JPS6131042B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the amount of hydrogen produced in a hydrogen production apparatus in which the flow rate of raw material is controlled in accordance with load fluctuations on the outlet side.

Oil refining and petrochemical plants have many hydrogen consuming equipment, and the hydrogen for this is either so-called off-gas discharged from various oil refining and petrochemical equipment, or steam made from hydrocarbons such as naphtha. Manufactured using the re-forming method.

This type of hydrogen production equipment includes a desulfurization device that removes sulfur from the raw material that adversely affects the reforming catalyst, a reformer that adds steam to the raw material in the presence of a catalyst, and a reformer. A decarboxylation device or the like is used to remove carbon dioxide from the purified gas. The amount of hydrogen produced is determined by the load on the hydrogen consuming equipment, but in the past, due to load fluctuations on the consuming equipment, the hydrogen producing equipment could not react quickly and excess hydrogen was released into the flare. Ta. This means that the product is being thrown away, which is an economic loss. In addition, when the load was insufficient, the raw material and steam control valves were opened to respond to the increase in load, but the operating status of the consuming equipment could not be grasped in advance on the hydrogen production equipment side, and the reaction was unpredictable. Since each controller was adjusted in a single loop, only skilled and experienced personnel could operate it.

The present invention has been made in view of the above-mentioned problems, and is designed to detect load fluctuations on the consuming device side using a pressure detector installed at the outlet side of the hydrogen production device, and to control the raw material flow rate according to the load fluctuations. This makes it possible to produce an amount of hydrogen according to the load.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of a hydrogen production apparatus for explaining the present invention. The figure shows an example of a system in which two systems of off-gas are used as raw materials and one system of backup naphtha is added. In the figure, A ₁ and A ₂ are analyzers installed in each raw material flow path. As the analyzer, for example, a gas chromatography analyzer is used. T ₁ to T ₃ are temperature detectors installed in each raw material flow path, P ₁ and P ₂ are pressure detectors, F ₁ to F ₃ are flow rate detectors, V ₁ to V ₃ are control valves, and C ₁ to _C3 is a flow rate controller that adjusts the control valves _V1 to _V3 so that the outputs of the flow rate detectors _F1 to _F3 are constant. CA ₁ to CA ₃ are computing units that calculate the corrected number of carbon moles, total number of moles, etc. in response to outputs from detectors installed in each raw material flow path. The steam carbon molar ratio S/C is calculated based on the outputs of these calculators, and the steam flow rate is controlled so that the S/C is constant. Alternatively, in some cases, control is performed so that the total number of moles remains constant.

The raw materials that have passed through each flow path join together at point A and enter the heating furnace 1. The sulfur content of the raw material heated in the heating furnace 1 is removed in the desulfurization tower 2. The raw material desulfurized in the desulfurization tower 2 reacts with steam in the reforming furnace 3 and is reformed into hydrogen (H ₂ ) and carbon dioxide (CO ₂ ). The reformed gas enters the subsequent decarboxylation device 4, where carbon dioxide gas is removed and it becomes product hydrogen.

P ₃ is a pressure detector set at the outlet of desulfurization tower 2;
C ₄ is a pressure regulator that receives the output of the detector, and the output is sent to the flow regulator C ₁ via a changeover switch SW.
or _C2 as a set value. V ₄ is a control valve provided at the inlet of the reforming furnace 3 , M is an operator that controls the control valve, and V ₅ is a control valve that controls the flow rate of steam supplied to the reformer 3 . Regulating valve _V5 is controlled by a steam flow regulator (not shown). The setting value of such a steam flow rate controller is determined, for example, by the steam carbon molar ratio S/C calculation or the total molar calculation described above.

E ₁ to E ₃ are heat exchangers provided at the outlet of the reforming furnace 3. P ₄ is a pressure detector installed on the outlet side of the product hydrogen, C ₅ is a pressure regulator that receives the output of the pressure detector, V ₆ is a control valve driven by the output of the regulator, and F ₄ is a flare valve. This is a flow rate detector that detects the flow rate of released hydrogen. A portion of the hydrogen outlet side flow path is branched so that a portion of the hydrogen is released to the flare via a control valve _V6 . That is, when the consumption amount on the side of the hydrogen consumption device (not shown) to which produced hydrogen is supplied decreases and the pressure on the outlet side increases,
The pressure is regulated by opening the control valve _V6 .

