“Mini Project Report”

Topic:

Flare Gas Utilization for the production of potable

water for Oil and Gas Field (MOL)

Project Supervisor:

Engr. Qurat-Ul-Ain

Group Members:

Ehsan Ullah 09PWCHE0533

Abdul Hai 09PWCHE0523

Kaleem Raza 09PWCHE0522

Bashir Ahmed 09PWCHE0501

Department:

Chemical Engineering

University of Engineering and Technology, Peshawar

Contents:

1) Introduction

2) Objective

3) Literature Review

4) Material Selection

5) Process Discussion

6) Cost Analysis

7) Material Balance

1) Introduction:

Water is a great necessity of life. Water makes up 70-75% of the body weight of the average

human being. A person can survive for up to 4 weeks without food but no longer than 3 days

without water. Water performs many different functions inside the body. It forms the bulk of

blood and tissue fluid and is therefore essential for transporting nutrients, hormones and waste

products around the body. Water helps control the delicate balances of concentrations within the

cells.

1.1.Water on Earth:

A question arises that how much water is there on, in, and above the Earth? As you know, the

Earth is a watery place. About 70 percent of the Earth's surface is water-covered, and

the oceans hold about 96.5 percent of all Earth's water. But water also exists in the air as water

vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers

etc. Water is never sitting still, though, and thanks to the water cycle, our planet's water supply is

constantly moving from one place to another and from one form to another. Things would get

pretty stale without the water cycle.

For a detailed explanation of where Earth's water is, look at the data table below. Notice how of

the world total water supply of about 332.5 million mi3 of water, over 96 percent is saline. And,

of the total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of

freshwater is in the ground. Rivers are the source of most of the fresh surface water people use,

but they only constitute about 300 mi3 (1,250 km

3), about 1/10,000

th of one percent of total

water.

Water Source Water volume, in cubic miles Percent

of Fresh

water

Percent of

total

water

Oceans, Seas, & Bays 321,000,000 0 96.54

Ice caps, Glaciers, & permanent snow 5,773,000 68.6 1.74

Ground water 5,614,000 0 1.69

Fresh 2,526,000 30.1 0.76

Saline 3,088,000 0 0.93

Soil Moisture 3,959 0.05 0.001

Ground Ice & Permafrost 71,970 0.86 0.022

Lakes 42,320 0 0.013

Fresh 21,830 0.26 0.007

Saline 20,490 0 0.007

Atmosphere 3,0955 0.04 0.001

Swamp water 2,752 0.03 0.008

Rivers 509 0.006 0.0002

Biological water 269 0.003 0.0001

Source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor),

1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press,

New York).

1.2.Water scarcity:

Water scarcity includes both water stress and water crisis

1.2.1. Water Stress:

The concepts of water stress and water scarcity are relatively new. Fifty years ago, when there

was fewer than half the current number of people on the planet, the common perception was that

water was an infinite resource. People were not as wealthy then as they are today, consumed

fewer calories and ate less meat, so less water was needed to produce their food. They required a

third of the volume of water we presently take from rivers. Today, the competition for water

resources is much more intense. This is because there are now over seven billion people on the

planet; their consumption of water-thirsty meat and vegetables is rising, and there is increasing

competition for water from industry, urbanization and bio-fuel crops.

The total amount of available freshwater supply is also decreasing because of climate change,

which has caused receding glaciers, reduced stream and river flow, and shrinking lakes. Many

aquifers have been over-pumped and are not recharging quickly. Although the total fresh water

supply is not used up, much has become polluted, salted, unsuitable or otherwise unavailable for

drinking, industry and agriculture. To avoid a global water crisis, farmers will have to strive to

increase productivity to meet growing demands for food, while industry and cities find ways to

use water more efficiently.

