Process Development

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Process Development

• CHEE 2404
• A Ghanem

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Process Development

• Development of new technologies and products is a
  Research and Development (RD) activity
• Goal produce the desired product
• In time
• At planned rates
• At projected manufacturing cost
• At desired quality standards
• Cost and planning are continually monitored from
  lab phase to production

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Product type and raw materials

• Type of product determines the way Process
  Development is conducted.
• Base chemicals (commodities) and intermediates
  can be dictated by the type of raw materials
  available.
• Base chemicals have a wide range of uses and a
  long lifetime.
• Benefit to lowering the cost of production.
  Process improvement.
• Consumer products on the other hand, will be
  quickly replaced (shorter lifetime). Product
  improvement.

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Base chemicals

• The technologies for the production of base
  chemicals and intermediates are well established.
• Development activities usually result in minor
  process improvements (example a new catalyst or a
  more energy efficient furnace)
• Still can have a large impact on overall costs
  due to the large volumes involved (example,
  saving dollars per tonne of acetic acid can have
  a large impact when you produce 500,000 t/a).
• Major new advances in processes are still worth
  pursuing
• More general drive is sustainability and process
  intensification

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Consumer Products

• In specialty chemicals, drive is toward modified
  or new products
• Motivated by market demands rather than cost
  savings
• Some market demands can include new products,
  product quality or environmental concerns.
• Some examples are environmentally friendly
  paints, varied detergents, wood composites used
  in building materials, new drugs, etc.
• More effort is required in determining the
  chemical route of manufacturing. For example, a
  when a new drug is approved the manufacturing
  route must also be approved.

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Bulk vs Specialty Chemicals
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Process Development

• Continuous interaction between experimentation
  and economics.
• Input chemical reaction in the lab
• Outcome production plant
• Development of a process to take the chemical
  reaction in the lab up to a large plant scale in
  an economic way.
• Enlargement of equipment in small steps?
  Empirical method, and practical for some
  applications but not generally for continuous
  process.

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Scale Up
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• Scale up in small steps is expensive especially
  for larger continuous production plants.
• Large safety margins are used.
• Time scale shown is very long (8 years...need to
  reduce time to process development) due to time
  associated with design/construction and operation
  of small steps.
• Predictive models Process steps described in a
  Mathematical model with predictive value
• Predictive models are used to scale up equipment
  and processes from laboratory data or pilot plant
  to eliminate steps and save time.

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• Exploratory phase the reaction provides
  satisfactory yields.
• Based on lab data and literature data, the
  process concept is put together.
• Individual steps are developed and tested on a
  lab scale (the reactor, does the required
  separation work?)
• A process flow sheet is drawn.
• A small scale plant is designed (mini-plant) to
  evaluate performance of the entire process.

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• A pilot plant may be designed and built for
  further testing.
• At each stage, evaluation occurs. Continue, stop,
  or go back to an earlier stage?
• Decisions are based on technical, cost and market
  considerations.

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Cyclic Nature of Modern Process Development
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Breakdown of Steps

• Exploratory Phase
• Discovery of a new product, a new chemical
  synthesis route, or an improvement to a process
• Focus on chemical reaction
• Obtain information
• what reactions take place
• thermodynamics and kinetics of the reaction
• selectivity and conversion rates and their
  dependence on process parameters
• Catalyst and catalyst deactivation rate

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Breakdown of Steps

• Preliminary Flowsheet
• Determine the availability and quality of raw
  materials (first design step would be compare raw
  material costs with product value)
• Draw up preliminary flowsheets and alternatives
• Typically underdefined, so we must make
  assumptions.
• What units should be used?
• How will the units be connected?
• What T, P and flowrates will be required?
• Difficult b/c there are many ways we can
  accomplish the goal, problem is open ended.

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• Process requirements
• Lowest cost
• Satisfies environmental constraints
• Easy to start up and operate
• We can eliminate alternatives based on the above
  considerations
• Make the optimal choice based on knowledge,
  experience and tools such as process simulation

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Input Information

• The reactions and reaction conditions
• Desired production rate
• Desired product purity ( vs. purity)
• Raw materials (also need vs. purity info here)
• Information on rate of reaction, catalyst
  deactivation
• Processing constraints? (ex. explosion limits,
  conditions that cause polymerization, etc.)
• Plant and Site data
• Physical properties of all components
• Information on safety, toxicity, environmental
  impact of materials involved in the process.
• Cost data for byproducts, equipment and
  utilities.

