JPS61238888A - Dispersion stabilizer for coal-water slurry - Google Patents

Abstract

PURPOSE:To provide the titled dispersion stabilizer capable of improving stationary stability and flowability, which comprises as an essential ingredient a polymer obtained by polymerizing an unsaturated carboxylic acid, alpha,beta-ethylenically unsaturated monomer, etc., using an org. thiol compd. as a chain transfer agent. CONSTITUTION:At least one monomer selected from among an unsaturated monocarboxylic acid (or its derivative) (A) (e.g.: acrylic acid), an alpha,beta-unsaturated dicarboxylic acid (B) (or its derivative) (e.g.: maleic acid) and an alpha,beta- ethylenically unsaturated monomer (C) other than the components (A) and (B) (e.g.: vinyl acetate) is provided. At least one monomer is (co)polymerized using an org. thiol compd. (e.g.: n-octyl mercaptan) of the formula R-SH (wherein R is a straight-chain or branched 8-24C alkyl, aryl etc.). The (co)polymer (salt) is incorporated as an essential ingredient to obtain an intended dispersion stabilizer for a coal-water slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a dispersion stabilizer for a water slurry of coal powder. More specifically, the present invention relates to a dispersion stabilizer for dispersing coal powder in water and stabilizing the dispersion to a state suitable for pipeline transportation.

[Conventional technology and problems]

In recent years, petroleum, which has been the most commonly used energy source, has reached the limit of its reserves and its price has skyrocketed, so diversifying energy sources and securing a stable supply have become important issues. There is. For these reasons, the effective use of coal, which has large reserves and is not unevenly distributed around the world, is being reconsidered. However, unlike petroleum, coal is a solid substance, so it is impossible to transport it by pipeline, and it is extremely disadvantageous in terms of handling. Furthermore, compared to petroleum, coal generally contains a large amount of ash, and has problems such as a decrease in calorific value and the disposal of fly ash.

In order to improve these handling disadvantages, various methods have been studied in which coal is pulverized and dispersed in water to form a slurry. However, in this case as well, if the coal concentration is increased, the coal will significantly thicken and lose fluidity, and if the coal concentration is decreased, the transportation efficiency will decrease and the dewatering process will also be costly, which is not practical. This is because the coal particles in the coal-water slurry aggregate in water, causing an increase in viscosity and a decrease in fluidity. The smaller the coal particles in the water slurry, the better the dispersion stability, but the cost of pulverization increases as the degree of pulverization increases. Currently, the amount of pulverized coal being burned in thermal power plants is 200 mesh, 80% pass,
That is, since the particle size is about 74 microns, it is expected that this particle will be used as a standard for the particle size of pulverized coal. When a surfactant, which is a dispersant, is added to the coal-water slurry, the surfactant adsorbs to the interface between the coal particles and water, and has the effect of loosening the coal particles and preventing them from agglomerating together. It is expected that this will lead to the creation of a good dispersion state.

The present inventors have already developed a dispersant that has such an effect (Japanese Patent Application Laid-open No. 56-20090, JP-A No. 56-216).
56. 56-57889. 56-57890. Same 5
6-57891).

However, although such a dispersant improves fluidity, if it is allowed to stand still, the sediment becomes compacted and forms a hard coo.
In practical terms, this was not necessarily satisfactory.

[Means for solving problems]

The present inventors conducted intensive research to improve the stationary stability and fluidity of the conventional coal-water slurry, and found that it contains an organic hydrophobic group such as a straight-chain alkyl group at the end of the molecular chain. The present invention was completed by discovering that a specific hydrophilic polymer is a dispersant stabilizer that has excellent effects on static stability and fluidity.

That is, the present invention provides a compound represented by the general formula (wherein R is a linear or branched alkyl group having 8 to 24 carbon atoms, or an aryl group or an arylalkyl group that may have an alkyl substituent.) A (co)polymer obtained by (co)polymerizing one or more selected from the group consisting of (b) to (d) below using an organic thiol compound (component a) as a chain transfer agent or a salt thereof is essential. The present invention provides a dispersion stabilizer for coal water slurry as a component.

(1)) Unsaturated monocarboxylic acid monomers, esterified products or amidated products thereof.

(Q) α,β-unsaturated dicarboxylic acid monomers, esterified products or amidated products thereof.

(d) α, β-ethylenically unsaturated monomers other than (1) I (0) above.

The dispersion stabilizer of the present invention is effective not only for ordinary coal but also for coal demineralized by flotation or underwater granulation.

