Abstract: This paper introduces a method of ultra-low emission retrofit for a 300MW unit, focusing on the process principle of a new desulfurization and dust removal integration technology. The technical investment is low and the operating cost is low, so it is worth learning from.
Key words: Efficient desulfurization dust removal two-phase rectifier mist eliminator
First, the overview
A power plant # 6 unit 300MW subcritical coal-fired generating units, put into operation in February 2006. The unit adopts low-nitrogen combustion technology to reduce the amount of nitrogen oxides, supporting the construction of high-efficiency SCR denitration process, bag-type dust removal and limestone-gypsum wet desulfurization process for boiler exhaust gas. In order to further improve the quality of the atmospheric environment and protect the ecological environment, the power plant is actively undertaking the technological transformation of ultra-low emissions in accordance with the requirements of the "Action Plan for Upgrading and Upgrading Coal-fired Energy-saving and Emission Reduction in 2014-2020". # 6 unit ultra-low emission reconstruction project officially started construction in April 2016, completed in June. The design indexes of this project are soot, sulfur dioxide and nitrogen oxide emission concentration respectively not more than 5mg / Nm3, 35mg / Nm3 and 50mg / Nm3.
Second, transform the content
# 6 unit to carry out ultra-low emissions The main content of the transformation of the original denitrification facilities SCR two layers based on the installation of a layer of catalyst and sootblower, install dilution fan and heater. Dust filter bag from the original filter cloth (PPS fiber + PTFE base cloth) replaced by ultra-fine, anti-oxidation, anti-corrosion, anti-wear material (fabric: PTFE; fiber: 30% PPS ultrafine +30% PPS +40 % PTFE blended), replacement bag holder. Desulfurization facilities demolition of the original GGH, the original two-tier roof demister replaced by three-tier efficient roof demister, absorber and flue re-preservation, DCS upgrade, the installation of trays (boiling foam desulfurization dust integrated device) . At the same time, the technical renovation of the total outlet of # 6 unit and the replacement of CEMS equipment will be carried out to meet the requirements of low-concentration pollutant discharge monitoring.
Third, advanced technology discussion
The transformation of advanced technology for dust removal desulfurization integrated desulfurization equipment. The original desulfurization absorption tower of the project is a liquid column + spray layer, and the absorption column slurry pool and the tower body are integrated. Absorber tower part of the size of 16.9m × 9.9m, with five side mixer. Absorption tower upper part of the size of 10.9 × 9.9m, set up three layers of spray layer, a spray layer, respectively, four slurry circulation pump configuration. The top of the spray layer is arranged with two-stage mist eliminator. In the first demister, the lower part of the second demister arranged a layer of cleaning nozzles, the absorption tower oxidation air system has three oxidation fan.
At present, with the improvement of national ultra-low emission standards, new requirements are put forward for domestic desulfurization and dust removal technologies, and the desulfurization efficiency and the dust removal efficiency need to be greatly increased. Domestic desulfurization manufacturers have their own technology upgrade development, in a flue gas bag dust on the basis of (dust collector outlet soot concentration of not more than 10mg / Nm3), in the subsequent desulfurization stage were proposed a new type of desulfurization dust In the absorption tower, the combination of special devices and sprinkler system in the absorption tower can effectively remove SO2 in the flue gas and remove the soot efficiently. Among them, the representative technologies are as follows: National Electric Investment Group, as far as the environmental protection of the two-phase rectifier + efficient demisters, GD clean exhaust coupled desulfurization + tube bundle precipitator, Kaidi environmental II efficient boiling tray tower + efficient demister Technology, Shanghai Long net single towers + efficient demister technology.
The transformation is the use of two-phase rectifier + efficient demister technology, flue gas through the biphasic rectifier device and the slurry generated uniform mixing, increased gas-liquid solid three-phase mass transfer rate, to complete a desulfurization dust, while achieving rapid cooling And flue gas are evenly distributed, combined with efficient demister, improve dust removal and desulfurization efficiency.
1, the main transformation content
(1)) The tower body between the upper part of the absorption tower inlet flue and the first injection layer shall be 2.5m higher and 1 set of dual-phase rectification devices shall be installed, including its supporting system and anticorrosiveness. So that the flue gas entering the absorption tower will flow more evenly through the device and the flue gas will collide with the liquid film of the slurry formed on the device to promote the reaction of the gas and liquid two-phase medium to enhance the overall desulfurization efficiency of the absorption tower; moreover, But also to avoid short-circuit the flue gas short-circuit phenomenon, in order to achieve higher desulfurization efficiency, transformation of the three injection layer slurry circulation pump, increased the amount of spray, the original layer of spray retained.
(2) The two-stage roof demister used in the original absorption tower is replaced with three-stage high efficiency roof demister, which can meet the droplet content of the outlet of the absorption tower after the replacement. The droplet size of the outlet is less than 15mg / Nm3. As the demister height increases, the height of the defogger area increases from the original 2.5 m to 4.5 m, and the total height of the # 6 absorption tower increases by 3.2 m in combination with the space requirement of the defogger.
(3) Boiling mass transfer member support Li old original 12.279m layer reserved for support beam installation. Boiling mass-transfer components are installed in a modular layout. The modules and beams are bolted. The pre-welded angles of the module and absorption tower walls are also bolted. Reinforcement ribs made of 2205 steel plates are used to reinforce the module. Boiling mass transfer components in accordance with the desulfurization efficiency of not less than 10% design, both dedusting function, opening aperture 35mm. Boiling mass transfer member set 4 pressure measurement points
2, boiling foam desulfurization dust removal device integration principle
Boiling foam desulfurization dust integrated technology core lies in the two-phase rectifier + three efficient demisters. The main principle lies in the full combination of gas and liquid phase, is conducive to the removal of smaller soot. The two-phase rectifier makes the flue gas distribution more uniform in the absorption tower. Through the CFD simulation, the non-uniformity of the entrance section of the absorption tower can be reduced from 36.4% to 6.2%. Therefore, the demister does not generate local super-flow phenomenon. Three efficient demister outlet drop content of not more than 20mg / Nm3.
The main technical composition and principle diagram:
Two-phase rectifier desulfurization technology is the use of a porous sheet-like device installed in the desulfurization absorption tower, so that the flue gas into the absorption tower after the flow field distribution more uniform, while the flue gas and the slurry formed on the device Membrane impact, and promote gas and liquid two-phase reaction medium to achieve the purpose of removing part of the sulfur dioxide. The technology has the characteristics of spray tower and bubble tower, to improve the desulfurization efficiency, reduce the amount of slurry circulation has a significant effect, can reduce investment and save operating costs.
Fourth, monitor the situation
After the transformation of the equipment, the power generation company commissioned the qualification unit to monitor the different operating conditions of the flue gas emission substation. In 90%, 75%, 50% of three kinds of load, burning nearly
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