æŽé’æŽåˆšCorrosion Problems and Selection of metal materials in the Pulp & Paper Industry[Abstract]This paperisanoverview of corrosion problems in the pulp & paperindustry,tocollect and compare the corrosion resistanceper for mance of several classes of alloys throughl aboratorytests,fieldtests,and serviceper for Mancein for mation.Labora torytestswere conducte dinenvironmentsthatretoptopulp paperindustry.It is purpose that fixativein dustry person inorder todecrease the dustry of the huge economiccostsas corrosion. Abstract: The corrosion problems in the pulp and paper industry are reviewed, through laboratory tests, field tests and inspections. The data service department collected and compared the corrosion resistance of several types of alloys. Laboratory tests are conducted in an environment related to the pulp and paper industry. Its purpose is to help people in related industries reduce the huge economic losses caused by corrosion to the industry. Key words Pulp and Paper Corrosion Corrosion Resistant Materials 1 Introduction The conditions for a combined pulp and paper mill medium range from cold water to molten salt, from oxidizing bleaching media to reducing pulp media, and from strongly acidic to hot strong alkaline solutions. . The equipment and materials involved include pipes for conveying wood chips and bark, carbon steel, low-alloy steel, stainless steel vessels and pipes, and titanium vacuum washers and glass fiber reinforced plastic pipes and tanks. Wait.
When chemicals or products are transferred from one process to another, the materials of the process vessels, pumps, valves, pipes, and tanks must be fully resistant to the above-mentioned corrosive media, and it is very difficult to do so. Because the corrosive environment between regions or factories is different, the problems that arise are also different. It is impossible to seek a universal solution that can solve problems widely in industry. The most common types of corrosion encountered in the pulp and paper industry include uniform corrosion, localized corrosion, stress corrosion cracking, and alternate wear-erosion effects. The wear-corrosion alternation is the least studied type of damage. This type of corrosion results in a lot of maintenance work. There are many factors affecting the alternation of wear-corrosion, including the corrosion resistance of the metal itself, such as the presence and stability of the passive film, and the environmental factors such as fluid velocity, turbulence conditions, impact conditions, and the number and characteristics of wear particles. The methods used to prevent wear problems are often ineffective due to the presence of corrosive fluids. For example, the dispersion hardened phase material can solve some solid particle erosion. However, due to the liquid erosion problem, the material matrix performance (ie, corrosion resistance) dominates. Another example is the consumption of corrosion-resistant elements in the matrix to form a hardened phase that is now hardened, and the presence of such hardened phases can increase the liquid erosion problem. Equipment subject to alternation of wear-corrosion includes pipeline systems (especially bends, elbows and T-tubes), stirrers, agitated vessels, heat exchange tubes, turbine blades, nozzles, conduits and steam lines, scrubbers , cutters, grinding plates, grinders, partitions and sprayed equipment.
The purpose of this paper is to help the relevant industry personnel to reduce the huge economic losses caused by corrosion to the industry by summarizing the corrosion problems that exist in the pulp and paper industry. 2 Corrosive continuous digesters, thermomechanical pulp systems, batch digesters, chlorine dioxide generators, tar oil recovery systems, steam condensing systems, drying cylinders, chippers, woodchip transport systems in the pulp and paper industry, Overflow equipment, boiler flue gas dust collectors and washers are all corrosive. The following is a detailed description of some of the most important corrosion problems that exist in the pulp and paper industry. 2.1 Stress Corrosion Cracking of Continuous Cooker Alkali cooking is performed in liquid media containing approximately 100 g/L sodium hydroxide and 35 g/L sodium sulfide and in large amounts of sodium carbonate, sulfate and thiosulfate at 1.1 MPa and 175°C. ongoing. Carbon steel continuous steam cookers often have cracks in the welded structure, which is caused by stress corrosion cracking in the alkaline medium. 2.2 Corrosion of chemical recovery boiler tubes The use of waste heat to increase the recovery of the first and second air temperatures in the furnace is increasing year by year. Water wall, superheater and generator (boiler) pipelines are used in different boilers. The first is the recovery and reuse of cooking chemicals. This involves the extraction, evaporation, and combustion of waste liquids from the pulp to produce steam and the bottom of the furnace to produce molten salts. The industrial trend to control the outflow and discharge as precisely as possible is that the optimum combustion rate and higher pressure boilers have changed the composition of molten salt or "smelting" and combustion gases and increased the temperature of certain parts of the boiler. In this case, the most prone to corrosion problems are the corrosion of the external piping caused by smelting and vulcanization and oxidation, as well as the overheating of pipes, fatigue, wear-corrosion, and corrosion on one side of the cooling pipe. 2.3 Equipment Corrosion in Bleaching and Washing Processes In multi-stage bleaching production lines, pulp must be cleaned in each stage to prevent residual chemicals in each process. The most common bleaching agent is based on oxidizing drug-based chloride ions. This bleach causes etchable localized corrosion of stainless steel cleaning drums and pipes used for cleaning. This corrosion is particularly severe at crevices, under the pulp deposits and at the welds. 2.4 Corrosion of Vacuum Pressure Roller Sheet dewatering is the basic process of papermaking. Before the paper sheet passes through the steam dryer, the dewatering is accomplished by drainage, vacuum suction, pressing and felt water absorption. Vacuum rolls are an important part of many paper machines, which have dense holes on the surface that allow the sucked water to pass through the roll wall. The damage of the vacuum roll is a long-standing problem for the paper machine, and the cause of damage is generally corrosion fatigue. 2.5 Corrosion and damage on the structure The atmosphere in the local processing sites of the pulp and paper mill contains water vapor and chloride, chlorine dioxide, sulfur dioxide, hydrogen sulfide and other corrosive gases, which are highly corrosive, and often Spills and leaks cause severe corrosion of steel and concrete structures such as floors, walkways, columns, beams, and foundations, and pump foundations, cable trays, pipe hangers, control equipment, and many other components often require repair or replacement. .
