A heat integration energy-saving process, device and application for a refinery unit

Abstract

The present invention provides a heat integration energy-saving process, device and application for a refinery unit, relating to the technical field of energy saving. Specifically, it includes the following steps: 1) Low-temperature heat-conducting oil exchanges heat with the heat-generating structure in the refinery unit, and then is wholly or partly transported into a heating furnace for temperature rise to obtain high-temperature heat-conducting oil; 2) The high-temperature heat-conducting oil is transported to a heat extraction device in the refinery unit for heat exchange to obtain medium-temperature heat-conducting oil; 3) The medium-temperature heat-conducting oil is transported into a steam generator to generate steam, and at the same time, the low-temperature heat-conducting oil used in step 1 is obtained. The present invention uses heat-conducting oil as the medium, exchanges heat and raises the temperature through the high-temperature heat-generating structure and the heating furnace in the refinery unit, and then successively passes through each heat extraction device and the steam generation device, thereby realizing the cyclic utilization of heat energy; the heat-conducting oil of the present invention has a wider temperature threshold and can achieve a wider range of application scenarios. At the same time, the load fluctuation of the heat extraction device is avoided, and the heat balance of heat utilization and heat extraction is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conservation, and more particularly, to a heat integration energy conservation process for a refinery unit, a heat integration energy conservation device for a refinery unit, and their applications. Background Art

[0002] At the same time, the heating methods adopted by current refinery units are generally divided into two types. One is that steam is transported to each unit through a pipe network, and the other is that fuel gas is burned in a heating furnace for heating. For the first scheme, there are defects such as the need for superheating and large heat losses during the steam transportation process. At the same time, steam cannot meet the usage conditions of some media. For the second scheme, the fuel gas consumed by the heating furnace is relatively expensive. At the same time, the heating furnace has problems with heating efficiency, has large heat losses, and is accompanied by defects such as large floor space occupied by the heating furnace.

[0003] Therefore, a high-temperature heat transfer oil system can be added to exchange heat between the high-temperature heat in the refinery and the heat transfer oil. After the heat transfer oil is heated and takes heat, it is sent to downstream units to replace the heating furnace in the unit to heat the original medium. This avoids a large amount of heat loss caused by steam transportation of high-temperature heat and the inability to meet the heating requirements, and also meets the situation where some media cannot use steam.

[0004] For example, the utility model (application number: 201020164345.8) discloses a high-temperature heat integration system for a refinery, including a fluid catalytic cracking unit, a catalytic reforming unit, a methyl ethyl ketone unit, a solvent oil hydrogenation unit, and a total heat transfer oil pipeline; the bottom of the fractionation tower of the fluid catalytic cracking unit is connected to the inlet of the bottom catalytic oil slurry pump, the outlet of the catalytic oil slurry pump is connected to the inlet of the tube side of the heat exchanger, the outlet of the tube side of the heat exchanger is connected to the inlet of the tube side of the newly added catalytic oil slurry - heat transfer oil heat exchanger, and another heat transfer oil heat exchanger group is newly added at the bottom of the dehexanizer of the catalytic reforming unit; a heat transfer oil buffer tank, a heat transfer oil replenishing tank, a heat transfer oil pump, a heat transfer oil aftercooler, and a post-cooler regulating valve are newly added on the total heat transfer oil pipeline.

[0005] This new type is larger than the existing technology system, has a reasonable process design, is easy to stably control, uses energy more reasonably, saves fuel, and reduces energy consumption. However, this new type still has a series of defects; for example, the temperature range of the heat transfer oil is relatively narrow, the load of the heat extraction device fluctuates, and there are easily situations such as unbalanced heat extraction and the heat transfer oil being unable to meet the heat demand.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The first object of the present invention is to provide a heat integration energy-saving process for a refinery unit, which uses heat transfer oil as the heat transfer medium, exchanges heat and raises the temperature through the high-temperature heat-generating structure and the heating furnace existing in the refinery unit, and then sequentially passes through each heat extraction device and steam generation device, thereby realizing the cyclic utilization of heat energy. Compared with the prior art, the heat transfer oil of the present invention has a wider temperature threshold and can achieve a wider range of application scenarios. At the same time, the load fluctuation of the heat extraction device is avoided, and the heat balance of heat extraction and heat utilization in the upstream and downstream is ensured.

