Casera T Bozzoni Ansaldo CLC srl

Via D'Annunzio 105,16121 Genova (Italy) G. Porcino. A. Pasquimtcci Eniclic/n s.p.a.

Via Taramelli 26,20124 Milano (Italy)

Introduction

Chemical and petrochemical industries generate large quantities of hydrogen-rich streams, in the range 50%-100% H2 concentration by volume, as by-products of electrochemical or de-hydrogcnalion processes, or exhausts/purging in hydrogenation processes. Due to safety aspccts, and because of the low density, which makes difficult transportation and storage, such streams often constitute a problem for plant managers. In most cases recycling within the plant processes is not possible, and transportation to other sites, generally by track after compression in cylinders, is not economical. Many of these streams arc therefore simply co-burned in plant boilers, and in some cases even wasted by venting or flaring. Their value ranges from zero (if vented), to the value of the fuel used in the boiler where they are co-bunied.

Hydrogen fuel cell units would offer an easy and safe way to manage such streams, getting revenues from generated electricity and heat. Working with hydrogen would make fuel cells reach their best in terms of elcctrical efficiency, high grade heat generation, availability, flexibility for installation and operation, and easy of licensing, thanks to their null or negligible environmental impact. Considering both technical and economic aspccts, the installation of hydrogen fuel cells in chcmical industry results practically interesting in many circumstances, even with present high investment cost.

Typical hydrogen quantities in chemical and petrochemical plants are sufficient to power fuel cells from some hundreds kWs to several MWs. Rough estimates, based on chlor-alkali industry alone, give hydrogen by-product availability sufficient to install up to 600 MW fuel cell power in Europe, which could double or more if chcmicai and petrochemical sectors are considered. Even if only a part of that hydrogen would be conveniently employed in fuel cells, this constitutes a niche market, which involves consistent volumes in the immediate.

Hydrogen Plants Concept

Hydrogen plants «ill be based on the 900 kW d.c. capacity module concept, developed by CLC from the phosphoric acid fuel cell ONS1 PC25 C (TM) natural gas plant concept. The module is conccivcd as a shop made package, adopting four phosphoric acid fuel ccll stacks identical to the ones installed into the PC25 C (TM) plant. It is designed as an independent operating, self controlled unit, suitable for unattended operation in single or multiple units installations. Package dimensions will be approximately equivalent to a standard commercial container.

Preliminary module characteristics arc:

Power Output 900 kW d.c.

Steam production (140 °C. 4 bar steam) 780 kg/li

Maximum Hydrogen Consumption 630 Nm3/h

Gross Electrical Efficicncy (d.c.) Gross Thermal Efficicncy Global Conversion Efficicncy Operation

more than 8000 lt/year

Studv of the !)00 lov fuel cclls hydrogen module - longitudinal section

To get the maximum flexibility for different site specific interface requirements, separate service systems will be provided, specifically designed for the management of process and electric interfaces between module and site facilities. Typical scrvice system functions will be hydrogen feed pressure control and purification, steam distribution to utilisation, condensate treatment, power voltage elevation and line connection, ctc.. Remote operator interface will be provided, generally to be loeated in the existing plant control room, to supervise and control module. Specific functions will be provided to co-ordinate modulc(s) operation, according to actual site operating requirements. The typical hydrogen fuel cell plant operating mode will be to modulate automatically clcctric power, in order to consume a fixed portion (or all) of the hydrogen feed.

Chlor-alkali Industry' and the Asscmini Project

Chlor-Alkali Industry, produces chlorine, caustic soda and hydrogen by electrolysis of brine, a sodium chloride water solution. It provides ideal conditions for fuel ccll integration (see fig 2), since very pure hydrogen is produced (especially from modem membrane clcctrolysers), at low pressure and temperature, which can be fed almost directly to the fuel cells. Fuel cell can generate up to 20% of the clcctric energy consumed by the clcctrolytic process, and steam to be used for caustic soda concentration. The conditioned d.c. energy generated by fuel cells can be supplied directly to the clcctrolytic process, thus avoiding the d.c. to a.c. clcctricity conversion, with equipment cost reduction and increase of efficiency.

INTEGRATION of CHLOR-ALKALI and FUEL CELLS

INTEGRATION of CHLOR-ALKALI and FUEL CELLS

For the above reasons, the chlor-alkali plant of Asseniini was identified, among other Italian by-product-hydrogcn sources suitable for application of fuel cells, as the most appropriate site for a first demonstration.

The Asscmini chlor-alkali plant. loeated in the island of Sardinia (Italy), is owned by EniChem, the greatest Italian chcmical company. It adopts monopolar membrane eleclrolyscrs. with a total capacity of 170.000 t/ycar chlorine. 150.000 t/ycar caustic soda, with by-product hydrogen production around 6300 Nm3/h. now almost totally burned in the plant boiler.

Basing on such hydrogen flowrate. fuel ccll capacity is dimensioned to 9 M\V d.c., constituted by 10 x 900 kW d.c hydrogen modules. The Asscmini Fuel Ccll Plant is planned to generate yearly about 68 GWh clcclricily, and 62.000 t of steam from 48 million Nm3 of hydrogen.

The projcct cost is estimated around 28 million USD. It will be founded by private capital and banking, and partially by government subsidies. First fuel cell modules are scheduled for delivery in early 1998. with immediale start-up and operation of each module, after installation and a short testing period. The plant will be completed in 1999, when full capacity will be reached.

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