Monday, September 24, 2012

Thar Coal Deposits need to apply State of Art selective mining method & Power Generation Plants associated with huge water supplies.

Time is money and money is time.

 Thar Coal Deposits need to apply State of Art selective mining method & Power Generation Plants associated with huge water supplies.

The evils confronting Pakistan’s economy and uncontrollable energy crisis in recent years are due to economic mismanagement and misplacement of priorities.

Today energy security is the major parameter to qualify a country as an independent. It is difficult to think that a country can protect its borders if its energy investment policy is fully import oriented.

Effective and rational applications of local fuel resources are of vital importance. Therefore the energy planning is also the planning of future of the country in order to avoid any foreseen economic crisis as Pakistan is facing  presently.

Quality Wise World’s Estimated Coal Reserves by Country.

Thar Lignite deposits of Pakistan have not been included in the above deposits of coal which have been estimated a total of 175 billion tons.

                                                                Thar Coal Resources

      Chemical Composition of Thar coal.

          Thar Coal Deposits are located 360 km away from Karachi.


Block-I  (SINGHAR  VIKIAN VARVAI  )      Area of 122 sq. k.m
Global Mining Company of China.
The GMC intends to develop coal mine of 5 million tonnes / annum initially and Power generation of 900MW is expected by 2014. The GMC consortium proposes to invest approximately $4.5 billion up to 2016 and another approx. $4 billion would be invested to research the target of producing 10,000MW.

 Block-II (SINGHARO BITRO)  Area of 66-1km2
 In May 2008, the Government of Sindh through the Mines and Mineral Development Department (the predecessor of Coal and Energy Department) offered a joint venture, a public private partnership, to the private sector with a 60:40 (Private : GOS) equity participation and management control with the private partner. A joint venture company with the name of Sindh Engro Coal Mining Company was formed and it started working on the work left unfinished by the Chinese in Block II and to put a Power plant of 600-1000 MW capacity. This project of mining and mouth power generation is dependent on being provided with a sizeable amount of 350 cusecs water from the Indus river irrigation system.


Exploration License
• Offer of Grant made on 17 November 2007
• Grant made on 16 September 2009, valid for 3 years
M/s. Cougar Energy had been allocated block III for underground coal gasification, to develop a 400 MW power plant.

BLOCK-IV             Area 82.5 km2  
Australian continental Energy will initially produce 6 million tonnes per annum of coal from it mine to generate a net 1,000 MW of power for the Pakistan grid. This production will be expanded over a 15 year period to 18 mtpa, generating 3,000 MW.

Block – V
Dr. Samar Mubark started Underground Coal Gasification Project and was to start burn-test in March 2011 over for a small experimental plant of 5 MW which would have later been expanded to 100MW till 2016.
Thar Coal Documentary by Imran Sultan 

Problems encountering at Thar U C G Project have already been braught to light on Sept. 3, 2012. Please refer the following Heading of
“Prospects of Underground Coal Gasification in view of the Specific Geological formation of Thar Coal Deposits”  at Build Industrial Pakistan posted on


Oracle Coalfields feasibility study underlines Thar's technical and economic viability.
Published on Mar 22, 2012

 Recent Reports.
As per recent reports Sindh Engro Coal Mining Company, Oracle Coalfields UK and Sino-Sindh Resources China have completed their Detailed Feasibility Studies and their projects of open cast mining are expected to start within this year. These three projects have total power generation planned in the first Phase is 2100 MW by 2016.

Taking into account the demand of water of just Sindh/ Engro project which is dependent on being provided with a sizeable amount of  350 cusecs water from the Indus river irrigation system, for which the Govt.of Sindh has sanctioned 176 million Rupees for a feasibility study. Prequalification of Consultants was advertised by the Dept. of Mines and Minerals under the World Bank Technical Assistance Program.

Understanding The Vital Issue of Managing Water Resources At Thar Coal Project.

High efficiency and consistent power generation is directly associated with high efficiency mining method and depends on how fast we can mine coal. To start  huge mining operations, coal handling & subsequent Thermal  Power Generation at Thar Coal require an enormous water supply ,an essential  prerequisite.

Comparative Water Demand For Various Energy Generating Sources.

Miners and other workers need fresh water most commonly drawn from the deep aquifers which does not exist before the beginning of dewatering and mining operations and is planned as post mining issues.

