Product development
Determining Calorific Values
Published
8 years agoon
By
adminKai-Oliver Linde from IKA-Werke GmbH & Co KG, Germany, expounds on the various methods for determining the gross and net calorific value of coal.
One of the main criteria to determine the monetary value of coal is its net calorific value (NCV). Coal is a natural product, and its quality can vary widely. In order to obtain a representative result of such a heterogeneous material, quite some effort is required. The biggest errors are often made during the sampling process and sample preparation – not with the analytical equipment itself.
After proper sampling, the coal needs to go through a number of drying and grinding stages before it is finally ground down to 212 ?m and is ready for analysis. In order to allow everybody to achieve a comparable result, each of the required steps from sampling to the final NCV is described in standards of organisations, such as ISO, DIN, ASTM, GB or GOST.
To determine the gross calorific value (GCV) of coal, so-called oxygen bomb calorimeters are used. To put it simply, a calorimeter determines the heat that is released by 1 gm of sample burned in a closed pressure vessel (decomposition vessel) at 30 bar of oxygen under controlled conditions. The heat released during the burning process needs to be measured under such controlled conditions so that no energy can get into the measuring system or escape from the measuring system. One of the influencing parameters disturbing the measurements with a calorimeter is the room condition. A calorimeter needs to operate ideally in an air-conditioned (controlled) environment.
Any direct sunlight, other sources of heat close to the unit or air draft should be avoided. The calorimeter’s measurement cell should also be operated close to the temperature of the room itself. The pressure vessel (decomposition vessel or "the bomb") in which the sample is burned, is usually surrounded by water. This is the so-called inner vessel of a calorimeter. A PT 1000 temperature sensor allows temperature changes of up to 0.0001 K to be measured within the water. The inner vessel is surrounded by an outer vessel (jacket) that contains water as well, which can be controlled in different ways. Depending on how the jacket’s water temperature is controlled during a measurement, the measurement method is called either adiabatic or isoperibol.
Adiabatic calorimeter
In an adiabatic calorimeter, the temperature in the outer vessel (Tov) is equal to the temperature of the inner vessel (Tiv) throughout the experiment. This is as close to a "perfect isolation" as possible. The temperatures are stable before the sampling is ignited and after the burning process. No correction calculations need to be done when compared with the isoperibol calorimeter.
Isoperibol calorimeter
In an isoperibol calorimeter, the temperature in the outer vessel (Tov) is kept constant throughout the experiment. This does not allow a "perfect isolation"; there are still small temperature fluctua-tions. A correction factor (Regnault-Pfaundler = ?) will be calculated after the experiment that takes these temperature fluctuations into account.
Static-jacket calorimeter
A third method used is the so-called static-jacket calorimeter that has no controlled jacket that may or may not contain water. In this example, the outer vessel is a combination of the pressure chamber, insulating air and the housing of the unit itself.
The jacket is not controlled nor filled with water. It is static. Looking at the temperature profile of the inner vessel of such a calorimeter, it behaves just like an isoperibol calorimeter. The same Regnault-Pfaundler correction calculations used in an isoperibol calorimeter can be applied (see temperature / time graph for isoperibol calorimeter below). The temperature increase ?T is the value an oxygen bomb calorimeter actually measures. In order to know the energy behind the increase of temperature, a calorimeter needs to be calibrated using a suitable substance with a known calorific value. The calibration material of choice worldwide is benzoic acid and is available in pure form and produced by standard institutes, such as the National Institute of Standards (US).
It is important to pay attention to the possibly required corrections of the reference calorific value based on the calorimetric measurement conditions, such as:
- Volume of the pressure vessel;
- Amount of water placed inside the pressure vessel;
- Temperature at the end of the experiment;
- Weight of the sample.
A correction equation to calculate the laboratory specific factor is usually shown in the standards, as well as within the certificate of the calibration material. The actual amount of work required related to the calibration itself in detail varies between the different standards. After the calibration value (C) is determined, the calorimeter can calculate the energy of an unknown sample based on the measured temperature increase. A linearity check of the calorimeter has to be done as well to ensure proper results at different temperature increases caused by higher or lower energy contai-ning samples. It is checked by varying the standard reference materials weight by ? 30 per cent.
After the combustion in a calorimeter, attention should be paid to a number of other reactions taking place during the combustion process. The main influences are caused by nitrogen (N) and sulphur (S). Since the decomposition vessel represents a closed (isochoric) system, the gases produced during the combustion cannot escape. They form acids and heat is released during the same formation, when dissolving in the water inside the decomposition vessel. Nitrogen is either present in the coal sample or can derive from the air that was inside the decomposition vessel when closed, unless the air was purged out of the pressure vessel before ignition. The amount of produced acid also depends on the achieved temperature increase respective of the calorific value of the sample.
