CN111836997A

CN111836997A - Heat production method of power device

Info

Publication number: CN111836997A
Application number: CN201980018230.1A
Authority: CN
Inventors: 雷约·莱卡加斯
Original assignee: Worth Ltd
Current assignee: Worth Ltd
Priority date: 2018-03-09
Filing date: 2019-03-11
Publication date: 2020-10-27
Also published as: FI128631B; FI20185222A1; US20200392884A1; WO2019170965A1; KR20200130261A; EP3762651A1

Abstract

A method of generating thermal energy from a hydrocarbon-containing fuel. According to the method, fuel is burned in a combustion device at an elevated temperature, the heat obtained from the combustion is recovered, and the exhaust gases and soot particles produced by the combustion are cleaned by catalytic exhaust gas combustion. Fuel and air are fed into the exhaust gas of the present invention to form a gas mixture which is then subjected to catalytic combustion at temperatures above 600 ℃ to reduce nitrogen oxides and oxidize carbon monoxide, hydrocarbons and soot particles. The method can be used for remarkably reducing the emission of NOx, CO and VOC in gas. The thermal energy generated by the catalytic combustion process may also be used to generate heat, in which case the feed of fuel is divided between the combustion device and the catalytic combustion device.

Description

Heat production method of power device

Technical Field

The present invention relates generally to reducing combustion gas emissions in energy plants. The invention also relates to heat production in boilers, gas turbines, diesel engines and similar power plants.

In particular, the invention relates to a method for catalytic cleaning of combustion gases containing nitrogen oxides, carbon monoxide, hydrocarbons and soot particles in a hydrocarbon-containing energy source device, according to the preamble of claim 1.

The invention also relates to a method for producing heat from a hydrocarbon-containing fuel according to the preamble of claim 19. According to this method, fuel is burned at an elevated temperature, the heat generated by the combustion is recovered, and the exhaust gas and soot particles generated by the combustion are purified by catalytic exhaust gas combustion.

Background

In order to limit the greenhouse effect, the production of nitrogen oxides (NOx), carbon monoxide (CO) and carbon dioxide (CO) in energy production is limited on a global scale₂) And emissions of hydrocarbons (VOC). In europe, several instructions for this have been issued for hot boilers, process equipment, fireplaces, and the like. In these directives, emission limits are set for greenhouse gases, either directly or with the aid of efficiency or emission limits. In the united states of america, the number of,EPA and CARB set limits on nitrogen oxides and hydrocarbons and their compounds. China is also developing correspondingly. For example, in Beijing, the boiler NOx emissions limit is 30mg/m³The CO limit is 80mg/m³. Such a severe limitation is not achievable with existing conventional thermal combustion devices without aftertreatment. The same strong tightening trend will continue in other industrialized regions of china.

Before the above emission limits were made, Beijing has begun to prepare for more severe limits. The limit for NOx is targeted to be zero, even with CO, the target limit is significantly lower than the previous limit.

Commercial manufacturers of ultra-low value NOx and NOx-free burners use flue gas recirculation, water emulsification and gas preheating in high efficiency hybrid burners instead of flue gas post-treatment. Although the name burner is NOx-free, none of the hot burner manufacturers achieve zero NOx emissions. The reported minimum NOx emission is 6ppm with 3% O₂And (4) content.

Another option is the purification of the flue gas. Generally, selective catalytic reducing agents and non-catalytic reducing agents are used for removing nitrogen oxides (hereinafter, selective catalytic reduction, abbreviated as "SCR", selective non-catalytic reduction, as "SNCR"). At best, catalytic SCR can reach 90-% purification levels at a temperature of about 350 ℃. EPA indicates in its report that the average NOx conversion for SCR is 85%. With the non-catalytic SNCR device, the purification effect was reduced by about 20%. Their use has been directed to diesel vehicles.

However, SCR devices require a separate reductant, urea or ammonia and their dosing equipment, which results in significant investment and operating costs. Decomposition of urea in a catalyst to ammonia (NH)₃) And carbon monoxide (CO). Ammonia and urea are transported and stored in aqueous solution. The ammonia content was 27% and the urea content was 32%. Ammonia is a highly toxic gas. Using an SCR device, NOx emission levels of about 7-30 ppm can be achieved. In addition, the limitation of CO emissions requires a separate oxidation catalyst. Ammonia is used as a reductant based on its ability to selectively reduce NOx in a lean gas mixture.

The ammonia (NH3) or urea required for selective catalytic reduction as a reductant, as well as expensive storage, dosing, heat transfer and reduction equipment, all contribute to the high cost of SCR technology. Further, the EPA estimates the replacement interval of the SCR catalyst to be 3 years. Among the SRC catalysts, the most commonly used active material, i.e. the catalyst, is vanadium (V) pentoxide₂O₅) It is relatively susceptible to the greatest noble metal toxicity. The SCR catalyst is large because of its low space velocity, i.e., 10000-. The space velocity of the noble metal catalyst is 5 … 10 times greater, i.e., the size of the noble metal catalyst is about one fifth to one tenth of the size of the SCR catalyst.

