Water Footprint

Water footprint poster
This poster shows a map with the water footprint of national consumption by country. The poster also shows the dependency of some countries on external water resources and the water footprints of a few typical food items.

Global Water Crisis

Global freshwater resources are threatened by rising demands from many quarters. Growing populations need ever more water for drinking, hygiene, sanitation, food production and industry. Climate change, meanwhile, is expected to contribute to droughts.

1.2 billion people all over the world live without clean drinking water and 2.6 billion people without sanitary facilities
Major Region : Southeast Asia, South Asia, Africa South of Sahara, East Asia

Status of Water Shortage

Because of the increase of the world's population, especially countries like Middle East, Africa, Indonesia, Vietnam, India, and etc. under rapid economic growth, significant reduction of water use per capita is happening.

The deepening of uneven distribution of global water resources, is occurring significant water shortages in specified countries. (1/5 countries around the world, 3 billion people)

Large amounts of sewage and waste water generated by the rapid industrialization are contaminating the ground and the underground water. The reduced amount of drinkable clean water causes various water-born diseases. (each year, 5 million people killed)

Water Conversion Methods

Water Conversion Methods

Definition Desalination and Global Situation

Desalination refers to any process that removes some amount of salt and other minerals from saline water. Desalination is being used as a solution to provide fresh water globally. With a higher salinity of the feed water, more energy is required in the desalination process. Salinity is defined according to the total dissolved solids (TDS) of the water, which is measured in milligrams per liter (mg/L) or parts per million (ppm). A common used definition for different grades of saline water measured in TDS are:

Seawater: 15,000-50,000 mg/l
Brackish water: 1,500-15,000 mg/l
Fresh water: less than 500 mg/l

The desalination market is growing very fast with the demand increasing in all continents. The global installed capacity is expected to double within a period of 8 years. This growth will create important additional energy requirements.

Water Conversion Methods

Reverse Osmosis(RO) Filter System

• Need for clean sea water : Serious sea water contamination issue in the island regions in the west and south seas in Korea ->Demand for tube well
• Must Operate Continuously : Intermittent operation, frequent filter replacements, unexpected increase of cost.
• Bacillus Not Eliminated : Dosing of chemicals (condenser, reducer: sulfuric acid, chlorine), increase of operating cost
• Pre and Post Treatment Systems / Professional Operator
  Required : Accident and risk in the handling of dangerous chemicals by non-professionals, operating cost increase

Evaporation Distiller System(MED, MSF & MVR)

Evaporation distiller system, as the name implies, involve the heating of saline water and collecting the condensed vapor (distillate) to produce pure water. Evaporation distiller systems have rarely been used for brackish water desalination, because of the high costs involved. They have however been used for seawater desalination and can be sub-divided into three groups:
Multi-Effect Distillation(MED), Multi-Stage Flash Distillation(MSF), and Mechanical Vapor Recompression Distillation(MVR).

Multiple-effect distillation :
Multiple-effect distillation (MED) is a distillation process often used for sea water desalination. It consists of multiple stages or "effects". In each stage the feed water is heated by steam in tubes. Some of the water evaporates, and this steam flows into the tubes of the next stage, heating and evaporating more water. Each stage essentially reuses the energy from the previous stage.
The tubes can be submerged in the feed water, but more typically the feed water is sprayed on the top of a bank of horizontal tubes, and then drips from tube to tube until it is collected at the bottom of the stage.

Multi-stage flash distillation
Multi-stage flash distillation(MSF) is a water desalination process that distills sea water by flashing a portion of the water into steam in multiple stages of what are essentially countercurrent heat exchangers.

Mechanical Vapor Recompression(MVR) :
The main principle of Mechanical vapor recompression(MVR) is a direct compression of the evaporated steam to a higher pressure, thus temperature, so it can be re-used for the heating process in the Evaporator.

MVR is utilized to re-use waste steam to replace expensive steam generation by taking it to a higher pressure level. The MVR system is an energy efficient solution, since only 20 kW electrical MVR power per metric ton of steam is needed to rise the temperature per stage by 6-7°C.

Specific Comparisons of MVR & RO Distiller

MVR System

MVR Distiller
Distillation of sea water, brackish water, infected underground water, malignant waste water through a very effective heat pump system using mechanical vapor recompression (MVR) method for production of high purity water for drinking and industrial reuse.

