Low-Carbon Cure

A Sri Lanka-based tire factory switches from fuel oil to biomass for steam generation in the tire-curing process.
By Ron Kotrba | June 24, 2019

Like many components of the energy-intensive modes of transportation on which people rely in pursuit of commerce, daily living and leisure, tires have become a subject of focus to reduce energy consumption and, as a result, greenhouse gas emissions. Proper inflation and low rolling resistance tires are the most common ways people know to help the environment with respect to their tires, but as they drive down the street or farm the land in cars or tractors running on ethanol or biodiesel, sitting on seats made of soy polymers or bioplastics with properly inflated tires, do they ever consider the energy consumed to manufacture those tires? Companies such as Trelleborg Group seek to spark this curiosity in consumers.

Trelleborg Group is a Sweden-based multinational manufacturer of engineered polymer solutions. The company has more than 24,000 employees in 51 countries. Trelleborg Wheel Systems, part of Trelleborg Group, is a leading global supplier of tires and complete wheels for agricultural and forestry machines, materials handling, construction vehicles, motorcycles, bicycles and other specialty segments. It offers highly specialized solutions to create added value for customers, and it partners with leading original equipment manufacturers (OEMs). Trelleborg Wheel Systems’ manufacturing facilities can be found on four continents in the countries of Italy, Latvia, the Czech Republic, Serbia, Slovenia, Sweden, China, Sri Lanka, the U.S. and, after the 2015 acquisition of Standard Tyres Group, Brazil.

In late April, Trelleborg Wheel Systems announced a full reengineering of its Sri Lanka facility’s steam production process by installing an advanced biomass boiler. The company says this major investment will not only reduce the plant’s environmental footprint, but it will also improve production efficiency. The Trelleborg facility in Sri Lanka is located in Makola, close to the capital city of Colombo, and employs more than 850 people. The manufacturing facility produces solid tires for the material handling and port industries, and pneumatic tires for agricultural applications.

Steam production is essential to the tire-curing process. “Tire curing is the process of applying pressure to the green tire in a mold in order to give its final shape,” Paolo Pompei, president of Trelleborg Wheel Systems, tells Biomass Magazine. “Steam curing is the method used to heat the molds to then stimulate a chemical reaction between the rubber compounds and other materials.”

Trelleborg’s Sri Lankan tire factory has traditionally used petroleum-based fuel oil for steam generation. “The Sri Lanka tire manufacturing facility consumed a large quantum of furnace oil—3.5 million liters per year producing more than 11,000 tons of CO2—in the traditional tire manufacturing process,” Pompei says. “The switch from fossil fuels to biofuels was a much-needed step change in the energy footprint. With the introduction of the biomass system, the carbon footprint will be reduced significantly by 90 percent.”

Pompei says Trelleborg constantly invests in reducing its carbon footprint. “It’s in line with Trelleborg’s Blue Dimension strategic initiatives,” he says. “At Trelleborg, we believe that the benefits of our solutions stretch beyond functionality and business performance. They reduce environmental impact by saving energy, cutting emissions and protecting the soil. This is what we call ‘Blue Dimensions-Solutions for Better Sustainability.’ ”

Thermax Combipac
The biomass boiler being installed at Trelleborg Wheel Systems’ tire factory in Sri Lanka is manufactured by India-based Thermax Ltd. “It is a custom-made, fully automated Combipac steam boiler,” Pompei says. In Trelleborg’s April announcement, the company referred to the biomass boiler as “advanced.” When asked what makes it advanced, Pompei says, “The boiler is designed for ‘no man’ operation with a higher degree of automation. It consists of an automated, moving floor along with a conveyer belt system, which manages the fuel feeding of the boiler. The furnace chamber is designed as per the reciprocating grate,” a Lambiyan design, he says, which is fully controlled by a supervisory control and data acquisition (SCADA) system with online emission monitoring capability. Added features, according to Pompei, include an economizer, or heat recovery system, an electrostatic precipitator for particulate control and a fully automated ash-handling system.  

“The model delivered to Trelleborg is a Combipac 12 TPH boiler with a reciprocating grate combustor,” says Rakesh Tripathi, the global head of Thermax’s heating business. “It is one of the most popular models of Thermax. It uses advanced combustion techniques resulting in a highly efficient and reliable operation to generate the process steam.” Tripathi says this was a turnkey installation, whereby concept to commissioning is carried out by Thermax. 

“Thermax is a pioneer in the boiler industry in the South Asian region,” Tripathi says. “Thermax introduced its first biomass boiler for heating applications in the 1980s. The biomass journey started with the introduction of small-sized boilers for process houses. Initial fuels were wood logs, wood chips and rice husk, which are abundantly available in South Asian markets.” Tripathi tells Biomass Magazine that Thermax is committed to providing a cleaner environment for future generations and has continuously worked on improving and introducing better combustion technologies in the markets in which it operates. “Consequently,” Tripathi says, “Thermax has been successful in providing solutions for combustion of more than 150 types of biomass fuels.” 

According to Thermax’s data sheet on its Combipac multisolid fuel-fired hybrid steam boilers, the system “is a hybrid smoke and water tube design boiler with the combustor based on the principle of fluidized bed combustion. The fuel bed is fluidized by the injection of air from the bottom of the bed, through a set of air nozzles, using a forced-draft fan. This produces a fuel bed resembling a boiling fluid, which helps achieve uniform mixing and efficient combustion.”

