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Showing posts with label Hydrogen rich syngas. Show all posts
Showing posts with label Hydrogen rich syngas. Show all posts

Wednesday, May 23, 2012

Liquid coal- a novel fuel to reduce greenhouse gas

Coal is the single largest fuel currently used for power generation all over the world due to its abundant availability and established infrastructure and technology. However greenhouse gas emission poses a significant challenge in continuing the usage of coal as prime fuel. Currently Natural gas is favored as fuel for power generation and number of LNG plants have been set up in many part s of the world. Coal seam methane gas is another potential source that competes with natural gas .Basically, Methane is the major constituent of such gases and they are suitable for both combustion as well as for gasification for power generation.Countries who are endowed with large deposits of coal such as Australia, South Africa, Indonesia have advantages in clean coal technologies and in reducing their greenhouse gas emissions. There is an opportunity for coal fired power plants to continue their operations if they can solve the greenhouse gas emission and other pollution problems associated with coal. Number of companies are now re-evaluating clean coal technologies such as IGCC and carbon capture and reuse. As we have seen in previous articles, Hydrogen is the key in developing clean coal technology of the future. That is why gasification technology such as IGCC (Integrated Gasification and Combined Cycle) is gaining importance over combustion technologies because, that is the only way we can introduce a Hydrogen molecule in the combustion by way of ‘Syngas’.By introducing Hydrogen, we not only improve the thermal efficiency but also utilize the heat of combustion to the maximum by combined cycle while reducing GHG emission. It also facilitates the usage of existing and known power generation technologies such as steam turbine and gas turbine as well as new technologies such as Fuel cell and Hydrogen turbines. Coal in the form of pumpable liquid (CWS –coal water slurry) is another key milestone in developing a clean coal technology. Countries like China and Indonesia have been using coal water slurry for power generation successfully. Finely powerdered coal is mixed with water in the ratio of 60:40 along with dispersant such as Lignosulfonate as additives to make a finely dispersed, viscous liquid that resembles heavy petroleum oil, ready for combustion. It is easier to handle pumpable oil than a solid coal. A novel products called ‘colloidal coal water’ (CCW) is a finely dispersed colloidal coal in water with additives such as surfactants and dispersants with specific formulating agents leading to certain rheological properties is a key development in clean coal technology. The coal water slurry currently used does not have long term stability and storage properties like colloidal coal water fuel. The work is under development and it is expected that such finely dispersed colloidal coal water mix resembling a liquid hydrocarbon may be named as ‘liquid coal’ for all practical purposes will become a low cost fuel in the future power generation. This ‘colloidal coal liquid’ can be easily gasified or used as liquid fuel for combustion equipments such as boilers and also serve as precursor for a number of chemical product synthesis as downstream products. The emitted Carbon dioxide can be captured cryogenically and separated in a pure form for potential application such as ‘Natural Refrigerant’ and to synthesize number of chemical products. Clean coal can become a commercial realty provided we re-evaluate the coal preparation, gasification methods and to contain emitted carbon into an useful product of commerce.

Wednesday, April 18, 2012

Plasma gasification for waste-to-energy

The World Bank development indicators 2008 shows that the wealthiest 20% of the world accounts for 76.6% of total private consumption. The poorest fifth just 1.5%.The report further states, “Today’s consumption is undermining the environmental resource base. It is exacerbating inequalities. And the dynamics of the consumption-poverty-inequality-environment nexus are accelerating. If the trends continue without change — not redistributing from high-income to low-income consumers, not shifting from polluting to cleaner goods and production technologies, not promoting goods that empower poor producers, not shifting priority from consumption for conspicuous display to meeting basic needs — today’s problems of consumption and human development will worsen. The real issue is not consumption itself but its patterns and effects. Inequalities in consumption are stark. Globally, the 20% of the world’s people in the highest-income countries account for 86% of total private consumption expenditures — the poorest 20% a minuscule 1.3%. More specifically, the richest fifth: • Consume 45% of all meat and fish, the poorest fifth 5% • Consume 58% of total energy, the poorest fifth less than 4% • Have 74% of all telephone lines, the poorest fifth 1.5% • Consume 84% of all paper, the poorest fifth 1.1% • Own 87% of the world’s vehicle fleet, the poorest fifth less than 1% • Runaway growth in consumption in the past 50 years is putting strains on the environment never before seen.” — Human Development Report 1998 Overview, United Nations Development. Clearly, the above consumption pattern indicates the amount of waste generated worldwide,especially in developed countries. Unfortunately bulk of the waste are not recycled thus creating enormous amount of strain on natural resources. A typical municipal solid waste consists of food, paper, plastic, metal, glass and garden waste etc.For example the amount of MSW collected in Metropolitan Melbourne for the year 2006-2007 was 1.315,119 Mt costing about a$163 million in service cost. Though Government of Victoria follows the policy of reuse, recycle and recover; only 567,117 Mt was recycled and reprocessed. There are number of methods to process waste and such process depends on the quantity , type of waste and the recovery of products. Gasification and Anaerobic digestion to generate syngas are two common methods of converting waste to energy. However a large volume of complex municipal, industrial and biological wastes require different methods of processing. ‘Desperate problems require desperate solutions’. One such solution is by Plasma Gasification and Vitrification. It has clear advantages over existing method of incineration. Plasma is called fourth state of matter after solid, liquid and gas and it is an abundant form of matter in the universe. When the MSW is heated to a high temperature up to 5000C using Plasma torch, it decomposes into syngas and verified mass. In Plasma gasification, MSW is subject to high temperature pyrolysis in the absence of air decomposing matter into its elemental state.Vitrification is process in which semi-liquid waste is mixed with glass converting them into a stable glass form. Even radioactive liquids and sludge are converted into vitrified glass. It is similar to Plasma welding electrodes where an Argon gas is heated into a plasma torch of high temperature up to 5000C.This plasma can treat a wide range of waste materials such as radioactive, biological, MSW, biosolids from sewage treatment plants and industrial wastes. The process is highly efficient.The process can be selectively used to generate syngas with high proportion of Hydrogen by carefully selecting the feedstock and process parameters. Bulk of the MSW is currently sent to landfill. Such landfills generate methane gas over a period of time and also leach toxic chemicals and material into the soil. Plasma gasification has distinct advantages over other conventional methods of waste-to energy technologies, especially when the volume is large and the waste contains highly toxic materials and metals.