Automatic control valve of titanium material for combined alkali device

Abstract

A titanium automatic control valve of a combined caustic device is disclosed in the application, which is applied to an automatic tower reversing system of a carbonization tower or an automatic vehicle changing system of external cooling, and comprises one or more of an eccentric rotary valve, a ball valve and a butterfly valve; the valve rod of the eccentric rotary valve, the ball valve and the butterfly valve is made of duplex steel 2205; the surface coating of the eccentric rotary valve and the ball valve contains 55-60% of Co, 28-32% of Cr, 7-9% of W and 1.2-1.7% of C in terms of mass percentage; and the Ti, Fe, O, C and N in the valve core base material of the eccentric rotary valve and the ball valve are ≥99.2%, ≤0.30%, ≤0.25%, ≤0.10% and ≤0.05% respectively. The application improves the corrosion resistance and wear resistance of the valve to the combined caustic medium, reduces the leakage of the valve and effectively prolongs the service life of the titanium automatic control valve in the combined caustic device.

Description

Technical Field

[0001] This invention belongs to the field of valve technology, and in particular relates to an automatic control valve made of titanium for a combined alkali plant. Background Technology

[0002] Titanium-coated automatic control valves in soda ash plants are mainly used in core operating conditions for measuring various mother liquors, semi-mother liquors, carbonized extracts, ammonia mother liquors, and other media. These media primarily contain: chlorides NH4Cl and NaCl; alkaline media Na2CO3, NaHCO3, (NH4)2CO3, and NH3 water; and acidic oxides CO2. The presence of numerous solid particles in these media causes significant wear and corrosion to the valves.

[0003] In practical industry applications, titanium is often used for the internal components of the aforementioned valves. However, there are many grades of titanium with varying compositions, different corrosion resistance, and relatively low hardness. Using titanium directly for the main valve components (valve core, valve stem, butterfly valve sealing ring) would negatively impact the valve's lifespan. Invention Content In view of this, the present invention aims to provide an automatic control valve made of titanium material for a combined alkali plant, in order to solve at least one technical problem in the prior art.

[0004] A titanium-based automatic control valve for a combined alkali plant is used in an automatic tower tilting system for a carbonization tower or an automatic vehicle switching system for external cooling. The titanium-based automatic control valve includes one or more of an eccentric rotary valve, a ball valve, and a butterfly valve. The stems of eccentric rotary valves, ball valves, and butterfly valves are made of duplex steel 2205. Duplex steel 2205 has significantly higher strength than austenitic steels 304 / 316 / 316L; in terms of corrosion resistance, it also exhibits better resistance to chloride stress corrosion cracking than austenitic steel. Furthermore, it has a low corrosion rate in weakly acidic and alkaline media environments (such as CO2 environments).

[0005] The core substrate of eccentric rotary valves and ball valves contains Ti ≥99.2%, Fe ≤0.30%, O ≤0.25%, C ≤0.10%, and N ≤0.05%.

[0006] Furthermore, the valve core material of the eccentric rotary valve and ball valve is made of titanium grade TA2. TA2 grade has superior resistance to chloride corrosion, and cobalt-based alloy No. 12 can improve the valve core's corrosion resistance and wear resistance to alkali media.

[0007] Furthermore, the surface coating of the eccentric rotary valve and ball valve has a Co mass percentage of 55-60%, a Cr mass percentage of 28-32%, a W mass percentage of 7-9%, and a C mass percentage of 1.2-1.7%.

[0008] Furthermore, the surface coating of the eccentric rotary valve and ball valve is made of cobalt-based alloy No. 12.

[0009] Furthermore, the ball valve includes one or both of the following: regulating ball valve and on / off ball valve.

[0010] Furthermore, the sealing ring substrate of the butterfly valve is made of TC4. TC4 material offers higher strength and hardness while ensuring a certain level of corrosion resistance; the DLC coating effectively prevents valve leakage caused by direct metal-to-metal friction between the sealing ring and the butterfly plate, thereby extending the service life of the butterfly valve in the soda ash plant.

[0011] Furthermore, the surface coating of the butterfly valve is a diamond-like composite layer.

[0012] Furthermore, the diamond-like carbon composite layer includes an adhesive layer, a transition layer, and a DLC layer; the adhesive layer, transition layer, and DLC layer are arranged sequentially, with the adhesive layer located on the side closest to the butterfly valve; Preferably, the thickness of the adhesive layer is 0.2~0.5 μm; the thickness of the transition layer is 1~1.5 μm; and the thickness of the DLC layer is 1.8-2.2 μm. The adhesive layer is a metal adhesive layer, preferably a Cr layer; The transition layer is a hardness gradient layer, and the elements of the hardness gradient layer include Cr, W and C; Preferably, the mass fraction of Cr is 25~29 wt.%, the mass fraction of W is <0.5 wt.%, and the mass fraction of C is 0.18~0.32 wt.%. The diamond-like carbon composite layer uses PVD technology, achieving a hardness of 2000 HV, a coefficient of friction of 0.1~0.2, and a heat resistance temperature of 300℃-350°C.

