JP2736669B2 - Method of estimating the location and amount of gas leakage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for estimating a location where gas is leaking. The method of the present invention is useful for danger prevention, particularly in industrial plants handling flammable or toxic gases. Here, "gas" is meant to include a volatile liquid vapor in addition to a gaseous substance in a normal state, and in the following description, both terms are represented by this term. In addition, "leakage" refers to the case where gas leaks from a part where gas should not go to the outside, such as the pipe flange, due to deterioration or damage of the material, and the case where the gas is released to the atmosphere such as a stack. This includes both cases where discharge occurs from the outlet due to a malfunction or a sudden cause, and both cases.

[Prior art]

For example, in various plants of the petrochemical industry, various combustible and toxic gases flow through piping and various facilities, and there is always a risk of leakage. Therefore, when there is a leak, it is necessary to quickly find the place and take safety measures to prevent a secondary disaster. For the purpose of knowing gas leakage, a gas detector is installed at some suitable locations in a plant. As a technique for estimating the location of a gas leak in a plant using a gas detector, a method has been proposed on the premise that gas detectors at at least three points detect gas (Japanese Patent Application Laid-Open No. Sho 61-1555932). issue). This method identifies the three points with the highest gas concentration in a virtually windless situation, and identifies the virtual leak source between the highest gas concentration point and the other two points by using these gas concentration points. A gas leak source is estimated from the virtual leak source based on the ratio of the distance between the virtual leak source and the virtual leak source. In windy conditions, three points with the highest gas concentration are also identified, the distance between the highest gas concentration point and the next highest concentration is determined, and the ratio of the gas concentration to the distance is used to determine the gas leakage. Estimate the source. However, in an actual industrial plant, the distance between the installed gas detectors is relatively long, and the gas detectors are only scattered in a large site. That is, if the facility that handles dangerous gas is indoors, the number of installations is calculated based on the number divided by 10 m around the perimeter and the outdoor area divided by 20 m, This is because they are often arranged so as to surround the equipment of the equipment. Under such conditions, gas leaks to a considerable extent and a considerable amount of time will elapse before gas is detected at three or more different points. Therefore, the above method quickly finds the location of gas leak,
In terms of safety measures, they are unsatisfactory and cannot achieve the intention of minimizing the effects of leakage, including the prevention of secondary disasters. The present inventors have established a method of estimating the location of a dangerous gas leak in an industrial plant when at least one gas detector detects a gas, and have established a method for quickly obtaining a result. (Japanese Patent Application No. 63-1985)
No. 49). As a result of the subsequent research, the present inventors have found a method of specifying a leak location more accurately without substantially increasing the required time by pursuing a gas leak location when two gas detectors detect gas. We have also found a method for estimating the amount of gas leakage using a similar technique.

[Problems to be solved by the invention]

An object of the present invention is to provide a method for quickly estimating the location and amount of a dangerous gas leak in an industrial plant based on the above knowledge, thereby making it possible to quickly take safety measures. An object of the present invention is to provide a method for estimating a quantity.

[Means for Solving the Problems]

