S.T.A.R.T: Multiphase Reactors

KNOWLEDGE CHECK: SHOW WHAT YOU KNOW?

What defines a multiphase process?

• • A) A process that involves only liquid reactants

• • B) A process that operates at high temperature and pressure

• • C) A process involving two or more distinct physical phases, such as gas, liquid, and solid

• • D) A process that only occurs in batch reactors

Answer explanation

Explanation: A multiphase process involves multiple phases (solid, liquid, gas) interacting in a system. These phases may coexist and engage in mass transfer, heat transfer, and chemical reactions.

KNOWLEDGE CHECK: SHOW WHAT YOU KNOW?

Which of the following is a common example of a multiphase process?

• • A) A solid dissolving in a liquid

• • B) A chemical reaction in a single-phase liquid system

• • C) A gas reacting with a liquid in the presence of a solid catalyst

• • D) An electric current passing through a conductor

Answer explanation

Explanation: A gas-liquid-solid system is a classic example of a multiphase process. The gas interacts with the liquid phase, and the reaction often takes place on the surface of the solid catalyst.

KNOWLEDGE CHECK: SHOW WHAT YOU KNOW?

In multiphase systems, mass transfer is important because:

• • A) It allows heat transfer between phases

• • B) It controls the rate at which chemical species move between different phases, affecting the overall reaction rate

• • C) It determines the system’s temperature

• • D) It reduces the need for reactant recycling

Answer explanation

Explanation: Mass transfer is critical in multiphase processes as it governs how fast reactants can move from one phase to another, which directly impacts the rate of the chemical reaction.

KNOWLEDGE CHECK: SHOW WHAT YOU KNOW?

Which of the following phenomena occurs in multiphase processes involving gas and liquid phases?

• • A) Vaporization of the gas

• • B) Condensation of the solid

• • C) Gas dissolving into the liquid

• • D) The liquid forming a gas phase

Answer explanation

Explanation: In gas-liquid multiphase processes, gas molecules can dissolve into the liquid phase, leading to reactions between the dissolved gas and liquid components.

BRAIN TEASERS: WHAT'S YOUR BEST GUESS?

Which of the following is required to apply a mass balance in a multiphase reactor?

• • A) Knowledge of the reactor's temperature profile

• • B) Identification of input, output, generation, and consumption terms for each phase

• • C) Only the phase distribution inside the reactor

• • D) The type of catalyst used

Answer explanation

Explanation: A mass balance requires identifying the inputs and outputs of mass, along with any generation or consumption (due to reactions), for each phase in the system. This is essential to model how mass is distributed and reacts in the reactor.

BRAIN TEASERS: WHAT'S YOUR BEST GUESS?

In mass transfer models, what does the mass transfer coefficient represent?

• • A) The capacity of the reactor to handle multiple phases

• • B) The rate at which mass is transferred between phases

• • C) The thermal conductivity of the reactor material

• • D) The total pressure drop in the reactor

Answer explanation

Explanation: The mass transfer coefficient is a measure of how quickly mass is transferred from one phase to another, such as from a gas to a liquid. It is a key parameter in modeling mass transfer processes in multiphase reactors.

BRAIN TEASERS: WHAT'S YOUR BEST GUESS?

Which of the following best describes Henry's Law as applied to gas-liquid equilibrium in multiphase reactors?

• • A) It describes the relationship between the temperature and pressure of a gas

• • B) It relates the concentration of a gas in a liquid to its partial pressure above the liquid

• • C) It is used to calculate the rate of reaction in multiphase reactors

• D) It applies to solid-gas equilibrium systems

Answer explanation

Explanation: Henry's Law states that the concentration of a gas dissolved in a liquid is directly proportional to its partial pressure in the gas phase, which is crucial for understanding gas-liquid equilibrium in multiphase systems.

BRAIN TEASERS: WHAT'S YOUR BEST GUESS?

In a solid-liquid multiphase reactor, what is the primary role of the solid phase?

• • A) To act as a heat exchanger

• • B) To catalyze the reaction or serve as a reactant

• • C) To increase the reactor volume

• • D) To ensure uniform temperature throughout the reactor

Answer explanation

Explanation: In solid-liquid systems, the solid phase often serves as a catalyst or as a reactant. The interaction between the solid and the liquid phase, governed by mass transfer, is critical for reaction progress.