CN117385962A - Construction method for safety and environmental protection of soil containing hydrogen sulfide - Google Patents

Abstract

The invention discloses a construction method for safety and environmental protection of soil containing hydrogen sulfide, which comprises the following steps: arranging a hydrogen sulfide detector: arranging a plurality of hydrogen sulfide detectors and two monitoring hosts in a constructed ship, wherein the height of each hydrogen sulfide detector from the ground is 30-60 cm; optimizing construction equipment: welding keels around and above a ship mud cabin, sealing the mud cabin by adopting a sealing film, wherein the sealing area is an area which is 15-20 meters close to the side of a driving platform and 10 meters at the rear section of the mud cabin, a high-power axial flow fan is arranged in the middle area, the interior of a mud door hole of a mud cabin deck is filled with an expansion foam agent, and a cover plate is additionally arranged outside to block the mud door hole; double-sided plow teeth are arranged at the wear-resisting block of the ship drag head; and (3) construction: before construction, the hydrogen sulfide gas is dispersed, the concentration value in a cabin is ensured to be in a normal range, an inner fan of a cabin of a ship is closed for external circulation in the construction process, an inner circulation mode is opened, and the air flow is quickened by utilizing the ventilation of the explosion-proof axial flow fan. The invention ensures the safe and efficient development of construction of the soil containing hydrogen sulfide.

Description

Safe and environmentally friendly construction methods for soil containing hydrogen sulfide

Technical field

The invention relates to the technical field of dredging engineering, and in particular to a safe and environmentally friendly construction method for hydrogen sulfide-containing soil.

Background technique

Hydrogen sulfide is an inorganic compound with the chemical formula H ₂ S. It is a flammable, explosive, highly toxic and corrosive gas. In waterway projects or dredging projects, the soil in the area to be dredged contains hydrogen sulfide gas. During the dredging process, the gas may spread with the disturbance of the soil. Improper protection will lead to immeasurable serious consequences and even casualties.

Rake-suction boats are mainly used in existing dredging construction. However, as the dredged soil becomes more and more complex, existing equipment and construction techniques cannot ensure safe production for soil containing hydrogen sulfide.

Contents of the invention

It is an object of the present invention to solve at least the above problems and/or disadvantages and to provide at least the advantages to be explained below.

Another object of the present invention is to provide a safe and environmentally friendly construction method for hydrogen sulfide-containing soil, which optimizes equipment and construction technology in view of the shortcomings of the existing technology to ensure safe and efficient construction of hydrogen sulfide-containing soil.

In order to achieve these objects and other advantages according to the present invention, the technical solutions of the present invention are as follows:

A safe and environmentally friendly construction method for soil containing hydrogen sulfide, including the following steps:

Step 1. Arrange hydrogen sulfide detectors: Arrange multiple hydrogen sulfide detectors and two monitoring hosts in the construction ship. The height of each hydrogen sulfide detector from the ground is 30 to 60cm;

Step 2. Optimization of construction equipment: weld the keel around and above the mud tank of the ship, and use a sealing membrane to seal the mud tank. The closed area is 15-20 meters near the bridge side and 10 meters behind the mud tank, with the middle High-power axial flow fans are deployed in the area, and the mud door holes of the mud tank deck are filled with expanding foam agent and blocked with cover plates on the outside; double-sided plow teeth are installed on the wear-resistant block of the ship's rake head;

Step 3. Construction: Disperse the hydrogen sulfide gas in the cabin before construction to ensure that the concentration of hydrogen sulfide in the cabin is within the normal range. During the construction process, the fan in the cabin of the ship closes the external circulation, turns on the internal circulation mode, and uses explosion-proof axial flow. Fan ventilation speeds up air flow.

Preferably, in step one, the detection alarm of the hydrogen sulfide detector is a secondary alarm mechanism, specifically including:

When the hydrogen sulfide detector detects that the hydrogen sulfide concentration is greater than 10 ppm and less than 20 ppm, the detector emits a buzzer and is accompanied by a yellow warning light. Construction workers wear hydrogen sulfide respiratory protectors and continue construction, adjusting the position of the ship according to the wind direction so that the driver can The platform, respirator, and engine room control room are all located upwind;

When the hydrogen sulfide detector detects that the hydrogen sulfide concentration is greater than 20 ppm, the detector emits a buzzer and is accompanied by a red warning light. Construction workers must wear respirators immediately, stop construction immediately, stay away from the construction area, and perform high-pressure flushing and ventilation of the construction area. .

