Canadian Consulting Engineer

Biomass Plant in Ajax

June 1, 2013
By James Gillis, Doherty Engineering

Index Energy’s Steam Plant in Ajax, Ontario is undergoing a complete revitalization to become a 25-MW biomass-fired cogeneration facility. Not only will the facility become one of the few biomass-fired power plants in Ontario, but also it...

Index Energy’s Steam Plant in Ajax, Ontario is undergoing a complete revitalization to become a 25-MW biomass-fired cogeneration facility. Not only will the facility become one of the few biomass-fired power plants in Ontario, but also it will provide steam to a local district heating system, which we believe makes it unique in the province. The plant will produce green electricity for export under the Ontario Power Authority’s feed-in-tariff (FIT) program for renewable energy. Doherty Engineering provided front end engineering design for the plant on behalf of Index Energy.

The history of the steam plant is deeply connected to the history of the town of Ajax and its preservation was a prominent aspect of the revitalization project. Originally constructed as a coal-fired facility in 1941, the plant was an essential part of the Canadian World War II economy, providing steam heat to munitions factories. Following the war, the plant remained a vital piece of the local economy by supplying local industrial clients with steam heating via below-ground distribution piping networks.

Index Energy is working closely with the Town of Ajax Heritage Advisory Committee and the architect to ensure that key historical elements of the plant are preserved. Original architectural features are to be incorporated in the revitalized facility, including a truss, window and several structural components. At the entrance a display will showcase the original plant equipment such as a cast iron coal bunker hopper door, a military style wooden door, steel windows and recording paper charts. On the exterior, the original boiler feed water pumps will be incorporated into an architectural heritage sculpture.

Energy efficiency for lower greenhouse gas emissions

Achieving a high overall energy efficiency and minimizing the environmental impact were the goals that drove the design of the revitalized plant.

The fuel source is waste wood originating from construction and demolition (C & D) waste. The waste will be sorted and chipped, and delivered by truck to the plant. This fuel source diverts the waste from landfills and furthermore is locally sourced to reduce the impact of vehicle emissions used in transportation. As a dedicated biomass facility, the plant will not consume any other types of fuel such as oil or natural gas to augment or supplement steam for power generation.

Power is generated through a traditional steam cycle using three steam turbine-generator sets with a total combined nameplate capacity of 25 MW. A contemporary hydraulic floor system transports chipped wood fuel from the storage area to the combustor area where it is individually metered to each combustor. The combustors are specially designed for wood combustion, and they employ hydraulic moving grates that ensure complete and uniform combustion of the fuel.

Medium-pressure exhaust steam from a backpressure turbine feeds two condensing turbines for additional power generation and to supply local industrial and commercial customers with steam heat through the district energy piping network. The controls design optimizes the turbine loading for maximum electrical efficiency based on the demand for the district heating steam.

A multi-step heat recovery process uses condensate to recover heat from the hydraulic combustor grate coolers and flue gas. The result is a significant reduction in the exhaust temperature of the flue gas exiting the emissions stack and a reduction in overall fuel consumption in the combustors.

All the equipment is selected for high thermal and electrical efficiency and to reduce greenhouse gas emissions. The heat recovery steam generators and economizers, for example, maximize heat transfer from the combustion gases to the feed water, and the condensing steam turbines operate under a strong vacuum to enhance the power production.

The nutrient-rich ash waste from the combustion process is recovered and conditioned for resale, primarily to customers in the agricultural industry.

Being a good neighbour

Air and noise pollution and waste management are critical to all industrial processes, especially those in close proximity to residential and commercial developments such as here. The plant is designed to address these concerns. Its flue gas emissions achieve lower particulate concentrations than are required by the Ministry of the Environment due to a two-step treatment process comprising cyclone separators and an electrostatic precipitator.

Sound attenuation is provided on all the major equipment, through building materials and by way of a sound attenuating barrier. The plant has to comply with strict acoustic criteria to minimize noise disruption to the surrounding community and future residential developments.

The plant is in the early stages of construction and scheduled for completion in late 2014, with operations expected to begin in the first quarter of 2015. It will divert millions of pounds of waste wood per year from landfills for the generation of green power and thermal energy for export.cce

James Gillis, EIT, is project manager for the Ajax Biomass Plant project with Doherty Engineering.

Project owner/client: Index Energy Road Mills Corp.

Engineering design and owner’s engineer: Doherty Engineering (Paul Doherty, P.Eng. Mike Savel, P.Eng., James Gillis, EIT)

Architect: J.R. Freethy


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