Description:
FIELD OF INVENTION
The present invention relates to co-processing of granulated waste plastic through Coke ovens in a Steel Plant. Particularly, it relates to a method and system of co-processing of granulated waste plastic through Coke ovens in a Steel Plant.

BACKGROUND OF INVENTION
Plastic has become one of the most pressing environmental issues that we are facing today. India is generating about 3.5 - 4.0 MT of plastic waste annually. The per capita plastic waste generation has almost doubled over the last five years. The utilization/disposal of plastic wastes is an important environmental issue and needs to be addressed. About 400 MT of plastics are produced per annum worldwide. End-of-life plastics disposal contaminates the waterways, aquifers and limits the landfill areas. Options for recycling plastic wastes include, feedstock recycling, mechanical /material recycling, industrial energy recovery, municipal solid waste incineration. Incineration of plastics containing E-Wastes releases noxious odours, harmful gases, dioxins, HBr, polybrominated diphenylethers and other hydrocarbons.
Most of the countries across the globe are exploring options for effective utilization of the plastic wastes and some countries are using these wastes in iron & steel industry. The amount of industrial and domestic plastic waste in India is increasing steadily.
US20070135667A1 relates to a method of reutilization of waste plastic, in particular a method of reutilization of waste plastic by dry distillation in a coke furnace and a method of shaping of waste plastic. A method of reutilization of waste plastic characterized by melting waste plastic at over 160° C. to 250° C. in temperature in part or whole, compression shaping it to thereby obtain a plastic granular material having an apparent density of 0.7 to 1.2 kg/liter, and mixing this plastic granular material with coal for carbonization in a coke oven.
JP2002012876A relates to a method of blending waste plastics into raw coal and treating the same in a coke oven, wherein the waste plastics is blended into raw coal so as to satisfy the following equation (1). Treatment method in coke oven. W / (ρ · V) ≦ 1.0 (1) Where, W: amount of waste plastics (% by mass), ρ: density of waste plastics at the time of mixing (g / c
m 3 ), V: volume (cm 3 ) per waste plastic at the time of compounding.
CN101831313A relates to a waste plastics pretreatment process based on coking by a coke oven having the steps of: (1) performing coarse crushing on the waste plastics by a crusher until the grain size is 8-12mm; (2) feeding the waste plastics with the grain size of 8-12mm after coarse crushing in a pyrolysis oven, heating to 225-275 DEG C under the condition of air isolation, pyrolyzing for 30-90min at a constant temperature and dissolving out pyrolysis gas; (3) cooling the fluid residue of the waste plastics after pyrolysis to form solid-state solids, and feeding the solid-state solids in the crusher again for crushing until the grain size is no more than 1mm; and (4) blending the solid-state solids in coking coal according to the proportioning of 1% by weight.
Krishnan, S. H., et al. "Use of waste plastics in cokemaking at Tata Steel." Ironmaking & steelmaking 33.4 (2006): 288-292 reports the waste plastics recycling process using stamp charged coke ovens.
Nomura, Seiji. "Use of waste plastics in coke oven: A review." Journal of sustainable metallurgy 1 (2015): 85-93 is a review publication which reports the a waste plastic-recycling process using coke oven.
There still exists a need to develop an efficient method and system for the effective utilization of the plastic wastes. The present inventors have surprisingly developed an efficient method and system which ameliorates the aforesaid shortcomings of the prior art.

OBJECTS OF THE INVENTION
It is an object of the present invention to overcome the shortcomings of the prior art.
It is an object of the present invention to provide a method for utilization of waste plastic in coke making.
It is another object of the present invention to provide a system for utilization of waste plastic in coke making.

