Keywords

1 Introduction

The increase in plastic using up has been going on speedily since the last 5–6 decades because of lightweight and ability of plastic to form. Today, the principal interests are the requirement for energy and the degradation of the environment, which are because of expanding population and accelerated industrialization [1]. Actions are initiated to defeat the fossil fuel crisis by looking for options to replace gasoline and diesel. The development of alternative fuel technologies is created to give the alternative to fossil fuels [2]. The techniques focused are bioethanol, biodiesel, biodiesel derived from lipids, recycling the waste oils, pyrolysis, gasification, dimethyl ether, and biogas [3]. The use of plastic in a world was about 5 million tons annually in 1950s has enlarged to 20 times from about 100 million tons [4]. Currently, most plastic waste is disposed of in landfills or deposits, which involve our precious land spaces. The disposal methods, such as landfills, reuse, and combustion, can produce serious risks, particularly in human and environmental health [5]. Only a small percentage of plastic waste enters the reuse/recycling options, such as the use as a filler on asphalt roads or as a raw material for secondary product generation, such as recycled rubber, nonnatural barriers, or breakwaters [6].

Therefore, plastic waste can be deemed an energy resource. It has a sizeable calorific value, a high volatile content, and decreased ash content than coal and bio-ass [7]. Therefore, the residual plastic is the right suitor for the utilization of thermal elimination. These characteristics present it a perfect element for thermal processes like pyrolysis and gasification. Waste into the energy is designed to process potential materials into waste that are plastics, biomass, and rubber tires to oil [8]. The pyrolysis is growing as a substitute to give biofuel for compensation of the fossil fuel [9, 10]. Plastic waste is studied in the study as an accessible technology. The pre-treatment of the material is comfortable, as described in the article. The plastic is necessary to be classified and dried. Also, pyrolysis is neither toxic nor dangerous to an environment, unlike incineration [11]. Pyrolysis found enormously flexible procedure fit for large- and small-scale production [12].

2 Materials and Methods

2.1 Types of Plastics, Properties, and Its Uses

The different kinds of plastic have various features such as moisture content, heat resistant, chemical resistance, surface phenomenon, etc., which can be the prominent phenomenon for typical household uses [13]. The classification of plastic based on properties is listed in Table 1.

Table 1 Plastic categorization depending upon properties and its uses
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2.2 Principle of Pyrolysis

Pyrolysis is an endothermic process, an ecologically attractive method to treat plastic waste. The method practices average temperatures (300–700) °C and an oxygen-independent atmosphere for chemical decomposition of solid plastic waste into coal, oil, and gas, as per Fig. 3, which produces a minimal discharge of the nitrogen oxide and sulfur compared to incineration, the most popular method of industry [14]. Pyrolysis method consists of a collection of waste plastic, weighing and adding a waste plastic including catalyst into the reactor, pyrolysis of this waste plastic and collection, analyzing the extracted oil of a waste plastic [15]. The systematic flowchart of this process is presented within the Fig. 1.

Fig. 1
figure 1

Flowchart for pyrolysis process

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The feedstocks utilized for the experiments were waste plastics having polyethylene terephthalate and high-density polyethylene and the same were obtained from the dumping place, and the little plastic recycling at Nagpur City, Maharashtra, India. The appearance of these feedstocks such as the collection of waste plastic, cleaning it, and shredding the waste plastics are shown in Fig. 2.

Fig. 2
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Typical pyrolysis process

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2.3 Experimentation on Pyrolysis Setup

Pyrolysis set-up as in Fig. 3 mainly comprises of reactor, GI coupling, GI pipe, condenser, water inlet, water outlet, RB flask, condenser, LPG gas cylinder, and iron stand.

Fig. 3
figure 3

Typical pyrolysis process, where 1—reactor, 2—GI coupling, 3—GI pipe, 4—condenser, 5—water inlet, 6—water outlet, 7—RB flask, 8—condenser, 9—LPG gas cylinder, and 10—iron stand

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The specification for material, top and bottom diameter, depth, volume, and weight of the reactor for pyrolysis setup is listed in Table 2.

Table 2 Dimensions of different elements of the setup
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In this process after the entire setup of pyrolysis was done, as it turned on and fired with the help of matchbox along with turning on the flow of cold water into a condenser and left for observation. The reactor gets consistently heated, which further raises a temperature of the reactor, causing the waste plastics to break and release vapors [16]. The air-packed manufacturing of reactor gives no leakage to the system and allows a vapor for flow through the outlet pipe, which then goes into the inner glass tube of the condenser [17, 18]. Meanwhile, the noncondensable vapors get out within the environment from the loosely tightened end of the condenser and the RB flask [19, 20]. The condensable vapor sticks to the inner wall of the tube and simultaneously forms droplets of oil as a result of heat exchanged with the cold water and get collected into the RB flask. After sometimes, it is seen that the flow of oil from the condenser stops, which shows that the number of plastics added into the reactor is pyrolyzed [21, 22]. Still to confirm that there are no leftover condensable vapors the reactor is heated for a few more minutes.

Subsequent cooling of reactor, remaining ash is there and plastic compressed like char, which needs to be separate using sieving. The char can be further utilized in road construction.

In the experimentation, 180–400 gm of the feedstock was supplied to a pyrolysis reactor. After this, pyrolyzer unit plus reformer was heated up to selected temperatures. Output obtained from a process in liquid form were got inside the RB flask

3 Results and Discussions

The amount of weight plastic 180 gm, 380 gm, 400 gm was tested for 1 h, 2 h, and 2 h 15 min, respectively. Amount of oil collected from waste plastic is, as presented in Table 3.

Table 3 Observations during experimentations
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The amount of fuel getting collected in the RB flask and fuel collected at the end of the experimentation is as presented in Fig. 4.

Fig. 4
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a Fuel getting collected in the RB flask, b Fuel collected at the end of the experiment

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Table 4 reflects the various properties of the liquid product for diesel grade.

Table 4 Physical properties of fuel extracted
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4 Conclusions

The conclusions reached by experimentations are,

  1. 1.

    Pyrolysis method looks an efficient waste-to-energy converter which is considered reasonable to turn plastic into liquefied outputs and to enhance the waste plastics.

  2. 2.

    Pyrolysis could be carried under minimal expenses for small-scale waste plastic oil extraction, and 10–20 ml could be obtained by burning 180–380 gm of plastic.

  3. 3.

    Rather than direct burning of plastic into the atmosphere, converting into fuel decreases 80 percent of CO2 emission in the atmosphere.

  4. 4.

    Fewer emissions of unburned hydrocarbons in plastic pyrolysis waste oil as comparing to diesel.

  5. 5.

    Obtained diesel oil or oil has better performance and, as compared, has 30–40% low production costs.

  6. 6.

    The waste plastic recycling will perform a crucial task in the transformation of a newer era.

  7. 7.

    The gas portion can be analyzed in the future with gas chromatography to know the contents of CO, CO2, H2, N2, and others.