The most effective way to solve these problems is to properly control comprehensive measures such as corrosion of smoke, steam and spillage, including ventilation. Structural steels can be coated with suitable protective coatings, such as primers containing polyurethanes, vinyls, epoxies, and zinc-rich primers. 3 Abnormal corrosion resistance of foreign alloys in the corrosive environment of simulated pulp and paper industry Introduction The selected alloys are carbon steel, 300-series austenitic stainless steel, 20-type stainless steel, duplex stainless steel and nickel-base alloy. Their nominal chemical compositions are as follows: Product names are listed in Table 1. The foreign laboratory tests collected were conducted in an environment corresponding to the alternating effects of uniform corrosion, localized corrosion, stress corrosion cracking, and various wear-corrosion encountered in the pulp and paper industry. Table 1 Nominal chemical composition of the alloy Ni Fe Cr Mo Cu C Other austenitic stainless steel 304L 8.0 18.0 - - ≤ 0.03 316L 12.0 More than 17.0 2.0 - ≤ 0.03 317L 13.0 More than 19.0 3.5 - ≤ 0.03 317LM 14.0 More than 19.0 4.25 - ≤ 0.03 20-type alloy Carpenter20CB-3 34.0 more than 20.0 2.5 3.5 ≤ 0.03 Nb: 1.0 INCO 904L 25.0 More than 19.5 4.5 1.5 ≤ 0.02 Hastelloy M-532 26.0 More than 22.0 5.0 - ≤ 0.04 Duplex alloy 3RE 60 5.0 More than 19.0 2.5 0.2 ≤ 0.04 N : 0.08 Ferraliumm225 5.0 More than 25.5 3.5 1.7 ≤ 0.04
When chemicals or products are transferred from one process to another, the materials of the process vessels, pumps, valves, pipes, and tanks must be fully resistant to the above-mentioned corrosive media, and it is very difficult to do so. Because the corrosive environment between regions or factories is different, the problems that arise are also different. It is impossible to seek a universal solution that can solve problems widely in industry. The most common types of corrosion encountered in the pulp and paper industry include uniform corrosion, localized corrosion, stress corrosion cracking, and alternate wear-erosion effects. The wear-corrosion alternation is the least studied type of damage. This type of corrosion results in a lot of maintenance work. There are many factors affecting the alternation of wear-corrosion, including the corrosion resistance of the metal itself, such as the presence and stability of the passive film, and the environmental factors such as fluid velocity, turbulence conditions, impact conditions, and the number and characteristics of wear particles. The methods used to prevent wear problems are often ineffective due to the presence of corrosive fluids. For example, the dispersion hardened phase material can solve some solid particle erosion. However, due to the liquid erosion problem, the material matrix performance (ie, corrosion resistance) dominates. Another example is the consumption of corrosion-resistant elements in the matrix to form a hardened phase that is now hardened, and the presence of such hardened phases can increase the liquid erosion problem. Equipment subject to alternation of wear-corrosion includes pipeline systems (especially bends, elbows and T-tubes), stirrers, agitated vessels, heat exchange tubes, turbine blades, nozzles, conduits and steam lines, scrubbers , cutters, grinding plates, grinders, partitions and sprayed equipment.
