Processes and systems for producing heat for rapid thermal processing of carbonaceous material

Abstract

Embodiments of processes and systems for producing heat for rapid thermal processing of carbonaceous material are provided. The process comprises the steps of contacting bubbles of an oxygen containing gas advancing through a fluidized bubbling bed with a grating to form smaller bubbles. The fluidized bubbling bed is contained in a reheater and comprises inorganic heat carrier particles and char. The reheater is operating at combustion conditions effective to burn the char into ash and heat the inorganic heat carrier particles to form heated inorganic particles. The heated inorganic particles are advanced to a reactor.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to processes and systems for thermal processing of carbonaceous material, and more particularly relates to processes and systems for producing heat for rapid thermal processing of carbonaceous material.BACKGROUND OF THE INVENTION[0002]The processing of carbonaceous feedstocks (e.g. biomass) to produce heat, chemicals or fuels can be accomplished by a number of thermochemical processes. Conventional thermochemical processes, such as combustion, gasification, liquefraction, and conventional pyrolysis are typical equilibrium processes and yield relatively low-value equilibrium products including major quantities of non-reactive solids (char, coke, etc.), secondary liquids (heavy tars, aqueous solutions, etc.), and non-condensible gases (carbon dioxide, carbon monoxide, methane, etc.). For example, combustion is used primarily for thermal applications, and gasification typically produces low energy fuel gases with limit...

AI Technical Summary

Benefits of technology

[0011]Processes and systems for rapid thermal processing are provided herein. In accordance with an exemplary embodiment, a process for providing heat for rapid thermal processing of carbonaceous material is provided. The process comprises the steps of contacting bubbles of an oxygen containing gas advancing through a fluidized bubbling bed with a grating to form smaller bubbles. The fluidized bubbling bed is contained in a reheater and comprises inorganic heat carrier particles and char. The reheater is operating at combustion conditions effective to burn the char into ash and heat the inorganic heat carrier particles to form heated inorganic particles. The heated inorganic particles are advanced to a reactor.

[0012]In accordance with another exemplary embodiment, a system for producing heat for rapid thermal processing of carbonaceous material is provided. The system comprises a reheater containing a fluidized bubbling bed that comprises inorganic heat carrier particles and char with bubbles of an oxygen containing gas advancing through the fluidized bubbling bed. The reheater comprises a grating disposed in the fluidized bubbling bed. The grating is configured for contacting the bubbles to form smaller bubbles. The reheater is configured to operate at combustion conditions effective to burn the char into ash and heat the inorganic heat carrier particles to form heated inorganic particles. A reactor is in fluid communication with the reheater to receive the heated inorganic particles.

Problems solved by technology

For example, combustion is used primarily for thermal applications, and gasification typically produces low energy fuel gases with limited uses.

Liquefaction and conventional pyrolysis often produce low yields of valuable liquids or gaseous products.

In addition, the liquid products that are produced often require considerable secondary upgrading.

However, over the past few decades fundamental pyrolysis research has found that high yields of primarily non-equilibrium liquids and gases (including valuable chemicals, chemical intermediates, petrochemicals and fuels) could be obtained from carbonaceous feedstocks through fast (rapid or flash) pyrolysis at the expense of undesirable, slow pyrolysis products.

This is problematic for a number of reasons.

Furthermore, when the bubbles become quite large they can accumulate and take up a significant amount of space in the fluidized bubbling bed.

This prevents good mixing of the air, sand and char, which is needed for mass transfer that creates a mixing reaction between the air and the char, and which is also needed for heat transfer from the burning char to the sand.

Without good mixing in the fluidized bubbling bed, the air bubbles and the char will not effectively react in the dense phase, resulting in a cooler dense phase.

The net effect is that the heat generated from burning char will not be effectively recovered by the sand, resulting in cooler sand being passed to the reactor.

Moreover, when the bubbles become quite large they take away space from the fluidized bubbling bed, which decreases the residence time for the char to burn in the reheater dense phase, resulting in an incomplete combustion of char to ash and a less efficient process resulting in a poor temperature profile and a temperature that may exceed the design temperature of the equipment in the down stream section with after burn.

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