The organic thiol compound as component (a) of the present invention is n
-octymerkabutane, t-octylmercaptan, n
-dodecylmercaptan, 1-dodecylmercaptan,
Alkyl mercaptan having a straight chain or branched alkyl group having 8 to 24 carbon atoms, such as n-tetradecyl mercaptan, or benzyl mercaptan, butylbenzyl mercaptan, n-octylbenzyl mercaptan, n-dodecylbenzyl mercaptan, t Examples include aromatic mercaptans that may have an alkyl group as a substituent, such as -dodecylbenzylmercaptan.

(1)) The unsaturated monocarboxylic acid monomers, their esterified products or amidated products include acrylic acid, methacrylic acid, or their esterified products such as methyl acrylate, ethyl acrylate, butyl acrylate, Octyl acrylate, lauryl acrylate, octadecyl acrylate, methyl methacrylate, ethyl methacrylate,
Examples include butyl methacrylate, octyl methacrylate, lauryl methacrylate, octadecyl methacrylate, and amidated products such as acrylamide and methacrylamide. Among these, acrylic acid and methacrylic acid are particularly preferred.

(c) Acid component α, β-unsaturated dicarboxylic acid monomers, esterified products or amidated products thereof include maleic anhydride, maleic acid, fumaric acid, itaconic acid, or maleic acid monomers which are esterified products thereof. butyl ester,
Maleic acid monooctyl ester, maleic acid cyphthyl ester, maleic acid dilauryl ester, itaconic acid butyl ester, or amidated products thereof, i.e., monooctyl maleate, monolauryl maleate, and the like. Among them, especially maleic anhydride,
Maleic acid etc. are preferred 0 (cl) component α other than the above (1)), (0),
Examples of β-ethylenically unsaturated monomers include vinyl acetate, vinyl chloride, olefins such as hasycyclopentene, dicyclopentadiene, butylene, pentene, diisobutylene, octene, and decene, and aromatic ring-containing vinyl monomers such as styrene. , or a vinyl monomer containing a sulfonic acid group such as vinyl sulfonic acid, styrene sulfone full, 2-7-9ylamido-2-methylpropanesulfonic acid, or acrylonitrile, methacrylonitrile, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, allyltriethyl Examples include ammonium chloride and methallyltriethylammonium chloride. Among these, acrylonitrile, methacrylonitrile, or a sulfonic acid group-containing vinyl monomer is particularly preferred.

The (co)polymer or salt thereof of the present invention is an essential component (a3 component compound is used as a chain transfer agent, (b) t (
c) One or more selected from I (+1) components in the presence of a peroxide or an azo catalyst, isopropyl alcohol,
It can be obtained by polymerizing by a known method in an organic solvent such as methanol or ethanol or a mixed solvent of these and water, and if necessary, further subjecting them to a salt-forming reaction.

In the (co)polymer or salt thereof of the present invention, the essential (a) component and the other (1)) l (0) * (c
In order to maximize the ability to stabilize the dispersion of coal particles, the molar ratio of the monomers of component L) should be (a) component compound/(1
:+).

(c) l (d) One or more component compounds; 115-1
/100 is preferable, more preferably 1/10 to 115
It is 0. The average molecular weight is adjusted by the amount of component (a) or other chain transfer agents, but is preferably 500 or more, more preferably 1000 to 10,000.
It is in the range of 0. Molecular weight is determined by gel permeation chromatography (GPC).

Preferred salts of the (co)polymer of the present invention include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as magnesium and calcium, ammonia, and amine salts.

Various studies have been made on vinyl polymer-based coal water slurry additives similar to the (co)polymer of the present invention or their salts (JP-A-56-57'889;
-57890, 5657891, 59-68592
, 59-68595, 59-86694. Same 59-
120232, 59-120253, 59-122
0234, 59-108092, 59-108 (1
93, 59-108094, 59-108095
(issues of each publication). However, these additives have disadvantages in that they require a large amount to be added and are insufficient in terms of fluidity and stabilizing effect on the slurry. In addition, it is absolutely necessary that the coal-water slurry maintains its fluidity and stability from the time it is produced until it is burned in the boiler.
The present inventors have discovered that the additives developed so far are extremely vulnerable to the high temperature shear forces that are expected to be experienced by the slurry during boiler combustion. i.e. 20-3
It has the disadvantage that when a slurry that is extremely fluid and easy to draw at 0°C is heated to 50 to 60°C and subjected to shearing force, it instantly loses its fluidity and turns into a gel. Therefore, in a slurry containing such additives, when the coal particles agglomerate during boiler combustion, which is heated to 50 to 60°C and sprayed with high shear force, the K
The combustion efficiency is very poor (a large amount of unburned coal particles remain). Therefore, the present inventors endeavored to develop a dispersion stabilizer for coal water slurry that does not lose fluidity even under high-temperature shear. They have discovered that by adding these compounds or their salts, they do not lose their fluidity even under high-temperature shearing stress, and exhibit an extremely excellent synergistic effect in terms of stability.

