Abstract:
A system for generating electric power and for producing gasoline from methanol, comprises: a gasoline production apparatus containing a catalyst layer for synthesizing gasoline from methanol, heat generated by the synthesis increasing a temperature of the gasoline production apparatus; a cooling apparatus for cooling the gasoline production apparatus with coolant to vaporize the coolant; and a power generation apparatus for generating electric power using the coolant vapor produced by the cooling apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. application Ser. No. 13/547,272 filed on Jul. 12, 2012. This Application claims priority from Japanese Patent Application No. 2011-156647 filed on Jul. 15, 2011, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a system for generating electric power and for producing gasoline from methanol. 
         [0003]    A catalyst for converting methanol to dimethyl ether (DME) or for converting methanol to gasoline through DME was already known (e.g., Japanese Patent Application Publication No. 50-076027 and Japanese Patent Application Publication No. 51-057688). A synthetic reaction for synthesizing DME or gasoline from methanol using this catalyst needs to be executed at as high a temperature as about 400° C., and because this reaction is an exothermic reaction, it is necessary to continuously cool the reactor in order to maintain the reactor within a predetermined temperature range. 
         [0004]    In addition, Japanese Patent Application Publication No. 10-506668 discloses that reactors having the catalyst for converting methanol to gasoline are provided on a plurality of stages, and by mixing methanol and dilution gas with emission gas product discharged from a reactor on a first stage, mixed gas is generated. Then, the temperature and components of the dilution gas are adjusted to bring the mixed gas into a predetermined temperature range, and this mixed gas is supplied to a reactor on a second stage in order to obtain new emission gas product. 
       SUMMARY OF THE INVENTION 
       [0005]    However, the method described in Japanese Patent Application Publication No. 10-506668 has the following problems: an apparatus for producing gasoline from methanol can become complicated in configuration and increase in scale; and an operation cost for maintaining the reactor within a predetermined temperature range can rise. 
         [0006]    Accordingly, in view of the above-described problems, an object of the present invention is to provide a system for producing gasoline from methanol with generation of electric power, in which, by cooling heat generated due to gasoline synthesis reaction of methanol, electric power is generated, thereby reducing total cost. 
         [0007]    To achieve the above-described object, according to an embodiment of the present invention, there is provided a method for generating electric power and for producing gasoline from methanol, the method including the steps of: synthesizing gasoline by reacting methanol under a catalyst; recovering heat generated from the gasoline synthetic reaction of methanol by cooling the reaction with coolant to vaporize the coolant; and generating electric power by using the coolant vapor produced in the heat recovery. 
         [0008]    The coolant may include water. The coolant vapor may include saturated water vapor. The power generation step may include generating electric power with at least one steam turbine using the saturated water vapor. Furthermore, the power generation step may include generating electric power with a plurality of steam turbines in series, further comprising: generating electric power with a first steam turbine of the plural steam turbines using a part of the saturated water vapor; superheating exhaust steam from the first steam turbine by another part of the saturated water vapor; and generating electric power with a second steam turbine of the plural steam turbines using the superheated exhaust steam. 
         [0009]    According to another aspect of the present invention, there is provided a system for generating electric power and for producing gasoline from methanol, the system including: a gasoline production apparatus containing a catalyst for synthesizing gasoline from methanol, heat generated by the synthesis increasing a temperature of the gasoline production apparatus; a cooling apparatus for cooling the gasoline production apparatus with coolant to vaporize the coolant; and a power generation apparatus for generating electric power using the coolant vapor produced by the cooling apparatus. 
         [0010]    The coolant may include water. The vapor may include saturated water vapor. The power generation apparatus may include at least one steam turbine. Furthermore, the power generation apparatus may include a plurality of steam turbines, the system further including: a line for supplying a part of the saturated water vapor to a first steam turbine of the plurality of steam turbines; a line for supplying exhaust steam from the first steam turbine to a second steam turbine of the plurality of steam turbines; and a superheater for superheating the exhaust steam of the second steam turbine using another part of the saturated water vapor. 
         [0011]    According to the present invention, because heat generated by gasoline synthetic reaction of methanol is cooled with coolant and this reaction occurs at about 400° C., when the coolant is water, it is possible to obtain water vapor of about 100 kg/cm 2 G (saturated at 310° C.). Such vapor enables power generation to be achieved sufficiently and consequently, apparatus cost and operating cost required for the cooling can be transformed to power generation cost. Thus, the system and method which can be expected to ensure a sufficient profit in terms of the total cost for gasoline production and power generation can be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic view showing an embodiment of a system for generating electric power and for producing gasoline according to the present invention; 
           [0013]      FIG. 2  is a schematic view showing another embodiment of a system for generating electric power and for producing gasoline according to the present invention; and 
           [0014]      FIG. 3  is an h-s diagram for steam showing changes in enthalpy and entropy of steam in the system according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in  FIG. 1 , a gasoline production power generation system  1  of the present embodiment includes mainly a reactor  10  for synthesizing gasoline from methanol, and a series of turbines for generating electric power with water vapor used for cooling the reactor, namely, a high-pressure turbine  30 , a medium-pressure turbine  40 , and a low-pressure turbine  50 . 
         [0016]    The reactor  10  synthesizes gasoline from methanol which is a raw material, through reactions shown in the following formulas. 
         [0000]      2CH 3 OH→CH 3 OCH 3 +H 2 O   (formula 1)
 
