Global Cement recently visited Breedon Group’s Hope Cement plant in Derbyshire, the largest cement plant in the UK, ahead of the visit by delegates of the Global CemProcess Conference & Exhibition on 25 May 2018.
The Breedon Group Hope cement plant began making cement in 1929. Initially with a capacity of just 50,000t/yr, it expanded to include five wet process lines by the 1960s before being extensively overhauled by former owner Blue Circle Cement in 1969-1970. Blue Circle installed two new dry process lines with preheaters from KHD and kilns from Polysius, which it operated until Lafarge took over the business in 2001.
Following more than a decade of extensive investment by Lafarge, Mittal Investments took hold of the plant in January 2013, rebranding the plant as Hope Cement (part of the newly-created Hope Construction Materials group) and injecting further capital. In August 2016 the plant once again changed hands when Breedon Group acquired the business from Mittal. Since 2017 the plant has operated under the Breedon Cement brand, which has continued to invest in process optimisation, efficiency and debottlenecking.
The plant continues to be known by the name Hope Works among locals and the wider UK cement industry. Due to the significant recent investment, the plant may now have a capacity in excess of 1.5Mt/yr, when fully optimised. Breedon Group is still in the process of optimising the new configuration.
Interviews with management
GC: Please could you take us through the production process used at the Hope plant?
Keith Rowland, Quarry Manager (KR): It all starts in the quarry, where we have two main sources of limestone: high-silica limestone and low-silica limestone. The upper beds have more of the high silica limestone due to their high chert content. Further down in the quarry we have lower silica limestone. We treat them as different materials and stockpile them accordingly. We currently have 13 operational benches in total.
We have our own shot-firing team, although we use an external drilling firm. We have two 90t excavators (1 x CAT 390F, 1 x Liebherr R976). There is also a CAT 990 wheel loader for back up and a smaller CAT 345 for quarry development. A fleet of four CAT 775 G dump trucks takes material from the blastpiles to the crusher in 60t payloads, which works out
at 1000t/hr.
Steve Groves, Production Manager (SG): The primary crusher is from Fuller Traylor, now part of FLSmidth. It was installed in 1952. It operates at 1200t/hr and is followed by twin line secondary and tertiary crushers, all are Sandvik H6000 Hydrocone crushers with pre-screens. The final limestone size is below 30mm, which is driven by the raw mill requirements. It is stored in a linear enclosure that has a storage capacity of around 25,000t.
From the raw stone store, the material splits in two for the two identical KHD kiln lines. Each line has a single chamber air-swept raw mill from Humboldt with static classifiers. They date from 1970 and have been upgraded with mill internals and a new drive system on line 2. The feed consists of limestone (85%) and shale-like materials or pulverised fuel ash (PFA) (15%).
After the raw mills, there are two blending silos and four storage silos with a combined storage capacity of 15,000t. The material from the storage silos is fed via a Claudius Peters kiln feed system. This was recently commissioned as part of a major project to improve the process at Hope. The raw mix is still fed pneumatically but now enters via a de-aeration system and air-slides into the top. This project released the kiln feed bottleneck when it was completed in May 2017.
Trevor Harrison, Projects Manager (TH): The kiln feed project was part of a wider capital expenditure project to increase capacity that was started under Hope Construction Materials. We knew that the existing feeding system was a bottleneck and we installed a de-aeration system at the top of the preheater towers for each kiln as part of that project, There is also a common standby system shared between the two kilns.
SG: The material enters the four-stage through-air preheater from KHD, also installed in 1970. During the Blue Circle days, we upgraded the riser section to facilitate tyre chip firing at the back end. In the last 2-3 years we have also upgraded the kiln inlet section of the riser to reduce the hearth velocity, increase capacity and mitigate some of the build ups we had seen following the introduction of alternative fuels.
The two kilns are from Polysius, also from 1970. Again, they are identical, both 4.8m in diameter and 70m long. In the past two years we have installed MAS burners from Unitherm. They worked very closely with us to design a special burner that can operate both clockwise and anti-clockwise. This is because the two kilns rotate in opposite directions and we needed a common spare that could be deployed on either of them.
The clinker coolers are originally from Fuller, now part of FLSmidth, although we upgraded with the help of IKN in the mid 2000s. We now have a hybrid system that helps to break down the snowmen seen previously. The clinker heads to a traditional tent-style clinker storage with up to 60,000t of capacity. If you were to design it these days, you’d build large vertical clinker silos or a dome.
There are two identical cement mills, which, by virtue of coming after the clinker storage, are shared by the two lines. These are FLSmidth / Fuller designed dual chamber compound ball mills. The cement onsite storage is around 20,000t and we have a relatively large depot system, so that also provides total cement storage capacity of 64,000t.
GC: What types of cement are made?
SG: There are two main types of cement, PC and PC Plus. They are both 52.5 N CEM I cements and they represent almost 90% of all the cement we make. There is also a CEM I 52.5 R cement and two CEM II A/LL 32.5 R bagged products for general purpose and trade use.
GC: Is the plant running at full capacity?
