Device and method for reducing concentration of combustible gas in twice sealed space of floating roof tank

Abstract

The invention discloses a device for reducing the concentration of combustible gas in a twice sealed space of a floating roof tank, which comprises an external floating roof oil storage tank, a secondary seal in the external floating roof oil storage tank is respectively communicated with a gas inlet conduit and a gas suction pipeline, and the other port of the gas inlet conduit is provided with a one-way valve; the pretreatment device is connected with a gas detection instrument through the gas extraction pipeline, the gas detection instrument is electrically connected with a control system and is connected with a gas recovery treatment device through the gas extraction pipeline, and the gas extraction pump is connected with the gas recovery treatment device through the gas extraction pipeline; and the sucking pump is electrically connected with the control system. The invention also discloses a method for reducing the concentration of combustible gas. According to the device and the method for reducing the concentration of the combustible gas in the two-time sealed space of the floating roof tank, the gas in the sealed space of the external floating roof tank is controlled within a safe range by detecting the concentration of the gas in the external floating roof tank and discharging the gas, so that a sealing ring fire caused by lightning stroke and static electricity is avoided.

Description

Technical Field

[0001] This invention belongs to the field of safety and environmental protection technology for external floating roof oil tanks, specifically involving a device for reducing the concentration of combustible gases in the double-sealed space of the floating roof tank, and also involving a method for reducing the concentration of combustible gases. Background Technology

[0002] Storage tanks, as commonly used storage equipment, are widely used in the petroleum and chemical industries. Dome-shaped tanks and floating roof tanks are the most widely used crude oil storage tanks. Floating roof tanks, by installing floating roofs within the tank body, seal the stored medium and reduce its temperature, thus achieving energy savings. In the past, during the operation of floating roof tanks, there have been cases of fires caused by lightning strikes or static electricity igniting the sealing rings. This is because the problem of oil adhering to the tank walls is difficult to avoid, and the issue of flammable gases remaining in the two sealed spaces due to the close proximity of the tank's two seals to the inner wall is difficult to resolve. Most fires in external floating roof oil tanks occur at the tank's sealing points; fires caused by lightning strikes or static electricity typically begin with a gas flash explosion within the primary and secondary sealed spaces.

[0003] To minimize losses from oil tank fires, existing technologies typically equip floating roof tanks with fire sprinklers, foam extinguishing systems, and fire detection devices, all interlocked and controlled within the station's systems. Fire sprinklers cool the outer walls of the tank, preventing the fire from spreading and affecting other tanks. Foam extinguishing systems fill the space between the inner wall of the tank and the foam weir, isolating the sealed space from air to extinguish the fire. Large oilfields are also equipped with fire trucks and other firefighting measures, and personnel involvement makes fire control more flexible and effective in initial fire control. However, these tank fire protection measures are reactive, extinguishing fires only after they have occurred. The system's detection and action have a certain lag, requiring a waiting period before foam and water reach the burning area, affecting the effectiveness of firefighting. In extreme weather conditions such as strong winds, fire foam can easily be blown away during its descent, rendering this method ineffective. Fire truck firefighting carries significant risks, including personnel injury, and has a limited scope of application. To minimize fire risks and avoid reactive firefighting, the invention patent "Active Safety Protection System and Method for External Floating Roof Oil Storage Tanks," filed on September 3, 2010 (publication number CN101985328A), addresses this issue. By injecting inert gas into the primary and secondary sealed spaces of the tank to dilute volatile gases and maintaining a slightly positive pressure in the sealed space, the volatile gases are directly released into the atmosphere, causing environmental pollution. Simultaneously, the diffusion of inert gas to the floating roof surface poses a risk of asphyxiation for operators. Furthermore, typical oil storage stations do not have inert gas facilities, requiring a separate inert gas generation and storage unit for this system, further increasing operating costs. External floating roof crude oil storage tanks are mostly built in large oil storage facilities for storing crude oil, and standards and regulations require these tanks to be equipped with sprinkler and foam fire suppression systems. Meanwhile, SY / T5921 "Operation, Maintenance and Repair Specifications for Vertical Cylindrical Steel Welded Oil Tanks" stipulates that "in summer, the concentration of combustible gas between the secondary seal or rain shield and the primary seal should not exceed 25% of the lower explosive limit." However, since the floating roof tanks of oil storage depots are often in a static state with the floating roof in contact with the tank wall, the crude oil adhering to the tank wall evaporates into the sealed space, which can easily cause the gas concentration to fail to meet the standard requirements. Summary of the Invention

