Dredging construction method for harbor basins and channels in soil containing hydrogen sulfide

Abstract

A dredging construction method for harbor basins and channels in soil containing hydrogen sulfide. The method comprises: step one, installing hydrogen sulfide detectors at different positions on a trailing suction hopper dredger, using a cloth membrane (5) to partially seal a hatch of a hopper (1), and arranging high-power axial flow fans; step two, on the basis of a wind rose diagram of a harbor basin and channel area, analyzing a prevailing wind direction, a secondary prevailing wind direction and wind speeds thereof, and formulating a trailing suction hopper dredger construction plan on the basis of the wind directions and the wind speeds; step three, adjusting the upward angle of a drag head lip, such that the drag head lip is separated from a mud surface at the bottom of a channel, and using high-pressure water flushing to first disperse mud at the bottom of the channel, such that part of hydrogen sulfide is first volatilized and dissolved in water; step four, using a full-hopper replacement construction method to suction the mud at the bottom of the channel into the hopper (1) of the trailing suction hopper dredger, and during the construction process, turning on the high-power axial flow fans to reduce the concentration of hydrogen sulfide in the air on the trailing suction hopper dredger; and step five, once the hopper (1) is full, driving the trailing suction hopper dredger to a designated mud dumping area for mud dumping.

Description

Dredging construction method for harbor channel in soil containing hydrogen sulfide Technical Field

[0001] The present invention relates to the technical field of waterway dredging construction, and more particularly to a method for dredging a harbor waterway in soil containing hydrogen sulfide. Background Art

[0002] Hydrogen sulfide gas is highly toxic and can easily cause death. It is 5 to 6 times more toxic than carbon monoxide. When inhaled, H2S is transported through the respiratory tract, lungs, and bloodstream to various organs. It first irritates the respiratory tract, dulling the sense of smell and causing coughing, and in severe cases, burns. It stings the eyes and can even cause blindness. It stimulates the nervous system, causing dizziness, loss of balance, and difficulty breathing. It also accelerates the heartbeat, and in severe cases, cardiac hypoxia can lead to death.

[0003] Currently, the dredging industry is struggling with the excavation of soil containing hydrogen sulfide gas using a trailing suction hopper vessel (TSV). Equipped with a drag head excavator and a dredger, a TDV employs a dredger arm and a suction device. During operation, the TDV lowers the dredger arm underwater to a certain depth, bringing the TDV into contact with the mud surface. The vessel's propulsion system drags the TDV forward, loosening and excavating the underwater silt. A dredge pump then pumps the excavated slurry through the TDV's suction port and discharges it into the vessel's own mud tank. Once the tank is filled with slurry, dredging ceases, the vessel begins dredging, and the TDV sails to a designated dumping area for disposal before returning to the vessel. Because TDVs load dredged material directly into their tanks and transport it to designated dumping locations, their open mud tanks inevitably cause hydrogen sulfide to diffuse, leading to concentrations on deck far exceeding safety limits. This makes conventional TDVs impractical for operation.

[0004] Summary of the Invention

[0005] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0006] Another object of the present invention is to provide a method for dredging a harbor channel in soil containing hydrogen sulfide, which effectively solves the problems of protection, collection, and discharge of toxic hydrogen sulfide gas.

[0007] In order to achieve these purposes and other advantages according to the present invention, a method for dredging a harbor channel in soil containing hydrogen sulfide is provided, comprising:

[0008] Step 1: Install hydrogen sulfide detectors at different locations on the TDSC, weld a keel around and above the mud tank of the TDSC, and partially seal the mud tank hatch with a cloth film set on the keel. The sealed area includes a front sealed area 12 to 20 meters away from the TDSC bridge and a rear sealed area 10 meters away from the rear of the mud tank. The middle area is open and equipped with a high-power axial flow fan. High-power fans are installed in the living quarters of the TDSC, and high-power axial flow fans are installed in the main engine room, pump room, and repair room of the TDSC. The mud door holes on the mud tank deck are filled with expanding foam and covered with cover plates to prevent hydrogen sulfide gas from being released outward through the mud door holes on the mud tank deck.

