DE9308772U1 - Device for operating a combustion system, in particular in the form of a cogeneration or a combined heat and power plant with an exhaust gas cleaning system, in particular for the combustion of heavy heating oil or heavy oil - Google Patents

Description

Applicant: Mr. Dipl.-Ing. Arno Schneider, 53343
Wachtberg, Marienforster Weg 7

Representative: Patent Attorney Dipl.-Phys. Theodor Koch,
Colmantstr. 20, 53115 Bonn

Designation: Device for operating a combustion plant, in particular in the form of a combined heat and power plant or a combined heat and power plant with an exhaust gas purification system, in particular for the combustion of heavy heating oil or heavy oil.

The present innovation relates to a device for operating a combustion plant, in particular in the form of a combined heat and power plant or a cogeneration plant, with diesel, pilot jet, gas/diesel, large gas-Otto engines, gas turbines and/or a boiler plant burning liquid, gaseous or solid fuels, in particular heavy oil, with an exhaust gas purification system consisting of at least one afterburning chamber of a process furnace or a boiler plant, the boiler or furnace plant having one or two afterburning stages and preferably being operable as a recuperator, so that the purified flue gas streams to be returned to the combustion plant can be cooled,
and a supply and mixing device as well as a control device for the first and second post-combustion stages, so that the fuel, oxygen or additive quantities to be mixed in these combustion stages for exhaust gas aftertreatment and to avoid the formation of pollutants or to reduce them can be injected into the post-combustion chambers and/or introduced beforehand.

are, whereby in the first post-combustion stage only with fuel supply and at elevated temperature flue gas components with smaller oxygen binding energies than C0~ can be burned out without additional combustion air supply, or whereby a device for measuring the free and bound residual 0~ quantities is installed in the flue gas duct before the first and/or second post-combustion stage and thus the fuel supply as well as the oxygen supply is carried out in a stationary and/or largely stoichiometric manner in relation to the mass flow to be converted, and that preferably for returning a part of the flue gas flow of the boiler or furnace system to the combustion chambers or combustion chambers of the combustion system, a line system is provided between the outlet of the boiler or furnace system and the inlet of the combustion chambers or combustion chambers of the combustion system. Such a device, in particular for operating combined heat and power plants or cogeneration plants, is known from DE 38 24 813 C2.

According to this patent, it is largely possible to clean the exhaust gas flow from combined heat and power systems in the process furnace or in a boiler system by post-combustion in such a way that it only has an extremely low pollutant load. Combustible residual components of the primary fuels from the main combustion process as well as combustible components from the post-combustion stage are largely eliminated from the flue gas when a precise control system is used, at least if no heavy oil or heavy heating oil is burned.

Exhaust gas purification for heavy oil or heavy heating oil is

This is problematic in that a large proportion of SO ₉ and NO is present in the flue gases of such primary fuels. It is practically impossible to inject additional primary fuel quantities into the unburned fuel quantities in the first post-combustion stage in such a way that a stoichiometric consumption of the total residual oxygen quantities occurs while reducing the NO and CO exhaust gas components.

The operation of such an exhaust gas purification system with a first and second post-combustion stage in a boiler system very often does not fall significantly below the limit values of the TA-Luft, particularly in stationary operation, where the addition of the primary material and oxygen quantities is done manually or where it is only done without measuring the remaining free and bound residual oxygen components in accordance with a characteristic field control.

In addition, the NO content cannot be significantly reduced in heavy oil and the like even by double afterburning in two afterburning stages according to DE 38 24 813 C2.

Even with exhaust gas purification in accordance with JP-OS 60 156, the nitrogen oxide content of the exhaust gases cannot be completely reduced.

With this known selective non-catalytic exhaust gas purification (SNCR), the exhaust gases from the combustion chambers still have the nitrogen oxide values that are usual for boiler exhaust gases, around 150-200 ppm. In particular, there is no complete burnout of the exhaust gases with regard to

It is possible to remove residual components that can be burned out at temperatures below 800 C.

The use of an exhaust gas purification process by afterburning the flue gases in a boiler or furnace system according to DE 38 24 813 C2, in particular by forming heat and power coupling, is desirable insofar as this afterburning ensures a high energy efficiency of the combustion system, taking into account the energy that can be obtained in the afterburning. In this respect, the diesel engine system and the boiler system are run in parallel, i.e., they are not operated separately in time. In this respect, the energy content of the fuels is optimally utilized.

Such a high level of energy efficiency cannot be achieved with a diesel engine system alone with only reduction and oxidation catalysts for exhaust gas purification.

The purpose of the present innovation is therefore to improve a device for operating an incineration plant with a boiler or furnace system for the afterburning of exhaust gases and for the reduction of their pollutants in accordance with DE 38 24 813 C2 in such a way that, on the one hand, the plant can be operated with a high level of energy efficiency and, on the other hand, the oxidation and reduction of the pollutants can be carried out more effectively, whereby in particular the combustion of heavy oil and heavy heating oil with reduction and oxidation of the NO components of the flue gas should be made possible. The oxidation of the pollutants in the exhaust gas purification system should

if possible in accordance with DE 38 24 813 C2 in such a way that S0~ is not converted into SOo. The formation of SOo, which usually occurs in selective oxidation catalysts due to the TiOp and platinum coating, should be excluded as far as possible when using such selective catalysts.