Other weaknesses of SCR catalysts are NH₃Leakage (2-5 ppm) and due to NH₃Toxicity and risks during handling and transportation. Particularly in the United states, it is required to replace the toxic SCR catalyst by, for example, nontoxic zeolites (V)₂O₅)。

Furthermore, there is a limit to what are known as catalyst poisons, which must not be contained in the combustion gas. Of the most important are silicones, heavy metals and phosphorus compounds, which permanently deactivate the catalyst. The sulfur-containing compound does not damage the catalyst activated by platinum, but causes corrosion if sulfuric acid generated in the reaction is concentrated on the heat exchanger surface at more than 100 ℃.

US 4118171, US 2017/153024 and US 2009/284013 are publications of the prior art.

Disclosure of Invention

The present invention aims to eliminate at least some of the problems of the prior art and to provide a completely new method for generating thermal energy from a hydrocarbon-containing fuel and, correspondingly, for catalytically purifying exhaust gases containing nitrogen oxides and carbon monoxide, hydrocarbons and soot particles, which are produced by energy plants using hydrocarbon-containing fuels.

In a first embodiment of the invention, the exhaust gases of the energy plant are led to an exhaust gas burner, where these gases are subjected to catalytic oxidation and reduction to reduce the NOx, CO, VOC and particle content of the exhaust gases and simultaneously to generate heat energy. Typically, NOx compounds are first reduced and then CO, VOC compounds and particulate impurities in the gas are oxidized, while generating recoverable thermal energy.

In a second embodiment of the invention, thermal energy is produced from at least two units. When thermal energy is generated in an energy plant by burning a fuel with a hydrocarbon-containing compound, the heat is recovered, for example, in a heat exchanger. Fuel and air are fed into the exhaust gas from the combustion to form a gas mixture, which is then subjected to catalytic combustion at elevated temperatures.

By combustion in the presence of a catalyst under reducing and corresponding oxidizing conditions of at least 600 ℃, the nitrogen oxides contained in the flue gas are reduced and carbon monoxide, hydrocarbons and soot particles are oxidized. The heat obtained from the catalytic combustion is also recovered.

More specifically, the method of the invention is primarily characterized in what will be presented in the characterizing part of the independent claim.

Significant advantages are obtained with the present invention.

As mentioned above, it is not possible to generate as clean thermal energy as currently required by beijing using thermal combustion or existing flue gas cleaning methods. However, this object is achieved with the process according to the invention, which by catalytic flue gas combustion can even reduce to virtually zero the NOx, VOC, CO and particulate flue gas emissions of already operating boilers, diesel engines and gas turbine power plants. Meanwhile, the small smoke particles generated by an oil-gas boiler and a diesel engine can be combusted.

By means of the present invention, a method is created for purifying the exhaust NOx, CO, HC and particulate matter of a thermodynamic device using a single apparatus, which is more efficient than using any existing production technology, and which at the same time is able to produce additional energy. All of the emissions listed above can be eliminated in a single device using the process of the present invention.

Thus, using the method of the present invention, NOx compounds can be reduced such that their residual content is less than 1ppm, and CO and VOC compounds can be oxidized to their residual content of less than 2 ppm. Small soot particles can also be burned in a flue gas burner at temperatures of 600 c or higher. The preferred temperature range for the burner is 850-. In this range, soot particles also burn rapidly.

The energy produced simultaneously also enables the flue gases of thermal boilers, turbines or diesel power plants and the like to be used as cooling and heat-transfer agents in catalytic combustion. The inert thermal mass of the flue gas and flue gas is then used for combustion to control the temperature and transfer heat. With the aid of flue gases, the temperature can be kept within the desired limits, preferably in the range of 850-.

Unlike other cleaning methods, the method of the present invention can be used to increase the heat generating capacity of a hot boiler by as much as 60%.

The flue gas burner can be added to all energy production plants which have a low sulfur and particulate emission and in which there are no so-called catalyst poisons, and on the other hand, the emission of NOx, CO and VOC from the energy source is of no practical significance. In the case of reburning, small soot particles produced by, for example, oil boilers and diesel engines are also burnt, and unless there is a stored POC catalyst or filter connected to the catalyst, an intermediate device is preferably arranged before the heat recovery, in which the particles have time to burn before the energy recovery.

