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i
THE COPPERBELT UNIVERSITY
SCHOOL OF TECHNOLOGY
CHEMICAL ENGINEERING DEPARTMENT
HYDROCHLORIC ACID PLANT
DESIGN
i
THE COPPERBELT UNIVERSITY
SCHOOL OF TECHNOLOGY
CHEMICAL ENGINEERING DEPARTMENT
HYDROCHLORIC ACID PLANT DESIGN
PREPARED BY:
1. MUTAMBANSHIKU LYASHI ARREN 98715747
2. ROMANSHI EMMY
3. SHIMOONJE HANS K 99229633
4. SICHALI RONNY KAPYELA 98611062
SUPERVISED BY:
Mr J.J. KANYEMBO
This paper is prepared in partial fulfilment leading to the award of a Bachelor of
Engineering (BEng) in Chemical Engineering.
i
LETTER OF TRANSMITTAL
The projects co-coordinator,
Chemical Engineering department,
Copperbelt University,
P.O BOX 21692,
Kitwe.
25th November 2005
Dear Sir,
RE: SUBMISSION OF DESIGN PROJECT.
We refer you to your request for a report on the design of a Hydrochloric acid plant as partial fulfillment for the award of a degree in Chemical Engineering.
We submit this report with the view that it meets the standards necessary for the assessment of this course (CE-500).
It is our sincere hope that this report will meet your expectations.
Yours faithfully,
Sichali Ronny Kapyela .................................................
Mutambanshiku Lyashi Arren ...............................................
Romanshi Emmy .................................................
Shimoonje Hans ...................................................
ii
DECLARATION
I Sichali Ronny having read the University Regulations on cheating plagiarism,
do by here declare that to the best of my knowledge the work contained in this
presentation is of my own working and that all material used print, electronic and
verbal have been dually acknowledged.
The examiners cannot, however, be held responsible for the views expressed,
nor the factual accuracy of the contents.
Sichali Ronny Kapyela
……………………………………………..
Mr J.J Kanyembo
(Supervisor)
…………………………………………………….
iii
DECLARATION
I Mutambanshiku Lyashi Arren having read the University Regulations on
cheating plagiarism, do by here declare that to the best of my knowledge the
work contained in this presentation is of my own working and that all material
used print, electronic and verbal have been dually acknowledged.
The examiners cannot, however, be held responsible for the views expressed,
nor the factual accuracy of the contents.
Mutambanshiku Lyashi Arren
……………………………………………..
Mr J.J Kanyembo
(Supervisor)
…………………………………………………….
iv
DECLARATION
I Romanshi Emmy having read the University Regulations on cheating
plagiarism, do by here declare that to the best of my knowledge the work
contained in this presentation is of my own working and that all material used
print, electronic and verbal have been dually acknowledged.
The examiners cannot, however, be held responsible for the views expressed,
nor the factual accuracy of the contents.
Romanshi Emmy
……………………………………………..
Mr J.J Kanyembo
(Supervisor)
…………………………………………………….
v
DECLARATION
I Shimoonje Hans having read the University Regulations on cheating plagiarism,
do by here declare that to the best of my knowledge the work contained in this
presentation is of my own working and that all material used print, electronic and
verbal have been dually acknowledged.
The examiners cannot, however, be held responsible for the views expressed,
nor the factual accuracy of the contents.
Shimoonje Hans
……………………………………………..
Mr J.J Kanyembo
(Supervisor)
…………………………………………………….
vi
ACKNOWLEDMENTS
RONNY SICHALI’S ACKNOWLEDGEMENT
I would like to take this opportunity to thank the almighty Jehovah GOD, without
who non-this would have been possible.
To my project supervisor, Mr J.J Kanyembo, for the guidance and patience
during the duration of this project, to you sir, I say thank you very much.
To my mum, Karen Sichali-Sichinga for the encouragement and believing in me.
Thanks a million, love you.
I would also like to thank the Sichali family for moral and financial support. And to
my sponsors, GRZ through the bursaries department.
A big thank you to some very good friends; Kabuswe Bwalya, Simon Bwalya and
family, Elias, Mr and Mrs C Bwembya, Lumbwa Kafwimbi, and to all my friends
thanks for being there.
MUTAMBANSHIKU’S ACKNOWLEDGEMENT
My thanks to the project supervisor Mr.J.J.Kanyembo and staff in the Chemical
Engineering Department. Thank you to the project team; Ronny, Hans, Emmie
and myself for the intellectual and fruitful arguments. My thanks go to my
classmates whose suggestions added value to this work.
My special thanks go to my family the driving force to this mission.
My special, special thanks to Jehovah God for the vision that He rekindles each new
day.
SHIMOONJE HANS’ ACKNOWLEDGEMENTS Firstly I would like to give thanks to the almighty God for blessing me with my
abilities and for carrying me this far.
I would also like to give passionate acknowledgements firstly to my mother, Mrs.
R.J Shimoonje, for her unconditional and undying support and love in all my
endeavors, and to my late father, Mr. J.M Shimoonje for laying a solid
vii
educational foundation on my life and for all the inspirational and motivational
words that I still carry deep within me.
To my brothers Hector, Shachillu and Mbaze, thank you for your love, it keeps
me going. To my sister Trina thanks for your love and financial support, I will
never forget!
To my group members, Arren, Ronny and Issa, your criticism has added to my
intellectual growth and working with you has opened my mind to new ideas, to
you I say thank you and job well done.
To my friends T.K, Martin, Yanda, Gilbert, Davies Z,Goli, Luke and Maimbo, the
memories we share I hold close to my heart, thank you for everything.
Last but not least , to our supervisor Mr. J.J Kanyembo thank you for all the
guidance and criticism which played a key role in shaping this report.
viii
ABSTRACT
The aim of this project is to design a plant that will be producing 150 tons a day
of Hydrochloric acid, with a quality of 20 ºBe´. Given Sodium Chloride NaCl
(Common salt) and Sulphuric Acid H2SO4 of 60 ºBe´ quality as raw materials.
This will include determining whether the project is viable or not through costing
and equipment sizing.
As the country currently has no HCl plant this project is worth carrying out as it
may provide not only local source for HCl required in Chemical and allied
industries, but also employment for the local people.
The production will be carried though the reacting of raw materials given, by heating
them to a required temperature and subsequent absorption of the gas
ix
TABLE OF CONTENT
Item age number
Letter of transmittal .............. I
Declarations .............. ii
Acknowledgments .............. vi
Abstract .......... vii
Table of contents ........... ix
List of tables ........... xii
List of figures and diagrams ............ xii
Chapter one
1.0 Introduction .............. 1
1.1 Process of design .............. 2
1.2 Uses of HCl .............. 4
Chapter two
2.0 Reactor (furnace design) ................... 5
2.1 Design objectives .................... 6
2.2 Process design ................. 6
2.2.1 Physical properties .................. 6
2.2.2 Process description .................. 8
2.3 Material balance ................ 10
2.3.1 Component balance .................. 11
2.4 Muffle furnace .................. 12
2.4.1 Operating conditions ...................... 12
2.4.2 Reaction kinetics .................... 12
2.5 Energy balances around the furnace ................. 16
2.5.1 Heat of reactions conversion for furnace duty..... 16
2.5.2 Furnace duty and fuel quantity .................... 17
2.5.3 Air and fuel analysis .................. 19
x
item page number
2.6 Selection of fuel .................... 20
2.7 Type of fuel ................... 21
2.8 Process control .................. 22
2.9 Mechanical design (muffle furnace) .................. 22
2.10 Costing of muffle furnace ................. 23
Chapter three
3.0 cooling of hydrogen chloride gas .................. 25
3.1 Introduction .................... 26
3.1.1 Advantages of the Trombone Cooler………….. 27
3.1.2 Industrial Applications ………….. 28
3.2 Process design ………… 28
3.2.1 Heat Flow through A Trombone Cooler ………… 28
3.2.2 Calculation of Outside Film Coefficient ………. 29
3.2.3 Heat load ……….. 30
3.2.4 Pressure drop …………. 35
3.3 Summary of process design …………. 36
3.4 Mechanical design ………….. 37
3.5 Unit Costing of Cooler …………… 38
Chapter four
4.0 Absorption column design …………… 40
4.1 Introduction …………… 41
4.2 Process Design …………… 43
4.2.1 Column diameter …………… 43
4.2.2 Selection of plate type …………… 43
4.3 Material balance ……………. 45
4.4 Equation of the operating line ……………. 47
4.4.1 Column diameter Calculation …………….. 50
xi
item age number
4.5 Unit Costing and Evaluation ……………. 53
Chapter five
5.0 site selection and safety ……………. 55
5.1 Occurrences of raw materials …………… 55
5.2 Site selection …………… 55
5.4 Safety factors …………… 56
Chapter six
6.0 project evaluation and cost ................. 58
6.1 Introduction ............... 58
6.2 Fixed and installation cost ………….. 59
6.2.1 Physical plant cost (PPC) …………. 60
6.2.2 Fixed capital cost (FCC) ………….. 60
6.2.3 Cost (expenditure) ………….. 60
6.2.4 Income per year ………….. 60
Conclusion …………. 64
Recommendations ………….. 67
Reference ……………. 69
Appendix …………… 71
xii
List of tables
Item Page number
Properties and composition of fuel selected table 2.1 18
Fuel air combustion analysis table 2.2 18
Fuel air combustion analysis table 2.3 19
Hydrocarbon fuel cost table 2.4 21
Furnace dimensions summary table 2.5 23
Solubility of HCl in water at 760mmHg table 4.1 41
Mechanical description table 4.2 52
Summary table cost evaluation table 6.1 61
Process design summary table 6.2 62
Mechanical design and costs summary table 6.3 63
LIST OF FIGURES AND DIAGRAMS
Item page number
Overall material balance diagram 2.1 10
Component material balance around the furnace fig 2.1 11
Energy balance around the furnace diagram 2.2 16
Trombone cooler Diagram 3.1 27
Falling film absorber Diagram 4.1 42
Summary of outcome of calculations diagram 4.2 47
Dimensions diagram 4.3 52
1
CHAPTER ONE
1.0 INTRODUCTION
Basilius Valentinus is credited with the production of hydrogen chloride in the
fifteenth century. Its commercial production awaited the Leblanc process for
sodium carbonate in which hydrogen chloride and salt cake are co products. For
a time, the gas was merely vented to the atmosphere, but legislation was
enacted prohibiting its indiscriminate discharge, and thus necessitating its
recovery.
