Flow Measurement & Control


Professional instrumentation for bleaching pulp suspensions

May 2017 Flow Measurement & Control

Unbleached pulp has a brown colour due to the remaining lignin of the mechanical pulp. As a result, it must be bleached to achieve the required quality for producing white paper.

Bleaching is a process which improves the purity and brightness of fibre suspensions using chemicals.

The process

Usually, a bleaching plant comprises the reaction container and machines, the piping, the equipment for refilling, storing and conditioning the bleaching chemicals, and the control system for pulp bleaching. A bleaching plant is normally made up of several bleaching stages, for economic reasons.

A conventional multi-stage bleaching plant comprises several bleaching towers and peroxide stages with downstream washing units. Using multi-stage systems on one hand reduces the expenditure regarding chemicals and heat, but on the other hand requires specific bleaching chemicals and processing conditions to achieve some targets (e.g. a high degree of whiteness combined with a low stability loss of the fibres).

Coloured pulp is conveyed from the digester via the delignification to the first stage of the bleaching system. The pulp reaches the first bleaching tower, where a hydrostatic pressure transmitter and electromagnetic flowmeters provide for constant levels and optimal production rates. Additionally, the chemicals are supplied to the bleaching tower.

Electromagnetic flowmeters are used for dosing control. Pressure transmitters, temperature sensors and pH measuring systems monitor the chemical reactions and reduce both quality variations and the energy cost.

After this, the pulp reaches the washing unit, where the unrequested bleaching products are removed by a wash filter. Conductivity measuring systems ensure an optimal washing process and provide for constant balancing of the salt content in the process. Filter and sieve monitoring for long-term efficient filtration is realised using differential pressure transmitters.

ABB Instrumentation

The process described here is repeated in the following oxygen and peroxide stages.

FSM400 electromagnetic flowmeter.
FSM400 electromagnetic flowmeter.

ABB offers instrumentation which is used in every phase of the bleaching process. Electromagnetic flowmeter FSM400 is suitable for multi-phase liquids, providing high performance due to DSP technology and short response time and undistributed output. It also offers local indication of measuring value and integrated monitoring and diagnosis functions.

ABB’s temperature sensor TSP121 with integrated head-mounted transmitter TTH300 features a universal design with various process connections. One of the advantages is that measuring inserts can be replaced during operation.

The 261G pressure transmitter offers a wide range of possible spans, and is compact with high operational reliability. It also allows for various process connections and is optimised for harsh process conditions. It comes in a robust stainless steel housing.

266 differential pressure transmitter.
266 differential pressure transmitter.

When the process requires a high-performance transmitter for the smallest measuring spans, ABB offers the 266 differential pressure transmitter. It has a high base accuracy of 0,04% and guarantees long-term stability.

TB82EC conductivity sensor.
TB82EC conductivity sensor.

pH/Redox measuring system with transmitter TB82pH and sensor TB557 is recommended due to the high-performance, long-life cycle and the minimum maintenance that it requires. The client has the benefit of selecting from a range of electrode models which are resistant to deposits.

Conductivity can be measured by using ABB’s TB82EC and TB465 sensor, which is a robust sensor and easy to install. It has a high pressure and temperature resistance which makes it ideal for seven paper bleaching processes.

For more information contact ABB South Africa, +27 (0)10 202 5000, instrumentation@za.abb.com, www.abb.com/measurement





Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Flowmeter for utility applications
November 2020, KROHNE , Flow Measurement & Control
As an addition to the Optiswirl family, KROHNE has introduced the Optiswirl 2100, a new vortex flowmeter aimed at basic utility applications.

Read more...
Safe operation of CNG stations
October 2020, SICK Automation Southern Africa , Flow Measurement & Control
The Flowsic500 compact ultrasonic gas meter enables extremely accurate natural gas distribution measurement.

Read more...
Ultrasonic flowmeter for wide ranges
September 2020, Instrotech , Flow Measurement & Control
Bi-directionally transmitted ultrasonic waves provide precise results of volume flow as the result of their transit time difference. Installed in any position, the units can measure ranges of 1:250.

Read more...
Turck standardises its fluid portfolio
September 2020, Turck Banner , Flow Measurement & Control
Turck’s new portfolio of fluid sensors offers a wide range of variants and combinations, while having common key features at the same time. The compact FS+ flow sensor with IO-Link now follows the launch of the PS+ pressure sensor.

Read more...
Safe operation of CNG stations
August 2020, SICK Automation Southern Africa , Flow Measurement & Control
SICK’s Flowsic500 gas meter, used in State Oil Company of Azerbaijan Republic’s (SOCAR) transfer and measurement stations, has shown to meet stringent compressed natural gas (CNG) production protocols. ...

Read more...
Flexim perfects the steam flowmeter
June 2020, Actum Group , Flow Measurement & Control
Flexim is proud to announce the manufacture of a robust, user-friendly and industry-certified ultrasonic steam flowmeter solution. For this accomplishment, the company has been nominated for the 2020 ...

Read more...
Emerson introduces software for flow measurement
July 2020, Emerson Automation Solutions , Flow Measurement & Control
Emerson has released Micro Motion ProcessViz, a standalone, cost-effective software solution for flowmeter process data visualisation. Having an instant visualisation of raw process data translates into ...

Read more...
Exceeding the limits
June 2020, ifm - South Africa , Flow Measurement & Control
The new SM flow from ifm electronic.

Read more...
The complexity of water management in mines
June 2020, Endress+Hauser South Africa , Flow Measurement & Control
Water is a critical resource for the mining industry, either in the mining processes, as a feed to the beneficiation of minerals process, or for potable use. With the growing demand and increased scarcity ...

Read more...
Electromagnetic flowmeter upgrade
May 2020, Instrotech , Flow Measurement & Control
Instrotech has announced that the Kobold magnetic inductive flowmeters MIM and MIS have been upgraded and further developed as follows: Kobold MIM, for measuring and monitoring of conductive liquids, ...

Read more...