Analysis of corrosion resistance of titanium pipe and titanium alloy pipe in chemical industry, petroleum industry and metallurgy industry
Table of Contents
- What is titanium?
- Chlor alkali industry
- Replacing cast iron pipe in ammonia condenser with titanium pipe
- Use titanium pipe instead of carbonization tower cooling cast iron pipe
- TC4 titanium alloy impeller replaces low alloy steel impeller of C02 turbine compressor rotor
- Replacing steel external cooler with titanium external cooler
- Using titanium plate cooler instead of cast iron pipe
- Using titanium alloy impeller instead of aluminum cast iron impeller of 8s alkali pump
- Application of Titanium Valve
- Application in petrochemical industry
- Petroleum Industry
- Metallurgical Industry
- Chemical fertilizer industry
Desalination and shipbuilding industry
- The main characteristics of titanium pipe used in seawater desalination are as follows
- Titanium pipe will gradually replace copper alloy pipe in seawater desalination equipment
- Development and application of titanium materials abroad
- Domestic listed companies involved in titanium pipe or seawater desalination titanium pipe:
- Shipbuilding Industry
- Power industry
- Coke industry
- Paper and textile industry
Another remarkable feature of titanium is its strong corrosion resistance, which is due to its strong affinity to oxygen, which can form a dense oxide film on its surface, which can protect titanium from corrosion by medium. Passivation oxide film can be formed on the surface of titanium in most aqueous solutions. Therefore, titanium has good stability in acidic, alkaline, neutral saline solutions and oxidizing media, and has better corrosion resistance than existing stainless steel and other non-ferrous metals, and even comparable with platinum. However, if the oxide film on titanium surface can be continuously dissolved in a certain medium, titanium will be corroded in this medium. For example, titanium is corroded in hydrofluoric acid, concentrated or hot hydrochloric acid, sulfuric acid, and phosphoric acid because these solutions dissolve the oxide film on the titanium surface. If oxidants or some metal ions are added into these solutions, the oxide film on the surface of titanium will be protected, and the stability of titanium is increased.
In chemical production, titanium is used as corrosion-resistant material instead of stainless steel, nickel base alloy and other rare metals, which is of great significance in increasing production, improving product quality, prolonging service life of equipment, reducing consumption, reducing energy consumption, reducing cost, preventing pollution, improving working conditions and increasing productivity.
In recent years, the range of titanium used in chemical industry in China is expanding, and its consumption is increasing year by year. Titanium has become one of the main anti-corrosion materials in chemical equipment. It is mainly used in distillation tower, reactor, pressure vessel, heat exchanger, filter, measuring instrument, turbine blade, pump, valve, pipeline, chlor alkali production electrode, synthetic tower inner lining and other acid resistant equipment lining. Titanium, as an excellent corrosion-resistant structural material used in chemical plant, has established its position and attracted more and more attention of engineers and technicians.
Chlor alkali industry
Titanium has good stability in all kinds of acid, alkali and salt media, except the above four inorganic acids and aluminum chloride, which is very corrosive. Therefore, titanium is an excellent anti-corrosion material in chemical industry and has been widely used. For example, the use of titanium anode and titanium wet chlorine cooler in chlor alkali industry has achieved good economic results, which is known as a great revolution in chlor alkali industry.
Chlor alkali industry is an important basic raw material industry, its production and development have a great impact on the national economy. This is because the corrosion resistance of titanium to chloride ion is better than that of stainless steel and other non-ferrous metals. At present, titanium is widely used in chlor alkali industry to manufacture metal anode electrolyzer, ion-exchange membrane electrolyzer, wet chlorine cooler, refined brine preheater, dechlorination tower, chlorine cooling washing tower, etc. In the past, non-metallic materials (such as graphite, PVC, etc.) were used as the main parts of these equipment. Due to the unsatisfactory mechanical properties, thermal stability and processing performance of non-metallic materials, the equipment is bulky, energy consumption is large, and the service life is short, and the product quality and environmental pollution are affected. Therefore, since the 1970s, China began to use metal anode electrolyzers and ion-exchange membrane electrolyzers to replace graphite electrolyzers, and titanium made wet chlorine coolers instead of graphite coolers, and achieved good results.
For example: the application of titanium wet chlorine cooler. A large amount of high-temperature wet chlorine gas is produced in the production of caustic soda by salt electrolysis. The temperature is generally 75 ~ 95 ℃, which needs cooling and drying before it can be used.
In the production of chlorine gas from salt electrolysis in China, the production and quality of chlorine gas were affected by unreasonable cooling process or corrosion of cooling equipment, and the environment was seriously polluted. Titanium cooler with high temperature and wet chlorine corrosion resistance was put into production, which changed the production of chlorine in chlor alkali industry. The corrosion rate of titanium is 0.000565mm/a in chlorine water at room temperature, 0.00431mm/a in chlorine water at 80 ℃, and 0.00096mm/a in 95% wet chlorine gas at room temperature. After using titanium wet chlorine cooler in many chlor alkali plants, some of them have been used for nearly 20 years and are still intact.
