Case 1 : Installation of High Capacity Chippers in the Chipper House Background

Chipper is the first major equipment in a paper plant. These chippers are used to produce wood chips, from the raw materials like hard wood, bamboo etc., for further processing in the digester house. Many of the old paper plants, in general, have chippers of lower capacity. The feed to the chippers were invariably, manual. This led to non-uniform feeding, which in turn affected the throughput through the system. This resulted in very high specific energy consumption in the chippers. The recent technological advancements have led to the development of high capacity chippers. These chippers are provided with mechanical feeding mechanisms, enabling consistent feed to the chipper and high throughput from the chippers. This results in lower specific energy consumption of the chippers. The installation of high capacity chippers is gaining increasing popularity, especially among the large integrated paper plants.

Previous Status

In a large integrated paper plant, the chipper house had a capacity to produce 25 TPH of chips. The chip preparation was performed by 5 numbers of 5 TPH (each) capacity disc chippers. This system had the following disadvantages:

Low capacity
Manual feeding leading to non-uniform feed distribution and throughput
High specific energy consumption (17-21kWh/ton)
Longer waiting time at the digester house, due to lower capacities and manual feeding
Very high dust generation and accumulation

The installation of high capacity drum chippers, can result in higher throughput and lower specific energy consumption.

Energy saving project

The high capacity drum chippers were installed in place of the older, low capacity disc chippers.

Concept of the project

These high capacity drum chippers have the following advantages over the low capaciy conventional chippers:

Higher capacity
Mechanical feeding leading to higher throughput
Lower specific energy consumption (about 7 kWh/ton)
High quality, uniform size chip preparation
Improved working conditions on account of low dust generation
Improved safety aspects, due to closed machinery moving parts

Hence, high capacity chippers can be installed in the chipper house to achieve maximum energy efficiency.

Implementation status, problems faced and time frame

Two numbers of high capacity drum chippers were installed in place of the earlier 5 numbers of disc chippers.
The implementation of this project was taken up in two phases. Initially, one drum chipper was installed and its performance was closely monitored. On achieving satisfactory operating results, the second drum chipper was installed. With this installation, all the old disc chippers in the chipper house were replaced.
There were no major problems faced during the implementation of this project. The implementation of this project was completed in 24 months.

Benefits achieved

The specific energy consumption reduced by one-third, with the installation of these high capacity drum chippers. A specific energy consumption of 7.0 kWh/ton was achieved with these drum chippers.
Besides, the energy savings, the installation of drum chippers also resulted in improved quality of chips produced, reduced dust generation and increase in throughput.

Financial analysis

The annual energy saving achieved was Rs.56.00 lakhs. This required an investment of Rs.240.00 lakhs, which had a simple payback period of 52 months.

Benefits of high capacity chippers

Lower specific power consumption - 7 kWh/ton
Mechanical feeding leading to higher throughput
Uniform chips size Cost benefit analysis
Annual Savings - Rs. 56.0 lakhs
Investment - Rs. 240.0 lakhs
Simple payback - 52 months