JP4774097B2 - Steam system and control method thereof - Google Patents

Description

  The present invention relates to a steam system and a control method thereof.

  The steam system of a chemical plant includes a boiler that generates steam and a turbine that uses the energy of the steam to provide work to the outside. The boiler uses the exhaust heat from the chemical plant manufacturing process to generate steam, the turbine drives the compressor used in the manufacturing process, and part of the steam generated by the boiler is supplied to the manufacturing process as process steam There is a case. This boiler using exhaust heat is called an exhaust heat boiler.

  When the turbine stops due to a trip, the manufacturing process stops, so the exhaust heat boiler stops generating steam. Even when the manufacturing process is stopped, it is necessary to continue to supply process steam to protect the chemical plant. For this reason, the steam system includes an auxiliary boiler that generates steam without depending on exhaust heat from the manufacturing process.

Patent document 1 is disclosing the control method of the turbine bypass valve at the time of a turbine trip.
JP 59-185808 A

  An object of the present invention is to provide a steam system and a control method thereof that require a small number of boilers.

  Hereinafter, means for solving the problem will be described using the numbers used in (Best Mode for Carrying Out the Invention). These numbers are added to clarify the correspondence between the description of (Claims) and (Best Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

  The steam system according to the present invention includes a first high-pressure header (21A), a first boiler (23A) for supplying steam to the first high-pressure header, a first low-pressure header (22A), and the first high-pressure header. The first turbine (24A) provided between the side header and the first low-pressure header and the flow rate of steam supplied from the first low-pressure header to the outside (10A) are controlled to the first flow rate set value. The first supply valve (33A), the second low-pressure header (22B), the auxiliary boiler (30) for supplying steam to the second low-pressure header, and the pressure of the second low-pressure header are set to the pressure set value. The auxiliary boiler controller (60) for controlling the amount of steam supplied from the auxiliary boiler to the second low-pressure header is connected to the first low-pressure header and the second low-pressure header. 1 line (40 A first check valve (41) provided in the first line, a pressure control valve (42) provided in the first line, the first low-pressure header and the second low-pressure header. , A second check valve (51) provided in the second line, and a flow control valve (52) provided in the second line. The first boiler stops generating steam when the first turbine stops. The first check valve allows the flow of steam from the first low-pressure header to the second low-pressure header along the first line. The opening degree of the pressure control valve is controlled based on the pressure in the first low-pressure header. The second check valve allows the flow of steam from the second low-pressure header to the first low-pressure header along the second line. The flow rate control valve controls the flow rate of steam flowing through the second line to a third flow rate set value.

  The steam system further includes a flow rate setting value changing unit (57) that changes the third flow rate setting value to the first flow rate setting value in response to the occurrence of a trip of the first turbine.

  The set flow rate changing unit gradually increases the third flow rate set value.

  The steam system further includes a pressure set value changing unit (80) that increases the pressure set value of the auxiliary boiler controller in response to the occurrence of the trip.

  The first boiler generates steam using the exhaust heat of (10A) from the first manufacturing system of the chemical plant. The first turbine drives a first compressor (14A) of the first manufacturing system. The first supply valve controls a flow rate of steam supplied as process steam from the first low-pressure header to the first manufacturing system.

  The steam system control method according to the present invention includes a step in which the first boiler (23A) generates steam supplied to the first high-pressure header (21A), and the first high-pressure header to the first low-pressure header (22A). ) Driving the first turbine (24A) with the steam flowing through, the step of controlling the flow rate of the steam supplied from the first low-pressure header to the outside (10A) to the first flow rate set value, and the auxiliary boiler ( 30) generating steam to be supplied to the second low-pressure header, and steam supplied to the second low-pressure header by the auxiliary boiler so that the pressure of the second low-pressure header becomes a pressure setting value. Controlling the supply amount. A first line (40) connecting the first low-pressure side header and the second low-pressure side header allows a flow of steam from the first low-pressure side header to the second low-pressure side header, Do not allow flow. The second line (50) connecting the first low-pressure header and the second low-pressure header allows a steam flow from the second low-pressure header to the first low-pressure header, Do not allow flow. The steam system control method includes the step of stopping the generation of steam supplied to the first high-pressure header by the first turbine being stopped, and the pressure in the first low-pressure header. And a step of controlling a flow rate of the steam flowing through the first line and a step of controlling the flow rate of the steam flowing through the second line to a third flow rate set value.

