JP2005193175A - Method and apparatus for treating exhaust gas from gas engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To purify an exhaust gas from a gas engine at high efficiency using a catalyst. <P>SOLUTION: In removing hazardous components contained in the exhaust gas from a gas engine, the untreated exhaust gas passes through a catalyst after heating by a heating means 20 up to a temperature not lower than the temperature at which the catalyst in a catalyst bed 30 is active. Heat is exchanged between the treated high-temperature exhaust gas from the catalyst bed and the untreated low-temperature exhaust gas in a heat exchanger 10 to save an energy cost. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gas engine exhaust gas treatment method and apparatus.

  A gas engine can be operated with higher thermal efficiency than an internal combustion engine using gasoline or heavy oil as a fuel, and is widely used as a power source for a cogeneration system. Further, the exhaust gas from the gas engine has less emission of harmful components such as unburned hydrocarbons and nitrogen oxides and less pollution to the environment than the exhaust gas from a normal internal combustion engine. However, although it is relatively small, it is true that unburned hydrocarbons and nitrogen oxides are contained, and detoxification treatment is desired. For this purpose, a catalyst is used to treat unburned hydrocarbons and nitrogen oxides, which are harmful components in the exhaust gas.

However, because the gas engine has high thermal efficiency, the temperature of the exhaust gas is low, and it is usually discharged at a temperature below the catalyst activation temperature such as an oxidation catalyst or a denitration catalyst. Just by contacting the exhaust gas and the catalyst as they are, The purification process with a sufficient catalyst does not proceed. Therefore, in Patent Document 1 (Japanese Patent Laid-Open No. 2002-266331), a catalyst layer is sandwiched between a pair of heat accumulators, and exhaust gas from a gas engine is passed through the flow direction by switching the flow direction alternately. A gas engine exhaust gas treatment method and apparatus have been proposed in which the exhaust gas purification efficiency is improved by the above.
JP 2002266663 A

  The method and apparatus described in Patent Document 1 are expected to efficiently purify the exhaust gas with a small amount of catalyst even when the exhaust gas temperature is low by effectively utilizing the heat capacity of the heat storage body. However, there is a structural complexity such as requiring a heat storage body and a means for alternately switching the flow direction of the exhaust gas alternately. There is also a disadvantage that untreated gas is generated when the flow direction is switched.

  The present invention has been made in view of the above circumstances, and an improved exhaust gas treatment method for efficiently purifying exhaust gas from a gas engine, which is often lower than the activation temperature of the catalyst. And an apparatus.

  In the gas engine exhaust gas treatment method according to the present invention, when a harmful component contained in the exhaust gas of a gas engine is treated with a catalyst, the temperature of the exhaust gas is raised to a catalyst activation temperature or higher by a heating means, and then the catalyst is allowed to pass through. It is characterized by that.

  Usually, an oxidation catalyst in which Pt and Pd are mixedly supported on a honeycomb substrate has an activation temperature of 400 ° C. to 500 ° C., and a denitration catalyst such as alumina and silver has an activation temperature of 500 ° C. ~ 600 ° C. On the other hand, as described above, the exhaust gas of the high-efficiency gas engine is discharged at a temperature of about 400 ° C. or less than 400 ° C. in steady operation. In the present invention, after such low-temperature exhaust gas discharged from the gas engine is heated to a catalyst activation temperature of, for example, 400 ° C. to 600 ° C. or higher by an appropriate heating means such as an electric heater or a gas burner. Let the catalyst pass through. Thereby, it is possible to always reliably achieve a high purification rate of exhaust gas.

  Preferably, heat exchange is performed between the untreated exhaust gas before heating and the high temperature exhaust gas after passing through the catalyst. Thereby, the amount of heat input by the heating means can be effectively recovered, and fuel consumption can be reduced. Preferably, the exhaust gas temperature and / or the catalyst temperature is measured by a temperature sensor, and the heating value of the heating means is controlled by the output. In this case, when the exhaust gas temperature from the gas engine fluctuates due to operating conditions, etc., the minimum amount of catalyst activity is always created by controlling the amount of heat input to the heating means according to the output of the temperature sensor. Therefore, a high purification rate can be stably achieved with high processing efficiency.

