COMMERCIAL OPERATION OF ISAB ENERGY AND SARLUX IGCC

Transcription

1 COMMERCIAL OPERATION OF ISAB ENERGY AND SARLUX IGCC Gasification Technologies 2001 San Francisco, California October 7-10, 2001 Guido Collodi Snamprogetti - Italy 1 INTRODUCTION The three Italian IGCCs from refinery residues (ISAB, SARLUX, API) are in commercial operation, having passed most of the contractual test-runs. This paper will give an update of the commercial status of ISAB Energy (approx. 510 MWe) and Sarlux (approx. 550 MWe), i.e. the two Italian IGCCs built by Snamprogetti in consortium respectively with Foster Wheeler Italiana and with Nuovo Pignone/General Electric. ISAB Energy has been the first Italian IGCC to go in commercial operation and has been taken over by the Owner on April 2000, while for Sarlux this happened on January The process layout of these complexes, the biggest of this kind in the world, is known to the GTC audience, and will be synthetically summarized. The paper will focus on the start-up activities, operational issues and main performances achieved by the two plants. The author wishes to thank Silvio Arienti - Foster Wheeler Italiana, Claudio Allevi - Saras, and Snamprogetti colleague Sergio Veronesi for their help in reviewing and completing the data presented. 2 THE TWO PROJECTS Snamprogetti has realised two Italian IGCC, namely the SARLUX project (in Sardinia), and the ISAB Energy project (in Sicily). The main features of the two IGCC are herebelow reported: ISAB ENERGY The guaranteed electrical production is approximately 510 MWe from asphalt gasification (approx. 130 t/h). The project is executed by a Consortium formed by Snamprogetti and Foster Wheeler Italiana. The split of work between SP and FWI is vertical for the engineering and procurement activities, while the construction, commissioning and other field activities are directly under the Consortium responsibility. The Combined Cycle Unit is supplied ready at site by Ansaldo Industria

2 SARLUX The guaranteed electrical production is approximately 550 MWe with co-production of approximately 40,000 Nm3/h of Hydrogen and 180 t/h of medium and low pressure steam. The normal feedstock to the gasification is Tar (approx. 150 t/h). A Consortium formed by Snamprogetti with Turbotecnica (Nuovo Pignone) and General Electric executes the project. The split of work among the parties is completely vertical being SP responsible for the supply of the process and utilities units, and NP/GE for the combined cycle. When the two IGCC are in operation, their total power production of more than 1000 MWe corresponds to about 3.5% of the Italian production, on annual basis. 3 ISAB ENERGY AND SARLUX: MAIN DIFFERENCES The Integrated Gasification Combined Cycle (IGCC) configuration is shown herebelow in the Process Block Diagram and is well known to this audience (see for example the paper presented last year - Reference 1). It is very similar in both Italian Snamprogetti projects. The main differences will be highlighted in the text. IGCC Complex Process Block Diagram AIR SOLIDS TO DISPOSAL AIR SEPARATION UNIT OXYGEN WASTE WATER PRETREATMENT WASTE WATER TO SULPHUR BIOTREATMENT SULPHUR RECOVERY NITROGEN FEEDSTOCK FEEDSTOCK PREPARATION SYNGAS GENERATION AND SOOT EXTRACTION GAS COOLING AND COS HYDROLYSIS HYDROGEN SULPHIDE SULPHUR REMOVAL (STEAM TO EXPORT) ELECTRIC POWER (STEAM TO EXPORT) COMBINED CYCLE UNIT STEAM SYNGAS SATURATION BOILER FEED (EXPANDER) (HYDROGEN PRODUCTION) (HYDROGEN) DEMIWATER (SYNGAS TO POST FIRING) DESALTED WATER DEMIWATER PRODUCTION Fig

