JPS6247480B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to solid fuel, and provides a solid fuel that absorbs sulfur dioxide gas generated during combustion to remove bad odors, and also fixes ash after combustion to facilitate disposal. There are various possible problems when using coal as a household heat source, one of which is that it contains harmful exhaust gas components. Coal is
It contains 0.2 to 1.0% by weight of sulfur as one of its components, which becomes sulfur dioxide gas when burned.
This sulfur dioxide gas is associated with pollution problems, and desulfurization is an essential condition. Despite this situation, conventional solid fuels such as briquettes have not been sufficient for desulfurization. Desulfurization agents conventionally used include slaked lime, iron oxide,
Alkaline earth metal oxides such as magnesia and zinc oxide are known, but although these desulfurization agents can certainly be expected to be effective to some extent, the reality is that the combustion temperature range in which they can be expected to be effective is limited. It was hot. In response to the above-mentioned current situation, the present inventors first added Ca(OH) ₂ to carbonaceous fuel as a desulfurization agent.
At least one member selected from the group consisting of CaCO ₃ and dolomite (CaCO ₃・MgCO ₃ ), and K ₂ CO ₃
proposed a solid fuel containing
(Japanese Patent Application Laid-open No. 57-70193)]. Although this product is certainly excellent from the viewpoint of desulfurization properties, it was not sufficient in the following points. In addition to exhaust gas, another problem when burning briquettes is the fixation of ash. Needless to say, the necessity of fixing ash is to fix the ash generated during combustion and to keep it in a stable combustion state at all times, to facilitate disposal, and to prevent ash from adhering to the walls of the combustor. Things like that. Due to this need, silica sand has conventionally been used. Silica sand is cheap and easy to obtain, so it is included in most commercially available products. The disadvantage of this silica sand is that it forms a glassy substance at high temperatures and ash adheres to the walls of the combustor. The present inventors also attempted to add silica sand to the above-mentioned desulfurization agent in accordance with conventional products, but it was found that by adding more than a certain amount of silica sand, the original performance of the desulfurization agent was not exhibited. The present invention eliminates such inconveniences. The solid fuel of the present invention _includes a desulfurizing agent consisting of K ₂ CO 3 and at least one selected from the group consisting of Ca(OH) ₂ , CaCO ₃ and dolomite, and MgAl ₂ O ₄ .
and ZrO ₂ , and is characterized in that it contains at least one heat-resistant filler selected from the group consisting of The reason for limiting the amount of silica sand added in the present invention will be described. Silica sand is an important compound that forms glass and forms compounds with various alkali metals. For example, potassium compounds are
K ₂ O・4SiO ₂ at 1040℃ K ₂ O・ZSiO ₂ at 976℃
Generates the compound K ₂ O・SiO ₂ . Therefore,
The desulfurizing agent component K ₂ CO ₃ reacts near the above-mentioned temperature, and the K ₂ CO ₃ effective for desulfurization is consumed in the reaction with SiO ₂ . For this reason, silica sand, which has been commonly used in the past, cannot be freely used. According to the study results of the present inventors,
The amount of SiO ₂ added is limited, and the amount of desulfurization agent such as Ca(OH) ₂ added is 3 to 20 parts by weight, and the amount of K ₂ CO ₃ added is 1 to 20 parts by weight per 100 parts by weight of carbonaceous fuel. ,Ten
Must be less than parts by weight. If _SiO2
If the amount added is 10 parts by weight or more, the effect as a desulfurizing agent will be lost for the reasons mentioned above. Furthermore, even if the amount of silica sand added is suppressed in this way, if solid fuel is made by adding only Ca(OH) ₂ , K ₂ CO ₃ , or SiO ₂ , these oxides will not produce ash. The ash will melt and form a glassy substance, making it difficult to fix the ash. In this situation, ash adheres to the wall of the combustor,
Not only is disposal not easy, but the life of the combustor itself is also shortened. Therefore, there is a need for a stable heat-resistant filler that does not chemically change with these ash contents. Heat-resistant fillers suitable for this purpose are MgAl ₂ O ₄ and ZrO ₂
It is. These compounds have the advantage that they are chemically stable, do not react with ash containing a desulfurizing agent, and can immobilize ash. Solid fuels made of the above materials not only have excellent desulfurization properties, but are also preferable from the viewpoint of ash fixation. Next, materials constituting the present invention will be explained. First, carbonaceous fuels are natural or artificially synthesized fuels whose main component is carbon, and include coal, coke, charcoal, graphite, activated carbon, etc. Among these, coal is an abundant and inexpensive resource. Among coals, anthracite with a carbon content of 90% by weight or more is particularly preferred as a raw material for briquettes and charcoal. Anthracite is preferable because it has a low volatile content and does not generate soot when burned. However, anthracite is expensive and cannot be produced domestically, so it is best to mix it with steam coal in moderation. Furthermore, ignitability,
Taking formability into consideration, it is optional to add coke, charcoal, graphite, activated carbon, etc. The sulfur content of these cokes and the like is 0.1 to 0.5% by weight. Next, we will discuss desulfurization agents. Currently, commercially available charcoal briquettes use slaked lime as a desulfurization agent.
