Patent Publication Number: US-4547199-A

Title: Use of aralkyl polyalkylene glycol ethers for the preparation of aqueous coal slurries

Description:
The invention relates to the use of aralkyl polyalkylene glycol ethers for the preparation of aqueous coal slurries. 
     Slurries of bituminous coal are known from German Auslegeschrift No. 1,141,601. According to this publication, ground bituminous coal can be pumped in the form of aqueous sludges through pipelines to the consumers. Since the conveying capacity depends on the viscosity of the slurry, efforts are being made to reduce the viscosity, while the water content remains the same, by adding surface-active substances or to increase the coal content, while the viscosity remains the same. German Auslegeschrift No. 1,141,601 proposes alkylphenols which are polysubstituted with alkylene oxide and contain, on the nucleus, a saturated or unsaturated, straight-chain or branched hydrocarbon radical with 1 to 30 carbon atoms as surface-active substances. 
     U.S. Pat. No. 4,302,212 suggests alkyl polyethylene glycol ethers having a sulpho group as surface-active substances to solve the same problem. 
     However, the known surface-active substances are unsatisfactory for industrial application, since the viscosities of the aqueous coal slurries thus prepared are too high, especially in the case of relatively high solids contents, to enable the slurries to be used as flowable mixtures in industry. 
     It has been found that aralkyl polyalkylene glycol ethers of the formula ##STR3## in which R 1  represents an optionally substituted aryl radical, 
     R 2  and R 3  are identical or different and denote hydrogen, alkyl or optionally substituted aryl, 
     x represents a number in the range from 1 to 3, 
     y represents a number in the range from 1 to 500, and 
     R 4  denotes hydrogen or one of the radicals ##STR4## in which M.sup.⊖ represents a metal ion or ammonium, 
     R 5  denotes hydrogen, alkyl or optionally substituted aryl and 
     R 6  denotes hydrogen or alkyl, it being possible for the radicals R 6  in the individual chain members of the polyalkylene glycol chain to be identical or different, 
     can be used in aqueous coal slurries. 
     In the context according to the invention, an aryl radical denotes an aromatic hydrocarbon radical from the benzene series with 6 to 18, preferably 6 to 12, carbon atoms. The phenyl, naphthyl and anthracyl radicals may be mentioned in particular. 
     The aryl radical may be optionally substituted. Possible substituents which may be mentioned are, in particular: straight-chain or branched alkyl radicals with 1 to 18, preferably 1 to 12, carbon atoms, aryl with 6 to 18, preferably 6 to 12, carbon atoms, alkoxy with 1 to 18, preferably 1 to 12, carbon atoms and halogen, such as fluorine, chlorine, bromine and iodine, preferably chlorine. 
     Possible substituents of the aryl radical which may be mentioned are, in particular, methyl and ethyl. 
     According to the invention, alkyl denotes a straight-chain or branched hydrocarbon radical with 1 to 18, preferably 1 to 12, carbon atoms. The following alkyl radicals may be mentioned as examples: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl, isohexyl, nonyl, isononyl, octyl, isooctyl and stearyl. 
     Possible metal ions are essentially those ions which form soluble sulphonium or phosphonium salts. Ions which may be mentioned here as preferred are those of the alkali metals, such as sodium and potassium, and of the alkaline earth metals, such as magnesium and calcium, and ammonium. 
     The index x indicates by how many radicals the benzene nucleus is substituted. According to the invention, it is, of course, possible to use pure compounds in which x represents an integer from 1 to 3. However, as a result of the preparation process, it is also possible to use mixtures of the aralkyl polyalkylene glycol ethers according to the invention, in which the statistical average of x can also be a fraction in the range from 1 to 3. According to the invention, aralkyl polyalkylene glycol ethers in which x has a value in the range from 2 to 3 are particularly preferred. 
     The index y indicates the length of the polyalkylene glycol chain. The polyalkylene glycol chain in general consists of 1 to 500 units. As a result of the preparation process, it may of course be that the statistical average of y also assumes a fraction value. y preferably has a value of 10 to 250, and particularly preferably a value of 30 to 150. 
     R 6  as a substituent of the polyalkylene glycol chain can denote hydrogen or lower alkyl (C 1  to about C 6 ). It is possible for the radicals R 6  in the polyalkylene glycol chain to have different meanings and to be distributed randomly or in blocks. 
     According to the invention, aralkyl polyalkylene glycol ethers of the formula ##STR5## in which R 9  denotes phenyl which is optionally substituted by lower alkyl radicals, 
     R 10  and R 11  are identical or different and denote hydrogen or methyl, 
     x&#39; represents a number in the range from 2 to 3, 
     y&#39; represents a number in the range from 10 to 250, 
     R 8  denotes hydrogen, --SO 3  NH 4 , --SO 3  Na or --SO 3  K and 