[0008] The second object of the present invention is to provide a heat integration energy-saving device for a refinery unit, which is adapted to the heat integration energy-saving process for the refinery unit.

[0009] The third object of the present invention is to provide a refining process, which includes the heat integration energy-saving process for the refinery unit, or uses the heat integration energy-saving device for the refinery unit.

[0010] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0011] A heat integration energy-saving process for a refinery unit includes the following method steps:

[0012] Step 1: The low-temperature heat transfer oil exchanges heat with the heat-generating structure in the refinery unit, and then all or part of it is transported into the heating furnace for heating up to obtain high-temperature heat transfer oil; wherein, the heat transfer oil for heating up accounts for 30% - 100% of the total mass of the low-temperature heat transfer oil, and the specific proportion can be adjusted adaptively according to the calorific value required downstream.

[0013] Step 2: The high-temperature heat transfer oil is transported to the heat extraction device in the refinery unit for heat exchange to obtain medium-temperature heat transfer oil.

[0014] Step 3: The medium-temperature heat transfer oil is transported into the steam generator to generate steam, and at the same time, the low-temperature heat transfer oil used in Step 1 is obtained.

[0015] The present invention cleverly arranges the heating furnace and the steam generator in the circulation of the heat transfer oil; when the heat transfer oil is difficult to provide enough heat for the heat extraction device, the temperature is controlled by a heat transfer oil furnace so that the load of the heat transfer oil meets the requirements. At the same time, when the heat demand of the device to be heated is insufficient, steam is generated by the steam generator to take away the excess heat in the heat transfer oil. Thus, the balance of heat extraction and heat utilization within the process circulation system is ensured.

[0016] Preferably, the temperature of the low-temperature heat transfer oil is 200°C - 240°C, and more preferably, the temperature of the low-temperature heat transfer oil is 220°C;

[0017] Preferably, the temperature of the high-temperature heat transfer oil is 340°C - 380°C, and more preferably, the temperature of the low-temperature heat transfer oil is 350°C.

[0018] In the present invention, the heating structure includes any heat source at a high temperature level, and the heat exchange between the low-temperature heat-conducting oil and the heating structure should be carried out in a heat exchanger carried by the heating structure itself or externally provided; preferably, the heating structure includes high-temperature equipment or high-temperature substances in a refining unit;

[0019] More preferably, the heating structure includes a catalytic slurry heat exchanger, coking heavy oil, hydrocracking bottom oil, or catalytic flue gas.

[0020] Preferably, the heat extraction equipment includes a hydrogenation unit, a jet fuel hydrogenation unit, a fluid catalytic cracking unit, a hydrofining unit, a hydrocracking unit, a reforming unit, or a coking unit;

[0021] More preferably, the location for carrying out the heat exchange in step two includes at least one of the feed inlet, the discharge outlet, the bottom of the reactor, or the inside of the reactor of the heat extraction equipment.

[0022] Preferably, in step two, they are connected in series in descending order of the temperature required by the heat extraction equipment;

[0023] More preferably, the heat extraction equipment does not use other heat sources.

[0024] Preferably, the pressure of the steam is 1.0 MPag to 1.5 MPag;

[0025] More preferably, the steam is also used as a heat source for heating heat extraction equipment with a lower temperature requirement in the refining unit. Specifically, it is transported to the steam pipe network in the refining unit, incorporated into the steam system through the steam pipe network, and transported to each unit for use.

[0026] Preferably, the heat-conducting oil circulates among step one, step two, and step three; after obtaining the low-temperature heat-conducting oil in step three, it is transported to a heat-conducting oil buffer tank for temporary storage, and then step one is carried out.

