Seawater cascade utilization system and method for integrated refining park

Abstract

The present application relates to a kind of integrated refinery park seawater cascade utilization system and method, including seawater preposition device, primary seawater utilization device and secondary seawater utilization device, seawater preposition device is used to extract seawater and pretreat seawater, primary seawater utilization device includes plate heat exchanger, closed circulating water system, device heat exchanger and corresponding pipeline, secondary seawater utilization device includes condenser, seawater siphon well and corresponding pipeline.The present application is through seawater cascade utilization, seawater is connected in series cascade utilization by the heat exchanger of primary seawater utilization device and the condenser of secondary seawater utilization device, make full use of the cooling capacity of seawater, reduce seawater usage;Through the siphon effect of siphon well, the delivery head loss of water pump is saved, and system energy loss is saved;The closed circulating water system of primary seawater utilization device, by the closed circulation of pipe network, the system resistance of circulating water system is adjusted to 20~25 meters head loss, and system energy loss is saved in large quantities.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of petroleum refining, in particular, especially relates to a seawater cascade utilization system and method for a refining and chemical integration park. BACKGROUND

[0002] Petroleum refining is a process of converting various oil products and chemical products from petroleum through a series of catalytic cracking, synthesis, separation, purification and other treatments. Each production step is very complex and covers a variety of chemical, physical processes and equipment. Main products include liquefied petroleum gas, gasoline, aviation kerosene, diesel, benzene, p-xylene, chemical light oil, polypropylene, MTBE, lubricating oil base oil, etc.

[0003] The process flow of refining and chemical integration is relatively long, and there are many direct feed materials between devices. The existence of direct feed materials reduces the heat load requirement of daily circulating cooling water, but at the same time causes waste of seawater direct cooling capacity.

[0004] The circulating cooling system is an important part of petroleum refining. In each device of petroleum refining, a cooling tower is generally used to cool circulating water, and a steam turbine condenser is mostly cooled by circulating water, and a small part is cooled by air. This cooling method causes a large amount of fresh water to evaporate and be lost. At the same time, due to the large pressure loss of the open cooling water return tower and the spraying pressure, the hydraulic loss of the overall open circulating water system is generally 45-55 meters, and the power consumption is relatively large. SUMMARY

[0005] According to the above technical problems, a seawater cascade utilization system and method for a refining and chemical integration park are provided. Since the seawater temperature is lower in winter, the present application fully utilizes the cooling capacity of seawater by using seawater cascade utilization, and reduces the seawater usage. In addition, the use of closed circulating water system avoids the water head loss of the return water tower pressure, and greatly saves the energy consumption of the circulating water pump.

[0006] The technical means adopted by the present application are as follows:

[0007] The application discloses a seawater step utilization system for a refinery-integrated park, which comprises a seawater preposition device, a first seawater utilization device and a second seawater utilization device.

[0008] Further, the seawater preposition device comprises a seawater pump, a seawater water-intaking filtering device, a seawater water-intaking sterilization device and a seawater pipeline, the seawater sterilization device is used for sterilizing the seawater, the seawater water-intaking filtering device is used for filtering the seawater, the filtered seawater is transported to a circulating water field through the seawater pump and a first seawater pipeline, is distributed to each plate heat exchanger through a pipeline, is collected to a second seawater pipeline after being exchanged with circulating water of the plate heat exchanger, is connected to a siphon well through a water outlet pipe of a surface air cooler after being supplied to a condenser of each device, and is collected into a seawater discharge channel after overflowing from an overflow weir of the siphon well and is discharged into the deep sea.

[0009] Further, the seawater water-intaking sterilization device of the seawater preposition device and a sterilization device arranged at the front end of the circulating water field both adopt sodium hypochlorite produced by seawater electrolysis.

[0010] Further, the closed circulating water system comprises a circulating water pump and a pressure stabilizing tank, the circulating water is pressurized by the circulating water pump, is sent to each device heat exchanger through a pipeline for heat exchange, enters the heat exchanger from the pipeline after the temperature of the circulating water is increased, is exchanged with seawater to reduce the temperature, is collected to the pipeline and then enters the circulating water pump, the pressure stabilizing tank is used for stabilizing the system pressure through nitrogen and stabilizing the liquid level of the pressure stabilizing tank through water supplement.

