The government of India has announced the National Policy on Biofuels, under which ethanol blending of petrol has already reached 10%, and is planned to go up to 20% by 2025. Blending locally produced ethanol with petrol will help India strengthen its energy security. It will enable local enterprises and farmers to participate in the energy economy and reduce vehicular emissions. This national goal can be met by augmenting supply chain for blending ethanol, where stainless steel has a significant role.
According to the Niti Ayog report ‘Roadmap for Ethanol Blending in India by 2020-25’ released in June 2021, phased rollout of 20% of ethanol blending by 2025 is very much possible. The report says “Most of the petroleum products are used in transportation. Hence, a successful E20 program can save the country US $4 billion per annum, i.e., Rs. 30,000 cr.” Besides, immense benefits can accrue to the country in terms of energy security, lower carbon emissions, better air quality, self-reliance, use of damaged food grains, increasing farmers’ income, employment generation, and greater investment opportunities, According to Niti Aayog, initially, pan-India ethanol production will be raised from the current ~700 crore litres to 1500 crore litres to make 20% target feasible. Ethanol’s price is around Rs. 50-60 per litre and therefore, its blending with petrol is highly cost effective. The differential price policy for ethanol blended petrol announced by Finance Minister in the Budget, making it cheaper by Rs. 2/Litre, will further improve its economics.
However, oil marketing companies can face challenges in terms of additional storage tanks for ethanol at refineries/terminals/depots and need for ethanol compliant dispensing units. Thus, the right casing material needs to be considered for its safe storage, supply and transportation. [2]. In addition, it is crucial to note that ethanol cannot be stored in an average container because it causes corrosion. Although 100% pure ethanol is not corrosive to most metals, its impurities such as oxygen that cause high level of corrosivity. Some of the contaminants like water, organic acids and chlorides can cause high level of corrosion in ordinary steels and disrupt operations of ethanol supply chain. There are two methods that can be used to store ethanol: Removing any oxygen content and other impurities in the ethanol sample, which is an expensive process [3], or storing it in a non-corrosive material which is more cost-effective.
Stainless steel is a corrosion resistant material which makes it the ideal choice for ethanol production and distribution systems worldwide. With stainless steel, pipes can often be made with a lighter wall thickness which makes it easier to distribute. In addition, stainless steel is easy to maintain which reduces costs implied with storage: no paint or other coatings on internal or external surfaces need to be maintained, surfaces remain smooth due to non-corrosion, has a longer life and allows for easier cleaning and disinfection and lower pumping costs. Therefore, stainless steel is the material of choice in Ethanol production and distribution systems worldwide
Secondly, ethanol is a highly flammable material and stainless steel is fire-resistant. Tanks containing ethanol are required to be fire resistant, and stainless steel will prevent the spreading of flames in the case of a standard structural conflagration.
Apart from the general benefits of using stainless steel, the successful impact really depends on the type of project it is used for. For example, tanks for food-grade ethanol are constructed using type 304(L) of stainless steel whereas very large tanks with heavy plates would use a high strength lean-duplex grade such as S32101. Type 304(L) is usually used in the more alkaline operating media of biodiesel processes, such as piping and tubing systems. Type 316(L) is used in places where the acid content is greater and the temperature is more extreme.
To summarize, the type of stainless steel normally required for ethanol projects is generally within grades of 304/316 and used in shell material for distillation columns, shell material for heat exchangers, fermenters and other process tanks, storage tanks, pipes and fittings, plates, tubes for heat exchangers, dryer and other equipment and ethanol tankers. A typical stainless-steel requirement for a 500 kilo litres per day ethanol plant is about 1300 tons. In line with the national priorities, stainless steel industry has geared up to meet this demand, with supplies expected to double this year.