System integrator Energy Ventures develops cost-effective solution for Dhampur Sugar Mills which dramatically reduces maintenance costs and enhances system reliability.
Background
Sugar production, an important industry in India for centuries, experienced dramatic growth during the post-colonial period. In the last half of the twentieth century, the number of sugar mills operating in the country tripled and the installed capacity increased by more than 10 times. Today, India ranks second only to Brazil as the world's largest sugar producer. The country generates between 15-20 million tons of sugar each year, and nearly all of it remains in the country for domestic use.
India's dramatic production gains were achieved in large part due to forward-looking companies, such as Dhampur Sugar Mills. Established in 1933 with a cane-crushing capacity of 300 tons of cane per day (TCD), Dhampur Sugar Mills has expanded from its initial site at Dhampur to four locations throughout Northern India and Nepal. Today, the combined crushing capacity of its facilities stands at 32 000 TCD, making Dhampur one of India's largest sugar producers. While most industries rely on external power sources to fuel their operation, sugar manufacturers can produce their own energy using a processing by-product.
Bagasse, the fibre of the sugar cane that remains after it has been crushed and the juice extracted, can be converted into an eco-friendly boiler fuel for co-generation. Co-generation is the simultaneous production of process steam and electricity. Historically, sugar mills in India were allowed to produce only the amount of energy needed for their own operations. However, in the mid-1990s, the Indian Ministry of Power began to allow companies to co-generate surplus energy and export it to the state electricity board or other manufacturers.
Dhampur Sugar Mills was one of the first Indian companies to take advantage of this new opportunity. Dhampur Sugar Mills is a US$111 million organisation employing more than 6000 individuals. In order to make its operations more sustainable, the group has diversified its offerings in recent years to include chemical manufacturing and co-generation export.
Challenge
Before the Ministry of Power's policy change, Indian sugar companies traditionally installed inefficient boilers and turbines in their captive power plants and created power only during the sugar season. Since they had an abundance of fuel and no opportunity to sell excess energy, sugar companies had no incentive to install efficient co-generation systems. Once exporting energy became a possibility, Dhampur Sugar Mills began to look for ways to increase the efficiency of its power plants.
To increase its energy-producing capabilities and facilitate year-round production at their Rauzagaon facility, Dhampur replaced the low-pressure boilers (21ata/340°C) and backpressure, turbo-alternators with two high-pressure boilers (65ata/480°C), one extracting/condensing turbine and one back pressure turbine. A distributed control system (DCS) running on Modbus was installed to control the system.
Initially, Dhampur was satisfied with the performance of its new system. However, ongoing maintenance proved very costly. The DCS system was designed using complicated FBD and STL programming languages. Despite extensive training, Dhampur's staff discovered that making even minor adjustments to the system logic was difficult.
On-site support by the system's supplier was often required, but the work was frequently delayed because the supplier had so few senior project engineers on hand to troubleshoot the system. In fact, the supplier often resorted to flying an engineer from Bangalore/Mumbai to the Rauzagaon site, which added transportation costs to already expensive service charges. In addition, the specialty analog PID modules, which controlled the temperature and steam pressure within the boilers, often failed and needed replacement. In fact, the replacement cost of the modules soon represented a significant proportion of the initial cost of the entire system. And even when the modules were operating correctly, they were allowing a boiler pressure variance of ±10%, which compromised the system's overall efficiency.
Solution
To improve the output of its co-generation system and control maintenance costs, Dhampur Sugar Mills required a new user-friendly, reliable control system. The company approached Energy Ventures, an authorised Rockwell Automation system integrator headquartered in New Delhi, for a solution. Since 1992, Energy Ventures has specialised in designing and installing automation and control systems for the sugar and energy industries.
It has quickly built a solid reputation for helping its customers achieve stable operation and maximum production - for minimal cost. After reviewing the existing co-generation system, Energy Ventures provided Dhampur with both distributed control and centralised control options that would meet its requirements. Ultimately, Dhampur selected a Rockwell Automation integrated process solutions based on Allen-Bradley, FlexLogix. Dhampur directed Energy Ventures to apply the new control solution to one of the two boiler systems in the power plant.
FlexLogix, a highly adaptable multiloop controller, is modular in nature and allows each segment of the co-generation system to be controlled by a separate FlexLogix unit. The system is based on open technology and can be easily expanded and networked in the future. The controller is programmed with user-friendly RSLogix5000, a Rockwell Software tag-based programming language that simplifies documentation and integration with visualisation programmes.
Finally, Rockwell Software RSView32, an integrated, component-based human machine interface (HMI), monitors the system. Designed for Microsoft Windows environments, RSView32 utilises open technologies to provide unprecedented connectivity to other Rockwell Software products and third-party applications. To cost-effectively monitor boiler temperature, third-party temperature scanners were integrated into the monitoring system via a Modbus communication port. The RSView32 software collects temperature data from these scanners, displays temperature values on colour graphic screens and, finally, logs the data to generate multiple graphs.
Results
With the new FlexLogix solutions running on one boiler system and the old control system running on the other, Dhampur Sugar Mills can easily evaluate the new system's effectiveness. With improved PID control, the temperature and pressure within the boiler utilising the new system is much less volatile. In fact, the variance within the boiler controlled by FlexLogix is ±5%, while the boiler running on the old system still has a variance of ±10%. This improved efficiency reduces the 'per unit' generating cost. In addition, since the new system is less volatile, the costly boiler and turbine are less prone to wear and tear.
Thanks to easy-to-use RSLogix5000 and RSView32, Dhampur Sugar's engineers and operators were quickly trained on the new system. And since Dhampur's engineers can easily make adjustments to the system themselves, there is little need for field support. The new system's hardware modules continue to perform reliably - service calls have been substantially reduced and costly spare parts are rarely needed. The overall reduction in maintenance expenses is dramatic. In fact, the new system cost less to install than the annual maintenance on the previous system.
The boiler upgrade was just the first of many successes at the Rauzagaon mill. The company also chose to convert its existing condensing turbine control system to the same FlexLogix system as the boiler. And an additional FlexLogix solution was installed to control a new, load-cell based system for juice weighing. FlexLogix also controls various operations in the sugar refinery and the mill house. Today, the boiler, juice weighing, sugar refinery and mill house FlexLogix are integrated on the same network. All systems send information to the master control room where hourly MIS reports are generated and sent to the central office server and can be accessed by the executive office and quality control. In the near future, Dhampur plans to use V-sat communication to transmit the MIS reports to its corporate office in Delhi.
Discussions are also underway to upgrade and integrate the second boiler system at the Rauzagaon facility. In addition, Dhampur Sugar has contracted with Energy Ventures to install FlexLogix systems at its chemical plant at Dhampur and sugar mills at Dhampur, Mansurpur and Asmoli.
The architecture shown in the diagram depicts Rockwell Automation's concept of an integrated architecture. The area outlined with a red dash line represents the present automation level under discussion in this document. The remaining portion illustrates a host of solutions that Rockwell Automation can provide today to integrate the plant floor to the enterprise and beyond.
For more information contact Rudolf Van Wyk, software capability manager, Rockwell Automation, +27 (0) 11 654 9700, [email protected]
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