         [0000]      1/2nCH 3 OCH 3 →(CH 2 )n+1/2nH 2 O   (formula 2)
 
         [0017]    In this way, methanol is converted to gasoline through a dimethyl ether (DME) synthetic reaction shown in formula 1 and a gasoline synthetic reaction shown in formula 2. In the reactor  10 , two kinds of the catalysts, i.e., DME synthetic catalyst and gasoline synthetic catalyst are provided on two stages, so that the two reactions can be progressed in stages. The reactor  10  includes a catalyst layer (not shown) which is filled with these catalysts, and methanol or DME passes through this catalyst layer. As the DME synthetic catalyst, it is permissible to use known catalysts, for example, aluminosilicate type zeolite base catalyst. As the gasoline synthetic catalyst, the known catalysts such as the aluminosilicate type zeolite base catalyst may also be used. These catalysts have been disclosed in detail in Japanese Patent Application Publication No. 50-076027 and Japanese Patent Application Publication No. 51-057688, which are incorporated herein by reference in their entirety. 
         [0018]    The synthetic reaction from methanol to DME is an exothermic reaction and a reaction heat thereof is 185 kcal per methanol of 1 kg. The gasoline synthetic reaction is also an exothermic reaction and a reaction heat thereof is 231 kcal per methanol of 1 kg. Thus, when synthesizing gasoline from methanol, a reaction heat thereof is 416 kcal per methanol of 1 kg. Electric power is generated using this reaction heat. As the condition for DME synthetic reaction, a pressure in a range of 35 to 45 kg/cm 2  is preferred and a temperature in a range of 250 to 300° C. is preferred. As the condition for gasoline synthetic reaction, a pressure in a range of 3 to 8 kg/cm 2  is preferred and a temperature in a range of 380 to 450° is preferred. 
         [0019]    The reactor  10  includes a methanol supply line  12  for supplying methanol to the reactor and a gasoline discharge line  14  for discharging gasoline synthesized by the reactor. The reactor  10  is cooled by coolant to control the temperature of the reactor within the above-described range. The reactor  10  is provided with a flow path (not shown) in which coolant flows along an outer periphery of the catalyst layer (not shown). Although the coolant is not restricted to any particular type as long as it is capable of cooling the reactor  10  within the above-mentioned temperature range, water is preferred. Thus, this system  1  includes a coolant discharge line  16  for discharging water vapor used for cooling the reactor from the reactor, a steam-water separator  20  for separating water vapor used for cooling, and a coolant circulation line  26  for supplying water separated by the steam-water separator to the reactor again. 
         [0020]    This system  1  includes a power generation water vapor line  22  for supplying saturated water vapor separated by the steam-water separator  10  in order to generate electric power with water vapor used for cooling the reactor, a power generation water vapor line  32  for supplying water vapor used for power generation in the high-pressure turbine  30  to the medium-pressure turbine  40 , and a power generation water vapor line  42  for supplying water vapor used for power generation in the medium-pressure turbine  40 , to the low-pressure turbine  50 . Superheaters  34 ,  44  for superheating water vapor whose pressure has been lowered due to the power generation in the turbines are arranged in the power generation water vapor line  32  and the power generation water vapor line  42 , which are located between the turbines. The superheaters  34 ,  44  are provided with superheating water vapor lines  24 A,  24 B for supplying water vapor having a high temperature in parallel to each other from the steam-water separator  20 . 
