ChE Calculations
SO3-free basis
An Orsat analysis of the flue gas when pyrite is roasted is on a/an
proximate analysis
Coal analysis which is based upon the volatilization characteristics of the fuel is the
input = output
For balances on atomic species, which of the following material balance is applied
Ash
In the combustion of solid fuels, the tie component between the feed and the refuse is the
modified proximate analysis
The analysis of coal given in %C, %N, %S %moisture , % net H, %combined water, and %ash is called
Chemical Engineering
The application of the physical sciences together with the principles of economics and human relations to fields that pertain directly to processes and process equipment in which matter is treated to effect a change in state, energy content or composition
Dulong formula
The empirical relation which allows one to compute for the net hydrogen in a given solid fuel is
Gross calorific value (Higher Heating Value)
The heating value measured when water formed from combustion is in the liquid state is the
tie substance
The material which remains unchanged in a process is called
2
The maximum number of independent equations that can be derived by writing the material balances for an input and output stream with two component substances is/are
relative humidity
The ratio of the partial pressure of a vapor to the vapor pressure in equilibrium with the liquid is called
Inherent moisture
Type of moisture in coal which assumed to be the water held within the pore system and capillaries of coal
By-pass
Type of process stream that can be used to control the composition of a final exit stream by skipping one or more stages of the process and goes directly to another downstream stage
Semi-batch
Type of process where a material enters the process during its operation, accumulates in the process vessel and withdrawn only after the process is over; neither batch nor continuous
It is computed based on how much fuel was burned in the reactor
Which is not true about the theoretical oxygen
It is the reactant that would disappear first if the reaction goes to completion
Which of the following best describes a limiting reactant
Low percentage excess air, high air inlet temperature
Which of the following combustion conditions will give the highest theoretical flame temperature
all of these
Which of the following terms could express the extent to which the limiting reactant
CGS system
a system similar to SI but uses cm, g and s for length, mass and time respectively
American Engineering System or English system
a system that uses ft, lbs and s for length, mass and time respectively
head
a term used to report pressure being the height of the column of a liquid of known density
Excess Air
amount by which the air fed to the reactor exceeds the theoretical air
Sulfates
are commonly employed in surfactant and detergents and as an additive to Portland cement
Nitrogen (N) and Sulfur (S)
both reflected in the VCM
Système Internationale d' Unitès
commonly used in the engineering and scientific community; also referred to as MKS system
Composition in wet basis
component mole fraction of product gas that involves water
Composition in dry basis (Orsat analysis)
component mole fraction of product gas which does not involves water
Water gas
consists of CO and H2 with small amount of N2 generated similar to a producer gas but blown with steam thereby decreasing the N2 content and doubling the heating value
Producer gas
consists of CO, H2, about 55% N2 and trace amounts of CO2 obtained by passing small amount of air through a hot bed of coal, peat, wood and other biomass
liquefied petroleum gas
consists of ethane, propane and butane
Cinder
contains unburned sulfur and non-combustible inert materials from the fuel
Single pass conversion (once-through conversion)
conversion of reactant based on the amount of material that enters (fresh feed + recycle stream) and leaves the reactor (gross product)
Overall conversion
conversion of reactant in a process based on the amount of material that enters(fresh feed) and leaves the reactor(overall product)
Octane number
determined from a calibration curve relating knock intensity to the % volume of i-octane(2,2,4-trimethylpentane) in a mixture of i-octane and n-heptane
Natural gas
found compressed in porous rocks and shale formations and composed of mixture of hydrocarbons and some traces of sulfur and organic nitrogen
Fractional conversion (% conversion)
fraction of feed or some component in the feed that is converted to products
Degree of completion
fraction of limiting reactant converted into products
Heating Value
heat released when the fuel initially at 25C reacts completely with oxygen and the products are returned to 25C
Lower Heating Value (Net Heating Value)
heating value when water comes out as vapor in the combustion reaction
Anthracite
highest rank of coal which contains the highest percentage of FC and percentage of VCM
Combined water (CW)
hydrogen in VCM combined with oxygen in the proportions H2O is called
Net hydrogen (NH)
hydrogen in VCM for which oxygen from the air must be supplied for its combustion termed as
Hydrogen (H)
in the solid fuel is present as ________ in adsorbed moisture
Carbon (C)
in the solid fuel is present in VCM and as FC
Crystallization
involves formation of solid particles within a homogeneous phase (i.e. liquid solutions) by either cooling or removing some of the solvent
