A design method for chemical cofferdam

Abstract

The present invention provides a chemical cofferdam design method, comprising the following steps: (1) clarifying the specifications of the storage tank to provide basic data for subsequent calculations; (2) establishing the Bernoulli equation to solve the maximum horizontal ejection velocity of the fluid at the leakage point; (3) calculating the horizontal ejection distance of the liquid; (4) calculating whether the cofferdam volume is sufficient to accommodate the leaked liquid. The present invention solves the maximum horizontal ejection velocity of the fluid at the leakage point based on the Bernoulli equation, and then establishes the horizontal ejection distance equation. By judging the distance from the cofferdam to the storage tank, the horizontal ejection distance is calculated. L And cofferdam height h 0 Whether the liquid can be blocked from being sprayed outside the cofferdam area, and at the same time, whether the cofferdam volume is sufficient to contain the leaked liquid, and the cofferdam parameters are designed. The present invention makes up for the low precision of the existing cofferdam design method and realizes the accurate design of cofferdam parameters; at the same time, the method of the present invention is simple, highly operable, and has high engineering application value.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical agent safety protection, and in particular relates to a chemical cofferdam design method. Background Art

[0002] The chemical industry is an indispensable and important part of the national economy, and its safe production has important practical significance for human economic and social development.

[0003] Due to the wide range of chemical industries, complex processes and diverse products, companies usually store a large amount of chemicals. Some chemicals are highly corrosive, flammable and toxic. Once leaked, they will seriously affect the ecological environment and endanger human health.

[0004] In order to ensure the safety of chemical storage tank areas and reduce and prevent the hazards of chemical leakage, national standards require that cofferdams should be set up in tank areas (for flammable liquids, firebreaks should be set up).

[0005] The national standards have made corresponding requirements for the parameter design requirements of cofferdams (firebreaks), such as:

[0006] GB 50351-2014 Firebreak Design Code for Storage Tank Areas 3.2.3 The distance from the tank wall of a vertical oil tank to the inner dike footline of the firebreak should not be less than half the height of the pipe wall; the distance from the pipe wall of a horizontal oil tank to the inner dike footline of the firebreak should not be less than 3m; for oil tanks built on the side of a mountain, the distance from the tank wall to the dike footline on the side facing the mountain should not be less than 3m. 3.2.5 The effective volume in the firebreak of an oil tank group should not be less than the nominal capacity of the largest oil tank in the oil tank group. 3.2.6 The top surface of the firebreak of an oil tank group should be 0.2m higher than the calculated liquid level. The firebreak of a vertical oil tank group should be no less than 1.0m higher than the designed floor level inside the dike, and no more than 3.2m higher than the designed floor level outside the dike or the ground of the fire road. The firebreak of a horizontal oil tank group should be no less than 0.5m higher than the designed floor level inside the dike.

[0007] GB 50160-2008 Fire Protection Design Code for Petrochemical Enterprises 6.2.12 The effective volume within fire dikes and dikes shall comply with the following provisions: (1) The effective volume within the fire dike shall not be less than the volume of the largest tank in the tank group. 6.2.13 The distance from a vertical tank to the inner dike footing line of the fire dike shall not be less than half the tank wall height, and the distance from a horizontal tank to the inner dike footing line of the fire dike shall not be less than 3m. 6.2.17 Fire dikes and dikes shall comply with the following provisions: (2) The height of the fire dike for vertical tanks shall be the calculated height plus 0.2m, but shall not be less than 1.0m (based on the designed floor elevation within the dike), and should not be higher than 2.2m (based on the designed floor elevation within 3m outside the dike); the height of the fire dike for horizontal tanks shall not be less than 0.5m (based on the designed floor elevation within the dike).

[0008] "SH 3011-2011 Petrochemical Process Plant Layout Design Code" 3.0.18 In areas that may be contaminated by flammable liquids, corrosive media or toxic materials during operation or maintenance, cofferdams should be installed. The setting of cofferdams should meet the following requirements: (a) The height of the cofferdam above the ground in the cofferdam area should not be less than 150mm.

[0009] In summary, there is basically no design data on chemical cofferdams in the industry (only SH3011-2011 clearly proposes the setting scenarios and height range of cofferdams). In actual design, the design requirements of fire protection are usually referred to, but the current data only gives the height range of fire protection dikes and the distance range from cofferdams to storage tanks, which makes it difficult to achieve quantitative design. Summary of the invention

[0010] The purpose of the present invention is to provide a chemical cofferdam design method to overcome the above technical problems existing in the prior art.