Preferably, step three specifically includes:

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

When the wind is blowing, construction is normal, and real-time attention is paid to the alarms of multiple hydrogen sulfide detectors arranged in the ship. The fans in the ship's accommodation cabin turn off the external circulation, turn on the internal circulation mode, and keep the explosion-proof axial flow fan on;

When there is cross wind, carry out construction in the inner channel area where hydrogen sulfide gas is relatively high; keep the explosion-proof axial flow fan always on;

When the wind is favorable, the ship stops construction.

Preferably, the quality inspection in steps three and two also includes: pre-construction cabin loading and ballasting: before construction, the ship cabin is filled with mud, the highest overflow is used, the front loading cabin is closed, and the rake head is opened for high-pressure water flushing and wear-resistant blocks The rake lip is raised to adjust the angle between the rake lip and the inside of the rake cavity, so that the rake lip is separated from the mud surface.

Preferably, step one also includes: equipping each construction worker with a portable hydrogen sulfide gas detector. When the concentration of hydrogen sulfide in the air is greater than 10 ppm, the detector emits a buzzer alarm. When the concentration of hydrogen sulfide in the air is greater than At 15ppm, the detector will sound a beep and the red alarm light will flash.

Preferably, step one also includes: each ship at the construction site is equipped with two four-in-one gas detectors for monitoring hydrogen sulfide gas and other toxic gases present in the air.

Preferably, step two also includes: equipping each room of the ship's accommodation cabin with a high-power vertical cabinet fan; placing 3000W high-power explosion-proof axial flow fans in the main engine room, pump room and repair room; The engine room control room and bridge are equipped with hydrogen sulfide respiratory protectors and emergency respirators that meet the needs.

Preferably, step three also includes: during the process of throwing mud, the ship keeps throwing mud against the wind or across the wind.

Preferably, in step one, the number of hydrogen sulfide detectors installed is 30, all fixed with steel frames, and the number of monitoring hosts is 2. The specific installation locations are: 21 in the engine room, 9 in the accommodation cabin and driving station. 21 hydrogen sulfide detectors in the engine room are connected in parallel to a 32-channel monitoring host. The 32-channel monitoring host is placed in the engine room monitoring room. The 9 hydrogen sulfide detectors installed in the accommodation cabin and driving station are connected in parallel to A 16-channel monitoring host is connected, and the 16-channel monitoring host is placed on the bridge.

Preferably, the hydrogen sulfide detector is a YT-95H-H ₂ SA fixed hydrogen sulfide alarm.

The present invention at least includes the following beneficial effects:

1. The present invention is a safe and environmentally friendly construction method for hydrogen sulfide-containing soil, optimizing equipment and construction techniques to ensure safe and efficient construction of hydrogen sulfide-containing soil.

2. In the safe and environmentally friendly construction method of hydrogen sulfide-containing soil of the present invention, the construction method is reasonably set according to the distribution and ventilation conditions of hydrogen sulfide soil in the outer channel and inner channel, taking into account construction safety and improving construction efficiency.

3. In the safe and environmentally friendly construction method for hydrogen sulfide-containing soil of the present invention, the safety of construction workers is ensured by arranging and equipping different alarms in different areas and different construction workers, and setting up different alarm mechanisms.

4. In the safe and environmentally friendly construction method for hydrogen sulfide-containing soil of the present invention, by making full use of the physical properties of hydrogen sulfide gas that diffuses quickly in the wind, rationally utilizing wind direction and wind speed, and selecting the appropriate wind direction for construction, it is convenient for ships to reasonably arrange construction and production. , Reduce the impact of hydrogen sulfide gas on construction safety.

5. In the safe and environmentally friendly construction method for hydrogen sulfide-containing soil of the present invention, by loading the tank with ballast before construction, the mud concentration in the mud tank will be further diluted, accelerating the volatilization and dissolution of hydrogen sulfide; by modifying it into double-sided plow teeth, Increase the crushing effect of the rake head on the soil in the construction area during construction, make full use of the characteristics of the plow teeth, and tamp the seabed soil. Combined with the action of high-pressure flushing, the tumbled soil is fully dispersed and the hydrogen sulfide in the soil is released. gas.

