The drying process has already begun when the freezing project is completed, because the structure of the ice is related to temperature and time. Prolonging the freezing process will cause a significant change in the structure of the slurry, indicating that the performance of the product is not constant.
The drying process consists of two phases. * The stage is the sublimation of ice in the slurry, which can be regarded as initial drying. Typically, this portion of the drying is characterized by a fixed relationship between shelf temperature, product temperature, and intracavity pressure. Fix two of these parameters, and the third parameter will not change. In this way, the shelf temperature and the intracavity pressure are maintained within a certain limit, and the sublimation rate of the product temperature will remain fixed. The drying rate is not only related to the temperature of the product, but also to the pressure in the chamber. Keeping a certain temperature constant, increasing the pressure in the chamber will cause the rate of sublimation to decrease. In addition, if a rubber stopper is used during the drying process, the temperature of the product must be determined in accordance with the state of the rubber stopper at the time of freeze-drying.
The second stage of drying is called secondary drying, also known as desorption drying. It begins at the end of the *drying, where the remaining water is removed from the cake as the product temperature approaches the initial dry shelf temperature. For a given intracavity pressure, the temperature between the shelf and the temperature is related to the free water remaining in the product. When the shelf temperature is close to the process temperature of zoi and the shelf temperature is close to the product temperature, the residual moisture in the product will be related to the total pressure in the drying chamber and the water vapor partial pressure. The former can be determined by a total pressure gauge, while the latter is determined by a residual gas mass spectrometer.
In determining the drying procedure of the drug, it is necessary to demonstrate the shelf temperature associated with the time, and the temperature of the product and the total pressure in the drying chamber exhibit a constant. During the drying cycle, especially at the end of the secondary drying, the reliability of the drying process is increased if the time performance of the total pressure in the drying chamber can be confirmed. Temperature-time items are class * performance, while stress is the second type of performance.
1 primary drying (sublimation)
As mentioned earlier, primary drying refers to the sublimation of ice in frozen products. During this process, heat is transferred to the sublimation surface through the product tray (if any) and the glass bottle from the shelf to the frozen solution; the sublimation of the ice and the formation of water vapor through the dry portion of the product to the surface layer; The water vapor from the surface of the product enters the condenser (cold trap) through the vessel; the water vapor condenses in the condenser.
The next step after the condenser is a heat flow from the condensed water. When considering the rate range of this process, this latter step is often overlooked unless the ice load exceeds the capacity of the condenser.
1.1 Heat transfer to the sublimation surface of the frozen block of the drug In the freeze-drying of the drug, the conversion of the thermal energy to the product is accomplished by circulating the heat transfer medium liquid in the shelf in which the glass bottle is placed. Thermal energy is from the lower end of the product container and is conducted to conduct the frozen block to the sublimation surface. For the heat transferred from the shelf to each sublimation surface, it is obstructed by shelves, trays, glass bottles and frozen solutions.
The heat is transmitted to the intermediate medium through which the sublimation surface passes. The large heat blockage is the space between the container tray and the shelf and between the bottom of the bottle and the tray. If the glass bottle is placed directly on the shelf, the thermal resistance only includes space between the bottom of the bottle and the shelf. In addition, increasing the total pressure of the drying chamber can greatly increase the rate of primary drying because high concentrations of gas molecules pass heat from the shelf to the glass via the intermediate space, thereby allowing sufficient heat to pass to the product. Increasing the pressure of non-condensable steam also increases the heat transfer between the heater and the product. Although increasing the pressure in the drying chamber can increase the heat transfer to the product, another factor to consider is how high the pressure in the drying chamber is. If the pressure in the drying chamber is too high, it is possible to prevent the conversion of water vapor from the product. . At the same time, the product temperature is higher than the initial melting temperature, and the fast drying rate of the Zui appears when the temperature of the freezing solution and the bottom of the bottle is high without causing melting of the frozen layer or causing damage to the product. In the freeze-drying process, because sublimation itself requires potential thermal energy, if no heat is transferred to the product, the temperature of the sublimated ice surface will drop. In theory, thermal energy should be balanced with the heat energy consumed by sublimation after it is transmitted to the product. If there is too much, excessive heat absorption leads to a significant increase in product temperature, which causes remelting. If the supply is too low, the rate of sublimation will be reduced.