[0013] Furthermore, butterfly valves include one or both of double eccentric butterfly valves and triple eccentric butterfly valves.

[0014] The titanium-based automatic control valve of the aforementioned alkali plant is applied to the automatic tower switching system of the carbonization tower or the automatic vehicle switching system of the external cooling system.

[0015] Compared with existing technologies, the titanium automatic control valve and its application in a combined alkali plant described in this invention have the following advantages: The valve stem of this application is made of duplex steel 2205 with a yield strength ≥450 MPa, which is significantly higher than that of austenitic steel 304 / 316 / 316L. In terms of corrosion resistance, its resistance to chloride stress corrosion cracking is also better than that of austenitic steel. In addition, it has a low corrosion rate in weak acid and alkaline media (such as CO2 environment). It can withstand high temperatures up to 300℃.

[0016] The main component of the TA2 grade valve core is Ti ≥99.2%, and the impurity content is (Fe ≤0.30%, O ≤0.25%, C ≤0.10%, N ≤0.05%). Compared with other titanium grades, it has better resistance to chloride corrosion in alkali media, and the corrosion rate is usually less than 0.01 mm / year.

[0017] The valve core coating uses a cobalt-based alloy No. 12, with main components of approximately 55-60% Co, 28-32% Cr, 7-9% W, and 1.2-1.7% C. The maximum hardness can reach 52 HRC. Compared with other cobalt-based alloys, the W content is moderate, which improves corrosion resistance and hardness while reducing the possibility of oxidation reaction with chlorides under high temperature and acid conditions. It is more suitable for corrosion and particulate conditions in soda ash plants.

[0018] During use, the sealing ring of a butterfly valve is in long-term contact with the butterfly plate. Therefore, this technology uses TC4 grade, which has higher strength and hardness, as the sealing ring base material while ensuring a certain degree of corrosion resistance. TC4 has a maximum tensile strength of 930MPa and a maximum hardness of 40HRC.

[0019] The sealing ring surface is coated with a diamond-like carbon (DLC) coating, which consists of three layers: a base layer, a transition layer, and a DLC layer. The base layer serves as a metal bonding layer with Cr as its main element. The transition layer is a hardness gradient layer composed primarily of Cr, W, and C. The surface functional layer is the DLC layer, composed primarily of C. The coating utilizes PVD technology, achieving a hardness of up to 2000 HV, a coefficient of friction (dry friction) of 0.1~0.2, and high-temperature resistance up to 350℃. This effectively prevents valve leakage caused by direct metal-to-metal friction between the sealing ring and the butterfly plate, thereby extending the butterfly valve's service life in the alkali treatment plant. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0021] The invention will now be described in detail with reference to the embodiments.

[0022] Example 1: Process medium: ammonia mother liquor (NH3 water: about 5%, NH4Cl: about 10%, NaCl: about 15~20%, CO2 about 5%, the remainder is water); operating temperature: 60℃; operating pressure: 0.5MPa-g; pipe diameter DN300, pipe material 316L.

[0023] In this implementation plan, the process medium contains solid particles, causing severe wear and corrosion to the valve. Furthermore, the pipe diameter is greater than DN250, and the operating conditions involve high differential pressure and large flow capacity. Therefore, an eccentric rotary valve is selected. The valve core material is TA2 with an STL12 coating. The main components of the coating are Co, Cr, W, and C. The mass percentages of Co are 55-60%, Cr 28-32%, W 7-9%, and C 1.2-1.7%. The valve stem is made of duplex steel 2205. The valve service life reaches 36 months.

[0024] Example 2 Process medium: carbonization extract (NaHCO3 crystals: approximately 15%, NH3 water: approximately 5%, NH4Cl: approximately 20%, NaCl: approximately 10%, CO2: approximately 5%, the remainder being water); operating temperature: 50℃; operating pressure: 0.1MPa-g; pipe diameter DN500, pipe material 316L.