  The control method of the steam system further includes a step of changing the third flow rate set value to the first flow rate set value in response to occurrence of a trip of the first turbine.

  In the step of changing the third flow rate set value to the first flow rate set value, the third flow rate set value is gradually increased.

  The control method of the steam system further includes a step of increasing the pressure set value of the auxiliary boiler controller in response to the occurrence of the trip.

  The first boiler generates steam using exhaust heat from the first production system (10A) of the chemical plant. The first turbine drives a first compressor (14A) of the first manufacturing system. In the step of controlling the flow rate of steam supplied from the first low-pressure side header to the first flow rate set value, the steam supplied from the first low-pressure side header to the first manufacturing system as process steam is controlled. The flow rate is controlled.

  ADVANTAGE OF THE INVENTION According to this invention, the steam system which requires few boilers, and its control method are provided.

  The best mode for carrying out a steam system and a control method thereof according to the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
Referring to FIG. 1, the steam system according to the first embodiment of the present invention includes a steam system 20A, a steam system 20B, an export line 40 connecting the steam system 20A and the steam system 20B, a steam system 20A and And an import line 50 for connecting the steam system 20B.

  The steam system 20A is provided corresponding to the methanol production system 10A. The methanol production system 10A includes a reaction device 11A, a cooler 12A, a purification device 13A, a compressor 14A, and a synthesis device 15A. The steam system 20A supplies steam A as process steam to the reactor 11A. Natural gas that has undergone the necessary pretreatment is supplied to the reactor 11A. The reactor 11A burns a part of natural gas. This heat converts the natural gas into a product gas mainly composed of hydrogen and carbon monoxide. The product gas is cooled by the cooler 12A and then supplied to the compressor 14A. The cooler 12A supplies the heat A taken from the generated gas during the cooling process to the steam system 20A. The heat A is exhaust heat from the methanol production system 10A. The compressor 14A receives work A from the steam system 20A, boosts the generated gas, and supplies it to the synthesizer 15A. The synthesizer 15A synthesizes methanol from the product gas. The purifier 13A purifies methanol into higher-purity methanol.

  The steam system 20B is provided corresponding to the methanol production system 10B. The methanol production system 10B includes a reaction device 11B, a cooler 12B, a purification device 13B, a compressor 14B, and a synthesis device 15B. The methanol production system 10B produces methanol as in the case of the methanol production system 10A. In the process of manufacturing methanol, steam B is supplied as process steam from the steam system 20B to the methanol manufacturing system 10B, and heat B as exhaust heat from the methanol manufacturing system 10B is supplied to the steam system 20B, and work is performed from the steam system 20B. B is provided to the methanol production system 10B.

  The steam systems 20A and 20B will be described with reference to FIG.

  The steam system 20A includes a high-pressure header 21A, a low-pressure header 22A, an exhaust heat boiler 23A, a turbine 24A provided between the high-pressure header 21A and the low-pressure header 22A, a turbine bypass line 25A, and a bypass valve. 27A and 28A, bypass valve controller 67A, turbine valve 36A, turbine valve controller 66A, desuper heater 29A, discharge valve 34A, discharge valve controller 64A, steam supply valve 33A, A steam supply valve controller 63A, a safety valve 31A provided on the high-pressure header 21A, and a safety valve 32A provided on the low-pressure header 22A are provided.

