Abstract:
A gas turbine system burning heavy-oil modified fuel and a method of operating the gas turbine system, which covers from a stage of modifying heavy oil and producing gas turbine fuel to a stage of operating a gas turbine, including startup, ordinary shutdown and emergency shutdown of the gas turbine. The gas turbine system burning heavy-oil modified fuel comprises a reactor for mixing heavy oil and water to cause reaction, thereby separating and removing a heavy component from the heavy oil, a gas-liquid separator for separating hydrocarbon gas and modified oil obtained in the reactor from each other, a gas turbine combustor for burning the hydrocarbon gas supplied from the gas-liquid separator, and a gas turbine driven by combustion gas produced in the gas turbine combustor. The system further comprises another line for extracting the hydrocarbon gas externally of a relevant system region. The other line is branched from a line for supplying the hydrocarbon gas from the gas-liquid separator to the gas turbine combustor.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a gas turbine system burning heavy-oil modified fuel and a method of operating the gas turbine system. More particularly, the present invention relates to a gas turbine system in which heavy oil is modified by reaction caused upon mixing with water and an obtained light component is burnt as fuel in a gas turbine for electric power generation, and to a method of operating the gas turbine system.  
         [0003]     2. Description of the Related Art  
         [0004]     Heavy oil contains considerable amounts of heavy metals and is not suitable as fuel for a gas turbine to generate electric power. Methods of removing metals from heavy oil for conversion to a useful energy source are therefore proposed so far. One of those methods includes the step of contacting high-temperature and high-pressure water with heavy oil under reaction conditions of not lower than 350° C. and not lower than 20 MPa, thereby decomposing the heavy oil (see, e.g., Patent Document 1; JP,A 2003-49180 (Abstract)). Hydrocarbon gas, a light oil component, a heavy component, and metal compounds, such as metal oxides, are obtained through decomposition of the heavy oil. Among them, the hydrocarbon gas and the light oil component are dissolved in the high-temperature and high-pressure water to obtain modified oil as gas turbine fuel. The metal compounds present in the heavy oil are removed in the form of calcium compounds or by combining them with a trapping agent, e.g., coke.  
       SUMMARY OF THE INVENTION  
       [0005]     Hitherto, many reports have been made regarding methods of modifying heavy oil and gas-turbine power generation systems using modified oil as fuel while discussing them as separate issues. There are however few reports regarding a system including a heavy oil modifying line and a gas-turbine power generation line in a combined manner.  
         [0006]     Controlling the heavy oil modifying line in link with the operation of a gas turbine is very important from the viewpoint of carrying out the modification of the heavy oil and the operation of the gas turbine with safety on a site.  
         [0007]     An object of the present invention is to provide a combined system of a heavy oil modifying line and a gas turbine, in which the gas turbine can be safely operated, including startup, ordinary shutdown, and emergency shutdown.  
         [0008]     To achieve the above object, the present invention provides a gas turbine system burning heavy-oil modified fuel, the system comprising a reactor for mixing heavy oil and water to cause reaction, thereby separating and removing a heavy component from the heavy oil; a gas-liquid separator for separating a light component obtained in the reactor into hydrocarbon gas and modified oil; a line for supplying the hydrocarbon gas separated by the gas-liquid separator to a gas turbine combustor; the gas turbine combustor for burning the hydrocarbon gas supplied through the line; a gas turbine driven by combustion gas produced in the gas turbine combustor; and another line for extracting the hydrocarbon gas separated by the gas-liquid separator externally of a relevant system region before the separated hydrocarbon gas is supplied to the gas turbine combustor.  
         [0009]     In the present invention, the gas turbine system may further comprise a modified oil tank for storing the modified oil separated by the gas-liquid separator. The modified oil tank preferably has a capacity enough to store the modified oil in amount required for operating the gas turbine by using the modified oil stored in the modified oil, as fuel, during a period from startup of the reactor to a time when the hydrocarbon gas is produced in the gas-liquid separator.  
         [0010]     The hydrocarbon gas extracted externally of the relevant system region before being supplied to the gas turbine combustor can be used to produce heating gas for heating the reactor.  
         [0011]     The present invention also provides a method of operating a gas turbine system burning heavy-oil modified fuel, the method comprising the steps of mixing heavy oil and water in a reactor to cause reaction, thereby producing a heavy component and a light component; separating the light component per phase of gas and liquid into hydrocarbon gas and modified oil; and operating a gas turbine by using the separated hydrocarbon gas as fuel, wherein the method further comprises the steps of stopping supply of the hydrocarbon gas as fuel to the gas turbine at the time of stop of the operation of the gas turbine and extracting the hydrocarbon gas supplied from the reactor externally of a relevant system region.  
         [0012]     In the method of operating the gas turbine system, the modified oil obtained by subjecting the light component to the gas-liquid separation may be stored and used as the gas turbine fuel at startup of the gas turbine during a period until the hydrocarbon gas is produced in the reactor and the gas-liquid separator.  
