JPS641518B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a solid fuel-water slurry with excellent storage stability. More specifically, the present invention provides finely powdered solid fuel such as coal or petroleum coke, etc., by controlling the contents of inorganic minerals and alkali metal bases or alkaline earth metal bases in a water slurry to maintain low viscosity, high concentration, and long-lasting fuel. The present invention relates to a method for producing a solid fuel-water slurry with excellent storage stability in which the solid fuel does not settle or become compacted during storage for a period of time. In recent years, solid fuels such as coal and petroleum coke have been reconsidered as energy sources. In particular, in order to turn solid fuel into a fluid fuel like petroleum, progress is being made in developing fluid fuels in which the solid fuel is pulverized and water is dispersed to create a solid fuel-water slurry. However, in general, in a method for producing a solid fuel-water slurry, increasing the concentration of solid fuel significantly increases the viscosity of the slurry, impairing the fluidity of the slurry and making handling and pipe transportation difficult. On the other hand, it is well known that reducing the concentration of solid fuel in order to lower the viscosity of the slurry lowers the transport efficiency and requires a dehydration process as a post-treatment in order to use it as a fuel or gasification raw material. It is being In order to solve these problems and produce a solid fuel-water slurry with low viscosity and high concentration, methods have been developed in which a dispersant is added or the particle size distribution of the solid fuel is adjusted. However, even in this case, if the slurry is allowed to stand for a long period of time, the solid fuel will settle due to the difference in specific gravity, and the dehydration phenomenon caused by the compaction of the sediment will form a strong solid sedimentary layer, making it easy to redisperse. Not. Therefore, it is of practical importance to produce a solid fuel-water slurry that has low viscosity, high concentration, and excellent storage stability. Conventionally, a method for producing a stable solid fuel-water slurry is known, for example, by adding a polymeric surfactant such as polyacrylamide or guar gum to a coal-water slurry (Japanese Patent Laid-Open No. 54-33805).
(see publication). Although it is possible to produce a stable coal-water slurry by adding such a polymeric surfactant, the viscosity of the resulting slurry is more than 20,000 cp, making it difficult to handle and transport and impractical (Comparative Example 5). reference). In addition, a method for producing a highly concentrated and stable coal-water slurry by adjusting the particle size distribution of coal and using alkaline earth metal salts of ligninsulfonic acid, inorganic alkali metal salts, etc. as organic dispersants. is known (see Japanese Unexamined Patent Publication No. 57-96090). However, even if attempts were made to adjust the particle size distribution of coal using the proposed method and increase the concentration by adding alkaline earth metal salts of ligninsulfonic acid,
A slurry with a sufficiently high concentration cannot necessarily be obtained (see Comparative Examples 6 and 7). Another known method is to mix small bubbles into a coal-water slurry to stabilize it (Japanese Unexamined Patent Application Publication No. 1983-1999).
(Refer to Publication No. 92089), a decrease in transportation efficiency is inevitable, and none of the methods is still sufficient for producing a practical solid fuel-water slurry, so there is room for improvement. In an attempt to improve the storage stability of solid fuel-water slurry, the present inventors investigated the effect of adding inorganic minerals such as pentonite in addition to the dispersant (Comparative Examples 3 and 4), and found that the storage stability Although the properties were improved, the slurry viscosity increased and fluidity was impaired. Furthermore, we discovered that slurry can be stabilized by adding an alkali metal or alkaline earth metal base in addition to a dispersant in some types of coal, but not in other types of coal, and we are investigating this difference. They found that this phenomenon was caused by the difference in the amount of inorganic minerals contained in the coal, which were liberated and dispersed in the slurry from the surface of the coal particles. This means that in a basic slurry obtained by adding an alkali metal or alkaline earth metal base to the slurry, inorganic mineral substances tend to swell in water and form a viscous gel. It is presumed that the pulverized coal is difficult to settle, and even if a sedimentary layer is formed by leaving it for a long time, the pulverized coal can be easily redispersed. The present invention provides that when a solid fuel-water slurry is produced by mixing finely powdered solid fuel with water or water and a dispersant, the slurry contains 0.01 to 3% by weight of inorganic minerals and an alkali metal or alkaline earth metal. The base is
The present invention relates to a method for producing a solid fuel-water slurry, characterized in that the content is adjusted to 0.05 to 2% by weight. The solid fuel-water slurry produced according to the present invention has a low viscosity, a high concentration of solid fuel, and can be stored for a long period of time. Therefore, the solid fuel-water slurry produced by the present invention does not require special equipment for tank storage, and can be used as a fuel for boilers, power plants, etc.
It is suitable for use as a gasification feedstock, such as in the production of carbon monoxide and the like. In the present invention, it is important to contain specific amounts of an inorganic mineral substance and an alkali metal or alkaline earth metal base in the slurry, and it is difficult to achieve the object of the present invention if each of them is used alone. In the present invention, inorganic mineral substances have effects such as increasing the concentration and stabilizing the slurry, but the amount of inorganic mineral substances liberated and dispersed in the slurry from the finely powdered solid fuel is 0.01 to 3% by weight in the slurry. It is not necessary to add inorganic mineral substances when the amount falls within the range of . If the amount of free and dispersed inorganic minerals is too large, it is preferable to adjust the amount of inorganic minerals by using, for example, petroleum coke, which has a low content of inorganic minerals, as the fine powder solid fuel. If the amount of inorganic mineral material is too small, it is preferable to add inorganic mineral material during slurry production to adjust the amount of inorganic mineral material contained in the slurry. The amount of inorganic minerals liberated and dispersed in the slurry from the pulverized solid fuel can be determined by, for example, treating the pulverized solid fuel with hydrocarbon oil and water to produce an aggregate of the pulverized solid fuel and hydrocarbon oil. A method of quantifying inorganic mineral substances dispersed in the filtrate by separating it from the mother liquor, and a method of comparing the amount of non-flammable matter in the aggregate with the amount of non-flammable matter in the raw material fine powder solid fuel, etc. You can find out at The inorganic mineral substance to be added may be an inorganic mineral substance that is separated from the aggregate of the pulverized coal and hydrocarbon oil produced by a conventionally known method such as pulverizing coal and treating it with hydrocarbon oil and water. In addition, quartz, which is a naturally occurring inorganic mineral, can be used.