     R 12  denotes hydrogen, methyl or ethyl, 
     are preferred. 
     The aralkyl polyalkylene glycol ethers according to the invention are known per se (German Auslegeschrift No. 1,121,814 and German Pat. No. 851,858) and they can be obtained, for example, by polyaddition of alkylene oxide onto aralkyl-substituted phenols and, where appropriate, by reaction of the resulting compounds with anhydrides or acid chlorides of sulphuric or phosphoric acid and subsequent neutralisation of the monoester. 
     The following aralkyl polyalkylene glycol ethers are particularly preferred: di-[phenethyl]-phenyl polyalkylene glycol ethers, tri-[phenethyl]-phenyl polyalkylene glycol ethers, di- and tri-[methylphenethyl]-phenyl polyalkylene glycol ethers and di-[phenethyl]-isooctyl or -[isononyl]-phenyl polyalkylene glycol ethers, wherein the polyalkylene glycol ether chains can consist of polyethylene oxides, random polyethylenepolypropylene oxide copolymers or polyethylenepropylene oxide block copolymers. 
     The aralkyl polyalkylene glycol ethers according to the invention are water-soluble. They are in general used in aqueous solution. 
     The compounds according to the invention are in general handled in aqueous solution in a concentration of 10 to 60% by weight, preferably 20 to 50% by weight, relative to the total solution. In the preparation of the mixtures according to the invention, this solution can then be further diluted to the desired concentration. However, the solid compounds can also be used, in the form of flakes or small beads. 
     It may be advantageous, especially with high concentrations of the aqueous aralkyl polyalkylene glycol ethers, also to add other organic solvents to reduce the viscosity and thus to facilitate application. Possible solvents are all the water-miscible solvents. Examples which may be mentioned are: lower aliphatic alcohols (C 1  to about C 6 ), such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol and isohexanol. 
     If additional organic solvents are used, these are in general employed in an amount of 5 to 40% by weight, preferably of 10 to 25% by weight, relative to the solution of the compounds according to the invention. 
     According to the invention, coal means mineral and processed coal. The following types of coal may be mentioned as examples: anthracite, coke, lignite, moor coal and, in particular, bituminous coal. 
     According to the invention, coal also includes pure carbon in the graphite modification. 
     The coal can be used in various particle sizes. Finely ground coal with a particle size of less than 300μ is preferred. A coal powder containing up to 75 to 100% by weight of particles which are smaller than 100μ is particularly preferred. 
     The aqueous coal slurries according to the invention contain the coal in an amount of 30 to 85% by weight, preferably 55 to 80% by weight. 
     The aqueous coal slurries according to the invention contain the aralkyl polyalkylene glycol ether in an amount of 0.01 to 5% by weight, preferably 0.2 to 2.0% by weight. 
     It is possible for the aqueous coal slurries according to the invention also to contain further amounts of other fuels. Examples of other fuels are heating oil, naphtha, crude oil, methanol and ethanol. It is thus possible, for example, for the aqueous coal slurries according to the invention to contain 1 to 60 parts by weight, preferably 1 to 30 parts by weight, of petroleum products. 
     The aqueous coal slurries according to the invention can be prepared by various processes. 
     Thus, it is possible first to prepare an aqueous solution of the aralkyl polyalkylene glycol ether and then to add the coal powder, while stirring. 
     According to another process variant, the aqueous solution of the aralkyl polyalkylene glycol ether is first mixed with coarse-particled coal and this mixture is then ground to a particle size of at most 300μ. 
     Compared with the known aqueous coal slurries, the aqueous coal slurries according to the invention have improved flow properties. This means that the mixtures contain more coal, while the viscosity remains the same, than the known aqueous coal slurries. 
     Coal water slurries are non-Newtonian plastic liquids with pseudoplastic behaviour and yield stress. Their viscosity depends on the shear rate (apparent viscosity). The viscosities of the coal water slurries according to the invention range from 3 mPa.s to 5000 mPa.s, preferably from 5 to 2000 mPa.s, at a shear rate of 225 s -1 . 
     In addition to the flow properties, the storage properties of the aqueous coal slurries according to the invention are particularly favourable. It is thus possible easily to start the aqueous coal slurries according to the invention moving again, even after storage, and to prevent cementing on temporary settling of the coal. This is particularly advantageous both during transportation and during combustion or further processing of the mixtures. 
     The aqueous coal slurries according to the invention can be fed directly, without further preparation, to combustion, for example in district heating power stations. 
     PREPARATION OF THE POLYGLYCOL ETHERS 
    
