A method for heat preservation of urea, NaOH, and Mg(OH)2 storage tanks

Abstract

A method for heat preservation of urea NaOH and Mg(OH)2 storage cabin, aiming at the ship equipped with SCR system, EGR system, iCER system and desulfurization system, and the ship needs to store urea, NaOH or Mg(OH)2. The condensate water of air conditioning unit is collected and introduced into the storage cabin by gravity, and the condensate water production and condensate water temperature of air conditioning unit are analyzed and calculated. Under the premise that the cabin capacity meets the conditions, the condensate water is used for cooling the urea cabin, and then discharged into the clean bilge water tank, which maximizes the cooling capacity of the condensate water. In winter or cold weather, when the air conditioning unit does not need to run, in order to avoid the temperature of the solution cabin being too low, the discharge water in the clean bilge water tank can be used to heat the storage cabin before discharging, which ensures that the storage temperature of urea, NaOH or Mg(OH)2 solution is 10~35℃.

Description

Technical Field

[0001] This invention belongs to the field of ship operation design, and specifically relates to a method for heat preservation of urea NaOH and Mg(OH)2 storage tanks. Background Technology

[0002] With increasingly stringent environmental requirements for ship operations, SCR systems, EGR systems, iCER systems, and desulfurization systems for treating emissions from main engines and generators are now widely used in all operating vessels. These systems require urea, NaOH, or Mg(OH)2 as raw materials for catalytic reduction reactions to reduce NOx or Sox levels in exhaust systems. Therefore, ships need to install urea, NaOH, or Mg(OH)2 storage tanks of a certain capacity for storing these solutions. The storage temperature for these solutions is 0–45°C, but to prevent crystallization or deterioration, the storage temperature is generally set at 10–35°C during ship operation. Since the engine room ambient temperature is set at 0–45°C, the urea, NaOH, and Mg(OH)2 storage tanks need to be heated or cooled to maintain the solutions within the 10–35°C environment. Currently, the commonly used heating or cooling methods are freshwater cooling and seawater cooling. Freshwater cooling increases the volume of the ship's cryogenic freshwater system, consequently increasing the capacity and power of the cryogenic freshwater cooling pumps, central plate heat exchangers, and main seawater pumps, thus raising the costs of ship construction and operation. Seawater cooling similarly requires increased capacity and power for the seawater pumps. Furthermore, due to the use of a seawater system, the related cooling pipes need to be made of stainless steel of 316L or higher, resulting in relatively high construction costs. Living quarters typically use air conditioning units for room cooling. During operation, these units generate a large amount of condensate, which is generally not utilized but directly discharged into the clean water bilge tanks or sludge wells, representing a degree of waste. The clean water vent tanks located at the bottom of the ship are generally used to store steam main vent water containing a certain amount of oil, main engine air cooler vent water, and generator vent water. This freshwater is generally discharged overboard after passing oil content monitoring, and the heat contained within the freshwater is not utilized, resulting in further waste. Therefore, the wasted fresh water and condensate can be used to cool the storage tanks of urea, NaOH, or Mg(OH)2, thereby saving energy. Summary of the Invention

[0003] To solve the above problems, the present invention provides a method for heat preservation of urea NaOH and Mg(OH)2 storage tanks, the technical solution of which is as follows:

[0004] A method for heat preservation of urea NaOH and Mg(OH)2 storage tanks, characterized in that an air conditioning unit is installed on the main deck, and the urea NaOH or Mg(OH)2 storage tank (hereinafter referred to as the urea storage tank) is located below the deck. The air conditioning unit is connected to the urea storage tank through pipelines, and heating and cooling coils are installed inside the urea storage tank. A first condensate drain shut-off check valve is installed on the passage from the air conditioning unit to the urea storage tank.

[0005] The condensate from the air conditioning unit is discharged by gravity into the clean water discharge tank after passing through the urea storage tank. The clean water discharge tank is then returned to the urea storage tank via a discharge pump. A three-way valve for evacuation and a heating shut-off check valve are installed sequentially on the passage from the clean water discharge tank back to the urea storage tank. One of the direct ports of the three-way valve for evacuation is connected to the evacuation pipeline. A second condensate discharge shut-off check valve is installed on the passage from the urea storage tank to the clean water discharge tank. The urea storage tank is connected to the evacuation pipeline via the clean water evacuation shut-off check valve.

[0006] The clean water discharge chamber is equipped with a low-level alarm level switch, a high-level alarm level switch, a high-level pump start level switch, and a low-level pump stop level switch. The high-level pump start level switch and the low-level pump stop level switch send signal commands to the discharge pump.

[0007] During summer operation, the first and second condensate drain check valves are opened, and the condensate is drained into the urea storage tank by gravity.

[0008] When operating in winter, the air conditioning unit stops running and clean water is discharged from the clean water tank. Before being discharged through the clean water discharge pump, the clean water first enters the urea storage tank and is heated. At this time, the condensate discharge shut-off check valve must be closed, and the clean water heating shut-off check valve and the clean water discharge shut-off check valve must be opened.

