Method of starting up a thermoreactor

Abstract

A method of starting up a thermoreactor arranged in an exhaust gas flow of an internal combustion engine includes igniting combustion gas by spark ignition in at least one cylinder of the internal combustion engine. The exhaust gas resulting from the combustion of the combustion gas is fed at least partially to the thermoreactor as an exhaust gas flow. The temperature of the exhaust gas resulting from combustion of the combustion gas is increased by the moment in time of the spark ignition being selected later in comparison with a present moment in time.

Claims

1. A method of starting up a thermoreactor arranged in an exhaust gas flow of an internal combustion engine, the thermoreactor including a first thermal storage mass and a second thermal storage mass which successively have a flow therethrough, the method comprising: igniting combustion gas by spark ignition in one cylinder of the internal combustion engine; and feeding exhaust gas resulting from the igniting of the combustion gas to the thermoreactor as the exhaust gas flow, wherein the feeding the exhaust gas includes alternatively feeding, according to a switching time, the exhaust gas to (i) the first thermal storage mass such that the exhaust gas fed to the first thermal storage mass then successively flows through the second thermal storage mass and (ii) the second thermal storage mass such that the exhaust gas fed to the second thermal storage mass then successively flows through the first thermal storage mass, and wherein the thermoreactor is heated by an external heat source, and the switching time during a start-up operation of the thermoreactor is reduced with respect to a normal operation of the thermoreactor for more rapidly heating up the thermoreactor during the start-up operation of the thermoreactor.

2. The method according to claim 1, wherein a temperature of the exhaust gas resulting from combustion of the combustion gas is increased by delaying a timing of the spark ignition with respect to a standard operation timing.

3. The method according to claim 1, further comprising reducing a power output of the internal combustion engine to reduce a mass flow of the exhaust gas flow.

4. The method according to claim 1, further comprising heating the exhaust gas fed to the thermoreactor using the external heat source, wherein the external heat source is an electrical heating device.

5. The method according to claim 1, wherein the switching time is set such that the exhaust gas is alternatively fed to the first thermal storage mass and the second thermal storage mass to prevent thermal equalization within the first thermal storage mass and the second thermal storage mass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in greater detail hereinafter by means of the Figures in which:

(2) FIG. 1 shows a diagrammatic view of an internal combustion engine with downstream-connected thermoreactor, and

(3) FIG. 2 shows (diagrammatically) the temperature pattern when starting up a thermoreactor.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows an internal combustion engine 1, from which untreated exhaust gas flows through the exhaust manifold 2 in the direction of a switching-over mechanism 4. From the switching-over mechanism 4 the exhaust gas flows further into the thermoreactor, in which case the switching-over mechanism 4 can alternately change the flow direction through the thermoreactor 3. The flow direction can either be firstly by way of the storage mass 5, the reaction chamber 7 and then the storage mass 6, or vice-versa. The exhaust gases then leave the plant by way of the conduit 8.

(5) The thermoreactor is heatable by the electrical additional heating means 10. Support gas can also be fed to the thermoreactor as additional heating, by way of a burner or injector 11. The gas for the burner or injector 11 can be taken from the fuel line 12.

(6) The open loop/closed loop control device 9, by way of the signal lines shown in broken line, receives signals from temperature sensors (not shown) from the region of the switching-over mechanism 4 and the reaction chamber 7. In addition from the internal combustion engine 1 the open loop/closed loop control device 9 receives signals which are characteristic of the operating state of the internal combustion engine 1. In dependence on the detected signals, the open loop/closed loop control device 9 gives commands to the switching-over mechanism 4 for reversing the flow direction through the thermoreactor 3.

(7) The open loop/closed loop control device 9 provides the internal combustion engine 1 with target values for the power output to be delivered and/or engine speed. An ignition device 13 is diagrammatically shown. It will be appreciated that, in reality, at least one ignition device 13 is associated with each piston-cylinder unit. The open loop/closed loop control device 9 gives the ignition device 13 commands, inter alia relating to the moment in time of spark ignition.

(8) The thermoreactor 3 can also assume other structural forms. Thus, for example, it can be provided that the switching-over mechanism 4 is in the form of a rotary slider, that is to say in the form of a plate with alternately closed and opened segments which alternately close or open the flow through the thermoreactor 3 which is arranged downstream of the rotary slider. It is, therefore, in no way necessary to have a separate housing for the storage masses 5 and 6, as diagrammatically shown in FIG. 1, but it is possible for the thermoreactor 3 also to be in the form of a one-piece column of storage masses, wherein the rotary slider in operation makes certain segments available for the flow therethrough and keeps other segments closed.

(9) FIG. 2 diagrammatically shows the temperature pattern when starting up a thermoreactor in accordance with the state of the art in comparison with the temperature pattern in accordance with the improved method of the present application. In the graph, the temperature is plotted on the y-axis in relation to time on the x-axis, wherein the time begins at zero at the origin of the co-ordinate system. The temperature in the reaction zone of the thermoreactor initially rises due to the transmission of heat from the exhaust gas to the reaction chamber and due to the electrical additional heating means which are active from the start onwards.

(10) To assess the start-up performance, that time is critical, which elapses until a first temperature plateau is reached at the temperature T2. The temperature T2 is selected approximately as being 630° C. It is only when that temperature is reached that the additional heating is begun using a burner or gas injection. Below that temperature no gas should be fed to the thermoreactor as conversion would not be guaranteed. Therefore, the duration until the temperature T2 is reached is the determining factor in respect of time for the start-up procedure.

(11) After initiation of the additional heating by a burner or gas injection the thermoreactor quickly reaches the operating temperature T3 of about 800° C.

(12) The broken line H1 shows the temperature pattern in the reaction zone when starting up a thermoreactor in accordance with the state of the art. The temperature pattern of the exhaust gas in accordance with a method according to the state of the art is represented by the dotted curve EXH1. Here, the exhaust gas temperature in the stable mode is at about 530° C. (T1). Time t1 marks the moment in time of initiating additional heating in the reaction zone with a method according to the state of the art.

(13) In comparison therewith the temperature of the reaction zone in accordance with the improved method of the present application, represented by curve H2, reaches the temperature T2 at which the additional heating may be activated, substantially earlier, namely at time t2. The displacement to earlier times is symbolised by the black arrow.

(14) Typical times for t1 are 10 hours when the installation is started up from ambient temperature, or 10 minutes when the installation is set in operation again after only a short stoppage time (for example after an inspection of two hours).

(15) Those times can be markedly reduced by using the methods described in the variants or embodiments by way of example.

LIST OF REFERENCES USED

(16) 1 internal combustion engine 2 exhaust manifold 3 thermoreactor 4 switching-over mechanism 5, 6 thermal storage masses 7 reaction chamber 8 exhaust gas conduit 9 open loop/closed loop control device 10 electrical heating device 11 burner/injector 12 fuel line H1 temperature pattern of thermoreactor in the state of the art H2 temperature pattern of the thermoreactor EXH1 exhaust gas temperature in the state of the art