CN102435581A - Natural gas heat value calculation method based on natural gas component spectrum analysis - Google Patents

Abstract

The invention discloses a natural gas heat value calculation method based on natural gas component spectrum analysis. In the prior art, the natural gas is still charged by using volume and the heat values of the natural gases from different gas sources are greatly different. In the method, a measured material is irradiated by using infrared light, the light absorbance of the measured material is measured and the content of the measured component is calculated according to the light absorbance. The volume fraction of the components of a mixed gas in a pipeline is calculated through the concentration of the components measured by infrared spectroscopic analysis by utilizing a Fourier infrared spectrometer to obtain the natural gas heat value, so that a possibility is provided for realizing that the natural gas is charged by using the heat value. According to the invention, the spectroscopic analysis technology is employed and is characterized by high resolution, high sensitivity, high signal-to-noise ratio and quickness, and the system is compact in volume and high in stability.

Description

A kind of heating value of natural gas computing method based on the gas component spectral analysis

Technical field

The invention belongs to the interleaving techniques field of spectroscopy, chemistry of fuel, be specifically related to a kind of heating value of natural gas computing method based on the gas component spectral analysis.

Background technology

Spectral analysis technique is based on material and radiation energy is done the time spent; Measurement is carried out the technology that material composition is analyzed by the wavelength and the intensity of inner emission, absorption or the scattered radiation that transition between the quantized level takes place and produce of material, has advantages such as analysis precision height, measurement range is big, speed is fast.The Chinese commodity rock gas still adopts the volume valuation at present; Because the heating value of natural gas of different sources of the gas is widely different, can cause the otherness of commodity use value under the equal value, and valuate with heating value of natural gas; The principle that embodiment is fixed the price according to the quality is the needs of development of commerce.The traditional natural gas calorific value detects and mainly utilizes caloric value instrument, uses heat balance principle, at first appearance gas is carried out Pressure-stabilizing pressure reducing; And record gas density; After the secondary decompression, fully mix, get into the firing chamber with combustion-supporting gas; Light, calculate heating value of natural gas through measuring the temperature difference T that gets into front and back, firing chamber mixed gas.The method needs extremely strict flow, air pressure and temperature control, and system is huge and complicated, and maintenance cost is high, and fault takes place frequently.

Summary of the invention

The present invention is directed to the prior art deficiency, adopt the on-the-spot mode that detects, utilize Fourier infrared spectrograph that gas component is carried out the accurate quantification analysis, use mathematical method that the sample calorific value is calculated again, for rock gas provides foundation with the calorific value valuation.The present invention realizes through following technical scheme:

A kind of heating value of natural gas computing method based on the gas component spectral analysis, its device comprise FTIS, thermometer, negative pressure tensimeter, vacuum pump, computing machine, rock gas (in pipeline, transmitting), resistance test pipeline (being provided with the exploration hole of withstand voltage transparent material) and a plurality of valve.Ducted rock gas sample introducing has been gathered in the pressure line of background spectra, under the gas transmission state, gathered frequency spectrum, drawn each ingredients constitute ratio, calculated heating value of natural gas according to the gas mixing rule.

The implementation step of the inventive method is:

Step 1: after putting up pick-up unit; (it is the measurement of system responses when not having sample gas at first to gather the background spectra of pipeline exploration hole scope; The sample frequency spectrum that spectrometer is collected comprises the characteristic of background spectra, need it be stored in the computing machine from the sample frequency spectrum, to remove to scale again).Need the pollution of original air in the vent line before the collection background spectra, use the vacuum pump vent line, gather background spectra subsequently, concrete steps are:

1, all close at all valves, detect in the pipeline and do not introduce under the prerequisite of rock gas, open the vacuum pump valve, the wait pressure gauge reading drops to below 0.1 mm Hg and keeps constant;

2, treat to have had no residual gas in the pipeline, gather background spectra.If the vibration interference of vacuum pump the collection of frequency spectrum, can close the vacuum pump valve earlier, after close vacuum pump, gather background spectra (note this moment pressure gauge reading do not have obviously change) subsequently.

