Environmental protection machine and equipments

1. Equipments for preventing air pollution
(1) Flue gas desulfurization (FGD)
Preventing air pollution is a cross boundary global problem. The emission of Oxysulfide sulfoxide X,nitrogen oxide(NOX), carbon dioxide , chlorofluorocarbon and other effluent will cause severe harm to human as well as to ecology environment, thus the emission must be limited. Among these, the emission of SO2 is the earliest problem people paid attention to, for the purpose of solving the harm caused by acid rain. Statistics show, the annual artificial emission of SO2 is about 140 million tons/ year; in order to reduce the loss caused by acid rain, the global SO2 emission each year should be reduced by 40 million tons. The emission of SO2 mainly comes from power plants that burn fossil fuel. The method of using pre burn treatment, heavy oil desulfurization and adopting natural gas can only solve half of the emission, and the rest emission must be solved by way of flue gas desulfurization. In the end of the twentieth century, the capacity of all the flue gas desulfurization of the world is tantamount to 0.2 billion kw, each year, which can delete an SO2 amount around 10 million tons, and large quantities of FGD are required to be installed in order to achieve ideal effect.

The flue gas desulfurization (FGD) processes include dry method and wet method, see the following table:

FGD process type

Wet
method
Process type
absorbentabsorbent
Status of absorbing liquid
Material
Byproduct
Lime-plaster method
Calcium sulfite CaSO3
Serosity
Calcium carbonate
White lime
Calces
CaCO3
Ca(OH)2
CaO
Plaster
CaSO4·2H2O
Mg-plaster method
Magnesium sulfite MgSO3
calcium sulfite CaSO3
Serosity
magnesium hydrate
white lime
calcium carbonate
Mg(OH)2
Ca(OH)2
CaCO3
Plaster
Na2SO3-Glauber salt method
sodium sulfite
Na2SO3
Solution
Caustic soda
NaOH
exhaust the Glauber salt liquid
Sodium sulfite reclaim method
Caustic soda
NaOH
Na2SO3
Sodium sulfite plaster method
Calcium carbonate
White lime
CaCO3
Ca(OH)2
CaO
Plaster
Sodium sulfite-sulfuric acid method
Caustic soda
NaOH
Sulfuric acid
Diluted sulfuric acid-plaster method
Diluted sulfuric acid
Solution
Sulfuric acid
Calcium carbonate
H2SO4
CaCO3
Plaster
NH3-ammonia sulfate method
Ammonium sulfite
(NH4)2SO3
Solution
Ammonium hydroxide
NH4OH
Ammonium sulfate
(NH4)2SO4
NH3- NH3-plaster method
White lime
Ca(OH)2
Plaster
Al-plaster method
Alkalinity aluminium sulfate
Al2(SO4)3Al2O3
Serosity
Aluminium sulfate
Calcium carbonate
Al2(SO4)3
CaCO3
Plaster
Mg method
Magnesium sulfite MgSO3
Solution
Magnesium hydrate
Mg(OH)2
Exhaust the bitter salt liquid MgSO4
Dry
method
Activated carbon absorption method
Activated carbon
Activated carbon
Sulfur
Spray drying method
Ca(OH)2
Na2CO3
Serosity
White lime
Sodium carbonate
Ca(OH)2
Na2CO3
Plaster and others

The FGD in firepower plant mainly refers to the limestone-plaster technique, and the less used is sodium sulfite technique. In Japan, 60% of FGD is limestone-plaster technique, 30% is sodium sulfite technique, and 10% is vitriol sorbent technique; in Germany, 80% is limestone-plaster technique.

In the FGD technique process, the environmental conditions have large variations, and for different fuel, the content of corrosive medium contained in the flue gas is different, see the table below. In some desulfurization techniques, sulfuric acid must be added, and the corrosion can be more severe, thus under condition that the nonmetal lining cannot satisfy the requirements, stainless steel should be chosen. Under strict condition, Nickel-base anti-corrosion alloy must be chosen, and different anti-corrosion materials shall be chosen according to the content of chloride and PH value of the environment. In the desulfurization process, the components in the flue gas will be concentrated, at some points they can reach a very high concentration, for example, the chloride can sometimes arrive at more than 100 thousand ppm. And the right anti-corrosion material should be chosen according to the detailed situation.

Flue gas components

Medium components
Fire coal
Heavy oil
SOX,ppm
NOX,ppm
HCl,ppm
HF,ppm
dust,mg/m3
300-1000
100-200
10-40
5-30
100-200
500-2000
60-100
<2
<3
20-50

The anti-corrosion material in FGD equipments commonly involve general stainless steel, high performance stainless steel and nickel-base anti-corrosion alloy, see the following Table 1. And it commonly follows the principle in Table 2 for choosing material for the different equipments in FGD.

