Abstract:
A process for preparing a solution of a liquid additive in a liquid base wherein the liquid additive tends to gel when mixed with the liquid base at temperatures less than a gelling temperature T G  includes the steps of providing a stream of the liquid base at a temperature T C  which is greater than ambient temperature and less than the gelling temperature T G ; feeding the stream to a mixer having a mixer inlet so as to impart energy to the stream; and adding the liquid additive to the stream downstream of the inlet, whereby the liquid additive mixes with the liquid base and the energy inhibits gelling of the liquid additive.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a process for preparing solutions with additives and surfactants and, more particularly, to a process effective in preparing such solutions where one or more additives have a tendency to gel. 
     Numerous industrial processes require additives for various purposes. These additives may be provided commercially at high concentrations, and are then typically diluted with a liquid base such as water to the desired concentration for use. 
     However, simple dilution of such additives are not always effective since some additives have a tendency to gel when directly mixed with water. Such additives have a gelling temperature profile, and gelling is particularly problematic when the mixture is carried out below the gelling temperature. 
     Surfactants are one type of additive, for example as can be used to manufacture emulsions and the like, which has a tendency to gel when mixed with water below the gelling temperature of the surfactant. This makes difficult the use of such additives in industrial processes and poses a problem for which a solution is needed. 
     It is therefore the primary object of the present invention to provide a process for effectively mixing a liquid additive with a liquid base without gelling. 
     It is a further object of the present invention to provide such a process which utilizes inexpensive and reliable equipment, and which can be readily installed in various industrial locations. 
     Other objects and advantages of the present invention will appear hereinbelow. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, the foregoing objects and advantages have been readily attained. 
     According to the invention, a process is provided for preparing a solution of a liquid additive in a liquid base wherein the liquid additive tends to gel when mixed with the liquid base at temperatures less than a gelling temperature T G , which process com rises the steps of providing a stream of said liquid base at a temperature T C  which is greater than ambient temperature and less than said gelling temperature T G ; feeding said stream to a mixer having a mixer inlet so as to impart energy to said stream; and adding said liquid additive to said stream downstream of said inlet, whereby said liquid additive mixes with said liquid base and said energy inhibits gelling of said liquid additive. 
     This process is particularly effective for preparing solutions of surfactants in water, wherein the surfactant has a tendency to gel at typical ambient temperatures. One such surfactant is ethoxylated nonylphenol, among others. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A detailed description of preferred embodiments of the present invention follows, with reference to the attached drawings, wherein: 
         FIG. 1  schematically illustrates a process in accordance with the present invention; 
         FIG. 2  illustrates the gel temperature profile for a typical surfactant material at different concentrations in water; 
         FIG. 3  illustrates a heat-only process that can be used to avoid gelling; 
         FIG. 4  illustrates a preferred embodiment of the present invention wherein some heat is applied, and mixing energy is used to avoid gel formation; and 
         FIG. 5  schematically illustrates a preferred mixture in accordance with the present invention, along with preferred placement of an additive injector. 
     
    
    
