5.2.2.1 Outfit condition of oil spill dispersant

Our company is provided with 15 tons of general gender oil spill and 5 tons of biodegradation oil dispersant; the detail is shown in table 5-9.

No.	Name	Model	QTY	Manufacturer name	Main technical parameters
1	Oil dispersant	Conventional type	15 tons	Qingdao Huahai	Appearance: lucidity, transparent, no lamination PH：7.1 Burning point＞70℃ Viscocity: 50mm2/s Rate of biodegradation＞30%
2	Biodegradation oil dispersant	Micro-P	5 tons	Qingdao Huahai

 

5.2.2.2 Influencing factor and application ratio of dispersion efficiency

The dispersant is not suitable for high viscosity oil.  The lower the oil viscosity is, the higher the dispersal efficiency. If the oil viscosity is very large, the dispersant will be fault.  Generally, dispersal efficiency of the dispersant is higher when kinetic viscosity of the oil is lower than 2000 cp.  Once the oil viscosity exceeds 2000 cp, the dispersal efficiency will be decreased.  When the oil viscosity reaches 5000 ~ 10000, the dispersant will be out of action.

Pour point of the oil will also influence the dispersal efficiency.  When the pour point is greater than or close to the ambient temperature, the dispersal efficiency is lower.  Generally when the pour point is 5℃ lower than the ambient temperature, the dispersant can be used.

The oil spill will be evaporated and emulsified in course of time to increase the viscosity and form the "Water in oil" emulsification substances, so the dispersant will lost its dispersion effect.  Even for the oil with lower viscosity and pour point, if the dispersant is used after two days of the spillage, the dispersal efficiency will be declined or the oil is even hard to disperse.

Most dispersants have better dispersal efficiency in seawater than in fresh water, and the higher the water temperature, the better the dispersion effect because the oil viscosity will be decreased when the temperature increases.

Owing to different composition of the dispersant and different solvents used, the dispersing power to the oil spill will be different. For example, the conventional dispersant is more suitable for high-viscosity oil. This is because the solvent of conventional dispersant is hydrocarbon compound with good solubility to oil, so that the dispersant is easy to infiltrate into the oil layer;

Stirring can intensively mix the dispersant and the oil in favor of the solvent of the dispersant entering into the oil layer.  When the oceanic condition is poor, it will enhance the dispersal effect.  Provided the dispersant is sprayed in plat surface, the manual stirring should be taken.

Application ratio of dispersant/oil is between 1/100 ~ 1/10 depending on oil type and oil film thickness. For oil spill of the same scale, application ratio of dispersant is larger for this large in specific gravity, high in viscosity, high in pour point and thick in oil layer; For the oil spill of same scale and type, the thicker the oil film, the more difficult the surface-active material in the dispersant entering into the oil layer, so the application ratio of dispersant is larger. Therefore floating oil film on the sea surface will be treated with the dispersant after the thick oil layer is recovered. In this way, the surface-active material is easy to enter into the oil layer so as to keep the dispersant at normal application ratio.

Conventional dispersant is strong in dissolving the oil spill and good in treating the high-viscosity oil and the weathered oil. Direct spraying should be made as well as stirring after the spraying.  This type of dispersant cannot be diluted by water before application; the application ratio (dispersant/oil) prefers 1:1 to 1:3.

5.2.2.3 Application and management of dispersant

Using dispersant to treat sea surface oil spill is to change the presence behavior of the oil in seawater but not change the chemical property of the oil spill; misapplication will cause the secondary pollution to the water substance. Application of the oil spill dispersant should meet the requirement of law, code and applicaiton criterias.

(1) Article 70 (3) of Marine Environment Protection Law of the People's Republic of China stipulates that, when chemical dispersant is used in vessel, wharf and facility, its trademark and composition shall be reported to Competent Authority for approval.

(2) Article 1 of regulations of the people's republic of china on the prevention of vessel- induced sea pollution stipulates that, After oil pollution accidents or discharges of oil in violation of the regulations have occurred, the vessels involved may not use oil-eliminating chemicals at their own discretion.  If oil-eliminating chemicals have to be used, applications by telephone or in written form shall be made to the harbor superintendencies in advance, with the brand names, amounts and the areas for the application of the oil-eliminating agents stated, and they may be used only with approval.

(3) GB18188.2-2000 "Oil spill dispersant --Application criteria" has stipulates the application principle and restriction principle of the oil spill dispersant.

The oil spill dispersant can be used to treat the surface floating oil or the accident oil spill on the following conditions:

The surface floating oil or the accident oil spill might move towards coast, aquiculture and other waters sensitive to the oil spill, thus will threat the commerce, environment or comfortability and cannot self-dissipate via natural evaporation or effect of wind, wave and current nor be contained or recovered for treatment by physical methods before it reaches the above sensitive areas;

For oil spill hard to be treated with physical mechanical method, total damage caused by using the oil spill dispersant to prompt its dispersing to the water body is smaller than leaving the oil on the surface without any treatment;

If the oil spill occurs in non harbor waters of the water depth greater than 20m, the dispersant can be used firstly and then the competent department be reported;

Type of surface floating or accident oil spill and water temperature are suitable for chemistry dispersing (generally the water temperature should be 5℃ above higher than the pour point of the oil to be treated); ambient conditions such weather and oceanic condition are suitable for diffusion of dispersal oil;

On irresistible conditions such as oil fire or explosion that endanger life or installation security having occurred or is likely to occur.

The oil spill dispersant is not suitable for the following conditions, but those irresistible conditions that endanger life or installation security are exclusive.

