DD250714A5 - METHOD AND COMPOSITION FOR IMPROVING COMBUSTION OF BURNING HYDROCARBON CONNECTIONS - Google Patents

Abstract

The invention relates to a method and composition for providing better combustion in combustion processes containing hydrocarbon compounds to reduce the level of harmful substances in the exhaust gases / effluents, comprising a liquid composition containing 10 to 80% by volume of peroxide. or peroxo compound contains, the combustion air or the fuel-air mixture is added.

Description

Field of application of the invention

The invention relates to a method and a liquid composition which initiates and optimizes combustion processes containing hydrocarbon compounds and thereby reduces the content of harmful substances in the exhaust gases or effluents, wherein a peroxide or peroxo compound containing liquid composition of the combustion air or the fuel Air mixture is supplied.

Characteristic of the known state of the art

In recent years, considerable attention has been paid to pollution of the environment and high energy consumption, mainly because of the dramatic decline in forest. However, exhaust has always been a problem in densely populated centers. Despite ever-improving engines and heating techniques with fewer exhaust products or exhaust gases, the increasing number of vehicles and incinerators has led to an overall increase in the amount of exhaust gas.

The main thing for dirty exhaust gases and high energy consumption is insufficient combustion. The design of the combustion process, the efficiency of the ignition system, the quality of the fuel, and the fuel-air mixture determine how effective combustion is and how many unburned and harmful substances the gases contain. Various techniques are used to reduce the amount of substances, for example, recirculation systems and the well-known catalyst technology, which results in combustion of the exhaust gases outside of the actual combustion process.

Combustion is the reaction of a substance with oxygen (O ₂ ) with heat generation. Substances such as carbon (C), hydrogen gas (H2), hydrocarbons and sulfur (S) generate sufficient heat for maintaining their combustion temperature while for example nitrogen gas (N ₂₎ requires heat for its oxidation. At a high temperature, 1 200 to 2500 ⁰ C, and a sufficient amount of oxygen complete combustion is achieved, in which each substance absorbs a maximum amount of oxygen. The final products are CO ₂ (carbon dioxide), H ₂ O (water), SO ₂ and SO ₃ (sulfur oxides) and some NO and NO ₂ (nitrogen oxides, NOx). The sulfur and nitrogen oxides are responsible for a large part of the acidification of the environment, their inhalation is harmful, and especially the latter withdraw energy from the combustion process. It is also possible to achieve cold flames, for example the blue flickering flame of a candle, which goes out when the temperature is only about 400 ° C. The oxidation then does not become complete

but the final products can be H ₂ O ₂ (hydrogen peroxide), CO (carbon monoxide) and possibly C (carbon black).

The last two substances are harmful like NO and could give off more energy if burned completely.

Gasoline is a mixture of hydrocarbons of crude oil with a boiling point in the range of 40 to 200 ° C. There are about 2000 different hydrocarbons containing 4 to 9 carbon atoms.

The actual combustion process is very complicated even with simple substances. The fuel molecules are decomposed into smaller units, most of which are the so-called free radicals, i. H. volatile molecules that react quickly with, for example, oxygen.

The most important radicals are the oxygen atom O :, the hydrogen atom H- and the hydroxyl radical OH-. Above all, the latter has great importance for the decomposition and oxidation of the fuel, both by direct binding thereto and by the removal of hydrogen, whereby water is formed.

At the start of the combustion, it becomes water after the reaction

H ₂ O + M -> H. + OH. + Μ

where is my other molecule, for example, nitrogen or a wall surface or spark plug surface with which the water collides. Since water is a very stable molecule, a very high temperature is required for the decomposition to take place. The better alternative is to add hydrogen peroxide, which decomposes in a similar way:

H ₂ O ₂ + M- ^ 2OH. + M

This reaction takes place much more easily and at a lower temperature, especially on surfaces where the ignition of the fuel-air mixture is easier and in a more controlled manner. Another positive effect of a surface reaction is that hydrogen peroxide easily builds up with soot and tar, and spark plugs are converted to carbon dioxide (CO ₂ ), resulting in cleaner electrode surfaces and a better spark.

When hydrogen peroxide and water are added, there is a drastic reduction in CO in the exhaust gases as follows:

1) CO + O ₂ - ^ CO ₂ + O: Introduction

2) 0: + H ₂ O - »2 OH branching

3) OH + CO- * CO ₂ + H propagation

4) H + O ₂ - ^ OH + O: branching

From reaction 2) it can be seen that water plays a catalyzing role because it is later remodeled. Since hydrogen peroxide gives a thousand times higher content of OH radicals than water, step 3) is considerably accelerated and removes most of the CO formed. This releases additional energy that helps maintain combustion.

