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Power plant desulfurization

Dry desulfurization:

The main thing is circulating fluidized bed desulfurization reactor. After adding limestone into circulating fluidized bed boiler, high temperature solid reaction occurs in two steps: decomposition and burning sulfur salting reaction, the reaction of the two desulfurization.

Wet desulfurization:

limestone / lime - gypsum wet, boiler flue gas booster fans pressurized by gas - gas heat exchanger to cool after switching into the desulfurization tower, bottom-up flow through the desulfurization tower, with the top down limestone / lime slurry is formed reverse flow, heat exchange and simultaneous chemical reaction to remove flue gas SO2. The purified flue gas demister to remove flue gas carried in droplets through the air - after the gas is discharged from the heat exchanger to heat up the chimney. CaSO3 reaction product into the bottom of the slurry tank desulfurization tower, oxygen is pumped through the drum air blower forced oxidation to form CaSO4, and then to form gypsum. To make the gypsum slurry tank to maintain a certain concentration, we need to continue to discharge the resulting gypsum, fresh limestone / lime slurry required trickle, dehydrated gypsum slurry obtained after high-purity gypsum.

Semidry desulfurization:

Spray drying flue gas desulfurization and flue gas desulphurization circulating fluidized bed (CFB Law) (may be a semi-dry, and finally the different). After crushing lime after digestion, mixed digester with desulfurization by-products and some ash, mixed into a slurry, the slurry pump boost into the rotary atomizer, by atomized uniformly dispersed in the tower. Hot flue gases from the top to cut into the flue gas distributor, while the droplet downstream. Dried droplet evaporation occurs simultaneously with chemical reaction in flue gas SO2.

Double alkali flue gas desulfurization technology to overcome limestone - lime method disadvantage easy fouling and developed. Traditional limestone / lime - gypsum flue gas desulfurization process using calcium-based sorbent after absorption of sulfur dioxide generated calcium sulfite, calcium sulfate, because of its low solubility, easy to form scale in the desulfurization tower and pipes, clogging . Plug fouling problems seriously affect the normal operation of desulfurization system, or worse still seriously affect the normal operation of the boiler system. In order to avoid calcium based sorbent unfavorable factors, mostly calcium desulfurization process required with the corresponding forced oxidation system (aeration system), thus increasing the initial investment and operating costs, with cheap desulfurizer easily understood cause plug fouling problems , simply use sodium-based desulfurization agent running costs are too high and the desulfurization products easy to handle, the two conflicting highlights, dual-alkali FGD process came into being, the process is better to solve the above contradictory problems.


Technical rationale

It is introduced from the rear of the boiler flue gas discharged sulfur throat circulating fluidized bed reactor, where the water, desulfurizer and also reactive cyclic sulfate by-product is mixed with a larger surface area to spread lime, and the role of smoke throughout the reactor down. Then into the upper cylinder, fly ash and flue gas desulfurization agent constantly tumbling, mixing, part of the lime in the flue gas entrained into the cyclone separator to capture particles down through Refeeder were taken back circulating fluidized bed of lime into the reaction column through the delivery means. Since the contact area is very large, lime and SO2 in the flue gas can be sufficiently contacted in the reactor during the drying process, and the SO2 is absorbed.

In the reactor, the chemical reaction of sulfur dioxide elimination as follows:

SO2 + Ca (OH) 2 + H2O = CaSO3 + 2H2O

Solid particles containing waste, residual lime and fly ash separated and recycled to the reactor in the subsequent cyclone because the cyclic portion of the solids portion of the reaction can, i.e., the unreacted lime is also part of the cycle and the flue gas the reaction of SO2, by making utilization of the lime circulation increased to the maximum.

Desulfurizer and SO2 in the flue gas and by-products after the boiler and fly ash together, and the reaction between the primary cyclone column cycle. Therefore, fresh lime and sulfur-containing flue gas to maintain a larger reaction area. The height of the reaction tower provides the proper chemistry and water evaporation endothermic reaction time and time and due to the strong turbulence effects of high concentrations of dry recyclable materials and the proper temperature, surface area kept clean and free of deposits within the reactor, which one of the main features of the system.

Finally, the excess desulfurization by-products to be imported from auger system to the ash hopper discharge field, in addition to flue gas SO2 after the introduction of bag filter or electrostatic precipitator through the flue, remove dust and ash particles, smoke purification gas through the chimney into the atmosphere.

Circulating fluidized bed flue gas desulfurization system mainly consists of the following system components, lime feed system, circulating fluidized bed desulfurization purification systems, monitoring and control systems, electrical systems, flue systems.


