HU207671B - Wet catalyzer solutions for burning processes and fuel preparations containing the same - Google Patents

Abstract

The invention relates to a aqueous catalyst solution for improved combustion of carbon and / or hydrocarbon-containing materials, such as heating oils, hot gases and solid fuels and / or for removal of rusz or tar deposits on surfaces of the combustion chamber and is primarily characterized in that the aqueous Catalyst solution has a p H value of at least 7 and in catalytically effective amount of tetravalent cerium (Ce4) and alkali, alkaline earth and / or magnesium compounds which react alkaline after their combustion or thermal decomposition, as well as complexing agent for this Ce4. {Katalysatorloesung , watery; Carbon; hydrocarbonaceous substances; Combustion, improved}

Description

The present invention relates to an aqueous combustion catalyst composition for improved combustion of fuels containing coal and / or hydrocarbons (fuel oils, heating gases and solid fuels) and / or to the removal of carbon black or tar deposits on tailings surfaces.

Almost perfect combustion of the used hydrocarbon and hydrocarbon fuels is required to prevent carbon black deposits on combustion surfaces. This can only be achieved with excess air, ie much more than the amount of air needed for stoichiometric combustion must be added to the fuel. While this is beneficial for perfect combustion, it is detrimental to the economical use of fuel because it requires unnecessary heating of the air and an increase in the amount of hot flue gas. The aim, therefore, is to burn hydrocarbon and hydrocarbon fuels with little or no soot formation, with little more than the amount of air required for stoichiometric combustion, which in practice is not always or completely successful. In the case of liquid fuels, the initial perfect setting of the burner is hampered by the slow setting of the fuel nozzle, which increases carbon black formation.

The formation of carbon black is detrimental to combustion, due to both the loss of heat generated and the reduced heat transfer due to the high thermal insulation carbon black. Therefore, it has been a long-time endeavor to use combustion catalysts to prevent or reduce the formation of soot and to burn off the soot and tar deposits already formed at low temperatures. The favorable combustion of the tar and soot already formed is most effectively achieved by the transition metal compounds which are known to exist in various valence forms. The metal compounds used so far are the chemical chromates of copper, manganese, cobalt, zinc and chromium. In particular, copper compounds and metal copper powder significantly reduce the combustion temperature of soot and tar. However, they have the disadvantage that toxic components are present in the flue gas and that the corrosion hazard of iron-based structural materials is greatly increased. In the electrochemical voltage series of the elements, the potential of copper is significantly more positive than that of iron, and therefore the precipitation of copper on iron structural materials commonly used in heat technology causes corrosion of iron-containing structural elements. This process is significantly accelerated by the presence of sulfuric acid or sulfuric acid produced during the combustion of sulfur-containing fuels.

Zinc chemical compounds are less toxic than copper compounds, and do not pose a significant corrosion risk to iron materials, but they are barely effective as a combustion catalyst in the combustion of soot and tar.

To date, chromium has been used primarily in the form of chromates, both for utilizing the combustion-catalyzing effect of metal ions and for validating the oxidation potential of chromates for carbon. However, due to the carcinogenic effect of some chromium compounds, these compounds are not eligible under current environmental requirements. The same applies to nickel and cobalt compounds, although cobalt in particular has a good catalytic effect on combustion.

Manganese, in particular in the form of permanganate ion, also exhibits good combustion catalytic properties

The oxidation potential of MnO ₂ + 2 H ₂ O = MnO ₄ - + 4 H ⁺ + 3 e 'is high (-1.70 V). however, manganese compounds also include substances classified as toxic or even carcinogenic.

Non-toxic transition metal is iron, which is often used in oil-soluble form (iron soap, Ferrocen) as a catalyst for the combustion of liquid fuels. Injection of an aqueous solution of iron salts (such as iron sulfate) into the flame has been proposed and has been practiced. Despite these positive catalytic properties for combustion, iron compounds were not sufficient to burn the soot and tar already formed. This is due to the relatively low oxidation potential of the trivalent iron compounds (-0.77 V for the Fe ⁺⁺ = Fe ⁺⁺⁺ + e ~ reaction).

