Brine Manufacturing

Industry: Refining, Chemical, Food and Beverage
Product: Inductive Conductivity Process Liquid Analyzer

Application

Brine is a solution of salt in water. While a typical expectation would be for it to contain sodium chloride (NaCl), the “salt” used to create the brine is not always pure NaCl. It could be a mixture of chlorides such as calcium chloride, magnesium chloride, and others.

Brine is used in a wide variety of applications from household food preparation to industrial processes such as cheese production, refining, textile dyeing, and chemical manufacturing. It is also used as an anti-icing or de-icing agent commercially or in municipalities as a final product applied to roadway pavement or parking lots.

Depending on the application, the salt concentration can range up to 26%. For example, 3.5% is a typical seawater salinity concentration whereas lower concentrations are used for brining food. Higher concentrations in the range of 23-24% are used for anti-icing. These concentrations are obtained either by mixing a full-strength solution with water or mixing a solid salt with water to achieve the desired concentration.

Challenges

Traditionally, a grab sample measurement—one sample taken at one time—is used to determine the brine concentration. The salometer and refractometer are common measurement instruments.

A Salometer is a hydrometer that indicates the percentage of salt in a solution by measuring the liquid density.

• Since a salometer is not temperature compensated, the brine mixture must be the same temperature as shown in a reference comparison table. 
• Air bubbles trapped within the system will affect the reading. 
• Proper test setup and reading level are imperative to ensure accurate measurement. 

A Refractometer works on the principle of light entering a prism that has a unique refractive index or a Brix reading depending on the solution and concentration. The most common field refractometers measure the salinity and/or specific gravity of the brine mixture.  

• Since the refractive index depends on temperature, it is vital to ensure that the instrument can compensate for temperature.
• Hand refractometers are light-sensitive and, due to the interpretation required to produce a reading, are vulnerable to human error.

Solution

Both measurements rely on grab sampling. Conductivity measurement can be used as a reliable indicator of the real-time brine concentration. Using an online process analyzer removes the need for timely grab sample analysis. Figure 1 shows the correlation between conductivity and concentration for four common salts. 

Some salts curves have a peak conductivity value before the saturation point. Before this peak value is reached, conductivity correlates positively with concentration; after the peak, it correlates negatively. In Figure 1, the example shows the calcium or magnesium chloride curve that exhibits this “peak.”

If the concentration range passes through the peak for that chemical, the conductivity value (except the peak value) represents two different concentration values. Therefore, any application near the peak of a particular solution must be carefully controlled. Normally, this is easily done when the starting concentration point is known and correlating flow and pump time.

Since conductivity measurement is also temperature-dependent, temperature compensation is needed. However, in some brine manufacturing processes, the starting sample and the water used may have varying temperatures—and the built-in temperature element used for compensation is not quick enough to respond. Therefore, a change in the conductivity reading that is simply due to the temperature change may be observed. To overcome this, a standard conductivity is used in conjunction with an external RTD that responds more quickly to temperature changes than the built-in RTD that is covered with polyether ether ketone (PEEK) material.

Key Advantages

Increased efficiency and reduced operating costs can be achieved by using the Yokogawa Inductive Conductivity series line of products. 

• One sensor will measure the entire conductivity range.
• Since the sensor is non-contacting, it is not affected by chemicals and requires less overall maintenance.

Product Recommendations

Toroidal or Inductive Conductivity Measurement:

Process Liquid Analyzer:
2-wire 24 VDC Loop powered FLXA202 analyzer
4-wire AC/DC FLXA402 analyzer

Sensor Selection: 

With the inductive conductivity, ISC40 series, one sensor can measure the full range of conductivity from 0-2000 mS/Cm. Steam sterilization capability is possible since the measurements can be performed at process solution temperatures of -10 to 130°C and pressures no greater than 2 MPa (20 kgf/cm2).

ISC40G General Purpose Sensor

ISC40S Intrinsically Safe Sensor

• Available in PEEK and PFA material for more aggressive chemicals

Process Connection/ Holder Selection:

Option 1: Flange connection

Option 2: ISC40FS/ISC40FF Insertion of flow-through assembly

Option 3: PR10 Retractable assembly

Note: For additional information on this application, please contact the Yokogawa Process Liquid Analyzer specialists.