CN107140132B

CN107140132B - Circulating dew-reducing and air-returning adjusting device for large low-temperature liquid cargo ship

Info

Publication number: CN107140132B
Application number: CN201710334198.0A
Authority: CN
Inventors: 陈瑞权; 石峰; 侯全振; 杨波; 周斌; 郑坤
Original assignee: China National Offshore Oil Corp CNOOC; CNOOC Energy Technology and Services Ltd; Oil Production Services Branch of CNOOC Energy Technology and Services Ltd
Current assignee: China National Offshore Oil Corp CNOOC; CNOOC Energy Technology and Services Ltd; Oil Production Services Branch of CNOOC Energy Technology and Services Ltd
Priority date: 2017-05-12
Filing date: 2017-05-12
Publication date: 2023-06-23
Anticipated expiration: 2037-05-12
Also published as: CN107140132A

Abstract

The invention discloses a circulating dew-reducing and air-returning adjusting device of a large-sized low-temperature liquid cargo ship, which comprises a cargo hold air-returning main pipe and a dry compartment air-returning main pipe which are connected with cargo hold/dry compartment emptying ports, wherein the cargo hold air-returning main pipe and the dry compartment air-returning main pipe are both connected to a balance valve, and one outlet of the balance valve is sequentially connected with a venturi tube, an air filter and a pressure balance tank; the two air outlets of the pressure balance tank are respectively connected to the blow-down pipe and the inlet end of the original drying and dew-lowering device of the ship, the water outlet of the air filter is connected to a residual condensed water discharging pipeline, the air supplementing port of the venturi tube is connected with a new air pipe, and the other outlet of the balance valve is connected to the blow-down pipe. The invention recycles the gas discharged from the cabin under a certain pressure and through drying and dew reduction, uses venturi tube and other devices to produce the functions of temperature reduction, pressure reduction and negative pressure adsorption, and mixes with supplementary air to regulate the pressure, so that the gas dew point at the inlet of the original drying and dew reduction device of the ship is continuously and circularly reduced.

Description

Circulating dew-reducing and air-returning adjusting device for large low-temperature liquid cargo ship

Technical Field

The invention relates to a drying dew-reducing technology in the loading process of a low-temperature liquid cargo ship, in particular to a circulating dew-reducing and air-returning adjusting device of a large-sized low-temperature liquid cargo ship.

Background

For LNG, the low-temperature cargo transportation ship of LEG reduces and keeps the low dew point value of the cargo tank and the dry compartment (such as a C-shaped independent cargo tank ship), if excessive moisture exists before loading, the cargo tank is affected in the cargo quality, the moisture can be condensed into micro-ice to affect the operation of the submersible liquid cargo pump, and the pump shaft and other parts are damaged; if the dew point of the dry compartment is too high, the heat preservation effect of the heat preservation layer is affected, and the heat preservation is seriously disabled, so that the dehumidification dew-reducing process is required to be carried out on the cargo hold and the dry compartment before loading according to the requirements of the process and the product specifications, the dew point generally needs to reach higher requirement values, for example, the dew point of the cargo hold and the dry compartment of the LNG carrier should be reduced to-50 ℃ to-60 ℃ or even lower. The low-temperature liquid cargo ship generally uses an air compressor and dehumidifying and dew-reducing equipment which are arranged on the ship to perform dew-reducing and cabin-flushing process on the dry compartment air of the cargo compartment.

The existing liquid cargo ship filling and dew-lowering widely used unidirectional opening operation method comprises the steps that after air is compressed by a compressor, dew-lowering treatment is carried out on the air, the air is discharged to a cargo hold and a dry bay by an air dryer, and the cargo hold and the dry bay are discharged to the atmosphere from the free end of a discharge port of each cargo hold, so that the liquid cargo ship filling and dew-lowering requirement is that high-quality and large-capacity dew-lowering equipment is firstly provided, a dew-lowering target can be achieved only after a certain time of flushing operation, and a flushing effect can be guaranteed only by using more than three times of gas displacement according to experience, for example: under ideal environmental conditions, if the exposure reduction treatment is needed for a single-cabin hold 8000 cubic meters of the cargo hold, the standard can be theoretically achieved after 3 times (8000 cubic meters) of treatment capacity by using 1000 cubic meters of dew point reduction equipment per hour in a common environment. If some areas are humid, the dew-reducing dehumidification process will digest longer.

