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EMISSIONS OF CO2 AND TOXIC GASES FROM POWER PLANTS AND THEIR
IMPACT ON THE ENVIRONMENT Rakhmonov I.U.1, Usmanaliev S.U.2, Latipov S.T.3
1Rakhmonov Ikromjon Usmonovich - DSc, Professor,
TASHKENT STATE TECHNICAL UNIVERSITY, 2Usmanaliev Sarvar Umarvoy ugli- leading specialist, "THERMAL POWER PLANTS "JOINT-STOCK COMPANY,
TASHKENT, REPUBLIC OF UZBEKISTAN 3Latipov Saidmurod Tuygunovich- PhD, Associate Professor, KARAKALPAK STATE UNIVERSITY, NUKUS, REPUBLIC OF KARAKALPAKSTAN
Abstract this article, the principles of how and where CO2 and toxic gases are generated in thermal power plants are illustrated through diagrams, with a detailed discussion on methods to achieve emissions reduction of CO2 and toxic gases. Additionally, the impact of each pollutant gas on living organisms and the environment is thoroughly presented through their characteristics. The article concludes with information on implementing renewable energy sources to reduce the impact of CO2 on the environment.
Keywords: thermal power plants, greenhouse gas emissions, Net-zero emissions, Fuels, Forecast, Atmosphere, Methods, Carbon neutrality, Renewable energy sources, Pollutants, Nitrogen oxides, Nitrogen dioxide, Sulfur dioxide, Carbon monoxide, Dust, Ammonia, Ozone, PM10, PM2.5, harmful gases.
According to the International Energy Agency (IEA), in 2022, global CO2 emissions related to energy increased by 0.9% or 321 Mt, reaching a new record high of over 36.8 Gt. Currently, oil and gas operations account for nearly 15% of global energy-related emissions, equivalent to 5.1 billion tons of greenhouse gas emissions. In the IEA's scenario for achieving net-zero emissions by 2050, the emission intensity of these activities is expected to decrease by 50% by the end of the decade. Along with a reduction in oil and gas consumption, this will lead to a 60% decrease in emissions from oil and gas operations by 2030.
Fig. 1. Forecast of fuel emissions.
When analyzing the composition of CO2 emissions by sources from 1990 to 2021, it can be noted that 79.1% of all emissions come from gas, while 9.7% from oil, 6.6% from coal, and 4.6% from the combustion of other gases, resulting in CO2 emissions being released into the atmosphere (Figure 2).
CO2 emissions by source during 1990-2021 (billion tons)
Fig. 2. Volume of CO2 emissions by source.
Considering the change dynamics from 2010 to 2021, it can be noted that CO2 emissions have increased from all sources. The largest increase was recorded for gas, rising from 85.2 million tons in 2010 to 96.2 million tons in 2021. For coal, emissions increased from 5.2 million tons to 8.1 million tons, while cement emissions rose from 2.9 million tons to 4.7 million tons. It is worth noting that the smallest increase (0.9 million tons) was observed for oil, which grew from 10.9 million tons in 2010 to 11.8 million tons in 2021[1,2].
Currently, there are three main methods to achieve carbon neutrality:
1. Directly reducing emissions and transitioning to renewable energy sources - hydropower, solar energy, wind
energy;
2. Capturing CO2 from the air;
3. Compensating by investing in projects that reduce carbon emissions.
In thermal power plants, the concentration of major pollutants measured at stationary monitoring points includes nitrogen oxides (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), suspended particles (dust), as well as ammonia (NH3) and ozone (O3).
Nitric oxide (NO) is a colorless, odorless, highly reactive gas that is harmless to humans on its own, classified as a risk level 3. However, when sunlight warms the air, nitric oxide transforms into the more hazardous nitrogen dioxide (NO2) through photochemical oxidation .
NO + O2 = NO2
Nitrogen dioxide (NO2) is a reddish-brown gas that forms "fox tail," classified as a risk level 2 substance. Major anthropogenic sources include high-temperature combustion processes in thermal power plants, industrial facilities, and vehicle engines using various fuels (natural gas, coal, gasoline, diesel).
Nitrogen oxides play a crucial role in photochemical processes in the troposphere under the influence of solar radiation, often leading to the formation of photochemical smog, high concentrations of ozone and formaldehyde at the surface, and acid rain.
The effects of nitrogen oxides on humans can lead to dysfunction of the lungs and bronchi, increased sensitivity to respiratory infections, and asthma attacks. Children and adults with cardiovascular diseases are more susceptible to the effects of nitric oxide.