[0011] To this end, the technical solution provided by the present invention is as follows: A chemical cofferdam design method comprises the following steps:

[0012] Step 1) Determine the specifications, possible leakage points and related parameters of the chemical storage tank;

[0013] Step 2) Calculate the maximum horizontal ejection velocity of the fluid at the possible leakage point;

[0014] Step 3) Calculate the horizontal spray distance of the fluid at the leak point S ;

[0015] Step 4) According to the size of the site around the chemical storage tank and the horizontal spraying distance S Determine the distance from the cofferdam to the tank L , when the site size is smaller than the horizontal spray distance S When , when the site size is not less than the horizontal spray distance S When ;

[0016] Then according to the horizontal spray distance of the fluid at the leakage point S , Distance from cofferdam to storage tank L The height of the cofferdam is determined by the volume of the leaked fluid. h 0 ;

[0017] Step 5) The cofferdam height determined in step 4) h 0 Add 0.2m to get h 0 ’ ,according to h 0’ Distance from cofferdam to storage tank L Carry out cofferdam design.

[0018] The specifications of the chemical storage tanks in step 1) include the tank diameter D and liquid level H .

[0019] The possible leakage point mentioned in step 1) is the pipe connection or flange interface. The relevant parameters of the leakage point include the leakage point height h and leak point diameter d .

[0020] The calculation method of step 2) is as follows:

[0021] According to Bernoulli's equation Available

[0022] in, P 0 Height of chemical storage tank H The static pressure of the liquid, P 1 is the height of the chemical storage tank h The static pressure of the liquid at the leak point, V 0 Height of chemical storage tank H The flow rate of the liquid, V 1 Height of chemical storage tank h The flow rate of the liquid in the chemical storage tank, P 0 = P 1, V 0 and V 1 The comparison can be approximated to 0.

[0023] Horizontal spray distance of dew point fluid in step 3) ,in, t is the time it takes for the fluid to fall from the leak point to the reference surface, .

[0024] Step 4) Height of cofferdam h 0 The determination method is: the distance from the cofferdam to the storage tank L Not less than the horizontal spray distance of the fluid at the leakage point S When the volume through the cofferdam is not less than the amount of fluid leaking, the height of the cofferdam is obtained. h 0 .

[0025] Step 4) Height of cofferdam h 0The determination method is: the distance from the cofferdam to the storage tank L Smaller than the horizontal spray distance of the fluid at the leak point S When the volume of the cofferdam is not less than the amount of leaked fluid, the cofferdam height h 0 Not less than the height of the fluid injection point on the cofferdam h 1 .

[0026] The volume of the cofferdam is not less than the amount of fluid leaking as expressed by:

[0027]

[0028] After sorting, the cofferdam height is obtained h 0 The following conditions should be met:

[0029]

[0030] Where: D is the tank diameter, H is the liquid level, L is the distance from the cofferdam to the storage tank, h is the height of the leak point.

[0031] The cofferdam height h 0 Not less than the height of the fluid injection point on the cofferdam , i.e. the height of the cofferdam , and at the same time satisfy the conditions , h 0 Take the larger value.

[0032] The beneficial effects of the present invention are:

[0033] The chemical cofferdam design method provided by the present invention solves the maximum horizontal injection velocity of the fluid at the leakage point based on the Bernoulli equation, and then establishes the horizontal injection distance equation. L And cofferdam height h 0 Whether it is possible to prevent the liquid from spraying outside the cofferdam area, at the same time, calculate whether the cofferdam volume is sufficient to accommodate the leaked liquid and design the cofferdam parameters.

[0034] The invention makes up for the deficiency of low precision of the existing cofferdam design method and realizes accurate design of cofferdam parameters; at the same time, the method of the invention is simple, highly operable and has high engineering application value.

[0035] The following will provide further detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The distance from the cofferdam to the storage tank of the present invention is Design schematics;

[0037] Figure 2 The distance from the cofferdam to the storage tank of the present invention is Design schematic. DETAILED DESCRIPTION

[0038] The following describes the implementation of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0039] The exemplary embodiments of the present invention are now described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention.

[0040] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0041] Embodiment 1:

[0042] This embodiment provides a chemical cofferdam design method, comprising the following steps:

[0043] Step 1) Determine the specifications, possible leakage points and related parameters of the chemical storage tank;

[0044] Step 2) Calculate the maximum horizontal ejection velocity of the fluid at the possible leakage point;

[0045] Step 3) Calculate the horizontal spray distance of the fluid at the leak point S ;

[0046] Step 4) According to the size of the site around the chemical storage tank and the horizontal spraying distance S Determine the distance from the cofferdam to the tank L , when the site size is smaller than the horizontal spray distance S When , when the site size is not less than the horizontal spray distance S When ;

[0047] Then according to the horizontal spray distance of the fluid at the leakage point S , Distance from cofferdam to storage tankL The height of the cofferdam is determined by the volume of the leaked fluid. h 0 ;

[0048] Step 5) The cofferdam height determined in step 4) h 0 Add 0.2m to get h 0 ’ ,according to h 0 ’ Distance from cofferdam to storage tank L Carry out cofferdam design.