    
     Example 1 
     94 g of phenol are reacted with 208 g of styrene in the presence of 1 g of p-toluenesulphonic acid at a temperature rising from 130° to 160° C. After a postreaction of 1 hour at 150° to 160° C., the mixture is cooled to 120° C. 3 g of powdered potassium hydroxide are added and the mixture is heated in order to dry it and to prepare the potassium phenolate. 3,520 g of ethylene oxide are metered into the reaction chamber, which has been gassed with nitrogen, at 130° to 160° C. The reaction product is a water-soluble, yellowish wax which has a melting point of 48° to 50° C. 
     Example 2 
     1,160 g of propylene oxide and then 3,520 g of ethylene oxide are added onto the aralkylphenol from Example 1, under the same conditions as described in that example. The reaction product is water-soluble and gives a 30 to 40% strength aqueous solution with no gel formation. 
     Example 3 
     94 g of phenol are reacted with 318 g of methylstyrene in the presence of 1 g of p-toluenesulphonic acid at a temperature rising from 130° to 160° C. After a postreaction of 1 hour at 150° to 160° C., the mixture is cooled to 120° C. 3 g of powdered potassium hydroxide are added and the mixture is heated in order to dry it and to form the potassium phenolate. 4,400 g of ethylene oxide are metered into the reaction chamber, which has been gassed with nitrogen, at 130° to 160° C. 
     The product is readily water-soluble and, at normal temperature, is waxy with a melting point of 58° C. 
     Example 4 
     108 g of cresol (technical grade mixture) are reacted with the same amounts of styrene and ethylene oxide under the conditions in Example 1. A water-soluble wax with a melting point of 45° to 47° C. is obtained. 
     A ready-to-use solution can be prepared with 55 g of this compound and 30 g of water and 15 g of methanol. 
     Example 5 
     To prepare an iso-alkyl-substituted product, 220 g of isononylphenol are reacted with 188 g of styrene and 4,400 g of ethylene oxide under the conditions in Example 1. The readily water-soluble wax has a melting point of 43° to 46° C. 
     Example 6 
     470 g of the product from Example 3 are dried at 100° C. in vacuo. A mixture of 6 g of urea and 10 g of amidosulphonic acid is then added at 75° C., and the mixture is heated, with thorough stirring, at 90° C. for 1 hour and at 100° to 105° C. for 6 hours. The mixture is then adjusted to pH 7 to 8 (measured in 10% strength aqueous solution) with about 0.5 to 1 ml ammonia solution. This product can be formulated, without a solvent, into a 60% strength aqueous solution. 
     USE EXAMPLES 
     Example 7 
     Bituminous coal having the following properties was used: 
     