Slaked lime decomposes into CaO during combustion, which reacts with generated SO ₂ and O ₂ in the air, and is fixed as CaSO ₄ . This CaSO ₄ is thermally stable and has a melting point of 1450°C, and begins to decompose into CaO and SO ₂ at around 1250°C. In addition, the decomposition temperature or melting point of various salts when fixed as sulfates is MgSO ₄ : 1185
℃, _BaSO4 : 1580℃, _SrSO4 : 1580℃ _{, K2SO4} :
1069℃, Na ₂ SO ₄ : 884℃. From these numbers, it can be seen that calcium salts and barium salts are preferable as desulfurizing agents. The combustion temperature of briquettes is
Although it varies depending on the amount of combustion air, the maximum value is approximately 1200℃. Therefore, if all the generated SO ₂ were immobilized as calcium salts and barium salts, no SO ₂ should be generated. However, the reality is that when the combustion temperature approaches 1000°C, the desulfurization effect of calcium salts drops to less than 50%. The reason for this is that CaO generated by thermal decomposition is
It is thought that the above heating causes sintering and becomes chemically inactive, resulting in a decrease in reactivity with SO ₂ . This means that Ca
This is supported by the fact that (OH) ₂ heat-treats CaCO ₃ at a high temperature of 1000℃ or higher before mixing, and then mixes it with coal to see the desulfurization effect, which is inferior to the unfired case. It will be done. Also generally CaCO ₃
It is said that Ca(OH) ₂ has a greater desulfurization effect than Ca(OH) 2, but this is also thought to be due to the difference in reactivity of CaO produced by thermal decomposition. For the above reasons, the necessary conditions for a desulfurizing agent include that the reactivity does not decrease even at high temperatures, and that the immobilized sulfate is thermally stable. From this perspective, Ca(OH) ₂ ,
It is not preferable to use CaCO ₃ or dolomite alone. The present invention significantly improves the reactivity at high temperatures by adding K ₂ CO ₃ to such a desulfurizing agent. The sulfate salt of K ₂ CO ₃ K ₂ SO ₄ has a low melting point of 1069° C., and when used alone, is not thermally stable at high temperatures and does not meet the above-mentioned requirements for a desulfurization agent. Therefore, although K ₂ CO ₃ is certainly effective as a desulfurization agent at low temperatures (below 1000°C), it is thought that it has some effect on the reactivity of CaO and SO ₂ . It can be done.
Although it is not clear whether the effect is on calcium salts or on the decomposition of coal,
By combining with Ca(OH) ₂ , CaCO ₃ and dolomite, a high desulfurization rate can be obtained due to the synergistic effect. Also, Ca alone without the addition _{of K2CO3}
When comparing the desulfurization effects of (OH) ₂ , CaCO ₃ , and dolomite, the order is Ca(OH) ₂ > CaCO ₃ > dolomite, but by combining K ₂ CO ₃ , there is no distinction between the three, and In either case, a high desulfurization rate can be obtained. Therefore, conventionally, from the viewpoint of reactivity,
Ca(OH) ₂ was used, but it is cheap
It becomes possible to use CaCO ₃ and dolomite. Dolomite is a eutectic of CaCO ₃ and MgCO ₃ .