[0011] Further, the pressure stabilizing tank stabilizes the circulating water backwater pressure of a circulating water pump inlet pipeline in the range of 0.2-0.4 Mpa by supplementing nitrogen and controlling the gas phase pressure of the upper part of the pressure stabilizing tank, stabilizes the circulating water supply pressure of the circulating water pump in the range of 0.4-0.6 Mpa, and buffers the pressure fluctuation of the circulating water system.

[0012] The application further discloses a seawater step utilization method for a refinery-integrated park, which comprises the following steps.

[0013] Real-time acquisition of primary seawater consumption and secondary seawater consumption, the primary seawater consumption is seawater consumption of the primary seawater utilization device, and the secondary seawater consumption is seawater consumption of the secondary seawater utilization device;

[0014] When the secondary seawater consumption is insufficient, the seawater of the circulating water station is directly transported to the secondary seawater utilization device to supplement the secondary seawater consumption by opening the secondary seawater cross-line valve.

[0015] When the primary seawater consumption exceeds the preset value of the secondary seawater consumption, the seawater of the primary seawater utilization device is directly discharged to adjust the seawater consumption by opening the secondary seawater discharge cross-line valve.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] The present application provides a seawater cascade utilization system and method for a refinery park, which can reduce energy loss of the system, and the heat of the entire refinery park is removed by seawater cooling instead of the evaporation of open circulating water, thereby saving a large amount of fresh water. Due to the cascade utilization of seawater and the siphon effect at the end of the seawater pipeline, the seawater pump only needs to provide a water supply pressure of not less than 0.25 MPa to meet the needs of the system, thereby saving 65% of the power consumption compared with a normal open circulating water system (0.45 MPa of water supply pressure). The pressure difference of the circulating water system of the present application is reduced to 0.25 MPa, which is 45% lower than the pressure difference of 0.45 MPa of the open circulating water system. The heat of the entire refinery park is removed by seawater cooling instead of the evaporation of open circulating water, thereby avoiding a large amount of evaporation loss, and the circulating water replenishment amount is only 1% to 1.5% of that of the open circulating water system, thereby saving a large amount of fresh water. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0019] Figure 1 The figure is a cascade seawater system diagram. DETAILED DESCRIPTION

[0020] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0021] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature, and is in no way limiting on the present application and its applications or uses. Based upon the embodiments herein, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of the present application.

[0022] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, devices, components and / or combinations thereof, but do not preclude the presence or addition of one or more other features, steps, operations, devices, components and / or combinations thereof.

[0023] The relative arrangement of parts and steps, numerical expressions, and numerical values set forth in the various embodiments are not intended to limit the scope of the present application unless otherwise specifically stated. It should also be clearly understood that the size of the parts shown in the attached drawings is not to scale, and that the dimensions of the parts are arbitrarily shown for clarity of the drawings. Techniques, methods, and apparatus known to those of ordinary skill are not discussed in detail because they would only serve to unnecessarily duplicate the relevant portion of the prior art and are fully intended to be understood by one of ordinary skill in the art. In all examples shown and discussed herein, any specific numerical value should be interpreted as merely an example, and not as a limitation. Other examples of the exemplary embodiments can therefore have different values. It should be noted that like reference numerals and letters refer to like items in the following drawings, and thus, once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0024] In the description of the present application, it should be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal", and "top, bottom" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the scope of protection of the present application: the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component itself.

[0025] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0026] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0027] like Figure 1 As shown in the figure, this invention discloses a tiered seawater utilization system for an integrated refining and chemical industrial park, including a seawater pretreatment device, a primary seawater utilization device, and a secondary seawater utilization device. The seawater pretreatment device is used to extract seawater and pre-treat it. The primary seawater utilization device includes a plate heat exchanger 2, a closed-loop circulating water system, a device heat exchanger 8, and corresponding pipelines. The secondary seawater utilization device includes a condenser 3, a seawater siphon well 4, and corresponding pipelines. The seawater provided by the seawater pretreatment device, after heat exchange with the circulating water return water of the closed-loop circulating water system through the plate heat exchanger, enters the device steam duct through pipelines. The turbine condenser receives seawater, which is then siphoned off by a seawater siphon well to reduce the condenser outlet pressure. The seawater overflows from the siphon well's overflow weir and enters the seawater discharge channel for direct discharge into the sea. The circulating water return from the primary seawater utilization unit exchanges heat with the seawater in a plate heat exchanger. The temperature of the circulating water decreases and it is sent to the heat exchangers of various units as cooling water. After exchanging heat with the circulating water, the seawater is collected in the secondary seawater pipeline 201 and supplied to the condensers 3 of various units. It is then connected to the siphon well 4 through the outlet pipe 301 of the surface cooler. After overflowing from the siphon well's overflow weir, the seawater flows into the seawater discharge channel 5 and is discharged into the deep sea. The seawater cascade utilization system utilizes two-stage heat exchange through the plate heat exchanger 2 and the device surface cooler 3 in the circulating water field, making full use of the heat exchange capacity of seawater and the heat exchange characteristics of the integrated refining and chemical circulating water. Through the siphon effect of the siphon well 4, the elevation loss of the system's inlet and outlet water is adjusted to 5 meters (0 meters elevation for inlet water and 5 meters elevation for outlet water). With the pipeline friction valves fully open, the seawater pump 1 only needs to overcome the resistance loss of the pipeline and the 5-meter elevation loss.