The developed world today describes this era as the information age following
successes of industrialization age; however, this idea has landed the least
developed countries on an unfair field of play. Though the theory of quantum leap
do apply in certain quotas but its not so in other quotas. There are no short cuts
to credible achievement or success as success should have a traceable root thus
has to be worked for. The labor of industrialization has built strong economies in
the developed countries. In particular, the chemical and allied industries have
been described to be the backbone of these successful economies.
The need for industrialization in developing countries and Zambia in particular is
therefore very obvious. Since 1964, Zambian industrialization process has
suffered a lot of set backs because of changes in both the political and economic
development. This has been seen by the closure of many manufacturing
industries and mines in particular. The few existing manufacturing plants driving
the Zambian economy are now being recapitalized by foreign investment and
others are still calling for recapitalization whose operations are far below their
capacity for instance Nitrogen Chemicals of Zambia (NCZ) plant. The status quo
of the industrialization crusade in Zambia is a challenge to the technocrats. The
need for new and viable projects in chemical and allied industries should be
regarded not only as a challenge but as an opportunity for economic growth.
This is report is on a project whose objective is to design a plant to produce 150
tones per day of hydrochloric acid (20oBe’) from sodium chloride and sulphuric
acid (60oBe’).There is no existing plant in Zambia producing hydrochloric acid
2
despite its wide application in both local and regional industries This report will
discuss the plant design of the commercial production of hydrochloric acid.
What is hydrochloric acid? Hydrochloric acid is a solution of hydrogen chloride
(HCl) in water. In industry it is referred to as the spirit of salt where it attracts a
wider application which will be discussed in detail later in the report. There are
four major known processes used commercially to produce hydrogen chloride
and hydrochloric acid. (1) the salt-sulphuric acid process, (2) the Hargreaves
process-salt, sulphur dioxide, air and water-vapor used as reactants, (3)synthetic
process or thermal process- combustion of hydrogen and chloride mixture, (4)the
by-product of organic chlorinations such as methane and benzene.
1.1 Process of design
The design approach to the stated objective will be the salt-sulphuric acid
process because of the specified raw materials in the design question. The HCl
plant will have three (3) main units and service equipment namely the furnace
(reactor), the cooler and the absorber and a compressor as a service unit. The
report will consider discussing each unit as an individual chapter. However, each
unit chapter will adopt the same outline of detailed discussion under the
subsections namely; the process design, mechanical design and unit costing.
The furnace which will be the reactor, the heart of the plant will be discussed in
chapter two. The physical properties of raw materials and products will be
discussed. The process description, the reaction chemistry, the reaction kinetics,
the material and energy balances, the type and analysis of fuel and its choice will
all be discussed in this chapter. Product gas temperature will be expected to
exceed that allowable for absorption. Methods of cooling do vary with
temperature volume of gas to be processed. Chapter three discusses in detail
the suitable type of cooling for the duty. Chapter four discusses in detail the
absorption of HCl gas in the absorber to produce the final product HCl acid.
Hydrogen chloride exerts a destructive action on the mucous membrane and
skin. For instance, exposure to HCl gas or acid may result in chemical burns or
3
dermatitis. Chapter five discusses safety, health and environment (SHE) in detail.
In order for the process to produce the HCl (20oBe’) with consistence, raw
materials and operating conditions must be adhered to. This important aspect
would be possible with a process control in place. Chapter six discusses briefly
the process control and the loop will be indicated on the overall plant design flow
sheet.
The overall plant costing versus the projected sales volume of the product and
the by product to ascertain the viability of the project will be discussed in detail in
chapter seven.
As earlier mentioned HCl attracts a wider industrial application, chapter eight will
discuss in detail its uses. The occurrence of raw materials and factors influencing
site selection will be discussed in detail in chapter nine.
It is the hope of the design project team that the report will have a conceptual
approach to provide workable solution to the design question.
4
1.2 Uses of HCl
A strong inorganic acid used in many industrial processes.
Regeneration of ion exchangers resins.
pH control in food, pharmaceutical, drinking water and neutralizing waste
streams. It is used to control the pH of the process streams.
Pickling is an essential step in metal surface treatment, to remove rust or
iron oxide scale from iron or steel before subsequent processing, such as
extrusion, rolling and galvanizing among many other techniques.
In the production of inorganic compounds such as flocculants and
coagulants useful in wastewater treatment, drinking water production, and
paper production.
Production of organic compounds; vinyl chloride for PVC and other
pharmaceutical products.
Leather processing, household cleaning and building construction.
Diluted to 10% to 12% strength is recommended for household purposes,
mostly cleaning.
Used as a form improver in the production of washing detergents.
5
CHAPTER TWO
2.0 REACTOR (FURNACE DESIGN)
NOMENCLATURE
νs volume of solid, m
h height of reactor,m
d diameter of reactor,m
νNaCl volumetric flow rate of sodium chloride, m3/s
ρNaCl density of sodium chloride, kg/m3
mNaCl mass flow rate of sodium chloride, kg/s
ө uncorrected residence time, s
к correcting factor for particles of nominal diameter 53-63microns
tr corrected residence time for a single particle, s
rA reaction rate for reactant A,
К reaction rate constant
CAO initial concentration of reactant A, kmol/m3
CBO initial concentration of reactant B, kmol/m3
CA final concentration of reactant A, kmol/m3
CB final concentration of reactant B, kmol/m3
νH2SO4 volumetric flow rate of sulphuric acid, m3/s
ρH2SO4 density of sulphuric acid, kg/m3
mH2SO4 mass flow rate of sulphuric acid, kg/s
XA fractional conversion of reactant A
FAO Initial molar flow rate, kmol/s.
τ residence time for the reaction mixture, s
Q heat added by fuel, kW
mf mass flow rate fuel,kg/s
CV calorific value of fuel, MJ/kg
6
2.1 design objective
To design a plant to produce 150 tones per day HCl (20oBe’) from
NaCl and H2SO4 (60oBe’).
This section of the project deals with the sizing of a furnace in which the raw
materials solid sodium chloride and liquid sulphuric acid will react to produce
hydrochloric acid gas the desired product and solid sodium sulphate a by-
product. The sizing will be based on reaction kinetics and the material balance.
The reaction requires a long reaction time and a high temperature. This is
achieved in a muffle furnace with a body of hearth which is heated with oil
burners to 550-660oC.
2.2 process design
ASSUMPTIONS
The process is a steady state flow
The process is endothermic and adiabatic.
The reactor is a non-catalytic CSTR.
The reactants are uniformly mixed.
The system is homogeneous on this basis.
The muffle furnace efficiency is 100%.
2.2.1 Physical Properties
Sulphuric Acid (H2SO4),
Colorless, viscous liquid, specific gravity of 1.835 and boiling point is 270oC. It is
a strong acid.
Feed conditions
Temperature = 20oC
Quality = 60oBe’
Specific gravity = 1.705
Flow rate = 3174.13kg/h
Enthalpy = -887.13kJ/mol
7
Sodium chloride (NaCl)
Ionic crystal, colorless and has closed packed lattices.
Specific gravity, 1.1978.
Specific heat, 12359 Cal/mol.
Lattice energy, 182 Cal/mol.
Solubility in water, 35.7g/100g in water at 0oC, 39.8g/100g in water at 100oC.