  The exhaust heat boiler 23A generates heat using the heat A and supplies the generated steam to the high-pressure header 21A. The turbine 24A is driven by steam supplied from the high-pressure header 21A, and provides work A for driving the compressor 14A. The turbine valve 36A controls the flow rate of steam supplied from the high-pressure header 21A to the turbine 24A. The turbine valve controller 66A controls the opening degree of the turbine valve 36A based on the pressure of the high-pressure header 21A and the first high-pressure header pressure set value. Part of the steam used to drive the turbine 24A is sent to a condenser (not shown). The remaining steam flows into the low-pressure header 22A via the desuper heater 29A.

  The turbine bypass line 25A is provided to have a parallel relationship with the turbine 24A, and connects the high-pressure header 21A and the low-pressure header 22A. The bypass valve 27A and the bypass valve 28A are provided in the turbine bypass line 25A so as to have a parallel relationship with each other. The bypass valves 27A and 28A bypass the turbine 24A and control the flow rate of steam flowing from the high-pressure header 21A to the low-pressure header 22A. The bypass valve controller 67A automatically controls the opening degree of the bypass valves 27A and 28A based on the pressure of the high-pressure header 21A and the pressure of the low-pressure header 22A. The bypass valve controller 67A bypasses based on the pressure of the high pressure side header 21A and the first bypass control high pressure side pressure set value, and on the basis of the pressure of the low pressure side header 22A and the first bypass control low pressure side pressure set value. The opening degree of the valves 27A and 28A is automatically controlled. For example, the bypass valve controller 67A obtains the opening operation amount based on the pressure of the high pressure side header 21A and the first bypass control high pressure side pressure set value, and the pressure of the low pressure side header 22A and the first bypass control low pressure side pressure. The opening operation amount is obtained based on the set value, and the opening amounts of the bypass valves 27A and 28A are controlled based on the opening operation amount indicating the larger opening amount.

  The discharge valve 34A controls the flow rate of the steam flowing out from the low-pressure header 22A. The discharge valve controller 64A automatically controls the opening degree of the discharge valve 34A based on the pressure of the low-pressure header 22A and the first low-pressure header discharge valve pressure setting value.

  The steam supply valve 33A controls the flow rate of the steam A supplied from the low-pressure header 22A to the reactor 11A. The steam supply valve controller 63A automatically controls the opening of the steam supply valve 33A so that the flow rate of the steam A matches the steam A flow rate set value.

  The steam system 20B includes a high-pressure header 21B, a low-pressure header 22B, an exhaust heat boiler 23B, a turbine 24B provided between the high-pressure header 21B and the low-pressure header 22B, a turbine bypass line 25B, and a bypass valve. 27B and 28B, bypass valve controller 67B, turbine valve 36B, turbine valve controller 66B, desuperheater 29B, discharge valve 34B, discharge valve controller 64B, steam supply valve 33B, A steam supply valve controller 63B, a safety valve 31B provided on the high-pressure header 21B, and a safety valve 32B provided on the low-pressure header 22B are provided.

  The exhaust heat boiler 23B generates steam using the heat B, and supplies the generated steam to the high-pressure header 21B. The turbine 24B is driven by steam supplied from the high-pressure header 21B, and provides work B for driving the compressor 14B. The turbine valve 36B controls the flow rate of steam supplied from the high-pressure header 21B to the turbine 24B. The turbine valve controller 66B controls the opening degree of the turbine valve 36B based on the pressure of the high-pressure header 21A and the second high-pressure header pressure set value. A part of the steam used to drive the turbine 24B is sent to a condenser (not shown). The remaining steam flows into the low-pressure header 22B through the desuper heater 29B.

  The turbine bypass line 25B is provided so as to have a parallel relationship with the turbine 24B, and connects the high-pressure header 21B and the low-pressure header 22B. The bypass valves 27B and 28B are provided in the turbine bypass line 25B so as to have a parallel relationship with each other. The bypass valves 27B and 28B control the flow rate of the steam that bypasses the turbine 24B and flows from the high-pressure header 21B to the low-pressure header 22B. The bypass valve controller 67B automatically controls the opening degree of the bypass valves 27B and 28B based on the pressure of the high-pressure header 21B and the pressure of the low-pressure header 22B. The bypass valve controller 67B bypasses based on the pressure of the high pressure side header 21B and the second bypass control high pressure side pressure set value, and on the basis of the pressure of the low pressure side header 22B and the second bypass control low pressure side pressure set value. The opening degree of the valves 27B and 28B is automatically controlled. For example, the bypass valve controller 67B obtains the opening operation amount based on the pressure of the high-pressure header 21B and the second bypass control high-pressure pressure setting value, and the pressure of the low-pressure header 22B and the second bypass control low-pressure setting. The opening degree operation amount is obtained based on the value, and the opening degree of the bypass valves 27B and 28B is controlled based on the larger opening degree among these opening degree operation amounts.