[0004] The primary objective of this invention is to provide a device for reducing the concentration of combustible gases in the secondary sealing space of a floating roof tank. By real-time detection and evacuation of the gas concentration in the external floating roof tank, the gas in the sealing space of the external floating roof tank is controlled within a safe range, thus preventing sealing ring fires caused by lightning strikes and static electricity.

[0005] Another object of the present invention is to provide a method for reducing the concentration of combustible gases.

[0006] The first technical solution adopted in this invention is a device for reducing the concentration of combustible gas in the double-sealed space of a floating roof tank, comprising an external floating roof oil storage tank. The external floating roof oil storage tank has a primary seal and a secondary seal within the edge of the floating plate. The secondary seal is connected to an air inlet pipe and an air extraction pipe, respectively. A one-way valve is provided at the other end of the air inlet pipe. The other end of the air extraction pipe is connected to a pretreatment device and an air extraction pump. The pretreatment device is connected to a gas detection instrument via the air extraction pipe. The gas detection instrument is electrically connected to a control system. The gas detection instrument is connected to a gas recovery and treatment device via the air extraction pipe. The air extraction pump is connected to the gas recovery and treatment device via the air extraction pipe and is electrically connected to the control system.

[0007] The first technical solution of this invention is also characterized by: The control system includes a PLC field control cabinet and a remote automatic control device. The PLC field control cabinet and the remote automatic control device are electrically connected, and the gas detection instrument is electrically connected to the PLC field control cabinet.

[0008] The air pump is electrically connected to both the PLC field control cabinet and the remote automatic control device.

[0009] Another technical solution adopted in this invention is a method for reducing the concentration of combustible gases, which employs a device to reduce the concentration of combustible gases in the double-sealed space of the floating roof tank. The specific steps are as follows: Step 1: Detect the gas concentration in the external floating roof oil storage tank and transmit the detection results to the control system; Step 2: When the detected gas concentration value exceeds the set concentration value, the control system controls the air pump to operate. When the gas pressure difference reaches the limit, the one-way valve opens to control the gas concentration in the sealed space within the set concentration value range.

[0010] Another feature of the technical solution of this invention is that: Step 1 is as follows: The gas in the external floating roof oil storage tank is transported to the gas detection instrument by the air pump. The gas concentration is detected by the gas detection instrument, and the detection result is transmitted to the PLC field control cabinet. The PLC field control cabinet then transmits the detection result to the remote automatic control device.

[0011] Step 2 is as follows: When the remote automatic control device receives a detection result that exceeds the set concentration value, it issues a command to control the air pump to increase its operating speed, extract some gas, and reduce the air pressure in the sealing ring to open the one-way valve, drawing in external air into the sealed space to replace the original gas until the gas concentration value is lower than the set concentration value. Then, the air pump operating speed is reduced to allow the air pressure to reach equilibrium, and finally the one-way valve is closed.

[0012] It also includes step 3, which specifically involves treating and discharging the gas that exceeds the set concentration value through a gas recovery treatment device.

