Gasification of Coal

Gasification of coal is a high temperature process which is developed to produce a fuel gas with minimal of liquid and solids. Coal Gasification take place in a gasifier, generally in a high temperature vessel where oxygen and steam directly contracted with the coal causing a series of chemical reactions to occur that convert the feed to syngas and ash. Syngas is composed primarily of the colourless highly flammable gases carbon monoxide (CO) and Hydrogen (H2).  Coal Gasification is considered as a partial oxidation process.

Applications of Coal Gasification:-

¨ One of the most abundant energy sources

¨ Can be used to produce ultra-clean fuel

¨ Leading source of electricity today

¨ Chemical Production (Methanol, ammonia, acetic acid etc)

¨ Hydrogen made from coal or other solid fuels can be used to refine oil, or to make products such as ammonia and fertilizer (urea).

¨ By product of burning (ash or slag) can be used for concrete and roadways

Gasification is attractive for its simple but brutal operation. Higher efficiency, cleaner output and more control over products can only help the economics. As other sensor technologies are introduced gasification could be a leading refining technique for a wide range of raw materials from trash to cultivated biomass and on to coal. Gasification might not be elegant – but the process enjoys the leading spot for going to commercial scale in today’s market for synthetic fuel process. Particularly in clean generation of electricity from coal, gasification may make an increasingly important part of the world’s energy and industrial markets.

Read More - Benefits of Multi Storey Buildings

Coal Storage: Performance Requirements for Maximum efficiency

Coal Storage:

Coal is a fossil fuel just like oil and natural gas. In thermal power plants, coal storage or petcoke storage (as the most exploited solid fuel) at large scale is preferred for the production of electric energy. A good preparation of coal before its combustion increases the homogeneity and efficiency of the fuel, reduces transportation costs and its displacement inside the plant produces less dust and reduces the emission of sulphur oxides. Besides, Preventive measures should be taken at every stage during the transport and bulk storage, in order to reduce any environmental impact, so that it became easier to maximize plant efficiency without any interference of any outside or environmental effects.

Performance Requirements for Maximum efficiency:

The large investment in a thermal power plant should be protected in best pos­sible way by maintaining the quality of resources (like coal, petcoke, lignite etc) and by uplifting the performance of their handling system. The coal handling system and equipment should perform satisfactorily to meet the guaranteed performance for maximum efficiency as stated here under:

1.      Efficient operation in thermal power plants means the careful use of fuels and other consumables resources includ­ing in-house consumption of electricity. High availability requires strong focus on maintenance, which in turns contribute as one of the factors in producing maximum efficiency.

2.      Stacker or reclaimer should be stable under a specified design condition and meet all the specified requirements. During unfavorable environmental conditions, the stacker or reclaimer should reclaim the coal in a way to avoid generation of well compacted, damp and sticky coal.

3.      Sulphur content in fuel always had an adverse effect on overall plant efficiency. ‘Corrosive acids formation’ and ‘heat loss in boiler’ can be evaded by properly supervising and removing the sulphur content in coal.

4.      Condition based maintenance uses intelligent measurements and assessments. These can include oil quality, differential pressure measure­ments, vibration readings and many more. By such applications, maintenance and renewal of plant components can be done exactly when needed.

5.      Fuel quality of coal, which is generally quoted in terms of its gross calorific value (GCV) along with its moisture and ash content impacts on whole plant operational efficiency. Assessing fuel quality and choosing fuel of maximum gross calorific value and less moisture & ash content improves combustion and power generation as well.

6.      Variation in the ambient temperature tends to affect plant performance and load capability of gas turbines along with the performance of cooling system. Hence, it is better to maintain the ambient temperature near a specific threshold during plant operation for maximum power output.

Using long-time experience of 30 years, It has been challenge for Hindustan Alcox Limited to identify and eliminate unnecessary energy losses from the processes by providing the best choice for covering coal stockpiles under Coal storage shed. Alternatively, Coal Storage and handling can be done under dome structure sheds (like Coal dome, petcoke dome).

  

--   Hindustan Alcox Limited, New Delhi

(Coal storage Shed Manufacturer)

Coal Storage : Types, Factors to maximize output Power, Safety Measures

Open Coal Storage

Coal is the primary fuel being used for power generation in thermal power plants. Most of the power generation in India is generated by coal based power plants where coal is received from coal blocks/Mines by means of transportation (by belt conveyors, by rail or by ship depending upon the distance and availability of transport). Then the Coal is dropped in a coal yard and stored in stockpiles.