Soda ash is one of the most basic chemical raw materials, which is directly related to the development of national economy. In the process of soda ash production, the gas medium is mostly NH3 and CO2, and the liquid medium is NaCl, NH4Cl, NH4HCO3 and solution with high concentration of Cl -, and the main equipment such as carbonization tower pipe, hot mother liquor cooler, cooler and crystallizing external cooler which are made of carbon steel and cast iron for carbonation reaction are not resistant to corrosion, with serious corrosion leakage and service life less than three years. From 1975 to 1977, Tianjin Soda Plant and Dalian Chemical Industry Company established factories to carry out titanium application demonstration work. The application effect of 63 × 2mm carbonization tower cooling pipe, titanium flat plate heat exchanger, titanium external cooler, titanium pump, CO2 turbine compressor rotor, Ti-6Al-4V alloy impeller, etc. were very good, which played a model role for the whole industry to carry out titanium technology transformation and build three soda ash plants with an annual output of 600000 tons.
For example: pure titanium pipe is used instead of cast iron pipe in ammonia condenser at the top of distillation tower in a soda ash plant. Ammonia condenser is a kind of equipment which condenses ammonia vapor from distillation tower in soda production process. It is composed of two cast iron cooling boxes, each of which has a diameter of 2.5m and a height of 1.2m. There are 214 cast iron pipes of Φ 63 × 6 × 2986mm in the original box, with 428 pieces in two boxes. Thermosetting phenolic varnish is used inside and outside the pipe for anticorrosion. The medium outside the pipe is NH3, CO2, H2O vapor, and the temperature is about 95 ℃. NH4Cl mother liquor is carried in the pipe to exchange heat with the medium outside the pipe. Under these conditions, the cast iron pipe is seriously corroded. Some pipes are corroded and perforated after one year’s use, and they have been seriously corroded and damaged in two years, so they are not used. In order to solve the serious corrosion problem of cast iron pipes in ammonia condenser, all cast iron pipes were replaced with TA2 titanium pipes with the specification of Φ 60 × 2 × 3010 mm. The O-type rubber ring was used to seal the titanium pipe end and the cast iron flower plate. This is the first distillation tower in soda industry in China. Pure titanium pipe is used as cooling pipe. It has been put into operation for more than two years, and no corrosion phenomenon has been found during macroscopic inspection. The service life is expected to be more than 20 years, which can be 10 times longer than that of cast iron pipe. Due to the corrosion resistance and good heat transfer efficiency of the titanium pipe (the heat transfer efficiency of the cast iron pipe is good in the early stage, poor in the middle stage and invalid in the later stage) during the three-year overhaul period. The NH4Cl mother liquor in the pipe is preheated to recover heat and increase the temperature of the mother liquor entering the distillation tower, which can save a lot of steam and bring obvious economic benefits.
The annual output of soda ash in soda plant of Dalian Chemical Industry Company is 720000t, which is produced by ammonia alkali process and combined soda production process. Since the late 1970s, in order to change the backward situation of equipment, some major equipment were gradually updated with titanium and thorium equipment. After 1983, the application scope of titanium materials was further expanded. The application situation is described as follows.
Replacing cast iron pipe in ammonia condenser with titanium pipe
Ammonia condenser is a kind of equipment which condenses the ammonia from distillation tower in soda production process. It is composed of two cooling boxes with 214 cast iron pipes of diameter 63mm * 6mm * 2986mm. Thermosetting phenolic varnish is used to prevent corrosion inside and outside the pipe. The outside medium is NH3, C02 and H2O steam, and the temperature is about 95 ℃. The inside medium NH4Cl mother liquid exchanges heat with the outside medium. Under these conditions, the cast iron pipes were seriously corroded, and some of them were corroded and perforated after one year’s service. After two years of service, the cast iron pipes in ammonia condenser were completely replaced when the distillation tower was overhauled for 3 years.
In 1977, the alkali plant of Dalian Chemical Industry Company listed the solution of serious corrosion problem of cast iron pipe in ammonia condenser into scientific research project, and ordered TA2 pipe with the specification of φ 60mm * 2mm * 3010mm from Baoji Nonferrous Metal processing plant, which was installed in 1979. This is the first titanium pipe equipment in the plant, and it is also the first time that pure titanium pipe is used in the industrial distillation tower of soda ash in China. It was put into production in December 1979 and has been used for 14 years. So far, no corrosion leakage has been found and the effect is good. According to the inspection and appraisal of the pumping pipe in September 1982 (2 years and 10 months of operation), the service life is expected to be more than 20 years.
Due to the corrosion resistance and good heat transfer efficiency of titanium pipe (the heat transfer efficiency of cast iron pipe is good in the early stage, poor in the middle stage and failure in the later stage) during the three-year period, the NH4Cl mother liquor in the pipe is preheated to recover heat, which improves the temperature of mother liquor entering into the distillation tower, thus saving a lot of steam, with obvious economic benefits (see Table 1). It can be seen from table 1 that the investment of titanium pipe can be recovered and a lot of maintenance time can be saved by using titanium pipe instead of cast iron pipe after running for more than one year. By 1980, titanium pipes were used in all ammonia condensers on the top of four distillation towers. In addition, 428 titanium pipes are also installed in the two water tanks inside the nitrogen liquid distillation tower, with a total of 8t titanium pipes.
