JPH11350942A - Internal combustion engine and rotation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent discharge into the atmosphere of unburned methane contained in the exhaust gas from the reciprocating-type gas engine equipped with the turbocharger and to effectively recover the energy from the methane. SOLUTION: The exhaust gas from an engine main unit 11 is first lead into a catalytic converter 18 and then into a turbine 17 of a turbocharger 15. The unburned methane content of the exhaust gas is oxidized to combust in the catalytic converter 18. With the temperature raised and enthalpy improved, the turbine 17 is rotationally driven and the intake air to the engine main unit 11 is compressed by a compressor 16. After the kinetic energy of the turbo charger 15 has been recovered, the thermal energy from an exhaust heat boiler 19 is recovered. Since the temperature of the exhaust gas coming into the catalytic converter 18 is high, the residual methane content can be sufficiently oxidized and burnt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas internal combustion engine and a rotary device used for constructing a power generation facility or a cogeneration system using city gas or the like as a fuel.

[0002]

2. Description of the Related Art Conventionally, a gas engine has been used as a power source of a private power generation facility using city gas as a fuel as shown in FIG. City gas is supplied from a fuel supply pipe 3 as energy for rotating the generator 2 by the reciprocating engine body 1. The engine body includes a plurality of cylinders, and city gas and compressed air are supplied into each cylinder. The compressed air is generated by compressing the atmosphere with the compressor 6 of the turbocharger 5. The energy for rotationally driving the turbocharger 5 utilizes the energy of the exhaust gas from the engine body 1 and guides the exhaust gas from the engine body 1 to the turbine 7 to generate it. The exhaust from which the energy is recovered by rotating the turbine 7 is burned by the catalyst 8 to be exhausted into the atmosphere. Such a configuration is based on the idea of treating the entire gas engine including the turbocharger 5 as a block having one function as a kind of black box and treating unburned hydrocarbons outside the black box.

[0003] When the engine body 1 and the lean gas engine are used, as in the case of the diesel engine, three to three fuels are usually used.
About 5% is directly discharged into the exhaust gas as unburned matter.
The catalyst 8 is provided to burn unburned components in the exhaust gas without releasing them to the atmosphere.

[0004]

As shown in FIG. 3, when city gas using natural gas or the like as a fuel is used as a fuel for a gas engine as shown in FIG. 3, methane (N) which is a main component of natural gas is used.
H ₄ ) becomes a main component even in the exhaust gas, and is not easily combusted by the catalyst 8 and is easily discharged into the atmosphere. In particular, in the case of a lean gas engine, about 90% of methane may be released to the atmosphere as it is.

Since the catalyst 8 burns the exhaust gas from the turbine 7 of the turbocharger 5, the temperature of the exhaust gas to be burned is relatively low. Therefore, only components that can be burned at a low temperature, such as hydrocarbons other than carbon monoxide (CO) and methane, are burned by the catalyst 8.

Therefore, the prior art as shown in FIG. 3 has the following problems. The energy of unburned methane cannot be used effectively. Releases methane gas with a strong greenhouse effect into the atmosphere.

[0007] If a substance capable of combusting methane is used as the catalyst 8, the above-mentioned problem is solved. However,
In a lean gas engine or a diesel engine, the exhaust gas has a temperature of 300 to 450 ° C and a pressure of atmospheric pressure, and there is no combustion catalyst capable of burning methane at a practical reaction rate.

An object of the present invention is to provide a gas internal combustion engine and a rotating device that can effectively utilize the energy of unburned methane and suppress the emission of methane gas.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a gas internal combustion engine including a reciprocating gas engine and an exhaust turbine supercharger that guides and drives the exhaust gas. A gas internal combustion engine characterized in that a catalyst for burning unburned components in exhaust gas is installed in a path leading to a supercharger.

