The St Marys Cement plant in Bowmanville, Ontario is the largest producer of cement clinker in Canada. In operation since 1968, the plant underwent a major upgrade in the early 1990s to replace two former wet process kilns with a single dry FLSmidth kiln with a preheater. To coincide with the tour by delegates of the IEEE-IAS/PCA taking place in nearby Toronto, Plant Manager Jim Storey recently took the time to speak with Global Cement about the plant's history, production process, markets and the future.
Global Cement (GC): Can you summarise the history of cement production on this site?
Jim Storey (JS): The St Marys Bowmanville plant has produced cement since 1968 when it began operation of a single 1000t/day wet process kiln. From the early 1970s until the 1980s, there was also a second wet kiln process, also rated at 1000t/day. In the late 1980s, the decision was taken to install a new 5000t/day FLSmidth dry process line with a preheater tower and separate line precalciner. The plant has continued to operate in this configuration since that time.
GC: Could you provide a run-down of the production process used at the plant?
JS: Our quarry is located directly adjacent to the plant to the east. It has approximately 90 years of suitable raw material at current usage rates. We blast our rock and haul it to a primary crusher where it is reduced to less than 20cm (8 inches) in diameter. It is then taken to a secondary crusher that further reduces it to less than 10cm (4 inches) in diameter.
From there we have an FLSmidth® ATOX® raw mill, where we grind up to 450t/hr to produce the raw feed for our kiln. It is stored in an FLSmidth continuous flow (CF) silo, which also homogenises the meal.
From the raw meal silo, we transfer material to our two-string pre-heater / precalciner tower. After this, the material passes to the kiln, which is 5m in diameter and 80m long. It was originally built by FLSmidth as a 5000t/day kiln, but in 1999 and 2000 we completed a number of projects to increase productivity up to 5800t/day. The clinker cooler has undergone modification over the years, but was originally installed as a FOLAX reciprocating grate cooler. It was later modified to include the addition of an IKN KIDS fixed inlet.
We have storage for up to 215,000t of clinker on site and there are three finish mills. Two of them are the original finish mills from when the plant was a wet process facility but the third was originally the slurry mill for the wet process feed. It was converted when the wet kilns were decommissioned.
1. Primary crusher.
2. Bank feeders.
3. Screening building.
4. Secondary crusher.
5. Limestone silos.
6. FLSmidth ATOX
raw mill building.
7. Coal unloading.
8. Coal mill building.
9. Kiln bypass baghouse.
10. FLSmidth CF raw meal silo.
11. Preheater tower.
12. Kiln.
13. Clinker cooler.
14. Kiln bypass baghouse.
15. Cooler baghouse.
16. Clinker transfer building.
17. Coarse clinker silos.
18. Clinker transfer silos.
19. Roller press building.
20. Clinker silos.
21. Cement grinding mills.
22. Gypsum unloading.
23. Gypsum crusher.
24. Cement silos.
Above: A schematic of the St Marys Cement Bowmanville plant.
GC: What is the capacity utilisation rate at present and how is this changing?
JS: We can produce around 1.8Mt/yr of clinker and are budgeted to produce more than 1.7Mt in 2015, so capacity utilisation will be pretty high in 2015. In 2009 production went as low as 1.2Mt, which was around 67% capacity utilisation.
GC: When did the plant last halt for maintenance and what work was conducted?
JS: Our last annual shutdown was in March 2014, during which we carried out fairly standard mechanical and electrical maintenance and refractory related work. We also completed basic maintenance on the lime hydrator and a modification was made to help improve isolation of the system for future maintenance.
The lime hydrator extracts calcined raw meal with a collecting cyclone in a slipstream between the calciner and upper stage cyclone. The material collected in the cyclone then drops through the lime hydrator, which uses atomised water to cool it to below 300°C and react a portion of the CaO within the material to create hydrated lime (Ca(OH)2). The material from the lime hydrator can then be metered into the feed to the preheater tower, which has been proven to be effective in the absorption of
SO2 emissions.
