Biomass energy conversion apparatus and method

Abstract

Method and apparatus are disclosed to utilize the energy in biomass (waste agricultural products). The inventive method and apparatus utilized heat and mass flow to efficiently generate a variety of products from biomass. In various embodiment, the invention may generate a liquid fuel (such as methanol or dimethyl ether), pure liquid CO2 (intended for CO2 sequestration), a soil enhancement product (intended to return to the agricultural site), process heat, and / or electricity. In one embodiment, the process requires no external energy inputs, and preserves a large percentage (ie. >50%) of the energy contained in the biomass. In another embodiment, the inventive method and apparatus can selectively be operated to produce electricity and or liquid fuels.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 952,506, filed Jul. 27, 2007, the entire contents of which are hereby incorporated by reference herein and made part of this specification.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention generally relates to the utilization of energy from biomass, and more particularly to a method and system that is capable of converting crop residues into one or more of a liquid fuel, electrical power or process heat.[0004]2. Discussion of the Background[0005]The prospect of converting biomass in the form of agricultural products and / or waste into fuels or energy is appealing, and is seen as a possible route to energy independence. Many such materials are considered to be waste or are disposed of in a manner that poses environmental problems. One such practice is the burning of agricultural waste, such as crop residues, in the field. Since the...

AI Technical Summary

Benefits of technology

[0008]In certain embodiments, the disadvantages of prior art are overcome by a method or apparatus which may include one or more of the following features: 1) gasifying the feedstock sequentially at increasing temperatures; 2) forming process oxygen from ambient air; 3) reacting the feedstock with oxygen; 4) providing heat for feedstock gasification from a fuel synthesis process; 5) reacting the gasified feedstock with water to produce a favorable hydrogen-to-carbon monoxide ratio, and then removing the carbon dioxide and excess water to produce a mixture useful for a conversion to fuels; 6) combining the oxidizing gas with water and / or recirculating evolved gasses to achieve the proper stoichiometry for hydrogen rich synthesis gas; 7) producing an oxygen rich gas using surplus thermal energy from partial oxidation; 8) removing and sequestering or utilizing the carbon dioxide from the biomass; 9) a flash cooling step to prevent soot formation; 10) providing the heat required for air separation from a gas cooling process; and an efficient and cost effective method for disposal of agricultural waste.

[0013]Certain other embodiments of a biomass to fuel conversion system or process may include, but are not limited to, one or more of the following: 1) the production of oxygen; 2) energy recovery from the system to produce oxygen or nitrogen depleted air; 3) the use of oxygen, or nitrogen depleted air as the oxidizer; 4) the removal of trapped ambient nitrogen from the biomass; 5) effectively remove tars and other buildup from the system; 6) a system that facilitates sequestering or using the CO2 from the biomass; 7) utilizing several conversion steps, some of which are endothermic and some of which are exothermic, and efficiently using energy by transferring heat from exothermic to endothermic process steps; and 8) operating one of the conversion steps according to the following competing reactions by recirculating gases and / or adding water: a) C+CO2→2 CO; b) C+H2O→CO+H2; c) C+2 H2O→CO2+2H2; d) CO+H2O→CO2+H2; e) CH4+2H2O→CO2+4H2; 9) prevention of soot formation from the unwanted reverse reaction of 8a) 2CO→C+CO2.; 10) Mixing the oxidizer with steam and introducing this mixture as the oxidizer with the benefit of improved thermal uniformity in the partial oxidation reaction; 11) Mixing the oxidizer with steam and recirculated expressed hydrocarbon gasses, thus partially oxidizing these gases prior to introduction to the gassifier, resulting in improved thermal uniformity in the gassifier and improved synthesis gas composition; or 12) utilizing the ash content of the gasified biomass product as an inert, thermal transfer medium, and controlling the ash volume in the gassifier.

[0014]Advantages over the prior art may include, but are not limited to: a) integration of oxygen production from air with the system; 2) providing for carbon dioxide sequestration; 3) eliminating nitrogen and / or argon contamination from the system; 4) incorporation of a cleaning cycle; 5) providing a smaller scale process with good efficiency and economics; 6) increasing the carbon conversion efficiency and fuel output by effectively using heat generated in the process; 7) lowering the temperature required to achieve proper synthesis gas composition; 8) provide for opportunistic electrical generation; 9) provide process heat for general use, for instance in HVAC systems; 10) reducing the operating and maintenance costs; and 11) increasing the amount of biomass that may be processed and / or reducing the processing time.

[0017]In certain embodiments, the fuel is produced in conjunction with electricity. For instance, when fuel demand is low, electricity can be produced and sold. Alternatively, when consumer electricity demand is high, electrical production may have higher value. A real time electro-mechanical system to monitor and configure the optimum product mix reduces operating labor while optimizing the economic value. The carbon dioxide from the system may be used to enhance oil recover or otherwise be sequestered or utilized. In one embodiment, the relative output levels of fuel and electricity is monitored and the system is automatically configured to match the application needs.

Problems solved by technology

Many such materials are considered to be waste or are disposed of in a manner that poses environmental problems.

However, burning these residues releases CO2 and pollutants into the air, and is often prohibited.

While there is great interest in using crop residue for producing liquid fuels or power, there is as yet no generally useful or economic means for doing so.

One problem with utilizing crop residue, is that the cellulosic materials in the residuals are notoriously difficult to refine into fuels.

Thus, for example, many prior art reactors for converting biomass into fuels result in tar, ash, and soot.

Tar can negatively effect the performance of the conversion and the reactors, and generally must be removed before fuel synthesis.

In addition, other problems in converting biomass to fuels include the high energy input needed to produce synthesis gas of sufficient quality to be used for liquid fuel synthesis, and the high capital cost associated with production of O2 gas, if it is to be used in the process.

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