Paper 2 Flashcards
Things that can go wrong with a catalyst
degradation e.g. sintering which reduces surface area, sulfur poisoning Pd by attaching to active sites, coking blocking access to surface of catalyst, thermal degradation, lifetime too short, someone else has the IP, may need high pressure leading to reactor failure
WFLITTENC
Waste, Financials, Location, Ingredients, Timescale, Toxics, Employment, Novelty, Catalyst
cash flow
net amount coming into a company in a set period of time. =income-expenditure
profit
sales revenue - total costs
gross profit is income minus expenditure, i.e. cash flow
taxable profit is profit minus allowance
net profit is gross profit minus tax
working capital
money needed to start up and run the plant before any sales generated. some recovered at end of project
can land be written off against tax?
no
book value of an asset
the depreciated value of the asset = historic cost minus accumulated depreciation
straight line depreciation
spreads the cost of the asset evenly through its useful life
declining balance or fixed annual percentage
e.g. annual depreciation charge=0.25*book value for each year.
which depreciation method should you use?
straight line for IP and buildings
UK prefers declining balance methods
are taxes rounded up or down?
down
“scrap value at the end of 6 years”
put the scrap in the year 5 row
limitations of RORI
only valid for an average year so doesn’t allow for changes in profits
does not consider time value of money
incremental RORI
further benefit over further cost
i.e. extra saving generated by the extra investment
interest
benefit gained without taking any risk
npv index
npv over capital required
for a project to be viable, want high NPV (>0) and high i* st the discount rate i is less than i* for the project
FAR
Number of deaths per 10^8 exposed hours (corresponding to a workforce of 1000 working for 50 years at 50 weeks per year and 40 hours per week)
how do chem eng’s write the second law of thermodynamics
dS=dq/T + dSgen where the dq is the same as dq appearing in the first law
dU=dq+dws-pdV
COP refrigeration cycle
do you want big or small COP?
COP refrig = heat in/net work in = ‘HINWI’
want small COP
what does presence of Re suggest
fluid flow, inertial and viscous forces present
what does Fr suggest
ratio of KE/PE where energy interchange btw these two forms is involved. suggests fluid flow subject to gravity/buoyancy
does temp change when you pass through a valve?
if ideal gas then no because isenthalpic, if real gas then temp changes even if isenthalpic
When was the Health and Safety at Work Act passed?
1974
concept of reasonably practicable
weighing a risk against the trouble, time and money needed to control it
decision weighted in favour of h & s
to avoid making sacrifice, duty-holder must demonstrate that the sacrifice is grossly disproportionate to the benefits of risk reduction that would be achieved
is reasonably practicable good?
can set goals for duty-holder without being prescriptive
subjective
can’t always rely on ‘good practice’ so can also use cost benefit analysis
what words does DiW love?
expertise, access, pipeline, utilities, licensed, plant capacity, supply chain, existing, meteorological, legislation
pros, cons and missing info
emplaces
expertise, meteorological, pipeline, legislation/license, access, capacity, existing, supply chain
also utilities
otto cycle is for petrol or diesel?
efficiency
limit on r
petrol
1-r^(1-gamma)
limit is r=10 with corresponding efficiency of 33%
Flixborough stats
1974
28 dead, 36 injured
piper alpha
1988
160+ dead
Chernobyl effect on emergency services
1986
30 firemen dead
birth defects
135,000 evacuated
bhopal
1984
4000 dead immediately
many blinded
Seveso short term health disorders
1976
2000+ skin complaints
10 square miles of contaminated land
example of panic buying
Buncefield 2005 - petrol
what does leakage imply?
that a normal stress will be zero. e.g. for caps fastened on the end of a cylinder, sigma L =0 at the leakage point because the caps are clear of the cylinder
what does the thin wall approximation lead to regarding the stress tensor?
tau xz=zx=yz=zy=0
note that tau zz is not necessarily zero
when can you say that molar GA= molar GB?