[0049] The chemical cofferdam design method provided by the present invention solves the maximum horizontal injection velocity of the fluid at the leakage point, and then establishes the horizontal injection distance equation. L And cofferdam height h 0 Whether it is possible to prevent the liquid from spraying outside the cofferdam area, at the same time, calculate whether the cofferdam volume is sufficient to accommodate the leaked liquid and design the cofferdam parameters.

[0050] The invention makes up for the deficiency of low precision of the existing cofferdam design method and realizes accurate design of cofferdam parameters; at the same time, the method of the invention is simple, highly operable and has high engineering application value.

[0051] Embodiment 2:

[0052] Based on Example 1, this example provides a chemical cofferdam design method. In step 1), the specification parameters of the chemical storage tank include the tank diameter. D and liquid level H Among them, the possible leakage point is the pipe connection or flange interface. The relevant parameters of the leakage point include the leakage point height h and leak point diameter d .

[0053] By establishing the Bernoulli equation , solve the maximum horizontal ejection velocity of the fluid at the leak point. For chemical storage tanks, the atmospheric pressure is evenly distributed inside, so when the Bernoulli equation is formulated, the left and right sides of the equation are P 0 = P 1. In this way, the atmospheric pressure can be directly regarded as zero and only the water pressure needs to be considered. When the fluid leaks, the diameter of the leak point at the same flow rate d Much smaller than the tank diameter D ,therefore, V 0 Approximately 0, at which point the maximum horizontal ejection speed V The expression of 1 is: .

[0054] in, P 0 Height of chemical storage tank H The static pressure of the liquid, P 1 is the height of the chemical storage tank h The static pressure of the liquid at the leak point.

[0055] Horizontal spray distance of fluid ,in, t is the time it takes for the fluid to fall from the leak point to the reference surface, .

[0056] In order to ensure that the leaked liquid is not enough to spray out of the cofferdam area, the distance from the cofferdam to the tank L Can be designed as: ,like Figure 1 shown.

[0057] In order to ensure that the cofferdam volume is sufficient to contain the leaked liquid, the volume of the cofferdam should not be less than the amount of leaked fluid, that is:

[0058]

[0059] After sorting, the cofferdam height is obtained h 0 The following conditions should be met:

[0060]

[0061] Where: D is the tank diameter, H is the liquid level, L is the distance from the cofferdam to the storage tank, h is the height of the leak point.

[0062] Some chemical storage tanks are located in restricted areas. ,like Figure 2 As shown, the cofferdam height h 0 Not less than the height of the fluid injection point on the cofferdam , then the design of the cofferdam height should meet two conditions: (a) the cofferdam height h 0Conditions met , after sorting, we get (b) the weir has sufficient capacity to contain the leaked liquid, h 0 should meet the following conditions: After calculation h 0 takes the larger value.

[0063] Embodiment 3:

[0064] Based on Example 2, this example provides a chemical cofferdam design method, comprising the following steps:

[0065] (1) Clarify tank specifications: Tank diameter D =1.50m, liquid level H =2.26m, the distance between the possible leakage point and the reference plane h =0.40m, leakage point diameter d =0.005m;

[0066] (2) According to the formula Solve for the maximum horizontal ejection velocity of the fluid at the leakage point and calculate V1=6.04m / s.

[0067] (3) According to the formula Solve for the horizontal spray distance of the liquid and calculate that S=1.73m.

[0068] (4) There are no obstacles around the tank area, and the distance from the cofferdam to the storage tank is designed to be L = 1.73m.

[0069] (5) According to the formula Solving for the height of the cofferdam, we calculated that h0=0.19m.

[0070] (6) Based on the existing data, the cofferdam height is increased by 0.2m based on the calculated value.

[0071] (7) The cofferdam parameters designed according to the above steps are: distance from the cofferdam to the storage tank L = 1.73m; cofferdam height 0.39m.

[0072] Embodiment 4:

[0073] Based on Example 2, this example provides a chemical cofferdam design method, comprising the following steps:

[0074] (1) Tank parameters: Tank diameter D =2.00m, liquid level H =3.82m, the distance between the possible leakage point and the reference plane h =1.91m, leakage point diameter d =0.006m.

[0075] (2) According to the formula Solve for the maximum horizontal ejection velocity of the fluid at the leakage point and calculate that V1=6.12m / s.

[0076] (3) According to the formula Solve for the horizontal spray distance of the liquid and calculate S =3.82m.

[0077] (4) The conditions around the tank area are limited, resulting in L =2.70m, that is: .

