Air Pollution Control Devices...

Air Pollution Control Devices Air pollution control devices (APCD) are a series of devices which are used to prevent a variety of different pollutants, both gaseous and solid, from entering the atmosphere mainly out of the industrial stacks. These control devices can be separated into two broad categories namely (i) devices which control the amount of particulate matter escaping into the environment, and (ii) devices which controls the acidic gas emissions into the atmosphere. By and large the air pollutants are generated due to the combustion of fuels in the furnaces. The major combustion-generated pollutants are the oxides of nitrogen (NOx), sulphur dioxide (SO2), carbon monoxide (CO), unburned hydrocarbons, and particulate matter. The generated pollutants are carried by the exhaust gases produced during the combustion of the fuel. These exhaust gases are then normally passed through the APCDs before releasing them to the atmosphere.  The pollutants are removed, destroyed, or transformed in the control devices before the discharge of the exhaust gas into the atmospheric air. Common methods for removing the pollutants from the exhaust gases work on the following principles. Destroying pollutants by thermal or catalytic combustion, such as by use of a flare stack, a high temperature incinerator, or a catalytic combustion reactor. This technique is used when the pollutants are in the form of organic gases or vapours. During flame combustion or catalytic process, these organic pollutants are converted into water vapour and relatively less harmful products, such as carbon dioxide (CO2). Changing pollutants to less harmful forms through chemical reactions, such as converting nitrogen oxides (NOx) to nitrogen and water through the addition of ammonia to the exhaust gas in front of a selective catalytic reactor. In the technique known as ‘absorption’, the gaseous effluents are passed through scrubbers or absorbers. These contain a suitable liquid absorbent, which removes or modifies one or more...

Protection of Environment in an Integrated Steel Plant...

Protection of Environment in an Integrated Steel Plant  The processes of an integrated steel plant are highly resource intensive, consequently emitting and discharging pollutants and therefore, the cause of environmental concerns. They have a variety of impacts on the environment. The main impacts come from the use of energy and raw materials, which result in emissions such as carbon dioxide (CO2), sulphur oxides (SOx), nitrogen oxides (NOx), dust emissions to air. Water is used throughout the plant for cooling or heat transfer of heat processing equipment. Water is also required for descaling, dust scrubbing, quenching and other processes. Direct contact water gets contaminated during use and when this contaminated water is discharged from the plant, it impacts the environment. Also solid wastes generated during the plant operations, need dumping in the land filling area. These wastes also have its effects on the environment. One more factor which affects the environment is the noise which is produced during the plant operations. In short, thera are four types of pollutants which are affecting the environments (Fig 1). These are (i) air emissions, (ii) liquid effluent discharges, (iii) solid waste dumping, and (iv) generation of noise. Fig 1 Types of pollutants affecting environment The steel plant is required to be in compliance with regulations for meeting both generic standards for air, water, noise, waste management as well as specific standards for steel industry. The plant is required to meet the environmental norms for coke ovens, sinter plant, blast furnace, steel melting shop, rolling mills etc. for stack emissions, fugitive emissions and effluent discharges. It is also to comply with the ambient air quality standards. The steel plant is to take measures to improve its environmental performance not only for complying with the statutory environmental norms but also...

Air pollution control – Control of particulate emissions Aug28

Air pollution control – Control of particulate emissions...

 Air pollution control – Control of particulate emissions Steel plant has many metallurgical processes which take place at high temperatures. Further many of these processes handle raw materials some of them are in the form of fines. Hence all these processes are prone to emit pollutant gases and particulate matter into the atmosphere. This in turn affects the quality of air around the plant. In order to improve and protect the quality of air, different pollution control devices are used for reduction of the emissions. Earlier for many years, pollution control equipments were used only for those processes where the pollutants amounts were very high or they were toxic in nature. These equipments were also earlier used where they had some recovery value. But today, with the environment laws becoming more and more tighter and with the increasing concerns of the society regarding the environment, it has become necessary for the steel industry to look into its emissions and install equipments in all the areas to reduce the emissions to minimum possible levels. The emission control equipments are basically of two types (i) particulate emission control equipments and (ii) gaseous emission control equipment. This article describes the particulate emission control systems. All particulate emission control equipments collects particulate matter by mechanisms involving an applied force. Various particulate equipments are settling chambers, cyclones, bagfilters and electrostatic precipitators. The mechanisms of dust removal in these equipments and the applied force are given in Fig. 1 Fig 1 Mechanisms of dust removals Settling chambers  Settling chambers was one of the first devices used to control the particulate emissions. However it is very rarely used today since its effectiveness in collecting particles is very low. The collection force in settling chamber is gravity. Large particles moving slow enough...