JPS603522A - Method of monitoring change of flow rate of plurality of fluid flow - 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 The present invention relates to monitoring flow rate changes in multiple fluid streams to identify their source.

It is relatively common to mix multiple fluid streams in a common vessel or conduit. As each fluid stream enters a container or conduit from each conduit, it is often desirable, and sometimes important, to be able to determine whether the mixed fluid consists of a predetermined proportion of the fluid obtained from each conduit. It is. When the number of conduits is small, the fluid supply from one conduit varies, e.g. increases, decreases, stops, etc.
There is usually no problem in deciding what to do (start).

However, when the number of conduits is large, it can be difficult to discern which conduits are providing flow at varying rates. It has long been highly desirable to devise a method for determining such altered flow rates, as such altered flow rates may involve fluids that are valuable or dangerous (or both).

The present invention provides a method for determining which of a plurality of fluid streams flowing through each conduit are flowing at varying flow rates, the method comprising: (a) common to all conduits; collecting a mixed sample of fluid from a sampling location (e.g., a single sampling location): (b) comparing the characteristics of the mixed sample to other mixed samples obtained from said sampling location at different times; and (c) determining from the change in the characteristics of the two samples which fluid streams are flowing at the changed flow rates.

The characteristic is the concentration (present or absent) or proportion of at least one substance in each mixed sample. Characteristics can be determined by convenient techniques, such as thermally conductive groups or Fi electrical conductivity, NMR, color, dielectric properties, emission spectra, xIlil! Determined by spectrum, heat of combustion, etc. When the fluid flow is entirely gaseous, the presence, concentration or proportion of at least one substance in each sample is determined by gas chromatography techniques. Whichever technique (or combination of techniques) is employed, step (c) is performed automatically by comparison to a library or database of desired blockage fluid flow characteristics.

Steps (a), (b) and (c) of the method of the invention are preferably repeated, the intervals between repetitions being preferably as short as possible for the type of equipment employed to carry out the method. Adequate and meaningful data can be obtained from discrete repetitions, especially compared to the period of time it takes for the characteristic to change from a changing or temporary value to a final or fixed value. The above data is obtained when the repetition interval is short.

In one embodiment, fluid flow enters the common conduit from each of the conduits, and the sampling points are located at suitable locations to collect a substantially representative sample from the common conduit.

In yet other embodiments, the method of the invention comprises (d)
monitoring the flow rate of the fluid in the common conduit at a time and place where the fluid being monitored has a composition substantially represented by the sample: (a) monitoring changes in the flow rate of the fluid in the common conduit; and (4) calculating from the results of step (e) and the corresponding results of step (c) the concentration of at least one component of the fluid stream flowing at the varied flow rate. . Step (f) is preferably performed automatically by a computer.

Preferably, the synchronizer performs steps (a), (b) and (d)
is employed to control the timing of the mixed samples and corresponding monitored flow rates at respective times and intervals.

The invention also includes an apparatus for performing the method described above.

The invention will be further described with reference to non-limiting examples given by way of illustration.

Operations carried out in processing units of petroleum refineries or petrochemical facilities produce standby gas in excess of the operating conditions. Since these excess gases are utilized intermittently, they cannot be used all the time in the refinery or plant. In most cases, the excess gas Vi is flammable and its disposal is carried out by burning the gas, for example in a flare. A typical refinery has hundreds of pipes each conducting excess gas from the processing unit to the flare. The release of gas from the treatment unit to the flare is controlled by a pressure reducing valve set to open at a selected pressure, and in parallel with this pressure reducing valve, a safety relief valve is provided to prevent the pressure from reaching dangerous levels. Removing the pressure previously created in the processing unit. Both pressure reducing valves and safety valves are prone to leaking, and such leakage K
This results in more unplanned gas losses and higher operating costs for the processing unit. It is possible to install a flow meter at or near the valve to determine the flow rate of discharge from each unit to each pipe, but this measure is extremely difficult since there are so many valves. It becomes expensive. The method and arrangement of the present invention provides a relatively low cost alternative that can be used reliably in all normal gland operating methods.

In the application of the present invention, a mixed gas sample is conveyed through each i+ tube from the processing binites and other gas sources.

It is sampled periodically from a common conduit that receives gas and supplies it to the flare.