[0025] In this implementation scheme, the process medium contains solid particles, causing severe wear and corrosion to the valve. Furthermore, the pipe diameter is greater than DN400, the operating conditions are low differential pressure, and the flow characteristics are not critical. Therefore, a triple eccentric butterfly valve is selected. The sealing ring uses TC4 with a diamond-like carbon (DLC) composite coating. The coating consists of an adhesive layer, a transition layer, and a DLC layer. The adhesive layer is a Cr layer with a thickness of 0.2~0.5μm; the transition layer is a hardness gradient layer with a thickness of 1~1.5μm, containing Cr, W, and C, with Cr having a mass fraction of 25~29 wt.%, W a mass fraction of <0.5 wt.%, and C a mass fraction of 0.18~0.32 wt.%; the DLC layer has a thickness of 1.8-2.2 μm. The DLC composite layer uses PVD technology, achieving a hardness of 2000HV, a friction coefficient of 0.1~0.2, and a high temperature resistance of 300℃-350°C. The valve stem is made of duplex steel 2205. The valve service life reaches 36 months.

[0026] The usage process of this patent: When measuring various mother liquors, semi-mother liquors, carbonized extracts, ammonia mother liquors, etc., where the medium contains chlorides such as NH4Cl and NaCl; alkaline media such as Na2CO3, NaHCO3, (NH4)2CO3, and NH3 water; and acidic oxides such as CO2, and the valve type is an eccentric rotary valve, ball valve, or butterfly valve, the valve core and coating, butterfly valve sealing ring and coating, and valve stem material can be selected with reference to this patent.

[0027] Compared with existing technologies, this patent can effectively improve the valve's corrosion resistance and wear resistance to the soda ash medium, reduce valve leakage, and extend the service life of titanium automatic control valves in soda ash plants.

[0028] Comparative Example 1 Process medium: ammonia mother liquor (NH3 water: about 5%, NH4Cl: about 10%, NaCl: about 15~20%, CO2 about 5%, the remainder is water); operating temperature: 60℃; operating pressure: 0.5MPa-g; pipe diameter DN300, pipe material 316L.

[0029] In this implementation plan, the process medium contains solid particles, causing severe wear and corrosion to the valve. Furthermore, the pipe diameter is greater than DN250, and the operating conditions involve high differential pressure and large flow capacity. Therefore, an eccentric rotary valve is selected. The valve core material is TA2 with an STL12 coating. The main components of the coating are Cr, W, and C. The mass percentage of Cr is 83-92%, W is 7-9%, and C is 1.2-1.7%. The valve stem is made of duplex steel 2205. The valve service life reaches 26 months.

[0030] Comparative Example 2 Process medium: ammonia mother liquor (NH3 water: about 5%, NH4Cl: about 10%, NaCl: about 15~20%, CO2 about 5%, the remainder is water); operating temperature: 60℃; operating pressure: 0.5MPa-g; pipe diameter DN300, pipe material 316L.

[0031] In this implementation plan, the process medium contains solid particles, causing severe wear and corrosion to the valve. Furthermore, the pipe diameter is greater than DN250, and the operating conditions involve high differential pressure and large flow capacity. Therefore, an eccentric rotary valve is selected. The valve core material is TA2 with an STL12 coating. The coating's main components are Co, W, and C. The mass percentage of Co is 83-92%, W is 7-9%, and C is 1.2-1.7%. The valve stem is made of duplex steel 2205. The valve's service life reaches 22 months.

[0032] Comparative Example 3: Process medium: ammonia mother liquor (NH3 water: about 5%, NH4Cl: about 10%, NaCl: about 15~20%, CO2 about 5%, the remainder is water); operating temperature: 60℃; operating pressure: 0.5MPa-g; pipe diameter DN300, pipe material 316L.

[0033] In this implementation plan, the process medium contains solid particles, causing severe wear and corrosion to the valve. Furthermore, the pipe diameter is greater than DN250, and the operating conditions involve high differential pressure and large flow capacity. Therefore, an eccentric rotary valve is selected. The valve core material is TA2 with an STL12 coating. The main components of the coating are Co, Cr, and W. The mass percentages of Co are 56.2%~61.7%, Cr 28%~32%, and W 7%~9%. The valve stem is made of duplex steel 2205. The valve service life reaches 32 months.

[0034] Comparative Example 4: Process medium: ammonia mother liquor (NH3 water: about 5%, NH4Cl: about 10%, NaCl: about 15~20%, CO2 about 5%, the remainder is water); operating temperature: 60℃; operating pressure: 0.5MPa-g; pipe diameter DN300, pipe material 316L.

[0035] In this implementation plan, the process medium contains solid particles, causing severe wear and corrosion to the valve. Furthermore, the pipe diameter is greater than DN250, and the operating conditions involve high differential pressure and large flow capacity. Therefore, an eccentric rotary valve is selected. The valve core material is TA2 with an STL12 coating. The main components of the coating are Co, Cr, W, and C. The mass percentage of Co is 62-67%, Cr is 28-32%, and C is 1.2-1.7%. The valve stem is made of duplex steel 2205. The valve service life reaches 30 months.

