IGCC: Integrated Gasification Combine Cycle Technology

Panel on “Clean Coal Technologies” in ODTU Alumni in Ankara

Dear Energy Professional, Dear Colleagues,

We had a meeting on Saturday afternoon 23rd February 2008 at the main conference room of “Chamber of Engineers” head office in Ankara Thessalonica Street. The meeting was held with participation of leading senior/ retired members of local energy business, former General Managers, former operation managers, senior researchers of various public enterprises, as well as senior local energy experts.

Flow Diagram IGCC

Flow Diagram IGCC

The subject was “Clean Coal Technologies” which is actually the code name for Integrated Gasification Combined Cycle technology. IGCC is a new technology to answer global warming.

This new technology produces synthetic gas from coal. Synthetic gas has almost one fourth of the heating value of average natural gas.

IGCC technology is first innovated by Germans during WW2 to produce gas and/or liquid fuel for the fighting war vehicles in an environment with no petroleum resources, and further developed in South Africa during world embargo against their apartheid practices in their domestic politics.

Since the equivalent cost per barrel is/was around 50 US Dollars for the synthetic fuel, it was not feasible in the past to apply “clean coal technologies” since it had no chance of competition against low petroleum prices then. However the time has changed and petroleum now costs more than 100 US Dollars per barrel, therefore IGCC technology is now an attractive fuel option.

Our guest speaker, Dr Iskender Gokalp is a Turkish national scientist, Directeur in ICARE, Institut de Combustion, Aérothermique, Réactivité et Environnement, UPR3021 du Centre National de Recherche Technologique, “Propulsion du Futur” in 1c, Av. de la Recherche Scientifique, 45071 Orléans cedex 2, France, http://www.cnrs-orleans.fr/icare/

He comes to Turkey, to his homeland, one week for each month to pursue and execute a project to grand PhD scholarships to young Turkish engineers/ scientists in France on coal utilization, combustion technologies, supported by Turkish Coal Board and European Union under current FB7 program.

He created many scientific publications, and also had great influence in international scientific circles. He recommends us to carry out more research on “Clean Coal Technologies” on local Turkish Lignite specifically on low heating value coal mines, to justify its application and competitiveness.

He advises that local lignite coal could be the best option for application of integrated gasification. Your humble writer sincerely feels that Dr.Iskender GOKALP has all reason to advise on application of “Clean Coal Technologies” in local lignite reserves.

It is also our sincere feeling that clean-coal technology is a must. Energy tops the agenda of all local winter meetings. Next-generation coal is going to need to continue to be part of our energy future for our country. It is abundant, it is locally available, in the sense that we control the supply.

Next-generation coal typically refers to capturing and somehow sequestering or storing the carbon that coal produces. It also envisions reducing or eliminating emissions as coal is burned. It is possible to continue relying on the fossil fuel while minimizing its impact on the environment.

We cannot ignore coal, we should find better ways to utilize local lignite coal. That is important because electricity demand will ever increase in the future.

We all know that Coal has a CO2 problem, Wind has a reliability problem, Solar has a price problem, Nuclear power plants have price, radiation and unsafe disposal problem, so all of those technologies have opportunities and they all have problems.

What we can say about coal, is that we have it locally. We have it in a greater supply.

Synthetic gas production could be a bid expensive but the rest of the system is well-known combined cycle power plant.

Prevailing overall market price is around 1200- 1500 US dollars per KW installed capacity for 600-1000 MWe power plant test sizes. By localizing the technology, we can substantially reduce that first installations cost.

On the other hand local low LHV lignite has current fuel cost less than 2 (two) US Dollars per million BTU gross, whereas imported coal cost is 6- 8 US Dollars gross, Natural gas cost is around 8-10 US Dollar, and imported LNG price in spot market is around 17-18 USD per million BTU.

Senior experts have an ideefixe for application of IGCC on high heating value bituminous coal or steam coal. On the other hand, Dr Gokalp says that IGCC has potential application on low heating value lignite. It is for sure that we do not know if IGCC is perfect match for our lignite. All we have to do is to allocate more funds for more research on local lignite.