Use titanium pipe instead of carbonization tower cooling cast iron pipe
Carbonation tower is the key equipment of soda ash production. There are eight cooling pipes in the lower part of the tower, and cast iron pipes are installed in the box. Thermosetting phenolic varnish is used to prevent corrosion inside and outside the pipe. The contact medium outside the pipe is ammonia salt solution with a large amount of nahc03 crystal from the upper part of the tower and the CO2 gas entering the lower part of the tower upward, and the seawater flows in the pipe, and the temperature in the tower is 50-68 ℃. The cooling pipe is corroded and perforated after only two years of service, and needs to be replaced after 3 years. Moreover, the sealing of the lead ring at the end of the pipe often leaks and has serious scarring, which has a great impact on the production.
Since 1979, TF1 pure titanium pipe and TA2 pure titanium pipe have been used to replace cast iron pipe in 7 towers. In 1981, TF1 recovered pure titanium pipe was installed in the No.5 tower. The weight of each pipe was 5.192kg, and the total weight was 8.17t. The price of each ton was 73500 tons, totaling 600000 yuan. Since it was put into operation in April 1982, no corrosion leakage has been found up to now. It is estimated that the service life can reach more than 20 years. If the service life is calculated as 20 years, the overhaul cost can be saved by 200000 yuan; the output value will be reduced by 8.64 million yuan and the profit will be reduced by 3.16 million yuan; the leakage loss will be reduced by 78.67 tons of ammonia and 240 tons of salt, and the conversion rate will be increased by 800 tons, with a total of 62000 yuan. Based on the above three calculations (excluding the production reduction caused by scab and cleaning pipe), the total loss of cast iron pipe can be reduced by 3.422 million yuan in 20 years. In addition, it can save a lot of maintenance time and improve the operating environment. In 1983, the pure titanium pipe with the specification of φ 63mm * 2mm * 3010mm produced by Baoji Nonferrous Metal processing plant was used. The cast iron pipes in 4 cooling boxes of 13 × 10 tower were replaced, with a total of 170t. The price of that year was 63000 yuan per ton. The factory and Dalian soda Research Institute jointly carried out the intubation test of TA2 pure titanium pipe in carbonization tower. After 406 days and 1149 days of operation, no corrosion was found in the pipes, and the pipes still flash as new.
TC4 titanium alloy impeller replaces low alloy steel impeller of C02 turbine compressor rotor
The impeller of C02 turbine compressor was originally made of 35crmov low alloy steel. In the process of operation, the inlets of stage 1 and stage 3 blades of the impeller were corroded and eroded by C02 water mist, so they could not be used for a short time. After anti-corrosion treatment, the impeller needs to be overhauled after three months of operation and replaced after one year’s operation. At present, investment casting TC4 alloy is used to replace 35crmov low alloy steel (120 kg titanium), which has the advantages of high mechanical strength, corrosion resistance, erosion resistance and good processing performance. The impeller has been running continuously since January 5, 1981. It is safe and stable with little maintenance work. After 5 years of operation, the inlet of impeller blades at all levels is in good condition, and the service life is expected to be more than 20 years. The original frequent maintenance condition is changed, and the economic benefit is very significant (see Table 2). At present, TC4 titanium alloy is used in 4 sets of turbine rotors for ammonia alkali process and 1 turbine rotor for combined soda production process in alkali plant of Dalian Chemical Industry Company.
Replacing steel external cooler with titanium external cooler
The external cooler is used to cool the mother liquor of ammonium chloride in the crystallizer, which is made of carbon steel. Although the inner pipes of the external cooler have been treated with anti-corrosion treatment, the service life of the inner pipes is only about 4 years because of the strong corrosiveness of ammonium chloride mother liquor. If the quality of anticorrosion coating is poor, its service life is only about one year. In February 1980, pure titanium external cooler was used. There were 511 pure titanium pipes with the specification of 51mm * 2mm * 6000mm. After 5 years of operation, no corrosion was found. Only 5 pipes were damaged by the diaphragm due to vibration. It has been used for 14 years so far, and its service life is expected to reach 30 years. The comparison of economic benefits is shown in Table 3. At that time, the investment per ton of titanium pipe was 140000 yuan, but the annual income was 10595 yuan. However, the maintenance of the steel external cooler is frequent, and the standby equipment must be provided to ensure the cleaning and maintenance. Therefore, among the 14 external coolers in the plant, 11 have adopted titanium external coolers.
