By Antonio de Freitas, Howden, with Apollo Americas Consulting, USA (first published in the March 2021 edition of International Cement Review)
Since its establishment over 160 years ago, many of the world’s most-renowned industrial fan technologies, companies and brands have become part of the Howden organisation. Within the cement industry the company’s process fans represent around 25 per cent of total installations globally. Having undertaken numerous retrofits in the sector, Howden presents two examples in North and South America of projects that have helped increase capacity and save power on kiln ID fans for producers.
Howden has a long history of offering a full line of fans for every industrial fan application and provides custom-designed process fans for the cement industry. This list includes brands such as Solyvent Ventec, Covent, Davidson, Buffalo Forge, TLT Babcock and Green Fans.
As of today, over 5000 cement process fans are operating worldwide, representing approximately 25 per cent of the total installations of process fans globally. This includes equipment for some of the most arduous service conditions that fans are exposed to in any industrial application.
Howden’s manufacturing facility in Chennai, India, produces custom-designed cement process fans and pre-engineered fans for delivery to locations throughout the world
Withstanding rugged conditions
Howden specialises in providing rugged fans for high-wear applications. One example is the raw mill exhaust fan which, depending on the severity of the application, can be armoured with various coverage and wear protection materials: abrasion-resistant steel, chrome carbide, or tungsten carbide wear plates.
The company also provides fans for high-dust and high-temperature applications such as preheater exhaust fans or kiln ID fans. Exposure can reach temperatures up to 450˚C (900˚F), where material build-up is a crucial design consideration.
In addition, smaller pre-engineered fans for under-grate cooler service and other miscellaneous service fans form part of Howden's portfolio.
The company’s support for the cement Industry starts with the detailed understanding of the application that allows it to provide customers with rapidly-developed, custom-engineered proposals beginning from the project development stage and budgetary proposals, all the way to final purchase. After purchase, support includes supervising equipment installation and start-up.
Uptime remote monitoring
The new Howden Uptime suite of products and services, powered by its physics based Digital Twin, a virtual replica based on equipment design knowledge, enables owners and operators to extend fan life, improve performance and avoid unplanned events.
The cloud-based solution is delivered via a web-based user interface, enabling secure access virtually anywhere and immediate software upgrades.
Additional analytic and maintenance services enable a comprehensive predictive maintenance programme tailored to individual site needs.
Combined with a long-term service agreement, Howden Uptime improves site safety and can reduce annual maintenance costs by as much as 20 per cent.
Service database
Howden is continuously developing new fan designs. Each Howden location has access to all data gathered by application engineers. Using this data during fan selection, engineers have a detailed understanding of past installations of similar scope.
Paired with the knowledge of any new challenge, like high tip speed, power consumption, static pressure, temperature, impeller diameter, or running speed, the application engineers can select the fan for the specific situation.
Improving fan performance with retrofit
With an extensive global installed base of industrial fans, Howden has added more references in recent years through acquisitions and superior retrofit and service capabilities. Despite the number of new build cement projects declining, Howden’s customer base has been expanding.
Expertise in air-flow technologies results in higher-efficiency equipment, allowing customers to improve power savings, increase equipment life span, and reduce vibration issues. These advantages are attainable under the cement industry’s normal strenuous operating conditions, such as high temperatures, highly-abrasive dust loads and material build-up.
Howden selection software
The Howden Selection Software was developed to size the most efficient fans for multiple applications effectively. In a recent upgrade, the software now has a retrofit mode that gives the engineers the exact fan model that fits the existing fan housing for optimal performance. This allows customers to avoid significant modifications, saving both installation time and money.
Recent retrofit projects
There are many retrofit projects that Howden has implemented over the years in the cement Industry. Two recent examples were installed in South America and North America, allowing both customers to increase capacity and save power on their kiln ID fans.
South America case study
A customer located in South America was having performance and vibration issues with its existing fan. The retrofit installation allowed the customer to increase capacity by approximately 10 per cent and save 644kW/h. This equates to a saving of roughly US$260,000 per year reaching full return on investment in less than three years.
Kiln ID rotor assembly with hollow shaft, South America
The customer kept the entire existing housing and ductwork, changing only the rotor assembly and inlet cones, reducing installation time, and saving extra money on parts. The wheel was specially designed to handle abrasive dust.
This particular customer also decided to install Howden Uptime, which will help it to save even more time and money by having proactive information from the software.
Kiln ID rotor assembly with hollow shaft
To achieve one of the customer’s needs, Howden utilised a hollow shaft to reduce weight and improve critical speed, resulting from roller-bearing grease lubricant and a better structure. This design allows for a smooth operation with low vibration even with high temperature and dust load.
North America project
A North American customer had a Howden legacy brand, Green Fan, installed, and it was operating without any performance or mechanical issues.
The installation of an extra preheater tower, including a new kiln ID fan, increased the plant’s capacity. The gas stream was divided in half, 50 per cent for the new fan and 50 per cent to the existing Howden fan. Due to this upgrade, the system curve was modified, reducing the current Green Fan performance, and generating more power consumption than necessary to carry the reduced amount of gas.
Knowing Howden’s capabilities, the customer entrusted it with solving that challenge. Howden offered a retrofit using the existing fan housing, improving performance, and reducing power to 400hp (300kW/h) with savings of US$180,000 per year.
The customer will also install a variable frequency drive (VFD) to control the fan speed, enabling it to keep a stable efficiency in four different duty loads. To allow the customer to control the fan via speed variation, Howden has evaluated many aspects such as shaft torsion analysis, rotor dynamics analysis, and utilisation of a unique coupling to be installed between fans shaft and new motor.
A performance test determined the new system curve according to AMCA 803-02. The Howden retrofit fan design increased the kiln’s capability by 10 per cent and replaced the existing 4000hp motor with a new 2500hp motor.
Conclusions
Howden's experts focussing on cement applications can help new and existing customers select the optimum equipment for new projects. Cement plants can benefit from process review and specific evaluations of wear and other issues due to extreme conditions in cement manufacturing.
Table 1: estimated power savings for the North America retrofit project