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The desulfurization system valve type selection

According to the way of control valve can be divided into: pneumatic, electric, hydraulic, manual, etc. Valve selection should consider the following factors: first, consider the medium, including: the temperature of the medium, flow, pressure, density, degree of superheat, and then erosion and flash vaporization. Valves are used in what kind of condition, then consider with what kind of material problem.

FGD (Flue Gas Desulfurization, FGD) is the coal measures to control sulfur dioxide emissions. The limestone wet flue gas desulfurization gypsum are the most used around the world and the most mature technology. Though about the valve of chemical equipment design, selection of a lot of resources, but in view of the limestone gypsum wet desulphurization system valve selection of information but not much, in combination with 2 x130t case/h environmental thermoelectric boiler flue gas desulfurization system, for small valves in the boiler of FGD system setup and selection method are summarized.

The desulfurization system valve

Valves are used in the pipe system of dealing with the fluid control equipment, select the valve before must first understand the functions of various kinds of valves. Application of FGD system is the main valve block valves, regulating valve, check valve, pressure reducing valve and relief valve. Used in slurry system is the first two. The block valves used to control the medium inside the pipeline through or truncate, isolates piping system. Regulator is used to adjust the medium flow rate and pressure of pipeline, the process parameters at desired range, stable in serious wear of slurry pipeline system should try to avoid in the throttle, speed pump and the switch valve operation can be used, or the operation of the other way, without the regulator, to avoid the wear of the valve.

Dielectric properties and valve type selection of FGD systems, many different kinds of valves, because of the desulfurization project in the pipeline more contact with the conditions of medium, fouling and plugging, corrosion, wear and tear is a common problem in the FGD system, seriously affect the operation rate of the system. Therefore, the correct selection of the valve also need to understand the nature of the contact medium.

FGD slurry system, according to the medium composition is different, divided into limestone slurry, gypsum slurry limestone and gypsum slurry three parts. Its main characteristics are as follows:

(1) granularity, wear resistance, the limestone slurry mass fraction is 55%, the density of 1500 kg/m3;

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

(3) the organic solution containing inert matter, corrosive organic solution;

(4) fast speed, general design of the slurry flow velocity under 2.5 m/s, the actual operation of up to 3.5 m/s, a particle jet flow phenomenon, circulating water, process water up to 5 m/s;

(5) the high concentration of Cl - : desulfurization engineering company generally designed by 20000 mg/L, the tower of actual up to about 180000 mg/L, 40000 mg/L in the waste water, besides has the acid corrosion, and strong oxidizing and reducing.

In general, the limestone slurry abrasion is more serious, more performance for corrosive gypsum slurry. For valve type selection, therefore, in addition to the regular requirements, such as excellent product design, torque, flexible motion, reliable operation, long service life, less maintenance costs, also require corrosion resistance, wear resistance, high quality anti-corrosion materials. To form a complete set of valve actuator, still need to be familiar with the function of each valve in FGD system, frequent degree and degree of difficulty of the operation.

Valve selection instance and properties

Comprehensive consideration of FGD system operation reliability and economy of the slurry pipeline in flue gas desulfurization project is mainly use the butterfly valve and control valve, instrument control a valve using the diaphragm valve, cut-off valve and ball valve. Below the setting of the valve and the valve characteristics is described.

According to the process to consider the state of the valve, pneumatic, electric or manual. What is the fault location valve state, etc.

According to the environmental consideration is to use explosion protection or not, and explosion-proof grade problem. According to the installation position, consider the protection grade of the valve, the desulfurization process of valve type to roughly the following:

Type butterfly valve, ball valve, needle valve, diaphragm valve, cut-off valve, self-reliance type valve, check valve, drain valve, safety valve, etc.

Butterfly: according to the type can be divided into: center line (low desulfurization in conventional products), eccentric single, double eccentric (medium voltage used for switch, adjust), three eccentric (high pressure used for switch, adjust) is commonly used in desulfurization for center line butterfly valve, and one of the most used in desulfurization process valves. Medium of the desulphurization process can be divided into: the process water, slurry, waste water, circulating water, tap water, compressed air, etc.

Valve body material generally divided into the following kinds: cast iron, ductile iron, carbon steel, etc. From cost to consider the use of cast iron and ductile iron general more, consider if it is the weather in the north is poor, carbon steel valve body. Butterfly valve seat is rubber lining, now application is generally is EPDM, 3-20 namely three yuan. Valve plate is usually consider: according to the medium in the desulfurization is generally the Cl ion concentration medium contained in them to consider the valve material. Generally fall into the valve material: ball iron plating chromium, iron line nylon, rubber fluorine rubber, 304, 316, 316 l, 2205, 2507, 1.4462, 1.4529, C276, etc.

