HYSYS_SIMULATION_REPORT_alshaoubka_m2.docx

King Fahd University for Petroleum and Minerals Department of Chemical Engineering Senior Project

FORMALINE PRODUCTION PROC HYSYS SIMULATION

Term – 121

Abbas Al-Salboukh 200764950 Mostafa Al-Osaif 200779610 Mohammed rajal Mohammed moaish

GROUP:C 21/11/20

Table of Contents: I. II. III. 1

Summary Introduction Formalin Production Process Process Description a) compressor b) c) d) e) f)

reactor type and methanol conversion

Flash feed condition Distillation column Recycle of benzeneAbsorber Efficiencies of compressor, pumps and heat exchanger pressure difference

2 . Alternative Process Description IV.

Justification of change in the process 1. Adding cooler before the reactor 2. Adding cooler after reactor 3. Removing air heater

V. VI. VII.

Explained Differences and Comparing. Conclusion Appendixs

I. Summary: Process simulation is a model-based representation of chemical, physical, biological, and other technical processes and unit operations in software. Basic 1

prerequisites are a thorough knowledge of chemical and physical properties of pure components and mixtures, of reactions, and of mathematical models which, in combination, allow the calculation of a process in computers. Process simulation software describes processes in flow diagrams where unit operations are positioned and connected by product streams. The software has to solve the mass and energy balances to find a stable operating point. The goal of a process simulation is to find optimal conditions for an examined process. This is essentially an optimization problem which has to be solved in an iterative process. Process simulation always uses models which introduce approximations and assumptions but allow the description of a property over a wide range of temperatures and pressures which might not be covered by real data. Models, also, allow interpolation and extrapolation - within certain limits - and enable the search for conditions outside the range of known properties. This report shows the process simulation of formalin production, describes the process that is done by HYSYS, and shows the comparison between the hand calculation results and HYSYS results. For example, the flow rate of the fresh methanol feed was calculated by hand to be 78.56 Kmol/h, unlike HYSYS, which calculated the flow rate to be 77.24 Kmole/h after adjusting some data.

II. Introduction: This report focuses on the task of simulating the formalin production process. The program used for simulation is HYSYS ASPEN which is available at KFUPM computers Labs. The report is divided into two sections. The first one describes the 2

simulated process and its alternative. The third one compare the results obtained from the simulation with that obtained in the mass and energy balance.

III. Formalin production process: Here the simulation was done using the basic PFD with little details using PengRobinson as a fluid package. Below are the process description and the details of additions and assumptions of the basic PFD.

1. Process Description: Formaldehyde is manufactured by reacting methanol over the catalyst as follows:

Main reaction

:

CH 3OH  12 O2  HCHO  H 2O

methanol Side reaction

:

formaldehyde

CH 3OH  HCHO  H 2

methanol

formaldehyde

The catalyst used in formalin production is bulk density with 1500 kg catalyst/m3 of reactor volume with void fraction of 0.5 . The catalyst particles are spherical, with a 1 mm diameter. Fresh methanol is pumped as liquid to increases the driving force to 3 atm .Then, methanol is heated to 150 C using water with inlet of 200C and outlet of 150C .Pure air (as a mixture of oxygen and nitrogen) is compressed to equalize the pressure with the methanol stream . Before introducing methanol and the compressed air to the reactor we mixes then at 3 atm .The reaction is taken place inside the conversion reactor to have single pass conversion of methanol to be 87.4%.The vapor product of the reactor has temperature of 745C and 3 atm .Then we cooled the product to 200C using a cooler .After the pressure is dropped to 1 atm using a pressure control valve ,it enter the absorber .80% of the formaldehyde is absorbed using water at 30C and rate of 100 Kmol/hr in 3 trays 3

absorber .the liquid outlet is heated to 102C before entering the destination column . In the destination column 93% of the methanol inlet is distillated while the remaining is recycled to be mixed with the fresh methanol.in the bottom formaldehyde is mixed with deionized water at 30C and 95.45 Kmol/hr to have formalin ( 37% of formaldehyde ) . Then it cooled to 40C before storage.