         [0021]    This system  1  is provided with a water vapor collection line  52  for collecting water vapor from the low-pressure turbine in order to use the water vapor used for power generation in the low-pressure turbine  50  as coolant again. This vapor collection line  52  includes a condenser  54  for condensing water vapor. Further, this system  1  includes a condenser  60  for condensing and collecting the water vapor, which has undergone heat exchange by the superheaters  34 ,  44 . Then, this system  1  includes a coolant collection line  62  for carrying the coolant condensed by the condenser  54  and the coolant existing within the condenser  60 , to the steam-water separator  20 . In the meantime, the vapor collection line  52  and the coolant collection line  62  have pumps  56 ,  64 , respectively. 
         [0022]    In this system  1  having the above configuration, first, methanol, which is a raw material, is supplied to the reactor  10  through a methanol supply line  12 . The reactor  10  induces DME synthetic reaction and gasoline synthetic reaction under a predetermined temperature and pressure to synthesize gasoline through the DME. Gasoline is discharged through the gasoline discharge line  14  and carried to a storage facility (not shown). Because both the DME synthetic reaction and the gasoline synthetic reaction are exothermic reactions, the reactor  10  is cooled with water as coolant in order to keep the reactor at a predetermined temperature. Consequently, the coolant turns to supersaturated water vapor, which is carried to the steam-water separator  20  through the coolant discharge line  16 . 
         [0023]    The steam-water separator  20  separates the supersaturated steam to saturated water vapor and water, and the water is carried to the reactor  10  through the coolant circulation line  26  to be used as coolant again. On the other hand, part of the saturated water vapor is carried to the high-pressure turbine  30  through the power generation water vapor line  22  and other part of the saturated water vapor is carried to the water vapor superheaters  34 ,  44  through the superheating water vapor lines  24 . A ratio between the power generation water vapor and the superheating water vapor is not restricted to any particular value because it changes depending on the number and performance of the turbines. However, the ratio is preferred to be 45 to 65 parts by weight with respect to 100 parts by weight of the power generation water vapor. 
         [0024]    By inflating the saturated water vapor in the high-pressure turbine  30 , the turbine is driven with its kinetic energy to generate electric power. Because the water vapor used in power generation by the high-pressure turbine  30  is in a supersaturated condition with a reduced pressure, the water vapor is superheated with the superheater  34  through the power generation water vapor line  32  to turn into a saturated or lower state and then is supplied to the medium-pressure turbine  40 . 
         [0025]    By inflating the saturated water vapor in the medium-pressure turbine  40  also, the turbine is driven with its kinetic energy to generate electric power. The supersaturated water vapor used in power generation in the medium-pressure turbine  40  is superheated by the superheater  44  through the power generation water vapor line  42  to turn into a saturated or lower state, and supplied to the low-pressure turbine  50 . Generation of electric power is carried out in the medium-pressure turbine  50  also. 
         [0026]    The water vapor used in power generation by the low-pressure turbine  50  is collected by the water vapor collection line  52  and condensed by the condenser  54 . The condensed coolant is carried to the condenser  60  by a pump  56 . The superheating water vapor, which has undergone heat exchange with the power generation water vapor in the superheaters  34 ,  44 , is carried to the condenser  60  through the superheating water vapor lines  24 A,  24 B and condensed there. Then, the condensed coolant in the condenser  60  is returned to the steam-water separator  20  through the coolant collection line  62  and a pump  64 , and used for cooling of the reactor  10  again. 
