Technique Features of Desulfurization, Denitration and Deep Dedusting Integrated Tower
◆ 高新技術 Advanced technology, International initiative
◆ 低排放 Ultra-low emissions
◆ 水系統全部閉式循環，無二次污染 Totally enclosed water circulation system, no secondary pollution
◆ 設備占地面積小 Equipment covers a small area
◆ 設備造價及運營成本比傳統工藝低 Equipment cost and operating cost lower than those of the traditional
Technique Features and Performance Parameters of Desulfurization, Denitration and Deep Dedusting Integrated Tower
（一）新技術的特點及優勢 / Features and advantages of the new technology
1. High denitrification efficiency
There is no special requirement for temperature of the flue gas, and the denitrification efficiency is up to 85 to 95% due to the adoption of advanced oxidation reduction technology and the synchronous completion of desulfurization. Therefore, the operating cost is low, which cannot be attained by "SCR" and "SNCR" currently. The used water of desulfurization and denitration applies closed cycle, and reclaimed water dechlorinating device has been deployed in order to avoid the discharge of waste water, without secondary pollution. In the desulfurization& denitration tower for flue gas, by multi-channel inverse&forward spray method, the absorption liquid has be injected into the flue gas. Under the drive of high speed airflow, the absorption liquid was blown into the mist shape with a larger specific surface area, allowing the gas-liquid contact more adequate, so as to ensure the stability of desulfurization and denitration efficiency.
2. Integration of desulfurization, denitration and dedusting
Due to the good activity of the recycled liquid undergoing oxidation and reduction, its absorption rate of SO2 is fast and efficient. According to the experimental results, the desulfurization efficiency reached 99.1%, which cannot be obtained by the lime - gypsum method and the limestone -gypsum method. Because the top tower body is equipped with a water washing dedusting device, the dedusting efficiency of the tower body has been greatly improved. In general, the dedusting efficiency of wet void tower spray technology is 60 to 80%, and the efficiency of wet static electricity is no more than 90%, while the efficiency of our wet water washing dedusting technology is up to 98.5%, meanwhile the emission concentration of particulate matter after desulfurization dropped to below 10mg/Nm3, reaching the ultra low emission standard.
3. Low investment, low failure rate
The currently applied wet electrostatic dedusting technology requires large investment, high operation cost and large power onsumption, as well as the problem of unstable operation. The circulated water in our wet dedusting technology is clean water, and losed cycle is applied, so the failure rate is low, the effect is stable. The system can guarantee long-term normal and stable operation, with ew maintenance quantity. Desulfurization& denitration tower does not contain components easy to cause scale formation and employs mmonia alkali solution as the absorption liquid, effectively avoiding the nozzle clogging and problems of scale formation and plugging. quipment maintenance does not affect the normal running of the system, and the system normal running rate reaches 98% or more, requiring low operating cost. Absorbent of desulfurization and denitrification accounted for a higher proportion in the traditional esulfurization& denitration operating cost, and the system uses ammonium sulfate as resource of ammonia, which has been recycled. The mmonium sulfate is not consumed in theory, while the matters in actual circulation are lime, tiny ammonia and catalysts, so the perating cost is lower.
（二）工藝流程及工作原理 / Process flow and working principle
1. 工藝流程圖 Process flow diagram
2. 設備連接 Device connection
3. 脫硫脫硝反應原理 Principle of desulfurization and denitrification reaction
The scheme adopts cycling ammonia-alkali method to absorb SO2 and NOx in flue gas, namely using ammonia alkali liquor as the absorbent of desulfurization and denitrification, and lime as ammonia alkali recycling agent. The basic principle is as follows: inject ammonia into the desulfurization tower to absorb sulfur dioxide and nitrogen oxides in the flue gas, and then use lime slurry (the main ingredient is Ca(OH)2) to regenerate the desulfurization and denitrification products for replacement of ammonia, finally the ammonia is returned to desulfurization& denitrification tower for desulfurization and denitrification.