[0013] The beneficial effects of this invention are: The present invention provides a device and method for reducing the concentration of combustible gas in the secondary sealing space of a floating roof tank. This involves real-time detection of the gas concentration in the extracted sealing space using a gas detection instrument. When the gas concentration exceeds the standard, the extraction pump operates rapidly, increasing the negative pressure in the sealing space. This opens the one-way valve at the air inlet, allowing external air to enter the sealing ring and displace the gas in the sealing space, thus reducing the gas concentration. Once the set low value is reached, the extraction pump returns to a slow operating state. This cycle repeats, controlling the gas in the sealing space of the external floating roof tank within a safe range and preventing sealing ring fires caused by lightning strikes or static electricity. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the device for reducing the concentration of combustible gas in the double-sealed space of the floating roof tank according to the present invention; Figure 2 yes Figure 1 A magnified view of a portion of point A in the middle.

[0015] The following are the labels in the diagram: 1. External floating roof oil storage tank, 2. Pretreatment device, 3. Gas detection instrument, 4. PLC field control cabinet, 5. Remote automatic control device, 6. Air pump, 7. Gas recovery and treatment device, 8. Secondary seal, 9. Air inlet duct, 10. Check valve, 11. Air extraction pipeline, 12. Primary seal, 13. Floating roof. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] The present invention provides a device for reducing the concentration of combustible gases in the secondary sealing space of a floating roof tank, such as... Figure 1 and Figure 2As shown, the system includes an external floating roof oil storage tank 1. The floating roof of the external floating roof oil storage tank 1 has a primary seal 12 and a secondary seal 8 within its edge. The secondary seal 8 is connected to an air inlet pipe 9 and an air extraction line 11, respectively. A one-way valve 10 is located at the other end of the air inlet pipe 9. The one-way valve 10 opens or closes when the pressure inside the sealing ring changes due to air extraction. The other end of the air extraction line 11 is connected to a pretreatment device 2 and an air extraction pump 6, respectively. The pretreatment device 2 filters and stabilizes the gas to ensure detection accuracy. The pretreatment device 2 is connected to a gas detection instrument 3 via the air extraction line 11. The gas detection instrument 3 is electrically connected to a control system. The gas detection instrument 3 is also connected to a gas recovery and treatment device 7 via the air extraction line 11. The air extraction pump 6 is connected to the gas recovery and treatment device 7 via the air extraction line 11 and is electrically connected to the control system. The control system includes a PLC field control cabinet 4 and a remote automatic control device 5, which are electrically connected. The gas detection instrument 3 is electrically connected to the PLC field control cabinet 4, and the air pump 6 is electrically connected to both the PLC field control cabinet 4 and the remote automatic control device 5. Among them, the one-way valve 10 serves as the inlet for air to enter the detection device from the outside; the air inlet duct 9 serves as the channel for air to enter the sealed space; the primary seal 12, the secondary seal 8, and the floating roof 13 are the original structure of the external floating roof oil storage tank 1. The primary seal 12 and the secondary seal 8 together form a relatively sealed space, which has the functions of preventing rain, snow and debris from falling into the tank from the upper part of the floating roof and preventing oil from overflowing onto the floating roof. The secondary seal has an opening for installing pipelines; the air extraction pipeline 11 connects the sealed space to the outside of the external floating roof oil storage tank 1; the gas detection instrument 3 detects the concentration of combustible gas in the extracted gas; the air extraction pump 6 extracts the gas in the sealed space to the outside, and after detection, it is delivered to the gas recovery and treatment device; the remote automatic control device in the control system compares the detected value with the set value, and the overall control system operates; the gas recovery and treatment device 7 absorbs and treats the gas extracted from the sealing ring.

[0018] The method for reducing the concentration of combustible gases proposed in this invention employs a device for reducing the concentration of combustible gases in the double-sealed space of a floating roof tank, and includes the following steps: Step 1: Detect the gas concentration in the external floating roof oil storage tank 1 and transmit the detection result to the control system; Step 1 is as follows: the gas in the external floating roof oil storage tank 1 is transported to the gas detection instrument 3 by the air pump 6, and then transported to the gas detection instrument 3 by the pretreatment device 2 for final gas concentration detection. The detection result is then transmitted to the PLC field control cabinet 4, and the PLC field control cabinet 4 transmits the detection result to the remote automatic control device 5.