         [0013]     Further, a process for stopping the operation of the reactor may be started after detecting a level of the modified oil in a tank at the time of stop of the operation of the gas turbine and confirming that the liquid level in the tank is enough to provide fuel in amount consumed by the gas turbine during the period until the hydrocarbon gas is produced in the reactor and the gas-liquid separator.  
         [0014]     According to the present invention, in a system covering processes from modification of heavy oil to generation of electric power, i.e., in a system including stages of reacting heavy oil with high-temperature and high-pressure water to modify the heavy oil and using an obtained light component as main fuel for a gas turbine to generate electric power, it is possible to realize superior operability in startup, ordinary shutdown, emergency shutdown, etc. of the gas turbine.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a diagram of a gas turbine system burning heavy-oil modified fuel according to one embodiment of the present invention;  
         [0016]      FIG. 2  is a flowchart showing a startup method;  
         [0017]      FIG. 3  is a diagram showing a control system for a reactor and a gas-liquid separator;  
         [0018]      FIG. 4  is a flowchart showing an ordinary shutdown method; and  
         [0019]      FIG. 5  is a flowchart showing an emergency shutdown method. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     An embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiment.  
       Embodiment  
       [0021]     In this embodiment, a system for mixing heavy oil with water to separate and remove heavy component from the heavy oil and supplying obtained heavy-oil modified fuel to a gas turbine for electric power generation will be described below with reference to  FIG. 1 .  
         [0022]     In this embodiment, heavy oil stored in a heavy oil tank  101  is pressurized by a heavy oil supply pump  31  and is then divided into two lines. The heavy oil in one line is supplied to a heavy oil combustion furnace  74  in which the heavy oil is mixed with air supplied from a blower  36  associated with the heavy oil combustion furnace  74  and is burnt, to thereby produce heating gas  116 . The heavy oil in the other line is supplied through a heavy oil supply valve  25  to a desalination apparatus  10  in which water-soluble impurities, such as sodium, potassium and chlorine, are removed, followed by being stored in a desalinated heavy-oil tank  102 . The desalinated heavy oil in the desalinated heavy-oil tank  102  is pressurized to 10-25 MPa by a desalinated heavy-oil pressurizing pump  32 .  
         [0023]     Water stored in a water tank  100  is pressurized to 10-25 MPa by a water pressurizing pump  30  and is supplied to a water preheater  41 . In the water preheater  41 , the temperature of the pressurized water is raised through heat exchange with modified oil  108  that is obtained as a liquid component after gas-liquid separation performed in a gas-liquid separator  5 . Because the temperature of the modified oil  108  varies in the range of room temperature to about 400° C., the temperature of the pressurized water at an outlet of the water preheater  41  is also changed depending on the temperature of the modified oil  108 .  
         [0024]     The water having the raised temperature and the desalinated heavy oil are mixed with each other into a fluid mixture that is sent to a mixing preheater  42  for heat exchange with the heating gas  116  generated in the heavy oil combustion furnace  74 . The temperature of the fluid mixture at an outlet of the mixing preheater  42  is raised to 430-460° C. by adjusting the opening of a preheater gas-flow adjusting valve  19  and controlling the flow rate of the heating gas  116  supplied to the mixing preheater  42 .  
         [0025]     The fluid mixture preheated to 430-460° C. is supplied to a reactor  1 . The reactor  1  is heated and held in a heated state by supplying the heating gas  116  generated in the heavy oil combustion furnace  74  to a heating furnace  52  surrounding the reactor  1 . The inner temperature and pressure of the reactor  1  are set to 430-460° C. and 10-25 MPa, respectively, by adjusting the opening of a heating furnace gas-flow adjusting valve  20  and controlling the flow rate of the combustion gas supplied to the heating furnace  52 . By setting an average residing time to 1.5-2.5 minutes in terms of density of steam under those temperature and pressure conditions, the heavy oil and the water in the fluid mixture react with each other to become a heavy component and a light component including steam. The light component is carried out of the reactor  1 , and the heavy component is subjected to gravity separation in the reactor  1 . Metals contained in the heavy oil are enriched in the heavy component and are extracted out of the reactor  1  by selectively opening and closing a reactor outlet valve  13  or an under-reactor valve  29  which are disposed in a heavy component extraction line  2 . When the heavy component is extracted through the reactor outlet valve  13 , a liquid level in a heavy component recovery tank  3  is measured. When the liquid level is high, the heavy component is extracted externally of the recovery tank  3  before supplying the extracted heavy component to the recovery tank  3  by opening a heavy component extraction valve  14  and closing the reactor outlet valve  13 . The extracted heavy component is supplied as fuel to the heavy oil combustion furnace  74 . On the other hand, when the heavy component is extracted through the under-reactor valve  29 , the extracted heavy component is directly supplied to the heavy oil combustion furnace  74  to be mixed with air and burnt therein.  