According to the present invention, the gas internal combustion engine includes a reciprocating gas engine and an exhaust turbine supercharger driven by using the exhaust gas. A catalyst that burns unburned components in the exhaust gas is provided in a path that guides the exhaust gas from the gas engine to the exhaust turbocharger. Since exhaust gas from the gas engine is guided to the catalyst, the temperature of the exhaust gas becomes high, and unburned components such as methane can be easily burned. Since the exhaust gas from which the unburned components are burned is led to the exhaust turbine supercharger, the energy of the unburned components such as methane burned by the catalyst is effectively recovered by the exhaust turbine supercharger, and the output of the gas engine increases. Thus, emission of methane gas and the like to the atmosphere can be suppressed.

Further, the present invention is characterized in that the gas engine is a lean-burn type reciprocating engine.

According to the present invention, since a lean-burn reciprocating engine is used as a gas engine, a rotational driving force can be efficiently generated. In a lean-burn gas engine, although unburned methane is likely to be emitted in the exhaust gas, it can be burned by a catalyst and recovered by an exhaust turbine supercharger.

Further, the present invention is characterized in that an exhaust heat boiler for recovering heat is installed on the exhaust side of the exhaust turbine supercharger.

According to the present invention, the kinetic energy of the exhaust gas from the catalyst for burning the high-temperature exhaust gas can be recovered by the exhaust turbine supercharger, and the heat energy can be recovered by the exhaust heat boiler.

Further, the present invention is a rotating device characterized in that any one of the above gas internal combustion engines is used as a prime mover.

According to the present invention, after effectively recovering energy from unburned methane in the gas internal combustion engine and suppressing the emission of methane into the atmosphere, the rotational driving force of the gas internal combustion engine is effectively used. For example, a rotating device such as a generator can be driven.

[0017]

FIG. 1 shows a schematic configuration of a cogeneration system 10 according to an embodiment of the present invention. The engine body 11 is a reciprocating gas engine, like the engine body 1 in FIG. Engine body 1
The output shaft 1 generates power by rotating the generator 12.
City gas is supplied to the engine body 11 through the fuel supply pipe 13 as fuel. The air supplied to the engine body 11 via the air supply pipe 14 is generated by compressing the atmosphere by a compressor 16 of a turbocharger 15. The compressor 16 of the turbocharger 15
The rotation is driven by the turbine 17. Turbine 17
Drives by driving exhaust gas from the engine body 11.

In the gas engine of the present embodiment, the exhaust gas from the engine body 11 is burned by the catalyst 18 and then guided to the turbine 17 of the turbocharger 15.
The exhaust gas at the inlet of the catalyst 18 has a temperature of about 500 ° C. and a pressure of about 1 kg / cm ² G, and the unburned methane can be sufficiently burned by the catalyst 18 having a practical size.

As in the present embodiment, the turbocharger 1
If methane can be combusted on the upstream side of 5, the following effects can be obtained.

The emission of methane, which is a greenhouse gas, into the atmosphere can be prevented. Due to the combustion, the exhaust gas temperature rises, and the energy of the exhaust gas increases. Since the enthalpy of the exhaust gas at the inlet of the turbine 17 of the turbocharger 15 increases, FIG.
It is possible to secure the outlet pressure of the compressor 16 required by the engine body 11 even under the condition that the inlet pressure is lower than that of the conventional configuration as shown in FIG. That is, even if the outlet pressure of the engine body is lowered, the shaft power required for the compressor 16 can be secured. Since the inlet pressure of the turbine 17 is substantially equal to the outlet pressure of the engine body 11, if the inlet pressure of the turbine 17 can be reduced,
The pumping loss of the engine body 11 can be reduced, and the thermal efficiency of the engine body 11 can be improved. Since methane burns and the temperature of the exhaust rises, the temperature of the exhaust from the turbine 17 also rises. Therefore, the exhaust heat boiler 19 can be installed to recover heat from the exhaust gas of the turbine 17. If you are recovering heat from the exhaust,
The overall efficiency, which is the sum of the mechanical efficiency and the thermal efficiency, is increased by 3 to 5%, which is the unburned methane fuel.