Calcium compounds have also been suggested for the removal of carbon black deposits, although calcium is an alkaline earth metal and not a transition metal. Calcium has a low catalytic effect, which can only be achieved at high combustion temperatures by the formation of hydroxide ions in the flame. However, as an alkaline earth metal, it neutralizes sulfuric acid and sulfuric acid when attached to non-thermally stable and non-combustible anions.

Hydrogen peroxide has also been used as a metal ion-free cleaning agent for the removal of coal deposits. This oxidant is also recommended in combination with free alkalis (alkaline hydroxides, carbonates and silicates), the carbon black is oxidized by carbon peroxide, the acids are the effect does not occur.

Examples of the patents disclosed in the subject are British Patent Publication No. 1252624 for Hydrogen Peroxide and Strong Aqueous Alkaline Solutions; U.S. Patent 2,413,520 for a metal powder based deodorant containing copper powder; U.S. Patent No. 4287090 for a catalytically active aqueous metal salt solution of manganese acetate, calcium nitrate, and copper acetate; Publication No. 2911259 A furnace containing copper carbonate as an oxidation auxiliary, based on a solution of an alkali metal iodate or an alkali metal periodate, containing ammonia or alkali metal carbonates to neutralize acidic ash components. cleaning agent.

In German Patent Publication No. 2228,467, the chemical carbon black

Potassium nitrate and ammonium nitrate (without catalytic effect on combustion) are described as swelling agents. British Patent No. 1303552 discloses ammonium nitrate in addition to potassium nitrate and / or sodium nitrate for the capture and concentration of sulfuric acid in flue gases.

A number of other cleaning agents for cleaning fireplaces in the firebox also contain oxidizing agents and catalytic combustion auxiliaries (ammonium nitrate, ammonium chromate, zinc and copper salts) for the removal of soot and tar (German Patent Publication No. 1810424).

For many years the Swedish NOBEL brand SP-SOTIN has been commercially available for cleaning of heating surfaces, which according to the manufacturer contains alkaline metal nitrates as the main constituent (which are not combustion catalysts).

All of the formulations listed are intended to remove soot and tar, but they do not fully meet the requirements of today's heat transfer, which is environmentally friendly and with no major losses. In addition to its good efficiency, catalytic combustion with suitable metals has the disadvantage of being toxic in the flue gases (copper, nickel, cobalt, chromium, manganese), while the oxidation potential of environmentally friendly metals (iron, calcium) is low. The use of oxidizing agents (nitrates, iodates or peroxides) has a one-off effect and once these materials are depleted of active oxygen, soot and tar can once again be deposited unhindered and deteriorate the thermal balance and damage the environment by releasing soot.

It should be borne in mind in this regard that a carbon black deposit of only 1 mm thick can increase the temperature of the flue gas by about 70 ° C and result in an excess of 5% fuel oil (fuel).

It is an object of the present invention to provide a combustion catalyst which has a high oxidation potential in the form of its non-toxic catalytic action in the presence of oxygen in the air, with a high oxidation potential for combustion of soot and tar at as low a temperature as possible It has.

Lanthanides, in particular divalent cerium compounds, have been found to be suitable combustion catalysts. The water-soluble cerium compounds are non-toxic, the lethal dose of cerium nitrate water (l / 6) (LD ₅₀ as determined in rats) is 4200 mg / kg, while the value for pure table salt is only 3000 mg / kg.

The divalent cerium compounds are strong oxidants, the oxidation potential of the Ce (IV) / Ce (III) system is 1.6 V, ie slightly less than 1.7 V for the aforementioned permanganate to manganese dioxide reaction, and more than twice greater than the potential of the Fe (III) / Fe (II) system. Oil soluble cerium compounds have previously been used as a fuel oil additive to improve combustion (according to German Patent Publication No. 2729365 and U.S. Patent No. 4462810). However, the described solutions use only oil soluble cerium compounds and not aqueous solutions of cerium compounds. In addition, cerium is present in trivalent and not quaternary forms in the additives of the solutions cited.