[0019] Step 2: When the gas concentration value is detected to exceed the set concentration value, the control system controls the air pump 6 and the one-way valve 10 to operate and control the gas concentration in the sealed space within the set concentration value range. Step 2 is as follows: When the remote automatic control device 5 receives a signal that the concentration of volatile combustible gas in the sealed space does not exceed the set concentration value, the vacuum pump 6 runs slowly; when the remote automatic control device 5 receives a signal that the concentration of volatile combustible gas in the sealed space exceeds the set concentration value, it issues a command to control the vacuum pump 6 to increase its operating speed, thereby increasing the slight negative pressure value in the two sealed spaces. When the pressure reaches the limit, the one-way valve opens, and at the same time, the one-way valve 10 opens, injecting external air into the sealed space to replace the original gas and extracting some of the excessively concentrated gas, thereby reducing the concentration of combustible gas in the secondary sealed space until the gas concentration value is lower than the set concentration value. Then, the operating speed of the vacuum pump 6 is reduced, and the pressure inside and outside the sealing ring tends to balance. The one-way valve closes, ensuring that the concentration of combustible gas in the sealing ring is within a controllable range.

[0020] Step 3: The extracted gas is transported to the gas recovery and treatment device 7 to complete the treatment of volatile gases.

[0021] Example 1 This embodiment provides a device for reducing the concentration of combustible gases in the double-sealed space of a floating roof tank, such as... Figures 1-2 As shown, the system includes an external floating roof oil storage tank 1. The external floating roof oil storage tank 1 has a primary seal 12 and a secondary seal 8 within the edge of the floating roof. The primary seal 12, secondary seal 8, and floating roof 13 are part of the original structure of the external floating roof oil storage tank 1. The secondary seal 8 is connected to an air inlet duct 9 and an air extraction line 11, respectively. The air extraction line 11 connects the sealed space to the outside of the external floating roof oil storage tank 1. The air inlet duct 9 serves as a channel for air to enter the sealed space. A one-way valve 10 is located at the other end of the air inlet duct 9, serving as the inlet for air to enter the detection device from the outside. The other end of the air extraction line 11 is connected to a pretreatment device 2 and an air extraction pump 6, respectively. The pretreatment device 2 is connected to a gas detection instrument 3 via the air extraction line 11. The gas detection instrument 3 is electrically connected to a control system. The gas detection instrument 3 is also connected to a gas recovery and treatment device 7 via the air extraction line 11. The gas recovery and treatment device 7 absorbs and treats the gas extracted from the sealing ring. The air extraction pump 6 is connected to the gas recovery and treatment device 7 via the air extraction line 11 and is electrically connected to the control system.

