Introduction to the working process of the steam generator

A steam generator is a mechanical device that uses heat from fuel or other energy sources to heat water into hot water or steam. The original meaning of the pot refers to the water container heated on the fire, the furnace refers to the place where the fuel is burned, and the boiler includes two parts of the pot and the furnace.

In the water vapor system, the feed water is heated to a certain temperature in the heater, enters the economizer through the water supply pipe, is further heated, and then sent to the drum, mixed with the pot water, and then descends along the down pipe to the water wall inlet header. The water absorbs the radiant heat of the furnace in the water wall tube to form a steam-water mixture and reaches the drum through the riser tube, and the water and steam are separated by the steam-water separation device. The separated saturated steam flows from the upper part of the drum to the superheater, continues to absorb heat to become superheated steam at 450 ° C, and is sent to the steam turbine. In terms of combustion and flue gas systems, the blower sends air to the air preheater to a certain temperature. Coal fines that are ground to a certain degree in the coal mill are carried by a portion of the hot air from the air preheater through the burner into the furnace. The mixture of pulverized coal and air ejected from the burner is mixed with the rest of the hot air in the furnace to burn a large amount of heat. The hot flue gas after combustion flows through the furnace, the condensate tube bundle, the superheater, the economizer and the air preheater, and then passes through the dust removing device to remove the fly ash, and then is sent to the chimney by the induced draft fan to discharge to the atmosphere.

Steam generator circulation

The boiler circulation mode refers to the flow mode of water vapor in the boiler evaporation system, which can be divided into natural circulation, auxiliary circulation, direct current and composite circulation.

The dust contained in the boiler flue gas (including fly ash and carbon black), sulfur and nitrogen oxides are all pollutants that pollute the atmosphere. When not purified, the emission index may reach several times to several tens of times the environmental protection regulations. Measures to control the discharge of these substances include pre-combustion treatment, improved combustion technology, dust removal, desulfurization and denitrification. The use of high chimneys only reduces the concentration of pollutants in the atmosphere near the chimney.

The forces used in dust removal are gravity, centrifugal force, inertial force, adhesion, and sound waves and static electricity. Gravity sedimentation and inertial force separation are generally used for coarse particles, and centrifugal separation is often used to remove dust at higher capacity. Electrostatic precipitators and bag filters have high dust removal efficiency. The water film in the wet and Wen's-water film dust collector can adhere to the fly ash, and the dust removal efficiency is high, and it can also absorb gaseous pollutants.

Flue gas desulfurization has an absorption method and a catalytic oxidation method. Alkaline alumina, semi-coke, activated carbon, etc. for dry absorption; ammonia, sodium carbonate, lime slurry, etc. for wet absorption. The catalyst can be used to oxidize most of the sulfur dioxide to sulfur trioxide at a certain temperature, thereby helping to absorb the desulfurization. Due to the high cost of flue gas desulfurization equipment and operation, most companies tend to use low-sulfur fuels to reduce sulfur oxide emissions.

The nitrogen oxides in the flue gas are mainly nitric oxide. Flue gas denitration has catalytic decomposition method, selective catalytic reduction method, and high temperature activated carbon absorption denitration.

In operation, coal-fired boilers must discharge a large amount of slag and fly ash collected by the dust collector, which is generally removed by water or mechanical means to the slag yard.