EA013898B1 - Coal with improved combustion properties - Google Patents

Abstract

A method for improving the combustion properties of a coal comprises 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

This invention relates to a method for improving coal combustion parameters, to coal with improved combustion parameters, and to a method for burning coal with a reduced amount of emissions.

Prototype description

Incomplete combustion of coal in coal-fired furnaces leads to an increase in the residual carbon content in the ash and a decrease in the efficiency of coal-fired furnaces. The presence of carbon in the ash leads to an increased amount of ash, reduces the efficiency of electrostatic dust collectors and leads to difficulty in utilizing the ash, for example, as a component of cement.

Many coal-fired power plants, including power plants located in Russia and China, use low-quality low-reactive coal. The main difficulties in using these coals are high carbon content in fly ash: up to 15-20%;

significant emissions ΝΟ _Χ .

The high content of unburned carbon leads to significant heat loss: up to 5% or more, depending on the amount of ash produced.

ΝΟ _Χ gas concentration in the exhaust gases when the air excess α = 1,4 is 700-900 mg / m ³ (based on ΝΟ ₂₎ depending on the power of the boiler.

Patent EP 1498470 cites several methods for reducing carbon in the ashes obtained from the combustion of coal. These methods include increasing the amount of excess air and adding metals such as calcium and magnesium. The disadvantage of these methods is that as the amount of air increases, the concentration of ΝΟ _Χ in the exhaust gases increases. Also metals calcium and magnesium are used in large quantities, which leads to clogging of the system. In the patent EP 1498470 it is proposed to add from 2 to 500 ppm of a compound containing manganese, preferably tricarbonyl manganese.

Brief description of the invention

According to one aspect of the present invention, a method for improving the combustion of coal is proposed, comprising treating a coal sample with metal porphyrin.

According to another aspect of the invention, carbon is provided with metalloporphyrin applied thereto.

The authors of the present invention, it was found that carrying out the process in accordance with this invention can increase the degree of combustion of carbon, which leads to a reduced carbon content in the ash. Also, the activation energy of the oxidation process of coal is reduced. The amount of oxides formed during combustion depends on the excess air; a larger excess of air compared to the stoichiometric ratio leads to more количеств and lower thermal efficiency. Increased combustion rates / lower activation energy reduce the requirements for excess air and the amount of oxides ΝΟΧ. Usually the air flow in the combustion chamber is constantly regulated. Air flow rate can be changed to optimize the combustion conditions in order to reduce the carbon content in the ash and reducing the amount of oxides ΝΟ _Χ.

The present invention is particularly applicable to low grade coal, such as brown and bituminous coal.

In accordance with this invention, metalloporphyrin contains a metal having two or more oxidation states. Such metals are transition metals, for example iron, cobalt or manganese.

Metalloporphyrin can be applied to the surface of a solid fuel from an aqueous solution by well-known methods, for example by spraying. Metalloporphyrin can also be applied by sublimation and by vapor deposition.

Porphyrins are widely distributed in nature and play an important role in various biological processes. Synthetic porphyrins, such as phthalocyanines, have industrial applications, for example, copper phthalocyanine is widely used as a blue pigment. Porphyrins are fully aromatic compounds capable of containing various metal atoms in their structure. Porphyrins also have high thermal stability. Porphyrins can be modified, for example, by sulfonation to increase their solubility in various media.

Brief Description of the Drawings

The invention is illustrated by the following figures, which are illustrative only, where:

in fig. 1-3 graphs of TG, DTG and DTA values of various samples of coal according to the invention;

in fig. 4-6 shows linearized graphs of DTG values of brown coal, brown coal, treated Ο ₂ 8Ο ₄ , and brown coal, treated with an iron-containing additive;

in fig. 7 and 8 are graphs of DTA values of untreated brown coal and brown coal treated with an iron-containing additive, respectively, and untreated and treated with a cobalt-containing brown coal additive, respectively, according to the invention;

- 1 013898 in FIG. 9-11 show TG curves,% mass loss of the sample and DTG for untreated brown coal and brown coal treated with iron and cobalt containing additives, respectively, according to the invention.