[0022] Example 2 This embodiment provides a device for reducing the concentration of combustible gases in the double-sealed space of a floating roof tank, such as... Figures 1-2As shown, the system includes an external floating roof oil storage tank 1. The outer edge of the floating roof of the external floating roof oil storage tank 1 is equipped with a primary seal 12 and a secondary seal 8. The primary seal 12, secondary seal 8, and floating roof 13 are part of the original structure of the external floating roof oil storage tank 1. The secondary seal 8 is connected to an air inlet duct 9 and an air extraction pipeline 11, respectively. The air extraction pipeline 11 connects the sealed space to the outside of the external floating roof oil storage tank 1. The air inlet duct 9 serves as a channel for air to enter the sealed space. A one-way valve 10 is located at the other end of the air inlet duct 9, serving as the inlet for air to enter the detection device from the outside. The other end of the air extraction pipeline 11 is connected to a pretreatment device 2 and an air pump 6, respectively. The pretreatment device 2 is connected to a gas detector 3 via an extraction pipeline 11. The gas detector 3 is electrically connected to a control system. The gas detector 3 is also connected to a gas recovery and treatment device 7 via the extraction pipeline 11. The gas recovery and treatment device 7 absorbs and treats the gas extracted from the sealing ring. The extraction pump 6 is connected to the gas recovery and treatment device 7 via the extraction pipeline 11. The extraction pump 6 is electrically connected to the control system. The control system includes a PLC field control cabinet 4 and a remote automatic control device 5. The PLC field control cabinet 4 and the remote automatic control device 5 are electrically connected. The gas detector 3 is also electrically connected to the PLC field control cabinet 4. Example 3 This embodiment provides a device for reducing the concentration of combustible gases in the double-sealed space of a floating roof tank, such as... Figures 1-2 As shown, the system includes an external floating roof oil storage tank 1. The external floating roof oil storage tank 1 contains a primary seal 12 and a secondary seal 8. The primary seal 12, secondary seal 8, and floating roof 13 are part of the original structure of the external floating roof oil storage tank 1. The secondary seal 8 is connected to an air inlet duct 9 and an air extraction line 11, respectively. The air extraction line 11 connects the sealed space to the outside of the external floating roof oil storage tank 1. The air inlet duct 9 serves as a channel for air to enter the sealed space. A one-way valve 10 is located at the other end of the air inlet duct 9, serving as the inlet for air to enter the detection device from the outside. The other end of the air extraction line 11 is connected to a pretreatment device 2 and an air pump 6, respectively. The pretreatment device 2 is connected to a... A gas detection instrument 3 is electrically connected to a control system. The gas detection instrument 3 is connected to a gas recovery and treatment device 7 via an extraction pipeline 11. The gas recovery and treatment device 7 absorbs and treats the gas extracted from the sealing ring. An extraction pump 6 is connected to the gas recovery and treatment device 7 via the extraction pipeline 11 and is electrically connected to the control system. The control system includes a PLC field control cabinet 4 and a remote automatic control device 5, both electrically connected. The gas detection instrument 3 is electrically connected to the PLC field control cabinet 4, and the extraction pump 6 is electrically connected to both the PLC field control cabinet 4 and the remote automatic control device 5. On-site and remote control are achieved through the PLC field control cabinet 4 and the remote automatic control device 5.

[0023] Example 4 This embodiment provides a method for reducing the concentration of combustible gases, employing the device for reducing the concentration of combustible gases in the double-sealed space of a floating roof tank provided in the above embodiment, such as... Figures 1-2 As shown, it includes the following steps: Step 1: Detect the gas concentration in the external floating roof oil storage tank 1 and transmit the detection result to the control system; Step 2: When the gas concentration value is detected to exceed the set concentration value, the control system controls the air pump 6 and the one-way valve 10 to operate and control the gas concentration in the sealed space within the set concentration value range. Step 3: The extracted gas is transported to the gas recovery and treatment device 7 to complete the treatment of volatile gases.

[0024] Example 5 Based on Example 4, step 1 is specifically as follows: the gas in the external floating roof oil storage tank 1 is transported to the gas detection instrument 3 through the pretreatment device 2 by the air pump 6, the gas concentration is detected by the gas detection instrument 3, and the detection result is transmitted to the PLC field control cabinet 4. The PLC field control cabinet 4 transmits the detection result to the remote automatic control device 5.

[0025] Step 2 is as follows: When the remote automatic control device 5 receives a signal that the concentration of volatile combustible gas in the sealed space does not exceed the set concentration value, the vacuum pump 6 runs slowly; when the remote automatic control device 5 receives a signal that the concentration of volatile combustible gas in the sealed space exceeds the set concentration value, it issues a command to control the vacuum pump 6 to increase its operating speed, thereby increasing the slight negative pressure value in the two sealed spaces. When the pressure reaches the limit, the one-way valve 10 opens, drawing external air into the sealed space to replace the original gas and extracting some of the excessively concentrated gas, thus reducing the combustible gas concentration in the secondary sealed space until the gas concentration value is lower than the set concentration value. Then, the operating speed of the vacuum pump 6 is reduced, and after the gas pressure is balanced, the one-way valve 10 closes, ensuring that the combustible gas concentration in the sealing ring is within a controllable range.