The particles of diesel engines are mainly small so-called nanoparticles. Wherein more than 90% of the particles have a diameter of less than 50 nm. They enter the lungs through the breathing air and partly through them into the short blood circulation, leading to massive death. The nanoparticles comprise carbon, water, hydrocarbons, usually also sulphur, and small amounts of other compounds. They are very porous. Once the hydrocarbons and sulfur compounds are oxidized and the water is evaporated, the carbon ignites and burns rapidly on all surfaces, while the gaseous compounds are slower. Exhaust gas temperatures in the above range (850-.

The use of waste gas burners can increase the emission levels of existing older, more polluting energy production facilities to new, more stringent, demand levels.

In principle, since catalytic combustion operates below the LEL limit, the exhaust gas burner can be used in conjunction with a boiler or heat exchanger to remove all gases containing NOx, CO and VOC emissions. This does not present the same safety risks as a hot boiler, where the combustion of volatile organic compounds has led to fatal accidents.

Since the amount of gas emissions is of little significance in particular with regard to the operation and cleaning result of the waste gas burner, there is freedom in the regulation of the energy source and in the choice of the device. The boiler does not require expensive low value NOx or ultra low value NOx burners and can optimize the air-fuel ratio for maximum output. In diesel engines, Exhaust Gas Recirculation (EGR) or very lean mixing ratios are not required to reduce NOx emissions, etc.

Exhaust gas burners are also suitable for energy plants which do not meet increasingly stringent emission standards. The investment for emission reduction is usually worthwhile because these plants have a long service life and require a large investment. The new device has new application.

In the following, the invention is described in detail with the aid of the description of the figures.

Figure 1 shows a flow chart of one embodiment,

figure 2 shows a flow chart of a second embodiment,

FIG. 3 shows a flow chart of a third embodiment, an

Fig. 4 shows a flow chart of the fourth embodiment.

Detailed Description

In this context, an "energy plant" is understood to mean, in principle, a combustion plant which generates thermal energy or heat and which generates energy from a fuel containing hydrocarbons by means of a boiler, a diesel engine or a gas turbine.

In a first embodiment, the term "carbonaceous fuel" refers to a fuel comprising compounds containing mainly, but not necessarily only, carbon and possibly hydrogen, such as hydrocarbons. In addition to hydrocarbons, the fuel may also contain oxygenates such as ethers, esters and alcohols. Examples of the carbonaceous fuel according to the first embodiment are oil, gasoline, diesel oil and natural gas.

In a second embodiment, the term "carbon-containing fuel" also refers to fuels that contain primarily carbon-containing compounds that contain alcohol (hydroxyl) groups, ether or ester groups, or combinations thereof, such as hydrocarbons substituted with these groups. These fuels are various biofuels which are produced from, for example, lignocellulose, vegetable oils and animal fats, the biomass of cultivated plants.

The expressions "CO" and "VOC emission" and correspondingly "NOx emission" and "soot emission" refer to the amount (by mass) of CO, VOC and NOx gases and correspondingly soot contained in the exhaust gas.

A "rich" fuel/oxygen (or fuel/air) mixture contains a greater stoichiometric amount of fuel (relative to oxygen), while a "lean" contains a lesser stoichiometric amount of fuel.

The present invention provides a method of treating exhaust gas and producing energy using a catalytic exhaust gas burner. As described in more detail below, the method may be used to generate heat and to purify exhaust gases.

In this process, additional air and fuel are supplied to the exhaust gas produced in the hot combustion to form a quantity of gas mixture necessary for catalytic combustion, and the resulting gas mixture is then passed into the catalytic combustion zone for combustion. Recovering heat generated by the combustion. As a result, CO, VOC, NOx and soot emissions in catalytic combustion exhaust gases are significantly reduced.

In one embodiment, the exhaust gas, fuel and air are mixed together uniformly to form a uniform gas mixture.

In this embodiment, additional air and fuel may be supplied to the exhaust gas burner, and the supply thereof may be controlled by controlling the temperature after the catalyst and the linear oxygen sensor according to the air/fuel mixture ratio required for each catalyst.

In order to carry out the reaction described below, it is most appropriate to add as much fuel as possible to the exhaust gas to form a rich mixture or to reach a stoichiometric ratio. In the former, NOxs is reduced to nitrogen (N) only₂) And oxygen (O)₂) And in the latter, additionally CO and VOCs are oxidized to carbon dioxide (CO)₂) And water (H)₂O)。

When the reaction is carried out with a rich mixture, it is most suitable to use a second catalyst if the required amount of additional air feed is provided to the lean mixture. Best results are obtained using separate oxidation and reduction steps.

If it is desired to generate the maximum amount of clean energy, air must be injected into the flue gas in addition to the fuel. In order that nitrogen oxides are not produced during the reburning, the temperature must be suitably limited to about 1000 ℃. Unlike other cleaning methods, this method can increase the heat generating capacity of the heat boiler by as much as 60%, which will be described in detail below.

In one embodiment, fuel and air are mixed in a nested porous feed tube and static mixer to form a uniformly mixed gas mixture.

