(73b) Tar Wars in a Complex Chemical Plant: A Fundamentals Approach to Problem Solving

Authors: 
Wright, L. G. - Presenter, The Dow Chemical Company
McCabe, T. - Presenter, The Dow Chemical Company
Bell, B. M. - Presenter, The Dow Chemical Company
Chauvel, J. P. - Presenter, The Dow Chemical Company
Holden, B. S. - Presenter, The Dow Chemical Company
Leng, R. B. - Presenter, The Dow Chemical Company
Christenson, C. P. - Presenter, The Dow Chemical Company
Lengyel, I. - Presenter, The Dow Chemical Company
Livingston, D. A. - Presenter, The Dow Chemical Company
Wood, D. B. - Presenter, The Dow Chemical Company

Problem solving in a chemical plant requires using data and
the fundamentals of chemistry and engineering to link ?cause and effect?
relationships between the chemistry, the process, the control system, and the
problem. Once the underlying cause is identified, it is about resolving the
root cause(s) that can be manifest in a myriad of symptoms in the plant. That
is the way problem solving should be approached. However, in manufacturing when
the process goes awry, demands for pounds are high, financial losses mount, and
frustration increases by the minute, it is easy to make changes to ?respond? to
the symptoms to show that ?something? is being done. These types of reactions
to drive ?solutions?, which are often not supported by data, typically fail to
solve the underlying problem because they address the symptom. Although the
problem may momentarily go away it will likely reappear in the future. In this
case, more pounds and money is destined to be lost.

The case study used to showcase Dow's approach to problem
solving focuses on how a decades-old fouling problem within a Dow plant was
solved. The highly-integrated plant is part of a much larger chemical complex
that produces several valuable products and intermediates for Dow. The
individual plants in the complex use different raw feedstocks. Streams from the
plants within the complex also supply reclaimed feedstocks, catalysts, and
chemical intermediates to each other. Outside the site they supply downstream
intermediates for other Dow plants. As expected, asset utilization losses in
any one of these plants quickly become upsets in all the plants.

During the summer of '05, a high frequency of plugging
incidents in a ?heavies? unit, used to separate catalyst and ?heavies? from a lighter
product stream, disrupted and limited sales for several of Dow's products. With
the impacted plant only operational for periods of 3 to 9 days followed by
plant shutdowns of 2 to 3 days for cleanup, each incident cost the business
critical pounds for one of its primary products. Unfortunately, plugging was
not a new occurrence for the plant, as the ?heavies? unit had experienced
severe plugging episodes in the past. Several previous efforts in the plant had
attempted to resolve the plugging problem over the years; however, those
efforts were unsuccessful.

Market demands and the earlier lack of success led the
business in the fall of '05 to form a multi-discipline team of chemists and engineers to understand the
fundamentals of plugging. The objective for the team was to use this
fundamental understanding to devise chemical, engineering, and operational
strategies to mitigate the effect of heavies so the plant could operate without
plugging for a minimum of 5 months. This paper will
discuss how that team worked together using the weapons of fundamental
chemistry, engineering, the scientific method, and Six Sigma to fight the
Tar Wars. The team won the decades' old battle in less than three
months by addressing the underlying cause of plugging.

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