With the rapid development of China's power industry, power plant pollution generated by each type of derivatives (such as SO2 and NOX) also increased, these exhaust gases not only pollute the environment, but these pollutants under certain conditions, will convert some of the strong corrosive substance related equipment for power plants have had a serious hazard.

Therefore, emissions, according to China State Power Corporation, "Power Plant Air Pollutant Emission Standards" (GB13223-1996), provides the end of 2005 units of electricity each plant dust emission rate can not exceed 2.4g/kwh, more than 2000 was down 17%. Unit of electricity produced by SO2 not greater than 5.8g/kwh, decreased by 25% compared to 2000. Harm to others and oneself in the face of these pollutants, as well as state of the ban, what measures can plant in it?
(A) flue gas desulfurization system (Flue Gas Desulfurizer-referred to as FGD system):
Usually we can in these emissions to the atmosphere prior to use spray method to absorb the sulfur oxides in flue gas, which is what we usually refer to the FGD system.
1, FGD system consists of the following elements:
- Spray water supply unit (where the water is usually used to spray lime - CaCO3)
- Washing unit
- Rinse / absorption unit (Scrubber / Absorber) This is the whole system of the most critical element.
- Flue
- Waste (CaCO4) recovery unit
- And above each unit connecting piping, ventilation channels, induction fan and mist eliminators, etc.
2, the desulfurization process:
The so-called desulfurization unit is in the wash and rinse / absorption unit will be a row of lime from the spray nozzle, and SO2 in the flue gas, and chemical reaction. Complete analysis of the reaction to the whole process would be more complicated; Simply put, SO2 generated under certain conditions, SO3, and the role of generation and CaCO3 CaSO4. The reaction is in the wash / absorber done. Finally, the resulting waste gypsum is CaSO4, was solid, chemically very stable, we can usually "turning waste into wealth" will be made of prefabricated panels for their house construction.
3, how to solve the desulfurization process of the corrosive effect:
After washing at the beginning of desulfurization, FGD units from each boiler, washing tower to the flue, full of mist droplets, especially in the house until the top of the chimney flue, the higher regions of the cloud point, at any time Some can cause severe corrosion on the surface of the condensation. In order to prevent the condensation of these moving objects produced by corrosion, we usually nickel alloy corrosion resistant material (such as using the company produces INCONEL alloy C-276 or other similar materials), as "wallpaper paste" as laid in the entire flue. Figure 2 shows one station in Ontario, Canada FGD system flush / absorbing device interior. We can see in the finished wall steel pipe with a round tower and C-276 alloy sheet as wallpaper paste made of the same lining, stitching in the alloy plate at the nickel alloy welding materials with similar welding and stud welding with will be fixed in the back of the steel liner on.
4, the nickel-based Welding Wires Manufacturers in the prevention of corrosion on the role:
Since many of the FGD system will be attached to the metal surface corrosion deposits, resulting in the formation of holes and a great opportunity gap, while coal by combustion of natural impurities also produced a series of corrosive compounds, such as holes and cracks caused by corrosion of chloride and acidic compounds. Meanwhile, the system environment in the dry / wet interface and boiler "evaporator" effect also increases the concentration of these acidic compounds, making the system extremely corrosive in many parts of the formation of the case. Therefore, the use of consumables, and requires the substrate (base metal) between the existence of a "super pro and relationships." Because the welding area is equivalent to a small cast, and their microscopic structure is a branched crystals, their branched chemical and micro-segregation is proportional to the crystal structure. As a result of micro-segregation and regional hole and crevice corrosion, prompted us to choose for the FGD system will need to use strong when welding corrosion-resistant elements such as nickel, chromium, molybdenum, tungsten, etc. made of welding consumables. In addition, when the base alloy and steel composite board manufacturing containers, the use of this super-pro and even more important role in welding, because the composite plate in welded steel base material layer can be diluted in a strong anti-corrosion elements. For these reasons we often use the INCO-WELD686 CPT instead of INCO-WELDC-276 to C-276 weld cladding layer with a steel plate. As in the production of these FGD systems for the complex shape of the inner wall of the container requirements of all-position welding and after welding requires very little dilution of the case; to meet these two conditions, we often use with a pulse of argon tungsten arc automatic welding (Pulse - Tig), while using a mixture of argon and helium gas for protection. (When mixed with pure argon helium gas, not only to improve the pool of infiltration, but also improve the deposition efficiency.)
5, using a suitable nickel-based welding consumables help to improve plant productivity:
When we choose a suitable nickel-based welding consumables and welding process used to produce reasonable within the lining of these structures, the key to corrosion within the pool elements (nickel, chromium, molybdenum) basically do not be "diluted" (that is, these elements still remain in the pool without being in the precipitation), thus surfacing layer formed remains a very strong resistance to corrosion, so that the entire FGD system can continue to work, or only a very short maintenance cycle that is great improves plant productivity.

(B) nickel-based welding consumables in low NOx boilers antiseptic effect:
1, H2S production:
In order to suppress low nitrogen oxide (NOx), many plants will use a low nitrogen oxide boilers, and the use of its special design of the incomplete combustion of coal, and to reduce the heat generated by the boiler, thus inhibiting the low- the generation of nitrogen oxides. But a side effect of doing so due to incomplete combustion of coal and produce H2S. <H2S would be the boiler wall, especially the serious water wall corrosion, the corrosion intensity can reach each 1.5mm-2.3mm, this plant requires frequent downtime for maintenance of the boiler. Six years, the company uses ERNiCrMo-10s material (ie the company's INCONEL622 filler metal), in reducing the corrosion has played a remarkable role. Traditionally, the use of these nickel-based TIG welding consumables (Tig), a low deposition rate welding on the boiler water wall.

2, typical welding process:
Because of the water wall for welding heavy workload, are generally used with a special automatic GTAW process control technology. To solve the nickel-based welding consumables in the viscosity of the molten state, usually with one kind of gun will be slightly faster swing. Such as the use of 1.2mm flat wire welding, the welding current is about 350A, welding voltage of about 28V and for the protection of pure argon gas, the deposition rates of up to 7-8 kg per hour, while nickel alloy welding consumables dilution rate very low, up to 5% -8% (ie, loss of pool corrosion-resistant elements in only 5% -8%)

3, increase productivity
Present study an important indicator of the efficiency of power plants is: outages - the maintenance cycle. When we use nickel-based Mig Welding Rods consumables with equipment to prevent corrosion of the wall is to make a direct result of reduced outages, productivity increased.

4, other nickel-based welding consumables:
In addition to INCONEL622 filler metal, also includes INCONEL625 filler metal (or INCONEL112 electrode) INCO-WeldC-276 filler metal, and so far, for the most intense corrosive environment Welding: INCO-Weld686CPT
From now until the end of 2005, urging the State Power Corporation put into operation and construction of FGD systems in the installed capacity of 18 million kilowatts (including circulating fluidized bed boiler 4 million kilowatts).