Valorization and characterization of CCRs of the Jerada thermal power plant in the northeast of Morocco

The thermal power plants are globally criticized for generating large amount of solid wastes often with a potential environmental impact. The main objective of this study is characterized the CCRs (Coal Combustion Residues) produced by the thermal power plant in the East region of Morocco (Jerada city). On other hand, in order to use this CCRs (fly ash and bottom ash) effectively, it is necessary to study the raw material of which they are trained in all their aspects and to check their behavior in the various employment possibilities. For this purpose, mechanical compressive test on 10x10x10 cm of mortar specimens and chemical test of X-ray on CCRs are performed. We did work on the use of CCRs as an addition in Portland cement. Firstly, compressive tests and chemical requirements were used to evaluate the pozzolanic activity index according to ASTM C618 which is about 89,75%. Indeed, the results of an experimental plan, on compressive strength of the new by-product (10% CCRs and 90% cement), gave a good response of our plan, it’s about 24,20 MPa. Secondly, we have added this new by-product with the clay to produce the fired compressed bricks according to a new experimental plan, where we found that the most response of the compressive strength equal to 3,12 MPa, in which a minimum volume of water of 581 cm and a minimum quantity of clay of 50% (by total mass of 1kg), were used. In order to valorize these residues, our results show a good correlation with the ASTM standard and we can use this by-products in bricks manufacture. Keyword-Fly Ash, Bottom Ash, Valorization, Waste, Coal, CCRs, Pozzolanic, CO2, by-product, Boiler.

a Estimation and extrapolation from available data. b Datum includes also Reclamation and Restoration utilization. Without including this, the CCRs utilization is 25,290 Mt with an average utilization rate of 52%.  [22] From where the valorization of the waste is a strategic gait for all country of the world, it is about the transformation of an unusable residual to a wealth. The valorization of CCRs is indeed very common in the cement industry as raw material in the production of the cement clinker, interground with the clinker, or blended with the finished cement [4], [23]. This procedure is profitable for our environment and witch has remarkable advantages. For our study, the objective is to valorize the solid residues generated by the coal power plant of Jerada city and to find efficient uses for this material that causes some problems for the thermal power plant in term of cost of evacuation as well as the environmental level.
At the time of this study a physicochemical characterization has been made to define the material, then several uses have been developed and have been tested.

II. DEFINITION OF THE WASTE
To the origin of all particular measure aiming the waste, there is the hypothesis that the very notion of waste can be defined. However, most authors agree to say that at the present, it's doesn't exists a satisfactory definition for the waste [24], [25], [26]. Indeed, the notion of waste can aim objects of nature and different functions.
To avoid the misunderstandings, the different actors implied in the management of the environment tempted to give a definition to the word "waste". There are actually several definitions that correspond to a particular objective. Every definition aims for actor's group to establish the set of the objects that should be the subject of a particular behavior or a particular attention, but it is lastly the legal definition that should act as reference [27].

A. Authorized Approach
For the legislator, it was above all about regulating the treatment of the waste as while prohibiting the reject in the environment or the resale within sight from escaping the legal obligations. It was necessary to be able to define exact manner what entered in the setting of the law therefore.

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VIII. THE POZZOLANIC PROPERTIES OF THE MINERAL COAL COMBUSTION RESIDUES
In the cements ASTM standard [34], the pozzolana are defined like the siliceous materials or aluminosilicate witch doesn't possess in themselves binding properties but that react chemically, in finely divided form and in the presence of moisture, with the calcium hydroxide at ordinary temperature to form compounds having binding properties. According to the standard [36], a material has the characteristic of a pozzolana if:  Its chemical composition checks: AL 2 O 3 + SiO 2 + Fe 2 O 3 > 70%  Its activity indication I is: 0,67 <I <1. Thus, based on the chemical composition of the CCRs, we can associate them a pozzolanic character. However few studies have been led on the potential pozzolanic properties of the bottom ash. In terms of the CCRs, the studies on the pozzolanicity, were more concerned the fly ash because they have the advantage to have a fine granulometry as the one of the cement. Nevertheless, since 1999 M. Cheriaf and some studies are also led on the potential use of the bottom ash as additive in the cement [35]. On the Brazilian CCRs, it is found that the bottom ash has a pozzolanic reactivity (of 88% in 28 days) permitting its use as additive in the Portland cement production. H. Kurama and al, also show that while substituting the cement by 15% of bottom ash, an increase of the resistances to bending and to the compression of the mortars is observed after 56 days of cure [36].

