Small biomass gasification devices are generally used as a source of cooking gas in rural areas. The gas produced by the gasifier does not require cooling and can be directly delivered to the stove. Due to low cost requirements, the gasification system is simple and cannot be equipped with complex gas purification devices. Therefore, it is technically difficult for a small biomass gasification device to reduce the tar content and ensure long-term stable operation of the device. The low-tar technical measures adopted in some large gasification units may not be suitable for small gasification units. As a practical technology to reduce the tar content in gas that meets the characteristics of small gasification devices, the following technical solutions can be considered.
1 High-efficiency gasifier integrating biomass gasification and tar cracking
Most of the small household biomass gasifiers are fixed bed suction type, and the gasifier outlet temperature is about 500e. If another cracking furnace is installed, it will obviously not reach the required cracking temperature. For this reason, in addition to adding catalysts such as dolomite or charcoal to the biomass entering the furnace to allow gasification and tar cracking to proceed at the same time, a catalytic cracking zone can also be set up in the furnace near the gas outlet so that the gas produced by gasification will immediately enter the cracking zone to make full use of the high temperature characteristics of the furnace to carry out the tar catalytic cracking reaction in the furnace.
2 Develop a purification device with simple structure and high tar recovery rate
Design a purification device with multiple functions such as cooling, dust removal and tar separation,
Small biomass gasifiers can be equipped with an efficient purification equipment that uses mechanical dust removal and can be combined with an attached tar separation or recovery device. During the cooling and flow process of the crude gas, the gaseous tar condenses into liquid droplets, which can be effectively separated from the crude gas together with the ash, and flows back to the high-temperature oxide layer in the gasifier through the circulation pipeline for cracking reaction.
3. Looking for catalysts more suitable for small biomass gasification devices
Strengthen research on the relationship between parameters such as temperature, contact time, catalyst particle size, and tar conversion rate. The adding method and location of the catalyst should consider the furnace type characteristics of the gasification furnace to achieve optimal performance matching and look for catalysts with low cost and high activity.
