Cereal Docks, an Italian company through and through, has been operating on the domestic market since 1983 and is a leading partner in the primary sector of agricultural commodity processing, bringing together the worlds of industry and agriculture. Today, Cereal Docks is a leading Italian industrial group processing cereals such as wheat and maize, and oil seeds, such as soya, rape and sunflower, for the food industry, for industrial and technical purposes and for the production of biofuels. It is the main harvester and stocker on the Italian market, with an annual processing capacity of 1,000,000 tons of raw material, thanks to a total storage capacity of over 500,000 tons. In line with the 3 areas of its payoff – Agriculture, Food and Environment, Cereal Docks has gained a reputation in recent years as a leading champion of the green economy and environmental sustainability, choosing to diversify its commitment to renewable energy sources, such as biodiesel for transport, and electricity from cogeneration plants, biomasses and photovoltaics.
At its Porto Marghera site, which has just undergone a major revamp, the need to choose a cogeneration plant was due, first and foremost, to the need to efficiently meet a considerable amount of the site's energy requirements, using a high performance engine, which, among other things, also enables the company to take part in the energy efficiency certificates scheme. A company like ours is energy-hungry because, to process raw materials, it uses large amounts of electricity and thermal energy with consequent and relative environmental and economic impact, that then affects the production cost of finished products. The importance of using cogeneration comes from wanting and needing to minimise impact. The plant behind us is an electric 4,400 kilowatt hours plant, and was chosen based on estimated maximum loads of electrical absorption, to make the plant autonomous from this point of view. In our specific case, with the right estimate, we're talking of electricity production, when fully operational, of over 30 million electric kilowatt hours per year, while from a thermal view point, energy requirements, converted into equivalent natural gas, are close to 16,500,000 standard m3 per year, which in this case is covered by a cogeneration efficiency of approximately 15-20%.
At our site, electricity is used for different purposes, from handling solids and liquids – we're talking about transport and pumping – to powering all machines used in the production process, as well as general site services. Thermal energy is also used to a certain extent throughout the process: starting with the heating of seeds in the first part of the production process up to the final stages, when the flours produced are desolventized and dried, and oil is distilled. At this point, we should mention the important economic benefits of using cogeneration. Without looking at the economics of it in detail, the most important figures are an annual saving of 4,000 tons for CO2 quotas produced and a greater global energy efficiency, such as the 17 kilos of steam per m3 of gas used produced by the Duplex, which were suggested as target figures during the decision-making stage – when we decided whether or not to go ahead with the investment – and were then confirmed in the first few months of plant operation.
Lastly, this greater efficiency will produce a return from the economic investment in less than two years. When fully operational, Cereal Docks can produce over 30 megawatts of electricity, thus guaranteeing energy self-sufficiency, along with the highest standards of safety and environmental compatibility. Our combined operation Duplex boiler has been at this Cereal Docks plant, at Porto Marghera, for more than two years. The Duplex boiler was designed to combine in a single body a flue gas recovery generator with a traditional flame generator to meet the plant's thermal requirements as fully as possible. With this particular type, an independent flue gas path is assigned to the cogenerator, so it can work independently of the burner being turned on. Similarly, the burner does not require the presence of the cogenerator, making the two sections entirely autonomous. The recovery section keeps the cogenerator constantly hot and reactive.
In this way, as soon as steam production required by facilities exceeds the steam available from recovered energy, the burner intervenes to make up the missing part with a high level of reaction, without being affected by delays due to thermal lag. In this case, flue gas from a 4.4 electric megawatts GE Jenbacher engine, model 624, is conveyed to the recovery part, while the flame side has a section that can produce 10 tons/hour of steam. The burner has extremely low NOx emissions, a zirconium oxide probe to regulate O2 in the flue gas, and also has an inverter on the fan to guarantee perfect combustion, even at very low operating loads. The two circuits both have economizers, to lower flue gas temperatures as much as possible, thus obtaining very high returns. All Duplex boilers have been designed to meet the different needs of customers, who are given the utmost assistance from the design stage right up to equipment start-up at the plant. Siat's mission, for more than 70 years, has been to guarantee its customers quality and reliability, at all times, through its expertise and strong spirit of innovation.