Stoichiometry
involves quantitative relationships between reactants and products in a balanced chemical reaction
Drying
involves removal of relatively small amount of water or other liquids from the solid material
Fixed carbon (FC)
is obtained by difference
SO3
is soluble in water and therecore not included in the dry analysis or orsat analysis of the burner gas
Volatile combustible matter (VCM)
is the loss in weight of the dried sample when heated for 7 min at 950C in a covered crucible
Moisture (M)
is the loss in weight of the sample when heated for 1 hour at 104C to 110C
Sub-bituminous
lesser grade of coal with more M and less FC
brown coal/lignite
lowest grade of coal formed from layers of sediment that accumulates over peat and has M and less FC than other grades of coal
Purge
material or energy stream bled off from a process to prevent accumulation of inert materials that may buildup in the recycle streams
Recycle
material or energy stream that leaves a downstream process unit and returned to the same process unit or upstream unit
Cetane number
measure of the fuel's ignition delay, that is, the period between injection and ignition
sealed-end manometer
measures absolute pressure
open-end manometer
measures relative or gauge pressure
Smoke point
measures the tendency of the fuel to form soot
Flash point
minimum temperature at which fuel will rapidly catch fire when exposed to an open flame located above the liquid
Auto ignition temperature
minimum temperature required for the fuel to initiate self-sustained combustion in a standard container in atmospheric air in the absence of a spark or a flame
Theoretical oxygen
mole or molar flow rate of oxygen necessary for the complete combustion or complete conversion of all the fuel fed to the reactor
Bituminous
most abundant and widely used rank of coal which is usually black or dark brown in color
Coal char
non-agglomerated and non-fusible residue from thermal treatment of coal
Coal
originated from the decay of biomass which is converted to peat by bacterial and chemical action and under the influence of time, pressure and temperature, metamorphoses to various ranks
Oxygen (O)
present both in M and CW of the VCM
Continuous
process where input and output flow continuously throughout the duration of the process
Batch
process where the feed is charged into the system at the beginning of the process and the products are all at once removed sometime later
steady-state
process wherein process variables does not vary with time
Transient or Unsteady-state
process wherein process variables varies with time
Stack gas or flue gas
product gas that leaves a combustion furnace
Theoretical air
quantity of air that contains the theoretical oxygen
based on reactant consumed
ratio of the amount of desired product to the amount of limiting reactant consumed
based on reactant fed
ratio of the amount of desired product to the amount of limiting reactant fed
based on theoretical amount of limiting reactant consumed
ratio of the amount of desired product to the amount product obtained if all limiting reactant had reacted and no side reactions occured
Fractional excess (% excess)
ratio of the amount present in excess to the amount stoichiometrically required
Extent of Reaction
ratio of the change in the number of moles of species, i and its stoichiometric coefficient of the species in reaction, j
Selectivity
ratio of the moles of desired product to the moles of the undesired product or by-product
Excess reactant
reactant present in more than its stoichiometric proportion relative to every other reactant
Partial or incomplete combustion
reaction in which CO is also formed
Complete combustion
reaction in which CO2 is also formed
Series reactions or consecutive reactions
reactions where the reactant forms an intermediate product which reacts further to form another product
Parallel reactions or competing reactions
reactions where the reactant is consumed by two different reaction pathways to form different products
Charcoal
residue from the destructive distillation of wood usually containing 10-15% M
Distillation
separation of mixtures based on the differences in volatilities by utilizing vapor and liquid phases at essentially the same temperature and pressure for the coexisting zones
Combustion
sequence of chemical reactions between a fuel and an oxidant accompanied by the production of heat(exothermic) and conversion of chemical species( C ->CO2 or CO, H2 ->H2O and S or N may be partially or completely converted to their oxides)
Coke
solid remains from the carbonization of coal, petroleum residues and other carbonaceous materials.
Limiting reactant
species present in the reaction that would be completely consumed theoretically if the reaction were to proceed to completion
Pour point
the lowest temperature at which a fuel will flow when cooled and a rough indication of the lowest temperature at which a liquid fuel can be pumped
Magma
two-phase mixture of mother liquor and crystals occupying the crystallizer and withdrawn as product is called
Orsat gas analyzer
used to analyze gas samples for its oxygen, carbon monoxide and carbon dioxide content
Evaporator
used to concentrate a solution consisting of a non-volatile solute and volatile solvent
Bourdon gauge
usually gives gauge pressure of the liquid
Free state or Raw sulfur
usually obtained in elemental form as contaminants of natural gas and petroleum refinery