         [0026]     The pressure in the reactor  1  is adjusted by a depressurizing valve  12  and a depressurizer  4 . To reduce pressure variations caused by variations in properties of the light component and the supply amounts of the water and the heavy oil, the opening of the depressurizing valve  12  is adjusted and an orifice is employed in the depressurizer  4  for depressurization. After having been depressurized to 2.5 MPa through the depressurizer  4 , the light component is supplied to the gas-liquid separator  5  where it is separated into hydrocarbon gas  107  containing steam, hydrogen, carbon monoxide, carbon dioxide, hydrocarbon gases (hydrocarbons with the carbon number up to about 15), etc. and modified oil  108  as a liquefied component. The gas-liquid separator  5  has a water spray nozzle  54  through which water stored in the water tank  100  is supplied to the gas-liquid separator  5  after being pressurized by a spray water pump  34 . The temperature in the gas-liquid separator  5  is adjusted by regulating the amount of spray water by a spray water regulator  55 . The temperature in the gas-liquid separator  5  is preferably set to a value at which steam contained in the light component is not liquefied. More specifically, the temperature in the gas-liquid separator  5  is desired to be not lower than a value given by adding the boiling point of water under the pressure of 2.5 MPa in the gas-liquid separator  5 , i.e., 224 ° C., and a temperature drop caused in a line downstream of the gas-liquid separator  5 . If the temperature in the gas-liquid separator  5  is too high, the amount by which the modified oil  108  is evaporated is increased, and the amount of the modified oil  108  remaining as a liquid in the gas-liquid separator  5  is reduced. The modified oil  108  in the form of liquid fuel is used as fuel at the startup of the gas turbine. It is therefore required that the modified oil  108  be stored in a modified oil tank  6  in an amount sufficient for operating the gas turbine at least for a period from the startup of the gas turbine to a time when the modified oil  108  is produced and flows into the modified oil tank  6 . Because a time of about 2-3 hours is taken to raise the inner temperature in the reactor  1  and the mixing preheater  42  to about 450° C., the capacity of the modified oil tank  6  is required to be triple or more the amount of fuel consumed per hour. Also, from the viewpoint of liquefying the hydrocarbon gas and increasing a production rate of the modified oil  108 , the temperature in the gas-liquid separator  5  is preferably set to the lowest possible value within a controllable range at a level higher than the boiling point of water under the pressure in the gas-liquid separator  5 . On the other hand, a further rise of the liquid level in the modified oil tank  6  is suppressed by increasing a production rate of the hydrocarbon gas. Accordingly, when a liquid level in the modified oil tank  6  is high during the ordinary operation, for example, the temperature in the gas-liquid separator  5  may be raised to reduce the amount of the modified oil  108  produced.  
         [0027]     The pressure in the gas-liquid separator  5  is controlled to be held constant by using a gas-liquid-separator pressure adjusting valve  17 . Between the gas-liquid separator  5  and a gas turbine combustor  60 , a line  50  is disposed for supplying the hydrocarbon gas  107  separated by the gas-liquid separator  5  to the gas turbine combustor  60 . The hydrocarbon gas  107  flowing through the line  50  is controlled in flow rate by a hydrocarbon gas flow control valve  16  and then supplied to the gas turbine combustor  60 . In the gas turbine combustor  60 , the supplied hydrocarbon gas  107  is mixed with air compressed by a compressor  62  and is burnt, thus producing combustion gas  114  that drives a gas turbine  61 . Resulting combustion exhaust gas is released to the atmosphere through a stack  53 .  
         [0028]     A liquid level of the modified oil  108  in the gas-liquid separator  5  is measured by a gas-liquid-separator level gauge  73 , and the opening of a liquid level adjusting valve  22  is adjusted so that the liquid level of the modified oil  108  is held constant. The modified oil  108  is extracted from the gas-liquid separator  5  through the liquid level adjusting valve  22  and is supplied to the water preheater  41 . After being cooled in the water preheater  41  to 60° C. through heat exchange with water pressurized by the water pressurizing pump  30 , the modified oil  108  is stored in the modified oil tank  6 . Alternatively, by changing over a ground flare combustion valve  28  to the side communicating with a ground flare  75 , the cooled modified oil  108  is supplied as fuel to the ground flare  75 .  
         [0029]     The modified oil  108  stored in the modified oil tank  6  is pressurized by a modified oil pump  33  and is supplied to the gas turbine combustor  60  while the flow rate of the modified oil  108  is controlled. Like the hydrocarbon gas  107 , the modified oil  108  is mixed with air compressed by the compressor  62  and is burnt, thus producing the combustion gas  114  that drives the gas turbine  61 . Resulting combustion exhaust gas is released to the atmosphere through the stack  53 .  
         [0030]      FIG. 2  is a flowchart showing a startup method. The startup method for the gas turbine system burning the heavy-oil modified fuel will be described below with reference to  FIG. 2  along with  FIG. 1 .  
         [0031]     In the gas turbine system burning the heavy-oil modified fuel, a time of about 2-3 hours is taken to raise the temperature in the reactor  1  for modifying the heavy oil or the temperature in the mixing preheater  42  for heating the heavy oil and water to a predetermined value. If the time of about 2-3 hours is required to start the gas turbine, applications of this system are limited for users desiring output power to be quickly changed. In the present invention, to avoid such a disadvantage, the gas turbine system burning the heavy-oil modified fuel is started in accordance with the following steps.  