Each mixed gas sample is compared to a previously taken mixed gas sample to determine whether the composition of the gas within the common conduit has changed. Changes in the composition of the gas within the common conduit are due to differences in the amount of gas from one or more processing units due to changes in the operating conditions of the processing units and/or changes in gas leakage from the processing units. By comparing the composition of successive (but not necessarily continuous) mixed gas samples, the composition of the gas that caused the change in composition can be determined. The composition of the gas that caused this change can be correlated with the known composition of the gas produced in the processing unit (e.g., from a library or database of such compositions), thereby determining the composition of the gas in the common conduit. A processing unit corresponding to the change can be identified. 1. Each mixed gas sample is suitably analyzed by a gas chromatography analyzer, which is connected to a microprocessor/comparator arrangement that compares each analysis with the previous analysis. The comparison is performed by determining the gas composition causing the change in composition by appropriate calculations and by utilizing a library or database of gas compositions to identify the gas source of the change in composition.

The method of the invention is partially or fully automated. In the latter case, the gas source of the change in gas composition is recorded and/or displayed.

In one embodiment of the invention, provision is made to determine the concentration or proportion of at least one component of a fluid stream flowing at a varying flow rate. In this embodiment, suitable equipment is employed to monitor the flow rate of the fluid in the common conduit from which the representative sample is taken, and changes in the flow rate are monitored to substantially the representative sample. Fluid composition (
and/or other characteristics).

If the initial flow rate Q1 of the fluid in the common conduit changes to a different flow rate Q2 due to a change in the flow rate of one of the fluid streams contributing to the overall flow in the common conduit, then The concentration of each component of the fluid stream (
C) can be calculated from the following formula.

Here, G1 and G2 are the flows t(h and G2
is the concentration of each component in the total flow of the common conduit when .

The method of the invention will be further explained with reference to a non-limiting example in which pipes A, B% C, O and E are utilized to direct gas from each source to the flare. In this example, the gas consists of components 1 to 8.

example In one test, the following data were obtained.

11 Analysis of the percentage of flare gas, which is the gas mixture obtained by combining the separate gas streams from pipes A to E, is determined by chromatography.

In the next test, the following data were obtained.

2 3 From the change in the composition of the flare gas, the composition of the gas stream that caused the change can be calculated as follows.

Flare gas 1 5.33 7.50 +4.17 2 33.33 25.00 -8.333 20.0
0 15.011 -5.004 10.00 7.5
0 -2.505 15.33 10.00 -3.5
36 6.66 15.00 +8.347 6.66
15.00 +8.348 6.66 5.00 -
1.66 Relative increase in proportions of components 1, 6 and 7 (overall 2
[1,851)], indicating that there was a relative decrease (total of 20.83) commensurate with the proportions of all other components. The slight differences between percentage increases and decreases are caused by changing the percentage to two decimal places.

Ingredients that made up the percentage composition after change determined above: 1.
The composition of the gas stream consisting of 6 and 7 is easily calculated as follows.

20.85 20.85 20.85 During normal operation of the plant, we would expect changes in flare gas composition between each analysis to be attributable to gases emitted from a single processing unit. Therefore, with the addition of gas emitted from one processing unit, a change in flare gas composition can be expected, with the additional emitted gas coming from 20 g of component 1.40 g of component 6 and 40 g of component 7. It has the following composition. With reference to a library or data base of the composition of the gases produced by the processing units, the processing units that have released additional gas can be easily identified and the operation of the processing units can be checked to ascertain the reason for the release and loss of gas. and, if possible, to change operating conditions to reduce or eliminate losses. Although it is clear from the data given in the first two tables that the additional gas in the flare gas is from Guib C,
It is not necessary to determine the composition or flow of gas in any one of the pipes communicating with the flare's common conduit.

A compositional analysis of the total gas flow before and after the flow rate change can be calculated using equation (11) shown above. Such a compositional analysis allows the identification of gas streams with changed flow rates, and /or previously given total 0K”°”C%N i
h, fc ;t! 2ゝ0-°1 to 1601.

Using the data given in Tables 1 and 2 according to 11, 200-150 is calculated for component 1 and C=201, which is consistent with the previous results.

Similar calculations for components 6 and 7 give the same results as before. It will be appreciated that this latter method of calculation is sufficient for specifying the gas flow and/or confirming the specifications obtained with the other methods mentioned above.

Other mathematical treatments of the different compositional data can be envisaged to define the composition of the leak stream in preparation for correlation with a library of known compositions.
O While the example data deals with changes caused by the addition of gas to the flare gas stream, the method of the present invention arises from the cessation or reduction of gas that was previously part of the flare gas stream. 6 It can similarly be applied to change. It is worth noting that a stepwise change in the amount of gas released from the processing unit typically changes the percentage amount of only a small fraction of the total number component (or key component) of the flare gas. be. Thus, in the example data, the addition of gas from pipe C causes an increase in three components and a decrease in five components.