[0009] Step 2: Analyze the main wind direction, secondary dominant wind direction and wind speed according to the wind rose diagram of the harbor channel area, and formulate the trailing suction hopper construction plan according to the wind direction and speed;

[0010] Step 3: Fill the chamber with water before construction, take the highest overflow, open the high-pressure water flushing of the rake head, adjust the upward angle of the rake lip to separate the rake lip from the mud surface at the bottom of the channel, and use high-pressure water flushing to break up the mud at the bottom of the channel so that the hydrogen sulfide will evaporate and dissolve into the water first;

[0011] Step 4: Use the full tank replacement construction method to suck the mud from the bottom of the channel into the mud tank of the trailing suction hopper vessel. During the construction process, turn on the high-power axial flow fan to reduce the concentration of hydrogen sulfide in the air on board;

[0012] Step 5: When the mud tank is full, move the hopper vessel to the designated mud dumping area to dump the mud.

[0013] Preferably, the construction plan of the trailing suction hopper vessel is formulated according to the wind direction and wind speed, including:

[0014] When there is no wind, increase the speed by 2.5 to 3 knots to reduce the time hydrogen sulfide gas accumulates on the ship;

[0015] When there is no wind, head wind or cross wind, carry out normal construction, pay attention to the hydrogen sulfide detector in the stern engine room, and keep the high-power axial flow fan on.

[0016] Preferably, when the mud at the bottom of the channel is sucked into the mud tank of the drag suction hopper ship, if the hydrogen sulfide detector continues to alarm, low-concentration external discharge construction is adopted. During construction, the drag head is turned on to flush with high pressure water, and the drag lip is raised and adjusted at an angle so that the high-pressure water first breaks up and dilutes the mud at the bottom of the channel, and then the diluted mud is sucked in by a mud pump and discharged directly overboard without loading. The high-power axial flow fans in the main engine room and pump room are turned on for timely exhaust. After the hydrogen sulfide detector detects that the hydrogen sulfide gas concentration returns to normal, the mud loading construction of step four is continued.

[0017] Preferably, the low alarm point of the hydrogen sulfide detector is set at 15 mg / m 3 The high alarm point is set at 30mg / m 3.

[0018] Preferably, during construction, if it is found that the hydrogen sulfide gas has reached the low alarm point of the hydrogen sulfide detector, the ship will immediately sound an alarm for the entire ship and require all on-duty personnel to carry emergency breathing apparatus. At the same time, the ship will adjust its position according to the wind direction to keep the bridge, cabins, and main engine room upwind. If the hydrogen sulfide detector continues to alarm and the concentration continues to increase, work will be stopped immediately. If the concentration decreases, construction will continue and real-time monitoring will be maintained. If it is found that the hydrogen sulfide gas has reached the high alarm point of the hydrogen sulfide detector, the ship will immediately sound an alarm for the entire ship and require all on-duty personnel to carry emergency breathing apparatus. The driver should immediately stop construction and drive the trailing suction hopper barge away from the construction area for ventilation.

[0019] Preferably, when the trailing suction hopper vessel is on its way to the mud dumping area, the vessel uses mechanical and natural ventilation to promptly complete the ventilation work inside the cabin. After ventilation, the ship's dedicated detection personnel use handheld detection equipment to go to each cabin for detection. After there is no hydrogen sulfide risk, normal mud dumping operations can be started;

[0020] During the mud dumping process, keep the ship dumping mud against the wind or across the wind to reduce the release of hydrogen sulfide generated during mud dumping.

[0021] Preferably, the mud tank of the trailing suction hopper ship is provided with a front baffle and a rear baffle, the heights of the front baffle and the rear baffle are both lower than the height of the top of the mud tank; a first plate body is arranged at intervals behind the front baffle, the height of the first plate body is the same as the height of the top of the mud tank, the lower end of the first plate body is higher than the bottom of the mud tank, the edge of the membrane portion of the front enclosed area is connected to the upper end of the first plate body, the water in the front enclosed area overflows from the top of the front baffle and flows along the gap between the front baffle and the first plate body to the middle area; a second plate body is arranged at intervals in front of the rear baffle, the height of the second plate body is the same as the height of the top of the mud tank, the lower end of the second plate body is higher than the bottom of the mud tank, the edge of the membrane portion of the rear enclosed area is connected to the upper end of the second plate body, the water in the rear enclosed area overflows from the top of the rear baffle and flows along the gap between the rear baffle and the second plate body to the middle area;

[0022] The mud pump outlet of the trailing suction hopper ship is arranged in the front closed area and the rear closed area;

[0023] The overflow well of the mud chamber is arranged in the middle area, and the middle area is also provided with an inverted V-shaped cover plate, the lower end of the cover plate is connected to the first plate body and the second plate body respectively, and a plurality of leakage holes are provided on the edge of the lower end of the cover plate. A slag powder barrel is provided above the middle area, and a discharge port is provided at the bottom of the slag powder barrel. An electric valve is provided at the discharge port to control the slag powder barrel to discharge slag powder into the middle area, so that the slag powder reacts with the hydrogen sulfide-containing water body overflowing into the middle area to form sulfide precipitation.

