JP2006160841A - Method and apparatus for gasifying gas hydrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for gasifying a gas hydrate, capable of effectively utilizing the energy in gasification. <P>SOLUTION: A gas hydrate H is heat-decomposed to form a gas G and water W. From a gasification tank 1 in a high pressure state, the formed gas G in a high-pressure state is fed as a fuel for a gas turbine generator 9. The water W kept at high pressure is withdrawn from the gasification tank 1 containing the formed water W, and its energy is recovered by a water wheel turbine generator 6. The recovered energy is utilized as a driving energy for the heat source pump 13 of a heat exchanger 12. The thus heated water W is returned to the inside of the gasification tank 1 and is used for the heat decomposition of a gas hydrate H. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas hydrate gasification method and gasification apparatus, and more particularly, to a gas hydrate gasification method and gasification apparatus that can effectively use energy in gasification. .

  In recent years, natural gas has a new gas hydrate that has high gas storability and can be transported and stored at normal and low temperatures (about -20 ° C) without the need for extremely low temperatures like liquefied natural gas. It is attracting attention as a means of transportation and storage.

  This gas hydrate is transported, stored, etc. in the form of pellets, powders, etc. When using the stored gas as energy, it is heated and decomposed into gas and water, and the gas generated by this decomposition Is supplied to various devices as an energy source.

  For example, in a device that requires high-pressure gas such as a gas turbine generator, gas hydrate is decomposed in a pressure-resistant vessel to generate gas and water. The produced gas is supplied as it is or with the pressure adjusted (see Patent Document 1).

  In addition, the gas hydrate is decomposed in the pressure vessel, and the product gas in a high pressure state is taken out from the pressure vessel as it is, and the external gas equipment is used by using this high gas pressure without using extra power. There has been proposed a method for conveying the produced gas to the maximum (see Patent Document 2).

Such a gas hydrate is heated and decomposed to generate gas and water, and the inside of the pressure vessel is in a high pressure state. . However, the high-pressure generated water is decompressed from the pressure vessel and discharged as it is, or is decompressed and stored in a storage tank or the like, and has not been used effectively.
Japanese Patent Laid-Open No. 2003-254084 JP 2003-322296 A

  An object of the present invention is to provide a gas hydrate gasification method and a gasification apparatus capable of effectively utilizing energy in gasification.

  In order to achieve the above object, the gas hydrate gasification method of the present invention is the above pressure vessel in which gas and water are generated by heating and decomposing the gas hydrate in the pressure vessel to generate a gas and water. In the gas hydrate gasification method for extracting the generated gas in a high pressure state, the generated water is extracted from the pressure vessel in a high pressure state, and the energy of the extracted high pressure water is recovered by an energy recovery device. It is characterized by doing.

  In addition, the gas hydrate gasification apparatus of the present invention generates a gas and water by heating and decomposing the gas hydrate accommodated therein, and can maintain the inside in a high pressure state, In a gas hydrate gasification apparatus having a gas discharge pipe for taking out the generated gas in a high pressure state, the gas discharge pipe for taking out the generated water in a high pressure state from the pressure vessel and the water discharge pipe An energy recovery device that recovers the energy of high-pressure water is provided.

  According to the gas hydrate gasification method of the present invention, gas and water are produced by heating and decomposing gas hydrate in a pressure vessel, and the gas produced from the pressure vessel in a high pressure state. In the gas hydrate gasification method for taking out water in a high pressure state, the generated water is taken out from the pressure vessel in a high pressure state, and the energy of the taken out high pressure water is recovered by an energy recovery device. Therefore, it is possible to effectively use the energy of water that inevitably becomes a high pressure state. Moreover, by recovering energy, this water is decompressed and post-processing becomes easy.

  According to the gas hydrate gasifier of the present invention, a pressure vessel capable of generating gas and water by heating and decomposing the gas hydrate accommodated therein and maintaining the inside in a high pressure state; In a gas hydrate gasifier equipped with a gas discharge pipe for taking out the generated gas in a high pressure state, a gas discharge pipe for taking out the generated water in a high pressure state from the pressure vessel, and a high pressure state taken out by the water discharge pipe. Since the energy recovery device for recovering the energy of water is provided, it is possible to effectively use the energy of water that is inevitably in a high pressure state in the high pressure pressure vessel. Moreover, by recovering energy, this water is decompressed and post-processing becomes easy.

  Hereinafter, the gas hydrate gasification method and gasification apparatus of the present invention will be described based on the embodiments shown in the drawings. FIG. 1 shows an overall outline of a gas hydrate gasifier.

