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Environmental Impact of Chemical Industry
Air Pollutants
(Sulfuric Acid Production )
Submitted to
Pr.D.Abdel zaher abouzeid
By
Farouk Mohamed
Faculty Of Engineering
Cairo university
Mining Department
Abstract :
The aim of this report is to show the great danger of air
pollutants in general with a special focus in Sulphuric acid
Production ,the report discuss the Impact of Sulphur emission
in the air and the health of people and the widely used way to
control the emission wet scrubber method , with an example
of Sulphur based emission in greater Cairo .
1.Introduction :
Chemical industry is recognized as one of the most powerful sources of
environmental pollution. Since all of the chemical manufacturing processes use
raw materials and consumables from each component of environment, it is clear
that damages resulting from the activities in chemical industry are not due to the
very industrial processes only, but because to exhaustion of natural resources
too. In the 20th century oil, coal, minerals, wood, etc. have been extracted at
extremely high rates, thus affecting the ecological balance in the nature and
damaging the landscape. The primary effect of chemical industry on environment
and on the lifestyle as well, is due to the pollution, arising from the industrial
activities, resulting in gas emissions, wastewater polluting the natural ponds and
underground water, solid and slurry waste, polluting the soil and underground
water, if not treated. However, even the complete control of emissions yields
additional pollution as waste to be treated or disposed. Moreover, since any
industry requires energy supply for mechanical processes, heating and electricity,
chemical industry indirectly charges the environment with emissions of sulfur
dioxide, nitrogen oxides and particulate due to energy production in heat power
stations. Production of oil and coal used as fuels and raw materials in chemical
industry also charge the environment by destroying fertile land due to mining
activities and oil extraction. (Beschkov, 2009)
The extension of chemical industry in the 20th century throughout the world lead
to dangerous trends: acid rains, greenhouse effect, ozone layer depletion, global
climate changes, exhaustion of fresh water, damaging fertile lands, etc.
It was clear, therefore, that global solutions have to be found to restrict the
adverse impact of industry on environment and to restore nature’s conditions as
far as it is possible.
A well defined approach is focused on environmentally sustainable industrial
development (ESID), considered in the development programs of the United
Nations and being the basic concept in the document approved at the Earth
Summit in Rio-de-Janeiro, 1992.
For chemical industry this approach is associated with pollution prevention as a
first step, saving of raw materials and energy, whenever possible and introduction
of clean technologies to avoid impacts on environment with pollution and
treatment facilities. Other options are to adjust manufacturing in a way to
generate less waste or those compatible with the self-regenerating capabilities of
environment. (Beschkov, 2009)
2.Sulfuric Acid:
Sulfuric acid is one of the basic chemicals with extremely large scale of annual
production throughout the world. Its applications cover different areas of human
activity, starting with fertilizers and ending with explosives. It is applied mainly in
chemical industry as acid, dehydrating and sulfonating reagent. Its annual
production per capita is an indicator for the industrialization level of a certain
country. For example, its annual production in the developed countries is
between 50 and 200 kg/capita, whereas for the developing countries these
figures are below 5 kg/capita. During the last decades its world production is large
enough to maintain its low prices. However, its production is associated with a
severe pollution of the environment, therefore deserving special attention.
(Beschkov, 2009)
Sulfuric acid is a compound that is often found in acid rain which forms when
atmospheric oxidization of sulfur dioxide occurs in the presence of water. Sulfur
dioxide exists in the atmosphere as a byproduct of the burning of sulfur
containing fuels, such as coal and oil. Sulfuric acid also forms through the
oxidization of sulfide-based minerals, like iron sulfide. The water by-product of
this process is highly acidic and is called acid mine drainage. This stream is so
acidic, it is capable of dissolving metals that are present in metal ores. The result
of this is brightly colored, highly toxic streams of water. (CLARK, 2019)
2.1 Manufacturing of Sulfuric Acid:
Step 1:
The Sulphur obtained from any kind of source is burned to form Sulphur dioxide
gas. Care is to be taken in this step so that the air supplied for combustion process
is dry. Any traces of water present will result in the formation of acid and cause
corrosion within the combustion equipment. Also if the Sulphur contains
carbonaceous impurities then it has to be filtered. If the gas is not filtered for the
impurities then they will be carried over through the equipment’s and if they
reach catalysts then they will tend to deactivate it. The oxidation of Sulphur to
Sulphur dioxide is a highly irreversible process. (world, 2018)
Step2
he catalyst used for the catalytic oxidation of Sulphur dioxide to Sulphur trioxide
is Vanadium Pentoxide. Before sending the Sulphur dioxide to the reactor the gas
is pretreated to remove any impurities if present by Wet Scrubbing and if there
are any fine particles present then the gas is passed through electrostatic
precipitator. The oxidation of Sulphur dioxide to Sulphur trioxide is a reversible
process. The pressure is maintained at 1.2-1.5 atm and temperature at 410-430°C.