         [0032]     In step S 1 , the liquid level of the modified oil  108  stored in the modified oil tank  6  is measured by a modified-oil-tank level gauge  72  to confirm that the modified oil tank  6  stores fuel in amount required by the gas turbine during a period from the startup of the system to the production of the modified oil  108 . Because about 2-3 hours are taken to start the system including the heating of the reactor  1 , etc., the amount of the modified oil  108  necessary for operating the gas turbine  61  for 3 hours or longer has to be stored in the modified oil tank  6 . If the amount of the modified oil  108  necessary for operating the gas turbine  61  for 3 hours or longer is stored in the modified oil tank  6 , the startup process advances to step S 2 , and if not so, it advances to step S 3  to produce the modified oil  108  while skipping step S 2 .  
         [0033]     In step S 2 , the modified oil  108  stored in the modified oil tank  6  is supplied as fuel to the gas turbine combustor  60  by the modified oil pump  33 . The gas turbine  61  is thereby started to start generation of electric power in a similar manner to that in an ordinary gas turbine system burning liquid fuel.  
         [0034]     In step S 3 , the heavy oil in the heavy oil tank  101  is supplied to the desalination apparatus  10  by the heavy oil supply pump  31  for removal of alkali metals such as sodium and potassium, alkali earth metals such as magnesium and calcium, and halogens such as chlorine and fluorine, which are mixed in the heavy oil. The desalinated heavy oil is stored in the desalinated heavy-oil tank  102 . The amount of the desalinated heavy oil stored in the desalinated heavy-oil tank  102  is not specified to a particular value. If the processing capacity of the desalination apparatus  10  exceeds the amount of fuel consumed by the gas turbine per hour, the startup process can advance to step S 4  at the same time when the desalinated heavy oil starts to be produced. As an alternative, it is also possible to advance the startup process to step S 4  at the same time when the heavy oil supply pump  31  is started, by always storing the desalinated heavy oil in the desalinated heavy-oil tank  102  in such an amount as enabling the gas turbine to be operated for the time required to heat the reactor  1  to the predetermined temperature, i.e., for about 2-3 hours. Further, in the case of purchasing the heavy oil that is already desalinated, the desalination apparatus  10 , the heavy oil tank  101 , and the heavy oil supply pump  31  can be dispensed with, and it is just required to store the desalinated heavy oil in the desalinated heavy-oil tank  102 .  
         [0035]     In step S 4 , the heavy oil combustion furnace  74  is started to generate the heating gas  116  for heating the reactor  1  and the mixing preheater  42 . The heavy oil extracted from the heavy oil tank  101  is pressurized by the heavy oil supply pump  31  and is supplied to the heavy oil combustion furnace  74  while the flow rate of the heavy oil is adjusted by a heavy-oil flow adjusting valve  26 . In the heavy oil combustion furnace  74 , the heavy oil is mixed with air supplied from the blower  36  associated with the heavy oil combustion furnace  74  and is burnt, to thereby produce the heating gas  116 . The temperature of the heating gas  116  is adjusted to about 525° C. by controlling the amount of air supplied from the heavy-oil combustion furnace blower  36 . From the viewpoint of shortening the startup time, it is preferable to raise the temperature of the heating gas  116  for increasing a temperature rising rate. However, a lower temperature is preferable in consideration of a corrosion rate causing a shortening of the life of the reactor  1  and the mixing preheater  42  and a rate of ash deposition causing a reduction of the heat transfer rate. In other words, if vanadium and sodium in the heavy oil form composite oxides, there is a possibility that those composite oxides are liquefied at temperatures near 525° C. and ash deposition progresses on external surfaces of heat transfer pipes of the mixing preheater  42  and an external surface of the reactor  1 . For that reason, the temperature of the heating gas  116  is preferably not higher than 525° C.  
         [0036]     In order to hold constant the pressure in the heavy oil combustion furnace  74 , a pressure gauge is provided to measure the furnace pressure. The measured furnace pressure is taken into a pressure controller, and the opening of a valve  27  is adjusted in accordance with the pressure information so as to properly regulate the flow rate of the heating gas  116 . As a result, the pressure in the heavy oil combustion furnace  74  can be held constant. The heating gas  116  discharged through the valve  27  is released to the atmosphere via the ground flare  75 .  
         [0037]     In step S 5 , the fluid temperatures in the mixing preheater  42  and the reactor  1  are raised to 430-460° C. by using the heating gas  116  produced by the heavy oil combustion furnace  74  of which operation has been started in step S 4 . The preheater gas-flow adjusting valve  19  is opened for supply of the heating gas  116  to the mixing preheater  42 . At the same time or thereafter, the heating furnace gas-flow adjusting valve  20  is opened, whereupon the heating gas  116  is supplied to the heating furnace  52  for heating the reactor  1 . If the temperature difference between the interiors of the mixing preheater  42  and the reactor  1  and the interior of the heating furnace  52  to be heated by the heating gas  116  is increased, there is a risk that stresses may be concentrated in welds, etc. to such an extent as causing cracks. In particular, a thick wall portion has a possibility that larger stress is generated therein. To avoid such a risk, substantially in match with the start of heating by the heating gas  116 , the water stored in the water tank  100  is supplied to the mixing preheater  42  and the reactor  1  by opening a water supply valve  24  and operating the water pressurizing pump  30  and the desalinated heavy-oil pressurizing pump  32 . The water heated by the mixing preheater  42  is supplied to the reactor  1 , thus heating the reactor  1  from the interior, which also contributes to increasing the temperature rising rate of the reactor  1  that has a large heat capacity.  