As far as optimum power generation is concerned, a healthy emphasis needs to be given for its bulk storage and  proper handling. Preparation of coal before feeding it  into the boiler plays crucial role for achieving better combustion. Irregular and big-sized  lumps of coal may cause the following problems:

• Improper combustion & inadequacy in furnace temperature.

• Increment in unburnts of the ash.

• Reduction in thermal efficiency.

Once Coal is reduced in size by crushing and pulverizing, crushed coal not only ensure efficient combustion but also become an economical asset  for power generation in thermal power plant.

Coal Storage Types

Coal storage can be done in two ways:

1.      Open coal storage

2.      Covered coal storage

Most of the coal stockpiles in the power plant are open type. But with the passage of time, various problems are experienced with open stockpile system and potential need for covered coal storage system is felt. The salient features and benefits of the covered coal storage as compared to open coal storage are as follows:

·        Reduction in spontaneous combustion of coal, by virtue of no exposure to sun.

·        Minimum dust emission in the stockpile.

·        No air pollution.

·        Elimination of rainfall and moisture problem :

·        Prevention of Loss of Gross Calorific Value (GCV) of coal

Stocking of coal in covered coal storage system not only minimizes the above various problems that had occurred in stocking of coal in open coal storage system, but also improves combustion, boiler efficiency and overall power generation in thermal power plant.

Factors to maximize output Power Generation

In coal/lignite storage systems, the implementation of a various factors needs to be performed to maximize power generation in a way, which is consistent and flexible enough to suit the requirements without extensive modifications. These major factors are as follows:

1.      ‘Fuel quality’: Fuel quality of coal which is generally quoted in terms of its gross calorific value (GCV) along with its moisture and ash content impacts on whole plant operational efficiency. Assessing fuel quality and choosing fuel of maximum gross calorific value and less moisture & ash content improves combustion and power generation as well. 

2.      ‘Reheat stages’: Earlier heat cycles were not used in power plants, but with time, the potential benefits of reheat cycles are considered and come as one of the correction factor in improving overall plant efficiency.

3.      ‘Maintenance of Ambient temperature’: Ambient temperature is the temperature in the surrounding of boiler during plant operation. Change in the ambient temperature tends to affect performance and load capability of gas turbines, cooling system performance . Hence it is better to keep the ambient temperature maintained during plant operation for maximum power output.

4.      ‘Fuel sulphur content’: Sulphur content in fuel have adverse effect on plant efficiency. ‘Formation of corrosive acids’ and ‘boiler sensible heat loss’ can be avoided by properly supervising and eliminating the sulphur content in coal.

5.      ‘Excess air and unburned carbon in ash’: One of the major operation issues in power plant is presence of excess air and unburned carbon content is ash which may directly affect boiler thermal losses and can be suppressed by site level operations.

Safety Measures to avoids hazards in coal storage

These safety measures are steps taken to increase or ensure safety or protection from perils of coal storage and handling. In the publications of National Fire Protection Association (NFPA), they identifiy the threats associated with coal storage, and its handling & gives recommendations for protection against these threats. In addition to those safety preventions, some addition safety measures are as follows:

·        The coal stockpiles should be kept away from moisture.

·        Coal storage or lignite Storage piles should be emphasized to prevent those pockets of coal, which are potential source of spontaneous combustion. Coal storage should be done for as short a duration as possible. In order to reduce air within the stockpile, Coal should be piled in layers.

·        Coal stockpiles should be monitored constantly for hot spots using temperature detection systems. These sensors are designed to avoid harsh conditions in coal handling and processing.

·        A management strategy should be followed to replace the ignited coal on its occurrence. In addition to this, the access should be provided for firefighting.

·        There should be no scope for dust to accumulate inside the coal storage shed. Otherwise, dust removal systems should be provided for all surfaces where dust may accumulate.

·        An absolute minimum distance should be maintained between Ignition sources and coal stockpile. Every electrical equipment should be properly grounded, to minimize the effect of static electricity hazards. All machinery and electrical equipment inside coal storage shed should be checked properly for use in hazardous locations.

·        There should be automation in turning all electrical circuits on/off without the need for personnel to enter dust-emitting locations.

·        In order to reduce the chance of methane (and, in case of fire, smoke) to occur around coal storage, a sufficient ventilation system should be provided. At the apex, adequate ventilation should be provided to take advantage of the chimney effect.