The purpose of this paper is to help the relevant industry personnel to reduce the huge economic losses caused by corrosion to the industry by summarizing the corrosion problems that exist in the pulp and paper industry. 2 Corrosive continuous digesters, thermomechanical pulp systems, batch digesters, chlorine dioxide generators, tar oil recovery systems, steam condensing systems, drying cylinders, chippers, woodchip transport systems in the pulp and paper industry, Overflow equipment, boiler flue gas dust collectors and washers are all corrosive. The following is a detailed description of some of the most important corrosion problems that exist in the pulp and paper industry. 2.1 Stress Corrosion Cracking of Continuous Cooker Alkali cooking is performed in liquid media containing approximately 100 g/L sodium hydroxide and 35 g/L sodium sulfide and in large amounts of sodium carbonate, sulfate and thiosulfate at 1.1 MPa and 175°C. ongoing. Carbon steel continuous steam cookers often have cracks in the welded structure, which is caused by stress corrosion cracking in the alkaline medium. 2.2 Corrosion of chemical recovery boiler tubes The use of waste heat to increase the recovery of the first and second air temperatures in the furnace is increasing year by year. Water wall, superheater and generator (boiler) pipelines are used in different boilers. The first is the recovery and reuse of cooking chemicals. This involves the extraction, evaporation, and combustion of waste liquids from the pulp to produce steam and the bottom of the furnace to produce molten salts. The industrial trend to control the outflow and discharge as precisely as possible is that the optimum combustion rate and higher pressure boilers have changed the composition of molten salt or "smelting" and combustion gases and increased the temperature of certain parts of the boiler. In this case, the most prone to corrosion problems are the corrosion of the external piping caused by smelting and vulcanization and oxidation, as well as the overheating of pipes, fatigue, wear-corrosion, and corrosion on one side of the cooling pipe. 2.3 Equipment Corrosion in Bleaching and Washing Processes In multi-stage bleaching production lines, pulp must be cleaned in each stage to prevent residual chemicals in each process. The most common bleaching agent is based on oxidizing drug-based chloride ions. This bleach causes etchable localized corrosion of stainless steel cleaning drums and pipes used for cleaning. This corrosion is particularly severe at crevices, under the pulp deposits and at the welds. 2.4 Corrosion of Vacuum Pressure Roller Sheet dewatering is the basic process of papermaking. Before the paper sheet passes through the steam dryer, the dewatering is accomplished by drainage, vacuum suction, pressing and felt water absorption. Vacuum rolls are an important part of many paper machines, which have dense holes on the surface that allow the sucked water to pass through the roll wall. The damage of the vacuum roll is a long-standing problem for the paper machine, and the cause of damage is generally corrosion fatigue. 2.5 Corrosion and damage on the structure The atmosphere in the local processing sites of the pulp and paper mill contains water vapor and chloride, chlorine dioxide, sulfur dioxide, hydrogen sulfide and other corrosive gases, which are highly corrosive, and often Spills and leaks cause severe corrosion of steel and concrete structures such as floors, walkways, columns, beams, and foundations, and pump foundations, cable trays, pipe hangers, control equipment, and many other components often require repair or replacement. .
The most effective way to solve these problems is to properly control comprehensive measures such as corrosion of smoke, steam and spillage, including ventilation. Structural steels can be coated with suitable protective coatings, such as primers containing polyurethanes, vinyls, epoxies, and zinc-rich primers. 3 Abnormal corrosion resistance of foreign alloys in the corrosive environment of simulated pulp and paper industry Introduction The selected alloys are carbon steel, 300-series austenitic stainless steel, 20-type stainless steel, duplex stainless steel and nickel-base alloy. Their nominal chemical compositions are as follows: Product names are listed in Table 1. The foreign laboratory tests collected were conducted in an environment corresponding to the alternating effects of uniform corrosion, localized corrosion, stress corrosion cracking, and various wear-corrosion encountered in the pulp and paper industry. Table 1 Nominal chemical composition of the alloy Ni Fe Cr Mo Cu C Other austenitic stainless steel 304L 8.0 18.0 - - ≤ 0.03 316L 12.0 More than 17.0 2.0 - ≤ 0.03 317L 13.0 More than 19.0 3.5 - ≤ 0.03 317LM 14.0 More than 19.0 4.25 - ≤ 0.03 20-type alloy Carpenter20CB-3 34.0 more than 20.0 2.5 3.5 ≤ 0.03 Nb: 1.0 INCO 904L 25.0 More than 19.5 4.5 1.5 ≤ 0.02 Hastelloy M-532 26.0 More than 22.0 5.0 - ≤ 0.04 Duplex alloy 3RE 60 5.0 More than 19.0 2.5 0.2 ≤ 0.04 N : 0.08 Ferraliumm225 5.0 More than 25.5 3.5 1.7 ≤ 0.04
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