         [0038]     The openings of the preheater gas-flow adjusting valve  19  and the heating furnace gas-flow adjusting valve  20  may be fully opened. If temperature adjustment of the heating gas  116  is required, it is also possible to reduce the openings of the preheater gas-flow adjusting valve  19  and the heating furnace gas-flow adjusting valve  20 . As in step S 4 , the opening of the valve  27  is similarly adjusted in step S 5  so that the pressure in the heavy oil combustion furnace  74  is held constant.  
         [0039]     The water supplied to the reactor  1  is extracted from the reactor  1  by opening the under-reactor valve  29  disposed under the reactor  1  and is sprayed to a heavy oil burning zone in the heavy oil combustion furnace  74 , followed by becoming a part of the heating gas  116 . After heating the mixing preheater  42  and the reactor  1 , the water (steam) in the heating gas  116  is released to the atmosphere via the ground flare  75 .  
         [0040]     After confirming that the fluid temperatures in the mixing preheater  42  and the reactor  1  have reached near the critical temperature of water, the startup process advances to step S 5  in which the temperature and pressure in the reactor  1  are adjusted respectively to 430-460° C. and 10-25 MPa, the gas-liquid separator  5  and the water preheater  41  are heated, and the temperature and pressure in the gas-liquid separator  5  are adjusted.  
         [0041]     A thermometer is placed in the outlet of the mixing preheater  42  to measure the fluid temperature in that outlet. The fluid temperature in the outlet of the mixing preheater  42  is taken into a temperature controller, and the temperature controller adjusts the opening of the preheater gas-flow adjusting valve  19  to control the flow rate of the heating gas  116  so that the interior in the outlet of the mixing preheater  42  is held at a predetermined temperature.  
         [0042]     Similarly to the temperature control for the mixing preheater  42 , a thermometer is disposed inside the reactor  1  to measure the fluid temperature therein. The fluid temperature in the reactor  1  is taken into a temperature controller, and the temperature controller adjusts the opening of the heating furnace gas-flow adjusting valve  20  to control the flow rate of the heating gas  116  so that the interior of the reactor  1  is held at a predetermined temperature.  
         [0043]     In step S 6 , before or at the same time as the startup of the water pressurizing pump  30  and the desalinated heavy-oil pressurizing pump  32  in step S 5 , a ground flare blower  37  and a ground flare pump  35  are started in operation to supply the modified oil  108  stored in the modified oil tank  6  to the ground flare  75  for burning therein. The level of the water having been condensed to a liquid in the gas-liquid separator  5  after passing through the mixing preheater  42  and the reactor  1  is measured by the gas-liquid-separator level gauge  73 , and the liquid level in the gas-liquid separator  5  is held constant by adjusting the opening of the liquid level adjusting valve  22  with a liquid level controller. The water having passed through the liquid level adjusting valve  22  is supplied to the ground flare  75  via the ground flare combustion valve  28  (a three-way valve) shifted to a position communicating with the ground flare  75 .  
         [0044]     The water supplied to the ground flare  75  contains a small amount of oil. Therefore, the supplied water is mixed with the modified oil  108  and burnt in the ground flare  75  such that the small amount of oil contained in the water is also burnt.  
         [0045]     In step S 7 , the pressure in the gas-liquid separator  5  is adjusted to about 2.5 MPa and the pressure upstream of the reactor  1  is adjusted to 10-25 MPa by regulating the depressurizing vale  12 . Thus, the pressures in the lines are adjusted to respective setting pressures. A method of controlling the various valves and devices in step S 7  will be described below with reference to  FIG. 3 .  FIG. 3  shows, in enlarged scale, the lines including the reactor  1 , the gas-liquid separator  5 , the gas turbine combustor  60 , and the heavy oil combustion furnace  74 , shown in  FIG. 1 , along with various controllers.  
         [0046]     The fluid mixture of the high-temperature and high-pressure heavy oil and water is supplied to the reactor  1  in which the heavy component is separated for removal. The separated heavy component is recovered into the heavy component recovery tank  3  through the reactor outlet valve  13 . On the other hand, the light component is depressurized through the depressurizing valve  12  and the depressurizer  4  and is then supplied to the gas-liquid separator  5 . In the gas-liquid separator  5 , the light component is separated into a liquid and gas. The level of the separated liquid component is measured by the gas-liquid-separator level gauge  73 , and the measured value is taken into a liquid level controller  121 , and the liquid level is controlled to be held constant by the liquid level adjusting valve  22 . The modified oil having passed through the liquid level adjusting valve  22  is supplied to the modified oil tank  6 . The separated gas component is supplied to the heavy oil combustion furnace  74  through the gas-liquid-separator pressure adjusting valve  17  or supplied to the gas turbine combustor  60  through the hydrocarbon gas flow control valve  16 .  