Using titanium plate cooler instead of cast iron pipe
In the heavy alkali workshop of ammonia alkali process, domestic titanium umbrella plate cooler was used instead of 13 mm and 18 mm. The heat exchange plate was made of TA2 plate, and the cooling area of each set was 60 m2. One titanium umbrella plate cooler can replace 1.5 spray cooling pipes with a cooling area of 3602. The heat exchange efficiency can be increased by 6 times, and the environmental pollution and equipment corrosion caused by seawater steam and seawater spraying are removed.
Titanium plate heat exchanger is used to replace steel pipe type CO2 and turbine compressor oil cooler
The T62 copper plate cooler was used to replace the steel pipe cooler in the oil cooler of C02 turbine compressor. The operation temperature rise and oil temperature of high-speed bearing were reduced by 10-13 ℃ and the amount of cooling sea water was also saved. However, the leakage was caused by corrosion of copper plate. Two domestic titanium plate heat exchangers were installed in 1984, and the trial operation results were satisfactory. After that, eight titanium plate heat exchangers were used in the turbine compressor oil coolers of ammonia alkali process.
Using titanium alloy impeller instead of aluminum cast iron impeller of 8s alkali pump
8s alkali pump is the equipment for conveying alkali liquor in soda production. The impeller is made of aluminum cast iron, which is not resistant to mother liquor erosion and corrosion, and has a very short service life. TC4 titanium alloy impeller was used in 8s pump in 1973. The results show that the impeller can resist the erosion and corrosion of mother liquor, and the effect is good. The service life can be increased by more than 40 times. The comparison of economic benefits is shown in Table 5. This is the first time that titanium alloy impeller has been used in soda pump in China’s soda industry. Titanium pump instead of aluminum cast iron pump
On the basis of the successful trial use of TC4 cast titanium alloy impeller for 8s pump, in order to solve the corrosion problem of alkali mother liquor pump body step by step, since 1983, 24 titanium pumps have been used instead of aluminum cast iron pumps, and good economic benefits have been achieved.
Application of Titanium Valve
The original valve is mostly cast iron, its service life is very short, more than half a year, less only about two months, not only frequent replacement, waste a lot of maintenance man hour, but also affect the output, environmental pollution. In 1989, the diameter of 100 mm titanium globe valve was first applied at the outlet of carbonation tower of ammonia alkali process. In 1992, 12 titanium valves with a diameter of 200 mm were used in the connecting pipe. The effect of application is good, and its economic benefit is very remarkable, and the annual savings are about 300000 yuan.
In the combined caustic soda production, the titanium cast valve seats are used for the outlet rubber film seats and the neutral water gel film seats. Their service life is incomparable to cast iron.
In a word, the application of titanium material in alkali plant of Dalian Chemical Industry Company shows that titanium is one of the most ideal materials for alkali making equipment. The equipment made of titanium has a long service life and remarkable economic benefits.
- The titanium heat exchange pipe project of the calciner gas condenser in Tianjin Soda Plant
- Shandong Haihua Group Co., Ltd
Application in petrochemical industry
In petrochemical industry, titanium is mostly used to manufacture chemical equipment. The material selection of chemical equipment is very important. A large number of pressure vessels, storage tanks, towers, heat exchangers, pipes and even fasteners and connectors should not only bear a certain load, but also be strongly corroded by many media under working conditions, so the working conditions are very harsh. In this case, if the material selection of many equipments is adjusted only on the basis of common stainless steel, it can’t be adapted. However, the mechanical properties of titanium and titanium alloy are similar to those of stainless steel, and their corrosion resistance is far superior. Therefore, in the important chemical equipment, titanium materials are gradually used in various forms, such as lining titanium, titanium steel composite and even all titanium.
The application of titanium in China’s petrochemical industry originated from the early 1980s in the ethylene unit and aromatics extraction unit of Shanghai Jinshan Petrochemical General Plant and the aniline hydrochloric acid production unit of Lanzhou oil and chemical plant. Due to the application of titanium material, the corrosion problem that has long troubled the production of enterprises has been solved. Subsequently, Shanghai Gaoqiao Petrochemical Company and Baling Petrochemical Company successively invested a lot of funds to apply titanium materials in petrochemical industrial equipment, and achieved good economic and social benefits.
In addition to the five organic acids (formic acid, acetic acid, oxalic acid, trichloroacetic acid and trifluoroacetic acid) at higher temperature, titanium has very good stability in organic compounds. Therefore, titanium is an excellent structural material in petroleum refining and petrochemical industry, which can be used to make various reactors, pressure vessels, heat exchangers, separator piping, distillation tower top condenser lining, etc.
In the process of oil and gas drilling and production, titanium drilling and production equipment is used in the UK, which contains 5% H2S and 25% NaCl at a depth of 600m and 262 ℃. The former Soviet Union used titanium pump, titanium valve and titanium flushing brine equipment. In China, Ti-6Al-4V valve plate, valve seat and valve stem are used to solve the corrosion of high temperature H2S, C02 and steam at 600-700atm in China, and the long-term application effect is very good.
