With the rapid development of China's electric power industry, the pollution generated by each thermal power plant derivatives (such as SO2 and NOX) increasing number of these exhaust gases not only pollute the environment, these pollutants will convert under certain conditions strong corrosive substances related equipment for power plants produce serious harm.
Emissions, the State Power Corporation of the thermal power plant air pollutant emission standards "(GB13223-1996), stipulates that by the end of 2005 units generating capacity of the plant soot emission rate can not be greater than 2.4g/kwh, compared to 2000 was down 17%. SO2 produced by the unit generating capacity can not be greater than 5.8g/kwh, decreased by 25% compared to 2000. In the face of evil and sinful pollution substances, as well as the ban of the country, power plants what countermeasures it?
(A) flue gas desulfurization system (Flue Gas Desulfurizer-referred to as FGD system): Usually we can in these exhaust emissions into the atmosphere to absorb the sulfur oxides in the flue gas before using the spray method, this is what we usually refer to the FGD system. 2, the desulfurization process: So-called desulfurization, that is, in the flush unit and flushing / absorption unit will limewater ejected from a row of nozzles, and SO2 in the flue gas, to produce a chemical reaction. Complete analysis of the reaction of the whole process will be more complicated; simple, SO2 to generate SO3, under certain conditions, produce CaSO4 and CaCO3 role. The entire reaction is conducted in rinse / absorption apparatus. The last waste generated CaSO4 is gypsum, is a solid, chemically very stable, usually we can "turning waste into treasure," they are made of prefabricated panels for the construction of housing. 3, how to solve the corrosive effect of the desulfurization process: FGD respective units from the boiler, washing tower to the flue at the start of desulfurization after flushing, everywhere was a mist of droplets, especially in flue internally within these regions until the top of the chimney, higher cloud point, at any time some serious corrosion equipment surface condensation. In order to prevent corrosion of the moving condensation, usually with a corrosion-resistant nickel alloy material (such as INCONEL alloy C-276 produced by the Company or other similar materials), like wallpaper paste as laid throughout the flue. Figure 2 shows in Ontario, Canada, the hydropower station one FGD system flush / absorption of the interior of the device. We can see the C-276 alloy sheet in the finished steel round tower and pipe wall like wallpaper paste made of lining in the for alloy plates stitching at similar nickel alloy welding consumables welding,Welding Electrode Supplier fixed the lining in the back of the steel structure. 4, the role played by the nickel-based welding consumables prevent equipment corrosion: Many metal surfaces will be in the FGD system as a whole with the corrosive sediments, resulting in the apertures and to form a slit opportunity, while the natural impurities generated upon combustion of the coal also produce a series of corrosive compounds, chloride and acidic compounds such as caused by the hole and crevice corrosion. System environment in the dry / wet interface as well as boiler evaporator effect "elevated concentration of these acidic compounds, many parts of the system extremely corrosive situation. Thus, a "super pro and relationships exist between the requirements for the use of welding consumables and substrate (base metal). Because the weld region is equivalent to a small castings, their microscopic structure is a branch-like crystals, the crystal structure for the micro segregation of their chemical and branched proportional. Prompted us to select welding consumables for the FGD system made of strong anti-corrosive elements, such as nickel, chromium, molybdenum, tungsten welding consumables need to use due to the microsegregation the regional small hole and crevice corrosion. In addition, when the alloy and steel base composite board manufacturing container, the use of such super-affinity interaction of consumables is more important, this is because the base steel material in the composite sheet can be diluted anti-corrosive effect of strong elements in the solder layer. For these reasons, we often INCO-WELD686 CPT instead the INCO-WELDC-276 to the steel plate welded with C-276 surfacing layer. Require the use of all-position Tungsten Welding Electrodes in the production of this type of FGD system for the complex shape of the inner wall of the container, and requires little case of dilution after welding; meet these two conditions, we often use the fully automatic with pulse Tungsten Inert Gas arc welding (Pulse - Tig), while using a mixed gas of argon and helium, for protection. (When helium is mixed with pure argon, not only to improve the wettability of the molten bath, but also improve the deposition efficiency.)
TIG welding (Gas Tungsten Arc Welding) in a pure Ar as the shielding gas tungsten as a welding electrode method. The straight strip supplier by TIG welding wire to a certain length (typically lm).
MIG welding i.e. protection of electric welding, metal inert gas such as Ar, inert gas as protective gas, including melting extremely pure Ar or Ar gas by mixing a small amount of reactive gas (such as less than 2% O2 or less than 5% of CO2 gas) electric arc welding method. The Mig Welding Wirescoiled layer around, or discoid supplier.
Mig Electrodemethods due mainly to pure Ar as a protective gas, so the outside air, oxygen, nitrogen, hydrogen, and other harmful gases are difficult to enter the molten bath; argon gas or impurities does not produce harmful weld properties; the argon welding wire and molten pool the alloy oxidation few etc. welded joints have a very excellent physical and chemical properties. But it may be detrimental to the welding efficiency and weld penetration. So to the constituent of the wire as much as possible close to the base material ingredient as the principle of the choice of the wire is suitable. TIG Welding Welding Precautions 1, protection of the gas flow requirements: when the welding current in the 100-200A between 7-12L/min;: when the welding current is between 200-300A for 12-15L/min suitable. Due to breakage of the feed pipe causing the protective gas is mixed with the wet air, the performance of the welded joint is influential; 2, tungsten projecting length relative to the nozzle should be as short as possible, the arc length to the arc length control in general 1-4mm quasi (welded carbon steel 2-4mm; welding of low alloy steel and stainless steel for 1-3mm); precautions when the wind speed is greater than 1.0m / s should be; attention to ventilation, to avoid injury to the operator welding; 4: strictly clear welding at the oil, rust, water impurities. 5: It is recommended that the steep drop of the external characteristics of DC power, tungsten is extremely positive. 6: In the more than 1.25% Cr low alloy steel welding, the back should also be protected.
MIG welding Notes 1, the shielding gas flow 20-25L/min appropriate; arc length is generally controlled at about 4-6mm; wind particularly adverse impact on the welding, precautions should be adopted when the wind speed is greater than 0.5m / s; attention to ventilation, to avoid injury to the operator; 4 using pulsed arc current, the spray arc stability, especially suitable for stainless steel, sheet metal, vertical welding, hardfacing welding; 5, Ar +2% O2 gas combination welding low carbon stainless steel, without applying Ar mixed with CO2 welding class steel; welding strict clear welded at the oil, rust, water impurities.