FI61041B - FOERFARANDE FOER HEL ELLER DELVIS NEUTRALISERING AV DE VID FOERBRAENNING AV SVAVELHALTIGT BRAENSLE BILDADE SURA FOERBRAENNINGSPRODUKTERNA SAMT MEDEL FOER ANVAENDNING VID FOERFARANDET - Google Patents

Description

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Vgra ^ frtent meddelat (51) Ky.lk.3 / lnt.ci.3 C 10 L 10/00 FINLAND — FINLAND (M) Ptt «nttlh * k« mui - Pat «nttn * 6knlnf T 827 06 (22) HtkemUpUvt - An * ttknln | tdtj Oi.09.76 'Γ' (23) Primary Cloud - Gittlf hattdtg Ot.O9.78 (41) Ttillut julklMktl - Bllvlt offentllf 0 '. 03.79

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Patents and registration certificates Arnokin utiijd och uti.skriften pubiicermd 29.01.02 (32) (33) (31) Requested request — Begird prlorltat 06.09-77 03.03.78 Denmark-Danmark (DK) 3967/77, 3627 / ^ (71) (72) Hans Christian Maack Andersen, no. 13, Nylandsalle, 8700 Horsens, Denmark-Danmark (DK) (7 * 0 Oy Jalo Ant-Wuorinen Ab (5U) Method for the complete or partial neutralization of acidic combustion products from the combustion of sulfur-containing fuel and the substance used in the method - Förfarande för hei eller delvis neutralization av The present invention relates to a process for the complete or partial neutralization of acidic combustion products from the combustion of sulfur-containing fuel by continuous injection of basic substances.

It is well known that sulfur-containing fuels, including oil as well as coal and lignite, produce sulfur dioxide and sulfur trioxide during combustion, causing harm and damage. This is partly due to the toxicity of SC 2 -containing flue gases, especially when SG> 2 is bound to fine soot particles, and partly because "sulfuric acid, which is or consists of flue gases, not only has a strong corrosive effect on the furnace and fuel but also corrodes and decomposes. building materials, etc. and damages wildlife in fresh water.

Sulfur-containing compounds are present in coal as well as in fuel oil, and in particular in the lower grades of the latter, there are 2,61041 substantial amounts of sulfur, corresponding to up to more than 5% by weight of sulfur.

In particular, in connection with this relatively cheap, high-sulfur oil, attempts have been made to find various solutions for reducing the concentrations of EC 2 and SO 2 in the flue gases.

One method reduces the sulfur content of the oil before combustion. This method is used to some extent, but it is quite expensive and therefore desulfurized oil is substantially more expensive than sulfur-containing oil, which of course -p'Atee also to oil which, when already found, has a low sulfur content.

Another method of preventing large amounts of particulate oxides from entering the atmosphere with flue gases is to wash the sulfur oxides out of the flue gases with aqueous sodium carbonate solution. However, this method requires a complex plant and the regeneration of the washing liquid is energy consuming.

Attempts have also been made to reduce the amount of acidic sulfur compounds in the flue gases by injecting powdered dolomite (Ca Mg (OO 2)) or magnesium carbonate directly into the flame. as a result of which it is necessary to inject very large amounts of dolomite or magnesium carbonate in order to reduce the concentration of acidic sulfur compounds in the flue gases, which makes the process laborious and can cause malfunctions. used.

It has been found that it is possible to effectively neutralize the acidic products formed by the combustion of sulfur by simultaneously injecting the following compounds according to the invention: a) sodium or potassium nitrate; b) ammonium nitrate; c) magnesium carbonate and / or calcium hydroxide; d) carbon; and e) ammonium carbonate.

It is self-evident that in the above list, the compounds are mentioned according to the technical properties of the substances in question.

3 61041

Thus, Terni ammonium carbonate also encompasses the technical product "ground ammonia" which contains essential components hydrogen carbonate and carbaminate. The word "carbon" is also used in a broad sense and includes e.g. pulverized coal including lignite and charcoal and pulverized coke.

The reaction mechanism that causes excellent neutralization has not been fully elucidated, but it is assumed that sulfur is primarily bound in the form of ammonium sulfate. The fact that magnesium carconate and calcium hydroxide produce a stronger neutralizing effect when sprayed together with other said compounds than when sprayed alone according to the prior art may be due to their indirect reaction with nitrates to form basic compounds containing ammonia which reacts efficiently with ammonia.

As a result of, among other things, the fact that important neutralization processes take place over a very wide temperature range, it is difficult to state exactly which reactions take place and the invention * is not bound by any particular theory in this respect. It should be noted, however, that the presence of carbon with nitrates is important to ensure that the compounds come into adequate contact with the sulfur-containing compounds to be neutralized. It is a fact that in the reaction of nitrate and carbon at the temperatures of the firing zone, a decomposition-like reaction takes place between the injected compounds, whereby the individual particles decompose and the substances are uniformly distributed over the combustion zone.

