How to increase the efficiency of the plastic recycling of small components, especially disposable crockery, such as plastic and paper-based cups, plates, and utensils?

 

Introduction

This article is to analyze the new technology invented by the National Institute of Technology, PATNA, INDIA. The invention as describes by the patent specification is a "Disposable Crockery Crusher." This device is designed to crush disposable crockery, such as plastic and paper-based cups, plates, and utensils, to make their disposal more efficient and environmentally friendly. The preeminent plastic consumer products in production encompass packaging crafted from LDPE (e.g., bags, containers, food packaging film), containers fabricated from HDPE (e.g., milk bottles, shampoo bottles, ice cream tubs), and PET (e.g., bottles for water and other beverages). Collectively, these items represent approximately 36% of plastic manufacturing. Additionally, the utilization of plastics in the realms of building and construction, textiles, transportation, and electrical equipment constitutes a substantial segment of the plastics market.[1] The invention which is relating to the efficient recycling of the elements that constitutes the above mentioned 36%.

 

Drawbacks in recycling the disposable crockery till now

 

o    There is a significant challenge in disposing of plastic crockeries due to their large volume, which makes transportation to recycling centers difficult and costly.

o   Existing crushers are not efficient for crushing crockeries due to their high energy and force requirements.

 

A plastic recycling crusher, also known as a plastic granulator, shredder, or grinder, is a specialized machine designed to reduce plastic waste into smaller, manageable pieces for subsequent recycling processes. The fundamental technical elements of a plastic recycling crusher encompass:

 

1. Cutting Mechanism:

   - Blades/Knives: Constructed with high-quality steel, these blades or rotary knives are utilized to cut and shred plastic materials. The design can vary, incorporating single-shaft, dual-shaft, or multi-shaft configurations, tailored to achieve the desired output size and application requirements.

   - Rotors and Stators: Collaboratively, rotating and stationary blades shear the plastic into smaller pieces. The rotor, featuring multiple blades rotating at high speeds, interacts with the stationary stator to provide the necessary counterforce for cutting.

 

2. Motor and Drive System:

   - Electric Motor: The power supplied by the electric motor drives the rotor. The motor's power rating, measured in kilowatts or horsepower, significantly influences the machine's capacity to process diverse types and volumes of plastic waste.

   - Gearbox/Transmission: This component ensures the efficient transmission of power from the motor to the cutting mechanism, often integrating speed reduction to optimize cutting force and efficiency.

 

3. Feeding Mechanism:

   - Hopper: Serving as a funnel-shaped container, the hopper accommodates the plastic materials before their introduction to the cutting chamber. The hopper's design is adaptable to accommodate varying shapes and sizes of plastic waste.

   - Feeding Rollers: These rollers guide and uniformly feed the plastic material into the cutting chamber, ensuring consistent operation and preventing potential jams.

 

4. Screen and Output Control:

   - Screens/Sieves: Positioned below the cutting chamber, these components regulate the size of the output granules. The size of the screen holes directly influences the final size of the recycled plastic pieces.

   - Adjustable Output: Certain crusher models allow for output size adjustments by altering the screen or adjusting the gap between the blades and the screen.

 

5. Safety Features:

   - Emergency Stop Button: Operators can swiftly shut down the machine in the event of an emergency.

   - Safety Interlocks: These mechanisms prevent the machine from operating unless all safety guards are in place.

   - Overload Protection: Safeguards the motor and other critical components from damage caused by excessive load or jamming.

 

6. Control System:

   - User Interface: Typically encompassing a control panel with buttons, switches, or touchscreen interfaces for machine operation.

   - Programmable Logic Controller (PLC): Advanced models may incorporate PLCs for automated control and monitoring of various parameters such as speed, feed rate, and blade wear.

 

7. Build and Material:

   - Frame and Housing: Fabricated from durable materials, such as steel, to withstand the demands of heavy-duty plastic crushing operations.

   - Wear-Resistant Components: Key parts, including blades and screens, are often composed of hardened steel or coated with wear-resistant materials to extend their operational lifespan.

 

8. Additional Features:

   - Noise Reduction: Integration of noise-dampening materials and design features to minimize operational noise levels.

   - Dust and Particle Control: Systems designed to manage dust and small particles generated during the crushing process, such as extraction fans or enclosed cutting chambers.