SG: Yes it is, to within practical limits. There are still some upgrades that we are only just starting to exploit however, so it has the potential to produce more. We are not quite sure how much we will be able to increase capacity before we find the next bottleneck. If we look back over the past few years, the plant has been running as much as it could in any given year, since about 2007.
GC: What major projects have been undertaken recently?
TH: As well as the kiln feed project, we undertook a process optimisation study to critically review the combustion line.
In 2015 we also had an internal survey of the main flue carried out by an external company during a rare period when both kilns were down. The company pointed out some internal problems with the brickwork but we didn’t want to stop both lines for a long time. We therefore thought ‘outside the box’ and installed a temporary stack in close discussion with the Environment Agency and local stakeholders.
During the kiln shutdown periods, we successfully rerouted exhaust gas from the kiln lines into the temporary chimney. This allowed the main stack to be repaired over a three month period while maintaining full production on both lines. The temporary structure has since been taken down.
On Kiln No. 2, we put in a new kiln tyre in 2015 after it showed signs of wear. It had also been deforming the kiln shell. We replaced the tyre and a section of kiln shell. We also installed a feeding system for solid recovered fuel (SRF) with Saxlund and FLSmidth in 2016. It is fed up an inclined drag conveyor into an FLSmidth Pfister weighfeeder and is then dosed to each kiln.
GC: When was the last plant shutdown and what work was completed?
John Mulryan, Maintenance Manager (JM): We had a shutdown in January 2018 for 23 days with quite significant work and was fully compliant with Construction Design and Management (CDM) regulations. This is about increased planning and organisation with respect to health and safety. This involved a larger degree of planning and supervision of sub-contractors than in the past. The shutdown saw a total of 35,000 man hours of work, 24/7, with a peak workforce of around 300 but there were only a few minor health and safety incidents. The weather was a challenge, as was maintaining momentum in the project.
One of the biggest challenges was installing and optimising the autobalancer on the preaheater fan, a similar system to a Sikorsky helicopter. It enables us to balance the fan on the fly and maintain production when the fan becomes unbalanced due to process build ups. We installed and commissioned this during the shutdown and there was no room for errors or wasted time.
GC: What is the most difficult part of the plant to maintain on an ongoing basis?
JM: The clinker coolers are always a challenge because you can’t see what state they are in for 11 months of the year, until you get in there. There’s always the potential for surprises. If you ever want to make a change to the cooler, you have to be absolutely sure of what you are doing.
GC: What parts are relatively straightforward?
JM: The dispatch areas are easier to maintain because they operate at far lower temperatures, there are more days available to maintain things and you can see what’s going wrong as it goes wrong.
GC: What is the most cost-effective repair that you have carried out?
JM: The smallest spends can give you the biggest impacts. We have a clinker breaker at the end of the cooler. If that trips out, the whole process would need to be stopped. We installed a Predator belt on the breaker of the type used in the recycling industry for turning scrap metal into cubes. It has vastly increased the reliability of a very critical part of the plant.
GC: What part of the plant keeps you up at night?
JM: The plant is solid and, if it goes wrong, we can engineer our way out of it. I am more concerned by the fact that some of our maintenance staff are due to retire shortly and we may lose a degree of their experience. However, we have a good apprentice programme that will help to replace experienced workers over the same period.
To help us to work smarter in light of this, we have started to use oil analysis and vibration analysis equipment more effectively to head off problems before they affect production. We also use ultrasonics and thermography instruments on the kilns.
GC: How will maintenance roles look in another 10 years given the increase in technology?
JM: The way we would use technology will be to monitor equipment before it has a problem. We could also look at how to remove staff from hazardous tasks, for example by automating some welds as we have done when replacing kiln shell sections.
GC: From where does the plant source its additives?
SG: Due to the chemical composition of the limestone, we actually don’t need any additional bulk raw material additives other than gypsum for the finish mills. Once the material is blended correctly, the chemistry is ideal for cement manufacturing. The gypsum comes from British Gypsum’s Fauld Mine in Staffordshire (75km).
GC: What fuels does the plant use?
SG: The plant uses around two thirds coal, all of which is from the UK, mainly Wales. There are also alternative fuels in the form of tyre chips at the back end (15-20%), solid recovered fuel (SRF) (8-12%), which is fed to the main burner and there is also a small proportion of two types of plastic waste. These are co-fired with the coal.
In the past the plant has also used dried sewage sludge. It also used meat and bone meal (MBM) until November 2017. We stopped using MBM for economic reasons. In the future we need to optimise and fully exploit the new investments. By gradually ramping up the plant, we hope to be able to reach up to 50% alternative fuels in the future. We are regularly approached by suppliers offering new fuels but we don’t have any plans to change the mix right now.
GC: What emissions abatement systems are used?
SG: The main stack has a bag filter from Lodge Cottrell, which was installed in the late 1990s. On the cooler end we have electrostatic precipitators, although they have been kept in good condition and operate well within authorised limits. For NOx we have a selective non-catalytic reduction system from 2006 from ABC&I. It uses a 24.5% ammonia solution. For HCl abatement we use hydrated lime. In the future there are no big changes planned to these systems but we do want to lower the amount of sulphur entering the system.
