EP0171602B1 - Aqueous coal dispersions - Google Patents

Description

The invention relates to aqueous, optionally methanol-containing pumpable and flowable coal dispersions with a special nonionic dispersant and the use of a special nonionic dispersant in coal-water dispersions.

Aqueous coal dispersions have become increasingly important in recent times, particularly with regard to their cheap transportation options, e.g. in pipelines.

From US Pat. No. 4,358,293, aqueous carbon dispersions are known which contain higher molecular weight polyalkylene oxides as nonionic surface-active dispersants. Among other things describe polyalkylene oxides of alkylphenols, such as nonylphenoxypolyethylene oxide with more than a hundred ethylene oxide units.

The various surfactants do not prove to be particularly suitable in all cases, i.e. they are not applicable to all types of coal. Furthermore, the dispersants used to date are sometimes difficult to handle because they may have a very slow dissolution rate in water and partially concentrated aqueous solutions cannot be prepared.

DE-OS-2 745 449 and 2 751 519 give polyalkylene oxide derivatives of bisphenol A derivatives, in particular in sulfated form, as dispersants for disperse dyes and for optical brighteners which are difficult or insoluble in water. 10 to 200% by weight of the dispersants mentioned are used, based on the amount of the dispersed substances. Such an amount is completely out of the question, for example, for aqueous coal dispersions.

The object of the present invention is to provide new dispersants for coal dispersions from different types of coal.

It has now been found that non-sulfated polyalkylene oxide bisphenol A derivatives are outstandingly suitable as dispersants for aqueous coal dispersions.

in der R¹ den Rest

und R² bis R⁴ ein Wasserstoffatom oder den Rest R¹ bedeuten und x 0 oder eine Zahl von 5 bis 400, bevorzugt 50 bis 200, und für y eine Zahl von 80 bis 800, bevorzugt 100 bis 400, stehen, wobei die Propylenoxid-Ethylenoxid-Blöcke miteinander vertauscht oder Propylenoxid und Ethylenoxid in statistischer Verteilung vorhanden sein können, enthalten sowie die Verwendung von Verbindungen der Formel I als Dispergiermittel in wäßrigen Kohledispersionen.Accordingly, the invention relates to aqueous, pumpable and flowable coal dispersions containing, in each case based on the total weight, 65 to 80, preferably 70 to 75% by weight of ground coal, 35 to 20, preferably 30 to 25% by weight of water, of which optionally 1 to 60 wt .-% are replaced by methanol, and conventional additives, characterized in that the dispersion 0.1 to 1.5, preferably 0.2 to 1.0 wt .-%, based on the total weight of the mixture , a nonionic dispersant of the formula

in R ¹ the rest

and R ² to R ^{4 represent} a hydrogen atom or the radical R ¹ and x is 0 or a number from 5 to 400, preferably 50 to 200, and y is a number from 80 to 800, preferably 100 to 400, the propylene oxide Ethylene oxide blocks interchanged or propylene oxide and ethylene oxide can be present in a statistical distribution, as well as the use of compounds of the formula I as dispersants in aqueous coal dispersions.

The coal dispersions according to the invention preferably contain a floated, ground coal with a suitable grain size distribution of less than 300 μ.

An exemplary and particularly expedient distribution means 100% less than 300 µ, 80% less than 200 µ and 50% less than 50 µ.

It goes without saying that coal with a high ash content is generally more difficult to disperse than coal with a low ash content. High ash content means approx. 8 to 12%, lower ash content less than 4% ash. The sulfur content of the preferably used floated coal is generally less than 1%.

The pumpable and flowable properties relate to the viscosity of the coal dispersion. As a rule, a dispersion with 2000 mPa.s is just barely flowable. In practice, in order to be able to transport with as little energy expenditure as possible, the desired values are 1000 mPa.s and below. The optimally desired range can be specified with <800 mPas. As shown in the examples, it is easily achieved in the coal dispersions according to the invention.

As already mentioned, 1 to 60% by weight of the water can be replaced by methanol. The addition of methanol serves for the purpose of lowering the viscosity, i.e. better pumpability, the coal dispersions

Temperatures below 0 ° C, for example, down to -20 ° C.

In addition, the coal dispersions according to the invention contain the usual additives known per se to the person skilled in the art:

Foam damper, conventional foam damper such as fatty acid polyalkoxylates, e.g. B. stearyl alcohol propoxylate with 10 to 50 propylene oxide units or silicone oils etc .; as a viscosity regulator soluble inorganic salts, e.g. B. ammonium chloride and carbonate, alkali and alkaline earth metal chloride and carbonate, especially sodium and calcium and magnesium, water-soluble phosphates and silicates, such as sodium hexametaphosphate or sodium metasilicate 9-hydrate; pH regulators, since a pH value of 8 to 10 is particularly expedient for practical use, such as alkali and alkaline earth metal hydroxides, ammonia and primary and secondary amines, stabilizing agents with protective colloid and / or thickening action, and polyethers are suitable for this (e.g. polyethylene oxide, copolymers of polyethylene oxide and polypropylene oxide), carboxymethyl cellulose, hydroxyethyl cellulose, polysaccharides (e.g. alginates), polyalcohols, polyacrylates and copolymers thereof; Biocides may also be mentioned as conventional additives.

The dispersants of the formula are known per se or can be prepared in a conventional manner by the processes described in DE-OS-2 745 449 and 2 751 519.

Particularly preferred dispersants of the formula are those in which x 0 and y are 80 to 400 and in which x is 50 to 150 and y is 200 to 400.