[0024] The present invention has at least the following beneficial effects: a targeted ship modification scheme and construction process effectively solves the problems of protection, collection, and discharge of toxic hydrogen sulfide gas, is easy to operate, economical and practical, enables the trailing suction hopper vessel to operate normally, improves the applicability of the trailing suction hopper vessel, and has significant economic benefits.

[0025] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic side view of the structure of a trailing suction hopper vessel according to an embodiment of the present invention;

[0027] FIG2 is a schematic diagram of the front structure of the mud tank according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0029] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "horizontal", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0030] The project is located in Dar es Salaam Port, Tanzania (hereinafter referred to as Dar Port). The project includes widening, deepening and dredging of the outer channel, channel entrance, turning circle and inner channel area.

[0031] According to the analysis of drilling exploration data provided by the owner, the soil containing hydrogen sulfide is mainly silt, containing shell fragments and organic matter. The moisture content of the mud surface is 100%, the moisture content 10m below the mud surface is 50%, the organic matter content is 8-16%, the undrained shear strength 2m below the mud surface is 2kPa, and the undrained shear strength 10m below the mud surface is 15kPa.

[0032] The areas known to contain hydrogen sulfide in the soil are the outer and inner channels. Contact with a contractor who previously worked on the site revealed similar conditions during their construction. However, the construction was carried out using a grab vessel, resulting in minimal disturbance and no widespread eruptions. Soil samples were sent to the laboratory, but no excessive levels of hydrogen sulfide were found, so no treatment was performed. A preliminary on-site investigation indicates that the hydrogen sulfide in this area is caused by the decomposition of animal remains, forming hydrogen sulfide gas that is dispersed throughout the construction soil. The outer channel has a thin, open, and well-ventilated mud layer. Although hydrogen sulfide alarms were triggered during construction, monitored concentrations remained within safe limits. Hydrogen sulfide soil is predominantly found in the inner channel. This area is located in a semi-enclosed area within the harbor, surrounded by urban buildings, with low wind speeds and poor gas diffusion conditions. Furthermore, the soil layer is approximately 2 meters thick and contains a high hydrogen sulfide content, making it a key challenge and challenge in handling hydrogen sulfide soil during construction.

[0033] In order to solve the above problems, the present invention provides a method for dredging a harbor channel in soil containing hydrogen sulfide, comprising:

[0034] Step 1: Install hydrogen sulfide detectors at different locations on the TDSC, weld a keel around and above the mud tank of the TDSC, and partially seal the mud tank hatch with a cloth film set on the keel. The sealed area includes a front sealed area 12 to 20 meters away from the TDSC bridge and a rear sealed area 10 meters away from the rear of the mud tank. The middle area is open and equipped with a high-power axial flow fan. High-power fans are installed in the living quarters of the TDSC, and high-power axial flow fans are installed in the main engine room, pump room, and repair room of the TDSC. The mud door holes on the mud tank deck are filled with expanding foam and covered with cover plates to prevent hydrogen sulfide gas from being released outward through the mud door holes on the mud tank deck.

[0035] Specifically, the project department and the ship communicated and discussed with domestic experts and hydrogen sulfide equipment manufacturers many times, and finally selected the YT-95H-H2S-A fixed hydrogen sulfide alarm based on the ship type and layout of the ship at the construction site. This detector has the functions of remote monitoring, explosion protection, two-level sound and light alarm, and temperature compensation, which can realize the monitoring of hydrogen sulfide in different temperature environments of the ship.

[0036] According to the ship type and layout of the trailing suction hopper vessel, the monitoring range of the hydrogen sulfide detector is 20-50m 2 The plan is to install 30 fixed hydrogen sulfide detectors and two monitoring hosts on the trailing suction hopper vessels. Each hydrogen sulfide detector will be located 30-60 cm above the ground and secured with a steel frame. The specific layout is as follows: 21 in the engine room and 9 in the living quarters and bridge. The hydrogen sulfide detectors will be connected in parallel to a 32-channel monitoring host located in the engine room monitoring room. Nine hydrogen sulfide detectors will be installed in the living quarters and bridge, connected in parallel to a 16-channel monitoring host located on the bridge.