Static mixers can be used to ensure homogeneity of the gas mixture, particularly preferred is homogeneous combustion.

In one embodiment, the catalytic combustion is carried out in one or more stages under reducing and corresponding oxidizing conditions.

In one embodiment, the catalytic combustion is carried out in at least two stages to reduce oxides of nitrogen, in particular, and to oxidize carbon monoxide, hydrocarbons and soot particles.

In one embodiment, the catalytic combustion is carried out in a three-way catalyst of an oxidation and reduction catalyst. The catalytic combustion of the gas mixture can take place, for example, in a three-way catalytic converter in the combustion device at a stoichiometric oxygen/fuel ratio, in order to oxidize the unburned CO and VOC compounds in the combustion device and to reduce NOx emissions and to oxidize soot particles.

If burned at temperatures above 600 c, the soot particles will also burn.

Alternatively, in the reduction portion of the two-stage catalyst, the rich mixture is used to reduce the NOx emissions to nitrogen (N)₂) And oxygen (O)₂) And oxidizing a majority of the CO and VOC emissions to carbon dioxide (CO)₂) And water (H)₂O)。

Thereafter, additional air is passed into the gas mixture to dilute it, and the resulting mixture is then passed through an oxidation catalyst. Wherein the remaining CO and VOC emissions are oxidized. In the following heat exchange stage, the generated heat energy is utilized, for example, by means of welded finned tube radiators in water, and the exhaust gases are then discharged from the boiler to a chimney, if necessary with the aid of a suction fan.

In one embodiment, the gas mixture is combusted in an oxidation and reduction catalyst, first with a rich additional fuel/oxygen mixture to reduce nitrogen oxides, and then with a lean additional fuel/oxygen mixture to oxidize CO, VOC compounds and soot particles.

In noble metal catalyst reduction, the reaction chain proceeds mainly through steam recombination and water-gas shift reactions:

H₂O+HC->H₂+ CO and H₂O+CO->H₂+CO₂

Then, the user can use the device to perform the operation,

H₂+NO_x->N₂+H₂O.

some of these reactions are direct oxidation and reduction reactions.

Catalytic combustion is always carried out below the Lower Explosive Limit (LEL). The fuel may typically be the same as the fuel in the primary energy production facility.

If the flue gas temperature before catalytic reburning is reduced to below 250 ℃ and the fuel is natural gas or other fuel with high ignition point, the structure of the catalyst should be a regenerative or regenerative heat exchanger, such as a metal cross-flow catalyst, or a fuel with low ignition point (such as methanol or ethanol) should be added as an auxiliary fuel to the fuel mixture in order to maintain combustion.

The catalyst used in combustion is preferably a stable metal oxide on the surface, especially an oxide whose cation is Al, Ce, Zr, L or Ba and which contains a noble metal such as Pd, Pt, Rh or a mixture thereof with a base metal.

These noble metal catalysts are non-toxic and do not produce toxic compounds in the reaction as do conventional SCR catalysts.

The temperature of the catalyst under reducing conditions, or under reducing and oxidizing conditions, is at least 600 deg.C, in particular 850-1000 deg.C.

In the three-way catalyst, the space velocity is maintained at 50000-1500001/h, for example at about 60000-1000001/h, whereas in the reduction and oxidation catalyst, the space velocity is, for example, at about 60000-2000001/h, preferably at 70000-1500001/h.

The invention is particularly applicable to situations where the fuel is or has been combusted in an oil or gas boiler, a gas turbine, a diesel engine or similar energy burning device.

In one embodiment, a method for purifying exhaust or flue gases and producing clean energy by only one or two-stage catalytic reduction and oxidation is provided. In the method, the flue gas also has the functions of heat bonding and transfer. Since catalytic combustion is much faster than thermal combustion, it is preferred to use substantially inert flue or exhaust gases to incorporate energy. In this way, excessive temperature increases can be avoided.

As described above, in one embodiment, the present techniques may be used to generate heat by combustion of a fuel containing hydrocarbons through at least two stages. In the method, a portion of the fuel is combusted in a first combustion stage of the combustion apparatus to produce heat and an exhaust gas containing oxides of nitrogen and oxygen. The heat and exhaust gases obtained from the first combustion stage are then recovered. In the second combustion stage, a second portion of the fuel is supplied to the exhaust gas obtained from the first combustion stage. Air is also fed to form a combustible gas mixture. The gas mixture thus obtained undergoes combustion to generate heat and decompose the oxides of nitrogen and oxygen. As mentioned above, in at least one catalytic zone, reducing conditions are maintained and combustion is carried out at temperatures above 600 ℃ under these conditions.

The heat obtained in the second combustion stage is also recovered.

In one embodiment, 10%, most preferably 15-80 mol% of the total amount of fuel containing hydrocarbons is combusted in the second combustion stage. By means of this method, a considerable part, about 60%, of the thermal energy outside the main energy source can be generated in the second combustion stage.

