Alstom now Offering Modular Design Dry Lime NID^TM FGD

Lars-Erik Johansson of Alstom told the Power-Gen India & Central Asia audience that reliable technologies exist to meet the future FGD market in India, but each case must be evaluated. An overview of typical key FGD parameters is given in Figure 1.

Figure 1. Typical Key Parameters for Different Technologies - Overview

A recent development with the Alstom NID system is modular design (NID-C), which offers arrangement flexibility and adaption to larger sizes of boilers. Shop fabrication is drastically cheaper than field fabrication and both truck and barge shipments are possible. The modules are independently isolatable with dampers upsteam of the reactor and downsteam of the fabric filter compartment. Each module handles a nominal gas flow of 15 to 70 MW, the system can be designed to achieve emissions guarantees at full load with one module out of service, and the modular system allows for turn-down up to 60 percent without recirculation.

A recent NID-C application was at 410 MW Indian River firing a 2.5 percent S coal. Ninety-six percent SO₂ removal was achieved along with HCl, SO₃, HF, and particulate reduction.

NID System for Minnesota Power 585 MW Boswell 4

Alstom has a contract to deliver an emission control system for Unit 4 of Minnesota Power’s Boswell Energy Center. Alstom’s NID™ semi-dry FGD system will reduce the plant’s environmental footprint by cutting mercury emissions by 90 percent and significantly curbing emissions of SO₂ and other pollutants. “When completed, Boswell 4 and our recently retrofitted Boswell 3 will be two of the cleanest coal-fired units in the nation,” said Al Hodnik, Chairman, President and CEO of ALLETTE, Inc, Minnesota Power’s parent company. The project is pending Minnesota Public Utilities Commission (MPUC) approval and a decision is anticipated from the MPUC in September.

NID System at Indian River 4 Averages 0.1 lb/MMBtu SO₂

Alstom installed an eight-compartment NID^TM dry FGD system at 410-MW NRG Indian River 4. Startup, tuning and testing of this system occurred in 2012. Unit 4 is load following and fires Eastern bituminous coal with sulfur up to 4.5 lb/MMBtu.  Guarantee requirements were less than or equal to 0.18 lb/MMBtu SO₂, less than or equal to 1 ppmv SO₃, less than or equal to 0.60 lb/TBtu mercury and less than or equal to 1 ppmv HCl.

A few issues were noted at startup of the NID system, but these issues did not affect SO₂ compliance. There were lime flow balance issues with the splitter conveyor and it was decided to convert to single feed. The inlet vanes designed to equalize gas and dust distribution to the fabric filter system were removed due to a pressure drop issue. After commissioning of the NID system, the CEMS recorded a typical 24 hour average of 0.1 lb/MMBtu SO₂. EGU MATS limits were easily achieved as well during performance testing.

Alstom to Supply NID FGD System to 2 x 660 MW Homer City 1, 2

Alstom has announced the award of a $95 million contract to supply its NID dry FGD systems for two 660 MW coal-fired units at the Homer City Generating Station in Indiana County, Pennsylvania. The project is designed to reduce emissions of SO₂, mercury and other pollutants. Alstom will supply NID system reactors, fabric filters, mixer and hydrators, inlet and outlet plenums, lime storage and feed systems, and activated carbon injection equipment to Kiewit Power Constructors under a turnkey EPC agreement for the environmental upgrades.

NID System for 630 MW Brayton Point 3

Alstom just finished installing a NID system at 440 MW NRG Indian River 4. Indian River 4 fires bituminous coal with an inlet loading of 4.5 lb SO₂/MMBtu. SO₂ will be reduced by 96 percent. Alstom is also installing a NID system at 630-MW Brayton Point 3. Inlet loading of SO₂ is 2.5 lb/MMBtu and SO₂ will be reduced by 98 percent. This system will be commercial in early 2014, reported Lawrence Gatton of Alstom.

The NID FGD is a dry process using a J-reactor and hydrated lime. The lime is hydrated onsite. Byproducts are CaSO₃/CaSO₄/ash. The stoichiometric ratio is 1.5 to 1.8; pressure drop is 13-15 in. w.g. Advantages of the modular NID process are

▪    Low load turndown, achieved through module isolation without gas recirculation

▪    Single system capacities>800 MW with multiple modular units

▪    Multi-pollutant control of SO₂, HCl, HF, SO₃, filterable particulate, and mercury with PAC

ALSTOM Supplies NID Dry FGD for Lithuanian Power Plant

ALSTOM has won a number of orders worth 23 million euros to supply air pollution control systems. The largest of these orders is from the JSC Lithuanian Power Station in Elektrenai, Lithuania for the supply of an electrostatic precipitator and a NID dry FGD system. The equipment will be installed on the newest of the power station’s twelve 410 MW boilers fueled by heavy fuel oil or Orimulsion. Also Alstom will install an SCR system on a crude oil furnace at Preem Raffinaderi AB’s plant in Gothenburg, Sweden, reducing NO_x emissions from the furnace by 90 percent. 

European Dry FGD Product Utilization

Alstom Power gave a paper at Power-Gen Europe 2001 highlighting European uses for dry FGD wastes. Dry FGD products are produced in different types of semi-dry FGD processes, such as spray dry absorption, CFB desulfurization systems, the NID process and others. The product consists of calcium compounds — mainly calcium-sulfur reaction products — and can contain  varying concentrations of flyash.

The largest utilization area for dry FGD product is as fill mixed with flyash. Depending on the application, such mixtures contain at least 30 percent flyash. Alternatively, the natural mixture produced in the dust collector can be used when there is no precollection of flyash. In the latter case, the dry FGD product is often 20-40 percent by weight of the total product used in civil works. The combination of good compressive strength and very low water permeability constitutes the basis for applying the mixture in civil works and also provides significant advantages for certain geotechnical parameters.

The application of these mixtures include:

·         fill and base material (industrial storage areas, parking lots, etc.)

·         road construction material (e.g., sub-base)

·         mine back-fills and mortars

·         stabilizing agent (surface/deep soil stabilization)

·         bottom sealing of ponds

·         top sealing and cover for landfills

·         vertical sealing walls to prevent leachate or ground water transport

·         noise barrier walls.

The use of dry FGD product as fertilizer in agriculture has been extensively tested in Denmark and Germany and provides positive effects on the yields of the investigated crops. Crops fertilized with dry FGD product are oilseeds (winter rape), mainly to boost yield, and cereals (wheat, rye, barley), partly to improve their baking quality.

Dry FGD product has proven to be an effective absorbent for SO₂ in wet FGD, replacing limestone or lime and producing high-quality gypsum as the end product. This has been demonstrated at two Danish power stations, which have met their environmental requirements on a symbiosis basis.