At the beginning of sublimation, the thermal energy converted to the product is balanced with the thermal energy required for sublimation. However, as the drying process progresses, the sublimation surface shrinks and the supply of heat energy begins to exceed the required thermal energy, as the dry layer of the sample forms an obstacle to the passage of water vapor. If the barrier is high enough, the product temperature will rise even if the shelf temperature is constant. Therefore, the heat supplied to the product during the drying process should be continuously reduced. In fact, in order to accurately balance the input thermal energy with the thermal energy required for sublimation, it is difficult to continuously reduce the shelf temperature. Constantly lowering the shelf temperature requires the use of a control device and carefully experimenting to find the rate of supply thermal energy reduction for precise balance and sublimation rate. If a precise balance is achieved, the product temperature will remain constant throughout the primary drying period. If absorbed by the product with the addition of excess heat, it is possible to separate the frozen sample from the container wall. The result is an accumulation of water vapor between the frozen sample and the glass bottle, severely reducing the heat transfer to the product, resulting in the formation of a frozen core which, upon melting, will create a wet area in the sample.
1.2 Sublimation of ice and passage of water vapor through the drying layer The sublimation process of ice depends on the temperature of the product and the resistance encountered by the water vapor passing through the dry portion of the product, which varies with its own temperature. The vapor pressure gradient of ice between the product and the condenser reflects the conversion of water vapor from the product to the condenser. Thus, for a given condensing temperature, the higher the product temperature (ie, the higher the vapor pressure of the ice), the greater the pressure differential and the faster the drying rate for the same other factors. This is why the frozen solution will complete drying as close as possible to the initial melting temperature without causing the intermediate to melt. The resistance of the dry portion of the product to the solid-vapor interface of the water vapor passage depends on the type of product to be dried. For some products, it is a serious problem because there will be a large pressure drop in the dry part, and the "circulating pressure freeze-drying" method can solve this problem. For the drug solution, although the vapor shift resistance through the dry layer increases as the drying process progresses, the pressure drop across the dried portion is not a serious problem unless the solution is highly concentrated. However, if the dry layer can be removed, it would also be very beneficial to actually remove the resistance of the steam and the drying rate will be greatly increased. If the dry portion of the frozen solution to be dried can be removed continuously, the obstruction of the vapor flow is virtually eliminated. In general, the method of continuously removing the dried portion of the frozen solution to be dried cannot be used for the solution in the bottle.
1.3 Water vapor transfer from the solid-vapor interface to the condenser (cold trap)
After passing through the surface of the dried layer, the water molecules reach the condenser and are transferred from the bottle through the intermediate space of the working chamber. Sealing is carried out throughout the drying period and, if properly placed, does not impede the overall drying rate. The transfer of water molecules to the condenser is primarily dependent on the local moisture pressure on the product. Therefore, sublimation will continue until the partial pressure of moisture on the surface of the product is equal to the vapor pressure of the ice inside the product. However, the pressure caused by surface gas molecules will increase to near this rate. In fact, the presence of gas molecules on the surface of the product and thus collisions with water molecules increases the likelihood of leaving a water molecule and returning a water molecule. Therefore, whether it is mechanically removed or by reducing the pressure on the product, the gas molecules on the product must be removed.
The method of removing gas molecules on the product allows the liquid to be frozen in a container, and the air is blown on the surface to remove moisture from the surface of the frozen block. This method cannot be applied to the production of pharmaceuticals because there are still some difficulties, such as the need to place the solution in the bottle, requiring aseptic conditions and the like. However, this method shows that no vacuum is required in lyophilization. Freezing at atmospheric pressure, the total pressure on the dried sample is not critical because the moisture is mechanically removed. However, in vacuum freeze-drying, the local water pressure on the surface of the product is controlled by the total pressure. For example, let us imagine that a drying chamber is at atmospheric pressure, the freezing solution is at -10 ° C, and the condenser (cold trap) is in - 80 ° C system. The water vapor pressure was 1950 μHg at -10 °C and 0.4 μHg at -80 °C. Despite a large vapor pressure differential, the drying rate will be slow because a water vapor interface layer is formed immediately on the product, and the water molecules reach the condenser along a random diffusion channel and undergo random random collisions. The role of the vacuum pump is to reduce the pressure on the surface of the product, creating a channel that is as "free" as possible for the water molecules (even if it is small by the collision probability) to reach the condenser. The result tells us that in order to dry quickly, one is to reduce the total pressure on the product to zero so that there is little or no collision of water molecules coming from the product to the condenser. Of course, such low drying chamber pressure will result in reduced thermal efficiency of conversion from thermal energy on the shelf to the product. In addition, too low a drying chamber pressure may cause volatile components in the sealing rubber plug to escape, thereby contaminating the product. In addition, when the vacuum pump is operated at a low pressure for a long period of time, it is possible to return the vacuum pump oil.