In one embodiment, flue gas from a boiler, turbine or diesel engine is used as a coolant and heat transfer agent in catalytic combustion. Without cooling the inert additive in stoichiometric catalytic combustion, the model shows that the temperature will rise above 2500 ℃. This is due to the fact that: catalytic combustion is about twenty times faster than thermal combustion. In the above embodiments, the temperature of the catalytic combustion is raised to at least 600 ℃, but preferably to 1000 ℃, and the flue gas of the thermal energy device is most suitably used as an inert heat storage and transfer agent to maintain the temperature of the catalytic combustion within a preselected temperature range. Studies have shown that unburned gases contained in flue gases, such as nitrogen and carbon dioxide, do not react under the conditions described, but rather act as inert components or even heat and prevent the temperature from rising uncontrollably.

In the above embodiment, the thermal energy contained in the gas generated by combustion is recovered. The recovery may be carried out in at least one heat transfer stage, the heat energy being most preferably transferred to water, air or other liquid or gaseous medium.

In a second embodiment, the invention is used for catalytic purification of exhaust gases from energy plants using hydrocarbon-containing fuels, containing nitrogen oxides and carbon monoxide, hydrocarbons and soot particles, under reducing and oxidizing conditions. In this method, fuel and air are supplied to the exhaust gas to form a gas mixture, and the gas mixture is subjected to one-stage or two-stage catalytic combustion at a temperature above 600 ℃ to reduce nitrogen oxides and oxidize carbon monoxide, hydrocarbons and soot particles.

Thus, the gas obtained by catalytic combustion has an amount of NOx emission of 1ppm or less and an amount of CO and VOC emission of at most 2 ppm. Small soot particles will also burn at the preferred temperature of the exhaust gas burner of 850-.

According to one embodiment, the method is carried out as a continuous process.

During this continuous operation, hydrocarbons are used as a reductant and as an energy source. Another characteristic of this process is the generation of additional energy.

In one embodiment, the oxidation of the particles and the generation of cleaning energy is achieved at high temperatures (at least 1000 degrees). Both require temperatures that both increase the conversion efficiency as a particulate oxidant and energy generator and increase with increasing temperature.

Exhaust gas burners using the same fuel as a hot boiler have several advantages over Selective (SCR) or non-Selective (SNCR) NOx emission reduction devices:

this is a more efficient scavenger of NOx, CO and VOC emissions. It can be used to achieve NOx emissions of about 1 and, depending on the catalyst used, CO and VOC emissions can reach levels of 2 ppm.

Can be used for burning small soot particles.

Can be used to increase the heat yield of the boiler by about 60%.

No separate additional fuel addition is required, nor a separate storage and dosing system.

The noble metal catalyst therein has a longer life than the SCR catalyst, the latter catalyst (V)₂O₅) Is less thermally and chemically durable than noble metals. New alternative SCR catalysts are various zeolites, which are sensitive to sulfur poisoning.

-the size of the SCR catalyst is 5-10 times larger than the noble metal catalyst. There is no significant difference in their prices because the difference in size can compensate for the difference in unit price. The noble metal catalyst has a cost of from about 60 to 70 {/dm { (A) } { (B) } of a noble metal catalyst³The cost of the SCR catalyst is about 10 {/dm³。

EPA has shown that the NOx removal cost for SCR catalysts is about $ 1400-2000/ton NOx. The cost of the catalytic flue gas burner is greatly reduced. The device is smaller and simpler. The reductant ammonia (NH3) or urea used in the SCR device is approximately the same price as the fuel of the present invention, but does not generate usable heat energy.

The greatest difference is that the use of a waste gas burner can produce more energy at competitive costs. And as an additional function, can eliminate NOx, CO and VOC emissions without additional cleaning costs.

Ammonia is transported and stored in the form of a 27% aqueous solution due to high toxicity.

During the SCR reduction, ammonia slip (EPA) of 2-5 ppm is produced, which must be catalytically oxidized.

The present invention will be verified in detail below with reference to the accompanying drawings.

Fig. 1 and 2 show two embodiments, fig. 1 showing a method in which the exhaust gases of an energy plant are purified mainly using a catalytic combustion process, and the fuel in the energy plant (power plant) will simultaneously produce thermal energy and electrical energy. As such, fig. 2 shows a method in which heat is generated in a thermodynamic device on the one hand and by a catalytic combustion process on the other hand.

As can be seen in the drawings,

reference numerals

10, 20, 30, and 50 show a hot combustion boiler using gas or liquid fuel, a diesel engine plant, a gas turbine, or other such energy source device or power plant. In the case of fig. 1, the fuel is mainly supplied to an energy source device, in which thermal energy is generated, and furthermore electricity is generated from at least a part of the thermal energy thus generated.