To solve this problem, the design of the device for operating an incineration plant of the type mentioned at the outset is provided in accordance with claim 1.

The exhaust gas purification system consists of a combined selective-catalytic exhaust gas purification system with at least one NO-selective reduction catalyst and possible oxidation catalysts for CO and CH combustion as well as an exhaust gas purification system according to DE 38 24 813 C2 with at least a first or also a first and second afterburning stage.

In principle, it is possible to install the selective catalysts upstream or downstream of the boiler and furnace system. With an upstream reduction catalyst, the NO is largely removed from the flue gas, e.g. from diesel engine exhaust gases, before the afterburning takes place.

The regulation of the reactant dosage (e.g. urea) and the stoichiometric addition of fuels in the first post-combustion stage and of fuels and oxygen in the second post-combustion stage of the boiler system can be carried out in the simplest way according to the performance of the diesel engines, whereby the main aim is to break down CO into CO2. A

simple characteristic field control instead of A control. It is therefore often no longer necessary to measure the residual oxygen content in the exhaust gas using a probe, as is provided for in the device according to the method DE 38 24 813 C2.

The operation of the first and second post-combustion stages can also be partially stationary. Post-combustion in a boiler has the advantage that a higher temperature level is achieved for the medium in the secondary circuit (thermal oil, steam, etc.) that is heated in a heat exchanger. When the two exhaust gas purification systems are combined in the boiler, there is no increase in volume due to the fuel supply, so that no large amounts of pollutants are produced. The fuel supply only leads to a larger mass of exhaust gases, i.e. the exhaust gases become denser.

If the primary fuel and oxygen addition in the first and second post-combustion stage as well as the addition of reactants to the exhaust gas stream before the NO exhaust gas stream is carried out almost stoichiometrically, the combination of the exhaust gas purification systems can achieve significantly low NO, CO and C H emission values.

x mn

to reach.

This applies in particular to the use of combined heat and power plants and cogeneration plants.

Due to the possible stationary operation of the first and second post-combustion stage or a simple characteristic field control of the boiler or furnace system, the necessary control and regulation technology

The effort required to operate the selective catalysts and the two afterburning stages is considerably lower than if the necessary exhaust gas purification is carried out individually.

In the catalytic exhaust gas purification system, the injection of reactants allows hydrocarbons present in the exhaust gas to be converted and the released carbon to be converted into carbon monoxide. The resulting amount of CO can then be oxidized to water vapor and carbon dioxide in subsequent oxidation catalysts. The higher hydrocarbons that make up the
The oxidizing agents that produce the typical diesel smell in the exhaust gases are effectively oxidized so that the exhaust gases become odorless. The reduction catalysts can be operated with conventional devices for dosing and spraying the nitrogen-containing reactant.
The same applies to the oxidation catalysts, where with normal mixing and catalyst expenditure a NO concentration

3
tration of less than 100-200 mg/m can be achieved.

To operate the catalytic exhaust gas purification system, in particular for urea injection, the four main components exhaust gas mixing and catalyst housing, reactant tank, reactant metering device and electronic system control are required, as claimed in detail in claims 2-15 and in particular for urea injection according to the Swiss patent application 00 556/92.

The urea addition can be achieved upstream of the catalyst with a very high degree of pyrolysis and mixing, whereby a largely complete

constant decomposition of the urea into ammonia and carbon dioxide or its conversion into ammonia, cyanuric acid and carbon dioxide is achievable. The pyrolysis must take place at temperatures higher than 270 C so that no cyanides and hydrocyanic acid are formed. The urea dosage is carried out according to the performance of the combustion engine, whereby a microprocessor control for the reactant control valve allows the reactant flow to take place depending on the generator power signal of the combustion engine according to a pre-programmed NO mass flow curve, and the combustion engine can be driven with variable performance. There is no need to control the urea dosage as a function of the resulting mass flow.

The handling of urea is less problematic than the injection of ammonia due to the lack of an unpleasant smell and the lack of risk of explosion.

Advantageous embodiments of the new
Device for operating a combustion plant with afterburning of the exhaust gases and a selective catalytic exhaust gas purification are furthermore evident from the protection claims and the following description of a preferred embodiment of the plant used, wherein the use of a simple reduction catalyst as well as a selectively acting double catalyst comprising an arrangement of reduction and oxidation catalysts is explained.

The drawings show:

Figure 1: A combined heat and power system with a diesel engine system and with exhaust gas purification in a boiler by exhaust gas afterburning as well as an upstream catalytic exhaust gas purification with reduction and oxidation catalysts, where urea is injected as a reactant into the exhaust gas to be fed to the reduction catalyst, pyrolyzed and mixed with the exhaust gas.

Figure 2: A schematic representation of the circuit of the exhaust gas routing of the diesel engine with integrated exhaust gas aftertreatment in a boiler in which additional amounts of fuel and/or oxygen are mixed with the exhaust gas in order to break down the pollutants in this boiler for exhaust gas aftertreatment in a first afterburning stage (reduction stage) and a second afterburning stage (oxidation stage).