         ______________________________________                                    
Carbon          82%                                                       
Hydrogen       4.5%                                                       
Nitrogen       1.1%                                                       
Oxygen         2.6%                                                       
Sulphur        1.2%                                                       
Total moisture 4.2%                                                       
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Sieve analysis (sieve residue)                                            
______________________________________                                    
192 μm        0%                                                       
 96 μm        9%                                                       
 64 μm       17%                                                       
 48 μm       24%                                                       
 24 μm       47%                                                       
 10 μm       59%                                                       
 8 μm        78%                                                       
 2 μm        93%                                                       
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     PREPARATION OF THE AQUEOUS COAL SLURRY 
     2.25 g of aralkyl polyalkylene glycol ether according to Example 3 (additive) were dissolved in 132.45 g of water. 365.3 g of the abovementioned finely ground coal (that is to say 350 g of dry coal) were added, while stirring. An aqueous coal slurry with a viscosity of 670 mPa.s was formed. The viscosity was measured at 20° C. using a Haake viscosimeter (MV II PSt measuring body); the viscosities given were determined at a shear rate D of 225 s -1 . Slurries having the following properties were obtained by varying the concentrations of coal or the amount of compound according to the invention (percentages relate to the total mixture): 
     
         ______________________________________                                    
                          Viscosity                                       
% of coal      % of additive                                              
                          [mPa · s]                              
______________________________________                                    
30             0.20          4                                            
50             0.30         36                                            
70             0.45         670                                           
72             0.45         960                                           
72             0.30       1,420                                           
74             0.55       2,390                                           
76             0.65       2,690                                           
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     Comparison Example 
     0.45% by weight of a stearyl alcohol polyethylene glycol ether (degree of polyaddition: 100) according to U.S. Pat. No. 4,302,212 was used, under otherwise identical conditions. A 72% strength coal slurry with a viscosity of 1,100 mPa.s was obtained. 
     Example 8 
     Bituminous coal having the following properties was used: 
     
         ______________________________________                                    
Carbon         68.2%                                                      
Hydrogen       4.3%                                                       
Nitrogen       1.4%                                                       
Oxygen         9.2%                                                       
Sulphur        0.9%                                                       
Total moisture 7.9%                                                       
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Sieve analysis (sieve residue)                                            
______________________________________                                    
192 μm        0%                                                       
 96 μm       11%                                                       
 48 μm       31%                                                       
 24 μm       53%                                                       
 16 μm       63%                                                       
 8 μm        78%                                                       
 2 μm        94%                                                       
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     Preparation and measurement of the slurries was carried out as described in Example 7. The aralkyl polyalkylene glycol ether according to Example 3 was used (additive). 
     Slurries having the following properties were obtained: 
     
         ______________________________________                                    
                          Viscosity                                       
% of coal      % of additive                                              
                          [mPa · s]                              
______________________________________                                    
69             0.40       1,060                                           
69             0.50         810                                           
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     The chain length (y) of the ethylene oxide adduct according to Example 3 was varied (69% of coal; 0.5% of additive). 
     
         ______________________________________                                    
y          Viscosity [mPa · s]                                   
______________________________________                                    
16         2,000                                                          
27         1,120                                                          
50         840                                                            
75         800                                                            
100        810                                                            
125        960                                                            
150        1,090                                                          
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     Comparison Examples 
     A nonylphenol polyethylene glycol ether (y=30) according to German Auslegeschrift No. 1,141,601 was used. The viscosity of the slurry was 1,320 mPa.s. 
     When a stearyl alcohol polyethylene glycol ether (y=50) according to U.S. Pat. No. 4,302,212 was used, a slurry with a viscosity of 980 mPa.s was obtained, under otherwise identical conditions. 
     Example 9 
     Bituminous coal having the following properties was used: 
     