-          Hindustan Alcox Limited, New Delhi.

Bulk Storage Domes for coal, lignite, limestone, gypsum, additives & Their Effective Usage In Industry

Bulk Storage Dome

Dome structure is a hemi-spherical hollow structure, used as roofing/ceiling. Earlier Domes were only used in constructing Architectural buildings, but with the passage of time their importance to endure under adverse climatic conditions is understood and now domes can be seen in almost every sphere of construction industry. In other words, a semi-spherical structure with the curvature on top, when usually created to cover a sufficient room for bulk storage like cement, limestone, coal, lignite, gypsum, additives and many more. Depending upon the material used for storage, followings are the storage domes with their usage in industry:

a) Slag Dome:

Slag is metal-separated stony waste material in form of their metal oxides mixed with silicon di-oxides. Industrially, its storage in Slag dome is generally carried for Metal ore smelting process to serve some useful purpose like ‘temperature control in Smelting’, ‘preventing re-oxidation of molten metal’, ‘removing waste from smelting process’.

Usages:

1.      Slag dome is useful in sustenance of its compaction characteristics of slag.

2.      Slag dome is also useful in keeping low risk of breakability and maintenance of maximum strength.

b) Additive Dome:

Additive storage

Additives are organic material added to subject material in purpose to improve its inherit properties, performance, efficiency and reduce cost. Industrially, Additive Dome covers a wide range of additives like antifoams, organic additives and other performance enhancement additives. Some well-known examples of additives are ‘fly ash’, ‘GGBFS’, and ‘silica fume’.

Usages:

1.   Additive dome covers large span to facilitate the storage of various additives under same shed.

2.      Storing Additives under domes facilitates maximum utilization of space in plant which may be used for other industrial purpose too.

3.  Ventilation facility and prevention from adverse conditions of environment under additive dome will eliminate the problem of oxidation, which causes clinical effects in labor.

c) Gypsum Dome:

Gypsum Storage

Gypsum is fine-grained calcium sulphate (CuSo₄) material industrially used as fertilizer/enhancer in subject material to improve its inherit qualities, performance, efficiency and reduce cost.

Usages:

1.      Gypsum Dome is very useful in controlling fugitive emission of gypsum.

2.      Storing Gypsum under domes facilitates maximum utilization of space in plant.

3.  Gypsum dome also helpful in prevention from vulnerability caused by adverse environmental conditions and rainfall.

d) Clinker Dome:

At sintering stage in cement manufacturing process, a nodular material is formed known as Clinker. In the Cement plant, Clinker is prepared by fusing various clays and limestone with additives by melting them below to the point of liquidation. ‘Silica fume cement clinker’, ’pozzolana cement clinker’, ‘ground granulated blast furnace slag cement clinker’ are most commonly formed Clinkers.

Usages:

1.      Clinker dome has a benefit of facilitating no spillage and zero dust pollution. This will not only prevent wastage of resources but also create health friendly environment for labor.

2.      Clinker storage under dome also help in prevention from heat which further facilitates setting up hot clinker to its favorable temperature before being converted into its grinded form, known as cement.

3.     Clinker dome protects clinker from being affected by Rainfall or heavy thunderstorms, which can harm the quality of clinker.

e) Cement Dome:

Cement Storage

The grinded form of clinker is cement. Cement is used as binding material that combines with water and other additives and sets to bind two other materials together. That is why it also called as Hydraulic binder. White cement, pozzolana cement, acid resistant cement, blast furnace cement, sulphate resistant cement, rapid hardening cement, quick-setting cement, high alumina cement, colored cement are some common types of cements in construction industry.

Advantages:

1.   Cement dome is highly non-vulnerable to maintain moisture and water resistance in heavy rainfall areas.

2.      Maintenance of temperature and adequate ventilation system is recommended for large scale storage, which can be fulfilled under cement dome.

3.   Cement dome is useful in providing maximum utilization of space in plant, which fulfills need of efficient loading and unloading of cement in order to feed power stations continuously.

f) Limestone dome:

Limestone is  composition of calcium carbonate, CaCo₃ with other minerals, generally found in organic sedimentary rocks formed from accumulation of shell, forms, coral etc. In clinker/cement formation, limestone is used as one of the major component. Moreover, In precious Architectural works, limestone is also used neutralize the effect of acidity caused by acid rain.