Figure 1: Process Description

\

a) Compressor : In the figure of the process flow diagram, it shows that a feed of O2 and N2 were mixed in the mixture in the compressor, and then used in the reactor. The initial condition is 25oC and 101.3 kpa , this unit operation yield to a mixture at 168.9 oC and a pressure of 3 atm , also the pump work used was calculated to have 9.269E5 kJ/hr . Another important parameter of this unit is the efficiency which equal to 75%.

b) Reactor type and methanol conversion : In this problem we choose a converter reactor for the process because the statement provides the conversion percent. The condition of the inlet feed was 4

161oC and 3 atm, also the molar flow rate is equal to 310.7 Kmol/hr. As the problem state that two reaction takes place in the reactor we found that 77.7 of the conversion from reaction 1 and 9.7 from the second reaction. Also we got that the total conversion is 87.4% and the selectivity as mentioned in the problem to be 9:1. The product composition steam has 0.1832 mol% of formaldehyde with flow rate of 343.7 Kmol/hr at 745.4 oC and the pressure at 3 atm.

c) Flash feed condition : Before the final operation of the process the feed mixture enters the distillation column at 102oC and 1 atm .the feed enter the distillation in stage number 3 with flow rate of 104.8 Kmol/hr.

d) Distillation Column : The result of the simulation of the process provides that the purity is equal to 93 % using 10 trays, whereas the problem state that the purity is equal to 98 %. And the reflux ratio is 1.2 to the condenser. Moreover the pressure in the boiler and the partial condenser is 1 atm. The composition outlet steam has 0.5915 mol% of formaldehyde with flow rate of 79.15Kmol/hr.

e) Recycle : An important step in the process is to recycle some of the methanol to the feed inlet to reduce the amount needed of the raw material and that will help to minimize the cost. Also the molar composition of recycle stream found to be 5

0.0166 methanol , 0.1377 formaldehyde and 0.8458 H2O at 68.3C and 25.62Kmol/hr.

f) Absorber : One of the important unit in the process is the absorber, the feed is cooled up to 200oC and the valve is used to decrease the pressure from 3 to 1 atm. we used a 3 trays absorber. The upper feed stream is pure water at temperature of 30 oC and 138 Kpa . The outlet of the convertsion reactor is the inlet of the absorber. Also all of the N2 , H2 and O2 are all in the off gas stream . The mole fraction of the bottom stream 0.0663 methanol, 0.4805 formaldehyde and 0.4532 H 2O. the flow rate was 104.8Kmol/hr at 78.92C and 1 atm.

g) The efficiency of the compressor ,pumps and heat exchanger pressure difference : In the process we use pump (p-101) to increase the pressure to 3 and have enough driving force to enter a heat exchanger (E-101) which vaporize the methanol by increasing the temperature to 150C with duty of 4.048*10 6 kJ/h and Ft factor of 0.807. Heat exchanger (E-102) used to cool the outlet of the reactor to 200C with duty of 7.142*106 kJ/h. Another Heat exchanger (E-103) used to heat the outlet of the absorber to 102C with duty of 1.645*10 6 kJ/h .before storing the formalin it beenig cooled to 40C using Heat exchanger (E-104) with duty of 3.91*105 kJ/h.

2. Alternative Process Description: Here the simulation was done using the alternative PFD which is similar to the basic one with the difference of removing the destination column. As result of this action the recycle is removed. The process description and the details of additions 6

and assumptions of this PFD are the same as the basic PFD exab that a coolar is added before the reactor to cool the methanol and compressed air to 48.95C . The outlet temperature of the reactor is adjusted to 103.4C to have 37% of formaldehyde as a liquid product of the absorber. This alternative is important in terms of utility which is translated in terms of money. The use of cooler before the reactor will add expense to the budgeted. Also, the duty needed to cool the steams before and after the reactor is vary huge which is about 1754 KW in order to have 37% of formaldehyde as a product.

Figure 2: Alternative Process Description

IV.

Justification of change in the process 1-Adding cooler before the reactor : A cooler has been introduce for stream# 8 in order to reduce the temperature

that entered the reactor because it was causing a problem where increasing the 7

temperature in stream#8 lead to increase in stream # 9 temperature. The temperature result without the cooler rise up to 900ºC which is very critical where it is need special martial of construction and will increase the production cost.so, adding the cooler will reduce the temperature entering the reactor stream #8 and cause the temperature in stream #9 to decrease to 379 ºC . 2- Adding cooler after reactor: A cooler has been adding after the reactor to decrease the temperature on stream #9 as preparation for the absorption process where the cooler reduce the temperature of absorber feed to 200 ºC instead of 272.5 ºC. if we don’t use the cooler a lot of formaldehyde and methanol will go with the off gas as waste which impact the environment and cost a lot of money. 3-Removing air heater: Heater E-102 has been removed from the process because there is no need for it since the temperature of the feed gas is increases in the compressor from 25 ºC to 168.9 ºC which is acceptable for the process .so, removing the air heater will not affect the process and will save energy and money. V.

