How to Choose the Desulphurization Valve

As a result of desulfurization project pipeline and more bad conditions of contact with the media, scaling, clogging, corrosion, wear and tear is a common problem in FGD system, seriously affected the system equipment operation rate. Therefore, the correct selection of the valve need to understand the nature of the media they are in contact.

Desulfurization system, according to the different media components, divided into limestone slurry, limestone gypsum slurry and gypsum slurry three parts.

(1）pH = 4 ~ 7, inorganic chemical weak acid corrosion;

(2) the content of limestone slurry can reach 55%, the density is up to 1500kg / m3;

(3) Organic solution containing inert substances, organic solution corrosive

(4)  flow rate is fast, the general design of the slurry flow rate control in the 2.5m / s the following, the actual operation of up to 3.5m / s, a particle jet phenomenon, the circulating water, the process Water up to 5m / s;

(5) Cl-concentration of high: desulfurization engineering company generally 20000mg / L design, the actual tower up to 180,000mg / L about 40000mg / L in wastewater, in addition to acid corrosion, There are strong oxidizing and reducing. In general, the limestone slurry is more abrasive and the gypsum slurry is more corrosive.

Therefore, the valve selection in addition to conventional requirements, such as excellent product design, torque, flexible, reliable operation, long service life, low maintenance costs, but also requires anti-corrosion, wear-resistant, high-quality anti-corrosion materials. Valve supporting the executive body, need to be familiar with the various FGD system valve function, the frequency of operation and ease of operation.

Desulfurization Valve Selection Examples and Performance

Considering the reliability and economy of the FGD system, the flue gas desulfurization project mainly uses the butterfly valve and the regulating valve, the diaphragm valve, the cut-off valve and the ball valve. In this case,

1. Butterfly valve: In accordance with the type can be divided into: centric type (low-pressure desulfurization in the conventional products), double eccentric (medium voltage for the switch, adjust the use), triple eccentric (high pressure used for switching regulator). Desulfurization commonly used in the middle butterfly valve, and the desulfurization process in the application of the most valves. Desulfurization process medium is divided into: process water, slurry, waste water, circulating water, tap water, compressed air. In this case,

Body material is generally divided into the following categories: cast iron, ductile iron, carbon steel and so on. Butterfly valve seat is EPDM, desulfurization medium is generally contained in the Cl ion concentration to consider the valve plate material. Valve plate material is generally divided into: ductile iron chrome, ductile iron lining nylon, lining fluorine rubber, 304,316,316 L, 2205,2507,1.4462,1.4529, C276 and so on. Process water, recycled water, valve plate material is generally used ductile iron chrome, 304 can be. Air or oxidized air chrome plated with nodular iron, 304. But for the oxidation of air seat to pay attention to medium temperature, the general seat with heat-resistant EPDM. Slurry and waste water containing high concentration of CL ions generally use 2205,2507,1.4462,1.4529, C276. Cl ion concentration is higher, the valve plate material should also be increased accordingly.

Small diameter butterfly valve generally use the folder or single clip way to connect more, the general diameter DN25-DN450. Diameter above DN500 is generally recommended to use flange connection.

 2. Diaphragm valve: In accordance with the structure is divided into: Weir-type diaphragm valve and straight-through diaphragm, all-pass diaphragm. Connection for the flange. In this case,

Conventional valve body is generally cast iron lined rubber, rubber-lined valve body is now less applied. In this case,

Weir-type diaphragm valve: mainly used for process water, waste water, acid, alkali and other media;

Direct-acting diaphragm valve: to be used for slurry media (slurry medium which contains solid particulate matter, not easy to plug).

3. Check valve: single-lined rubber swivel type (medium for the corrosive type, such as slurry), the folder-type valve chamber full rubber butterfly check valve (medium for the process water and air), Swing Check valve (high temperature type medium, such as high temperature oxidation air). In this case,

4. Globe valve: generally in the instrument with the air system, process water mains, accident sprinkler piping, instrument system used in the selection of needle valve, made of 304 stainless steel. Other valves according to the pipeline material to be. Cast iron, cast steel and copper alloy can be used for the pump cooling water system. In this case,

5. Manual ball valve: generally smaller diameter case, the medium for process water or compressed air, the use of ball valve. In the absence of requirements: DN50 and above the flange connection method, DN50 following the use of threaded connection.

6. Self-operated pressure control valve: valve selection requires customers to provide the following parameters: media, temperature, post pressure, flow, and then based on these parameters for selection.

7. Traps: to consider the actual use of pressure, hydrophobic, medium temperature.

Temperature: Note that the maximum temperature of the medium, due to different temperatures, the valve body and trim material can be different.

Hydrophobic: is a very important parameter to select the trap, condensate displacement is a very important parameter to select the trap. In this case,

"Safety factor" to have, and no need to infinite zoom, different types of trap "safety factor" is different. In this case,

8. Safety valve: to clear set take-off pressure, that is, safety pressure, so as to ensure safety. Valves should pay attention to safety.

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