SUMMARY OF THE INVENTION
According to an aspect of the present invention there is provided a method of co-processing of granulated waste plastic through coke ovens.
According to another aspect of the present invention there is provided a system of co-processing of granulated waste plastic through coke ovens.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1: Schematic drawing shows various components of the system
Figure 2: Photographic image of in-house structure fabricated and erected beside coal conveyor
Figure 3: is a view of a compression shaping machine for waste plastic using the present invention
Figure 4: Process flow chart of pretreating plastic waste to waste plastic granules required for co-processing
Figure 5: Photographic image of waste plastic granules obtained by pre-treatment

DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.
Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the scope of the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.
It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, steps or components but does not preclude the presence or addition of one or more other features, steps, components or groups thereof.

The present invention relates to co-processing of granulated waste plastic through Coke ovens in a Steel Plant. Particularly, it relates to a method and system of co-processing of granulated waste plastic through Coke ovens in a Steel Plant.

The waste plastics of the non-industrial waste types are collected as forms of bags, films, foamed bodies and powders. Therefore, it is necessary to pre-treat the collected waste plastics and change their shape and size to make them suitable for charging into coking chambers. After waste plastics are pre-treated, they are mixed with coal blends, charged into coke ovens and carbonized. Waste plastics are carbonized at high temperature and decomposed into coke, tar, light oil and gas.
Recycling this plastic waste through the coke making process can be a good green initiative with the added bonus of savings in costly coking coal.
Co-processing of waste plastic using coke ovens is superior in that a large amount of waste plastics can be treated, useful materials can be recovered using the existing facilities, coke quality can be kept the same and the chlorine released from waste plastics can be absorbed in the existing ammonia liquor spray system.
Whatever, waste plastic will generate within plant will be utilized in coke making. It is also reflected in the environment sustainability.

The present invention provides a method for co-processing of granulated waste plastic in coke oven comprising the steps of:
i. Pretreating the plastic waste to form waste plastic granules;
ii. Mixing the waste plastic granules of step (i) with coal blend for carbonization in a coke oven.

In an embodiment, the said pretreating of plastic waste to form plastic waste granules comprises the steps of:
a. Shredding of the plastic waste to a grain size less than 10 mm;
b. Washing of the shredded plastic waste of step (a);
c. Drying of the washed plastic waste of step (b);
d. Agglomeration of the dried plastic waste of step (c) to a size ranging from 5 to 8 mm and density ranging from 0.8g/cc.to 0.9 g/cc to obtain waste plastic agglomerates; and
e. Converting the agglomerates of step (d) to cylindrical granules of 2 mm to 3mm diameter and 2-3 mm length and a density of 1.2 - 1.3 g/cc by extrusion at a temperature of 150-200 oC to form the waste plastic granules for co-processing.
The granule size and shape resembles the coal particle size, shape and density, preventing segregation as the coal-plastic mix is charged in the coke oven.

In an embodiment, the waste plastic granules are mixed with coal blend in a mass ratio ranging from 0.2% to 1.0 mass %.
In an embodiment, the crushing index of each coal charge is maintained from 80 to 82 % of less than 3.2-mm size fraction and the moisture ranges from 7 to 9 % before charging the blends into the coke oven.
In an embodiment, the coking duration is of 18 hours.
In an embodiment, the end coke mass temperature ranges from 1000 to 1010 ºC.

The present invention also provides a system for co-processing of granulated waste plastic in coke oven.

Reference numbers of the components according to various embodiments of the present invention are listed below for ready reference. However it is to be understood that the present invention is not limited to these components and may include other components.
Reference No Name of the components
100 System for co-processing of waste plastic granule
101 Granulated plastic storage bin
102 Discharge hopper for plastic granules
103 Existing coal blend discharge conveyer belt
104 Conveyer belt of plastic granules

Figure 1 illustrates a system according to the present invention for co-processing of granulated waste plastic Figure 2: Photographic image of in-house structure fabricated and erected beside coal conveyor Figure 3: is a view of a compression shaping machine for waste plastic using the present invention. The compression shaping machine is used after transformed into agglomerate of waste plastic.
The system (100) for co-processing of granulated waste plastic in coke oven comprises:
A. Granulated plastic storage bin (101);
B. Discharge hopper for plastic granules (102);
C. Coal blend discharge conveyer belt (103); and
D. Conveyer belt of plastic granules (104).