[0027] A heat integration energy-saving device for a refining unit is used for carrying out the heat integration energy-saving process for the refining unit; it includes the following elements or components connected in sequence: a heat-conducting oil buffer tank, several heat exchange components, and a steam generator, and the steam generator is also connected to the heat-conducting oil buffer tank; the heat exchange components are connected to the heating structure or the heat extraction equipment in the refining unit.

[0028] Preferably, the device further includes a heat-conducting oil expansion tank, and the heat-conducting oil expansion tank is connected to the heat-conducting oil buffer tank; the heat-conducting oil expansion tank plays a role in buffering pressure fluctuations, supplying heat-conducting oil, and removing non-condensable impurities in the system, thereby realizing the stability of the total circulation volume of the heat-conducting oil in the device.

[0029] Preferably, each component or assembly is connected through pipelines and pumps, and those skilled in the art can make routine settings for the specific layout of the pipelines and the selection of pumps.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) In the present invention, the heat-conducting oil is heated by a high-temperature device, replacing the process of directly generating steam by the high-temperature device in the current process; the obtained heat-conducting oil has a better applicable range compared with traditional steam, avoiding the defect that the material cannot be heated due to the substandard steam temperature or the material properties not matching the steam. At the same time, for the process of directly generating steam by the medium- and high-temperature devices, there is a situation where some materials that cannot be heated are directly heated by fuel. When the heat-conducting oil process of the present invention is adopted, the cost of this part of fuel and heating furnace can be cancelled, having better economic benefits.

[0032] (2) In the present invention, by setting a heating furnace for heating up the heat-conducting oil, the situation that the heat-conducting oil lacks heat during the heat supply process due to the heat extraction fluctuation of the upstream device is avoided; and technicians can adjust the temperature of the heating furnace according to the heat supply demand, making the process system have strong flexibility.

[0033] (3) In the present invention, the process temperature of the heat-conducting oil is controlled by adopting the method of generating steam, avoiding the situation that the temperature of the cooling medium needs to be frequently adjusted when other media are adopted; after adopting the steam generator, only the steam pressure needs to be controlled to control the cooling temperature of the heat-conducting oil.

[0034] (4) For the steam produced and consumed by the entire refinery, when the assumed demand or consumption is certain, since the main devices for producing steam in the refinery are the catalytic device and the boiler, when the amount of steam produced by the catalytic device is too much, the amount produced by the power boiler part will be reduced, resulting in too much reduction in the load of the boiler, and then the situation of low-load operation of the power boiler will occur, which is not conducive to the operation of the power boiler. Therefore, reducing the steam production of the catalytic device can increase the steam production of the power boiler, ensuring the stable operation of the power boiler; at the same time, when the load of the power boiler increases, the adjustment of the steam pipe network of the whole plant will be more appropriate, avoiding the situation that the catalytic device cannot be adjusted due to production requirements.

[0035] (5) The layout of the heat extraction equipment in the present invention follows the principle of cascaded utilization of heat. First, the heat-conducting oil is used in places for high-temperature heating, and then in places for low-temperature heating, enabling the cascade utilization of its heat and avoiding large-temperature-difference heat exchange during the heat utilization process. Description of the Drawings

[0036] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 The device (heating-up part) adopted in the embodiment of the present invention is provided;

[0038] Figure 2 The device (heat supply part) adopted in the embodiment of the present invention is provided;

[0039] Figure 3 The device (circulation part) adopted in the embodiment of the present invention is provided.

[0040] Reference numerals:

[0041] 1 - Catalytic slurry heat exchanger; 2 - Bottom oil heat exchanger of coking fractionating tower;

[0042] 3 - Heat transfer oil heating furnace; 4 - Reboiler of kerosene hydrogenation fractionating tower;

[0043] 5 - Reboiler of diesel hydrogenation fractionating tower; 6 - Reboiler of stripping column in hydrotreating unit;

[0044] 7 - Reboiler of pre-hydrogenation fractionating tower in continuous reforming unit;

[0045] 8 - Reboiler of C6 removal tower in continuous reforming;

[0046] 9 - Reactor inlet heater of kerosene hydrogenation unit;

[0047] 10 - Steam generator; 11 - Heat transfer oil buffer tank;

[0048] 12 - Heat transfer oil circulation pump; 13 - Heat transfer oil expansion tank. Specific embodiments

[0049] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0050] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0051] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] Embodiment

[0053] This embodiment adopts the device as shown in Figure 1 , Figure 2 , Figure 3 to implement the heat integration energy-saving process of the present invention.

