Inorganic oxides for co2 capture from exhaust systems

Abstract

This invention relates to the utilization of regenerable water tolerant solid materials for the abatements of CO2 emissions from internal combustion engine exhaust streams through repetitive sorption / desorption cycles. The system, which is designed to be used in a gasoline, lean gasoline, diesel passenger car, diesel truck, stationary engine with 50 Hz or 60 Hz electrical frequency, or a SOFC, will contain a solid sorbent which contains zirconium and will be able to reduce on board the average carbon emissions by up to 10 wt %. The preferred materials have been selected from the class of hydrotalcite type compounds and / or earth and alkaline earth zirconates.

Description

BACKGROUND OF THE INVENTION [0001]1. Field of the Invention[0002]The invention relates to regenerable inorganic oxides, mixed oxides and / or layered double hydroxides for the capture of CO2 emissions from engine exhaust streams through repeated adsorption—desorption cycles under dynamic temperature fluctuations during the engine operation cycles.[0003]2. Description of the Related Art[0004]A current problem with tremendous implications at various levels is the CO2 emission from fuel combustion in different sectors of industry. Aiming to reduce these emissions, the concept of CO2 capture and storage (CCS) has been introduced in practice and important projects are under development or have been implemented already in industry. This concept deals with the CO2 capture from various sectors of industry, its transport through pipelines or tankers and its storage into deep saline aquifers, depleted oil and gas reservoirs or unmineable coal seams.[0005]In the case of gas-fired power station w...

AI Technical Summary

Benefits of technology

The invention relates to the use of regenerable and water-tolerant inorganic oxides and mixed oxides to capture CO2 emissions from engine exhaust streams through repeated adsorption-desorption cycles to reduce CO2 emissions by 10% or more. The invention can be applied to any engine exhaust system and the overall CO2 reduction will be greater than 5 wt % and even better if by 10 wt % or more. The sorbent system is replaceable and recyclable and can be positioned at various points in the exhaust system depending on the specific engine and temperature requirements. It can be housed as pellets or granules in a canister or coated onto a substrate. The system should have multiple capture systems so that simultaneous adsorption and desorption cycles can take place, and the weight of sorbent can be minimised. The captured CO2 can be stored either on the sorbent or in additional storage devices such as pressurised cylinders that can be emptied or regenerated at set intervals. The weight of the inorganic sorbent should not exceed the weight of fuel for mobile engines and greater quantities of sorbent can be used for stationary engines where weight and size issues are less of a constraint.

Problems solved by technology

A current problem with tremendous implications at various levels is the CO2 emission from fuel combustion in different sectors of industry.

An analogy to the big power plants can lead us to the idea of using amines for such purposes, but their major drawbacks are the high toxicity, physical form, operating temperatures and cost inefficiency making them inappropriate.

Thus, alkaline or alkaline-earth metal oxides posses high capacities and recyclability, but present the disadvantage of having high desorption temperatures (˜850° C.).

Complex metal oxides, as ones mentioned above, present high capacities and operation temperatures, but slow kinetics which can make them difficult applicable when the aim is to capture the CO2 from continuous gas streams such as engine exhausts.

Their main drawback is their relative small capacity compared to other inorganic sorbants such as lithium zirconate, but this can be improved by doping with other elements such as potassium, magnesium or cocktails of various metal oxides.

The major drawback of these systems is their sensitivity to water which requires to be removed from the system prior the adsorption.

Also, these systems are not operational in the temperature ranges which are characteristic to gas exhaust.

The proposed material has limited applicability and would not be suitable for the dynamical conditions associated with a combustion exhaust stream where humidity is present.

The method might be suitable for steam generating boilers, but would have limited suitability for some internal combustion engines from stationary and mobile sources as they are energy intensive.

In the car exhaust systems for example the dynamicity is different, especially not constant, so it would be difficult to use such a system as the periods when the CO2 can be desorbed would be more or less frequent.

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