CS272768B2 - Method of combustion improvement during combustion processes with hydrocarbon compounds combustion - Google Patents

Abstract

When burning hydrocarbon fuels, improved combustion according to this invention is achieved by adding a liquid mix containing peroxide or a peroxide compound and water to the mixture of fuel and air, whereas this mixture containing 10 to 80 % by volume of peroxide or peroxide compound and water is added either directly to the combustion chamber without prior decomposition of the peroxide or to the precolumn, in the which the fuel mixture with the liquid mixture ignite inside the combustion chamber. This achieves not only improvement of combustion, but also reduction of the content of damaging materials in exhaust or waste gasses.

Description

The present invention relates to improved combustion in hydrocarbon compound combustion processes which optimizes and initiates combustion of these kinds of compounds, thereby reducing the content of harmful substances in the exhaust, flue gas and waste gases.

Recently, more and more attention has been paid to the protection of the environment from pollution by various harmful substances and, in addition, attention has been focused in the technical operations on avoiding high energy consumption. Environmental pollution is largely reflected in the death of forest stands, which has been increasing in recent times. Exhaust gases have always been a major problem in areas with high population concentrations. Despite the continuous improvement of engines and combustion techniques associated with the reduction of specific amounts of exhaust, flue or waste gases, the increasing number of vehicles and combustion equipment results in an overall increase in exhaust and flue gases of all kinds.

Insufficient combustion is a major cause of exhaust gas pollution and high energy consumption. The course of the combustion process, the efficiency of the ignition system, the quality of the fuel and the fuel / air mixture determine how efficient the combustion is and how many unburned and hazardous substances the exhaust or gaseous fumes contain. Various techniques, such as recirculation systems, and a known catalyst method are used to reduce the amount of these substances in the gases, which provide combustion of the exhaust gases outside the actual combustion process.

Swedish patent SE-B-429.20I discloses a liquid mixture containing 1 to 10 hydrogen peroxide, the remainder consisting of water, an aliphatic alcohol and a lubricating oil and optionally a corrosion inhibitor, the liquid mixture being added to the combustion air or to fuel-air mixtures. With such a low hydrogen peroxide content, an insufficient amount of OH 'radicals is formed to react with both the fuel and the carbon monoxide formed. In addition, there is no spontaneous ignition of the fuel obtained, so that the improved combustion process achieved in this manner is only small compared to the addition of mere water.

NSR DAS No. 2,362,082 discloses the addition of an oxidizing agent, such as hydrogen peroxide, but this hydrogen peroxide decomposes into water and oxygen by means of a catalyst before it is added to the combustion air.

In addition, it is known from German Pat. No. 2,625,766 to dispose of liquid combustibles by means of hydrogen peroxide, in which the liquid fuel is mixed with hydrogen peroxide prior to adding the mixture to the combustion chamber, which is a substantial difference from the process of the present invention. , which will be described below, because according to the present process, hydrogen peroxide reacts with the liquid fuel before being introduced into the combustion chamber, and there are therefore other processes compared to the invention.

In combustion, the combustion substance reacts with oxygen to release heat. Combustion of substances such as carbon, hydrogen gas, hydrocarbons and sulfur releases sufficient heat to maintain their combustion temperature, while for example nitrogen gas requires heat to be oxidized.

At a high temperature in the range of 1200 to 2500 ° C and with sufficient oxygen present, a perfect combustion is achieved in which each of the combustion substances reacts with the maximum amount of oxygen. The resulting products are carbon dioxide C0 _2, the water H ₂ 0, S0 ₂ sulfur dioxide, sulfur trioxide and SOg small amounts of nitric oxide NO and nitrogen dioxide NO2 · The notch sulfur and nitrogen oxides includes a large proportion of the acidity contained in the environment. These substances are harmful by inhalation and in particular nitrogen oxides reduce the energy balance of the combustion process.

Burning can also produce a cold flame, for example a blue, flickering flame

CS 272 768 02 extinguishing candles whose temperature is only about 400 ° C. In this case, the combustion will be incomplete, but the resulting products may be hydrogen peroxide 11 ₂ 0 ₂ , carbon monoxide CO□ or carbon (carbon black). Like the nitric oxide, the latter are harmful to health and can give off additional heat when burnt completely.