         [0047]     When the gas turbine  61  is not yet started, the hydrocarbon gas  107  supplied to the gas turbine is directly leaked to the exterior. In that state, therefore, the hydrocarbon gas flow control valve  16  is not opened to block passage of the steam and the hydrocarbon gas  107  through it.  
         [0048]     Variations of the pressure and temperature change the states of the reactor  1  and the gas-liquid separator  5 , thus changing not only a removal rate of vanadium from the heavy oil and a gas-liquid separation ratio of the modified oil, but also the compositions of the modified oil  108  and the hydrocarbon gas  107 . From the limitation in response speed of the pump and controller, it is impossible to control an abrupt change of the fuel composition by changing the flow rate of the modified oil supplied by the modified oil pump  33 . Stated another way, the abrupt change of the fuel composition may impair combustion stability of the gas turbine combustor  60  and may extinguish fire, thus making unstable the operation of the gas turbine  61  to generate electric power. A method of properly controlling the temperatures and pressures in the reactor  1  and the gas-liquid separator  5  will be described below.  
         [0049]     In order to adjust the pressure upstream of the reactor  1  to the setting value (10-25 MPa), a pressure gauge  211  is disposed at the outlet of the reactor  1 , and the measured value is taken into a reactor pressure controller  122 . Then, the reactor pressure controller  122  outputs, to the depressurizing valve  12 , a command for adjusting its opening so as to hold the pressure upstream of the reactor  1  at the setting value. As a result, the pressure upstream of the reactor  1  can be held constant at the setting value.  
         [0050]     Also, in order to adjust the pressure in the gas-liquid separator  5  to the setting value (about 2.5 MPa), a pressure gauge  212  is disposed at the outlet of the gas-liquid separator  5 , and the measured value is taken into a gas-liquid-separator pressure controller  120 . Then, the gas-liquid separator pressure controller  120  outputs, to the gas-liquid-separator pressure adjusting valve  17 , a command for adjusting its opening so as to hold the pressure in the gas-liquid separator  5  at the setting value. As a result, the pressure in the gas-liquid separator  5  can be held constant at the setting value. Further, when the gas turbine  61  is already started, the hydrocarbon gas flow control valve  16  is opened to allow the hydrocarbon gas  107  containing the steam to flow into the gas turbine combustor  60  in which the hydrocarbon gas  107  is burnt. Higher efficiency is obtained in the generation of electric power by burning the hydrocarbon gas  107  in the gas turbine combustor  60  to drive the gas turbine  61  as compared with the case of burning the same in the heavy oil combustion furnace  74 . Therefore, the gas-liquid separator pressure controller  120  controls the hydrocarbon gas flow control valve  16  so that the flow rate of the hydrocarbon gas  107  passing through the gas-liquid-separator pressure adjusting valve  17  is minimized and the flow rate of the hydrocarbon gas  107  supplied to the gas turbine combustor  60  is maximized. In other words, the opening of the gas-liquid-separator pressure adjusting valve  17  is set to zero, and the opening of the hydrocarbon gas flow control valve  16  is decided by the gas-liquid-separator pressure controller  120  such that the measured value of the pressure gauge  212  is held at the setting pressure.  
         [0051]     In order to hold the gas-liquid separation ratio constant and to stabilize the fuel properties, the temperature in the gas-liquid separator  5  is held at constant. In this embodiment, the spray water pump  34  is actuated to spray water through the water spray nozzle  54  so as to hold the temperature in the gas-liquid separator  5  at constant. The liquid temperature in the gas-liquid separator  5  is measured by a thermometer  202 , and the measured temperature value is taken into a gas-liquid-separator temperature controller  123 . The flow rate of the water supplied from the spray water pump  34  is controlled in accordance with a command from the gas-liquid-separator temperature controller  123  so that the internal liquid temperature is not lower than the boiling point of water under the pressure in the gas-liquid separator  5 , thereby adjusting the amount of the spray water. Further, one or both of the temperatures measured by thermometers  201  and  203  are taken into the gas-liquid-separator temperature controller  123 . When there is a possibility that moisture contained in the hydrocarbon gas is condensed at the inlet of the gas turbine combustor  60 , the gas-liquid-separator temperature controller  123  outputs a command for reducing the amount of the water sprayed from the water spray pump  34 .  