Explained Differences and Comparing. This part compares and explained differences between the results obtained from

mass and energy balance with that obtained from HYSYS simulation with the basic PFD only. It is expected that there are some differences but also there are a lot of similarities. Table 1 below shows the comparison and discusses it in terms of the reasonability.

8

In the problem given, there has been some changes in terms of equipments and streams (adding / removing). Due to that, some flow rates, which have been calculated with certain assumptions, have some errors when they get compared with the HYSYS results. Starting from the beginning of the simulations, the flow rate of the streams 3, 4 and 6 is 91.44 kmol/hr, which equals to the flow rate assumed in the hand calculation. This equality is caused because in the HYSYS and the hand calculations the assumption of the basis was the same flow rate. The same thing can be applied to stream 1, 5 and 7 which have the flow rate of 217.6 kmol/hr. As a result of that, the flow rate of stream 8 is the same in both the hand and the HYSYS calculations. But stream 2, in the HYSYS, has the flow rate of 66.39 kmol/hr, while using the hand calculation stream 2 has a flow rate of 78.56 kmol/hr. This different in the calculations has been caused by the difference in the recovery value of formaldehyde in the distillation column. Also, stream 15 has some differences between the HYSYS calculations and the hand calculations caused by the difference in the recovery value. Streams 9 and 10, using HYSYS, have a flow rate of 341.5 kmol/hr, while using the hand calculations the flow rate is 353.5 kmol/hr, which isn't that much difference. This difference in the flow rate is caused by the difference in the flow rate of the recycle stream (stream 15).

9

Stream 11, in HYSYS, has a very low value (100 kmol/hr) compared to the hand calculations (256.5 kmol/hr). This big difference caused because if stream 11 flow rate increases, the composition of the formaldehyde in stream 13 (absorber's stream outlet) would be lower than 0.3 wt%. As a result of this big difference in the flow rate of stream 11, the remaining streams (13, 14, 16, 17, 18, 19 and 20) have a very big difference in HYSYS calculations compared to the hand calculations. In addition, this difference can be done because in the hand calculations there were a lot of assumptions which are rejected (or not applied) by the HYSYS.

VI.

Conclusion: To sum up, material and energy balance calculations are shown for the process

with detailed information about the composition of all streams as well as the duty of equipment. The objective of the process is to produce formalin by reacting methanol over an Ziegler-Natta catalyst with maximum rate of return on investment. In order to produce this amount of formalin we should have a full knowledge about what we are required to have in each stream to produce this amount which calculated using the material balance.

10

VII. Appendix’s : A. Streams Summary Table Table A.1: Streams Summary Table. B. Equipment Summary Tables Table B.1: Hear Exchangers. Table B.2: Reactor Column. Table B.3: Pumps. Table B.4: Absorber Column. Table B.5: Distillation Column. Table B.6: COMPRESSOR. Table B.7: Valve.

A. Streams Summary Table 11

Table 1: Streams Summary Table. Name 1 Vapor / Phase Fraction 1 Pressure [Kpa] 101.3 Temperature [ºC] 25 Molar Enthalpy 190.1 [kJ/kmole*ºC] Molar Flow [kmole/h] 217.6 Composition [%Mole ] Methanol 0.0000