The results with regards to the process and effectiveness of the lime hydrator have been extremely positive. When in operation, the plant is able to reduce SO2 emissions to below targeted limits without the use of purchased hydrated lime.
GC: What type of cement and clinker are produced on the site?
JS: We make a Type I clinker, used to produce all of our cement products; which include Type GU (General Use Cement), GUL (General Use Limestone) and HE (High Early Strength) for the Canadian Markets, as well as Type I, Type II and Type III cements for the US market. Our Type I and Type GU combined constitute around 90% of our cement production. The remaining 10% consists of Type III, Type HE and our high-limestone product, known as GUL.
Nick Papanicolaou, Production Manager (NP): GUL stands for 'General Use,- high Limestone.' It is a higher Blaine cement product that contains a high proportion of limestone. GUL has a higher loss on ignition, but a higher Blaine gives greater strength. This reduces the amount of clinker required, which in turn reduces the amount of CO2 produced by the final concrete product. We have been producing GUL since 2011, but it's still being assessed with respect to things like market acceptance.
GC: Where does the plant source its gypsum, iron, sand and other additives?
JM: Our gypsum is shipped by barge from Nova Scotia. We are very fortunate that, due to the nature of our limestone, we require very few additional raw feed additives. The small amount of iron and sand materials that are used are sourced locally in the Bowmanville area.
GC: Are there any planned changes to the production process or expansions in the pipeline?
JS: We are not directly involved in implementing any major projects at plant level, but there may be discussions happening at a higher level regarding overall operations in North America.
GC: Could you take us through the types of fuels used at the plant at present?
JS: We primarily use coal and petcoke, which are both sourced by our corporate procurement department. The origin of the fuel will vary, but at the moment the majority of our fuels are imported from the US.
Both fuel types are ground in an FLSmidth® Tirax® grinding mill with a drying chamber. After this, they are stored in two fuel storage bins, one for the kiln burner and one for the calciner burner. We deliver the fuel to both processes via Schenck fuel delivery systems.
GC: As a fossil fuel user, is the plant currently reaping the benefits of lower fuel prices?
JS: While diesel and oil prices have dropped, we are not really seeing any impact on coal or petcoke pricing in North America at this time.
GC: Does the plant have any plans to use alternative fuels?
Ruben Plaza, Environmental Manager (RP): We are not using alternative fuels at present, but have obtained a permit to use plastics (post composting and industrial sources), woody residuals and paper fibres in a trial later on in 2015. The trial will be for 90 days at up to 30% substitution. We hope to conduct this trial during the summer or autumn of 2015. We want to demonstrate that these fuels can be used to the benefit of the environment without affecting the quality of the final product.
Separately, we have put in an application for a permit to burn woody biomass from construction and demolition materials as an alternative fuel on an on-going basis. That will let us use just 100t/day, but at least it's a start on the right path. We intend to use the same feeding system for the trial and the wood.
GC: How long has the plant been pursuing alternative fuels?
RP: The plant has been in the application process for maybe 10 years! There is a long history of plants trying to get permits to use alternative fuels in Ontario but it is really difficult to do so. However, our recent permit applications show that we can make progress and the process seems to be getting slightly quicker.
GC: Why do you think it's so hard to get a permit here?
RP: Part of it is public perception and fear of alternative fuels and part of it is political caution. Unfortunately for us, these two things can reinforce each other.
GC: What types of emissions are limited by the plant's permit and how are these controlled?
RP: The limits we have are for NOx, SO2 and dust. To control NOx we have a selective non-catalytic reduction (SNCR) system that injects aqueous ammonia into the calciner and kiln exhaust streams. That was installed in 2006. There is also a lime injection system to control SO2 emissions. Dust is controlled through the plant by more than 100 dust collectors.
GC: Are there any changes on the regulatory horizon?
