JPS61159143A - Adjusting device for calorific value of natural gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a natural gas heat generation control device suitable for use in a small-scale liquefied natural gas vaporization supply station.

(Prior art) Natural gas (abbreviated as NG) is usually stored as liquefied natural gas (abbreviated as LNG) that is liquefied at extremely low temperatures, and the required amount for consumption is revaporized into natural gas at room temperature using a vaporizer. and supplied.

However, since natural gas is a multi-component gas consisting mainly of paraffin homologs such as methane as a main component, ethane as a sub-component, and propane, each having its own heat value, its calorific value is not constant.

In other words, the calorific value of natural gas varies in the range of 9,700 to 11,200 Kcal/Nm3 due to differences in the composition of each component. Due to the complex flow phenomena based on the interaction between phase flow (liquefied natural gas flow) and gas phase flow (natural gas flow), the composition of revaporized natural gas fluctuates with a certain time period and therefore its The amount of heat generated also fluctuates.

However, natural gas has a certain standard calorific value (for example, the standard calorific value when supplying natural gas as city gas is 1100 l) due to combustibility during consumption and transaction reasons.
It is 0Kcal/Nm3. ), and it becomes necessary to adjust the calorific value of natural gas.

Conventional techniques for adjusting the calorific value of natural gas include measuring the calorific value of natural gas using a gas calorimeter such as a so-called Junkers calorimeter or a sigma calorimeter;
It is constructed by mixing other types of gas having an appropriate calorific value with natural gas based on this measured value.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional technology, the response speed of the calorimeter is slow, resulting in a measurement delay of usually 3 to 10 minutes. There is a problem in that when the heat is intense, the amount of heat generated cannot be adjusted accordingly. This problem is caused by the large number of vaporizers in operation in large-scale liquefied natural gas vaporization supply plants,
Natural gases with different compositions are mixed inside the Ohonname plant.
However, in small-scale liquefied natural gas vaporization supply plants where such economies of scale cannot be expected, the calorific value of the supplied natural gas may differ greatly from the standard calorific value. There was a fear that such inconvenience would occur.

By the way, due to the above-mentioned compositional characteristics of natural gas, its calorific value (higher calorific value Kcal/Nm3) is
If the specific gravity (assuming the specific gravity of air is 1; the same applies hereafter in Honkawa IS) is ρ, then as shown in Figure 4, H=
14559Xρ+1473 It is known that the correlation shown by (Equation 1) holds true, and in a hydrometer for measuring the specific gravity of a gas, such as a so-called Lauter hydrometer, its response is similar to that of a calorimeter. It is also known that measurements can be performed continuously with a delay of usually several tens of seconds, including the sampling time.

Therefore, if the specific gravity of natural gas is measured using a hydrometer and the calorific value of natural gas is adjusted using this measured value as an index, it is possible to improve the ability to follow the fluctuations in calorific value of natural gas to some extent. Even in this case, as mentioned above, it is inevitable that an error in adjustment will occur due to measurement lag of about several tens of seconds in the hydrometer.

Therefore, the present invention is to make natural gas whose specific gravity is measured by a hydrometer wait for a time corresponding to the measurement delay of the hydrometer, and then undergo adjustment of the calorific value. Mixing and averaging natural gases with different compositions to reduce the range of variation in calorific value that needs to be adjusted.
This is a technical problem to be solved.

(Means for solving the problem) A technical means for solving the above problem is to measure the specific gravity of natural gas corresponding to the calorific value of the natural gas using a hydrometer installed in the natural gas flow path, Based on this measured value, the calorific value adjusting device adjusts the excess or deficiency of the calorific value of natural gas with respect to the standard calorific value in an adjustment section having a calorific value adjusting means provided in the natural gas flow path. A predetermined volume of natural gas with a wide range of stirring means is placed in the flow path between the adjustment section and the flow path.
A mixing tank is installed, and a calculation unit connected to the hydrometer is equipped with a simulation program that predicts and calculates the specific gravity of the natural gas stirred and mixed in the mixing tank based on the specific gravity measurements input sequentially from the hydrometer. However, the adjustment section is controlled based on this predicted calculation value.