[0009] Furthermore, in the above-mentioned method for heat preservation of urea NaOH and Mg(OH)2 storage tanks, a temperature sensor is installed inside the urea storage tank to trigger a high-temperature alarm when the solution temperature is above 30°C and a low-temperature alarm when the solution temperature is below 10°C.

[0010] Furthermore, in the above-mentioned method for heat preservation of urea NaOH and Mg(OH)2 storage tanks, the temperature sensor is set at a height 30% below the volume of the urea storage tank and away from the heating and cooling coils inside the urea storage tank.

[0011] Furthermore, in the above-mentioned method for heat preservation of urea NaOH and Mg(OH)2 storage tanks, the clean water discharge tank is located at a lower position than the urea storage tank.

[0012] Furthermore, in the above-mentioned method for heat preservation of urea NaOH and Mg(OH)2 storage tanks, when the solution temperature in the urea storage tank is maintained at 10~35℃ and there is no need for cooling or heating, the air conditioning unit is still running, adopting the system operation mode of summer conditions, and the condensate is discharged through the urea storage tank.

[0013] Furthermore, in the above-mentioned method for heat preservation of urea NaOH and Mg(OH)2 storage tanks, the capacity of the urea storage tank is 60m³. 3 .

[0014] For ships equipped with SCR, EGR, iCER, and desulfurization systems, and requiring the storage of urea, NaOH, or Mg(OH)2, a design scheme is provided that utilizes condensate from the air conditioning units and drain water from the clean bilge tanks for cooling and heating of the tanks. The condensate from the air conditioning units is collected and introduced into the storage tanks by gravity. The condensate generation and temperature are analyzed and calculated to determine the maximum permissible storage tank volume. Under the condition that the tank volume meets the requirements, the condensate is used to cool the urea tanks before being drained into the clean bilge tanks, maximizing the utilization of the condensate's cooling capacity. In winter or cold-weather regions, when the air conditioning units are not operating, to prevent the solution tank temperature from dropping too low, drain water from the clean bilge tanks can be used to heat the storage tanks before unloading, ensuring that the storage temperature of the urea, NaOH, or Mg(OH)2 solution remains between 10 and 35°C. This design saves on the capacity and power of seawater pumps, freshwater pumps, and intercooler plate coolers used in ship operation, conserving energy while reducing unnecessary seawater and freshwater piping and lowering construction costs. This design is suitable for all ships using SCR, EGR, iCER, and desulfurization systems that require the storage of urea, NaOH, or Mg(OH)2 solutions. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the system of the present invention. Detailed Implementation

[0016] The invention will be further described with reference to the accompanying drawings.

[0017] A method for insulating urea, NaOH, and Mg(OH)₂ storage tanks is disclosed. The air conditioning unit 1 is typically installed in a separate air conditioning unit room 2, usually located on the main deck below the living quarters. At sea, where air humidity is high, water vapor in the air condenses inside the air conditioning unit during operation, forming condensate. The condensate temperature is generally 10-15°C. For an air conditioning unit serving a 32-person living area, the condensate flow rate is approximately 208 kg / h. This cooling water flow rate can cool approximately 0.83 m³ of urea, NaOH, or Mg(OH)₂ solution from 45°C to below 35°C within one hour, and can cool 60 m³ of urea, NaOH, or Mg(OH)₂ storage tank 3 to below 35°C within 72 hours. This fully meets the cooling requirements of urea, NaOH, or Mg(OH)₂ storage tanks on most ships. Meanwhile, a temperature sensor 4 is installed in the urea, NaOH, or Mg(OH)2 storage tank 3 for temperature display. It triggers a high-temperature alarm when the solution temperature exceeds 30°C and a low-temperature alarm when it falls below 10°C. To ensure accurate temperature measurement, this temperature sensor needs to be installed at a low position within the tank, below 30% of the tank's height, and away from the heating and cooling coils 6 of the urea, NaOH, or Mg(OH)2 storage tank. Additionally, a level sensor is required in the urea, NaOH, or Mg(OH)2 storage tank for level display. It triggers a high-level alarm when the solution level exceeds 85% and a low-level alarm when the level falls below 30%. The heating and cooling coils 6 are installed inside the urea, NaOH, or Mg(OH)2 storage tank to cool or heat the solution based on the temperature display and alarms from the temperature sensor, thus controlling the solution temperature. The condensate from the air conditioning unit is discharged by gravity into the clean water discharge compartment (part number 7) after passing through the urea, NaOH, or Mg(OH)2 storage tank. The clean water discharge compartment is equipped with a low-level alarm level switch 8 and a high-level alarm level switch 9 for level alarm purposes. It also has a high-level pump start switch 11 and a low-level pump stop switch 12 to start and stop the clean water discharge pump 13. The pump automatically starts when the level is high and automatically stops when the level is low to prevent the clean water discharge pump from running dry. The clean water discharge compartment also needs to be equipped with a temperature sensor to detect the temperature of the clean water inside, which determines whether the urea, NaOH, or Mg(OH)2 storage tank needs to be cooled or heated using the clean water.