NO and NO ₂ are very toxic compounds, about four times as toxic as carbon monoxide. In acute poisoning lung tissue is damaged. NO is an undesirable by-product of combustion. In the presence of water, NO is oxidized to HNO ₃ and is responsible for about half of the acidification in this form, the other half being caused by H ₂ SO ₄ . One problem is that NOx can decompose ozone in the upper part of the atmosphere.

A large part of NO comes from the reaction between the oxygen and the nitrogen of the air at a high temperature and is therefore independent of the composition of the fuel. How much NOx is formed is also dependent on the conditions under which the combustion takes place. If the temperature decrease can be very slow, this leads to a balance at moderately high temperatures and a low final concentration of NO. The following methods can be used to minimize the formation of NO:

1. Combustion of a fuel-rich mixture in two stages.

2. Low combustion temperature

a) high excess air

b) strong cooling

c) recirculation of the combustion gases.

In the chemical analysis of the flame, it has often been observed that the concentration of NO in the flame is much higher than afterwards. It is a process by which NO is decomposed. A "possible reaction is

CH ,. + HO> ... HCH + HpO

Thereafter, the conversion of N ₂ is assisted by conditions leading to high concentrations of CH ₃ by a hot, fuel-rich flame.

Fuels containing nitrogen, for example in the form of heterocyclic hydrocarbons such as pyridine, have been found to give more NO.

The content of N in different fuels (approximate):

Crude oil 0.65% asphalt 2.30%

- heavy oils 1,40%

- light oils 0.07%

- Carbon ibis 2%

In SE-B-429.201 a liquid composition is presented which contains 1 to 10% by volume of hydrogen peroxide and in which the. remaining amount of water, aliphatic! Alcohol and lubricating oil and possibly a corrosion inhibitor, wherein the liquid composition of the combustion air or the fuel-air mixture is supplied. With such a low content of hydrogen peroxide, an insufficient amount of OH radicals is formed for the reaction with the fuel and the CO formed. In addition, no auto-ignition of the fuel is achieved, so that the achieved improvement in combustion compared to the addition of only water is low.

DE-A-2,362,082 discloses the admixing of an oxidizing agent, for example hydrogen peroxide, in connection with combustion, but the hydrogen peroxide is decomposed to water and oxygen by means of a catalyst before being supplied to the combustion air.

Object of the invention

The object of the invention is to provide an improved combustion and thereby a reduction in the emission of harmful exhaust gases in connection with combustion processes containing hydrocarbon compounds, by better initiation of combustion and the maintenance of optimal and complete combustion under such favorable conditions the content of harmful exhaust gases is greatly reduced.

Explanation of the essence of the invention

According to the invention this is achieved by the fact that the combustion air or the fuel-air mixture is a liquid composition containing a peroxide or peroxo compound and water, fed, wherein a liquid composition is selected, the 10 to 80 vol .-% the peroxide or peroxo compound contains. Under alkaline conditions, hydrogen peroxide is decomposed to hydroxyl radicals and superoxide ions as follows

H ₂ O ₂ + HO ₂ - * HO. + O ₂ + H ₂ O

The hydroxyl radicals formed can on the one hand react with themselves and on the other hand with the superoxide ions or with hydrogen peroxide. These reactions involve sequentially forming hydrogen peroxide, oxygen gas and hydroperoxide radicals according to the following reaction formulas:

HO. + HO- * H ₂ O ₂

HO. + OJ. ~ 3 O ₂ + OH

HO. + H ₂ O ₂ - ^ HO ₂ . + H ₂ O '. -

It is known that the pKa value for the hydroperoxide radicals is 4.88 ± 0.10, which means that all hydroperoxide radicals are dissociated to superoxide ions. Superoxide ions can also react with hydrogen peroxide as well as with themselves or act as scavengers of singlet oxygen (single "oxygen).

O ₂ ". + H ₂ O ₂ -" O ₂ + HO. + OH "

O ₂ ". + O ₂ ". + H ₂ O - » ¹ O ₂ + HO ₂ " + OH "

O ₂ ". + ¹ O ₂ ^ - ³ O ₂ + O ₂ ". + 22kcal

In this way, oxygen gas and hydroxyl radicals as well as singlet oxygen and hydrogen peroxide and triplet oxygen (triplet oxygen) are formed with a waste of energy of 22 kcal.