Description of the drawings

Figure 1 is a schematic flow chart of the safe and environmentally friendly construction method for soil containing hydrogen sulfide according to the present invention;

Figure 2 is a schematic diagram of full warehouse replacement construction in the safe and environmentally friendly construction method for soil containing hydrogen sulfide according to the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it with reference to the text of the description.

It should be noted that the test methods in the following embodiments, unless otherwise specified, are all conventional methods, and the materials, unless otherwise specified, can be obtained from commercial sources.

<Example 1>

As shown in Figures 1 to 2, taking the Dagang Harbor channel dredging project in Tanzania as an example, a safe and environmentally friendly construction method for soil containing hydrogen sulfide is carried out.

1. Situation of soil areas containing hydrogen sulfide:

1.1. The dredging project includes the outer channel, channel entrance, U-turn circle and inner channel area. The dredging project volume is approximately 10 million m ³ . The outer channel 1 is 2165m long, and the design width of the bottom edge gradually changes from 240m to 190m; the arc length of the curve is 1527m, the radius is 2040m, and the design width of the bottom edge is 210m; the outer channel 2 is 1222m long, and the design width of the bottom edge gradually changes from 210m to 170m; the channel entrance is long 1309m, with various bottom edge design widths; the turning circle radius is 260m; the internal channel is 1778m long, and the bottom edge design width is 215m.

Hydrogen sulfide-containing soil is mainly distributed in the outer channel and inner channel, and in the inlet channel and U-turn circle in the middle area. The construction soil is mainly sand, and there is no hydrogen sulfide-containing soil.

1.2. Flow speed in the construction area: There is a semi-enclosed harbor within the entrance. Except for the influence of ebb and flow, the flow speed in the harbor is about 0.2m/s; the main flow rate in the coastal waters outside the port area is the South Equatorial Current, with a speed of 0.5~0.6m/s. Within the range, the flow direction is northeast.

1.3. Waves: From January 2001 to December 2020, the general direction of sea waves was found: in the offshore area, the dominant direction is east-southeast, and the highest waves come from the south-southeast direction; the minimum significant wave height recorded is 0.8m , the annual average wave height is 1.6m; on August 12, 2010, the maximum wave height was 4.6m, and the direction was 174°N (south-southeast); 70% of the wave directions are located in E~S, and 30% of the wave directions are located in N~ E; From April to November, the dominant wave direction is southeast, and the highest wave occurs from June to August. For nearshore areas, the highest waves come from the northeast, and the maximum wave height is 2.4 to 3.4m.

1.4. Tide: The local area has regular semidiurnal tide, with high tide 3.2m and low tide 1.2m.

1.5. The project location has a savanna climate, which is mild and dry, with very little fog throughout the year. Even if there is occasional short-term fog, it will only have a small impact on the construction. The local area is affected by monsoons. The construction period is from December to March, mainly affected by northerly and northeasterly winds; the construction period is from April to September, mainly affected by southeasterly and southwesterly winds. According to the statistical data analysis results of the above two time periods and combined with the wind and wave resistance of our ships, the wind conditions in this area have little impact on our construction ships.

1.6. Hydrogen sulfide soil quality: Hydrogen sulfide-containing soil is mainly silt, containing shell fragments and organic matter. It is very soft to soft. The moisture content of the mud surface is 100%. The moisture content 10m below the mud surface is 50%, and 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.

2. The hazards of hydrogen sulfide:

Hydrogen sulfide is an inorganic compound with the chemical formula H ₂ S. It is a flammable, explosive, highly toxic and corrosive gas. Under normal circumstances, it is a colorless gas with a typical smell of rotten eggs, with a relative molecular mass of 34.08, a density of 1.539kg/m ³ , a relative density of air of 1.19, a melting point of -82.9°C, and a boiling point of -60.3°C. , can be dissolved in water. At 0°C, 1 mole of water can dissolve about 2.6 moles of H ₂ S. Its solubility decreases as the temperature of the water increases.