[0018] When the air conditioning unit needs to operate during summer and the temperature inside the cabin is high, requiring cooling through condensate, the condensate drain check valve 14 and condensate drain check valve 16 are opened, and the condensate is discharged by gravity to the urea, NaOH or Mg(OH)2 storage tank.

[0019] When operating under winter conditions, the air conditioning unit is not running, and the engine room temperature is low, making it impossible to use condensate for cooling or heating, clean water from the clean bilge water tank 7 can be used. Before being discharged through the clean water discharge pump, this water enters the urea, NaOH, or Mg(OH)2 storage tank for heating. Since other clean drain water sources besides air conditioning condensate, such as steam main drain water, main engine air cooler drain water, and generator drain water, have relatively high temperatures (generally 25~75℃) and large flow rates (generally 5 m³ / h), this is sufficient to meet the heating requirements of the 60 m³ urea, NaOH, or Mg(OH)2 storage tank. When using clean water from the clean bilge tank 7 for heating, the condensate drain check valve 16 needs to be closed, while the clean water heating check valve 15 and the clean water discharge check valve 18 are opened. In addition, the clean water discharge three-way valve 17 is opened to the storage tank direction to ensure that the clean water heats the urea, NaOH or Mg(OH)2 storage tank before being discharged.

[0020] When the solution temperature in the urea, NaOH, or Mg(OH)2 storage tank is maintained at 10~35℃ and no cooling or heating is required, the single air conditioning unit can still operate under summer operating conditions. The condensate can be drained through the urea storage tank because the condensate temperature is 10~15℃, which will not cause the solution temperature in the urea, NaOH, or Mg(OH)2 storage tank to drop below 10℃ or rise above 35℃.

[0021] This patent utilizes the heat contained in the condensate from the air conditioning unit and the cleaning water from the bilge water tanks to heat or cool urea, NaOH, or Mg(OH)2 storage tanks, ensuring the solution temperature in the storage tanks is maintained between 10 and 35°C. This provides better storage conditions for the solutions, preserving their chemical and physical properties. Simultaneously, it eliminates the need for additional freshwater or seawater cooling systems, saving on the capacity and power required for these systems, reducing ship operating costs, and also reducing the number of related cooling pipes, lowering the requirements for pipe materials, and saving on construction costs. This method of utilizing the heat from condensate and cleaning water, which are otherwise unusable by the ship, aligns with the current trend of green shipbuilding and can be applied to all ongoing projects, possessing significant promotional value.

Claims

1. A method for heat preservation in urea NaOH and Mg(OH)2 storage tanks, characterized in that, An air conditioning unit is installed on the main deck. A urea NaOH or Mg(OH)2 storage tank, hereinafter referred to as the urea storage tank, is located below the deck. The air conditioning unit is connected to the urea storage tank through pipelines. Heating and cooling coils are installed in the urea storage tank. A first condensate drain shut-off check valve is installed on the passage from the air conditioning unit to the urea storage tank. The condensate from the air conditioning unit is discharged by gravity into the clean water discharge tank after passing through the urea storage tank. The clean water discharge tank returns to the urea storage tank via the discharge pump (13). A three-way valve (17) and a heating shut-off check valve (15) are installed in sequence on the passage from the clean water discharge tank back to the urea storage tank. One of the direct ports of the three-way valve is connected to the discharge pipeline. A second condensate discharge shut-off check valve (16) is installed on the passage from the urea storage tank to the clean water discharge tank. The urea storage tank is connected to the discharge pipeline via the clean water discharge shut-off check valve (18). The clean water discharge chamber is equipped with a low-level alarm level switch (8) and a high-level alarm level switch (9), a high-level pump start level switch (11) and a low-level pump stop level switch. The high-level pump start level switch and the low-level pump stop level switch send signal commands to the discharge pump. When in summer operation, the first condensate drain stop check valve (14) and the second condensate drain stop check valve (16) are opened, and the condensate is drained into the urea storage tank by gravity. When the air conditioning unit stops operating during winter, the clean water in the clean water discharge tank is used. Before being discharged through the clean water discharge pump, the clean water enters the urea storage tank and is heated. At this time, the condensate discharge shut-off check valve must be closed and the clean water heating shut-off check valve (15) and the clean water discharge shut-off check valve (18) must be opened. The urea storage tank is equipped with a temperature sensor that triggers a high-temperature alarm when the solution temperature exceeds 30°C and a low-temperature alarm when the solution temperature falls below 10°C. The temperature sensor is set at a height 30% below the volume of the urea storage tank and away from the heating and cooling coils inside the urea storage tank. When the solution temperature in the urea storage tank is maintained at 10~35℃ and there is no need for cooling or heating, the air conditioning unit is still running, adopting the system operation mode of summer conditions, and the condensate is discharged through the urea storage tank.

2. The method for heat preservation of urea NaOH and Mg(OH)2 storage tanks according to claim 1, characterized in that, The clean water discharge chamber is located below the urea storage chamber.

3. The method for heat preservation of urea NaOH and Mg(OH)2 storage tanks according to claim 1, characterized in that urea... The storage compartment has a capacity of 60m³. 3 .

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