Sulphur is preferably determined with sulphur analysers, since these can reach a higher temperature for a longer period of time. This also allows the cracking of inorganic bonds between sulphur and, for example, iron (FeS2). Some standards do allow determining the sulphur after combustion in a calorimeter in the washings by titration. Also the nitric acid formed during the combustion process is usually titrated manually.
These energies need to be deducted from the preliminary gross calorific value to obtain the final gross calorific value at constant volume:
Parallel to the determination of the calorific value, the coal sample is often dried in a nitrogen-purged oven at 105 ?C until the weight is constant. Nitrogen purging avoids further oxidation of the coal during the drying process. Many coals show such behaviour and can appear even heavier after the drying process than before, if dried under normal atmosphere conditions. The moisture determined that way is called analytical moisture.
If the sample was not completely dried before analysis, the weighed-in quantity is not correct since a part of the sample weight was just water. This correction can show quite a strong effect on the final GCV result. At the same time, the GCV corrected for the analytical moisture of the coal is the only basis to be able to compare results with each other properly. The repeatability limit defined in DIN 51900, for example on a coal sample, is 120 J / g if determined consecutively at the same laboratory, by the same operator and under the same conditions.
The GCV is still not yet the final value that is usually reported by a coal laboratory or used to determine the monetary value of the coal. Further analysis and effort is required to get to the so called NCV at constant pressure Hu, p (an). The NCV represents a much more realistic value of energy that will be delivered when burned in a power plant. Therefore further analysis is required with elemental analysis equipment to determine the carbon, hydrogen and sulphur content. Again, the ash content needs to be determined in a furnace that complies to proper standards.
No matter which above mentioned measuring principles (adiabatic, isoperibol, static-jacket) is used by a laboratory, all must lead to the same result within the repeatability and reproducibility limits. Coal analysis laboratories have to verify and be able to prove the proper performance of all their instruments used in the laboratory anytime.
Especially when accredited, according to ISO 17025, it is required to ensure the results produced by the laboratory can be trusted. For this purpose, it is necessary to test the calorimeter’s performance continuously and also record the results in control charts. Besides the standard control methods by using pure calibration standards or other so-called control standards with a known calorific value, it is required to regularly check the procedure with real coal or coke samples. Therefore the laboratories also have to participate successfully in proficiency testing programmes on a regular basis each year. It is demanded to participate in such a programme for each matrix (for example, coal, coke, wood) and each single parameter measured by either device needs to pass the test. The successful parti-cipation is expressed in the so call z-score, which is shown on the certificates of the proficiency test providing company. The z-score has to be = ? 2.
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Marketing strategies of cement companies have undergone gradual transformation owing to the change in consumer behaviour. While TV commercials are high on humour and emotions to establish a fast connect with the customer, social media campaigns are focussed more on capturing the consumer’s attention in an over-crowded virtual world. Branding for cement companies has become a holistic growth strategy with quantifiable results. This has made brands opt for a mix package of traditional and new-age tools, such as social media. However, the hero of every marketing communication is the message, which encapsulates the unique selling points of the product. That after all is crux of the matter here.
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Indian cement industry is well known for its energy and natural resource efficiency
Published
2 years agoon
November 18, 2022By
adminDr Hitesh Sukhwal, Deputy General Manager – Environment, Udaipur Cement Works Limited (UCWL) takes us through the multifaceted efforts that the company has undertaken to keep emissions in check with the use of alternative sources of energy and carbon capture technology.
Tell us about the policies of your organisation for the betterment of the environment.
Caring for people is one of the core values of our JK Lakshmi Cement Limited. We strongly believe that we all together can make a difference. In all our units, we have taken measures to reduce carbon footprint, emissions and minimise the use of natural resources. Climate change and sustainable development are major global concerns. As a responsible corporate, we are committed with and doing consistent effort small or big to preserve and enrich the environment in and around our area of operations.
As far as environmental policies are concerned, we are committed to comply with all applicable laws, standards and regulations of regulatory bodies pertaining to the environment. We are consistently making efforts to integrate the environmental concerns into the mainstream of the operations. We are giving thrust upon natural resource conservation like limestone, gypsum, water and energy. We are utilising different kinds of alternative fuels and raw materials. Awareness among the employees and local people on environmental concerns is an integral part of our company. We are adopting best environmental practices aligned with sustainable development goals.
Udaipur Cement Works Limited is a subsidiary of the JK Lakshmi Cement Limited. Since its inception, the company is committed towards boosting sustainability through adopting the latest art of technology designs, resource efficient equipment and various in-house innovations. We are giving thrust upon renewable and clean energy sources for our cement manufacturing. Solar Power and Waste Heat Recovery based power are our key ingredients for total power mix.