A method for estimating a gas leak location according to the present invention is a method for estimating a gas leak location in a plant, and comprises the following steps. 1) When the two gas detectors D ₁ and D ₂ detect the gas, the diffusion angle α of the gas is calculated based on the data on the wind direction and the wind speed at that time, and the average swing angle β of the wind direction is calculated. 2) From the gas detectors D ₁ and D ₂ , the above angle (α +
β) draws two straight lines, and the area between those two straight lines
To define the A ₁ and A _2, 3) based on the status of the change in weather conditions in the past within a predetermined period to select the parameter a of the formula that, logC = a · logX + b 4) gas detectors D ₁ and D Using the values of the gas concentrations C ₁ and C ₂ detected in ₂ , the distance from the leak location to the gas detector D ₁ is X, and the value of the distance ΔX in the average wind direction between the gas detectors D ₁ and D ₂ also _{used, logC 1 = a · logX +} b logC 2 = a · log (X + ΔX) + b relation to calculate the X from, 5) to windward along the average wind direction from a gas detector D ₁ X
In that back by the length of, make a vertical line to a straight line of the average wind direction, the vertical line is within the area A ₁ and A ₂ line
To draw the W _1, 6) is subjected to the above 1) to 5) after a time lapse, to draw the new line segment W _2, and 7) have an intersection near the line W ₁ and W _2, and gas leakage location Estimate. Further, a method for estimating a gas leakage amount according to the present invention is a method for estimating a gas leakage amount in a plant, and comprises the following steps. 1) Calculate the average swing angle β of the wind direction and obtain the average wind direction according to step 1) of the above-described method of estimating the location of gas leakage. 2) Based on the situation of changes in weather conditions within a certain period of time in the past. that Te selecting parameters a following equation, logC = a · logX + b 3) using the value of the gas detector D ₁ and the gas is detected in D ₂ concentrations C ₁ and C _2, gas leakage location detector D ₁ the distance to the X, and b from the average also using the value of the distance [Delta] X in the wind _{direction, logC 1 = a · logX +} b logC 2 = a · log (X + ΔX) + b of the relationship between the gas detectors D ₁ and D ₂ And 4) knowing the wind speed u when the gas is detected by the wind direction anemometer, and based on the value of the parameter b, the value of (gas amount Q / wind speed u) and the parameter b The leak gas amount Q from the relationship A.

[Operation]

Several theoretical equations expressing gas diffusion have been submitted, but the following "Sakagami equation" is well known in Japan. C (x, y, z): gas coordinates at an arbitrary position (x, y, z) where coordinates of a leak source are (0, 0, H) Q: leak gas amount u: wind speed q _A , φ _A , q _B , φ _B : _A parameter determined by the height of the leak source from the surface and the atmospheric stability J ₀ (iξ): A first-order Bessel function of order 0 with ξ as a variable, and i is an imaginary unit. Therefore, when the amount of leaked gas is constant, the leak source height is H = 0, and the atmospheric stability is calculated for three cases of “unstable”, “neutral”, and “stable”, the simulation will be described later. As shown in FIG. 1, the gas concentration C at the point of the distance X from the leak location becomes substantially a straight line when conceptually shown in a log-log graph.
Therefore, it can be expressed by the following equation. logC = a * logX + b This line changes its position depending on the amount of leaked gas, but is parallel in each atmospheric stability. That is, the parameter a is a value determined by the atmospheric stability, and the parameter b is a value determined by the atmospheric stability and the amount of leaked gas. Estimation of gas leakage location is based on the following grounds. That is, first, the diffusion angle α of the gas is determined based on the data of the wind direction and the wind speed at the time when the gas detector detects the gas. In a state where the wind direction and the wind speed are constant and the gas leakage amount is also constant, the diffusion of the gas is represented by spindle-type isoconcentration lines (C ₁ , C ₂ , C ₃ ...) As shown in FIG. If a gas concentration is focused on a predetermined concentration C _C , for example, a concentration level considered to be dangerous (for example, C _{2 in the} figure), and a tangent is drawn from the gas leak location P to the isoconcentration curve, an angle α sandwiched therebetween is obtained. Is the gas diffusion angle. On the other hand, the change in the wind direction within a certain period of time from the time when the gas is detected is determined by the average swing angle β of the wind direction.
In this case, the angle at which gas may diffuse is (α + β) with respect to the average wind direction as shown in FIG. Is the direction of diffusion. This means that the area where the gas leaks detected by the gas detectors D ₁ and D ₂ may exist, as shown in FIG. 5, on the windward side of each, as shown in FIG. This is a region sandwiched between two straight lines forming an angle (α + β). Area for the gas detectors D ₁
It is A _1, a region A ₂ for the D _2. D ₁ and since both D ₂ is the detected gas, the leak location must be in a region overlapping the A ₁ and A _2. When X the average distance wind direction and gas leakage location and gas detectors D ₁ in FIG. 5, the distance between the leakage location and gas detectors D ₂ is a X + [Delta] X. As already described, if the amount of leaked gas is constant, the relationship between the distance from the leak location and the gas concentration can be represented by a straight line in a log-log graph, and the relationship in FIG. 5 is logC ₁ = a · logX + b logC ₂ = a · log (X + ΔX) + b. The value of ΔX is known from the positional relationship between the gas detectors D ₁ and D ₂ , and the parameter a is calculated in advance by performing a simulation and can be determined according to the atmospheric stability at the time of detection. The values of X and the parameter b are obtained from the above relationship between the gas concentrations C ₁ and C ₂ . Then, the gas leakage location is taken to the gas detectors D ₁ and D _2, to the extent that the gas leakage location upwind described above may exist, with respect to the straight line of the average wind direction through the gas detector D _1, from D ₁ When catching a vertical line in the X distance, there should be a gas leak location on a line segment W ₁ that is within the above range. After a certain period of time, the same operation is performed using the gas concentration detected by each of the gas detectors D ₁ and D ₂ , the average value of the wind direction and the wind speed up to that point, as shown in FIG. Draw a _second line segment W2. Then, the gas leakage location, should be present near the intersection of the first line segment W ₁ and the second line segment W _2. On the other hand, the estimation of gas leakage is based on the following grounds. That is, as is apparent from FIG. 1 referred to above, the parameter b increases as the leaked gas amount Q increases. The relationship between b and the value (Q / u) obtained by dividing the leaked gas amount Q by the wind speed u takes the form of the curve shown in FIG. 2 as in the simulation example described later. Using this relationship, a simulation is performed in advance to determine the parameter a, and the parameter b
A graph or an expression representing the relationship between and (gas leakage amount Q / wind speed u) is prepared. If the gas leak is detected, the parameter a is selected according to the atmospheric stability, and the parameter b is calculated by the above equation. (Q / u) is obtained from the expressed gram or equation, and the wind speed u is known as a measured value, so that the gas leakage amount Q can be estimated.