Temperature = 50oC
Flow rate = 3789.52kg/h
Enthalpy = -411.38kJ/mol
Product conditions from the furnace
Hydrochloric (HCl) gas,
Colorless or slightly yellow, fuming gas, suffocating odor, very soluble in water; in
alcohol and ether and its non-flammable
Specific gravity = 1.16.
Melting point = -114oC
Boiling point = -85oC
Solubility= 72g/100g in water (20oC)
Temperature = 537oC
Quality = 20oBe’
Specific gravity = 1.16
Flow rate = 2364.4kg/h
Enthalpy = -92.31kJ/mol
Sodium sulphate (Na2SO4) (s)
Temperature = 527oC
Specific gravity =
Flow rate = 4599.24kg/h
8
Enthalpy = -1382.81kJ/mol
Reaction Chemistry
Common salt, sodium chloride and 60oBe’ sulphuric acid react readily to form
hydrogen chloride and the acid sulphate, NaHSO4, at temperatures in the range
of 148.9oC and finally the normal salt, Na2SO4 at 527.8oC. The reactions are
endothermic and are represented as follows:
NaCl (s) + H2SO4 (l) →NaHSO4(s) + HCl (g)
NaCl (s) + NaHSO4(s) →Na2SO4(s) + HCl (g)
2NaCl (s) + H2SO4 (l) →Na2SO4 (s) + 2HCl (g)
2.2.2 Process description
The sodium chloride is ground in a mill, mixed with current of hot compressed air
to 50oC and liquid sulphuric acid are charged through a feed inlet through the
cover of the furnace. This is an externally heated furnace in which the process
stream is heated primarily by radiactive and conductive heat transfer from the
flame and hot gases and is known as Continuous Mechanical Muffle furnace.
This furnace as it is referred to comprise the combustion chamber, the work
space, the stationary circular muffle with a bottom concave pan and a domed
cover separated by a cylindrical mantle or steel column and the plough mounted
on rotating arms fixed to a central under driven shaft.
The combustion chamber is where the fuel/air combustion takes place to produce
combustion gases, CO2 and H2. Hot flue gases are circulated around the muffle.
The work space which is sufficiently tight to keep out contaminants is where the
actual decomposition of the reactants takes place to produce HCl gas and solid
Na2SO4.This is an externally heated furnace in which the process stream is
9
heated primarily by radiative and conductive heat transfer from the flames and
hot gases (combustion gases) above the dome and the pan transmit the required
heat for the reaction by radiation from the cover and by conduction through the
pan (there is no direct contact between the combustion gases and the
reactants/products). The reaction mass is agitated by the ploughs. The rotating
ploughs move the reacting mass toward the periphery of the pan where the salt
cake, sodium sulphate is discharged. Hydrogen chloride (30- 36% by weight) and
air are withdrawn from an outlet in the cover and transferred to coolers and
absorbers.
Combustion chamber temperatures of about 1202oC (1475K) are used for
heating. The reaction between sodium chloride and sulphuric acid takes place at
temperatures ranging 500 to 550oC. The product hydrogen chloride gas is
discharged at temperature 537oC and the byproduct sodium sulphate is
discharged from the hearth at about 527oC.
10
2.3 Material balance
Overall material balance diagram 2.1
OVERALL
MATERIAL BALANCE
2NaCl(s) + H2 SO4 (l) → Na2SO4 (s) + 2HCl (g)
(98) (117) (142) (73)
Na2SO4 (S)
HCl(g)
NaCl (s)
H2SO4 (l)
Basis: 150t/day of HCl (20oBe’)
(150 x 1000) / 24 = 6250kg/h HCl acid
But the amount of HCl gas which is leaving the reactor (furnace) to be absorbed
with water at 95% efficiency is obtained by:
Consider solubility ratio of 0.561: 1 that is HCl/water ratio
(0.561/1.561) x 6250 = 2246.15kg/h HCl to be absorbed in water
Therefore at 95% efficiency of the absorber, this implies that
95% HCl acid leaving the absorber = 2246.15kg/h giving 35.9% by wt HCl acid
100% HCl gas entering the absorber = x
x = (100 x 2246.15)/95 = 2364.4kg/h
This value serves as a basis for the material balance at the reactor
11
2.3.1 component balance
Component material balance around the furnace fig 2.1
NaCl (s)
HCl (gas)
H2SO4(l)
Na2SO4(s)
Basis: 2364.4kg/h of HCl gas
Feed:
H2 SO4 (l): (98/73) x 2364.4 = 3174.13kg/h
NaCl (s): (117/73) x 2364.4 = 3789.52kg/h
Product:
HCl (g): 2364.4kg/h
% wt: [2364.4/ (3174.13 + 3789.52)] x 100 = 33.95%
(It is within the expected value ranging between 30-36% for the
conventional sulphate process)
By-product
Na2SO4 (s): (142/73) x 2364.4 = 4599.24kg/h
12
2.4 Muffle Furnace
2.4.1 Operating Conditions
Combustion chamber:
Temperature = 1202oC
Pressure = 6.8atm
Work space:
Temperature = 500-550oC
Pressure = 1.5atm
Reaction kinetics
Diameter of the reactor = 3m
Height of the reactor = 6m
Average particle diameter of NaCl(s) = 53-63 microns.
Residence time,
2.4.2 Reactor kinetics
H2 SO4 (l) + 2NaCl(s) → Na2SO4 (s) + 2HCl (g)
particlesNaClforfactortimereactiontheiswhere
st
micronsdiameteraverageofparticlesforttimeresidence
sv
s
smm
NaClofratefeedvolumetric
mhd
reactortheinsolidofvolume
r
r
Nacl
s
min42896.0482
,6353 ,
48210788.8
424.0
/ 10 788.88.11973600
52.3789
424.001.04
63
4
,
4
34-
322
13
Since sulphuric acid is more expensive than sodium chloride (natural salt), it is
taken as a limiting reagent and the basis for the calculations in reactor kinetics,
Let A, and B represent sulphuric acid and sodium chloride respectively.
2
BAA CkCr
3
3
/48.205.58
8.1197
/39.1798
1705
42
42
mkmolM
lC
mkmolM
C
NaCl
NaCBo
SOH
SOH
Ao
14
0001665.0
98.010997.8
/10809.4
71.18
10997.8
/10997.8
983600
13.3174
/0001665.0
2984.03742.0005.0
/9277.098.039.17248.202
/3478.098.0139.171
3
34
3
3
3
2
3
3
A
AAo
o
Ao
Ao
o
Ao
Ao
A
A
AAoBoB
AAoA
r
XFV
smV
C
FV
skmolF
smkmolr
r
mkmolXCCC
mkmolXCC
15
The conversion of the reaction is at 0.98
min3.18
10809.4
01.09.52
9.52
0001665.0
98.010997.8
/10809.4
71.18
10997.8
/10997.8
983600
13.3174
/0001665.0
2984.03742.0005.0
/9277.098.039.17248.202
/3478.098.0139.171
4
3
3
34
3
3
3
2
3
3
o
A
AAo
o
Ao
Ao
o
Ao
Ao
A
A
AAoBoB
AAoA
V
V
mV
r
XFV
smV
C
FV
skmolF
F
smkmolr
r
mkmolXCCC
mkmolXCC
16
2.5 Energy balance around the furnace
energy balance around the furnace diagram 2.2
The reference state is 22oC and 1atm
2.5.1 Heat of reactions conversion for furnace duty evaluation…..
2NaCl(s) + H2 SO4 (l) → Na2SO4 (s) + 2HCl (g)
-411.38kJ/mol -887.13kJ/mol -1382.81kJ/mol -92.31kJ/mol
H2 SO4 (l):
[3174.13/3600]/98*[-887.13*103] = -7981.48kW.
ENERGY BALANCE
AROUND THE FURNACE
2NaCl(s) + H2SO4 (l) HCl(g) + Na2SO4
• The reference state is 22oC and 1atm
Qin
(ΔH) Flue gas
(ΔH) HCl(g)(ΔH) NaCl(s)
(ΔH) H2SO4 (l)
(ΔH)Na2SO4(s)
enthalpy
feeds
enthalpy
products
added
heat
17
2NaCl(s):
[3789.52/3600]/58.5*[-822.73*103] = -14804kW.
Na2SO4:
[4599.24/3600]/142*[-1382.81*103] = -1248.87kW.
2HCl:
[2364.4/3600]/36.5*[-184.62*103] = -3322.04kW.
