power plant engineering

VAPOUR ABSORPTION MACHINES (VAM):         The vapour absorption machines are becoming popular. The vapour compression machines use secondary energy in the form of electricity which is normally costly and these machines use CFC based refrigerant which may cause environmental pollutions like warming up or ozone depletion. On account of power shortage, and with increasing availability of natural gas the vapour absorption machines are becoming popular and attractive. The absorption system uses lithium bromide as absorbent and water as refrigerant. The machines are available with dual fired boilers so that they can be operated by using high speed diesel in emergencies when there is a disruption in the gas supply. These machines have no moving parts and are thus noiseless and vibration less. The maintenance costs are negligible as compared to vapour compression machines. Various options are available with single stage, two stage , parallel flow and series flow machines ...

Molecular Weight :            2.016 Density :                             0.0898 gms / liter Solubility :                          Slightly soluble in alcohol.                          1.82 % soluble in water. Hazardous Characteristics : Explosive Limit in Air, percent ( V / V ) :           Upper Explosive Limit (UEL) :       74.2 %           Lower Explosive Limit (LEL) :       4.0 % Explosive Limit in Oxygen, percent ( V / V ) :           Upper Explosive Limit (UEL) :          94.0 %      ...

Rating of transformer:       Transformers are generally specified with Apparent power rating rather than active power rating due to following reasons:  Reason (1) : Rating of a transformer depends upon temperature rise which depends upon the losses taking place in the Transformer. The temperature can be maintained within permissible limits by using proper cooling system. M ore the effectiveness of cooling system more will be the rating of transformer. For a given cooling system rating of any electrical machine is indirectly determined by the losses present in the machine In a transformer      Constant losses depends on the voltage rating      Variable Losses depend upon current rating      Total losses depends upon v and I ratings ∴ Transformer rating is in terms of v*I which is called as Apparent power rating Reason (2) : During manufacture stage of the transformer, the manufacturer...

        There is a physical law which states that the solubility of any gas in a liquid is directly proportional to the partial pressure of the gas above the liquid surface. Another law states that the solubility of a gas in a liquid decreases with an increase in temperature of the liquid. These principles are employed in the operation of Deaerator.         A Deaerator utilizes steam by spraying the incoming water into an atmosphere of steam in the pre-heater section (1st stage). It then mixes this water with fresh incoming steam in the Deaerator section (2 nd stage).

         The  function  of  the  Deaerator is  to  remove  dissolved non-condensable gases and to heat boiler feed water. It consists of a pressure  vessel  in which water and steam are mixed  in  a  con­trolled  manner. When this occurs, water temperature  rises,  and all non-condensable dissolved gases are liberated and removed and the effluent  water  may be considered corrosion  free  from  an oxygen or carbon dioxide stand point. Free air  or other  non-condensable gases should be vented prior permitting the fluid  to enter the Deaerator.         Deaerator protects the feed pumps, piping, boiler and any other piece  of equipment that is in the boiler feed and  return  cycle from the effects of corrosive gases i.e. oxygen and carbon  dioxide, to a level where they are no longer a corrosion fa...

here's something you must ALWAYS remember Complete Combustion always produces the products of Carbion dioxide and Water.  INComplete Combustion tends to produce the products of Carbon Monoxide and water...  Carbon monoxide is produced from the lack of oxygen in the atmosphere during combustion, hence smaller carbon compounds are made...  Ok...you HAVEN'T done the reaction yet, as seen in your question, so you CAN'T tell whether it's complete or not...  go to the reaction and balance it out if there are CO2, then it was COMPLETE, and ...  if there was CO, then it was INCOMPLETE Complete combustion:  CH4(g) + 2 O2(g) →  CO2(g) + 2 H2O(l) Incomplete combustion: CH4(g) + 1.5 O2(g) → CO(g) + 2 H2O(l) Incomplete combustion: CH4(g) + 1 O2(g) → C(s) + 2 H2O(l) Complete combustions needs the most oxygen. Insufficient oxygen produces incomplete combustion.

primary air density (cold air) more than flue gas (hot air)

Depending are two types of boiler depending on pressure:- Positive pressure :- When the pressure in combustion area of the boiler is more than atmospheric pressure, normally forced draft boilers, HRSG are positive pressure. Negative pressure :-When the pressure in combustion area of the boiler is less than atmospheric pressure. This is achieved in balanced draft boilers by using Forced draft fans to force air into boiler (pressuring it)and Induced draft fans to remove air from the boilers to create negative pressure. In general negative pressure boilers are preferred as any flames or exhaust from boiler don't have a tendency to spread outside as the pressure inside is lower. The air ingresses inside incase of small leaks between boiler tube fins( large boiler are not perfectly sealed and have small gaps between fins) and contains the flames in the boiler. It also reduces the risk of explosions in boilers w.r.t. positive pressure boilers.

Deaerator at height not only provides Available suction head at boiler feed pump at higher side than required NPSH but also makes recirculation valve discharge to remain in liquid state and not the gaseous state. because feed water temperature to the BFP (and also the temperature after the throttling in ARC valve) is lower than the saturation temperature of the return line of re-circulation to deaerator.

The overall coal plant efficiency ranges from 35 % to 48 %. The value varies with the technology, material, parameters (Temp., Pressure) used. At condenser comes the big loophole in plant efficiency. The steam is condensed for reuse. During this process the latent heat of condensation is lost to the cooling water. This is the major loss and is almost 40 % of the energy input.