  Since this gasifier supplies the gas G to the gas turbine generator 9 that requires high-pressure natural gas, the inside of the gasification tank 1 for gasifying the gas hydrate H is in a high-pressure state. Thus, a predetermined amount of water W for heating the gas hydrate H is accommodated.

  Connected to the upper surface of the gasification tank 1 are a hydrate supply pipe 4 connected to a hydrate supply drum 8 for supplying a gas hydrate H, and a gas discharge pipe 10 for supplying a gas G to a gas turbine generator 9. Has been.

  Control valves 4a and 4b are provided in the gas hydrate supply pipe 4 upstream and downstream of the gas hydrate supply drum 8, respectively. The upstream gas hydrate supply pipe 4 is connected to a gas hydrate storage tank (not shown). Yes.

  A water discharge pipe 2 having one end connected to a generated water storage tank 7 installed outside is connected to the bottom of the gasification tank 1, and a water reflux pipe 3 branches from the middle of the water discharge pipe 2 to gas. It is connected to a water spray pipe 11 arranged above the inside of the chemical bath 1.

  The water discharge pipe 2 is provided with a circulation pump 5 and a turbine turbine generator 6 serving as an energy recovery device having control valves 14a and 14b arranged on both sides. The water reflux pipe 3 is provided with a heat exchanger 12 equipped with a heat source pump 13 as a heating means for the gas hydrate H inside the gasification tank 1.

  Control valves 2a, 3a, and 10a are provided in the vicinity of the connection end portions of the water discharge pipe 2, the water reflux pipe 3, and the gas discharge pipe 10 connected to the gasification tank, respectively. 10a and the control valve 4b of the gas hydrate supply pipe 4 are simultaneously closed to bring the gasification tank 1 into a sealed state.

  Hereinafter, a procedure for gasifying the gas hydrate H will be described. A predetermined amount of water W is stored in the gas hydrate supply drum 8, the upstream control valve 4 a is opened, and a predetermined amount of gas hydrate H is supplied from a gas hydrate storage tank (not shown). The valve 4a is closed. Thereafter, the control valve 4 b on the downstream side is opened to supply a predetermined amount of gas hydrate H to the gasification tank 1. By alternately opening and closing the control valves 4a and 4b and the stored water W, it is possible to prevent the gas G from blowing out from the gasification tank 1 in a high pressure state. In the hydrate supply drum 8, for example, water W is replenished from a water reflux pipe 3 described later.

  The supplied gas hydrate H is heated by water W inside the gasification tank 1 and decomposed into gas G and water W. The inside of the gasification tank 1 in a sealed state becomes a high pressure state by the generation of the gas G by this decomposition, that is, gasification. For example, for the gas turbine generator 9 requiring a gas pressure of about 3.0 MPa, the control valve 10a is opened with the gasification tank 1 inside in a high pressure state of about 3.5 MPa, and the gas in this high pressure state is opened. G is supplied as fuel through the gas discharge pipe 10.

  In the gasification tank 1, in addition to the generated gas G, there are water W generated by decomposition and water W that has been heated to remove the heat from the gas hydrate H and has become low in temperature. If the temperature of the water W inside the tank 1 is too low, the gas hydrate H is difficult to gasify. Further, the amount of water in the gasification tank 1 is increased by the generated water W.

  Therefore, the control valve 2 a is opened, water W is taken out from the gasification tank 1 through the water discharge pipe 2, a part of the water W is returned to the water reflux pipe 3 by the circulation pump 5, and the heat source pump 13 is used. While heating in the heat exchanger 12 into which the heat source fluid is sent, other increased water W is stored in the generated water storage tank 7 to keep the amount of water W inside the gasification tank 1 constant. .

  The heated water W is sprayed from the water spray pipe 11 inside the gasification tank 1 through the water reflux pipe 3 opened by the control valve 3a, and is returned to the gasification tank 1 again to be gas hydrate H. Used to warm up.

  In order to keep the water amount inside the gasification tank 1 at a predetermined amount, for example, a water amount sensor is provided inside the gasification tank 1, and the control valves 2a and 14a of the water discharge pipe 2 are detected by the detection signal of the water amount sensor. , 14b is controlled to temporarily store the increased amount of water W in the generated water storage tank 7 installed outside.

  Since the inside of the gasification tank 1 is in a high pressure state, the water W flowing through the water discharge pipe 2 is necessarily in a high pressure state. Thus, the turbine turbine generator 6 is operated using the high-pressure water W to generate power and recover energy. Since the water W used for power generation is depressurized, post-processing is facilitated and stored in the generated water storage tank 7 or is directly discharged to the outside.