In the embodiment described above, the power and heat of the lean-burn gas engine are recovered to constitute the cogeneration system 10. However, the exhaust heat boiler 19 is not provided and only the generator 12 is used as the prime mover. The engine body 11 can also be used. Further, instead of the generator 12, the engine main body 11 can be used as a prime mover that obtains a rotational driving force by an engine-driven rotating device such as a compressor or a chiller.

[Embodiment] Assuming that an SR6 type engine manufactured by Mitsubishi Heavy Industries, Ltd., which is a typical commercially available lean gas engine, is used, the following theoretical calculation can be performed.

Assumptions for Calculation (1) Engine output 404 kW (shaft end) (2) Engine efficiency η _s = 37.0% (shaft end) b
y LHV (mechanical efficiency η _m = 0.90) (3) Steam recovery rate 20% (4) Air ratio λ = 2.0 (5) Exhaust port pressure P ₂ 1 kg / cm ² G (turbocharger input) Temperature T 793.15 ° K (520
° C) (6) Unburned matter in exhaust gas 2000 ppm C _ub = 0.0
02 (7) Cylinder bore (D) 0.17 m Stroke (L) 0.18 m 6 cylinders (8) Rotation speed 1800 rpm (9) Power recovery method Turbocharger efficiency is obtained by burning unburned matter under constant conditions. The power is recovered by utilizing the energy by lowering the exhaust port pressure to reduce the power required to supply the exhaust gas in the cylinder, thereby increasing the effective output at the end of the engine shaft. (10) Physical property parameters Exhaust gas specific heat C _p = 0.31
8 kcal / Nm ³ (11) Catalyst pressure loss ΔP _c = 0.002 kg / cm ² Work w input to the turbine 17 of the turbocharger 15 is expressed by the following first equation. Here, the entrance condition is 2,
Exit conditions are indicated by a subscript of 1. R is a gas constant.

[0024]

(Equation 1)

In the first equation, K represents a specific heat ratio, and V represents a volume. From the premise (9) of the above calculation, the turbine 17 with the catalyst 18 for oxidizing and burning unburned components is installed.
Since the input w 'and the work w when not installed are equal,
The following second equation is obtained.

W = w ′ (2) Accordingly, the following third expression is obtained.

[0027]

(Equation 2)

Here, T ₂ ′ is expressed by the following fourth equation.
Here, Q is the combustion energy in the oxidation catalyst, w _EX is the flow rate of the exhaust gas, and q is the heat quantity per unit volume (LHV) of the fuel gas, for example, 9930 kcal / Nm ^3.
And

[0029]

(Equation 3)

By transforming the third equation, the following fifth equation is obtained.

[0031]

(Equation 4)

In the fifth equation, the values of T ₂ and T ₂ ′ and P ₁ =
By substituting 1.033, P ₂ = 2.033, and K = 1.4, the value of P ₂ ′ is calculated by the following equation (6).

P ₂ ′ = 1.926 kg / cm ² A (6) The recoverable work amount W is expressed by the following seventh equation.

[0034]

(Equation 5)

Here, n is 6 in the number of cylinders, and D = 0.
17 m, L = 0.18 m, P ₂ = 2.033, P ₂ ′ =
Substituting 1.926, ΔP _c = 0.002 gives the following eighth
The value of W is obtained as in the equation.

W = 3.53 kW (8) Accordingly, the efficiency increase Δη _m is calculated as in the following ninth equation.

[0037]

(Equation 6)

That is, by implementing the present invention, the power generation efficiency of the engine can be improved by about 0.3%.

Further, the amount of steam that can be recovered from the exhaust gas by the exhaust heat boiler 19 is improved by an amount corresponding to the amount of work W recovered from the combustion energy Q generated by oxidation by the catalyst 18 per unit time. Here, Q is expressed by the following equation (10).