A. Physical and chemical characterization of the solid residues of TPP
The International ASTM (American Society for Testing and Material), is an organism of normalization that writes and produces the technical standards concerning the materials, the products, the systems and the services. It has been founded in 1898 in the United States under the direction of Charles Benjamin Dudley. Its founders were scientists and engineers. Its creator wanted to reduce the number of ruptures of railroad rails that often arrived in this industry in full growth. The group developed a standard concerning steel used for the rails manufacture.
Today, international ASTM has more than 12 000 standards in its catalog. The yearly publication of the ASTM standards book is composed of seventy-seven volumes.
The association members are the representatives of the industrial, the users, the governments and the universities of more than hundred countries [37]. Chemical composition of the CCRs: The chemical composition of the sample is given by the following analyses: According to the standard ASTM [40], the fly ash present themselves in two classes: The only difference between the two classes is the percentage of calcium oxide. For the C class the percentage of calcium oxide is >20%.
For our sample the calcium content is low (<1%), therefore it is fly ash of F class

B. Physical characteristics of CCRs 1) Experimental calculation of total humidity:
It is about taking a sample of the by-product whose mass is known and to dry it in an oven during 24 hours then calculate the new mass, by the following formula:

Humidity = (1 -M final /M initial ) x100
(1) Results obtained: humidity of sample = 2.5% 2) Experimental calculation of Loss on Ignition ratio: It is about heating a dry sample of known mass to 750°C during 3 hours and to measure the new mass after leaving the oven.
The calculation of the percentage of the unburned consists in first place to calculate the percentage of the organic matter, so it is given by the following formula:

Results obtained: LOI = 10%
3) Fineness test: The principle is to use a sieve of 45 micrometer to filter a quantity of the sample and then measuring the mass retained by the sieve.
Results obtained: 76% of the particles have a fineness lower to 45µm.

4) Calculation of the density:
The real density of the by-product is the weight by volume unit of the sample in very fine powder. To determine the real density, the sample is dispersed in the water. The quantity of water dispersed by gram of the fly ash gives the true density of them. This density, which varies from 2 g/cm 3 to 2,8 g/cm 3 , determines the volume that it must occupy for a given mass. Changes in density can indicate a source of different coal.
The procedure is to take a pot of measuring graduated in ml, clean thoroughly with pure water. Take some water in the ball until a certain level and note its level (first reading). Deposit slowly 20 grams of the sample provided in the jar. Shake the jar during a certain time. Note eater's level in the jar (final reading). Repeat this operation for 4 samples or more and compile the results. Divide the difference of the final and initial value in weight of the sample to obtain the real density.   For the 1 st factor (the clay quantity), the low level is equal to 50% and the high level is equal to 80%, and for the 2 nd factor (the water volume), the low level is 581 and the high level is 633, the study field of 1 st factor is therefore [50%, 80%] and for 2 nd factor we have [581, 633], as shown in Fig. 13. The field of study is made up of all points whose coordinates are inside the areas of each factor. We will perform an experience plan of two factors where we involve four experiments, see Table XIII. In the same way carried out in the previous experiment plan, our mathematical model becomes as the following: Y = 2.8075 -0.0775x 1 -0.2625x 2 -0.0275x 1 x 2 (7) At the center of the domain, the compressive strength is 2.8075 MPa, see Fig. 14.In fact, the effect of the clay quantity is -0.0775; That means a negative effect, in other words, when the quantity of clay passes from the central point of the study field (65% clay and 607 cm3 of water) to point G, the compressive strength decreases. Thus, when the clay quantity passes from point O to point F, the compressive strength increases, as shown in Fig. 15 [14], [15], he results fou mixture) by a n d our goal tha the ASTM sta ume. erformed, we eriment, we fo m 3 and a minim ed out with th ents to carry o r on the respon issue of this w o reuse them i tion curve for the ce study of the fa ation Plot of the 2
[13]- [22], by chosen the la n FA only and experimental p nt material to % CCRs and ks on the bas t bricks were t lans method, w he amount to u vironmental im manufacture. y its exploitati ast five works d applying the plans [41].