#
Feasibility Study of the CO_{2} Regenerator Parameters for Oxy-Fuel Combustion Power Cycle

^{*}

## Abstract

**:**

## 1. Introduction

#### 1.1. Low-Carbon Power Production

_{2}capture are known, their wide introduction is limited by the rapid increase of produced electricity price [4]. This is due to the carbon dioxide low partial pressure in flue gases.

#### 1.2. Oxy-Fuel Combustion Technology Challenge

#### 1.3. Thermal-Hydraulic Characteristics for PCHE Heat Exchangers

## 2. Materials and Methods

#### 2.1. Heat Balance of the Allam Cycle

_{2}flow supplied to the turbine cooling. The first heat exchanger power is an order higher than the second one, therefore this work discloses verifying of the first heat exchanger operation parameters.

_{2}in the waste heat exchanger. The service medium is cooled in the separator feed cooler, thereafter moisture is removed from the cycle, and a part of a carbon dioxide flow is sampled for disposal. The rest of the flow goes to recycling: it is partially compressed in the cooled compressor and cooled prior to compression in the carbon dioxide pump. After compression, a part of the flow is sampled for cooling down of the gas turbine, and the main flow is heated in the waste heat exchanger and delivered to the combustion chamber. The cycle is closed.

_{1}and h

_{2}are specific enthalpies of the medium before and after the process of pressure variation, kJ/kg;

_{2}′—a specific enthalpy of the medium caused by isentropic pressure variation, kJ/kg;

_{oi.T}—isentropic turbine efficiency.

_{oi.C}—isentropic compressor efficiency.

_{11}and h

_{21}are specific enthalpies of hot and cold flows at the heat exchanger inlet, kJ/kg;

_{12}and h

_{22}—specific enthalpies of hot and cold flows at the heat exchanger outlet, kJ/kg;

_{1}and G

_{2}—flow rates of hot and cold heat-transfer media, kg/s.

_{net}—the power unit net electrical capacity, MW;

^{3}of oxygen equal to 0.714 kWh/m

^{3}and the maximum output of 3400 m

^{3}/h.

#### 2.2. Heat Exchange Equipment

_{h}, G

_{c}—cumulative flow rates of hot and cold heat-transfer media, kg/s;

^{2}°C), which is determined by the following equation:

_{h}and ${\alpha}_{c}$—heat exchange coefficients in hot and cold channels, W/(m

^{2}°C);

^{2}/s,

_{h}—character dimension, m, determined as:

^{2};

_{c}—semicircle diameter, m.

^{3};

^{2}.

#### 2.3. Methodology of Feasibility Study

_{gas}—natural gas fuel price, RuR/m

^{3};

^{3};

- The Allam cycle heat flow analysis, calculation of the basic operation parameters of the regeneration system;
- Structural analysis of the heat exchanging device based on the heat flow analysis of different heat exchanger configurations;
- Analysis of the regenerator underheating and pressure losses influence upon the facility efficiency and the fuel expenses;
- Analysis of the regenerator underheating and acceptable pressure losses influence upon the regenerator dimensions and price;
- Summarizing fuel and regenerator manufacturing expenses, comparison with the basic version, determination of the nest parameters.

- Channel manufacturing by photo-chemical etching has constant price per an area unit;
- The nonproductive expenses, taxes, administrative expenses, etc., are taken into account by a multiplying coefficient k = 1.45;
- The fuel natural gas price is assumed as the mean whole sale Russian power production industry price.

## 3. Results and Discussion

#### 3.1. The Cycle Thermodynamic Analysis

#### 3.2. The Design Parameters of the Regenerator

_{2}mixture with water shows a non-linear change in its performance (Figure 10d).

#### 3.3. Change in the Energy Efficiency of the Power Facility

#### 3.4. Optimization of Design Parameters of the Regenerator

## 4. Conclusions

- Underheating increase in the feed heating system by 1 °C leading to efficiency factor drop of the net Allam cycle by an average of 0.13% and increases fuel costs by 0.28%. Increase of pressure drop in the hot channel by 1% reduces efficiency of electrical power generation by an average of 0.14%.
- Increase of underheating in the regenerator from 12.5 °C to 15 °C results in reduction of the required heat exchange area by an average of 42.5%, from 15 °C to 20 °C—by 40%, and from 20 °C to 25 °C—by 30.5%, for the channels of all shapes under review.
- Transition from straight semicircular channels to more complicated shapes is accompanied by a reduction of the required heat exchange area: under pressure drop of 1% and underheating of 15 °C, heat exchange area in the apparatus with zigzag channels is 1.78 times less than in case with straight channels, with airfoil fins—1.89 times, and with S-shaped fins—1.91 times. Meanwhile the most cost-efficient set of geometric parameters of the regenerator is determined by operating parameters of the apparatus.
- The maximum increment of cumulative costs is achieved under underheating and pressure drop equal to 23 °C and 4%—for straight semicircular channels (−32 mln. RuR/year as compared to the base level), 23 °C and 4% – for zigzag channels (−29.8 mln. RuR/year), 20 °C and 4%—for channels with airfoil fins (−45.75 mln. RuR/year), and 21 °C and 4%—for channels with S-shaped fins (−46.83 mln. RuR/year).

