JPH0132875B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an additive for pulverized coal flocculation that can significantly increase the flocculation effect and significantly improve the pulverized coal recovery rate in a method of flocculating and recovering pulverized coal from an aqueous slurry using oil. In recent years, due to the depletion of petroleum energy, the use of coal has been reaffirmed, and various ways of using it are being considered. Among them, there is a method to improve handling by making a water slurry by pulverizing coal and mixing it with water.
Research and development on water slurry, such as methods for crushing coal in water to create a water slurry for deashing, is underway. However, in general, such a water-dispersed slurry of coal powder has small particles, making filtration and dewatering processes difficult. Therefore, attempts have been made to agglomerate the dispersed particles in order to separate the water and the dispersoid when the use as a slurry during pipe transportation is completed. Wet granulation is an operation for agglomerating particles in such a slurry and growing and compacting the agglomerates, and research on this has been ongoing for a long time. Namely, (1) a method of adding an electrolyte to lower the zeta potential of particles and aggregating them; (2) a method of adding a polymer flocculant to form polymer crosslinks between particles and aggregating them; (3) ) A method in which a second liquid that is immiscible with the dispersion medium and has affinity with the particles is added, and this liquid forms liquid bridges between the particles to cause aggregation. As a specific method, JP-A-53-70076 discloses that emulsified oil is added to coal-water slurry, mixed, and this operation is repeated two or more times to improve the recovery rate; It has been described that cationic detergents, nonionic detergents, fatty acid soaps, sodium C8-C20 alkylbenzene sulfonates, sodium C8-C20 alkyl sulfates, sodium C8-C20 secondary sulfates, etc. are used as surfactants for the preparation. Furthermore, JP-A-56-88495 discloses that the nitrogen atom of an alkylene oxide adduct starting from an amino compound having two or more active hydrogens in the molecule as a surfactant is made cationic using a cationizing agent. It has been described that adding a cationic surfactant and oil to promote granulation. However, the surfactant disclosed herein does not sufficiently agglomerate the powdered coal, requiring a large amount of time and energy for granulation by agglomeration, and oil, which is an immiscible liquid that must be added to the water slurry. Because of the drawbacks such as the need for a large amount of oil, it has become necessary to develop a surfactant that uses a small amount of oil and does not require time and energy for granulation. Under such circumstances, the present inventors have worked hard to find an additive that can significantly increase the agglomeration of pulverized coal and significantly improve the recovery rate of pulverized coal by simply adding it to coal slurry together with oil and mixing it without any complicated operations. As a result of repeated research, we have come to provide the present invention. That is, in recovering powdered coal from coal-water slurry using oil, the number of nitrogen atoms is 7 to 200,
Preferably, a polyalkylene imine having 9 to 100 atoms is used as a starting material, and an alkylene oxide is added to this to add a polyether compound with a molecular weight of 1000 to 600,000, preferably 6000 to 300,000, as an essential component. This is an additive for powdered coal flocculation (hereinafter referred to as an additive), which is characterized by: Coal used in the coal-water slurry includes various types of coal such as anthracite, bituminous coal, subbituminous coal, and brown coal.
Any material can be used, regardless of type, origin, chemical composition, or moisture content. Such coal is dry-pulverized or coarsely crushed in a gas (air, nitrogen, combustion exhaust gas, etc.) in a conventional mill, or crushed or coarsely crushed in water to form a water slurry. The coal concentration in the coal-water slurry is not particularly limited, but is usually about 10 to 65%, and the average particle size of powdered coal is generally smaller than about 10 mm.
Coal concentration and particle size can be changed depending on the purpose. Naturally, wet powdered coal produced during coal mining and water slurry can also be used. What is the coal-water slurry that is subject to coagulation recovery?
This applies to all water slurries, and the purpose of use of the slurry is not limited. In addition, pulverized coal-water slurry in which coarse particles are removed from the coal-water slurry in advance,
Coal-water slurry with added water or partially dehydrated, etc.