It is a naturally occurring source of calcium salt. K ₂ CO ₃ can be used either anhydrous or with bound water. Also
KOH is a potassium salt other than K ₂ CO ₃ , but it is unstable and does not release into the air during storage.
Since it absorbs CO ₂ and becomes K ₂ CO ₃ , this may be used as a starting material. Desulfurization agents used in the present invention include Ca(OH) ₂ , CaCO ₃ , and dolomite, but are limited to the above three types from the viewpoint of thermal stability of sulfate and low cost. Next, the amount of desulfurization agent added will be described. The desulfurization effect can be expected to increase as the amount of the desulfurizing agent increases, but if too much is added, the calorific value of the solid fuel decreases, so it is preferably within 20 parts by weight per 100 parts by weight of the carbonaceous fuel. It is effective as a desulfurizing agent when the amount is 3 parts by weight or more, but it is preferably 5 parts by weight or more. Although it is 10 parts by weight or more that provides a substantially constant desulfurization effect, 20 parts by weight or less is sufficient from the viewpoint of the particle size of the carbonaceous fuel, which is another factor that controls the desulfurization effect. Next is K ₂ CO ₃ , which is a carbonaceous fuel 100
It is 1 to 20 parts by weight. If it is less than 1 part by weight, no synergistic effect with the desulfurizing agent can be expected, and if it is more than 20 parts by weight, the solid coal will swell due to the deliquescent property of K ₂ CO ₃ . The amount of K ₂ CO ₃ added is determined based on the balance with the desulfurization agent, and the appropriate amount is 0.2 to 10% when the ratio of the desulfurization agent to K ₂ CO ₃ is within the range of parts by weight mentioned above. It is desirable that the 0.2
Below, that is, when the amount of desulfurization agent is small and the amount of K ₂ CO ₃ added is large, a desulfurization effect can be expected at temperatures below 1000°C, but above that, the effect decreases due to the decomposition of K ₂ CO ₃ . On the other hand, if the desulfurization agent is 10 or more and the K ₂ CO ₃ is small, there is not enough K ₂ CO ₃ to match the reactivity of the desulfurization agent, and the present invention depends on the desulfurization effect of the desulfurization agent alone. Unable to satisfy the purpose. Therefore, the appropriate range is 0.2 to 10
within More preferably, it is 0.3 to 5. Next, we will discuss the particle size of carbonaceous fuel, desulfurization agent, and K ₂ CO ₃ , which are important factors governing the desulfurization effect. Since the reaction between the SO ₂ generated from the carbonaceous fuel and the desulfurization agent is a gas-solid catalytic reaction, it is preferable that the desulfurization agent be located near the generated SO ₂ .
Therefore, when the particle size of the carbonaceous fuel is large, the probability that SO ₂ generated within the particles will come into contact with the desulfurization agent in the vicinity decreases, making it impossible to expect a high desulfurization rate.
This also applies to the particle size of the desulfurization agent and K ₂ CO ₃ . Furthermore, with regard to the desulfurizing agent, if the particle size is too large, only the surface becomes sulfate, which not only makes it impossible to use the desulfurizing agent effectively, but also requires a larger amount to be added, which is not preferable. From the above points of view, the particle size of carbonaceous fuel is
It is preferable that 60% by weight or more of the material passes through a 5-mesh sieve. 5 mesh is a standard Tyler sieve with a sieve opening of 3.962 mm, and the material that passes through this sieve accounts for the entire carbonaceous fuel.