2.1. Flammability

Forms a flammable mixture with air, the lowest auto-ignition temperature (260°C) occurs at a concentration of about 15%; burns at higher concentrations or insufficient oxygen to form water and sulfur: 2H ₂ S+O ₂ = 2H ₂ O+2S↓, At a lower concentration or with sufficient oxygen, the combustion products form water and sulfur dioxide: 2H ₂ S + 3O ₂ = 2H ₂ O + 2SO _2. When burned, a light blue flame is produced, and SO ₂ gas is produced that is harmful to human eyes and lungs. . Insufficient oxygen Sufficient oxygen Inhaling a small amount of high-concentration H ₂ S can be fatal in a short period of time. Low concentrations of H ₂ S have effects on the eyes and central nervous system.

2.2. Explosiveness

When the H ₂ S concentration is between 4.3% and 46%, the mixed gas formed in the air will explode violently when exposed to fire.

2.3. Toxicity

H ₂ S gas is a highly toxic gas that can easily cause death. Its toxicity is 5 to 6 times that of carbon monoxide. A person's sensitivity to H ₂ S weakens as the number of times he or she is exposed to H ₂ S increases, with the second exposure being more dangerous than the first and so on. When H ₂ S is inhaled into the human body, it will be transported to various organs of the human body through the respiratory tract, lungs, and blood. First, it stimulates the respiratory tract, dulling the sense of smell, causing coughing, and in severe cases, burns; the eyes are stung, and in severe cases, blindness; it stimulates the nervous system, causing dizziness, loss of balance, and difficulty breathing; the heart beats faster, and in severe cases, death occurs due to lack of oxygen in the heart. . Alcohol in the blood increases the chance of H ₂ S poisoning.

The effects of H ₂ S depend on the duration of the effect and the concentration of exposure, as well as individual differences in physical conditions, so it is difficult to provide a set of fixed rules. The concentration of H ₂ S is usually expressed in ppm (parts per million), but usually the effects of different concentrations of H ₂ S on humans are as follows: Under normal circumstances, when repeatedly exposed to an environment of 10 ppm, the average level that the body can tolerate concentration. A normal 8-hour working day does not harm health. This concentration is called the threshold limit value. If exposure is only for a short period of time during the day, the concentration level can be increased to 15 ppm for a maximum of 15 minutes. A maximum of 4 times in a working day, with at least an interval of 60 minutes in between, is called the short-term exposure limit.

3. Construction technology

3.1. Equipment:

Ship: Rake suction ship (Tongxu wheel, used for dredging), grab ship group (obstacle salvage and dredging): Jinhang Dredging 407 (grab), Jinhang Barge 48 (mud barge), Jinhang Barge 49 ( Mud barge) and Tianjin Air Barge 51 (mud barge), boat (Darun 66, emergency rescue).

Other equipment: 40 gas masks (EHFR-5000, anti-virus), 13 cabinet fans (KS-04X60Dg, ventilation), 10 four-in-one gas detectors (detection), portable hydrogen sulfide gas detector (CLIP-H ₂ S, testing), 20 explosion-proof axial flow fans (1000w, 3000w, ventilation), 5 oxygen bottles and breathing masks (anti-virus), 57 emergency respirators (THB/15-I, anti-virus), fixed 30 hydrogen sulfide monitoring probes (YT-95H-H ₂ SA, detection), 30 audible and visual alarms (detection), 1 monitoring host (32 channels, integrated monitoring) and 1 monitoring host (16 channels, integrated monitoring) tower.

3.2. Investigation of construction area conditions:

Currently, the areas where soil is known to contain H ₂ S are the outer channel and the inner channel. After understanding with the contractor who had worked on the site, similar situations also occurred during the construction. However, it was a grab boat construction, so the disturbance was small and there was no large-scale outbreak. Moreover, soil samples were sent to the laboratory, and no large-scale explosion occurred. It was found that the H ₂ S content exceeded the standard, so no treatment was performed. After on-site investigation, it can be preliminarily determined that the H ₂ S in this area is formed by the decay of animal remains and is dispersed in various parts of _the construction soil layer.

The mud layer in the outer channel is thin, open and unobstructed, and the ventilation conditions are good. Although there are H ₂ S alarm values during the construction period, the monitored H ₂ S gas concentration values are within the safe range.

A large amount of soil containing H ₂ S is distributed in the inner channel. This area is located in a semi-enclosed area of the port and is surrounded by urban buildings. The wind value is small and the gas diffusion conditions are not good. The thickness of the soil layer is about 2m, and the H ₂ S content is high. , is the difficulty and focus of the H ₂ S soil quality in the construction of this project.

