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Hydrogen Economy Now 2

ALLAM Cycle flow analysis Mohideen Ibramsha 1968 Alumni of Thiagarajar College of Engineering, Madurai, TN, India 1974 intellectual son of PhD guide Prof. V.Rajaraman & Mrs. Dharma Rajaramn, CS, EE, IIT, Kanpur, UP, India 1991 First HOD of CSE, CEC [now BSAU] Chennai, TN, India Associate Professor (Retd), Computer Science, Framingham, MA, USA Consultant R&D, M A M College of Engineering, Trichy, TN, India Advisor, HyDIGIT Pte Ltd, Singapore Email: ibramsha7@yahoo.com

This article was posted elsewhere on Wednesday, March 28, 2018 - 01:06 pm and is reposted here without modifying the posted content except some formatting changes.

Introduction The designer of the ALLAM cycle, Rodney Allam and 9 more authors presented “Demonstration of the Allam Cycle: An Update on the Development Status of a High Efficiency Supercritical Carbon Dioxide Power Process Employing Full Carbon Capture” in the 13th International Conference on Green House Gas Technologies GHGT-13 held at Lausanne, Switzerland from 14th to 18th November 2016. The abstract is available at https://www.sciencedirect.com/science/article/pii/S187661021731932X . This URL indicates that the document was made online on 18th August 2017. The above URL has a link to the full text PDF of the article, given below. https://ac.els-cdn.com/S187661021731932X/1-s2.0-S187661021731932X-main.pdf?_tid= 216eeec7-cae9-4d7b-a3bf-5c96d0fdaa42&acdnat=1520950536_3683bd79435d14399b08b2c17 53cf056 We use the data given in the PDF for our analysis of the 300 MWe ALLAM power plant. Add flow descriptions By combining the flow numbers in Figure 1 and the flow characteristics given in Table 1 of the PDF, we get the following list. We have not changed the values of temperature, pressure, and mass flow. They are as given in the PDF.

  1. Turbine exhaust is at 727 C, at 30 bar pressure and a flow of 923 Kg/s.

  2. The temperature is reduced to 43 C at a pressure of 29 bar giving ‘Cooled Turbine Exhaust’ of 564 Kg/s.

  3. After draining out the moisture in the ‘Cooled Turbine Exhaust,’ of 1 Kg/s we get ‘Dry CO2’ of 563 Kg/s at a temperature of 17 C and a pressure of 29 bar.

  4. ‘Compressed CO2’ of 909 Kg/s is at a pressure of 100 bar and a temperature of 23 C.

  5. The ‘Circulating CO2’ is 881 Kg/s at a pressure of 100 bar and 23 C temperature.

  6. ‘CO2 from burnt fuel’ is 28 Kg/s at 100 bar and 23 C.

  7. The ‘Circulating CO2’ gets cooled and becomes ‘Cold Circulating CO2’ with a flow of 881 Kg/s and pressure of 100 bar but at a temperature of 16 C.

  8. The ‘Cold Circulating CO2 part’ is 689 Kg/s at 100 bar and 16 C.

  9. ‘Hot Circulating CO2’ is 586 Kg/s at a pressure of 312 bar and a temperature of 717 C.

  10. ‘CO2 for adding Oxygen’ is 191 Kg/s at 16 C and a pressure of 100 bar.

  11. ‘Oxygen’ of 41 Kg/s is at 16 C and 100 bar.

  12. ‘Oxygen added CO2’ is 233 Kg/s at a pressure of 99 bar and a temperature of 2 C.

  13. ‘Supplemental Oxygen’ is 233 Kg/s at 310 bar pressure and 717 C temperature, and

  14. ‘Gaseous fuel’ is 10 Kg/s at 33- bar and 266 C.

