JP2534418B2 - Calorimeter - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a calorimeter, and more particularly to a standard laminar flow meter under the condition that a thermal flow meter and a laminar flow meter are connected in series to make the output of the thermal flow meter constant. By detecting the pressure loss in the state, the calorific value of the fuel gas is measured as a function of the loss pressure, and the calorific value is corrected based on the concentration of a specific gas component contained in the fuel gas. Regarding the total.

[0002]

2. Description of the Related Art Fuel gas and natural gas are legally stipulated to detect and record the amount of heat and combustibility at the time of manufacturing and shipping, and a calorimeter for measuring the amount of heat of a mixed gas is stipulated based on this stipulation. Has been. A typical calorimeter is the Junkers-type running water calorimeter. This calorimeter completely burns the mixed gas fuel together with air, cools the waste gas produced by combustion to the initial gas temperature, condenses the generated steam, and collects the total amount of generated heat into the water flowing through the calorimeter. The principle is that the amount of flowing water corresponding to a fixed mixed gas sample is multiplied by the temperature difference between the temperature at the inlet and the outlet of the flowing water, and the total amount of heat is obtained from the multiplication result.

This calorimeter is used as a reference calorimeter, but in the test, the temperature difference between the water temperature and room temperature is ±
The conditions for measurement are strict, such as matching within 0.5 ° C and keeping the temperature change of water within 0.05 ° C within one measurement time. Since it is not suitable for use in a production line because it has a poor response, it is also approved to use a quick response type calorimeter because it is not suitable for use in a production line. , Is continuously performed by a quick response calorimeter. The fast-response type calorimeter measures the fuel gas and the air by metering them with a flow meter, mixes them, burns them with a burner, and burns them with the temperature of the exhaust gas and the temperature of the combustion air at the burner inlet. Detecting with a temperature detector such as a thermocouple, each temperature difference and the specific gravity of the fuel gas with respect to the air are detected, and the Woppe which is the ratio of the total calorific value of the sample gas to the square root of the specific gravity of the sample gas with respect to the air. An index (referred to as W.I) is obtained, and the heat quantity of the fuel gas to be tested is calculated as W.I. It is calculated as the product of I and the square root of the specific gravity of the sample gas with respect to air. As another heat quantity detection method, it has been attempted to calculate the heat quantity from the density measurement result of the mixed gas based on the experimental result that the heat quantity of the mixed gas and the density have a proportional relationship.

However, the above-described quick-response calorimeter is a practical calorimeter that replaces the Junkers-type running-water calorimeter, which is a highly accurate reference calorimeter, but its measured values drift when used for a long time. Therefore, the measurement accuracy is low, and the measured value is corrected twice a day during continuous operation time. This correction operation is troublesome, and in the method of detecting the density, the density meter is usually expensive and inexpensive, and the calorific value cannot be easily obtained. On the other hand, the applicant has proposed the following simple calorimeter.

The "calorimeter" in Japanese Patent Application No. 2-205378 is a thermal type flow meter which outputs a mass flow rate signal of the fuel gas to a flow path of the fuel gas, and a constant output of the thermal type flow meter. And a laminar flow meter that detects the temperature and pressure of the fuel gas and outputs the volumetric flow rate in a standard state as a differential pressure signal, are connected in series, and the heat quantity of the fuel gas is controlled. Is calculated and output as an amount proportional to the reciprocal of the differential pressure signal. Usually, city gas is natural gas whose main component is methane gas, but when transferring city gas, heat amount is adjusted by mixing high calorific hydrocarbon gas such as propane gas or butane gas with natural gas as a base gas. . However, some specific fuel gases include hydrogen gas or carbon dioxide gas. When the base gas contains a certain amount of hydrogen gas or carbon dioxide, it is possible to calibrate with a mixed actual gas. However, when hydrogen gas and carbon dioxide gas in the base gas are indeterminate, there is a problem that the correlation between the calorific value and the differential pressure is lost and the calorimeter measurement accuracy is lowered.

[0006]

[Purpose] The present invention has been made in view of the above situation, and measures the calorific value of a fuel gas with high accuracy without being affected by the amount of gas concentration of hydrogen gas, carbon dioxide gas, etc. contained in the fuel gas. The purpose is to provide a simple calorimeter that can be used.

[0007]

According to the present invention, in order to achieve the above object, a thermal type flow meter for outputting a mass flow rate signal of the fuel gas and a constant output of the thermal type flow meter are provided in a flow path of the fuel gas. A control means for controlling the flow rate, a laminar flow meter for detecting the temperature and pressure of the fuel gas and outputting the volumetric flow rate in a standard state as a differential pressure signal, and a laminar flow meter according to a specific gas concentration contained in the fuel gas. And a gas detector that outputs a gas concentration signal are connected in series, the calorific value of the fuel gas is calculated in proportion to the reciprocal of the differential pressure signal, and the calculated calorific value is corrected based on the gas concentration signal. It is characterized in that it is configured with a container, and will be described below based on an embodiment of the present invention.

