Integrated Gasification Combined Cycle (IGCC): Trend of the Future
Power plants have various attributes and architecture, both based on the nature of work for which they have been erected. They vary in efficiency, in operations and in their degree of emissions. Integrated Gasification Combined Cycle (IGCC) is very much a futuristic trend and is considered as a clean mainstream commercial offering for ‘clean coal.’
The demand of electricity the world over has increased the demand for building new power plants with a tinge of innovation. Innovation, however, does not mean to curb the traditional backdrop involved in building power plants. Although there are certain interest in using renewable energy for constructing power plants, the abundance of coal supply along with volatile oil prices create a demand for Integrated Gasification Combined Cycle (IGCC).
An optimal combination of combined cycle turbine system along with gasification generates electricity. The process by which electricity generated gets worked through a power plant called famously as Integrated Gasification Combined Cycle (IGCC). This process aids in using the most environment-friendly way to produce low cost energy.
Operational Synopsis of Integrated Gasification Combined Cycle (IGCC)
The process involves the use of oxygen or air produced via air separation unit (ASU), for its combination with high pressure, high temperature gasifier so as to enable gasification of hydrocarbon feedstock. Syn-gas (synthesis gas) so resulting from the process of gasification is made to cool down, before making entry into gas turbine. For the purpose of driving steam turbine, steam is produced by making gas turbine hot exhaust flow through heat recovery steam generator (HRSG).Both steam as well as gas turbine generators are optimal for the production of electric power. Next, very low levels of volatile mercury along with critical air pollutants are produced by Integrated Gasification Combined Cycle (IGCC). Further, emission forming constituents are eradicated from pressurized syngas.
State of art design for Integrated Gasification Combined Cycle (IGCC)
The basic Integrated Gasification Combined Cycle design has experienced many variations. The current Integrated Gasification Combined Cycle design equips gas turbine compressor to render 25 to 50 percent of oxygen supply to the air separation unit (ASU), while the rest of oxygen supply is sought by the ASU from air compressor which stands as a separate entity.
Further, Compression of the syngas is protected by preferring pressurized gasification to prevent auxiliary power loses of enormity. Most of the IFCC applications select entrained flow gasifiers. Higher temperature slagging regions are preferred for the flow of such gasifiers. Tar formation as well as certain other related intricacies is avoided by such entrained-flow gasifiers.
In order to satisfy market recommendations of large commercial turbines, building single gasifiers with large outputs is found as optimal. Large components of IGCC plant comprise of the gasifier, syngas coolers, HRSG sections, gas turbine, and the ASU including cryogenic cold box. As a matter of fact, the aforesaid components can be fabricated or customized in the shop before being transported to the site. Just like pulverized coal plant, three years of time span is estimated for its construction and installation.
Integrated Gasification Combined Cycle (IGCC) compared with other combined cycle electric technologies
The nature of operations is what dictates the kinds of power plants. Some prefer a particular operation while the others opt for operation of different nature. As regards to combined cycle power plants, the Coal power plants prefer to cater to base load nature of operations. The IGCC power plants prefer the same, whereas Natural Gas combined cycle power plants prefer to cater to peak capacity. Parameters such as cost of energy production, capital costs, factors impacting the environment, carbon dioxide capture cost-effectiveness and its potential, can be base upon which IGCC could be compared to super critical pulverized coal (SCPC) with feasibility. An additional comparison with natural gas combined cycle could be optimal.
United States and most of the other nations regulate air pollutants emitted from power plants or certain other stationary sources, as well as vehicles. Criteria air pollutants, as they are so-called, include carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), and particulate matter (PM). New Source Performance Standards for large-scale, power plants based on combustion and which use coal, has been established by the U.S. Environmental Protection Agency (EPA). IGCC facilities of current as well as future generation act in tandem with the regulatory whereby: (1) the EPA’s standards are either met or exceeded (2) air pollutants based on criteria are emitted lesser than SCPC plants; and (3) natural gas combined cycle (NGCC) facilities are favorably compare with.