[0028] The number of plate heat exchangers mentioned in the embodiment is at least one, and when there are multiple plate heat exchangers, the specifications of the plate heat exchangers are the same or different in order to cope with different working conditions. Specifically, the plate heat exchanger is used to cool the circulating water by filtered seawater to complete the heat exchange of the circulating water. Four openings are provided on the plate heat exchanger, and the inside is divided into two kinds of pipelines, i.e. cold medium pipeline and hot medium pipeline. The cold medium inlet and the cold medium outlet are the two ends of the cold medium pipeline, and the hot medium inlet and the hot medium outlet are the two ends of the hot medium pipeline. The circulating water backwater with relatively high temperature to be circulated back to the factory area flows in the pipeline between the hot medium inlet and the hot medium outlet. The first-stage seawater after treatment flows in the cold medium inlet and the cold medium outlet. The circulating water at the hot medium outlet becomes the cooled water and is supplied to the specific device heat exchanger as the circulating water inflow.

[0029] As an optional embodiment, the seawater pre-treatment device comprises a seawater pump 1, a seawater intake filtering device, a seawater intake sterilization device and a seawater pipeline. The seawater sterilization device is used for sterilization treatment of seawater. The seawater pump 1 is used for lifting seawater. The seawater intake filtering device is used for filtering treatment of seawater. The filtered seawater is transported to the circulating water field through the seawater pump and the first-stage seawater pipeline, distributed to each plate heat exchanger through the pipeline, and then collected to the second-stage seawater pipeline after heat exchange with the circulating water of the plate heat exchanger. After being supplied to the condenser of each device, the seawater is connected to the siphon well through the outlet pipe of the surface air cooler, and then flows into the seawater discharge channel and is discharged into the deep sea after overflowing from the overflow weir of the siphon well. The circulating water field mentioned in the embodiment is a factory area capable of providing space storage capacity, and the circulating water pipeline and the first-stage seawater utilization device are arranged therein.

[0030] Specifically, the seawater pre-treatment device increases the pressure of seawater to 25 meters through the seawater pump, and then transports the seawater to the circulating water field through the first-stage seawater pipeline, and distributes the seawater to each plate heat exchanger through the pipeline. As an optional embodiment, a first-stage cross-line device and a second-stage cross-line device can also be provided to call seawater in special cases. Specifically, the first-stage cross-line device comprises a pipeline 103 and a valve arranged thereon. One end of the pipeline 103 is arranged on the pipeline after the seawater pre-treatment device and before the plate heat exchanger, and the other end is arranged on the pipeline after the plate heat exchanger and before the condenser. The second-stage cross-line device comprises a pipeline 202 and a valve arranged thereon. One end of the pipeline 202 is arranged on the pipeline after the plate heat exchanger and before the condenser, and the other end is arranged on the pipeline after the condenser and before the siphon well.

[0031] As an optional embodiment, the seawater intake sterilization device of the seawater pre-treatment device and the sterilization device arranged at the front end of the circulating water field both use sodium hypochlorite produced by seawater electrolysis.

[0032] Specifically, the seawater system conventional sterilization treatment is continuous bacteriostatic addition (0.3ppm) and impact sterilization addition (2-3ppm) of sodium hypochlorite at the seawater intake. Due to the long seawater pump delivery pipeline, after the front sterilization treatment, with the sterilizing agent attenuation of several kilometers of delivery pipeline, in the plate heat exchanger 2 of the circulating water field, it is extremely easy to occur the case that the heat exchange capacity is rapidly reduced due to the microbial growth and the plate clogging. Through the reasonable setting of the impact addition time and frequency, the post-sterilization treatment process ensures the sterilization effect of the single heat exchanger and the qualified discharge of the residual sterilizing agent of the seawater outlet manifold 201 of the multiple heat exchangers. Through the setting of the post-sterilization treatment process, the cleaning period of the plate heat exchanger is extended from 1-2 months to 2 years, which greatly improves the heat exchange condition of the plate heat exchanger and reduces the workload of inspection and maintenance, compared with the traditional seawater utilization.

