JPS6151659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel gas supply method and apparatus for supplying superheated fuel gas to a gas combustion internal combustion engine, that is, a gas turbine and a gas engine.

In general, the fuel gas in the gas-fired internal combustion engine is conventionally supplied to the internal combustion engine as it is after increasing the pressure using a compressor.If the temperature of the gas compressed by the compressor is too high for the internal combustion engine, an aftercooler is used. It was supplied chilled.
However, it is necessary to cool it with an aftercooler. In addition, when cooled by the aftercooler, some components of the fuel gas condense and liquefy as the temperature drops, producing drain. This drain mist clogs the internal combustion engine's fuel control system and causes various troubles.

In order to solve this problem, the inventors heated the saturated or supersaturated fuel gas after cooling it in an aftercooler with a heater 1 using an external heat source as shown in FIG. I considered doing so. In FIG. 1, 2 is a mist separator, 3 is a compressor, 4 is an aftercooler, 5 is a drain separator, 6 is a gas combustion internal combustion engine, 7 is a load connected to this internal combustion engine 6, 8 is a pressure control device, 9 is a pressure regulating valve controlled by a pressure control device. The heater 1 in this example is a heat exchanger whose heat source is a heating fluid sent from the outside. and,
Further, a temperature control device 10 is provided, and the temperature control device 10 controls the flow rate regulating valve 11 while constantly detecting the temperature of the fuel gas sent to the internal combustion engine 6.
This controls the heating by the heater 1 to prevent the heating gas sent to the internal combustion engine 6 from being overheated or underheated.

However, as a result of studies, it has been found that the above-mentioned conventional fuel gas supply apparatus, which generates superheated gas using an external heat source, has the following points. (1) A special external heat source is required.

(2) Generally, when the internal combustion engine load is 100%, heater 1
In order to determine the capacity of the internal combustion engine 6, when the load becomes small and the amount of gas sent to the internal combustion engine 6 decreases, the problem of overheating occurs in the heater 1, and therefore, as mentioned above, the temperature control device 10 is particularly required. .

(3) In the case of the heater 1 using a heat exchanger, if leakage occurs between the fuel gas and the heating fluid in the heater 1, it will cause a big problem.

(4) If the heater is an electric heating type, the surface temperature of the heater becomes high, so there is a problem that it does not comply with domestic regulations as an explosion-proof product.

This invention was proposed in order to eliminate the above-mentioned conventional drawbacks all at once, and uses the discharged fuel gas of the compressor as a heating source, eliminating the need for an external heat source and achieving energy savings. It is an object of the present invention to provide a fuel gas supply method and a simple-configured fuel gas supply device that can safely supply fuel to an internal combustion engine by self-adjusting the fuel gas temperature even without the provision of such a fuel gas.

An embodiment of the present invention will be explained below with reference to the drawings.

In FIG. 2, 20 is a mist separator;
1 is a positive displacement type, turbo type, axial type, etc. compressor, 22
is a heat exchanger, 23 is an aftercooler, 2
4 is a drain separator, 25 is a filter, 26 is a gas combustion type internal combustion engine such as a gas turbine or gas engine, 27 is a load, and 28 is an auxiliary drain separator for use before starting the internal combustion engine. Then, piping is arranged so that the fuel gas supplied from the gas inlet 29 is sent through the mist separator 20, the compressor 21, the heat exchanger 22, the aftercooler 23, and the drain separator 24, respectively, as shown by arrow A,
Furthermore, piping A downstream of the drain separator 24
is the pipe B of the bypass system that returns to the mist separator 20, and the pipe C of the internal combustion engine system that is sent to the internal combustion engine 26 via the heat exchanger 22 and the filter 25 (C ₁ is the pipe upstream of the heat exchanger 22, The piping is designated as _C2 ). Furthermore, pressure control devices 30 and 31 are provided at the downstream portion of the drain separator 24, immediately before the pipe A branches, and at the mist separator 20, respectively, to detect the gas pressure and output a control signal in accordance with the detected pressure. , the pipe B is provided with a pressure regulating valve 32. This pressure regulating valve 32 is normally controlled by the pressure control device 30 of the pipe A, but the pressure inside the mist separator 20 (i.e., the pressure in the compressor 21
When the suction pressure of the mist separator 2 decreases abnormally, the selection control device 33 switches the mist separator 2
It is activated by a control signal from the pressure control device 31 on the 0 side.

Next, the operation of the above-mentioned fuel gas supply device will be explained.