2.5.2 Furnace duty and fuel quantity…..
Furnace duty = Heat added by fuel
Heat added by fuel, Q = (Heat in Products)-(Heat in Reactants)
= -4570.91-(-22785.48)
= 18214.57kW
Therefore, quantity of HFO required for this duty is:
Q = CV*mf
Where mf = mass flow rate of fuel (HFO), kg/s
CV = calorific value of fuel, kJ/kg
mf = 18214.57kJ/s*[1/42.9*103kJ/kg] = 0.425kg/s (1528.49kg/h) or 63.68tpd
Volumetric flow = [1528.49kg/h]/[960kg/m3] = 1.59m3/h (1592.18l/h)
18
Table Showing Properties and Composition of Fuel Selected table 2.1
Fuel
Relative
Density
Composition % by
mass
Calorific
value
(MJ/Kg)
C H O N S Ash Gross Net
Heavy
Fuel
Oil
0.96
85.4
11.4
2.8
1.0
0.5
1.5
42.9
40.5
table 2.2
3.169TOTAL
0.025__0.025Ash
0.010.005 S(S)+ 02(g) S02(l)
0.005S
0.01__0.01N
_- 0.028_ 0.028O
1.0260.9122H2(g)+ 02(g) 2H20(l) 0.114H
3.132.28 C(s)+ O2(g) CO2(g)0.854C
Products per Kg
of fuel
Oxygen required
Per Kg of fuelCombustion equationMass / kg
fuel
Component
element
FUEL AIR COMBUSTION ANALYSIS
19
table 2.3
2.5.3 Air and fuel analysis
100.0100.0Wet:0.5906
Dry: 0.5336
100.0Wet:17.20
Dry:16.17
total
0.040.030.0002640.00060.01S02
83.2875.30.44442872.312.43N2
3.373.00.018323.50.60102
9.70.057186.01.026H2O
13.3112.00.0714418.23.13CO2
% by Vol.
Dry basis
% by Vol.
Wet basis
Kmol per
Kg Fuel
M
Kg/Kmol
%
By MASS
Mass per
Kg FuelPRODUCT
FUEL AIR COMBUSTION ANALYSIS
hKg
hfuelKgfuelKgflueKgoutgivengasflue
hKg
fuelhKgfuelkgairKgfurnacetofiredAir
Therefore
Kg fuel Kg air / .
.% .
ratiostioc A/F%excess ratiostoic A/F Actual A/F
.atiotric A/F rstoichiome
fuel kg air/kg..
.of Fuel ed per Kg Air requir
f Air is % excess oAssume
/68.24715
/ 49.1528 / 17.16
/19.25923
/49.1528 / 96.16
,
1916
4913209913
1
3913
49132330
1693
suplied.20
20
2.6 Selection of fuel
For selecting a particular type of fuel, the following factors are taken into
consideration:-
1. Suitability to process.
2. Supply position. Supply position with regard to availability in sufficient
quantity will be considered. Reliability of supply is also taken into consideration.
Factors which may affect the reliability of fuel supply are: life of reserves,
international politics, wars, labor difficulties and weather disturbances.
3. Cost of fuel. Cost of fuel depends on the following factors:-
(i) Cost of fuel per unit of calorific value (C.V.).
(ii) Cost incurred in its tapping and transport.
(iii)Efficiency of utilization. A fuel may be utilized efficiently only with a particular
set of equipment. For example efficiency of the fuel in the furnace can be
achieved if heat recovery equipment is incorporated in the plant.
(iv) Maintenance of equipment. Cost of maintenance, storing, handling and
burning of fuel must be considered. Such cost is higher in the case of coal than in
case of oils.
(v)Labor and convenience. For example, labor is required for moving the fuel
when the coal is burnt while no such labor is required for gaseous and liquid
fuels.
(vi) Refuse handling and burning quality. When coal is burnt some labor is
required to remove ash. No such labor is required when oil or gas is burnt.
Whether it burns efficiently and without smoke.
(vii) Auxiliary power. Cost of auxiliary power required with a particular type of fuel
is taken into consideration. For example, power is required for conveying coal or
for pulverizing or pumping coal; power is required for supply of air or steam for
atomization of oil, and for supplying air of combustion.
21
2.7 Types of fuel
Basically there are three types of fuel to select from namely coal, diesel or heavy
fuel oil (HFO).
Hydrocarbon fuel cost table 2.4
FUEL CV
MJ/t
DENSITY
Kg/l
COST
US $
COST
ZM K
Diesel 51700 0.87 509.04 2,063,027.13
HFO 42400 0.96 265.00 1,073,986.70
Coal 30400 1.10 135.29 548,300.61
Muffle furnace does not favor the use of coal because of its ash accumulation
nature. Therefore, the choice is reduced to either HFO or diesel but despite the
higher CV of diesel than HFO, the cost implications disadvantage its choice for a
suitable fuel. HFO is a residue fuel from the refinery and costs less and able to
meet the energy demand for the design.
22
2.8 Process control
The salt is dosaged by means of a belt weigher, the quantity of acid is
measured by flow measurement and controlled by an electropneumatic
positioner.
Based on raw material analyses, the quantity ratio of the materials is then
controlled by a human operator.
The reaction between sulphuric acid and potassium chloride requires a
long reaction time and a high temperature.
Producing sulphate that is free of sulphuric acid and hydrochloric acid
requires equivalent amounts of acid and salt.
The furnace will have both the temperature and pressure sensors installed
to ensure operating conditions are monitored and adhered to.
2.9 Mechanical design (muffle furnace)
The continuous mechanical muffle furnace is primarily a stationary circular muffle
comprising a bottom concave pan (hearth). It consists of a circular refractory
hearth, up to 6m in diameter, with a silicon carbide hearth. And a domed cover
separated by a cylindrical mantle. The external structure has a steel shell with
two main access doors. The muffle furnace consists of basically two apartments.
The 1st apartment is the combustion chamber where the fuel/air combustion
takes place. The 2nd apartment is the work space where the reaction between the
reactants (sodium chloride and sulphuric acid) to produce desired product (HCl
gas) and by-product (Na2SO4) takes place.
The 1st apartment- combustion chamber is has an acidic refractory lining to
protect the steel shell high temperature combustion gases and their acidic
nature.
The 2nd apartment- work space comprises a circular refractory hearth with a
silicon carbide hearth. The acidic refractory lining is used because of the acidic
nature of the feed material and the product material.
23
The muffle would be cast iron with refractory lining and steel enclosure supported
on steel columns.
The internal diameter of the furnace is 3m with a refractory lining of thickness
10cm. Muffle thickness is 3cm. The combustion chamber spacing 1.5m and shell
thickness of 3cm (includes corrosion allowance). The overall shell diameter is
3.34m.
The depth of the reaction volume is 6m. The overall height of the furnace is
10.78m.
Furnace dimensions summary table 2.5
ITEM DIAMETER (m)
HEIGHT (m)
Work space (depth)
1x 3.0
1 x 6.0
Refractory thickness
6 x 0.1
6 x 0.1
Muffle thickness
4 x 0.03
4 x 0.03
Support (columns)
0.5 x 2
0.5 x 2
Combustion space
1.5 x 2
1.5 x 2
Shell thickness
0.03 x 2
0.03 x 2
OVERALL
7.28
10.78
24
2.10 COSTING OF MUFFLE FURNACE The cost of furnace is based on the furnace energy demand. Furnace duty = Heat added by fuel
= 18214.57kW Ce = CSn
Where Ce = purchased equipment cost, ₤.
S = characteristic size parameter, KW.
C = constant taken from table.
n = index for the type of equipment
= 220 x 18214.57 0.77 = 419,695.958
= ₤ 419,695.96 (ZK 292,347,614.90)
Exchange rate as at 23.11.05 ZK 6,969.57 is equivalent to £ 1.00 (British Pound) ZK 4,052.78 is equivalent to $ 1.00 (US Dollar)
25
CHAPTER THREE
3.0 COOLING OF HYDROGEN CHLORIDE GAS
NOMENCLATURE
Q heat load ,W
U overall heat transfer coefficient,W/m2o
C
A effective heat transfer area,m2
T temperature ,oC
FT temperature correction factor
Өln log mean temperature difference
G,G mass velocity
H heat transfer coefficient,W/m2o
C
hi inside(tube-side) heat transfer coefficient,W/m2o
C
ho outside heat transfer coefficient
Do outside diameter ,m
Di Inside diameter ,m
C OPH 2 heat capacity of water,Kj/KgK
C OPH 2 heat capacity of hydrochloric acid gas,Kj/KgK
Өcorr corrected temperature ,oC
m mass flowrate ,Kg/s
Re Reynolds’s number
µ viscocity,Ns/m2
M mass flowrate ,Kg/s
Ρ density,Kg/m3
∆P pressure drop, Kpa
U velocity, m/s
jf dimensionless friction factor
m
W
- viscosity correction factor
L,I length m
26
3.1 Introduction
Product gas temperatures from the reactor (furnace) exceed those allowable for
absorption. The method used for absorption varies with the temperature and
volume of the gas being processed. Some cooling is achieved in the pipeline
carrying the gas from the generating unit to the cooler or cooler-absorber. In the
cast-iron or steel flue carrying the high-temperature gas from the salt-sulphuric
acid process, some heat is removed by radiation to the atmosphere. In synthesis
plants using impervious graphite or silica coolers, the pipe may be cooled with
external water sprays.
Generally, the high-HCl low-volume gases are cooled in tubular equipment, and
the low-HCl high-volume gases by heat interchange with concentrated
hydrochloric acid in packed towers. For this design particular design the cooling
was achieved by a tubular exchanger known as the Trombone Cooler. Other
names for the trombone cooler include trickle coolers or cascade coolers.