How much pressure does it take to control the pressure in the drying chamber? The water vapor flow rate in a bottle per unit time (i.e., flux) is almost linearly dependent on the total dry chamber pressure at a temperature between 40 and 260 [mu]Hg. It is important that the water vapor flux is doubled from 40 to 260 μHg. From 260 to 1300 μHg, the increase in flux is not significant. For low initial melting temperature solutions, such as at -35 ° C to -40 ° C, in order not to stop drying or to remelt the product, there are certain restrictions on the pressure conditions. For the solution, when the total pressure of the drying chamber is lower than the vapor pressure of the ice in the product, it is seen that the drying rate is significantly enhanced. In summary, an equilibrium pressure is required between very high and very low pressures during primary drying.
1.4 Condensation of water vapor in the condenser If the heat flow of the condensed steam is neglected, this is a step after the water molecules are removed from the product. Typically, the condenser temperature ranges from -50 ° C to -75 ° C, and during primary drying, the product temperature ranges from -10 ° C to -35 ° C. Depending on the nature of the product itself, it can also work at lower temperatures. However, at -76 ° C, the ice vapor pressure has been quite low (0.76 μHg), and the condenser is operated below a lower temperature and there is no significant increase in the drying rate. The latter step of the general zui usually does not limit the drying rate of the entire process unless the condenser does not meet the low temperature conditions, or the design is defective or exceeds the working capacity of the condenser.
1.5 Eutectic Melting and Destruction During primary drying, depending on the characteristics of the dried solution, two problems must be avoided: eutectic melting (remelting) and destruction of the mother liquor. Both results in damage to the product or loss of the normal desired characteristics of the freeze-dried product. The eutectic melting includes melting in a eutectic state, thereby causing the frozen matrix to melt. It occurs without any temperature change and is dried by liquid dehydration, and the matrix is ​​destroyed at the sublimation ice interface. Both of these conditions occur simultaneously, with eutectic melting occurring in a true low melting matrix (such as a sodium chloride solution) and the latter in forming a frozen amorphous parent (such as a sugar solution). In addition to the “retrograde failure†after sublimation, the main result is that the product temperature (acting on the sublimation interface) rises too high during the primary drying period. The ways to avoid these phenomena are as follows: increase the crystal solute and have a higher destruction temperature. The substance, to help raise the destruction temperature of the mixture, this crystallization aid helps to form a more stable matrix; "heat treatment" to make metastable crystals precipitate; strict control of freeze-drying conditions.
2 secondary drying (desorption)
Secondary drying is the removal of moisture absorbed in the product, which does not separate the moisture from the ice during freezing. If the product is not subjected to secondary drying at room temperature, then sufficient moisture in the product will quickly decompose the product.
The degree of residual moisture of the product determines the time for secondary drying. For pharmaceutical preparations, a humidity of less than or close to 1% is ideal. Since it is impossible to make the humidity percentage of the dried product zero, there is a limit condition of less than about 1%. In order to achieve the purpose of dehydration, it is first necessary to increase the temperature of the product and reduce the pressure in the working chamber. Although the secondary drying is after primary drying, some of the absorbed moisture can still be removed along with the sublimation of the ice.
During the secondary drying, the temperature at which the product should be elevated must be carefully considered. For example, exposing a non-thermostatic substance to an elevated temperature for a long period of time may cause serious decomposition. Sometimes it can be chosen such that it is exposed to high temperatures for a short period of time or to low temperatures for extended periods of time. During the secondary drying, the product temperature usually rises gradually, and after Zui is equal to the shelf temperature. If there is no precise way to determine if the temperature meets the requirements and the shutdown is completed, the drying will continue. If the product dries quickly, this will result in unnecessary energy and time wastage. On the other hand, if the absorption of moisture occurs very slowly, the humidity content may exceed the requirement due to insufficient time.
