Jul 30, 2015
In 2011, after years of careful planning and conducting numerous studies, Suzano Pulp and Paper decided to go forward with the most ambitious and challenging project of the South American pulp industry in a decade: to build the most energy-efficient mega mill in the world – to be constructed near the city of Imperatriz, in the north of Brazil.
Valmet was selected to accomplish the task, supplying the main technology for pulp production and recovery. The scope of the supply included: wood preparation with three high-capacity chipping lines, a cooking system, a fiberline with press technology, two pulp drying lines and five baling lines, an evaporation plant, recovery and a power boiler. Valmet’s contract also included the construction and erection of its equipment and the automation system for the entire mill.
The city of Imperatriz is located in Maranhão state in the north of Brazil. The state is one of the less developed in the country, and Suzano’s investment was the first of its kind in the region.
The city is located 600 km from Itaqui harbor and very close to the equator. The climate in the region is similar to that found in the Amazon forest, with temperatures close to 30oC throughout the year and two well-defined seasons: the dry season (winter) and the rainy season (summer), marked by six months of heavy rain. Such a climate brought great challenges to the workers during the construction period. At the peak of the construction, there were over 11,000 workers involved with 7,000 of them employed by Valmet.
“A project of this size had never been executed in this part of the country in such a short timeframe,” points out Edmund Schwarz, Valmet’s Project Director. “The roads were not prepared to transport such heavy equipment, sometimes weighing up to 200 tonnes such as the boiler drum, or measuring more than six meters in width, such as the evaporation effects. The heavy rain and high moisture during the summer also demanded extra efforts during the construction phase.”
On the other hand the region does have efficient logistics with a railway connecting the mill to the harbor. All exported pulp will be transported by trains and shipped to customers in the USA, Europe and Asia.
“The location of the mill was chosen in an area where land was freely available for tree plantations and there was no competition with food production. Being close to the equator saves four days of transportation to our customers in the USA and Europe, saving fuel and CO2 emissions,” says Adriano Canela, Suzano’s Project Director.
At the end of 2013, Suzano and Valmet had achieved the completion of the mill and the first bales were produced. At the same time, Brazil was facing an energy crisis caused by an unusual lack of rain in the previous season. The country is heavily dependent on hydro power generation, representing 87% of Brazilian energy capacity. With low levels of water in the reservoirs and with the national grid using power stations fueled by natural gas to generate electricity, there was an opportunity for Suzano to contribute with a more sustainable source of energy.
“We have designed our mill to have a surplus of energy. In the design of our system we have selected the most efficient technology available in order to save steam and electricity for internal use and to make available as much energy as possible for power generation,” says José Alexandre de Morais, Suzano’s Industrial Operations Director. “We have been exporting an average of 80 MW of electricity based on liquor and biomass sources, with the advantage of having our forest as a source of energy, capturing CO2 in the process”.
Such a surplus of energy is only possible due to the choices made by Suzano to have the most efficient technology installed in its mega mill.
“Valmet’s compact cooking G2 digester, employed at the Suzano mill, is the most efficient digester on the market, consuming less than 350 kg of steam per tonne of pulp produced (50% of other market technologies). Combined with our press technology in the fiberline, which consumes very little steam and water, it generates only 10 m³/tonne of effluent at a low temperature. Most of the energy stays in the process, reducing the internal consumption of the mill”, adds Paulo Aguiar, Valmet’s Senior Sales Manager for pulp technology. “In addition, Valmet’s drying machines have been operating with a steam and electricity consumption 20% lower than with other technologies on the market”.
Fernando Scucuglia, Sales Manager for recovery and energy adds, “The recovery boiler supplied to Imperatriz is not only the biggest in operation in the world, but also one of the most efficient. With high power features it can generate more energy for the same amount of dry solids burned in other boilers.”
Along with the further improvements in other processes of the mill, Suzano is generating enough power for its own consumption and a surplus of 2.0 GWh per day. This is enough electricity to supply a city of a million inhabitants* with green energy from 100% planted trees.
* According to Brazilian energy ministry, an average family has 3.2 persons and consumes 169 kWh/month of energy.
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The pulp mill has a total capacity of 1.5 million tonnes per year of bleached hardwood market pulp. The technology supplied by Valmet includes a wood yard with three lines, each one occupying a space of 420 m³/h. There is also a fiberline with four bleaching stages, and two pulp drying machines with a capacity of 5,000 tonnes per day. The recovery island includes a six-effect evaporation plant with a total evaporation capacity of 1,600 tonnes of water per hour. The recovery boiler is one of the largest in the world with the capacity to burn 7,000 tonnes of dry solids per day. The white liquor plant is able to produce 16,000 m³ per day of white liquor and has two lime kilns with the capacity to produce 600 tonnes of lime per day. Valmet’s delivery also includes a fluidized bed boiler producing 120 tonnes of steam per hour, fueled by forest biomass.