Clinker inhibitor

Abstract

To provide a clinker inhibitor capable of suppressing adhesion of clinker even in biomass fuel with a large amount of low melting point components.SOLUTION: A clinker inhibitor of the present invention is a clinker inhibitor for a combustion facility using fuel in which a total content of a potassium oxide (K2O) and a sodium oxide (Na2O) in combustion ash is 10 mass% or more. Since an aluminum oxide (Al2O3) source and a magnesium oxide (MgO) source are provided, it is possible to suppress adhesion of clinker derived from biomass fuel.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a clinker inhibitor, and more particularly to a clinker inhibitor for combustion equipment using biomass fuel.

Background Art

[0002] From the viewpoints of preventing global warming and forming a recycling-oriented society, the utilization of carbon-neutral biomass fuel is being promoted.

[0003] Biomass fuel contains more low-melting-point components in combustion ash than fossil fuels such as petroleum and coal. These low-melting-point components are melted when exposed to high temperatures and adhere as clinkers to heat exchangers, exhaust paths, etc.

[0004] When clinkers adhere to heat exchangers, exhaust paths, etc., problems such as a decrease in heat recovery efficiency and blockage of the exhaust path occur. Therefore, it is necessary to stop the operation of the combustion furnace, etc., and perform cleaning work to remove the clinkers adhering to the heat exchanger, exhaust path, etc.

[0005] Patent Document 1 discloses that by adding a clinker preventive agent containing desired metal compound particles to fuel, the adhesion of clinkers can be suppressed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the clinker preventive agent described in Patent Document 1 uses a metal compound in which the metal component is a single component, such as magnesium oxide or iron oxide, and the effect of suppressing the adhesion of clinkers is not yet sufficient.

[0008] The present invention has been made in view of the problems of such conventional technologies, and an object thereof is to provide a novel clinker inhibitor capable of suppressing the adhesion of clinker even in biomass fuel having a large amount of low-melting components.

Means for Solving the Problems

[0009] As a result of intensive studies to achieve the above object, the present inventor has found that by using two or more metal components that become metal oxides in combination instead of using a single metal component that becomes a metal oxide, the generation of clinker derived from biomass fuel can be suppressed more than before, and the present invention has been completed.

[0010] That is, the above problems are solved by the present invention described in any one of the following items (1) to ( 3 ) item. (1) A clinker inhibitor for combustion equipment using a fuel in which the total content of potassium oxide (K2O) and sodium oxide (Na2O) in combustion ash is 10% by mass or more, An aluminum oxide (Al2O3) source and a magnesium oxide (MgO) source composed of the aluminum oxide source is kaolin, the mass ratio of the kaolin to the magnesium oxide source (kaolin / MgO) is 3 / 7 to 5 / 5 A clinker inhibitor characterized by the above. (2) The clinker inhibitor according to item (1) above, characterized in that the potassium oxide content in the combustion ash of the above fuel is 15% by mass or more. (3) characterized in that the combustion temperature of the combustion equipment is 600°C or higher and 1200°C or lower The clinker inhibitor according to item (1) or (2) above.

Effects of the Invention

[0011] According to the present invention, since an aluminum oxide (Al2O3) source and a magnesium oxide (MgO) source are contained, it is possible to provide a clinker inhibitor capable of suppressing the adhesion of clinker derived from biomass fuel.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0013] The clinker inhibitor of the present invention suppresses the adhesion of clinker generated by burning biomass fuel, and contains an aluminum oxide (Al2O3) source and a magnesium oxide (MgO) source.

[0014] As the above aluminum oxide source, those that generate aluminum oxide by combustion can be used. For example, in addition to aluminum compounds such as aluminum hydroxide, aluminum carbonate, and aluminum oxide, ores containing aluminum oxide such as kaolin and feldspar can be used.

[0015] Also, as the magnesium oxide source, those that generate magnesium oxide by combustion can be used. For example, magnesium compounds such as magnesium oxide, magnesium hydroxide, magnesium acetate, and magnesium nitrate can be used.

[0016] The combustion ash of biomass fuel has a different problem from coal ash in that it contains a large amount of low melting point components such as potassium oxide (K2O) and sodium oxide (Na2O) compared to the combustion ash of coal, and the melting point is lower than the temperature of the combustion chamber, so a molten liquid is generated and the combustion ash becomes sticky and adheres to heat exchangers and exhaust paths.

[0017] Table 1 shows the amounts of potassium oxide and sodium oxide contained in the combustion ash of typical biomass fuels and coal. The combustion ash of biomass fuels has a total content of potassium oxide and sodium oxide of 10% by mass or more, and in particular, the content of potassium oxide is high. This potassium oxide melts by forming eutectics with other components in the fuel during combustion and adheres as clinker to heat exchangers, exhaust paths, etc.

[0018]

Table 1

[0019] Also, Fig. 1 shows the relationship between the melt volume and temperature of the combustion ash of herbaceous pellets measured with a thermomechanical analyzer (TMA), together with the relationship between the melt volume and temperature when the clinker removed from the heat exchanger is heated. Fig. 2 shows the relationship between the melt volume and temperature of the combustion ash of coal.