3 The oxygen necessary for the partial oxidation into gasifiers is supplied by an Air Separation Unit, ASU, located outside the IGCC battery limits and operated by Air Liquide, for both plants. Both complexes use the Texaco quench gasification process technology (3 trains Sarlux / 2 trains ISAB) to produce the syngas required by the Combined Cycle. The Gasification which converts heavy oil feedstock into syngas, takes place at the conditions of about 1400 C and 40 barg (Sarlux)/ 70 barg (ISAB). The water-saturated syngas leaving the syngas scrubber, goes to the Heat Recovery section which recovers the low level heat to preheat the water for syngas moisturization and to produce medium/low pressure steam. This steam is used for process heating and export to refinery, if required. The syngas is then heated and sent to the COS Hydrolysis Unit, and the hydrolyzed syngas is cooled and fed to the Sulphur Removal Unit. Two different systems have been selected: physical (Selexol - UOP) for Sarlux and hybrid (MDEA - Dow Chemical) for ISAB. The acid gas mainly containing hydrogen sulphide and carbon dioxide is sent to the Sulphur Recovery and Tail Gas Treatment where hydrogen sulphide is converted into elemental sulphur in an oxygen Claus plant licensed in both cases by Lurgi. The tail gas is treated and incinerated, in ISAB case, while in Sarlux it is compressed and recycled back to the Selexol unit. The clean syngas, now containing only about 30 ppm of sulphur, is sent (in Sarlux case) to the Hydrogen Removal and Recovery Units. These units, supplied by UOP, include a membrane section and a pressure swing absorption section (PSA) to produce pure hydrogen (more than 99% vol.) available to refinery battery limits. In case of ISAB the clean syngas is, instead, sent to an Expander where the higher gas pressure is recovered into energy. The final syngas preparation step is, in both plants, the Syngas Saturation. The moisturized syngas with a low heating value ranging from 1700 to 2100 kcal/kg and a water content of 35-40% mol. is sent to the gas turbines of the Combined Cycle Unit, at about 20 (Sarlux)/23 (ISAB) barg and 200 C where the electric power is generated. The Combined Cycle Unit is mainly consisting: - for Sarlux, of three Single Shaft combined cycle units General Electric, STAG 109E, each one including one gas turbine MS9001E, one double end generator, one condensing steam turbine and one Heat Recovery Steam Generator (HRSG); - for ISAB, of two Siemens/Ansaldo combined cycle units, each one including one gas turbine Siemens V94.2, one HRSG with post combustion, and one condensing steam turbine. Each GT and ST has its own generator

4 4 COMMERCIAL OPERATION 4.1 ISAB ENERGY COMMISSIONING The majority of the Utility Units of the Complex, cooling water, sea water desalination, compressed air, fuel gas, water demineralization, machinery cooling water etc., have been successfully commissioned during the last two months of 1998 and, since then, kept in operation to support the start-up of the production units. In November 1998 the first gas turbine was started with the auxiliary fuel, gasoil. After few weeks of intermittent operation, for testing and running, in December 1998 the generator was connected to the national grid and the power increased up to design value. Simultaneously the connected waste heat boiler started steam production at conditions sufficient to test the steam turbine for power production. During this period several functional tests have been completed, such as load rejection, overspeed tests, control, alarm and emergency shutdown tests, etc. In March 1999 the same start-up procedure with gasoil was initiated and completed, in early May, for the second combined cycle. At the end of March the first process unit of the Complex, the Solvent Deasphalter, built and commissioned by Foster Wheeler Italiana, was put in operation. The unit operated continuously since start-up in recycle conditions, i.e. deasphalted oil and asphalt were recombined and sent back to the Refinery fuel oil blending. In the middle of June the SDA passed the performance tests successfully. On July 17 th the gasifier n 1 started to produce syngas, processing low sulphur fuel oil; the syngas produced, after treating for sulphur removal, was flared. The gasifier was kept in operation for approximately six weeks, processing visbroken vacuum tar at a capacity variable between 70 and 100%. During this period one gas turbine was operated on syngas for short periods, followed by cooling and inspection, to control mainly the combustion system. Each time the switch from gasoil to syngas was smooth and the full capacity of the gas turbine was reached successfully. The second gasifier was commissioned in September 99 and a number of contractual functional tests have been completed successfully. In November the plant was in operation ready to start the performance tests, but an equipment failure forced a shut-down for repairing. The plant was restarted in January 2000 and in the following two months the units were aligned, all the parameters optimised and the complex was ready for the performance tests. OPERATIONAL ISSUES The main problems encountered during the initial operation are here reported. The H2/CO ratio was higher than expected especially with light feedstock and this restricted for some time the use of the syngas in the gas turbine, and was resolved by operating the gasifier at lower temperature and lower steam to oil ratio, thus moving in the direction of higher soot production. When processing heavier feeds, such as asphalt, the H2/CO ratio of the syngas is no - 4 -

