Cleaner technologies reduce pollution

Paul Boughton

Coal-fired power generation is being dominated by the emergence of new technologies designed to boost efficiency and reduce pollution. These include mega generation units, conversion of coal into gas for power generation, and further developments in carbon capture.

Construction of the new coal-fired power plant at Kozienice in Poland has reached an important milestone with the erection of the first of four boiler columns on the site.

The ultra-modern bituminous coal power plant is being built by Mitsubishi Hitachi Power Systems Europe (MHPSE) and consortium partner Polimex-Mostostal (PXM); the purchaser is Polish energy supplier ENEA Wytwarzanie.

The plant is designed for an installed capacity of 1075MW and a 45.59% net efficiency. On being placed into operation as planned in 2017, it will rank among the most efficient of its type in the world and join an existing plant on the Kozienice site.

The four columns of the boiler supporting structure are currently fixed on its foundation. The total weight of this structure amounts to 3250 tonnes. More than 100 highly-qualified engineers will participate in the assembly process. Construction of the main supporting structure of the boiler is expected to be complete shortly.

The most important components for the ultra-modern unit either come from companies within the corporate group or from parent company Mitsubishi Hitachi Power Systems (MHPS). These include the utility steam generator including coal bunkers, coal mills, firing equipment, flue gas cleaning, and some balance-of-plant. MHPS supplies the steam turbine, generator and auxiliary equipment. Babcock-Hitachi (BHK) supplies the flue gas desulphurisation plant. PXM is responsible for the construction, assembly and supply of the service equipment of the power plant.

"The construction of the new 1075MW power unit is an extremely complex process, requiring perfect co-operation of all involved in the project parties, beginning with the project, through deliveries, adjusting of the contractors' and sub-contractors' schedules, ending with quality assurance and supervision. Important is the fact that all those actions are happening within the existing infrastructure of the Kozienice power plant,” noted Krzysztof Sadowski, president of the ENEA Wytwarzanie board of directors.

Across the Atlantic, Mississippi Power’s Kemper County energy facility’s combined cycle unit has been placed into commercial operation, marking the facility’s most significant milestone to date.

The unit was originally synchronised to the grid on 5 October last year during testing using natural gas as fuel. Over the past 11 months, critical testing was done on various components. The testing culminated with the combined cycle unit passing all applicable performance and environmental tests and being made available at full output for commercial operation.

During the course of the testing, the Kemper combined cycle unit logged more than 1,200 hours on line generating power for homes and businesses. To date, the Kemper combined cycle unit has generated enough energy to supply 23,000 homes for a year.

The project earlier reached two major milestones with the testing of the combined cycle unit and pressure testing of both gasifiers. Another significant milestone – the first gasifier heat up – is scheduled for later this year.

The gasifiers at Kemper are the core of the integrated gasification process, which will be used to convert lignite into synthesis gas. The company says that use of Mississippi lignite adds fuel diversity at low costs and stable prices for its customers.

Construction progress continues at the Kemper County energy facility which will use innovative clean coal technology to deliver safe and reliable Mississippi Power customers. The 582 MW generating facility is scheduled to begin operation in the second quarter of 2015.

Mississippi Power is a subsidiary of Southern Company and produces energy for more than 186,000 customers in 23 southeast Mississippi counties. 

Carbon capture 

The US Department of Energy (DOE) is providing financial assistance to Petra Nova to demonstrate the addition of a commercial-scale post-combustion carbon capture technology at the coal-fired WA Parish generating station located in Thompsons, Texas. 

The project will demonstrate the ability of an advanced amine-based carbon dioxide capture system to capture 90% of the carbon dioxide emitted from a flue gas stream equivalent to 240MW in size. The host power generation unit will not be derated because the power and thermal energy required to operate the carbon dioxide capture and compression system will be provided by a cogeneration plant comprised of a combustion turbine with a heat recovery boiler. This advancement is anticipated to reduce carbon capture costs and increase system flexibility and efficiency.

The captured carbon dioxide will be compressed and transported through an 80 mile pipeline to an operating oil field where it will be utilised for enhanced oil recovery (EOR) and ultimately sequestered. The scale of the project has been increased because the original 60 MW project was determined to be too small to immediately induce significant oil production.

A portion of the flue gas from WA Parish unit eight that has already been treated to reduce nitrogen oxides (NOx), particulate matter, and sulphur dioxide will be diverted from the existing stack to the carbon dioxide capture system. 

When entering the carbon dioxide capture system, the flue gas is first routed to the flue gas cooler for conditioning, such as cooling and dehydration, and additional sulphur dioxide removal. The flue gas is cooled because the absorption of carbon dioxide is favoured at lower temperatures. The cooled flue gas will contact a circulating sodium hydroxide solution for polishing sulphur dioxide removal, where 98% of the remaining sulphur dioxide is removed from the stream because it interferes with the amine’s ability to react with carbon dioxide.

The conditioned flue gas will be routed to the absorber, where carbon dioxide is captured by the amine-based solvent through a chemical reaction. The carbon dioxide rich solvent stream is sent to the regenerator, or stripper, where the carbon dioxide is released from the solvent using low pressure steam. Heat from the steam breaks the weak bond between the carbon dioxide and the solvent, liberating the carbon dioxide and leaving the solvent behind for additional carbon dioxide capture use. 

The captured carbon dioxide will be compressed, dried, and then transported via pipeline to the West Ranch oil field, located near Vanderbilt, Texas.

US utility plans further coal to gas conversion

Indianapolis Power & Light Company (IPL) is shortly to file plans with the Indiana Utility Regulatory Commission (IURC) to repower unit seven at Harding Street generation station (HSS) from coal-fired to natural gas. This conversion is part of IPL’s overall wastewater compliance plan for its power plants. 

“IPL has a commitment to provide affordable electricity, and converting Harding Street unit seven to natural gas is the best plan for our customers because it is the reasonable, least cost option,” said Kelly Huntington, IPL president and ceo. “Compliance with current and future EPA standards will continue to increase the cost of electricity for our customers.” 

In May, IPL received approval from the IURC to convert Harding Street units five and six from coal to natural gas. IPL plans to stop burning coal at the Harding Street power plant in 2016, if plans to convert unit seven are approved.This plan would reduce IPL’s dependence on coal from 79% in 2007 to 44% in 2017, making natural gas IPL’s largest fuel generation source.  IPL also remains a leader in wind and solar generation. A recent study by Environment California Research & Policy Centre indicated that Indianapolis ranks fifth in the USA for solar per capita.

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