Usages:

1.  Limestone dome costs less as compared to reinforced concrete silo for storage. Therefore limestone dome gives you economical storage solution.

2.  Limestone dome provide best protection against moisture and rainy weather, as limestone is highly susceptible to moisture.

f) Coal/Lignite dome:

Coal Storage

Extracted from the ground by coal mining, coal is the biggest source of energy for the worldwide electricity generation. In simple terms, there exist four types of coal - peat, lignite (brown coal), bituminous, and anthracite(highest quality coal). Coal/Lignite storage is done in large quantities and requires stacking in open areas. 'Production in mild climatic condition and market it in winter season’, ‘Feed the thermal power stations continuously' are some of the key reasons for coal storage, which we understand the most.

Usages:

1.   Coal/lignite domes are made in such way to prevail cross ventilation at very corner inside it which can be done to prevent heat accumulation.

2.   Coal dome provide best protection against moisture and rainy weather since coal is vulnerable to moisture.

-          ---     Hindustan Alcox Limted, New Delhi

Quality Coal Storage - A Boon To Potential Power Generation

Bulk Storage

Now-a-days, Being the biggest source of energy the share of coal for electricity generation is raised. Coal storage plays crucial role in producing global energy, especially for power generation, but there is need to use it efficiently. An efficient thermal power plant consumes less coal and discharges less poisonous gases like Carbon-di-oxide, Carbon monoxide etc.

The following points will ensure how quality coal storage responsible for potential power generation:

·        Coal storage and handling should be managed in such way to prevail cross ventilation at very corner inside it to prevent heat accumulation as well as reduce the chances of spontaneous combustion of coal. This enhances potential power generation and reduces the coal consumption.  

·        Since coal is highly susceptible to moisture, coal storage inside Coal dome provide best protection against moisture and rainy weather. This maintains the efficiency of coal to produce power.

·        By proper rotation of coal under storage shed, we can keep coal effective to feed to boiler and in turn maximize power generation. In an ability to cater maximum Space for storing coal, our team also has expertise in making hemi-spherical hollow structure, used as roofing, known as Dome structure.

·        Use of automatic fire extinguishers systems and dust proof electrical wiring systems will add additional security to the power plant, if there occur any chance of coal combustion.  

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-          Coal storage shed manufacturer (Hindustan Alcox Limited, New Delhi)

Coal Storage- A solution to Spontaneous Combustion

Coal Storage

Coal storage is done in large quantities and requires stacking in open areas. 'Production in mild climatic condition and market it in winter season’, ‘Feed the thermal power stations continuously' are some of the key reasons for coal storage, which we understand the most. Although many issues encountered in bulk storage but in case of storing coal, combustibility comes as a special case and need cautious treatment.
The Spontaneous Combustion of coal in the coal storage is serious issue now a days due to global warming and other exothermic processes such as microbial metabolism, oxidation at low temperature, absorption & desorption of water by virtue of differences between real and equilibrium moisture content in coal and air. These above processes largely contribute to spontaneous combustion of coal.

How coal storage sheds helpful in solving the problem of Spontaneous Combustion?

Coal Storage Shed

The Following points will clarify the importance of our sheds in solving the above-discussed issue:
• Our Coal storage sheds are made in such way to prevail cross ventilation at very corner inside it. Good cross ventilation of air across the storage sheds helps in the prevention of heat accumulation and thereby helpful in keeping self-heating of coal away from the plant.
• The covering keeps the environment of the Captive thermal power plant inside shed cool not only to avoid spontaneous combustion of coal but also create suitable temperature for efficient working of staff.
• Coal combustion can also be avoided by proper rotation of coal in power plant which needs maximum storage space.  In an ability to cater maximum Space for storing coal, our team also has expertise in making hemi-spherical hollow structure, used as roofing, known as Dome structure since dome shape provides us more space than any other structural shape per unit area by 30%.
• Moreover, use of automatic fire extinguishers systems and dust proof electrical wiring systems will add additional security to the power plant, if there occur any chance of coal combustion.

We at Hindustan Alcox Limited pay special attention towards adhering to the highest standards of quality. We offer complete solutions right from the design to the erection phase to ensure creation of coal storage sheds that are not only compatible with client needs but also offer the assurance of long life and great functionality.