1 The fuel gas at the gas inlet 29 is normally at room temperature and has a pressure of 1.0 to 7.0 Kg/cm ² A (absolute pressure).

2 The mist separator 20 reduces the amount of normal mist.
90% removed.

3 At the suction port of the compressor 21, the pressure is usually about 0.2 to 0.2 to less than the pressure at the gas inlet 29 due to pressure loss in the mist separator 20 and piping system.
1.0Kg/ ^cm2 lower.

4 On the discharge side of the compressor 21, the discharge pressure is usually 10
~16Kg/cm ² A (this is the discharge pressure equal to the required gas pressure of the internal combustion engine 26 plus the pressure loss of the piping system between the compressor 21 and the internal combustion engine), and the discharge temperature is 90 to 130°C It is.

Note that the discharge temperature is determined by the following equation.

Td＝Ts×(Pd/Ps)〓〓〓〓 ……() However, in the case of reversible adiabatic compression (positive displacement compressor) Td＝Ts×(Pd/Ps)〓 ……() However, in the case of polytropic compression (Turbo compressor) Where, Td: Discharge temperature (〓) Ts: Suction temperature (〓) Pd: Discharge pressure (Kg/cm ² A) Ps: Suction pressure (Kg/cm ² A) K: Gas constant ratio cp/cv Cp: Specific heat at constant pressure Cv: Specific heat at constant volume n: Index in case of polytropic change As is clear from the above equations () and (),
If the discharge pressure Pd of the compressor 21 is lowered, the discharge temperature
Td also decreases. And the discharge pressure of the compressor 21
Pd can be lowered by lowering the set value of the pressure control device 30.

5. In the heat exchanger 22, the high-temperature gas discharged from the compressor 21 gives thermal energy to the low-temperature gas flowing through the pipe C of the internal combustion engine system to heat it. Note that this heat exchange phenomenon will be described in more detail later.

6. The high-temperature fuel gas that has been slightly cooled in the heat exchanger 22 is cooled again to near room temperature in the aftercooler 23. At this time, some components contained in the fuel gas are condensed and liquefied as the temperature decreases.

Note that, depending on the type of cooler, some of this condensed liquid may be discharged through the drain outlet of the cooler.

7. The condensate entrained in the cooled fuel gas is separated and removed by the drain separator 24.

8 In addition, from the gas inlet 29 to the drain separator 24
Fuel gas corresponding to the capacity of the compressor 21 flows between the downstream pipe A and the pipe A.

9. The amount of fuel gas required by the load of the internal combustion engine 26 is branched and sent to the pipe C of the internal combustion engine system.

The fuel gas, which was in a saturated or supersaturated state before entering the heat exchanger 22, is heated by the heat exchanger 22 to become superheated gas and is supplied to the internal combustion engine 26.

10 Since the fuel gas sent to the pipe C of the internal combustion engine system only flows in an amount corresponding to the load 27 of the internal combustion engine 26 as described above, the excess fuel gas returns to the gas inlet 29 via the pressure regulating valve 32 and the pipe B. .

Therefore, by detecting the pressure with the pressure control device 30 and adjusting the opening degree of the pressure regulating valve 32 according to the detected pressure, the pressure of the fuel gas sent to the pipe C of the internal combustion engine system is adjusted. can be kept constant.

In addition, gas inlet 2 is connected from piping B of the bypass system.
The fuel gas returning to 9 must pass through the aftercooler 23. Because compressor 2
Even if 1 is a positive displacement type, it is not compressed by a complete reversible adiabatic change, but is actually heated excessively by the friction heat of the compressor, so the compressed high temperature gas is passed through a pressure regulating valve. Even if it is adiabatically expanded at 32, the temperature of the supplied gas will not drop to the original supply gas temperature. Therefore, assuming that this bypass gas is circulating, the gas will be synergistically heated by the compressor 21, and its temperature will increase. This is because the temperature of the gas discharged from the compressor 21 increases as a result, causing mechanical problems.