The drying process consists of two phases. * The stage is the sublimation of ice in the slurry, which can be regarded as initial drying. Typically, this portion of the drying is characterized by a fixed relationship between shelf temperature, product temperature, and intracavity pressure. Fix two of these parameters, and the third parameter will not change. In this way, the shelf temperature and the intracavity pressure are maintained within a certain limit, and the sublimation rate of the product temperature will remain fixed. The drying rate is not only related to the temperature of the product, but also to the pressure in the chamber. Keeping a certain temperature constant, increasing the pressure in the chamber will cause the rate of sublimation to decrease. In addition, if a rubber stopper is used during the drying process, the temperature of the product must be determined in accordance with the state of the rubber stopper at the time of freeze-drying.
The second stage of drying is called secondary drying, also known as desorption drying. It begins at the end of the *drying, where the remaining water is removed from the cake as the product temperature approaches the initial dry shelf temperature. For a given intracavity pressure, the temperature between the shelf and the temperature is related to the free water remaining in the product. When the shelf temperature is close to the process temperature of zoi and the shelf temperature is close to the product temperature, the residual moisture in the product will be related to the total pressure in the drying chamber and the water vapor partial pressure. The former can be determined by a total pressure gauge, while the latter is determined by a residual gas mass spectrometer.
In determining the drying procedure of the drug, it is necessary to demonstrate the shelf temperature associated with the time, and the temperature of the product and the total pressure in the drying chamber exhibit a constant. During the drying cycle, especially at the end of the secondary drying, the reliability of the drying process is increased if the time performance of the total pressure in the drying chamber can be confirmed. Temperature-time items are class * performance, while stress is the second type of performance.
1 primary drying (sublimation)
As mentioned earlier, primary drying refers to the sublimation of ice in frozen products. During this process, heat is transferred to the sublimation surface through the product tray (if any) and the glass bottle from the shelf to the frozen solution; the sublimation of the ice and the formation of water vapor through the dry portion of the product to the surface layer; The water vapor from the surface of the product enters the condenser (cold trap) through the vessel; the water vapor condenses in the condenser.
The next step after the condenser is a heat flow from the condensed water. When considering the rate range of this process, this latter step is often overlooked unless the ice load exceeds the capacity of the condenser.
1.1 Heat transfer to the sublimation surface of the frozen block of the drug In the freeze-drying of the drug, the conversion of the thermal energy to the product is accomplished by circulating the heat transfer medium liquid in the shelf in which the glass bottle is placed. Thermal energy is from the lower end of the product container and is conducted to conduct the frozen block to the sublimation surface. For the heat transferred from the shelf to each sublimation surface, it is obstructed by shelves, trays, glass bottles and frozen solutions.
The heat is transmitted to the intermediate medium through which the sublimation surface passes. The large heat blockage is the space between the container tray and the shelf and between the bottom of the bottle and the tray. If the glass bottle is placed directly on the shelf, the thermal resistance only includes space between the bottom of the bottle and the shelf. In addition, increasing the total pressure of the drying chamber can greatly increase the rate of primary drying because high concentrations of gas molecules pass heat from the shelf to the glass via the intermediate space, thereby allowing sufficient heat to pass to the product. Increasing the pressure of non-condensable steam also increases the heat transfer between the heater and the product. Although increasing the pressure in the drying chamber can increase the heat transfer to the product, another factor to consider is how high the pressure in the drying chamber is. If the pressure in the drying chamber is too high, it is possible to prevent the conversion of water vapor from the product. . At the same time, the product temperature is higher than the initial melting temperature, and the fast drying rate of the Zui appears when the temperature of the freezing solution and the bottom of the bottle is high without causing melting of the frozen layer or causing damage to the product. In the freeze-drying process, because sublimation itself requires potential thermal energy, if no heat is transferred to the product, the temperature of the sublimated ice surface will drop. In theory, thermal energy should be balanced with the heat energy consumed by sublimation after it is transmitted to the product. If there is too much, excessive heat absorption leads to a significant increase in product temperature, which causes remelting. If the supply is too low, the rate of sublimation will be reduced.
