Additional industrial chemistry Flashcards
3 ways to organise the operation of a chemical manufacturing process
batch process
continuous process
semi-continuous process
batch process
raw materials place into a vessel (batch reactor) and allowed to react together, conditions are monitored. when reaction finished, products are isolated and process repeated with fresh batch of raw materials
continuous process
raw materials fed in at one end of processing plant and product is continuously removed at other end
example of continuous process
the manufacture of ammonia
semi-continuous process
combination of batch and continuous processes. first part is a batch process to make the product, second stage involves continuous process where product is purified using materials from several batch reactors
example of semi-continuous process
soft drink industry, soft drink is produced in a batch process and the addition of carbon dioxide and bottling is continuous
advantage of batch processing
more effective for smaller quantities of materials and the same vessel can be used for a range of products
disadvantage of batch processing
they require larger workforces and contamination can occur from batch to batch
advantage of continuous processing
better suited to larger quantities, low risk of contamination and can run for long periods of time with low labour needs
disadvantage of continuous processing
the plant is expensive to build, is not flexible for other products and hence may not be cost effective
feedstock
reactants used - produced from the raw materials
rate
conditions involved chosen for optimum rate
real conditions may not be necessarily the ideal, compromises must be made to ensure that it is cost effective
production yield
conditions chosen to produce a reasonable yield of product in reasonable time - compromises must be made
co-products
other products made alongside the main product
can be sold or separated and disposed of appropriately
waste disposal and effluent control
contaminated water may contain hazardous material and has to be treated before it is released - some gases can be dangerous (produce acid rain or damage ozone layer), must be purified and monitored
quality control
the quality of the feedstocks and products are constantly checked in laboratories so that they are of a required standard
safety
staff trained on site and continuous monitoring of hazards - safety features incorporated e.g safety glasses, first aid etc.
3 costs
capital costs
fixed costs
variable costs
capital costs
cost involved in setting up the plant
fixed costs
salaries, repayments of loans, plant depreciation
variable costs
raw materials, waste disposal, plant maintenance
ways of reducing costs
recycling of unreacted feedstocks, use of heat exchanger selling of co-products, essential equipment
sit location
access to roads, ports etc. for transport
available cheap energy and water
available skilled workforce
tax incentives etc.
suitable materials for construction of chemical plant
do not react with feedstocks, catalysts or solvents
resistant to corrosion, long-lasting
withstand temperatures and pressures used
process for manufacture of ammonia
continuous process
manufacture of ammonia by
IFI in Cobh, Co.Cork
manufacture of ammonia
feedstock
raw materials compressed of air, natural gas and water
nitrogen - compressed air
hydrogen - natural gas and water
manufacture of ammonia
do to air first
filtered to remove dust
manufacture of ammonia
do to water first
passes through ion exchange resins to deionise it
manufacture of ammonia
natural gas first
methane coming from Kinsale gas field, piped underwater to Inch beach in East Cork and supplied underground to IFI in cork, mercaptans added to ensure it has an odour
manufacture of ammonia
how do they ensure that the catalyst is not poisoned
first the sufur compunds are removed from naturl gas by mixing incoming gas with hydrogen and passing it over a cobalt/nickel/alumina catalyst
hydrogen sulfide is formed and then removed
manufacture of ammonia
where does the hydrogen come from
recycled from later on in the process
manufacture of ammonia
primary steam reforming
methane gas heated with steam in the presence of a catalyst to produce hydrogen
90% of methane consumed, reaction occurs in a reforming furnace, which contains 520 catalyst filled tubes
manufacture of ammonia
equation of primary steam reforming
CH4 + H2O ⇌ CO2 + 3H2
manufacture of ammonia
heat change of forward reaction in primary steam reforming
endothermic
manufacture of ammonia
secondary reforming
remaining 10% of methane
manufacture of ammonia
equation for secondary reforming
CH4 + 2O2 -> CO2 + 2H2O
manufacture of ammonia
removal of carbon monoxide equation
CO + H2O ⇌CO2 + H2
manufacture of ammonia
heat change of forward reaction in secondary steam reforming
exothermic
manufacture of ammonia
name of reaction of secondary steam reforming
shift reaction
manufacture of ammonia
significance of secondary steam reforming being exothermic
allows for heat recovery which emphasises the thermal efficiency of the ammonia process
manufacture of ammonia
explain the removal of carbon dioxide
the gas is scrubbed with a hot potassium carbonate under high pressure and temperature to form potassium hydrogen carbonate, it is then removed from the system
manufacture of ammonia
equation for removal of carbon dioxide
CO2 + K2CO2 + H2O -> 2KHCO3
manufacture of ammonia
methanation
the gas is hydrogenated using a catalyst to convert remaining CO and CO2 into methane, as traces of these gases could poison the catalyst in the manufacture of NH3
manufacture of ammonia
equation for methanation
CO + 3H2 -> CH4 + H2O
manufacture of ammonia
heat change of methanation
exothermic
manufacture of ammonia
feedstock
nitrogen and hydrogen
manufacture of ammonia
according to Le Chatelier’s Principle, what are the ideal conditions?
low temperature and high pressure
manufacture of ammonia
low temperature
slow reaction
manufacture of ammonia
high pressure
expensive vessel
manufacture of ammonia
actual conditions
high pressure of 200 atm and temperature of 500ºC
manufacture of ammonia
catalyst
divided iron
manufacture of ammonia
promoter
aluminium oxide
manufacture of ammonia
how much of the nitrogen and hydrogen react to form ammonia
about 17%
manufacture of ammonia
what is done to the ammonia
liquified and stored at -33ºC at atmospheric pressure, or sent directly to urea plant
manufacture of ammonia
co-product
carbon dioxide
manufacture of ammonia
how is the carbon dioxide released
can be released from potassium hydrogencarbonate by heating it and reducing the pressure
manufacture of ammonia
what is done with the CO2 made?