Slurry that has undergone some kind of processing is also eligible. The coal concentration in the coal-water slurry immediately before the aggregation operation may be anywhere from 1 to 65%, preferably from 5 to 50%, and more preferably from 10 to 40%. The oil added to the coal-water slurry is crude oil or various fractions obtained from crude oil, such as kerosene, light oil, A heavy oil, B heavy oil, C heavy oil, etc., tar or shale oil, ethylene cracked residual oil, or various blended oils. Refers to mineral oils such as oils generally used as fuel, lubricating oils, and cleaning oils, and also includes mixtures thereof. Furthermore, oils insoluble in water such as benzene, toluene, xylene, and animal and vegetable oils can also be used. Among these, heavy oils such as C heavy oil, tar, and residual oil are particularly preferred because they are inexpensive. This oil has a 20%
% or less is sufficient, and since the effect of the additive of the present invention is very large, for example, even if the amount is 10% or less,
The lime can be completely agglomerated, so there is no need to add a large amount. Next, the additive of the present invention having a nitrogen atom number of 7 to 200
The alkylene oxide adduct of polyalkyleneimine having 1 to 100 atoms, preferably 9 to 100 atoms, is represented by the following general formula (1), and has a primary amino group, a secondary amino group, and a tertiary amino group in a proportion of about 1:2: Contains at a rate of 1,
It has a branched structure. [In the formula, R and A represent an alkylene group having 2 to 4 carbon atoms. n indicates the degree of polymerization of alkylene oxide corresponding to the molecular weight. x and y represent numbers corresponding to 7 to 200 nitrogen atoms. ] The polyalkylene imine used as the starting material for the alkylene oxide adduct of polyalkylene imine is one having, for example, 70 to 200 nitrogen atoms;
Preferably, it refers to polyethyleneimine, polypropyleneimine, etc. having a molecular weight of 9 to 100. Alkylene oxide refers to, for example, ethylene oxide, propylene oxide, butylene oxide, etc., and it is preferable to copolymerize propylene oxide and ethylene oxide. In the case of copolymerization, either block copolymerization or random copolymerization may be added first, but in order to effectively exhibit surface active ability,
It is more preferable to use block copolymerization. When the alkylene oxide is added, the molecular weight of the resulting polyether compound is from 1000 to 600,000, preferably
The ratio is between 6,000 and 300,000. Preferably, the polyether compound contains ethylene oxide as alkylene oxide, and the content thereof is 3 to 80% by weight of the polyether compound, more preferably 10 to 50% by weight.
% by weight, which provides even better performance. The method for producing an alkylene oxide adduct of a polyalkylene imine is usually carried out by charging a polyalkylene imine as a starting material into an autoclave, and adding an alkylene oxide without a catalyst, using an acid catalyst or a basic catalyst. The additive of the present invention can of course be used alone or in a mixture of the additives of the present invention, but it may also be used in combination with one type or other types of other surfactants. However, in this case, the amount of other surfactants should be less than 50% by weight based on the additive of the present invention. Since the additive of the present invention exhibits a very excellent flocculating effect, the amount added is 0.005 to 1% by weight, preferably 0.01 to 0.5% by weight, based on the coal in the coal-water slurry to be flocculated. The quantity is sufficient. The additive of the present invention may be added directly to the slurry, dissolved in a solvent such as isopropyl alcohol, ethyl cellosolve, butyl cellosolve, etc. and then added to the chiller, or dissolved in the oil used in advance and then added to the slurry. Further, the additive of the present invention may be added together with oil in an O/W type emulsion system. That is, since the effect of the additive of the present invention is excellent, there is no need to particularly limit the method of addition. The effect of the additive of the present invention does not change when the coal-water slurry is used as it is or when an alkali or the like is added to adjust its pH. The basics of the flocculation treatment method are to add oil and additives to the coal-water slurry, or to make a water slurry after treating the coal with oil and additives, followed by stirring. It is easy to operate, and either a batch type or a continuous type may be used. Since the water additive of the present invention exhibits an extremely excellent flocculation effect, there is no need to use a special stirrer, and flocculation can be quickly caused by simply performing low shear stirring with an ordinary stirrer. Since the aggregates are granulated into large particles, they are easily dehydrated by filtration, centrifugation, or the like. In addition,
The ash present in the coal is not aggregated due to the unique effect of the water additive and floats in the water, so it is separated from the coal in this process. Considering the reason why the additive of the present invention exhibits excellent effects, starting material is a polyalkylene imine having 7 to 200 nitrogen atoms, preferably 9 to 100, and alkylene oxide is added to this,