GC: What other future projects are there?
TH: The plant has been very well invested in by all of its recent owners. We now have a 10 year plant plan that looks at what needs to be invested for the good of the plant as a whole. The first project is to replace the drive on raw mill one, as this is still from the 1970s and the motor is showing signs that it is coming to the end of its useful life. The other raw mill drive has already been replaced.
Furthermore, we are looking to improve the lifting equipment for the two new kiln burners to help the maintenance team. It is a fairly complicated structural task that we are keen to get on to.
Alongside this we have been replacing the old compressor air systems to improve the electrical efficiency of the works. We want to further consolidate the systems and control of the system, that will also give maintenance benefits.
We are also working on a clinker store bypass to enable us to manage stock more effectively.
GC: What is the most cost-effective project the plant has implemented in the past 10-20 years?
TH: The best low-cost investments have been in the abatement systems for NOx and HCl. This is because it is reliable, low cost equipment that enables us to comply with legislation.
On the higher end of the cost spectrum, the new rail infrastructure, installed in 2008, has enabled us to transport far more cement to the south east of England than before. This has helped with sales and reduced the amount of cement transported by road, which helps the plant and our immediate neighbours.
GC: What piece of equipment would you change at the plant if you could, if money were no object?
TH: What would be good is to make better use of our waste energy. We already switch off non-essential equipment during energy demand peaks. It would be ideal to be able to continue running that equipment using our waste heat. Solar power energy stored in some kind of battery would also be a great benefit. One plant in the UK, at Ketton, already uses
solar power.
GC: Where are the main markets for the Hope plant at present and how are they served?
Edward Cavanagh, Works Manager (EC): Throughout the transition from Hope Construction Materials to Breedon we maintained our network of distribution terminals. These are at Dewsbury (West Yorkshire), Walsall (West Midlands), Theale (Berkshire) and Dagenham (Greater London). We supply these four depots by train with around 1Mt/yr of cement. The split is not completely equal between the sites and it flexes to meet demand accordingly.
Of late, distribution from Dagenham has grown as we ramp up the use of the site. It was only commissioned fully in 2016. We also bag cement in Dagenham, unlike everywhere else, where sales are in bulk only. The proportion of bagged cement is growing gradually over time and is currently around 5-10% of all distribution.
The remainder of our output is distributed by road, although we are limited to 586,000t/yr, the capacity of the former wet kilns. However, we are not close to that limit at the moment. The local market has been stable for the past few years or so, perhaps with slight growth.
We seek to optimise output to as much rail as possible because it is more efficient, takes vehicles off the local roads and reduces our carbon footprint. Breedon has also invested in more efficient tractor units for its road distribution. In general the Group invests in its own distribution network rather than lease or use sub-contractors.
GC: How is the plant’s health and safety at present, especially with respect to the change of ownership?
EC: We have not seen any negative changes as a result of the change of ownership, either from Lafarge to Hope Construction or from Hope Construction to Breedon. Loss of safety performance is a risk when the plant has weak procedures, but our procedures are strong and they underpin everything we do. We have had no lost time incidents since autumn 2016, which was a low-level incident. However, it was still treated seriously.
We put quite a focus on health as well as safety because it is recognised that there is a lot more time lost to illness than injury. This is reflected in things like our on-site gym and golf course, which is built on a former shale quarry.
GC: How does the plant benchmark itself against other facilities now that it is a ‘standalone facility?’
EC: While we are the only cement plant in the group, we do still maintain a network because it has historically been part of a much bigger whole. We also network with and visit other independent plants, sharing best-practice examples between us. There is also a number of consultants that help the independents with different projects, plus the engineers from the major equipment suppliers.
GC: How has the prospect of Brexit affected the business so far, if at all?
EC: The only effect seen as a result of Brexit so far is that it is a technical drain. There have been a lot of difficult discussions regarding what might happen, especially in the spheres of energy, emissions trading and other regulatory areas. We have to send members of the technical team down to London for several days at a time to discuss aspects of Brexit to prepare ourselves as best as we can. The result is that they cannot perform their day-to-day tasks as easily. Time is being lost to lobbying rather than performing their usual tasks.
GC: What are the biggest threats facing the plant in the future?
EC: Some large-scale changes to emissions regulations as a result of Brexit would disrupt our entire industry significantly. However I don’t think that is likely and, in any case, Hope has consistently been ahead of the curve with respect to environmental performance.
Elsewhere, I would say that we would be really exposed right now if we had not prepared the plant’s succession planning for future growth. We saw a few years ago that if we didn’t plan ahead, we would face a lack of expertise due to the retirement of experienced workers. It takes up to three years to train a control room operator and then they gain further experience on the job itself.
GC: What is the biggest opportunity for the plant going forward?
EC: The biggest opportunities are related to the high cost of fuel and electricity. If we can find additional efficiencies, the plant can make significant savings. This may involve reopening long-mothballed project ideas like waste heat recovery, which may be becoming economical for a plant such as Hope.
This article was written before Breedon took over Lagan Group, including its cement plant in Ireland, on 20 April 2018.