Mercury emitted from power plants remains an unsorted issue since a long time. However, on March 15, 2005, the issue got submerged in a semi-solution when Clean Air Mercury campaign issued by the EPA, called for a two phase mercury reduction. The second phase being due by 2018 will further see limitations in mercury emissions via pro rata national limits. It was suggested by December 2002 study that Integrated Gasification Combined Cycle plants have a n edge when compared with other combustion based plants and where mercury control is the issue, Natural gas and gasifier syngas have been treated with commercial methods for eradicating traceable amounts of mercury from them, that 90 to 95 percent efficiency of mercury removal has been seen when activated carbon beds and molecular sieve technology have been used for the same.
However, in consideration with statistics and certain other studies the cost incurred or expensed for undertaking mercury removal has been estimated to $3,412 per pound of mercury removed, by 18-month carbon replacement cycle, which is much lesser (1/10) than expense estimated for mercury removal via SCPC.
As compared with other coal combustion based power plants, Integrated Gasification Combined Cycle has least environmental impact in relation to both – waste material volume produced as well as its capability to leach toxic substances underground. Slag also known as bottom ash is the largest solid waste stream produced by Integrated Gasification Combined Cycle. Moreover, gasifier slag is detected to be ‘non-leachable’, unlike other combined cycle plants, wherein the slag has demonstrated to be leechable.
Large volume of carbon dioxide (CO2) which is emitted by coal-based power plants has become a long drawn concern for global environmental activists as well as the greenhouse proponents. Of all the pollutants, CO2 is termed to be greenhouse gas, the emission of which could disturb the global climate balance.
Where the capture of CO2 by coal plants seems viable, it is agreed to be an expensive proposition. The CO2 capture done by Integrated Gasification Combined Cycle plant is also suggested as an expensive projection, however the difference in CO2 capture cost from Integrated Gasification Combined Cycle is mainly due to the differentials in process of capture. Like in Integrated Gasification Combined Cycle, CO2 gets removed from syngas before process of combustion, unlike other process of power plants where CO2 is separated post-combustion.
Comparison based on Economic costs
SCPC power plant costs 20 to 25 percent lesser than comparable Integrated Gasification Combined Cycle power plant. However, at 2005 Gasification Technologies Conference it was suggested that a further reduction of 10 percent capital cost per premium will be observed in Integrated Gasification Combined Cycle market price.
Cost of Electricity
A gap of 20 to 25 percent capital cost premium causes gap differential of cost-of-electricity mainly due to environmental benefits conferred by Integrated Gasification Combined Cycle. In comparison, Integrated Gasification Combined Cycle could be more expensive than SCPC plants, however the benefits to be derived from it sideline the cost burden. However for some, the results derived from SCPC and Integrated Gasification Combined Cycle is at parity.
Integrated Gasification Combined Cycle is now getting a commercial viability, as it is getting recognition as hedging strategy for long term, against rise in the price of oil. Moreover, US recommendations to shift towards gasification via coal use, is believed to place a long term ceiling on the oil prices. Integrated Gasification Combined Cycle has faced competitions from various modulations of power plants in general, and combined cycle plants to be precise.
However, Integrated Gasification Combined Cycle stands far tall where carbon capture is concerned or has to be considered. Integrated Gasification Combined Cycle lay a long term proven capture methodology which separates carbon even before combustion process. In the U.S., such procedure via Integrated Gasification Combined Cycle is called as carbon sequestration.
However, apart from carbon sequestration Integrated Gasification Combined Cycle is recognized as the cleanest technology for generating electricity. Gasification itself stems from Integrated Gasification Combined Cycle’s attribute to enable mitigate volatility of fuel price along with protecting environment. Also, excluding recent nuclear plants, one could trace a viable thermal power option only in Integrated Gasification Combined Cycle. In fact, Integrated Gasification Combined Cycle is now experiencing lot of reforms, from the governmental regulations as well as the modern entrepreneurs who seem to have found a gold mine in combined cycle plant of rare cadre. With all the reforms and innovations in technological space, in relation to combined cycle power plants, it would not be too long for Integrated Gasification Combined Cycle to overtake its competition.