At the beginning of sublimation, the thermal energy converted to the product is balanced with the thermal energy required for sublimation. However, as the drying process progresses, the sublimation surface shrinks and the supply of heat energy begins to exceed the required thermal energy, as the dry layer of the sample forms an obstacle to the passage of water vapor. If the barrier is high enough, the product temperature will rise even if the shelf temperature is constant. Therefore, the heat supplied to the product during the drying process should be continuously reduced. In fact, in order to accurately balance the input thermal energy with the thermal energy required for sublimation, it is difficult to continuously reduce the shelf temperature. Constantly lowering the shelf temperature requires the use of a control device and carefully experimenting to find the rate of supply thermal energy reduction for precise balance and sublimation rate. If a precise balance is achieved, the product temperature will remain constant throughout the primary drying period. If absorbed by the product with the addition of excess heat, it is possible to separate the frozen sample from the container wall. The result is an accumulation of water vapor between the frozen sample and the glass bottle, severely reducing the heat transfer to the product, resulting in the formation of a frozen core which, upon melting, will create a wet area in the sample.
1.2 Sublimation of ice and passage of water vapor through the drying layer The sublimation process of ice depends on the temperature of the product and the resistance encountered by the water vapor passing through the dry portion of the product, which varies with its own temperature. The vapor pressure gradient of ice between the product and the condenser reflects the conversion of water vapor from the product to the condenser. Thus, for a given condensing temperature, the higher the product temperature (ie, the higher the vapor pressure of the ice), the greater the pressure differential and the faster the drying rate for the same other factors. This is why the frozen solution will complete drying as close as possible to the initial melting temperature without causing the intermediate to melt. The resistance of the dry portion of the product to the solid-vapor interface of the water vapor passage depends on the type of product to be dried. For some products, it is a serious problem because there will be a large pressure drop in the dry part, and the "circulating pressure freeze-drying" method can solve this problem. For the drug solution, although the vapor shift resistance through the dry layer increases as the drying process progresses, the pressure drop across the dried portion is not a serious problem unless the solution is highly concentrated. However, if the dry layer can be removed, it would also be very beneficial to actually remove the resistance of the steam and the drying rate will be greatly increased. If the dry portion of the frozen solution to be dried can be removed continuously, the obstruction of the vapor flow is virtually eliminated. In general, the method of continuously removing the dried portion of the frozen solution to be dried cannot be used for the solution in the bottle.
1.3 Water vapor transfer from the solid-vapor interface to the condenser (cold trap)
After passing through the surface of the dried layer, the water molecules reach the condenser and are transferred from the bottle through the intermediate space of the working chamber. Sealing is carried out throughout the drying period and, if properly placed, does not impede the overall drying rate. The transfer of water molecules to the condenser is primarily dependent on the local moisture pressure on the product. Therefore, sublimation will continue until the partial pressure of moisture on the surface of the product is equal to the vapor pressure of the ice inside the product. However, the pressure caused by surface gas molecules will increase to near this rate. In fact, the presence of gas molecules on the surface of the product and thus collisions with water molecules increases the likelihood of leaving a water molecule and returning a water molecule. Therefore, whether it is mechanically removed or by reducing the pressure on the product, the gas molecules on the product must be removed.
The method of removing gas molecules on the product allows the liquid to be frozen in a container, and the air is blown on the surface to remove moisture from the surface of the frozen block. This method cannot be applied to the production of pharmaceuticals because there are still some difficulties, such as the need to place the solution in the bottle, requiring aseptic conditions and the like. However, this method shows that no vacuum is required in lyophilization. Freezing at atmospheric pressure, the total pressure on the dried sample is not critical because the moisture is mechanically removed. However, in vacuum freeze-drying, the local water pressure on the surface of the product is controlled by the total pressure. For example, let us imagine that a drying chamber is at atmospheric pressure, the freezing solution is at -10 ° C, and the condenser (cold trap) is in - 80 ° C system. The water vapor pressure was 1950 μHg at -10 °C and 0.4 μHg at -80 °C. Despite a large vapor pressure differential, the drying rate will be slow because a water vapor interface layer is formed immediately on the product, and the water molecules reach the condenser along a random diffusion channel and undergo random random collisions. The role of the vacuum pump is to reduce the pressure on the surface of the product, creating a channel that is as "free" as possible for the water molecules (even if it is small by the collision probability) to reach the condenser. The result tells us that in order to dry quickly, one is to reduce the total pressure on the product to zero so that there is little or no collision of water molecules coming from the product to the condenser. Of course, such low drying chamber pressure will result in reduced thermal efficiency of conversion from thermal energy on the shelf to the product. In addition, too low a drying chamber pressure may cause volatile components in the sealing rubber plug to escape, thereby contaminating the product. In addition, when the vacuum pump is operated at a low pressure for a long period of time, it is possible to return the vacuum pump oil.
