Kapaia Power Station (KPS) Feasibility Study of Simple-Cycle GE LM2500-PH GT Conversion to Methanol Firing

Transcription

1 Kapaia Power Station (KPS) Feasibility Study of Simple-Cycle GE LM2500-PH GT Conversion to Methanol Firing November, 2013

2 Table of contents 1. Executive Summary 2. Simple-Cycle LM2500-PH GT operation mode 3. Preliminary performance estimation of different fuel alternatives 4. Techno economical evaluation 5. Conclusions

3 1. Executive Summary Over the past years there has been a dramatic increase in the regulatory requirements for low emissions from both new and existing utility boilers and gas turbines. Traditional methods of reducing NOx emissions are very expensive. Hence, before implementation of the expensive measures, it is necessary to evaluate all low cost alternatives. One of the attractive alternative fuels for combustion in utility boilers and gas turbines may be methanol. Existing experience has shown that with minor system modifications, methanol is easily fired and is fully feasible as an alternative fuel. Results obtained from firing of methanol in specific gas turbine (CAESAREA FT4C TWIN PAC 50 MWe GT, commissioned in the middle of the 1970's) owned by the Israel Electric Corporation (IEC), clearly show that with minor cost fuel system retrofit methanol firing significant NOx, SO 2 and particulates emission reduction is acheived. NOx emissions were reduced by more than 75% to 75 mg/dnm 3 at 15%O 2. This is less than required even with water injection operation mode (the standard 86 mg/dnm 3 at 15%O 2 ). SO 2 emissions were reduced from 50 mg/dnm 3 at 15%O 2 with LFO, to zero. Particulate emissions vary from 1.3 to 1.6 mg/dnm3 at 15% O 2 with methanol firing, while with LFO this parameter was mg/dnm3 at 15% O 2. IEC is nowadays in the last stage of a full conversion of the same unit, stationed in the southern city of the state of Israel Eilat. This 3M$ project involves a new dual fuel (Methanol or LFO) delivery system and all auxiliary systems, with the aim of attaining the full capacity of the unit. This project will serve as a demonstration one, and is a first of a kind worldwide. The startup is scheduled for Dec We believe that the conclusions of the performed work are general in nature, and can be applied to other gas turbines as well.

4 2. Simple-Cycle LM2500-PH GT The heart of the KPS facility is a venerable GE LM2500-PH rated at 27.5 MW and operated in Super STIG configuration [Cheng]. For comparison purposes, the standard GE-designed LM2500 STIG can ingest up to 50,000 lb/hr of steam, whereas the Cheng version has been kicked up to a maximum of 72,000 lb/hr, limited only by the maximum allowable compressor discharge pressure of 282 psig. The KPS, which supplies over 50% of the island s electrical load, is designed to load-follow demand from 60% to 100% of turbine load. The unit is normally fueled by naphtha but occasionally by JP4 or JP5 jet fuel, depending on availability. Because the plant operates 24/7 (unusual for a simple-cycle gas turbine), it racks up a lot of operating hours in short order. Up to 75,000 lb/hr of injection steam at 282 psi/875f comes from a once-through steam generator from Innovative Steam Technologies (Cambridge, Ont.) that is designed to operate dry and be started hot if necessary. Simply described, an One Through Steam Generator consists of: An enclosed structure with an inlet at the bottom end that accepts heated air (usually exhausted at high velocity from a gas turbine) and an outlet at the top of the structure that allows the air to escape; Inside this enclosed structure is an uninterrupted bank of high quality steel tubes. Feed water is fed into the top of the tube bank and heated by the turbine s exhaust gas to create steam at the outlet end of the tube bank. The GT is equipped with only one liquid fuel system, which can be used to burn oil No. 2 or naphtha. Note, that steam is produced at the OTSG and injected back to the combustion chamber for NOx emission reduction. Here may be noted that methanol firing will lead to drastic NOx reduction even without steam injection. Estimated comparison of NOx emission for liquid fuels and methanol firing is shown in Fig. 1

5 Estimated Emission Methanol Methanol firing will also lead to zero SO 2 emission and drastic particulates emissions reduction. 3. Preliminary performance estimation for different fuel alternatives In order to evaluate GT performance characteristics we run simulation for simple cycle at ISO conditions based on LM 2500 PH Gas Turbine. Our estimations were based on Cheng cycle performance data. For this purpose, we have used results presented in "CLN development to reduce NOx and greenhouse gas" that was prepared by Dr. Dah Yu Cheng. The results are summarized in Table1. Table 1. Cheng cycle performance Based on this table we estimated GT capacity and Heat Rate for steam injection Lb/hour indicated as maximum possible value for GT LM2500 PH