         [0052]     If the temperatures and pressures in the reactor  1  and the gas-liquid separator  5  are increased to and stabilized at the setting temperatures and the setting pressures in step S 7 , the startup process advances to step S 8 . In step S 8 , the water supply valve  24  is closed, a desalinated heavy-oil supply valve  18  is opened, and the heavy oil is supplied by operating the desalinated heavy-oil pressurizing pump  32 . When the heavy oil passes through the mixing preheater  42  and the reactor  1 , the temperature in the outlet of the mixing preheater  42  and the temperature in the outlet of the reactor  1  are changed due to the difference in specific heat between the heavy oil and water. Responsively, the openings of the preheater gas-flow adjusting valve  19  and the heating furnace gas-flow adjusting valve  20  are adjusted so that the internal temperatures are adjusted to fall in the predetermined range of 430 to 460° C.  
         [0053]     After confirming that the internal temperatures have become steady, the under-reactor valve  29  is closed and the opening of the reactor outlet valve  13  is increased, thus causing the heavy component  105  to be extracted through the heavy component extraction line  2  and recovered into the heavy component recovery tank  3 . The liquid level in the heavy component recovery tank  3  is controlled such that 0.5-10 wt % of the desalinated heavy oil having been supplied by the desalinated heavy-oil pressurizing pump  32  is extracted as the heavy component  105 . By opening the heavy component extraction valve  14 , the heavy component  105  is supplied to the heavy oil combustion furnace  74  in which it is mixed with air supplied from the heavy-oil combustion furnace blower  36  and is burnt.  
         [0054]     In step S 9 , after confirming that the mixing preheater outlet temperature, the reactor outlet temperature, and the liquid temperature and the gas temperature in the gas-liquid separator have been stabilized, a flow of the modified oil  108  having been supplied to the ground flare  75  through the heat exchange in the water preheater  41  is changed to direct toward the modified oil tank  6  by operating the ground flare combustion valve  28 . For the ground flare  75  for which the supply of the modified oil  108  after being subjected to the heat exchange is stopped, the supply of the modified oil  108  stored in the modified oil tank  6  and the operation of the ground flare blower  37  are also stopped. After confirming that the liquid level in the modified oil tank  6  supplied with the modified oil  108  has elevated, the startup process advances to step S 10 .  
         [0055]     In step S 10 , when the gas turbine  61  is already started, the operation mode shifts to the ordinary operation at once. When the gas turbine  61  is not yet started, the gas turbine  61  is started using the modified oil  108  stored in the modified oil tank  6 , followed by shifting to the ordinary operation. After coming into the ordinary operation, supply of the hydrocarbon gas  107  to the gas turbine combustor  60  is started and all the amount of the hydrocarbon gas  107  is supplied to the gas turbine combustor  60 . The gas turbine system burning the heavy-oil modified fuel is started through the above-described steps.  
         [0056]     An ordinary shutdown method for the gas turbine system burning the heavy-oil modified fuel will be described below. Because the hydrocarbon gas is generated by thermal decomposition of the heavy oil in this system, the generated hydrocarbon gas has to be released from the gas turbine combustor  60  to another place when the gas turbine  61  is stopped. Also, if the heavy oil is left remaining in the mixing preheater  42  and the reactor  1  at high temperatures, there is a possibility that the heavy oil may cause coking and clogging may occur in pipes, etc. in the system. Therefore, the system has to be completely shut down after purging the heavy oil. To that end, the gas turbine system burning the heavy-oil modified fuel is shut down in the ordinary case in accordance with a flowchart shown in  FIG. 4 .  
         [0057]     In step S 1 , the hydrocarbon gas flow control valve  16  is closed and the opening of the gas-liquid-separator pressure adjusting valve  17  is adjusted so that the pressure in the gas-liquid separator  5  is about 2.5 MPa, thereby releasing the hydrocarbon gas  107  to the heavy oil combustion furnace  74 . The gas turbine  61  is thus brought into the state where only the modified oil  108  is burnt.  
         [0058]     If the modified oil  108  remains in the modified oil tank  6  in amount capable of operating the gas turbine for  3  hours or longer, this means that the gas turbine can be immediately started at the next startup of the system. By measuring the liquid level in the modified oil tank  6 , it is confirmed whether the modified oil  108  remains in amount capable of operating the gas turbine for 3 hours or longer. If remains, the shutdown process advances to step S 8  in which the ground flare  75  is started, and if not so, it advances to step S 2  to start the operation for stopping the gas turbine.  
         [0059]     In step S 8 , the modified oil  108  stored in the modified oil tank  6  is supplied to the ground flare  75  by the ground flare pump  35 , in which the modified oil  108  is mixed with air supplied from the ground flare blower  37  and is burnt.  
         [0060]     In step S 9 , the ground flare combustion valve  28  is operated to allow the modified oil  108  to flow toward the ground flare  75 , whereby the modified oil  108  supplied from the gas-liquid separator  5  through the water preheater  41  is introduced to the ground flare  75  and is burnt therein.  
         [0061]     After step S 1  or step S 9 , the operation of stopping the gas turbine  61  is commenced in step  2 . First, the supply of the modified oil  108  stored in the modified oil tank  6  to the gas turbine combustor  60  is stopped in the ordinary shutdown process. At the same time, the modified oil pump  33  is stopped.  