Fig. 3-7: Alternative arrangements of the catalysts used for selective catalytic exhaust gas purification,
reduction and/or oxidation catalysts constructed as honeycomb catalysts, whereby, according to Figure 3, a reduction catalyst is installed upstream of the boiler used for afterburning,

According to Figure 4, a selectively acting double catalyst consisting of a reduction and an oxidation catalyst is installed upstream of the boiler,
According to Figure 5, the boiler only has a
Reduction catalyst is connected downstream,
According to Figure 6, the downstream connection of several reduction and oxidation catalysts is provided and according to Figure 7, reduction catalysts are connected upstream of the heating boiler and oxidation catalysts are connected downstream of it.

In the diesel engine system (2) of a combined heat and power plant with flue gas cleaning shown in Figure 1, the flue gas is first fed into a selective catalytic exhaust gas cleaning system (4). There, a reactant is injected into the flue gas to reduce NO in an arrangement of three reduction catalysts (22). Two oxidation catalysts (23) are also provided for CO and CH combustion. The flue gas is then fed to a post-combustion device (1) with a boiler (3).

Figure 1 shows the basic structure of the selective catalytic exhaust gas purification system (4).

A reactant storage tank (24) prepared

10

Aqueous urea solution is homogeneously mixed into the hot exhaust gas flow (30) of the diesel engine or diesel/gas engine exhaust gases, which has an excess air of λ = 1.5 - 2.5, inline by a mixer (34) arranged in a mixing channel (25). In an in-line reaction channel (26), the reducible exhaust gas components are reacted with the aqueous urea solution in three selective, non-zeolite-containing reaction catalysts (22) and then the oxidizable exhaust gas components without reactants in the two oxidation catalysts (23) to produce harmless gases for a largely complete reaction as required.

The urea is introduced into a pyrolysis channel (27) upstream of the mixing channel (25) through a two-component nozzle device (28) opening there, with the urea being supplied via a urea conductor (29) guided coaxially inside a jacket pipe. A finely divided spraying of the aqueous urea solution via a nozzle (31) of the two-component nozzle device (28) is achieved via compressed air guided coaxially outside the urea conductor in the jacket pipe.

The electrical system control (33) for reactant injection is housed in a control cabinet (33) and monitors and controls a tank agitator and the tank level in the reactant storage tank (24), a reactant pump (34), a nozzle air compressor (35), a reactant control valve (36) with switchover for the working and blow-out position of the two-fluid nozzle device (28), the reactant controller in the control cabinet (33') for setting the operating states of the selective catalyst system with digital display of the target and

Actual values of the reactant quantity, the exhaust gas temperature, the exhaust gas back pressure and an electronic error message.

The control is carried out in accordance with Euronorm EN 60 204, whereby a microprocessor control for the reactant control valve (36) ensures that the diesel engine system (2) can be operated with variable power and that the reactant flow is controlled depending on the generator power signal of the diesel engine system according to a pre-programmed NO mass flow curve.

The mixing channel (25), the reaction channel (26) and the pyrolysis channel (27) of the exhaust gas purification system (4) can be arranged in a compact arrangement instead of in an elongated arrangement of the channels, whereby these are arranged one above the other in a housing. The individual channels as well as the reduction and oxidation catalysts (22, 23) are housed in a closed and insulated stainless steel reactor housing. Screwed covers are attached to the stainless steel reactor housing for replacing and maintaining the reduction and oxidation catalysts (22, 23).

The inlet and outlet exhaust gas lines are connected to the housing via standard flanges. The exhaust gas temperature for an optimal catalytic reaction is between 350 and 450 C. A reactant metering device arranged in a machine cabinet (32) consists of the reactant pump (34), a pressure holding valve, the electric reactant control valve (36), a reactant pressure measurement, an electric reactant flow measurement, the nozzle air compressor (35), a nozzle air pressure measurement and the necessary

Wiring of the components to each other and to the control cabinet (33*) or the electrical system control there (33). The hydraulic and pneumatic connections to the reactor housing of the exhaust gas purification system (4) and to the reactant tank are made using high-strength hoses with quick connectors. The control and power cables are connected to the control system via a terminal block.

A 40% urea water solution is used as the reactant, which is stored, for example, in a reactant day tank.

The use of reactants to reduce nitrogen oxides in exhaust gases by means of selectively acting reduction catalysts is described in US patent 4,978,514, in accordance with international patent application WO 91/04 224, and US patent 5,139,754, and the injection of reactants specifically in the form of an aqueous urea solution and the construction of an exhaust gas purification system used for this purpose is described in Swiss patent application No. 00 556/92.

The catalytic exhaust gas purification system shown in Figure 1 (4) according to Swiss patent application No. 00 556/92 ensures a largely complete decomposition of the urea into ammonia and carbon dioxide or its conversion into ammonia, cyanuric acid and carbon dioxide before the urea-containing water droplets in the exhaust gas flow hit a hot metal surface and form intolerable deposits.