Calculating the unspecified flows The turbine has inputs of 9, 13, and 14 giving a total of 586 + 233 + 10 = 829 Kg/s. However the output from the turbine, flow 1 is 923 Kg/s. There is no indication for the amount of ‘turbine cooling flow which also enters the turbine. The difference between 923 and 829, that is, 94 Kg/s is the ‘Turbine Cooling Flow.’ The CO2 compressor has ‘Ancillary Bypass Flow’ and flow 3 as inputs with flow 4 as output. With 563 Kg/s of flow 3, the ‘Ancillary Bypass Flow’ has to be 346 Kg/s to match 909 Kg/s of flow 4. Flow 6, ‘Export CO2’ and flow 5 added match flow 4. Thus the CO2 produced by burning the gaseous fuel is 28 Kg/s. The gaseous fuel 14, CH4, is 10 Kg/s. From CH4 + 2O2 ‘gives’ CO2 + 2H2O, we find 16 Kg of CH4 produces 44 Kg of CO2. Thus 10 Kg/s of CH4 produces 10 x 44/16 = 27.5 Kg/s of CO2. This 27.5 Kg/s is rounded to 28 Kg and reported in Table 1 of the PDF. Flow 7 of 881 Kg/s splits into two flows, flow 8 of 689 and flow 10 of 191 giving a total of 880 Kg/s. The difference of 1 Kg/s is ignored. To burn 16 Kg of CH4 we need 64 Kg of Oxygen. For 10 Kg/s of CH4 we need 10 x 64/16 = 40 Kg/s of Oxygen. Flow 11, Oxygen is given as 41 Kg/s. We ignore the difference of 1 Kg/s. Flow 12, being sum of flows 10 and 11 should be 232 being the sum of 191 and 41, is reported as 233 Kg/s. Again, we ignore the difference of 1 Kg/s. The Recuperator has ‘Heat Recuperation’ and flows 1, 8, and 12 as input. The outputs are: ‘Turbine Cooling Flow’; ‘Ancillary Bypass Flow’; and flows 2, 9 and 13. We calculated the ‘Turbine Cooling Flow’ to be 94 Kg/s. Likewise, the ‘Ancillary Bypass Flow’ was found to be 346 Kg/s. The total output of the Recuperator is 94 + 346 + 564 [flow 2] + 586 [flow 9] + 233 [flow 13] = 1843Kg/s. The sum of flows 1, 8, and 12 is 923 + 689 + 233 = 1845 Kg/s. The ‘Heat Recuperation’ turns out to be a negligible -2 Kg/s. Thus we ignore this negligible negative value and assume that there is no ‘Heat Recuperation’ flow. The unspecified flows are listed below.