Therefore Pre-mining evaluation of  huge water supply for Mining and subsequent Power Generation is of  utmost importance and must be included on top priority of any feasibility study of the Thar Coal Projects.

Location of Power Plants in Southeast Asia, and Projected Water Stress in 2025.

The map above shows that the trend of building power plants in places facing worsening water stress is prevalent throughout South East Asia. The blue spots show the locations of hydroelectric, nuclear, and thermal power plants, while the redder regions of the map are places projected to experience severe increases in water stress driven by climate change, increased water use, and economic development.

Pakistan is classed as a water-stressed country.
Due to a fast rising population, insufficient water reservoirs, uncertain rainfall and in efficient use of water, Pakistan is now classed as a water-stressed country, with less than 1,000 cubic meters per capita water availability, down from 5,500 cubic meters per capita in the 1950s.

The Indus River, which provides 80 percent of water for agriculture, is fed mainly by the glacier systems of the Hindu Kush and Himalayan mountain ranges. But global warming is shrinking their snow cover rapidly, which could affect the river’s base-flow.
According to studies by the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, run-off into the Indus is predicted to decrease by 27 percent by the year 2050.

Distribution of composite groundwater quality in the Indus Basin of Pakistan.

Left Bank Outfall Drain (LBOD)

 In 1980s and 90s the Left Bank Outfall Drain (LOBD) was designed by the Government of Pakistan(WAPDA) to correct the problem of water logging, salinity and to channel excessive irrigation water during floods in Punjab, Sukhar, Shaheed Benazirabad (formally Nawabshah), Sanghar and Mirpurkhas districts and was additionally meant to carry industrial and municipal effluent from urban centres into the Arabian Sea at Zero Point in Badin district. Below is the map of LBOD Sindh Province.
The project was to build a large artificial water ways roughly east of and parallel to river Indus .It was funded by the Asian Development Bank (ADB) and the World Bank (WB).
The LBOD was completed in 1997. It has a capacity of 4600 cusec of water with a provision of certain amount of rainfall.

 However, rapidly changing weather patterns have upset all estimates of engineers and also due to numerous gaps in the design, operational, technical and monitoring dimensions, the drain has in fact been causing heavy damage from time to time. The sufferers include human populations, biodiversity and crops, especially when the lower  Sindh area is hit by cyclones and heavy rains.

World Bank LBOD Project Ruins Sindh  (Bolta Pakistan - 8th Sept 2011)
Media Report.

Status of water availability in Sindh with reference to Thar Coal Project.

The Nara Irrigation System in Sindh.

Going back to the history of British India, the Nara Irrigation System came to maturity with the commissioning of the Sukkur Barrage in 1932, regulating the flow of Indus River, and supplying channels through the bed of the Upper Nara. This enabled perennial irrigation of dry crops (e.g. Cotton & wheat) in a large part of Nara Canal command. Rice cultivation was promoted in the main area designated for non-perennial irrigation at the tail of the eastern Nara canal.  Before the construction of Sukkur Barrage the Nara canal was an inundation channel, which follows the course of Old Hakro River that ceased to flow in the 19th century. In 1932, the designed Canal Command Area was 2.069 million acres.


Nara canal runs from left bank above the Sukkur Barrage through the Khairpur , Sanghar and  Tharparkar Districts to the Jamrao Canal.

With a designed discharge capacity of 14,452 cusecs, the Nara canal is Sukkur Barrage’s one of the four off taking canals, located on the left side of the barrage.

Chotiari Dam Sanghar.
The Chotiari water reservoir characterised as wetlands complex lies in Sindh on western wings of Nara desert some 35 kilometres northeast of Sanghar town.
The project approved in 1992 was started in 1994. It was to be completed in three years, by December 1997, at a cost of Rs1.5 billion, the Left Bank Outfall Drain (LBOD) being recognised as feeder canal of the dam. However, due to ineffective planning and alleged corruption, the project was completed in December 2002, at a total cost of Rs6 billion.

 Prime Minister Zafarullah Jamali inaugurated the reservoir in Feb, 2003.
With storage capacity of around 0.71 million acres feet (MAF), it was built with the financial assistance of Saudi Arabia and technical assistance of China.