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1. Reactor system2. Separations

• Reactor System
• First step
• Includes reactor, feed, product gas and liquid
  recycle streams.
• Influences the yields, product distribution and
  separations.
• example coal gasification, the amount of H2 and
  CO2 formed are very different for a moving bed,
  fluidized bed, and entrained flow reactor.
• Determine T and P, type of catalyst, phases of
  reactant and products

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Reaction Information

• Stoichiometry of reactions taking place
• Range of T and P for the reactions
• Phases of the reactions
• Product distribution vs. conversion
• Conversion vs. residence time
• Information on the catalyst
• Often available from the literature
• Identify any side reactions that may take place

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Decision 1 Batch vs. Continuous?

• Production rates
• Capacity 10x106 lb/year, usually continuous
• Capacity 1 x 106 lb/year usually batch.
• Multiple products in same equipment?
• Market Forces
• Seasonal products (fertilizer)
• Products with a short lifetime
• Operational Problems
• Reaction is very slow
• Slurry pumping, materials handling
  considerations.
• Rapidly fouling materials

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Conceptual Design

• Continuous Process
• Select the units needed
• Choose the interconnections between these units.
• Identify process alternatives that should be
  considered.
• List the dominant design variables.
• Estimate optimum processing conditions.
• Determine the best processing option

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Conceptual Design

• Batch process (in addition to previous decisions)
• Which units in the flowsheet should be batch and
  which should be continuous?
• Which steps can be carried out in a single vessel
  vs. using a special separate vessel for each
  step?
• Is it advantageous to use parallel batch units?
  Think about scheduling.
• Intermediate storage requirements?

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Decision 2 inputs and outputs

• Should you purify the feed streams before they
  enter the process?
• Should you remove or recycle a by product?
• Should you use a gas recycle or purge stream?
• Should you recycle unreacted reactants?
• How many product streams will there be?

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Decision 3 Separations

• Reaction product contains multiple components,
  you must decide how they will be separated and at
  what conditions.
• Look at the components and how they differ (ie
  boiling point, solubility)
• Identify possible unit operations (ie.
  Distillation, absorption, adsorption, solvent
  extraction, etc.)
• If reactor effluent is a liquid, use liquid
  separation system
• distillation
• liquid extraction, etc.
• Avoid gas absorbers, gas adsorbers.

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• If reactor effluent is a 2 phase mixture, send
  liquid to a liquid system, cool the vapour and
  send to vapour recovery
• Condenser
• Absorption
• Adsorption
• membrane separations).
• If either stream has reactants, recycle these.
• Reactor effluent all vapour cool to attempt to
  condense liquid. Follow up by sending vapour to
  vapour recovery, liquid to liquid recovery.

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Heuristic rules for distillation sequence

• Remove corrosive or hazardous components as soon
  as possible
• Remove reactive components or monomers as soon as
  possible
• Remove products as distillates
• Remove recycles as distillates, particularly if
  they are recycled to a fixed bed reactor
• Remove most plentiful first
• Remove Lightest first
• High recovery separation last
• Difficult separation last

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Example Production of cyclohexanone

• Product mixture
• cyclohexane 94
• Light products 0.5
• Cyclohexanone 3.0
• Cyclohexanol 1.5
• Heavy products 1.0

Boiling point

• All products are similar in terms of
  corrosiveness, hazard and reactivity.
• Remove cyclohexane first (most plentiful and
  lightest)
• Separating cyclohexanone and cyclohexanol is the
  most difficult, so do this last.
• Remove heavy or light components next? Heavy
  since they are more plentiful.
• Remove light products

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• Draw the flowsheet of selected operations
• Sizing of unit operations is done based on
  available information at that time (this is
  preliminary as not all data is available yet, an
  iterative process).
• Develop and test the individual steps.
• Laboratory tests conducted on mixtures prepared
  from pure materials, typically short duration,
  may not show some problems.
• Pilot plants are the next step

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Pilot Plants

• An experimental system that represents the part
  it corresponds to in an industrial unit.
• Can range in size from lab scale (mini plant) to
  commercial unit (demonstration plant).
• Used to
• generate more product to develop a market
• confirm feasibility of the process
• check design calculations
• solve scaleup problems on novel processes
• gain operational know-how
• Determine long term effects of operation
• Typically run to 10 of the commercial plant cost.