It has been found that the Danish patent no. 111 335 discloses a substance for preventing sulfur deposits and corrosion in furnaces, said substance containing alkali metal nitrate, carbon and magnesium oxide. However, this known substance is not used, continuously, but only, for example, for half a minute a day, because its purpose is to burn off soot deposits and neutralize sulfuric acid that may have condensed in the combustion chamber or air ducts. Thus, the use of this known substance does not lead to a substantial reduction in the amount of acidic sulfur compounds released into the air, and even if said known substance were used for continuous spraying, it would not be particularly suitable for effective neutralization because it does not contain ammonium carbonate. to achieve results.

The quantitative ratio of the five components (a) to (e) is not critical but experiments have shown that the best results are obtained by a process characterized by the invention that the compounds are injected in amounts calculated as weight percent of the total amount of compounds (a) + (b) + (c ) + (d) + (e) are as follows: (a) sodium or potassium nitrate 20-55% (b) ammonium nitrate 7-15% (c) magnesium carbonate and / or calcium hydroxide 15-40% (d) carbon 1 - 4% (e) ammonium carbonate 15-40%

The amount of said five components injected per hour will, of course, depend on the amount of sulfur burned with the fuel per hour. It has been found that efficient neutralization is obtained according to the invention by using compounds (a) to (e) in a total amount of 50 to 250 g per kg of sulfur in the fuel. This corresponds in total to the injection of 1 to 6 kg of compounds (a) to (e) for each tonne of oil with a sulfur content of 2.5%.

It cannot be ignored that said satisfactory effect could be obtained by simultaneously injecting the compounds separately, but for practical reasons as well as to ensure the best possible contact between the different components, it is most suitable to carry out the process using a substance according to the invention; (a) sodium or potassium nitrate (b) ammonium nitrate (c) magnesium carbonate and / or calcium hydroxide (d) carbon (e) ammonium carbonate

As indicated above, the preferred embodiment of this substance is characterized in that the compounds (a) to (e) are present in the following amounts by weight: (a) sodium or potassium nitrate 20 to 55% (b) ammonium nitrate 7 to 15% (c) magnesium carbonate and / or calcium hydroxide 15 to 40% 5 61041 (d) carbon 1 to 4% (e) ammonium carbonate 15 to 40%

As indicated above, the substance is used primarily to neutralize acidic products formed during the combustion of sulfur, especially sulfur dioxide. Its use still leads to the same advantages as the use of a substance known from the above-mentioned Danish patent specification, so that the combustion chamber remains free of soot precipitation. Even more surprisingly, an improvement in combustion economy is also achieved, which can be due to the fact that the use of the substance increases the carbon dioxide content of the flue gas, which far exceeds the increase that could be expected just as a result of the oxidation capacity of the substance. Therefore, it can be assumed that the reaction of the substance in the mixture produces certain compounds which have a catalytic effect on combustion.

As will be appreciated, calcium hydroxide (preferably in the form of dry hydrated lime) and magnesium carbonate may be interchangeable in the substance in question. However, experiments have shown that the best results are obtained with calcium hydroxide.

The efficiency of the substance was tested especially in oil combustion plants, but it is obvious that it also has a beneficial effect in burning coal with a substantial sulfur content. Especially when the latter combustion takes place in a liquid layer, the conditions for the use of the substance are favorable.

Although the substance contains ammonium nitrate together with a carbon which acts as a reducing agent, it can nevertheless be handled quite safely without the risk of explosion due to the relatively high content of calcium hydroxide and / or magnesium carbonate and ammonium carbonate. According to the preparation, no carbon and nitrates should be combined until calcium hydroxide and / or magnesium carbonate, which are inactive with respect to the reaction of said two components, are mixed with one of these components.

It has been found that sulphates formed in the reaction of the substance with the sulfur-containing compounds in the combustion zone do not cause problems because they are eliminated with the flue gas and do not lead to the formation of a visible cloud of smoke above the chimney. Sulfate-containing flue gas is substantially less harmful to health and less corrosive than the gas formed when no neutralizing agent is used.

6 61041

The process according to the invention is illustrated by the following examples:

Example 1:

In one heating plant, oil containing 2.5% sulfur was used.

Flue gas analysis with a Dräger tube showed a sulfur dioxide content of 52 mg / m 3 in the flue gas before the test.

For each tonne of oil destined for combustion, 3 kg of a mixture containing: sodium nitrate 38% by weight ammonium nitrate 11 "magnesium carbonate 24" carbon 3 ammonium carbonate 23 "was added to the combustion zone by spraying with secondary air. / m of flue gas, thus the experiment resulted in a very efficient neutralization Example 2:

The oil used in this example also contained 2.5% by weight of sulfur. A probe was placed in the chimney of the chimney and the flue gas was sucked through a series of vacuum flasks containing 10% by weight of aqueous sodium carbonate solution using a constant speed vacuum pump. In each experiment, pulping lasted for half an hour.