Detailed description

Thermal analysis methods such as thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) are widely used to study the properties of coal.

Thermogravimetry is widely used to study the reactivity of coal / charcoal. It is widely known that the reactivity depends on the grade of coal, the composition and / or temperature of charring. The reactivity of coal combustion was measured using TG under two conditions: (ί) isothermal, at a constant temperature, and (and) non-isothermal, with a constant degree of heating. Differential thermogravimetry (DTG) under non-isothermal conditions evaluated the combustion profile and calculated such reactivity parameters as temperature at maximum rate (peak) of combustion (PT), temperature of combustion (TS) and temperature of activation energy.

The effect of additives on the kinetic parameters of coal combustion was determined using thermal analysis methods (TG, DTA).

Coal specification.

The coal used in this study was brown coal from the Novomoskovsk coal basin.

Example 1

The phthalocyanine of iron (II) (0.1-0.2 g) was dissolved in concentrated sulfuric acid (50-60 ml). A sample of brown coal (~ 2 g) (particle size 2-3 mm) was mixed with the resulting solution for 2 h and left overnight. The next day, the phthalocyanine-coated coal was filtered. The residual concentration of phthalocyanine iron (II) was determined using spectrophotometric analysis of the visible / UV spectrum. The amount of deposited coal was determined on the basis of the difference in the concentrations of the initial and final solutions. The filtered carbon was washed with water until neutral pH and dried in air to constant weight for 72-144 hours. According to the calculations, 0.2% of phthalocyanine of iron (II) was applied to the coal. This corresponds to about 200 ppm of iron. After drying, the coal sample was ground in a mortar for further analysis using the DTA / DTG method.

The measurement results were compared for untreated brown coal and brown coal treated as described in Example 1 using concentrated sulfuric acid without the addition of iron phthalocyanine (an iron-containing additive). Results and calculations are shown as graphs in FIG. 1-6. Explanations are given below.

The results of DTA showed a higher exothermic activity of samples treated with an iron-containing additive, compared with untreated brown coal. This effect is especially noticeable at temperatures of about 100, from 350 to 450 and from 600 to 800 ° C. Thermogravimetric measurements were carried out to constant weight. The treated sample lost 91.2% of the original weight, while the untreated sample lost 86.6%. The sample of treated coal reached a constant weight at about 800 ° C, while the untreated sample reached a constant weight of about 850 ° C. These results confirm that the additives described in this invention are surprisingly effective in burning solid fuels.

Reaction model

When processing DTG data, in accordance with existing publications, it was assumed that coal oxidation proceeds by a first-order reaction with an exponent in the kinetic equation 0.5 <n <1 and that under the experimental conditions the diffusion effect can be neglected. Therefore, ΰα / άτ = k (1-α) ^η 'where α is the degree of transformation;

τ is the time;

k is the rate constant depending on temperature according to the Arrhenius equation, k = L-shr (-AE7PT);

B is the gas constant;

parameters A and AE * - frequency factor and activation energy.

The degree of transformation α is determined by the ratio a = (t _| -t _t ) / (t _| -t _[ ). where t ₁ and t £ are the initial and final masses, in percent; t _t is the mass in percent, during τ, recorded during the TG experiment. Time and temperature are correlated through a constant heating rate T = T ₀ + (\. Assuming that n = 1, you can get straight lines by plotting the coordinates in coordinates 1n [-1n (1-a) T ² ] on the ordinate, and 1 / T is on the abscissa axis. The value of the activation energy can be obtained from the angle of inclination of the straight lines.

The first peak, observed at about 100 ° C, corresponds to a loss of residual moisture. The second peak, observed at about 300-400 ° C, corresponds to the release of volatile substances. The third stage is a sharp peak corresponding to the burning of coal.