The dispersion stabilizer of the present invention has a concentration of 0.0 to the water slurry.
1-5.0% by weight, preferably 0.05-2.0% by weight
By adding it, the coal particles can be dispersed in the water.

The fluidity of a coal-water slurry generally varies depending on the type and particle size of the coal powder, but when no dispersion stabilizer is added, the viscosity increases rapidly when the coal concentration exceeds 50% by weight. On the other hand, when a predetermined amount of the dispersion stabilizer of the present invention is added, coal particles are dispersed, fluidity is significantly improved, and a highly concentrated slurry can be obtained. A slurry with excellent storage stability that does not form can be obtained. If the concentration of coal constituting the coal-water slurry is too low, the transportation efficiency will be poor and the dewatering process will be expensive, making it meaningless. Also, if it is too large, the viscosity will be too high, so
Although it varies depending on the type and viscosity of the coal, it is generally 30 to 85% by weight, preferably 50 to 78% by weight.

The coal used in the present invention may be of various types such as anthracite, bituminous coal, sub-bituminous coal, lignite, etc., and is used after being pulverized. The particle size of this coal powder may be any particle size that allows direct combustion in the boiler, but the general particle size currently used in thermal power plants for this purpose is 200 mesh with a pass rate of 70 to 90%. It is of granularity.

Any mixed layer of coal, dispersion stabilizer, and water may be used, but the dispersion stabilizer may be dissolved or dispersed in water, coal may be added thereto, and the layer may be prepared using a suitable mixing device or crushing device.

The dispersion stabilizer of the present invention is similar to other known dispersion stabilizers for coal water slurry (JP-A-52-71506, JP-A-56-2).
1656, 56-20090, 56-126891
, 56-115192, 56-57889, 56
-57890, 56-57891, 54-6255
8, No. 56-147595, and No. 56-102994) and other anionic, cationic, nonionic, or amphoteric surfactants can be used in combination. Specifically, "Surfactant Handbook" (Kogaku Tosho Publishing, Takahashi,
Even better dispersion ability may be obtained by using a small amount of any of the surfactants described in Synergy et al., pages 16 to 23. In the slurry, fatty acids such as oleic acid, phosphate esters such as tributyl phosphate, metal soaps such as aluminum stearate, aliphatic alcohols having 6 to 12 carbon atoms, sorbitan fatty acid esters, or polydimethylsiloxane,
By adding a silicone compound such as dimethyl silicone oil or fluorosilicone oil, a stable slurry with less air bubbles can be obtained.

Furthermore, even better stabilizing ability may be obtained by using together a thickener such as a natural polymer such as xanthan gum or guar gum, or a modified cellulose derivative (carboxymethyl cellulose, hydroxyethyl cellulose, etc.).

Currently, consideration is being given to removing the ash from coal using various methods and burning it as a deashed coal-water slurry in a heavy oil-fired boiler. Coal deashing methods in this case include a method that applies the principle of flotation and uses scavenging agents and foaming agents to collect coal by keeping it in ash-containing water and adsorbing it to foam, and a method that uses oil or emulsion in coal slurry. An underwater granulation method in which coal is selectively granulated and recovered by adding and stirring coal (for example, Japanese Patent Application Laid-Open No. 52-3
No. 7910) is attracting attention. The dispersion stabilizer of the present invention exhibits extremely good dispersion stability even in coal slurry deashed by such a method. However, the dispersion stabilizer of the present invention exhibits excellent performance without losing its dispersion effect even in systems where such hydrocarbon oils coexist.

The water slurry of coal powder obtained by adding the dispersion stabilizer invented by the US has a small increase in viscosity even at high concentrations, has good fluidity, does not lose fluidity even under high temperature shear stress, and can last for a long time. In order to maintain good dispersion stability without forming a hard cake even after storage, the coal powder obtained using the dispersion stabilizer of the present invention can be transported by pipeline, stored at the foot of a tank, or directly burned in a boiler. The water slurry has few bubbles during production, the increase in volume of the slurry is small, and thickening due to air bubbles is prevented, so that it can have good properties.

