KR20090045325A - Coal with improved combustion properties - Google Patents

Abstract

A method for improving the combustion properties of a coalcomprises treating said coal with a metal porphyrin. The invention also provides a coal having a metal porphyrin deposited thereon, and a method of producing heat, comprising combusting the coal.

Description

COAL WITH IMPROVED COMBUSTION PROPERTIES}

The present invention relates to a method for improving the combustion properties of coal, coal with improved combustion properties and combustion processes for reducing coal emissions.

The present invention relates to a method for improving the combustion properties of coal, a process for the combustion of coal with improved combustion properties and coal with reduced emissions.

Incomplete combustion in coal-fired furnaces leaves carbon in ash and adversely affects the efficiency of coal-fired power plants. Carbon present in ash has a problem of increasing total ash emissions, reducing the efficiency of electrostatic precipitators for ash removal, and making it difficult to make as a component of cement, for example.

Many coal-fired power plants, including those in Russia and China, use low-grade coal with low reactivity. The main problem with burning these low-grade coals is the high content of carbon in the fly ash, which is 15 to 20%, resulting in significant NOx emissions.

The high amounts of unburned carbon present in the fly ash generate significant heat losses, which lead to heat losses at 5% or even higher, depending on the coal ash content.

The concentration of NOx at doubled in excess air (α) of 1.4 ranges from 700 to 900 gm / m3 (reconverted to NO ₂ ), depending on boiler power.

EP1498470 discloses several methods including reducing excess carbon present in ash from coal combustion, including increasing excess air introduced with fuel or adding metals such as calcium and manganese. This method has an undesirable effect: increased air results in higher NOx emissions, and the use of metals such as calcium and manganese is required in large quantities and causes fouling of the system. EP1498470 proposes the addition of 2-500 ppm manganese compounds, preferably tricarbonyl manganese compounds.

In order to achieve the above object, a first embodiment of the present invention provides a method for improving the combustion properties of coal, the method comprising treating coal with metal porphyrin.

A second embodiment of the present invention provides coal with metal porphyrin deposited thereon.

The inventors of the present invention provide an improved carbon burnout to provide a method that can reduce the carbon content in the ash. The activation energy required for oxidation can also be reduced. NOx production in combustion is related to the supply of excess air to equivalent requirements: higher excess means higher NOx and lower thermal efficiency. Improved burn rate / reduced activation energy lowers excess air requirements and results in lower NOx production. Combustion chamber air flows are typically actively managed and can be altered to optimize combustion conditions that minimize NO x and carbon content present in the ash.

The present invention is particularly applicable to lower coal such as brown coal or bituminous coal.

The metal porphyrins of the present invention preferably include metals having two or more possible oxidation states. Examples include transition metals such as iron, cobalt or manganese.

Metal porphyrin additives are applicable as aqueous solutions or solid fuels by methods well known in the art. For example, there is a method of spraying on a solid fuel. Alternatively metal porphyrins can be applied by sublimation and vapor deposition.

Porphyrins exist extensively in nature, and they play an important role in various biological processes. Synthetic porphyrins, such as phthalocyanine, are used for industrial use, for example phthalocyanine copper is widely used as a cyan-based pigment. Porphyrins are completely aromatic, can host a wide range of metal atoms, and have high thermal stability. Porphyrins can also be improved by methods such as sulfonation, for example, to change their solubility in various media.

The present invention will be described in more detail through the following examples, which are accompanied by the following drawings by reference.

1 to 3 show the results of TG, DTG and DTA in Examples and Comparative Examples of the present invention, respectively.

4 to 6 show that untreated lignite, sulfuric acid-treated lignite and iron-added lignite show linearity in the DTG data, respectively.

7 and 8 show the respective DTA data in the treated lignite treated with untreated lignite and the iron-based additive according to the present invention and the cobalt-based additive according to the present invention. 9-11 show the% sample weight loss and DTG results, respectively, in untreated lignite and lignite treated with iron and cobalt additives according to the present invention.

Thermal analysis methods such as thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) have been extensively performed in investigations regarding the availability of coal.

