The shift conversion reaction taking place during water gas manufacture is given by
In a pulverised-fuel-fired large power boiler, then heat transfer from the burning fuel to the walls of the furnace is
Bomb calorimeter is used to determine the calorific value of
Match List I with List II and select the correct answer:
Volumetric analysis of sample of dry products -of combustion gave the following results: CO2 = 10% CO = 1% O2 = 8% N2 = 81%
Their proportions by weight will be
Conversion from volumetric to gravimetric is done as below:
solid or liquid fuel can be determined, as the water vapour formed is carried away by the exhaust gases
.Reason (R): The lower calorific value of a fuel is the net value of heat available found by subtracting the latent head of the water formed and carried away by exhaust gas from the higher calorific value.
The higher heating value is experimentally determined in a bomb calorimeter by concealing a stoichiometric mixture of fuel and oxidizer (e.g., two moles of hydrogen and one mole of oxygen) in a steel container at 25 °C. Then the exothermic reaction is initiated by an ignition device and the combustion reactions completed. When hydrogen and oxygen react during combustion, water vapor emerges. Subsequently, the vessel and its content are cooled down to the original 25 °C and the higher heating value is determined as the heat released between identical initial and final temperatures.
The calorific value determined by the bomb calorimeter is
Which one of the following gaseous fuels does not have different higherand lower calorific values?
Since CO does not have hydrogen content; the HCV and LCV are same
Consider the following statements:
The difference between higher and lower heating values of the fuels is due to
1. Heat carried by steam from the moisture content of fuel.
2. Sensible heat carried away by the flue gases.
3. Heat carried away be steam from the combustion of hydrogen in the fuel.
4. Heat lost by radiation On these statements
2 is wrong therefore correct choice will be (c)
Consider the following:
What is the amount of oxygen (in kg) required for complete combustion ofeach one of the above respectively?
In Combustion process, the effect of dissociation is to
The amount of CO2 produced by 1 kg of carbon on complete combustion is
Methane burns with stoichiometric quantity of air. The air/fuel ratio by weight is
The mass of air required for complete combustion of unit mass of fuel canalways be calculated from the formula, where C, H, O and S are inpercentage.
Mass of air for complete combustion is 0.1152C + 0.3456 (H - 0.125 O) + 0.0432 S.
One mole of hydrogen is burnt with chemically correct quantity of air andcooled to N.T.P The change in volume in mole is
Match List I with List II and select the correct answer.
Cyclone Furnaces: Cyclone furnaces were developed after pulverized coal systems and require less processing of the coal fuel. They can burn poorer grade coals with higher moisture contents and ash contents to 25%. The crushed coal feed is either stored temporarily in bins or transported directly to the cyclone furnace. The furnace is basically a large cylinder jacketed with water pipes that absorb the some of the heat to make steam and protect the burner itself from melting down. A high powered fan blows the heated air and chunks of coal into one end of the cylinder. At the same time additional heated combustion air is injected along the curved surface of the cylinder causing the coal and air mixture to swirl in a centrifugal "cyclone" motion. The whirling of the air and coal enhances the burning properties producing high heat densities (about 4700 to 8300kW/m2) and high combustion temperatures.
The hot combustion gases leave the other end of the cylinder and enter the boiler to heat the water filled pipes and produce steam. Like in the pulverized coal burning process, all the fuel that enters the cyclone burns when injected once the furnace is at its operating temperature. Some slag remains on the walls insulating the burner and directing the heat into the boiler while the rest drains through a trench in the bottom to a collection tank where it is solidified and disposed of. This ability to collect ash is the biggest advantage of the cyclone furnace burning process. Only 40% of the ash leaves with the exhaust gases compared with 80% for pulverized coal burning. Cyclone furnaces are not without disadvantages. The coal used must have a relatively low sulfur content in order for most of the ash to melt for collection. In addition, high power fans are required to move the larger coal pieces and air forcefully through the furnace, and more nitrogen oxide pollutants are produced compared with pulverized coal combustion. Finally, the actual burner requires yearly replacement of its liners due to the erosion caused by the high velocity of the coal.
Consider the following statements:
1. Pulverised fuel gives high and controlled burning rate
2. Insufficient air causes excessive smoking of exhaust
3. Excess air is provided to control the flue gas temperature
4. Effect of sulphur in fuel is to give high heat transfer rate.Which of these statements are correct?
Coal fired power plant boilers manufactured in India generally use:
Coal fired power plant boilers manufactured in India generally use pulverised fuel combustion which can only offer high capacity of boilers compared to other choices
Consider the following statements regarding the fluidized bed combustionboilers:
1. The combustion temperatures are low, around 900oC.
2. The formation of oxides of nitrogen is low.
3. It removes sulphur from coal during combustion process.
4. It requires high quality of coal as fuel.Which of these statements are correct?
Which one of the following statements is not correct? In a fluidized-bedboiler?
Fluidized bed combustion has emerged as a viable alternative and has significant advantages over conventional firing system and offers multiple benefits – compact boiler design, fuel flexibility, higher combustion efficiency and reduced emission of noxious pollutants such as SOx and NOx. The temperature of about 870oC is reasonably constant throughout the process because of the high turbulence and circulation of solids. The low combustion temperature also results in minimal NOx formation.