Yokogawa's New Flow Measurement Solution for Continuous Digesters

Industry: Papermaking

Products: Electromagnetic flowmeter, ADMAG AXF series

Introduction

Development of a new electromagnetic flowmeter for KP continuous digester

1.Stable cooking degree

The new electromagnetic flowmeter for digesters can accurately and stably measure the black liquor in the circulation pipeline, helping users to stabilize the degree of digestion to determine

Chip quality during cooking.

2. Optimize slurry water balance

The new electromagnetic flowmeter for the digester can accurately and stably measure the black liquor in the extraction pipeline.

The important factor, the flow rate of the extraction line, is now available.

3. Better yield control

The new ceramic electromagnetic flowmeter can accurately and stably measure the pulp in the blowpipe, helping users to better monitor and control production

The amount of pulp in the

4. Reduced maintenance costs

The new electromagnetic flowmeter can withstand extremely harsh digester conditions without the need for regular maintenance. Five years of field testing have proven that

It is effective in reducing hazardous maintenance work under extreme heat/pressure conditions.

background

The continuous digester is the heart of many paper mills and its technology is constantly facing challenges to achieve the best performance in the paper industry. Improving digester performance means improving quality and reducing costs, while contributing to protecting the environment and conserving natural resources for the entire industry.

The extremely high temperatures, pressures, and corrosive alkaline liquids with high pulp content in the continuous digester present a host of challenges for those working to improve this core pulp production equipment. For many years, Yokogawa has been accompanying the paper industry, helping it achieve its dual goals of quality production and environmental protection through innovative sensing and control technologies. Yokogawa has been working with the paper industry for the past decade to develop new flow measurement solutions for continuous digesters.

challenge

Stable and accurate flow measurement is the key to improving continuous digester performance. There are three areas where traditional measurement methods need to be comprehensively improved: black liquor circulation piping, black liquor extraction piping and pulp blowpipe. Better measurement should allow users to minimize cooking temperature fluctuations in the circulation piping, achieve accurate pulp and water balance in the extraction piping, and control the amount of pulp produced in the blowpipe.

The fluid in the black liquor circulation pipeline and extraction pipeline is usually measured by a combination of orifice plates and differential pressure transmitters. Due to the high temperature/pressure/corrosiveness of the fluid, there is no alternative product so far. The solution of the orifice plate and differential pressure transmitter combination is also limited because the inevitable slurry accumulation on the orifice plate and the blockage of the impulse pipeline will cause the measurement performance to deteriorate. In some cases, the membrane seal will also fail due to corrosion or hydrogen permeation. Therefore, most orifice plate/differential pressure transmitter applications in these channels will fail within two years of installation and stop working, and users can only guess based on experience.

Pulp blow pipes present their own challenges. Although PFA-lined electromagnetic flow meters have been used in traditional measurement methods, the high temperature of the slurry will cause wear of the electromagnetic flow meter lining and fluctuations in the output signal. Regular and costly maintenance work is required, which makes it difficult to perform accurate and continuous measurements. [page]

solution

Yokogawa engineers work closely with users, sharing a passion to face seemingly impossible challenges and develop innovative sensor solutions that provide stable and accurate measurements in applications, even achieving goals that some users thought were impossible.

While conventional PFA-lined electromagnetic flowmeters in pulp blowpipes require regular maintenance due to constant wear of the slurry, Yokogawa has adopted its newly developed ceramic-lined electromagnetic flowmeter. The unique feature of this electromagnetic flowmeter is that it has an integrated platinum-alumina-cermet electrode, and its body is made of fired powder. The aluminum has a purity of 99.9%, a strength of 520MPa (53kgf/mm²), and a Weibull modulus of 15.0. This design is completely leak-proof. Its alumina-ceramic lining has high resistance to slurry adhesion and can provide stable and accurate measurements without regular maintenance.

Yokogawa engineers took the lead in investigating the feasibility of using ceramic-lined electromagnetic flowmeters, as conventional orifice/DP solutions were not up to the task under the extreme conditions of circulation and extraction piping. In joint studies and trials with users, the ceramic detector alternative solutions we investigated were not 100% reliable under the extremely high pressure/temperature/high corrosion conditions in certain special applications. Although PFA-lined detectors performed best, existing PFA electromagnetic flowmeters experienced lining creep under extreme high temperatures, which posed a risk of compromising seal integrity in many applications.

Faced with the challenge, Yokogawa engineers developed a PFA-lined electromagnetic flowmeter that can withstand cooking conditions. A new insertion electrode was developed to prevent lining creep. In addition, it has a special set of grounding rings to prevent the inner diameter of the inlet duct from deforming under extreme conditions. After taking a series of measures, the new "Cooker Electromagnetic Flowmeter" can stably and accurately measure flow under extremely high temperature/pressure conditions (170 degrees Celsius and 1.3MPa), which is far beyond the technical scope of conventional PFA electromagnetic flowmeters.

Expanding the temperature/pressure range of the PFA-lined "digester electromagnetic flowmeter"

in conclusion

Yokogawa's engineers showed great perseverance, and the customer allowed Yokogawa to install the new electromagnetic flowmeter next to the existing sensor. The customer's engineers played an important role in the subsequent extended field test, and they and the Yokogawa team worked together to meet the various challenges faced when applying new technologies. The field test lasted for more than five years, and both the ceramic electromagnetic flowmeters in the blowpipe and the digester electromagnetic flowmeters in the circulation and extraction pipes passed the field test. They continue to guarantee the greatly improved flow measurement output without any accidents.

On-site test environment

Left: The new digester electromagnetic flowmeter is installed in the circulation and extraction pipelines/

Right: The new ceramic electromagnetic flowmeter is installed in the blowdown pipe and connected in series with a conventional PFA electromagnetic flowmeter to compare their outputs

Even if the ceramic electromagnetic flowmeter of the blowpipe is flawless and withstands pressure tests up to 6.0MPa, the user should still select test equipment to confirm the degree of corrosion after five years of stable use in the field. Although this requires moving and cutting off the electromagnetic flowmeter, the user insists on conducting these tests at his own expense to ensure that the data obtained is beneficial to the entire production. The test results show that the corrosion depth of the ceramic lining does not exceed 0.1mm per year. This field data clearly shows the availability of ceramic electromagnetic flowmeter technology in blowpipe applications, greatly reducing maintenance work and improving measurement accuracy and production efficiency.