Trombone coolers are S-shaped bends, consisting of a bank of standard pipes
one above the other in series and over which water trickles downward, partly
27
evaporating as it travels (see diagram below)
Trombone cooler Diagram 3.1
Tubes are made out of impervious ceramic material for cooling corrosive gases
at atmospheric pressure, such as HCl and NO2 that may be cooled by exterior
water or may be jacketed. Trombone coolers are also available in cross-flow
types and banks of impervious graphite tubes have been used which are
submerged in running water. Packed columns may also be used for the low
volume gases.
3.1.1 Advantages of the Trombone Cooler
Its pipes are made of ceramic material which offers a very good
resistance to high temperature corrosive gases.
It does not consist of a lot of components hence it is easier to design
than most other types of coolers.
28
It’s relatively cheaper to design compared to other types of coolers.
3.1.2 Industrial Applications
Trombone coolers have been used extensively in the following industries
heavy chemical
brewing
Coke
petroleum and
ice-making industries.
3.2 Process design
3.2.1 Heat Flow Through A Trombone Cooler
When calculating the heat flow through ceramics the resistance of the pipe wall
must be included. The basic design equation is
Q = UA∆T
Where,
Q = heat load,W
U = overall heat transfer coefficient,W/m2oC
A = the effective heat transfer area,m2
The trombone cooler presents two problems:
(1) the evaluation of the outside film coefficient and
(2) calculation of the cross flow true temperature.
Temperature difference in the Trombone Cooler
Bowman, Mueller, and Nagle have prepared correction factors FT by which the
true temperature difference ∆t can be obtained as the product
FT x LMTD
for both the return-bend and helical types of trombone arrangement.
29
3.2.2 Calculation of Outside Film Coefficient
In calculating the outside film coefficients, the following assumptions are made:
(1) no evaporation occurs from the surface of the water although it is exposed to
the atmosphere.
(2) half of the liquid flows down each side of the pipe in streamline
flow. The criterion of streamline flow is a Reynolds’s number,
'4G, of less than
2100,
where G = L
m
2, m is the water rate in kilograms per hour, and L is the length
of each pipe in the bank in meters. The equation for the transfer coefficients
within ±25% is given by the dimensional equation
h = 65
Do
G' 1/3
where Do is the outside diameter of the pipe in meters. When the value of the
Reynolds’s number exceeds 2100,it is to be expected that the rates will be
somewhat higher. Any appreciable evaporation will also increase the film
coefficient. Large fouling factors and low outlet-water temperatures are
recommended, particularly when the water has a large mineral content.
30
3.2.3 Heat load
It is desired to cool gaseous hydrochloric acid from the reactor temperature of
5370C to 60OC before it is fed into the absorption column. The mass flowrate of
the gaseous HCl is 2364 Kg/hr. In cooling the gas, the temperature of water is
raised from 20oC to 90oC.The process design was carried out as follows:
CHcl @Tav =
2
60537 = 0.84Kj/Kg
CH20 @ tav =
2
2090 = 4.2 Kj/Kg
Heat load of cooler,
Q = m OH2 x Cp OH2
x ∆T
= 3600
2364 x 0.84 x (537 – 60)
= 263.1KW
Cooling water flow,
mH2O = )( 12 ttm
Q
hcl
= )2090(2.4
1.263
= 0.89 Kg/s
= 3204 Kg/hr
Log Mean Temperature Difference(LMTD),
Өln =
)(
)(ln
)()(
12
21
1221
tT
tT
tTtT
=
)2060(
)90500(ln
)2060()90500(
31
=
40
410ln
40410
= 159oC
Correction factor FT,
R = 2060
60500
= 6.3
This value is out of range of fig.20(Kern pg728) so the reciprocal is used,
R
1= 0.16
S = 20500
20900
= 0.15,use RS = 0.95
@ (R
1, RS) FT = 0.9
Corrected temperature,
Өcorr = FT∆Өln
= 0.9 x 159OC
= 143.1oC
Tube-Side Coefficient:
Using 3in. IPS pipes(Kern Table11 Pg 844),
Flow area per pipe ,
ta = 7.38in2
All pipes in series therefore,
Total flow area = 144
38.7
= 0.052ft2 (0.0048m2)
32
Mass velocity,
Gt = ta
m=
0048.0
2364
D = 3.068in x 0.0254m/in = 0.078m
@ Tav = 280oC,
hcl = 0.25 x 10-4Nsm-2 {fig 15,p825}
Reynolds’s number,
Re =
tDG
Friction factor jH = 790
Thermal conductivity Khcl = 0.12W/oC {kern table 5,p801}
3/1
k
c= (0.84 x 0.25 x 10-4 / 0.12)1/3 = 0.06
inside coefficient,
hi =
3/1
k
c
a
kj
t
H
= 790 x
078.0
12.0x0.06= 72.9 W/m2oC
outside coefficient,
hio= hi x OD
ID = 72.9 x
50.3
068.3 = 63.9 W/m2oC
Overall heat transfer coefficient without fouling,
Uclean = ioi
ioi
hh
hh
=
)9.639.72(
)9.639.72(
x = 34.1 W/m2oC
33
Allowing a dirt coefficient of Rd = 0.01,overall coefficient with fouling becomes,
hd = 01.0
1 = 100
overall coefficient with dirt is given by,
Udirt = )(
)(
dclean
dclean
hU
xhU
= )1001.34(
)1001.34(
x
= 25.4 W/m2oC
Overall heat transfer area is given by
A = )( corrd xU
Q
= )1.1434.25(
101.263 3
x
x = 72.4m2 (779ft2)
from table 11 Kern p844,
external surface/lin ft = 0.917
therefore,
number of pipe lengths = )8917.0(
779 2
inx
ft = 106tubes
Outside Coefficient:
02Hm = 2988Kg/hr = 6587lb/hr
OH2 @ 55oC= 0.00034lb/ftsec = 1.22lb/fthr
34
Mass velocity,
G = L
m OH
2
2 = )82(
6587
x = 411.7kg/hrm2
Reinhold’s number,
Re =
'4G
= 22.1
7.4114x
= 1350 (streamline flow)
Outside diameter,
Do = 12
5.3 = 0.292 ft ftin 12.1{ }
Coefficient given as,
ho = 65
3/1
'
oD
G
= 65
3/1
292.0
7.411
= 729W/m2oC
35
3.2.4 Pressure drop
Tube-Side Pressure Drop
The pressure drop suffered by the gas in flowing through the entire tubular length
of the cooler is given as,
∆Pt = 8jf
id
L' ρ 2
2tu
m
w
Where,
∆Pt = pressure drop in tubes, Pa
jf = dimension friction factor = 1.7
L’ = effective pipe length = 8in x 90tubes
di = tube inside diameter= 3.068in
ρ = density of fluid,kg/m3 ≈ 600kg/m3
2
tu = tube-side velocity, m/s =
G = 0.0058m/s
m
w
= viscosity correction factor ,m= -0.14 for turbulent flow.
Therefore,
∆Pt = 8 x 1.7 x
3
890x x 600 x
2
0058.0 2
x 14.0
4
4
10215.0
1025.0
x
x
≈ 0.03 Kpa
36
3.3 Summary of process design:
Overall heart transfer coefficient = 25.4W/m2oC
Heat transfer area ,A =72.4m2
Tube-side coefficient, hi =72.9w/m2oC
Outside coefficient, ho =729W/m2oC
Total number of tubes required =106
Reynolds’s number, Re =1350
37
3.4 Mechanical design
Stoneware ceramic has the following physical properties which make it the best
choice for this particular construction:
Tensile strength = 28.6 Kpsi
Compressive strength = 325kpsi or 2241
Young’s modulus = 45 x 10-6
Shear Modulus=45 x10-6Mpa
Fracture toughness= 3.7Mpa m
Hardness = 1160 kg/mm2
With these properties the heat exchanger will have the following notable
attributes:
High durability
High resistance to corrosion
Low maintenance costs
38
3.5 Unit Costing
The material chosen to construct the tubes of the cooler is ceramic material
known as stoneware. From chemical engineering vol.6,table …,
cost per unit volume,m3,of stoneware = £620,
The cost of construction the equipment was performed as follows,
Volume of 1 tube = pi 4
)( 2
12 dd l
Where ,
l = length of one tube = 8in = (8 x.0.0254)m
therefore,
volume of 1 tube= 3.142 x 4
)078.0( 2
x (8 x 0.0254)
= 1.5m3
Total volume = 1.5m3 / tube x 106tubes
= 159m3
Purchase cost = 159m3 x £620
= £98,580
therefore,
Cost of construction = purchase cost x material factor
= 98,580 x 0.03
= £2957.40
39
The exchange rate for the pound by mid-1998 was taken as,
1£ = K6969.57
Hence,
Cost of construction = 2957.40 x 6969.57
= K20, 611, 806
≈ K 21, 000,000
40
CHAPTER FOUR
4.0 ABSORPTION COLUMN DESIGN
Nomenclature
A Heat transfer area
at Area of the tubes
a’t lin surface area of a tube
L(b) Baffle spacing
Cp Heat capacity at constant pressure
Ds Shell diameter
di Tube inside diameter
do Tube outside diameter
g Gravitational acceleration
Hgf Sensible heat of vapour
ho Heat transfer coefficient
j Heat transfer factor
Nb Number of baffles
N Number of tubes
P Total pressure
ΔPs Shell pressure drop
ΔPr Tube pressure drop due to tube resistance
ΔPt Tube pressure drop due to fluid flow
Q Heat transfer in unit time
Vv Vapour velocity
Vl Liquid velocity
W Mass flow rate of fluid
μ Viscosity of bulk fluid
ρ Fluid density
41
4.1 Introduction
Absorption or gas absorption is a unit operation used in chemical industry to
separate gases by washing or scrubbing a gas mixture with a suitable liquid. One
or more of the constituents of the gas mixture will dissolve or be absorbed in the
liquid and can thus be removed from the mixture.