Table 1 - The anti-corrosion material for FGD

Material name
Main alloy components
316L
317L
317LM
317LMN
2205 double phase steel
Alloy 255
254SMO
654SMO
Incolog825
904L
Soniero-28
20Nb-3
20Mo-6
HastellogG
HastellogC-276
HastellogC-22
00Cr17Ni14Mo2
00Cr19Ni13Mo3
00Cr19Ni15Mo4
00Cr19Ni15Mo4N
00Cr22Ni5Mo3N
00Cr25Ni5Mo3Cu2N
00Cr20Ni18Mo6CuN
00Cr24Ni22Mo7NCu
0Cr22Ni42Mo3Cu2
00Cr21Ni25Mo5Cu2
00Cr27Ni31Mo3Cu
00Cr20Ni34M2Cu4N
00Cr23Ni34Mo6Cu3
0Cr22Ni44Mo7Cu2Nb2w
00Cr16Ni56Mo16w4
00Cr22Ni61Mo13w3Fe3
YUS 260 (Japan)
YUS 270 (Japan)
00Cr20Ni15Mo3Cu2N
2Cr20Ni18Mo6CuN

Table 2 - The guide for choosing stainless steel and nickel alloy to make FGD washing tower

Weak
Medium
Strong
Super strong
Chloride
ppm
100   500
1000   5000
10000  50000
100000  200000
Weak
PH6.5
316L   316L
316L   317M
Alloy 904L Alloy G3
Alloy G3  Alloy 625
Medium
PH4.5
316L   316L
317M   Alloy 904L
Alloy G3  Alloy G3
Alloy 625 Alloy 625
Strong
PH2.0
317LM  317LM
Alloy 904L Alloy G3
Alloy G3  Alloy G3
Alloy 625 Alloy C276
Super strong
PH1.0
Alloy 904L Alloy 904L
Alloy G3  Alloy G3
Alloy G3  Alloy 625
Alloy C276 Alloy C22

The status of stainless steel and anti-corrosion alloy of the operating FGD is shown in the table below. For the differences between fossil fuel and minor discrimination between desulfurization, in different countries, there exist differences in material application for the purpose of solving problems of flue gas desulfurization including uniformed corrosion, corrosion pitting, crevice corrosion, and condensate corrosion, but in consideration of anti-corrosion and cost of stainless steel, the super austenite stainless steel(654SMO)has better performance and price advantages.

The operating situation of stainless steel and anti-corrosion alloy in FGD equipments

Name of equipment
Material
Pre-washing tower container
00Cr17Ni14Mo2,HastellogG,00Cr19Ni13Mo3 C-276 alloy
Chill/absorbing tower container
HastellogG,Js-700,00Cr17Ni14Mo2 C-276,00Cr19Ni13Mo3,904L,317LM,Inconel625,654SMO,254SMO
Outlet pipe and reheater
Hastellog C-22 ( outlet pipe lining ), reheater pipes and the hull of 00Cr17Ni14Mo2, C-22, C-276, Inconel625, 317LM, 904L, 654SMO
Chimney
C-276, wallpaper steel lining YUS260, YUS270

2. Dust removal equipment.
In the industry areas including chemical processing, food and metallurgy, dust removal equipment is widely used. In some industries, the purpose of dust moving is to prevent pollution to the products by dust, and in most industry, the purpose is to reduce the dust pollution to the environment. Stainless steel is widely used to make anti-corrosion and heat resistant components in various dust removal equipments, see the following table:

Stainless steel in dust removal equipments

Name of the equipmet
Material
Cyclone dust collecting equipment
0Cr18Ni9 is used to make the dust receiving equipment and components that contact with corrosive gas
Venture scrubber
0Cr18Ni9: used when temperature >600℃ , to make air channel, air blower hull
0Cr17Ni12Mo2 00Cr17Ni14Mo2: scrubber, blade of the blower
Electric dust removal
0Cr17Ni12Mo2: scrubber hull, dust collector, blower hull, blower blade
0Cr17Ni14Mo2: discharge electrode

3. Waste water treating equipments
Living waste water and industrial waste water are the main sources for causing water contamination; for environmental protection, the waste water must be treated to reach qualified standards before exhausting or must be regenerated for usage. The treating methods include physical method, chemical method and biochemical method. These methods are commonly not used singly, but in combination, thus to achieve ideal results. The waste water treating technique does not use a lot of stainless steel, and only at some corrosive points that stainless steel is used. The application of stainless steel in waste water treating industries is shown in the following table:

The application of stainless steel in waste water treating industry

Name of equipment and part
Material
Filtration web, filter
0Cr18Ni9: Minutia filtration web , frame chain, slag filtrating components inside the filter
Precipitation slot, separating slot
0Cr18Ni9,0Cr17Ni12Mo2: For making the collector of corrosive waste water mud , stirrer
Neutralizing slot, drug adding container
0Cr18Ni9,0Cr17Ni12Mo2: For making the axis, wings of stirrer,
Filter
fastening piece
Centrifugal separator
0Cr25Ni6Mo2(SCS11), CD-4MCu cast copper
Pump, valve, instrument
0Cr18Ni9,0Cr17Ni12Mo2: The pump for transporting corrosive waste water, bobber of tank gauge, flow test riser
Ion exchanging equipment
0Cr18Ni9,0Cr17Ni12Mo2: Used to make the baffle for preventing resin over brimming

4. Ordure treatment.
The PH value of ordure is 7-9, but it contains small sums of H2S and will require large sum of water for flushing, the environment is comparatively corrosive, some treating devices and equipments are made of anti-corrosion stainless steel, and the application of stainless steel in ordure treatment is shown in the table below:

The application of stainless steel in ordure treatment

Name of the equipment
Material
Filtration web for eliminating impurities
0Cr18Ni9
Spin-drier, screw punch, disintegrator
0Cr18Ni9
Heat exchanging pipe for deodorization with burning
0Cr18Ni9
Burning deodorization reaction room
0Cr18Ni9,0Cr25Ni20
Valves for digesting treatment method, inlet part for the air absorbed by booster
0Cr18Ni9
Deposit mud carrier for second treatment at the sedimentation basin
0Cr18Ni9
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