         [0027]    The embodiment shown in  FIG. 1  indicates a case of providing the reactor  10 , which synthesizes gasoline from methanol by executing the two reactions based on formulas 1 and 2. However, as shown in  FIG. 2 , together with a gasoline reactor  10 B for synthesizing gasoline, it is permissible to provide a dimethyl ether (DME) reactor  10 A for obtaining dimethyl ether through only the reaction of formula 1. Consequently, the DME can be produced as well as gasoline. The DME is available as a fuel alternate to liquid petroleum gas (LPG). 
         [0028]    In this case, as shown in  FIG. 2 , the DME reactor  10 A and the gasoline reactor  10 B are provided with steam-water separators  20 A,  20 B and coolant circulation lines  26 A,  26 B, respectively. A power generation water vapor line  22 B from the gasoline reactor  10 B is extended up to the high-pressure turbine  30 , and a power generation water vapor line  22 A from the DME reactor  10 A is extended up to a power generation water vapor line located between the high-pressure turbine  30  and the medium-pressure turbine  40 . Because, as described above, the reaction temperature and the reaction heat are lower in the DME synthetic reaction than in the gasoline synthetic reaction, supplying the water vapor used for cooling the DME reactor  10 A to the medium-pressure turbine  40  enables thermal energy to be recovered more effectively. 
         [0029]    Further, as shown in  FIG. 2 , a heat exchanger  66  may be provided on a downstream side of the superheaters  34 ,  44  in the superheating water vapor lines  24 A,  24 B. In the heat exchanger  66 , the condensed coolant flowing through the coolant collection line  62  is heated by the superheating water vapor superheated by the superheaters. Consequently, the entire thermal efficiency can be increased by preheating coolants in the coolant collection lines  62 A,  62 B. 
         [0030]    Although in the embodiment shown in  FIG. 1 , the DME synthetic reaction and the gasoline synthetic reaction for producing gasoline from methanol are executed with the single reactor  10 , these reactions may be carried out with independent reactors each. In this case, a line for supplying DME is provided between the DME reactor which carries out the DME synthetic reaction shown in formula 1 mentioned above and the gasoline reactor which carries out the gasoline synthetic reaction shown in formula 2 mentioned above. 
         [0031]    Although the gasoline production power generation system of the present invention may be built at a place of production of methanol, which is a raw material, or a place of production of natural gas, which is a raw material for methanol, it is preferred to be built at a consumption place of gasoline or nearby places. Because methanol remains in a liquid state at a normal temperature and normal pressure, and is easy to handle, transportation of the methanol to a consumption area of gasoline or nearby areas, for example, metropolitan area after the methanol is produced at a production place of natural gas such as Middle Eastern area enables transportation cost to be reduced largely compared to transportation of natural gas in a liquefied state. Further, because the consumption place of gasoline usually has a high demand for electric power, electric power can be supplied effectively to users by generating the electric power at the consumption place of gasoline or nearby areas. 
       EXAMPLE 
       [0032]    A simulation about power generation efficiency was carried out on a system shown in  FIG. 1 . Table 1 and  FIG. 3  show a result thereof. In the meantime, the reactor  10  was cooled under a condition of using water as coolant and cooling in calorific value of 80.9×10 6  kcal/h and another condition that an obtained water vapor was at 100 ata and 310° C. Further, as a predetermined condition, this saturated water vapor was supplied to the high-pressure turbine  30  by 100 ton/h for the purpose of power generation and by 54.6 ton/h for the purpose of superheating. Of this amount of the water vapor, 22.4 ton/h (7.3×10 6  kcal/h as converted to calorific value) was supplied to the superheater  34  and 32.2 ton/h was supplied to the superheater  44 . Air discharged from the low-pressure turbine  50  was set to 0.05 ata. 
         [0000]    
       