- Hindustan Alcox Limited, Delhi

Coal Storage and handling in Captive Thermal Power Plants

Coal Storage Shed

Coal, a non-renewable combustible black sedimentary rock composed of carbon and hydrocarbons, whose combustible quality can be used for electricity generation. Peat, Lignite, black coal and anthracite are four most common forms of coal. Coal based captive thermal power plants are plants, which makes the use of coal for combustion and generate electricity by virtue of heat generated in combustion of coal. Coal Handling in Coal handling Plants/Unit takes place in following three steps:

•     Bunkering of coal
•     Unloading of coal
•     Stacking of coal

Bunkering and Unloading of coal is done whenever coal mines are far away from power plant. The Transportation mode for coal will be purely dependent on the power plant location, location of coal mines and available methods of transportation. Coal handling including bunkering and unloading, now called as ‘Out-plant Coal Handling’ and handling excluding bunkering and unloading known as ‘In-plant Coal Handling’. During out-plant coal handling, coal quality may get affected as it tends to absorb moisture and oxygen of air. This problem losing coal quality can be eliminated by coal storage.

A large machine known as Stacker or Reclaimer mainly used for bulk storage and inside bulk storage shed facility. As the name suggests, the two main functions of stacker are:

•         Stacking
•         Reclaiming

Coal Stacking/Reclaiming

In Stacking Process, coal stock travel on conveyor rail in horizontal as well as in vertical direction.  Stackers may be used to form two different patterns- ‘cone’ , ‘chevron’ either on one or both sides of stacker. Main motive of coal stacking is to produce efficient industrial outcome from coal by avoiding problems faced in coal stacking like oxidation of coal, spontaneous combustion, self-heating of coal, increase in moisture and many more.

In Reclaiming process, the two modes of operations are performed by stacker.

1.      On/Off mode: In this mode of operation,  Material to be reclaimed are not only easy to handle but also it maintains reclaimer efficiency. The material is carried on the belt driven by the constant speed and then discharged to the discharged/feed bin.

2.      Direct mode: In direct mode of operation, it is difficult to handle the material to be reclaimed but this mode gives benefit to eliminate the need of intermediate bins.

Earlier, Stacker/Reclaimer run manually by operators but now due to advancement in technology, their operations are made to run on PLC-based automation, which not only make the operations cost effective but also saves the time to complete operations. This Coal Storage and handling can be done under bulk storage dome (like Coal dome, lignite dome) and horizontal semi circular storage sheds   
We, at Hindustan Alcox Limited, satisfy our clients the best available solution in storage and handling of any type of bulk storage.

-Coal storage shed Manufacturer in India

Challenges & Our solutions- Coal Storage

Practical Challenges faced in dealing Coal Storage

Open Bulk Storage

Bulk storage Under sheds

‘Meeting the customer demands’, ‘Production in mild climatic condition and market it in winter season’, ‘Feed the thermal power stations continuously' are some of the key reasons for coal storage. Followings are the Challenges to be faced practically in dealing with Coal Storage:

1. Sponteneous Combustion Problem / Self-ignition:  The property of self-heating of coal due to auto oxidation results into its ignition and may sometimes causes loss to property as well as lives.

Storage Protection under Rainfall

2. Rainfall (moisture) Problem: 

Keeping Intrusion of rainfall away from entering the Coal storage system is very tough task. It will not only increase moisture and reduces the inherit qualities of coal, but also all efforts may go in vain, in case of heavy rainfall. Rainfall Protection under storage sheds can also be used for protecting Limestone storage, Additive storage, clinker storage, gypsum storage, lignite storage and any other type of bulk storage.

3.Affecting Labor Health from Air pollution: Gaseous Pollutants like So₂, No_x, Vocs  etc emitted from stack emissions will not only pollute air quality around coal storage plant, but also causes breathing problems in labor while dealing coal storage.

4. Quality Loss due to Wind Erosion: Loss of Quality Coal due to wind erosion largely depends upon the weather conditions and location of stockpile. Like In port areas, wind erosion is more and quality loss will be more.

5. Risk of life due to explosion: Sometimes Spontaneous combustion of coal is so intense that chaining of such combustion may also cause heavy Explosion, which will be dangerous for people working under coal storage sheds.

6. Co-firing while fusing biomass fuels with Coal: Mixing of biomass with coal is done to reduce Green house gas emissions. The Co-firing incident mostly occurs on mixing biomass with the coal before the burners.

                                                                We at Hindustan Alcox Limited provide practical solutions to these above challenges, in most efficient and cost reducing ways.

-Coal Storage Shed Manufacturers in India (Hindustan Alcox Limited, New Delhi)