The New York Times article, "Southeast Drought Study Ties Water Shortage to Population,

Not Global Warming", summarizes the findings of Columbia University researcher on the

subject of the droughts in the American Southeast between 2005 and 2007. The findings were

published in the Journal of Climate. They say the water shortages resulted from population size

more than rainfall. Census figures show that Georgia’s population rose from 6.48 to 9.54 million

between 1990 and 2007. After studying data from weather instruments, computer models and

measurements of tree rings which reflect rainfall, they found that the droughts were not

unprecedented and result from normal climate patterns and random weather events. "Similar

droughts unfolded over the last thousand years", the researchers wrote, "Regardless of climate

change, they added, similar weather patterns can be expected regularly in the future, with similar

results." As the temperature increases, rainfall in the Southeast will increase but because of

evaporation the area may get even drier. The researchers concluded with a statement saying that

any rainfall comes from complicated internal processes in the atmosphere and are very hard to

predict because of the large amount of variables.

1.2.2. Water Crisis:

A water crisis is a situation where the available potable, unpolluted water within a region is less

than that region's demand. The United Nations and other world organizations consider a variety

of regions to have water crises such that it is a global concern. Other organizations, such as

the Food and Agriculture Organization, argue that there is no water crisis in such places, but that

steps must still be taken to avoid one.

Manifestations:

There are several principal manifestations of the water crisis.

Inadequate access to safe drinking water for about 884 million people

Inadequate access to water for sanitation and waste disposal for 2.5 billion people

Groundwater over drafting (excessive use) leading to diminished agricultural yields

Overuse and pollution of water resources harming biodiversity

Regional conflicts over scarce water resources sometimes resulting in warfare

Waterborne diseases and the absence of sanitary domestic water are one of the leading causes of

death worldwide. For children under age five, waterborne diseases are the leading cause of death.

At any given time, half of the world's hospital beds are occupied by patients suffering from

waterborne diseases. According to the World Bank, 88 percent of all waterborne diseases are

caused by unsafe drinking water, inadequate sanitation and poor hygiene.

Water is the underlying tenuous balance of safe water supply, but controllable factors such as the

management and distribution of the water supply itself contribute to further scarcity.

A 2006 United Nations report focuses on issues of governance as the core of the water crisis,

saying "There is enough water for everyone" and "Water insufficiency is often due to

mismanagement, corruption, lack of appropriate institutions, bureaucratic inertia and a shortage

of investment in both human capacity and physical infrastructure".

It has also been claimed, primarily by economists, that the water situation has occurred because

of a lack of property rights, government regulations and subsidies in the water sector, causing

prices to be too low and consumption too high.

Vegetation and wildlife are fundamentally dependent upon adequate freshwater

resources. Marshes, bogs and riparian zones are more obviously dependent upon sustainable

water supply, but forests and other upland ecosystems are equally at risk of significant

productivity changes as water availability is diminished. In the case of wetlands, considerable

area has been simply taken from wildlife use to feed and house the expanding human population.

But other areas have suffered reduced productivity from gradual diminishing of freshwater

inflow, as upstream sources are diverted for human use. In seven states of the U.S. over 80

percent of all historic wetlands were filled by the 1980s, when Congress acted to create a “no net

loss” of wetlands.

In Europe extensive loss of wetlands has also occurred with resulting loss of biodiversity. For

example many bogs in Scotland have been developed or diminished through human population

expansion. One example is the Portlethen Moss in Aberdeen shire.

On Madagascar’s highland plateau, a massive transformation occurred that eliminated virtually

all the heavily forested vegetation in the period 1970 to 2000. The slash and burn agriculture

eliminated about ten percent of the total country’s native biomass and converted it to a barren

wasteland. These effects were from overpopulation and the necessity to feed poor indigenous

peoples, but the adverse effects included widespread gully erosion that in turn produced heavily

silted rivers that “run red” decades after the deforestation.

1.3.Oil and Gas Fields:

Oil and gas fields are mostly in arid regions. And in arid region there is a great shortage of

potable water. But as we know that in oil and gas fields Produced water is also produced along

with the oil and gas. Oil and gas reservoirs have a natural water layer (formation water) that lies

under the hydrocarbons. Oil reservoirs frequently contain large volumes of water, while gas

reservoirs tend to have smaller quantities. To achieve maximum oil recovery additional water is

often injected into the reservoirs to help force the oil to the surface. Both the formation water and

the injected water are eventually produced along with the oil and therefore as the field becomes

depleted the produced water content of the oil increases.

