The present invention relates to a spark-ignited Otto gas engine and a procedure for running a spark-ignited Otto gas engine having a combustion chamber and an exhaust gas duct and a thermal reformer, the reformer being connected to at least a part of the exhaust gas duct for supplying the reformer with heat.

It is known from EP 1 712 517 Al to produce H2 out of steam using catalysts and solar energy. During this process, the H-molecule is separated from the H20 at 500°C to 800°C and implemented in the catalyst structure. The regeneration of the catalyst requires temperatures of 1050°C to 1300°C. But temperatures of 1050°C to 1300°C are not obtainable from a gas engine, i. e. the exhaust gas.

DE 2 056 131 A discloses a procedure for running an Otto- engine using petrol or fuel and adding hydrogen. The hydrogen is produced by catalytic reforming of hydrocarbons; in doing so, the energy for generating hydrogen is taken from the exhaust gas.

Object of the invention is to configure and arrange a spark-ignited gas engine in such a way that a higher degree of efficiency is realized.

According to the invention, the aforesaid object is achieved in that said reformer is supplied with water and converts water (H20) into hydrogen (H2) according to the following reactions:

Rl: O _r e _d + H20 «-» M0 _OX + H2 (separation), R2: M0 _OX «-» MO _r ed + 02 (regeneration) and in that there are additional heating means powered by a part of the gas the engine is powered with in order to achieve one or both of the following exothermic oxidation reactions :

R3: CH4 + 202 «-» 2H ₂ 0 + C0 ₂ (oxidation), R3' : C _n H _m + ₍ n/2 ₎ 02 <<->> _(m/2) H2 + _n C0, (partial oxidation) whereby the heating means are thermodynamically coupled to the reformer for additionally heating the reformer. Due to the fact that the reformer is being supplied with additional heat by the heating means, particularly process R2 is supplied with extra heat to regenerate the catalyst and discharge H2.

According to the invention, the aforesaid object is also achieved by said procedure in which said reformer is supplied with water and converts water (H20) into hydrogen (H2) according to the following reactions::

Rl: O _r ed + H20 «-» 0 _OX + H2,

R2: 0 _OX «-» M0 _red + 02,

and in that there are additional heating means, said heating means being powered by a part of the gas the engine is powered with in order to achieve the following exothermic oxidation reaction:

R3: CH4 + 202 «-» 2H ₂ 0 + C0 ₂ ,

R3' : C _n H _m + ₍ n/2)02 «-» _(m/2 ,H2 + _n C0,

whereby the heating means are thermodynamically coupled to the reformer and are additionally heating the reformer.

The invention is to transform the exhaust energy of the engine via reactions Rl, R2 into chemical stored energy in form of H2, using a part of the gas, the engine is powered with .

In case of reaction R3' the product gas carbon monoxide is charged to the engine, too. The same engine that has produced the chemical stored energy (H2) is supplied with the energy restored in H2. The reformer is supplied with the exhaust gas as well as with further thermal energy, achieved by oxidation of for example methane during the processes R3, R3' . The methane is part of the gas the engine is powered with. Reactions Rl and R2 which are endothermic are coupled with reactions R3, R3' which are exothermic.

The produced H2 is mixed to the gas mixture which increases the efficiency of the engine. Though the efficiency asset results in part from the methane for the oxidation reaction R3, R3' , energy is recharged with H2 , produced by using ex ^¬ haust gas energy.

The efficiency of the H2 production by a chemical reaction is not subject to restrictions like a thermo dynamic cyclic process. Therefore, the thermal exhaust energy used in this chemical process is reformed with a much better degree of efficiency which leads to a better degree of efficiency overall .

Moreover recharging this produced H2 leads to a combustion which is better, faster and more balanced. In addition to this, it is possible to reduce the nitrogen oxide (N0 _X ) and the formaldehyde, i. e. methanal (CH ₂ 0) emissions, because the added H2 has a catalytic effect on the combustion. For this the efficiency of the engine is increased, too.

A normally driven 1 MW engine with a coupled generator has a degree of efficiency of about 43,7 %. If this engine is driven with said reformer (Rl and R2 ) including the oxida ^¬ tion step R3, the degree of efficiency raises up to about 50,5 %. It can also be an advantage to have at least one compressor for loading a combustion chamber with an air-gas-mixture, whereby at least one compressor is motor-driven. Additionally to the energy of reaction R3, R3' , the exhaust gas turbine of the turbo charger could be replaced and the air compressor could be driven by electricity. This allows the exhaust gas to keep more of its thermal energy, i.e. higher exhaust gas temperatures of about 550° C to 600° C, which are 100° C to 150° C higher as in case of an exhaust gas turbine. These temperatures are used for the reactions Rl and R2. In this case, the degree of efficiency raises up to about 53 %.

Over all an increase of about 10 % for a normally driven 1 MW engine is possible.

A successive alternation of two reactors is possible. While one is producing H2, the other is regenerated. The two re ^¬ actors are placed within the exhaust gas stream.

Although energy is required to drive the electric motor, the overall engine efficiency is higher. One reason is the fact that the efficiency of the reforming process is much higher than the efficiency of the turbine.

