Repowering Project for Package Boilers – Redesign & Retubing

Helfrich Brothers Boiler Works was selected as the EPC for the repowering project. Three of the four package boilers were completely retubed with many furnace design changes implemented. A fifth unit was added to the plant as part of the repower project.

THE CHALLENGE:

• The existing common breaching duct leading into the stack needed to be replaced in a extremely fast timeline.
• The duct was 260 feet long and weighed over 65 tons.
• All 3 EfW boilers fed into the duct and replacement required all 3 units to be offline.
• Plant had no drawings of the duct work that could be used for new fabrication.

A 55 megawatt renewable energy power plant needed an additional spray attemperation system added to the boiler.

The boiler at the facility is a Foster Wheeler design that went into operation approximately 2007. The boiler is a natural circulation, superheated, balanced draft design, single furnace, stoker fired unit firing biomass, including poultry litter. The boiler is rated to produce steam for a steam turbine generator rated approximately 55 MW. The boiler produces 490,000 pph of steam at 1,555 psig and 980 °F.

The boiler has three superheater sections; primary, intermediate, and final. There is currently a spray attemperation system located at the intermediate superheater outlet. The client has indicated that the steam temperatures at the outlet of the intermediate superheater are higher than desired for reliable long term operation, and desired the addition of spray attemperation at the outlet of the primary superheater, among other measures, to reduce the excessive tube temperatures.

Scope of Work

• Field Inspection
• Engineering and design
  • Prepare piping layout
  • Determine pipe layout of piping and support locations
  • Determine pipe sizes and thickness
  • Review of suspension level steel in vicinity of new pipe for support location development
  • Prepare general arrangement drawing
  • Develop design criteria
  • Evaluate piping using STAAD computer modeling
  • Prepare pressure parts calculations
  • Specify spray station nozzles, valves, and instruments
  • Prepare general arrangement of attemperation water system piping

A 55 megawatt renewable energy power plant needed to replace 86 intermediate super heater assemblies.

The boiler at the facility is a Foster Wheeler design that went into operation approximately 2007. The boiler is a natural circulation, superheated, balanced draft design, single furnace, stoker fired unit firing biomass, including poultry litter. The boiler is rated to produce steam for a steam turbine generator rated approximately 55 MW. The boiler produces 490,000 pph of steam at 1,555 psig and 980 °F.

The Superheater

Scope of Work

• Field Inspection
• Engineering (Installation/arrangement and shop fabrication drawings)
• Material procurement
• Fabricate 86 intermediate superheater pendants complete with 360 degree Inconel weld overlay in lieu of tube shields, S.S. hand-cuff tube supports, and all solid ties.
• HB Field Services performed the demo and installation on the new elements.

A long-time client of Helfrich Brothers is a global supplier to the industrial gas market with vaporizers manufactured in compliance with ASME, EU PED, SQL, ATEX and many other codes.

Helfrich brothers was asked to take on a fast-track project in the Fall of 2017.

Scope of Work

• Material procurement
• ASME vessel fabrication
• Burner installation
• Fab and install gas train skid
• Install, wire, and test control system

Rochdale Village, Inc. Power is a total energy 21 MW facility that generates all the electrical power, heating, air-conditioning and domestic hot water services for a residential co-op and two shopping malls that is home to nearly 25,000 residents.

The facility originally had four replicate Riley-Union Iron Works MH type packaged boilers that went into operation approximately 1963. Each boiler is a natural circulation, “A” type, superheated, pressurized design, natural gas fired unit firing natural gas. Each boiler was originally designed to produce 100,000 pph of steam at 650 psig and 650 °F at the superheater outlet. Each boiler had two burners and a packaged fin tube economizer.

Helfrich Brothers Boiler Works was selected as the EPC contractor for the repowering project. Three of the four package boilers were completely re-tubed with many furnace design changes implemented.

A fifth unit was added to the plant as part of the repower project. HBBW installed the cold iron piping and the fifth boiler.

HBBW Scope of Work

• Engineering
  • Re-design the outer casing of the superheater side to a membrane wall with side walls extended out to fully enclose the superheater
  • Re-design of the rear furnace wall to membrane fin design
  • Thermal analysis of the boiler to establish temperature, pressure and flow profiles for the steam and flue gas paths
  • Stress analysis of membrane walls
  • Installation/arrangement and shop fabrication drawings
• Complete re-tubing of the boiler, superheater, and economizer. Only steam and mud drums remained.
• Material procurement
• Steam drum assessment/inspection
• All demolition and installation
• Insulation and lagging

Plainfield Renewable Energy (PRE) is a net 37.5 MW woody biomass electrical generation facility located in Plainfield, Connecticut. The facility was experiencing extended forced outages due to tube failures in the high temperature T91/P91 superheater assembly.

PRE utilizes a state-of-the-art staged fluid bed gasification system and an Alstom steam turbine to generate approximately 290,000 MW annually. The plant is equipped with a baghouse for particulate control, urea injection for NOx control, and limestone and hydrated lime injection combined with a circulating dry scrubber for sulfur dioxide control.

The boiler is a modularized HRSG (heat recovery steam generator) type originally provided by an Outotec (formerly Energy Products of Idaho or EPI), with a bubbling fluidized bed gasifier. The facility went into operation approximately December of 2013. The boiler is a natural circulation, superheated, balanced draft design unit firing biomass waste. The boiler was originally designed to produce 366,648 pph of steam at 1550 psig and 955 °F at the superheater outlet.

HBBW Scope of Work

HBBW’s scope included a complete design analysis, fabrication and installation of a shop-fabricated Superheater #1 section in two harps using stainless steel for all tubes and headers. The superheater was re-designed and replaced to improve the reliability with replacement of the T91 tubing and P91 headers with stainless steel.

The boiler design analysis included a thermal and hydraulic analysis to review the existing design. A thermal model was prepared of the steam and flue gas temperature, pressures, and flow profile through the boiler. A hydraulic model was prepared to evaluate the steam side distribution through the harp tubing. The hydraulic flow imbalance of the existing superheater was calculated to be below generally accepted industry standards which resulted in unstable, unpredictable steam flow in the circuits and lead to high tube metal temperatures. Hydraulic flow imbalance to the final leg of the high temperature superheater was improved by underdrilling the inlet header of the final superheater pass.

• Engineering
  • Re-design of the final superheater to eliminate T91/P91 components and replace with stainless steel material
  • Thermal analysis of the boiler (HRSG) to establish pressure, temperature, and flow profiles of the steam and flue gas paths
  • Hydraulic analysis to correct steam side flow unbalance with the addition of orifices
  • Stress analysis to support material change to stainless steel
  • Flexibility analysis to accommodate the thermal expansion characteristics of stainless steel
  • Required ASME Code alteration documentation and calculations
  • Installation/arrangement and shop fabrication drawings
• Complete removal of the existing superheater
• Material procurement
• Fabrication
• Installation of the redesigned superheater and interconnecting high pressure piping
• Refractory, insulation and lagging