  Preferably, the gas engine exhaust gas treatment apparatus according to the present invention is assembled as a unit as a whole. By making it a unit, it becomes portable and can be retrofitted to an existing gas engine. Therefore, it can greatly contribute to exhaust gas purification of gas engines used in cogeneration systems that are already in operation.

  Furthermore, the gas engine exhaust gas treatment apparatus of the present invention basically only needs to include a simple heating unit such as an electric heater or a gas burner, a heat exchanger, and a catalyst layer, and the flow direction of the exhaust gas is only one direction. Therefore, there is no need to provide a heat storage layer or flow path switching means, and there is an advantage that the configuration is simplified.

  According to the gas engine exhaust gas treatment method and apparatus according to the present invention, although it has a simple configuration, a high-purity catalyst purification process is performed on exhaust gas from a gas engine that is normally discharged at a temperature lower than the catalyst activation temperature. It is possible to carry out with high efficiency and low fuel consumption.

  Hereinafter, the present invention will be described based on embodiments. FIG. 1 is a conceptual diagram of an exhaust gas treatment method and apparatus for a gas engine according to the present invention. In FIG. 1, reference numeral 10 denotes a heat exchanger, which may be any conventionally known one as long as it is of a type that can exchange heat between gases. Reference numeral 20 denotes a heating unit, which includes arbitrary heating means such as a burner and an electric heater. Reference numeral 30 denotes a catalyst layer on which at least a conventionally known oxidation catalyst and denitration catalyst are disposed. 40 and 41 are temperature sensors such as thermocouples provided in the heat exchanger 10 and the catalyst layer 30, and 50 indicates the amount of heat input by the heating means in the heating unit 20 according to the output from the temperature sensors 40 and 41. It is a control device for controlling.

  Exhaust gas from a gas engine (not shown) at around 400 ° C. or below 400 ° C. is sent to the first flow path of the heat exchanger 10, passes through it, and flows into the heating unit 20. In the heating unit 20, heat is input from an appropriate heating means such as a gas burner, and the temperature of the exhaust gas is raised to, for example, about 600 ° C to 700 ° C. The heated exhaust gas then flows into the catalyst layer 30.

  The catalyst activation temperatures of the oxidation catalyst (for example, Pt, Pd, etc.) and the denitration catalyst (for example, alumina, silver, etc.) accommodated in the catalyst layer 30 are about 400 ° C. to 500 ° C. and 500 ° C. to 600 ° C., respectively. Any catalyst easily rises to its activation temperature by the heat of the inflowing exhaust gas. Thereby, the oxidation treatment of unburned hydrocarbons contained in the exhaust gas and the denitration treatment of nitrogen oxide proceed quickly and completely, and a high purification rate by the catalyst can be obtained.

  The exhaust gas that has passed through the catalyst layer 30 passes through the second flow path of the heat exchanger 10 and is released to the atmosphere. The exhaust gas that has passed through the catalyst layer 30 is still in a high temperature state, and heat exchange with the low-temperature untreated exhaust gas that passes through the first flow path of the heat exchanger 10 preheats the untreated exhaust gas. Thereby, the heat input by the heating unit 20 is recovered, and fuel consumption is reduced.

  The exhaust gas temperature after the temperature is raised by the heat exchanger 10 is detected by the temperature sensor 40, and a signal is output to the control device 50. Further, a catalyst temperature signal from a temperature sensor 41 attached to the catalyst layer 30 is also output to the control device 50. The control device 50 compares the two signals and outputs a signal to the heating unit 20 so that an amount of heat that can create a minimum temperature for the catalyst activity in the catalyst layer 30 at all times can be input to the exhaust gas. In this way, by controlling the amount of heat input in the heating unit 20 according to the exhaust gas temperature of the gas engine, the catalyst temperature can always be kept at the minimum temperature, so that the processing efficiency does not vary depending on the operating conditions.

  FIG. 2 shows an example of a gas engine exhaust gas apparatus according to the present invention, which is assembled as one unit. A cross-flow type (cross-flow type) heat exchanger is used as the heat exchanger 10, and the first flow path 11 that is in the back direction from the front in the figure and the second that is in the right-to-left direction orthogonal thereto. The flow path 12 is provided. The first flow path 11 is an inflow path of untreated exhaust gas, and a temperature sensor 40 that is a thermocouple is attached to the outlet side of the first flow path 11.

