Objective
The aim of the "E.A.S.E. SYSTEM" project is represented by the electric energy production from the recovery of the energy delivered by natural gas in the depressurization. The specific purposes, which differentiate this project from other similar initiatives in this field, are represented by an original arrangement of the expander, allowing a significantly wider range of operanting flow and as a consequence the continuous operation of the plant during the whole year, and by the introduction of a regenerator for the heat exchange between hot gas at the outlet and cold gas at the inlet of the expander, which permits to develop the gas expansion at high temperatures with consequent increase of the electrical output.
In the first six-month operation period (october 96- march 97), the electrical energy production by the two Spilling expanders of the EASE system has been 2.200.000 kWh. The cogeneration units gave a 3.804.000 kWh additional contribution to the electricity production in the same period.
The inlet gas flow is divided in two streams, which are sent separately to two expansion units, represented by a four-cylinder two-stage unit suitable for a gas flow up to 16.000 Scm/h and a three-cylinder three stage unit suitable for a gas flow up to 7.000 Scm/h. The two expansion units are placed at the opposite sides with a two-shaft synchronous generator with disconnectable couplings. In peak load condition in winter, both the expanders shall be in operation and shall deliver the maximum gas flow of 23.000 Scm/h. In mid-seasons, only the four cylinder expander shall run, while in summer only the three-cylinder unit shall be utilized.
The natural gas at the inlet of each expansion stage is heated by means of steam and hot water derived from a cogeneration plant (not included in the eligible costs for E.E.C. contribution).
In the three-cylinder unit, the expansion is developed exclusively at high temperature by utilizing a regenerator between hot gas at the outlet and cold gasat the inlet. This solution allows a great improvement in electrical production.
The innovation of the "E.A.S.E. SYSTEM" is synthetized in the name itself of the project: Efficient All-Season Expander. By dividing the cylinders of the expander in two parts placed at each terminal of a two-shaft generator with disconnectable couplings, it is possible to run the plant both with high gas flow in wnter and with low gas flow in summer.
As a second and even more important innovation, the regenerator (heat exchanger between outlet gas and inlet gas) allows to develop the expansion at high temperatures and as a consequence with a higher enthalpy drop and an increase in the electric energy production in parity conditions of gas flow and pressures.
In comparison with conventional expansion plants with the same gas flow and gas inlet/outlet pressures, the "E.A.S.E. SYSTEM" shall allow a 31% increase in the production of electricity. As far as economical aspects are concerned, the overcosts of the "E.A.S.E. SYSTEM", compared to conventional expansion plants, are due to the following items:
1. presence of two gas expansion units, instead of one, with the relevant doubling of some plant devices and part of the instrumentation;
2. higher complexity of the electrical generator (with two shaft ends) equipped also with two disconnectable couplings;
3. increase in the number of heat exchangers for the gas heating.
The above aspects cause an increase of about 15% in the investment cost for the expansion plant, which is much lower than the increase of 31% obtainable in the electric energy production, so that the electric energy production cost is remarkably lower.
Programme(s)
Topic(s)
Call for proposal
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DEM - Demonstration contractsCoordinator
24100 Bergamo
Italy