  The air discharge valve 34B controls the flow rate of steam flowing out from the low-pressure header 22B. The discharge valve controller 64B automatically controls the opening degree of the discharge valve 34B based on the pressure of the low-pressure header 22B and the second low-pressure header discharge valve pressure setting value.

  The steam supply valve 33B controls the flow rate of the steam B supplied from the low-pressure header 22B to the reactor 11B. The steam supply valve controller 63B automatically controls the opening degree of the steam supply valve 33B so that the flow rate of the steam B matches the steam B flow rate set value.

  The steam system 20B includes an auxiliary boiler 30 and an auxiliary boiler controller 60. The auxiliary boiler 30 generates steam supplied to the low-pressure header 22B. The auxiliary boiler 30 supplies steam to the low-pressure header 22B via the check valve 35. The auxiliary boiler 30 generates steam without depending on the heat A or the heat B. The auxiliary boiler controller 60 uses a PI controller to control the amount of steam supplied from the auxiliary boiler 30 to the low-pressure header 22B so that the pressure of the low-pressure header 22B becomes the auxiliary boiler control pressure set value SV60. Control automatically.

  The export line 40 is provided with a check valve 41 and an export valve 42. The check valve 41 allows the flow of steam from the low-pressure header 22A to the low-pressure header 22B and does not allow the reverse flow. The export valve 42 controls the flow rate of steam flowing through the export line 40. The export valve controller 43 automatically controls the opening degree of the export valve 42 based on the pressure of the low-pressure header 22A and the export valve pressure set value.

  The import line 50 is provided with a check valve 51 and an import valve 52. The check valve 51 allows the flow of steam from the low-pressure header 22B to the low-pressure header 22A and does not allow the reverse flow. The import valve 52 controls the flow rate of steam flowing through the import line 50. The import valve controller 53 automatically controls (feedback control) the opening of the import valve 52 so that the flow rate of steam flowing through the import line 50 matches the import valve flow rate setting value.

  The turbine 24A outputs a trip signal PSD indicating whether or not a trip has occurred to the import valve controller 53, the discharge valve controller 64A, the turbine valve controller 66A, and the bypass valve controller 67A.

  The import valve controller 53 will be described with reference to FIG. The import valve controller 53 includes a flow rate set value changing unit 57 and an import valve controller 56. The flow rate set value changing unit 57 includes a signal switch 54 and a rate limiter 55. Based on the trip signal PSD, the signal switching unit 54 converts one of the signal indicating the plant operating flow rate set value SV56-1 (0 t / h) and the signal indicating the plant stop flow rate set value SV56-2 to the rate limiter 55. Output to. The signal switch 54 outputs a signal indicating the plant operation flow rate setting value SV56-1 when the trip signal PSD indicates no trip, and when the trip signal PSD indicates a trip presence, the plant stop flow rate setting value SV56-. 2 is output. The rate limiter 55 outputs a signal indicating the import valve flow rate setting value SV 56 to the import valve controller 56 based on the signal from the signal switch 54. The rate limiter 55 limits the rate of change of the import valve flow rate set value SV56 to be equal to or less than the set rate of change. The import valve controller 56 is an import valve opening manipulated variable indicating the opening of the import valve 52 based on a signal indicating the detected value PV56 of the flow rate of steam flowing through the import line 50 and a signal indicating the import valve flow rate setting value SV56. A signal MV56 is output to automatically control the opening degree of the import valve 52. Here, the plant stop flow rate set value SV56-2 is equal to the steam A flow rate set value. However, when it is necessary to supply steam from the low pressure side header 22A to the reactor other than the reactor 11A when the methanol production system 10A is stopped, the plant stop flow rate set value SV56-2 is larger than the steam A flow rate set value.