It means 60% by weight or more. From the point of view of effective utilization, it is better for the desulfurization agent and K ₂ CO ₃ to be finer than the carbonaceous fuel, and it is preferable for all of them to be 5 mesh or less. In the case of carbonaceous fuel, it is also preferable that the particle size is 5 meshes or less, but because coking coal may contain large grain particles, at least 60% by weight should be 5 meshes or less. It is desirable that there be. 5 meshes or less
If it is less than 60% by weight, a high desulfurization effect cannot be obtained. Next, the heat-resistant filler will be described. Conventionally, a commonly used filler is silica sand, but in the present invention, when this is used, it is used in an amount of 10 parts by weight or less per 100 parts by weight of carbonaceous fuel in the desulfurization agent composition described above. If it exceeds 10 parts by weight, it will react with the desulfurizing agent and reduce the desulfurizing effect. Although it is preferable not to add SiO ₂ , since it is cheap and easily available, it is used within the limited range as described above. Substances that reduce the effectiveness of desulfurization agents are
It includes not only SiO ₂ but also minerals containing SiO ₂ as a component, such as mullite (3Al ₂ O ₃ .2SiO ₂ ), feldspar, and waxite (Al ₂ Si ₄ O ₁₀ (OH) ₁₀ ). Like SiO ₂ , these minerals also reduce the performance of the desulfurization agent, so the amount added is limited. Preferred heat resistant fillers for the present invention are:
Selected from the group consisting _{of MgAl2O4} and _ZrO2 . MgAl ₂ O ₄ , also called cryolite, is a mineral with a spinel structure, and exists both naturally and synthetically, both of which can be used. Instead of using MgAl ₂ O ₄ by itself, it can be mixed with magnesium salts [MgCO ₃ or Mg(OH) ₂ ] and aluminum salts [Al ₂ O ₃ or Al(OH) ₃ ], which form MgAl ₂ O ₄ on combustion. A combination of these may be added. It is also possible to use MgCO ₃ or Al ₂ O ₃ alone, but when used alone,
Similar to SiO ₂ , the performance of the desulfurization agent decreases, and by combining the two, it shows the same performance as MgAl ₂ O ₄ . When combining a magnesium salt and an aluminum salt, it is most desirable from the viewpoint of heat resistance that the stoichiometric composition becomes MgAl ₂ O ₄ , but the present invention does not limit their composition ratio. part,
Once MgAl ₂ O ₄ is formed, the remaining MgO and Al ₂ O ₃
The MgAl ₂ O ₄ barrier suppresses vitrification and melting. Like MgAl ₂ O ₄ , ZrO ₂ is also a mineral with high heat resistance and is commonly used as zirconia porcelain.
Although ZrO ₂ can be used alone,
Crystal transformation occurs at around 1100℃, so Ca, Y,
Products stabilized with oxides such as Mg and Ce are commercially available. In the present invention, it is possible to use all of these, but the most common and easily available
Preferably, it is stabilized with CaO. The heat-resistant fillers mentioned above may be used alone or
It is optional to use them in combination, and the amount to be added is also determined in consideration of other additive substances. A suitable addition ratio of the heat-resistant filler is 10 to 20 parts by weight per 100 parts by weight of carbonaceous fuel. If the amount is more than this, the calorific value as a fuel will decrease, and if it is less than this, the effect as a filler cannot be expected. However, if SiO ₂ is used in combination, the amount of SiO ₂ should be 10 parts by weight or less. Furthermore, it is optional to add clay such as bentonite as a forming aid if necessary, but the amount added is 5 parts by weight per 100 parts by weight of carbonaceous fuel.
It is desirable that the content be less than parts by weight. Binders are usually molasses, carboxymethyl cellulose,
Although tar, pitch, and pulp waste liquid are used, it is optional to use these binders in the present invention. Next, an example will be described. Example 1 Coal (Hoongay No. 3 from North Vietnam, sulfur content 0.7% by weight) was used as the carbonaceous fuel, and 100 parts by weight of the coal was added with a desulfurizing agent, K ₂ CO ₃ , and a heat-resistant filler in the proportions shown in the table. The desulfurization effect was investigated by mixing. All particle sizes are 5 mesh or less. As an evaluation method, in an oxygen atmosphere (100c.c./min)
Approximately 1 g of solid fuel was burned on a porcelain board in an electric furnace with a set temperature of 1000°C. The generated exhaust gas was passed through a 1% hydrogen peroxide solution to absorb sulfur dioxide gas. This absorption liquid was neutralized and titrated with a 1/20 normal NaOH solution to determine the sulfur content discharged from the solid fuel. On the other hand, the sulfur content in the case of burning only coal was determined by the same operation, and the theoretical value of the sulfur content that would be emitted from the solid fuel was calculated. The difference between this theoretical value and the measured value is fixed by a desulfurizing agent or the like, and the ratio to the theoretical value is expressed as the purification rate here. A comparison of this purification rate and ash content is shown in the table. In addition, the state of ash content indicates a state in which ash does not adhere to the inside of the porcelain board and is not melted. △ indicates a state in which the material has slightly adhered to the inside of the board and is molten, and X indicates that it has adhered to the board and has become completely molten.