used in the manufacture of urea on site and can also be sold to soft drink companies and breweries
manufacture of ammonia
what do they treat the effluent with?
the plant effluent is treated with ion exchange resins to facilitate the recycling of ammonia and carbon dioixed back into the production steam
manufacture of ammonia
rate of treatment
225 m3 per hour of water recovered
manufacture of ammonia
what are air emissions monitored for?
the presence of ammonia, oxides and nitrogen
manufacture of ammonia
CO2
emitted to atmosphere
manufacture of ammonia
steam
emitted to atmosphere
manufacture of ammonia
ammonia
flamed and emitted as nitrogen
manufacture of ammonia
2 other products
nitrous oxides
water
manufacture of ammonia
2 procedures to analyse the gas mixtures at all stages of the ammonia production
gas chromatography
infra red spectroscopy
manufacture of ammonia
safety
2 alarm systems, fire alarm and alarm to indicate gas release
workforce trained in first aid and fire fighting
site designed to allow fire engines into central parts
manufacture of ammonia
fixed costs
labour costs, plant depreciation and repayment of loans
manufacture of ammonia
variable costs
raw materials, heat and electricity and waste disposal
manufacture of ammonia
cost of natural gas
increased as running out in Kinsale, is now obtained from the North Sea - more expensive due to transport costs
manufacture of ammonia
who supplies water and how much
supplied by local council - 4.5 million L per day
what reduces the cost
recycling and sale of the co-product
heat exchangers in the exothermic reactions
use of catalyst to allow lower temperatures
manufacture of ammonia
site location
marino point in Cobh, Co.Cork
manufacture of ammonia
4 reasons for location
natural gas nearby
skilled personnel in Cork area
seawater available for cooling
rail and sea available for transport of products
manufacture of ammonia
construction materials
mild steel on a deep concrete foundation
stainless steel for reaction chambers and compressors - low rate of corrosion
3 uses of ammonia
manufacture of urea
manufacture of nitric acid
manufacture of fertilisers
manufacture of urea
where?
by IFI in Cobh, Co.Cork
manufacture of urea
type of process
continuous process
manufacture of urea
raw materials and where do they come from
anhydrous ammonia and potassium hydrogen carbonate
produced by IFI
manufacture of urea
what is done to the potassium hydrogen carbonate
heat and pressure reduced to produce carbon dioxide
manufacture of urea
equation for producing carbon dioxide
2KHCO3 -> CO2 + H2O + K2CO3
manufacture of urea
feedstock
ammonia and carbon dioxide
manufacture of urea
first step
ammonia and carbon dioxide reacted together to form ammonium carbamate
manufacture of urea
equation for reaction with ammonia and carbon dioxide
CO2 + 2NH3 ⇌ NH2COONH4
manufacture of urea
heat change in forward reaction of ammonia and carbon dioxide
exothermic
manufacture of urea
ideal conditions
carried out at high temperature to favour the forward reaction and heat produced in removed immediately to ensure completion of reaction
manufacture of urea
what happens to ammonium carbamate
ammonium carbamate loses water to form urea n a carbamate condenser
manufacture of urea
equation for when ammonium carbamate loses water
NH2COONH4 ⇌ CO(NH2)2 + H2O
manufacture of urea
heat change when ammonium carbamate loses water
endothermic
manufacture of urea
speed of reaction when ammonium carbamate loses water
slow but sped up with high temperature
manufacture of urea
left over ammonium carbamate
decomposed to form ammonia and carbon dioxide and these gases are recycled to the condenser to react
manufacture of urea
what is done to the urea
changed into molten urea in an evaporator, then prilled
manufacture of urea
prilling
process that involves spraying the molten urea downward from the top of a tall prill tower against an upward flow of air, causes urea to solidify into small spherical particles called prills
manufacture of urea
co-products
there are no co-products
manufacture of urea
waste disposal and effluent control
treated with steam to hydrolyse urea to ammonia and carbon dioxide which is recycled
air emissions monitored for the presence of urea dust
manufacture of urea
quality control
gas chromatography and infra red spectroscopy are carried out to analyse the gas mixtures at all stages of the ammonia production
manufacture of urea
safety
2 alarm systems, fire alarm and alarm to indicate gas release
workforce trained in first aid and fire fighting
site designed to allow fire engines into central parts
manufacture of urea
fixed costs
labour costs, plant depreciation and repayment of loans
variable costs
raw materials, heat and electricity and waste disposal
manufacture of urea
reduce costs
recycling and sale of the co-product
heat exchangers in the exothermic reactions
use of catalyst to allow lower temperatures
manufacture of urea
site location
marino point in Cobh, Co.Cork
manufacture of urea
why that location?
natural gas nearby
skilled personnel in Cork area
seawater available for cooling
rail and sea available for transport of products
manufacture of urea
construction materials
mild steel on a deep concrete foundation is used in some areas of the plant
stainless steel is used in parts of the plant - reaction chambers and compressors, low rate of corrosion
3 uses of urea
as a fertiliser
on runways as a non-corrosive de-icer
manufacture of MDF (medium density fibreboard)
2 other important chemicals produced in Ireland
Nitric acid
magnesium dioxide
where is nitric acid produced?
from ammonia by IFI in Arklow, Co.Wicklow
where is magnesium dioxide produced?
from seawater by Premier Periclase in Drogheda
