WO2023024301A1

WO2023024301A1 - Lng dual-fuel ship voc recycling system and process based on intermediate medium heat exchange

Info

Publication number: WO2023024301A1
Application number: PCT/CN2021/133647
Authority: WO
Inventors: 朱建鲁; 李玉星; 王武昌; 胡其会; 韩辉; 刘翠伟; 刘金华; 李子禾
Original assignee: 中国石油大学(华东)
Priority date: 2021-08-26
Filing date: 2021-11-26
Publication date: 2023-03-02
Also published as: CN113654373A; AU2021427875B2; AU2021427875A1

Abstract

The present invention relates to an LNG dual-fuel ship VOC recycling process based on intermediate medium heat exchange. The process uses a three-stage condensation circulation system, and the intermediate media use but are not limited to ethane, propane, ethylene glycol, and water. The LNG sequentially cools ethylene, propane, ethylene glycol, and water. The VOC firstly enters a third condenser to be subjected to primary condensation by cooled ethylene glycol and water, and then enters a third separator to be subjected to primary gas-liquid separation; residual gas enters a second condenser to be subjected to secondary condensation by cooled propane, and then enters a second separator to be subjected to secondary gas-liquid separation; and residual gas enters a first condenser to be subjected to tertiary condensation by cooled ethane and then enters a first separator to be subjected to tertiary gas-liquid separation, and discharged gas is gas meeting an emission standard. According to the present invention, condensation recycling of VOC and cold energy utilization of LNG can be achieved, the emission standard can be met, energy loss is reduced, and the problem of waste of cooling capacity produced in an LNG gasification process in a conventional dual-power ship is also solved.

Description

VOC recovery system and process for LNG dual-fuel ship based on intermediate medium heat exchange

technical field

The invention belongs to the field of gas treatment, and in particular relates to a VOC recovery process for an LNG dual-fuel ship based on intermediate medium heat exchange.

Background technique

The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and is not necessarily taken as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

Crude oil transport ships or tankers are the main means of marine transportation of crude oil. Crude oil is a mixture of various liquid hydrocarbons, and the hydrocarbon components are highly volatile, so a large amount of VOC (volatile organic compounds, volatile organic compounds) gas will be produced during crude oil storage, transportation and loading and unloading. Multiple crude oil storage tanks (cargo tanks), the crude oil stored in it will evaporate and generate VOC during transportation. For safety, in order to maintain the pressure of the crude oil storage tank, the VOC generated in the crude oil storage tank needs to be discharged to the outside. However, the direct emission of VOC gas will not only cause a lot of energy waste, but also cause serious environmental pollution. Therefore, countries and the International Maritime Organization have strict requirements on VOC emission standards. At present, the widely used VOC recovery methods mainly include condensation method and adsorption method. The adsorption method is mainly used when the heavy hydrocarbon component is not high, it cannot be used continuously (for example, the activated carbon cannot be regenerated after adsorption) and the use range is relatively narrow. In comparison, the condensation method is a more applicable method, but its purification degree is limited by the condensation temperature, and the condensation temperature must reach about -110°C to ensure that the VOC recovery rate meets the national emission standards. Moreover, the components of VOC gas will vary with the origin of crude oil, and the corresponding cooling capacity requirements of the refrigeration system will also change, so the refrigeration system is required to have a certain cooling capacity adjustment capability.

On the other hand, due to the increasingly stringent environmental protection requirements in recent years, the sulfide emission standards of ships have also become higher and higher. It is necessary to add expensive and bulky desulfurization and denitrification devices to make the final exhaust gas meet the corresponding requirements. The use of LNG as fuel is a very good solution, which can basically make the VOC emission of ships meet the standard. However, the cost of pure LNG fueled ships is high, so LNG dual-fuel ships have become a better choice, which is the development trend of ships in the future. At present, there are actual ships powered by LNG and diesel fuel, and shipyards have such ships. The number of orders is also increasing year by year.