Step 2: gather rock gas sample frequency spectrum immediately after gathering background spectra.Concrete steps are:

1, close the vacuum pump valve, close vacuum pump after, the recording thermometer reading.Slowly open and adjust pipeline left side valve, after rock gas is full of pipeline, open the right valve of pipeline, make rock gas be same as under the pipeline pressure continuous stream through detecting pipeline;

2, gas flow rate is stable in detecting pipeline, and the recording manometer reading with infrared spectrometer scanning mixed gas sample, produces the spectroscopic data sample.Spectroscopic data is received through data-interface with computing machine, the SVM calibration model processing of spectroscopic data sample in computing machine draws mixture gas component concentration and the component kind is extrapolated each component.Utilize on-the-spot pressure, the temperature of light to be inverted parameters, carry out inversion procedure, draw, the volume accounting that normal atmosphere is depressed at 20 ℃ according to laboratory data.

Step 3: calculate heating value of natural gas according to the gas mixing rule.In the practical application, the water vapor of combustion gas is discharged with gaseous state usually, so the present invention calculates with the rock gas Lower heat value.According to ISO 6976:1995; Under burning reference temperature

; The metering reference temperature is

, and the rock gas ideal gas volume net heat value of pressure for

is calculated as follows:

（1）

In the formula;

---mixed gas volume of ideal net heat value,

;

---component j gas volume of ideal net heat value,

(specifically consulting data);

---the volume fraction of component j gas.

The true net heat value of gas need be used to be revised, and is calculated as follows:

（2）

---real gas volume net heat value in the formula,

;

---the compressibility factor of gas under the metering reference condition.

Compressibility factor is calculated by following formula by gas composition:

（3）

---the summation factor of component j gas is specifically consulted data in the formula.

The present invention relates generally to infrared absorption spectroscopy, and its basic skills is, shines measured matter with infrared light; Measure its absorbance, calculate tested components contents according to absorbance again, its theoretical foundation is lambert-Beer law: A=aCl; A represents absorbance; A represents absorptivity, the concentration of C representative sample (being the number of absorbing particle in the unit volume), and l represents optical path length.Utilize Fourier infrared spectrograph, each concentration of component of mixed gas in the pipeline that records through IR spectroscopy is calculated volume fraction, calculates the calorific value of rock gas, maybe for realizing that rock gas provides with the calorific value valuation.

The inventive method compared with prior art, the improvement that obtains shows:

1, application of spectral analytical technology has high resolving power, high sensitivity, high s/n ratio, characteristics fast, and system bulk is compact, stability is high;

2, lossless manner detects rock gas, does not waste resource, and is safe;

3, utilize the on-the-spot mode that detects, dirigibility is strong, and detection efficiency is high; Calorific value calculation has guaranteed the reliability of data with reference to international standard.

Along with country in the rapid progress aspect the spectral instrument, the continuous enhancing of national purchasing power, and the cry of rock gas with calorific value valuation grown with each passing day, the inventive method will possess application prospects.

Description of drawings

Fig. 1 is an equipment therefor synoptic diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing the present invention is described further.As shown in Figure 1, the inventive method hardware configuration comprises: the natural gas line under the gas transmission state (1), pipeline left side valve (2), resistance test pipeline (3), vacuum pump (4), vacuum pump valve (5), thermometer (6), withstand voltage transparent material exploration hole (7), spectrometer (8), computing machine (9), the right valve (10) of pipeline, negative pressure tensimeter (11).Vacuum pump should guarantee that before cutting out valve (4) closes, and goes in the system of negative pressure with the oil vapour suck-back that prevents vacuum pump.Its implementation method is specially:

Step 1, gather background spectra:

1, all close at all valves, detect in the pipeline (3) and do not introduce under the prerequisite of rock gas, open vacuum pump valve (5), wait tensimeter (11) reading drops to below 0.1 mm Hg and keeps constant;

2, treat had no residual gas in the pipeline (3), gather background spectra with spectrometer (8).If the vibration interference of vacuum pump (4) collection of frequency spectrum, can close vacuum pump valve (5) earlier, after close vacuum pump (4), gather background spectra (note this moment tensimeter (11) reading do not have obviously change) subsequently.