FIG. 1 is a structural block diagram for explaining an embodiment of a calorimeter of the present invention. In the figure, 1 is a fuel gas passage, 2 is a pressure reducing valve, 3 is a filter, 4 is a pressure gauge, 5 is a control valve, 6 is a thermal type flow meter, 7 is a laminar flow meter, 8 is a differential pressure transmitter, 9 is a thermometer, 10 is a pressure gauge, 11
Is a gas detector, 12 is a calculator (with display), and 13 is PI
It is a D (proportional, integral, derivative) controller.

In the figure, the fuel gas for measuring the amount of heat becomes clean fuel gas at a low pressure near atmospheric pressure via the pressure reducing valve 2 and the filter 3, and becomes a control valve 5, a thermal type flow meter 6, a laminar flow rate. It flows out through a total of 7. As is well known, the thermal flow meter 6 heats a mixed gas by winding a heater around a measuring tube that flows in a laminar flow, and changes a resistance value by a temperature difference caused by heat exchange of the mixed gas in a front-back flow of the measuring tube. Is incorporated in a bridge circuit and detected as a voltage signal. The output voltage V is V = K ₁ · Cp · ρ · Q (1) (K ₁ : constant, Cp is constant pressure specific heat, ρ is measured gas density, Q
Is a volumetric flow rate), and the output voltage V is a linear output proportional to the mass flow rate ρ · Q and the constant pressure specific heat Cp.

As is well known, the laminar flow meter 7 is a flow meter that utilizes the fact that the volumetric flow rate Q of a fluid flowing at a low Reynolds (Re) number is proportional to the pressure loss ΔP of a flow path of the fluid. Then, the volumetric flow rate Q of the gas at a pressure near the atmospheric pressure is expressed by Q≈K ₂ ΔP / μ (K ₂ : constant, μ: viscosity of fuel gas) (2).

On the other hand, the calorific value H (Kcal / N) of the fuel gas
It is known that m ³ ) is proportional to the density ρ of the fuel gas and to the inverse of the viscosity μ and the constant pressure specific heat Cp. (The above-mentioned patent specification) ρ = K ₃ H (K ₃ : constant) (3) μ = K ₄ / H (K ₄ : constant) (4) Cp = K ₅ / H (K ₅ : constant) (5) and when the output V of the thermal type flow meter is constant in (1) to (5), H = KΔP (K: constant) (6) is obtained.

The control valve 5 is a valve device for controlling the flow rate of the fuel gas in order to make the output of the thermal type flow meter 6 constant, and is driven via the PID controller 13 based on the set value of the calculator 12. To be done. In addition, the differential pressure Δ of the laminar flow meter 7
P is measured by the differential pressure transmitter 8 and is the temperature T of the fuel gas flow path 1.
Also, the absolute pressure P is detected by the thermometer 9 and the absolute pressure gauge 10, respectively, and the volume flow rate Q is calculated by the calculator 12. In the calculator 12, the heat quantity H of the fuel gas is calculated based on the equations (1) to (6) and is output and displayed. Further, for the heat quantity H, the gas detected by the gas detector 11 is calculated. The correction of the heat quantity H is calculated according to the concentration.

When hydrogen gas or carbon dioxide gas is contained in the fuel gas, the proportional constant of the heat quantity and the density is changed. Since the gas detector 11 is a sensor for correcting the amount of heat according to the gas concentration, any detection method may be used as long as it outputs a signal according to the gas concentration.
For example, known gas detectors include a heat conduction type gas detector that compares the conductivity with a reference gas by utilizing the difference in the proportional conductivity (air reference) of the measurement gas, or the refractive index of light. There is an optical interference gas densitometer or the like that forms a moire fringe with a reference gas by utilizing it and detects the gas concentration from the fringe density of the moire fringe. By correcting the fuel gas heat quantity based on these gas concentrations, it is possible to detect the fuel gas heat quantity with high accuracy.

[0014]

As is apparent from the above description, according to the present invention, the calorific value of the fuel gas is configured by using a flowmeter including a simple thermal type flowmeter and a laminar flowmeter, and the calorific value is further increased. A simple and highly accurate calorimeter can be provided because the gas concentration of a specific gas that affects the relational expression for configuring the meter is detected and corrected.

[Brief description of drawings]

FIG. 1 is a configuration block diagram for explaining an embodiment of a calorimeter of the present invention.

[Explanation of symbols]

1 ... Fuel gas flow path, 2 ... Pressure reducing valve, 3 ... Filter, 4 ... Pressure gauge, 5 ... Control valve, 6 ... Thermal flow meter, 7 ...
Laminar flow meter, 8 ... Differential pressure transmitter, 9 ... Thermometer, 10 ... Absolute pressure gauge, 11 ... Gas detector, 12 ... Computer (with display), 13 ... PID (proportional, integral, derivative) control vessel.

Claims (1)

(57) [Claims] 1. A thermal type flow meter for outputting a mass flow rate signal of the fuel gas to a flow path of the fuel gas, a control means for controlling the flow rate so that the output of the thermal type flow meter is constant, and A laminar flow meter that detects the temperature and pressure of the fuel gas and outputs the volumetric flow rate in a standard state as a differential pressure signal, and a gas detector that outputs a gas concentration signal according to a specific gas concentration contained in the fuel gas. Is connected in series, the heat quantity of the fuel gas is calculated in proportion to the reciprocal of the differential pressure signal, and the calculated heat quantity is corrected based on the gas concentration signal. Calorimeter.