- 2 013898

The obtained activation energy values are given below.

Brown coal without additives, raw H ₂ 8O ₄ : LE * = 16.8 k1 / sho1.

Brown coal without additives, treated with H ₂ 8O ₄ : LE * = 6.7 k1 / sho1.

Brown coal with an iron-containing additive: LE * = 11.3 k1 / sho1.

The use of an iron-containing additive led to a decrease in the activation energy by 5.5 kJ / mol, this is 33% of the initial value of 16.8 kJ / mol. The additive also improves the combustion of coal, which leads to weight loss.

Additive Carbon reduction in ash Its content '29%

Weight loss occurred at a lower temperature, which proves the catalytic effect of the additive.

Additive Total weight loss - 87.6% / 850 ° С Its content 91.2% / 800 ° С

The linear regression data for FIG. 4-6 are given in table. 1-3. Linear regression for brown coal (Fig. 4)

Υ = A + B * X

Table 1

Parameter Value Mistake BUT -11.90344 0.06974 AT -2020.06766 59.95073 AT 8ϋ N R I -0.98832 I I one 0.03655 29 <0.0001

Linear regression for a sample of brown coal treated with sulfuric acid (Fig. 5) = A + B * X

Table 2

I

I

I

I

I |

Parameter Value one Error 1 BUT -12.01109 0.04844! one AT -2008.73036 42.37233! one

Linear regression for a brown coal sample with an iron-containing additive (Fig. 6) Υ = Α + Β *

Table 3

Parameter ί Value one one Mistake ^BUT -12.69625 0.04571 ^AT -1359.01275 40.74655 one one one at I I I δϋ N R -0.98678 0.02659 32 <0.0001

- 3 013898

Example 2

The application was carried out according to Example 1 using cobalt phthalocyanine disulfonate as metal porphyrin and distilled water instead of sulfuric acid.

The results are shown in FIG. 7-11.

The invention has been described with reference to specific examples. It should be understood that the examples do not limit the scope of the present invention, which is limited only by the claims.

Claims (15)

CLAIM 1. A method of improving the combustion of coal, characterized in that the coal is treated with metal phthalocyanine. 2. The method according to claim 1, characterized in that the metal is a transition metal capable of taking different degrees of oxidation. 3. The method according to PP.1, 2, characterized in that the metal is selected from the group of metals, including iron, cobalt, manganese or a mixture of two or more metals. 4. The method according to claims 1, 2, characterized in that the metal phthalocyanine is iron phthalocyanine. 5. The method according to claims 1, 2, characterized in that the coal is brown coal. 6. The method according to PP.1, 2, characterized in that the processing of coal occurs using a solution obtained by dissolving metal phthalocyanine in a liquid medium, followed by filtration and forced or natural drying of the solid phase. 7. The method according to claim 6, characterized in that the coal is washed with water after removal of the solution. 8. The method according to PP.1, 2, characterized in that the coal is treated with phthalocyanine deposited from the vapor phase. 9. Coal coated with phthalocyanine. 10. Coal according to claim 9, characterized in that the metal is a transition metal capable of taking different degrees of oxidation. 11. Coal according to any one of paragraphs.9 and 10, characterized in that the metal is selected from the group comprising iron, cobalt, manganese, or a mixture of two or all metals. 12. Coal according to any one of claims 9 to 11, characterized in that the metal phthalocyanine is iron phthalocyanine. 13. Coal according to any one of paragraphs.9-12, characterized in that the coal is brown coal. 14. Coal according to any one of paragraphs.9-13, characterized in that the metal phthalocyanine is present in a concentration in the range of 0.05-0.5 wt.%. 15. A method of burning coal, comprising treating coal with metal phthalocyanine and burning treated coal in a combustion chamber with a reduced excess of air in the combustion chamber.