Process water, circulating water, the valve material generally ball iron chrome plated, 304. Air or air ball iron chrome oxide, 304. But air oxidation for seat must pay attention to the medium temperature, heat resistant EPDM seat used. Slurry and waste water containing CL ion concentration high medium with 2205, 2507, 1.4462, 1.4529, C276. Cl ion concentration is higher, also want to increase the valve material.

Butterfly valve connection mode can be divided into: the clamp, clamp, flange, etc.

Small butterfly valve generally USES the clip or a single clamp connection is more, size generally DN25 - DN450. Flange connection sizes above DN500 generally recommended. Butterfly valve minimum DN25, body of aluminum alloy material, which can replace the diaphragm valve is used for sampling. The location of the liquid level meter generally choose the single clip.

About manual butterfly valve: DN200 worm gear should be chosen and above butterfly valve, now we also produce low torque butterfly valve, also can use handle within 12.

According to industry regulations DN250 and above the wafer butterfly valve generally USES special flange connection. The best butterfly valve door manufacturers supporting the supply.

Diaphragm valve: according to the structure is divided into: weir diaphragm valve (A - TXXXX) and straight through the diaphragm valve (KB - TXXXX), the general formula diaphragm valve (K - TXXXX). For flange connection way.

Regular body is cast iron lining rubber, generally not present application of rubber lining body is less.

Weir diaphragm valve: it is mainly used for process water, wastewater, acid, alkali and other media; Straight through the diaphragm valve:

Mainly used for slurry medium (grout medium containing solid particles and not easy to jam). Through the diaphragm valve conventional DN80 biggest do. In may, when through the diaphragm valve is greater than the DN80, can proper deviation for butterfly valves.

Check valve: single rubber lining swing H44J - 10 (medium for corrosive classes, such as slurry), wafer all type line with rubber butterfly check valve valve cavity SH77J - 10/16 (medium for process water and air), H71-10/16/25/4 w / 40 (type high temperature medium, such as high temperature oxidation air) including swing check valve for DN250 and above, delivery time is long, easy to malfunction. (when the medium for slurry, diameter for DN250 and above, what to choose?) Can choose the valve body and internal parts for dual phase steel quality. SH77J - 10/16, production of coated nylon material, which can be used for sea water medium, but can not be used in slurry.

Manual stop valve: generally, in the instrument air system, process water main accident spray pipe, such as type is the needle valve is used in the system is used in the apparatus, the material is 304 stainless steel. Other valves for piping material. Cast iron, cast steel and copper alloy can be used in the cooling water system of the pump. When manual stop valve diameter or greater DN200, USES the deviation depends on the application and working condition to decide, can some deviation, some can"t deviate from.

Manual ball valve: each environmental protection company chooses different ball valve, are generally under the condition of smaller diameter, medium for process water or compressed air, choose ball valve. In the absence of requirements: the selection of flange connection (or more (Q41F - 16), (the following selects the thread connection (Q11F - 16)

Self-reliance type pressure regulating valve: the valve selection need to provide the following parameters: the medium, temperature, valve before/after pressure, flow, and then according to the selection of these parameters, calculate the valve diameter and inner diameter, clear is the valve before/after stabilized (control valves before/after: ZZYP - K/B), in general, can be reducing.

Self-reliance type valve for quick opening forms in general.

Trap: to consider the actual use of pressure, drain water, medium temperature. Pressure: water valve pressure level should be equal to or slightly higher than the operating mode of the pressure.

Temperature: pay attention to the highest temperature medium, because of different temperature, the material of valve body and trim can be different.

Thin water: is that the choice of very important parameters of trap, the water discharge is to choose the trap is a very important parameter.

"Safety factor" to be, and it is not necessary to infinite amplification, different types of trap "safety factor"

Pressure relief valve: to clear set takeoff, namely safety pressure, so as to ensure safety. The valve should pay attention to safety.

Actuators, pneumatic, electric, hydraulic and electric hydraulic, etc., most used now is pneumatic and electric actuators.

1, the pneumatic actuators: the gear and rack type and piston, controlled by gas source and regulating valve switch.

Both can be divided into single and double the role

Attachment: external regulation: the locator air filtering pressure reducing valve handwheel and solenoid valve

Air filtering pressure reducing valve solenoid switch type: travel switch the handwheel

2, electric actuators, the voltage type torque/thrust stroke switch/external regulation

Split type/integral/intelligent type such as out of stock:

Out of stock of valves in addition to the above the desulfurization of the valve, the key to out of stock is the copper, and explosion-proof. Choose babbitt general stop valve sealing surface. Regulating valve tends to feedback and explosion-proof.


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