Important features of the Combipac steam boiler, according to the boilermaker, include its suitability for burning fine particles; the controlled bed temperature; operation flexibility; rapid response to load; maximum unburnt losses; low excess air required and, hence, higher efficiency; fully automatic operation; uniform heat flux ensuring longer refractory life; specially designed air nozzles for optimum performance; and the ability to handle high moisture, up to 35 percent in coal. Tripathi says the boiler installed at the tire factory in Sri Lanka is capable of handling high-moisture rubber wood chips, Trelleborg’s feedstock of choice. 

The fuel feeding system offers the flexibility of firing a wide variety of solid fuels. Thermax’s Combipac boilers are equipped with both under-bed and over-bed feeding systems. The under-bed feeding system, which consists of a rotary feeder and a booster fan, is appropriate for fuels such as rice husks and various types of coal. The over-bed feeding system is fed by a screw feeder and is suitable for biomass such as paddy husks, wood pellets and palm kernel shells, as well as coal.

The membrane panel assembly of the Combipac steam boiler features a D-type membrane panel for a controlled bed temperature and to better achieve water circulation. The design also reduces stress concentration on the shell tube plate. Thermax says the D-type membrane panel provides effective radiative heat transfer due to the optimum distance between the membrane panel assembly and the bed. The Combipac membrane panel is also equipped with integrated in-bed tubes to recover heat from the radiation zone and maintain uniform bed temperature. Important features of the in-bed tubes include the fact that all bends are placed outside the fuel bed zone, which helps eliminate erosion levels. Due to a higher pitch, a lower air and particle velocity is achieved between tubes, which also aids in ensuring a reduction in erosion levels. Furthermore, tube overheating is eliminated thanks to the design, allowing for a very high circulation ratio and water velocity.

The boiler shell assembly, according to Thermax, features an efficient and dependable convective pass design with optimally sized diameter tubes, no flue gas turning in the convective bank and a reduction in tube and tube-plate erosion. The company also says the shell assembly design provides high-quality steam and better load response thanks to a higher steam/water interface area and higher freeboard. The wire coil inserts provide improved flue gas turbulence and velocity and improved heat transfer performance. The simple layout of the shell assembly, according to Thermax, allows for easy cleaning via hinged-door smoke chambers.

Ultimately, Thermax says its Combipac line of boilers improves overall combustion efficiency and provides better response to steam load resulting from higher turbulence levels, better residence time, low excess air and uniform distribution of air and fuel.

Full Steam Ahead
Pompei wouldn’t disclose how much the conversion project is costing the tire manufacturer. When asked of the price tag, Pompei simply says, “This is a key milestone project in achieving a reduction in the carbon footprint within the whole organization—something where we have put huge investment.”

Pompei says energy is a “significant element” in manufacturing costs, and the new boiler and wood chips as fuel will bring a “significant reduction” to the cost of steam generation. “Further,” he says, “entering into fixed-term contracts with new raw material suppliers would help us reduce possible market fluctuations.”

The biomass boiler will use nearly 2,700 kilograms per hour (kg/hour) of rubber wood chips, according to Tripathi, for generating steam at its full capacity at standard operating conditions. “This is equivalent to 830 liters of diesel firing for same heat delivery,” he says. “Use of biomass in place of fossil fuel such as diesel will result in a reduction of 15,000 tons of CO2 emissions per year.” Tripathi says the boiler is capable of generating 12,000 kg/hour of steam, which is equal to 7.5 MW of effective heat delivered to the process.

Biomass delivery will be entirely fulfilled by local producers, Pompei says, “thus shortening the supply chain, further reducing our carbon footprint and supporting the local economy.”

Biomass Magazine reached out to Sri Lankan native Lucky Dissanayake, founder of Biomass Group Ltd. and its Sri Lanka-based subsidiary Biomass Supplies, which is developing a supply chain of Gliricidia Sepium—a rapidly growing, short-rotation tree found wild throughout the island nation—based on an outgrower, or contract farming, basis. Dissanayake says Biomass Supplies is not involved in the supply of rubber wood chips to Trelleborg. She says until very recently, many local industrial companies in Sri Lanka seeking biomass supplies would simply “hire a man with a saw and a van and really didn’t care as to where the biomass came from, which inevitably meant that trees were being cut down within a radius of the factory.” Tragic events this spring, however, changed this, Dissanayake says.

This past Easter Sunday, April 21, a series of bombs in churches and hotels killed hundreds of people in Colombo. “The chainsaws and machetes belonging to laborers were confiscated, and many industries are now asking for our biomass supplies,” she tells Biomass Magazine. “So we are doing tests now to determine how best to deliver volumes to industry.”

Interestingly, Trelleborg Wheel Systems is not the first tire factory in Sri Lanka to go green with biomass boilers. In January 2017, Global Rubber Industries Pvt. Ltd. broke ground on a new specialty tire factory adjacent to its exiting solid tire manufacturing facility in Colombo. It features solar panels, biomass boilers and recyclable waste management systems.

Trelleborg’s biomass conversion project began last year and will be completed by the end of June. Pompei says GRI’s foray into biomass at its Sri Lankan plant did not influence Trelleborg’s decision to switch from fuel oil to biomass. He does, however, say that this project may lead to more like it within the expansive network of Trelleborg factories.

“In line with Trelleborg Group’s Blue Dimension approach for better sustainability, these kinds of studies are always a top priority for new ways of exploiting green energy over time,” Pompei says. “This new biomass boiler investment will be a pilot project to be evaluated for the rest of the group.”

Author: Ron Kotrba
Senior Editor, Biomass Magazine
218-745-8347
rkotrba@bbiinternational.com