[0037] Fixed hydrogen sulfide detector system set to 15mg / m 3 (10ppm) low alarm value, if it reaches 10ppm, the detector will emit a "beep beep" beep and accompanied by a yellow alarm light alarm, when the concentration of hydrogen sulfide in the air reaches 30mg / m 3 When the concentration of HCl is below 20ppm, the detector emits a beeping sound and a red alarm light comes on.

[0038] During the ship construction phase, attention was paid to the crew's personal protection while the ship was being modified. During loading, hydrogen sulfide-containing mud crashed from the hatchway onto the tank bottom, converting potential energy into kinetic energy, releasing a large amount of hydrogen sulfide gas. This gas then recoiled along the mud bulkhead to the upper portion of the tank, where it then diffused, resulting in a higher density at higher points than at lower points.

[0039] Therefore, keels were welded around and above the mud tanks, and the tanks were sealed with a cloth membrane. The sealed area was approximately 15-20 meters from the bridge and 10 meters aft of the mud tank. High-power axial flow fans were installed in the middle area to disperse hydrogen sulfide and prevent it from entering the tank through the front and rear air inlets. This ensured that the hydrogen sulfide concentration in the bridge, living quarters, and engine room remained within the normal range. At the same time, high-power fans were installed in the living quarters of the tractor hopper carriers, and in areas with poor air circulation, such as the main engine room, pump room, and repair room, to speed up air circulation and prevent the accumulation of hydrogen sulfide.

[0040] The inside of the 24 small mud door holes on the mud tank deck are filled with expanding foam and covered with covers to prevent hydrogen sulfide from being released outwards through these holes during construction.

[0041] Step 2: Analyze the main wind direction, secondary wind direction, and wind speed based on the wind rose diagram of the harbor channel area. At the same time, check the direction of the ship's construction channel. Take full advantage of the physical property of hydrogen sulfide gas, which diffuses quickly in the wind, and rationally utilize wind direction and wind speed to reduce the impact of H2S gas on construction safety. The ship should use a wind direction and anemometer to observe the ship's relative wind direction at all times to facilitate the ship's reasonable arrangement of construction production, and try to work against the wind and crosswind.

[0042] Specifically, when there is no wind, increase the ship's speed by 2.5 to 3 knots to reduce the time hydrogen sulfide gas accumulates on the ship;

[0043] When there is no wind, head wind or cross wind, carry out normal construction, pay attention to the hydrogen sulfide detector in the stern engine room, and keep the high-power axial flow fan on.

[0044] Vessels must not carry out construction when the wind is favorable.

[0045] Step 3: Fill the chamber with water before construction, take the highest overflow, open the high-pressure water flushing of the rake head, adjust the upward angle of the rake lip to separate the rake lip from the mud surface at the bottom of the channel, and use high-pressure water flushing to break up the mud at the bottom of the channel so that the hydrogen sulfide will evaporate and dissolve into the water first;

[0046] If the high-pressure water flushing pressure is low, two high-pressure water flushing pumps are connected in series to one rake head and used in single rake construction. The rake head on one side with high-pressure water flushing is used to dredge the mud, and the rake head on the other side uses a combined pump to pump clean water into the cabin, so that the mud concentration in the mud cabin will be further diluted, accelerating the volatilization and dissolution of hydrogen sulfide.

[0047] Step 4: Use the full tank replacement construction method to suck the mud from the bottom of the channel into the mud tank of the trailing suction hopper vessel. During the construction process, turn on the high-power axial flow fan to reduce the concentration of hydrogen sulfide in the air on board;

[0048] Specifically, when the mud at the bottom of the channel is sucked into the mud tank of the drag-suction vessel, if the hydrogen sulfide detector continues to alarm, low-concentration discharge construction is adopted. During construction, the drag head is turned on to flush with high pressure water, and the drag lip is raised to adjust the angle so that the high-pressure water can first break up and dilute the mud at the bottom of the channel. The diluted mud is then sucked in with a mud pump and discharged directly overboard without loading. The high-power axial flow fans in the main engine room and pump room are turned on for timely exhaust. After the hydrogen sulfide detector detects that the hydrogen sulfide gas concentration has returned to normal, the mud loading construction can be continued.