The aqueous coal dispersions are prepared in the customary manner. As a rule, a concentrated aqueous solution which contains 40 to 70% by weight of dispersant according to the invention and which, in contrast to some dispersants of the prior art, can be easily prepared, is added to the required amount of water which, with vigorous rotation, the ground coal and optionally further additives are added.

Examples

• a) 228 g (1 Mol) 4,4'-Dihydroxy-diphenyl-dimethyl-methan, 104 g (1 Mol) Styrol und 1,66 g p-Toluolsulfonsäure als Katalysator werden bei Raumtemperatur vermischt und anschließend erwärmt. Bei ca. 60°C erfolgt die exotherme Reaktion und Temperaturanstieg auf 120 bis 130°C. Bei dieser Temperatur können gegebenenfalls weitere 1 bis 3 Mol Styrol innerhalb von ca. 2 Stunden zugetropft werden. Es wird noch 1 Stunde zur Vervollständigung der Reaktion bei 130°C nachgerührt. Es wird ein rotbraunes, viskoses Öl erhalten, die Ausbeute ist quantitativ.
• b) Das aus der Stufe a) erhaltene Produkt wird mit 1 Gew.-% Kaliumhydroxid versetzt und unter Rühren werden bei 120 bis 130°C portionsweise Propylenoxid und Ethylenoxid, gegebenenfalls in umgekehrter Reihenfolge, so aufgepreßt, daß der Druck 8 bar nicht übersteigt.

I Preparation of dispersants of the formula

• a) 228 g (1 mol) of 4,4'-dihydroxy-diphenyl-dimethyl-methane, 104 g (1 mol) of styrene and 1.66 g of p-toluenesulfonic acid as a catalyst are mixed at room temperature and then heated. At about 60 ° C, the exothermic reaction and temperature rise to 120 to 130 ° C. At this temperature, a further 1 to 3 mol of styrene can optionally be added dropwise within about 2 hours. The mixture is stirred at 130 ° C for 1 hour to complete the reaction. A red-brown, viscous oil is obtained, the yield is quantitative.
• b) The product obtained from stage a) is mixed with 1% by weight of potassium hydroxide and, with stirring, propylene oxide and ethylene oxide are injected in portions at 120 to 130 ° C., optionally in the reverse order, so that the pressure does not exceed 8 bar.

11 application examples

• 70 Gew.-% polnische Importkohle (Steinkohle, flotiert, gemahlen)
• 0,5 Gew.-% Dispergiermittel der Formel gemäß Tabelle 1
• 29,5 Gew.-% Wasser

Composition of the coal-water dispersions:

• 70% by weight Polish imported coal (hard coal, floated, ground)
• 0.5% by weight of dispersant of the formula shown in Table 1
• 29.5% by weight water

The dispersant is dissolved in water and the coal is added with stirring with the aid of a pilot dissolver at about 1000 to 2000 rpm in the course of 3 minutes and then dispersed at 6500 rpm for 20 minutes.

Vergleich

• 1. Ethylendiamin mit 30 % Propylenoxid und 70 % Ethylenoxid MG 15 500 (Tetronic 1307) 460
• 2. Blockpolymerisat aus 20 % Propylenoxid und 80 % Ethylenoxid, MG 8500 (Pluronic 6800) 960
• 3. i-Nonylphenol mit 200 Ethylenoxid 710

The viscosity [mPa.s] is determined with a rotary viscometer at 20 ° C and a shear rate D of 220 s ^-1 .

comparison

• 1. ethylene diamine with 30% propylene oxide and 70% ethylene oxide MG 15 500 (Tetronic 1307) 460
• 2. Block polymer made from 20% propylene oxide and 80% ethylene oxide, MW 8500 (Pluronic 6800) 960
• 3. i-Nonylphenol with 200 ethylene oxide 710

The table shows that a comparison was made with dispersants from US Pat. No. 4,358,293:

The comparison shows that useful values are achieved with alkoxylated ethylenediamine and nonylphenol, but the dispersants of the formula I are always more favorable.

As is known, the alkoxylated ethylenediamines are difficult to handle, and only 17% aqueous solutions can be prepared.

The dispersants according to the invention give 50 to 60% aqueous solutions without difficulty, which is a significant advantage for industrial handling.

Claims (4)

1. An aqueous pumpable free-flowing coal dispersion containing from 65 to 80 % by weight of ground coal, from 35 to 20 % by weight of water, from 1 to 60 % by weight of which may be replaced with methanol, and conventional additives, the percentages in each case being based on the total weight, wherein the dispersion contains from 0.1 to 1.5 % by weight, based on the total weight of the mixture, of a non-ionic dispersant of the formula I

where R¹ is

, R2, R3 and R⁴ and are each hydrogen or R¹, x is 0 or from 5 to 400, and y is from 80 to 800, and the propylene oxide and ethylene oxide blocks may be interchanged, or propylene oxide and ethylene oxide may be present in random distribution.

2. An aqueous coal dispersion as claimed in claim 1, wherein, in the dispersant of the formula I, x is 0 and y is from 80 to 400 or x is from 50 to 150 and y is from 200 to 400.

3. An aqueous coal dispersion as claimed in claim 1 or 2, which contains from 0.2 to 1 % by weight, based on the total weight of the mixture, of a non-ionic dispersant of the formula I.

4. Use of a compound of the formula I as a dispersant in an aqueous coal dispersion in an amount of from 0.1 to 1.5 % by weight, based on the total weight of the mixture.