Gas distributor for a rotary kiln

Abstract

A rotating air distributor for rotary reactors such as rotary kilns for the gasification of biomass and other carbonaceous materials for efficient mixing and maximum conversion of solid biomass and other carbonaceous materials into synthesis fuel gas is disclosed. The invention includes a gas distribution port comprises of one main supply from which several discharge nozzles emerge at different angles and at different locations along the length of the reactor to provide distribution of gas throughout the intended length of the reactor. The discharge of gas from the gas distribution port is adjusted by the variable position of a plug inside the port that can be adjusted during the operation of the kiln to achieve optimum gas-solid interaction along the length of the reactor. The rotating action of the gas distribution port also facilitates and eases the passage of reacted biomass solid and other carbonaceous material residue through the reactor.

Description

BACKGROUND OF INVENTION1. Field of InventionThis invention relates to rotary reactors such as rotary kiln for the gasification of solid carbonaceous materials such as biomass and solid wastes and particularly to the gas distributor for introducing gases such as air, oxygen, and steam to the interior of the rotary kiln wherein this gas distributor assures gas solid mixing inside the reactor to promote gas solid reaction.2. General Background and the State of the ArtIn the last two decades or so, interest in biomass gasification has picked up as means of producing energy from renewable resources to supplement fossil fuels as well as to develop strategy for distributed generation for reasons of meeting energy security needs. This renewed interest has encouraged development of new and improved methods for making biomass gasification efficient and fuel gas generated from these cleaner in terms of its tar content. Biomass typically comprises collectable, plant-derived materials that may b...

AI Technical Summary

Benefits of technology

According to a preferred embodiment of the present invention, there is provided a port assembly secured by the stationary plate of the rotary kiln and positioned for communication with the interior of the rotary kiln. The port assembly comprises of a main conduit for introducing gases such as air, oxygen and steam into the kiln as well as several nozzles extending from the main conduit for distribution of gases into the kiln as well as to promote intimate mixing between gases emerging from these nozzles and solids present in the kiln. The main conduit extends approximately two thirds of the way into the kiln if the kiln is operating as a gasifier. The conduit will extend all the way to the end of the kiln if the kiln is operating as a combustor. A movable gas plug is inserted inside of the main conduit. The position of this gas plug determines the length of the kiln into which reactant gases are introduced. This flexibility is essential because in the case of gasification of the carbonaceous material, it is first necessary to combust portion of the carbonaceous material with air or oxygen to provide energy necessary to carry out the reactions between gases and solids and also to maintain temperature in the reactor that would sustain endothermic reactions between steam and the carbonaceous materials to yield synthesis fuel gas. In contrast, combustion of carbonaceous material is completely consumed by air or oxygen supplied to the kiln and therefore the air is supplied throughout the reactor. In fact, for combustion, additional air beyond that required for complete combustion is introduced into the kiln to absorb the heat and to control run away condition with respect to temperature. The conduit is blocked at the far end of the assembly so that there is sufficient discharge of gases through the nozzles.

In general, the diameter of the nozzles at any given circumference of the port assembly will be identical, although not necessary. However, the diameter of nozzles as they move into the kiln will become successively larger along the main conduit to reduce the pressure drop across them so that the gas flow can pass unhindered through all the nozzles.

Problems solved by technology

Even though this art provides means of introducing air into the kiln either below the material charge of the bed or when the ports are above the bed, its operation, control, and maintenance is cumbersome.

If aforesaid apparatus is operated to process mixed size materials containing particles having smaller diameter than the port, these smaller particles may enter the ports and the associated piping causing the clogging of the ports and thereby restricting the flow of air into the reactor.

This sort of impairment also increases the necessity of maintenance and hence increases the downtime of the reactor.

While this improvement acts to prevent particulate material from entering the associated port pipe, some of the very smallest particulate material will eventually elude this screening mechanism and pass into the piping and eventually cause a restriction for the air flow into the reactor.

In this study it is implied that significant amount of carbon is left in the solid residue and unless used as fuel for indirect heating of the kiln shell, the process efficiency for converting biomass into fuel gas is greatly diminished.

This distributor has limited ability to cause intense mixing between the gas and solids in the reactor which is a prerequisite for causing optimum conversion of solid biomass and other solid carbonaceous fuels into gaseous fuel.

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