  With reference to FIG. 4, control of the steam system when a trip occurs in the turbine 24A will be described. When the trip signal PSD changes from a state indicating no trip to a state indicating a trip, the turbine valve controller 66 closes the turbine valve 36A regardless of the pressure in the high-pressure header 21A. When the turbine 24A stops due to a trip, the generation of steam by the exhaust heat boiler 23A stops.

  In response to the occurrence of the trip, the control mode of the bypass valve controller 67A and the discharge valve controller 64A transitions from the automatic control mode for executing the automatic control to the manual control mode (sequence control mode). The bypass valve controller 67A controls the opening degree of at least one of the bypass valves 27A and 28A to be fully open in the manual control mode. The discharge valve controller 64A controls the opening degree of the discharge valve 34A to be fully open. Thereby, the pressure rise of the high-pressure header 21A and the low-pressure header 22A is suppressed, and the safety valve 31A and the safety valve 32A are prevented from operating. The manual control mode of the bypass valve controller 67A ends at time T1, and the bypass valve controller 67A returns to the automatic control mode. The manual control mode of the discharge valve controller 64A ends at time T2, and the discharge valve controller 64A returns to the automatic control mode.

  In response to the occurrence of the trip, the signal output from the signal switching unit 54 is switched from a signal indicating the plant operating flow rate set value SV56-1 (0 t / h) to a signal indicating the plant stop flow rate set value SV56-2. For example, the plant stop flow rate set value SV56-2 is equal to the steam A flow rate set value described above. Therefore, the import valve flow rate setting value SV56 increases at a constant rate over time T3 from 0 t / h to the plant stop time flow rate setting value SV56-2, and then maintains that value. This constant change rate matches the set change rate of the rate limiter 55. The time T3 is, for example, 4 minutes. As a result, the flow rate of the steam flowing through the import line 50 from the low-pressure header 22B to the low-pressure header 22A gradually increases from 0 t / h to the flow rate set value SV56-2 at the time of plant shutdown, and then maintains that value. Is done. Here, since the auxiliary boiler controller 60 controls the auxiliary boiler 30 so that the pressure of the low-pressure header 22B becomes the auxiliary boiler control pressure set value SV60, in response to the increase in the flow rate of steam flowing through the import line 50, The amount of steam supplied from the auxiliary boiler 30 to the low-pressure header 22B increases.

  According to this embodiment, it is possible to supply steam A as protective steam from the low-pressure header 22A to the reactor 11A without providing an auxiliary boiler for the low-pressure header 22A. Therefore, the cost can be reduced.

  Here, the setting change rate used by the rate limiter 55 is preferably slower than the follow-up speed of the auxiliary boiler 30 (upper limit value of the rising speed of the steam supply amount). By doing in this way, the pressure fluctuation of the low-pressure header 22A and the low-pressure header 22B is suppressed.

(Second Embodiment)
In the steam system according to the second embodiment of the present invention, the steam system according to the first embodiment is changed so that the auxiliary boiler control pressure set value SV60 increases in response to the occurrence of a trip.

  Referring to FIG. 5, the steam system according to the present embodiment includes a pressure set value changing unit 80 that outputs a signal indicating auxiliary boiler control pressure set value SV60 to auxiliary boiler controller 60. The turbine 24 </ b> A also outputs the trip signal PSD to the pressure set value changing unit 80.

As shown in FIG. 6, the pressure set value changing unit 80 increases the auxiliary boiler control pressure set value SV60 by 1 K / G in response to the occurrence of the trip. Here, “K / G” means “kg / cm ² G”.