3.3. Construction process:

Step 1. Arrange hydrogen sulfide detectors: According to the ship type and ship layout of "Tongxu Lun", the monitoring range of H ₂ S detectors is 20-50m ² , and 30 fixed H ₂ S detectors are installed on "Tongxu Lun" Detector, 2 monitoring hosts. Each H ₂ S detector is 30-60cm away from the ground and fixed with a steel frame. Its specific layout is: 21 cabins, 9 accommodation cabins and driving stations, and 21 H ₂ S detectors in the cabin are connected in parallel. 32-channel monitoring host, the host is placed in the engine room monitoring room. Nine H ₂ S detectors are installed in the accommodation cabin and the bridge, and are connected in parallel to a 16-channel monitoring host. The host is placed on the bridge. The specific installation distribution quantity is shown in Table 1 below;

Equip each construction worker with a portable hydrogen sulfide gas detector. When the concentration of hydrogen sulfide in the air is greater than 10ppm, the detector will sound a buzzer alarm. When the concentration of hydrogen sulfide in the air is greater than 15ppm, the detector will sound a buzzer alarm and With the red alarm light flashing;

Each ship at the construction site is equipped with two four-in-one gas detectors to monitor the presence of hydrogen sulfide gas and other toxic gases in the air;

Among them, the hydrogen sulfide detector is a YT-95H-H ₂ SA fixed hydrogen sulfide alarm, and the detection alarm is a secondary alarm mechanism, specifically including:

When the hydrogen sulfide detector detects that the hydrogen sulfide concentration is greater than 10 ppm and less than 20 ppm, the detector emits a buzzer and is accompanied by a yellow warning light. Construction workers wear hydrogen sulfide respiratory protectors and continue construction, adjusting the position of the ship according to the wind direction so that the driver can The platform, respirator, and engine room control room are all located upwind;

When the hydrogen sulfide detector detects that the hydrogen sulfide concentration is greater than 20 ppm, the detector emits a buzzer and is accompanied by a red warning light. Construction workers must wear respirators immediately, stop construction immediately, stay away from the construction area, and perform high-pressure flushing and ventilation of the construction area. ;

Step 2. Optimization of construction equipment:

The keel is welded around and above the mud tank of the ship, and a sealing membrane is used to seal the mud tank. The closed area is 15-20 meters near the bridge side and 10 meters behind the mud tank. High-power axial flow fans are arranged in the middle area. The mud door hole of the mud tank deck is filled with expanding foam agent inside, and a cover plate is installed on the outside to block it; in order to maximize the release of H ₂ S gas in the soil, double-sided plow teeth are installed at the wear-resistant block of the rake head to increase the construction period. The rake head crushes the soil in the construction area and makes full use of the characteristics of the plow teeth to pound the seabed soil. Combined with the action of high-pressure water, the pounded soil is fully dispersed and the H ₂ S gas in the soil is released; wherein , the sealing membrane is a special cloth membrane, and its specificity is not limited, as long as it can seal the mud tank;

A high-power vertical cabinet fan is equipped in each room of the ship's accommodation cabin; a 3000W high-power explosion-proof axial flow fan is placed near the mud tank on the main deck, the main engine room, the pump room, the hydraulic room and the repair room in the engine room; in the accommodation cabin and pump room , the engine room control room, and the bridge are equipped with hydrogen sulfide respiratory protectors and emergency respirators that meet the needs; the emergency respirators can last for 10-15 minutes. When the general audible alarm system sounds or the H ₂ S gas detector detects that the concentration exceeds the standard Wear it when wearing it. Relevant personnel wearing this equipment are only used for "escape" and not for "work" or rescue. Its distribution is shown in Table 2.

Step 3. Construction:

Inject mud into the cabin before construction, adopt the highest overflow, close the front loading cabin, open the rake head high-pressure water flushing wear-resistant block and a place inside the rake cavity, raise the rake lip to adjust the angle, separate the rake lip from the mud surface, use high pressure When flushing water, first break up the mud on the seabed, so that H ₂ S can evaporate or dissolve into part of the water first. If the high-pressure flushing pressure is small, two high-pressure flushing pumps can be connected in series to a rake head, and single rake construction should be adopted (with high-pressure flushing). The rake head on one side is flushed for dredging, and the rake head on the other side uses a pump to pump clean water into the tank, so that the mud concentration in the mud tank will be further diluted and the volatilization and dissolution of H ₂ S will be accelerated.

