S1 2015 Flowsheeting

Department of Mining Engineering and Metallurgical Engineering WESTERN AUSTRALIAN SCHOOL OF MINES

Process Engineering 451/661 – S1 2015

PROCESS ENGINEERING PRRE4001/6003

2

MODULE 1: “Do-it-Yourself Flowsheets”

Why would you do it yourself?

3

Kidd Creek Copper and Zinc Mine (Canada), www.mining-technology.com

Flowsheet

Metallurgical flowsheets - Visual and quantitative; static or dynamic - Process design and plant operation

4

1. Mixing – 2 or more input streams are combined to form a single output stream

2. Splitting – an input stream is divided into 2 or more output streams of identical composition (or size distribution, for solids)

3. Separation – an input stream is divided into 2 or more output streams of different composition (or size distribution for solids)

4. Reaction – refers to alteration of minerals and other materials by chemical reaction

5. Material transfer – mostly involves the movement of liquids, gases and slurries through pipes, etc.

6. Energy transfer – heating, cooling, heat recovery and recycling

Unit Processes

5

Flowsheet Features

IMPORTANT TERMS: ■ Input stream ■ Feed stream ■ Product and waste streams – tailings, concentrate ■ Recycle and bypass streams

6 A process flowsheet summarising the steps taken in the treatment of bauxite ore to

produce aluminium metal (Hayes, P. , 1993, pp 9)

Flowsheet

7

Numbering Unit Processes

8

First: Choose the “ Main Flow”

9

Second: Identify Branches

10

Third: Number Unit Processes to Follow Main Flow

11

Fourth: Number Streams to Follow Unit Processes

12


13

Tutorials – First: Choose the “Main Flow”

14

Second: Identify Branches

15

Tutorials – Second: Identify Branches

16

Third: Number Unit Processes to Follow Main Flow

Tutorials – Third: Number Unit Processes to Follow Main Flow

Tutorials – Third: Number Unit Processes to Follow Main Flow

19


20

Tutorials – Fourth: Number Streams to Follow Unit Processes

21

Tutorials – Fourth: Number Streams to Follow Unit Processes

22

Numbered Flowsheet

23

Stream Characteristics

Species – uniquely distinguishable material entity within a stream Examples: ● Furnace gas: SO2, O2, CO, CO2, N2 ● Slurry: water, solids ● Matte: Cu2S, FeS

Stream Information:

Note: Stream unknowns; Assignment of stream unknowns (pp 11-12)

24

MASS BALANCE: Unknown Stream Flows

Streams 1 and 3 – contain relationships between total flow and species flow Stream 4 – contains similar relationship as 1 and 3; modified Stream 2 – no useful equation; contains trivial information

25

MASS BALANCE: Stream Equations

26

Stream Equations: Gas Volume to Mass Conversion

Units: ● Standard Cubic Metre, Nm3 – a cubic metre of ideal gas at STP (O0C and 1 atmosphere pressure) ● 1 mole (STP) 22.4 x 10-3 Nm3 (22.4 L) ● vol % = mol% for ideal gases

Moles of SO2 = 0.065 (Total Moles in Gas)

27

MASS BALANCE EQUATIONS

Total Mass Balance: ΣMass Flow for Input Streams = ΣMass Flow for Output Streams

28

MOLE BALANCE: Unknown Stream Flows

Mole balance: more convenient to use when stoichiometry of species within streams is well defined or when a number of gas streams are involved

29

MOLE BALANCE: Stream Equations

30

MOLE BALANCE EQUATION

31

Solve Linear Equations using Matrix Inversion

32

19

Heat Balance Equation

20

Heat Balance Equation Terms

21

Sensible Heat

36

Heat of Reaction

37

Sensible Heat

26

Sensible Heat Data – FREED Database

27

Sensible Heat Data – FREED Database

28

LABELS for SENSIBLE HEAT Data

29

Thermodynamic Data – FREED Database

30

Heat Balance Data in Excel from FREED

31

Simple Maths for Flowsheets

44

Set up unknowns Find all independent equations between them through examining: o Stream Characteristics o Mass and Mole Balances o Heat Balances o Unit Process Characteristics Analyse each unit process separately

Need Systematic Approach to:

32

Important Definitions

33

o Process Components o Common Stream Variables o Active Components

Analysis of Unit Processes

47

Process Components

Note: A determination of the number of components for a unit process is fundamentally important knowledge for a material balance since one independent material balance can be written for each component within the unit process.

