Material balance

A quantitative accounting of material entering, leaving, accumulating, or reacting within a defined system. It applies conservation of mass to processes and changing inventories.

Conservation of mass: The physical principle that mass is neither created nor destroyed in ordinary chemical and physical processes. It supplies the fundamental accounting rule behind a material balance.
System boundary: The real or imagined surface separating a system from its surroundings. The boundary fixes which material transfers count as inputs or outputs.
Chemical process engineering: The engineering discipline that designs and operates processes for transforming materials and energy. Material balances are a standard foundation for analyzing its process flowsheets.
Component balance: A balance equation tracking one chemical component across a system boundary and within the system. It resolves individual species rather than only the total material amount.
Recycle stream: A process stream that returns material from a later stage to an earlier one. A balance around the full process distinguishes internal recycle from net fresh feed.
Control volume: A defined region in space across whose boundary mass and energy may flow. Choosing its boundary determines which inputs, outputs, and accumulation a balance counts.
Mass fraction: The mass of a component divided by the total mass of a mixture. Component balances often use mass fractions to express mixture composition.
Process flow diagram: A schematic showing the major equipment and material streams in a process. Its streams and equipment provide a structured basis for writing balances.
Energy balance: An accounting of energy entering, leaving, accumulating, or being converted within a system. It uses a parallel conservation framework but tracks energy instead of material.
Purge stream: A stream deliberately removed from a process to prevent unwanted material buildup. Its flow can be calculated from a balance on accumulating inerts or impurities.

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