  1. Turbine Cooling flow is 94 Kg/s

  2. Ancillary Bypass flow is 346 Kg/s

  3. Export CO2 is 28 Kg/s and

  4. Heat recuperation flow is 0 Kg/s.

Consistency check The flow of CH4 is 10 Kg/s. The burning of 16 Kg of CH4 produces 36 Kg of steam. Thus 10 Kg/s of CH4 produces 36/16 x 10 = 22.5 Kg/s of steam. Thus flow 1, the exhaust from the turbine has 900.5 Kg/s of CO2 and 22.5 Kg/s of steam. The water separator has flow 2 as input and flow 3 as output. Flow 2 is 564 Kg/s and flow 3 is 563 Kg/s. Thus the water removed at the water separator is just 1 Kg/s. What happens to the 21.5 Kg/s of steam that is the difference between 22.5 Kg/s produced and 1 Kg/s extracted? We assume, subject to consistency that the 21.5 Kg/s of steam is removed by the Recuperator as the temperature of flow 2 is only 43 ˚C. The ‘Ancillary Bypass Flow’ and Flow 3 are mixed and compressed to get flow 4. Flow 4 is at 23 ˚C and flow 3 is at 17 ˚C. The heat of flow 4 is 23 x 909 while that of flow 3 is 17 x 563. The difference 20907 – 9571 = 11336 must be supplied by the ‘Ancillary Bypass Flow’ of 346 Kg/s. Thus the temperature of the ‘Ancillary Bypass Flow’ is 11336/346 = 32.76 ˚C. We understand that the cooled exhaust after the heat exchanger is passed through a set of strainers to remove the water mixed with the CO2. We believe there is no need for any strainer in between the stages of the heat exchanger. From the article by Rodney Allam and co-authors, we find: === Three of the four stages and the associated pipework have been delivered to site in La Porte, Texas with the remaining stage well into the construction phase at Heatric’s main manufacturing base in Poole, England. === The temperature of the turbine exhaust is 717 °C and that of flow 2 is 43° C, the temperature of the exhaust after three stages of the heat exchanger would be 717 – (717 – 43) x ¾ = 717 – 505.5 = 211.5 °C. There would be no condensation of the steam inside the heat exchanger and the steam condenses possibly under transport in the 4th stage. Accordingly, the output from the heat exchanger is strained in the Recuperator. The final output from the strainers is assumed to be dry and is collected as ‘Ancillary Bypass Flow.’ It stands to reason, in view of the following property of the Heatric strainer. https://www.heatric.com/heat_exchanger_strainers.html === Heatric recommend strainers (typically 330 micron) as standard fitment for all Heatric exchangers during normal operation in order to remove particulates that may cause blocking of the units. === The sum of Ancillary Bypass Flow and flow 2 is 346 + 564 = 910 Kg/s which is more than 923 – 21.5 = 901.5 Kg/s which is the rate of CO2 minus the rate of steam’ removed from the Recuperator. The 1 Kg/s of water removed by the water separator is present in flow 2. After the 1 Kg/s of water is removed, the total CO2 is 900.5 Kg/s. Accordingly flow 4 is corrected to 900.5 Kg/s. With flow 4 at 900.5 Kg/s and flow 3 being 563 Kg/s, the Ancillary Bypass Flow is 900.5 – 563 = 337.5 Kg/s. Flow 6 is the CO2 from burning 10 Kg/s of CH4 and thus is 27.5 Kg/s. Flow 5 becomes 900.5 – 27.5 = 873 Kg/s. Flow 7 equals flow 5 at 873 Kg/s. Flow 7 splits into flow 8 and flow 10. Flow 8 is given as 689 Kg/s and flow 10 at 191 Kg/s add to 880 Kg/s instead of 873 Kg/s. We reduce them in proportion. Flow 8 is reduced to 689/880 x 873 = 683.5 Kg/s. Flow 10 becomes 873 – 683.5 = 189.5 Kg/s. We need 64 Kg of O2 for 16 Kg of CH4. For 10 Kg/s of CH4 we need 64/16 x 10 = 40 Kg/s of O2. Thus flow 11 is 40 Kg/s and flow 12 is 189.5 + 40 = 229.5 Kg/s. Flow 12 passes through the Heatric heat exchanger and remains 229.5 Kg/s at 717 ˚C. The Recuperator has inflows of 1, 8, and 12 with 923 Kg/s, 683.5 Kg/s, and 229.5 Kg/s respectively. Out of the 22.5 Kg/s of steam in flow 1, 21.5 Kg/s is removed from flow 1 as water and this water out of the Recuperator is not shown. Thus the total outflow from the Recuperator must be 923 + 683.5 + 229.5 – 21.5 = 1836 – 21.5 = 1814.5 Kg/s. The outflows are flows 2, 9 13 and the ‘Turbine Cooling Flow.’ Flow 2 is 901.5 Kg/s as calculated earlier. Flow 9 is the same as flow 8 at 683.5 Kg/s, and flow 13 is the same as flow 12 at 229.5 Kg/s. Thus the ‘Turbine Cooling Flow’ is 1814.5 – 901.5 - 683.5 – 229.5 = 1814.5 – 1814.5 = 0 Kg/s. Turbine has inflows of flows 9, 13 14, and ‘Turbine Cooling Flow’ and one outflow, flow 1. The sum of flows 9, 13, and 14 is 683.5 + 229.5 + 10 = 923 Kg/s. From the mass balance of turbine also we find ‘Turbine Cooling Flow’ to be 0 Kg/s. However the turbine must be cooled. The only explanation is the sum of flows 9 and ‘Turbine Cooling Flow’ must be kept at 683.5 Kg/s. Flow 9 is at the temperature of 717° C, the same as the temperature of the turbine exit. Thus any part of flow 13 could not be used for cooling the turbine. The Heatric heat exchanger is in four stages. The ‘Turbine Cooling Flow’ is possibly drawn after just 3 stages from flow 9 at a temperature of 717 – (717 – 43)/4 = 548.5 °C. To avoid confusion, the ‘Turbine Cooling Flow’ is shown as ‘X’ and flow 9 is shown as ‘683.5 – X.’ It is observed that the Recuperator is shown to be made of 8 vertical strips and the ‘Turbine Cooling Flow’ leaves the Recuperator after 6 strips while flows 9 and 13 leave after 8 strips. The flow diagram could be seen in the paper by Rodney Allam and co-authors. In that paper, flow 9 is shown to be 586 Kg/s. With the sum of flow 9 and the ‘Turbine Cooling Flow’ becoming 683.5 Kg/s now, the nominal ‘Turbine Cooling Flow’ becomes 683.5 – 586 = 97.5 Kg/s. The values 586 and 97.5 are shown in parentheses in the augmented flow list. The augmented list of flows follows.. The augmented flows are 2A, 8A, 9A, 9B, and 12A.

  1. Turbine Exhaust is 923 Kg/s at a temperature of 727 C and a pressure of 30 bar.

  2. At a temperature of 43 C, the ‘Cooled Turbine Exhaust’ is 564 Kg/s with a pressure of 29 bar. The ‘2A Ancillary Bypass Flow ‘ is 337.5 Kg/s with a pressure of 29 bar and a temperature of 32.8 C. [The balancing equation is 923 = 564 + 337.5 + 21.5 of H2O removed from the Recuperator and discarded.]

  3. Dry CO2 is at a pressure of 29 bar, a temperature of 17 C and is 563 Kg/s.

  4. Compressed CO2 is 900.5 Kg/s after subtracting the 22.5 H2O removed at the Recuperator from the 923 Kg/s of the Turbine Exhaust which is CO2 plus steam.

  5. Circulating CO2 is 873 Kg/s at 100 bar and 23 C.

  6. CO2 from burnt fuel is 27.5 Kg/s at 100 bar and 23 C. The sum of ‘Circulating CO2’ and ‘CO2 from burnt fuel’ equals 900.5 Kg/s corresponding to the CO2 in the Turbine Exhaust.