[0026] The device for reducing the concentration of combustible gas in the double sealing space of the floating roof tank provided by this invention uses a gas detection instrument 3 to detect the gas concentration in the extracted sealing ring in real time. When the gas concentration exceeds the standard, external air is introduced into the sealing space to replace the gas in the sealing space, thereby reducing the gas concentration and controlling the gas in the sealing ring of the external floating roof tank within a safe range, thus avoiding sealing ring fires caused by lightning strikes and static electricity.

Claims

1. A device for reducing the concentration of combustible gases in the secondary sealing space of a floating roof tank, characterized in that, The system includes an external floating roof oil storage tank (1), which has a primary seal (12) and a secondary seal (8) inside the edge of the floating roof. The secondary seal (8) is connected to an air inlet pipe (9) and an air extraction pipe (11) respectively. A one-way valve (10) is provided at the other end of the air inlet pipe (9). The other end of the air extraction pipe (11) is connected to a pretreatment device (2) and an air extraction pump (6). The pretreatment device (2) is connected to a gas detection instrument (3) through the air extraction pipe (11). The gas detection instrument (3) is electrically connected to a control system. The gas detection instrument (3) is connected to a gas recovery and treatment device (7) through the air extraction pipe (11). The air extraction pump (6) is connected to the gas recovery and treatment device (7) through the air extraction pipe (11). The air extraction pump (6) is electrically connected to the control system.

2. The device for reducing the concentration of combustible gas in the double-sealed space of a floating roof tank according to claim 1, characterized in that, The control system includes a PLC field control cabinet (4) and a remote automatic control device (5). The PLC field control cabinet (4) and the remote automatic control device (5) are electrically connected. The gas detection instrument (3) is electrically connected to the PLC field control cabinet (4).

3. The device for reducing the concentration of combustible gas in the secondary sealing space of a floating roof tank according to claim 2, characterized in that, The air pump (6) is electrically connected to the PLC field control cabinet (4) and the remote automatic control device (5), respectively.

4. A method for reducing the concentration of combustible gases, characterized in that, The specific steps of using the device for reducing the concentration of combustible gases in the double-sealed space of a floating roof tank as described in claim 3 are as follows: Step 1: Detect the gas concentration in the external floating roof oil storage tank (1) and transmit the detection result to the control system; Step 2: When the gas concentration value is detected to exceed the set concentration value, the control system controls the air pump (6) to operate. When the gas pressure difference reaches the limit, the one-way valve (10) opens to control the gas concentration in the sealed space within the set concentration value range.

5. The method for reducing the concentration of combustible gas according to claim 4, characterized in that, Step 1 specifically involves: using the air pump (6) to transport the gas from the external floating roof oil storage tank (1) to the gas detection instrument (3), using the gas detection instrument (3) to detect the gas concentration, and transmitting the detection result to the PLC field control cabinet (4), which then transmits the detection result to the remote automatic control device (5).

6. The method for reducing the concentration of combustible gas according to claim 4, characterized in that, Step 2 is as follows: When the remote automatic control device (5) receives the detection result exceeding the set concentration value, it issues an instruction to control the air pump (6) to increase its operating speed, extract some gas, and reduce the gas pressure in the sealing ring to open the one-way valve (10), drawing external air into the sealed space to replace the original gas until the gas concentration value is lower than the set concentration value. Then, the air pump (6) is reduced to make the gas pressure tend to be balanced, and finally the one-way valve (10) is closed.

7. The method for reducing the concentration of combustible gas according to claim 6, characterized in that, It also includes step 3, which is: discharging and releasing the gas exceeding the set concentration value through the gas recovery treatment device (7).

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