The reservoir is  filled by floodwater coming into the Nara canal. Water is put in the reservoir through the Ranto Canal, an offshoot of Nara canal, controlled at Jamrao Head.

The reservoir was built upon small lakes– Gawari, Tajar, Phulel, Seri and Sao Naro. 

Chotiari Dam on duck hunting Sanghar.

Above mentioned reservoir is 13 kilometres wide and 16 km long, covering an area of 45,000 acres at pool level. It is enclosed by high sand dunes of the Thar Desert in the northeast. The reservoir’s storage capacity is 0.71 Million Acre Feet (MAF), of which 0.64 MAF is live capacity, while 0.04 MAF is its dead level. The highest level is 96.5 feet and a normal level is 85.7 feet. Minimum operating level is 69 feet and dead storage level is 64.5 feet. The water stored in the reservoir was to help Rabi crops. The reservoir provides water to southern Khipro sub-division of Sanghar and Umerkot districts for both irrigation and drinking purposes.

Sindh Governament is planning to prepare a feasibility report for provision of water to Thar coal project from the Chotiari Dam.

As per reports, topographically Islamkot is located at a higher elevation than the canal system. Closest possible gravity flow of water from Nara-Jamrao Canal  to the Thar Coal Project is needed to be surveyed and a scheme be devised  to divert the flood water towards any artificial lake or reservoir, be made near Thar Coal Project, from where the water could most economically be pumped up slope for usage of mines operators and  mine mouth  power generation plants.

Other Small Water Resources in South Nagarparkar Near Thar Coal Deposits (Needs to preserve as source of drinking water).

Nagarparkar Nadi.

Bhodesar Dam.
Bhodesar dam is an old water reservoir for collection of rain water, located near Bhodsar mosque Nagarparkar, Sindh.
Maya Dam.

In the absence of rain, Thar is a Semi arid region with scorching hot summers and relatively cold winters. It is one of the most densely populated deserts of the world with over 91 thousand inhabitants in Thar Sindh Pakistan. The livelihood of the population is dependent on agriculture and livestock. In Thar region the layer of fresh groundwater is so thin that it does even not suffice to provide domestic water. The rainfall pattern however is highly variable and characterized by spells of dry years, causing out migration as even drinking water sources fail.

Rain in Thar (Sindh)

Present availability of water is proved to be insufficient for irrigation and Rabi Crops and likely to be continued with the increase in population.

As per recent report, Sindh province will remain 18% deficient of water in current year. So how much load can be put on existing water resources for Thar Coal Project is a question mark.
Thermal power plants are just as dependent on water as hydroelectric plants. Thermal power plants either at mine mouth or away, need enormous water to produce steam and keep their equipment cool and functioning.

The development of the massive coal base Thermal power Plants in Thar area will also drain polluted water need to be properly planned and separated from ground water resources if not , will in turn make worse drought as there will be less usable water available.
Therefore the availability of water for Thar coal project is to be properly planned on top priority, inadequate water supplies due to lack of rain or any water logging in the system, will be threatening the thermal power plants to shutdown.

Open pit  mining is used for shallow  deposits which are extracted by digging  a succession of benches from the surface of the ground ,breaking and removing the overburden down ward. This is also known as open-cast mining; open cut mining or strip mining. 

Open-cast, or strip, lignite coal mining at GarzweilerGermany

To make the movement and operation of heavy machinery safe and bulk material handling reliable, Civil and Mining engineers have been building structures on or in rocks. Also the problems associated with de-watering of aquifers overlying/ underlying  the lignite seams are to be handled during mining operation as dewatering changes the mechanics of the rocks.

Above figure shows a wedge failure controlled by two intersecting structural features in the bench of an open pit mine. Rock could act both as an elastic material and a discontinuous mass. There has always been a tendency to equate rock mechanics with laboratory testing of rock specimens during mine operation to make it safe.

Decisions regarding mine operation, and even which mines to open and close, are based on costs of operation, amount of ore to be extracted, and the value of the product in the markets.

Need To Deploy Efficient Mining Machinery.    

In open cast mining , overburden material has to be removed to extract the coal seam. The choice of mining method and deployment of efficient mining machinery both play an important role to reduce the down time and the cost of excavation and disposal of material.

Bucket shovel / excavator and haul trucks.