Silicic raw materials such as cristobalite and tridymite, kaolinous raw materials such as feldspar, silica sand, and mica minerals, pyrophyllite raw materials such as waxite, and clay raw materials such as montmorillonite raw materials such as pentonite are also easily available. Easy to use. Among them, montmorillonite raw materials are particularly effective and can be preferably used. In addition, aluminum chloride, aluminum sulfate, iron sulfate, iron chloride, etc., and inorganic polymers thereof can also be used as inorganic mineral substances that are expected to have excellent effects. When adding these inorganic mineral substances, the amount of inorganic mineral substances that are liberated and dispersed in the slurry from the particle surface of the finely powdered solid fuel is included in the slurry.
It is added and used in an amount such that the content is in the range of 0.1 to 2.8% by weight, preferably 0.1 to 2.8% by weight. If the amount of inorganic minerals is too small than the above range, the amount of gel formed from the inorganic minerals in the basic slurry will be insufficient, causing sedimentation, agglomeration and compaction of the finely powdered solid fuel, resulting in poor storage stability. is not sufficiently exhibited, and if the amount is too large, the gelled inorganic mineral material itself will form strong aggregates in the slurry, impairing the fluidity of the slurry, and making it impossible to increase the concentration of the finely powdered solid fuel. In addition, the particle size of the inorganic minerals to be added is approximately 44 microns or less, and it is appropriate to use the geometric average diameter of approximately 10 microns or less, and when the solid fuel is pulverized, the inorganic minerals are pulverized together with the solid fuel. is appropriate. Typical alkali metal or alkaline earth metal bases include sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide when incorporated with inorganic minerals. Sodium is preferably used. The content of the alkali metal or alkaline earth metal base in the slurry is adjusted by adding and dispersing them during slurry preparation. The amount of these alkali metal or alkaline earth metal bases added to the solid fuel-water slurry is 0.05 to 2.
% by weight. If the amount of the alkali metal or alkaline earth metal base added is too small than the above range, gelation of the inorganic mineral will not occur sufficiently and the stability effect will not be exhibited; if the amount added is too large, gelation will progress. Too much slurry impairs fluidity. In the present invention, it is not necessary to use a dispersant, but when a dispersant is used together with water, a solid fuel-water slurry with a lower viscosity and higher concentration can be produced than when no dispersant is used. As the dispersant, any conventionally known dispersant for solid fuel-water slurries can be used. Examples of dispersants include naphthalene sulfonates, lignin sulfonates, and formalin condensates thereof, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, polyglycerin sulfates, and melamine. Examples include sulfonate salts of resins, polycarboxylate salts, sulfonate salts of petroleum extracts, and the like. The amount of dispersant used is suitably 0.01 to 3 parts by weight per 100 parts by weight of the solid fuel-water slurry. The type of pulverized solid fuel used in the present invention is not particularly limited, and examples include lignite, subbituminous coal, bituminous coal,
Examples include anthracite, petroleum coke, and mixtures thereof. These include particles with a particle size of 149 microns or less that account for 90% by weight or more, and a particle size distribution with a standard deviation σg of about 4 to 12 in a lognormal distribution. It is preferable to use one within this range. Geometric standard deviation (σg) is the ratio of the geometric mean diameter to the particle diameter that corresponds to 15.87% of the cumulative passing weight% (geometric mean diameter/particle diameter that corresponds to 15.87% of the cumulative passing weight) σg ₁
The arithmetic mean ( _σ
g ₁ +σg ₂ /2), and the terms geometric mean diameter and geometric standard deviation are terms commonly used to define the particle size of powder and its distribution. For the geometric mean diameter, the cumulative passing weight% is 50%.
The particle size corresponds to In the present invention, the mixing order of the pulverized solid fuel, water, dispersant, inorganic mineral, alkali metal or alkaline earth metal base, etc. is not particularly limited, but the addition of the alkali metal or alkaline earth metal base may Preferably, the fine powder solid fuel, inorganic minerals, etc. are crushed and dispersed while the fine powder solid fuel-water slurry is kept basic. For example, a basic aqueous solution is prepared by dissolving or dispersing a dispersant and an alkali metal or alkaline earth metal base in water in advance, and solid fuel and inorganic minerals are mixed as necessary, and wet pulverization is carried out. It is preferable to do so. In the slurry, which is kept basic, the desired amount of inorganic minerals forms a weakly cohesive gel that is itself viscous, making it difficult for the finely divided solid fuel to settle, even after long periods of standing. Even if a sedimentation layer is formed, the solid fuel is prevented from solidifying, and therefore the fine powder solid fuel in the slurry can be kept stable for a long period of time. Next, examples and comparative examples will be shown. In each example, "preparation of pulverized solid fuel", "preparation of solid fuel-water slurry", and "storage stability test of solid fuel-water slurry" were conducted in the following manner. [Preparation of finely powdered solid fuel] Solid fuel with the properties shown in Table 1 (industrial analysis) was crushed into an average diameter of about 90 microns using a Nara-style free crusher, and the same coarsely granular solid fuel was crushed into a ball mill. and ultrafine powder solid fuel wet-pulverized to an average diameter of approximately 9 microns in a 60:40 weight ratio on an absolute dry basis, and mixed to prepare a fine powder solid fuel.
When using coal with a particularly high content of inorganic minerals as a solid fuel, part of the pulverized coal is replaced with coal coke with a low content of inorganic minerals, and it is liberated and dispersed in water during slurry formation. The amount of inorganic minerals used was adjusted so that it was within an appropriate range.