【Example】

In the "expression Sakagami" supra, leakage gas quantity ^{Q = 0.00208~16.7 [Nm 3 / sec} ] Wind u = 1.0 [m / sec] atmospheric stability: Unstable, neutral, stable leakage source height H = 0.0 [ m] Gas detection position x = 1 to 1000 [m] y = 0 [m] z = 0 [m] The relationship between the distance from the leak location and the gas concentration is calculated as shown in FIGS. 7 to 9. The graph shown in the figure was obtained. FIG. 7 shows the case where the state of the atmosphere is "unstable", FIG. 8 shows the case of "neutral", and FIG. 9 shows the case of "stable". The parameters a and b of the formula logC = a.logX + b were calculated by the method of least squares. 7 to 9
The following table shows the corresponding values when the graph is shown in the figure. It is clear from the table that the parameter a is constant for each atmospheric stability, and only the parameter b increases as the amount of leaked gas increases. In addition, a graph showing the relationship between the parameter b and the (gas leakage amount Q / wind speed u) is as shown in FIGS. 10A and 10B. FIG. 10B shows the left end of the graph of A, that is, Q / u = 0 to 0.1.
3 is a graph showing an enlarged range. It goes without saying that the graph of FIG. 10 has a relationship in which the vertical axis and the horizontal axis are interchanged with the conceptual graph of FIG. In conducting such a simulation and proceeding to the location of gas leaks or estimating the amount of leaked gas, further consider factors specific to the plant, such as nearby terrain and seasonal wind and wind speed trends. Therefore, it is preferable to correct the parameters a and b from various viewpoints in order to make an estimation closer to actuality.

【The invention's effect】

ADVANTAGE OF THE INVENTION According to this invention, when a dangerous gas leaks in a plant, a gas leak location can be quickly determined from the detection data of a gas detector and the data of the wind direction and wind speed, and the amount of leaked gas can be estimated. If the location of the leak is specified and the amount of leaked gas can be estimated, the diffusion area of the leaked gas can be predicted based on that, and the rate of expansion of the dangerous gas concentration area can be predicted, and a certain point is left before the point becomes dangerous. It is also possible to calculate the elapsed time. For the prediction of the diffusion region of the leaked gas, a method separately proposed by the present inventors is useful. Such predictions make it easier to take appropriate safety measures. Therefore, the present invention contributes to improving the safety of various industrial plants and is useful for preventing damage to the surroundings.