Related Video.
The above  Bucket shovels and haul trucks shown in the video, are the conventional equipments commonly deployed in open cast mining . But specifically for deposits like Thar Coal  where we have to remove layers of massive over burden, the deployment of such machinery will be time and fuel consuming and will cause increased pollution from dust and coal handling . However there is no alternative left to deploy the conventional  Bucket shovels and haul trucks till such time we get the efficient machinery, discussed below.

Giant Bucket Wheel Excavator & Conveyer System.

An efficient machine to remove overburden and excavation of coal, being used in Germany , Australia ,different European countries and now in Indian lignite mines is the Bucket Wheel Excavator.

The Giant Bucket Wheel Excavator eliminates the use of several single bucket shovels / excavators and haul trucks transportation. As per manufacturer, It takes two years to make the parts and another two years to build on site.

  After removing the over burden, the Coal excavation starts , shown below.

Bucket wheel excavators with integrated buckets of different sizes (depending on the size of mine)  now a days are applied in the open pit mines, operating in soils as sand, gravel, clay, lignite and other soft to slightly consolidated soils.

The Coal is then transported through connecting bridge conveyers and unloading units system to stockyard shown below.

 The system, comprising Bucket Wheel Excavator, connecting bridge and unloading unit, is part of a handling line which also includes conveyer belts, a spreader and the general power supply shown above.
Lignite currently covers about 25 percent of Germany’s primary energy requirements, Abundant lignite deposits lie only a few hundred feet below the ground and are readily extracted by imposing bucket wheel surface excavators, some heavier than the Eiffel Tower (10,000 tons). Mining 175 million tons of lignite per year therefore becomes comparable to excavating the original Suez Canal (74 million cubic meters) every three weeks.
 Mega Bucket Wheel Excavators.
Related videos.
Coal Preparation, Storage and Transport.
Once lignite is mined as brown coal,it is porous in its natural form, light in weight and contains a high percentage  of moisture and volatile matters as compared  to Fixed  Carbon. Because of low heating value in lignite and also its susceptibility to spontaneous  combustion , its transportation, over long distances is uneconomical.  Therefore, this fuel is ideally suitable for running Lignite based power generation plant located close to mining operation.

Coal Preparation Plants:
The traditional method is supplying mined coal as received with all undesired unburnable sand, ash, moisture etc. To make it more valuable, Lignite is passed through Upgrading processes.
Coal preparation generally comprises of following processes.
i)Coal washing plant:


Dry destoning of Coal  (Eliminates the water consumption ).

An alternative to coal washing plants is dry destoning of coal has proven effective for de- shaling and removal of Sulphur of Coal as shown in the video ( Sulphur is not an issue of Thar coal).

Related video:

ii) Coal Rotary Drum Drying Plant:

Because of inherent high moisture content, when employed in conventional power plants, a considerable portion of the lignite's energy content is needed to evaporate this high proportion of water prior to combustion. The lignite is dried at a high temperature level of 900 – 1,000°C  and the evaporated coal-inherent water leaves the power plant together with the flue gas without being used as a source of energy.

 If lignite drying is done separately  from the rest of the process of combustion, the drying procedure may be carried out at a low temperature level, which is energetically more efficient, and  drying can be optimized as a separate process step.
Depending on the technology type drying is achieved either via a discrete operation or part of a process.

To remove moisture from lignite as a part of the process commonly Rotary Drum Drying Process is employed. By means of thermal drying, the wet coal is brought into contact with a source of heat, directly via hot gas shown blow)

The increase in temperature increases the vapor pressure of the water and once it becomes higher than the partial pressure of the drying gas or surrounding air, the water changes into the gaseous state and is carried away in the gas stream.
Related Video.

Indirect Heating Lignite By Conduction or Radiation Through Heated Surface.

Energy is transferred to the wet coal indirectly through a heated surface by conduction as shown below . The source of heat may be a waste heat of boiler and turbines of the power plant.


The process developed in Australia to upgrade lignite. Australian lignites have high moisture content, generally around 60%. However, they have low ash and low sulphur. Two proposed processes, binderless briquetting (by White Energy Australia) and pelletisation (developed by ECT, ‘Coldry’ Australia) said to have a potential to reduce the moisture to around 12%, with a specific energy between 23 and 24 MJ/kg. The ash in the processed product would be around 3–4%, and sulphur around 0.3%. 