The main reaction mechanism is as follows:
（1）二氧化硫、氮氧化物的吸收反應 Absorption reaction of SO2 and NOx
（2）氨堿液再生反應 Ammonia alkali regeneration reaction
（3）氨堿液再生反應 Intra-system side reaction
In the above, the function of catalyst 1 or catalyst 2 is to largely increase the reaction rate of (1-3), (2-1) and (2-2).
（三）設計原則 / Design principles
(1) The desulfurization and denitrification process follows the principle of mature technology, advanced equipment, stable running, convenient operation and maintenance, high degree of automation, low operating costs and none secondary pollution. High availability, high desulfurization and denitrification rate, low lime consumption, low power consumption and low water consumption are ensured, and the standard of environmental protection is fully met.
(2) The desulfurization and denitrification system takes the boiler type, load, furnace rear desulfurization and denitrification sites, and many other factors into consideration, putting forward a reasonable desulfurization and denitrification process program.
(3) The desulfurization and denitrification process fully considers the characteristics of the boiler. The system resistance is stable. The desulfurization and denitrification device doesn’t affect the normal operating of the boiler in the start, stop, operating and accident handling conditions.
(4) The desulfurization and denitrification process adapts to air quantity, temperature, concentration of SO2 or NOx and other load changes and fluctuations of the boiler.
(5) The deploy of desulfurization & denitrification processes and devices is reasonable, meeting the requirements of placement of eneral layout proposed by the owner. The system and layout described in this paper are the basic requirements by detailed process design, all the engineering demands are achieved to construct a complete desulfurization and denitrification device.
(6) Material conveying and circulation of absorbent of desulfurization and denitrification and the by-products are smooth, with capability matching.
(7) The service life of the main equipment for desulfurization and denitrification is designed to be no less than 15 years.
(8) The absorbent of desulfurization and denitrification is relatively inexpensive and easy to be obtained.
(9) The desulfurization and denitrification device adopts DCS control, and takes the signal connection with the main project into consideration, reserving communication interface.
(10) Water content of desulfurization and denitrification by-product gypsum is less than 10%, and automobile is used for outward transport and comprehensive utilization of the by-product.
(11) The flue gas after desulfurization and denitrification is collected for discharge through chimney (anticorrosion is required and the demander is in charge).
(12) The deploy of all the buildings (structures) in the entire flue gas desulfurization and denitrification system should coordinate with the main project. The deploy should be optimized in the given area according to its engineering design and deploy requirements, so that the process flow and deploy are reasonable, safe and economic.
(13) For the use of water, electricity and gas in the area of desulfurization and denitrification, metering mechanism will be installed on the sub pipeline connected to the total pipeline of the main plant, and the energy metering data is incorporated in the control system for display, reserving the information interface jointing the CEMS system of the main device.
(14)The supplier puts forward requirements on water quality, water pressure and water volume of the industrial water (process water, cooling water of the rotating equipment) required by the flue gas desulfurization and denitrification system, as well as the requirements on the consumption of compressed air for instrument and related parameters. The demander will be responsible for the industrial water source used in the flue gas desulfurization and denitrification system. The demander is also responsible for the compressed air source used by the flue gas desulfurization and denitrification system. Before handing over of the flue gas desulfurization and denitrification system, the industrial water and steam used in construction and commissioning will be provided by the demander.
the industrial water (process water, cooling water of the rotating equipment) required by the flue gas desulfurization and denitrification system, as well as the requirements on the consumption of compressed air for instrument and related parameters. The demander will be responsible for the industrial water source used in the flue gas desulfurization and denitrification system. The demander is also responsible for the compressed air source used by the flue gas desulfurization and denitrification system. Before handing over of the flue gas desulfurization and denitrification system, the industrial water and steam used in construction and commissioning will be provided by the demander.
（四）性能參數及運行分析 / Performance parameters and operation analysis