Alternatives to reduce energy consumption in the factory injection and rejection system

In addition to sugar and ethanol, today energy cogeneration occupies an important place in the Colombian cane industry. The figures reveal this: according to XM SA, an entity that operates the Colombian National Interconnected System (SIN), in the 2017 the mills generated 1487 GWh of electrical energy, becoming the second power generators in the region, enough to supply the 35% of the electricity demand of a city the size of Cali.

In addition to sugar and ethanol, today energy cogeneration occupies an important place in the Colombian cane industry. The figures reveal this: according to XM SA, an entity that operates the Colombian National Interconnected System (SIN), in the 2017 the mills generated 1487 GWh of electrical energy, becoming the second power generators in the region, enough to supply the 35% of the electricity demand of a city the size of Cali.

The increase in installed capacity in the generation of electrical energy in the sugar mills in recent years has been key to growing as cogenerators and injecting surplus electricity from the productive activity into the national interconnection network.

Given this reality, Cenicaña is currently investigating strategies that allow reducing own consumption of thermal and electrical energy in the production processes of the sugarcane agro-industry, with the aim of further increasing the contribution of electrical energy to the SIN, this with with a view to expanding its participation in the national energy matrix.

In one of these investigations, an energy saving potential was identified in the injection and rejection system, where large amounts of electrical energy are required to circulate the water necessary to condense the vegetable vapors from the sugar manufacturing process. Figure 1.

Figure 1. Matrix of electrical energy consumption in a pilot mill.

As a result of the investigation, Cenicaña estimated a potential energy saving in said system, considering the implementation of the following actions:

»Reduction of the height of the barometric condensers:

It was observed that, in a large part of Colombian sugar mills, the barometric condensers are installed at heights that exceed the minimum value necessary in the conditions of the Cauca river valley (9.5 m - 10.2 m), reaching in some cases up to 20 m in height. height, which imposes an additional demand for power to pump the water.

Reducing the height of the barometric condensers to 10.2 meters would represent a 17.5% reduction in the energy consumption required in the injection pumps.

»Increased efficiency of the cooling pool:

The cooling pools are in charge of reducing the water temperature of the injection and reject system through direct contact with the ambient air, in order to use it again in barometric condensers.

The efficiency of the cooling pools depends on the sprinkling of the water and impacts the energy consumption of pumping; It is estimated that for each percentage unit of increase in the efficiency of the pool, the required energy consumption of pumping is reduced by 1.5 percentage units. To increase this efficiency, Cenicaña proposed the following strategies:

  • Refurbish the cooling pools with wide water spray nozzles to increase the contact of the water with the ambient air.
  • Increase the pool's spray area in order to separate the nozzles and form a wide curtain of water. It is recommended to cool 750 kg / h of water per m2.
  • Use of pools in parallel for a closer approximation of the water temperature with the air temperature.
  • Increase pool maintenance frequency to unclog clogged nozzles.

A pilot plant welcomed some recommendations and overhauled its cooling pool, replacing the failed nozzles and installing new nozzles where they were absent.

Figure 2 shows the results obtained from the thermographic analysis carried out before and after the modifications implemented by the mill. From these measures, the mill managed to increase the efficiency of its cooling pool from 29% to 55%, which represents a 39% potential energy saving for the mill.

A simulation of the implementation of all the proposed actions demonstrated its viability with a 51% reduction (3.1 kWh / t cane) in the consumption of the electrical energy required for pumping; This surplus is equivalent to $ 372 per ton of cane that can be sold to the National Interconnected System (SIN).

Cenicaña will continue with the formulation of this type of proposal in order to contribute to improving the energy efficiency of the mills and continue to grow in the cogeneration market with more environmentally responsible proposals. .

Figure 2. Thermography performed on the cooling pool.

Author:

ANDRÉS FELIPE OSPINA. Mechanical Engineer, Factory Process Program - Cenicaña.

Information letter 
Year 6 / Number 2 / October 2018Full text in version:
PDF Animated
Scroll to Top
Search