JPS63134501A - Method for controlling rate of feeding in hydrogen production apparatus - Google Patents

Abstract

PURPOSE:To prevent the lowering of S/C value (molar ratio of steam/carbon) in the case of load variation, by setting the ratio of the flow rate of steam to that of raw material gas corresponding to the desired S/C value and controlling the flow rate of raw material gas from the set ratio and the flow rate of steam. CONSTITUTION:True flow rate and molar ratio of carbon are calculated by a anthmetic unit W1 which performs temperature and pressure corrections to reduce the flow rate of raw material gas controlled by a flow rate controller FIC1 and measured by a detector Q1 to standard state and performs specific gravity correction when there is a variation in the raw material composition. Separately, true flow rate and molar ratio of steam are calculated by a anthmetic unit W1 which performs temperature and pressure corrections to reduce the flow rate of steam controlled by a flow rate controller FIC2 and measured by a detector Q2 to standard state and the values are transmitted to the arithmetic unit W1 to calculate the S/C value. The ratio of the flow rate of steam to that of the raw material gas corresponding to the S/C value is set and the set level of the flow rate setting device CF2 is increased in the case of increased load to increase the flow rate of steam. The flow rate of the raw material gas is controlled by the set ratio and the flow rate of steam.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling the supply amount in a hydrogen production device that uses hydrocarbons as a raw material and produces hydrogen by steam reforming the raw material gas, and particularly relates to The present invention relates to a method for controlling the supply amount of raw material gas and steam during load fluctuations.

[Conventional technology]

In oil refining or petrochemical plants, so-called off-gas, which is mainly composed of light hydrocarbons such as methane, ethane, and propane, discharged from various oil refining or petrochemical equipment is used as a raw material for hydrogen production by steam reforming of hydrocarbons. is used.

When hydrogen is produced using off-gas as a raw material, the composition, flow rate, etc. of the off-gas generally vary significantly. When the load fluctuates, conventionally the composition of the off-gas at the inlet of the reformer is analyzed using a gas chromatography analyzer, etc., the number of carbon moles in the raw material gas is calculated, and the steam flow rate corresponding to the load is calculated. Condition changes have been made manually. Furthermore, a method for automatically controlling the above-mentioned condition changes has also been proposed. That is, the steam/carbon molar ratio (hereinafter referred to as B10 value) is calculated from the flow rate, temperature, pressure, and composition detectors installed in the raw material gas flow path and the steam flow path, and the BlCj value is calculated based on the steam flow rate and the raw material gas flow rate. This is a method of converting it into a ratio value with the flow rate, and controlling the ratio value, the raw material flow rate, and the amount of system steam (Unexamined Japanese Patent Application Publication No. 2003-2022).
.

[Problems that the invention attempts to solve]

However, in the conventional method described above, the amount of steam is changed according to fluctuations in the raw material flow rate, so when the load increases,
There was a problem in that the zero value decreased and carbon was deposited in the reformer tube, resulting in destruction of the catalyst or damage to the tube.

In other words, the conventional method for controlling the flow rate ratio of two or more types of fluids consists of a master flow control system (main flow control system) and a slave flow control system (slave flow control system). The flow rate is controlled by multiplying by a certain ratio. This method controls the slave flow rate in response to changes in the master flow rate, and the flow rate ratio may temporarily deviate from the desired value due to a delay in the response of the control system, especially a delay in the response of the slave flow control system. K becomes. This phenomenon is such that when the master flow rate increases, the master flow rate>ratio×slave flow rate, and conversely, when the master flow rate decreases, the master flow rate<ratio×slave flow rate.

The above-mentioned problem of carbon precipitation corresponds to the case where raw material gas is introduced into the master flow rate control system and steam is introduced into the slave flow rate control system, which promotes carbon precipitation when the load increases.

On the other hand, a system in which steam is introduced into the master flow rate control system and raw material gas is introduced into the slave flow rate control system does not promote carbon deposition when the load is reduced, and promotion of carbon deposition cannot be avoided in either combination. do not have.

Such problems are not limited to cases where off-gas is used as a raw material, but are always faced when there are variations in the composition and flow rate of hydrocarbons as a raw material.

[Means for solving problems]

In view of the above situation, the present inventors have determined that Bl during load fluctuation.
In order to prevent a decrease in the O value and suppress carbon precipitation, we have investigated various control methods and decided to set a ratio value between the steam flow rate and the raw material gas flow rate that corresponds to the desired BIO value.For example, when the load increases, First, increase the steam flow rate.

Next, the present invention was completed by discovering that by adopting a method of controlling the raw material gas flow tube based on the set ratio value and the steam flow rate, it was possible to change the conditions without reducing the TotoK]810 value.