Reference numeral 5 denotes an arithmetic and control device that receives the outputs of the pressure detector P ₄ and the flow rate detector F ₄ and provides a set value to the operator M so that the hydrogen outlet side pressure becomes constant. As the arithmetic and control device, for example, a microcomputer is used. When the opening degree of the control valve V ₄ at the inlet of the reformer is changed, the pressure at the inlet naturally changes. Pressure detector P ₃ detects this pressure change as a pressure regulator.
Tell _C4 . Pressure regulator _C4 generates a control signal to compensate for this pressure change. SW is a changeover switch that applies the output of the controller as a set value to either the raw material flow rate controller C ₁ or C ₂ .
To explain the operation of the device configured in this way,
It is as follows.

When the hydrogen production device is operating normally, the pressure detected by the pressure detector _P4 is lower than the set value of the pressure regulator _C5 . Therefore, the control valve _V6 driven by the controller is in a closed state. At this time, the output of the flow rate detector _F4 is naturally 0.
Now, assuming that the load on the hydrogen consuming device is lowered and the amount of hydrogen consumed is accordingly lowered, the pressure measurement value of the pressure regulator _C5 gradually increases and eventually exceeds the set value. Thereby, the controller _C5 gives a drive signal to the regulating valve _V6 to open the valve. In this state, the arithmetic and control unit 5 receives the outputs of the pressure detector P ₄ and the flow rate detector F ₄ and, when the conditions are satisfied, subtracts a certain value α from the setting signal MV to the operating device M to set a new setting. value
Let it be MV′. That is, a new set value MV' such that MV'=MV-α (1) is given to the operating device M. When the set value changes from MV to MV′, control valve V ₄ is closed accordingly. When V ₄ is closed, the gas pressure at the reformer 3 outlet decreases.

In this state, a timer built into the arithmetic and control unit 5 starts, waits for the system to stabilize, and then checks the detectors P ₄ and F ₄ again. By repeating such operations, the raw material flow rate is controlled by reducing the load. Although the flow rate of the raw material can be controlled by the above-described operation, the flow rate is throttled by the control valve _V4 , and as a result, the pressure in the earlier stage increases. In order to compensate for this pressure increase, pressure regulator C ₄ is a pressure detector.
Upon receiving the output of P ₃ , a control signal is sent to the controller on the raw material flow path side to change the set value of controller C ₁ or C ₂ ,
The inflow of off-gas should be restricted at the inlet of the device. As a result, the pressure at the outlet of the desulfurization tower 2 is maintained at a normal value. In addition, the changeover switch
The SW is used to select which of the two flow paths is used for base load or variable flow, and when a load fluctuation occurs, it is switched to the flow path for variable flow to increase the desulfurization tower outlet pressure. The flow rate is controlled to be constant.

The flow rate control operation when the load decreases has been described above, but the decrease α in the setting value of the setting device M usually has a value of several percent, and if α is lowered all at once, it will cause a large disturbance to the control system. This makes it difficult to maintain normal operating conditions. Therefore, in the present invention,
A change amount α ₀ per unit time is defined for the change amount α per time, and α and α ₀ can be set from the outside. α, _α0 are input to the arithmetic and control unit 5. The set time n of the built-in timer is automatically calculated from α and _α0 . A relationship as shown in the following equation is established between these.

α=nxα ₀ (2) FIG. 2 is a diagram showing the change mode of α. The vertical axis is the amount of load fluctuation, and the horizontal axis is time. In the figure, T ₁ is the allowable change time and T ₂ is the stability time. As a result of changing α in small increments in this way, hydrogen can be generated in accordance with the load reduction without causing a large disturbance to the control system. Incidentally, if the amount of change α per time is gradually decreased in steps of α ₀ in this way, the pressure regulation system consisting of pressure detector P ₄ , controller C ₄ and controller C ₁ (or C ₂ ) will be reduced. Naturally, control operations will also be affected by this.

Next, a case where the load increases will be explained.
As the load increases, the pressure on the hydrogen outlet side decreases.
Upon receiving the output of the pressure detector _P4 and detecting a pressure drop, the controller _C5 closes the control valve _V6 if it is open. The arithmetic and control unit 5 receives the output of the pressure detector _P4 and checks whether certain conditions are met. If the conditions are met, the setting value of the operating device M is changed to increase the valve opening and the pressure is adjusted. In this case, the operations performed when the load decreased are reversed. That is, the change amount α is added to the set value MV to obtain a new set value MV'. At this time
The relationship between MV′ and MV is as shown in the following equation.

MV'=MV+α (3) Since the amount of change α increases in small increments of step _α0 , hydrogen can be produced in accordance with the increase in load without causing any disturbance to the control system.