Another increase in efficiency is achieved with an exhaust gas turbine and with at least one further compressor, said further compressor being mechanically operated via the ex ^¬ haust gas turbine, said exhaust gas turbine being positioned downstream to the reformer. Adapted to the procedure, the engine has an exhaust gas turbine and at least one further compressor for loading a combustion chamber with an air-gas-mixture, said further compressor being me ^¬ chanically operated via the exhaust gas turbine, said tur ^¬ bine being positioned downstream to the reformer. The pres- sure of the exhaust gas can be used for a pre-compression of the air-gas-mixture. Thus, the energy for the electri ^¬ cally driven compressor is reduced.

Especially stationary engines which are integrated in a cogeneration process are supplied with natural gas, for which a addition of hydrogen is advantageous, especially in view of generating a higher rate of combustion. Other advantages and details of the invention are explained in the claims and in the description as well as shown in the figures, in which:

Figure 1 shows a schematic diagram of a supply chain of an engine generator unit with a H2 reformer;

Figure 2 shows a schematic diagram similar to figure 1 with an electrically driven compressor.

The schematic diagram in Figure 1 shows the supply chain of a spark-ignited gas engine 1 with an air-gas mixture and the exhaust system of the spark-ignited gas engine 1.

Starting from a gas mixer 18 at which the ambient air is mixed with the combustion gas, an air-gas duct 22 is conducted via a compressor 2 and an air-gas mixture cooler 8 to the gas engine 1 or to a combustion chamber 1.1 of the gas engine 1. A throttle valve 10 that is controlled based on the output of the gas engine 1 is provided in this air- gas duct 22 immediately upstream of the gas engine 1.

The gas engine 1 comprises an exhaust gas duct 6 in which an exhaust gas turbine 5 is provided downstream from the gas engine 1 that is used to drive the above-mentioned compressor 2. After passing through the exhaust gas turbine 5, the exhaust gas is conducted through a reformer 3 where it dissipates heat to the reformer 3 or the first reactor 3.1 or the second reactor 3.2, respectively. The exhaust gas passes the reformer 3 in parallel via two separate exhaust gas streams that are coupled or controlled, respectively, via a valve for exhaust gas 15 and associated with the respective reactor 3.1, 3.2. The valve for exhaust gas 15 is followed by a heat exchanger or superheater 13, respective ^¬ ly, and a downstream evaporator 14 for the water circuit 23 described below. An exhaust gas heat exchanger 11 is provided downstream before the exhaust gas is carried off to the exhaust system not shown here.

A water circuit or water duct 23 is provided for supplying the reformer 3 with water for producing hydrogen. First, the water carried in it is preheated by a heat exchanger for water 23.1 coupled to the air-gas duct 22, wherein the heat is taken from the compressed exhaust gas-air mixture. Then the water is heated in the evaporator 14 mentioned above, and the vapor is overheated accordingly in the downstream superheater 13 before it is returned to one of the two reactors 3.1, 3.2 of the reformer 3 via a respective valve for water 17. The hydrogen that is produced during reformation is fed to the gas mixer 18, and thus to the air-gas mixture, for combustion in the gas engine 1 via a hydrogen duct 12 and a condenser 12.1. The oxygen generated during hydrogen generation is carried off into the environ ^¬ ment via a waste gate 3.3.

In order to achieve the temperatures required in the respective reactor 3.1, 3.2 or in the reformer 3, respective ^¬ ly, the respective reformer additionally comprises heating means 7.1, 7.2 that are also supplied with the air-gas mixture fed to the gas engine 1. For this purpose, the air-gas duct 22 comprises an air-gas valve 22.1 via which the re ^¬ quired air-gas mixture is supplied via another air-gas valve 16 to the respective reactor 3.1, 3.2 or the respective heating means 7.1, 7.2. The C0 ₂ exhaust gas that is produced when operating the respective heating means 7.1, 7.2 is carried off via a waste gate 3.3.

In addition, the gas engine 1 comprises a cooling circuit 9 with an engine heat exchanger 9.1 for cooling the gas engine 1. The cooling circuit 9 is also connected to an oil cooling exchanger 19.

The measure described above for the reformer 3 considerably improves the efficiency of a gas engine 1-generator 21 unit .

According to the functional diagram shown in Figure 2, the compressor 2 is driven by an electric motor 20. The exhaust gas turbine 5 as shown in Figure 1 is eliminated. The exhaust gas, when it enters the reformer 3, has a temperature that is 100°C to 150°C higher. This higher temperature serves improved operation of the reformer 3 or the respective reactor 3.1, 3.2 such that the heating means 7.1, 7.2 can generate less heating output.

Additionally to that there is one further compressor 4 for preloading the air-gas-mixture, said further compressor 4 being mechanically operated via an exhaust gas turbine 5, said exhaust gas turbine 5 being positioned downstream to the reformer 3. Reference list spark-ignited gas engine, gas engine combustion chamber

compressor

reformer

first reactor

second reactor

waste gate of reformer

further compressor

exhaust gas turbine

exhaust gas duct, exhaust gas stream heating means

heating means

air-gas-mixture cooler

cooling system / circuit

cooling water heat exchanger

throttle valve

exhaust gas heat exchanger

hydrogen duct

condenser

superheater

evaporator

valve for exhaust gas

valve for air-gas

valve for water

gas mixer

oil cooling exchanger

electric motor

generator

air-gas-duct

air-gas-valve water circuit, water duct heat exchanger for water