That is, the gist of the present invention is that in an apparatus for steam reforming raw material hydrocarbons to produce hydrogen, a raw material supply flow path is provided with a
A detector is installed to detect the temperature, pressure, flow rate, and composition of the source gas, and the carbon solubility is calculated from the detected values.On the other hand, a detector is installed in the steam supply flow path to detect the temperature, pressure, and flow rate. , calculate the number of steam moles from the detected value, calculate the force - number of carbon moles and the number of steam moles, calculate the steam/carbon molar ratio (a/a value), and calculate the s
In order to adjust the 7'c value to a predetermined value, a ratio value between the steam flow rate and the blowing gas flow rate corresponding to the S/C value is set, and when the load increases, the steam flow rate is first increased, and then the set ratio value and the steam flow rate are set. A supply amount in a hydrogen production apparatus characterized in that the raw material gas flow rate is controlled by the flow rate, and on the other hand, when the load is reduced, the raw material gas flow rate is first reduced, and then the steam flow rate is controlled by the set ratio value and the raw material gas flow rate. There are several control methods.

Hereinafter, the present invention will be explained in detail.

FIG. 1 is a block diagram showing an example of a hydrogen production apparatus controlled according to the method of the present invention. The structure of the method of the present invention will be explained in sections with reference to FIG.

[1] Control system configuration and individual equipment functions ■ Symbols
Abbreviation F engineering Cn: Flow rate controller (n-/~ko) OPl: Ratio setter OF2: Flow rate setter Wn: Arithmetic unit 'rn: G degree detector (n=/~2) Pn: Pressure detector (n =/~ko) A1: Composition detector Qn: Flow rate detector (n=/~ko) Cvn: Flow rate control valve (n=/~ko) xn: Signal receiving terminal (n=/~ri Yn: Signal Output terminal (n=/~ko) Pv: Process variable (flow rate) Sv: Flow rate set value Het: High signal selector 18IJ: Low signal selector Cn: Computing unit (n;/~) R: Reforming furnace 0: Carbonic acid Also, the broken lines represent signal wiring, and the dashed-dotted lines represent signal paths inside the flow rate controller.

■ Detector functions ("11P1, Ql, AS s
T*, Pl, and Q are installed in the raw material gas flow path and steam flow path to detect the state quantities of each flow path, where T is temperature, P is pressure, Q is flow rate, and A is analyzer (composition). It is. The subscript is /
indicates the raw material gas flow path, and ko indicates the steam flow path. Analyzer A
For example, an infrared analyzer, a gas chromatography analyzer, etc. are used.

■ Arithmetic unit (Wt, W2) Processes the signal output from the detector and outputs the signal necessary for control.

Wl: Raw material gas computing unit Changes in temperature, pressure, and specific gravity of raw gas Calculation of correction coefficient due to motion (fl).

Calculation of corrected flow rate of source gas (Qsx).

Calculation of steam/carbon molar ratio (1310 value).

Steam/carbon molar ratio +7) difference Value detection.

W, calculation unit for Nisteam Correction staff due to changes in steam specific gravity Operation of numbers (f,).

Calculation of corrected steam flow rate (Qss).

■ Flow rate setting device, ratio setting device (OF, , OF,): Flow rate setting device By operating cp when the load is increased or decreased, it is possible to set the flow rate of the entire control system.

OPl: Ratio setting device Steam/carbon molar ratio (s/c value) as the steam/carbon flow rate ratio Setting device converted to . For OPI settings A new S10 value is set.

■ Flow rate controller (F Engineering CIs 5C) F engineering C! : Raw material gas flow rate controller Controls raw material gas flow rate to desired value.

Abnormality diagnosis and abnormality of system component equipment Constant treatment.

710 Okinisimu Flow Controller Control the steam flow rate to the desired value.

Abnormality diagnosis and abnormality of system component equipment Constant treatment.

■ Control valve (cvl, cvl) A valve that directly controls the flow rate of each flow path based on the control signal from the controller (FohFohFox).

CVl: Raw material gas flow rate adjustment valve aV, Nisteam flow rate adjustment valve ■ Reforming furnace (R) A reforming furnace that reforms a mixed gas of raw material gas and steam into hydrogen and carbon dioxide ■ Carbon dioxide removal device (0) Reforming Functions and features of the carbon dioxide removal device [2] control system that removes the carbon dioxide generated in the furnace R■ Correction of the flow rate of the raw gas and calculation of the number of moles (carried out by the computer unit W1) First, the computer unit wl uses a flow rate controller. The true flow rate and the number of carbon moles are calculated by performing temperature and pressure correction to convert the raw material gas adjusted in r-process C1 to the standard state based on the flow rate value at detector q1, and specific gravity correction that occurs when the raw material composition fluctuates. calculate. That is, in order to convert the flow rate value detected by Q, l to the standard state at 0° C./atmospheric pressure, K needs to be corrected if the temperature, pressure, and specific gravity deviate from the design conditions of Ql. If the true flow rate is Qss, and the temperature, pressure, and specific gravity correction coefficients are fl, the following equation holds true. Note that f□ is obtained by calculating the signal of Tl s PI%AI, but the method will be omitted.