         [0062]     In step S 3 , the liquid level in the modified oil tank  6  is checked again to confirm that the modified oil  108  remains in amount capable of operating the gas turbine for  3  hours or longer. If confirmed, the water supply valve  24  is opened and the desalinated heavy-oil supply valve  18  is closed to stop the supply of the heavy oil, thereby purging the heavy oil, the heavy component  105 , and the modified oil  108  which are remained in the lines including the mixing preheater  42 , the reactor  1 , the gas-liquid separator  5 , and so on. At the same time, the desalination apparatus  10  is stopped to stop the production of the desalinated heavy oil.  
         [0063]     If the ground flare  75  has not been started in step S 8 , the ground flare  75  is started in steps S 10  and S 11  in the same manner as that in steps S 8  and S 9 . If the ground flare  75  has already been started, the shutdown process advances to step S 4 .  
         [0064]     In step S 4 , the heavy oil, the heavy component  105 , and the modified oil  108  remaining in the lines including the mixing preheater  42 , the reactor  1 , the gas-liquid separator  5 , etc. are purged by operating the desalinated heavy-oil pressurizing pump  32  and the water pressurizing pump  30 . To purge the oil components remaining in the lines, the reactor outlet valve  13  is closed and simultaneously the opening of the under-reactor valve  29  is set to such an extent as not lowering the pressure in the reactor  1 , whereby the heavy component  105  is supplied to the heavy oil combustion furnace  74  and is burnt therein.  
         [0065]     By monitoring the combustion temperature of the ground flare  75 , it is confirmed that the modified oil  108  has been replaced with water. Similarly, by monitoring the combustion temperature of the heavy oil combustion furnace  74 , it is confirmed that the heavy component  105  and the hydrocarbon gas  107  have been replaced with water. The steam sole operation in step S 4  is continued until the above two points are confirmed.  
         [0066]     After the end of step S 4 , the operation of cooling the entire system is started in step S 5 . The depressurizing valve  12  is closed to stop the flow toward the line downstream of the gas-liquid separator  5  for cooling it. Also, the preheater gas-flow adjusting valve  19  and the heating furnace gas-flow adjusting valve  20  are closed and the heating gas  116  is released through the valve  27 , thus stopping the supply of the heating gas  116  produced by the heavy oil combustion furnace  74  to the mixing preheater  42  and the reactor  1 .  
         [0067]     In step S 6 , the steam remaining in the lines and containing a small amount of the oil components mixed therein is released for depressurization. The steam cannot be directly released to the atmosphere because of containing the small amount of the oil components. Therefore, the under-reactor valve  29  is opened, whereby the steam flows into the heavy oil combustion furnace  74  and the pressure in the reactor  1  is dropped to a level about twice that in the heavy oil combustion furnace  74 . After confirming the drop of the pressure in the reactor  1 , the supply of the heavy oil to the heavy oil combustion furnace  74  is stopped in step S 7  and the heavy-oil combustion furnace blower  36  is also stopped. As a result, the heavy oil combustion furnace  74  is stopped and all the lines are completely shut down. The ordinary shutdown of the system can be performed through the above-described steps.  
         [0068]     An emergency shutdown method for the gas turbine system burning the heavy-oil modified fuel will be described below. Because the hydrocarbon gas is generated by thermal decomposition of the heavy oil in this system, the generated hydrocarbon gas has to be released from the gas turbine combustor  60  to another place at the same time as when the gas turbine  61  is stopped. Also, as in the ordinary shutdown, if the heavy oil is left remaining in the mixing preheater  42  and the reactor  1  at high temperatures, there is a possibility that the heavy oil may cause coking and clogging may occur in pipes, etc. in the system. Therefore, the system has to be completely shut down after purging the heavy oil. To that end, the gas turbine system burning the heavy-oil modified fuel is shut down in the emergence case in accordance with a flowchart shown in  FIG. 5 .  
         [0069]     In the emergency shutdown, the gas turbine  61  is emergently stopped in step S 1 . In step S 2 , the hydrocarbon gas flow control valve  16  is closed to emergently cut off the fuel, and the modified oil pump  33  is stopped to stop the supply of the modified oil  108  from the modified oil tank  6 . At that time, the opening of the gas-liquid-separator pressure adjusting valve  17  is adjusted so as to emergently release the hydrocarbon gas  107  to the heavy oil combustion furnace  74 .  
         [0070]     After step S 2 , the emergency shutdown process is executed through the same steps as those in the ordinary shutdown process, whereby the system can be safely shut down.  
         [0071]     According to this embodiment, in the gas turbine system burning heavy oil as fuel, it is possible to eliminate restrictions imposed on the operation of the gas turbine, which are caused by a time delay until the modified oil is produced in the heavy oil modifying line and a time delay until the heavy oil is purged, and to perform the startup and shutdown of the system in a smooth and quick manner. Further, the system can be safely shut down in both the cases of the ordinary shutdown and the emergency shutdown.  
         [0072]     Thus, since the system including the heavy oil modifying line and the gas-turbine electric power generating line can be safely operated including the startup, the ordinary shutdown and the emergency shutdown, the present invention is applicable to a wide range of fields with very valuable advantages.