Before construction, the hydrogen sulfide gas in the cabin should be dispersed to ensure that the hydrogen sulfide concentration in the cabin is within the normal range.

During the construction process, the fan in the ship's cabin turns off the external circulation, turns on the internal circulation mode, and uses the explosion-proof axial flow fan for ventilation to speed up the air flow. During the construction process, it is necessary to select the appropriate wind direction for construction and analyze the main wind direction, secondary wind direction and wind speed. , while checking the direction of the ship's construction channel, making full use of the physical properties of H ₂ S gas that diffuse quickly in the wind, and rationally utilizing the wind direction and speed to reduce the impact of H ₂ S gas on construction safety. Ships need to observe the relative wind direction of the ship at any time according to the wind direction and anemometer, so that the ship can reasonably arrange construction and production, and try to work against the wind and across the wind. Specifically include:

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

When the wind is blowing, construction is normal, and real-time attention is paid to the alarms of multiple hydrogen sulfide detectors arranged in the ship. The fans in the ship's accommodation cabin turn off the external circulation, turn on the internal circulation mode, and keep the explosion-proof axial flow fan on;

When there is cross wind, carry out construction in the inner channel area where hydrogen sulfide gas is relatively high; keep the explosion-proof axial flow fan always on;

When the wind is favorable, the ship ceases construction;

Among them, after the construction is completed and on the way to the mud throwing area, the ship uses mechanical and natural ventilation to complete the ventilation work inside the cabin in a timely manner. After ventilation, the ship's full-time detection personnel use detection equipment to go to each cabin for detection. After there is no risk of H ₂ S, normal operations will begin. During the mud throwing process, the ship should keep the mud thrown against the wind or across the wind to reduce the possible release of H ₂ S during mud throwing. , after the mud throwing is completed, 30 minutes before arriving at the construction area, the ship's bridge notifies the engine room of the start time of construction, non-operators remain on standby in the cabin, operators prepare protective devices for work, and bridge operators prepare for construction and arrive at the construction area Then continue the construction according to the above construction technology.

During ship construction, on the one hand, attention was paid to the personal protection of the crew, and on the other hand, the ship was modified. During the tank loading construction, the mud containing H ₂ S hits the bilge from the hatch, and the potential energy is converted into kinetic energy, releasing a large amount of H ₂ S gas. The H ₂ S gas recoils along the mud bulkhead to the upper part of the mud tank, and then diffuses. The overall density is higher at high places than at low places.

The keel is welded around and above the mud tank, and a special cloth membrane is used to seal the mud tank. The enclosed area is about 15-20 meters from the bridge side and 10 meters behind the mud tank. High-power axial flow fans are arranged in the middle area to disperse H ₂ S, prevent H ₂ S gas from entering the cabin from the front and rear air inlets, and ensure that the H ₂ S concentration values in each cabin on the bridge, accommodation cabin and engine room are within the normal range.

The 24 small mud door holes on the mud tank deck are filled with expanding foam agent, and a special cover plate is installed on the outside to prevent H ₂ S from being released outward through here during construction (no small mud door operation is required for excavation and throwing operations) .

When H ₂ S gas is found in the dredged material during construction, deck operations are strictly prohibited. The chief mate and first engineer of the ship are responsible for the opening and closing of the ship's deck and engine room respectively. It is strictly forbidden to open the hatches during the construction process. After leaving the H ₂ S area during raking and throwing mud, ventilate the area in time and in large quantities. Mud throwing is carried out against the wind or across the wind.

Ship pilots should observe changes in wind direction and wind speed in a timely manner, maintain navigational observation and lookout, pay attention to H ₂ S concentration monitoring at all times, and make preparations for H ₂ S protection.

