Folien

Many thanks ___ for the introduction. I am going to give you and insight today about a drying technique that some of you may be familiar with or actually work with.

First of all, I would like to give you an overview of my presentation. It is divided into 5 parts/It consist of the following sections

I will begin with .. Then I’ll show you the operating principle

Furthermore we will look at the place of use and the impact on the fuel system

And finally I would like to present you a case study that contrasts different application scenarios

And then we will take a closer look at the application by means of a case study

In times of the decarbonization of the energy industry in the industrial sector, an energy-efficient manufacturing process is becoming increasingly important. Especially energy-intense drying processes and rising primary energy costs require innovative solutions.

The low temperature drying technology is an option to dry bagasse by using waste process heat. In addition to improving the energy efficiency of the plant, the dried bagasse offers the potential to generate more steam, which increases the export of "green" electricity.

>> But what is a low temperature dryer which waste process heat does it use?

The LTD is a well approved technology for decades in the sugar beet industry to dry beet pulp, but a new method for the drying of bagasse in the sugar cane industry

So this drying technology requires a heat source that comes from the plant (, such as…). But what are usable sources of waste heat?

In the cane sugar industry low-temperature dryer (LTD) can be applied to reduce the water  content of wet bagasse to a moisture content

Depending on the existing heat excess of the plant, lower moisture contents are possible. But bagasse boiler plants are not thermodynamically designed for low water load and the conversion of existing plant is difficult

>> The operating principle is quite simple.

Here, I would like to only briefly discuss this, since it was already explained by Swiss Combi earlier.

Bagasse is applied/fed to/on a perforated conveyor belt, and is transported to the right here. Meanwhile heated air or flue gases flow in crossflow through the bulk material and fans at the bottom discharge the saturated drying air upward.

The figure illustrates a heat exchanger in which ambient air is heated from 25 to 44 by hot tail water.

>> Where this technology is used in the process and what benefits it can bring is shown in this slide

As you can see, the LTD is located between the milling and steam generation station

Here we can see wet bagasse, which leaves the sugar mill station and enters the low temperature dryer. After drying by heated ambient air or boiler flue gases, the dried bagasse enters the bagasse boiler. Due to its lower moisture content, the boiler needs less fuel to generate the same amount of steam. This offers the opportunity to store the dried bagasse for off season or for sale, which could be an option, if the bagasse price is high enough. Furthermore  are  or to increase the steam production, which leads to a higher power export.

>> The relationship between drying and fuel consumption is illustrated by the following graph.

The horizontal axis represents the rising moisture content from zero to 80. The three vertical axes show the gross calorific value, the boiler efficiency and the fuel consumption.

As demonstrated the gross calorific value as well as the related boiler efficiency decreases with increasing moisture content. Since the efficiency of the boiler is lower at higher moisture content, the fuel consumption increases.

Using an LTD shifts the moisture content from 50% to a lower level, resulting in a higher boiler efficiency and lower fuel consumption.

>> So much for the theory, lets switch over to a case study

Cane crushing rate

The crop season lasts for … days

The prior goals through the use of an LTD are on the one hand cost savings by … and more profit by sale of dried bagasse or increased power electricity export by more steam production

The selection of measures depends on the local conditions.

In this study, the increase in efficiency is used for the extension of the off season and the higher electricity export

But there would also alternatives like the installation of .. But, this in turn leads to higher investment costs.

Another option is the sale of dried bagasse for …, which requires even lower moisture contents than 35 %. So far, there is hardly any sales market for it, but this could establish itself.

>> Now I would like to present three scenarios for drying bagasse and after that, i’ll come to the results

The first one is the drying by hot boiler flue gases, which is a option with low investment costs

The second is a version based only on the heating of air.

The third option is a combination of flue gases and heated ambient air.

>> Lets consider one operating principle in detail

Bagasse enters the LTD with a moisture of 50 percent and leaves 35 % water load. This dried bagasse is then burned in the bagasse boiler. Flue gases, generated by combustion of this dried bagasse are mixed with ambient air. This step is necessary because the conveyor belt is designed for temperatures up to 120 °C only.

Please note that the amount of flue gases refers to the moisture content of bagasse after LTD.

In consequence the boiler system needs less bagasse. As previously mentioned, the excess bagasse in this case study offers the potential to extend the off season to generate more steam and finally sell more electricity.

>> So lets switch over to my next slide, which shows the revenue by electricity sale per season after drying bagasse

 If you look at this graph, may have already noticed, that the additional power export revenues increases with decreasing moisture content, but with a non-linear trend. This is because boiler efficiency does not increase linearly with decreasing bagasse moisture content, as does the calorific value

>> Nevertheless, it is still interesting to see  whether it is more value to save coal by burning dried bagasse or to export the surplus of generated power by burning bagasse. And the answer is: no

(It is still interesting whether the … can compete with..)

This graph depicts the revenues from power export in grey and from coal in black. And as this bar chart shows, the revenue from coal is twice as high as the revenue from power export. It gets clear, that at current power export prices, it is worthwile to save coal. Another positive aspect is that CO2 emissions can be saved as a result.

>> But probably the most important aspect is what payback you can expect

The following statements can be derived from this figure

•       The payback period increases as the moisture content decreases

•       ´Due to the current price levels for electricity and coal, lower payback periods can be achieved by coal savings than by increasing electricity generation capacity

•       As shown for a moisture content of 35%, the payback period for application B is higher than for application C, Since no hot boiler flue gases are considered, the payback period shifts from 6.3 years to 9.3 years

But on the long run A achieves lower revenues than …

>> But how does the situation compare across countries?

In order to evaluate the low temperature bagasse drying technology, electricity export prices from Mauritius, a country that is already well developed in terms renewable energy use compared to other cane sugar producing countries, were used. The country stands out for its broad and diverse experience with sugar processing and co-generation strategies.

With electricity export revenues of 280,000 USD per extended off-crop campaign under Pakistani conditions, the investment in a low-temperature dryer would pay for itself after about 20.2 years. With higher electricity prices at 0.06 USD/kWh in India, the plant would pay for itself with 420,000 USD in electricity export revenues after 13.2 years. With Mauritian electricity prices, the payback is 6.1 years, which in India can only be achieved through coal savings.

>> But in terms of availability on the local market, the sale of dried bagasse can also be worthwhile

In India, the undeveloped market for dried bagasse is a site-specific boundary constraint. Few buyers can be found for dried bagasse, so the selling price cannot yet compete with other measures.

This is presented in Figure 14, which shows the different sources of income from dried bagasse to 15% moisture content.

The highest revenue is achieved by coal savings, which results in a payback of 8.1 years. The revenue from sale of dried bagasse with 83.3 USD/t dried sugarcane bagasse corresponds to a revenue of 1 million USD. The payback period of 12.5 years here is below the payback period of the plant financed by electricity export revenues. As a result, at site the sale of dried bagasse is currently more profitable than the increase of power export. However, a requirement for this is a steady market for the sale of dried bagasse.

This ratio may yet change, given the ongoing energy crisis

To conclude, the low temperature drying is a suitable drying technology for bagasse.

Depending in the requirements, different dryer applications are possible.

So the dryer to date have reasonable investment costs and moderate paybacks, which are increasingly interesting at higher power export prices. In addition, however, the sale of renewable energy offers the possibility of acquiring CO2 certificates.

The drying to very low moisture contents offers to open up new markets like particle boards, bagasse pellets. But full drying by low-temperature dryers require further research and development.

The same applies to drying with flue gases which has to be proven in practice.