Stream species – represent all of the physically distinguishable elements, compounds or materials which collectively constitute a given stream. Process components – represent the minimum number of independently distinguishable physical entities present amongst the species of a unit process, from which all input and output species can be assembled, taking into account all intrinsic relationships which exist amongst the species, such as stoichiometric linkages and chemical reactions.

48

Species and Components

49

Use one material balance equation for each common stream variable assigned to the

process.

What is a common stream variable?

Common Stream Variables

Note: When the flow of a species in two different streams can be represented by the same unknown, the unknown is called a common variable.

50

Common Stream Variables in a Mixer

51

The number of components for which a material balance equation can still be written after the assignment of flow unknowns is the number of “active components”

Active Components

52

Mixers

Splitters

Separators

Reactors

Characteristic Equations for Unit Processes

53

Unit Process Analysis

54

No reactions Number of components C is equal to the number of neutral species S

C = S

Write one material balance for each Active Component

MIXER

Example: Mixer material balance, pp 28

55

Operating Parameter: Split Fraction

ΣSFj = 1, SF = OS-1

Write SE = Cactive(OS-1) splitter equations

SPLITTER

56

Splitter Equations

Splitter Equations

57

58

C = S

Write one material balance for each Active Component

(OS-1) independent split fractions

Create an unknown for each undefined split fraction

Write SE splitter equations where:

Splitter Analysis

59

Operating Parameter: Separation Coefficient

Total Independent SC’s = S(OS-1)

SEPARATOR

48

Independent SC’s = S(OS-1) = 3(2-1)=3

SCA2 = 1 SCB2 = 0 SCC2 =0.15

Independent Separation Coefficients

61

Write SCE independent separator equations: Example: Cactive = 1 Equation: mC(2) = 0.15mC(1)

Independent Separator Equations

62

C = S Write one material balance for each Active Component

Total Independent Separation Coefficients SC = S(OS-1)

Use Common Variable for each SC = 1

Write SCE independent separator equations, where:

Separator Analysis

51

Key Parameter: R = Number of independent reactions

C = (SR –R) + S

Write one material balance for each component

C < S

REACTOR

52

Number of Independent Reactions

53

Finding the Independent Reactions

See Appendix 4 for details

54

Finding the Independent Reactions

Combine the reactions to eliminate elements not in the set: Eliminate C (1) – (3) CO + 2H2 CH4 + O (1A) Unchanged: H2 + O H2O (2) Eliminate O (1A) + (2) CO + 3H2 CH4 + H2O (1B) (2) + (3A) CO2 + H2 CO + H2O (2B) Or (4)-(1)-2x(2) CO2 + 4H2 CH4 + 2H2O for 1B

55

Identifying Reaction Components

56

Identifying Reaction Components

57

Other Reaction Equations

58

Example: Component Balance Method for a Reactor

Neutral Species: N2 (S = 1) Reaction Species: H2, O2, H2O (SR = 3) Independent Reactions: H2 + 0.5O2 H2O (R = 1) Neutral Components: N2 (1) Reaction Element Components: C = (SR – R) = (3-1) = 2

Example: pp 38

59

So far …

60

Main Steps for Unit Process Analysis

61

Method for Unit Process Analysis 1. Choose a mole or mass balance 2. Summarise the input/output – diagram 3. Annotate the input/output diagram – identify and name

streams, show known species, stream flow rates, temperatures (if relevant pressures)

4. Analyse the unit process – determine the number of unknowns, active components, restrictions, DOF

5. Write out the equation set for the unit process – component balance equations, restriction equations, any heat balance equation

6. Solve the equation set – Matrix Inversion for linear; Solver for non-linear

7. Summarise the final stream data 8. Verify the balances – total mass balance, individual element

and neutral species balances for a mole balance within reactor

62

Summarise Analysis Using Table

Example: pp 44

63

Unit Process Analysis Examples

Linear Equations: Example 1, pp 45 – Gas Mixer Example 2, pp 49 – Reactor (Refine) Example 3, pp 51- Reactor (Burner) Non-Linear Equations: Example 4, pp 60 – Reactor (Equilibrium) Example 5, pp 64 – Reactor (Burner FT) Heat Balance: Example 7 – Reactor (Burner FT) Example 8 – Reactor (Heat Loss) Tutorials 7,8,9

63

Example 1 – Gas Mixer

See Copy of EJG Flowsheeting Worksheet (Blackboard) for details

Natural gas containing 90.0% methane, 6.0% ethane and 4.0% nitrogen by mass is mixed with normal air (79.0% N2, 21.0% O2 by volume) such that the availability of oxygen is 15% in excess of that required to produce CO2 and H2O upon subsequent combustion. Complete a material balance to determine (1) the appropriate flow of air to mix with 100 kg/h of natural gas and (2) the flow rate and composition of the mixed gas.

