CONTROL OF NOx EMISSIONS IN A CONTINUOUS TITANIUM SHEET METAL PICKLING BATH

Project Scope

A large stainless steel and titanium pickling and finishing company had an issue with visible NOx fumes discharging out of one of their Midwest facilities. The plant had been tasked with the elimination of the fumes that were being generated from their various pickling baths they utilize. Visible threshold limits for NOx gas are generally 300-400 ppm depending on weather conditions. One of the facilities pickling baths is particularly aggressive and pickles a continuous titanium sheet on a coiler machine and has twice the residence time of other treatments in turn generating high levels of NOx. This can overwhelm the stack gas scrubber, causing NOx levels to rise well over 600 ppm with orange plumes emanating from the plant which are visible to the public.

The company’s environmental department reached out to USP Technologies (USP) for assistance. Initial discussions with USP confirmed successful implementation of their hydrogen peroxide (H2O2) technology to pickling baths can specifically inhibit NOx formation. USP had done prior work for stainless steel finishers and it was deemed the technology was transferrable to titanium processing.

Technology

On a mass basis, the H2O2 demand is a composite of that due to NO2 and NO, with the typical 50:50 ratio producing a theoretical demand of approximately 1.0 parts H2O2 per part NOx.

HNO2 + H2O2 → HNO3 + H2O Wt. ratio: 0.4

2NO + 3H2O2 2HNO3 + 2H2O Wt. ratio: 1.7

As shown in the reactions above, oxidation of NOx by H2O2 in-bath, produces nitric acid, thereby allowing recovery and reuse of a critical process reagent.

Solution

After initial testing, a full-scale demo was put in place for several months on the coiler bath at the plant. USP’s turn-key supply scope included 50 percent technical grade H2O2, a 3,000 gallon double walled bulk storage and an automated feed system. The turn-key system was solely maintained by USP. The program also included USP’s ChemWatch™ – advanced control system with remote telemetry, allowing tank monitoring for inventory and pump systems control and analysis.

The tank and pump system are located in the middle of the coil storage area. Since the delivery connection is outside of the building, the system employs a remote delivery alarm system. Results shown in Figure 1 demonstrates how after an initial high dose of H2O2 to treat the NOx that had already built up in the bath, the NOx emissions were effectively controlled with a steady feed rate of 5 gph.

Read More Download Case Study_Pickling Bath-17-HR (pdf)

Cooling Towers and Process Water System Cleaning Applications Using Hydrogen Peroxide

[vc_row][vc_column][vc_column_text]The unique properties of hydrogen peroxide (H2O2) make it a good technology for keeping cooling loops, process water loops and heat exchangers clean from fouling that can occur due to various contaminants in the water. Hydrogen peroxide works well in removing organic fouling on surfaces through mechanical means and in specific applications through biocidal mechanisms. Hydrogen peroxide can be used in a shock treatment mode where it is fed based on a timer set-up. It can also be used occasionally at higher concentrations for maintenance cleaning purposes of fouled heat exchangers, cooling water loops and process water loops. Performing an occasional shock cleaning of a heat exchanger with hydrogen peroxide can remove buildup from surfaces and can result in improved heat transfer efficiency. By removing surface fouling, hydrogen peroxide may also improve the efficiency of other biocides such as bleach, bromine and non-oxidizers.

Before and After Cleaning

  Download our Case Study for Cooling Tower Cleaning (pdf)[/vc_column_text][/vc_column][/vc_row]

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