What impact does cement production have on the environment? Elaborate the major areas affected.
The major environmental concern areas during cement production are air emissions through point and nonpoint sources due to plant operation and emissions from mining operation, from material transport, carbon emissions through process, transit, noise pollution, vibration during mining, natural resource depletion, loss of biodiversity and change in landscape.
India is the second largest cement producer in the world. The Indian cement industry is well known for its energy and natural resource efficiency worldwide. The Indian cement industry is a frontrunner for implementing significant technology measures to ensure a greener future.
The cement industry is an energy intensive and significant contributor to climate change. Cement production contributes greenhouse gases directly and indirectly into the atmosphere through calcination and use of fossil fuels in an energy form. The industry believes in a circular economy by utilising alternative fuels for making cement. Cement companies are focusing on major areas of energy efficiency by adoption of technology measures, clinker substitution by alternative raw material for cement making, alternative fuels and green and clean energy resources. These all efforts are being done towards environment protection and sustainable future.
Nowadays, almost all cement units have a dry manufacturing process for cement production, only a few exceptions where wet manufacturing processes are in operation. In the dry manufacturing process, water is used only for the purpose of machinery cooling, which is recirculated in a closed loop, thus, no polluted water is generated during the dry manufacturing process.
We should also accept the fact that modern life is impossible without cement. However, through state-of-the-art technology and innovations, it is possible to mitigate all kinds of pollution without harm to the environment and human beings.
Tell us about the impact blended cement creates on the environment and emission rate.
Our country started cement production in 1914. However, it was introduced in the year 1904 at a small scale, earlier. Initially, the manufacturing of cement was only for Ordinary Portland Cement (OPC). In the 1980s, the production of blended cement was introduced by replacing fly ash and blast furnace slag. The production of blended cement increased in the growth period and crossed the 50 per cent in the year 2004.
The manufacturing of blended cement results in substantial savings in the thermal and electrical energy consumption as well as saving of natural resources. The overall consumption of raw materials, fossil fuel such as coal, efficient burning and state-of-the-art technology in cement plants have resulted in the gradual reduction of emission of carbon dioxide (CO2). Later, the production of blended cement was increased in manifolds.
If we think about the growth of blended cement in the past few decades, we can understand how much quantity of , (fly ash and slag) consumed and saved natural resources like limestone and fossil fuel, which were anyhow disposed of and harmed the environment. This is the reason it is called green cement. Reduction in the clinker to cement ratio has the second highest emission reduction potential i.e., 37 per cent. The low carbon roadmap for cement industries can be achieved from blended cement. Portland Pozzolana Cement (PPC), Portland Slag Cement (PSC) and Composite Cement are already approved by the National Agency BIS.
As far as kilogram CO2 per ton of cement emission concerns, Portland Slag Cement (PSC) has a larger potential, other than PPC, Composite Cement etc. for carbon emission reduction. BIS approved 60 per cent slag and 35 per cent clinker in composition of PSC. Thus, clinker per centage is quite less in PSC composition compared to other blended cement. The manufacturing of blended cement directly reduces thermal and process emissions, which contribute high in overall emissions from the cement industry, and this cannot be addressed through adoption of energy efficiency measures.
In the coming times, the cement industry must relook for other blended cement options to achieve a low carbon emissions road map. In near future, availability of fly ash and slag in terms of quality and quantity will be reduced due to various government schemes for low carbon initiatives viz. enhance renewable energy sources, waste to energy plants etc.
Further, it is required to increase awareness among consumers, like individual home builders or large infrastructure projects, to adopt greener alternatives viz. PPC and PSC for more sustainable
resource utilisation.
What are the decarbonising efforts taken by your organisation?
India is the world’s second largest cement producer. Rapid growth of big infrastructure, low-cost housing (Pradhan Mantri Awas Yojna), smart cities project and urbanisation will create cement demand in future. Being an energy intensive industry, we are also focusing upon alternative and renewable energy sources for long-term sustainable business growth for cement production.
Presently, our focus is to improve efficiency of zero carbon electricity generation technology such as waste heat recovery power through process optimisation and by adopting technological innovations in WHR power systems. We are also increasing our capacity for WHR based power and solar power in the near future. Right now, we are sourcing about 50 per cent of our power requirement from clean and renewable energy sources i.e., zero carbon electricity generation technology. Usage of alternative fuel during co-processing in the cement manufacturing process is a viable and sustainable option. In our unit, we are utilising alternative raw material and fuel for reducing carbon emissions. We are also looking forward to green logistics for our product transport in nearby areas.