RP: There is a lot of discussion about a cap-and-trade system for CO2 emissions, but that will happen in the next few years. There are interested parties pushing for trading schemes in both Ontario and in Canada as a whole but we must wait and see.
GC: The plant at St Marys has trialled the use of algae for CO2 capture. What can you tell us about this project and could it ever come to the Bowmanville plant?
RP: The Algae Project at the St Marys plant takes some of the flue gas from the plant stack and injects it into a series of tanks that contain algae. The algae is stimulated with an LED light and grows as it absorbs the CO2.
There is currently a lot of research being conducted into things like the timing of the lights, which are used to simulate the sun. We can use these to grow the algae more rapidly than it would normally. Research like this will increase the efficiency of the process but there is still a lot of work to be done. Eventually the intention is to convert the algae into a fuel, which would be used in the cement plant, effectively 'recycling' the carbon that was captured earlier.
There is discussion about bringing this technology to the Bowmanville plant in 2015 or early 2016, but the decision has not yet been made. A lot will depend on any information that is forthcoming regarding the cap-and-trade schemes that may be implemented by government.
GC: What geographical areas define the plant's natural market and what transport methods are used?
JS: Our main market is the Great Lakes region in both Canada and the United States. Of the 1.7Mt of clinker that we are set to make in 2015, 0.67Mt will be sent via barge through the Great Lakes to our grinding terminal in Detroit, Michigan. From there, cement is dispatched by our colleagues in the US. We will also send approximately 0.5Mt of cement to locations in the US throughout 2015.
Canada will take the remaining volume of our cement production. Domestically we dispatch by road and rail, which we access immediately to the north of the plant property. Our trucked cement services the Greater Toronto Area and south-eastern Ontario. Further west we have the St Marys cement plant, so we can be called to supply its usual market and vice-versa.
GC: Which types of companies does St Marys serve within Canada?
JS: The primary consumer in Canada is Canadian Building Materials (CBM), our ready-mix concrete division. Aside from CBM, we supply a large range of other customers in the construction materials market.
GC: Is cement demand strong in the local market at present?
JS: The picture is improving, slowly but surely. However, from a plant perspective we need to be careful how we interpret our production levels due to the fact that we have other plants serving the Great Lakes market. While we expect to make more than 1.7Mt of clinker in 2015, we made around 1.5Mt in 2014. However, in 2013 we made 1.7Mt. The levels will depend a lot on logistics and interaction between us and our other plants in the Great Lakes region.
GC: How do dispatches change throughout the year in Ontario?
JS: The construction market is very seasonal due to the weather. Indeed, our main export route, the Welland Canal closes at the end of December due to ice. Therefore, we have a lot of space for inventory in the plant to buffer us through the busy summer season. In addition to the 215,000t of clinker storage capacity we also have 110,000t of cement silo capacity.
GC: What are your expectations of Canadian cement demand through the rest of 2015?
JS: I think that stronger market conditions will continue. It's a slow recovery, but it looks promising.
GC: What ambitions or targets does the Bowmanville plant have for the rest of the year?
JS: Our primary focus is to meet our production target for the plant and complete the trial with alternative fuels. From a wider perspective we want to continue with our drive to increase plant efficiency. We are the first plant to be ISO 50001 certified in North America, which is a major milestone. Working with 360 Energy, we also have a Certification in Energy Excellence in 2009 from the UK-based National Energy Foundation. We have since undergone its re-certification process which requires demonstration of improvements in energy-efficiency and
energy management.
GC: What one change to the Canadian cement industry would help you 'sleep easier' with respect to the plant's long term prospects?
NP: I would like to raise awareness of the role that cement plays in sustainable construction. So many 'green' initiatives have cement at their core, but this is rarely highlighted. I think that government organisations appreciate this fact but the end user does not currently consider cement to be 'green.'
GC: Gentlemen, thank you for your time.
JS: You are very welcome.