[0049] During construction, if it is found that hydrogen sulfide gas has reached the low alarm point of the hydrogen sulfide detector, the ship will immediately issue a ship-wide alarm and require all on-duty personnel to carry emergency respirators. At the same time, the ship will adjust its position according to the wind direction to keep the bridge, cabins, and main engine room upwind. If the hydrogen sulfide detector continues to alarm and the concentration continues to increase, work will be stopped immediately. If the concentration drops, construction will continue and real-time monitoring will be maintained. If it is found that hydrogen sulfide gas has reached the high alarm point of the hydrogen sulfide detector, the ship will immediately issue a ship-wide alarm and require all on-duty personnel to carry emergency respirators. The driver should immediately stop construction and drive the trailing suction hopper away from the construction area for ventilation.

[0050] Step 5: When the mud tank is full, move the hopper vessel to the designated mud dumping area to dump the mud.

[0051] Specifically, when the trailing suction hopper vessel is on its way to the mud dumping area, the vessel uses mechanical and natural ventilation to promptly complete the ventilation work inside the cabin. After ventilation, the ship's dedicated detection personnel use handheld detection equipment to go to each cabin for detection. After there is no hydrogen sulfide risk, normal mud dumping operations begin;

[0052] During the mud dumping process, keep the ship dumping mud against the wind or across the wind to reduce the release of hydrogen sulfide generated during mud dumping.

[0053] The targeted ship modification scheme and construction process of the above embodiment effectively solves the problems of protection, collection and discharge of toxic hydrogen sulfide gas, is easy to operate, economical and practical, enables the trailing suction hopper vessel to operate normally, improves the applicability of the trailing suction hopper vessel, and has significant economic benefits.

[0054] As shown in Figures 1 and 2, in another embodiment, a front baffle 2 and a rear baffle 3 are provided in the mud tank 1 of the trailing suction hopper barge, and the heights of the front baffle 2 and the rear baffle 3 are both lower than the top height of the mud tank 1; a first plate body 4 is arranged at intervals behind the front baffle 2, and the height of the first plate body 4 is the same as the top height of the mud tank 1, and the lower end of the first plate body 4 is higher than the bottom surface of the mud tank 1, and the edge of the cloth membrane 5 of the front closed area is connected to the upper end of the first plate body 4, and the water in the front closed area overflows from the top of the front baffle 2 and flows along the gap between the front baffle 2 and the first plate body 4 to the middle area; a second plate body 6 is arranged at intervals in front of the rear baffle 3, and the height of the second plate body 6 is the same as the top height of the mud tank 1, and the lower end of the second plate body 6 is higher than the bottom surface of the mud tank 1, and the edge of the cloth membrane 5 of the rear closed area is connected to the upper end of the second plate body 6, and the water in the rear closed area overflows from the top of the rear baffle 3 and flows along the gap between the rear baffle 3 and the second plate body 6 to the middle area;

[0055] Here, the front baffle 2, the rear baffle 3, the first plate 4 and the second plate 6 are connected to the inner walls of the mud tank 1 on both sides respectively;

[0056] The mud pump outlet of the trailing suction hopper ship is arranged in the front closed area and the rear closed area;

[0057] The overflow well 7 of the mud chamber 1 is arranged in the middle area, and the middle area is also provided with an inverted V-shaped cover plate 8. The lower ends of the cover plate 8 are respectively connected to the first plate body 4 and the second plate body 6, and the lower end edge of the cover plate 8 is provided with multiple leakage holes. A slag powder barrel 9 is provided above the middle area, where the slag powder barrel 9 can be connected to the keel 10 around and above the middle area of ​​the mud chamber 1 through a connecting rod. A discharge port is provided at the bottom of the slag powder barrel 9, and an electric valve is provided at the discharge port to control the slag powder barrel 9 to discharge slag powder into the middle area, so that the slag powder reacts with the hydrogen sulfide-containing water overflowing into the middle area to form sulfide precipitation.