The plastic storage bin (101) is configured to store the pre-treated granulated waste plastic. The discharge hopper for plastic granules (102) is in-house fabricated and erected beside coal conveyor (103) having features of capacity of 5000 kg / batch, synchronized plastic flow with coal flow for regulated addition of plastic and safety interlocking between coal conveyor (103) and conveyor belt of plastic granules (104).

EXAMPLES:
The following examples are meant to illustrate the present invention. The examples are presented to exemplify the invention and are not to be considered as limiting the scope of the invention.
EXAMPLE 1:
A pilot scale study was carried out to analyze the effect of using waste plastic granules in coal blend.
Step I] Pre-treatment of plastic waste into granules:
Analysis of waste plastic, in mass %
Ash 4.9
Carbon 78
Hydrogen 12
Sulphur 0.9
Chlorine 1.4
Alkali 0.15
Table 1
Figure 4 illustrates a process flow chart of pre-treating plastic waste to waste plastic granules required for co-processing and Figure 5 is a Photographic image of the waste plastic granules obtained by pre-treatment.
Pre-treating of plastic waste to form plastic waste granules involves the following steps:
a. Shredding of the plastic waste to a grain size less than 10 mm;
b. Washing of the shredded plastic waste of step (a);
c. Drying of the washed plastic waste of step (b);
d. Agglomeration of the dried plastic waste of step (c) to a size ranging from 5 to 8 mm and density ranging from 0.8g/cc.to 0.9 g/cc to obtain waste plastic agglomerates; and
e. Converting the agglomerates of step (d) to cylindrical granules of 2 mm to 3mm diameter and 2-3 mm length and a density of 1.2 - 1.3 g/cc by extrusion at a temperature of 150-200 oC to form the waste plastic granules for co-processing.

The aforesaid pre-treatment step helps to achieve the granule size and shape of the pre-treated waste plastic granules that resembles the coal particle size, shape and density, preventing segregation as the coal-plastic mix is charged in the coke oven.

STEP II] Co-processing of the waste plastic granules with coal in coke oven:
The crushing index of each coal charge was maintained at 81±1% of <3.2-mm size fraction. Working moisture was adjusted to 8±1% just before charging the respective blends into the pilot oven. Carbonization tests were carried-out in the electrically heated movable wall pilot coke oven (250 kg capacity) of Carbolite Make, UK. The following carbonization conditions were maintained during the test campaign:
 Coking Period : 18 hrs.
 End Centre Coke Mass Temperature : 1000 + 10 ºC

Waste plastic granules were added in coal blend from 0.5 % to 3% to determine the effect on coke quality and operational factors.
The cokes resistance represents the sum of the resistance at compression, shearing, friction, pressing, dynamic shock and it is determined using samples in which the coke is the subject of hitting and friction efforts through rolling in a tambour. The resistance is determined at the carbonization plant, as well as at the furnace (the resistance indices is greater, the coke being stabilized during transport and depositing). The resistance, in Micum drum, is an international standardized method, being the most used one, indices obtained in the test are: M40= mechanical resistance M10 = abrasion. Larger values of M40 and smaller values of M10 indicate strong coke. The CSR (Coke Strength after Reaction) represents the resistance of coke after the reaction with CO2. The percentage weight loss after reaction is known as the coke reactivity index (CRI).
The results are shown in Table 2 below:
Base
Plastic 0.5 % Plastic 1 % Plastic 2 % Plastic 3 %
M40, % 81.5 83.2 84.0 81.5 81.8
M10, % 10.0 10.0 9.8 10.6 10.0
CRI, % 31.9 30.5 29.9 32.2 32.6
CSR, % 42.9 46.8 50.9 45.2 44.1
Table 2
Abbreviations: M40: mechanical resistance; M10: abrasion; CSR: Coke Strength after Reaction; CRI: Coke reactivity index.