It has also been demonstrated that heavy metal ions present in the catalytic decomposition of hydrogen peroxide give hydroxyl radicals and superoxide ions.

From the above and previously known, the following findings on the velocity coefficients are presented, for example as follows for a typical alkane of gasoline.

The velocity coefficients for the attack of n-octane with H, 0 and OH:

k + Aexp (E / RT) E (kJ / mol) reaction A (cm ³ / mol: s) 35.3 nC ₈ H ₁₈ + H 7.1: 10 ^u . 19.0 + 0 1.8: 10 ¹⁴ 3.9 + 0H 2,0: 10 ¹³

From the example, it can be seen that the attack of the OH radical can be faster and at a lower temperature than H and O.

The velocity coefficient for CO + OH -> CO ₂ + H has an unusual temperature dependence due to its negative activation energy and its high temperature coefficient. It can be written as 4,4 10 ⁶ T ^t5 exp (3,1 / RT). The reaction rate is then nearly constant at about 10 ^1l cm ³ / mol · s to less than 1 OQO ⁰ K lying temperatures, ie, all values to room temperature, lie. At temperatures higher than 1 000 ⁰ K, the reaction rate is increased many times. As a result, this reaction is the most prevalent for the conversion of CO to CO ₂ in the combustion of hydrocarbons. The early and complete combustion of CO improves the thermal efficiency.

An example shows that the antagonism between O ₂ and OH were the reactions NH ₃ -H ₂ O ₂ -NO and the addition of H ₂ O _{2 leads to} a reduction of 90% NOx in an oxygen-free environment. On the other hand, if O _{2 is} present, even if only 2%, the NO _x reduction is drastically reduced.

For the provisioning of OH radicals according to the invention, H ₂ O _{2 is} used, which is dissociated at about SOO ⁰ C. They have a maximum lifetime of 20 ms.

In a normal combustion of ethanol, 70% of the fuel is consumed by the reaction with OH radicals and 30% with Η atoms. By the invention, in which OH radicals are supplied already at the initiation of combustion, the combustion is improved considerably by immediate attack of the fuel. By supplying a liquid composition with a high content of hydrogen peroxide (over 10%), sufficient OH radicals are available for the immediate oxidation of the CO formed. With a low content of hydrogen peroxide, the OH radicals formed are insufficient for the reaction with the fuel and with the CO.

The liquid composition is supplied so that no chemical reaction takes place from the liquid container to the combustion chamber, i. a decomposition of hydrogen peroxide to water and oxygen gas will not occur, but the liquid will go in perfect condition directly to the combustion or alternatively in an antechamber in which a mixture of the liquid and the fuel is ignited outside the actual combustion chamber.

If the concentration of hydrogen peroxide is sufficiently high (about 35%), autoignition of the fuel can occur and combustion can be sustained as well. The ignition of the liquid-fuel mixture may be by autoignition or by contact with a catalyzing surface, with no need for spark plugs or the like. The ignition may also be achieved by ignition with thermal energy, for example a spark plug, an incandescent body, an open flame or the like.

The incorporation of an aliphatic alcohol in hydrogen peroxide can trigger auto-ignition. This may be desirable especially in pre-chamber systems where the hydrogen peroxide and alcohol may not mix before they reach the pre-chamber.

By providing a liquid composition injector for each cylinder, a very accurate metering of the liquid adapted to all operating conditions is enabled. By means of control means for controlling the injection valves and a number of signal transmitters connected to the engine, which provide signals to the control means indicating the position of the crankshaft, the engine speed and load, and possibly also the temperature of the gas, is a successive injection and synchronization possible with the opening and closing of the injectors and a dependent not only on the load and the required power output, but also on the engine speed and the temperature of the injection air metering, which leads to a good run under all conditions. The liquid mixture replaces the air supply to a certain extent.

A series of comparative tests were carried out to find out the differences in the effect between water and hydrogen peroxide mixtures (23% and 35%, respectively). The selected loads correspond to driving on trunk roads and in cities. The test engine was a B 20 E, which was connected to a liquid brake. The engine was preheated before the test started.

In the case of long-distance road traffic, the emissions of NOx and CO and HC increased when hydrogen peroxide was used instead of water. The content of NOx decreased with a larger amount of hydrogen peroxide. Also, with water, the NOx content was reduced, but four times as much water was required at this load as at 23% peroxide to achieve the same reduction in NOx content.

In urban traffic, 35% hydrogen peroxide was initially added, increasing engine speed and torque slightly (20 to 30 U / 0.5 to 1 Nm).