2 0 101.3 25

3 0 304 33.81

4 0 304 33.89

5 1 304 168.9

6 1 304 150

8 0.836 304 161.0

9 1 304 745.4

46.69

51.14

58.22

192.6

178.3

194.1

218.6

67.64

93.03

93.03

217.6

93.03

304.0

330.1

1.0000

0.7316

0.0000

0.2191

0.0250

0.0112

0.1832

0.0265

0.2164

0.1472

0.0561

0.0000

0.0192

0.5534

0.5002

14 0.4041 101.3 102

0.7316 0.037 5 0.230 9 0.000 0 0.000 0 0.000 0 15 0 101.3 68.30

16 0 101.3 101.6

18 0 101.3 30

Formaldehyde

0.0000

0

0.0375

Water

0.0000

0.0000

0.2309

Oxygen

0 .201

0.0000

0.0000

Hydrogen

0 .0000

0

0.0000

Nitrogen

0 .7899

0.0000

0.0000

11 0 138.0 30

12 1 101.3 74.72

0.7316 0.037 5 0.230 9 0.000 0 0.000 0 0.000 0 13 0 101.3 78.92

7.823

179.4

84.17

128.5

36.78

106.0

7.823

100

338.9

104.8

104.8

25.39

79.15

95.45

0.0000 0.0048

0.0663

0.0000

0.4805

0.0167 0.137 3 0.846 0 0.000

0.0824

0.0000

0.0663 0.480 0.0373 5 0.453 0.3744 2 0.0569 0.000

0.5915

0.0000

0.3261

1.000

0.0000

0.0000

Name 10 Vapor / Phase Fraction 1 Pressure [Kpa] 101.3 Temperature [ºC] 199.8 Molar Enthalpy 198.9 [kJ/kmole*ºC] Molar Flow [kmole/h] 343.7 Composition [Mole %] Methanol 0.0250 Formaldehyde Water Oxygen

0.1832

0.1192 1.0000 0.0561

0

0.0000 0.0000 0 .2101 0 .0000 0 .7899

0.4532 0.0000

12

Hydrogen Nitrogen

B.

0 0.000 0.0192 0 0.0195 0.0000 0 0.5002 Name 0.0000 0.507119 0.000 0.0000 20 0 Vapor / Phase Fraction 0 0 Pressure [Kpa] 101.3 101.3 Temperature [ºC] 67.31 40 Molar Enthalpy 53.97 45.44 [kJ/kmole*ºC] Molar Flow [kmole/h] 174.6 174.6 Composition [%Mole ] Methanol 0.0374 0.0374 Formaldehyde 0.2681 0.2681 Water 0.6945 0.6945 Oxygen 0.0000 0.0000 Hydrogen 0 .0000 0.0000 Nitrogen 0 .0000 0.0000

0 0.000 0 0.000 0

0.0000

0.0000

0.0000

0.0000

Equipment

Summary Tables Table B.1: Hear Exchangers. Name E-101

Duty[kJ/h] 4.048 E+006

Pressure Drop[Kpa] 0

Delta T [C] Tube side=116.1

E-102 E-103 E-104

7.142 E+006 1.645 E+006 4.048 E+005

0 0 0

shell side=-50 -545.4 23.08 -27.31

Table B.2: Reactor Column. Name Vessel Temperature Vessel Pressure Reaction Heat [kJ/Kmol] Liquid Volume Percent [%]

CRV-101 304.0 745.4 4.048 E+005 50 13

Table B.3: Pumps. Name Delta P [Kpa] Adiabatic Efficiency [%]

P-100 202.65 75 0.25062 Duty [kW] 3 NPSH available [m] 9.819 Delta T [C] 0 Pressure Head [m] 25.82 -1.597EVelocity Head [m] 06 Friction Loss Power [kW] 0 Table B.4: Absorber Column. Name Number of Stage Top Stage Temperature [C] Bottom Stage Temperature [C] Top Stage Pressure [Kpa] Bottom Stage Pressure [Kpa] Reflux Ratio Efficiency

T-101 3 78.9 74.7 101.3 101.3 0.3211 1

Table B.5: Distillation Column. Name Number of Stage Inlet Stage Top Stage Temperature [C] Bottom Stage Temperature [C] Top Stage Pressure [Kpa] Bottom Stage Pressure [Kpa] Reflux Ratio Condenser Duty [kJ/h] Reboiler Duty [kJ/h]

T-102 10 3 99.67 95.85 101.3 101.3 1.2 14

Table B.6: COMPRESSOR. Name Power [kW] Adiabatic Efficiency[%] Polytropic Efficiency[%] Delta T [C] Delta P [Kpa] Polytropic Head [m] Adiabatic Head [m] Dynamic Head [m] Polytropic Fluid Head [kJ/kg] Adiabatic Fluid Head [kJ/kg] Dynamic Fluid Head [kJ/kg] Polytropic Head Factor Polytropic Exponent Friction Loss Power [kW] Duty [kJ/h]

K-100 257.481 75 78.405 143.9 202.6 1.18 E+004 1.129 E+004 1.18 E+004 115.8 110.72 115.8 1.0006 1.5589 0 9.269E+005

Table B.7: Valve. Pressure Drop[Kpa] Percentage Open[%] Flow Rate [Kg/h]

202.6 50 8951

15