[0036] Comparative Example 5 Process medium: carbonization extract (NaHCO3 crystals: approximately 15%, NH3 water: approximately 5%, NH4Cl: approximately 20%, NaCl: approximately 10%, CO2: approximately 5%, the remainder being water); operating temperature: 50℃; operating pressure: 0.1MPa-g; pipe diameter DN500, pipe material 316L.

[0037] In this implementation scheme, the process medium contains solid particles, causing severe wear and corrosion to the valve. Furthermore, the pipe diameter is greater than DN400, the operating conditions are low differential pressure, and the flow characteristics are not critical. Therefore, a triple eccentric butterfly valve is selected. The sealing ring uses TC4 coated with a diamond-like carbon (DLC) composite coating, which consists of an adhesive layer, a transition layer, and a DLC layer. The adhesive layer is a Cr layer with a thickness of 0.2~0.5μm; the transition layer is a hardness gradient layer with a thickness of 1~1.5μm, containing Cr, W, and C, with Cr having a mass fraction of 25~29 wt.%, W having a mass fraction of 1 wt.%, and C having a mass fraction of 0.18~0.32 wt.%; the DLC layer has a thickness of 1.8-2.2μm. The DLC composite layer uses PVD technology, achieving a hardness of 2000HV, a friction coefficient of 0.1~0.2, and a high temperature resistance of 300℃-350°C. The valve stem is made of duplex steel 2205. The valve service life reaches 24 months.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A titanium-based automatic control valve for a combined alkali plant, characterized in that: The titanium-based automatic control valves, used in automatic tower tilting systems for carbonization towers or automatic vehicle switching systems for external cooling, include eccentric rotary valves, ball valves, and butterfly valves; the valve stems of the eccentric rotary valves, ball valves, and butterfly valves are made of duplex steel 2205. The surface coating of eccentric rotary valves and ball valves contains 55-60% Co, 28-32% Cr, 7-9% W, and 1.2-1.7% C by mass. The valve core substrate of eccentric rotary valves and ball valves contains Ti ≥ 99.2%, Fe ≤ 0.30%, O ≤ 0.25%, C ≤ 0.10%, and N ≤ 0.05%.

2. The titanium automatic control valve for a combined alkali plant according to claim 1, characterized in that: The valve core substrate of eccentric rotary valves and ball valves is made of titanium, grade TA2.

3. The titanium automatic control valve for a combined alkali plant according to claim 1, characterized in that: The surface coating of eccentric rotary valves and ball valves is made of cobalt-based alloy No.

12.

4. The titanium automatic control valve for a combined alkali plant according to claim 1, characterized in that: Ball valves include one or both of the following: regulating ball valves and on / off ball valves.

5. The titanium automatic control valve for a combined alkali plant according to claim 1, characterized in that: The sealing ring material of the butterfly valve is grade TC4.

6. The titanium automatic control valve for a combined alkali plant according to claim 1, characterized in that: The surface coating of the butterfly valve is a diamond-like composite layer; Butterfly valves include one or both of the following: double eccentric butterfly valves and triple eccentric butterfly valves.

7. The titanium automatic control valve for a combined alkali plant according to claim 6, characterized in that: The diamond-like carbon composite layer includes an adhesive layer, a transition layer, and a DLC layer; the adhesive layer, transition layer, and DLC layer are arranged in sequence, with the adhesive layer located on the side closest to the butterfly valve.

8. The titanium automatic control valve for a combined alkali plant according to claim 7, characterized in that: The thickness of the adhesive layer is 0.2~0.5μm; the thickness of the transition layer is 1~1.5μm; and the thickness of the DLC layer is 1.8~2.2μm. The adhesive layer is a metal adhesive layer.

9. The titanium automatic control valve for a combined alkali plant according to claim 8, characterized in that: The metal bonding layer is a Cr layer; the transition layer is a hardness gradient layer, and the elements of the hardness gradient layer include Cr, W and C.

10. The titanium automatic control valve for a combined alkali plant according to claim 8, characterized in that: The mass fraction of Cr is 25~29 wt.%, the mass fraction of W is <0.5 wt.%, and the mass fraction of C is 0.18~0.32 wt.%.

11. The titanium automatic control valve for a combined alkali plant according to claim 7, characterized in that: The diamond-like carbon composite layer uses PVD technology, has a hardness of 2000 HV, a coefficient of friction of 0.1~0.2, and a heat resistance temperature of 300℃~350°C.