DIRTY BIOMASS TECHNOLOGIES

“Technology is Technology – it is replicable, transferable but best effectiveness comes with cross-industry application” Today, India is considered leader in biomass technology and the credit is to the entrepreneurs who showed the courage and risk to be part of the development cycle.

In late 80’s and early 90’s, a few small companies developed technologies for rice husk and other benign biomass against the strong negative protests by the large players. Later, almost all large players followed the same technology path by modifying/ upgrading the technologies demonstrated by these small players.

In late 90’s and early 2000, there came another biomass revolution. This was time for dirty and aggressive biomass. The biomass that was rich in sodium, potassium, chlorides and silica. The first high pressure boiler (supplied by a large boiler company) lasted a few months while another build by Indian government with Danish technology was shut in a month’s time. Some enthusiastic technocrats took the challenge and developed the new technology for these dirty biomasses. These technologies were closely guarded so none of the large companies claimed success. These technologies included for high chlorides fuels (reported up-to 1%) such as mustard, cotton, maize and paddy straws. These plants are numbered, and our team members were part of this revolution.

Another important achievement was that the hype about the reciprocating and water-cooled grates was successfully broken for dirty biomass with proper selection of grate material, air and gas temperature profiles and the air/ pressure distribution under the grate for efficient cooling.

In around 2004, some consultants recommended 67 bar and 425 Deg C configurations without proper thermodynamic analysis. This analysis requires complete knowledge of power plant design and not only the boiler. In 2004, one plant was commissioned with 67 bar and 425 Deg C configuration. This plant was overall 22-25% expensive (at that time!) and less efficient than 45 bar/ 425 Deg C. The high auxiliary consumption (+4.5% approximately) and little efficiency gain of increased pressure ultimately proved the concept wrong. No other plant was ever built again with this configuration.

Palm waste availability in India is limited and hence this was never taken seriously. In fact, the paying capacity of the palm mills, world over, was too low to afford high end technology. The current boiler technologies are low end and marred with low efficiency, high maintenance and low pressure/ temperature configurations. The current market players recommend 67 bar and 415 Deg C configuration for new projects. Further, the available designs are based on waste heat recovery boilers – long tail designs with high back end velocities based on aggressive heat transfer areas. The high velocities result in high erosion rates and ash accumulation limiting the best run ability between 40 to 60 days. Some players now talk of 90 days operation. This is like late 90’s in India.

Our technology was demonstrated on a small boiler (15 TPH) at a palm mill five years ago. This factory has two boilers. One is ours and second from a reputed company. Even after five years of operation, the boiler operates for whole reason without planned shutdown and its response to the load changes is far excellent. The other boiler needs cleaning every 40 days or so. Our boiler design is based on patented.

parallel flow black liquor recovery boiler, which typically have 23% Alkali contents. The fact that our company has not sold any spares to this customer in last 5 years speaks about the design and technology.

Another revolutionary concept is De-alkalization of fuel. This is latest technology fad in USA and Europe to produce biomass for gasification, biodiesel and black pellets. Our team members mastered this about 10 years ago with support from Germany by operating one plant for several years. This was shut down 2 years ago due to other priorities. The biomass was chemically treated to remove about 90% of all the alkalis and chlorides. There exists opportunity to use this technology in sugar cane trash, king grass, palm and other energy fuels. In one of the large projects built by a reputed boiler company have failed to perform in Latin America. The prime reasons are standard design techniques and lack of experience on dirty biomass. Our several years of experience culminates in recommended single boiler capacity of 40 to 45 Tons per hour (Maximum) for trouble free operations. Customer engineers should not try to get emotional with large capacities of 70 or 90 TPH.