By the way, as for the raw material side, a constant amount is supplied regardless of the change in the rear stage, so the pressure up to the desulfurization tower 2 increases or decreases depending on the rear stage. Therefore, in the present invention, when the load increases, the pressure regulator is
The set value output of _C4 is maintained to the controller on the variable load side, and the supplied off gas is increased as the load increases.

In addition, in order to ensure safety, the arithmetic and control unit 5
receives the output of detectors P ₄ and F ₄ at the hydrogen outlet,
If both do not satisfy the predetermined conditions, no setting signal is given to the setting device M, and the operator of the device is notified of this by displaying it on a CRT (not shown).

FIG. 3 is a block diagram showing another embodiment of the present invention, and parts that are the same as those in FIG. 1 are omitted.
In the figure, the same parts as in FIG. 1 are designated by the same numbers. In the apparatus shown in Fig. 1, when a load change occurs, first, the set value of the operating device M is changed to change the amount of raw material supplied to the reforming furnace 3, and the pressure at the hydrogen outlet is adjusted _. A two-stage system is adopted in which the pressure on the desulfurization tower outlet side is adjusted by changing the opening degree by adjusting the flow rate on the raw material flow path side. On the other hand, the device shown in Fig. 3 adds a delay time element to compensate for the delay time, instead of having such a two-stage configuration, and receives pressure changes at the hydrogen outlet. The flow rate of the raw material on the raw material flow path side is directly adjusted using a controller. In the figure, _C10 is a pressure regulator that receives the output of pressure detector _P4 in parallel with _C5 , and the set value of _C10 is set to a slightly lower pressure than the set value of _C5 . The normal operating pressure is regulated by the C ₁₀ setpoint, and hydrogen is released to the flare only when the C ₁₀ setpoint is exceeded and the _C5 setpoint is exceeded. X is a delay element that is combined with the pressure regulator to form a regulator with dead time compensation. For example, Smith's dead time compensation is used as the delay element.

In the above description, the case of two off-gas systems is taken as an example, but the present invention is not limited to this, and any number of systems may be used. Further, the raw material is not limited to off-gas as long as it is a hydrocarbon, and gases such as propane and butane, naphtha, etc. may be used.

As described above in detail, according to the present invention, load fluctuations on the desulfurization equipment side are detected by a pressure detector installed at the exit side of the hydrogen production equipment, and the raw material flow rate is controlled in a predetermined manner according to the load fluctuations. This makes it possible to produce an amount of hydrogen according to the load without causing any disturbance to the control system.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure shows a mode of change in the amount of change α, and FIG. 3 is a configuration diagram showing another embodiment of the present invention. 1... Heating furnace, 2... Desulfurization tower, 3... Reforming furnace,
4... Decarboxylation device, 5... Arithmetic control device, A ₁ ,
A ₂ ... Analyzer, T ₁ ~ T ₃ ... Temperature detector, P ₁ ~ _{P 4}
...Pressure detector, F ₁ ~ F ₄ ...Flow rate detector, C ₁ ~
_C5 ...controller, M...operator, _V1 to _V6 ...control valve, SW...changeover switch, _E1 to _E3 ...heat exchanger.

Claims (1)

[Claims] 1. A desulfurization device that uses hydrocarbons as a raw material and desulfurizes at least the hydrocarbons, a reformer that steam-reforms the desulfurized hydrocarbons, and removes carbon dioxide from the reformed gas. In a method for controlling the amount of hydrogen produced in a hydrogen production device comprising a decarboxylation device, a pressure sensor installed on the outlet side of the hydrogen production device detects changes in the load of a consuming device that consumes the produced hydrogen, and When controlling the raw material flow rate in response to fluctuations, the flow rate is changed in subdivided amounts until a preset amount of change is reached.
A method for controlling the amount of hydrogen produced in a hydrogen production apparatus, characterized in that the flow rate of the raw material is controlled by detecting it with the pressure detector after a predetermined period of time has elapsed. 2 The control of the raw material flow rate detects the pressure on the hydrogen production equipment outlet side with a pressure detector and adjusts the gas flow rate at the desulfurization equipment outlet, and also controls the raw material flow rate on the desulfurization equipment inlet side by changing the pressure of the desulfurization equipment outlet gas. 2. A method for controlling the amount of hydrogen produced in a hydrogen production apparatus according to claim 1. 3. A method for controlling the amount of hydrogen produced in a hydrogen production apparatus according to claim 1, characterized in that the control of the flow rate is control of the flow rate on the inlet side of the desulfurization apparatus with an added delay time element.