However, there are many problems in the current VOC condensation recovery system. The heat exchanger used in the conventional VOC condensation system is a common shell-and-tube heat exchanger, which has low heat exchange efficiency and large volume. The main problem is that due to the complex composition of VOC and water content, when using a single heat exchanger for condensation, it is inevitable that when the VOC is not completely condensed, the water in it freezes at a low temperature and has a high freezing point. Condensation into a solid phenomenon. The former will cause ice blockage, while the latter will adhere to the wall of the heat exchanger. Both will greatly reduce the heat exchange efficiency and make the heat exchanger unable to work normally. In the past, the solution was to set two sets of condensing systems to work alternately, and when one set was in normal operation, the other set would defrost to ensure that one set of condensing systems was always working normally. But this not only increases the construction investment cost and operating cost, but also takes up more shipboard area, and the economy is not high. In addition, when LNG is used as marine fuel, it needs to be gasified first, and a large amount of cold energy in the gasification process is often not utilized, resulting in a great waste of resources.

Contents of the invention

The object of the present invention is to provide a method for reliquefying VOC by utilizing the cooling capacity of LNG gasification and using it as fuel for the VOC volatilization gas produced in the process of storing and transporting crude oil by LNG and diesel dual-fuel powered ships, especially large oil tankers. Marine VOC condensation liquefaction system and method.

The invention can realize the condensation recovery of VOC and the cold energy utilization of LNG, which can not only meet the emission standard, but also reduce the energy loss, and also solve the waste of cold energy produced in the LNG gasification process in the traditional dual-power ship.

In order to realize the above-mentioned technical purpose, the present invention adopts following technical scheme:

The first aspect of the present invention provides a VOC recovery system for LNG dual-fuel ships based on intermediate medium heat exchange. The system is a three-stage condensation cycle system, including: a first condenser, a first separator, a first Heat exchanger, second condenser, second separator, second heat exchanger, third condenser, third separator, third heat exchanger;

The gas inlet of the first heat exchanger is connected with the LNG gas pipeline, the gas outlet of the first heat exchanger is connected with the gas inlet of the second heat exchanger; the gas outlet of the second heat exchanger is connected with the third The gas inlet of the heat exchanger is connected;

The VOC pipeline is connected to the gas inlet of the third condenser, the gas outlet of the third condenser is connected to the gas inlet of the third separator, and the gas outlet of the third separator is connected to the gas inlet of the second condenser The gas outlet of the gas of the second condenser is connected with the gas inlet of the second separator, the gas outlet of the second separator is connected with the gas inlet of the first condenser, and the gas outlet of the first condenser is connected with the gas inlet of the second separator. The gas inlet of the first separator is connected;

The liquid inlet of the first condenser is connected with the liquid outlet of the first heat exchanger, the liquid inlet of the second condenser is connected with the liquid outlet of the second heat exchanger, and the liquid inlet of the third condenser is connected with the third heat exchanger. The liquid outlet of the heat exchanger is connected.

The present invention has developed a VOC condensation recovery system suitable for LNG dual-fuel ships, which can fully condense VOC step by step to avoid ice blockage and other phenomena, and can also utilize a large amount of cooling capacity generated during LNG gasification, both It can save resources and greatly reduce investment costs.

The second aspect of the present invention provides a VOC recovery process for LNG dual-fuel ships based on intermediate heat exchange, including:

LNG sequentially cools the mixed liquid of ethylene, propane, ethylene glycol and water to obtain the cooled mixed liquid of ethylene, propane, ethylene glycol and water;

VOC is first contacted with the cooled mixture of ethylene glycol and water for primary condensation, and then a gas-liquid separation to obtain VOC after a gas-liquid separation;

The VOC after the primary gas-liquid separation is first contacted with the cooled propane, undergoes secondary condensation, and then performs secondary gas-liquid separation to obtain the VOC after the secondary gas-liquid separation;

The VOC after the secondary gas-liquid separation is firstly contacted with cooled ethylene, condensed three times, and then gas-liquid separated three times to obtain the final product.

The third aspect of the present invention provides the application of any one of the above-mentioned systems in the field of gas treatment.