[0058] When using the above-mentioned trailing suction hopper vessel for mud loading, the front closed area and the rear closed area of ​​the front mud tank 1 are first filled with seawater. The mud pump of the trailing suction hopper vessel sucks mud from the drag head and sends it to the mud pump discharge outlet along the mud transportation pipeline. Since the mud pump discharge outlet is arranged in the front closed area and the rear closed area, the mud can be directly discharged into the seawater in the front closed area and the rear closed area. This full-tank replacement overflow loading construction method can reduce mud loading disturbance, reduce the overflow rate of hydrogen sulfide gas, and reduce the deposition concentration of hydrogen sulfide on the deck. At the same time, since the top of the front closed area and the rear closed area are covered with a cloth film 5, the hydrogen sulfide gas is confined to the closed area of ​​the mud tank 1 and is difficult to spread onto the deck.

[0059] After hydrogen sulfide gas evaporates from the mud, it will also dissolve in the seawater. At this time, the seawater containing hydrogen sulfide gas overflows from the top of the front bulkhead 2 and flows along the gap between the front bulkhead 2 and the first plate body 4 to the middle area. It also overflows from the top of the rear bulkhead 3 and flows along the gap between the rear bulkhead 3 and the second plate body 6 to the middle area. The cover plate 8 can limit the surge of the seawater containing hydrogen sulfide in the middle area, preventing hydrogen sulfide from escaping from the seawater and depositing on the deck. At the same time, the solenoid valve at the discharge port of the slag powder barrel 9 can be opened to allow the slag powder in the slag powder barrel 9 to slide along the top inclined surface of the cover plate 8 through the leakage hole into the seawater in the middle area. Here, the slag powder is preferably iron slag or copper slag. Since this slag powder contains iron ions and copper ions, it can form iron trisulfide and copper sulfide precipitation with hydrogen sulfide, thereby eliminating the hydrogen sulfide component in the seawater. The other components of the slag powder are dispersed in the seawater and separated and discharged through the overflow well 7 in the middle area. In this way, the low-grade iron and low-grade copper in the iron slag and copper slag can be enriched, which is convenient for their re-refining, thereby improving resource utilization.

[0060] When dumping mud, the mud door holes at the bottom of the mud tanks in the front and rear closed areas are opened to dump mud, while the sediment in the middle area can be sucked to the shore for retention.

[0061] In the above embodiment, a two-flow overflow method is adopted. The first overflow separates the silt from the seawater containing hydrogen sulfide, and the second overflow separates the precipitate generated by the reaction of the seawater containing hydrogen sulfide with the slag powder. This not only eliminates hydrogen sulfide and reduces its concentration, but also enriches and separates low-grade copper and iron compounds, achieving two goals at one stroke.

[0062] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for dredging a harbor channel in soil containing hydrogen sulfide, characterized in that: include: Step 1: Install hydrogen sulfide detectors at different positions on the hopper, weld keels around and above the mud tank of the hopper, and partially seal the hatch of the mud tank with a cloth film set on the keel. The sealed area includes the front sealed area in the 12-20m section near the side of the hopper's driving platform and the rear sealed area in the 10m area of ​​the rear section of the mud tank. The middle area is open and equipped with a high-power axial flow fan. A high-power fan is installed in the living cabin of the hopper, and a high-power axial flow fan is installed in the main engine room, pump room, and repair room of the hopper. The mud door hole on the mud tank deck is filled with an expansion foam agent, and a cover plate is installed outside the mud door hole to prevent hydrogen sulfide gas from being released outward through the mud door hole on the mud tank deck; Step 2: Analyze the main wind direction, secondary dominant wind direction and wind speed according to the wind rose diagram of the harbor channel area, and formulate a trailing suction hopper construction plan according to the wind direction and speed; Step 3: Fill the cabin with water before construction, take the highest overflow, open the rake head for high-pressure water flushing, adjust the rake lip upward angle to separate the rake lip from the mud surface at the bottom of the channel, use high-pressure water flushing to break up the mud at the bottom of the channel first, so that the hydrogen sulfide will evaporate and dissolve into the water first; Step 4: Use the full tank replacement construction method to suck the mud at the bottom of the channel into the mud tank of the trailing suction hopper ship. During the construction process, turn on the high-power axial flow fan to reduce the concentration of hydrogen sulfide in the air on board; Step 5: When the mud tank is full, drive the suction hopper to the designated mud dumping area to dump the mud.