Table 1. Distribution quantity of fixed H ₂ S detectors on ships

Table 2. Distribution quantity of emergency respirators

Among them, the construction speed calculation is implemented as follows:

The length of the H ₂ S concentration area is 2000m. In order to prevent the concentration of H ₂ S during construction in this area, a method is implemented to leave the H ₂ S concentration area and go to other construction areas within one hour of construction. The U-turn time during construction is 8 minutes, excluding the ballast time before construction, so the construction speed in this area is calculated as:

Length of construction area÷1852×one round trip÷(1 hour-8min/60)

2000÷1852×2÷(1-8/60)＝2.5kn

Therefore, in order to reduce the time it takes for the "Tongxu Lun" to construct the H ₂ S concentrated area, the construction speed in this area is controlled at 2.5kn.

Calculation of hydrogen sulfide retention time in the hull:

"Tongxu Lun" is a forecastle-type ship. The rake is at the stern of the ship. The double rakes rake across the seabed, causing H ₂ S gas to escape from the disturbed soil layer. The ship has already left the area before the H ₂ S gas rises from the sea bottom to the surface. Little harm to ships. However, after the H ₂ S gas sucked into the soil of the mud tank through the mud pump is released, all of it will remain on the ship.

According to the analysis of the turbulence field characteristics of the flow around the square bluff body, when the incoming flow hits the three-dimensional block, due to the obstruction of the bluff body, the velocity of the fluid along the direction of motion on its front surface is stagnant to zero, and then turns 90° to accelerate in the vertical direction. Very complex changes occur in the boundary layer on the surface around the square bluff body. Since the wall velocity of the bluff body is zero, when the fluid flows through its 90° corner, viscous force changes and the formation of vortices will occur. The fluid will separate at the front corner of the top of the cube and generate a period at the tail after bypassing the bluff body. The falling Karman vortex street.

The distance between the front end of the Tongxu mud tank and the stern of the ship is 105m, and the position of the ship's position is the engine room. After the H ₂ S is released, the ship continues to move forward, and the H ₂ S above the mud tank will gradually leave the ship, from stopping the pump to The time for H ₂ S to dissipate on the ship is calculated as:

Length of entering piping system ÷ flow rate + diffusion time of mud containing H ₂ S + residence time of H ₂ S in the hull:

60÷6÷60+1+105÷(2.5÷1.852)÷60＝2.5min

That is, after the ship stops pumping, the H ₂ S that has diffused above the ship will basically leave the hull after 2.5 minutes.

Hull replacement fresh air time:

The total cabin area of Tongxu is 30300m ³

The fan flow is 48000m ³ /h

The time required to replace the hull with fresh air = 30300÷48000×60＝38min

That is, after the ship is stopped, the entire ship will be replaced with fresh air after 38 minutes. If it is confirmed that there is no risk, opening the hatch will speed up the air change.

In summary, the safe and environmentally friendly construction method for hydrogen sulfide-containing soil of the present invention ensures safe and efficient construction of hydrogen sulfide-containing soil through reasonable optimization of equipment and construction technology.

Although embodiments of the present invention have been disclosed above, they are not limited to the uses set forth in the specification and description. It can be applied to various fields suitable for the present invention. Additional modifications can be readily implemented by those skilled in the art. Therefore, the invention is not limited to the specific details and illustrations shown and described herein without departing from the general concept as defined by the claims and their equivalent scope.

Claims (10)