11 Pressure control device 31 on the mist separator 20 side
outputs a control signal in the same way as the pressure control device 30 of the pipe A downstream of the drain separator 24, and is normally ignored by the selection control device 33, but when the amount of fuel gas supplied to the gas inlet 29 is When the suction pressure of the compressor 21 decreases and falls below a certain value, the selection control device 33 performs switching, and the pressure regulating valve 32 is controlled only by the pressure control device 31 on the mist separator 20 side. Ru. In this case, the pressure control device 30 of the pipe A is ignored, and the pressure regulating valve 32 is opened so as to return the gas on the discharge side of the compressor 21 to the suction side and prevent a pressure drop on the suction side of the compressor 21. Control is exercised. This is because if the suction pressure of the compressor 21 decreases, it will have an abnormal effect on the compressor 21 and cause it to malfunction. In other words, this is to prioritize protection of the compressor 21 over supply to the internal combustion engine 26. In this way, when the supply amount at the inlet 29 decreases and the pressure in the pipe C of the internal combustion engine system drops below a certain value, either switch to another fuel system (not shown) (usually liquid fuel), or
Alternatively, the operation of the internal combustion engine 26 is stopped.

12 In addition, the auxiliary drain separator 28
This is used when starting internal combustion engine 2.
Close the valve 34 in front of the compressor 21 and open the valve 35 on the side of the auxiliary drain separator 28.
The internal combustion engine 26 is operated to circulate fuel gas to warm the cold pipes, and after each pipe is warmed up, the internal combustion engine 26 is started. This makes it possible to supply preferable superheated gas to the internal combustion engine 26 from the beginning of startup.

Next, the phenomenon of heat exchange in the heat exchanger 22 described in the above section (5) will be described.

Generally, the amount of heat exchanged Q in a heat exchanger is determined by the following equation.

Q = U × A × △tm ... () U: Overall heat transfer coefficient A: Heat transfer area (constant) △tm: Logarithmic mean temperature difference △t ₁ = T ₂ −t ₁ △t ₂ = T ₁ −t ₂ T ₁ : Temperature of heating fluid at the inlet of the heat exchanger T ₂ : Temperature of the heating fluid at the exit of the heat exchanger t ₁ : Heat of the heated fluid Temperature at the exchanger inlet t ₂ : Temperature of the heated fluid at the heat exchanger outlet When the flow rate of the heated fluid (i.e., the flow rate in pipe C of the internal combustion engine system) decreases and the gas flow rate decreases,
The overall heat transfer coefficient U becomes smaller. Also, although the temperature t ₂ at the outlet of the heated fluid increases, the temperature difference between the heated fluid and the heated fluid, that is, T ₁ − t ₂ (=△t ₂ )
becomes smaller, and the numerical value of the numerator in equation () becomes larger, but the numerical value of the denominator also becomes larger, so the logarithmic mean temperature difference △tm becomes smaller (this means that the mathematical operation in equation () ). Therefore, as the flow rate G of the fluid to be heated decreases, the amount of heat exchange Q also decreases.

By the way, as the amount of heat transferred in a heat exchanger having a fixed heat transfer area, the temperature rise of the heated fluid is determined by the following equation.

△t = Q/G Since the exchange amount Q also becomes small, the temperature rise Δt of the heated fluid does not become so large.

In other words, even if the load on the internal combustion engine 26 decreases and the amount of gas flowing into the piping C of the internal combustion engine system decreases (the limit is generally about 40% of the flow rate at rated load).
%), the heat exchanger 22 will not overheat. In this way, in the present invention,
By using the discharged fuel gas of the compressor as the heating fluid of the heat exchanger 22, this heat exchanger 22
has a self-adjusting ability to prevent overheating, and can keep the temperature rise of the fuel gas sent to the internal combustion engine 26 within the permissible value without installing a temperature control device 10 such as the device shown in FIG. It is now possible to fit the

Furthermore, even if there is a case where the temperature rise exceeds the allowable value, the discharge pressure of the compressor 21 can be reduced by lowering the discharge pressure within the pressure range required by the internal combustion engine 26 (usually 8 to 14 kg/cm ² G (gauge pressure)). By lowering the temperature, the temperature of the fuel gas sent to the internal combustion engine 26 can be kept within an allowable value. To explain this situation in detail, as is clear from the above-mentioned equations () and (), if the discharge pressure Pd of the compressor 21 is lowered, the discharge temperature Pd will also be lowered. Since the discharge pressure Pd of the compressor 21 can be lowered by lowering the setting value of the pressure control device 30, the setting value of the pressure control device 30 can be lowered within the pressure range required by the internal combustion engine 26. By setting, the discharge temperature of the compressor 21 can be lowered, and as a result, the gas temperature in the pipe _C2 of the internal combustion engine system can be lowered.

The set value of the pressure control device 30 may be changed manually. Such a change in the set value is preferably performed when there is a significant difference in the temperature of the fuel gas supplied from the gas inlet 29 between summer and winter. Further, as shown in FIG. 3, a temperature control device 36 is installed in the pipe _C2 of the internal combustion engine system to detect the temperature and output a control signal according to the detected temperature.
By this control signal, the pressure control device 30 of pipe A
The setting value of the pressure control device 30 may be changed automatically by such cascade control.

