AN ENVIRONMENTAL RETROFIT OF A UREA SYNTHESIS PLANT
T. M. Hellman, Director
Environmental Services
Carl G. Swanson, Jr., Manager
Technical and Environmental Control
Agricultural Division
Allied Chemical Corporation
Omaha, Nebraska 68107
INTRODUCTION
The Allied Chemical Omaha nitrogen fertilizer complex is located on an 80 acre portion of 900 acres of Allied land at the confluence of the Platte and Missouri Rivers in
Sarpy County, Nebraska.   The complex consists of plants which produce ammonia,
nitric acid, urea, ammonium nitrate and our liquid nitrogen fertilizer called UranB. The
ammonia plant produces   500 tons per day of anhydrous ammonia by steam reforming
natural gas in a Selas furnace.   This furnace was recently converted to a proprietary
process of vaporizing fuel oil as the energy source.   The 450 tone per day urea plant
produces urea by reacting at elevated pressures anhydrous ammonia and by-product
carbon dioxide from the steam reforming area.   Nitric acid, all of which is neutralized
with ammonia into ammonium nitrate, is formed at a 280 ton per day rate by oxidation of ammonia in the presence of a platinum catalyst.   The ammonium nitrate and
urea produced are admixed to form the final product, a liquid fertilizer called UranB,
which is nonpressure and contains 32% nitrogen by weight (see Figure 1).   Twenty
wells supply approximately 20 million gallons per day of 13 C water.   Five   hundred
thousand gallons per day are used in process; the balance is used for non-contact cooling.   The effluent water with a temperature of 30-34 C flows to the Missouri River
via a three mile open and unlined outfall located entirely on company property.   The
urea plant uses 25 C water reclaimed from the ammonia plant cooling water system.
The NPDES Permit for the Omaha facility became effective on October 30, 1973.
Duration of the Permit was for five years.   The NPDES Permit abatement program
was based upon achieving a set of Interim Effluent Limitations by October 30, 1974
and a set of Final Effluent Limitations by June 30, 1977.   The Interim Effluent Limitations were achieved by June 30, 1975, after EPA approved variances to install necessary interim measures.   The plant is now operating under a Nebraska Department of
Environmental Control variance to allow time for completion of an Energy Conservation
Program in the Ammonia Plant, including several associated environmental projects.
Explicit in the Permit is the concept of a two outfall system; Outfall No. 001  is to
carry non-contact cooling water and Outfall No. 002 is to carry process wastewater
following end of pipe treatment.   This required a revision of the former one outfall
system, which carried both non-contact cooling water and process wastewater, to the
dual system.   Although the dual system was installed, end of pipe treatment was
abandoned because of the associated energy costs.   Instead the principles of recycle, recovery and reuse were employed.
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