  For example, in a gasification apparatus installed in a coastal area, seawater that is a heat source fluid is sent to a heat exchanger 12 by a heat source pump 13, and water W whose temperature has dropped in the gasification tank 1 is heated by heat exchange. The gasification tank 1 is refluxed. In order to heat the gas hydrate H and decompose it into the gas G and the water W, a large amount of heat of about 808 kcal / kg (gas weight) is required. The power consumption of the heat source pump 13 to be fed increases. Therefore, the energy obtained by the turbine turbine generator 6 can be effectively used as the motive energy of the heat source pump 13 to improve the energy efficiency.

  In the embodiment, the turbine turbine generator 6 is provided on the downstream side where the water reflux path 3 of the water discharge pipe 2 is branched, but may be provided on the upstream side. Further, the energy recovered by the turbine turbine generator 6 is not limited to use as power energy of the heat source pump 13 shown in the embodiment, and can be used for other devices.

  Below, when natural gas is supplied to the gas turbine generator 9 at 50 ton / hr, the energy that can be recovered by the present invention is estimated. The weight composition of the gas hydrate H is approximately 13% for natural gas (methane gas) and 87% for water. Therefore, when natural gas is gasified at 50 ton / hr, 335 ton / hr of water is generated. The amount of heat required for gasifying the gas hydrate H is about 808 kcal / kg.

  In the case of gasification by heat exchange with seawater fed by the heat source pump 13, the temperature change of the seawater is about 6 ° C. under a predetermined condition considering the operating conditions of existing similar equipment, and the required amount of seawater is about 6731 tonnes. / Hr, the power required for the heat source pump 13 for sending seawater to the heat exchanger 12 is about 324 kW. On the other hand, when the power that can be recovered by the turbine turbine 6 using the generated water of 335 ton / hr under a predetermined condition, it is about 263 kW. Thereby, the power consumed for gasification becomes about 61 kW (= 324-263).

  From the above results, it can be seen that according to the present invention, 80% or more of the power required for gasification can be recovered and energy can be used effectively.

It is explanatory drawing which shows the whole outline | summary of the gasification apparatus of the gas hydrate of this invention.

Explanation of symbols

1 Gasification tank
2 Water discharge pipe 2a Control valve 3 Water return pipe 3a Control valve 4 Gas hydrate supply pipe 4a, 4b Control valve
5 Circulation pump
6 Turbine turbine generator 7 Generated water reservoir 8 Hydrate supply drum
9 Gas Turbine Generator 10 Gas Discharge Pipe 10a Control Valve 11 Water Spray Pipe 12 Heat Exchanger
13 Heat source pump 14a, 14b Control valve H Gas hydrate
G gas
W Water

Claims (6)

    Gas hydrate gasification method for generating gas and water by heating and decomposing gas hydrate in a pressure resistant vessel, and taking out the generated gas in a high pressure state from the pressure resistant vessel in a high pressure state The gas hydrate gasification method characterized in that the generated water is taken out from the pressure vessel in a high pressure state, and the energy of the taken out high pressure water is recovered by an energy recovery device.   The gas hydrate gasification method according to claim 1, wherein the energy recovered by the energy recovery device is used as gas hydrate heating means in the pressure vessel.   3. The gas hydrate gasification method according to claim 2, wherein the heating means heats a part of the water taken out in the high pressure state by heat exchange and recirculates the water into the pressure vessel.   A pressure vessel capable of generating gas and water by heating and decomposing gas hydrate contained therein, and maintaining the inside in a high pressure state, and a gas discharge pipe for taking out the generated gas in a high pressure state In the gas hydrate gasification apparatus, a gas discharge pipe for taking out the generated water from the pressure vessel in a high pressure state and an energy recovery device for collecting the energy of the high pressure water taken out by the water discharge pipe are provided. A gas hydrate gasifier characterized by the above.   A water reflux path that branches from the water discharge pipe and connects to the pressure vessel, a circulation pump that circulates water through the water reflux path, and water that circulates through the water reflux path and returns to the pressure vessel is added. The gas hydrate gasifier according to claim 4, further comprising a heating means for heating and heating the gas hydrate in the pressure vessel, wherein the energy recovered by the energy recovery device is used for the heating means. .   6. The gas hydrate according to claim 5, wherein the heating means is a heat exchanger that exchanges heat with a heat source fluid sent by a heat source pump, and uses energy recovered by the energy recovery device as power of the heat source pump. Gasifier.

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