Pyrolysis as a Modeling Approach to Saving Energy Usage - Essay Sample

Introduction

Pyrolysis is a conventional process that has a role to play in the conversion of wastes such as scrap, tires, bamboo, plastics, and other agricultural wastes to carbon residues, gases, and liquid hydrocarbon as well. The products are critical since they could substitute fuel while at the same time, they become useful biofuels and biochemical as well. It is essential to understand that the pyrolysis process usually occurs in a vacuum. In most cases, products are typically recovered. Besides, pyrolysis is a process that is beneficial in in-waste treatment mainly due to the commodities generated and the energy recovered when compared to the different other methods. Therefore, this report represents an overview of the figures and facts regarding biodegradable plastics in certain conditions for packaging.

Is your time best spent reading someone else’s essay? Get a 100% original essay FROM A CERTIFIED WRITER!

Save 25%

Methods

The first step that was critical for the study was the fact that the samples, biomass A and plastic B, were subjected to experimental research leading to results that aided in modeling the progress of the pyrolysis.

Experimental study

Thermal analysis was carried out on the samples that are referred to as feedstocks in the rest of the paper. The feedstocks in question were biomass A and plastic B. Plastic B comprised of pellets obtained from suppliers. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were carried out on the samples. Besides, for the mixed-waste approach, the samples were mixed in the ratio 1:0, 1:3, 1:1, 3:1 and 0:1 before the commencement of TGA/DTA analysis. The analysis had a role to play in providing information on the loss of kinetics and heat flow that enabled the comparison of the pyrolysis behavior of the two feedstocks. In addition to that, it offered the kinetic parameters useful for describing the progress of the pyrolysis.

Modeling Study

Importantly, mixed-feedstock pyrolysis was developed to describe the progress of the pyrolysis of the bulk particles using kinetics obtained from both the TGS and DTA experiment. For this to be effective, some assumptions had to be made. The hypothesis include the fact that the pyrolising particle was spherical, the particles transferred heart to each other via conduction mode only, the volatiles that left the particles did not yield any interference directly with the pyrolysis gas, and the only form of inter-particle interaction is the transfer of heat. A MATLAB platform helped in constructing the model and aid in evaluating the proposed mixed feedstock pyrolysis approach.

Thermal analysis

Before the commencement of thermogravimetric analysis, the biomass and plastic were subjected to an investigation, both proximate and ultimate and the results summarized. It is essential to understand that thermogravimetric analysis was paramount and useful to study and comprehend the behavior of the pyrolysis and the kinetics of the different feedstocks. The investigation is a high method of precision used at low-heating rates and under defined conditions as well. Additionally, the plastic sample used in the study was homogenous implying that mass loss is likely to occur at a narrow temperature range while the biomass sample has some components namely hemicellulose, cellulose, and lignin and the loss of weight is expected to be observed at a high and wide range of temperature. The TG profiles shifted from left to right as the blend ratio of the plastic mixture increased between the temperature ranges of 300-440. The blend ratio of the plastic as aforementioned had a significant influence on the final mass fraction. The TG profiles were used for the modeling of the kinetics. During the TGA analysis, DTA (differential thermal analysis) measurement was carried out simultaneously to record the difference in temperature between a sample and a reference material that later reflects the heat flow to and from the feedstock during the pyrolysis process. The baseline method assisted in the construction of the DTA baseline for obtaining of the heat flow.

Results

The behavior of cellulose, lignin, and hemicellulose are essential for a researcher to understand more on the pyrolysis of biomass A. among all these crucial components of biomass, hemicellulose are the first to be pyrolyzed since it has a linear structure of its polymer while also contains short side chains (Oyedun et al., 2014). Cellulose, on the other hand, consists of a semi-crystalline structure chain that is linked to one another while lignin has a complex structure that has strong and durable composite materials. From the research carried out, hemicellulose decomposed between the temperatures of 200 to 350 degrees centigrade while cellulose from 305-375 and lignin 250-500 degrees Celsius.

Thermogravimetric (TG) Analysis

The lignocellulosic biomass structure can be identified quantitatively from a TG analysis. The weight losses observed from the TG and DTG curves are essential to the composition of the biomass components. The TG curves of all the samples tested in the study are shown and represented in the figure below.

From the curve, one can distinguish three diverse regions regardless of the materials that were tested in the experiment. Oyedun et al. (2014) indicate that the change of weight as noticed in a sample is typically recorded as a function of time or temperature. A TG curve has a role to play in portraying the weight change in an example during the design process. In addition to that, the curve helps in conveying information on the behavior of solid fuels when exposed to heat in pyrolytic conditions. In addition to that, a DTG curve helps to emphasize the reaction zone where different steps of a reaction occur over a particular temperature change. In the figure above, the different decomposition changes were shown articulately. The first stage where the temperature was below 200 degrees shows drying periods where the light volatiles especially water were liberated. From the graph, one can notice a slight decay of the sample, which in this case was biomass A.