In contrast to the exhaust gas purification system according to DE 3 830

045 Al, in which a reduction of nitrogen oxides in exhaust gases is made possible by a zeolite-containing catalyst, even with a low hydrocarbon content of the exhaust gases, non-zeolite-containing catalysts are used in the selective catalytic exhaust gas purification system (4) shown, with which practically exclusively harmless gases are emitted, without impairing the high pollutant conversion rates and economical operation that can be achieved.

The aqueous urea solution of various concentrations is injected into the hot exhaust gas stream and then an at least one-stage, catalytic reaction of the harmful gaseous exhaust gas components is carried out with a reduction or a reduction and an oxidation stage, whereby the added aqueous urea solution is finely sprayed by means of a compressed air stream in the direction of the exhaust gas stream into the pyrolysis channel (27) and is homogeneously mixed in-line by mixers arranged in the mixing channel (25). At least two cross-flow mixers (34) arranged at a distance are used.

and in the reaction channel (26), depending on the type of afterburning in the device (1), at least the reducible exhaust gas components are largely reacted with the decomposition product (N0~) of the aqueous urea solution in at least one selective, non-zeolite-containing reduction catalyst (22), or additionally also the oxidizable exhaust gas components without reactants in at least one oxidation catalyst (23) to form harmless gases.

In the reaction channel (26) in the direction of the exhaust gas

The honeycomb-shaped reduction catalysts (22) and oxidation catalysts (23) are installed in the stream.

The two-component nozzle device (28) extends into the pyrolysis channel (27), where the finely sprayed urea solution is fed into the hot exhaust gas flow marked with an arrow (30). The feed line for the raw flue gases flows into the pyrolysis channel (27) immediately before the two-component nozzle device (28). The pyrolysis, in other words the decomposition of the urea into ammonia and carbon dioxide, possibly with the formation of cyanuric acid, takes place immediately in the pyrolysis channel and runs off completely. The exhaust gas flow with finely divided ammonia and carbon dioxide then enters the mixing channel (25) and runs in the opposite direction through three cross-flow mixers (34) of conventional design.

The exhaust gas flow, now homogeneously mixed with the decomposing reactant, is diverted into the reaction channel (26), where it is first guided through the two reaction catalysts (22) arranged at a distance, then through two oxidation catalysts (23) which are also arranged at a distance and have the same geometric design, which can also be removed or switched off without the oxidation process. The exhaust gas flow, which has now been largely freed of gaseous pollutants, now flows into the device (1) for exhaust gas afterburning in the boiler (3) there and then into a heat exchanger and exits via a chimney.

In the reduction and oxidation catalysts shown

The selective catalysts (22, 23) indicate that they have a honeycomb structure with longitudinal channels. A perforated plate is arranged in front of the first reduction catalyst (22) as a flow straightener. The exhaust gas flow flows laminarly in the area of the catalysts (22, 23) and turbulently in the areas between these catalysts. In each turbulent zone, a subsequent mixing takes place. The selective catalysts (22, 23) are arranged in modules, each comprising several honeycomb bodies. The honeycomb bodies can be arranged next to one another, one above the other and/or one behind the other. The longitudinal channels of the honeycomb bodies are expediently square and have a side length of 2-8 mm. This allows a laminar flow to be generated in the longitudinal channels of the honeycomb bodies. The number, arrangement and length of the modules are determined not only by economic but also by technical conditions. In the reduction stage, the extruded honeycomb bodies consist of titanium, tungsten or vanadium oxide, for example, or an inert base structure is coated with at least one of these materials. In addition to the catalyst composition, the channel opening and number of channels, the web width and the number of honeycomb rows can vary depending on the design.

The reactants nitrogen oxide, ammonia and oxygen of the exhaust gas flowing laminarly through the longitudinal channels of the honeycomb structures reach the fine-pored structure of the honeycomb walls through diffusion and adsorption and react there at the active centers through selective catalytic reduction. The reaction product is water, nitrogen and carbon dioxide.

Due to pore blockage and/or catalyst poisons, which

destroy the active centers, the catalyst gradually loses its activity over a long period of operation. When a minimum level of activity is reached, the catalyst honeycombs are replaced and recycled. The drop in activity and the time of replacement are calculable.

The oxidation catalysts (23) consist of extruded honeycomb bodies with a ceramic base structure, in whose surface catalytically active precious material, such as platinum, rhodium and/or palladium, is embedded. The geometry of the honeycomb bodies and the type of active coating can be selected depending on the design.

In contrast to the selective reduction process, the oxidation takes place without an additional reactant. The oxidation catalyst causes the oxidizable gaseous exhaust pollutants to burn flamelessly even at very low concentrations and far below the auto-ignition temperature. For this oxidation process, it is necessary that a minimal amount of residual oxygen is present in the exhaust gas. The reaction products of the oxidation are carbon dioxide and water.

The transport of the gas molecules to be oxidized from the longitudinal honeycomb channel into the active coating occurs as with the selective catalytic reduction catalyst through diffusion, caused by the decrease in concentration in the area of the active coating.

The oxidation catalyst is also subject to aging, and due to catalyst poisons and deposits it gradually loses its activity. After reaching a minimum

Activity, the catalyst honeycombs are replaced and recycled.