By reducing clinker – cement ratio, increasing production of PPC and PSC cement, utilisation of alternative raw materials like synthetic gypsum/chemical gypsum, Jarosite generated from other process industries, we can reduce carbon emissions from cement manufacturing process. Further, we are looking forward to generating onsite fossil free electricity generation facilities by increasing the capacity of WHR based power and ground mounted solar energy plants.
We can say energy is the prime requirement of the cement industry and renewable energy is one of the major sources, which provides an opportunity to make a clean, safe and infinite source of power which is affordable for the cement industry.
What are the current programmes run by your organisation for re-building the environment and reducing pollution?
We are working in different ways for environmental aspects. As I said, we strongly believe that we all together can make a difference. We focus on every environmental aspect directly / indirectly related to our operation and surroundings.
If we talk about air pollution in operation, every section of the operational unit is well equipped with state-of-the-art technology-based air pollution control equipment (BagHouse and ESP) to mitigate the dust pollution beyond the compliance standard. We use high class standard PTFE glass fibre filter bags in our bag houses. UCWL has installed the DeNOx system (SNCR) for abatement of NOx pollution within norms. The company has installed a 6 MW capacity Waste Heat Recovery based power plant that utilises waste heat of kiln i.e., green and clean energy source. Also, installed a 14.6 MW capacity solar power system in the form of a renewable energy source.
All material transfer points are equipped with a dust extraction system. Material is stored under a covered shed to avoid secondary fugitive dust emission sources. Finished product is stored in silos. Water spraying system are mounted with material handling point. Road vacuum sweeping machine deployed for housekeeping of paved area.
In mining, have deployed wet drill machine for drilling bore holes. Controlled blasting is carried out with optimum charge using Air Decking Technique with wooden spacers and non-electric detonator (NONEL) for control of noise, fly rock, vibration, and dust emission. No secondary blasting is being done. The boulders are broken by hydraulic rock breaker. Moreover, instead of road transport, we installed Overland Belt Conveying system for crushed limestone transport from mine lease area to cement plant. Thus omit an insignificant amount of greenhouse gas emissions due to material transport, which is otherwise emitted from combustion of fossil fuel in the transport system. All point emission sources (stacks) are well equipped with online continuous emission monitoring system (OCEMS) for measuring parameters like PM, SO2 and NOx for 24×7. OCEMS data are interfaced with SPCB and CPCB servers.
The company has done considerable work upon water conservation and certified at 2.76 times water positive. We installed a digital water flow metre for each abstraction point and digital ground water level recorder for measuring ground water level 24×7. All digital metres and level recorders are monitored by an in-house designed IoT based dashboard. Through this live dashboard, we can assess the impact of rainwater harvesting (RWH) and ground water monitoring.
All points of domestic sewage are well connected with Sewage Treatment Plant (STP) and treated water is being utilised in industrial cooling purposes, green belt development and in dust suppression. Effluent Treatment Plant (ETP) installed for mine’s workshop. Treated water is reused in washing activity. The unit maintains Zero Liquid Discharge (ZLD).
Our unit has done extensive plantations of native and pollution tolerant species in industrial premises and mine lease areas. Moreover, we are not confined to our industrial boundary for plantation. We organised seedling distribution camps in our surrounding areas. We involve our stakeholders, too, for our plantation drive. UCWL has also extended its services under Corporate Social Responsibility for betterment of the environment in its surrounding. We conduct awareness programs for employees and stakeholders. We have banned Single Use Plastic (SUP) in our premises. In our industrial township, we have implemented a solid waste management system for our all households, guest house and bachelor hostel. A complete process of segregated waste (dry and wet) door to door collection systems is well established.
Tell us about the efforts taken by your organisation to better the environment in and around the manufacturing unit.
UCWL has invested capital in various environmental management and protection projects like installed DeNOx (SNCR) system, strengthening green belt development in and out of industrial premises, installed high class pollution control equipment, ground-mounted solar power plant etc.
The company has taken up various energy conservation projects like, installed VFD to reduce power consumption, improve efficiency of WHR power generation by installing additional economiser tubes and AI-based process optimisation systems. Further, we are going to increase WHR power generation capacity under our upcoming expansion project. UCWL promotes rainwater harvesting for augmentation of the ground water resource. Various scientifically based WHR structures are installed in plant premises and mine lease areas. About 80 per cent of present water requirement is being fulfilled by harvested rainwater sourced from Mine’s Pit. We are also looking forward towards green transport (CNG/LNG based), which will drastically reduce carbon footprint.
We are proud to say that JK Lakshmi Cement Limited has a strong leadership and vision for developing an eco-conscious and sustainable role model of our cement business. The company was a pioneer among cement industries of India, which had installed the DeNOx (SNCR) system in its cement plant.
Concrete
NTPC selects Carbon Clean and Green Power for carbon capture facility
Published
2 years agoon
October 12, 2022By
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