Dry and semi-dry desulfurization desulfurization which is better?

Comparison of the two is not very good: dry flue gas desulfurization process began in the 1980s, compared with the conventional wet process lower investment costs, desulfurization products easy to dispose of, saving demister and heat exchanger installation and operating costs, equipment difficult to corrosion, less prone to fouling and clogging. But its shortcomings are more obvious: the utilization of absorbent far below the wet process, from high sulfur coals of poor adaptability, dry ash and desulfurization products can not be separated utilization. Currently desulfurization equipment design code requirements or large capacity unit design coal sulfur content of more than 2% of the unit preferably wet process, more than 90% desulfurization efficiency requirements. 200MW or less remaining life of less than 10 years old units, and unit design coal sulfur content of less than 2%, we recommend the use of dry, semi-dry or other costs relative economic desulfurization technology, desulfurization efficiency requires only 75 %. So if you belong to the latter case, according to the local water conditions such as comprehensive assessment of the basic benefit is relatively close, but far better than dry semidry edge.


Power dry desulfurization and wet desulfurization What is the difference, what desulfurization processes are used?

A little water (calcium lactate) a more water (calcium water)

With a jet nozzle (similar detergent factory spray drying nozzle), using a large flow of solid cone nozzle

A small pump (making emulsion system and injection system i), a lot of the pump (pulp, waste water, spray, transport, etc.)

A dust collector is the main, and a dust collector okay

Desulfurization system two kinds of methods is the biggest difference, that you can be found online, a lot a lot.

General 30MW look dry, 30 ~ 60MW both row, 60MW above are basically wet

The former small investment, big investment in the latter. The quality of both methods are super small, experts are still under discussion,

The principle of wet FGD technology, process and so on?

Wet FGD technology

First, the technical principles

Flue gas into a wet absorption tower desulfurization equipment, and top-down spray alkaline limestone slurry droplet countercurrent contact, wherein the acidic oxide and other pollutants SO2 HCL, HF, etc. are absorbed, the flue gas can be sufficiently purified; slurry reactor to absorb SO2 after generation CaSO3, by in situ forced oxidation, crystal formation CaSO4 • 2H2O, dehydrated commercial grade obtained after desulfurization by-product - gypsum, ultimately comprehensive management of sulfur-containing flue gas.

Technical Features

⑴, absorbing a wide range of application: it can be used in a variety of FGD absorber means, including limestone, lime, magnesium stone, waste soda solution and the like;

⑵, a wide range of fuels: apply to coal combustion exhaust gas treatment, heavy oil, orimulsion, and fuels such as petroleum coke boiler;

⑶, the range of fuel sulfur change adaptability: can handle up to 8% fuel sulfur content in flue gas;

⑷, load change unit adaptable: to meet the unit steady in the range of 15 to 100% load change operation;

⑸, high desulfurization efficiency: generally greater than 95%, up to 98%;

⑹, patented tray technology: effectively reduce the liquid / gas ratio is conducive tower uniform airflow, saving energy and material consumption, easy absorption tower internals overhaul;

⑺, absorbent high utilization rate: calcium to sulfur ratio as low as 1.02 to 1.03;

⑻, a by-product of high purity: more than 95% purity to produce commercial grade gypsum;

⑼, high-efficiency coal-fired boiler flue gas dust: 80% to 90%;

⑽, cross spray pipe installation techniques: help reduce the absorption tower height.

Sixth, the recommended scope

⑴, 200MW and above units in large new or modified;

⑵, fired sulfur content of 0.5 to 5% or more;

⑶, desulfurization efficiency requirements more than 95%;

⑷, limestone rich and comprehensive utilization broader region.

Usually there are two kinds of power plant desulfurization desulfurization methods:

First, the combustion desulfurization, desulfurization of combustion furnace is divided into pulverized coal fired circulating fluidized bed desulfurization and desulfurization two kinds. These are two kinds of desulfurization in the furnace combustion desulfurization, this method does not produce gypsum desulfurization, containing only produce calcium sulfite, calcium sulfate ash and desulphurization.

Second, flue gas desulfurization, flue gas desulphurization also have a good variety, now more mature limestone wet desulphurization, flue gas after ESP is combusted after chemical reaction with limestone slurry is mixed after the event to generate the gypsum.


Now dry desulfurization and also out of stock become the trend, our new reference standard stock has been stipulated, while desulfurization out of stock See Chinese Academy of Sciences Coal Chemistry, process, Zhejiang University was activated carbon, ionic liquids desulfurization out of stock. Desulfurization single function may decline in market research are relatively backward.