5 longer a problem. Furthermore, several tests carried out by Ansaldo/Siemens in a pilot plant demonstrated the capability of the burners to treat without problems also syngas having H2/CO ratio higher than design. Severe corrosion developed in several components of the soot water and grey water circuits. This corrosion was mainly caused by lower than expected ph and was particularly severe in presence of high fluid velocity, such as valves and pump impellers. The remedial actions have been: a) the change of metallurgy of several items ; b) ph neutralization in the circuit. The syngas expander, immediately after start-up, during an overspeed test, had a failure with syngas release through the seals and was shipped back to the manufacturer for extensive repairing. Plant operation was started again without expander, using a bypass control valve. The expander is now back at site and in operation. In November '99, with the plant in operation, an equipment failure and operator error in one gasification train forced a shut-down for repairing. Some hot spots were already observed in both gasifiers in the first months of operation. The problem has been solved in strict co-operation with Texaco with some modification in the burner and using a more resistant refractory in the gasifier. On the gas turbine burners Nickel (mainly) deposits are periodically found, probably caused by the decomposition of Ni-carbonyls at the temperature reached in the GT combustion section. Nicarbonyls are formed by reaction of CO with Nickel, and is a gaseous compound stable up to C. Such compound can be removed by activated carbon, and several tests on the plant are in progress. PERFORMANCE TESTS The ISAB Energy IGCC has successfully performed all the contractual tests. The first, called MPS (Minimum Performance Standard), was carried out between March and April 2000 and consisted of ten days of sustained load, including 48 hours at 95% of guaranteed NPO. In Fig. 2 the average Net Electric Power Output got day by day is represented, as well as the average requirements for the 48 hours MPS (486.4 MWe) and 10 days Reliability test ( MWe). During the 48 hours (March 28 th & 29 th in Fig.2) the average NPO obtained was 499 MWe. During the ten days the average net power output reached was MWe. After these tests the plant was taken over by the Owner. A second test, called GPS (Guaranteed Performance Standard), was carried out on October 2000 consisting of 30 days at an average of 93% of guaranteed NPO, including 48 hours where all the production/consumption figures needed to be demonstrated. The test achieved an average 95% of guaranteed NPO during the 30 days (90% excluding operation with gasoil), and approx. 510 MWe (i.e. the guaranteed value) during the 48 hours

6 Asphalt feed and oxygen consumption were well below 8 to 12% - the guaranteed figures. All the emissions were below the maximum allowed. ISAB Energy MPS and Reliability Test Tests result: MPS = 499 MW Reliability = MW 486,4 437, /03/00 26/03/00 27/03/00 28/03/00 29/03/00 30/03/00 31/03/00 01/04/00 02/04/00 03/04/00 04/04/00 Fig. 2 After this test the plant continued to show a very temping performance of more than 90% availability from December 2000 to July 2001 (except April). The plant seems to have margin of improvement in terms both of operation and availability. 4.2 SARLUX COMMISSIONING The Utilities Units were all in operation to support the start-up of the production units from the end of The first firing with distillate oil and subsequent synchronization with ENEL grid of the three Combined Cycle Units occurred between December 1999 (first CCU) and February 2000 (third CCU).The total peak production on gasoil was 502 MWe. At the end of April 2000 the first gasifier started to produce syngas from high sulphur oil at 70% load with downstream units (soot recovery, WWPT, sulphur removal) on line and we were approaching the time to feed the gas turbine when a trouble shutting in the refinery, beginning of May, forced the IGCC to shut-down. The first gasifier was restarted with high sulphur oil on August 5 th and the first syngas admission to the gas turbine with power production was achieved on August 13 th