If the temperature rises above 430°C then the equilibrium is displaced away from
Sulphur Trioxide, hence it is very important that operating temperature should be
maintained in this range. Commonly the catalytic reactor is designed as a four
stage bed reactor. When the gas is passed to one catalyst bed it’s temperature
rises from the range of 410-430°C to about 600°C hence after each stage the gas
has to be cooled to the optimum temperature again before passing it to the next
stage. (world, 2018)
Step 3:
The Sulphur trioxide is hydrated by absorption in a packed tower which is filled
with Sulphur Acid of a specific range. This specific range is 98-99%. If this
concentration happens to be on lower side then Sulphur trioxide is not properly
absorbed and forms a troublesome mist. If the concentration happens to be on
the higher side then vapors become very significant inside the tower. Hence it is
important to maintain a good operation concentration. The resulting acid
strength can be adjusted by controlling the flow rates of Sulphur trioxide and
water. The resulting acid strength can be varied from 91 to about 100% Sulphur
acid.
2.2 .Market volume of sulfuric acid worldwide from 2015 to
2020, with a forecast for 2021 to 2026(in million metric tons)
2.3 Impact Of Sulfuric Acid
The biggest risk associated with sulfuric acid is its high level of corrosiveness.
These corrosive properties are greatly accentuated by the fact that sulfuric acid is
highly exothermic which means it is reactive with water. Because of this, burns
from sulfuric acid are generally considered extremely dangerous due to the
dehydrating properties of this acid. Capable of dissolving paper, metal, some
stones, and skin, sulfuric acid must be handled with extreme care. On top of being
so corrosive, it is slippery in nature. Spills on roads have been known to cause
accidents and dangerous conditions.
At high concentrations, aerosol sulfuric acid causes severe damage to the open
membranes, such as the eyes and nose. It can also cause blistering, tissue
damage, and extreme respiratory tract irritation. Exposure can cause headaches,
nausea, and vomiting. Extended exposure can cause damage to the teeth, skin,
organs, and lungs. If ingested, this acid is especially dangerous, as it causes
irreversible burns, organ damage, and even death. Acid mists containing sulfuric
acid are considered highly carcinogenic and have been linked to cancers of the
throat and lungs.
Much of the sulfuric acid in the air is formed from sulfur dioxide released when
coal, oil, and gas are burned. The released sulfur dioxide slowly forms sulfur
trioxide, which reacts with water in the air to form sulfuric acid. Sulfuric acid
dissolves in the water in air and can remain suspended for varying periods of
time; it is removed from the air as rain. Sulfuric acid in rain contributes to the
formation of acid rain. Sulfuric acid in water separates to form hydrogen ions and
sulfate. The ability of sulfuric acid to change the acidity (pH) of water is
dependent on the amount of sulfuric acid and the ability of other substances in
the water to neutralize the hydrogen ions (buffering capacity). (disease, 1998)
2.4 Sulfuric Acid Pollution control (Wet Scrubber System)
The most widely used method of abatement for streams containing sulfuric acid is
a wet scrubber. A wet scrubber is a type of pollution control equipment that is
designed to remove harmful gases and particulates from industrial exhaust
streams. It works by funneling the sulfuric acid through the bottom of a packed
tower and then it passes through an engineered packing, where a solution from
specialized nozzles is sprayed countercurrent to the exhaust stream flow.
Because sulfuric acid is very corrosive, specially designed materials must be used
to build the scrubber. Stainless steel alloy is the most commonly used material,
however there are other very good options. Fiber reinforced plastic,
polypropylene, or Polytetrafluoroethylene (PTFE) fiberglass reinforced plastic
(FRP) are commonly used.
When the waste gas has lower solubility, chemicals are usually added to the
solution. These chemicals are carefully chosen to react with the sulfuric acid
released in the exhaust stream. After the sulfuric acid is treated, the stream is
released, clear of the dangerous sulfuric acid and other targeted chemicals and /
or particles. Although it is clear of dangerous compounds, the gas released from
the scrubber often looks like steam. (CLARK, 2019)
wet scrubber
3.Greater Cairo case :
Greater Cairo is the largest urban area in Egypt. it consisting of Cairo governorate,
Giza city, 6th of October City, Shubra El-Kheima and Obour City. Its population
density is 13107 people/km2.19,20 The rapid urban growth and highly population
density has created overcrowded streets, which contain high density of vehicles.
Increase in vehicles density leads to increased ambient air pollution. Moreover,
urban growth leads to increase industrial activities. Because of high density of
vehicles and industrial activities in Greater Cairo, which are used by fossil fuels,
emissions levels of PM (PM10 and PM2.5) and SO2 are increased. Since 1999, The
Black Cloud phenomenon has appeared during October and November months
each year. This phenomenon is due to open burning of rice straw in the
temperature inversion months leads to environmental and health problems.21
Between the period 2010 - 2020, the numbers of children suffering from hospital
admission respiratory diseases are increased and the number of people suffering
from cardiovascular disease and chronic pulmonary are increased.22 High
concentration levels of PM (PM10 and PM2.5) and SO2 could be occur due to
poor ventilation in urban areas and low dispersion of ambient pollutant due to
bulky building blocks and narrow streets.23 Petkova et al.24 mentioned that PM
levels in Greater Cairo, Egypt were increased than the guidelines by several times.