The beneficial effects of the present invention are:

(1) The present invention can recover and liquefy the VOC evaporated in the petroleum cargo tank during operation, and be used for the dual-fuel engine on board. By combining volatile organic compounds with liquefied natural gas and using them as fuel, it can not only achieve significant environmental benefits such as a large reduction in carbon dioxide emissions, but also greatly reduce the loss of crude oil and the waste of LNG cold capacity.

(2) The operation method of the present application is simple, low in cost, universal, and easy for large-scale production.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

FIG. 1 is a schematic structural diagram of the system of the present application.

Among them, E101 first heat exchanger, E102 second heat exchanger, E103 third heat exchanger, E104 first condenser, E105 second condenser, E106 third condenser, E107 preheater, V101 first separation device, V102 second separator, V103 third separator, MIX100 mixer, P100 pump, Q100 electric energy, Q101 cooling capacity.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

A VOC recovery process for LNG dual-fuel ships based on intermediate medium heat exchange, including a three-stage condensation cycle system, the intermediate medium is respectively but not limited to ethylene, propane, ethylene glycol and water, ethane, propane, butane, ammonia, refrigeration Agent R22, refrigerant R410, refrigerant R44, carbon dioxide, three-stage condensation of VOC. There are three heat exchangers, three condensers and three gas-liquid separators. LNG enters the first heat exchanger to cool ethane, then enters the second heat exchanger to cool propane, and finally enters the third heat exchanger to cool ethylene glycol and water before being discharged as a gas. VOC first enters the third condenser and is cooled by ethylene glycol and water for primary condensation, and then enters the third separator for the first gas-liquid separation; the remaining gas enters the second condenser and is cooled by propane for secondary condensation , and then enter the second separator for the second gas-liquid separation; the remaining gas enters the first condenser to be cooled by ethane for third-stage condensation, and then enters the first separator for the third gas-liquid separation, and the exhaust gas is in line with Emission standard gas.

In some embodiments, the temperature of the heat exchanger decreases, which is generally divided into three stages. The purpose of the high-temperature heat exchanger is to remove water and prevent freezing, and the general temperature is greater than 0°C; the temperature of the medium-temperature heat exchanger is generally based on VOC The temperature is -30 to -60°C; the temperature of the low temperature heat exchanger is -80 to -120°C. If there is no low boiling point composition in the VOC, the low temperature heat exchanger can be omitted.

In some embodiments, the first heat exchanger, the second heat exchanger, and the third heat exchanger are respectively filled with different intermediate media, and the freezing point of the intermediate medium in the first heat exchanger is lower than that of the second heat exchanger. device; the freezing point of the intermediate medium of the second heat exchanger is lower than that of the third heat exchanger.

In some embodiments, the intermediate medium includes: ethylene, propane, ethylene glycol, and water. Preferably, in the mixed solution of ethylene glycol and water, the volume fraction of ethylene glycol is 20-60%.

In some embodiments, the liquid outlet of the first condenser is connected to the liquid inlet of the first heat exchanger.

In some embodiments, the liquid outlet of the second condenser is connected to the liquid inlet of the second heat exchanger.

In some embodiments, the liquid outlet of the third condenser is connected with the liquid inlet of the third heat exchanger.

In some embodiments, a gas mixer and a preheater are further arranged between the VOC pipeline and the gas inlet of the third condenser.

In some embodiments, the inlet ends of the gas mixer are respectively connected to the nitrogen pipeline and the VOC pipeline.

The present invention will be described in further detail below in conjunction with specific examples. It should be pointed out that the specific examples are to explain rather than limit the present invention.

Example 1:

LNG: LNG conducts the first heat exchange with ethylene at -90°C, the temperature changes from -162°C to -93.56°C, and then conducts a second heat exchange with -30°C propane, the temperature becomes -55.75°C, and finally with 5°C The ethylene glycol aqueous solution is used for heat exchange, and the temperature becomes 2.817°C.

