Introduction

Gasification is an old technology widely used during World War II for running vehicles. After World War II, this technology remained dormant for a long period of time. Today, because of increased diesel prices and environmental concerns, there is renewed interest in  this technology. Serious R&D efforts were made only during the last ten years achieving some breakthrough. Small scale power generation is the main advantage of gasification technology, whereas steam turbine technology is not viable for capacity of less than 1 MW. Gasification for power generation is often attractive when compared with diesel based electricity generation, and it is a big boon for very small scale power producers who are not connected to the grid, and depend upon diesel.

Gasification Technology

There are different types of gasifiers available in the market and the selection of the technology mainly depends on the type of fuel used, the equipment supplier’s experience and credibility.  The technology is used for several applications such as water pumping, thermal usage and power generation. Although there are several suppliers who claim that their technologies are the best in the market, only very few suppliers have mastered the technology. Today, it remains a great challenge for the buyers to identify the right suppliers who have really mastered the technology. Though several electricity generation plants are in operation in Asia, not all projects are successful.

Gasifier Fuel

Gasification can be done with most of the biomass including rice husk, coconut shell, coconut husk, rice straw, sugarcane bagasse, sugarcane trash etc. Although most of these can be used, their form of usage varies with the manufacturers. For example, in the case of rice husk, some manufacturers produce gasifiers in which the rice husk can be directly used. For others the rice husk needs to be briquetted.  Gasification plant with dual fuel engine (Biomass + Diesel) is also another option.

Plant Life

The life of the gasifier plant depends, to a large extent, on its operation. For a well operated and maintained gasifier, the plant life is around 20 years. However, the engine life is generally 10 years and the engine has to be overhauled after every 5.000 hours of usage. Engines Although the market is yet to come up with an engine exclusively designed for gasification, engines designed for natural gas and biogas are being used for gasification purposes. The capacity of the engine produced in India varies and the maximum is 250 kW. For higher capacities these engines are being used in multiple numbers as modules. For example, in a 1 MW gasification power plant, a single gasifier and four engines are used. In China, 500 kW units are newly produced. Though these units are being used in several plants already, they have not been tested for reasonable number of operating hours to validate the performance. A few engine manufacturers supply gas engines with higher efficiencies even at low load operation, but the price is also high as compared to the other gas engines.

Plant Operation

Gasification plant requires highly trained people who have the passion to operate the gasifier. For a 1 MW gasification plant, for each shift, 2 engineers, 6 skilled labourers and 6 unskilled labourers are required. However, this may vary depending on the fuel, site condition and the manufacturer. Auxiliary Power Consumption In general, around 120 kW of power is required to operate a 1 MW gasification power plant i.e. out of a 1 MW gasification power plant, only 880 kW will be available for usage. When the size of the gasifier reduces, the auxiliary power consumption becomes higher. For example in a 500 kW gasifier, 15% (75 kW) is needed to operate the power plant.