Step 2, gather rock gas sample frequency spectrum:

1, close vacuum pump valve (5), close vacuum pump (4) after, recording thermometer (6) reading.Slowly open and adjust pipeline left side valve (2), after rock gas is full of pipeline, open the right valve (10) of pipeline, make rock gas be same as under pipeline (1) pressure continuous stream through detecting pipeline (3);

2, gas flow rate is stable in detecting pipeline; Recording manometer (11) reading; With the frequency spectrum of spectrometer (8) collection rock gas, be inverted parameters (can adopt supporting vector machine model) with on-the-spot pressure, temperature, carry out inversion procedure with computing machine (9) according to laboratory data; Extrapolate each component at 20 ℃, the volume accounting that normal atmosphere is depressed.

Step 3: the step 3 according to summary of the invention is calculated rock gas sample calorific value.

Embodiment (one)

The volume constituents that records rock gas by the aforementioned operation step is as shown in table 1:

Table 1 embodiment (one) gas component

Component	Methane	Ethane	Propane	Normal butane	Isobutane	N-pentane	?
									Volume fraction	0.9247	0.0350	0.0098	0.0022	0.0034	0.0006	0.0175	0.0068

Known conditions and calorific value calculation procedure parameter are listed in shown in the table 2, calculate the rock gas net heat value by aforementioned computing formula.

Table 2 heating value of natural gas characterisitic parameter reckoner (20 ℃, 101.325kPa)

By formula the desirable net heat value of rock gas is calculated in (1); At [20 ℃;

(20 ℃, 101.325kPa)] under the condition:

By formula compressibility coefficient is calculated in (3):

By formula the true net heat value of rock gas is calculated in (2):

After rounding, the net heat value that obtains the sample rock gas be 34.57

.

Claims (1)

1. heating value of natural gas computing method based on the gas component spectral analysis is characterized in that this method may further comprise the steps:

Step 1: the background spectra of gathering pipeline exploration hole scope;

1-1, all close, detect in the pipeline and do not introduce under the prerequisite of rock gas, open the vacuum pump valve, wait for that pressure gauge reading drops to below 0.1 mm Hg and keeps constant at all valves;

1-2, treat to have had no residual gas in the pipeline, gather background spectra; If the vibration interference of vacuum pump the collection of frequency spectrum, can close the vacuum pump valve earlier, after close vacuum pump, gather background spectra subsequently;

Step 2: gather rock gas sample frequency spectrum immediately after gathering background spectra;

2-1, close the vacuum pump valve, close vacuum pump after, the recording thermometer reading; Slowly open and adjust pipeline left side valve, after rock gas is full of pipeline, open the right valve of pipeline, make rock gas be same as under the pipeline pressure continuous stream through detecting pipeline;

2-2, gas flow rate is stable in detecting pipeline, and the recording manometer reading is gathered the frequency spectrum of rock gas with spectrometer; With on-the-spot pressure, temperature is inverted parameters, carries out inversion procedure with computing machine according to laboratory data, extrapolates each component at 20 ℃, the volume accounting that normal atmosphere is depressed;

Step 3: calculate heating value of natural gas according to the gas mixing rule; According to ISO 6976:1995; Under burning reference temperature

; The metering reference temperature is

, and the rock gas ideal gas volume net heat value of pressure for

is calculated as follows:

（1）

In the formula,

---mixed gas volume of ideal net heat value;

---component j gas volume of ideal net heat value;

---the volume fraction of component j gas;

The true net heat value of gas need be used

to be revised, and is calculated as follows:

（2）

---real gas volume net heat value in the formula;

---the compressibility factor of gas under the metering reference condition;

Compressibility factor

is calculated by following formula by gas composition:

（3）

---the summation factor of component j gas in the formula.