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published on 13 June 2022

Spent caustic recycle

CeraMem proposes to spent caustic recycle and surfactants using tangential filtration CeraMem® ceramic membranes.

CeraMem® ceramic membrane in housingCeraMem® Ceramic Membrane in housing

 

The Client

PRO-TEC Coating Company was established as a joint partnership in 1990 and is strategically located in Northwestern Ohio.

Their 730,000-square-foot plant, located near Leipsic, Ohio, produces high quality coated steel products with output of over 1.1 million tons annually.

PRO-TEC is recognized as a leader in Advanced High Strength Steels (AHSS) in the United States.

 

Project Background

PRO-TEC’s plant in Leipsic is one of the largest facilities in North America producing hot-dipped galvanized/galvannealed steel products. The process of galvanizing/galvannealing begins with high-quality, cold rolled steel coils.

PRO-TEC Coating Company’s plant in Leipsic - spent caustic recyclePRO-TEC Coating Company’s plant in Leipsic

 

Rolled Steel Preparation

Management of Spent Caustic recycle

Prior to surface treatment, the raw steel is cleaned with a caustic degreaser. This process results in substantial quantities of spent caustic cleaner that contains oils and greases, grit, water, and other solids. The spent cleaner is collected and sent to disposal offsite.

The disposal of the spent cleaner represents a significant expense in not only disposal, but also in the costs of replacing the caustic degreaser for production.

Despite several attempts to solve this issue, a cost-effective and technically feasible solution could not be achieved. PRO-TEC contacted CeraMem to explore alternative technologies and processes. The solution required that both certain cost and performance objectives be met.

 

Performance Testing

Chemical Recovery and Waste Reduction

CeraMem proposed a system comprised of CeraMem® ceramic membranes. CeraMem membranes are ideal for this application due to the ability to tolerate high operating temperatures, aggressive cleaning regimens, and resistance to high pH levels. After some initial laboratory testing, a full-size, crossflow membrane system was designed and built in 2009. The goal of the system was to recover the spent caustic degreaser to a specified rate and quality, in order to vastly reduce the amount of waste generated.

CeraMem® ceramic membrane system to spent caustic recycleCeraMem® Ceramic Membrane System

 

The design criteria of the caustic recovery system  were the following:

  • UF (Ultrafiltration) membrane : Titanium oxide, 0.01μm pore size
  • Recovery: 95%
  • UF feed composition : 4% TSS, 1% oil & grease
  • Permeate composition: : TSS and Oil & Grease <10 mg/l, Turbidity <5 NTU
  • Operating temperature: > 50˚C; pH 10-13

 

System highlights

  • >95% Caustic cleaner recovery resulting in 95% reduction in chemical make-up costs
  • Reduced environmental impact
  • >20x less waste sludge and associated disposal costs
  • Short payback period
  • The system is fully automated. And the system was pre-engineered and required minimal installation and commissioning
  • The system achieved 95% recovery and the permeate quality met the design criteria for TSS and dispersed oil & grease.

 

Spent Caustic Recycle Results

Satisfied that the system met the design requirements during commissioning, the system was fully integrated into PRO-TEC’s caustic degreaser blow down treatment operation, and has been operated by PRO-TEC since 2010.

To date, the CeraMem system at PRO-TEC has exceeded performance requirements while achieving a large reduction in the degreaser waste and makeup (>95%) for the facility. Recycling the caustic and the surfactants has minimized the impact to the environment.

Spent Caustic Recycle - Process OverviewSpent Caustic Recycle - Process Overview