Sulfur dioxide (SO2) is a colorless gas with a distinctive sharp odor (the smell of burning sulfur), classified as a risk level 3 substance. Major sources include emissions from ferrous and non-ferrous metallurgy, as well as the production of ceramics, caprolactam, linoleum, roofing felt, glass, polystyrene, mineral fiber boards, food, textiles, and paper industries, as well as thermal power plants (TPPs, state power stations, and boilers).
At concentrations above the maximum permissible levels, the effects of sulfur dioxide can significantly increase the incidence of various respiratory diseases, affecting the mucous membranes and leading to inflammation of the nasopharynx, bronchitis, coughing, hoarseness, and throat pain. High sensitivity to sulfur dioxide is particularly observed in individuals with chronic respiratory conditions and asthma.
High concentrations of sulfur dioxide can cause serious harm to plants. Acute damage from sulfur dioxide manifests as white spots on broadleaf plants (especially spinach, lettuce, cotton, and alfalfa) and pine needles. The effect of SO2 on soil reduces its fertility due to acidification. Additionally, the presence of sulfur dioxide accelerates the corrosion of metals in the air.
Carbon monoxide (CO) is a colorless, odorless gas, also known as carbon oxide, classified as a risk level 4 substance. It is produced as a result of the incomplete combustion of fuels (coal, gas, oil) under conditions of oxygen deficiency and at low temperatures. Of all carbon monoxide emissions, 63% come from the energy sector, 21% from the metallurgy industry, 11% from the transportation system, and 5% from the construction industry. Extreme concentrations are often observed in areas with increasing anthropogenic loads: during peak traffic hours or under conditions that promote inversion, which hinders air circulation. When inhaled, carbon monoxide forms strong
complex compounds with hemoglobin in human blood, blocking the flow of oxygen. This can lead to headaches, nausea, and at high concentrations, it can be fatal.
Ammonia (NH3) is a colorless gas with a sharp, distinctive odor (the smell of ammonia), classified as a risk level 4 substance. It is produced during the decomposition of organic compounds containing nitrogen. Anhydrous ammonia gas is lighter than air and therefore rises, typically dispersing and not accumulating in low-lying areas. However, at high relative humidity, anhydrous ammonia can form heavier vapors that may accumulate at ground level or in depressions.
Approximately 80% of the ammonia produced industrially is used as fertilizer in agriculture. Ammonia is also utilized in refrigeration, the production of plastics, explosives, textiles, pesticides, paints, and other chemical products. It is present in many household and industrial cleaning solutions. Household products containing ammonia are produced with 5-10% ammonia, while industrial solutions may have concentrations as high as 25%, making them caustic.
Suspended particulate matter (dust) is a widespread air pollutant, consisting of a mixture of solid and liquid particles in suspension. Suspended particles include fine particles such as PM10 and PM2.5.
PM10 andPM2.5 are fine particles with diameters less than 10 microns (PM10) and 2.5 microns (PM2.5), which remain suspended in the air. They are generated from construction, manufacturing (especially cement, ceramics, brick production, etc.), road surface erosion, and the friction of brake pads and tires, as well as the combustion of solid fuels (coal, oil).
In large cities, PM2.5 particles are constantly present in the air, and people inevitably breathe them in. If more harmful particles enter the body than are expelled on a daily basis, they accumulate in the body. The main risk of PM2.5 is not the sharp changes in concentration, but the chronic exposure of these particles to the body. Symptoms of "poisoning" from PM2.5 can develop insidiously.
The average urban resident breathes in about 200 billion PM2. 5 particles each day, with half of them accumulating in the lungs. Such exposure can occur without severe immediate consequences; however, over time, PM2.5 levels in the body can exceed critical thresholds [3, 4].
This leads to an increased risk of respiratory and cardiovascular diseases, such as asthma, respiratory illnesses, and elevated mortality rates from cardiovascular issues, respiratory diseases, and cancer.
Today, the production of clean electrical energy, the reduction of carbon dioxide (CO2) emissions, and achieving zero emissions have become key issues for many countries, particularly in fulfilling the Paris Agreement. As a result, numerous scientific studies are being conducted in many countries to reduce CO2 emissions.
Uzbekistan has set a goal to rapidly develop renewable energy sources and transition to a carbon-free energy sector. According to adopted documents, by 2030, the country aims to reduce greenhouse gas emissions by 35% compared to 2010 levels, increase the installed capacity of renewable energy sources to 15 GW, and raise their share in total electricity generation to over 30%. Additionally, it plans to improve energy efficiency in industry by at least 20% [5].
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