The oil spill is the volatile clean oil such as gasoline and kerosene, or thin oil film appearing rainbow feature;

The oil spill is that high in wax content and pour point and hard to chemically disperse;

The oil spill does not show the fluid state under environment water temperature or will form the thick fragment of the water in oil emulsification substance with clear edge after several days of weathering.

The oil spill occurs in closed shallow water or flat water;

The oil spill occurs in fresh water sources or areas significantly influencing the fishery resources.

5.2.2.4 Application and restriction of dispersant

Using dispersant to treat the oil spill on sea surface possesses many advantages. During the application process of dispersant, region allowed to use the dispersant, the consumption and other matters and application ratio.

Requirement to application of dispersant in different water is quite different. Waters using the dispersant are classified into three conditions according to water depth, exchange capacity of water substances and marine lives, as is shown in table 5-10.

a) The dispersant is allowed.  When the dispersed oil mixed enters into the water body evenly and occurs large-scale mixing dilution to reduce the oil concentration to quite low level, it will not cause any influence to any creature in that water. This water has not restriction to the application of dispersant; the application amount is determined in term of the oil mass.  Open ocean of the water length more than 20 m belongs to this type.

b) The dispersant is allowed but the usage time or the consumption is restricted.  For example, for closed bay and harbor, if this type of water possesses strong water body exchange capacity of more than 90% in one day, the dispersant is allowed.  During the application, season, water depth and tide feature should also be taken into account, e.g. the dispersant will be restricted or limited during the breeding season of sensitive creatures.

c) Generally the dispersant is not allowed at locations such as sensitive coastline.  However if the influence cycle of the oil is long, the dispersant is also taken into account.

For water of the depth less than 20m and on condition of the oceanic zoology permits, allowable dosage of the dispersant should be determined according to the water depth.  The allowable dosage should be calculated per the mixture strength of uniformly mixed oil dispersant at each water layer (from surface layer to bottom layer). The consumption is shown in table 5-11.

 

For certain specific bodies of water, how to judge if the dispersant can be used? If allowed, what's the consumption? The determinatin can be made according to the suggestion in table 5-10 and practical situation of that water. If allows, the suggestion in table 5-11 should be referred to determine the consumptin according to the actual water depth and the condition of marine lives.

5.2.2.5 Spraying of dispersant

The dispersant can be sprayed via the vessel or manually.  Spraying method depends mainly on type of dispersant, position and area of oil spill as well as availability of vessel spraying the dispersant. Our company provide 4 sets of vessel carried spraying devices and 8 sets of portable spraying devices. Detailed model and performance are shown in table 5-12.

No.	Name	Model	QTY	Manufacturer name	Main technical parameters
1	Spraying device	PS140	4	Qingdao Huahai	Mostly used to treat and disperse various water area oil spill Max. sprinkling range is 12m Sprinkling speed is 8.4 t/h
2	Portable spraying device	PS40	8	Qingdao Huahai	Max. flow is 2.4 t/h

 

3 oil spill emergency treatment marine stores of our company have the function of spraying the oil spill dispersant can capable of conducting the vessel spraying indepandantly.

The dedicated vessel spraying device is composed of corrosion resistant dispersant storage tank, dispersant pump/ water pump, measuring meters, nozzle with jet and hoses. During the spraying operation, the vessel can make the stirring via the marine propeller to fully mix the dispersant, oil an seawater.

Advantages of vessel dedicated spraying device:

Oil film having been treated via the propeller or other stirring device will mix the dispersant and the oil to enhance the dispersing effect.

8 10 m spraying arm can realize large area spraying, quick in speed and high in efficiency.

It can be used to spray both conventional dispersant and concentration dispersant.

The vessel speed should be kept between 4 and 10 n-mith in order to ensure the best stirring action.

If the spraying arm is mounted on the stem, problem caused by the bow wave will be solved and the vessel can carry out the spraying operation at high cruise speed.  This is because it needs less stirring and is high in flexibility and oil treatment capacity.  In addition, the bow wave also takes the effect of stirring.  Owing that for most vessels, the freeboard is higher than the bow, the spraying arm can be extended and the spraying width can be increased thus to improve the potential treatment capacity.

Size of spraying rate depends on type of oil spill, oil film thickness and flow state.  Two methods can be adopted to control the spraying rate, i.e. changing the pump speed, or keeping the pump speed while changing the cruise speed.  Discharging rate of the pump is calculated as follow:

Discharging rate of pump (L/min)= 0.003 × spraying rate (L/ha) × cruise speed (knots) × spraying width (m)

Generally the spraying is started from thicker oil film and external margin of the oil film instead of the middle or thinner places.

If the oil film is at offshore area, the recommended operation mode is parallel to the coastline as possible.

The vessel should operate down the wind to prevent the dispersant from being blown to the deck.

If the oil band is narrow and vertical to the wind direction, the vessel should be at the upwind of the oil film and make the spraying along the oil band.  Whereas the dispersant spraying will appear lateral deviation by the effect of the wind, the vessel can only use the lee-side single arm to spray.

Spraying of dispersant should be carried out in shortest periods after the oil spill accident occurs as possible. Because weathering of the oil will cause the "emulsification" and reduce the dispersal effect if the time is too long.

Application of dispersant at coastline depends on physical circumstances without general approaches. However for the oil spill on the ocean beach, the dispersant should not be sprayed directly but sprayed in short periods of time (30 min) after the seawater is washed away.  For coastline with spring tide, the spraying should be made before the rising tide to prevent the oil from being brought into the sublayer.  Rinsing of rock, revetment and other artificial structures, the manual brushing is usually adopted and then the high pressure water is used.

It should be noticed that, when the dispersant is used at coastline, it is forbidden at sensitive areas such as industrial water catchment and salt field.

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