at equilibrium btw a phase A and B of a PURE substance
assumptions for Claudius Clapeyron
equilibrium between a phase A and B of a PURE substance, one phase is vapour, vapour is ideal gas
permit to work system
controls implementation of potentially hazardous tasks
clear identification of who may authorise particular jobs
instruction in the issue, use and closure of permits
auditing to ensure sys works as intended
clear and standardised identification of tasks, risk assessments, permitted task duration
signature by designated authority
Piper alpha - new shift crew didn’t realise a maintenance task incomplete
duty of care
employer assumes duty of care as part of voluntary contract with employee
provide safe premises, sys of work, materials & equipment, machinery, competent personnel
else law of negligence
for which years do you calculate qualifying value and capital allowances?
the OPERATING years of the project
is there an allowance on working capital?
no. you recover it the same year that you recover the scrap
turbine isentropic efficiency
actual work out/ideal work out
when can you say that Ws. = V. /\P ?
for an incompressible liq flowing through an isentropic pump
partial molar property
change in total theta when one mol of species i added to very large amount of mixture
sequence of steps for doing the partial molar property proof
differentiate property of the mixture wrt x1, notice that gibbs-duhem can be cancelled out, rearrange for partial molar theta, sub back into property of the mixture
quotation for inherent safety
what you don’t have can’t leak
what went wrong in Bhopal?
used a toxic intermediate methyl isocyanate. Water leaked into tanks leading to explosion and 42 tonnes of MIC released
examples of protective devices for engineered safety
pressure safety release valves (last resort), non-return valves, high/low temp/pressure alarms, flameproof electrical equipment, process interlocks, fire detection and fighting systems
are aqueous or oil based hydraulic fluids safer?
aqueous
Law of strict liability
possessor of hazardous substance is prima facie responsible for damage caused by its escape
item 7 of HASAWA 1974: take reasonable care of all, comply with duties - makes negligence a criminal offence
cost index formula
current cost = cost in year 1 * current cost index/cost index, year 1
i.e. cost/cost index is a constant for each year
what might be the reason for a high ratio of one component of a feedstream to another?
maximising selectivity
critical point
point of inflexion on P-V graph.
can’t have liq at temp above critical temp
thermodynamic properties of liq and vap identical
crit temps low for small molecs
when T less than Tc both liq and vap states can exist - which is more stable depends on pressure
when wouldn’t you have a discontinuity in V-T graph?
when plotting at the critical pressure, there will be no step change in the graph.
What is the dSgen term at equilbrium?
dSgen=0
fine vs bulk
more expensive, lower volume, greater variety, greater complexity, greater added value, fewer application, various multi step syntheses possible, rarely need catalyst, greater raw material consumption, energy consumption, by-products, toxic compounds (e.g. phosgene, HCN), usually batch, greater investment/kg, greater labour, greater market fluctuations, fewer producers
Raoult’s law
yiP=xiPisat
under what conditions is a turbine adiabatic?
ideal gas, no friction in turbine, gamma indep of T
for equilibrium of two phases in direct contact need
P, T and mu the same
also dmuA=dmuB
dGA=dGB
definition of NPV
cumulative sum of DCF’s from year 0 to end of project
value today of the surplus a project is predicted to make over its lifetime over what it would make in a bank by investing at the company’s chosen rate i.
when does Raoult hold
liq ideal mixt @ VLE
i.e. 1-1, 1-2 interactions identical
what is ideal mixt
delta mix H and V are zero for IM
interactions equivalent
dG=VdP-SdT
yield
mols of rctnt converted to specified product/mols of rctnt in feed
selectivity
mols of rctnt converted to specified product/mols of rctnt consumed
recycle ratio
recycle flowrate/fresh feed flowrate
reduced temp
Tr=T/Tc
when does Gibbs phase rule apply?
at eq, no chem rxn
princ of corr states
all fluids similar at same Tr and Pr
isolated sys
no energy no matter
closed sys
energy but no material
cts sys at SS
dU/dt =0
dV/dt =0
when does the SFEE apply
open sys at SS i.e. dU/dt=0 and dV/dt=0