[0054] (1) Heating part (corresponding to the device of Figure 1 )

[0055] The heat-conducting oil output from the heat-conducting oil buffer tank 11 enters the catalytic slurry heat exchanger 1 and the bottom oil heat exchanger 2 of the coking fractionating tower for heat exchange. After heat exchange, the temperature of the heat-conducting oil reaches 320 °C, and then after merging, it is sent to the heat-conducting oil heating furnace 3 for partial heating to 350 °C, and then sent to the following various devices through the heat-conducting oil pipeline network for heat supply.

[0056] (2) Heat supply part (corresponding to the device of Figure 2 )

[0057] The high-temperature heat-conducting oil obtained through the heating section is successively fed into the reboiler 4 of the aviation kerosene hydrogenation fractionation column, the reboiler 5 of the diesel hydrogenation fractionation column, and the reboiler 6 of the stripping column of the hydrotreating unit for heat supply. The media at each heat-using point exchange heat with the heat-conducting oil to meet the process requirements. At this time, the heat-conducting oil is cooled to about 280°C. Then, the heat-conducting oil is utilized in a cascade manner and sent to downstream units with relatively low requirements for the temperature of the heat-conducting oil, that is, it successively passes through the reboiler 7 of the pre-hydrogenation fractionation column of the continuous reforming unit, the reboiler 8 of the C6 removal column of the continuous reforming unit, and the reactor inlet heater 9 of the kerosene hydrogenation unit for heat supply. At this time, the temperature of the heat-conducting oil drops to about 240°C. The equipment that originally used a heating furnace among the equipment with reference numerals 4 to 9 can be deactivated or removed.

[0058] (3) Circulation section (corresponding to Figure 3 the device)

[0059] The heat-conducting oil output from the heat supply section enters the steam generator 10, and steam at 1.3 Mpag is generated and sent into the pipeline network for utilization; after generating steam, the temperature of the heat-conducting oil drops to 220°C, then it enters the heat-conducting oil buffer tank 11, and then is sent to the heating section of step (1) through the heat-conducting oil circulation pump 12; in addition, a heat-conducting oil expansion tank 13 is also provided and is connected to the heat-conducting oil buffer tank 11.

[0060] In this embodiment, only the heat-conducting oil heating furnace 3 uses fuel gas; the actual consumption of fuel gas is: 540 kg / h, and the designed heat load is: 5 MW. The amount of steam obtained by the steam generator 10 is 10 t / h.

[0061] As comparative data to intuitively reflect the beneficial effects achieved by this embodiment in terms of energy conservation, the energy consumption parameters of a certain refinery are given below. Table 1 gives the specification parameters of some devices and equipment.

[0062] Table 1

[0063] Device Name Equipment Name Inlet / Outlet Temperature of Heated Material (°C) Material Flow Rate (t / h) Reforming Unit Pre-Hydrogenation Reactor Furnace 241 / 281 227.6 Reforming Unit Pre-Hydrogenation Stripping Tower 192 / 201 324.3 Reforming Unit Naphtha Fractionating Tower 164 / 167 319.3 Diesel Hydrogenation Fractionation Furnace 271 / 290 631

[0064] The above-mentioned devices and equipment all use a heating furnace to burn fuel gas for heat supply, and Table 2 gives the energy consumption indexes of each device and equipment.