Gasoline is a mixture of hydrocarbons from crude oil, boiling in the range of 40 to 200 ° C. Gasoline contains about 2,000 different hydrocarbons having 4 to 9 carbon atoms.

In a detailed analysis, the combustion process appears to be very complex even for simple substances. Molecules of the combusted substance decompose into smaller units, most of which are so-called free radicals, ie. volatile molecules that react quickly with oxygen, for example.

The most important radicals are the O atom, the hydrogen atom H * and the hydroxyl radical 0H H. In particular, this hydroxyl radical is very important for the decomposition and oxidation of the fuel, on the one hand, by binding directly to the fuel, and on the other hand, by splitting off hydrogen to form water.

At the beginning of the initiation, water decomposes according to the following reaction:

H ₂ 0 + M -> H '+ OH' + M where M represents another molecule, for example nitrogen or a wall or electrode surface in a spark plug with which water comes into contact. Since the water molecule is very stable, high temperatures are required for its decomposition. A better alternative is to add hydrogen peroxide, which decomposes in a similar way:

11 ₂ 0 ₂ + M 2 OH + M

This reaction proceeds much more easily and at a lower temperature, especially on the surface on which the fuel-air mixture ignites more easily and in a more controlled manner. Another beneficial effect of the surface reaction is that hydrogen peroxide readily reacts with the soot and tar on the walls and on the spark plugs to produce CO ₂ , resulting in a clean electrode surface and a better spark spark.

□ Although both hydrogen peroxide and water are added to the material to be burned, there is a significant reduction in the carbon monoxide CO content of the exhaust gases according to the following reactions:

WHAT + ° 2 0: h ₂ o OH ' 4 · WHAT H ’ + ° 2

-> C0 ₂ + 0: initiation (1) X 2 OH ' branching (2) r in. co ₂ + H ' promotion (3)  r -> OH ' + 0: branching (4)

It can be seen from reaction (2) that water plays the role of a catalyst, in which water is re-formed in another. Since hydrogen peroxide provides many thousands of times more OH 'radicals than water, the step described in Reaction (3) is substantially accelerated and removes most of the carbon monoxide CO formed. During this process, additional energy is released, which helps to keep the combustion running.

Nitric oxide NO and NO ₂ are very toxic compounds, approximately four times more toxic than carbon monoxide. In acute poisoning, they cause lung tissue damage. Nitric oxide is an unwanted by-product of combustion. In the presence of water, nitric oxide is oxidized to nitric acid HNOg, causing it to contribute about half of the acidity of the atmosphere, while the other half of the acidity of the atmosphere is caused by sulfuric acid H ₂ SO ₄ . A serious problem is that nitrogen oxides ΝΟ _χ can

CS 272 768 02 decompose ozone in higher atmosphere layers.

Much of the nitrogen oxide comes from the reaction of oxygen with nitrogen from the air at high temperature and therefore does not depend on the fuel composition. How much nitrogen oxides Ν0 _γ is produced depends, among other things, on the conditions of combustion. Although the temperature drop proceeds very slowly, an equilibrium state is reached at slightly elevated temperatures, resulting in a lower resulting nitric oxide concentration.

In order to maintain a low degree of nitric oxide formation, the following conditions must be observed:

- incinerate the fuel-rich mixture in two stages,

- keep the combustion temperature low with

(a) use of large excess air;

b) strong cooling,

(c) flue gas recirculation.

In the chemical analysis of the flame, it has often been observed that the concentration of nitric oxide in the flame is much greater than that behind the flame, when nitric oxide decomposes. The following reaction is likely to occur in this decomposition:

CHg *

NO

HCN

Well

HgO

3e thus the formation of nitrogen is supported by conditions that allow a high concentration of CFIg ‘. the first condition relating to the combustion of the high-fuel mixture.

It is known from practical experience that nitrogen-containing fuels, for example in the form of heterocyclic hydrocarbons such as pyridine, release more nitric oxide.

The nitrogen content of the various fuels is approximately as follows:

crude oil 0.65 asphalt 2.30 heavy oils 1.40 light oils 0.07 coal I to

%%

%%

%

It is an object of the present invention to achieve improved combustion, thereby reducing the amount of harmful exhaust gas discharged during combustion of hydrocarbon compounds by improving combustion initiation and maintaining optimal combustion and complete combustion under favorable conditions such that the exhaust gas content is significantly reduced.