Offshore oil and gas exploitation must endure seawater corrosion and stress corrosion for a long time. Ti-6Al-4V is widely used in foreign countries as oil platform support, rope support, high-pressure pump, riser and coupling of seawater circulation and pressure system. Because Ti-6A1-4V is not only resistant to seawater corrosion, but also has high toughness, high yield strength and high fatigue limit. Recently, the prestressed production pipe joint of titanium has been selected abroad. This kind of joint is easy to assemble, light in weight and keeps elastic sealing. Titanium is the best material to be selected. China’s offshore oil industry is entering the stage of large-scale development. At present, the structural parts and key components and equipment of the platform are imported from abroad, and domestic materials are rarely used. But it can be expected that titanium will find a broad market here.
Titanium is a kind of active metal with good gettering property. It is an excellent degassing agent in steel-making industry. It can combine oxygen and nitrogen precipitated from steel during cooling. The addition of a small amount of titanium (< 0.1%) into the steel can make the steel tough and elastic. Titanium is also an important alloy additive in steel-making, aluminum smelting and other industries. Titanium is a common superconducting material because of its superconductivity. In addition, titanium has good stability in acidic solution containing metal ions, so titanium is used in hydrometallurgical industry, such as copper, nickel, cobalt, manganese and other non-ferrous metals
Since the early 1970s, Yunnan Smelter, Shanghai smelter, Huludao Zinc Plant and other non-ferrous metallurgical industries took the lead in the use of titanium materials in electrolytic copper, electrolytic nickel and lead-zinc smelting, which solved the corrosion problem that seriously troubled the production and development of enterprises. The successful application of titanium and titanium equipment in these enterprises also greatly promoted the civilian application of titanium industry in China.
Since the 1980s, many domestic hydrometallurgical enterprises have begun to select titanium materials in technical transformation. Jinchuan Nonferrous Metals Company, Shenyang smelter, Tongling Nonferrous Metals Company, Daye Nonferrous Metals Company. In recent ten years, Fushun Aluminum Plant and other enterprises have consumed hundreds of tons of titanium. The use of these new technologies and equipment has brought the equipment of China’s nonferrous hydrometallurgy industry closer to the world’s advanced level. In the electrolytic production of titanium, it is widely used.
Chemical fertilizer industry
Urea is an important chemical fertilizer. In the production process, urea, ammonia, ammonium carbamate and their mixture are highly corrosive under high temperature and high pressure. The service life of the equipment is greatly increased and the maintenance time is greatly reduced by using titanium instead of stainless steel. Therefore, titanium materials are used in the main equipment of urea production at present.
Desalination and shipbuilding industry
The ability of titanium to resist seawater corrosion is better than that of all other metals. Titanium has special stability in both static and high-speed flowing seawater. Therefore, titanium is an ideal material for seawater desalination. Titanium will be used more and more in this field. Titanium is an ideal structural material for shipbuilding industry because of its strong resistance to seawater and air corrosion, high strength and light weight. It has been widely used in many parts of naval vessels and deep-water submarines.
At present, desalination has spread over more than 60 countries and regions in the world. There are more than 6 million desalination plants in the world. The daily output of desalination is about 35 million tons, and it is increasing at a rate of more than 10% every year. Seawater desalination has become one of the best methods to solve the problem of water shortage. At present, there are three main desalination methods in the world, including MSF, LT-MED and ro. Each of the three methods has its own advantages and disadvantages, and its applicable conditions and scope are also different. In China, LT-MED and RO are mainly used. In the next few years, there will be many desalination projects in China. In the next 3-5 years, seawater desalination will have great development space.
Due to the fact that the current technology has cost advantages for large-scale application of seawater desalination, compared with the south to North Water Diversion Project, the cost per ton of water is lower. The state has issued a series of incentive policies, and the scale of desalination in the next 10 years will be 5 times that of the present. It is the future trend to replace copper alloy with titanium alloy in seawater desalination equipment. The multi-directional advantages of titanium determine the wide application space in the field of seawater desalination pipe in the future. It is estimated that in the next decade, the demand for titanium seawater desalination pipe in China will be about 9500-23520 tons, and that in the world will be about 14063-2812500 tons. Although the preliminary domestic demand is not large, the domestic demand only accounts for 1.6% of the total international demand, which can be said that the overall development space is very large.
The main characteristics of titanium pipe used in seawater desalination are as follows
- The density of titanium is 4.51g/cm3, which is higher than that of aluminum but lower than that of steel, copper and nickel. However, the specific strength is the first in metal, which is 3 times of stainless steel and 1.3 times of aluminum alloy.
- Good corrosion resistance: titanium is a very active metal, its equilibrium potential is very low, and its thermodynamic corrosion tendency in the medium is large. But in fact, titanium is stable in many media, such as oxidation, neutral and weak reducibility media is corrosion-resistant. This is because titanium has a great affinity with oxygen. In air or oxygen containing medium, a dense, strong adhesion and inert oxide film is formed on the surface of titanium, which protects the titanium matrix from corrosion. Even due to mechanical wear, it will self heal or regenerate quickly. This indicates that titanium is a metal with strong passivation tendency. When the medium temperature is below 315 ℃, this characteristic is always maintained.