Switching to 23% hydrogen peroxide reduced engine speed and torque while increasing NOx levels. When supplying pure water, it was difficult to keep the engine running. The HC content had increased significantly.

Thus, the hydrogen peroxide improved combustion while reducing the NOx content achieved. Tests conducted on the Swedish Motor Vehicle Inspectorate with a SAAB 90Oi and a Volvo 760 Turbo with and without admixture of 35% hydrogen peroxide to the fuel gave the following results regarding the emission of CO, HC, NOx and CO ₂ . The percentages indicate the result obtained with a mixture of hydrogen peroxide. In comparison to the result without this mixture.

SAAB 90Oi warm start Warming up Warming up Neutral cold start CO: -54% CO: -54.3% CO: -76% CO: -90% CO: -23% HC: ± 0% HC: -2.3% HC: -7% HC: -50% HC: + 6% NOx: -12% NOx: -8.3% NOx: -23% NOx: -25% CO ₂ : + 4% CO ₂ : + 5% CO ₂ : + 33% HCD (road procedure) CO: -41% HC: + 8% NOx: -15% CO ₂ : + 3% VOLVO 760 Turbo Neutral CO: -73% HC: -18% NOx: -21%

In the experiments carried out with a Volvo 245 GL4FK / 84, the car had a CO content of 4% and an HC content of 65 ppm without impulse air (exhaust gas purification) during idling. By mixing in a 35% solution of hydrogen peroxide, the CO content was lowered to 0.05% and the HC content to 10 ppm. The ignition timing was 10 ° and the idle speed was 950 in both cases.

In tests carried out by the Norwegian Technical Naval Research Institute A / S in Trondheim, the HC, CO and NOx emissions of a Volvo 760 Turbo were determined in accordance with ECE Regulation No. 15.03 with an initially warm engine and without admixing a 35% solution examined by hydrogen peroxide for combustion. Test results:

ECE 15.03 idling

HC 4.3 g / trial 340 ppm

Without hydrogen peroxide CO 70 g / test 0.64%

NOx 4.8 g / run 92 ppm

With admixture of a 35% solution of hydrogen peroxide HC 4.2 g / experiment 280 ppm

CO 32 g / test 0.17%

NOx 4.4 g / trial 73 ppm

Above, only the use of hydrogen peroxide was discussed. It can be assumed, however, that a similar effect could also be achieved with other peroxides and peroxo compounds, inorganic and also organic.

The liquid composition may contain, in addition to peroxide and water, up to 70% of an aliphatic alcohol of 1 to 8 carbon atoms and up to 5% of an oil added with a corrosion inhibitor.

The amount of a mixture of the liquid composition in the fuel may vary from a few tenths of a percent of liquid composition per fuel amount to a few hundred percent. The higher amounts are used, inter alia, for fuels whose ignition is difficult.

The liquid composition is intended for use in internal combustion engines and in other hydrocarbon compounds, such as oil, coal, biomass, etc. combustion processes in incinerators to achieve more complete combustion and a reduction in the level of harmful substances in the effluents.

Claims (9)

Claims: I A method of providing better combustion in combustion processes containing j hydrocarbon compounds to reduce the level of harmful substances in the; To reduce exhaust gases / exit products, wherein a peroxide or peroxo compound and water-containing liquid composition of the combustion air or the fuel-air mixture is added, characterized in that a liquid composition is used, the 10 to 80Vol .-% peroxide or Contains peroxo compound. 2. The method according to claim 1, characterized in that the liquid composition is passed directly into the combustion chamber without prior decomposition of the peroxide or peroxo compound. , 3. The method according to claim 1, characterized in that the liquid composition is passed into an antechamber in which a mixture of the fuel and the liquid composition is ignited outside the actual combustion chamber. 4. The method according to claim 3, characterized in that an aliphatic alcohol having 1 to 8 carbon atoms is passed separately into the pre-chamber and the alcohol after mixing with the liquid composition leads to spontaneous combustion of the fuel. 5. A composition for providing better combustion in combustion processes containing hydrocarbon compounds, according to the method of claim 1, characterized in that a liquid composition containing 10 to 80VoI .-% of a peroxide or peroxo compound is used. 6. A composition according to claim 5, characterized in that it contains up to 70% of an aliphatic alcohol having 1 to 8 carbon atoms. Composition according to Claim 5 or 6, characterized in that it contains up to 5% of an oil containing a corrosion inhibitor. 8. A composition according to any one of claims 5 to 7, characterized in that it contains at least 30% peroxide or peroxo compound. Composition according to any one of Claims 4 to 8, characterized in that the peroxide is hydrogen peroxide.