In both figures, the exhaust gases of the energy supply device are led from the exhaust line to the mixing chamber 12, 22, in which additional air is blown in and injected into the fuel. The mixing chamber may include a distribution network.

In one embodiment, a hybrid honeycomb structure is used. Examples of such are the methods disclosed in utility model 10627 or CN 205001032. The distribution network may thus consist of diagonally corrugated steel split sheets folded in such a way that they are placed on top of each other or folded, with the corrugations crossing. The split sheets may be secured to each other at a fold-over point, for example by resistance welding or brazing. The flow channels formed in each layer of the honeycomb intersect each other, which results in mixing and turbulence at higher flow rates.

In a straight channel honeycomb, the flow is laminar. The dimensionless Sheward (Sh) number, which represents mass transfer, was about 3 and the flow rate was 10 m/s. In a mixed metal honeycomb, the Sh number is about 10 to 12.

The gas flowing out of the mixing chamber flows through the

static mixer

13, 23 to the

catalyst

14, 24, 25. Behind the catalyst (in the direction of flow of the gas mixture) is a linear lambda sensor (not shown) for measuring and regulating the air/fuel ratio and a temperature sensor for controlling the temperature.

After one or two catalysts 14; 24. 25, the gas flows to a connection, for example made of welded ribbed tubes, or to a plurality of

heat exchangers

15, 27, where the heat is transferred to water or for other purposes. Embodiments of the

heat exchangers

15, 27 may be welded tubes, for example preferably made of ribbed tubes.

Fig. 3 and 4 show the structure of the catalytic combustion system in more detail.

In the figures, primary energy production (for example, using a diesel engine, a gas turbine or a combustion boiler) is indicated by the

numerals

30 and 50, and fuel is fed into the exhaust gas along the

feed pipes

31, 51. To form the gas mixture, air is supplied by the

fans

37, 57. The mixture is directed through

static mixers

38, 58 for mixing prior to the catalytic zone. Preferably, the mixture entering the catalytic zone is a concentrated mixture.

In the case of fig. 3, the catalytic zone comprises a cross-flow catalyst 33. In the case of fig. 4, the catalytic zone comprises a recuperative catalytic heat exchanger.

The gas mixture flowing from the first catalytic zone 33, 53, which is usually reducing, is led to a second

catalytic zone

35, 55 comprising an oxidation catalyst. Then, the

secondary blowing fans

39 and 59 blow the additional air into the mixed gas.

Prior to start-up, the catalyst or catalysts are typically preheated, for example using a heat fan, a gas burner or some other heater to raise the reaction temperature.

If the temperature difference between the temperature of the exhaust gas and the ignition point of the fuel is small (<150 c), the first catalyst of the exhaust gas burner may be a conventional straight tube type catalyst. If carbon monoxide (CO) and Nitrogen Oxides (NO) are present in the exhaust gas₂) High, the carbon monoxide will ignite in the catalyst at a temperature of about 150 c and the second oxygen in the nitrogen oxides is easily separated and reacts violently.

When the temperature of the inlet gas is significantly lower (>150 ℃) than the ignition point of the fuel used in the catalyst, a cross-flow or rotating honeycomb regenerative catalytic heat exchanger 53 is required.

In the apparatus of the present invention, the space velocity in the three-way catalyst depends on the fuel and is 50000-1500001/h, preferably 60000-1000001/h. In the reduction and oxidation catalyst, the space velocity is 70000-2000001/h, preferably 60000-1500001/h.

In the second catalytic zone, the thermal energy of the hot gas obtained is recovered in the

heat exchangers

36, 56, for example by transferring it to water. The

heat exchangers

36, 56 may be manufactured from, for example, welded tubes, preferably ribbed tubes.

After heat transfer,

suction fans

40, 60 may be provided unless the output of the primary energy source device and the additional air blower are sufficient to deliver sufficient gas through the device. The exhaust gases, i.e. the cleaned exhaust gases, are led from the device to outlet pipes,

e.g. exhaust pipes

41, 61.

In one embodiment, the apparatus of the invention for combusting a flowing fuel with hydrocarbons in the presence of oxygen or air comprises, in the flow sequence of the substances, a flow of the substances to be treated,

-a mixing zone, a catalytic combustion zone, a heat recovery zone and a degassing zone, wherein

The mixing zone is equipped with a feed for purge gas, a feed for fuel and a static mixer for homogeneous mixing of the gas and the fuel,

the catalytic combustion zone comprises, in the direction of flow, at least two successive combustion zones, of which the first is under reducing conditions and the second is under oxidizing conditions, and

the heat recovery zone comprises a heat transfer element connected to the catalytic zone to recover the heat released therein.