Given that the two processes produce a product of similar qualities, the choice of process will be largely dependent on their cost of fuel at the power station gate, the readiness for process rollout and the quality of the water by-product. The above processes of Briquetting or Pelletizing are expensive and not yet commercialized proven technologies.

Coal Transportation Method’s.

Once the coal is processed it is shipped to wherever it is needed, by rail or trucks or through conveyers specifically at mouth of mine power plants. Transportation methods depend on the quality of coal, distance to be traveled and access to existing transportation systems.

i) Conveyer Coal Transportation & Handling System for Power Plants at mouth of mine.

As per report, the Conveyer shown in the above video was under construction not quite finished. There will be a hood over the conveyor to shield the coal from rain. There are analyzers along the conveyor to test the coal as it heads from the mine to the plant. Analyzers are pretty sophisticated in that they can test for sulfur, BTU content, moisture and ash content. It gives a heads-up on what kind of coal quality will be coming in, so that operators can adjust operation for burning coal.

Bulk material handling system at the San Miguel Lignite Power Plant in Texas.

ii) Coal transportation through trucks:
Common problems associated with trucking operations are:

-          Increased pollution from coal handling and diesel fuel.
-          Increased transportation cost for power generating plants located at distant from mines.
       -     Blockage of highway, wasting too much time and effort managing coal stockpiles    
iii) Coal transportation through Coal Trains:
US Coal Trains.
In USA the train hauling after processing coal from mine to power plants is considered the most efficient and economical transportation which weighs 1,4000 tons when a train is full.

 Related video:
German Coal Trains
The electric locomotives and freight cars are supplying coal to three lignite- fired power generation plants north of Cologne Germany.

An Over View Of Power Generation Plants.

Worldwide chief use of coal is now electricity generation which is set to continue, with coal fueling 44% of global electricity in 2030.

 After coal is mined, it is processed and transported to power plants by trainstrucks or a conveyor belt  for a mine mouth power generating unit ,carries the coal to a Pulveriser, where it is ground to the fineness of talcum powder. The powdered coal is then blown into a combustion chamber of a boiler. Surrounding the walls of the boiler room are pipes filled with water. Because of the intense heat, the water vaporizes into superheated high-pressure steam that drives a turbine which produces electricity by moving an electrical generator.


Related video:

Old coal-fired power plants had a thermal efficiency of only 35 % HHV, and emitted SO2, NO2, particulates and mercury.

Super-critical and Ultra-supercritical coal-fired plants have been developed which represents up to a 40-45% improvement over old coal-fired plants.


The burning of coal can produce combustion gases as hot as 2,500° C (4,500° F), but the lack of materials that can withstand such heat, forces even modern power plants to limit steam temperatures to about 540° C (1,000° F)—even though the thermal efficiency of a power plant increases with increasing operating fluid (steam) temperature.

Lay out scheme of  supercritical pulverised coal plant for electricity production.

Development of advanced stainless steel boiler tubes.

Advanced ultra-supercritical is the technology to improve the power generation efficiency by increasing the steam temperature and pressure of pulverised coal fired power generation.

Ultra-supercritical plants operate at very high temperatures and pressures. Advances in metallurgy have allowed the use of higher temperatures and pressures in boilers and turbines. Continuing research is aimed at further improvements and the building of advanced ultra-supercritical coal-fired plants.

Sumitomo Metals Japan developed fine-grained 18%Cr steel by using its unique control technology to precipitate niobium carbide and attained high temperature strength and steam oxidation resistance.

Japans Sumitomo Metals advanced this technology by developing significantly stronger steel that contains copper. The resulting new 18%Cr steel has shown the highest-strength achieved for steel for this application.


As per reports, China has jumped into the ultra-supercritical game and is busy building ultra supercritical power plants.

 On average, the world’s coal-fired power plants consume 480 g of coal to produce a kilowatt-hour of electricity. In doing so, they release between 1,000 and 1,200 g of CO2 into the air, or some eight billion tons a year. One of the most efficient coal-fired power plants in the world, the Block Waigaoqiao III in China, for which Siemens
Germany delivered two 1,000-MW turbines to China, burns only 320 g of coal per kilowatt-hour, and thus emits only 761 g of CO2.

