JP2011006576A - Emergency shutdown system for gasification facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emergency shutdown system for a gasification facility capable of sensing generation of a fault in an early stage in a gasification facility so as to assure safety from the initial stage of the fault generation.SOLUTION: The emergency shutdown system for a gasification facility comprises a material blocking means 7 for blocking supply of a material (organic substance) to a gasification furnace 2, an oxygen meter 8 for measuring the oxygen concentration in gas piping 4, a gas holder 12 provided midway of the gas piping, a flare stack 9 branched from the gas piping, and a gas blocking means 13 for blocking supply of a gasified combustible gas to a gas user.

Description

  The present invention is obtained by gasifying a substance containing organic matter such as coal, pitch, oil coke, waste oil, biomass such as organic sewage sludge and waste wood, waste plastic, general household waste, fiber waste in a gasifier. In a gasification facility that transfers flammable gas (referred to as “gasification flammable gas” in the present invention) to a gas usage destination through a gas pipe, when an abnormality occurs, the gasification flammable gas is transferred to the gas usage destination. And an emergency stop device for a gasification facility that shuts down the gasification facility in an emergency.

  In recent years, the need for depletion of petroleum resources and reduction of carbon dioxide emissions has been increasing as attention has been focused on resource problems and environmental problems. For this reason, biomass utilization and waste recycling are being promoted as alternative energy for fossil fuels. Alternative technologies for fossil fuel include processing natural fiber and starch into ethanol, processing waste wood and waste plastic into solid fuel (RPF), converting waste plastic into hydrocarbon oil, waste wood, sewage Methods such as converting organic sludge and waste plastics into flammable gases and using them in steelmaking facilities such as blast furnaces and coke ovens are being used.

  Among these methods, organic materials such as coal, pitch, oil coke, waste wood, organic waste sludge, waste plastic, general household waste, organic industrial waste such as clothing waste and reinforced plastic, construction waste containing wood, etc. The method (gasification technique) for converting a substance containing flammable gas has an advantage that various organic substances can be used, and there is no problem even if a mixture thereof is used.

  However, particularly when waste such as waste plastic is gasified, since the waste contains a large amount of foreign matter, the supply of raw materials to the gasification furnace may be stopped. In addition, gasified combustible gas obtained by gasification contains a lot of impurities, and the gas processing apparatus for purifying the gasified combustible gas and the impurities adhere to and grow inside the gas piping connecting the devices. It is possible that the gas facility shuts down. Furthermore, there is a possibility that an outside air is mixed by opening holes in the gas pipe due to corrosion or the like, and an explosive gas is generated by mixing gasified combustible gas and oxygen, resulting in an accident. For this reason, in gas facilities that generate and use gasified combustible gas, it is particularly required to stop the facility safely and promptly when an abnormality occurs.

  Conventionally, as an emergency stop device of a gas facility, for example, as described in Patent Document 1, there has been a device provided with a flare stack that burns and diffuses gasified combustible gas when an abnormality occurs.

  However, with the flare stack alone, there is a problem with the safety at the beginning of the abnormality. That is, even if the occurrence of an abnormality is detected, it takes time to switch the gas path to the flare stack side for the combustion and diffusion of the gasified combustible gas. It may lead to an accident. Further, in order to prevent unburned gasified combustible gas from being emitted from the flare stack, it is necessary to always ignite the flare stack, resulting in wasted energy.

  Furthermore, in order not to expand the abnormal situation, it is important to detect the occurrence of the abnormality at an early stage. However, in Patent Document 1, it is assumed that the gasification facility has tripped (completely stopped). There is no means to detect the occurrence of.

JP 2002-22127 A

  The problem to be solved by the present invention is to provide an emergency stop device for a gasification facility that can detect the occurrence of an abnormality in the gasification facility at an early stage and can ensure safety from the beginning of the occurrence of the abnormality.