Q = (exhaust gas amount per 1 Nm ³ of fuel at a predetermined air ratio λ) × unburned fuel concentration × heat generation amount per 1 Nm ³ of fuel × fuel amount per unit time = 50.5 kW (10) The amount of steam that can be recovered from the exhaust gas increases by QW = 47.0 kW per unit time. Since the steam recovery rate is Δη _m = 0.0430,
It turns out that it increases about 4.3%.

FIG. 2 shows an example of experimental results on the combustibility of methane, which is a main component of unburned components in exhaust gas. (A) is T
= 550 ° C, (b) shows the results at T = 500 ° C. In addition, a circle indicates a case where 20 g of palladium (Pd) and 5 g of platinum (Pt) are used as a catalyst, and a triangle indicates 20 g of Pd.
The case where 2.5 g of Pt is used is shown (per liter). GHSV on the horizontal axis is the gas space velocity,
2 shows the gas volume delivered per hour per effective volume of the catalyst layer. That is, as the number increases, the contact time between the catalyst and the gas decreases, and as the number decreases, the contact time with the catalyst increases, and the reaction proceeds easily. In the installation conditions of this embodiment, the temperature is 500 to 550 ° C., the pressure is 2
atma, and GHSV = 4 which is a practical reaction condition
At 0000 h ^-1 , it can be seen that catalyst 18 has achieved sufficient oxidation and is capable of burning 80% or more of methane (CH ₄ ). Such reaction conditions can be obtained with a 500 kW class gas engine and a catalyst amount of about 30 liters.

As shown in FIG. 3, when the catalyst 8 is installed on the outlet side of the turbocharger 5 in the conventional configuration, the turbocharger outlet conditions are a temperature of 420 ° C. and a pressure of 1 atma.
The reaction rate of methane at GHSV = 40000h ^-1 is 10%
It will be as follows.

[0043]

As described above, according to the present invention, since the catalyst is installed in the path for guiding the exhaust gas from the gas engine to the exhaust turbine supercharger, the combustion of unburned methane and the like in the exhaust gas is easy. The catalyst can act at a relatively high temperature, thereby suppressing the emission of methane into the atmosphere and effectively utilizing the energy of methane.

Further, according to the present invention, since the reciprocating gas engine is of the lean burn type, it is possible to efficiently generate a rotational driving force with a small amount of fuel, and to effectively use methane contained in the exhaust gas with a catalyst. Combustion can recover energy.

According to the present invention, unburned methane or the like contained in exhaust gas is burned by a catalyst, and its kinetic energy is recovered by an exhaust turbine supercharger, and then thermal energy is recovered by an exhaust heat boiler. Can be.

Further, according to the present invention, the rotational driving force of the gas engine that suppresses the methane gas contained in the exhaust gas and effectively recovers the energy can be effectively used as a prime mover.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a cogeneration system 10 according to an embodiment of the present invention.

FIG. 2 is a graph showing an example of experimental results of flammability of methane burned by a catalyst 18 in the embodiment of FIG.

FIG. 3 is a block diagram showing a configuration of a conventional gas engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cogeneration system 11 Engine main body 12 Generator 15 Turbocharger 16 Compressor 17 Turbine 18 Catalyst 19 Exhaust heat boiler

Claims (4)

[Claims] 1. A gas internal combustion engine comprising a reciprocating gas engine and an exhaust turbine supercharger for guiding and driving the exhaust gas, wherein the exhaust gas from the gas engine is guided to an exhaust turbine supercharger, A gas internal combustion engine comprising a catalyst for burning unburned components in exhaust gas. 2. The gas internal combustion engine according to claim 1, wherein said gas engine is a lean-burn type reciprocating engine. 3. The gas internal combustion engine according to claim 1, wherein an exhaust heat boiler for recovering heat is installed on an exhaust side of the exhaust turbine supercharger. 4. A rotating device comprising the gas internal combustion engine according to claim 1 as a prime mover.