[0033] As an optional implementation, the closed circulating water system includes a circulating water pump 7 and a pressure stabilizing tank 6. The circulating water is pressurized by the circulating water pump, sent to each device heat exchanger through the pipeline for heat exchange, and then enters the circulating water pump after being collected in the pipeline after the heat exchange with seawater in the heat exchanger to reduce the temperature. The pressure stabilizing tank is used to stabilize the system pressure by nitrogen and the liquid level by water supplement. The closed circulating water system of the first seawater utilization device pressurizes the circulating water by the circulating water pump 7, sends it to each device heat exchanger 8 through the pipeline 701 for heat exchange, and then enters the circulating water pump after being collected in the pipeline 601 after the heat exchange with seawater in the heat exchanger 2 to reduce the temperature. Compared with the conventional open circulating water system, the head of the closed circulating water pump only needs to overcome the resistance loss of the pipeline along the way of 15-20 meters, without needing to overcome the 20-meter elevation loss of the open circulating water backwater tower. The influence of different installation heights of 7-50 meters of the device heat exchanger does not need to be considered.

[0034] In the closed circulating water system, the circulating water is heat-exchanged and cooled with seawater, without evaporation loss of the open circulating water, only a small amount of pipeline leakage and periodic backwash and blowdown, and the water supplement amount of the system is only 1%-1.5% of that of the open circulating water, saving a large amount of fresh water resources.

[0035] As an optional implementation, the pressure stabilizing tank controls the gas phase pressure at the upper part of the pressure stabilizing tank by supplementing nitrogen, stabilizes the circulating water backwater pressure of the circulating water inlet pipeline 601 in the range of 0.2-0.4 Mpa, stabilizes the circulating water supply pressure in the range of 0.4-0.6 Mpa, and buffers the pressure fluctuation of the circulating water system.

[0036] In this embodiment, the overflow weir of the siphon well 4 is 5 meters above the sea level, and the seawater pipe 301 in front of the overflow weir is completely submerged under the water surface. In the case that the sealing of the outlet pipeline of the condenser 3 is good, the outlet valve of the condenser 3 can be kept in an open state by the action of siphon, and the water head loss of 7 meters from the outlet of the condenser (12 meters high) to the overflow weir (5 meters high) is recovered.

[0037] In this embodiment, there are a large number of direct feeds between devices in the device process of the integrated refining and chemical plant. In the case of direct feed between devices, circulating water cooling is not needed for the direct feed. When the direct feed process has problems and needs to be transferred in the intermediate tank area, circulating water cooling is needed before the direct feed is sent to the tank area. Therefore, the circulating water heat load of the device design is higher than that in the normal direct feed operation. In the case of normal device direct feed, the seawater temperature rise of the primary seawater utilization device is relatively low, which can reduce the amount of seawater and the number of seawater pumps in operation. In the device heat exchanger 8, a large number of device direct feeds do not need heat exchange of the heat exchanger, so the seawater heat load of the circulating water field is relatively small. In the case that the seawater inlet temperature is highest at 26℃ in summer, the temperature rise of the primary seawater is only 4-6℃, and the inlet temperature of the condenser is only 30-32℃, which is far lower than the design condition 34℃ of the condenser. In the case that the direct feed needs heat exchange, the temperature rise of the primary seawater is 8℃, and the inlet temperature of the condenser is 34℃, which can meet the requirements of the system in the worst summer condition.

[0038] In the case that the winter temperature of seawater is relatively low, the amount of seawater can also be reduced. In the case that the average winter temperature of seawater is only 4℃, the heat exchange load of low-temperature seawater can be fully utilized, and through operation adjustment, the seawater consumption in winter is only 75%-80% of that in summer.