SUMMARY OF THE INVENTION A method of improving combustion in hydrocarbon compound combustion processes to reduce the pollutant content of exhaust or waste gases, wherein a liquid composition comprising a peroxide compound or peroxy compound and water according to the present invention is added to the combustion air or fuel / air mixture. in that the liquid mixture contains 10 to 80% by volume of a peroxide compound or peroxy compound in water and the mixture is fed either directly to a combustion chamber without prior decomposition of the peroxide compound or peroxy compound, or to a pre-chamber where the fuel / liquid mixture outside the combustion chamber.

The advantages of the process according to the invention are that the combustion of hydrocarbon fuels is improved while at the same time reducing the pollutant content of the exhaust gases.

It is also preferred that said liquid composition comprises up to 5% oil containing a corrosion inhibitor.

CS 272 768 112

The peroxide compound is preferably hydrogen peroxide. The feed liquid composition preferably contains at least 30% peroxide or peroxy compound.

Preferably, the liquid mixture comprises up to 70% of a C 1 -C 8 aliphatic alcohol, the alcohol being fed separately to said pre-chamber. This alcohol mixed with the liquid mixture will cause the fuel to ignite automatically.

Under alkaline conditions, hydrogen peroxide decomposes into hydroxyl radicals and peroxide ions according to the following reaction scheme:

H ₂ 0 ₂ + H _{2 2} . -> HO '+ 0. + H ₂ 0

The hydroxyl radicals formed can react with themselves, with peroxide ions or with hydrogen peroxide. Thus, these reactions give rise to hydrogen peroxide, oxygen gas and hydrogen peroxide radicals according to the following reaction schemes:

HO '+ HO * -> H ₂ 0 ₂

HO '+ 0. -> ³ 0 ₂ + OH

HO * ^N 2 ° 2 ho ₂ . ₊ II ₂ 0

As is known, the pKa for the hydrogen peroxide radical has a value of 4.88-0.10, which means that all hydrogen peroxide radicals are dissociated into peroxide ions. Peroxide ions can also react with hydrogen peroxide, themselves, or they can bind a single oxygen molecule according to the following equations:

o ₂ .

^H 2 ° 2 o ₂ + ° 2 + h ₂ o

HO ^{- 1} o '

OH

H ₂ O + OH ° 2 ⁺

On kcal

Thus, gaseous oxygen, hydroxyl radicals, hydrogen peroxide ions, singlet oxygen, hydrogen peroxide and triplet oxygen are produced and energy of 22 kcal is released. It has also been shown that the heavy metal ions present in the catalytic decomposition of hydrogen peroxide make it possible to obtain hydroxyl radicals and peroxide ions.

From the foregoing and known to date, the following reaction velocity coefficients are shown, with an effect on the following alkane as an example of the effect of hydrogen, oxygen and the hydroxyl radical on gasoline components.

The reaction rate coefficients for the reaction of n-octane with hydrogen, oxygen and the hydroxyl radical are shown in the following table:

CS 272 768 B2 k = A exp (E / RT) reaction AE (cm / mol.s) (kC / mol) ⁿ ' ^C 8 ^H 18 * ^H 7.1.10 ¹⁴ 35.3 n-CgHig + O 1.8.10 ¹⁴ 19.0 ^n_C 8 ^H 18 * ° ^H 2.0.10 ¹³ 3.9

From this example it is apparent that Me reaction of n-octane with OH radicals proceeds faster and at a lower temperature than reaction with hydrogen and oxygen.

The reaction rate coefficient for the reaction CO + OH = CO ₂ + H is characterized by an unusual temperature dependence due to its negative activation energy and high temperature coefficient. Thus, the reaction rate can be expressed as

4.4. 10 T 'exp (3.1 L / RT). Thus, the reaction rate will be almost constant, at about 113 cm / mol at temperatures below 1,000 K, i.e. at all temperatures up to room temperature. At temperatures above 1000 K, the reaction rate is several times higher. As a result, this reaction is predominant in the conversion of carbon monoxide to carbon dioxide in the combustion of hydrocarbons. The early and complete combustion of carbon monoxide thus improves thermal efficiency.