A polyether compound having a molecular weight of 1000 to 600,000, preferably 6000 to 300,000, is produced as shown in the general formula (1) above, and its starting material, polyalkyleneimine, is a general aliphatic amine. On average, there is a branch every third nitrogen atom in the chain. Therefore, polyalkyleneimine contains all of primary amino groups, secondary amino groups, and tertiary amino groups in its molecule, and has a very large number of active hydrogens, 9 or more. Because it has such a branched structure,
The polyether compound obtained by adding alkylene oxide to these starting materials has a bulgy three-dimensional structure and has many adsorption contacts with coal particles, making it easier to capture oil, shortening the aggregation speed and reducing the amount of oil. It is thought that a small amount will have an excellent aggregation effect. In addition, when the polyether compound contains ethylene oxide as an alkylene oxide and the content is 3 to 80% by weight, preferably 10 to 50% by weight based on the polyether compound, the hydrophilic balance is within the optimum range. In this case, it seems to be particularly effective because it pushes the oil most toward the surface of the coal particles. According to the present invention, without complicated operations,
Adding the additive of the invention to a water slurry along with oil;
Just by mixing, it is possible to significantly increase the flocculation of powdered coal and completely recover the coal. Next, typical examples of the present invention will be shown. Example (1) 500g of coal-water slurry having a predetermined coal concentration is placed in a 1000ml glass beaker and mixed using a stirrer with three blades. Add the additives and oil shown in Table 1 to this mixture individually, or add and mix oil in which a predetermined amount of the additives shown in Table 1 are dissolved, or add the additives shown in Table 1 together with the oil. /W
Add and mix in an emulsifying mold. The agglomeration rate was calculated by filtering the coal-water slurry after the aggregation treatment through a 48-mesh sieve, quantifying the agglomerated lime remaining on the sieve after drying, and using the following formula: Aggregation rate (%) = sieve top Coal weight (g)/
Weight of coal in water slurry (g) x 100 The particle size of coal in water slurry before testing is:
200# pass 60%, 48# on0.0%. The above test results are shown in Table 2. As is clear from Table 2, if the additive of the present invention is used in combination with oil,
The flocculation rate was 80% or more, and the amount of oil used was also significantly reduced, proving that the additive of the present invention has an extremely excellent flocculation effect. In addition, the effect is almost the same whether this additive is added in an O/W type emulsified system with oil or without emulsifying oil, and regardless of the method of addition,
It was also demonstrated that the effect of the additive according to the invention is significantly superior. On the other hand, even when ordinary alkylene oxide adducts of aliphatic amines other than those of the present invention are used in combination with oil, the aggregation rate is 80% or more and the amount of oil used is small.
Almost the same effect as the additive of the present invention was observed. Furthermore, even when a cationic surfactant made of an alkylene oxide adduct of an amino compound is made cationic using a cationizing agent, the aggregation rate is low even when used together with oil.
At 80% or more, the same effect as the additive of the present invention was observed. (2) Coal particles agglomerated using the additives shown in Table 1 were filtered through an 8# sieve, and the agglomeration rate was measured in the same manner as above. The test results are also shown in Table 2. As is clear from Table 2, when tested using an 8# sieve,
It was demonstrated that the coal agglomerated using the additive of the present invention has large particles and an agglomeration rate (%) of 80% or more. On the other hand, cationic surfactants made by making alkylene oxide adducts of aliphatic amines and alkylene oxide adducts of amino compounds cationic with a cationizing agent other than those of the present invention have a high aggregation rate (%).
The effect was 60-70%, which was poor. Due to their limited efficacy, these drugs have been demonstrated to have a weak ability to grow into large particles.

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Claims (1)

[Claims] 1. In recovering pulverized coal from a coal-water slurry using oil, a polyalkylene imine having 7 to 200 nitrogen atoms, preferably 9 to 100 nitrogen atoms is used as a starting material, and alkylene oxide is added to this polyalkylene imine. and increase its molecular weight from 1000 to 600,000, preferably from 6000 to
An additive for pulverized coal flocculation characterized by the addition of a 300,000% polyether compound as an essential ingredient. 2. The powdered coal according to claim 1, wherein the polyether compound contains ethylene oxide as the alkylene oxide, and the content thereof is 3 to 80% by weight, preferably 10 to 50% by weight based on the polyether compound. Additive for flocculation.