  The present invention is an emergency stop device for a gasification facility that gasifies organic matter in a gasification furnace and transfers the obtained gasification combustible gas to a gas usage destination through a gas pipe. Raw material shut-off means for shutting off the supply, an oxygen concentration meter for measuring the oxygen concentration in the gas pipe, a gas holder provided in the middle of the gas pipe, a flare stack provided by branching from the gas pipe, and a gas usage destination And a gas shut-off means for shutting off the supply of gasified combustible gas.

  The most important thing in gasification facilities is the inflow of oxygen into the gas piping. In the present invention, an increase in oxygen concentration can be detected at an early stage by providing an oxygen concentration meter that measures the oxygen concentration in the gas pipe.

  When the oxygen concentration rises, it is necessary to shut off the supply of gasified combustible gas to the gas user by the gas shutoff means and to burn and dissipate the gasified combustible gas in the flare stack. The gas piping of the chemical facility has a large diameter, it takes time to shut off, and it takes time to switch the gas path to the flare stack side, so there is a problem in safety at the beginning of the occurrence of an abnormality. In the present invention, a gas holder is provided in the middle of the gas pipe so that gasified gas combustible gas can be stored in the gas holder until the operation of each device for emergency stop is completed. it can.

  Furthermore, in the present invention, by providing a raw material shut-off means for shutting off the supply of the raw material (organic matter) to the gasification furnace, the supply of the raw material can be stopped quickly when an abnormality occurs, and the gasification combustible gas is diffused during an emergency stop. Can be minimized.

  In the present invention, the flare stack is preferably branched from the upstream side of the gas holder. Further, it is preferable that a switching valve is provided at the branching portion so that the flare stack is not used during normal operation but is used only when an abnormality occurs. This saves energy by eliminating the need to ignite the flare stack at all times. The switching valve is preferably configured to operate on the safe side (flare stack side) in the event of a power failure or failure of the control device. In the present invention, since the gas holder is provided in the middle of the gas pipe as described above, safety is ensured even if the activation of the flare stack is delayed. It is also preferable to provide a gas pipe connected to the flare stack from the downstream side of the gas holder in order to dissipate the oxygen-containing gas, the purge gas, and the starting gas before starting up inside the gas holder and in an abnormal state.

  A gas booster is usually installed in the gas piping of a gasification facility for gas transfer. In this case, the oximeter is downstream from the gas booster and upstream from the branch to the flare stack. It is preferable to install on the side. If a gas booster is installed, the upstream side may be negative pressure and the outside air may flow in. However, if an oximeter is installed upstream of the gas booster, it will be between the oximeter and the gas booster. It cannot be detected when there is an inflow of outside air. Further, if the oxygen concentration meter is installed downstream of the branching portion to the flare stack, it cannot be detected that the abnormal situation has been recovered.

  In order to maximize the effect of the gas holder described above, the oxygen concentration meter is preferably installed on the upstream side of the gas holder.

  Furthermore, the oxygen concentration meter has a straight line portion that is at least five times the diameter of the gas pipe from the installation position to the gas booster and has a diameter of 3 of the gas pipe to the branch to the flare stack. It is preferable to install it at a position having a linear portion more than double. This is because there is a possibility that the oxygen concentration cannot be measured correctly because the gas flow drifts before and after the bent part or the branched part of the gas pipe. By having a linear distance of 5 times or more and 3 times or more of the diameter of the gas pipe from the installation position of the oxygen concentration meter to the upstream side and the downstream side, gas mixing is sufficiently promoted, and the oxygen concentration is reduced. Accurate measurement.

  The Reynolds number of the average flow rate of the gasified combustible gas flowing through the gas pipe is preferably 3000 or more. If it is less than 3000, turbulent flow is not sufficiently formed, and mixing may not be sufficiently performed.

  In addition, when the gas pipe for installing the oximeter is not in the vertical direction, the oximeter is preferably installed on the upper surface from the horizontal with respect to the gas pipe. This can prevent impurities and drains in the gasified combustible gas from entering the oxygen concentration meter due to gravity. As a countermeasure against intrusion of impurities into the oxygen concentration meter, the oxygen concentration meter may be purged with an inert gas such as nitrogen.