  According to this embodiment, the pressure drop of the low-pressure header 22A is suppressed. As a result, since the steam is prevented from flowing from the high-pressure header 21A to the low-pressure header 22A by the automatic control of the bypass valve controller 67A, the pressure drop of the high-pressure header 21A is also suppressed.

(Third embodiment)
In the steam system according to the third embodiment of the present invention, a header whose set pressure is lower than that of the low-pressure header 22A is added to the steam system according to the first or second embodiment.

  Referring to FIG. 7, the steam system 20A includes a low-pressure header 70 whose set pressure is lower than that of the low-pressure header 22A. In the present embodiment, the low-pressure header 22A is referred to as a medium-pressure header 22A. The low-pressure header 70 and the intermediate-pressure header 22A are connected by a line 71. The line 71 is provided with a valve as necessary. The low-pressure header 70 is provided with a safety valve 72 and an air discharge valve 73. A turbine may be provided between the intermediate pressure side header 22A and the low pressure side header 70 as necessary.

(simulation result)
The simulation result about the steam system which concerns on 1st and 2nd embodiment is demonstrated below.

  8 to 11 show simulation results for the steam system according to the first embodiment.

  FIG. 8 shows a change in the pressure of the high-pressure header 21A after a trip occurs. The pressure of the high-pressure header 21A is maintained at a pressure set value of −10 K / G or more. Here, the pressure setting value is the first high-pressure header pressure setting value.

  FIG. 9 shows changes in the pressure of the low-pressure header 22A and the low-pressure header 22B after a trip occurs. The pressure change of the low-pressure header 22A is indicated by a circle symbol, and the pressure change of the low-pressure header 22B is indicated by an X symbol. The pressures of the low-pressure header 22A and the low-pressure header 22B are slightly lower than the pressure set value −0.5 K / G about 300 seconds after the trip occurs, but are generally kept at the pressure set value −0.5 K / G or more. Here, the pressure setting value of the low pressure side header 22A is the first bypass control low pressure side pressure setting value, and the pressure setting value of the low pressure side header 22B is the second bypass control low pressure side pressure setting value. In this simulation, the first bypass control low pressure side pressure set value and the second bypass control low pressure side pressure set value are equal.

  FIG. 10 shows a change in the steam flow rate of the import line 50 after the occurrence of a trip. The steam flow rate of the import line 50 is controlled according to the import valve flow rate setting value SV56.

  FIG. 11 shows the change in the flow rate of the steam A after the occurrence of a trip. The required flow rate of the steam A is ensured except for a short period immediately after the occurrence of the trip.

  12 and 13 show simulation results for the steam system according to the second embodiment.

  FIG. 12 shows a change in the pressure of the high-pressure header 21A after a trip occurs. In the second embodiment, the pressure of the high-pressure header 21A is maintained at a higher pressure than in the first embodiment.

  FIG. 13 shows a change in the pressure of the low-pressure header 22A and the low-pressure header 22B after a trip occurs. The pressure change of the low-pressure header 22A is indicated by a circle symbol, and the pressure change of the low-pressure header 22B is indicated by an X symbol. In the second embodiment, the pressures of the low-pressure header 22A and the low-pressure header 22B are maintained at a pressure higher than that in the first embodiment, and it is possible to prevent the pressure from falling below the pressure set value −0.5 K / G. It is.

  Also in the second embodiment, as in the first embodiment, the steam flow rate of the import line 50 is controlled according to the import valve flow rate setting value SV56, and the flow rate of the steam A is necessary except for a short period immediately after the occurrence of the trip. A flow rate is secured.