  In FIG. 2, a catalyst layer 30 is assembled on the right side of the heat exchanger 10. For example, a catalyst in which an appropriate oxidation catalyst and a denitration catalyst are supported on a honeycomb base material is disposed on the catalyst layer 30, and a temperature sensor 41 that is a thermocouple is also attached. A heating chamber 20 is assembled on the right side of the catalyst layer 30, and an electric heater 21 is attached to the heating chamber 20 as a heating source in this example.

  The untreated exhaust gas flowing out from the first flow path 11 of the heat exchanger 10 passes through the exhaust gas flow path 60 and enters the heating chamber 20. The untreated exhaust gas is heated to a required temperature by the electric heater 21 in the heating chamber 20 and then flows into the catalyst layer 30. Therefore, catalyst heating up to the catalyst activation temperature and purification treatment with the catalyst are performed, and the treated exhaust gas that is still in a high temperature state is released to the atmosphere through the second flow path 12 of the heat exchanger 10. At that time, heat exchange with the untreated exhaust gas flowing through the first flow path 11 is performed. The temperature of the untreated exhaust gas that has passed through the first flow path 11 is measured by the temperature sensor 40, and the temperature of the catalyst is measured by the temperature sensor 41. The signal is sent to a power load control device (not shown), and the amount of power input to the heating electric heater 21 is controlled.

  As shown in FIG. 2, the gas engine exhaust gas treatment apparatus is unitized, and is carried into an existing gas engine facility as it is. The inflow side of the first flow path 11 of the heat exchanger 10 is connected to the exhaust port of the gas engine. By connecting to (not shown), it is possible to easily and reliably purify the exhaust gas from the gas gas engine with a catalyst. The heat exchanger 10 may be a parallel flow type or a counter flow type instead of the cross flow type (cross flow type), and the heating means may be a gas burner instead of the electric heater 21.

The conceptual diagram of the exhaust gas treatment method and apparatus of the gas engine by this invention. It is a figure explaining one Embodiment of the gas engine waste gas processing apparatus by this invention, FIG. 2a has decomposed | disassembled and shown each member, FIG. 2b has shown the state assembled | attached as one unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Heat exchanger, 20 ... Heating part, 30 ... Catalyst layer, 40 ... Temperature sensor, 50 ... Control apparatus

Claims (8)

  A gas engine exhaust gas treatment method characterized in that when a harmful component contained in exhaust gas of a gas engine is treated with a catalyst, the temperature of the exhaust gas is raised to a catalyst activation temperature or higher by a heating means, and then the catalyst is allowed to pass through. .   The gas engine exhaust gas treatment method according to claim 1, wherein the catalyst is an oxidation catalyst and / or a denitration catalyst.   The gas engine exhaust gas treatment method according to claim 1 or 2, wherein heat exchange is performed between the exhaust gas before heating and the high temperature exhaust gas after passing through the catalyst.   The gas engine exhaust gas treatment method according to any one of claims 1 to 3, wherein the exhaust gas temperature and / or the catalyst temperature is measured by a temperature sensor, and the calorific value of the heating means is controlled by the output.   A gas engine exhaust gas treatment apparatus comprising a heat exchanger having a first flow path and a second flow path, a heating unit, and a catalyst layer, wherein the exhaust gas to be treated is a first flow path of the heat exchanger After passing through the heating section and flowing into the catalyst layer, the treated high-temperature exhaust gas that has passed through the catalyst layer passes through the second flow path of the heat exchanger, and after heat exchange with the treated exhaust gas flowing there, A gas engine exhaust gas treatment apparatus characterized by being discharged into the atmosphere.   The gas engine exhaust gas treatment apparatus according to claim 5, wherein the catalyst layer includes an oxidation catalyst and / or a denitration catalyst.   The first flow path outlet and the catalyst layer of the heat exchanger are provided with a temperature sensor, and further includes control means for controlling the amount of heat generated in the heating unit according to the output of the temperature sensor. The gas engine exhaust gas treatment apparatus according to claim 6.   The gas engine exhaust gas treatment apparatus according to claim 6 or 7, wherein the whole is assembled as a single unit.

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