Water in oil analyser turns to tar

An Able Instruments and Controls product story

Edited by the Engineeringtalk editorial team Feb 14, 2008

New method gives Corus engineers more accurate analysis of a whole tanker load with improved control of the tar loading operation.

A Drexelbrook CM6 online water in oil analyser has successfully passed acceptance testing for measuring coke tar moisture at Corus Steel Plant in Scunthorpe.

The analyser was trialled to replace the current method using a Karl Fischer technique.

Corus Steel Plant in Scunthorpe is one of the UK's three integrated steelworks.

There are two coke-making plants at Scunthorpe and their main purpose is to convert coal into metallurgical coke for use in the blast furnaces.

Tar is an important byproduct of the coke-making process and is transported via road tankers off site to tar distillation companies for processing.

It is important to measure the moisture content of the tar to ensure the correct quality of tar is being transported to the distillation company.

The existing method of despatch tar moisture analysis at both Dawes Lane and Appleby Coke ovens has involved the operator taking a "spot" sample during the tanker loading operation.

The sample is then collected by the coke oven laboratory chemist and taken back to the laboratory and analysed using a Karl Fischer technique.

There have been many disadvantages with this testing method, causing possible inaccuracies in measurement and impacting on both time and costs.

The spot sample only provides a "snapshot" of the tanker load, and so may not be fully representative of the moisture content of the whole tanker load.

In addition, the tanker driver has often left the site by the time the analysis is completed and may not be aware of the moisture content of the load.

There is also a time and cost impact because a chemist may have to travel to and from the plant simply to pick up and analyse a single tar sample.

Analysing the sample using this method involves undesirable, indirect contact with the tar, both for the chemist and plant operator.

There is an environmental impact and cost regarding the safe disposal of contaminated plastic sample pots, gloves, plastic syringes and rags.

An engineer at Corus noticed an advert in International Environmental magazine for the Drexelbrook CM6 online water in oil analyser.

The instrument consists of a sensing element and RF transmitter unit and operates on the principle that the capacitance of the oil is proportional to the water content.

Previous attempts to measure the moisture content of coke oven tar using this technique had not been successful; Able Instruments was confident, however, that the CM6 analyser was proven technology on heavy oils and did not have any reservations with regard to moisture in tar applications.

It was agreed with Able that the instrument would be assessed for a trial period at Appleby Coke Ovens.

The sensing probe was installed on 2nd October 2007 on a vertical down-facing section of the tar delivery pipe just outside the pump house.

During the trial, the online moisture analyser compared well with the laboratory results.

The instrument has been online for approximately 3 months and has performed very well, not requiring any significant maintenance.

Section Chemist, Roy Scott, comments: "This new method has ensured that we have more accurate analysis of the whole tanker load with improved control of the tar loading operation, for example, reduction of despatch tar tankers leaving with high moisture content, improvement to health and safety operation for plant operator and chemist".

"Furthermore, the benefits of Able's solution include, reduced chance of exposure to tar, reduced environmental impact and costs regarding disposal of contaminated plastic sample pots, gloves, pipettes and cleaning fluids/cloths and finally, time and fuel savings for chemist having to pick up and analyse single tar samples".