Thermogravimetric analysis (TG) is widely used to investigate coal / char reactivity. It is well known that the reactivity depends on the coal rank, the maseral composition and / or the charring temperature. Coal combustion reactivity was measured by TG and was usually measured at two conditions: (i) isothermal, constant temperature conditions and (ii) non-isothermal, constant heating rate. In non-isothermal conditions, nominal combustion profiles, derivative thermogravimetry (DTG) was used to obtain reactive parameters such as maximum (peak) burn rate temperature (PT), burnout temperature (BT), and activation energy. .

Thermal analysis method (TGDTA) was used to study the rate of combustion improvement based on kinetic parameters in coal combustion.

The coal used in this study was lignite from Novomosvsk coal basin.

Example 1

Phthalocyanine iron (II) (0.1-0.2 g) was dissolved in concentrated sulfuric acid (50-60 ml). Lignite (˜2 g) samples (2-3 mm grain size) were stirred in this solution at room temperature for 2 hours and left overnight for soaking. After stirring, coal with deposited phthalocyanine was filtered off. The residual concentration of phthalocyanine iron was determined by UV / visible spectrophotometry. The amount of iron-based additive deposited was determined by the difference in concentration of the original and residual solution. The filtered coal was washed with water for neutral pH and air dried to constant weight over 72-144 hours. In terms of conversion, 0.2% phthalocyanine iron (II) was added to coal. This corresponds to about 200 ppm of iron. After drying, coal samples were ground in mortar for DTA / DTG analysis.

Comparative measurements were performed on lignite treated under the same conditions as in Example 1, except that concentrated diffusion was used without being dissolved in untreated lignite and phthalocyanine iron (iron additives). The results and translations are shown in FIGS. 1-6, discussed below.

The results of DTA showed that the exothermic activity of Fe-treated toavf was much higher than that of untreated lignite. This effect was particularly different around 100 ° C, 350-450 ° C, and 600-800 ° C. Thermal gravimetric measurements continued until a constant weight was obtained with the treated sample losing 91.2% of its initial weight compared to 86.6% of the untreated sample. Furthermore, the treated coal reached a constant weight in the untreated coal compared with 850 degreeC compared with 800 degreeC in the treated coal. These results demonstrate that the additives of the present invention have a surprising effect in improving combustion of solid fuels.

Reaction model Model )

In processing the obtained DTG data, our inventors have determined that the dynamics of coal combustion are governed by a first order chemical reaction with a kinetic component of 0.5 <n <1, and the diffusion effect can be neglected under the experimental conditions used. Similar to existing papers.

dα / dτ = k (1-α) ⁿ

Where α is the conversion degree, τ is the time, k is the temperature dependent Arrhenius rate constant, and k = A exp (-ΔE ≠ / RT). R is a gas constant and the model parameters A and ΔE ≠ are frequency factors and activation energies. The degree of conversion α is expressed as follows. α = (m _i to m _τ ) / (m _i -m _f ) _i , where m _i and m _f are the initial and final weight% and m _τ is the weight% at time τ when recorded during the TG experiment . The actual time and temperature are simply related to the constant heating rate T = To + β _τ . We can assume that n = 1 straight line by plotting ln [−ln (1-α) T ² ] versus 1 / T. The activation energy value can be obtained from the inclination of the obtained straight line.

In the vicinity of 100 ° C., the first peak corresponds to the loss of residual water, and in the vicinity of 300 to 400 ° C., the second peak corresponds to the release of the active substance. In the third stage, sharp peaks are observed because of char combustion.

The activation energy obtained is as follows.

Additive-free and sulfuric acid-free lignite, ΔE ≠ = 16.8 kJ / mol.

Additive-free and sulfated lignite, ΔE ≠ = 16.7 kJ / mol.