In some systems this gaseous constituents forms a physical solution with the
liquid or the solvent and in other cases, it reacts with the liquid chemically the
purpose of such scrubbing operations may to the following:
i) gas purification
ii) product recovery
iii) production of solution of gases for various purposes
Gas absorption is carried out in vertical countercurrent columns. The solvent is
fed at the top of the absorber. Whereas the gas mixture enters from the bottom
Hydrochloric acid can be produced to any specification, ranging from technical or
chemical quality to foodstuffs quality. Weak acid can be fed into the absorber as
absorbing liquids and brought up to the required acid concentration.
Solubility of HCl in water
HCL is a relatively stable compound with slight evidence of dissociation at
temperatures above 1500°c it is completely miscible with water foaming a max
building azeotropic that boils at 108.58°c at 1 atm and contains 20.22%
Solubility of HCl in water at 760mmHg table 4.1
Temp 0 30 40 50 60
Solubility, g HCl / 100g H2O 82.31 67.30 63.07 59.59 56.10
The classical equipment for hydrogen chloride absorption was a system of
cellarius focrills or woulfe modern time’s use cooled – absorption towers.
The cooling – absorber is essentially a vertical shell and tube heat exchanger of
impervious graphite or glass such as the one shown below.
42
Diagram 4.1 Falling film absorber
Production of hydrochloric acid in a concentration of 1 to 40 % HCl acid from
chlorine and hydrogen, using water or weak hydrochloric acid as the absorbing
liquid. System of failing – film cooler – absorbers has been used for recovering
hydrogen chloride from gases as dilute as 5 – 10 % HCl. This is accomplished by
increasing the mass – transfer surface, by adding one or two absorbers and
possibly increasing the length of the tubes.
The absorption of HCl in water however generates heat as the process is highly
exothermic. This makes the falling firm cooler – absorber ideal.
However there is not enough information available for the design of the type of
absorber. Therefore a sieve plate water cooled tower will be opted for.
43
4.2 Process Design
Plate spacing
The overall height of the column will depend on the plate spacing. Plate spacing
from 0.15m (6in) to 1m (36in) are normally used. The spacing chosen will depend
on operating conditions.
Closed spacing is used with small – diameter columns and where head room is
restricted as it will be when a column is installed in a building.
4.2.1 Column diameter
The principal factors that determine the column diameter is the vapor from rate.
The vapor velocity must be below that which would cause excessive liquid
entrainment or a high pressure drop. The equation given which is based on the
well known sounders and Brown equation Lowenstein (1961) can be used to
estimate the maximum allowable superficial vapor velocity and hence the column
area and diameter.
Uv - must allowable vapor velocity
Lt – plate spacing
D – diameter
4.2.2 Selection of plate type
Principal factors to consider when comparing the performance of bubble cup,
sieve and valve plates are cost, capacity, operating, efficiency and pressure
drop.
Cost.
212
)()047.027.0171.0(
v
vlltlU tv
pvUu
VwD
4
44
Bubble cup plates are appreciably more expensive than sieve or valve plates the
relative cost will depend on the material of construction used for mild steel the
ratio is;
Bubble – cup: sieve: valve plates
3.0: 1.5: 1.0
Capacity.
There is little difference in capacity rating of the three types (the diameter of the
column required for a given flow rate) the ranking is sieve, valve and bubble.
Operating.
By operating range it means the range of vapor and liquid rate over which the
plate will operate satisfactorily (this is the most significant) some flexibility will
always be require in an operating plant to allow for changes in production rate
and to cover start – up and shut down conditions.
The ratio of the highest to the lowest is termed as the turn down ratio.
Bubble – Cups have a partial liquid seal and can therefore operate efficiently at
very low vapor rates.
Sieve plates rely on the flow of vapor through the hole to hold the liquid on the
plate and can not operate at very low vapor rates. But with good design sieve
plates can be designed to give a satisfactory operating range typically from 50 –
120%
Valve plates are intended to give greater flexibility than sieve plates at a lower
cost than bubble – cups.
Efficiency.
The Murphree efficiency of the three types of plates will be virtually the same
when operating over their design flow range and no real distribution can be made
between them.
Pressure drop.
The pressure drop for the design of columns. The plate pressure drop will
depend on the detailed design of the plate but in general. Sieve plates give the
45
lowest pressure drop followed by valve plates with bubble – cup giving the
highest.
Summary
Sieve plates are the cheapest and are satisfactory for most applications.
4.3 Material balance
For an inlet temperature of 60°c the solubility is 56.10g HCl / 100g H2O
Overall material balance around.
Given that the amount of product is 150 ton/day
As the basis and at a temperature of 60°c
hrkgdayhrs
tonkgton/6250
/24
/1000*150
46
Ratio since the solubility at 60°c is 56.10g HCl/ 100g water.
HCl: H2O
56.1: 100
0.561: 1
HCl in (y kg/hr)
Total ratio = 1+ 0.561 = 1.561
H2O into absorber (x kg/hr)
Assuming an efficiency of 95% for the HCl y will be as follows,
The HCl loss in the out let purge will therefore be.
hrkgy
y
/2.2246
6250*561.1
561.0
hrkgx
x
/84.4003
6250*561.1
1
hrkgy
y
y
/4.2364
095
2.2246
2.224695.0
HCl.2H2O
(6250
kg/hr)
HCl
Y kg/hr
Water
X kg/hr
47
Summary of outcome of calculations diagram 4.2
4.4 Equation of the operating line
Assuming is solubility
hrkg /2.1182.22464.2364
48
nn
nn
nnnn
nnnn
nnnn
yy
xx
G
L
xxGyyL
GxGxLyLy
LyGxGxLy
1
1
11
11
111
)()(
49
Material balance
Based on the figure above
Equation of the absorber is them and by
Dividing through out by G
Therefore equation of the operating line becomes
Were liquid L = 6250kg/hr and gas G = 2364.4 kg/hr
Therefore the equation reduces to
Values obtained from the above equation. And these are plotted on a graph.
X 0.1 0.5
Y 0.389 0.546
LB
LxBxVyo
11
101
110
110
LxGyLxGy
LxLxGyGy
LxGyLxGy
nn
nn
nn
01
101
)( yxxG
Ly
xG
Lyx
G
Ly
nnn
nn
01 yxG
Lyn
35.064.2
4.2364
6250
1
01
xy
yxy
n
n
50
The above graph gives two stages
Mechanical design
Based on the vapor flow rate of 2364.4kg/hr
Therefore basis = 2364.4 kg/hr
4.4.1 Column diameter Calculation
Most of the above factors that affect column operation are due to vapor flow
conditions: either excessive or too low. Vapor flow velocity is dependent on
column diameter. Weeping determines the minimum vapor flow required flooding
determines the maximum vapor flow allowed, hence column capacity. Thus if the
column diameter is not sized properly, the column will not perform well. Not only
will operational problems occur, the desired operational duties will not be
achieved.
51
State of Trays and Packings.
Since actual number of trays required for a particular separation duty is
determined by the efficiency of the plate and the packings, if packings are used.
Thus any factors that cause a decrease in tray efficiencies are affected by fouling
wear and tear, corrosion and the rates at which these occur depends on the
properties of the liquid being processed. Thus appropriate material should be
specified for tray construction.
Weather Conditions.
Most distillation columns are open to the atmosphere, although many of the
columns are insulated, changing weather conditions can still affect the operation.
Thus the reboiler must be appropriately sized to ensure that enough vapors can
be generated during cold or windy spells and that it can be turned down
sufficiently during hot seasons. The same applies to condensers.