The honeycomb bodies of the reduction and oxidation catalysts are each surrounded lengthwise by an elastic stocking made of knitted or woven glass fibers. This stocking serves as protection against impacts and also seals the adjacent honeycomb bodies, which prevents the exhaust gas flow from flowing past the honeycombs or longitudinal channels.

The device for operating the diesel engine system (2) in the form of a combined heat and power system with a gas turbine system and a heating boiler or a furnace system (3) for the afterburning of the resulting flue gases is shown schematically in Figure 2. The selective catalytic catalysts are connected upstream or downstream of the heating boiler or furnace system (3) according to Figures 3 - 6.

According to DE 38 24 813 C2, in a first post-combustion stage, depending on the oxygen concentration measured in the flue gas, on the free or bound reactive or molecular oxygen quantities (e.g. NO , SO ₉ , CO) and on the measured exhaust gas concentrations, exhaust gas proportions, exhaust gas quantities, the flow velocities in the exhaust gas, the mass flows of the exhaust gas and the exhaust gas temperature as well as the pressure, additional amounts of fuel are added and mixed into the exhaust gas flowing into the boiler (3), so that in a first post-combustion stage an almost stoichiometric consumption of the entire residual oxygen quantities takes place with a reduction in the exhaust gas components such as NO , CO, which have smaller oxygen binding energies than CO ₉ . The fuel supply can be regulated without additional combustion air supply or with additional measurement of the 0 ₉ content with stoichiometric addition of combustion air. The fuel supply must be in such a quantity that an almost stoichiometric reduction of all free oxygen and reactive, bound residual oxygen quantities of these exhaust gas components to be burned or split up is achieved, except for the residual oxygen quantities of the hydrocarbons and hydrocarbon compounds that cannot be burned at these temperatures and which have higher binding energies.

than CO« occurs, whereby due to the lack of combustion air and despite the high exhaust gas temperatures that arise during this afterburning, the formation of pollutants such as NO and CO is kept low from the outset and their amount is reduced. In particular, the NO pollutants that arise when heavy oil is burned cannot be completely broken down in this way. In this respect, according to the innovation, residual exhaust gas purification is also carried out in a catalyst that acts selectively for NO (see Figure 7).

The oxidation and decomposition of the hydrocarbons and/or hydrocarbon compounds also takes place catalytically or as far as possible in the boiler. In the second post-combustion stage there, the decomposition of these pollutants takes place almost stoichiometrically by metered addition of fuel and oxygen or combustion air at the combustion temperatures required for this, so that due to the continued lack of combustion air and oxygen, additional formation of pollutants such as NO and CO essentially cannot occur even when the flue gases are cooled. The addition takes place depending on the composition of the exhaust gas and/or the exhaust gas temperature and other parameters that influence the combustion and chemical decomposition of the hydrocarbons and/or hydrocarbon compounds in the desired stoichiometric manner.

In particular, in conjunction with the selective catalytic exhaust gas purification system (4) according to Figure 1, the combustion of heavy oil, e.g. in a pressure atomizer burner, is also possible, whereby the TA

In Germany, the nitrogen oxide emission limit values of 450 g/m3 specified for the combustion of heavy heating oil with a sulphur content of 1 % in combustion plants with an output of 50 MW can be exceeded by a long way.

In diesel-powered combined heat and power plants, this type of downstream flue gas cleaning with afterburning and selective catalytic exhaust gas cleaning achieves above-average economic efficiency compared to a gas engine due to a higher yield of electrical energy. There are also clear economic advantages in the boiler area. Compared to LOW-NO technology, significantly lower emission values can be achieved, whereby the costs for the catalyst technology and the afterburning in the boiler are extremely low compared to the actual fuel costs.

In the boiler (3) which forms a combined heat and power system with the diesel engine system (2) and its generator (1), the combustion of a large part of the fuels still present in the exhaust gas, such as soot components, as well as the additional fuel quantities (13) to be injected in accordance with the fuel control for a stoichiometric combustion of the pollutants, takes place with a very high thermal efficiency. The control of the addition of additional fuel quantities (13) as well as oxygen and combustion air, in particular for the second post-combustion stage, takes place by means of control devices by which the fuel supply and, if necessary, an oxygen supply are controlled via a computer-controlled and/or programmable control and regulation unit (5) in the first and second post-combustion stages in such a way that

are such that at least a nearly stoichiometric reduction and oxidation or splitting of the pollutants present in the exhaust gas takes place.

This is done depending on the mass flow of the exhaust gas determined by measuring devices (e.g. an oxygen probe), the exhaust gas flow velocity, the reactive and/or molecular oxygen quantities in the exhaust gas, the oxygen concentration, the exhaust gas temperature and/or the hydrocarbons or hydrocarbon compounds present and burned in the exhaust gas.

The control and regulation unit (5) is operated automatically or manually. Manual operation or regulation takes place as long as the diesel engine system (2) and/or the boiler (3) have not yet reached almost stationary operating conditions. Manual regulation initially takes place in accordance with the basic parameters or operating conditions known to the operator (e.g. when the exhaust gas mainly contains NO). Automatic regulation using the control and regulation unit (5) takes place when the operating conditions of the system are sufficiently stationary so that safe automatic regulation is possible.