The reaction between ammonia, hydrogen peroxide and nitrogen oxides ΝΟ _{χ is an} example of the contradictory action of oxygen O ₂ and OH radicals, where the addition of hydrogen peroxide causes a 90% reduction of nitrogen oxides ΝΟ _χ in an oxygen-free environment. On the other hand, if oxygen is present, even in an amount of only 2%, the reduction ΝΟ _{χ is} greatly reduced.

To form OH radicals, hydrogen peroxide, which decomposes at a temperature of about 500 ° C, is preferably added in the combustion of hydrocarbon fuels. These radicals have a maximum life of 20 ms.

In normal ethanol combustion, 70% of the fuel is consumed to react with OH radicals and 30% to react with hydrogen atoms. According to the present invention, OH radicals are already supplied at the initiation of combustion and combustion is greatly improved by reacting these radicals immediately with the fuel. Addition of a high hydrogen peroxide-containing liquid mixture (i.e., more than 10% hydrogen peroxide) produces sufficient OH radicals to oxidize the carbon monoxide formed immediately. At a lower hydrogen peroxide content, there is not enough OH radicals to react with both fuel and carbon monoxide.

The liquid mixture used for combustion in the process of the present invention is fed to the combustion so that there is no chemical reaction in the area beginning with the liquid container and ending with the combustion space, i.e. hydrogen peroxide decomposes into water and gaseous oxygen, but the liquid mixture reaches not disposed directly into the combustion chamber or, alternatively, into a pre-chamber in which the liquid-fuel mixture ignites outside the combustion chamber itself.

□ although the hydrogen peroxide concentration is sufficiently high (approximately 35%), fuel can ignite spontaneously and maintain fuel combustion. The fuel / fuel mixture may ignite spontaneously or on contact with the catalytic surface, without the need for spark plugs or other similar devices. It can also ignite

CS 272 768 B2 may be caused by heat, for example from a spark plug, glowing body, open flame and the like.

The admixture of the aliphatic alcohol with hydrogen peroxide may advantageously initiate autoignition. This may be particularly useful in pre-chamber systems, whereby hydrogen peroxide must not be mixed with alcohol before it reaches the pre-chamber.

A very accurate liquid metering, adapted to all operating conditions, is achieved by providing a liquid mixture injector for each cylinder of the engine. By means of a control device controlling the operation of the injection valves and by means of a series of signal sensors connected to the engine which give signals to the control device indicating the crankshaft position, engine speed, load and possibly also the inlet gas temperature, successive injection and synchronization with opening can be performed. by closing the injection valves and dispensing the liquid mixture, depending not only on the load and the required output power, but also on the engine speed and the mixing air temperature, which ensures good operability under all conditions. The liquid mixture replaces to some extent the air supply.

A number of comparative tests were performed to determine the difference in effect using a mixture of water with 23% hydrogen peroxide and 35% hydrogen peroxide. The selected loads corresponded to highway and city traffic. The engine tested was a B20E engine coupled with a hydraulic brake. The engine was warmed up before starting the test.

When the engine load, which corresponds to driving on the motorway, the nitrogen oxide emissions _ΝΟ χ, and oxides and hydrocarbons .uhelnatého increased when the hydrogen peroxide was replaced with water. The content of nitrogen oxides ΝΟ _χ decreased with increasing amount of hydrogen peroxide. Also, water reduced the content of nitrogen oxides Ν0 _χ , but this load required four times the amount of water compared to 23% hydrogen peroxide in order to achieve the same reduction in the content of nitrogen oxides Ν0 _χ .

At a city traffic load, 35% hydrogen peroxide was added first, with engine speed and torque increasing somewhat (20 to 30 rpm, 0.5 to 1 Nm)

By switching to 23% hydrogen peroxide, the engine speed and torque have decreased, while at the same time the nitrogen oxide content ΝΟ _{χ has} increased. Adding clean water made it difficult to keep the engine running. The hydrocarbon content increased significantly.