(Function) After the specific gravity of the natural gas, which is vaporized by the vaporizer and whose specific gravity fluctuates corresponding to the variation in calorific value, is continuously measured by a hydrometer installed in the flow path, the natural gas is It flows into the mixing tank and is stirred and mixed. Since the mixing tank has a predetermined capacity, the natural gas that has flowed into the mixing tank remains in the mixing tank for at least a time corresponding to the measurement delay of the hydrometer.

During this time, the specific gravity measured by the hydrometer is continuously input to the calculator with a measurement delay of a certain time.

Based on these measured specific gravity values, the computing unit predicts and computes the specific gravity of the natural gas after being mixed in the mixing tank, and sends a control command to the adjustment unit based on this computed value.

Then, at this point, the natural gas corresponding to the calculated value has flowed out of the mixing tank and reached the adjustment section, so that the calorific value of this natural gas is adjusted based on the calculated value.

(Example) Next, an example of the present invention will be described based on FIGS. 1 to 3.

The liquefied natural gas stored in the tank 1 is sent to a vaporizer 3 by a pump 2, and after being vaporized there, it flows into a mixing tank 5 through a supply pipe 4.

The mixing tank 5 has a predetermined capacity, that is, a capacity capable of retaining the inflowing natural gas for at least a time corresponding to a measurement delay of the hydrometer 19, which will be described later. The supply pipe 4 introduced into the mixing tank 5 is connected to one or more branch pipes 6, and the branch pipes 6 are extended to an appropriate position to uniformly stir the gas inside the mixing tank 5. It is set up. At the tip of the branch tube 6, there is a nozzle 7 formed by narrowing the branch tube 6 to a small diameter, and a tapered nozzle provided so as to surround the opening edge of the nozzle 7 at a constant interval. A mixing ring 8 forms an ejector 9. Further, an outlet port 10 is provided in the mixing tank 5 at a location away from the direction in which the gas body is introduced by the ejector 9.

Next, at the narrow end of the supply pipe 11, one end of which is connected to the outlet port 10, there is an adjustment section 12 for adjusting the heat generation of the natural gas.
has been established. This adjustment section 12 connects a supply pipe 14 for sending heating gas through a flow m control valve 13 and a supply pipe 16 for sending dilution gas through a flow m control valve 15 in a mixing section 17. It is connected to 12. A supply pipe 18 is extended from the mixing section 17 to send the heat-adjusted natural gas to a supply port (not shown).

The heating gas mentioned above is a gas that exhibits a certain calorific value higher than that of natural gas, such as propane gas or butane gas. Incidentally, the calorific value of butane gas is 31,920 Kcal/Nm3. Further, the diluting gas is a gas that exhibits a certain calorific value lower than that of natural gas or has a calorific value of pyro, such as air or hydrogen gas.

The natural gas supply pipe 4 is equipped with a hydrometer 19, and the supply pipe 1 is also equipped with a hydrometer 19.
1 is provided with a flow meter 20, and the opening degree of the flow control valve 13, 15 is controlled by a computing unit 21 into which these measured values are input. Further, the calculator 21 includes a simulation program that preliminarily calculates the specific gravity of the natural gas stirred and mixed inside the mixing tank 5 based on the specific gravity measurement values sequentially inputted from the hydrometer 19.

Incidentally, as the stirring means in the mixing tank 5, a stirring propeller may be provided instead of the ejector 9. Further, the hydrometer 19 may be of any mechanism or type as long as it is a gas hydrometer that has less measurement delay than a calorimeter.

Since this embodiment is configured as described above, it has the following effects.