 

Operation Process:

   1. Loading: Introduction of plastic waste into the hopper.

   2. Feeding: Uniform feeding of the material into the cutting chamber.

   3. Crushing/Shredding: The rotating blades cut the plastic against the stationary blades.

   4. Screening: The shredded plastic undergoes screening to achieve the desired granule size.

   5. Collection: The processed plastic is gathered for subsequent recycling processes.

 

Collectively, these features ensure the efficacy of a plastic recycling crusher in reducing plastic waste into uniform, manageable sizes for recycling purposes, thereby contributing to efficient waste management and material recovery.

 

Description of the invention

 

• The crusher includes a base frame and a crusher assembly mounted on it.
• The crusher assembly features a crankshaft connected to a connecting rod and motor, which drives a piston within a sleeve.
• The sleeve has openings for accepting disposable crockeries and a hopper equipped with sensors to detect and manage the waste.
• The sensors ensure only disposable crockery is processed, stopping the machine if other materials are detected.
• The crushed crockery is then discarded through an opening into a waste receptacle.
• The crankshaft is secured to the base frame with ball bearings and converts rotational motion from the motor into translational motion via the connecting rod and piston.
• The motor used is typically a 12V DC motor operating at 8 to 12 RPM.
• Materials used include mild steel for the frame and moving parts, and high-density polyethylene or similar plastics for the sleeve.
• The crusher is designed to be cost-effective, using materials that can include scrap metals, and is cheaper than existing metal can crushers.

Objects of the Invention:

• To provide a crusher that requires less force and energy for crushing disposable crockeries.
• To create a cost-effective, easily accessible, and user-friendly device.
• To integrate a crank mechanism that converts rotational motion into translational motion for the crushing process.

The invention was granted with patent ( Indian Patent No. 541788), on 13/06/2024. The concept and science behind the invention will increase the efficiency of the recycling and helps to reduce the environmental pollution.

Cost efficiency of the invention( Indian Money Rate)

Component Details (Table 1)

This table lists the different components of the crusher along with their dimensions and materials:

• Base Frame: Dimensions 50×20×13 cm, made of Mild Steel.
• Crank Shaft: Diameter 17 cm, made of Mild Steel.
• Connecting Rod: Length 20 cm, made of Mild Steel.
• Piston: Length 13 cm, diameter 9.5 cm, made of Mild Steel.
• Sleeve: Length 20 cm, diameter 11 cm, made of PVC.
• Hopper: Dimensions 10×11×10 cm, made of Spokes.

Cost Estimation (Table 2)

This table provides a cost breakdown for manufacturing the disposable crockery crusher, including the cost of materials, labor, and overhead charges:

1. Material Costs:
• Mild Steel (for Piston, Crankshaft, Connecting Rod, Base Frame): 4 kg at 100 INR/kg, totaling 400 INR.
• Sleeve (PVC): 1 unit at 80 INR.
• Motor: 1 unit at 185 INR.
• Adaptors: 1 unit at 280 INR.
• Total Material Cost: 945 INR.
2. Labor Costs:
• Labor cost is estimated at 300 INR.
3. Manufacturing Cost:
• Calculated as the sum of Material Cost and Labor Cost: 945 INR + 300 INR = 1245 INR.
4. Overhead Charges:
• Estimated at 20% of the Manufacturing Cost: 20% of 1245 INR = 249 INR.
5. Total Cost:
• Calculated as the sum of Material Cost, Labor Cost, and Overhead Charges: 945 INR + 300 INR + 249 INR = 1494 INR.

Additional Notes:

• The analysis mentions that the use of scrap metals can further reduce the cost, making the crusher more economical compared to conventional crushers available in the market.
• The total estimated cost of 1494 INR reflects an economical alternative for users, providing a cost-effective solution for crushing disposable crockery.

This cost analysis demonstrates the economical feasibility and cost-effectiveness of the disposable crockery crusher, highlighting its potential benefits for both manufacturers and users in terms of reduced production costs and improved efficiency in waste management

 

 

---

[1] Environment, U. N. (21 October 2021). "Drowning in Plastics – Marine Litter and Plastic Waste Vital Graphics". UNEP - UN Environment Programme. Retrieved 21 March 2022