  The vertical relationship between the pressure set values is, for example, that the first high pressure side header pressure set value is lower than the first bypass control high pressure side pressure set value, and the first low pressure side header discharge is lower than the first high pressure side header pressure set value. The valve pressure set value is low, the export valve pressure set value is lower than the first low-pressure header discharge valve pressure set value, the first bypass control low-pressure side pressure set value is lower than the export valve pressure set value, and the second bypass control high pressure The second high-pressure header pressure setting value is lower than the second high-pressure header pressure setting value, the second low-pressure header pressure setting value is lower than the second high-pressure header pressure setting value, and the second low-pressure header discharge valve pressure setting value The auxiliary boiler control pressure setting value SV60 is lower, the second bypass control low pressure side pressure setting value is lower than the auxiliary boiler control pressure setting value SV60, and the auxiliary boiler control pressure setting value is lower than the first low pressure header exhaust valve pressure setting value. SV60 is low, the first bypass control low pressure side pressure setting value is lower than the auxiliary boiler control pressure setting value SV60, the export valve pressure setting value is lower than the second low pressure side header discharge valve pressure setting value, and the export valve pressure setting value is lower The second bypass control low pressure side pressure set value is low, and before the auxiliary boiler control pressure set value SV60 is increased in response to trip occurrence, the auxiliary boiler control pressure set value SV60 is lower than the export valve pressure set value and responds to trip occurrence. After the auxiliary boiler control pressure set value SV60 is increased, the auxiliary boiler control pressure set value SV60 is higher than the export valve pressure set value. The pressure set value can be appropriately changed within a range in which there is no contradiction in the vertical relationship.

  The steam system according to the above embodiment is not limited to the case where the methanol production system 10A and the steam system 20A are added to the existing methanol production system 10B and the steam system 20B, but also the methanol production system 10A, the steam system 20A, and the methanol production system. The present invention can also be applied to the case where 10B and the steam system 20B are provided simultaneously.

  The steam system which concerns on the said embodiment is applicable also to chemical plants other than a methanol plant. The steam system according to the above embodiment can also be applied to a power plant.

FIG. 1 is a block diagram of a chemical plant to which a steam system according to a first embodiment of the present invention is applied. FIG. 2 is a block diagram of the steam system according to the first embodiment. FIG. 3 shows an import valve controller according to the first embodiment. FIG. 4 is a timing chart for explaining the control method of the steam system according to the first embodiment. FIG. 5 shows a pressure set value changing unit provided in the steam system according to the second embodiment of the present invention. FIG. 6 is a timing chart for explaining a control method of the steam system according to the second embodiment. FIG. 7 shows a medium pressure side header and a low pressure side header according to the third embodiment of the present invention. FIG. 8 shows the pressure change of the high-pressure header in the steam system according to the first embodiment. FIG. 9 shows the pressure change of the low-pressure header in the steam system according to the first embodiment. FIG. 10 shows the steam flow rate change in the import line in the steam system according to the first embodiment. FIG. 11 shows changes in the flow rate of steam A in the steam system according to the first embodiment. FIG. 12 shows the pressure change of the high-pressure header in the steam system according to the second embodiment. FIG. 13 shows the pressure change of the low-pressure header in the steam system according to the second embodiment.

Explanation of symbols

10A, 10B ... Methanol production systems 11A, 11B ... Reactors 12A, 12B ... Coolers 13A, 13B ... Refiners 14A, 14B ... Compressors 15A, 15B ... Synthesizers 20A, 20B ... Steam systems 21A, 21B ... High pressure side headers 22A , 22B ... low-pressure headers 23A, 23B ... exhaust heat boilers 24A, 24B ... turbine (condensate turbine)
25A, 25B ... Turbine bypass lines 27A, 27B, 28A, 28B ... Bypass valves 29A, 29B ... Desuperheater 30 ... Auxiliary boilers 31A, 31B, 32A, 32B ... Safety valves 33A, 33B ... Steam supply valves 34A, 34B ... Air vent Valve 35 ... Check valve 36A, 36B ... Turbine valve 40 ... Export line 41 ... Check valve 42 ... Export valve 43 ... Export valve controller 50 ... Import line 51 ... Check valve 52 ... Import valve 53 ... Import valve controller 54 ... Signal switching unit 55 ... Rate limiter 56 ... Import valve controller 57 ... Flow rate set value changing unit 60 ... Auxiliary boiler controllers 63A, 63B ... Steam supply valve controllers 64A, 64B ... Ventilation valve controllers 66A, 66B ... Turbine valve controllers 67A, 67B ... Bypass valve controller 70 ... To low pressure side Da 71 ... Line 72 ... relief valve 73 ... blow-off valve 80 ... pressure setting value changing portion