Qss = /I x Qt'
(1) Calculation of the number of carbon moles is performed by determining the components of the raw material gas using the general formula On''m+1 for saturated hydrocarbons.

n is the number of carbons], and when the molecular weight of anHsn+Maro is MY, the following formula holds true.

(Atomic weight of carbon)xn+(Atomic weight of hydrogen)X (Jn-
1-J) = MY (2) (2
) By substituting the atomic weight/J of carbon and the atomic weight l of hydrogen into the equation and rearranging the equation, the number n of carbons is expressed by the following equation.

n=(Mw-ko)//Reference □(3) Since n in formula (3) represents the number of carbon per mole, the number of carbon moles c can be calculated by multiplying the total number of moles of the raw material gas by 1. can be found.

0 (-EA〆) = ((MY-x)li days x IF (sand)
-(4) Total number of moles F of the raw material gas shown in equation (4)
To calculate the total number of moles of the raw material gas, the Qsl determined by the formula (1) is divided by the volume of 1 mole in standard conditions of 0° C. and /atmosphere, ≠t.

■ Steam flow rate correction and mole calculation (performed with calculator W!) Calculator W! So, flow rate controller 1 work 0! The true flow rate and steam output are calculated by correcting the temperature and pressure of the steam amount adjusted by the flow rate value at the detector Q2. As with the raw material gas, it is necessary to correct the flow rate value detected at Ks Qs in accordance with the deviation of Q and s from the design conditions. The true flow rate is Q
If sl is the correction coefficient and I is the correction coefficient, then the following equation holds true. In addition,! , is T8, P! The signal is required, but the method is omitted.

Qax = f@X Q,s (
5) Calculation of the number of moles of steam C. Calculate the number of moles of steam Q by dividing by the molecular weight of ass t -A.

Q, (mol) = Q, sl//I
(6>■ Steam/carbon molar ratio (sy
a value) calculation (carried out by calculation unit W1) calculation unit W! The number of steam moles calculated by is calculated by the calculation unit Wt
K is taken in and the steam/carbon molar ratio (E110 value) is calculated.

The steam/carbon molar ratio (S/C value) is determined by the following formula from the number of carbon moles 0 (-v-ru) determined by formula (4) and the number of steam moles Q (mol) determined by formula (6).

8/C= Q (mol)/C (mol) -(7)■
The control operation of the entire flow rate control system will be explained in the next section [3], and here the operation of the aeohyIC will be briefly explained.

The flow rate controller F 0hFIC, is the arithmetic unit W1, W! Flow rate correction coefficient calculated by /, , /, and flow rate detector Q
! s Q4') Calculate Qax and Qsl.

A control signal is output to the flow control valves cvl, ov so that the obtained Qax and QsH become desired values.

(3) Operation of the control system when the load increases or decreases Regarding the operation of the control system when the load increases or decreases, the control system is all stable and the flow rates Qs1, Qax, and steam/carbon molar ratio are controlled to the desired values. The state in which the load changes from increase to decrease will be explained.

(1) Increase in load■ Increase the setting of the flow rate setting device APL. The increase is ΔC
P! shall be.

■ The load increase signal is from cp to F engineering 0! is input to Xs of

■ Is the signal input to Xs of F engineering C, no) signal selector HI3? , +, low signal selector L
BXs are compared respectively.

■ What about HBL? Calculate the raw material gas flow rate and ratio setting value signals output from Yl of IC1, and compare the value obtained by converting the raw material gas flow rate to a steam flow rate with the ap, Yoshi signal, and select the one with the higher signal value. is output as the SV value of the control calculation unit. Therefore, as long as the condition that the output signal of op≧the steam flow rate scale conversion value of the raw material gas flow rate is satisfied, that is, until the output signal of OPm = steam flow rate, the output signal of OPI will be the SV value of the control unit. Increase flow rate.

■ For I and 8L, compare the steam flow rate signal and the output signal of OPm, and select the one with the lower signal value as Yl#)FIC! Output to x4 of 1. Therefore, while the condition that the output signal of CP≧steam flow rate is satisfied, the steam flow rate is output to x4 of Fl- until the output signal of th OPI=steam flow rate.

■The value calculated from the 9 steam flow rate signal input to FFCl2x4 and the ratio value set by the ratio setting device CPS is the SV value of the control calculation unit. To increase.

