Guided radar displaces displacer at crude tar plant

Pungent-smelling, viscous and abrasive, crude tar is the by-product of the coal used in coke ovens in the steel manufacturing process. It is also the source of oil products required for timber processing and tyre manufacturing. However, given its aggressive chemical properties and high process temperatures, ensuring minimal downtime at a crude tar refining plant can be a challenge. Koppers Australia accomplished reduced downtime and lower maintenance costs by implementing a level measurement solution from Endress+Hauser.

At its facility in Newcastle, Koppers operates two continuous tar distillation units and a naphthalene still to produce coal tar by-products, carbon black and timber preservation chemicals. Heat is applied to distillation columns containing crude tar and the resulting vapours of naphthalene and creosote are captured and condensed. The entire process consists of a series of distillation columns each with precise level measurement and control. In the distillation columns, temperatures exceed 350 °C and the condensate is corrosive and abrasive.

Koppers operated its plant using displacer level measuring devices which work on the principle of buoyancy. This mechanical level measuring instrument is sometimes used in chemical and petrochemical plants. In a crude tar distillation process, the displacer frequently gets coated, leading to a change in the buoyancy of the displacer and therefore inaccurate measurements. Tar deposits on the arm and joint mechanism also impair movement leading to faulty readings. The distillation columns are connected in series and production of the entire line is affected if there is a fault on any one column. Failure to control levels within optimal and safe limits can also result in damage to the plant. As a result, the Koppers team had settled into a routine of high maintenance and frequent calibration since the cost of failure and downtime is very high.

Given the mechanical displacer’s high maintenance and frequent calibration requirements, and potential hazards, the Koppers team were keen to identify a reliable, safe alternative. After careful evaluation, they settled on Endress+Hauser’s Levelflex FMP45, which uses guided radar to measure the distance to the surface of the product. This version is ideally suited to the harsh operating conditions, being able to withstand pressures up to 400 bar, and temperatures from -200 to +400 °C. There are no moving parts and the distillate properties have no adverse affect on Levelflex’s reliability or accuracy. “Since installing Levelflex, we have not encountered any reliability issues due to the coating effect,” says Barry Colefax, Engineering Superintendent at Koppers. Eliminating the need for frequent calibration is another significant benefit. In fact, Endress+Hauser’s Levelflex needs a calibration only once a year and this can be done without disconnecting the instrument from the process.

Setting up Endress+Hauser’s Levelflex was extremely simple. As Barry Colefax and his team discovered, these instruments do not require a deep technical understanding of guided radar measurement principles. “We are not experts, but after a verbal explanation from the Endress+Hauser engineer, the set-up was straightforward and intuitive. We did not even consult the manual,” says Colefax.

The Levelflex FMP 45 offers proven reliability in the most difficult operating conditions — including combinations of foaming, turbulence, product build-up, varying density, varying product properties and irregularly shaped vessels.

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