7 The second gasifier was put in service on August 16 th and the third on August 24 th. During this period one CCU was in service on syngas producing about 190 MWe, that, considering the high ambient temperature of the Sardinian summer C during the day - was an encouraging performance, while the other two where fed by gasoil. Fuel switch from gasoil to syngas and vice-versa was tested during this period. The first power production from all three CCU units running with syngas happened on October. The months of November and December 2000 were used to perform functional tests and to align the plant in preparation of the test. Hydrogen unit was the last put in service shortly before the test commencement. OPERATIONAL ISSUES The main problems encountered during the initial operation are here reported. Soot carryover was experienced in Sarlux plant especially when the operating conditions are unstable (load change, pressure fluctuation etc.). A number of operating instruction have been prepared in co-operation with Texaco and Sarlux, concerning for example the optimisation of the nozzle scrubber pressure drop, syngas scrubber level and tray wash rate. Also it was found that recycling a small stream of water containing Selexol into the quench ring was cause of foaming and subsequent carryover. The elimination of the recycle greatly improved the operation. Long term solution may consist in the improvement of the vane separator coalescing capacity in the syngas scrubber and the addition o BFW spray system on the syngas scrubber overhead system. In the Hydrogen removal system severe membrane damage took place when in contact with minor amount of Selexol entrained with the clean syngas. The inconvenient, causing a rapid decrease of membrane selectivity with dilution of the permeate gas, is going to be solved by adding new separators equipped with high-efficiency coalescing elements in lieu of conventional demisters. The system is carefully and continuously monitored. PERFORMANCE TESTS The Sarlux IGCC has been taken over by the Owner, having passed the MPS test on January Such test has been carried out over 96 hours during which the plant had to produce at least 90% of the guaranteed NPO, i.e. 500MWe, and 90% of hydrogen and steam to refinery. The main results are summarised in Fig

8 Sarlux MPS Test Target Actual Net Power Output, MWe Hydrogen prod., Nm3/h Fig. 3 Similarly to ISAB, Sarlux has passed the 30 days reliability test on February 2001 and the GPS test on July The 30 days test demonstrated a production of more than 93% of guaranteed NPO (average 516 MWe) together with 90% of hydrogen and steam export. The NPO production during the GPS test was about 560 MWe with all the consumption figures below the guaranteed ones, specifically the feed consumption was 7% below the guaranteed. All the emissions were below the maximum allowed values. 5 CONCLUSIONS With the commercial operation of the three Italian projects, IGCC takes a further step towards its "maturity". The involved technologies still need to be improved and optimised, but an important role is played by the EPC contractor whose capabilities, for this kind of projects with high degree of complexity, should include: access to leading technologies today available on the market, analysis, evaluation and engineering of different technical solutions, support to the Client in the preparation of an appropriate financing package (e.g. Project Financing), management of LSTK contracts of high value, Client assistance during the plant operation, etc. Above considerations are even more significant in the light of the foreseeable market trend for the IGCC, giving rise to a big challenge that we are ready to accept. REFERENCES 1. Collodi G., - "Operation of ISAB Energy and Sarlux IGCC projects" Gasification Technologies Conference, San Francisco - October SFA Pacific Gasification Worldwide Use and Acceptance January Arienti S., Collodi G., - "Esercizio Commerciale di un Impianto IGCC" - X Convegno Tecnologie e Sistemi Energetici Complessi - Genova