FIG. 4 shows another specific example.
It supplies fuel to two gas turbines 40 and 40 with a rating of 2500KW. and suction pressure
Two-stage reciprocating compressors 41 and 42 are provided to compress from 1.033 Kg/cm ² A to a discharge pressure of 17.3 Kg/cm ² G, and an intermediate cooler 43 and an intermediate mist separator 44 are provided. The intermediate cooler 43 and the aftercooler 23 are air-cooled when the atmospheric temperature is at a maximum of 45°C. In addition, the capacity of the heat exchanger 22 is equivalent to two gas turbines with a rating of 2500KW, and is approximately
Heat transfer area 1.4 with exchange heat capacity of 10000Kcal/H
A double pipe heat exchanger of m ² is used. In addition, the second
Portions common to those in the figures are designated by the same reference numerals, and description thereof will be omitted. The properties of the fuel gas used shall be as follows.

Components, molar ratio (%) at the inlet of the first stage compressor 41 Methane 15.82 Tetane 13.84 Propane 22.26 Isobutane 6.26 Normal butane 13.99 Normal pentane 5.50 Hexane 4.40 Heptane 3.69 Water vapor 3.14 Hydrogen sulfide 3.95 Nitrogen 0.87 Carbon dioxide 1.34 Total 100% Above fuel The results when gas is used are as shown in each stage of Fig. 4, and the gas turbine 4
It was possible to supply fuel gas at 65°C to 0.

In the above embodiment, the capacity of the aftercooler 23 is the same as that of the heater 1 using an external heat source as shown in FIG.
The capacity of the heat exchanger 22 is
It has become possible to reduce the size by the equivalent of 10,000 Kcal/H.

Further, the amount of fuel gas supplied to the gas turbine 40 side is at its minimum when one gas turbine is in no-load operation, but the fuel gas sent to the gas turbine 40 at this time is heated to the maximum in the heat exchanger 22, and at that time The gas temperature was 77°C. This temperature is within an acceptable range for fuel gas sent to a gas turbine.

As explained above, according to the fuel gas supply method and device of the present invention, the fuel gas sent to the internal combustion engine via the cooler is heated by the heat exchanger that uses the fuel gas discharged from the compressor as the heating fluid. This is made into superheated gas.

(1) Energy saving is achieved without the need for a special external heat source.

(2) The capacity of the cooler can be smaller than conventional ones.

(3) This heat exchanger has a heating temperature self-adjustment function that reduces the amount of heat given when the flow rate of the heated fluid decreases, so the load decreases and the amount of fuel gas sent to the internal combustion engine decreases. It also doesn't overheat.

(4) Since the heating gas and the gas to be heated are originally the same in the heat exchanger, there is no danger even if there is internal leakage, and if it is a small amount, it will not adversely affect performance.

Various excellent effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a fuel gas supply device studied by the proponents of the present invention prior to this invention, FIG. 2 is a system diagram showing one embodiment of the present invention, and FIG. System diagram showing an example, No. 4
The figure is a system diagram showing yet another embodiment. 21...Compressor, 23...Aftercooler, 24
...Drain separator, 26...Internal combustion engine, 22...
...Heat exchanger, 29...Gas inlet, 30, 31...
Pressure control device, 32...Pressure regulating valve, 33...Selection control device, 40...Gas turbine, 41...1
Stage compressor, 42... Second stage compressor, 43... Intermediate cooler.

Claims (1)

[Scope of Claims] 1. In a method for supplying fuel gas to an internal combustion engine using a compressor, the fuel gas discharged from the compressor is cooled and at least part of the condensate generated during cooling is removed, and then the fuel gas is cooled. A method for supplying fuel gas in a gas combustion type internal combustion engine, characterized in that the fuel gas is heated by the discharged fuel gas and then supplied to the internal combustion engine. 2. In a fuel gas supply device having a compressor that compresses fuel gas and a cooling condensate separation means that cools the discharged fuel gas and removes at least a part of the condensate generated during cooling, the compressor and the cooling condensate are separated. A heat exchanger is provided between the compressor and the separation means, the heating fluid being the fuel gas discharged from the compressor, and the fuel gas having a lower temperature than the discharged fuel gas passing through the cooling condensate separation means being the heated fluid. A fuel gas supply device for a gas-fired internal combustion engine.