Examples

Production of additional energy

Natural gas heating boiler with output power of 60MW

Exhaust gas input 61.000Nm³/h

35.000Nm additional air input³/h

At 96.000Nm³Middle extraInputting natural gas 24g/Nm³

35.2MW of extra energy from combustion, i.e. 59% (calorific value 55MJ/k)

-if the input temperature is 150 ℃ and the post-combustion temperature is 920 ℃,

reduction of nitrogen oxides

500mg/Nm of-NOx emission³

Total NOx 61.000Nm³/h x 500mg/Nm3＝30.5kg/h

Comparison with SCR devices

The cost of SCR device reduction is $ 1400/ton 30.5kg/h x0.98 $ 41.8/h, based on the lowest cost calculated by EPA.

The annual cost of using SCR technology is 8000h/a x 41.8.41.8 dollars/h 344.400 dollars/a.

If the energy produced by catalytic reburning is not more expensive than the equivalent energy production, then removing NOx from the hot boiler does not cost any cost, i.e., a savings of $ 344.400 per year. At the same time, with two-stage combustion (fig. 4), it is possible to reduce the NOx emissions to a level of 1ppm and the CO and VOC emissions to a level below 2 ppm.

To achieve the object, the invention has the characterizing features set forth in the independent claims.

Industrial applicability

The method is suitable for being used as a synchronous power cleaner for NOx, VOC and CO emissions of boilers, diesel engines, gas turbines and the like. The method of the present invention is also suitable for burning pellets such as solid fuel boilers and diesel engines without any additional equipment or additional cost. It is also suitable for generating additional energy with boilers, diesel engines, gas turbines, etc.

Using the process of the present invention, nitrogen oxides (NOx) can be reduced to residual levels of less than 1ppm, and carbon monoxide (CO) and hydrocarbons (VOCs) can be oxidized to residual levels of less than 2 ppm. These values can be achieved even if the primary energy emission is high. Small soot particles can also be burned in the exhaust gas burner, so that the particle filter of boilers and diesel engines can be replaced using the method according to the invention.

According to the method of the present invention, the primary energy device does not require low NOx or ultra-low NOx burners, nor does the diesel engine require EGR or very low mixing ratios to reduce NOx emissions. The output of the primary energy device can be maximized. In addition, the primary energy source can generate up to about 60% additional heat energy using the method of the present invention. This is particularly true when the exhaust gas produced in the first combustion is used as a cooling and heat exchange agent in catalytic combustion, and when fuel is fed into the exhaust gas for the second stage of catalytic combustion.

Description of the reference numerals

10 primary energy production

11 electric generator

12 distribution network

13 static mixer

14 three-effect catalytic converter

15 heat exchanger

20 primary energy production

22 distribution network

23 static mixer

24 reduction catalyst

25 air distribution network

26 oxidation catalyst

27 heat exchanger

30 primary energy production

31 feeding pipe

32-concentrated mixture

33 cross-flow catalyst

34 dilute mixture

35 oxidation catalyst

36 heat exchanger

37 Fan

38 static mixer

39 secondary air supply fan

40 vacuum fan (if necessary)

41 outlet pipe (exhaust pipe)

50 primary energy production

51 feed pipe

52 concentrated mixture

53 backheating type catalytic heat exchanger

54 dilute mixture

55 oxidation catalyst

56 heat exchanger

57 fan

58 static mixer

59 secondary air supply fan

60 vacuum fan (if necessary)

61 outlet pipe (exhaust pipe)

Reference publications

Patent document

US 4 118 171

US 2017/153024

US 2009/284013

Claims

1. A process for the catalytic purification, under reducing and oxidizing conditions, of a combustion gas containing nitrogen oxides and carbon monoxide, hydrocarbons and soot particles, produced by an energy plant using a hydrocarbon-containing fuel,

fuel and air are fed into the exhaust gas, forming a gas mixture, and

-the gas mixture is subjected to one or more stages of catalytic combustion at a temperature above 600 ℃ to reduce nitrogen oxides and oxidize carbon monoxide, hydrocarbons and soot particles.

2. The method of claim 1, wherein the emission level of NOx gases obtained from catalytic combustion is 1ppm or less and the emission level of CO and VOC is at most 2 ppm.

3. The method as claimed in claim 1 or 2, wherein the catalytic combustion is carried out in a catalyst maintained at a temperature of 850 ℃ and 1000 ℃.

4. The method according to any one of claims 1-3, wherein the gas mixture is combusted in a three-way catalyst at a stoichiometric oxygen/extra fuel ratio for the oxidation of CO and VOC compounds not combusted in the combustion device, the reduction of NOx emissions and the oxidation of soot particles.

5. A method according to any one of claims 1-4, wherein the gas mixture is combusted in a redox catalyst, first a rich additional fuel/oxygen mixture is used for reducing nitrogen oxides and then a lean additional fuel/oxygen mixture is used for oxidizing CO and VOC compounds and soot particles.