From the aforesaid Table 2, it was found that the optimum usage level of waste plastic is about 0.5 to 1 mass% in the coal blend where there is a slight improvement in coke quality. There was no adverse effect on operation of the coke oven including wall pressure generation.

EXAMPLE 2:
Based on aforesaid results in Example 1, industrial scale trial in coke ovens was taken up. Pre-treatment of the plastic waste was done according to Step I of Example 1. The crushing index of each coal charge was maintained at 81±1% of <3.2-mm size fraction. Working moisture was adjusted to 8±1% just before charging the respective blends into the pilot oven. Carbonization tests were carried-out in the electrically heated movable wall pilot coke oven (250 kg capacity) of Carbolite Make, UK. The following carbonization conditions were maintained during the test campaign:
 Coking Period : 18 hrs.
 End Centre Coke Mass Temperature : 1000 + 10 ºC

About 45 t of granulated waste plastic was charged in 4 numbers of batteries over 10 days at usage level of 0.2 +0.1 mass% of coal charge. It was added through feed to coal tower numbers 3 & 5 for small batteries numbering 5 & 6 and coal tower number 6 for tall batteries numbering 9 & 10.
Results are shown below in Tables 3 to 6 for coal oven battery (COB) numbers 5, 6, 9 and 10 respectively:
Abbreviations: CVT: Control Vertical Temperature, V.T.P: vertical top pressure F.S.T: Free Space Temperature

Table 3

Table 4

Table 5

Table 6
Results from aforesaid Tables 3 to 6 showed no adverse impact on battery operation or battery health. There was no deterioration in coke quality both in terms of cold and hot strength of coke. Gas and tar quality remained the same. Hence, waste plastic co-processing through coke ovens of steel plants seems to be technically viable.
It is to be understood that the present invention is susceptible to modifications, changes and adaptations by those skilled in the art. Such modifications, changes, adaptations are intended to be within the scope of the present invention.
, Claims:
1. A method for co-processing of granulated waste plastic in coke oven comprising the steps of:
i. Pretreating the plastic waste to form waste plastic granules;

ii. Mixing the waste plastic granules of step (i) with coal blend for carbonization in a coke oven;

Wherein the said pretreating of plastic waste comprises the steps of:
a. Shredding of the plastic waste to a grain size less than 10mm;
b. Washing of the shredded plastic waste of step (a);
c. Drying of the washed plastic waste of step (b);
d. Agglomeration of the dried plastic waste of step (c) to a granule size ranging from 5 mm to 8 mm and density ranging from 0.80g/cc to 0.90 g/cc to obtain waste plastic agglomerates; and
e. Converting the agglomerates of step (d) to cylindrical granules of 2 mm to 3mm diameter and 2-3 mm length and a density of 1.2 - 1.3 g/cc by extrusion at a temperature of 150-200oC to form the waste plastic granules for co-processing.

2. The method as claimed in claim 1, wherein the waste plastic granules are mixed with coal blend in a mass ratio ranging from 0.2 to 1.0 mass %.

3. The method as claimed in claim 1, wherein the crushing index of each coal charge is maintained from 80 to 82 % of less than 3.2-mm size fraction and the moisture ranges from 7 to 9 % before charging the blends into the coke oven.

4. The method as claimed in claim 1, wherein the coking duration is of 18 hours.

5. The method as claimed in claim 1, wherein the end coke mass temperature ranges from 1000 to 1010 ºC.

6. A system for co-processing of granulated waste plastic in coke oven comprising:
A. Granulated plastic storage bin (101);
B. Discharge hopper for plastic granules (102);
C. Coal blend discharge conveyer belt (103); and
D. Conveyer belt of plastic granules (104);
Wherein the plastic storage bin (101) is configured to store the pre-treated granulated waste plastic;
Wherein the discharge hopper for plastic granules (102) is fabricated and erected beside coal conveyor (103) having features of capacity of 5000 kg / batch, synchronized plastic flow with coal flow for regulated addition of plastic and safety interlocking between coal conveyor (103) and conveyor belt of plastic granules (104).