Process and apparatus for high energy efficiency chemical looping combustion

Abstract

Process and apparatus are provided for a high energy efficiency chemical combustion process. The process provides two reaction steps, both of which are exothermic. First, a reduced oxygen carrier is contacted with oxygen in a reactor to form an oxidized oxygen carrier, such as metal oxide or metal suboxide, and then the oxidized oxygen carrier is fed to a second reactor and combusted with a fuel. The reaction produces the reduced oxygen carrier and carbon dioxide. The reduced oxygen carrier from the second reactor is recycled back to said first reactor. Carbon monoxide can also be produced during the process depending on stoichiometric amounts of the reactants. Though the process can be performed in various types of reactor systems, one preferred embodiment is the flash furnace with the production of fly ash during combustion. The process is highly efficient and produces a large amount of usable work.

Description

FIELD OF THE INVENTIONThe present invention relates to apparatus and methods of high efficiency generation of useful work via combustion, more specifically, in combustion looping systems, for high efficiency energy production and more particularly, the chemical looping combustion in furnaces of fuel sources using metal oxides. The invention relates to clean coal technology with carbon dioxide capture and sequestration. The invention also relates to the removal of fly ash produced during the combustion process that can be further utilized in ferroalloy processes.BACKGROUND OF THE INVENTIONThe burning of fuels is currently the main mechanism that the world utilizes in order to meet its energy needs. Global warming is the increase in the average temperature of the Earth's near-surface air and oceans. Global warming was first noticed in the mid-20th century and scientists have projected its continuation. The Intergovernmental Panel on Climate Change (IPCC) has noted that the global surf...

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Benefits of technology

FIG. 20 is a graph showing the equilibrium composit

Problems solved by technology

Such changes could be enough to cause glaciers to melt, which would cause coastal flooding.

The expenditure has been unsuccessful to date in that there is not a single commercial scale coal fired power station in the United States that captures and stores more than token amounts of carbon dioxide.

Such technologies, however, also have potential negative effects on the environment, such as underground leaking, contamination of waters, and potential health effects on plants and animals.

Thus, these technologies are in development and testing and are not yet considered to be a final solution for carbon dioxide reduction in the atmosphere.

Unfortunately, some sequestration technologies are still subject to potential leaks into the environment with harmful consequences.

Concerns exist regarding the economic viability of these technologies and the timeframe of delivery, potentially high hidden economic costs in terms of social and environmental damage, and the costs and viability of disposing of removed carbon and other toxic matter.

The plant is state owned because of the high costs of this technology.

A major disadvantage to IGCC technology and SCPC technologies are the major technical modifications required for retrofitting existing power plants, involving massive costs.

Such costs may thus prove prohibitive for implementing clean air technology.

This technology however, presents other environmental concerns associated with coal mining.

A common problem with all transitional metal oxygen carriers is the formation of carbon deposits (i.e. coke) on the surfaces of carrier particles during the reduction phase. M. Ishida and H. Jin have reported that carbon deposits cause degradation of the physical strength of the particles and their chemical stability.

The figures demonstrate that reaction (2) is highly exothermic with adiabatic temperatures exceeding 3000° C. Such high temperatures make it difficult to control and maintain the temperature in the fluidized bed reactor below the melting point of either the metal oxide or the metal.

In addition, in order to avoid forming sintered build-ups, good temperature control and cooling is required, lack of which in the prior art processes results in increased heat losses from the process.

The endothermic step of these two reactions consumes substantial energy from the exothermic reaction step and this heat transfer cannot be realized with zero heat loss.

As a result, the thermal efficiency of the chemical looping combustion processes of the prior art is poor and a process for improved thermal efficiency is needed.

Heat transfer and endothermicity of reaction are also substantial problems in various other industrial processes.

The heat necessary to do this can be readily generated by burning some fuel; however, transferring the heat to where it is needed within the reactor system is a difficult and expensive problem.

Solid fuel material CLC processing of coal is desirable but is less effective due to the restrictions of the solid to solid reactant mass transfer limitations of the process.

In addition, when processing coal as the fuel material, the oxygen carrier becomes “poisoned” over time by the non-combustible mineral components contained in the coal, known as fly ash.

This contamination affects the reactivity and porosity of the heterogeneous oxygen carrier system rendering the metal oxide and support ceramic unusable.

Rejuvenation of the metal oxide and separation and recovery of the substrate ceramic waste components is a costly process which has an adverse impact on the overall cost of the CLC processes of the prior art.

Limited studies have been performed with oxygen carriers used to combust liquid fuels.

The use of liquid fuels raises specific problems of implementation that are different than for gas or solids.

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