Under the unidirectional open dew-lowering cabin-filling mode, the cabin-filling gas with certain pressure subjected to dew-lowering treatment is directly emptied to cause waste, meanwhile, for middle and large LNG with larger cabin capacity, the LEG ship is limited by the processing capacity of air dew-lowering equipment, if the processing capacity exceeds that of a dryer, the load of the dryer is increased, the dew-lowering effect is deteriorated, the processing capacity of the air-intake dew-lowering process in the high-temperature high-humidity environment is obviously reduced, the dew point requirement value of the LNG, the LEG ship has strict standard, and the ship operation time and the cargo loading efficiency are seriously influenced due to overlong ship dew-lowering process operation. In addition, the ship gas drying system adopts an adsorption type drying mode (or a combined suction drying mode), and is used in overload for a long time, so that the energy consumption of the drying equipment can be increased, and the consumption products such as an adsorption filter are increased, and the service life of the whole equipment is shortened.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a circulating dew-reducing and air-returning adjusting device for a large-sized low-temperature liquid cargo ship, which fully recycles the cabin-filling exhaust gas which has certain pressure and is subjected to drying dew reduction. The device uses venturi tube and other devices to produce the functions of temperature reduction, pressure reduction and negative pressure adsorption, and is mixed with supplementary air to regulate the pressure, so that the gas dew point at the inlet of the original drying dew-reducing device of the ship is continuously and circularly reduced.

The technical scheme adopted by the invention is as follows: the circulating dew-reducing and air-returning adjusting device of the large low-temperature liquid cargo ship comprises a cargo hold air-returning main pipe connected with a cargo hold emptying port and a dry compartment air-returning main pipe connected with a dry compartment emptying port, wherein the cargo hold air-returning main pipe and the dry compartment air-returning main pipe are connected to a balance valve, and one outlet of the balance valve is sequentially connected with a venturi tube, an air filter and a pressure balance tank; the two air outlets of the pressure balance tank are respectively connected to the blow-down pipe and the inlet end of the original drying and dew-lowering device of the ship, the water outlet of the air filter is connected to a residual condensed water discharging pipeline, the air supplementing port of the venturi tube is connected with a new air pipe, and the other outlet of the balance valve is connected to the blow-down pipe.

And the cargo hold emptying port returns to the cargo hold return air main pipe through a return air branch pipe system.

And the dry compartment emptying port is returned to the dry compartment air return main pipe through an air return branch pipe system.

And the new air pipe is provided with an adjusting valve.

And a valve group is arranged on the blow-down pipe.

The beneficial effects of the invention are as follows:

1. the circulating dew-reducing and air-returning adjusting device can reintroduce the reflux gas of the emptying port (or the emptying pipeline of the dry compartment) of the cargo compartment into the inlet main pipe of the original drying dew-reducing device of the ship, so that the dried gas after dew reduction can be recycled, the purpose that the cabin gas is quickly dew-reduced to reach the dew point is accelerated, the dew-reducing effect is obviously improved, the load of the original drying dew-reducing device of the ship can be reduced, the dew-reducing process quality of high-capacity gas is ensured, the dew-reducing process time of the ship is saved, and precious time is saved for the production and operation of the ship, thereby improving the production efficiency.

2. The circulating dew-reducing and air-returning adjusting device can be used for recycling the cabin-filling gas, so that the capacity of processing capacity of compression and drying equipment carried by a ship can be improved, the maintenance frequency of equipment replacement of an air filter and a drying filter can be reduced, and the operation and maintenance cost of the whole equipment can be reduced, thereby prolonging the service life of the original drying dew-reducing device of the ship.

3. In the invention, the circulating dew-reducing and air-returning adjusting device consists of venturi tubes and other devices, so that the balance of the pressure and the flow of the inlet air of the original drying dew-reducing device of the ship can be ensured, the pressure can be adjusted and set according to the requirements of the original drying dew-reducing device of the ship, and the negative pressure is effectively prevented from occurring.

4. According to the invention, the circulating dew-reducing and air-returning adjusting device is provided with the gas filter and the buffer tank, so that the cleanliness and pressure stability of the return gas entering the original drying dew-reducing device of the ship can be kept, the system stability is high, the buffer tank can be provided with the indicators of parameter values such as temperature, pressure, dew point and the like, the inlet of the drying system is conveniently monitored, the convenience of use is realized, the pressure stability of the inlet of the air compressor device can be kept, the impact on the ship drying system is avoided, and the whole system is more practical and efficient.

5. According to the invention, the regulating valve is additionally arranged at the inlet of the circulating dew-reducing and air-returning regulating device, so that the air quantity of fresh air entering the drying system can be regulated, and the fresh air can completely enter the dew-reducing drying system from the outside when needed, thereby improving the management convenience;

6. in the invention, the pressure balance tank is connected with the blow-down pipe and the valve group for centralized and directional discharge, so that the discharge of the gas discharged from the cargo hold with too low oxygen content or poisonous and harmful gas in a specified direction can be effectively ensured.

Drawings

Fig. 1: the invention is a schematic structural diagram.