[0020] The combustion ash of herbaceous pellets has a melt volume exceeding 20% at 800 °C, and the combustion ash is sticky and easily adheres to heat exchangers, exhaust paths, etc. On the other hand, for coal ash, the melt volume exceeds 20% at 1200 °C or higher, and hardly any melt is generated at 800 °C.

[0021] The present inventors searched for components that can suppress the adhesion of clinker even when burning biomass fuels that produce such low melting point components.

[0022] 10% by mass of a clinker suppression component was added to the combustion ash of herbaceous pellets, and the temperature at which the melt volume of the combustion ash became 10% was measured. The combustion ash of herbaceous pellets alone without the addition of a clinker suppression component had a temperature of 764.9 °C at which the melt volume became 10%. Fig. 3 shows the increase in temperature when a clinker suppression component was added with respect to this temperature.

[0023] For Ca(OH)2, the temperature at which the melt volume became 10% decreased, and for SiO2, no clinker suppression effect was confirmed. For Fe2O3 and ferric polysulfate, the above temperature increased, but the increase amount was small.

[0024] Al2O3, MgO, and Mg(OH)2 showed a large increase in the above temperature and a confirmed clinker suppression effect. In particular, kaolin with 2SiO2Al2O3·2H2O as the main component (80% by mass or more) had a greater clinker suppression effect compared to Al2O3 alone or SiO2 alone among its constituent components, and it was confirmed that there was a possibility of improving the clinker suppression effect by mixing two or more metal components constituting the metal oxide.

[0025] Therefore, when a 1:1 mixture of Mg(OH)2 and Al2O3 and a 1:1 mixture of Mg(OH)2 and kaolin, which showed a large increase in the temperature at which the melt amount of the combustion ash reached 10%, were added, the clinker suppression effect was greater than when each was added alone.

[0026] Next, the relationship between the melt amount and temperature was examined by changing the mixing ratio of the MgO source and the Al2O3 source. The measurement results are shown in Fig. 4.

[0027] In the range where the melt amount was less than 10% and the adhesion of the clinker could be effectively suppressed, the mixture of Mg(OH)2 and kaolin at a 1:1 ratio had a smaller melt amount than the mixture of Mg(OH)2 and Al2O3 at a 1:1 ratio.

[0028] When added by changing the mixing ratio of Mg(OH)2 and kaolin, a clinker suppression effect was achieved at all mixing ratios. However, the mixture of Mg(OH)2 and kaolin at a 1:1 ratio had the highest clinker suppression effect and was capable of combustion at high temperatures.

[0029] Also, the crushing strength of the clinker, that is, the ease of removing the adhered clinker, was examined. The measurement results are shown in Fig. 5.

[0030] The crushing strength was measured by filling the combustion ash into a cylindrical mold with a diameter of 10 mm and a height of 8 mm, applying a load under the conditions of 200 Kg for 3 minutes to form a combustion ash tablet, firing this at 800 °C for 2 hours to produce a clinker, and measuring the lateral crushing strength of the cylindrical clinker using an autograph.

[0031] Although the mixture of Mg(OH)₂ and kaolin has the same constituent components as the mixture in which Mg(OH)₂, SiO₂, and Al₂O₃ are mixed respectively, its crushing strength decreased.

[0032] The reason for this has not been clearly elucidated. However, in addition to the Mohs hardness of kaolin being 1 - 2, which is much lower than that of SiO₂ (8.5 - 9) and Al₂O₃ (9), and kaolin having cleavage properties, it is speculated that this may be because the properties of kaolin are maintained in the temperature range below its melting point, for example, in the range of 600°C - 1200°C, which is the combustion temperature range of combustion equipment using biomass fuel.

[0033] It can be seen from Figure 5 that when the mass ratio of kaolin to Mg(OH)₂ (kaolin / Mg(OH)₂) is in the range of 3 / 7 - 5 / 5, the crushing strength of the clinker decreases and it becomes easier to remove the attached clinker.

[0034] The clinker inhibitor of the present invention is in powder or slurry form and can suppress the adhesion of clinker by adding it together with biomass fuel, or in addition to the combustion furnace of combustion equipment, to heat exchangers and exhaust paths where clinker is likely to adhere. In particular, it is useful for biomass fuels in which potassium oxide in the combustion ash is 15% by mass or more.

Claims

1. A clinker inhibitor for combustion equipment that uses a fuel with a total content of potassium oxide (K ２ O) and sodium oxide (Na ２ O) of 10% by mass or more. Aluminum oxide (Al ２ O ３ ) source and a magnesium oxide (MgO) source, and The aluminum oxide source is kaolin, A clinker inhibitor characterized in that the mass ratio of the kaolin to the magnesium oxide source (kaolin / MgO) is 3 / 7 to 5 / 5.

2. The clinker inhibitor according to Claim 1, characterized in that the potassium oxide content in the combustion ash of the fuel is 15% by mass or more.

3. The clinker inhibitor according to Claim 1 or 2, characterized in that the combustion temperature of the combustion equipment is 600°C or higher and 1200°C or lower.

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