  7. Cold Circulating CO2 is 873 Kg/s at a temperature of 16 C and 100 bar pressure.

  8. The ‘Cold Circulating CO2’ is split into ‘Cold Circulating CO2 part’ of 683.5 Kg/s and ‘CO2 for adding Oxygen’ of 189.5 Kg/s. The ‘Cold Circulating CO2 part’ enters the Recuperator and is withdrawn in two flows of ‘Hot Circulating CO2’ after four stages of the Recuperator and as ‘Turbine Cooling Flow’ after three stages of the Recuperator. The amount of ‘Turbine Cooling Flow’ is dependent on the load on the turbine and is denoted as X Kg/s. The sum of the ‘Hot Circulating CO2 part’ and the ‘Turbine Cooling Flow’ must equal 683.5 Kg/s. Thus the 8A – Hot Circulating CO2 is (683.5 – X) Kg/s at 100 bar and 717 C.

  9. ‘Hot Circulating CO2’ is at a temperature of 717 C at a pressure of 300 bar. It is (683.5 – X) Kg/s where X Kg/s is the amount of ‘Turbine Cooling Flow.’ Flow 8A leaves the Recuperator at a temperature of 717 C at a pressure of 100 bar. This low pressure flow is compressed by a specially designed reciprocating pump to a pressure of 300 bar. The quantity is decreased as the ‘Turbine Cooling Flow’ leaves the entered Flow 8 after 3 stages of the heat exchanger. Flow 8A becomes flow 9 after the compressor. The flow 9A, Turbine Cooling Flow is X Kg/s at 100 bar and 548.5 C. With Flow 9 at 586 Kg/s the ‘9A Turbine Cooling Flow’ becomes 683.5 – 586 = 97.5 Kg/s. The ‘9A Turbine Cooling Flow’ varies with load. When the ‘9A Turbine Cooling Flow’ changes, Flow 9 also changes. To clarify this inter dependence between flow 9 and ‘9A Turbine Cooling Flow’ we have used the variable X. The ‘9A Turbine Cooling Flow’ is compressed after it leaves the Recuperator to 300 bar and becomes ‘9B Turbine Cooling Flow’

  10. ‘CO2 for adding Oxygen’ is 189.5 Kg/s at 199 bar pressure and 16 C temperature.

  11. ‘Oxygen’ is 40 Kg/s at 16 C temperature and 100 bar pressure.

  12. ‘Oxygen added CO2’ has a pressure of 99 bar and 228.5 Kg/s. The temperature is given as 2 C which is possibly a typo. We ignore this temperature. After passing through the Recuperator, ‘12A Hot Oxygen added CO2’ has a flow of 229.5 Kg/s, a pressure of 99 bar and a temperature of 717 C.

  13. ‘Compressed Oxygen added CO2’ called ‘Supplemental Oxygen’ is 229.5 Kg/s with a temperature of 717 C at a pressure of 300 bar.

  14. The ‘Gaseous Fuel CH4’ is 10 Kg/s at a pressure of 330 bar and a temperature of 266 C.

The low pressure flows - 8A, 12A, and ‘Turbine Cooling Flow A’ are compressed by specially designed reciprocating pumps to a pressure of 300 bar currently supported by the industry. The reduced pressure from 310 bar to 300 bar requires the turbine to operate possibly at a pressure of 290 bar. In case the CO2 pressure inside the turbine must be maintained at 300 bar, these special compressors could be designed for 310 bar without lubricating oil. Instead of waiting for a new compressor to be designed and manufactured, we recommend reducing the pressure in the turbine to 290 bar even if such a reduction results in reducing the amount of circulating super critical CO2. Conclusion The ‘First Fire’ of the 50 MWth Demonstration Plant at La Porte, TX was expected in 2016 itself. Then it was expected in 2017 as quoted below. https://www.technologyreview.com/s/608755/potential-carbon-capture-game-changer- nears-completion/ === Potential Carbon Capture Game Changer Nears Completion August 30, 2017 So until Net Power is up and running, it’ll be impossible to say whether it can really operate as efficiently, cheaply, and reliably as hoped. But the early major test is fast approaching, with “first fire” scheduled for late November or early December. (The area around the site has sustained flooding as a result of Hurricane Harvey, but as of Tuesday, the facility itself has drained as designed and remains undamaged.) === We are yet to read about the ‘First Fire.’ Even a search on March 22, 2018 did not locate any documents related to the ‘First Fire’ at La porte, TX. In case pressurizing the flows 8 and 12 before they enter the Heatric heat exchanger causes difficulty – we don’t know the cause – it is hoped that the changes suggested above would result in successful ‘First Fire’ soon.

Earlier posts on this topic:

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