Thus, the two known applications are not designed for and do not purify the furnace from soot and tar.

It has also been found advantageous for the purification of fireplaces if, after the combustion of soot and tar and the thermal decomposition of the divalent cerium compound in aqueous solution, there is an alkaline reserve for neutralizing the acids derived from the fuel burned. Neutralization of inorganic acids (sulfuric acid, sulfuric acid) and organic acids (acetic acid, propionic acid, formic acid) reduces the deposition of wet, sticky carbonaceous plaque on solid surfaces, especially heat transfer surfaces, and inhibits the corrosion effect of these acids on structural materials. The use of an aqueous solution of tetravalent cerium compounds in the alkali reserve discussed above has the advantage that the pH of these combustion-catalyzed solutions can be adjusted in the neutral range (about pH 7) or in the form of slightly acidic or alkaline aqueous solutions. may be present.

The present invention relates to aqueous catalyst solutions containing cerium salts containing at least one of the aqueous catalyst solutions for the better combustion of materials containing coal and / or hydrocarbons (heating oils, heating gases and solid fuels) and / or for removing soot or tar deposits on combustion surfaces. and containing 0.115% by weight of tetravalent cerium based on the total amount of your catalyst, and after incineration or thermal decomposition, an alkali metal, alkaline earth or magnesium compound and an additive that maintains the cerium compounds in the form of complex compounds. Further advantageous features of the present invention are set forth in the claims and the specification.

Thus, it provides adequate corrosion protection to treated metal surfaces against strongly acidic solutions (e.g., cerium nitrate). Highly alkaline aqueous solutions also pose a threat to metallic and particularly mineral-based structural materials (chamotte), and the users are exposed to etching during application.

The invention is further illustrated by the following examples.

Example 1

In 77.4 parts of water, 6 parts of trivalent cerium nitrate [Ce (NO ₃ ) ₃ x 6 H ₂ O] are dissolved and 2.2 parts of 35% by weight hydrogen peroxide are oxidized to 2 vals in the final solution. Corresponds to Ce ⁴⁺ ion concentration. In addition, 3 parts by weight of citric acid are added and 2 parts by weight of the sodium salt of a maleic acid acrylic copolymer having an average molecular weight of 70,000 are added as a complexing agent.

Adjust the pH to 9 with 4.4 parts by weight of potassium hydroxide. To further moisten the solid surfaces coated with carbon black and tar, 2 parts by weight of carbon monoxide (13 moles) substituted with 9 moles of ethylene oxide are added to the aqueous solution. A clear reddish-brown, clear solution is obtained.

The solution thus prepared is sprayed onto the surface coated with carbon black and tar. Subsequently, during normal use, the treated surfaces burn off carbon and hydrocarbon deposits (soot, tar) in a catalyst-assisted manner.

The solution discussed above can be advantageously applied to heat transfer surfaces and other surfaces subject to the risk of soiling after mechanical cleaning, which is mandatory in many countries, and serves as both a protection against como and a particularly catalytically effective surface, which greatly inhibits the formation of soot and fumes. recurrence.

After combustion of organic matter (including citric acid and maleic acrylic copolymer), from the solution discussed above (100%), 1.9% by weight of tetravalent cerium (predominantly in the form of cerium dioxide) and 5% by weight of caustic soda ( 4.4% by weight of potassium hydroxide and the sodium salt of the copolymer) for the catalytic combustion of soot and tar and the neutralization of mineral acids (in particular sulfuric and sulfuric acids) and organic acids (in particular acetic acid produced by burning wood),

Example 2

The aqueous catalyst solution of Example 1 was diluted 1:10 with water and periodically applied to the heat transfer and other degreasing surfaces using a mechanical, in-line sprayer. It is proved that, depending on the heating power and the degree of soot formation, it is sufficient to perform periodic spraying at intervals of 2 to 24 hours in order to prevent soot deposition and to achieve the best possible heat transfer and thus fuel utilization. This method is particularly applicable to high performance equipment, ie industrial equipment and thermal power plants.