[Solid fuel-water slurry storage stability test]

Solid fuel - Water slurry is placed in a 1000c.c. sample tube container, left to stand, and after a certain period of time, a glass rod is inserted to examine the presence of sediment near the bottom of the container and the degree of compaction. - Evaluate the stability of the water slurry, and mark Γ if no solid sedimentation layer is observed, and mark × if it is observed. Examples 1 to 5 Petroleum coke as a finely powdered solid fuel, formalin condensate of sodium β-naphthalenesulfonate as a dispersant (0.5 parts by weight per 100 parts by weight of slurry),
A solid fuel (petroleum coke)-water slurry with a solid fuel concentration of 69% by weight was prepared using sodium hydroxide as the alkali metal base and those listed in Table 2 as the inorganic minerals, and the fluidity of the slurry, The results of the stability investigation are shown in Table 2, and all slurries were stable with no solid sedimentation layer observed even after standing for 10 days. Comparative Examples 1 to 4 Solid fuel (petroleum coke) was prepared in the same manner as in Example 1 except without adding either or both of the inorganic mineral (bentonite) and the alkali metal base (sodium hydroxide). A water slurry was prepared, but it separated into a solid fuel layer and a water layer after one day, and the solid fuel layer formed a strong consolidated layer.
Difficult to redisperse and slurry viscosity is 10000cp
The situation has become even more illiquid. The results are shown in Table 2.