They were attributed high levels of PM to desert areas surrounding Cairo, large
numbers of vehicles, industrial activities and Khamasin storms during spring and
fall. Mostafa & Zakey25 founded that the annual PM2.5 and PM10 levels at 17
sites during 2001 - 2002 were 85 and 170 g/m3, respectively. Wheida et al.26
reported that the temporal and spatial variability of PM10 concentrations during
2000-2004 and 2010-2015 at 18 stations in Greater Cairo. They found that the
areas with low pollution levels were El-Abbasseya, Nasr City, and New Cairo, while
areas with high pollution levels were El-Maasra, El-Maadi, El-Kolaly, and Abo-
Zabaal. Pollutants are the major factors in disease of humans. PM and SO2 are
penetrate the respiratory system via inhalation, causing hospital admision
respiratory and cardiovascular diseases, central nervous system dysfunctions and
finally cancer.27,28 In developing countries like Egypt, pollution is serious
because high population density and uncontrolled industrialization and
urbanization.29 SO2 is a harmful gas, which emitted mainly from combustion of
fossil fuel.27 It affects human, plant and animal life. The mainly health problems
of exposure to sulfur dioxide emissions are respiratory diseases, bronchitis and
broncho-spasm, where SO2 is irritant and penetrates deep into the lung causing
broncho-constriction. Moreover, it damage to the eyes and cause cardiovascular
disease. (Atef MF Mohammed, August 31, 2020)
3.1 Egyptian Laws, Regulations and Policies for controlling emission :
The government of Egypt has various laws and regulations related to the
environment. Egyptian Environmental Affairs Agency (EEAA) was established by
presidential Decree No. 631/1982. The first modern and comprehensive law
regulating the protection of the land, air and water environment from pollution in
Egypt was law No. 4/1994. Some articles of Law No. 4/1994 were improved by
Laws No. 9/2009 and 105/2015, and its Executive Regulations improved by Prime
Minster Decrees No. 1095/2011, 710/2012, 964/2015, and 75/2017, which
commonly known as the Environmental Protection Law.
3.2 Role of Egyptian government to improve ambient air quality:
The Egyptian government is interested by reducing environmental impacts from
ambient air pollution. The government was invested in infrastructure such as
highways, bridges and ring roads around the Greater Cairo to decrease traffic
density. Also, the Egyptian government was established eight towns to decrease
population density in Greater Cairo. The government was facilitating natural gas
to use as the main fuel source in houses, industrial, power plants and transport
sectors. Additionally, The government has been encouraged private cars and taxis
to switch to natural gas as fuel. The Second Egypt Pollution Abatement Project
(EPAP II) with the European Investment Bank (EIB), the Agency Française de
Development (AFD), the World Bank and the Japan International Cooperation
Agency (JICA) to achieve environmental subjection with the Egyptian
environmental law. The Egyptian environmental protection Law #4 of 1994 was
improved (by Law #9 of 2009), which forbid waste burning. EEAA has established
continuous 24-hour monitoring for stacks emission in the cement industry. Also,
regional EEAA offices are carrying out inspection monitoring in factories in
Greater Cairo, Noncompliant factories are fined.
3.3 Sampling and analysis:
The methods of monitoring process in the national Network are as follows: The
first method: through instantaneous automatic devices operated 24h/7day,
where the data records and Statistical calculations done on hourly and daily basis.
The second method: carried out through semi-automatic sampling devices
(collection on filters), later these samples are analyzed in chemical laboratory to
evaluate concentration level.
SUMMARY :
Aire pollutants are very danger on the environment and can
lead to serious environmental problem which can Impact the
health of people and the plant and water pollution ,its very
important to control and prevent this emission as possible as
we can ,many technology are available to prevent emission of
sulfur based pollutant in the air such as wet scrubber
technology .
Uses of this technology should be forced by the government
by law to prevent the air pollution and preserve environment
And preserve the health of population
References
Atef MF Mohammed, I. A. ( August 31, 2020). A review of sulfur dioxide and particulate matter (PM2.5
and PM10) in greater Cairo, Egypt. International Journal of Biosensors & Bioelectronics.
Beschkov, V. o. (2009). CONTROL OF POLLUTION IN THE CHEMICAL INDUSTRY. In V. Beschkov,
POLLUTION CONTROL TECHNOLOGIES.
CLARK, C. (2019, 2 19). Golf Coast Environmantal System. Retrieved from Golf Coast Environmantal
System: http://www.gcesystems.com/sulfuric-acid/
disease, A. f. (1998). Public health statement sulfur trioxide and sulfiric acid . Agency for toxic substances
and disease.
Fernández, L. (2019). statica . Retrieved from statica :
https://www.statista.com/statistics/1245226/sulfuric-acid-market-volume-worldwide/
world, c. e. (2018). chemical engineering world. Retrieved from chemical engineering world:
https://chemicalengineeringworld.com/sulphuric-acid-manufacturing-process/