The liquefied natural gas stored in the tank 1 is sent to the vaporizer 3 by the pump 2, where it is vaporized to become natural gas. The specific gravity of this natural gas is continuously measured by a hydrometer 19 while passing through the supply pipe 4 , and then passes through a branch pipe 6 and is ejected from a nozzle 7 into the mixing tank 5 . Since such a jet of natural gas generates negative pressure inside the mixing ring 8, the area near the ejector 9,
The natural gas that has already been introduced into the mixing tank 5 is sucked into the ejector 9 in the direction shown by arrow A in FIG. 3, and mixed with the natural gas jetted out from the nozzle 7 in the direction shown by arrow B in FIG. 3. It's blown out. Further, such a flow of natural gas causes convection and mixing of the natural gas inside the mixing tank 5, and as a result, the composition of the natural gas is averaged.

Furthermore, the natural gas ejected from the nozzle 7 from the MPA connection between the ejector 9 and the outlet port 10 does not immediately go to the outlet port 10, but flows into the mixing tank for a predetermined period of time corresponding to the capacity of the mixing tank 5. It stays inside 5.

On the other hand, the calculator 21 predicts and calculates the specific gravity of the natural gas whose composition has been averaged inside the mixing tank 5 based on the measured specific gravity values of the natural gas that are sequentially inputted from the hydrometer 19. , sends a control command based on this calculated value to the adjustment section 12. The content of this control command is to open the flow control valve 15 or 13 by the required opening degree for the required time, depending on whether the above-mentioned calculated value is excessive or insufficient with respect to the specific gravity value corresponding to the standard heat generation value 1 of natural gas. It consists of selectively supplying a required amount of gas or diluent gas to the mixing section 17.

However, as described above, since the design is such that the measurement delay time in the hydrometer 19 corresponds to the residence time of natural gas in the mixing tank 5, the natural gas whose composition has been averaged in the mixing tank 5 is is the supply pipe 11
When the natural gas reaches the mixing section 17, the heating gas or the diluting gas is supplied to the mixing section 17 according to a control command based on the calculated value of the specific gravity corresponding to this natural gas, and is mixed with the natural gas. The calorific value of natural gas can be adjusted without causing errors due to a total of 19 measurements.

Incidentally, the flow rate of natural gas, in other words, its moving speed is detected by a flow meter 20 installed in the supply pipe 11, and this measured value is inputted to the calculator 21, which sends the control command to the adjustment section. Fine adjustments are made to the timing of the output.

(Effects) The present invention improves the followability of heat generation adjustment to fluctuations in the calorific value of natural gas, eliminates adjustment errors due to measurement delays of hydrometers, and also enables the composition of natural gas to be averaged in advance. This has the advantage that the range of variation in the amount of heat generated is small, making it easier to make accurate adjustments.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the present invention, Figure 2 is a style diagram of a mixing tank, Figure 3 is an enlarged view of its main parts, and Figure 4 is a graph showing the correlation between calorific value and specific gravity in natural gas. . 5...Mixing tank 12...Adjustment section 19...Specific gravity meter 21...Calculator

Claims (1)

[Claims] The specific gravity of the natural gas corresponding to the calorific value of the natural gas is measured using a hydrometer installed in the natural gas flow path, and based on this measurement, the excess or deficiency of the calorific value of the natural gas relative to the standard calorific value is determined. In the calorific value adjusting device that adjusts the calorific value in an adjusting section having a calorific value adjusting means provided in a gas flow path, a mixing tank of a predetermined capacity is provided with a natural gas stirring means in the flow path between the hydrometer and the adjusting section. At the same time, a simulation program is set in the calculator connected to the hydrometer to predict and calculate the specific gravity of the natural gas that is stirred and mixed in the mixing tank based on the specific gravity measurement values sequentially input from the hydrometer. A natural gas calorific value adjustment device, characterized in that an adjustment section is controlled based on a predicted calculated value.