- Good heat transfer performance: Although the thermal conductivity of titanium is lower than that of carbon steel and copper, the wall thickness can be greatly reduced due to the excellent corrosion resistance of titanium. Moreover, the heat transfer mode between the surface and steam is dropwise condensation, which reduces the heat group. The thermal resistance can also be reduced if there is no scaling on the surface, so that the heat transfer performance of titanium is significantly improved.
- Good heat resistance: the new titanium alloy can be used at 600 ℃ or higher temperature for a long time.
- Good chemical resistance to low temperature: titanium alloys TA7 (ti-5al-2.5sn), TC4 (Ti-6Al-4V) and ti-2.5zr-1.5mo are representative of low-temperature titanium alloys, whose strength increases with the decrease of temperature, but the plasticity changes little.
- The tensile strength is close to its yield strength: this property of titanium indicates that its yield strength ratio (tensile strength / yield strength) is high, which indicates that the plastic deformation of titanium is poor during forming. Due to the large ratio of yield limit and elastic modulus of titanium, the springback ability of titanium during forming is large.
Titanium pipe will gradually replace copper alloy pipe in seawater desalination equipment
- Under the same operation conditions, the wall thickness of titanium pipe is thinner and the amount of pipe material is less. Generally, the wall thickness of copper alloy pipe is 0.9mm-1.2mm; titanium pipe is used instead, and thin-walled pipe with wall thickness of 0.5mm can be used in places with small corrosivity.
- Titanium pipe has good thermal conductivity. The thermal conductivity of titanium is 17 w / (m · K), that of aluminum brass is 10 W / (m · K), and that of 70 / 30 white copper is 29 w / (m · K). However, the thermal conductivity of thin-walled titanium pipe is worse than that of aluminum brass, but it is equivalent to 90 / 10 white copper and better than 70 / 30 white copper.
- Titanium pipe is more cost-effective. The titanium pipe can be counterbalanced with the copper alloy pipe. Because of the low titanium density and the simultaneous interpreting of the same wall thickness, the titanium pipe with the same length is only 50% of the copper alloy pipe. When the thickness of the titanium pipe is 50% of the copper alloy pipe, the titanium pipe with the same heat transfer area is only 1 / 4. of the copper alloy pipe, and the titanium pipe is competitive in price.
- The service life of titanium pipe is longer. Due to the fact that seawater is often mixed with sediment and marine organisms, they adhere to the heat transfer pipe and the pipe end, which will erode the copper alloy pipe, and the copper alloy will also be corroded by Br – in seawater. The titanium pipe will not have this problem, especially when oxygen has to be injected in order to kill the bacteria in seawater, the titanium pipe with good corrosion resistance is needed.
Development and application of titanium materials abroad
0.5mm thick titanium welded pipe is used for condenser of power station produced by Hitachi, Mitsubishi and Toshiba, and 0.5mm-0.7mm titanium welded pipe is used for seawater desalination plant produced by Mitsubishi, Kawasaki, Hitachi, Mitsui and Kobe Steel. In 1983, in 16 years, Japan produced 4038t thin-walled titanium welded pipe for desalination equipment all over the world, and no damage has been caused by seawater corrosion.
Ventilated condensers and jet compressors
The real seawater desalination equipment in Japan is 2650t / D seawater desalination equipment built by Matsushima carbon Mine Co., Ltd. in 1967. Due to the corrosion of Br – in seawater, the heat transfer pipes and pipe sheets of the ventilating condenser and jet compressor of the unit can not be made of copper alloy. After replacing with titanium, the failure caused by corrosion has not occurred.
Heat release condenser
The multi-stage flash condenser uses sea water as cooling water to cool the steam generated by flash chambers at all levels. Because the sea water is often mixed with sediment and marine organisms, they adhere to the heat transfer pipe and the end of the pipe and erode the copper alloy pipe. Therefore, titanium pipes are used in almost all the heat transfer condensers of MSF desalination equipment. Especially in order to kill the bacteria in the sea water, it is necessary to use titanium pipe with good corrosion resistance when oxygen has to be injected.
Heat recovery condenser
The heat transfer area of the condenser in the heat recovery section is large. Due to economic reasons, copper alloy pipes are usually used, but titanium pipes are only used in special occasions. For example, the medium containing ammonia or hydrogen sulfide will cause severe corrosion to copper alloy. In 1977, the 3600t / D MSF desalination plant exported to Germany used titanium instead of copper alloy because it was an accessory equipment of ammonia. Due to the corrosion of oxygen sulfide, the 3120t / D MSP desalination plant in Peru suffered corrosion of aluminum brass pipes after one year of operation, and the whole heat transfer pipes were replaced by titanium pipes.
It is reported that there are 60000 titanium pipes used in the desalination plant with a daily output of 100 tons. In the past 30 years from 1967 to 1994, 52 sets of condensers for thermal power generation and 7 sets of seawater desalination equipment were produced. A total of 11000t titanium welded pipes were used.