Thus, in the tests performed, it was found that the addition of hydrogen peroxide greatly improved combustion and at the same time reduced the nitrogen oxide content ΝΟ _χ . In tests conducted by the Swedish Inspectorate of Motor Vehicles with SAAB 900i and Volvo 760 Turbo engines with and without the addition of a mixture containing 35% hydrogen peroxide to the fuel, the following values were found for carbon monoxide, hydrocarbons, nitrogen oxides ΝΟ _χ and carbon dioxide emissions. The percentages represent the results obtained with the hydrogen peroxide mixture as compared to the results obtained without the addition of the mixture. The results are shown in the following tables.

Starting with a cold engine start with warm engine SAAB 900i Drive with warm engine idling HCD (road driving) CO: -23% CO: -54% CO: -76% CO: -90% WHAT: 41% C _x H _y : + 5% C _x H _y : 10% C _x H _y : -7% C _x H _y : -50% ^C x ^H y : +8% ΝΟ _χ : -25% ΝΟ _χ : -11% Ν0 _χ : -22% Ν0 _χ : -15% C0 ₂ : +33% C0 ₂ : + 4% C0 ₂ : + 5% C0 ₂ : +3%

C _x Hy = hydrocarbons

CS 272 768 B2

Volvo 760 Turbo idling Drive with warm engine CO: -73% WHAT: -54.3% C _x H _y : -18% CH: x y - 2,3% Ν0 _χ : -22% Ν0 _χ : - 8.3%

C Η = hydrocarbons x y

In the tests carried out with the Volvo 245 GL 4FK / 84, the idle carbon monoxide content was 4% and the hydrocarbon content 65 ppm without the air pulses produced by the exhaust gas cleaning. Addition of a 35% hydrogen peroxide solution reduced the carbon monoxide content to 0.05% and the hydrocarbon content to 10 ppm. In both cases the ignition timing was 10 ° and the idle speed was 950.

In the tests conducted by the Norwegian Maritime Technical Research Institute A / S in Trondheim, emissions of hydrocarbons, carbon monoxide and nitrogen oxides Ν0 _χ were measured on a Volvo 760 Turbo according to ECE S 15.03 when starting with a hot engine, adding 35% hydrogen peroxide solution to the fuel, and without the addition of hydrogen peroxide. The results are shown in the following table.

Test results: ECE 15.03 Idle run No peroxide added ^C X ^H at ^{: 4.3} 9 / ^test 340 ppm hydrogen CO: 70 g / test 0.64% Ν0 _χ : 4.8 g / test 92 ppm With 35% added ^C x ^H y ^{: 4.2} 9 / CO test: 32 g / test 280 ppm peroxide solution 0.17% of hydrogen Ν0 _χ : 4.4 g / test 73 ppm

C H = hydrocarbons x y

The use of hydrogen peroxide is described above. However, it can be assumed that the corresponding effect is also achieved with other peroxides and peroxo compounds, both inorganic and organic.

The liquid composition used in the process of the invention may preferably contain up to 70% aliphatic alcohol having 1 to 8 carbon atoms and up to 5% oil containing a corrosion inhibitor in addition to peroxide and water.

The amount of liquid composition added to the fuel may range from a few tenths of a percent of the liquid composition, based on the amount of fuel, to several hundred percent. These larger quantities are used inter alia for fuels which are difficult to ignite.

The liquid mixture used in the process of the present invention is intended for use in internal combustion engines and other combustion processes using hydrocarbon compounds such as petroleum, coal, oil, biomass and the like in combustion plants for improved combustion and reduced content. of harmful substances in the exhaust gases.

Claims (4)

A method for improving combustion in hydrocarbon fuel combustion processes to reduce the pollutant content of exhaust or waste gases, comprising adding to the combustion air or fuel-air mixture a liquid mixture comprising peroxide or peroxy compound and water, This mixture containing 10 to 80% by volume of peroxide or peroxy compound in water is fed either directly to the combustion chamber without prior decomposition of the peroxide or peroxy compound, or to a pre-chamber where the fuel-liquid mixture ignites outside the combustion chamber. 2. The process according to claim 1, wherein the feed mixture comprises at least 30% peroxide or peroxy compound, preferably hydrogen peroxide. 3. The process according to claim 1, wherein the liquid mixture comprises up to 70% of an aliphatic alcohol having 1 to 8 carbon atoms, the alcohol being fed separately to said pre-chamber. 4. A process according to any one of claims 1 to 3, wherein the feed liquid composition comprises up to 5% oil containing a corrosion inhibitor.