The drawings are marked: 1. a cargo hold return air main pipe; 2. a dry compartment return air main pipe; 3. a venturi tube; 4. a new air pipe; 5. an air filter; 6. a pressure balancing tank; 7. a condensate water residue discharge pipeline; 8. a balancing valve; 9. blow-down pipe; 10. a regulating valve; 11. the inlet end of the original drying dew-reducing device of the ship.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in figure 1, the circulating dew-reducing and air-returning adjusting device of the large-sized low-temperature liquid cargo ship comprises a cargo hold air-returning main pipe 1 connected with a cargo hold emptying port and a dry compartment air-returning main pipe 2 connected with a dry compartment emptying port, wherein the cargo hold/dry compartment emptying port is respectively returned to the cargo hold/dry compartment air-returning main pipe 1/2 through an air-returning branch pipe system. The cargo compartment return air main pipe 1 and the dry compartment return air main pipe 2 are connected to a balance valve 8, and one outlet of the balance valve 8 is sequentially connected with a venturi tube 3, an air filter 5 and a pressure balance tank 6; two air outlets of the pressure balance tank 6 are respectively connected to an air vent pipe 9 and an inlet end 11 of an original drying and dewing device of the ship, a water outlet of the air filter 5 is connected to a condensate water residue discharging pipeline 7, an air supplementing port of the venturi tube 3 is connected with a fresh air tube 4, and an adjusting valve 10 is arranged on the fresh air tube 4; the other outlet of the balance valve 8 is connected to the blow-down pipe 9, and a valve group is arranged on the blow-down pipe 9.

In the invention, the return air branch pipelines of the cargo hold/dry compartment are respectively connected back to form a summary and are converged to the main pipe 1/2 of the cargo hold/dry compartment, in the process of drying and inflating the cargo hold/dry compartment of a ship, the pressure in the main pipe 1/2 of the cargo hold/dry compartment is gradually increased to a certain value along with the original drying and dewing device of the ship to gradually increase the pressure in the cargo hold/dry compartment to a certain value, when the pressure is higher than the ambient air pressure through the venturi tube 3, the connection mode can smoothly realize the drying circulation because the exhaust air pressure is always higher than the ambient air pressure, the external supplementary air from the fresh air supplementing tube 4 and the regulating valve 10 is absorbed due to the negative pressure absorption effect of the depressurization (dewing) of the return air at subsonic speed through the venturi tube 3, the mixed air passes through the filter 5 and the pressure balancing tank 6, and then enters the inlet end 11 of the original drying and dewing device of the ship to form a circulating re-drying and dewing process until the air dewing reaches a qualified value, when the pressure of the pressure balance tank 6 is regulated due to maintenance and other reasons or needs, the conversion balance valve 8, the fresh air pipe 4 and the regulating valve 10 are regulated, so that the external fresh air can be completely used, the fresh air directly enters the system to reach the inlet of the original drying and dewing device of the ship, and meanwhile, the blow-down pipe 9 and the valve group are required to be opened to intensively blow down the gas in the cargo hold/dry cabin, or the gas in the cargo hold/dry cabin is exhausted through the original discharge ports of each cabin.

The invention comprehensively considers the running environment and the safety requirement of the low-temperature liquid cargo ship, and the arrangement and the structure of the device can lead the low Wen Yehuo ship to play advantages in the aspects of the dry-compartment dew-reducing treatment efficiency and convenience of the cargo hold, thereby greatly improving the energy-saving and environment-friendly effects of the ship.

Claims

1. The circulating dew-reducing and air-returning adjusting device for the large low-temperature liquid cargo ship is characterized by comprising a cargo hold air-returning main pipe connected with a cargo hold emptying port and a dry compartment air-returning main pipe connected with a dry compartment emptying port, wherein the cargo hold air-returning main pipe and the dry compartment air-returning main pipe are connected to a balance valve, one outlet of the balance valve is sequentially connected with a venturi tube, an air filter and a pressure balance tank, two air outlets of the pressure balance tank are respectively connected to an air discharge pipe and an inlet end of an original drying dew-reducing device of the ship, a water outlet of the air filter is connected to a residual condensed water discharge pipeline, a fresh air pipe is connected to a gas supplementing port of the venturi tube, and the other outlet of the balance valve is connected to the air discharge pipe; wherein, the new air pipe is provided with an adjusting valve;

in the process of drying and inflating the ship cargo hold and/or the dry compartment, along with the continuous pressurization of the original drying and dew-reducing device of the ship to the cargo hold and/or the dry compartment, the pressure in the cargo hold air return main pipe and/or the dry compartment air return main pipe is gradually increased to a set value, and when the pressure is higher than the ambient air pressure through the venturi tube, the drying circulation is realized, and the subsonic reflux gas absorbs the external supplementary air from the fresh air tube and the regulating valve through the depressurization negative pressure adsorption effect generated by the venturi tube, and the mixed gas passes through the air filter and the pressure balance tank and then enters the inlet end of the original drying and dew-reducing device of the ship, so that the circulating re-drying dew-reducing process is formed until the air dew-reducing reaches a qualified value.

2. The circulating dew-reducing and air-returning adjustment device for a large-sized low-temperature liquid cargo ship according to claim 1, wherein the cargo hold emptying port is returned to the cargo hold air-returning main pipe through an air-returning branch pipe system.

3. The circulating dew-reducing and air-returning adjustment device for the large-sized low-temperature liquid cargo ship according to claim 1, wherein the dry compartment emptying port is returned to the dry compartment air-returning main pipe through an air-returning branch pipe system.

4. The circulating dew-reducing and air-returning adjusting device for a large-sized low-temperature liquid cargo ship according to claim 1, wherein a valve group is arranged on the blow-down pipe.