6 equipped with Cheng cycle using extrapolation method. It is very preliminary estimation and for RFP actual data will be taken into consideration. As result we have decided to perform our economical evaluation also for average reported Heat Rate. In order to calibrate our model, we run simulation at ISO conditions without steam injection for diesel oil and methanol. In addition, after correspondence with Dr. Cheng we got actual heat balance for naphtha firing at different loads. Dr. Cheng heat balance is presented in table 1.1. (at 27C and RH=100%). We also performed our economical evaluation using Dr. Cheng Heat Balance. Simulation results are summarized in Table 1 and 1.2 and in heat balance diagram Fig Table1. Simple cycle performance comparison based on GT LM2500 PH equipped with Cheng cycle at Kauai Island Utility Cooperative s (KIUC) Kapaia Power Station (KPS) for different fuels GT parameter Simple Cycle Diesel Oil NO steam injection Gross Power, Mw 27.5 Methanol NO steam injection Estimated 28.1 Exhaust temperature, C Exhaust temperature flow, t/h Fuel flow rate, t/h Steam flow rate, t/h 0 0 Gross Heat rate based on LHV, kcal/kwh 2150 Estimated 2088 Specific fuel consumption based on LHV, g/kwh Equivalent to Oill#2 Specific fuel consumption based on LHV, g/kwh LHV, kcal/kg HHV, Kcal/kg As can be seen, simple cycle GT capacity is about 27.5 Mw for diesel oil without water injection. Methanol firing at the same condition leads to increasing GT capacity to 28.1 Mw. It is very difficult to estimated Heat Rate for Cheng cycle without detail heat balance. Our estimation were based on the test results presented in "CLN development to reduce NOx and greenhouse gas" prepared by Dr. Dah Yu Cheng. Therefore, our estimation were performed both for data

7 reported by KPS heat rate and actual heat balance submitted by Dr. Cheng. Results of GT tests on methanol performed in IEC are presented in appendix1. Table 1.1 Cheng LM2500 PH heat balance Comparison between naphtha and methanol firing based on Dr. Cheng is presented in table 1.2 Table1.2 Simple cycle performance comparison based on GT LM2500 PH equipped with Cheng cycle at Kauai Island Utility Cooperative s (KIUC) Kapaia Power Station (KPS) for different fuels burning based on Cheng actual HB GT parameter Naphtha with steam injection Methanol With steam injection Gross Power, Mw Exhaust temperature, C Fuel flow rate, t/h 4.9 Estimated Steam flow rate, t/h Gross Heat rate based on LHV, kcal/kwh Specific fuel consumption based on LHV, g/kwh Equivalent to Oill#2 Specific fuel consumption based on LHV, g/kwh Estimated 1945 Estimated Estimated LHV, kcal/kg HHV, Kcal/kg

8 Fig.1 Diesel oil simple cycle heat balance diagram no steam injection.

9 Fig.2 Methanol simple cycle heat balance diagram no steam injection

10 Fig.3 Naphtha simple cycle heat balance diagram with steam injection based on Cheng Heat Balance

11 Fig.4 Methanol simple cycle heat balance diagram with steam injection based on Cheng HB.

12 4. Techno economical evaluation The calculations were carried out for the same alternatives as mentioned above. Table 2 Comparison between Naphtha and Methanol with steam injection for reported HR Naphtha with Methanol with Item steam steam Comments injection injection Fuel demand, t/hr Heat content based on LHV, kcal/h Heat content based on HHV, kcal/h Heat content based on LHV, MMBTU/h Heat content based on HHV, MMBTU/h Fuel price, $/ton Fuel price, $/MMBTU LHV Fuel price, $/MMBTU HHV Hourly fuel cost, $ Simple cycle fuel cost, $/kwh Extra electricity production, MW Revenue from energy sale, $/hr 6,080 5, Extra capacity revenue, $/hr 0 18 Profit (-)/loss(+), $/hr Conversion return, $/hr Total Profit (-)/loss(+), $/hr Methanol firing profitable is Table 3 Comparison between Naphtha and Methanol with steam injection for HR estimated based on Cheng actual Heat Balance

13 Naphtha with Methanol with Item steam steam Comments injection injection Fuel demand, t/hr Heat content based on LHV, kcal/h Heat content based on HHV, kcal/h Heat content based on LHV, MMBTU/h Heat content based on HHV, MMBTU/h Fuel price, $/ton Fuel price, $/MMBTU LHV Fuel price, $/MMBTU HHV Hourly fuel cost, $ 5,762 4,946 Simple cycle fuel cost, $/kwh Extra electricity production, MW Revenue from energy sale, $/hr Extra capacity revenue, $/hr 0 18 Profit (-)/loss(+), $/hr 0-1,105 Conversion return, $/hr Total Profit (-)/loss(+),$/hr 0-1,005 Methanol firing profitable is Based on the obtained results one may conclude that methanol firing, on top of environmental merits, is also economically justified and may be recommended as the main fuel for Gas Turbine operation. 5. Conclusion The results of the performed analysis indicates that methanol firing potentially promises low cost fuel alternative for emission reduction and may be

14 implemented in existing gas turbines. The results presented here clearly show that methanol firing causes an improvement in unit heat rate, leads to emission reduction and is economically justified in comparison with other possible fuel alternatives. The methanol firing has no impact on GT performance and provides safe operation. A transfer from one fuel to the other is very smooth. The computer simulations provide strong support for these conclusions. Prepared by: B. Chudnovsky L. Levin M. Keren

15 Appendix 1

16