Claims (10)

A first high-pressure header,
A first boiler for supplying steam to the first high-pressure header;
A first low pressure side header;
A first turbine provided between the first high-pressure header and the first low-pressure header;
A first supply valve that controls a flow rate of steam supplied from the first low-pressure header to a first flow rate set value;
A second low-pressure header;
An auxiliary boiler for supplying steam to the second low-pressure header;
An auxiliary boiler controller that controls the amount of steam supplied to the second low-pressure header by the auxiliary boiler so that the pressure of the second low-pressure header becomes a pressure set value;
A first line connecting the first low-pressure header and the second low-pressure header;
A first check valve provided in the first line;
A pressure control valve provided in the first line;
A second line connecting the first low-pressure header and the second low-pressure header;
A second check valve provided in the second line;
A flow control valve provided in the second line,
The first boiler stops generating steam when the first turbine stops,
The first check valve allows the flow of steam from the first low-pressure side header to the second low-pressure side header through the first line,
The opening degree of the pressure control valve is controlled based on the pressure in the first low-pressure header,
The second check valve allows the flow of steam from the second low-pressure side header to the first low-pressure side header through the second line,
The flow control valve controls a flow rate of steam flowing through the second line to a third flow rate set value. The steam system according to claim 1, further comprising a flow rate setting value changing unit that changes the third flow rate setting value to the first flow rate setting value in response to occurrence of a trip of the first turbine. The steam system according to claim 2, wherein the set flow rate changing unit gradually increases the third flow rate set value. The steam system according to claim 2, further comprising a pressure set value changing unit that increases the pressure set value of the auxiliary boiler controller in response to the occurrence of the trip. The first boiler generates steam using exhaust heat from the first production system of the chemical plant,
The first turbine drives a first compressor of the first manufacturing system;
The steam system according to any one of claims 1 to 4, wherein the first supply valve controls a flow rate of steam supplied as process steam from the first low-pressure header to the first manufacturing system. Generating steam supplied to the first high-pressure header by the first boiler;
Driving the first turbine with steam flowing from the first high-pressure header to the first low-pressure header;
Controlling the flow rate of steam supplied to the outside from the first low-pressure header to a first flow rate setting value;
Generating a steam supplied to the second low-pressure header by an auxiliary boiler;
Controlling the amount of steam supplied by the auxiliary boiler to the second low-pressure header so that the pressure of the second low-pressure header becomes a pressure setting value,
A first line connecting the first low-pressure header and the second low-pressure header allows a steam flow from the first low-pressure header to the second low-pressure header and allows a reverse flow. Without
A second line connecting the first low-pressure header and the second low-pressure header allows a steam flow from the second low-pressure header to the first low-pressure header and allows a reverse flow. Without
Stopping the generation of steam supplied to the first high-pressure header by the first boiler by stopping the first turbine;
Controlling the flow rate of steam flowing through the first line based on the pressure in the first low-pressure header;
And a step of controlling the flow rate of the steam flowing through the second line to a third flow rate set value. The steam system control method according to claim 6, further comprising a step of changing the third flow rate set value to the first flow rate set value in response to occurrence of a trip of the first turbine. The steam system control method according to claim 7, wherein in the step of changing the third flow rate setting value to the first flow rate setting value, the third flow rate setting value is gradually increased. The method of controlling a steam system according to claim 7 or 8, further comprising a step of increasing the pressure set value of the auxiliary boiler controller in response to the occurrence of the trip. The first boiler generates steam using exhaust heat from the first production system of the chemical plant,
The first turbine drives a first compressor of the first manufacturing system;
In the step of controlling the flow rate of steam supplied from the first low-pressure side header to the first flow rate set value, the steam supplied from the first low-pressure side header to the first manufacturing system as process steam is controlled. The steam system control method according to claim 6, wherein the flow rate is controlled.

Images