Historically, produced water was disposed of in large evaporation ponds. However, this has

become an increasingly unacceptable disposal method from both environmental and social

perspectives. Produced water is considered an industrial waste. But unfortunately there are still

some oil and gas fields where this produced water is disposed in large evaporation ponds which

is causing all type of danger for the people living nearby as well as the workers/engineers

employed in the company. To be more specific, MOL is still using evaporation ponds for its

produced water disposal and there is no action taken to treat this water.

But the interesting thing is that MOL buys water for the potable use of their employees and

workers, and it’s really uneconomic that they have their own huge amount of produced water

which can be treated to fulfill the potable water use for the company.

The produced water produced in oil and gas field contains huge amount of amine salts in it and

these amine salts are really hazardous for humans, it can cause skin cancer when its contact is

excessive with skin. The amount of amine salts in the produced water produced in MOL is

14000mg/L. This value shows clearly that amount of salts is way too high in produced water.

2) Objective:

As we discussed about the production of produced water in oil and gas field, there is also some

flare gases which is produced along with this produced water, oil and gas. And these flare gases

are burned in the atmosphere/surrounding and by doing so, the heat produced by these flare gases

is wasted.

Our main objective is to utilize/use the heat produced from these flare gases to treat the produced

water so that it can be ready for potable use. Doing so won’t be an easy task but as the huge

amount of heat as well as water is being wasted, there should be thought of a way to make use of

one for another i.e. heat for water.

3) Literature Review:

In 2012 Kim Choon Ng et;al studied the conventional desalination is used to discharge water

but it is not environmentally friendly, because it uses electricity and for each kilowatt hour

energy is used, an unavoidable amount of emissions of CO2 at the power stations occurs, also

hazardous salts are discharged into environment. So new method of adsorption desalination is

studied and compared with different technologies such as RO, MSF, MED etc. AD desalination

and cooling has low payable energy cost for desalination because thermal energy is taken free

from solar energy (renewable or waste heat energy etc).[1]

Different techniques of MED-VC is assisted with solar power is analyzed by M.A. Sharaf

et;al in 2011. The comparison between the two technologies i-e MED TVC and MED-PF-MVC

is analyzed. In MED-PF-MVC solar energy is used directly in the boiler heat exchanger unit

through steam ejector, while in MED-PF-MVC electrical power is generated by SORC to power

on the vapor compression. The comparison is performed in the parabolic trough collector. In first

technique hot oil is considered in solar field and water in the boiler, while in the second

technique toluene organic oil and water as W.F is used. It is concluded that PTC(solar collectors)

is more efficient and MED-PF-TVC gives attractive result compared with MED-PF-MVC in

accord with lower SPC, stream flow rate, total water price and thermo-economic product cost. It

is also concluded that the existence of steam ejector reduce may reduce the need of more

evaporators to increase the GR.[2]

Veera Gnaneswar Gude et;al in 2011 discussed about phase change desalination process and

six examples of applications for the illustration of a process for sustainable desalination. Three

examples are about the use of solar energy for desalination purposes and the other three

examples i-e waste heat rejected by an absorption refrigeration unit driven by grid power and by

solar collector and the third by photovoltaic array. A solar heat of waste heat cycle is proposed

for desalination purposes.[3]

Quen chen et-al in 2012 suggested various materials for the boiler designing . As low grade

fuel i.e natural gas etc is used in indirect boiler and the steam produced is used in the tube, for

indirect heat transfer for various applications etc. To avoid the pipe from corrosion etc, copper

pipe is coated with polypropylene and for boiler is manufactured from stainless steel material to

increase the lifetime of boiler.[4]