Further, devolatilization is another essential step in the thermochemical process of conversion that involves biomass. The level is represented by the second decomposition stage that takes place between the temperatures 200-500 degrees. At this stage, one is likely to observe significant slopes of the TG curves that correspond to a substantial drop in weight. The weight changes result from the liberation of hydrocarbon from the rapid decomposition of the hemicellulose present in biomass A, cellulose and some lignin following exposure to heat. During the design process, one is likely to observe a significant decline of below 50 percent of the weight of the tested materials apart from the sample of lignin. The weight change could be associated with the fact that 80 percent weight of biomass is formed from a volatile fraction and only 20 percent of the product is in the form of a carbonaceous residue. From this, one can see that the volatile products have an essential role to play in the pyrolysis process of biomass A and the composition of the gas.

Nonetheless, in stage 3, the loss of weight was not as much as it was exhibited in step 2 due to the various decomposition of the heavy components that emanated primarily from lignin. Two indicators that included T-50 and R-50 conferred a depth assessment of weight loss between the samples that underwent testing. T-50 recorded in degrees Celsius represented the temperature at 50 percent loss of weight while R-50, which stands for percentage minutes minus one represented the reactivity at T-50. The values acquired from the experiment were obtained in the figure below.

From the second figure above, the T-50 values tend to range from 363-410 degrees for the materials except for commercial lignin that has its temperature ranging from 607 degrees. Lignin has a high thermogravimetric as compared to other components present in biomass A. The reactivity levels of the parts differ from 2.9- and 3.19 min-1 apart from lignin whose reactivity level is 1.80 percent min-1. It is essential to understand that when an element has a more significant value of reactivity, the materials tend to become more active. Therefore, this revealed that at a temperature of between 363-410 degrees, 50 percent of weight tends to be lost from all the samples apart from lignin that losses 50 percent of its weight at a temperature of 410 degrees.

TG, DTG and GC Analysis

Further, to get an in-depth analysis of the behavior of the samples, biomass A and plastic B, in a pyrolysis environment, it would be paramount to plot and present TG/DTG curves separately as shown in the figure below.

It is essential to understand the fact that the pyrolysis of biomass material is a complex phenomenon since it involves several reactions in series forms. Oyedun et al. (2014) assert that performing a pyrolysis study on the decomposition mechanism of an individual's biomass fractions has a role to play in assisting a researcher or designer in understanding how a biomass sample behaves as a whole through different and wide temperature ranges in pyrolytic conditions. The temperature that shows the first sign of weight loss in a unit is usually denoted as the initial temperature whose symbol is Ti. At the starting point of the first inverse curve that represents the DTG line, the start point temperature is recorded often as Ts.p while Te.p is usually recorded at the end of a curve to show the end-point temperature. In addition to that, one is likely to realize that from the DTG curve, Tmax is recorded to show the temperature at which a sample undergoes a maximum reaction. The values of the remaining weights of the biomass A and plastic B samples at a temperature of 900 degrees were recorded in the table below.

The primary focus for this study was analyzing is there exists a synergistic reaction between biomass A and plastic B in matters regarding energy relations. The calculated energy of mixed-blend was determined from pyrolysis of the biomass A and plastic Band compared to energy usages determined using two approaches of modeling. The formula for calculating energy usage for the different rations was as follows.

Energy calculated= Xbiomass A Energy biomass A +X plastic B energy plastics

Depending on the modeling studies, the energy used for pure biomass A and purified samples of plastic B were 1.24 and 2.08MJ/kg respectively depending on the initial research. Besides, the energy requirement of plastic B is high since it reaches an endothermic peak during the volatile decomposition.

Further, in the modeling study, the heating rate of 30C for every minute was the factor considered during the simulation process. Mainly, this could be attributed to the experimental heat flow analysis as described in the table below for heating rates of 10C for every minute and 30C at varying blending ratios.

From the table, the heat flow values show that the trend of heat flow for the two rates of heating was similar to the changes in the blended ratios. In addition to that, the heating rate often does not have any effect on the trend of the actual difference in the total energy usage of biomass A pyrolysis at varying pyrolysis temperatures and the stock size of the feeds. With this in mind, it is expected that the rate of heating is not likely to affect the energy increase of the mixed feed as a percentage of plastic B in the feed increments. The modeling results are represented in the figure below as it shows the energy usage for each blended ratio at varying approaches for modeling.

The results discussed above tend to give an articulate comparison between the expected energy usage and that of the two approaches used for the stu...