【table】

[Table] Comparative Examples 5 to 7 Solid fuel (petroleum coke) at the concentrations listed in Table 3 using polyacrylamide or calcium lignin sulfonate as a dispersant and without adding inorganic minerals and alkali metal bases. A water slurry was prepared, and although the stability of the slurry was maintained in Comparative Example 5, the viscosity of the slurry was extremely high and had almost no fluidity, and in Comparative Examples 6 and 7, the slurry viscosity was increased to increase the solid fuel concentration. was extremely high, making it difficult to increase the concentration of the slurry. The results are shown in Table 3.

[Table] Examples 6 to 11 Example 1 and solid fuel (petroleum coke-coal) in which part of the solid fuel (petroleum coke) was replaced with pulverized coal without adding inorganic minerals (pentonite)
A solid fuel-water slurry was prepared in the same manner as in Example 1, except that the amount of inorganic minerals contained in the slurry was supplemented with inorganic minerals liberated and dispersed in the slurry from coal particles. . The slurry was a stable slurry with no solid sedimentation layer observed even after standing for 10 days. The results are shown in Table 4.

【table】

[Table] Examples 12 to 15 Inorganic minerals were added (Examples 12 to 14) or not added (Example 15), and the solid fuel concentrations listed in Table 5 were adjusted to the concentrations listed in Table 5. A solid fuel-water slurry was prepared in the same manner as in Example 1 using a solid fuel and an inorganic mineral, and then the slurry was charged into a stability test container and left to stand for 20 days. The stability of the solid fuel-water slurry was evaluated by taking out the slurry from each part and measuring the solid fuel concentration and slurry viscosity at each part. The results are as shown in Table 5, and there was almost no difference in solid fuel concentration between each part, there was little difference in viscosity, and the stability of the slurry was good. The stability test container has a bottomed cylindrical shape with an inner diameter of 36 mmφ and a height of 18 mm, with a slurry outlet for the lower layer at the bottom, a slurry outlet for the middle layer, and a slurry outlet for the middle layer at a position 60 mm above the bottom. The one in which the slurry outlet in the upper layer was provided 60 mm above the slurry outlet was used.

【table】

Claims (1)

[Claims] 1. When producing a solid fuel-water slurry by mixing pulverized solid fuel with water or water and a dispersant, the slurry contains 0.01 to 3% by weight of inorganic minerals and 0.05% of an alkali metal or alkaline earth metal base. ~2
1. A method for producing a solid fuel-water slurry, which comprises adjusting the solid fuel-water slurry content to be % by weight.