Pre-combustion CO2 capthre

CHENG Jian Aug. 16 2012

Content

• Climate change • CCS method • Pre-combustion system introduction • Pre-combustion process selection • Pre-combustion system design • System energy comsumption

Climate change

Global average temperature is ascending obviously. It caused by greenhouse.

Climate change

• The aggravation of global warming is caused by intensifying greenhouse effect.

• The radiation intensity of CO2rose by more than 20% between1995 and 2005, the highest speed during the past 200 years.

• The greenhouse effect caused by CO2 accounts for 77% of all greenhouse gases.

• Control of CO2emission is the key issue in tackling climate change!

Climate change

• Change the fuel used in power plant, for example develop nuclear power, hydro power, natural gas and renewable energy (wind, biomass, solar…)

• Improve the plant efficiency (use large scale SC/USC units and

IGCC units).

• Carbon capture and storage (CCS).

CO2 capture technologies

Pre-combustion capture

Post –combustion capture

CO2 capture

CO2 storage

CCS in Huaneng GroupS •Chinese coal-based energy structure will not change in the long term. •Power generation is the primary CO2 emission source. It accounts for about 50％of the total emission in China, and will increase in the future. •Huaneng Group develop clean energy and CCS technologies to face the climate challenge .

CCS in Huaneng Group

120,000t/a CCS system in Shanghai Shidongkou power plant

3000t post-combustion CCS system in Beijing power plant

CCS in Huaneng Group • CO2 concentrations in a coal –fired power station is 12% ~ 14%, the

pressure is 1 atm., so capture method only select MEA chemical absorption method is fit for post-combustion power plant. It need a lot of solvent and much steam to capture CO2, so the energy consumption for post-combustion will be very great.

• Pre-combustion CO2 capture due to the high CO2 concentrations and high total pressure, this make the use of physical absorption method for trapping, pre-combustion capture CO2 has certain advantages in energy consumption, so pre-combustion method is more prominent than the post-combustion method.

• Huaneng Group planed to develop pre-combustion technologies and set up a 30MW th pre-combustion system.

CCS in Huaneng Group Pre-combustion CO2 capture system

The first 250MWe IGCC demonstration power plant was built in Tianjin; a 30MWth pre-combustion CO2 capture and storage system will be built on the basis of the demo IGCC plant .

CCS in Huaneng Group

CO2 compress and transport to oil well for EOR and storage

CCS in Huaneng Group

Pre-combustion system Air

Seperation

GasificationHigh Tem. Clean up

Air

Coal

petroleum coke and residue

O2

N2,ArNG

Heat/power/cool cogeneration

IGCC or GCC

chemical products

Liquid fuel

others

Syngas

ShiftSteam

Seperation

Heat/power/coal cogeneration

Fuel cell

Large-scale power

generation

Seque-stration

Dry ice

ferti-lizer

algae plant growth

CO2+H2

CO2H2

Commercial building

residential

enhancement of CBM

A pre-combustion system must be set up based on a gasifier.

Pre-combustion system A pre-combustion CCS system includes: • Water–gas shift • Desulfurization • Decarburization and H2 seperation • purify CO2 to industry stage • CO2 compress and transport • CO2 inject into oil well CO2 capture rate and energy consumption must be

considered in the system design.

21

工艺流程中应考虑的问题：

1、根据原料气co含量,满足变换率的要求

分段和段间降温方式

达到催化剂反应温度降低能耗

2、防止催化剂超温

3、反应余热的充分利用，

4、蒸气的回收和利用 降低外供蒸汽消耗

5、延长催化剂寿命

介质的净化

Water- gas shift process

CO+ H2O CO2+H2+Q

Water- gas shift process

Desulfurization • The Rectisol is a physical absorption method. The 1m3 solvent

can absorb 160 ~ 180m3 CO2 at 3.0MPa pressure so solution cycle is .

• Simultaneous removal of impurities such as CO2, H2S and COS, CO2select absorbent strong and H2S, high degree of purification.

• The disadvantage is operating under a low temperature of -40 ℃, so low temperature materials is required, so the system investment maybe higher.

Desulfurization

• MDEA is a good method to absorb CO2 and H2S. • H2S is priority selected to removal to a few ppm. • 1% -5% of the activated MDEA CO2 can remove CO2 and

H2S at the same time. • Low energy consumption, generally 1.6-2.OkJ/Nm3.C02; • less investment in equipment;

Desulfurization and carbon capture

Desulfurization and carbon capture

Desulfurization and carbon capture

• Common MDEA process: CO2 with H2S to the tarch is around 26.4% of shifting gas CO2 。

• Common MDEA carbon capture with PSA: MDEA CO2 capture ratio is only around 66%。

• MDEA H2S-CO2 co-removal: CO2 capture ratio will reach 90%

• Thus, H2S-CO2 co-removal process is one of best options for pre-combustion CO2 capture

Energy concumption 项目 单位 单位折能MJ MDEA消耗 硫碳共脱消耗

中压蒸汽 t/h 2793 5.66 1.95

低压蒸汽 t/h 2754 4.5

电 kWh 11.84 1723 1755

锅炉给水 t/h 28.470 1.566 1.5

冷却水 t/h 2.512 498 605

产品氢气 Nm3/h 10.79 －6941 －7100

变换回收热量 GJ 10. 54 10.54

合成气 Nm3/h 9.45 10000 10000

产品CO2 万吨/年 6.12 7.35

操作时间 8000h

Energy consumption

• Energy consumption for common MDEA desulfurization with pressure swing adsorption CO2 capture is around 6.08GJ/tCO2,

• H2S-CO2 co-removal: 5.17GJ/tCO2， • Energy consumption gradually increase with CO2 capture ratio • Comparison: Huaneng Beijing Thermal Power Plant Post

combustion CO2 capture, steam energy consumption 3.6GJ/tCO2, power 75KW , CO2 compression and refining 175kW，Total energy consumption 6.55GJ/tCO2。

Energy consumption

• However, since pre-combustion CO2 capture have longer process, with shifting reaction, desulfurization, carbon capture and CO2 compression

• If one would like compare the energy consumption between pre-combustion CO2 capture and post-combustion CO2 capture, we need to remove the MDEA desulfurization energy cost

• Thus, we can get pre-combustion CO2 capture energy consumption at 2.50GJ/tCO2, which is far lower than post-combustion CO2 capture

• From the simulation, it can be indicated that the energy consumption CO2 capture energy consumption can be further lowered by full utilize the shifting process waste heat and to reduce the steam consumption

Energy consumption