[Table] In the table, Samples No. 1, 2, and 3 are comparative examples. No.1
has a high purification rate, but the ash content is poor. No.2 is
Since the amount of SiO ₂ added is large at 12 parts by weight per 100 parts by weight of carbonaceous fuel, the purification rate is poor and the ash content is also poor. In No. 3, the amount of SiO ₂ added was 10 parts by weight, and the purification rate and ash content were somewhat satisfactory. No. 4 to No. 10 had good purification rate and ash content. Example 2 In No. 9 of Example 1, the heat-resistant filler Al ₂ O ₃
The purification rate when using Al(OH) ₃ instead of is 97
%, the ash content was good. Example 3 In No. 4 of Example 1, when the amount of Ca(OH) ₂ added was changed to 1, 2, 3, 5, and 7 parts by weight, the purification rates were 53%, 61%, and 61%, respectively. 81%, 87%, 91%
The ash content was all 0. This result shows that it is effective to add Ca(OH) ₂ in an amount of 3 parts by weight or more per 100 parts by weight of carbonaceous fuel. Example 4 In No. 4 of Example 1, the amount of K ₂ CO ₃ added was
The purification rates when changing to 0.8, 1, 3, 15, 20, and 22 parts by weight are 51%, 79%, 91%, 98%, and 99%, respectively.
%, 99%. However, when the amount added was 22 parts by weight, the sample was wet after being mixed and the state of the ash was poor. The ash content of all other examples was 0. From this result, the amount of K ₂ CO ₃ added is
3 to 20 parts by weight per 100 parts by weight are effective. Example 5 Calories of the solid fuel having the composition No. 4 of Example 1 were measured using a calorimeter based on JIS.
It was 6450Kcal/Kg. Similarly, No. 4 Ca
When the amount of (OH) ₂ added was changed to 20 and 25 parts by weight, the calories were measured, and the results were 5250 and 4750 Kcal/Kg. In addition, when we measured the purification rate, we found that each
%, 99%, and the state of the ash was △ and ×.
As a result of decreased calories and ash status, Ca
The upper limit of the amount of (OH) ₂ added is 20 parts by weight per 100 parts by weight of carbonaceous fuel. Example 6 In No. 7 of Example 1, 100 parts by weight of coal was
The purification rate when changing to 90 parts by weight of coal and 10 parts by weight of charcoal, and 90 parts by weight of coal and 10 parts by weight of coke is:
Each was 98%, and the condition of the ash was also ○. The sulfur contents of the charcoal and coke used here were 0.3% by weight and 0.27% by weight, respectively. Example 7 In No. 5 of Example 1, instead of ZrO ₂
When stabilized zirconia containing 20 mol% of CaO was used, the purification rate was 97%, and although the ash content was 0, it had better heat resistance than No. 5.

Claims (1)

[Claims] 1. Ca(OH) ₂ to 100 parts by weight of carbonaceous fuel,
3 to 20 parts by weight of at least one desulfurizing agent selected from the group consisting of CaCO ₃ and dolomite;
1 to 20 parts by weight of K ₂ CO ₃ , MgAl ₂ O ₄ , MgCO ₃ or Mg(OH) ₂ and Al ₂ O ₃ to produce MgAl ₂ O ₄
combination with Al(OH) ₃ and at least one heat-resistant filler selected from the group consisting of ZrO ₂
Solid fuel containing 10 to 20 parts by weight. 2 Ca(OH) ₂ to 100 parts by weight of carbonaceous fuel,
3 to 20 parts by weight of at least one desulfurizing agent selected from the group consisting of CaCO ₃ and dolomite;
1 to 20 parts by weight of K ₂ CO ₃ , MgAl ₂ O ₄ , MgCO ₃ or Mg(OH) ₂ and Al ₂ O ₃ to produce MgAl ₂ O ₄
A total of 10 to 20 parts by weight of SiO ₂ and at least one heat-resistant filler selected from the group consisting of Al(OH) ₃ and ZrO ₂ (however, the above-mentioned heat-resistant filler and SiO ₂ are not 0 parts by weight, and SiO ₂ is not more than 10 parts by weight).