained at +20°C and the relative humidity increases to 90-95%.

At a relative humidity of atmospheric air 90% of the water injection is maintained approximately at the same level, temperature satoh the air after evaporation of the water until full saturation is stabilized at the level of ˜ 23°C.

When ambient temperature is below 10°With modulated water in the fan may be terminated.

In the cold season air is heated by compression in the fan allows for a long period, don't waste steam to heat the air in the heater installed at the entrance to the filter 3 before the air compressor installation.

Periodically, the injection of demineralized water for a short time for washing is increased to prevent salt deposits in the flowing part of the fan with the diversion of water from a fan in the drainage.

With the intensification of plants UKL-7 principal differences from the invention in comparison with described there. Accordingly, a set of high-pressure fan performance 88-90 nm3/h of air and the pressure of 11-12 kPa.

Example 2, figure 2.

In regions with hot climates and/or high dust air on the suction side of the fan 1 is set to the coarse filter air 3 and the washing scrubber 2 circulation of demineralized water by means of a pump 4.

When the contact of air with the water mass transfer nozzle scrubber 2 is the saturation of air with water vapor. The saturation process occurs with varying degrees of cooling air, depending on the relative humidity.

At a relative humidity of 40-50% and so is the ambient air temperature value +30° Since the air is cooled to a temperature close to the temperature of the wet thermometer", in this case up to 22°C.

When the compression of the air with regard to cooling by evaporation is carried out with air drops and additionally injected water at the outlet of the fan 1 temperature ˜25°and will have a moisture content close to full saturation. Through the scrubber 2 to install the AK-72 passes ˜220 thousand nm3/h air, in the installation of UKL-7 - 90 thousand nm3/h, in the scrubber enter fresh water in a quantity equal to the amount of evaporated water and bred in the form of drainage of collected dust.

In the scrubber should not be britholite; if the ash water spray is insufficient to remove the heat of compression air their evaporation, the fan is supplied through nozzles additional water.

The examples and drawings to them illustrate the application of the method how to install AK-72 and UKL-7 that does not exhaust the scope of the invention. It can be used for any plants nitric acid production.

Among the most important advantages, providing significant economic benefits in the process, include:

- low capital gains power;

- short time-to-market, and without stopping the current installation;

- by intensification increases the pressure in the system is IU, that allows it to implement in existing process equipment without lowering the concentration of nitric acid and deterioration of discharge of harmful substances into the atmosphere from the tail gases;

- reduced the cost of production.

Literature

1. The production of nitric acid in the units of large capacity, edited by V.M. Olevsky. M.: Chemistry, 1985, p.94-306.

2. Directory of apothica, vol. 2. M.: Chemistry, 1987, p.66-92.

Table 1

Table of results of computational studies of the modes of operation of the existing GTT-12
Options012345678
Atmospheric pressurekg/cm21.001.001.001.001.001.001.001.001.00
The pressure behind the fankg/cm21.001.091.091.091.091.091.091.091.09
Press OKkg/cm23.904.234.32 4.514.554.604.474.524.57
Pressure before LVkg/cm23.403.693.733.953.973.983.923.943.95
The pressure for low-voltagekg/cm29.209.8910.3810.4210.7011.0710.3810.6611.04
The gas pressure before TVDkg/cm28.408.959.389.439.6810.019.409.659.99
The rotor speed OKrpm486049305050496050355 130496050405 130
The rotor speed NNrpm488048405000483049005000480048704970
Stability margin OK%18.818.423.917.820.9 25.218.621.826.2
Stability margin NN%44.742.546.242.343.746.043.344.847.2
Temperature atmospheres. air°202020202020202020
The temperature of the air before OK°203030202020202020
The air temperature at the exit OK°187201205196198200195197200
The temperature of the air before LV°656570707070707070
The air temperature at the outlet LV°215213226217221227207210216
The temperature of the gas before the turbine°745745745745745745745745745
The temperature of the gas turbine°391385380380377374380377373
The steam flow to the turbinet/h1.01.01.01.51.51.51.01.01.0
The power of the steam turbinekW17001700240017002050255095012501700
The total steam consumptiont/h414157424961243041
The air flow before OKt/h254.0270.7283.7284.5Compared with RUB 292.1302.1284.5292.2302.5
Performance%- 6.611.712.015.018.912.015.119.1

Table 2

Table of results of computational studies of the modes of operation of the existing GTT-3 in UKL-7
№ p/pIndicatorsUnit.Options
0.11.10.21.2
1Barometric air pressurekPa99,399,396,696,6
2Air pressurekPa
2.1for inflatable fan-110,0-to 106.0
2.2- suction OK9510592102
2.3- discharge TSN716780680745
2.4before GT560609540580
3Temperature°
3.1- air suction OK20203025
3.2- the tail gas before GT680680690690
4The rotor speedrpm5100510051005100
5Air consumptiont/h
5.1before OK100108,485,397,2
5.2- technology7278,561,5770,8
6The natural gas consumptionmetro3/h1680180015001725
7Power consumptionkWh
7.1- fan-400-370
7.2- PHASE-800350150400200
8The increase in production HNO3%-9-15

1. Method of intensification of installations for the production of nitric acid, including compressed air in the air compressor, the stage of oxidation of ammonia by oxygen and absorption of oxides of nitrogen under pressure, the recovery of energy from the hot tail gas in a gas turbine, wherein the inlet of the air compressor creates excessive pressure pre-compression of atmospheric air in the high-pressure fan, and in the warm season warm compression assign direct contact of air with the water.