1. A safe and environmentally friendly construction method for soil containing hydrogen sulfide, which is characterized by including the following steps: Step 1. Arrange hydrogen sulfide detectors: Arrange multiple hydrogen sulfide detectors and two monitoring hosts in the construction ship. The height of each hydrogen sulfide detector from the ground is 30 to 60cm; Step 2. Optimization of construction equipment: weld the keel around and above the mud tank of the ship, and use a sealing membrane to seal the mud tank. The closed area is 15-20 meters near the bridge side and 10 meters behind the mud tank, with the middle High-power axial flow fans are deployed in the area, and the mud door holes of the mud tank deck are filled with expanding foam agent and blocked with cover plates on the outside; double-sided plow teeth are installed on the wear-resistant block of the ship's rake head; Step 3. Construction: Disperse the hydrogen sulfide gas in the cabin before construction to ensure that the concentration of hydrogen sulfide in the cabin is within the normal range. During the construction process, the fan in the cabin of the ship closes the external circulation, turns on the internal circulation mode, and uses explosion-proof axial flow. Fan ventilation speeds up air flow. 2. The safe and environmentally friendly construction method for hydrogen sulfide-containing soil as claimed in claim 1, characterized in that in step one, the detection alarm of the hydrogen sulfide detector is a secondary alarm mechanism, which specifically includes: When the hydrogen sulfide detector detects that the hydrogen sulfide concentration is greater than 10 ppm and less than 20 ppm, the detector emits a buzzer and is accompanied by a yellow warning light. Construction workers wear hydrogen sulfide respiratory protectors and continue construction, adjusting the position of the ship according to the wind direction so that the driver can The platform, respirator, and engine room control room are all located upwind; When the hydrogen sulfide detector detects that the hydrogen sulfide concentration is greater than 20 ppm, the detector emits a buzzer and is accompanied by a red warning light. Construction workers must wear respirators immediately, stop construction immediately, stay away from the construction area, and perform high-pressure flushing and ventilation of the construction area. . 3. The safe and environmentally friendly construction method for hydrogen sulfide-containing soil as claimed in claim 1, characterized in that step three specifically includes: When there is no wind, increase the speed by 2.5-3 knots to reduce the time when hydrogen sulfide gas accumulates on the ship; When the wind is blowing, construction is normal, and real-time attention is paid to the alarms of multiple hydrogen sulfide detectors arranged in the ship. The fans in the ship's accommodation cabin turn off the external circulation, turn on the internal circulation mode, and keep the explosion-proof axial flow fan on; When there is cross wind, carry out construction in the inner channel area where hydrogen sulfide gas is relatively high; keep the explosion-proof axial flow fan always on; When the wind is favorable, the ship stops construction. 4. The safe and environmentally friendly construction method for hydrogen sulfide-containing soil as claimed in claim 1, characterized in that the quality inspection in step three and step two also includes: tank loading and ballast before construction: mud is injected into the ship tank before construction, and the highest overflow is used. Flow, close the front loading compartment, open the rake head to flush the wear-resistant block and a place inside the rake cavity with high pressure, and raise the rake lip to adjust the angle to separate the rake lip from the mud surface. 5. The safe and environmentally friendly construction method for hydrogen sulfide-containing soil as claimed in claim 1, characterized in that step one also includes: equipping each construction worker with a portable hydrogen sulfide gas detector. When the hydrogen sulfide concentration in the air is greater than 10 ppm , the detector will sound a buzzer alarm. When the concentration of hydrogen sulfide in the air is greater than 15ppm, the detector will sound a buzzer alarm and the red alarm light will flash. 6. The safe and environmentally friendly construction method for hydrogen sulfide-containing soil as claimed in claim 1, characterized in that step one further includes: each ship at the construction site is equipped with two four-in-one gas detectors for monitoring the presence of gases in the air. Hydrogen sulfide gas and other toxic gases. 7. The safe and environmentally friendly construction method for hydrogen sulfide-containing soil as claimed in claim 1, characterized in that step two further includes: equipping each room of the ship's accommodation with a high-power vertical cabinet fan; 3000W high-power explosion-proof axial flow fans are placed in the room; hydrogen sulfide respiratory protectors and emergency respirators that meet the needs are equipped in the accommodation cabin, pump room, engine room control room, and bridge. 8. The safe and environmentally friendly construction method for hydrogen sulfide-containing soil according to claim 1, characterized in that step three further includes: during the process of throwing mud, the ship keeps throwing mud against the wind or across the wind. 9. The safe and environmentally friendly construction method for soil containing hydrogen sulfide as claimed in claim 1, characterized in that in step one, the number of hydrogen sulfide detectors installed is 30, all of which are fixed with steel frames, and there are 2 monitoring hosts. , the specific installation locations are: 21 engine rooms, 9 accommodation cabins and driving stations. 21 hydrogen sulfide detectors in the engine room are connected in parallel to a 32-channel monitoring host. The 32-channel monitoring host is placed in the engine room monitoring room, and the accommodation cabin and 9 hydrogen sulfide detectors installed on the bridge, which are connected in parallel to a 16-channel monitoring host, and the 16-channel monitoring host is placed on the bridge. 10. The safe and environmentally friendly construction method for soil containing hydrogen sulfide according to claim 9, characterized in that the hydrogen sulfide detector is a YT-95H-H ₂ SA fixed hydrogen sulfide alarm.