Application

• Island region with drinking water insufficiency
• Inland region with underground water contamination
• Facilities creating malignant waste water

Applications : MVR Drinking Water Conversion System

Features

• Simple design and constituents, only electric power source needed for operation
  - no heat sources
• Low specific energy consumption (coefficient of performance →20)
• Easy maintenance due to a compact MVR system with high speed turbo steam compressor
• Simple and reliable automation system without special crew training for operation
• Easy full access to heat transfer surfaces and steam compressor for after service
• Simple raw water pre-treatment, selectable Heat Exchanger materials
  (sea water : Titanium, muddy river & underground water : STS316L, STS304)

Research & Development Goal : Energy recovery & saving

Using the evaporation method to get clean water or salt is very common. Nowadays, reducing the energy needed to run the evaporation method based machines is a hot issue.

First, the simple SE(Single Effect) method takes about 620kcal to make 1L of distilled water. We boil the water and collect the steam. Finally, we cool it down to get pure water from the steam. But, this means that we are throwing away all the heat energy into air through cooling water. The water manufacturing cost increases as we waste more energy. To prevent the energy loss, people put the machines in serial lines, which is called MED or MSF method. But these were not quite satisfactory for us.

So, we thought to compress the low pressure steam with a compressor(which works with 20kcal of electric energy). We then used this compressed steam to boil the original water where the steam came from via heat exchangers. This became an ideal machine, MVR, which can recycle up to 90% of the original input energy shown in the SE method.

Energy Balance Scheme of MVR Distiller

When 1 liter of 20°C raw water receives 620 kcal of energy, saturated steam is made through 100°C saturated liquid.
As this low pressure steam is compressed with a turbo compressor, using approximately 20 kcal of electric energy, the temperature rises up to 107°C.
Thermal energy of this high pressure 107°C steam is transferred to 100°C raw water through a large latent heat exchanger and the energy of the 107°C condensed water is transferred to 20 ℃ raw water through small sensible heat exchangers, finally condensed water of 25°C is made.
For an efficiently energy utilization, the variety of operational temperature difference is achieved by variable speed operation of steam compressor (3~10°C).
By inputting 20 kcal of electric energy, 620 kcal of thermal energy is recovered and recycled.

Original technologies required for developing MVR

• High speed blower, steam compressor, plate & pipe type heat exchanger
  : designing/manufacturing/operating technologies
• Automation/control and system integration technologies
• 100% self-developed technologies

Main Component

• evaporation tank
• condensation tank
• (pipe type) latent heat exchanger
• turbo steam compressor
• circulation pump
• sensible heat exchangers
• electric heater
• condensed/concentrated/raw water pump
• equipment controller & automatic operation panel

MVR Distiller Model & Specification

Turbo Steam Compressor for MVR Distiller System

1. Extensive Experience / Usage
We developed highly reliable and efficient high-speed turbo blower and steam compressor with a user-friendly automatic controller, after over 20 years of experience in development.
These Turbo systems are suitable for the aeration of sewage and waste water disposal plant that required oil-free compressed air, conveying chemical/cement/crop powders, supplying oxygen in fish farms, incinerator, other industrial use, and specially compressing low pressure steam for a MVR distiller.

2. Design and Manufacture through Optimization Analysis
Main components of Turbo system are optimized ; a high-speed impeller using a complete 3-dimensional aerodynamic flow analysis and CATIA modeling, the tilting pad bearings and high-speed gears using vibration and rotor dynamic analysis.

3. Compact Turbo system & Simple repair
One of the typical characteristics of turbo machines is that when the impeller, a major part of the machine, rotates at high speeds, its size reduces in reverse proportion to the speed. It is easy to maintain and repair small components including the impeller, but not everyone can develop high-speed turbo machines. It is pure technological strength that matters.

4. Convenient Operation
The Turbo system provides a visually operated and easy-to-use true color HMI control panel, which takes user input parameters required for the operation, and displays the status map, the trends of major parameters, alarms and causes of error, and the storage capacity of operational data.

5. No additional Facilities
The Turbo system generally uses oil to protect the bearings and gears, and it requires cooling water to cool the unit continuously. This requires a cooling tower, large and separate equipment installed on the outside. This is prone to causing problems, such as germ problems inside the tower in the summer and the freezing and bursting of pipe in the winter.
Our Turbo system has applied an air-cooling system to replace this hassling system, minimizing in the process of the cooling load of the gear and bearing oil, and reducing the maintenance and repair items.

Water Production Cost Analysis

Drinking Water Quality Check By Governmental Institute

Installation Case

• Maritime Affairs and Fisheries Office Control Center at Busan New Port
• Water Consumption : 20 ~ 50 (ton/day)