[0039] The application also discloses a seawater step utilization method for an integrated refining and chemical park, which comprises the following steps:

[0040] Real-time acquisition of the primary seawater consumption and the secondary seawater consumption, wherein the primary seawater consumption is the seawater consumption of the primary seawater utilization device, and the secondary seawater consumption is the seawater consumption of the secondary seawater utilization device;

[0041] When the secondary seawater consumption is insufficient, the seawater of the circulating water station is directly transported to the secondary seawater utilization device through the opening of the primary and secondary seawater cross-line valve to supplement the secondary seawater consumption.

[0042] When the primary seawater consumption exceeds the preset value of the secondary seawater consumption, the seawater of the primary seawater utilization device is directly discharged through the opening of the secondary seawater discharge cross-line valve to adjust the seawater consumption.

[0043] The present application utilizes seawater in a step-by-step manner. The seawater is used in a step-by-step manner through heat exchangers of a circulating water field and condensers of the device, the cooling capacity of the seawater is fully utilized, and the amount of seawater used is reduced. The elevation loss of the seawater system is reduced to 3-5 meters through the siphon effect of a siphon well, compared with the 20-meter elevation loss of a conventional open circulating water system, the water head loss of the water pump is greatly saved, and the energy loss of the system is saved. The closed circulating water system of the first seawater utilization device adjusts the system resistance of the circulating water system to 20-25 meters of water head loss through the closed circulation of the pipe network, without considering the installation height (7-50 meters) of the heat exchanger of the device, the water supply system resistance loss of the system is adjusted from the 50m+ lift of the conventional circulating water pump to the 20-25m lift, the energy loss of the system is greatly saved, the heat of the circulating water is all taken away by the seawater cooling, the open circulating water evaporation heat removal mode is replaced, and the use of a large amount of fresh water is saved.

[0044] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A tiered seawater utilization system for an integrated refining and chemical industrial park, characterized in that, The seawater pre-device is used for extracting seawater and pre-treating seawater, the first seawater utilization device includes a plate heat exchanger, a closed circulating water system, a device heat exchanger and corresponding pipelines, and the second seawater utilization device includes a condenser, a seawater siphon well and corresponding pipelines. The seawater pre-device includes a seawater pump, a seawater water-taking filtering device, a seawater water-taking sterilization device and seawater pipelines, the seawater water-taking sterilization device is used for sterilizing seawater, the seawater water-taking filtering device is used for filtering seawater, filtered seawater is delivered to a circulating water field through the seawater pump and a first seawater pipeline, and is distributed to each plate heat exchanger through pipelines; after seawater is exchanged with circulating water of the plate heat exchanger, the seawater is collected to a second seawater pipeline, is supplied to a condenser of each device, is connected to a siphon well through a water outlet pipe of an air cooler, and is collected to a seawater discharge channel after overflowing from an overflow weir of the siphon well to be discharged into the deep sea. The closed circulating water system includes a circulating water pump and a pressure stabilizing tank, circulating water is pressurized by the circulating water pump, is delivered to each device heat exchanger through pipelines to be exchanged, after the temperature of the circulating water is raised, the circulating water is delivered to the heat exchanger through pipelines to be exchanged with seawater to reduce the temperature, and then is collected to pipelines to be delivered to the circulating water pump. The pressure stabilizing tank stabilizes the pressure by supplementing nitrogen, controls the gas phase pressure of the upper part of the pressure stabilizing tank, stabilizes the circulating water backwater pressure of the circulating water pump inlet pipeline in the range of 0.2-0.4 Mpa, stabilizes the circulating water supply pressure in the range of 0.4-0.6 Mpa, buffers the pressure fluctuation of the circulating water system, and reduces the pressure difference of the circulating water system to 0.25 Mpa.

2. The sea water cascade utilization system for refinery integrated park according to claim 1, characterized in that, The seawater water-taking sterilization device of the seawater pre-device and the sterilization device arranged at the front end of the circulating water field both use sodium hypochlorite produced by seawater electrolysis.

3. A method for using the sea water cascade utilization system of claim 1 or 2, characterized in that, Real-time acquisition of first seawater consumption and second seawater consumption, the first seawater consumption is the seawater consumption of the first seawater utilization device, and the second seawater consumption is the seawater consumption of the second seawater utilization device; When the second seawater consumption is insufficient, a first-second seawater cross-line valve is opened to directly deliver seawater of the circulating water station to the second seawater utilization device to supplement the second seawater consumption; When the first seawater consumption exceeds a preset value of the second seawater consumption, a second seawater discharge cross-line valve is opened to directly discharge seawater of the first seawater utilization device to adjust the seawater consumption. ​

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