Process Refractometers for Black Liquor and Green Liquor Processes in Pulp and Paper

The only thing that a pulp and paper plant doesn't reuse is the "shade the building casts". When you consider reuse of energy and byproducts, the processes used in the production of pulp and paper are very efficient. Efficiency is costly however, because of the very hostile environments and demanding operating conditions endured by the plant's process equipment.

As an example, the "Kraft Process" (also known as the sulfate process) is the method of converting wood chips into pulp and cellulose fibers. The wood chips are mixed with sodium hydroxide and sodium sulfate, then soaked, cooked and processed.

A very fundamental explanation of the Kraft Process:

Wood chips are soaked and processed as "white liquor" in a mixture of sodium hydroxide and sodium sulphates. After impregnating the wood chips with white liquor, they are then cooked in digesters to break wood into cellulose. The solid pulp is then separated and the rest of the fluid is called the "black liquor". Black liquor is also processed for the removal of solids and chemicals to be reused during pulping. One of the final by-products is "green liquor" which contains both sodium carbonate and sodium sulfide and is then reacted into more white liquor with the addition of lime. All of these processes expose instruments, processing equipment, piping and valves to very harsh environments and chemicals. 

Electron Machine Corporation, a manufacturer of extremely robust process refractometers, has for over 40 years, been actively perfecting the use of refractometers for the measurement of green and black liquor density. 

Scaling of the sensor head: A key issue for keeping the system operational.

 MPR E-Scan and heated high-pressure cleaning system.

The problem of scaling in black liquor and green liquor applications is a major concern. It results in an optical coating on the sensor head of the refractometer the deteriorates performance. This scaling needs to be kept in-check in order to permit an acceptable duration of online measurement. With a means of effective removal at the time the the coating happens, the refractometer accuracy can maintained with minimum maintenance and downtime.

Electron Machine's decades of effort and experience in the pulp and paper industry led to the development of their MPR E-Scan refractometer in tandem with their heated high-pressure cleaning system. The resulting combination ensures efficient optical coating removal  and maintenance minimization so as to ensure a reliable measurement source for automatic online control.

For more information about the use of process refractometers in pulp and paper production contact Electron Machine Corporation by calling 352-669-3101 or visit their website at https://electronmachine.com.