63

Example 2 – Reactor (Refine)


100 tonnes of “hard” lead (97.5 wt% Pb, 2.5 wt% Sb) are melted in a steel kettle and treated with 5.0 tonnes of lead oxide in an attempt to reduce the antimony in lead. The PbO reacts with the Sb to produce a slag consisting of PbO and Sb2O3, assaying 23.0 wt% Sb, plus a Pb-Sb alloy with negligible oxygen. Perform a material balance to calculate the final wt% Sb in the alloy.

63

Example 3 – Reactor (Burner)


63

Method for Solving Coupled Linear and Non-Linear Equations

1. Guess initial values for an appropriate number of unknowns within the linear set to give a DOF = 0;

2. Also guess initial values for any flow unknowns present in the non-linear equation set, which are not present in the linear equation set;

3. Use matrix inversion to provide a placeholder solution for the linear set; 4. Create placeholder solutions for each of the non-linear equations by writing

each into a separate cell from the matrix inversion calculation; 5. Initiate the solution, by selecting a cell containing a non-linear equation

placeholder solution as the Set Objective cell within Solver, with the objective value set to the correct equation solution; others as Constraints within Solver;

6. Finally, select all cells containing initial guesses for unknowns in the By Changing Cells box within Solver, and use Solver to vary their values until the Objective and all Constraints achieve their required values.

Study Example 4, pp 60 – Reactor (Equilibrium)

63

Example 7 – Reactor (Burner FT)

See Copy of EJG Flowsheeting Worksheet (Blackboard) for details Do Example 8, pp 66

Solution of Equation Set (from Example 3) nN2 – 0.79NAir = 0.143 (R1) nCO2 = 6.010 (R2) 2nH2O = 23.641 (R3) 0.20NOffgas + 2nCO2 + nH2O – 0.42NAir = 0 (R4) 0.90NOffgas – nN2 – nCO2 – nH2O = 0 (R5)

Soln Nair 113.869

NOffGas 119.922 nN2 90.100

nCO2 6.010

nH2O 11.821

63

Flowsheet Analysis

Method for Flowsheet Analysis: 1. Sketch and annotate an input/output diagram for

the flowsheet 2. Analyse each unit process separately within the

flowsheet, using the established method 3. Summarise the number of unknowns, active

components, restrictions, DOF, and other operating parameters

4. Solve the total flowsheet 5. Finally, verify the flowsheet balance (total mass

balance, element and neutral species balances)

63

Hematite Reduction Linear Equations

Simple Flowsheet Analysis Example

83


A Direct Iron Reduction (DRI) plant employs hydrogen to reduce 2000 kg/h of Fe2O3 through the reaction Fe2O3(s) + 3H2(g) 3H2O(g) + 2Fe(s). The reduction gas is obtained by mixing recycle gas with fresh gas containing 99.0% H2 and 1.0%N2 by volume. Upon leaving the furnace, the exit gas is passed through a condenser to remove all water vapour. A portion is then bled to control N2 build up before being mixed with fresh furnace reduction gas and recycled to the reactor. Analyse and complete a material balance for the total flowsheet to determine the %N2 entering the reactor when 8% of the gas exits the bleed. Also determine the recycle/feed ratio necessary to maintain a H2O/H2 ratio of 0.26 in the reactor off-gas, which is required to ensure complete reduction of iron oxide.

64

65

65

66

67

68

69

70

71

72

73

74

75

76


Hematite Reduction Non-Linear Equations

77

78

79

80

Solve Non-Linear Equations Using Solver

81


82


83

Solve Linear Equations Separately

84

85

Write non-linear equations in separate cells

86

Run Solver with Matrix Inversion to Solve

87

Sensitivity Analysis

88

NiO Reduction mole and heat balance


NiO Reduction with Hydrogen Mole and Heat Balance

Basis 1 kg mol NiO

89

Flowsheet Annotation Solve mole and heat balances

to find T, T4 and all flows. Basis 1 kg mol NiO

90

91

94

95

96

5 linear equations, 3 non-linear heat balances

97

Solve Linear Equations with Matrix Inversion

98

99

100

Thermodynamic Table

101

Heat Balance Fluid Bed Reactor

102

1 Equation 4 Unknowns

nH2, nH2(5), T, T4

Heat Balance Fluid Bed Reactor

103

Placeholder Heat Balance Solution

104

105

Documents

S1 2015 Flowsheeting