The experiments were performed both when the furnace was burned without spraying the substance in question and when about 5 kg of oil having the following composition was injected there.

potassium nitrate 38% by weight ammonium nitrate 11 "calcium hydroxide 25" carbon 3 ammonium carbonate 23 "7 61041

Sulphites are determined first of all with sodium carbonate solution, through which the flue gas was blistered half hours, using the case of agent (A), a second, similar solutions, through which the flue gas was blistered in half an hour while at the same time the substance in question was injected into the flame (B), and finally the sulphite content was determined from the corresponding sodium carbonate solution through which no flue gas has been passed (C). The results were as follows: (A) Sulphite content calculated as SO 2: 5.0 mg / l (B) "" ": 1.7 mg / l (C) (O-test): 0.3 mg / l

It should be noted that the conditions under which the tests were performed appeared to indicate that the absorption of SO 2 into the sodium carbonate solution has not been complete under the conditions used. However, the fact that the amount of absorbed SO2 in the test in which the substance was injected is less than 1/3 of the amount absorbed when the substance was not injected must be considered to indicate that the use of the substance results in an effective reduction of SO2 in the flue gas.

Example 3: This experiment was also carried out in a furnace of a heating plant where the fuel was heavy fuel oil, the oil furnace was a rotary kiln and the boiler had a yield capacity of 1.78 x 10 ^ kcal / h and a heating surface of 60 m.

The material used had the same composition as in Example 2 and was introduced into the furnace with secondary air. According to the ejector principle, the powder was absorbed and injected on the suction side of the secondary air valve in an amount of 3.5 kg per tonne of oil.

The composition of the flue gas before and during the treatment was measured at the Jysk Teknologisk Institut in Arhus, where e.g. sulfur dioxide and sulfur trioxide concentrations were made and the flue gas temperature was checked.

The sulfur trioxide content was determined by extracting part of the gas stream and condensing the amount of SC 2 at 73 ° C and then titrating the condensate with NaOH solution. The result is given in ml / spent UaOH solution.

8 61041

The sulfur dioxide content was determined from the gas after condensation by passing the gas through two successive wash bottles containing 3% hydrogen peroxide, each of which absorbed SC> 2, and was quantified.

The experiments were performed by first taking two sets of measurements without the addition of substance. Then, a continuous increase in material and half an hour after the following two-taussarjaa what was done. The hardened results are shown in the following table: without addition with difference difference% analyzes ka analyzes 1 2___3 I 4____

Sulfur dioxide (mg / dm3) 2.35 1.84 2.09 1.58 1.56 1.57 -25

Poc trioxide (ml / m3) 4 3.57 3.79 2 1.98 1.99 -47.5

Flue gas temperature (C °) 210 210 210 190 190 190 - 9.5

As can be seen from the table above, the SO 2 and SO 2 concentrations in the flue gases were reduced by 25% and 47.5%, respectively, and a significant decrease in flue gas temperature was obtained, which can be attributed to the removal of a significant amount of soot mainly from soot. -lasaostumaa.

It can be reasonably assumed that a greater reduction in SC> 2 and SO 2 concentrations in the flue gas could have been obtained if the experiments had been performed in a boiler with less precipitation than in this case, as some of the sulfur oxides found in analyzes 3 and 4 released by the use of the substance.

Indicative experiments performed in a smaller boiler have further shown e.g. good neutralizing capacity of mixtures of the following compositions: 12 3 (a) sodium nitrate,% by weight: 25 36 50 (b) ammonium nitrate, ": 15 9 7 (c) calcium hydroxide,": 40 17 25 (d) carbon, ": 233 (e) ) ammonium carbonate, ": 18 35 15

Claims (7)

9 61041 A process for the complete or partial neutralization of acidic combustion products from the combustion of sulfur-containing fuel by continuous injection of basic substances into the combustion zone, characterized by continuous injection of: (a) sodium or potassium nitrate (b) ammonium nitrate (c) magnesium carbonate and (c) magnesium carbonate ) carbon (e) ammonium carbonate. Process according to Claim 1, characterized in that the compounds are injected in amounts which, calculated as a percentage by weight of the total amount of the compounds (a) + (b) + (c) + (d) + (e), are as follows: (a) sodium or potassium nitrate 20-55% (b) ammonium nitrate 7-15% (c) magnesium carbonate and / or calcium hydroxide 15-40% (d) carbon 1-4% (e) ammonium carbonate 15-40% Process according to Claim 1 or 2, characterized in that compounds (a) to (e) are used in a total amount of 50 to 250 g per kilogram of sulfur in the fuel. Substance for use in the process according to claim 1, characterized in that it contains a mixture of the following compounds: (a) sodium or potassium nitrate (b) ammonium nitrate (c) magnesium carbonate and / or calcium hydroxide (d) carbon (e) ammonium carbonate Substance according to Claim 4, characterized in that it contains compounds (a) to (e) in the following amounts, calculated as a percentage by weight; w 61041 (a) Sodium or potassium nitrate 20-55% (b) Ammonium nitrate 7-15% (c) Magnesium carbonate and / or calcium hydroxide 15-40% (d) Carbon 1-4% (e) Ammonium carbonate 15-40 % Substance according to Claim 4 or 5, characterized in that component (c) is calcium hydroxide. Substance according to Claims 4 and 5, characterized in that component (c) is magnesium carbonate.