Application of ceramic lined ball valves in flue gas desulfurization

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1.General

Flue gas desulfurization is the main action to control the discharge of SO2 in the coal power plant . There are several desulfurization process in the international market , that is wet desulfurization ,dry desulfurization ,semi dry desulfurization and ammonia process of desulfurization. The limestone-gypsum wet flue gas desulfurization process is the most popular for high efficiency ,large capacity ,good compatibility ,reliability . Beside that , limestone work as absorber ,have a low cost and a wide availability characteristic ,its by product gypsum can be recycled after water removing . At present , the limestone-gypsum wet flue gas desulfurization process is the main process among desulfurization in the coal –fired power plant .

FGD (Flue gas desulfurization ) is a process which absorb SO2 as well as other contaminative gas by lime stone slurry in the power plant , by the same time it can produce the lime gypsum slurry by product . limestone-gypsum wet flue gas desulfurization process is realized by the following :absorption liquid with limestone is put into desulfurizing absorption tower by slurry pump ,then pulverization by atomizing nozzle and become many small liquid drops ,spraying into absorption tower all over the section .When liquid drops contact with flue gas ,it can absorb the SO2 in the flue gas . Absorbing reactant will become gypsum after oxidizing & neutral reaction at the bottom of absorption tower.

However ,the difficulties to promote Flue gas desulfurization process is high abrasiveness and high corrosiveness of limestone and gypsum slurry to the relative equipment . This will lead to the high cost and maintenance cost of the equipment . So ,It is necessary to choose the suitable valve and pipes to make sure FGD system in a steady running . The application of ceramic material becomes a trend as its anti –abrasive as well as anti corrosive performance .Though it have a higher price ,it can guarantee the system in normal running and reduce the failure rate of equipment .This article introduces the detail application ceramic ball valve in the FGD system ,and described why it can reduce the cost , times of shutdown, frequency of exchange equipment.

2.Ceramic lined ball valve applied in the desulfurizer.

The cost of FGD  remains in higher stage ,it is only used in most of the developed countries ,including united states ,European countries and Japan . Generally speaking ,the main reason of high cost is the heavily damage to equipment lead by limestone slurry and gypsum slurry.

Fig 1 Spraying tower technology

At earlier stage, fluid control equipment which include pump ,valve ,pipes can only  avoid  abrasive or corrosive problem . Only one of two problem can be solved ,not both of them . For stainless steel valve and pipes ,they can not stand so tough working conditions ,frequency replace of equipment lead to high cost of desulfuration . On the other hand ,the result of desulfuration is difficult  to get expecting  effects .

   Fig 2 : The in site photo for ball valve installed at FDG system

Take coal fired power plant as example ,ceramic lined ball valves are usually installed at the most tough working condition ,such as limestone slurry inlet and outlet areas .There are two kind of types , v port ball valve and O type ball valve . For V type ceramic lined ball valves ,it is easily to work as control valve to adjust flow rate .So the v type ceramic lined ball valve is usually work as the adjusting the flow rate of slurry in FDG system . For O type ball valve , it usually work as stop valve ,stop or connect the fluid .

3. The characteristic of fully lined ceramic ball valve

For the ceramic material ,there are alumina ceramic and zirconia ceramic can be selected .For 99.5% ceramic material ,the hardness can up to HRA 88 ,which have a good anti abrasive and anti corrosive performance . 99.5% alumina ceramic material compare to zirconia ceramic material, because of good chemical stability and lower cost ,it has a popular application . For zirconia ceramic material ,it can bear high mechanical impact due to good tenacity .

Fig 3 . The cross –section view of fully lined ceramic ball valve

Many material of valve body can be selected for ceramic lined ball valves in FDG system , such as A105N，SS304，SS316，SS316L etc . Three pieces structure , simple and reliable ,valve body have a higher strength to protect ceramic parts .

As we known ,almost all the medium in desulfurization system is corrosive gas . Ceramic material is used in the inner valve body ,valve ball and valve seat , it has a good chemical unreactiveness and will not act with corrosive gas and slurry . Because the harness of ceramic can up to HRA 88 , only less than diamond , it will not be wear out by high flow rare lime stone slurry . The FREE BRAND ceramic ball valve remains in good situation after two years installation in FDG system .

4.Development prospect for ceramic lined ball valve in FDG system

For the FDG system in coal fired power plant all over the world ,many imported ceramic lined ball valve made in European countries  are installed . As the development of FREE VALVE ,more and more power plants select FREE brand ceramic lined ball valve ,so it appears a increase  status in sales figures . Moreover ,the storage of coal is largely more than gas and oil ,so coal fired generating power method still popular . Due to the protection of environment ,it will be a higher demand of FDG system ,especially wet desulfurization system . At the same time ,the additional cost and shutdowns at power plant is increasing  due to high abrasive of general metal ball valve . So select the right valve is necessary . Fully ceramic lined ball valve is to be promoted in FDG system ,and it will keep a large demand in the power plant industry .

5.Conclusion

FREE BRAND The ceramic lined ball valve in this article overcome the high corrosive and high abrasive working condition in FDG system . It extends the lifetime of valve due to advance ceramic material , improves the working efficiency ,reduced the maintain cost . FREE brand ceramic lined ball valve have been replaced by importing valve and have a good value in promoting .

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