[0065] Table 2

[0066] Device Name Equipment Name Actual Consumption of Fuel Gas (Nm3 / h) Design Heat Load (MW) Reforming Unit Pre-Hydrogenation Reactor Furnace 698 6.4 Reforming Unit Pre-Hydrogenation Stripping Tower 1085 15.3 Reforming Unit Naphtha Fractionating Tower 700 14.88 Diesel Hydrogenation Fractionation Furnace 1326 24.4

[0067] In the current process, the temperature of 717.6 t / h catalytic slurry (corresponding to the catalytic slurry heat exchanger 1 of this embodiment) is 332 °C, which is mainly used to generate steam at 3.8 MPag. The steam generator generates approximately 75 t / h of steam (with a heat of approximately 40.6 MW), and then it is sent to the pipe network for the use of the pipe network. The traditional technology generates 75 t / h of steam, but the amount of fuel gas consumed also reaches 3809 Nm3 / h, which is equivalent to a fuel amount of 3.9 t / h. The price of fuel gas is 4122 yuan / ton, while the price of steam is only 190 yuan / ton. The price of fuel gas far exceeds that of steam, resulting in uneconomical energy use. However, after passing through the heat transfer oil system, 3809 Nm3 / h of fuel gas can be saved. At the same time, no steam is generated in the fluid catalytic cracking unit; instead, steam is used to replace fuel gas; the energy-saving benefit reaches 1826 yuan / hour.

[0068] Although the present invention has been illustrated and described with reference to specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A heat integration energy-saving process for a refinery unit, characterized in that, it comprises the following steps: Step 1: Low-temperature heat transfer oil exchanges heat with the heat-generating structure in the refinery unit, and then is wholly or partly transported into a heating furnace for temperature rise to obtain high-temperature heat transfer oil; Step 2: The high-temperature heat transfer oil is transported to the heat extraction equipment in the refinery unit for heat exchange to obtain medium-temperature heat transfer oil; the heat extraction equipment is connected in series in descending order of the required temperature; Step 3: The medium-temperature heat transfer oil is transported into a steam generator to generate steam, and at the same time, the low-temperature heat transfer oil for Step 1 is obtained; The heat transfer oil circulates among Step 1, Step 2 and Step 3; The temperature of the low-temperature heat transfer oil is 200°C to 240°C, and the temperature of the high-temperature heat transfer oil is 340°C to 380°C; the pressure of the steam is 1.0MPaG to 1.5MPaG.

2. The heat integration energy-saving process for a refinery unit according to Claim 1, characterized in that, the temperature of the low-temperature heat transfer oil is 220°C; and / or, the temperature of the high-temperature heat transfer oil is 350°C.

3. The heat integration energy-saving process for a refinery unit according to Claim 1, characterized in that, the heat-generating structure includes high-temperature equipment or high-temperature substances in the refinery unit; the heat-generating structure includes a catalytic slurry heat exchanger, coking heavy oil, hydrocracking bottom oil or catalytic flue gas.

4. The heat integration energy-saving process for a refinery unit according to Claim 1, characterized in that, the heat extraction equipment includes a hydrogenation unit, a fluid catalytic cracking unit, a reforming unit or a coking unit.

5. The heat integration energy-saving process for a refinery unit according to Claim 1, characterized in that, the positions for heat exchange in Step 2 include at least one of the feed inlet, the discharge outlet, the reactor bottom or the inside of the reactor of the heat extraction equipment.

6. The heat integration energy-saving process for a refinery unit according to Claim 1, characterized in that, in Step 2, no other heat source is used for the heat extraction equipment.

7. The heat integration energy-saving process for a refinery unit according to Claim 1, characterized in that, the steam is transported into the steam pipe network of the refinery unit and is transported through the steam pipe network to each demand device for use.

8. The heat integration energy-saving process for a refinery unit according to Claim 1, characterized in that, after the low-temperature heat transfer oil is obtained in Step 3, it is transported into a heat transfer oil buffer tank for temporary storage, and then Step 1 is carried out.

9. A refining process, characterized in that, it includes the heat integration energy-saving process for a refinery unit according to any one of Claims 1 to 8.

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