Sephton in 1982 increasing the rate of evaporation , vapor tube foam evaporation is

used(VTFE). In this brine side heat transfer coefficient is increased by this temperature needs to

drive evaporation and energy requirement is reduced. In turn evaporation rate and evaporation

capacity is increased under constant temperature conditions. The application of VTFE in this

research is presented. It is applied to multiple effect evaporators, to evaporation with vapor

compression to drive the process and to waste heat evaporation of aqueous solution. VTFE is

considered effective and achievable improvement of industrial evaporation. Waste heat VTFE is

used to many existing power plants to increase turbine efficiency, produced distilled water for

boiler feed and potable or in plant use. VTFE reduces the cost of distilled water to the lowest

attainable industry because of the only pump cost and free waste heat.[5]

4) Material Selection:

It is obvious that we needed something to treat the water, and for that purpose we decided to get

all the given materials.

4.1.Boiler:

For boiler we decided to get a carbon sheet of 0.07in thickness. And then this carbon sheet was

rolled in the diameter of 12in having the height of 15.5in. The allowable pressure for this

material is 8.5 bar.

4.2.Evaporating pond:

As we planned to treat the water in evaporating pond, so for that purpose we needed to make a

small evaporating pond for our experiment. The material of construction for the evaporating

pond is Polyvinylchloride (PVC) with an internal diameter of 13in and height of 5in. Its capacity

is 10litres.

4.3.Other accessories:

For completing our fabrication of the equipment, we also needed some more accessories for this

purpose. The accessories are;

1) Temperature Sensor: It’s a type of thermocouple with the temperature measuring range

of 0-400C. As we’ll use the waste heat from flare gases so there might be some

temperature at which the boiler is not safe to handle, so it’s purely for safety purpose as

well as the reading of process data.

2) Pressure Sensor: Its type of bourdon gauge and its pressure measuring range is 0-35bar.

As the steam generates in the boiler, there might also be some pressure which should be

present in the boiler and as boilers are known for its bursting when not handled carefully

that’s why we are using pressure sensor to keep of process in safe conditions.

3) Insulation: As there might be some heat losses if the boiler surface is left bare to the

environment, so we used packing material as an insulator between the boiler’s surface

and the surrounding. The thickness of the packing material is 0.25in.

4) Copper pipe: This is the most important material used in our equipment because it not

only connects the boiler and evaporating pond together, it is also a medium for the flow

of steam from boiler to the evaporating pond. Not only the flow, it is also the medium for

the heat transfer between the steam and the produced water in the evaporating pond.

5) Process Discussion:

In process discussion, the most important part is the process flow sheet/diagram. It is given

below.

As we discussed in the objective section about the utilization heat generated by flare gases for

the production of potable water. So the above figure shows the idea of using that flare heat. The

heat generated by flare gases will be given to the boiler for vaporization purpose.

In this process the boiler is filled with the fresh water and the evaporating pond is filled with the

produced water. The boiler and evaporating pond is connected to each other with the help of a

copper pipe.

There are four operations taking place in this process, two vaporization processes and two

condensation processes;

1. Vaporization of fresh water

2. Condensation of fresh water

3. Vaporization of produced water

4. Condensation of produced water

5.1.Vaporization of fresh water:

As the boiler is filled with the fresh water and it is heated by the heat generated for the flare

gases. Because of the heat, the fresh water present in the boiler reaches it saturation temperature

and when the heat is constantly given to the boiler, the vapor generation/vaporization of the fresh

water starts and these vapors/steam passes through the copper tube to reach the evaporating

pond.

5.2.Condensation of fresh water:

When vapors/steam passes through the evaporating pond, it heats the water present in the

evaporating pond with the process of heat transfer i.e. conduction between the surface of copper

and produced water and convection between the molecules of potable water. And because of that

heat transfer, the steam condenses and the condensed steam is collected in the condensed water

tank.

5.3.Vaporization of Produced water:

As the heat transfer between the produced water and the steam occurs, because of this heat

transfer vapor generation also starts and these vapors are from the produced water. Our aim is to

vaporize all the produce water and leave the salts behind in the evaporating pond, so for that

purpose, this process will take some time.