     DETAILED DESCRIPTION 
     The invention relates to a process for preparing solutions of additives and surfactants wherein heating and a static mixer are used to avoid gel formation of the additives. 
     As set forth above, numerous additives are provided at high concentration and, when diluted or added to water or other liquid bases, such additives have a tendency to form gels which interfere with effective mixing. 
       FIG. 1  schematically illustrates a process wherein several additives  10 ,  12 ,  14  are to be added to a stream  16  of water. In accordance with this embodiment of the present invention, additives  10  and  14  are water soluble, and do not gel, and can therefore be added at any convenient point. 
     Additive  12 , however, is an additive which tends to gel if mixed with water at ambient temperature. Stream  16  is therefore fed to a heater  18  to increase the temperature of stream  16  from ambient temperature to a temperature T C  which is greater than ambient temperature, and which is preferably less than the maximum gelling temperature T G  of additive  12 . The heated stream  20  is then fed to a static mixer  22 , through a static mixer inlet  24 , to impart energy to the stream. Once at least some energy has been imparted to the stream, additive  12  is then added to static mixer, preferably at an additive inlet  26  which is schematically illustrated in FIG.  1 . 
     The energy imparted to stream  20  within mixer  22  has advantageously been found to be sufficient to prevent gel formation of additive  12 , despite the fact that the temperature of stream  20  has not been heated to a temperature above the gelling temperature T G.    
     Stream  28  exiting static mixer  22  advantageously comprises a substantially homogeneous and gel-free mixture of water  16  and additive  12 , along with any other additives  10  and the like which may have been provided as desired. 
     As set forth above, additives  10  and  14  are water soluble, and can be added at any point. Thus, in the embodiment illustrated in  FIG. 1 , additive  10  is added to stream  16  upstream of heater  18  and static mixer  22 , while additive  14  is added downstream of mixer  22 . 
     Still referring to  FIG. 1 , stream  28  can itself be fed, at temperature T C , to further processing steps such as an emulsion forming step or the like, particularly when such process is effective at temperature T C . This is advantageous since the heat used to form the solution can be used again in such emulsion preparation, thereby enhancing process efficiency. 
     For other processes, wherein lower temperatures are required, stream  28  can be fed to a cooler  30  as schematically illustrated so as to reduce the temperature to a temperature T P  which is more suitable to the desired process. 
     Referring to  FIGS. 2-4 ,  FIG. 2  shows a typical gel temperature profile for a liquid additive having gelling tendencies, and shows the gelling temperature T G  at concentrations of the additive in water. As shown, at high concentrations the additive is liquid at substantially any temperature. As should also be clear, however, if such material is merely added to water, so as to reduce concentration at a low temperature, the additive will certainly gel and cause various problems. 
     One class of additives which has a gelling profile as illustrated in  FIG. 2  are surfactants for use in making oil/water emulsions. For example, ethoxylated nonylphenol (NPE) has a profile as illustrated. NPE is typically provided commercially having a concentration in water of at least about 80% weight and typically about 90% weight or higher, which generally corresponds to point  32  shown in FIG.  2 . It is typical to use such surfactant at a concentration of less than about 1% weight, and preferably about 0.2% weight, which corresponds to point  34  shown on FIG.  2 . In accordance with the present invention, the process provided allows for dilution from point  32  to point  34  without the need to heat in excess of temperature T G , and without the formation of gel. Other examples of similar additives that tend to gel include tridecyl ethoxylated alcohols, polymers that are soluble in water, and the like. 
       FIG. 3  illustrates the heating and cooling that would be necessary to go from ambient temperature to a processing temperature while heating to a temperature above T G . While this would avoid formation of gel, it should readily be appreciated that the heating and cooling costs would be substantial. 
     Turning now to  FIG. 4 , the preferred process of the present invention is shown wherein the additive is diluted with water at a temperature that is heated to a temperature T C  that is greater than ambient temperature, but less than the highest temperature for gel existence T G . This moves the additive sufficiently high on the gel formation profile that energy imparted from the static mixer can successfully prevent formation of gel and allow effective mixture with the liquid base or water as desired. 
     It should readily be appreciated that the heating and cooling costs in the process of the present invention are substantially reduced as compared to that in FIG.  3 . Further, a static mixer which is used to provide the energy desired is likewise efficiently operated, reliable and inexpensive. 
     Turning now to  FIG. 5 , a preferred placement of additive inlet is illustrated.  FIG. 5  schematically shows a static mixer wherein mixer  22  has a series of swirling flow imparting element  36  each having a length L m  corresponding to a 90° rotation along mixer  22 . Mixer  22  and elements  36  also have a diameter d o . In accordance with the present invention, a surfactant or additive inlet  38 , or preferably a plurality of inlets  38 , are advantageously positioned downstream at the beginning of the third swirling flow imparting member  36  by a distance L b  which is preferably approximately equal to L m /4. Furthermore, inlet or inlets  38  advantageously extend inwardly into mixer  22  by a distance h which is preferably equal to about d o /4. This advantageously injects the additive into the stream at a point where sufficient swirling energy has been imparted that gel formation can be avoided at temperatures less than the gel formation temperature. This advantageously provides for the excellent results obtained in accordance with the present invention. 
     It should readily be appreciated that the process provided can be carried out in a continuous manner, and provides for manufacture of downstream products such as viscous hydrocarbon in water emulsions with a high degree of quality since surfactant concentration is homogeneously distributed through the water phase. Furthermore, it should readily be appreciated that this process provides such excellent results with a minimum amount of energy used for heating and/or cooling, and utilizing a mixer which requires a minimum amount of maintenance. 
     The following examples demonstrates the excellent results obtained in accordance with the present invention. 
     EXAMPLE 1 
     In this example, a Kenics™ mixer having ¾inch×12 elements was used to mix an ethoxylated nonylphenol with water at a temperature of 35° C. This water had been heated to 35° C. from ambient temperature. Mixing was carried out at various water flow rates and additive flow rates, with mixing energy imparted by the static mixer being determined based upon the materials fed to the mixer, the process temperature and specifics of the mixer. Table 1 below sets forth the amounts of dissolution obtained in each case. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Water Flow 
                 Additive Flow 
                 Mixing Energy 
                 Dissolution Degree 
               