We shall have a panel on “Clean Coal Technologies” in ODTU Alumni Association Visnelik premises in Ankara on 10th March 2008 Monday at 1900 hours.

Dr Iskender Gokalp will be one of four distinguished panelists. The other panelists are Prof Dr Bekir Zuhtu UYSAL, Director of Clean Energy Institute of Gazi University, Dr Selahaddin ANAÇ GM of Turkish Coal Board, and Mr. Orhan Baybars ME’79, former site construction manager of Afsin Elbistan-B thermal power plant.

Panel will be conducted in Turkish, and it is open for all interested parties. Entrance is free-of-charge. We have free coffee/ tea services. Please do participate if you would be in Ankara on that day. Your comments are always welcome.

Haluk Direskeneli
ODTU ME’1973 – Ankara MMO 6606

Sample calculations of Boiler Pumps and ID / FD Fans

Sample sizing calculations for BFW pumps and Fans for a typical Coal fired Boiler generating steam of 50,000 Kg/hr at 67 kg/cm2 and 485 degC. (110,000 lb/hr at 950 PSI & 905 F). Feed Water inlet at 105 C and Exhaust gas temp at 150 C.
Let us first calculate heat load and fuel consumption of the above boiler.

coal boiler

coal boiler

Pressure and temp at 1. Superheater Outlet : 67 Kg/cm2 & 485 C
2. Steam Drum : 73 Kg/cm2 & Saturated
3. Economizer inlet : Water inlet at 105 C

From Steam tables,
Enthalpy of Superheated steam , Hsh = 809 Kcal/ kg = 1456 BTU/lb
Enthalpy of Drum water , Hdwat = 305 Kcal/kg = 549 BTU/lb
Enthalpy of inlet water , Hwat = 105 Kcal/kg = 189 BTU/lb

Assume 3% Blowdown from Boiler.

Total Heat Load of the Boiler = Total heat absorbed by water to convert to steam + heat absorbed to get superheated + Blow down losses
= 50000(809-305) + 50000 x 1.03 x (305-105)
= 35.5e06 Kcal/hr = 140.87e06 BTU/hr

Fuel consumption = Heat Load/ (HHV x Efficiency)
= 35.5e06/ (7278 x 0.8649)
= 5639 Kg/hr = 12428 Lb/hr of coal

From previous article on Combustion and efficiency,
Wet gases = 14.05 and Air = 13.12 kg / kg of coal

Therefore, Exhaust gases produced = Fuel consumption x UnitWetGas
= 5639 x 14.05
= 79,228 Kg/hr of wet gases
Combustion Air required = 5639 x 13.12
= 73,984 Kg/hr of combustion air

Feed Water required = 50,000 x 1.03 : 3% Blowdown
= 51,00 Kg/hr

Sizing Calculations :
a) Boiler feed Water Pumps :

Two pumps of 100 % capacity are required one for working and one for standby.

Each pump discharge capacity minimum= 51500 Kg/hr
= 51500/950 : 950 kg/m3 water density
= 53.8 m3/hr
Margin on discharge capacity : 15- 25 %.
Take 20% margin in this case.

So discharge capacity of each pump : 53.8 x 1.2
= 64.6 m3/hr =say 65 m3/hr

If Recirculation valves are not provided, you need to add min recirculation flow to the above figure, which may be about 6-10 m3/hr depending up on pump type and make.

Pump head required = Drum Pressure + Drum elevation + Piping Losses + Control Valve Loss + Other valve losses

= 75 Kg/cm2 + 2.0 + 2.0 +5.0 +2.0
= 86 Kg/cm2
= 86 x 10/0.95 mts of water head at 105C
= 905 mts of WC

Provide up to 5% margin on head. So final Pump head is 905 x 1.05 = 950 m of WC
So BFW pumps (2 nos) rating is 65 m3/hr at 950 m of WC with feed water at 105 C.

b) Sizing calculations of FD Fan :
Forced Draft Fan is required to pump in primary combustion Air into the Boiler furnace. Air from FD fan passes through Air Heater before entering furnace through Grate. Secondary Air Fan (SA fan) supplies secondary combustion air in to the furnace. Usually primary air is 70 -80 % of the total air and balance is supplied as secondary air through SA fan. Secondary air is supplied at a higher pressure to help fuel spreading on the grate called as pneumatic spreading.