Iron additives treated lignite, ΔE ≠ = 11.3 kJ / mol

The use of iron additives lowers the activation energy of 5.5 kJ / mol, corresponding to 33% of the initial value of 16.8 kJ / mol. Additives tested on lignite show improved carbon burnout, resulting in higher total weight loss.

additive Reduction of carbon content in ash Iron additives 29%

Weight loss is achieved at lower temperatures, which shows the catalytic action of the additive.

additive Total weight loss No addition 87.6% / 850 ℃ Iron additives 91.2% / 800 ℃

The linear regression data of FIGS. 4 to 6 are shown in Tables 3 to 5 below.

4 No treatment  Lignite Linear Regression Data

Y = A + B * X

parameter value error A -11.90344 0.06974 B -2020.06766 59.95073 R SD N P -0.98832 0.03655 29  <0.0001

Linear regression data of sulfuric acid treated lignite of FIG. 5

Y = A + B * X

parameter value error A -12.01109 0.04844 B -2008.73036 42.37233

Linear Regression Data of Iron Additive Treated Lignite of FIG. 6

Y = A + B * X

parameter value error A -12.69625 0.04571 B -1359.01275 40.74655 R SD N P -0.98832 0.02659 32  <0.0001

Example  2

It was carried out in the same manner as in Example 1 except that cobalt phthalocyanine disulphonate was used as the metal porphyrin and water was used instead of sulfuric acid as the fluid carrier.

The results are shown in Figures 7-11.

Although the present invention has been described with reference to the above specific embodiments, it should be understood that improvements or modifications from them may not be made without departing from the scope of the invention as defined in the following claims.

Coal treated with the metal porphyrin of the present invention, the coal is excellent in combustion properties, reducing the carbon content in the ash, and reduces the content of nitrogen oxides.

Claims (24)

A method of improving coal combustibility comprising treating coal with metal porphyrins. The method of claim 1, wherein the porphyrin comprises phthalocyanine. 3. The method of claim 1 or 2, wherein the metal is a transition metal having one or more oxidation states. The method of claim 1, wherein the metal is selected from the group consisting of iron, cobalt, manganese or mixtures thereof. The method of any one of claims 1 to 4, wherein the metal porphyrin is phthalocyanine iron. A method according to any one of claims 1 to 5, wherein the coal is lignite. 7. The coal treatment step according to any one of claims 1 to 6, wherein the coal treating step comprises treating the coal with a metal porphyrin solution dissolved in a fluid carrier, filtering the solids, allowing the solids to dry or allowing the solids to dry. A method for improving coal combustion properties, comprising: 8. The method of claim 7 wherein the fluid carrier comprises concentrated sulfuric acid. 8. The method of claim 7 wherein the fluid carrier comprises an aqueous liquid. 10. The method of any one of claims 7 to 9, further comprising washing the coal with water after removing the solution. The method of any one of claims 1 to 6, wherein the coal treatment step involves vapor-depositing the metal porphyrin. Coal deposited on top of metal porphyrin. 13. Coal according to claim 12, wherein the metal porphyrin is phthalocyanine. 14. Coal according to claim 12 or 13, wherein the metal is a transition metal having at least one oxidation state. 15. Coal according to any of the claims 12-14, wherein the metal is selected from the group consisting of iron, cobalt, manganese or mixtures thereof. 16. The coal according to any one of claims 12 to 15, wherein the metal porphyrin is phthalocyanine iron. The coal according to any one of claims 12 to 16, wherein the coal is lignite. 18. Coal according to any of claims 12 to 17, wherein the metal porphyrin is present at a concentration of 0.05 to 0.5% by weight. 18. Coal according to any one of claims 12 to 17, wherein the metal porphyrin is present at a concentration of 0.1 to 0.3% by weight. 18. Coal according to any one of claims 12 to 17, wherein the metal porphyrin is present at a concentration of 0.2% by weight. 21. A method of producing heat comprising burning coal of any of claims 12-20. A method of reducing combustion emissions comprising adding metal porphyrin to coal to produce treated coal and combusting the treated coal in a combustion chamber with reduced excess air present in the combustion chamber. . Use of metal porphyrins as a combustion improving additive for coal. Use of iron phthalocyanine as a combustion improving additive for lignite.

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