How much pressure does it take to control the pressure in the drying chamber? The water vapor flow rate in a bottle per unit time (i.e., flux) is almost linearly dependent on the total dry chamber pressure at a temperature between 40 and 260 [mu]Hg. It is important that the water vapor flux is doubled from 40 to 260 μHg. From 260 to 1300 μHg, the increase in flux is not significant. For low initial melting temperature solutions, such as at -35 ° C to -40 ° C, in order not to stop drying or to remelt the product, there are certain restrictions on the pressure conditions. For the solution, when the total pressure of the drying chamber is lower than the vapor pressure of the ice in the product, it is seen that the drying rate is significantly enhanced. In summary, an equilibrium pressure is required between very high and very low pressures during primary drying.
1.4 Condensation of water vapor in the condenser If the heat flow of the condensed steam is neglected, this is a step after the water molecules are removed from the product. Typically, the condenser temperature ranges from -50 ° C to -75 ° C, and during primary drying, the product temperature ranges from -10 ° C to -35 ° C. Depending on the nature of the product itself, it can also work at lower temperatures. However, at -76 ° C, the ice vapor pressure has been quite low (0.76 μHg), and the condenser is operated below a lower temperature and there is no significant increase in the drying rate. The latter step of the general zui usually does not limit the drying rate of the entire process unless the condenser does not meet the low temperature conditions, or the design is defective or exceeds the working capacity of the condenser.
1.5 Eutectic Melting and Destruction During primary drying, depending on the characteristics of the dried solution, two problems must be avoided: eutectic melting (remelting) and destruction of the mother liquor. Both results in damage to the product or loss of the normal desired characteristics of the freeze-dried product. The eutectic melting includes melting in a eutectic state, thereby causing the frozen matrix to melt. It occurs without any temperature change and is dried by liquid dehydration, and the matrix is ​​destroyed at the sublimation ice interface. Both of these conditions occur simultaneously, with eutectic melting occurring in a true low melting matrix (such as a sodium chloride solution) and the latter in forming a frozen amorphous parent (such as a sugar solution). In addition to the “retrograde failure†after sublimation, the main result is that the product temperature (acting on the sublimation interface) rises too high during the primary drying period. The ways to avoid these phenomena are as follows: increase the crystal solute and have a higher destruction temperature. The substance, to help raise the destruction temperature of the mixture, this crystallization aid helps to form a more stable matrix; "heat treatment" to make metastable crystals precipitate; strict control of freeze-drying conditions.
2 secondary drying (desorption)
Secondary drying is the removal of moisture absorbed in the product, which does not separate the moisture from the ice during freezing. If the product is not subjected to secondary drying at room temperature, then sufficient moisture in the product will quickly decompose the product.
The degree of residual moisture of the product determines the time for secondary drying. For pharmaceutical preparations, a humidity of less than or close to 1% is ideal. Since it is impossible to make the humidity percentage of the dried product zero, there is a limit condition of less than about 1%. In order to achieve the purpose of dehydration, it is first necessary to increase the temperature of the product and reduce the pressure in the working chamber. Although the secondary drying is after primary drying, some of the absorbed moisture can still be removed along with the sublimation of the ice.
During the secondary drying, the temperature at which the product should be elevated must be carefully considered. For example, exposing a non-thermostatic substance to an elevated temperature for a long period of time may cause serious decomposition. Sometimes it can be chosen such that it is exposed to high temperatures for a short period of time or to low temperatures for extended periods of time. During the secondary drying, the product temperature usually rises gradually, and after Zui is equal to the shelf temperature. If there is no precise way to determine if the temperature meets the requirements and the shutdown is completed, the drying will continue. If the product dries quickly, this will result in unnecessary energy and time wastage. On the other hand, if the absorption of moisture occurs very slowly, the humidity content may exceed the requirement due to insufficient time.
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AAA) YANMAR DIESEL ENGINE
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CCC) NIIGATA DIESEL ENGINE
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DDD) AKASAKA
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GGG) MAN B&W
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SJ700~SJ1800/SJ 2000
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