If the total flow rate of flare gas is recorded (using - flowmeters), the change is more likely to result from the addition of a single 3-component flow than from the cessation of a 5-component flow. It is clear that it is highly sensitive.

It must be recalled that the example only refers to five guides that can feed the flare. In fact, there are many cases in refineries, typically 3
There are 00 to 500 74 Eves. However, a skilled technician will appreciate that it is necessary to monitor only those gas components by weight in identifying processing units capable of releasing gas into a flare.

The present invention is useful for monitoring the normal operation of processing units. When there is a major disturbance in the operation of the plant that causes abnormal operation of a number of processing units, the plant's conventional monitoring equipment may be employed to ascertain the cause of this disturbance and make adjustments.

The invention can be applied to streams other than gas streams, including liquid streams and solid streams (e.g., mixtures of particulate solids), and mixtures of at least two of gas streams, liquid streams, and solid streams. be able to.

In the drawings, excess waste gas released from a processing unit (not shown) is burned in a flame 10 at the top of the flare stack 11. The waste gas is sent to the flare stack 11
are joined by a common conduit 12 to supply the conduit 12
receives gas from the processing unit via a plurality of mother tubes, indicated generally by reference numeral 13.

Common conduit 12 includes a flow meter 14 and a flow indicator 15 displays and/or records the flow rate measured by the flow meter. The gas mixture sample is collected at the sampling point of conduit 12】6
Gas analyzer N18 is preferably sampled through valve 17, which is opened synchronously (e.g., every 5 to 10 minutes) by a signal from a timing device (not shown) associated with gas analyzer N18. is a gas chromatograph, in which a signal representing a differential analysis of at least selected components of a continuous (but not necessarily continuous) gas sample is displayed and recorded via line 20. Either directly to the device 19 or first to a comparator 21 which compares the signal with a signal obtained from a database contained in a suitable storage device 22. The result of the operation of the comparator 21 is displayed on the recording device 19.
(or to another equivalent device) which indicates and/or records that the processing unit is causing a change in the composition of the gas sampled at the sampling point 16.

The method of the present invention uses equation (1) to identify a flow of varying flow rate and/or to verify the identity of the flow.
The flow rate in the common conduit 12 as detected by the meter 14' is outputted to the computer 23, which also detects the gas composition from the gas analyzer 18. Receive data.

Computer 23 is programmed to sum the concentration of each component or selected component using equation (1).

In the apparatus as shown in the figures, the flow meter 14 is located slightly upstream of the sampling point 16. In order to ensure that the flow rate data from the flow rate a↑14 and the component data from the gas analyzer 18 correspond to the same sample, the gas analyzer M], 8 is activated with an appropriate delay relative to the computer 23. This delay is controlled by a synchronization signal input to analyzer 18 from a suitable device (not shown) associated with flowmeter 14 or computer 23.

[Brief explanation of the drawing]

The drawings are detailed illustrations of the invention. 10...Flame, ]2...Flare Stack, 12...
Common conduit, 13... i4 Eve, 14... Flow meter, 1
6... Sample collection point, 18... Analyzer, 21...
・Comparator, 22...Storage device 0

Claims (7)

[Claims] (1) A method for determining which fluid streams of a plurality of fluid streams flowing through each conduit are flowing at varying flow rates, the method comprising: (b) comparing the characteristics of said composite sample with the characteristics of other composite samples obtained from said sampling location at different times; and (c) collecting the characteristics of said composite sample from said sampling location; A method comprising the step of determining from a change in the characteristics which fluid streams are flowing at a changed flow rate. (2) The method according to claim 1, wherein the characteristics of the sample consist of its value or composition. (3) The method according to claim 1 or I'i2, wherein the characteristic is the concentration or ratio of at least one substance in each mixed sample. 4. The method of claim 3, wherein said fluid stream is any gas stream and said concentration or ratio is determined by chromatography. (5) The step (c) is performed automatically by comparison with a database of fluid flow characteristics. Method. (6) A method according to any one of claims 1 to 5, characterized in that steps (a), (b) and (c) are repeated. (7) The fluid streams enter a common conduit from each conduit, and the sampling points are located at suitable locations to collect a substantially representative sample from the common conduit. The method according to any one of Ranges 1 to 6.