Circulation mode of steam generator

Steam Generator Circulation Method

The steam generator circulation method refers to the flow pattern of water within the boiler evaporation system, which can be categorized into natural circulation, assisted circulation, once-through, and combined circulation.

The dust (including fly ash and soot), sulfur, and nitrogen oxides contained in flue gas are substances that pollute the atmosphere. Without purification, their emission levels can exceed environmental protection standards by several to dozens of times. Measures to control the emissions of these substances include pre-combustion treatment, improved combustion technology, dust removal, desulfurization, and denitrification. The use of tall chimneys can only reduce the concentration of pollutants in the atmosphere near the chimney.

The forces used in flue gas dust removal include gravity, centrifugal force, inertial force, adhesion, as well as sound waves and electrostatic forces. Coarse particles are generally separated using gravity settling and inertial forces, while centrifugal separation is commonly employed for dust removal at higher capacities. Electrostatic precipitators and bag filters offer high dust removal efficiency. In wet water-film dust collectors, water droplets and films can adhere to fly ash, achieving high dust removal efficiency and also absorbing gaseous pollutants.

Flue gas desulfurization methods include absorption and catalytic oxidation. Dry absorption uses alkaline alumina, semi-coke, activated carbon, etc.; wet absorption uses ammonia, sodium carbonate, lime slurry, etc. Using catalysts such as vanadium pentoxide at certain temperatures can oxidize most sulfur dioxide into sulfur trioxide, thereby facilitating absorption desulfurization. Due to the high cost of flue gas desulfurization equipment and operation, most enterprises prefer using low-sulfur fuels to reduce sulfur oxide emissions.

The main nitrogen oxide in flue gas is nitric oxide. Flue gas denitrification methods include catalytic decomposition, selective catalytic reduction, and the use of high-temperature activated carbon for absorption denitrification.