[Brief description of the drawings]

FIGS. 1 to 6 are for explaining the principle of the method for estimating a gas leakage location according to the present invention, and FIG. 1 shows the relationship between the distance from the gas leakage location and the gas concentration. FIG. 2 is a graph conceptually shown, and FIG. 2 shows a parameter b of an equation representing the graph of FIG.
FIG. 3 is a graph also conceptually showing the relationship between and the (gas leakage amount Q / wind speed u). FIG. 3 is a diagram showing a gas isoconcentration curve and a gas diffusion angle. FIG. 5 is a view showing a direction in which gas may be diffused. FIG. 5 shows, from the viewpoint of a gas detector, a region where a gas leakage site may exist, and in particular, a region where a leakage site should exist thereabove. FIG. 6 shows that the intersection of the line segment in FIG. 5 is determined to be a gas leak location. FIGS. 7, 8, and 9 are actual examples of graphs corresponding to FIG. 1, which are created by simulation in the embodiment of the present invention. FIGS. 10A and 10B are actual examples of graphs corresponding to FIG. 2 and also created by simulation in the embodiment of the present invention, where A is a range where the value of (gas amount Q / wind speed u) is large, and B is Is in a small range. P ...... gas leakage location _{C 1, C 2, C 3} ...... gas such as concentration curves D _1, D ₂ ...... Gas detectors α ...... gas diffusion angle, the average deflection angle W of β ...... wind direction _1, W ₂ …… A line segment on which a gas leak location should exist

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junichi Sato 1282-1, Kamikurata-cho, Totsuka-ku, Yokohama-shi, Kanagawa-ken 59-28 Shineicho, Soka City, Saitama Prefecture (56) References JP-A-61-155932 (JP, A)

Claims (2)

(57) [Claims] 1. A method of estimating the leakage location of the gas in the plant, when the method 1) two gas detectors D ₁ and D _2, characterized in that it consists of stages below detects a gas Then, the diffusion angle α of the gas is calculated based on the data of the wind direction and the wind speed at that time, and the average deflection angle β of the wind direction is calculated. 2) The gas detectors D ₁ and D ₂ are directed to the windward, respectively. The angle (α +) around a straight line that represents the average wind direction
β) draws two straight lines, and the area between those two straight lines
To define the A ₁ and A _2, 3) based on the status of the change in weather conditions in the past within a predetermined time period, selecting the parameter a of the following equation, logC = a · logX + b 4) gas detectors D ₁ and Using the values of the gas concentrations C ₁ and C ₂ detected at D ₂ , the distance from the leak location to the gas detector D ₁ is X, and the distance in the average wind direction between the gas detectors D ₁ and D ₂ △ X Calculating X from the relationship logC ₁ = a · logX + b logC ₂ = a · log (X + △ X) + b, also using the value of 5) From the gas detector D ₁ to the windward along the average wind direction X
In that back by the length of, make a vertical line to a straight line of the average wind direction, the vertical line is within the area A ₁ and A ₂ line
To draw the W _1, 6) is subjected to the above 1) to 5 after time, to draw the new line segment W _2, and 7) have an intersection near the line W ₁ and W _2, gas leakage location and estimated To do. 2. A method for estimating the amount of gas leakage in a plant, comprising the following steps: 1) An average wind direction deflection angle β according to step 1) of claim 1.
2) Select the parameter a in the following equation based on the change of weather conditions within a certain period of time in the past, logC = a · logX + b 3) Gas detector D ₁ Using the values of the gas concentrations C ₁ and C ₂ detected at D and D ₂ , the distance from the leak location to the gas detector D ₁ is represented by X, and the distance between the gas detectors D ₁ and D ₂ in the average wind direction △ The value of X is also used to calculate b from the relationship logC ₁ = a · logX + b logC ₂ = a · log (X + △ X) + b. 4) The wind speed u at the time when gas is detected by the anemometer To obtain the leaked gas amount Q from the relationship between the parameter b and the value of (gas amount Q / wind speed u) created in advance based on the value of the parameter b.