  The oximeter is preferably optical. In particular, an infrared oximeter is preferred because of its high accuracy. By using an optical oximeter, it is possible to quickly measure changes in the oxygen concentration, detect an abnormality, and quickly stop the gasification facility. Gas analysis methods such as gas chromatography take time, and it is difficult to detect abnormalities quickly.

  In the present invention, it is preferable that the residence time of the gasified combustible gas in the gas holder is 1.2 times or more of the total of the measurement delay time of the oximeter and the operation time of the gas shut-off means. Thereby, it is possible to reliably prevent the gasification combustible gas containing oxygen or the like from being supplied to the gas use destination at the time of emergency stop of the gasification facility. The preferable range of specific residence time is about 15 minutes to 1 hour.

  In the present invention, it is preferable to use a variable volume type gas holder whose internal volume can be changed as the gas holder. By using the variable volume gas holder, the volume is increased during the gas shut-off time, so that the outflow to the downstream side can be prevented even if the generation of gasified combustible gas continues.

  When using a variable volume gas holder, the amount of gasified combustible gas stored in the gas holder is subtracted from the maximum amount stored in the gas holder by the amount of gasified combustible gas that flows into the gas holder within the time required to shut off the gas. It is preferable to control the amount to less than or equal to the above amount. In this way, during normal operation, by allowing the gas holder volume to have a margin equivalent to the amount of storage required for the time required to shut off the gas, the gasified combustible gas can flow out to the downstream side of the gas holder when an abnormality occurs. Can be prevented.

  In the present invention, it is preferable to use a water-seal type gas blocking means as the gas blocking means. Since gasified combustible gas often contains foreign matter such as dust and tar, it is assumed that foreign matter adheres to the gas shut-off means during operation and does not completely close even if the closing operation is performed. If the water seal type gas shut-off means is used, the gas can be shut off completely by the water seal even if the gas shut-off means itself is not completely closed.

  According to the present invention, the occurrence of abnormality in the gasification facility can be detected at an early stage, and the gasification facility can be urgently stopped while ensuring safety from the beginning of the occurrence of the abnormality.

It is a block diagram of the gasification facility to which the emergency stop device of the present invention is applied. It is a figure which shows the installation position of an oxygen concentration meter. It is a figure which shows the driving | running state of a gas holder. It is a figure which shows the structure of a gas interruption | blocking means. It is a figure which shows the emergency stop operation | movement by the emergency stop apparatus of this invention.

  Embodiments of the present invention will be described below based on examples shown in the drawings.

  FIG. 1 is a configuration diagram of a gasification facility to which the emergency stop device of the present invention is applied.

  First, the basic configuration of the gasification facility will be described. In the gasification facility, the organic material as the raw material is supplied from the raw material supply device 1 to the gasification furnace 2 for gasification. Specific examples of the raw material include raw materials containing organic matter such as coal, pitch, oil coke, waste oil, biomass such as organic sewage sludge and waste wood, waste plastic, general household waste, and fiber waste. This is gasified in the gasification furnace 2 and converted into gasified combustible gas.

  Gasification furnace 2 types include shaft type, rotary kiln type, fluidized bed type, etc. Basically, gasification flammable gas is obtained by dry distillation of organic matter or reaction with water vapor or oxygen. It is. For example, in a shaft type gasification furnace, oxygen or air is blown from the bottom of the furnace, the raw material is partially burned in the furnace to generate heat, and the generated heat is heat exchanged with the raw material to perform a pyrolysis reaction. The organic matter is gasified by controlling the gasification reaction.

  The gasified combustible gas thus obtained contains impurities such as dust and tar as well as combustible carbon monoxide, hydrogen, methane, and so on. Then, clean up to a level that can be used at the place where the gas is used by performing a process such as dust removal. The purified gasified gas is pressurized by a gas booster 5 provided in the middle of the gas pipe 4 and sent to a gas use destination by a gas blower 6.