Example 3

The aqueous catalyst solution of Example 1 was diluted 1:20 with water, which means that the diluted solution contained about 1000 ppm of a divalent cerium ion. From this, 1 part by weight of diluted aqueous solution is introduced into the air into the burner of the larger heaters and boilers by fine atomization, based on 50 parts by weight. Relatively low, 20 ppm. Bacharach, according to Bacharach, achieves a 3-point reduction in carbon black content due to tetravalent cerium ion content.

Example 4 4 parts of a tetravalent water-dispersible cerium hydrate are finely divided in 79 parts of water. To do this, 10 parts by weight of sodium polyacrylate having an average molecular weight of 4000 and 1 part by weight of 7 mol of ethylene oxide substituted nonylphenol are dissolved.

The cerium hydrate contains 89% cerium dioxide. The particles have a size of 15 μιη and a crystal size (XRD) of about 9 nm. The cerium (IV) ion content of the dispersion is 7.2% by weight.

The aqueous dispersion described above is sprayed on tar deposited in wood-fired equipment and then briefly burned with an increased excess air. It is proved that the catalytic effect of tetravalent cerium can almost completely burn off tar residues which are harmful to health and flammable.

Example 5 10 parts by weight of water are dissolved in 10 parts by weight of trivalent cerium nitrate and 3 parts by weight of 35% hydrogen peroxide are oxidized to a tetravalent value (corresponding to 3.4% by weight of cerium (IV) ion). Further, 10 parts by weight of magnesium nitrate, 5 parts by weight of a 2000 molecular weight Na-polyacrylate are dissolved and adjusted to pH 8 with potassium hydroxide.

This solution, when applied to soiled with soot and tar, improves the combustion of these noxious deposits, as described in Example 1. For oily and greasy soot deposits, addition of wetting agents is recommended. Nonionic or anionic surfactants (ethylene oxide substituted compounds, alkane sulfonates, alkylaryl sulfonates) are preferably used. Although cationic detergents are also suitable, they often reduce the interfacial tensions between the aqueous catalyst solution and the oily / tar deposits, and are also less economical.

During the combustion of soot and tar, magnesium nitrate also undergoes thermal decomposition and, as an alkaline oxide / hydroxide, can neutralize mineral acids and organic acids produced during the combustion of sulfur-containing oil and coal, as well as wood, straw and the like.

Example 6

Prepare the solution in a manner similar to that of Example 5, except that magnesium nitrate is replaced by barium nitrate. In this case, too, we experience the alkaline reserve through thermal decomposition and the discussed catalysis of the combustion process.

Example 7

Similar to Examples 5 and 6 except that calcium nitrate is used instead of magnesium nitrate.

Example 8

The solution of Example 1 was prepared except that the potassium hydroxide was lithium hydride.

EN 207 671 Β oxide-water (l / l). Not only does lithium hydroxide neutralize acids, it also catalyses combustion processes by supporting the action of quaternary cerium.

Example 9 5 parts by weight of water were dissolved in 5 parts by weight of cerium nitrate [Ce (NO ₃ ) ₂ x 6 H ₂ O] and oxidized to 2 values by valence with 2 parts (35% by weight) of hydrogen peroxide [1.71% cerium (IV) ion -concentration]. Further, 25 parts by weight of a 40% solution of tetrasodium ethylenediamine tetraacetate and 1 part by weight of a wetting agent are added. This solution is used as an aqueous based combustion catalyst in a manner similar to that described in the previous examples.

Example 10

The solution of Example 9 was prepared except that sodium nitrilotriacetate was used in place of tetrasodium ethylene diamine tetraacetate.