VOC: VOC at 50°C is mixed with nitrogen at 50°C. After mixing, the temperature becomes 13.15°C. Then the mixture is heated to 50°C. Glycol solution (0°C), after pre-cooling, the temperature drops to 5°C, and then the gas-liquid separation is carried out to remove the high freezing point substances such as water vapor, and the separated gas 1 is condensed, and the cold source comes from the cooling of the heat exchanger. Propane (-40°C) at the end, after condensation, the temperature of the gas drops to -40°C, and then it is separated to remove the hydrocarbons, and the separated gas 2 is then exchanged with ethylene at -100°C, and the temperature changes after the heat exchange -80°C, and finally, gas-liquid separation.

Intermediate medium: The intermediate medium is mainly exchanged by the intermediate medium heat exchanger, the upper part is the cold end, and the lower part is the hot end.

The ethylene at -90°C first exchanges heat with the LNG at -162°C at the cold end, and the temperature becomes -100°C, and then exchanges heat with the gas 2 at -40°C at the hot end, and the temperature becomes -90°C. cycle.

Propane at -30°C first exchanges heat with LNG (-93.56°C) that has been heated once, and the temperature becomes -40°C after the heat exchange, and then exchanges heat with gas 1 at 5°C, and the temperature becomes -30°C after the heat exchange Celsius, and so on.

The ethylene glycol aqueous solution at 5°C first exchanges heat with the LNG (-55.75°C) that has been heated twice. After the heat exchange, the temperature becomes 0°C, and then exchanges heat with the mixture of nitrogen and VOC heated to 50°C. After heating, the temperature is changed to 5°C, and then the solution is transported to the cold end of the heat exchanger with a pump to circulate.

Example 2

A VOC recovery process for LNG dual-fuel ships based on intermediate medium heat exchange, including a three-stage condensation cycle system, the intermediate medium is respectively but not limited to ethylene, propane, ethylene glycol and water, ethane, propane, butane, ammonia, refrigeration Agent R22, refrigerant R410, refrigerant R44, carbon dioxide, three-stage condensation of VOC. There are three heat exchangers, three condensers and three gas-liquid separators. LNG enters the first heat exchanger E101 to cool ethane, then enters the second heat exchanger E102 to cool propane, and finally enters the third heat exchanger E103 to cool ethylene glycol and water before being discharged in the form of gas. VOC first enters the third condenser E106 for primary condensation with cooled ethylene glycol and water, and then enters the third separator V103 for the first gas-liquid separation; the remaining gas enters the second condenser E105 for cooling with propane Secondary condensation, and then enter the second separator V102 for the second gas-liquid separation; the remaining gas enters the first condenser E104 for tertiary condensation with cooled ethane, and then enters the first separator V101 for the third gas-liquid separation Separation, the exhaust gas is a gas that meets the emission standards.

In some embodiments, the first heat exchanger E101, the second heat exchanger E102, and the third heat exchanger E103 are respectively filled with different intermediate media, and the freezing point of the intermediate media in the first heat exchanger E101 is lower than The second heat exchanger E102; the freezing point of the intermediate medium of the second heat exchanger E102 is lower than that of the third heat exchanger E103.

In some embodiments, the intermediate medium includes: ethylene, propane, ethylene glycol, and water. Preferably, in the mixed solution of ethylene glycol and water, the volume fraction of ethanol is 20-60%.

In some embodiments, the liquid outlet of the first condenser E104 is connected with the liquid inlet of the first heat exchanger E101.

In some embodiments, the liquid outlet of the second condenser E105 is connected with the liquid inlet of the second heat exchanger E102.

In some embodiments, the liquid outlet of the third condenser E106 is connected with the liquid inlet of the third heat exchanger E103.

In some embodiments, a gas mixer MIX100 and a preheater E107 are further arranged between the VOC pipeline and the gas inlet of the third condenser E106.

In some embodiments, the inlet ends of the gas mixer MIX100 are respectively connected to the nitrogen pipeline and the VOC pipeline.

In some embodiments, Q100 and Q101 are energy flows, for example: the pump P100 needs power consumption Q101 , and the preheater E107 needs cooling capacity Q100 .