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Mini-plant

• To demonstrate process feasibility or generate
  design data for a process, then a mini plant may
  be more appropriate than a pilot plant.
• Includes all recycle streams and can be
  extrapolated reliably
• Uses same components as the lab testing (ie
  pumps, etc.), which is often standardized and can
  be used in many other mini plants
• Operated continuously for weeks or months so some
  automation is required.
• Is used in combination with process modeling and
  simulation of the industrial scale process.
• Typically produces 0.1-1 kg product per hour.

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Relationships of scale
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Miniplants

• Can help to speed up process development and at a
  lower cost.
• Useful to test catalyst stability under practical
  conditions.
• Incorporate recycle streams to detect buildup and
  effect of impurities.
• Some unit operations not easily scaled from
  miniplant data (extraction, crystallization,
  fluidized beds) due to flow characteristics.
• See fig 13.3 for some scaleup values

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Requirement for Pilot Plant Testing
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Reactor Scale Up

• Homogeneous Reactors (single fluid phase)
• Easier to scale up than heterogeneous
• Batch or semi-batch reactor
• Main issue is heat removal in highly exothermic
  reactions
• Continuous tubular reactor
• Main issue is heat transfer and T profile in the
  reactor, kinetic modeling of reactions is used to
  relate the reaction to temperature
• Continuous stirred tank reactor
• Scale up from batch reactor kinetic data

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Heterogeneous Reactors

• Examples include steam reforming, ammonia
  synthesis, hydrotreating.
• Main issues are T control, P drop and Catalyst
  deactivation
• Temperature control
• In endothermic reactions the T drop may be severe
  resulting in an excessively long reactor
• Reaction mixture must be heated rapidly to keep
  the reaction rate at a high enough level
• One way of doing this is to conduct reaction in
  tubes in a furnace (steam reforming)

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• Temperature control
• Exothermic reactions need to be cooled
• This can be done by external heat exchangers,
  injection of cold feed gas.
• Pressure Drop
• Pressure drop across a catalyst bed must be
  limited
• Reduce the bed height, use larger particles,
  apply axial flow or structure the reactor.
• Catalyst deactivation
• Design strategies depend on the mechanism of
  catalyst deactivation

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• Catalyst deactivation
• For example, if the catalyst is deactivated by
  coke deposits, regeneration occurs by burning off
  coke. This can be done in a fluid bed reactor.
• Impurities may build up in the system that are
  undetected at lab scale (low concentration), that
  may affect the catalyst if they are recycled.
  Larger scale reactions are needed to detect these
  so processes can be established to deal with
  them.
• Install pretreatment units, purge some of the
  recycle stream.

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• Hyrodynamics
• Fluid distribution in a heterogeneous reactor may
  change as you make a reactor larger.
• Gas-liquid, solid-liquid contacting
• Parameters include diameter and height, residence
  time, catalyst particle size

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Safety and Loss Prevention

• Chemical plants involve process, storage and
  transport of hazardous materials.
• Increasing plant size increases risks
• Plants are often located close to dense
  populations.
• Loss prevention identify the hazards of a
  chemical process plant and eliminate them.
• Major hazards
• Explosion
• Fire
• Release of toxic substance

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Flammability

• Fires and explosions
• Fuel, oxidizer and ignition source

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Toxicity

• The dose makes the poison
• Hazard depends on the inherent toxicity
• Frequency and duration of exposure
• Acute vs. chronic effects
• LD50 lethal dose that kills 50 of test animals
• TLV threshold limit value, conc of exposure for
  8 hours a day, 5 days a week, without harm.
• Strategies substitution, containment,
  ventilation,disposal provisions, Good
  manufacturing practices (GMP)

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Reactivity Hazards

• Exothermic runaway reactions
• Reactions can occur anywhere
• Unused Catalysts may mediate undesired reactions
• Have good knowledge of reaction chemistry and
  reaction enthalpies
• Use of nitrogen blanket to keep systems inert

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Process Evaluation

• Evaluate at each stage of development
• Is the process technically feasible?
• This is determined at the laboratory, flowsheet
  design, and pilot plant level
• Is it economically attractive?
• How big is the risk (economically, technically)?