■ Due to the above operations, when the load increases, the flow rate increases in the following order. ap, increase → steam flow rate increase → source gas flow rate increase.

Therefore, it is possible to increase the load without decreasing the steam/carbon molar ratio.

(2) Reduction of load ■ Decrease the set value of OF.

■ The load reduction signal is F engineering C! XiK is input.

■The X and K input signals of F engineering C, are HBL.

The comparison is made in the same way as when the load increases in LBL.

(2) In LBL, while the condition of output signal 0Pfi≦steam flow rate signal is satisfied, the signal OF is output to x4 from Yl to pPro. Therefore, the 8v value of Fl- decreases and the raw material gas decreases.

■ In H[3I+, as long as the output signal of CP≦the steam flow rate scale conversion value of the raw gas is established, the value obtained by converting the raw gas flow rate to the steam flow rate scale is output as the SV value of F process C. , the steam flow rate decreases only after the raw material gas flow rate decreases.

(3) As shown in the explanation above, PIC! HBL and LBL within
The increase/decrease signal of yICt%F engineering C1 depending on the operation of
By distributing the flow rate to the set flow rate SV, the entire control system can be controlled to a desired flow rate and steam/carbon molar ratio without promoting carbon precipitation.

The point is that HBL always converts the output of CAP and the raw material gas flow rate into a steam flow scale, compares the nine values, and uses the high signal as the SV value for steam flow control calculation.
and XrBX, the output of K OPl and the steam flow rate are compared, and the value obtained by multiplying the low signal by the ratio of OPl is used as the SV value for raw material gas flow rate control calculation.

[4] Abnormality diagnosis and treatment of system component devices - Since the system component devices send and receive signals to each other, even if a problem occurs in seven devices, it will have a large impact on the entire system.

Therefore, in order to quickly detect trouble and switch the entire system to the safe side, it is desirable to automatically perform abnormality diagnosis and its treatment.

FIG. 1 is a block diagram showing a preferred example of such an automatic system for diagnosing and treating abnormalities.

In the system shown in Figure 1, the computing unit "1 s"
Nine correction coefficients are output from the snow: 71. Detects the rate of change of /, and if it exceeds the set value, controller yxct, FIO! is the control mode O, A B (cascade control) during normal operation.
automatically switches to VAN (manual control) mode. In addition, from the controllers FIOt and IFIO, the flow rate control valve cvl,
Since the control signal output to the CV is shifted to the VAN mode with the control signal value at the time when an abnormality in the correction coefficient is detected, there is almost no influence on the process. Here, the rate of change of the correction coefficient (Δf/Δt) is detected using the detector "1 s Pi s At and 'r
, s P* and the arithmetic unit Wl s "This is because they are highly efficient anomaly detection elements that can representatively detect snow anomalies.

〔Effect of the invention〕

According to the present invention, conditions can be changed without reducing the steam/carbon molar ratio (8/C! value) when the raw material gas load fluctuates, so carbon precipitation in the reformer tube can be reduced. Can be suppressed.

[Brief explanation of the drawing]

FIG. 7 is a block diagram showing an example of a hydrogen production apparatus controlled according to the method of the present invention. R: Reforming furnace, C: Carbon dioxide removal device, "1 s" snow: Computing unit, F'xC1, F'IC! :Flow rate controller, O
Pl: Ratio setting device, cp: Flow setting device. FIG. 2 is a block diagram showing an example of an automatic system for diagnosing and treating abnormalities in the control system shown in FIG. 1. Patent applicant Mitsubishi Chemical Industries, Ltd. Agent Patent attorney Hase -tl/name

Claims (1)

[Claims] (1) In an apparatus that produces hydrogen by steam reforming raw material hydrocarbons, a detector is installed in the raw material supply flow path to detect the concentration, pressure, flow rate, and composition of the raw material gas, and from the detected values, carbon On the other hand, the steam supply flow path is equipped with a detector that detects temperature, pressure, and flow rate, and from the detected values, the number of steam moles is calculated, and from the carbon mole number and the steam mole number, the steam / carbon molar ratio (hereinafter abbreviated as S/C value) is calculated, and in order to adjust the S/C value to a predetermined value, a ratio value between the steam flow rate and the raw material gas flow rate corresponding to the S/C value is set. When the load increases, the steam flow rate is first increased, and then the raw material gas flow rate is controlled by the set ratio value and the steam flow rate, while when the load is decreased, the raw material gas flow rate is first decreased, and then the raw material gas flow rate is controlled by the set ratio value and the raw material gas flow rate. A method for controlling the supply amount in a hydrogen production device, characterized by controlling the steam flow rate by.