Sushant Kumar

A comparative study of CO2 sorption properties for different oxides

It is essential to capture CO2 from flue gas stream, which is considered as one of the prime reasons of global warming. Although various CO2 capture technologies already exist, most of these techniques are still unfit to be employed at a large scale. In the past one decade, oxides have emerged as a strong candidate to capture CO2 for post-, pre- and oxy-combustion conditions. Oxides combine with CO2 present in the flue gas and form carbonate, which when heated regenerates the oxides and thus liberates almost pure stream of CO2. The selection criteria for potential oxides entail their CO2 capture capacity, absorption rate, thermal stability, regeneration heat, cost and structural properties. Thus, here, we review the technical merit of all the suitable oxides which can be used for CO2 capture at any fossil fuel burning plants.

Catalytic Studies of Sodium Hydroxide and Carbon Monoxide Reaction

We have studied the effect of ball milling on alumina mixed nickel, magnetite and Raney nickel on the reaction: 2NaOH(s) + CO (g) = Na2CO3 (s) + H2 (g) and determined the optimum particle size for the catalysts. The best performance was shown by a 2 h ball milled Raney nickel with average crystallite size of 209 A. This reaction serves the dual purpose of carbon sequestration and yielding hydrogen gas.

Role of Hydrogen in the Energy Sector

The vast depletion of fossil fuels, the increase in carbon dioxide levels in the atmosphere, and the related environmental hazards represent a growing concern for the mankind. Therefore, over the past few decades, significant efforts have been made to establish hydrogen economy. Hydrogen is a high-efficiency energy carrier, which can lead to zero or near-zero emissions at the point of use. Moreover, it has been technically shown that hydrogen can be used for transportation, heating, and power generation, and could replace current fuels in all the present applications. Besides the challenge of storing hydrogen, development of clean hydrogen production methods is considered as a prime hindrance to establish the hydrogen economy. Here, the focus is to provide a brief overview of all the processes based on both renewable and non-renewable energy sources that have been proposed to produce clean hydrogen.

Modified Steam Methane Reformation Methods for Hydrogen Production

Over the past few decades, extensive efforts have been made to modify the conventional hydrogen production technologies. In particular, a review of those methods that are intended to reduce the carbon emission and improve the process efficiency for steam methane reformation (SMR) is provided here. So far, several such methods have been proposed based on both fossil and non-fossil energy sources which primarily include the use of membranes, metal oxides as a CO2 sorbent, and nuclear and solar energy. Moreover, this section also includes a brief summary of an innovative process which suggests the inclusion of sodium hydroxide as a reactant to the SMR process. The addition of sodium hydroxide to the SMR process can serve the dual purpose of hydrogen production and CO2 capture. Certainly, these methods have the potential to reduce CO2 emission during hydrogen production. Therefore, here, the status and perspective of all these methods are presented.

Sodium Hydroxide for Clean Hydrogen Production

Hydrogen can be generated in several ways utilizing either renewable or non-renewable sources. However, the lack of a clean hydrogen generation methods at a large scale is considered to be one of the obstacles to implement hydrogen economy. The role of sodium hydroxide is increasing as a valuable ingredient to produce hydrogen. However, the vast use of sodium hydroxide is limited due to its (i) corrosive nature and (ii) high-energy-intensive production method. Various current technologies include sodium hydroxide to lower the operating temperature, accelerate hydrogen generation rate as well as sequester carbon dioxide during hydrogen production. Sodium hydroxide finds applications in all the major hydrogen production methods such as steam methane reforming (SMR), coal gasification, biomass gasification, electrolysis, photochemical and thermochemical. Sodium hydroxide, being alkaline, acts as a catalyst, promoter or even a precursor.

Modified Coal Gasification Process for Hydrogen Production

A significant amount of work has been performed to modify the conventional coal gasification process. This chapter presents a brief review of the methods that are supposed to reduce the vast emission of carbon dioxide during the process. Most of these proposed methods include CaO as a CO2 sorbent. Moreover, efforts have also been made to integrate gasification of coal and biomass which can offer several advantages. Similar to Chap. 3, the present chapter briefs about the addition of sodium hydroxide (as a reactant) to the conventional coal gasification process. The sodium hydroxide-assisted reaction operates at a relatively mild condition and has potential to substitute the conventional method. However, there are several existing issues related to the proposed technique which needs to be resolved prior to its deployment.