How a Simple In-Line Filter Restored Catalyst Performance in a CHDA Plant

During routine performance monitoring, the CHDA (1,4-cyclohexanedicarboxylic acid) plant I oversee reported a marked drop in reactor conversion efficiency. Analysis of spent catalyst revealed oil contamination originating from the pneumatic convey blower.

Investigations traced the contamination to oil‑laden discharge piping on the Roots rotary‑lobe blower that transferred purified terephthalic acid (PTA) from dry‑bulk trailers to the mixing tank. A lubricator’s routine top‑off, combined with an eight‑year lapse in maintenance, had allowed leaking mechanical seals to inject oil into the process gas stream.

PTA Unloading Blower Package

Replacing the blower was cost‑prohibitive (over $150,000 for new catalyst), so we pursued a low‑life‑cycle‑cost solution. We selected a ZC 1‑µm in‑line filter rated for 800 cfm of hot, 20 psig nitrogen, achieving virtually zero pressure drop while capturing 100 % of oil mist from bearing or seal failures.

Filter Installation

The filter was installed with a simple pipe modification and a differential‑pressure gauge for real‑time monitoring. The entire project cost under $3,000, and the filter itself was less than $1,000. Since installation, no further discharge contamination has been detected.

Alongside the filter, we instituted a preventive‑maintenance program: monthly vibration analysis, scheduled oil changes, leak inspections, and mandatory reporting of abnormal oil use by lubricators.

Kevin G. Bellamy, principal reliability engineer at Eastman Chemical Company, led the initiative.