               
                 (l/s) 
                 (ml/min.) 
                 (W/Kg) 
                 (grs dissolved/total grs) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0.42 
                 303 
                 199 
                 0.99 
               
               
                 0.33 
                 240 
                 104 
                 0.98 
               
               
                 0.24 
                 180 
                 40 
                 0.94 
               
               
                 0.12 
                 84 
                 4 
                 0.78 
               
               
                   
               
             
          
         
       
     
     As shown, excellent dissolution was obtained at mixing energy of 40 W/Kg and above for the flows shown. At a mixing energy of only 4 W/Kg only 78% dissolution was obtained. Thus, the mixing energy provided by the static mixer in accordance with the present invention clearly helps to avoid gel formation and enhances complete dissolution of the additive. 
     EXAMPLE 2 
     In this example, a Sulzer™ mixer SMX, with 1.5 inch×8 elements, was used to mix water at 35° C. with the same surfactant as it Example 1. Table 2 below sets forth the water flow, additive flow, mixing energy and dissolution degree obtained. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Water Flow 
                 Additive Flow 
                 Mixing Energy 
                 Dissolution Degree 
               
               
                 (l/s) 
                 (ml/min.) 
                 (W/Kg) 
                 (grs dissolved/total grs) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1.42 
                 1052 
                 341 
                 0.92 
               
               
                 1.24 
                 894 
                 231 
                 0.94 
               
               
                 0.92 
                 666 
                 99 
                 0.69 
               
               
                 0.57 
                 408 
                 85 
                 0.63 
               
               
                   
               
             
          
         
       
     
     As shown, dissolution with this mixer was not as effective as with the mixer of Example 2. Thus, the geometric configuration of the mixing elements of the mixer, which are different in both commercial mixers, is important. 
     EXAMPLE 3 
     In this example, a stream of heated water was mixed with surfactant in three different locations along the mixer in order to demonstrate the advantageous position of injectors for the additive. 
     In the first instance, the additive was injected at the entrance to the mixer, along with the water. In the second evaluation, the additive was injected through a single injector at a point as selected according to the illustration of FIG.  5 . Finally, in a third evaluation, additive was injected through two injectors positioned at a point as illustrated in FIG.  5 . 
     With the additive introduced at the entrance to the mixer, only 72% dissolution was obtained. With additive introduced through a single injector downstream of the inlet, 80% dissolution was obtained. With the additive injected through two Injectors downstream of the inlet as illustrated in  FIG. 5 , 94% dissolution was obtained. This, positioning of the injector or inlet for the additive in accordance with the present invention provides for enhanced dissolution as desired. 
     It is to be understood that the invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts and details of operation. The invention rather is intended to encompass all such modifications which are within its spirit and scope as defined by the claims.