5.4.Condensation of Produced water:

The vapors/steam generated by the process of heat transfer are condensed in a heat exchanger

and then collected in the treated water tank. And the salt left behind in the evaporating pond is

also collected.

6) Cost Analysis:

The total cost for the procurement and fabrication of our project is Rs.5750. The detailed cost is

given in the table below.

Equipment Cost

Boiler Rs.1320

Copper pipe Rs.480

Sensors Rs.1650

Evaporating pond and other accessories Rs.1300

Manufacturing cost Rs.1000

Total Rs.5750

7) Material Balance:

Material balance is based on law of conservation of mass. It is mathematically written as;

[Mass In] – [Mass Out] = [Mass Accumulated]

Material balance is done on individually on four equipments.

1) On Boiler

2) On Condensed water tank

3) On Evaporating pond

4) On treated water tank

7.1.On Boiler:

At start of the process, 10L of fresh water is added to the boiler, the density of this fresh water is

1kg/L. It is shown mathematically below;

V1 = 10L

Density = 1kg/L

So,

Mass, M1= (V1)(Density)

= (10L)(1kg/L)

M1 = 10kg

So the mass inlet to the boiler is 10kg.

M1 = 10kg M2 = 1kg/hr

Boiler

7.2.On Condensed water tank:

The inlet stream of condensed water tank is the outlet stream of the boiler. Its balance can be

shown mathematically by;

V2 = 2L in 2hrs

Density = 1kg/L

So,

Mass, M2 = (V2)(Density)

= (2L)(1kg/L)

M2 = 2kg in 2 hrs

So in 10 hrs, M2 = 10kg

And as there is no accumulation, Hence

M1 = M2 in 10hrs

7.3.On Evaporating pond:

The volume of evaporating pond is 6L and it will be filled with produced water.

V3 = 6L

Concentration of salts = 0.014kg/L

Mass of salt in produced water = (V3)(Conc. Of salt)

= (6L)(0.014kg/L)

M2 = 1kg/hr Output = 0

Condensed water tank

= 0.084kg

As, M3 = 6kg (water + salt)

So,

M3 = (6-0.084)kg

M3 = 5.916kg (water)

7.4.On treated water tank:

The outlet of evaporating pond is the inlet of treated water tank. The water from the evaporating

pond evaporates at the rate of 0.65kg/hr

M4 = 0.65kg in 1 hr

As total mass of water is 5.916kg.

So,

All water will be evaporated in 9.1 hrs

M3 = M4 in 9.1 hrs

M3 = 6kg

M4 = 0.65kg/hr

Evaporating pond

M4 = 0.65kg/hr Output = 0

Treated water tank

The table below shows the whole material balance clearly;

Component Mass In Mass Out Mass

Generated

Mass

Consumed

Boiler 10 Kg 1 Kg/hr 0 Kg 0 Kg

Condensed water

tank

1 Kg/hr 0 Kg 0 Kg 0 Kg

Evaporating tank 6 Kg 0.65 Kg/hr 0 Kg 0 Kg

Treated water

tank

0.65 Kg/hr 0 Kg 0 Kg 0 Kg

References:

1. Kim Choon Ng, Kyaw Thu, Youngdeuk Kim, Anutosh Chakraborty, Gary Amy.

“Adsorption desalination: An emerging low-cost thermal desalination method”,

Desilination, 2012.

2. M.A. Sharaf, A.S. Nafey , Lourdes García-Rodríguez “ Thermo-economic analysis of

solar thermal power cycles assisted MED-VC (multi effect distillation-vapor

compression) desalination processes”, Energy 36(2011)2753-2764.

3. Veera Gnaneswar Gude a, Nagamany Nirmalakhandan, Shuguang Deng, “Desalination

using solar energy: Towards sustainability”, Energy 36(2011)78-85.

4. Qun chen, Karen finney, hanning li, xiaohui zhang, vida sharifi, jim swithenbank,

“condensing boiler applications in the process industry”, Applied energy 89(2012)30-36.

5. HUGO H. SEPHTON “Vertical tube foam evaporation for water desalination”,

Desalination 42 (1982) 27-35.