  In such a configuration, the emergency stop device of the present invention shown in FIG. 1 includes a raw material shut-off means 7, an oximeter 8, a flare stack 9, switching valves 10 and 11, a gas holder 12, and a gas shut-off means 13. It consists of.

  The raw material shut-off means 7 operates when the oxygen concentration in the gas pipe 4 measured by the oxygen concentration meter 8 exceeds a specified value, and shuts off the supply of the raw material from the raw material supply device 1 to the gasifier 2. .

  The oxygen concentration meter 8 is installed downstream of the gas booster 5 and upstream of the branching portion 14 to the flare stack. More specifically, as shown in FIG. 2, a straight line portion L1 that is at least five times the diameter D of the gas pipe from the installation position of the oximeter 8 to the gas booster 5 (see FIG. 1). And a straight line portion L2 that is at least three times the diameter D of the gas pipe between the branch portion 14 and the flare stack.

  Returning to FIG. 1, the flare stack 9 is provided to be branched from the gas pipe 4 at the branch portion 14, and burns and diffuses the gasified combustible gas when an abnormality occurs. Switching to the flare stack 9 is performed by the switching valves 10 and 11 and the gas blocking means 13. That is, during normal operation, the switching valve 10 and the gas shut-off means 13 are opened, the switching valve 11 is closed, and the flare stack 9 is not used. On the other hand, when an abnormality occurs, the switching valve 10 and the gas shut-off means 13 are closed, and the switching valve 11 is opened to burn and diffuse the gasified combustible gas from the flare stack 9.

  The gas holder 12 is provided in the middle of the gas pipe 4 on the downstream side of the branch portion 14. The main body of the gas holder 12 shown in FIG. 1 is separated into an upper tank 12a and a lower tank 12b. The upper tank 12a has a bottom surface opened, and the lower tank 12b has a top surface opened. Both the upper tank 12a and the lower tank 12b are steel polygonal pillars or cylindrical containers, and the projected shape onto the ground is such that the upper tank 12a fits inside the lower tank 12b. Water 15 is stored in the lower tank 12b, and the gas storage part of the upper tank 12a is blocked from the outside air by the water 15. As the upper tank 12a moves up and down, the internal volume of the gas holder 12 changes, and the structure is such that an appropriate residence time is always maintained against fluctuations in the gasified combustible gas amount. The residence time is set to be 1.2 times or more of the total of the measurement delay time of the oximeter 8 and the operation time of the gas shut-off means 13.

  Further, as shown in FIG. 3, the storage amount of the gasified combustible gas in the gas holder 12 during normal operation is the gasified combustible gas that flows into the gas holder from the maximum storage amount of the gas holder 12 within the time required to shut off the gas. The amount is controlled to be equal to or less than the amount of gas, that is, the amount obtained by subtracting the amount stored during emergency stop. In this way, by performing the emergency stop ensuring operation that secures the storage amount at the time of emergency stop, it is ensured that gasified combustible gas flows out to the downstream side of the gas holder 12 when an abnormality occurs (at the time of emergency stop). Can be prevented.

  The gas shut-off means 13 shuts off the supply of the gasified combustible gas to the gas use destination when an abnormality occurs. In FIG. 1, a shutoff valve 13a is provided at the bottom of the gas pipe 4 bent into a U shape as shown in FIG. 4, and shutoff water is supplied from the storage tank 13b to the U shaped portion of the gas pipe 4 when the gas is shut off. To seal with water. It is preferable that this water seal height has a margin of 20% or more with respect to the higher operating pressure of the gasifier and the operating pressure of the gas utilization destination. By using the water-sealed gas shut-off means 13 in this way, the gas can be completely shut off by water sealing even if the shut-off valve 13a is not completely closed.

  Next, an emergency stop operation by the emergency stop device of FIG. 1 will be described with reference to FIGS. 1 and 5.

