1. Dynamic Steady State Continuous Discrete Deterministic Stochastic

2. Synthesi s Needs Flowsheet Analysis Heat and Material Balances Size and Costing Economic Evaluatio n Parameter Optimization Structual Optimization Final Flowsheet

3. Problem: Compute Material Balance Compute Energy Balance How to compute?

4. Sequential Modular Approach Equation Solving Approach Simultaneous Modular Approach

5. Aspen & ChemCad use the sequential modular approach Specify flowsheet (topology) as series of process blocks connected by process streams System determines a computational sequence -- you can override You specify inputs, process conditions and how to compute physical properties Simulator computes output flows from these data. Simulator also computes energy usage, etc.

8. Simple Example Flow: 1000 lb/hr Pressure: 200 psia Temperature: 300 F Composition: 100% water Flash a water stream Flash vessel is well insulated Flashed to 20 psia Given Inputs Operating Conditions Desired All flows Temperature Pressure

9. Flow: 1000 lb/hr Pressure: 200 psia Temperature: 325 F 20 psia Flow: ? Temperature: ? Pressure: 20 psia Flow: ? Temperature ? Pressure: 20 psia Vapor Liquid Q = 0

10. Mass Balance: F = V + L Energy Balance: F*H F = V*H V + L*H L Note: Since vapor and liquid, system is at saturation, so temperature is known (from steam tables)

11. Mass Balance:1000 lb/hr = V + L Energy Balance: 1000lb/hr*296 Btu/lb = V*1156.2 Btu/lb+ L* 196.25 Btu/lb Note: Since vapor and liquid, system is at saturation, so temperature is known (from steam tables = 228 F and get enthalpy data from steam tables) L = 896.1 lb/hrV = 103.9 lb/hrT = 228 F