These are some of most important factors that can cause poor distillation column
performance. Other factors include changing operating conditions and throughputs,
brought about in changes in up stream conditions and changes in the demand of the
products. All these factors including associates control systems should be considered at
design stage because once a column is built and installed nothing much can be done to
rectify the situation without incurring significant costs. The control of distillation column
will be looked at later
Column diameter
Were Vm – is the maximum allowable flow
pL – liquid density
UL – vapor calculated
Therefore the column diameter will be
Column height (m)
It is given by the number of plates x spacing + 2 x spacing
The number of plates is 2
52
dimensions diagram 4.3
Mechanical description table 4.2
Item Actual calculated value Nearest number estimation
Column diameter (m) 0.9605m 1m
Column height (m) 4.8m 5m
Number of plates 2 2
4.5 Unit Costing and Evaluation
mh
h
h
8.4
4.24.2
2.122.12
53
Ce = CSn
Where
Ce – purchased equipment cost
C – cost constant from appendix 1
S – characteristic size diameter appendix 1
n – index for that type of equipment
Data (adsorption column)
Dc – 0.96309 m
Hc – 4.8m
Area of column therefore A (m2)
Cost of shell
Material factor at (s.s) stainless steel = 2.5
Cost = 7.5 x 1000
= $ 7 500
Therefore cost
= 7500 x 2.5
= $ 18 750
Cost of the two plates
From appendix 2 (fig 6.7)
Bare cost = $ 1 600
Material factor – 1.7
Installed cost = bare cost + material factor
= 1600 x 1.7
= $ 2 720 / plate
= $ 2 720 x 2
2631.3
4
8.496309.0
4
mA
A
dhA
54
= $ 5 440
Total cost for the absorption column will be
Cost of shell + cost of plates
= 18 750 + 5 440
= $ 24 190
Conversion in Kwacha based Bank Of Zambia exchange rate obtained from The
Time of Zambia news paper dated 02/11/2005
$1 – K4 321.11
= 43211.1 x 24190
= K 104,527,650.9
= K 104.53 million
55
CHAPTER FIVE
5.0 SITE SELECTION AND SAFETY
5.1 Occurrences of raw materials
Sodium chloride occurs in solution in sea water.
Also occurs in dry deposits as rock salt and brine.
There are sodium chloride deposits in Kaputa and Mkushi districts in
Zambia It can be acquired from neighboring Congo D.R., Mozambique
and Angola.
Sulphuric acid can be obtained from Mbwana Mkubwa acid plant in Ndola
or KCM acid plant in Kitwe.
5.2 Site selection
The plant will best be located in Ndola, because of the following factors;
It is a central town in terms of the acquisition of factors of production; raw
materials, labor and transport net work.
Sulphuric acid will be acquired from Bwana Mkubwa and Konkola Copper
(Kitwe) mines.
Sodium chloride deposits in Kaputa and Mkushi districts in Zambia are
accessible and easily are transported to Ndola.
The energy source electricity, coal, diesel or oil is easily accessible
because of the already existing national power grid and both the rail and
road network.
It will be located near Kafubu River as source industrial water and for
treated wastewater disposal.
Since Ndola is a central town ,our product and by product can find ready
market in the following industries:
The main product hydrochloric acid will find market in the mines, cement
industry, textile industry, and leather industry.
The by-product, sodium sulphate which is used in glass manufacturing, for
example the coming back into life of Kapiri glass factory.
56
Sodium sulphate is used by detergent manufacturing companies as a
‘builder’ and in dyeing to standardize dyes, therefore Ndola is nearby for
marketing.
5.4 SAFTY FACTORS
A report prepared By: U.S. Office of Air Quality Planning and Standards, Air
Quality Strategies and Standards Division, Integrated Strategies and Economics
Group, Research Triangle Park, North Carolina out lines the hazardous
associated with HCl gas and acid.
There are Regulatory issues such as national emission standards for hazardous
air pollutants (NESHAP) for hydrochloric acid (HCl) production facilities, including
HCl production at fume silica facilities. The EPA has identified these facilities as
major sources of hazardous air pollutant (HAP) emissions; primarily HCl.
Hydrochloric acid is associated with a variety of adverse health effects. These
adverse health effects include chronic health disorders (e.g., effects on the
central nervous system, blood, and heart) and acute health disorders (e.g.,
irritation of eyes, throat, and mucous membranes and damage to the liver and
kidneys).
The production processes NESHAP affect are processes that routes a gaseous
stream that contains HCl to an absorber, thereby creating a liquid HCl product.
Among these various processes are:
i) Organic and inorganic chemical manufacturing processes that produce
HCl as a byproduct;
ii) The reaction of salts and sulfuric acid (Mannheim process);
iii) The reaction of a salt, sulfur dioxide, oxygen, and water (Hargreaves
process);
iv) The combustion of chlorinated organic compounds;
v) The direct synthesis of HCl through the burning of chlorine in the
presence of hydrogen
It is important to note that most HCl production is as a by-product of other
processes such as aliphatic and aromatic hydrocarbon chlorination, the
57
phosgenation of amines for isocyanates, and halogenations for making
chlorofluorocarbons. Only about 5 percent of HCl is produced as primary product.
Production from the U.S. HCl industry is roughly 4.2 million tons/year as of 1997.
Most of the production is captive capacity; that is, the HCl is produced as an
intermediate product to be used in final output. Given that about 5 percent of HCl
produced in the U.S. is as primary product, this means that only about 200,000
tons of primary HCl output is generated in a typical year.
It’s therefore imperative that safety attire be emphasized at all times, it the
responsibility of there company as well as the workers for such a plant to ensure
that safety attire are worn, in addition to the regulatory bodies assigned to the
tusk.
58
CHAPTER SIX
6.0 PROJECT EVALUATION AND COST
6.1 Introduction
The use of HCl in the production of other chemicals is the major way in which
HCl is used in the U.S. Thirty percent of HCl produced in the U.S. goes into
production of other chemicals. The next most common uses of HCl are steel
pickling (20 percent), oil well acidizing (19 percent), and food processing (17
percent). Other uses for HCl include semiconductor production and regeneration
of ion-exchange resins for water treatment.
The U.S. imports and exports very little HCl. In 1997, the U.S. imported 85,000
tons of HCl, or only 2 percent of U.S. capacity. During that same year, the U.S.
exported 60,000 tons of HCl or only 1.5 percent of U.S. production capacity.3
hence, the U.S. imports as much or more HCl as it exports, but the trade balance
is negligible compared to the output consumed within the U.S. Most of this trade
is with Canada.
The growth in U.S. HCl production averaged about 4.2 percent per year from
1993 to 1998. Growth has averaged roughly 3 percent per year from 1985
through 1998, so there has been some increase in production growth in the
decade of the 1990's.4 Prices for HCl have increased considerably from 1992 to
1998. These prices generally ranged from $40/ton to $57/ton in 1992 and 1993,
but rose to over $90/ton in 1998 due to railroad disruptions that occurred late in
1997 and continued into 1998. Projected growth is expected to be about 2.5
percent per year through 2003, though this amount could be an underestimate if
continued strength in oil drilling leads to additional demand for HCl.
As of 2003 the price of HCl acid stood at $92.25 /ton therefore the estimated
revenue from the sales of HCl acid is about
$92.25 /ton x 150 ton/day x 350 days/year = $4, 843, 125. /year
In kwacha $4, 843, 125 X K4, 052.00 = K19, 624, 342, 500. /year
59
6.2 Fixed and installation cost
Using the factorial method of overall project estimation we can estimate the cost
of this project and determine of it’s viable or not. This is based on the following,
Taking into consideration of the PCE at $ 36,340.87
item PCE
f1 – equipment erection 0.4
f2 – Piping 0.7
f3 – instrumentation 0.2
f4 – Electrical 0.1
f5 – Building process 0.15
f6 – Utilities 0.5
f7 – storage 0.15
f8 – site development 0.05
f9 – ancillary building 0.15
Total 3.40
PCE which is the purchased cost is total of cost of all the major units
PCE = $ 36,340.87
PCE = K 417.88m
6.2.1 Physical plant cost (PPC)
PPC = PCE (1+ f1 + …. + f9)
PPC = 36,340 x 3.40
PPC = $ 123,556
6.2.2 fixed capital cost (FCC)
Item PPC
f10 – design and engineering 0.3
f11 – constructor’s fee 0.05
f12 – contingency 0.1
Total 1.45
60
FCC = PPC x 1.45
FCC = 123,556 x 1.45
FCC = $ 179,156.2
Simple mathematics
6.2.3 Cost (expenditure)
Cost (expenditure) = $ 179,156.2
Or = 179,156.2 x 4053 = K 726,119,268.
K 726.12m
This is what it will cost just the project to start running and buy all the equipment
needed. Plus variable cost which are about 10% of FCC = $ 17,215.62
Therefore total cost for one year = $ 196,371.82
6.2.4 Income per year
From HCl sold in one year = $4, 843, 125. /year
The by product sold in one year will be
Na2SO4 = $ 60 / ton
Production is at = 4.6 ton/hr or 39,744 ton/year
Therefore 39744 ton x $ 60 = $ 2,384,640/ year
Total income is $ 7, 227, 765/year
The pay back time for this project will be in the first month of sales and
production. See summary table below.
