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...

Cleaning of Blast Furnace Gas Jan22

Cleaning of Blast Furnace Gas...

Cleaning of Blast Furnace Gas The process of liquid iron production in the blast furnace (BF) generates gas at the furnace top which is an important by-product of the BF process. This top gas of the blast furnace is at the temperature and pressure existing at the BF top and usually contaminated with dust and water particles. This top gas is having substantial calorific value and is known as raw BF gas or contaminated BF gas. The composition and quantity of this top gas depend on the nature of the technological process in the blast furnace and the type and the quality of the raw materials used for the iron production in the blast furnace. In order to further use the raw BF gas, it is necessary to clean it by using certain process systems which reduces its content of the solid particles. The top gas contains carbon mono oxide (CO) and is known as blast furnace gas after its cleaning. It is used as fuel gas for heating blast air in the hot blast stoves as well as supplemental fuel in the steel plant. For the BF gas to be used as fuel gas, it is necessary that the raw BF gas is cleaned and cooled to reduce gas volumes and moisture content. Prior cooling and reduction in gas volume is also necessary since it results in substantial savings in delivery costs throughout the extensive distribution system of the steel plant. Typical analysis of the blast furnace gas for a blast furnace operating with pulverized coal injection (PCI) is given in Tab 1. The process systems for the gas cleaning are either wet gas cleaning system or dry cleaning system. High-efficiency gas cleaning systems are vital for the reliable operation and long campaign...