As per reports, large-scale castings for 1000MW Ultra Supercriticle steam turbine already can be made in China. Large-scale forgings (forgings have better engineering strength than castings for this application) have been also trial-produced. High-purity low alloy steel forging for low pressure rotor and 12%Cr high-quality forged rotor for 1000MW USC steam turbine high pressure rotor are being made in China.  

China’s strategy to meet its greenhouse gas reduction commitment is to continue full steam ahead converting its coal-fired power plant fleet from a conventional one to an ultra-supercritical one.

Most importantly, the engineering expertise the Chinese have developed building these plants has reduced the cost of building one to 33% of what it would cost to build a less efficient coal-fired conventional power plant.

The modernized Lippendorf  power plant is now producing 16,000MW.

The fuel for running the plant is guaranteed by long-term supply contracts concluded with central German lignite producers Vereinigte Mitteldeutsche Braunkohlenwerke AG (MIBRAG).

Related Videos

Water Reservoir at German power plant.

Power Technology at Lippendorf  power plant .

Germany to Build Twenty Three New Coal-Fired Power Plants
Reported on  by Ammoland     

The above decision by German officials has been taken to cop up the problems arising due to inconsistent power supply by Wind power Projects and expensive Solar power plants.

The water-saving technologies.

Dry destoning of coal eliminates the water consumption discussed above.

Post combustion lignite drying to remove inherent moisture, depending on the technology type, drying is achieved either part of the process or discrete upgrading process discussed above. This inherent moisture in lignite may be conserved depending on the cost of technology employed.

The water-saving technologies in power plants are improving, and there is also a trend toward cooling systems in which more water is recycled like “Closed Circle Cooling Cycle” Power Plants. Closed-cycle cooling is used at several New York power plants today and overall, 53% of the electric generating capacity in the United States uses closed-cycle cooling systems.

( The water-saving technologies need to be discussed separately ).


1)  We have lost time and continue to lose more and unable to recover fast in due time. We have spent one billion Rupees on Underground Coal Gasification Experiment even though the reports of drilling data were available, indicative of the weak strata, permeable rocks layers and presence of pressurized aquifers underneath.

2) With due apology, repeated thrilling statements like,’ Pakistan has the potential to produce about 100,000 MW a year from Thar Coal for a century or longer’, will not resolve our energy crisis because of insufficient water supply. It rather tends to divert our attention from actual problems to be resolved on priority. Massive water supply is one of the most vital requirements at Thar Coal to start mining operation and subsequent power generation. It is the bottleneck to start speedy development of Thar coal project.

3) Capacity of our existing water reservoirs and irrigation system is already under water stress throughout Pakistan and always be deficient in supplying water for drinking and Rabi Crops. Would it be possible for present Sindh irrigation system to spare any  water for Thar Coal Projects from Indus river through  Nara- Jamrao  canals or any other route, is a question mark and need to be addressed on priority.

4) Islamkot is located topographically at higher elevation than the canal system. Closest possible gravity flow of water from Nara-Jamrao Canal  to the Thar Coal Project is needed to be surveyed and a scheme be devised  to divert the flood water towards any artificial lake or reservoir, be made near Thar Coal Project, from where the water could most economically be pumped up slope for usage of mines operators and mine mouth power generation.  

5) In case of any short fall in the water reservoir due to lack of rain or water logging , Federal government should make legislation and monitoring system with the consciences of all provinces for the provision and maintaining water level of the proposed water reservoir, required to avoid any interruption in mining operation and subsequent power generation.

6) President Putin is due to visit Pakistan in first week of Oct, 2012. Russian Government  has shown its interest to invest in Thar Coal Project, the above problem of water management may be the part of help, sought during the visit (As per reports, World Bank has already suspended the Thar Project till Bankable feasibility report is prepared).    

7) The water-saving technologies in power plants are improving, and there is a trend toward cooling systems in which more water is recycled like “Closed Circle Cooling Cycle” Power Plants need to be chosen,

8)  Need to address the question, how fast can we mine coal?  We bought F-16 to defend our Air space and Submarine   Agosta 90B to defend our Mari time Shores. In order to defend our economic borders, without lapse of time, needs to deploy state of art selective mining machinery and Power Generation plants rather than cheap traditional mining and Power Generation plants for better and efficient exploitation of the available Thar lignite coal resources, like few  discussed above.

(Discussion continue)