Domestic listed companies involved in titanium pipe or seawater desalination titanium pipe:
Panzhihua Iron and Steel Co., Ltd. (the largest titanium resource reserve in China, produces titanium materials and titanium concentrates), will benefit from the large volume of titanium demand and the production of titanium materials in the future;
Jiuli special materials (17.50, – 0.30, – 1.69%) benefited from the gradual application of seawater desalination titanium pipes;
BaoTi shares (25.53, – 0.26, – 1.01%) (the leader of titanium materials), the comprehensive strength of titanium materials and titanium pipes is leading, benefiting from the rapid development of the industry in the future.
With the development of society, the demand for natural resources is increasing, and the development and application of marine resources are paid more and more attention. Some people say that the 21st century is the century of marine development.
The development of ocean needs various equipment, and the realization of any equipment function depends on material technology. Titanium material is a kind of natural marine equipment structural material, which has the characteristics of adapting to the marine environment, such as corrosion resistance, non-magnetic, high comprehensive mechanical properties and machinability. These characteristics of titanium materials provide an important material technology platform for the research and development of new marine products, marine engineering machinery and devices. Therefore, since the end of the 1950s, the application of titanium materials in ship and ocean engineering not only gradually broadens the field, but also increases the consumption.
With the long-term development of marine titanium alloy technology, the marine titanium alloy system has been formed. The semi-finished products of titanium metallurgy used in this industry mainly include plates, forgings, castings, wires and pipes of different specifications. Among them, the consumption of plates is the largest, accounting for more than 70%, followed by forgings (about 15%), castings (12%), and the rest are wire and pipe materials. In order to ensure the construction quality of ships and offshore engineering equipment, the isotropy, moderate microstructure and grain size of various titanium materials with different specifications, plate production, bending, stamping and welding, as well as the preparation of forgings and castings, are the key technologies. In addition, the domestic research and development experience of marine titanium alloy also shows that a new titanium alloy material used in marine products must be improved The verification test of large-scale structure simulation was carried out to investigate its usability and establish the corresponding experimental technology.
Due to the wide range of applications of marine titanium materials, in addition to the general requirements of marine environmental corrosion resistance, other research focuses are:
- ① high performance (high strength, impact toughness, fatigue resistance), high function (high sound permeability), and adapt to the operating environment;
- ② adaptability of material construction process, safety and reliability;
- ③ variety / specification serialization and matching of materials (such as corresponding welding wire material), practicability, low cost.
Ship and ocean engineering depends on its performance and quality, but also depends on whether its price is acceptable. Low cost is an important goal of current research on marine titanium alloy materials and manufacturing technology. The research on low cost of titanium alloy is very active at home and abroad.
Titanium has good stability in many corrosive hot water containing chloride and sulfide, so it has been widely used as cooling pipe of heat exchanger in thermal power plant. The use of thin-walled titanium pipe instead of copper nickel alloy pipe not only greatly improves the service life, but also greatly reduces the maintenance time, and the economic effect is very significant.
Titanium and titanium alloy have good corrosion resistance and are also used in anticorrosive lining of steel chimney. In the domestic Zhangzhou Houshi Power Plant in Fujian Province, the titanium plate is used as the anti-corrosion lining of the steel chimney in the seawater desulfurization system without GGH and bypass. Industrial pure titanium is a kind of thermodynamically unstable metal. If Ti2 + can be produced by dissolution, the standard electrode potential of titanium ionization is – 1.63 V, which makes titanium easy to dissolve in water and release hydrogen. However, in a variety of corrosive media, titanium has a very strong corrosion resistance, which is due to the great passivation of titanium. Its passivation is better than that of cobalt, nickel and stainless steel. It is very corrosion-resistant in many active media, especially for oxidizing medium and medium containing chlorine and chloride. However, the stability of titanium in sulfuric acid and hydrochloric acid is poor. In order to solve the problem that the corrosion resistance of conventional titanium and titanium alloy in reducing medium such as sulfuric acid and hydrochloric acid is not strong, adding molybdenum element (10% 32%) to titanium alloy can greatly improve the corrosion resistance of titanium alloy in reducing medium. The higher the content of molybdenum, the better the corrosion resistance, but the more difficult the melting and processing. It is mainly manifested in the strengthening of the alloy, which affects the application of the alloy to a certain extent. The corrosion resistance of Ti Mo alloy is shown in Table 2. Ti Mo alloy is more suitable for corrosion protection of steel chimney than pure titanium. Ti-20mo and above titanium molybdenum alloy can meet the requirements, and because of its strong chloride corrosion resistance, it is especially suitable for power plants using seawater desulfurization.