  When the oxygen concentration in the gas pipe 4 measured by the oxygen concentration meter 8 exceeds a specified value, it is determined that an abnormality has occurred and the material blocking means 7 and the gas blocking means 13 are closed, and at the same time, the flare stack 9 is ignited. . After the flare stack 9 is ignited, the switching valve 10 for the gas holder 12 is closed and the switching valve 11 for the flare stack 9 is opened in order to burn and dissipate the gasified combustible gas from the flare stack 9. The reason why the switching operation by the switching valves 10 and 11 is performed after the flare stack 9 is ignited is that the unburned gas is diffused from the flare stack 9 when the switching is completed before the flare stack 9 ignites. Note that broken lines in FIG. 5 represent switching and ignition.

  The amount of gas stored in the gas holder 12 during this series of emergency stop operations and the gas flow rate to the gas use destination are as shown in FIG.

  Operations of the raw material shut-off means 7, the gas shut-off means 13, the flare stack 9, and the switching valves 11 and 12 based on the abnormality detection by the oximeter 8 can be executed by a control device (not shown). Alternatively, it may be executed manually. Further, in addition to the oxygen concentration meter 8, another abnormality detection means may be provided, and when an abnormality is detected by any abnormality detection means, it may be determined that an abnormality has occurred.

DESCRIPTION OF SYMBOLS 1 Raw material supply apparatus 2 Gasification furnace 3 Gas processing apparatus 4 Gas piping 5 Gas pressure | voltage riser 6 Gas blower 7 Raw material interruption | blocking means 8 Oxygen concentration meter 9 Flare stack 10, 11 Switching valve 12 Gas holder 12a Upper tank 12b Lower tank 13 Gas interruption means 13a Shut-off valve 13b Storage tank 14 Branch 15 Water

Claims (9)

  This is an emergency stop device for gasification facilities that gasifies organic substances in a gasification furnace and transfers the resulting gasification combustible gas to a gas user through gas piping, and shuts off the supply of organic substances to the gasification furnace Raw material shut-off means, oxygen concentration meter for measuring oxygen concentration in gas piping, gas holder provided in the middle of gas piping, flare stack provided by branching from gas piping, and gasification to gas use destination An emergency stop device for a gasification facility, comprising gas shut-off means for shutting off the supply of combustible gas.   The emergency stop device for a gasification facility according to claim 1, wherein a switching valve is installed at a branching portion to the flare stack.   The gas booster is installed in the middle of the gas pipe, and the oxygen concentration meter is installed downstream from the gas booster and upstream from the branching portion to the flare stack. Emergency stop device for gasification facilities.   The oximeter has a straight line part that is more than 5 times the diameter of the gas pipe from the installation position to the gas booster and is 3 times the diameter of the gas pipe to the branch to the flare stack. The emergency stop device for a gasification facility according to claim 3, wherein the Reynolds number of the average flow velocity of the gasified combustible gas that is installed at a position having the above straight line portion and flows through the gas pipe is 3000 or more.   The emergency stop device for a gasification facility according to any one of claims 1 to 4, wherein the oxygen concentration meter is optical.   The gas according to any one of claims 1 to 5, wherein a residence time of the gasified combustible gas in the gas holder is 1.2 times or more of a total of a measurement delay time of the oximeter and an operation time of the gas shut-off means. Emergency stop device for chemical facilities.   The emergency stop device for a gasification facility according to any one of claims 1 to 5, wherein the gas holder is a variable volume type gas holder capable of changing an internal volume.   The amount of gasified combustible gas stored in the gas holder is controlled to be equal to or less than an amount obtained by subtracting the amount of gasified combustible gas flowing into the gas holder from the maximum amount stored in the gas holder within the time required for gas cutoff. Emergency stop device for gasification facilities described in 1.   The emergency stop device for a gasification facility according to any one of claims 1 to 8, wherein the gas shut-off means is a water-sealed gas shut-off means.

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