[0078] (5) According to the formula Calculate the cofferdam height and calculate h 0 =0.96m; according to the formula Solve for the cofferdam height and calculate h 0 =0.15m. After comparison, take the larger value to determine h 0 =0.96m.

[0079] (6) Based on the existing data, the cofferdam height h 0 Add 0.2m to the calculated value.

[0080] (7) The cofferdam parameters designed according to the above steps are: distance from the cofferdam to the storage tank L =2.70m; cofferdam height 1.16m.

[0081] Embodiment 5:

[0082] Based on Example 2, this example provides a chemical cofferdam design method, comprising the following steps:

[0083] (1) Tank parameters: Tank diameter D =3.00m, liquid level H =4.24m, the distance between the possible leakage point and the reference plane h =0.50m, leakage point diameter d =0.008m.

[0084] (2) According to the formula Solve for the maximum horizontal ejection velocity of the fluid at the leakage point and calculate that V1=8.57m / s.

[0085] (3) According to the formula Solving for the horizontal spray distance of the liquid, we calculated that S=2.74m.

[0086] (4) The surrounding conditions of the tank area are limited, resulting in L =1.80m, that is: .

[0087] (5) According to the formula Calculate the cofferdam height, calculated h 0 =0.28m; according to the formula Solve for the cofferdam height and calculate h0 =0.98m. After comparison, take the larger value, and we get h 0 =0.98m.

[0088] (6) Based on the existing data, the height of the cofferdam h 0 Add 0.2m to the calculated value.

[0089] (7) The cofferdam parameters designed according to the above steps are: distance from the cofferdam to the storage tank L =1.80m; cofferdam height 1.18m.

[0090] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A chemical cofferdam design method, characterized by: The following steps are involved: Step 1) Determine the specifications, possible leakage points and related parameters of the chemical storage tank; Step 2) Calculate the maximum horizontal ejection velocity of the fluid at the possible leakage point; The calculation method is as follows: According to Bernoulli's equation Available in, P 0 is the height of the chemical storage tank H The static pressure of the liquid, P 1 is the height of the chemical storage tank h The static pressure of the liquid at the leak point, V 0 is the height of the chemical storage tank H The flow rate of the liquid, V 1 is the height of the chemical storage tank h The flow rate of the liquid in the chemical storage tank, P 0= P 1, V 0 and V 1 can be approximated to 0; Step 3) Calculate the horizontal spray distance of the fluid at the leak point S ; Step 4) According to the size of the site around the chemical storage tank and the horizontal spraying distance S Determine the distance from the cofferdam to the tank L , when the site size is smaller than the horizontal spray distance S When , when the site size is not less than the horizontal spray distance S When ; Then according to the horizontal spray distance of the fluid at the leakage point S , Distance from cofferdam to storage tank L The height of the cofferdam is determined by the volume of the leaked fluid. h 0; Cofferdam height h 0 Determination method: the distance from the cofferdam to the tank L Smaller than the horizontal spray distance of the fluid at the leak point S When the volume of the cofferdam is not less than the amount of leaked fluid, the cofferdam height h 0 is not less than the height of the fluid injection point on the cofferdam h 1; The volume of the cofferdam is not less than the amount of fluid leaking as expressed by: After sorting, the cofferdam height is obtained h 0 should meet the following conditions: Where: D is the tank diameter, H is the liquid level, L is the distance from the cofferdam to the storage tank, h is the height of the leakage point; The cofferdam height h 0 is not less than the height of the fluid injection point on the cofferdam h 1= , i.e. the height of the cofferdam , and at the same time satisfy the conditions , h 0 takes the larger value; Step 5) The cofferdam height determined in step 4) h Add 0.2m to 0 to get h 0 ’ ,according to h 0 ’ Distance from cofferdam to storage tank L Carry out cofferdam design.

2. A chemical cofferdam design method according to claim 1, characterized in that: The specifications of the chemical storage tanks in step 1) include the tank diameter D and liquid level H .

3. A chemical cofferdam design method according to claim 1, characterized in that: The possible leakage point mentioned in step 1) is the pipe connection or flange interface. The relevant parameters of the leakage point include the leakage point height h and the leak point diameter d .

4. A chemical cofferdam design method according to claim 1, characterized in that: Horizontal spray distance of dew point fluid in step 3) ,in, t is the time it takes for the fluid to fall from the leak point to the reference surface, .

5. A chemical cofferdam design method according to claim 1, characterized in that: Step 4) Height of cofferdam h 0 Determination method: the distance from the cofferdam to the tank L Not less than the horizontal spray distance of the fluid at the leakage point S When the volume through the cofferdam is not less than the amount of fluid leaking, the height of the cofferdam is obtained. h 0.

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