Table 2 corrosion resistance data of Ti Mo alloy
Medium mass fraction / temperature / C
Annual corrosion amount (/ mm · year – 1)
Thin wall titanium pipes are used in condensers of Binhai power station. Before the 1960s, aluminum brass or B30 white copper pipes were used. With the increasingly serious pollution of seawater, the service life of the pipes decreased significantly. All titanium condensers have been used in Britain as early as the 1960s. In the 1970s, Japan launched the condenser with thin-walled (0.3-0.5mm) welded titanium pipes, and the cost was greatly reduced. Up to 1987, 30% of the industrial developed countries used titanium condenser. Due to the high requirements for safe operation and reliability of nuclear power plants, special attention is paid to the use of titanium condensers, most of which are thin-walled welded titanium pipes and seamless titanium pipes. China began to test domestic titanium pipes in the late 1970s. Since 1983, 18 titanium condensers have been used in 9 power plants, including Taizhou Power Plant in Zhejiang Province, Jinshan thermal power plant in Shanghai and Zhenhai Power Plant in Zhejiang Province, sharing 700T titanium pipes.
With the rapid development of China’s iron and steel industry, the demand for coke is increasing. In the production of by-products such as sulfur and ammonia, a large amount of coke gas is required to be treated in the production of coke oven gas. At present, the main gas purification processes are as process (nitrogen and sulfur combined washing method) and HPF method (sulfur ammonia method with ammonia as alkali source). As method is characterized by high investment, difficult operation and high efficiency; HPF method is simple, less investment and relatively low efficiency. Because the gas contains highly corrosive H2S, NH3 and HCN, the equipment corrosion is very serious. Titanium materials are used for main equipment in foreign countries, while titanium materials are only used in dust removal device of coke quenching tower in the early 1980s; in the early 1990s, Shijiazhuang coking plant in China introduced the I set of as process gas purification production line in China, including titanium deacidification tower, titanium plate heat exchanger, etc. In 1992, the first set of domestic as process gas purification project was put into operation in Maanshan Iron and steel company. A large number of titanium equipment were used, including titanium deacidification tower, titanium ammonia distillation tower fractionator, ammonia distillation tower and volatile ammonium tower, titanium plate heat exchanger, titanium valve, titanium pipeline, titanium meter, flowmeter, etc. the application effect is very good. After more than ten years of application of as and Tianjin Iron and Steel Co., Ltd., there have been no quality problems in any iron and steel company, such as Baotou Iron and Steel Co., Ltd. In recent years, in order to save investment, our country has developed a new process to remove H2S and HCN from coke oven gas by using HPF high-efficiency composite catalyst. This process has been applied in Wuxi coking plant, Hangang coking plant, Beitai coking plant, Taiyuan coal gasification Co., Ltd., Anyang Iron and Steel Co., Ltd. Titanium materials are used in ammonia fractionator, distillation tower tray, ammonia condenser, coke quenching and dust suppression device. At present, more than 20 iron and steel companies are still under construction. Therefore, the application prospect of titanium equipment in coking industry is very broad.
Development of titanium bubble cap tray
The coke oven gas contains highly corrosive N2S, NH3 and HCN. The upper temperature of fixed ammonium tower and volatile ammonium tower is high, especially the bubble cap tray corrosion at the gas-liquid intersection is more serious. Glass fiber reinforced plastics (FRP) is used in the tray of bubble cap abroad, which has the advantages of heavy wall thickness, high energy consumption, short service life and frequent replacement. In view of this situation, the titanium bubble cap tray is selected, and all the indexes meet the design requirements. The performance is advanced, the application effect is good, and there is no corrosion sign. Therefore, the application prospect is very broad.
Application of titanium in coal gangue
The utilization of coal gangue is a pioneering work to turn waste into treasure. Coal gangue is the waste in coal mining, which is estimated to be hundreds of millions of tons in China. Since 1972, China has been using coal gangue to produce aluminum chloride or aluminum sulfate. The corrosion of stainless steel concentrator is very serious in the renewal process. The titanium reactor, agitator and coil heater (for aluminum chloride) and concentration heater (for aluminum sulfate) have been operated for more than ten years in China.
Economic benefit analysis
A series of titanium equipment, such as titanium bubble cap tray, titanium deacidification tower, titanium ammonia tower separator and titanium plate heat exchanger, are applied in coking industry, which reduces the corrosion of equipment, improves the service life of equipment, reduces the number of start-up and shutdown and the consumption of maintenance manpower and material resources, which has considerable economic and social benefits. The titanium equipment used in coking industry is feasible and reasonable, and the economic and social benefits are very significant. It has wide application value and broad prospect.
Paper and textile industry
Titanium has special corrosion resistance to chlorine dioxide, chlorite, chlorite and other bleaching agents. Therefore, titanium has an important application in bleaching equipment of textile printing and dyeing industry and paper industry. For example, the sub bleaching machine made of titanium has a good effect. Others such as agitator, bleaching tower, heating pot, reaction tower piping, etc.
In the textile industry, synthetic fiber is used as spinneret, continuous bleaching machine, distillation tower, reaction tank, condenser, heat exchange pipe, centrifugal separator, spinneret, valve and pump.
Titanium has been used as a corrosion-resistant metal for 30 years in China. The state attaches great importance to the application and promotion of titanium materials. Through the recent research and application results, it can be predicted that titanium and titanium alloys will have a broader development prospect and application value in the field of corrosion protection in the future.
Source: China Titanium Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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