Method for preparing salt solutions having desired properties
AssigneeMartin Marietta Energy Systems, Inc.
InventorsMoonis R. Ally, Jerry Braunstein
Life of this patent
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Abstract
The specification discloses a method for preparing salt solutions which exhibit desired thermodynamic properties. The method enables prediction of the value of the thermodynamic properties for single and multiple salt solutions over a wide range of conditions from activity data and constants which are independent of concentration and temperature. A particular application of the invention is in the control of salt solutions in a process to provide a salt solution which exhibits the desired properties.
Claims13
A method of making a salt solution exhibiting a desired value of a selected thermodynamic property which comprises determining the water activity, a, in the solution at two different concentrations of the salt in solution at a reference temperature, T.sub.r, wherein the water activity is related to the mole fraction of water, x.sub.w, in the solution according to the general equation ##EQU18## calculating the value of the left-hand side of the general equation at each value of a and x.sub.w, plotting the values of the left-hand side of the general equation versus a to obtain a line, setting the value of the slope of the line equal to the (c-1)/cr portion of the right-hand side of the general equation and setting the value of the intercept of the line equal to the 1/cr portion of the general equation to provide slope and intercept equalities expressed in terms of c and r, calculating c and r from the slope and intercept equalities, calculating .epsilon. from the equation c=exp[.epsilon./TR.sub.r ], selecting a test condition of concentration x.sub.x and test temperature T.sub.x, calculating the value of c.sub.x at T.sub.x from c.sub.x =exp[.epsilon./RT.sub.x ], calculating a at T.sub.x and x.sub.x from the general equation at r=r, c=c.sub.x and x.sub.w =1-x.sub.x, calculating the value of the thermodynamic property from the value of a at x.sub.x and T.sub.x according to a thermodynamic expression relating the value of a and the value of thermodynamic property at x.sub.x and T.sub.x, determining the extent of any variation between the desired value of the thermodynamic property and the calculated value and, to the extent of any variance between the calculated and desired values of the thermodynamic property in excess of the an acceptable maximum variation, adjusting the value of at least one of the test conditions to reduce the variance between the calculated and desired values of the thermodynamic property to at or below the accepted maximum variance to cause the solution to exhibit the desired value of the property within the accepted variance, and incorporating in water an amount of the salt which in its resulting concentration in the solution causes the thermodynamic property to be within the accepted variance based on the adjusted value of X.sub.x or Tx which causes the solution to exhibit the desired property.
In a process employing a salt solution of known concentration x.sub.s flowing in a fluid stream, an improved method of controlling a thermodynamic property of the salt solution to maintain the value of the property at a desired level comprising determining the water activity, a, in the solution at two different salt concentrations at a reference temperature, T.sub.r, wherein the water activity is related to the mole fraction of water, x.sub.w, in the solution according to the general equation ##EQU19## calculating the value of the left-hand side of the general equation at each value of a and x.sub.w, plotting the values of the left-hand side of the general equation versus a to obtain a line, setting the value of the slope of the line equal to the (c-1)/cr portion of the right-hand side of the general equation and setting the value of the intercept of the line equal to the 1/cr portion of the general equation to provide slope and intercept equalities expressed in terms of c and r, calculating c and r from the slope and intercept equalities, calculating .epsilon. from the equation c=exp[.epsilon./RT.sub.r ], temperature T.sub.s of the solution, calculating the value of c.sub.s at T.sub.s from c.sub.s =exp[.epsilon./R.sub.s T], calculating a at T.sub.s and x.sub.s from the general equation at r=r, c=c.sub.s and x.sub.w =1-x.sub.s, calculating the value of the thermodynamic property from the value of a at x.sub.s and T.sub.s according to a thermodynamic expression relating the value of a and the value of the thermodynamic property at x.sub.s and T.sub.s, determining the extent of any variation between the desired value of the thermodynamic property and the calculated value and, to the extent of any variance between the calculated and desired values of the thermodynamic property in excess of an acceptable maximum variation, adjusting at least one of the values of the temperature T.sub.s and/or concentration x.sub.s to reduce the variance between the calculated and desired values of the thermodynamic property to at or below the accepted maximum variance to cause the solution to exhibit the desired value of the property within the accepted variance and incorporating in the fluid stream an amount of the salt solution and adjusting the concentration of the salt solution to cause the thermodynamic property to be within the accepted variance based on the adjusted value of Xx or Tx which causes the solution to exhibit the desired property.
Dependencies are inferred from the claim text.