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Flues Gas Desulfurization

Scope of supply

Flue gas desulfurization EPC  

 Desulfurization engineering design  

 Desulfurization equipment supply  

 Construction & Installation of desulfurization engineering 

Commissioning and technical service of desulfurization engineering  

 Operator training of desulfurization system  

 After-sales service of desulfurization engineering  

 Technological development and EPC of flue gas denitrification

Waste gas emission standard

Local standard and related provisions on FGD

The emission concentration specified in Integrated Emission Standard of Air Pollutants (DB37/2376-2013) can be met by the flue gas purification technology.

 Dust concentration:  10~20mg/Nm3;

 SO2 concentration:  100mg/Nm3;

 NOX concentration (based on NO2): 200mg/Nm3

Technology introduction

Ultra-low emission FGD technology for pollutants from coal burning 

Mainstream technologies of FGD for coal-fired power plant

 Wet process: wet limestone/lime-gypsum, ammonia scrubbing and seawater scrubbing desulfurization process

 Dry process: Limestone injection into furnace, electron beam radiation desulfurization and denitrification process

 Semi-dry process: spray drying, Limestone injection into furnace and activation of calcium, circulating fluidized bed desulfurization process

Comparison of common FGD technologies

 


Technology-wet process

Desulfurization reaction shall occur when flue gas contacts with the solutions containing desulfurizer, and desulfurization products shall be generated and dealt with in wet state.


Advantages:

 Gas liquid reaction, high reaction rate;

 High desulfurization efficiency, generally above 90%;

 Mature technology, wide applications;

 Safe and reliable production operation; more than 80% of total installed capacity for desulfurization

Disadvantages:

 Difficult to deal with the produced liquid or sludge;

 Serious corrosion to equipment;

 High energy consumption and large occupied area due to reheating the flue gas after washing;

 High investment and operating cost;

 Complicated system, huge equipment, high water consumption and initial investment

Technology-wet limestone/lime process

 Limestone/lime slurry shall be pumped into absorption tower;

 SO2 in flue gas shall react with CaCO3 to generate CaSO4 ;

 CaSO4 at a certain saturation level shall crystallize to form dehydrate gypsum;

 Gypsum slurry shall be dehydrated in the tower with moisture control at 10%;

 Produced gypsum shall be stored in the silo by conveyor;

 After being demisted, desulfurized flue gas shall be discharged into atmosphere via chimney.

System composition

 Limestone slurry preparation system

 Flue gas delivery and heat exchange system

 SO2 absorption system (including slurry circulation and oxidation)

 Gypsum treatment system

 Waste water treatment system

Process flow

Technology-ammonia process

System compostion

 

Besides main systems shown in the left diagram, there are also the following auxiliary systems:

 Process water supply system

 Power supply and distribution system

 Instrumentation and control system

 Water supply and drainage system

 Heating and ventilation system

Process flow:

Technical feature

 Advanced control method of ammonia loss

 Advanced ammonium sulfite oxidation method

 Advanced ammonium sulfate crystallization method

 Advanced corrosion control method

 Advanced operating optimization and control metho

 Advanced design and manufacturing method of large desulfurizing tower

In terms of reaction principle, ammonia desulfurization technology shall belong to instantaneous reactions and have multiple functions. It can not only realize the desulfurization and denitrification, but also perform the dust removal. The closed circulation system shall be adopted at the system process, and effective safe measures shall be taken to avoid ammonia leakage.

Technology-dry/semi-dry process

The desulfurization product is in dry state.

Desulfurizer:

Dry state:

 Limestone injection into furnace

 CFB flue gas desulfurization

 Dry catalytic desulfurization

 Wet state:

 Spray drying

 Limestone injection into furnace and activation of calcium (LIFAC)

Main feature:

The desulfurization process mainly in dry state

Less reduction of flue gas temperature, demisting and reheating unnecessary

Advantages:

 Gas-gas reaction

 Relatively low investment and operating cost, easy operation

 Simple equipment, small occupied area, not easy for fouling and clogging

 Low energy consumption, easy disposal for product, without waste water treatment system

Disadvantages

 Slow reaction rate, low desulfurization rate (60-80% at most)

 Low absorbent utilization

 

Spray drying desulfurization

 Slaked lime shall be injected into atomization device inside absorption tower by the pump;

 As an absorbent, slaked lime shall react with SO2 to generate CaSO3;

 Flue gas after desulfurization shall be purified by deduster and discharged into atmosphere;

 Collected deposits from deduster shall be recovered for use in slurry preparation system;

 With simple technology and equipment, this process is carried out in three kinds of state (gas, liquid and solid);

 Its products of dry CaSO4 and CaSO3 are easy for treatment;

 No serious equipment corrosion and clogging, and less water consumption.

System Composition

 Absorbent preparation system

 Absorption tower system

 Dedusting system

 Desulfurization ash recirculating system

 Water spray system

 Flue gas system

 Ash conveying system

 Electric control system

Process flow

Technology comparison


Cost Comparison of Several Common Desulfurization Systems

 


Techno-economic Comparison of Three Kinds of Desulfurization Method

  

Development Trend of FGD Technology
In the future, the FGD technology development shall be directed towards the improvement of existing process, exploration on new desulfurization technology and development of new absorbent and etc. With people’s growing awareness of the importance of environment management and increasing emissions of industrial flue gas, the FGD technology with low investment and operating cost, high desulfurization efficiency and desulfurizer utilization, little pollution and without secondary pollution shall become the mainstream.