Introduction

Wyeth Nutritionals Ireland (WNI), a subsidiary of American Home Products Corporation, is one of the largest infant nutritional manufacturing facilities in the world, with European affiliates in 12 of the 15 EU Member States. The Askeaton plant manufactures both powder and liquid infant formulas and employs 500 people.
The project is an innovative system of emission control system for the simultaneous scrubbing of SO2 and particulates from boiler flue gases, giving pH-correction of an alkaline effluent stream and significant heat recovery.

Objectives and target audience

Process

Financial Resources and Partners involved

The total cost of the work was € 853,238 contribution with LIFE amounted to € 359,258.
The beneficiary is: AHP Manufacturing BV, Askeaton, Limerick, Ireland.

WNI identified the potential for applying a single solution to the two problems of atmospheric emissions and effluent pH-correction by combining the two waste streams in an innovative way.
Significant savings in plant operating costs were a potential added benefit.
The idea was to utilise the untreated dairy waste water as a boiler exhaust gas-scrubbing medium in a non-clogging fluidised bed scrubber system. This results in pH-correction of the waste water prior to biological treatment and thus allows a substantial reduction in the volume of acid previously used for this purpose. Finally, the waste heat energy from the boilers is recovered from the exhaust gases, creating additional savings in energy consumption.
The first stage of heat recovery then takes place in economisers, where the heat is removed from the flue gases and put into the boiler feed water. The flue gases then pass through the scrubber tower, where contact with the dairy waste water strips SO2 and particulates from them. The cleaned gases are reheated and exhausted to the atmosphere.
The dairy waste water is circulated continuously over the scrubber tower, with raw effluent make-up and overflow bleed-off. The secondary stage of heat recovery takes place when heat is removed from this liquid and put into the boiler fresh-water make-up system.
The re-circulated waste water becomes acidic following the take-up of SO2. The overflow is discharged to the effluent treatment plant according to pH-correction requirements, thus eliminating the need for hydrochloric acid for this purpose. The particulates are also carried off into the treatment plant, where they are combined with the normal sludge for disposal.

Results

SO2 removal
The baseline established at the plant was around 2 400 mg/Nm3. The recognised emissions standard is 1 700 mg/Nm3. The equipment consistently operates at a level below 600 mg/Nm3, which has become a requirement of the integrated pollution control licence at the plant. The system has the capability of 99 % removal of SO2.
Particulate removal
The system removes particulates below mg/Nm3, well in excess of the recognised standard of 30 mg/Nm3.
Energy savings
The system has been shown to achieve energy savings of around 1.4 MW. This equates to savings of around IEP 175 000 per year. There is also a surplus of heat that has no use in this application. In theory, 2.64 MW is available.
Chemical use savings
The management information systems in the plant have proven that the use of HCl in pH-correction has been virtually eliminated as a result of the installation of this system. This generates savings of around IEP 124 000 per year.

Critical Success Factors / Challenges