Example 11 Part (trivalent) cerium nitrate was dissolved in 60 parts by weight of water, oxidized to 20 parts by weight with 35% hydrogen peroxide (equivalent to 13.3% by weight of cerium (IV) ion). In addition, 60 parts by weight of glycolic acid are added and the pH is adjusted to 7 with potassium hydroxide. The solution is used as an aqueous-based combustion catalyst for liquid, solid, and gaseous fuels as in the previous examples.

EXAMPLE 72 Parts of cerium nitrate (trivalent) are dissolved in 60 parts of water, oxidized to 3 parts by weight of hydrogen peroxide (35 parts by weight) (equivalent to 3.3% by weight of cerium (IV) ion). Further, 20 parts by weight of a solution of 7 parts by weight of potassium carbonate and 40% by weight of tetrakotassium ethylenediaminetetraacetate are added. The solution thus obtained is dispersed in the fuel oil in a 1: 1000 weight ratio based on mechanical principle in the form of very fine particles. By burning the water / oil emulsion, the formation of carbon black is greatly prevented. Due to the neutralizing effect of potassium hydroxide, sulfur trioxide and sulfuric acid are primarily bound, so that even when sulfur-rich fuel oil is fired, the fume gas is predominantly weakly acidic and thus less aggressive and corrosive sulfuric acid or sulfuric acid.

Preferably, the cerium (IV) ion content of the catalyst solution of the present invention is 0.1 to 15% by weight of the catalyst solution, and the metal ion content of the basic reactant is preferably 0.1 to 30% by weight of the catalyst solution. Preferably, the cerium (IV) ion content of the liquid or solid fuel is from 1 to 100 ppm based on the fuel.

Your catalysts according to the invention have a pH of at least 7 and the solution is neutral or alkaline. This takes into account the necessary corrosion protection. Preferably, the complexing agent is present in the catalyst solution in an amount that prevents the precipitation of cerium in the hydroxide form. The complexing agent may be present in a concentration range of 1-401%, preferably 2-101%, based on the total amount of catalyst.

Claims (9)

PATENT CLAIMS 1. Aqueous catalyst solutions containing cerium salts for improved combustion of coal and / or hydrocarbon fuels and / or for removal of carbon black or tar deposits on combustion surfaces, characterized in that the aqueous catalyst solutions have a pH of at least 7 and a total of 0.1 -15% by weight of tetravalent cerium, 0.1-30% by weight of alkali metal, alkaline earth metal and / or magnesium compounds after combustion or thermal decomposition, 1-40% by weight of hydroxy acids, acrylic polymers or alkali salts of copolymers or alkalines of polyamines and optionally 0.5 to 4% by weight of a wetting agent, preferably nonionic or anionic surfactants. Your catalyst according to claim 1, wherein the alkali metal compounds are organic potassium, sodium, lithium salts and soaps. Your catalyst according to claim 1, characterized in that it contains, after thermal decomposition, organic calcium, magnesium or barium compounds as alkaline compounds. Your catalyst according to claim 1, characterized in that after thermal decomposition it contains nitrates of alkali metals, alkaline earth metals or magnesium as alkaline compounds. Catalyst solution according to claim 1, characterized in that it contains carbonates of alkali metals, alkaline earth metals or magnesium as alkaline compounds. Your catalyst according to claim 1, characterized in that it contains polycarboxylates of alkali metals, alkaline earth metals or magnesium as alkaline compounds. 7. Your catalyst according to claim 1, wherein the alkali metal, alkaline earth metal or magnesium hydroxycarboxylates are the alkaline compounds. 8. Catalysts according to any one of claims 1 to 3, characterized in that they contain from 2 to 10% by weight of a complexing agent. Liquid or solid fuel composition, characterized in that it contains an aqueous catalyst solution according to claim 1 in an amount corresponding to a cerium (IV) ion content of 1-100 ppm, preferably 15-35 ppm, based on the total amount of the fuel composition.