         
               
               
             
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Enthalpy 
               
               
                   
                 of steam 
               
               
                   
                 (kcal/kg) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Power generation water vapor line 22, 
                 660 
               
               
                 Superheating water vapor line 24 
               
               
                 Power generation water vapor line 32 (before superheating) 
                 630 
               
               
                 Power generation water vapor line 32 (after superheating) 
                 730 
               
               
                 Power generation water vapor line 42 (before superheating) 
                 605 
               
               
                 Power generation water vapor line 42 (after superheating) 
                 710 
               
               
                 Water vapor collection line 52 (before condensation) 
                 585 
               
               
                 Water vapor collection line 52 (after condensation) 
                 30 
               
               
                 Superheating water vapor line 24A (after superheating) 
                 334 
               
               
                 Superheating water vapor line 24B (after superheating) 
                 334 
               
               
                   
               
             
          
         
       
     
         [0033]      FIG. 3  illustrates a plotting of the result of Table 1 on an h-s diagram for steam. As shown in  FIG. 3 , electric power could be generated with thermal energy possessed by the coolant effectively by adopting a three-stage system comprised of the high-pressure turbine  30 , the medium-pressure turbine  40 , and the low-pressure turbine  50 . Of course, a two-stage system comprised of the high-pressure turbine and the low-pressure turbine may be adopted or a system with four or more stages may be adopted. 
         [0034]    As a result, electric power generated by the high-pressure turbine  30  was 3,488 kw, electric power generated by the medium-pressure turbine  40  was 11,395 kw, and electric power generated by the low-pressure turbine  50  was 14,535 kw. The total output was 29,418 kw. Because input heat was 80.9×10 6  kcal/h, a steam efficiency of 31.3% could be attained. 
         [0035]    Table 2 shows a result of the simulation about power generation efficiency on the system shown in  FIG. 2 . The DME reactor  10 A was cooled in calorific value of 98.0×10 6  kcal/h, and the gasoline reactor  10 B was cooled in calorific value of 122.4×10 6  kcal/h. Under such conditions, the DME reactor  10 A can obtain water vapor of 30 ata and 233° C., and the gasoline reactor  10 B can obtain water vapor of 100 ata and 310° C. As another predetermined condition, saturated water vapor of 188.4 ton/h for power generation was supplied from the DME reactor  10 A, and saturated water vapor of 100 ton/h for power generation was supplied from the gasoline reactor  10 B. Further, the saturated water vapor for superheating was supplied from the gasoline reactor  10 B by 133.8 ton/h, while 42.2 ton/h (13.8×10 6  kcal/h as converted to calorific value) was supplied to the superheater  34  and 91.6 ton/h (29.9×10 6  kcal/h as converted to calorific value) was supplied to the superheater  44 . Air discharged from the low-pressure turbine  50  was set to 0.05 ata. Calorific value in the heat exchanger  66  was set to 17.6×10 6  kcal/h. 
         [0000]    
       
         
               
               
             
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Enthalpy 
               
               
                   
                 of steam 
               
               
                   
                 (kcal/kg) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Power generation water vapor line 22A 
                 668 
               
               
                 Power generation water vapor line 22B, 
                 660 
               
               
                 Superheating water vapor line 24 
               
               
                 Power generation water vapor line 32 (before superheating) 
                 630 
               
               
                 Power generation water vapor line 32 (after superheating) 
                 703 
               
               
                 Power generation water vapor line 42 (before superheating) 
                 605 
               
               
                 Power generation water vapor line 42 (after superheating) 
                 710 
               
               
                 Water vapor collection line 52 (before condensation) 
                 585 
               
               
                 Water vapor collection line 52 (after condensation) 
                 30 
               
               
                 Superheating water vapor line 24A (after superheating) 
                 334 
               
               
                 Superheating water vapor line 24B (after superheating) 
                 334 
               
               
                 Superheating water vapor lien 24 (after heat exchange) 
                 60.9 
               
               
                 Coolant collection line 62 (before heat exchange) 
                 40.9 
               
               
                 Coolant collection line 62 (after heat exchange) 
                 136.5 
               
               
                   
               
             
          
         
       
     
         [0036]    In the system shown in  FIG. 2 , electric power generated by the high-pressure turbine  30  was 3,488 kw, electric power generated by the medium-pressure turbine  40  was 32,400 kw, electric power generated by the low-pressure turbine  50  was 41,340 kw, and a total output was 77,228 kw. Because total input heat was 220.4×10 6  kcal/h, steam efficiency of 30.1% could be attained.