[Action/Effect]

The mechanism of how the (co)polymer of the present invention or its salt exhibits the excellent effects of the present invention is not necessarily clear, but the It is thought that the organic hydrophobic group has an affinity for coal particles and does not affect the dispersibility of the polymer itself, so it exhibits excellent dispersibility even at high temperatures. Therefore, in the present invention, the hydrophobic group (R-) of the organic thiol compound that is component (a) may have a straight or branched alkyl group having 8 to 24 carbon atoms, or an alkyl substituent, as described above. It is important that it is a certain aryl group or arylalkyl group, and if it is off, the effect of the present invention will not be obtained.
extremely critical.

〔Example〕

The present invention will be specifically explained below by way of examples, but the present invention is not limited to these examples.

Examples 1-18. Comparative Examples 1 to 9 (1) Deashed coal preparation method 1) Deashed coal manufacturing method by underwater granulation method Belmont coal with the following composition of 200 mesh 80% pass 428 t (contains 7.0% moisture) Therefore, 400 t of pure coal is dispersed in water at room temperature and stirred to obtain a coal-water slurry. Add 2 parts of heavy oil A to this mixture.
In addition to 02, lab body spar at room temperature (Tokushu Kikako East)
The mixture was stirred at 11,000 rpm for 30 minutes to decalcify and granulate it.

The mixture thus obtained was passed through an 8-mesh sieve to remove the ash and dried at 105°C to obtain deashed, dehydrated, and granulated material (referred to as deashed coal A). The residual ash content of this product was 4.8 wt% (based on coal).

11) Method for producing deashed coal by flotation method Similar to 1), 428 t of Belmont coal is dispersed in water at room temperature, and placed in the F-WJ flotation machine together with 0.5 t of pine oil for flotation treatment. Then, the deashed coal slurry collected together with the foam is dehydrated under reduced pressure to obtain deashed coal B. The residual ash content of this product was 4.0 wt% (based on coal).

Jail 1 Persevent coal calorific value 6900 kQal/kl (J Engineering 8M881
4) Ash content 7.1% (1 bulb M8812) Moisture 5.0% (J Engineering EIM8811) Fixed carbon 59
．． 7% (J Engineering S M 8812) Table 1 Test coal list (2) Water slurry preparation and fluidity evaluation table 20 Tomb 1 Compound 1.96f was dispersed in 87.6 tons of water and this mixture was added to Table 1. Test coal A1 Pelmont coal 410.5F
was added little by little at room temperature. After the entire amount was added, the mixture was stirred for 5 minutes at 5000 rpm using a homo mixer (Tokushu Kikako Tobu) to prepare a coal-water slurry.

When the viscosity was measured at 20° C., it was found to be 850 centivoids, and the fluidity was good. Add this slurry to 60
While keeping the temperature at 60°C, the viscosity was measured at 60°C after stirring for 5 minutes using sooOrpm. The result was 900 centivoids and good fluidity.

The results are shown in Tables 5 and 4, including examples and comparative examples, using the test coal shown in Table 1 and the dispersion stabilizer shown in Table 2 under the same conditions.
Shown below.

(3) Evaluation of stability of water slurry The stability of the slurry was determined by keeping the slurry in a cool place for 30 days after production, and then gently inserting a stainless steel rod (50f) in diameter into the slurry to observe its sedimentation state. The slurry prepared in (2) had good stability), and even after 30 days, there was almost no consolidation in #1. The results, including other examples and comparative examples, are shown in Tables 3 and 4.
It is ℃.

Claims (1)

[Scope of Claims] 1 General formula R-SH (wherein R is a linear or branched alkyl group having 8 to 24 carbon atoms, or an aryl group or arylalkyl group that may have an alkyl substituent) A (co)polymer obtained by (co)polymerizing one or more types selected from the group consisting of (b) to (d) below using an organic thiol compound (component a) represented by (a) as a chain transfer agent, or a (co)polymer thereof. A dispersion stabilizer for coal water slurry that contains salt as an essential ingredient. (b) Unsaturated monocarboxylic acid monomers, esterified products or amidated products thereof. (c) α,β-unsaturated dicarboxylic acid monomers, esterified products or amidated products thereof. (d) α,β-ethylenically unsaturated monomers other than the above (b) and (c).