Total combustion Air, Kg/hr = 73,984
= 73994/(1.17 x 3600) m3/s :Air density-1.17kg/m3
= 17.56 m3/s

Primary Air , 70% of total , m3/s = 0.7 x 17.56
= 12.3 m3/s

Take 20% margin on discharge capacity. So FD Fan flow is 1.2 x 12.3 = 14.76 m3/s

Head required = Draft loss across Air Heater + Grate + Ducting & others
= 75 mmWC + 75 + 50 mm : Approximate
= 200 mm WC (approximate)
Take 15-20 % margin on head. So FD fan head should be about 230 mm of WC.

Therefore, FD fan rating is 15 m3/s of air at 230 mm WC static head.

Power requirements of FD Fan :
Let us assume Fan efficiency as 75% and Motor Efficiency as 90%.
Power required for FD Fan, BHP = Flow x Head / ( Efficiency x 75.8 )
= 15 x 230 / ( 0.75 x 75.8 )
= 60.7 HP

Motor HP required = 60.7 / 0.9 = 68 HP
Annual cost of operation assuming 7 cents per KWH and 7200 hrs of operation per annum. 0.74 is factor for converting HP to KW. Pl note that unit Electricity charges vary widely across different countries.

= 68 x 0.74 x 0.07 x 7200
= $ 25, 362 /-

c) Sizing calculations of SA Fan :
Secondary Air Fan (SA fan) supplies secondary combustion air in to the furnace.
Secondary Air , 30% of total , m3/s = 0.3 x 17.56
= 5.27 m3/s

Take 20% margin on discharge capacity. So SA Fan flow is 1.2 x 5.27 = 6.3 m3/s
SA fan static head is about 630 mm WC.
Therefore, SA fan rating is 6.3 m3/s of air at 650 mm WC static head.

Power requirements of SA Fan :
Let us assume Fan efficiency as 70% and Motor Efficiency as 90%.
Power required for FD Fan, BHP = Flow x Head / ( Efficiency x 75.8 )
= 6.3 x 650 / ( 0.7 x 75.8 )
= 77.1 HP

Motor HP required = 77.1 / 0.9 = 86 HP
Annual cost of operation assuming 7 cents per KWH and 7200 hrs of operation per annum. 0.74 is factor for converting HP to KW. Pl note that unit Electricity charges vary widely across different countries.

= 86 x 0.74 x 0.07 x 7200
= $ 32,075 /-

d) Sizing calculations of ID Fan :
Induced draft fan or ID Fan is required to evacuate the exhaust gases from Boiler to atmosphere through Duct collectors and chimney. Usually ID should take care of draft loss across the Boiler from furnace to Air heater and then draft loss across Duct Collectors like ESP, Wet Scrubber or mechanical type Cyclone dust collectors .etc.
Total wet gases, Kg/hr = 79,228

Gas Density = 1.3265 Kg/Nm3
Therefore, gas flow in Nm3/hr = 79,228 / 1.3265
= 59227 Nm3/hr
= 16.6 Nm3/s

Gas flow at 150C in m3/s = 16.6 x (273+150)/273 = 25.7
ID Fan capacity taking 20% margin on flow = 25.7 x 1.2
= 30 m3/s

ID Fan static Head = Draft Loss in (Boiler + Duct + Dust collector)
= 150 + 50 + 50 mm WC : Approximate
= 250 mmWC

Taking 20% margin on head, ID Fan head = 250 * 1.2 = 300 mm WC

Power requirements of ID Fan :
Let us assume Fan efficiency as 75% and Motor Efficiency as 90%.
Power required for ID Fan, BHP = Flow x Head / ( Efficiency x 75.8 )
= 30 x 300 / ( 0.75 x 75.8 )
= 158 HP

Motor HP required = 158 / 0.9 = 175 HP
Annual cost of operation assuming 7 cents per KWH and 7200 hrs of operation per annum. 0.74 is factor for converting HP to KW. Pl note that unit Electricity charges vary widely across different countries.
= 175 x 0.74 x 0.07 x 7200 = $ 65,268 /-