2. The method for dredging a harbor channel in soil containing hydrogen sulfide according to claim 1, characterized in that: The construction plan of the trailing suction hopper vessel is formulated according to the wind direction and speed, including: When there is no wind, increase the speed by 2.5 to 3 knots to reduce the time that hydrogen sulfide gas accumulates on the ship; When there is no wind, head wind or cross wind, carry out normal construction, pay attention to the hydrogen sulfide detector in the stern engine room, and keep the high-power axial flow fan turned on.

3. The method for dredging a harbor channel in soil containing hydrogen sulfide according to claim 1, characterized in that: When the mud at the bottom of the channel is sucked into the mud tank of the suction hopper ship, if the hydrogen sulfide detector continues to alarm, low-concentration external discharge construction is adopted. During construction, the suction hopper head is turned on with high-pressure water flushing, and the suction hopper lip is raised to adjust the angle so that the high-pressure water flushing can first break up and dilute the mud at the bottom of the channel. The diluted mud is then sucked in with a mud pump and discharged directly overboard without loading. The high-power axial flow fans in the main engine room and pump room are turned on for timely exhaust. After the hydrogen sulfide detector detects that the hydrogen sulfide gas concentration has returned to normal, the mud loading construction in step four can be continued.

4. The method for dredging a harbor channel in soil containing hydrogen sulfide according to claim 1, characterized in that: The low alarm point of the hydrogen sulfide detector is set at 15 mg / m 3 The high alarm point is set at 30mg / m 3 .

5. The method for dredging a harbor channel in soil containing hydrogen sulfide according to claim 4, characterized in that: During construction, if it is found that the hydrogen sulfide gas has reached the low alarm point of the hydrogen sulfide detector, the ship will immediately issue a ship-wide alarm and require all on-duty personnel to carry emergency respirators. At the same time, the ship will adjust the position of the ship according to the wind direction to keep the bridge, cabins, and main engine room upwind. If the hydrogen sulfide detector continues to alarm and the concentration continues to increase, work will be stopped immediately. If the concentration drops, construction will continue and real-time monitoring will be maintained. If it is found that the hydrogen sulfide gas has reached the high alarm point of the hydrogen sulfide detector, the ship will immediately issue a ship-wide alarm and require all on-duty personnel to carry emergency respirators. The driver should immediately stop construction and drive the trailing suction hopper away from the construction area for ventilation.

6. The method for dredging a harbor channel in soil containing hydrogen sulfide according to claim 1, characterized in that: When the hopper vessel is on its way to the mud dumping area, the ship uses mechanical and natural ventilation to complete the ventilation work inside the cabin in time. After ventilation, the ship's dedicated detection personnel use handheld detection equipment to go to each cabin for detection. After there is no risk of hydrogen sulfide, normal mud dumping operations begin; During the mud dumping process, the vessel should be kept dumping against the wind or across the wind to reduce the release of hydrogen sulfide generated during mud dumping.

7. The method for dredging a harbor channel in soil containing hydrogen sulfide according to claim 1, characterized in that: The mud tank of the trailing suction hopper is provided with a front baffle and a rear baffle, the heights of the front baffle and the rear baffle are both lower than the height of the top of the mud tank; a first plate body is arranged at intervals behind the front baffle, the height of the first plate body is the same as the height of the top of the mud tank, the lower end of the first plate body is higher than the bottom of the mud tank, the edge of the membrane portion of the front closed area is connected to the upper end of the first plate body, the water in the front closed area overflows from the top of the front baffle and flows to the middle area along the gap between the front baffle and the first plate body; a second plate body is arranged at intervals in front of the rear baffle, the height of the second plate body is the same as the height of the top of the mud tank, the lower end of the second plate body is higher than the bottom of the mud tank, the edge of the membrane portion of the rear closed area is connected to the upper end of the second plate body, the water in the rear closed area overflows from the top of the rear baffle and flows to the middle area along the gap between the rear baffle and the second plate body; The mud pump outlet of the trailing suction hopper is arranged in the front closed area and the rear closed area; The overflow well of the mud tank is arranged in the middle area, and the middle area is also provided with an inverted V-shaped cover plate, the lower end of which is connected to the first plate body and the second plate body respectively. A plurality of leakage holes are arranged on the edge, a slag powder barrel is arranged above the middle area, a discharge port is arranged at the bottom of the slag powder barrel, and an electric valve is arranged at the discharge port to control the slag powder barrel to discharge slag powder into the middle area, so that the slag powder reacts with the hydrogen sulfide-containing water overflowing into the middle area to form sulfide precipitation.

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