         ______________________________________                                    
Carbon         77.4%                                                      
Hydrogen       4.2%                                                       
Nitrogen       1.5%                                                       
Oxygen         4.1%                                                       
Sulphur        0.9%                                                       
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Sieve analysis (sieve residue)                                            
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192 μm       6%                                                        
128 μm      21%                                                        
 96 μm      26%                                                        
 64 μm      41%                                                        
 48 μm      51%                                                        
 24 μm      76%                                                        
 8 μm       95%                                                        
 2 μm        0%                                                        
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     An aralkyl polyalkylene glycol ether according to Example 3 (additive) was used. The slurry was prepared as described in Example 7. 
     Slurries having the following properties were obtained (0.5% of additive): 
     
         ______________________________________                                    
           Viscosity                                                      
% of coal  [mPa · s]                                             
______________________________________                                    
30          5                                                             
50          42                                                            
68         390                                                            
70         620                                                            
72         950                                                            
74         1,180                                                          
76         2,200                                                          
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     Effect of the temperature and the pH value (70% of coal, 0.5% of emulsifier): 
     
         ______________________________________                                    
             Viscosity [mPa · s]                                 
______________________________________                                    
T =        10° C.                                                  
                   680                                                    
           20° C.                                                  
                   620                                                    
           30° C.                                                  
                   490                                                    
pH =        7      620                                                    
            9      610                                                    
           11      550                                                    
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     Example 10 
     The procedure followed was as in Example 7, but the aralkyl polyalkylene glycol ether according to Example 6 was used (0.5% of additive). Coal slurries having the following properties were obtained: 
     
         ______________________________________                                    
Type of coal   % of coal  Viscosity [mPa · s]                    
______________________________________                                    
Bituminous coal                                                           
               72         1,020                                           
according to Example 7                                                    
Bituminous coal                                                           
               69           910                                           
according to Example 8                                                    
Bituminous coal                                                           
               72         1,050                                           
according to Example 9                                                    
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     Example 11 
     An aralkyl polyalkylene glycol ether according to Example 5 (additive) was used to prepare a slurry. A slurry having the following properties was obtained, under conditions otherwise identical to those described in Example 7: 
     
         ______________________________________                                    
% of coal   % of additive                                                 
                       Viscosity (mPa · s)                       
______________________________________                                    
70          0.45         720                                              
72          0.45       1,020                                              
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     Example 12 
     An aralkyl polyalkylene glycol ether according to Example 1 (additive) was used to prepare a slurry. Slurries having the following properties were obtained under conditions otherwise identical to those described in Example 7: 
     
         ______________________________________                                    
% of coal   % of additive                                                 
                       Viscosity (mPa · s)                       
______________________________________                                    
70          0.55         710                                              
72          0.55       1,010                                              
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     Example 13 
     The procedure followed was as described in Example 7 or 8, but some of the water was replaced by methanol. Slurries having the following properties were obtained: 
     
         ______________________________________                                    
               % of                                                       
               additive                                                   
               according  % of                                            
       % of coal                                                          
               to Example 3                                               
                          methanol Viscosity                              
______________________________________                                    
(according to                                                             
         72        0.45       10     940                                  
Example 7)                                                                
(according to                                                             
         67        0.45        0     960                                  
Example 8)                                                                
(according to                                                             
         67        0.45       10     820                                  
Example 8)                                                                
(according to                                                             
         67        0.45       33     870                                  
Example 8)                                                                
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     Example 14 
     An aralkyl polyalkylene glycol ether according to Example 2 (additive) was used to prepare a slurry. Slurries having the following properties were obtained under conditions otherwise identical to those described in Example 9: 
     
         ______________________________________                                    
% of coal   % of additive                                                 
                       Viscosity (mPa · s)                       
______________________________________                                    
68          0.55       400                                                
70          0.55       630                                                
72          0.55       980                                                
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