2. The method according to claim 1, characterized in that the air is cooled during the compression process by the injection of water through a nozzle at the inlet of the fan.

3. The method according to claim 1, characterized in that the air is cooled in the scrubber when in contact with water, mixing the cooling air with the preliminary cleaning of dust and chemical contaminants.

4. The method according to claim 1, characterized in that the absorption of oxides of nitrogen is carried out under the same pressure as the oxidation of ammonia, or a higher pressure.



 

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8 cl, 1 tbl, 5 ex

FIELD: chemical industry; production of nitric acid.

SUBSTANCE: the invention is dealt with production of nitric acid with the help of oxidation of ammonia by oxygen of the air and absorption of nitrogen oxides by water in installations with uniform pressure at the stages of oxidation of ammonia and absorption of nitrogen oxides. The method of production of nitric acid in the installations with uniform pressure at the stages of oxidation of ammonia and absorption of nitrogen oxides provides, that compression of the air up to a uniform terminal pressure is conducted continuously within one stage without intermediate cooling and after that the compressed and so heated air is divided into two streams, one of which intended for production of nitric acid is directed to be cooled with further mixing with ammonia, and another is fed directly into a fuel combustion chamber connected with a recuperation turbine. The design embodiment of the installation for production of nitric acid provides for usage in the gas-turbine plant as an air engine for compression of air of an axial-flow compressor mounted directly on a common shaft with the recuperation turbine, at which near the outlet of the air engine the line of a compressed air stream is divided into two parts, one of which intended for production of nitric acid is first connected with a compressed air cooler and then with a mixer of ammonia with air, and the second intended for incineration of fuel is directly connected with the recuperation turbine combustion chamber. Besides in the capacity of a the compressed air cooler they use a "boiling" economizer connected to a line of a feed water for a boiler-utilizer and with a vapor collector of the boiler-utilizer by a line of steam-and-water mixture. The line of the air intended for production of nitric acid is also connected through the reheater of ammonia with a nitric acid blowing column. The technical result is simplification of the method, decreased investments and specific consumption of fuel.

EFFECT: the invention ensures simplification of the method, decreased investments and specific consumption of fuel.

4 cl, 1 dwg

The invention relates to a device and method of removal of N2About during the manufacture of nitric acid

The invention relates to a catalyst and process for the oxidation of ammonia in the production of weak nitric acid

The invention relates to the production of nitrous oxide by oxidation of ammonia with oxygen or oxygen-containing gas

The invention relates to processes of high-temperature catalytic conversion of ammonia in a two-stage catalytic system in the production of nitric acid

The invention relates to a method of heat recovery nitrous and tail gas emissions in installations for the production of nitric acid

FIELD: chemical industry; production of nitric acid.

SUBSTANCE: the invention is dealt with production of nitric acid with the help of oxidation of ammonia by oxygen of the air and absorption of nitrogen oxides by water in installations with uniform pressure at the stages of oxidation of ammonia and absorption of nitrogen oxides. The method of production of nitric acid in the installations with uniform pressure at the stages of oxidation of ammonia and absorption of nitrogen oxides provides, that compression of the air up to a uniform terminal pressure is conducted continuously within one stage without intermediate cooling and after that the compressed and so heated air is divided into two streams, one of which intended for production of nitric acid is directed to be cooled with further mixing with ammonia, and another is fed directly into a fuel combustion chamber connected with a recuperation turbine. The design embodiment of the installation for production of nitric acid provides for usage in the gas-turbine plant as an air engine for compression of air of an axial-flow compressor mounted directly on a common shaft with the recuperation turbine, at which near the outlet of the air engine the line of a compressed air stream is divided into two parts, one of which intended for production of nitric acid is first connected with a compressed air cooler and then with a mixer of ammonia with air, and the second intended for incineration of fuel is directly connected with the recuperation turbine combustion chamber. Besides in the capacity of a the compressed air cooler they use a "boiling" economizer connected to a line of a feed water for a boiler-utilizer and with a vapor collector of the boiler-utilizer by a line of steam-and-water mixture. The line of the air intended for production of nitric acid is also connected through the reheater of ammonia with a nitric acid blowing column. The technical result is simplification of the method, decreased investments and specific consumption of fuel.

EFFECT: the invention ensures simplification of the method, decreased investments and specific consumption of fuel.

4 cl, 1 dwg

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