6. The process according to claim 4 or 5, wherein the space velocity of the three-way catalyst is 50000-1500001/h, preferably 60000-1000001/h, and the space velocity of the reduction and oxidation catalyst is 60000-2000001/h, preferably 70000-1500001/h.

7. The process according to any one of the preceding claims, wherein the catalytic combustion is carried out in at least two stages under reducing and corresponding oxidizing conditions.

8. A method for producing thermal energy from a hydrocarbon-containing fuel, in which method,

-the fuel is burnt in the combustion device at an elevated temperature,

the heat generated by the combustion is recovered, and

the burnt exhaust gases and soot particles are cleaned by catalytic exhaust gas combustion,

it is characterized in that the preparation method is characterized in that,

fuel and air are fed into the exhaust gas to form a mixture, and

-catalytic combustion of the gas mixture at a temperature of at least 600 ℃, preferably above 600 ℃, to reduce nitrogen oxides and oxidize carbon monoxide, hydrocarbons and soot particles.

9. The process according to claim 8, wherein the catalytic combustion is carried out in one or more stages, preferably at least two stages, under reducing and corresponding oxidizing conditions.

10. The method of claim 8 or 9, wherein the exhaust gas, fuel and air are uniformly mixed together in a nested, perforated feed tube and static mixer to form a gas mixture.

11. The method according to any one of claims 8-10, wherein the gas mixture is catalytically combusted in a three-way redox catalyst.

12. The method according to any one of claims 8-11, wherein the gas mixture is combusted in the three-way catalyst at a stoichiometric oxygen/extra fuel ratio for oxidizing unburned CO and VOC compounds in the combustion device, reducing NOx emissions and oxidizing soot particles.

13. The method according to any one of claims 8-11, wherein the gas mixture is first combusted in a rich additional fuel/oxygen ratio mixture in a redox catalyst to reduce nitrogen oxides and then combusted with a lean additional fuel/oxygen ratio mixture to oxidize CO and VOC compounds and soot particles.

14. The process as claimed in any of claims 8 to 13, wherein the temperature in the catalyst under at least reducing conditions or under reducing and oxidizing conditions is 850 ℃ > 1000 ℃.

15. The process as claimed in any of claims 8 to 14, wherein the space velocity of the three-way catalyst is 50000-1500001/h, preferably 60000-1000001/h, and the space velocity of the reduction and oxidation catalyst is 60000-2000001/h, preferably 70000-1500001/h.

16. A method according to any of claims 8-15, wherein the fuel is burned in a combustion device, which is an oil or gas boiler, a gas turbine, a diesel engine plant or a similar energy device.

17. Method according to any of claims 8-16, wherein additional air and fuel are supplied to the exhaust gas burner and the temperature after the catalyst and the linear oxygen sensor are controlled to control their supply in dependence of the air/fuel mixture ratio required by the catalyst.

18. Method for generating heat from fuel with hydrocarbons by at least two stage combustion according to any of claims 8-17, characterized in that it is combined as:

in a first combustion stage, part of the fuel is combusted in a combustion device to produce heat and an exhaust gas containing oxides containing nitrogen and oxygen,

-recovering the heat obtained in the first combustion stage and the exhaust gases separately,

-in a second combustion stage, feeding the off-gas obtained from the previous combustion stage together with a second portion of fuel and air to form a gas mixture,

-the gas mixture thus obtained is subjected to catalytic combustion to generate heat and decompose oxides containing nitrogen and oxygen,

recovering heat obtained from the second combustion stage after combustion at a temperature above 600 ℃ while maintaining reducing conditions in at least one of the catalyst zones.

19. A method according to claim 18, wherein in said second combustion stage at least 10%, most preferably 15-80% of the total amount of hydrocarbon containing fuel is combusted.

20. The method of claim 18 or 19, wherein the primary energy source generates up to about 60% additional thermal energy.

21. The method of any one of claims 8 to 20, wherein the flue gas of the thermal energy device is used as an inert heat storage and transfer agent to maintain the temperature of the catalytic combustion within a preselected temperature range.

22. A method according to any one of claims 8 to 21, wherein the surface of the catalyst used in combustion is a stable metal oxide, preferably the oxide is an oxide in which the cation is Al, Ce, Zr, L or Ba and a precious metal such as Pd, Pt, Rh or a mixture thereof with a base metal.

23. The method of any one of claims 8-22, wherein the noble metal catalyst is non-toxic and does not produce toxic compounds in the reaction as do conventional SCR catalysts.

24. A method according to any of claims 8-23, characterized in that the thermal energy contained in the gases produced in the combustion is recovered in at least one heat exchange stage when transferring the thermal energy to water, air or other liquid or fuel.

25. Use of the method according to any one of claims 1-7 for producing recoverable thermal energy.