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 7.**Calculation results of the Allam cycle heat balance: (

**a**) parameters in the main units; (

**b**) T-S diagram.

**Figure 10.**Distributions at hot flow velocity 5 m/s of: (

**a**) heat transfer coefficient, (

**b**) regenerator pressure losses; (

**c**) fluid velocity; (

**d**) thermal conductivity.

Parameter | Value |
---|---|

CO_{2} turbine inlet temperature, °C | 1100 |

CO_{2} turbine inlet pressure, MPa | 30 |

CO_{2} turbine outlet pressure, MPa | 3 |

CO_{2} turbine coolant temperature, °C | 200 |

Multi-stage intercooled compressor massflow, kg/s | 600 |

Isentropic efficiency of turbines and compressors, % | 90 |

Pumps isentropic efficiency, % | 75 |

Mechanical efficiency of turbines, compressors, pumps, power generator % | 99 |

Power generator and electric motor efficiency, % | 99 |

Cooler-separator exit working fluid temperature, °C | 55 |

Minimum working fluid temperature, °C | 30 |

ASU power, MW | 31 |

Parameter | Value |
---|---|

Plate thickness, mm | 1.5 |

Plate width, mm | 600 |

Semi-circular | |

Channel pitch p_{c}, mm | 2.4 |

Channel diameter d_{c}, mm | 2 |

Zigzag channel | |

Channel angle ϴ, ° | 52 |

Channel pitch, mm | 2.4 |

Channel diameter, mm | 2 |

Channel step, mm | 7.565 |

Airfoil fins | |

Fin depth, mm | 0.94 |

Pin pitch on the x-axis L, mm | 8 |

Pin pitch on the y-axis H, mm | 2.2 |

Fin length l, mm | 4 |

Fin width h, mm | 0.8 |

Fin profile | NACA0020 |

S-shape | |

Fin pitch p_{x}, mm | 7.565 |

Fin depth, mm | 0.94 |

Hydraulic diameter, mm | 1.09 |

Parameters | Hot Channel | Cold Channel |
---|---|---|

CO_{2} temperature at the unit inlet, °C | 665 | 60 |

CO_{2} temperature at the unit exit, °C (varies) | 75 | 652 |

Fluid massflow, kg/s | 637 | 543 |

Fluid pressure, MPa | 3 | 30 |

Molar moisture content in the CO_{2} flow, % | 6.9 | 0.6 |

Heat power, MW (varies) | 462 |

Parameter | Value |
---|---|

Fuel price, RuR/m^{3} | 5.67 |

Block annual operation, hr | 6000 |

Low heating value, MJ/m^{3} | 35.59 |

Regenerator estimated life, years | 20 |

Plate photo-chemical etching, RuR/m^{2} (1$ = 70 RuR) | 11,900 |

Inconel 617 price, RuR/kg | 10,500 |

SS316 price, RuR/kg | 1400 |

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**MDPI and ACS Style**

Kindra, V.; Komarov, I.; Osipov, S.; Zlyvko, O.; Maksimov, I.
Feasibility Study of the CO_{2} Regenerator Parameters for Oxy-Fuel Combustion Power Cycle. *Inventions* **2022**, *7*, 66.
https://doi.org/10.3390/inventions7030066

**AMA Style**

Kindra V, Komarov I, Osipov S, Zlyvko O, Maksimov I.
Feasibility Study of the CO_{2} Regenerator Parameters for Oxy-Fuel Combustion Power Cycle. *Inventions*. 2022; 7(3):66.
https://doi.org/10.3390/inventions7030066

**Chicago/Turabian Style**

Kindra, Vladimir, Ivan Komarov, Sergey Osipov, Olga Zlyvko, and Igor Maksimov.
2022. "Feasibility Study of the CO_{2} Regenerator Parameters for Oxy-Fuel Combustion Power Cycle" *Inventions* 7, no. 3: 66.
https://doi.org/10.3390/inventions7030066