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or part of them may be equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

A VOC recovery system for LNG dual-fuel ships based on intermediate heat exchange, characterized in that the system is a three-stage condensation cycle system, including: a first condenser, a first separator, a first heat exchanger, a second Condenser, second separator, second heat exchanger, third condenser, third separator, third heat exchanger;

The gas inlet of the first heat exchanger is connected with the LNG gas pipeline, the gas outlet of the first heat exchanger is connected with the gas inlet of the second heat exchanger; the gas outlet of the second heat exchanger is connected with the third The gas inlet of the heat exchanger is connected;

The VOC pipeline is connected to the gas inlet of the third condenser, the gas outlet of the third condenser is connected to the gas inlet of the third separator, and the gas outlet of the third separator is connected to the gas inlet of the second condenser The gas outlet of the gas of the second condenser is connected with the gas inlet of the second separator, the gas outlet of the second separator is connected with the gas inlet of the first condenser, and the gas outlet of the first condenser is connected with the gas inlet of the second separator. The gas inlet of the first separator is connected;

The liquid inlet of the first condenser is connected with the liquid outlet of the first heat exchanger, the liquid inlet of the second condenser is connected with the liquid outlet of the second heat exchanger, and the liquid inlet of the third condenser is connected with the third heat exchanger. The liquid outlet of the heat exchanger is connected.
According to claim 1, the LNG dual-fuel ship VOC recovery system based on intermediate medium heat exchange is characterized in that the first heat exchanger, the second heat exchanger, and the third heat exchanger are respectively filled with different intermediate media, The freezing point of the intermediate medium of the first heat exchanger is lower than that of the second heat exchanger; the freezing point of the intermediate medium of the second heat exchanger is lower than that of the third heat exchanger.
The LNG dual-fuel ship VOC recovery system based on intermediate medium heat exchange according to claim 1, wherein the intermediate medium includes: ethylene, propane, ethylene glycol and water, ethane, propane, butane, ammonia, refrigerant R22 , Refrigerant R410, refrigerant R44, carbon dioxide.
The LNG dual-fuel ship VOC recovery system based on intermediate heat exchange according to claim 1, wherein the liquid outlet of the first condenser is connected to the liquid inlet of the first heat exchanger;

Or, the temperature of the intermediate medium in the first heat exchanger is -80 to -120°C.
The LNG dual-fuel ship VOC recovery system based on intermediate heat exchange according to claim 1, wherein the liquid outlet of the second condenser is connected to the liquid inlet of the second heat exchanger;

The temperature of the intermediate medium of the second heat exchanger is .
The LNG dual-fuel ship VOC recovery system based on intermediate heat exchange according to claim 1, wherein the liquid outlet of the third condenser is connected to the liquid inlet of the third heat exchanger;

The temperature of the intermediate medium of the third heat exchanger is greater than 0°C.
The LNG dual-fuel ship VOC recovery system based on intermediate medium heat exchange according to claim 1, wherein a gas mixer and a gas mixer are also arranged between the VOC pipeline and the gas inlet of the third condenser Preheater.
The LNG dual-fuel ship VOC recovery system based on intermediate medium heat exchange according to claim 1, wherein the gas inlet end of the gas mixer is connected to the nitrogen pipeline and the VOC pipeline respectively;

Or omit the first condenser, the first separator and the first heat exchanger.
A VOC recovery process for LNG dual-fuel ships based on intermediate heat exchange, characterized in that it includes:

LNG sequentially cools the mixed liquid of ethylene, propane, ethylene glycol and water to obtain the cooled mixed liquid of ethylene, propane, ethylene glycol and water;

VOC is first contacted with the cooled mixture of ethylene glycol and water for primary condensation, and then a gas-liquid separation to obtain VOC after a gas-liquid separation;

The VOC after the primary gas-liquid separation is first contacted with the cooled propane, undergoes secondary condensation, and then performs secondary gas-liquid separation to obtain the VOC after the secondary gas-liquid separation;

The VOC after the secondary gas-liquid separation is firstly contacted with cooled ethylene, condensed three times, and then gas-liquid separated three times to obtain the final product.
Application of the system described in any one of claims 1-8 in the field of gas treatment.