Of the measuring points, measuring point (10) is located in the exhaust gas flow of the chimney system (9). This measurement is used specifically to carry out an exhaust gas check. Measuring point (11) is located in the exhaust gas flow immediately behind the diesel engine system (2), while measuring point (10') is located in the post-treated exhaust gas flow flowing out of the boiler.

In addition to gas and oil, coal, coal dust and other combustible solid, liquid or gaseous fuels may also be used as additional fuels to be introduced into the combustion chamber of the boiler (13).

The combustion of the unburned hydrocarbons and hydrocarbon compounds still present in the exhaust gas can also take place in a second downstream boiler, whereby after removal of the gases already reduced by the exhaust gas treatment, such as N~, N0~, fuel quantities (13) and oxygen are introduced in such a way that the previously unburned hydrocarbons and compounds burn for the most part in the second boiler (3) in a stoichiometric manner.

The exhaust gas flowing out of the boiler (3) is either released into the atmosphere via the selective catalysts (22, 23) and/or fed in whole or in part as an exhaust gas flow (6) via a compressor or a blower (7) to the combustion chambers or combustion spaces of the diesel engine system (2) and/or a gas turbine system.

Using an exhaust flap system (21), it is possible to feed the exhaust gas flow (18) of the diesel engine system (2) completely or partially to the combustion chamber of the boiler (3) or to lead it as a partial exhaust gas flow (8) into the combustion chambers of the diesel engine system (2) and/or gas turbine system or to discharge it directly into the chimney system (9).

Preferably, a control is carried out at the measuring point (10) in the exhaust gas flow before the outlet of the chimney system.

measurement of the parameters relevant for fuel control and oxygen supply or for achieving stoichiometric combustion in the boiler (3), i.e. the exhaust gas quantity, the exhaust gas temperature, the exhaust gas pressure, the pollutant concentration in the exhaust gas (e.g. NO, CO, CH, SO ₉ ) and other parameters necessary for the manual or automatic control and regulation of the process.

The cooling system of the diesel engine system (2) is identified in Figure 2 with the reference number (12). The cooling water is fed to the cooling system (12) of the diesel engine system (2) via a circulation pump (14) with pressure maintenance via a return line (15). The cooling or heating circuit then runs via line (16) into the heat exchanger installed in the boiler and from there into the flow line (17) to a heat consumer or to the selective catalytic exhaust gas purification system (4) according to Figure 1.

At the same time, a valve device can be used to ensure that part of the heat flow is cooled in a cooling tower, so that the heat flow then has the appropriate process temperature with the portion leaving the heat consumer's heat exchanger in order to achieve optimal combustion of the primary fuels in the diesel engine and gas turbine system. The return of the heating and heat circuit is provided with the circulation pump (14), so that the cooling medium to be returned ensures the appropriate combustion temperatures.

In this respect, it is also possible to influence the formation of pollutants in the combustion chambers and combustion chambers of the diesel engine system (2) and thereby also

to reduce the formation of pollutants in the exhaust gas, while also reducing the damage caused by diesel operation.
can be largely eliminated.

the pollutants produced by diesel operation such as SO

In order to achieve the most ideal possible combustion of the primary fuels, the cleaned exhaust gas from the second post-combustion stage is partially returned to the combustion chambers or combustion spaces of the diesel engine system, thereby reducing the combustion temperatures that occur there during operation and reducing the resulting NO pollutant formation. This is done via the pipe system (19) running between the boiler (3) and the diesel engine system (2).

Figures 3 - 6 show a schematic representation of the arrangement of the diesel-powered combined heat and power system consisting of the diesel engine system (2) and a gas turbine system, the generator driven by it and the boiler or furnace system (3) used for the afterburning of exhaust gases to be cleaned. Alternatively, the arrangement of a selectively acting reduction catalyst for NO reduction and a selectively acting "double catalyst" with an additional oxidation catalyst upstream or downstream of the boiler or furnace system (3) is shown. The honeycomb structure of the selective catalysts is shown in the drawings by squares arranged in a honeycomb shape. Furthermore, the injection of the reactant is indicated as a function of the reactant controller (33) controlled by a generator power signal, whereby the size of the reactant flow is controlled according to a pre-programmed NO mass flow curve.

Figure 7 shows the preferred embodiment of the device for operating a combustion system with diesel engines and/or diesel/gas engines, whereby in addition to post-combustion in the boiler or furnace system (3), a selective catalyst system consisting of a reduction catalyst (22) upstream of the boiler or furnace system (3) and oxidation catalysts (23) downstream of this or the boiler and/or furnace system (3) is used.

The catalytic exhaust gas purification of diesel engine exhaust gases can take place in the reduction catalysts (22) even when the diesel engine exhaust gases have a significant residual oxygen content, which is approximately 12 °L . With such a high residual oxygen content, the injection of a reactant is necessary in NO reduction catalysts. In the case of ammonia, NO reduction takes place as follows:
4 NO + 4 NH ₃ + O ₂ --> 4 N ₂ + 6 H ₂ O
6 NO ₂ + 8 NH ₃ --> 7 N ₂ + 12 H ₂ O.