61
Summary table cost evaluation table 6.1
Expenditure for given month sales or income for given month
Month/year Fixed cost $ Variable cost $ Sales $ Operating cost $
1m 19,259.34 963 0 0
2m 104,297.0 10,430 0 0
3m 36,340.87 3,634 0 0
4m 50,800.00 25,343 602,313.75 12,046.28
5m 0 25,343 602,313.75 12,046.28
6m 0 25,343 602,313.75 12,046.28
2y 0 433,665.9 7,227,765 72,277.65
3y 0 433,665.9 7,227,765 72,277.65
4y 0 433,665.9 7,227,765 72,277.65
5y 0 433,665.9 7,227,765 72,277.65
6y 0 433,665.9 7,227,765 72,277.65
7y 0 433,665.9 7,227,765 72,277.65
Total cost 210,696.34 2,693,052. 45,173,531.25 469,804.74
Grand total Expenditure = $ 3,373,553.08 Income = $ 45,173,531.25
Profit Up to year 7 $ 41,799,977.92
The pay back time for this project is 4 months just in the first month of sales
and production. with the total investment being $ 263,112.62 for the plant to be
complete and start running.
Therefore it’s a viable project with a good pay back time.
62
Process design summary table 6.2
FLOW- RATE(kg/h)
ENERGY (kW)
TEMP. oC)
PRESSURE (atm)
FURNACE
Sodium chloride 3774.13 -14804 50 1.0
Sulphuric acid 3174.13 -7981.48 20 1.0
HCl(gas) 2363.4 -3322.04 537 1.5
Sodium sulphate 4599.2 -1248.87 527 1.0
FUEL (HFO) 1528.49 18214.57 6.5
COOLER
Process Stream: -
HCl (gas) (inlet) 2363.4 - 537 1.5
HCl (gas) (outlet) 2363.4 - 60 1.4
Service Stream:
H2O (inlet) 3204 - 22 1.0
H2O (outlet) 3204 - 90 1.0
COMPRESSOR
HCl (gas) in 2363.4 - 60 1.4
HCl (gas) out 2363.4 - 61 1.5
ABSORBER
HCl(gas) 2363.4 - 60 1.5
H2O 4003.98 - 22 1.0
HCl (vent) 118.2 - 62 1.1
HCl(aq) 6250.0 - 60 1.5
63
Mechanical design and costs summary table 6.3
Item/ units units Furnace Cooler Absorber
Diameter m 7.28 0.0078 0.9605
Height m 10.78 4.8
Length m - 0.02032 -
Area m2 - 72.4 -
# Tubes Nil - 106 -
# Plates Nil - - 2
Material of
Construction
Nil Refractory
brick & steel
Stone ware
ceramics
Stainless
steel
Cost of unit $ 6,969.57 5,181.3 24,190
Cost of unit K (m) 292.35 21.0 104.53
Sales HCl K / year 19,629,185,625m
Sales Na2SO4 K / year 9,664,945,920m
Total sales K 29,294,131,545m
64
CONCLUSION
To design a plant which will be producing 150tpd HCl (20oBe’) from sodium
chloride and H2SO4 (60oBe’), the salt-sulphuric acid process has been adopted
because of the specified raw materials in the question. Although there are three
other methods used to produce HCl but there use in the question is not favored
because of other raw materials used in other processes.
The design process adopted for this design question uses three (3) main units
and service equipment namely the furnace (reactor), the cooler and the absorber
and a compressor as a service unit. The muffle furnace is operated at 500 to
550oC in the work space heated by indirect heat from the combustion chamber
operating at temperature as high as 1205oC. The furnace is operated at 1atm.
Heavy fuel oil is suitable for the muffle furnace. The reaction volume of the
reactor is 52.8m3 and the residence time is 18.3minutes. The duty of the furnace
is 18214.57kW. The cost of the furnace based on the energy demand is
£419,695.96 (ZK 292,347,614.90).
HCl gas leaves the furnace at 537oC temperature which exceeds that suitable
absorption temperature of 60oC. For this particular design the cooling has been
achieved by a tubular exchanger known as the Trombone Cooler and operates at
atmospheric pressure. Total heat transfer area for the trombone cooler is 72.4m2
giving a total number of 106 tubes. The cost of the trombone cooler is £ 2,957.40
(ZK 21,000,000.00).
At the cooler there is a pressure drop in the flow of HCl gas and therefore a
compressor has been used to compensate for pressure loss prior to absorption
form 1.4atm to 1.5atm. Gas absorption is carried out in a vertical countercurrent
column. The solubility of HCl in water at 60°C is 56.10g HCl/ 100g water. The
column diameter is 0.96m and height of the absorber is 4.8m and the number of
plates is 2. The cost for the absorption column is K 104.53 million.
Plant location has been influenced by raw material availability, other factors of
production and main product and by-product market forecast. Other than
importing sodium chloride from Congo DR, Mozambique and South Africa, it can
65
also be sourced locally form Kaputa and Mkushi districts. Sulphuric acid will be
sourced from Mbwana Mkubwa acid plant in Ndola or KCM acid plant in Kitwe.
The plant will best be located in Ndola, because it central to sources of raw
materials and product market. Environmental, safety and health (SHE) issues
have been considered for instance plant location is far from the residential areas
because of the dangers hydrogen chloride gas and acid pose on human tissue,
potentially damaging respiratory organs, eyes, skin and intestine. Plant location
near the stream which provides service water through out the year makes it
possible to treat waste streams before they are disposed to the environment.
Quality assurance of the project has been taken into account by incorporating a
process control system to monitor that specific operating conditions are adhered
to, namely, raw material flow rates, operating temperature and pressure at the
furnace, the temperature of process and service streams at the cooler and the
flow rates and temperatures of water and HCl gas at the absorber.
HCl acids attracts a wider application in industry among these include;
Regeneration of ion exchangers resins. pH control in food, pharmaceutical,
drinking water and neutralizing waste streams. It is used to control the pH of the
process streams. Pickling is an essential step in metal surface treatment. The by-
product sodium sulphate also attracts a wider application in industry among
these include glass manufacturing, detergent manufacturing used as form builder
and in some types of cement it is used for cement setting property a substitute
for gypsum.
Using the factorial method the overall project cost has been estimated taking into
account the costs for equipment erection, piping, instrumentation, electrical,
building process, utilities, storage, site development and ancillary building, to
determine its viability.
The total investment cost is $ 251,066.34 (ZK 1,017,320,809.68) and operating
cost for plant start up is $12,046.28 (ZK 48,811,526.56). The plant grand total
cost is $263,112.62 (ZK 1,066,132,336.24)
The unit price of HCl is $92.25 /ton and the total HCl sold in one year is $4, 843,
125. /year (ZK 19,624,342,500.00/year). The unit price of Na2SO4 (by-product) is
66
$ 60 / ton and the total Na2SO4 is $ 2,384,640/ year (ZK 9,662,561,280.00/year).
The projected sales volume gives a grand total income of $ 7, 227, 765/year
(ZK 29,286,903,780.00/year). The pay back time for this project is 4 months just
in the first month of production and sales. Therefore, this project is viable.
67
RECOMMENDATIONS
A detailed analysis of this report reveals that the costs of implementation of this
project are outweighed by the various benefits that it has to offer hence the
project team recommends this project as a viable project and worth undertaking.
This project has the potential to add major growth to the Zambian economy.
Therefore, if this project were to be undertaken, the project team recommends a
subsidy, by government, on certain materials of construction. This can be
achieved by reduction of import duty on those materials that have to be imported
from outside the country.
Additionally the team also recommends that government makes available
research scholarships for Zambian chemical engineers to expose them to heavily
industrialized countries where technology such as HCl production is a practical
reality. This would result in highly competent Zambian engineers and hence get
rid of the dependency on expatriates.
As with any other plant design, this undertaking is heavily material dependent
hence special factors pertaining to site selection have to be considered in order
to optimize on transportation costs. The plant must be centrally located in terms
of easy access to market as well as easy access to raw materials and thus Ndola
has been recommended.
Safety factors, however, should also to be observed as pertaining to the location
of the plant, bearing in mind that hydrochloric acid is a hazardous air pollutant
(HAP) associated with a variety of adverse health effects. Therefore, the plant
must be located at a healthy distance away from residential areas to allow for
dilution in case of accidents and effluent and emission standards should strictly
be observed.
68
To the department, we would first of all like to commend you for a job well done
on the supervision and guidance of the projects, and at list we are now seeing an
increase in the number of project the are practical and an involvement of
industries in the projects, this is good as it will increase cooperation between the
University and the industry.
We would like to recommend the following;
i) Some of the small scale projects done by students are manageable
financially; the department should try and actually do some of these
projects for income generation.
ii) We recommend that the projects done by previous students be made
available to the student by means of a department library or the library it
self, after all what power does knowledge have if it can’t be shared.
All in all we commend you for job well done given the conditions.
69
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71
APPENDIX
Appendix 1
Muffle Furnace
72