Poker in Guildford!

Playing poker in London with my best friends, far away from research and Lab! I needed it!

New model for batch leaching

Today I developed a new mathematical model for batch leaching test on the basis of Fick's law! Chemical reactions and diffusion have been included in this model. Finger cross for the model which I will put in practice next week!

No more research this weekend!

well, after two days hard work in the lab, carrying out Mass Transfer test and preparing the lab for nex week experiments (Leachin contact time), no more research this bank holiday weekend!

Third yera presentation, After it!

What a wonderful day! It was really great...Well the story: I was had 30 min which the guy before took 10 min of my time! So I had only 20 min for the presentation and question part! So I did it very fast. I talked like hell, a very short introduction, assuming that I am doing in a chemical engineering department, full of chemical engineers! But I slowed down in the rseults and discussion part, the mjor part of my work.

I undestood that no one listened to me! No one red the forst slide! No one knew my name except few people which I appreciate them. My supervisor is a great man, he always supports me and I appreciate his kindness and helps.

But the battle field was the question part, when the assessor asked an old question: Where is your model?

Just read his comment on my presentation:

Needs a outline (PS. I am sure he did not linsten ver well)
Thesis should have clear modelling and analysis of equilibrum.diffusion.

I have to add that in this project modelling was in the pbjectives. But I included Mass Transfer tests. Well, in reality, it is impossible to model leachability of trace elements from fly ash, where structure of a fly ash to another one is different. On the other hand, it will be useless to model leaching when the model will be applied on only one type of fly ash! There is no point in modelling fly ash leaching when to can not generilise it. I think the assessor does not know about these facts. He is assessing the project from his point of view and I strongly disagree with him.

Leaching Net

Check it out!

Third year presentation

Tomoroow I have to give a presentation on my PhD research. I am going to talk about batch leaching tests (Availability, TCLP and BS EN tests). I believe these tests do not present actual scenario happing in the environment! We need to design more real tests close to the enviornmnetal conditions. In addition to these, I will talk about leaching behaviour of UK fly ash and effects of pH and LS (Liquid-to-Soild) ratio on leaching process..

Free lime and Arsenic leachability

Well, after months working in the lab, today we found a relationship between free lime content of PFA (coal combustion fly ash) and arsenic leachability. I was very exciting. It was found that during combustion part of the CaO racts with As and the product is an insoluble form of arsein. On the other hand less arsenic will leach. For more information please contact.

Happy Nowruz

Happy New Year (Nowruz 1384) to all my friends and Iranian chemical engineers!

PS You can read more about Persia, persian culture and history on: www.iranchamber.com

Free lime in fly ash

We tried to determine free lime inside fly ash samples. It seems very difficult. Results showed very samll quantities of free lime in the first run! Chemical reactions are unknown at this time and we will try to identify them.

Haloscan commenting and trackback have been added to this blog.

Availability Test

Determining maximum leachable contituents from fly ash is a hard job. It takes at least 6 hours to carry on the test. During the experiment, solution or leachate can contact the atmosphere and some elements may precipitate! This may affect final results and leads to underestimation of all available elements to leaching! So I believe it would better to proceed the test in a closed environment.

The world without engineers
By MZ

World Press Photo

Have a look!

Redox Potential

pH, LS (liquid-to-solid) ratio, temperature and of course fly ash composition are the most important parameters affecting leachability of trace elements from coal fired fly ash. How about redox potential? I believe Eh (or pE) may influence the stability of trace elements in fly ash. However, pH and Eh are related together. On the other hand, decreasing pH leads to increasing Eh. So how can I measure effects of Eh on mobility of trace elements from my fly ash samples in constant pH! How can I keep pH constant and change Eh?

Unit Converter

A powerful program from TCE...Simple to use and very handy!

Removing high volatile trace elements in coal power station by injecting high carbon fly ash

Coal as available source of energy is consisting of carbon and a mixture of various materials including trace elements. Thus value of coal is partially offset by environmental impacts of its combustion. In coal-fired power station, pulverised coal consisting 10% to 30% minerals (depending type of the coal) is burned at temperatures higher than 1600°C. In combustion zone, minerals and trace elements go under different processes including decomposition, diffusion and agglomeration. Trace elements in the coal are redistributed into vapour phase, bottom ash and fly ash during and after combustion. Coal fly ash, or pulverised fuel ash (PFA) is the well known coal combustion by-product which has been used for many years for a wide range of construction applications (Sear, 2001). The main constituents of fly ash are glassy aluminosilicate phases with lesser of mullite, quartz, magnetite, hematite and carbon (Swaine, 1995). However, composition of fly ash depends on several factors including:
- coal composition;
- furnace configuration; and
- combustion conditions.

In a 500 MW power plant, the coal feed is about 5000 t/d (using a typical UK bituminous coal). If the ash content is 15%, then some 750 t/d of ash passes through the boiler (Couch, 1994). In a recent study, fate of trace elements from a 1050 MW power station has been studied (Llorens et al., 2001). In order of magnitude, the transfer of trace elements from the power plant studied to be surrounding environment exceeds more than 10 t/year of As, Cr, pb, V, Li and B through atmospheric emissions, while more than 1 t/year of Li, Ba, Cr, Sr, V, Mo and B from fly ash and Sr and B from bottom ash was estimated to be potentially mobilised by leaching of solid combustion by-products. Hence, a typical power plant produces large amount of waste per day and it only needs a tiny proportion of this contaminates environments of power plants. In a modern power station burning pulverised coal, more than 99% of the fly ash is removed from the flue gases by some means of particle attenuation, usually electrostatic precipitators or the use of fabric filters. This means that most trace elements are also removed, the separation efficiency being 95 to 99% (Godbeer and Swaine, 1995). Trace elements with high volatility leave power station with gaseous phase. Albeit the proper operation of electrostatic precipitators or fabric filters ensures that most particles larger than 10 mm are removed from flue gases, there is possibility some large particles (larger than 10 mm diameter) escape power stations. These particles would return to earth’s surface promptly and hence near the source. However, fine particles are removed form the atmosphere by rain, snow and fog depends on local climate of power station.
There are several methods to control concentration high volatile elements such as mercury in exit of power station. One of these methods is adding additives like activated carbon. Activated carbon may be injected in top of furnace and then removed by electrostatic precipitators. Although activated carbon is an excellent adsorbent, it is expensive. Another alternative adsorbent is high carbon fly ash. It is reported that there is always some carbon in fly ash (Swaine 1995, Watt and Throne 1965, Roy et al. 1981 and Suloway et al, 1983). Amount of this carbon in fly ash depends on combustion condition in power station. Tighter emissions standards have meant the fitting of low NOx burners in power stations. These changes have lead to higher carbon in ash and also deposition pattern in the boiler. This high carbon fly ash can be injected into top of the furnace after air heater in duct and adsorb high volatile elements and then collected by electrostatic precipitators or flue gas clean up section.
In order to model adsorption of mercury by high carbon fly ash, Langmuir hypothesis were developed. Assuming that the adsorption process is not diffusion limited and concentration of mercury in top of furnace is 1 mg/m3 (average concentration of mercury in UK coals is 1 ppm). Therefore ω can be calculated for residence time in duct. At adsorbent injection rate of 1000 g high carbon fly ash per unit volume of gas, 18.9% mercury would be removed.

Please Do Not Park, Tehran-Iran
By MZ

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