The NO reduction using urea occurs as

follows:

4 NO + 2 ((NH ₂ ) 2 CO) + 2 H ₂ O + O ₂ --> 4 N ₂ + 6 H ₂ O + 2 CO, 6 NO ₂ + 4 ((NH ₂ ) 2 CO) + 4 H ₂ O --> 7 N ₂ + 12 H ₂ O + 4 CO ₂ -

In the reduction catalysts, some of the hydrocarbons in the exhaust gas are converted and the carbon released is converted into carbon monoxide. This results in an increase in the amount of CO in the reduction stage, which can reach several 100 mg/m.

The conversion of the nitrogen oxides NO and NO,-, with the reactant also produces water vapor, nitrogen and carbon dioxide.

Due to the afterburning at least in the first afterburning stage according to DE-PS 38 24 813 in the boiler and furnace system (3), it is not absolutely necessary that the reactant mass flow in the upstream reduction catalysts is dosed exactly stoichiometrically to the NO mass flow. This is because in the afterburning stage of the boiler system and/or furnace system (3) a further reduction of the exhaust gas components such as NO and CO takes place.

Due to the upstream reduction catalyst for NO, the residual oxygen content of the diesel engine exhaust gases is already reduced on the way to the boiler system and/or furnace system, a smaller addition of primary fuel quantities is required in order to carry out the necessary stoichiometric reduction of the remaining free oxygen and reactive, bound residual oxygen quantities of the flue gas components to be burned or split in the first post-combustion stage.

In particular, there is no longer any need for an exact stoichiometric reduction of these oxygen and residual oxygen quantities, whereby the addition of primary fuel quantities and oxygen in the first and/or second post-combustion stage can be carried out manually or stationary or simply in the secondary field control.

Oxidation catalysts are used to supplement or replace the second post-combustion stage in the boiler and/or furnace system (3).

Claims (24)

