As cement plants seek to minimise dust emissions, they face the choice between building new or converting existing equipment. Using a local implementation setup, FLSmidth
Airtech accelerated Thailand’s Siam Cement conversion to a new fabric filter solution.
Dust and gaseous emissions from cement plant operations is an area of increased focus. Not only are cement plant operators required to meet ever more stringent emissions legislation, but they also have a vested interest in reducing emissions, which is minimising their impact on the environment.
Air pollution control (APC) equipment plays therefore an increasingly important role, with many cement plants choosing now to upgrade their existing filter equipment. In particular, fabric filters are becoming more popular as they are proving to reduce emissions levels to extremely low limits that have previously been unattainable. As cement plant operators consider their options, they are faced with two possible options: build new or convert. Both solutions present advantages and disadvantages.
Conversions often involve less capital expenditure, because existing equipment can be reused. However, the conversion process will inevitably involve a shutdown period, which has an impact on the plant’s short-term productivity. New builds are usually more capital-intensive, but the shutdown period is typically lower, as the equipment can be moved in and installed at a convenient time. According to Henrik Vittrup Pedersen, General Manager, FLSmidth Airtech, an increasing number of ESP filters are being converted to fabric filters. In response to the demand, FLSmidth has developed specialist competencies. “At our project office in Denmark, we combine knowledge and utilise global engineering resources to provide fast, efficient support to customers in these types of projects,” he says.
One cement giant to choose conversion is Thailand’s Siam Cement Company. Its Thung Song plant was unable to meet emissions targets with its existing APC system. Its electrostatic precipitators were detoriating to such a state that they needed replacing. Local legislation in Thailand demands that dust emissions from stacks are less than 80 mg/Nm3, but according to Khun Wichet Chuchaeu, production manager at the Thung Song plant, the goal is to keep emissions under 10 mg/Nm3.
“We required a filter system that was effective and easy to operate and that could give us 100 percent control over dust emissions,” - Khun Wichet Chuchaeu, production manager, Thung Song plant
The decision was made to convert from ESPs to fabric filters. Not only could the fabric filters deliver extremely low emission levels (less than 2 mg/Nm3), but their larger, more efficient process filtration ability would increase the plant’s production capacity.
The costs of conversion were offset thanks to the ability to reuse elements of the ESP, such as the casing, steel support and transport dust system.
Fabric filter retrofit
The installation at Thung Song involved removing the entire ESP casing and replacing it with a new fabric filter solution – FLSmidth Airtech’s RetroClean™ fabric filter type.
Behind the decision to choose FLSmidth’s filter equipment was the ability for online maintenance. Plant operators can perform maintenance tasks, such as changing filter bags, when the raw mill is in operation. The filter is divided into several compartments that can be completely isolated from the gas stream. Inside the filter, gas blocking walls are installed between the fabric filter compartments, and the inlet and outlet can be blocked as required.
The filters allow the use of long filter bags – typically 10 m in length. In addition to reducing maintenance costs, the space within the refurbished ESP is utilised to fit the long bags and top box complete with purging tubes. The filters also feature a unique gas distribution system ensuring that gas is evenly spread over the entire filtration area and FLSmidth Airtech´s SmartPulse Controller® advanced control system for fabric filters.
Fast conversion minimises downtime
But technology is not the only prerequisite to an effective solution. At Thung Song, it was not just a matter of providing the best solution for the plant’s future; it was also a matter of close teamwork, good service and attending to the customer’s needs. For the filter exchange on one of Thung Song’s cement lines, a short shutdown time of 35 days was planned. During this time, the upper part of the existing ESP was removed, the longitudinal hopper was rebuilt into a pyramid hopper, and, finally, the new fabric filter internals were installed. In addition to engineering a new layout for the inlet and outlet ducts and supervising the erection and commissioning, FLSmidth ensured support for the entire preassembly process and provided project management assistance to the local contractor. During and after the process, the plant’s operators were trained in how to make best use of the filters by FLSmidth’s specialist engineers.
Michael Thorsfelt, Project Manager at FLSmidth Airtech, was responsible for this RetroClean filter project at Thung Song. He explains that to achieve the most effective solution and to meet performance objectives, a thorough analysis of the process data was necessary: “This meant we could design a perfectly suited solution, and it was actually different than the solution originally
intended. We also discovered we could reuse the original hoppers by redesigning them to the benefit of the customer and the environment.”
FLSmidth Airtech’s engineers used 3D scanning to help accurately design a solution matching the existing plant layout. “This technology helped us to design an effective and accurate solution for access facilities and ducts without possible physical collisions, which we might have overlooked if we just used drawings as the design basis,” he explains.
Local setup, better support
FLSmidth deployed South East Asian field engineers and European supervisors to achieve an appropriate balance between the right know-how for the project and a higher level of local involvement. The local field engineers received specialist training before, during and after the installation.
This reflects FLSmidth’s ability to draw upon a strong global network of expert resources to provide process expertise, maintenance and service, spare parts, quality assurance, commissioning and troubleshooting to customers throughout South East Asia. Teamwork was very important for meeting the project deadline, which of course was critical for Siam Cement’s ability to resume production. Michael Thorsfelt explains: “We often need to make fast decisions during installation and we see that the mix of highly experienced supervisors and local field engineers is very effective. The supervisors know the importance of the fast decisions that need to be made and the local field engineers can act on the decisions quickly based on their knowledge and experience of the local environment.”
Henrik Vittrup Petersen comments on the importance of a local and global support network: “We have seen situations where plants have purchased filters from other suppliers but have been unable to get support. So when repairs were needed, plant managers needed to source support from abroad, which was expensive, or alternatively get help from local suppliers who may lack the necessary experience. The result was a poorly operating installation, which is simply not acceptable in today’s competitive environment. FLSmidth’s deployment of local field engineers makes it affordable to get skilled support.”
At Thung Song, two fabric filter conversions were successfully completed at the plant’s Lines 5 and 6 in 2014 and 2015 respectively, with both contributing positively to plant operations. A third conversion on Line 4 is currently underway and is expected to be completed during 2016. Khun Wichet Chuchaeu, production manager at the Thung Song Plant, is delighted with the results: “Thanks to the solution provided by FLSmidth, we have been able to reduce dust emission levels significantly by converting our ESPs to much more efficient fabric filters. The cost of the conversion process was reduced by reusing existing elements of our ESPs, and the support we have received throughout the process ensures that we will be able to maintain efficient operations in the future.”
A long-lasting relationship
Already in 1913, when FLSmidth built Siam Cement´s first cement line in Thailand, a good working relationship was established between the two companies, and this has been continued with the supply of spare parts and new equipment to different Siam Cement plants. A recent example was FLSmidth’s gas suspension absorber, the FLS-GSA®, which was installed in three of the plant’s raw mill systems in 2012.