Protection claims Device for operating a combustion plant, in particular in the form of a combined heat and power plant or a cogeneration plant, with diesel, pilot jet, gas/diesel, large gas-Otto engines, gas turbines and/or boiler plants using liquid, gaseous or solid fuels, in particular heavy oil, with an exhaust gas purification system, consisting of at least one afterburning chamber of a process furnace or a boiler plant, wherein
the boiler or furnace plant has one or two afterburning stages and can preferably be operated as a recuperator, so that the cleaned
Flue gas streams can be cooled, and from a supply and mixing device as well as a control device for the first and second post-combustion stage, so that the fuel, oxygen or additive quantities (13) to be mixed in these combustion stages for exhaust gas aftertreatment and to avoid the formation of pollutants or to reduce them can be injected and/or introduced into the post-combustion chambers beforehand, whereby in the first post-combustion stage, flue gas components with smaller oxygen binding energies than CC>2 can be burned out only with the supply of fuel and at an increased temperature without additional combustion air supply, or whereby in the flue gas duct upstream of the first and/or second post-combustion stage, a device for measuring the free and bound residual 0~ quantities is provided and both the fuel supply and the oxygen supply are regulated in relation to the Mass flow to be converted stationary and/or
is carried out largely stoichiometrically, and that preferably for returning part of the flue gas flow of the boiler or furnace system to the combustion chambers or combustion chambers of the combustion system, a line system is provided between the outlet of the boiler or furnace system and the inlet of the combustion chambers or combustion chambers of the combustion system, according to DE 38 24 813 C2, characterized in that as an additional exhaust gas purification system (4) of the boiler or furnace system (3) at least one selective NO reduction catalyst (22) with a device (28,31,31',32,33,24) for metering and spraying nitrogen-containing reactants, such as ammonia or an aqueous urea solution, is connected upstream and/or downstream, so that at least some of the reducible NO exhaust gas components still present before or after the afterburning stage(s) are catalytically broken down, or that in addition to the reduction catalyst(s) (22) at least one Oxidation catalyst (23) for CO and CH combustion is connected downstream, so that additionally after the second post-combustion stage or the NO reduction catalysts (22) still present
oxidizable exhaust gas components can be brought to a largely complete reaction to form harmless gases without reactants. 2. Device according to claim 1, characterized in that
the exhaust gas purification system (4) with the selective NO reduction catalyst (22) and/or with the additionally provided oxidation catalyst (23) has a reactant metering device (32), a reactant tank (24), a metering and supply device (28,34,35,36) with a nozzle device (31) for the reactant of the reduction catalyst (22) and an electrical system control and regulation (33), so that the reactant can be introduced into the hot exhaust gas flow (30) and can be finely sprayed in the direction of the exhaust gas flow (30). 3. Device according to claim 2, characterized in that
the nozzle apparatus (31) for the reactant is arranged in a pyrolysation channel (27) and the exhaust gas purification system (4) has, in addition to the pyrolysation channel (27), a connecting mixing channel (25) with at least one mixer (34) arranged there for the inline homogeneous mixing of the reactant into the exhaust gas flow and an inline connecting reaction channel (26) with at least one selective, non-zeolite-containing NO reduction catalyst (22) or also with a CO or HC oxidation catalyst (23). 4. Device according to claim 2 or 3,
characterized in that in the pyrolysis channel (27) a two-fluid nozzle device (28) is arranged opening into it with a switching valve (36) for switching from the working to the blow-out position and with a jacket pipe opening into the area of the exhaust gas flow for the compressed air supply and with a spaced-apart Reactant conductor (29) guided through a jacket pipe and a nozzle (31') for spraying the reactant. 5. Device according to claim 4, characterized in that the nozzle (31 ¹ ) of the two-fluid nozzle apparatus (28) has inclined slots and/or channels for imparting swirl for rotating the compressed air conveying the reactant. 6. Device according to claim 5, characterized in that the two-fluid nozzle apparatus (28) has an electrically controlled 3-way ball valve (36) for switching off the supply of the reactant and for simultaneously connecting the line path for the reactant leading to the nozzle (31') to the compressed air. 7. Device according to one of claims 1 and 3-6, characterized in that the reduction and oxidation catalysts (22, 23) installed in the reaction channel (26) are honeycomb bodies (38) with a particularly square, hexagonal or rectangular cross-section, with a perforated plate preferably being arranged in front of the first reduction catalyst as a flow straightener. 8. Device according to claim 7, characterized in that the honeycomb bodies (38) are constructed in a modular manner, with several modules with a cross section of preferably about 150 x 150 mm and a length of 50, 150 or 300 mm, arranged side by side, one above the other and/or one behind the other, butted or spaced apart. 9. Device according to claim 7 or 8,
characterized in that
the honeycomb bodies (38) are longitudinally
elastic, slightly flush stocking made of fire-resistant material, preferably made of glass fibre knit. 10. Device according to one of claims 1-9,
characterized in that
at least the active surface of the reduction catalysts (22) consists of titanium, tungsten and/or vanadium oxide and at least the active surface of the oxidation catalysts (23) consists of a noble metal, preferably platinum, rhodium and/or palladium. 11. Device according to one of claims 2-10,
characterized in that
the electrical system control and regulation (33) for introducing and spraying the reactant into the exhaust gas flow (30) is designed such that the reactant can be metered in fully automatically and exactly stoichiometrically with respect to the NO mass flow to be reduced. 12. Device according to one of claims 1-11,
characterized in that
the oxidation catalysts (23) are constructed and arranged in such a way that they act selectively with respect to the CO, CH ■ and/or S02~ components. 13. Device according to claim 11, characterized in that
the electrical system control and regulation (33) has a control signal input for an engine power signal or an electrical generator power signal of the combustion and generator systems (1,2), furthermore a target value curve of the reactant to be injected and a controller in which the target value for the reactant flow can be compared with the actual value and from which a control signal for the reactant regulation can be formed. 14. Device according to claim 13, characterized in that
the system control and regulation (33) is designed in such a way that the NO values can be maintained at a constant level higher than the target curve by means of a substoichiometric reactant dosage. 15. Device according to one of claims 13-14,
characterized in that the system control and regulation (33) is designed in such a way that the setpoint signal from the controller works as a higher-level control signal and quickly compensates for rapid load changes in the combustion system (2). 16. Device according to one of claims 1-15,
characterized in that
when burning heavy heating oil or heavy oil, at least one selective catalyst (22) with reactant injection (for NO reduction) of the boiler or Furnace system and at least one oxidation catalyst (23) for CO and HC combustion and for desulfurization by SO~ combustion is connected downstream of the boiler or furnace system (3). 17. Device according to one of claims 1-16,
characterized in that a blower (14) for conveying the flue gas flow to be returned is installed in the pipe system between the outlet of the boiler or furnace system (3) and the inlet of the combustion chambers or combustion chambers of the combustion system (2). 18. Device according to one of claims 1-17,
characterized in that
the boiler or furnace system (3) downstream of the combustion system (2) is designed in such a way that it acts as a single structural unit simultaneously as a silencer, recuperator and device for exhaust gas aftertreatment. 19. Device according to one of claims 1-18,
characterized in that
as a boiler or furnace system (3) one or more boilers, furnaces, rotary kilns, pressure units or silencers with a combustion chamber enabling afterburning are installed. 20. Device according to one of claims 1-19,
characterized in that in the pipe system between the boiler or furnace system (3) and the combustion system (2) a return pipe (8) for a partial flow of the flue gas flow (18) which flows into and can be connected directly from the outlet of the combustion plant. 21. Device according to one of claims 1-20, characterized in that
a condenser is connected downstream of the boiler or furnace system (3), in which components of the exhaust gases can be condensed out and cooled below their condensation temperature. 22. Device according to one of claims 1-21, characterized in that
the selective oxidation catalysts (23) are arranged in the exhaust gas stream so that they can be switched on and off. 23. Device according to one of claims 1-22, characterized in that
in the case of one or more selective catalysts (22) connected upstream of the boiler or furnace system (3), one or more oxidation catalysts (23) are connected downstream of the boiler or furnace system (3) in such a way that, in addition to or instead of the second post-combustion stage of the boiler or furnace system (3), the oxidation catalysts can be connected into the exhaust gas flow downstream of the boiler or furnace system (3). 24. Device according to one of claims 1-23, characterized in that
the additional exhaust gas purification system (4) comprises a selectively catalytic exhaust gas purification system for injecting aqueous urea solution according to one of claims 13-20 of Swiss patent application No. 00 556/92.