Methanol Evaporators and Condensers for Biodiesel Production

Biodiesel Production Case Study: Background

SACOME was commissioned with the execution of the manufacturing of the tubular heat exchangers within a system of production of biodiesel coming from palm oil. We collaborated actively with our client that was an engineering company in biodiesel technologies, bringing our expertise and know-how in the thermal and mechanical design both for the condensers and the evaporators of methanol and ethanol-based fluids:

• • Condensers: The duty of the heat exchangers was to condense either pure methanol or a mixture of vapors phases (composed by condensable components as methanol and water, and non-condensable ones, as air). Moreover the condensation had to take place in vacuum conditions.A correct thermal design of the heat exchangers was a critical point in this case. For condensation of gas mixtures (further having non-condensable phases as mentioned) the process doesn’t take place in isothermal conditions like it happens with pure components, demanding thus a very accurate calculation to be done by our engineers. Besides, our Technical Department advised the client for each case about the use of the most suitable cooling fluid, as tower water, or glycol solutions.

• • Evaporators: The calculation of the boiling process had several details to be taken into account, as the risk of having mist flow or the difficulty of getting complete boiling, among others.

Our experts in the thermal design, backed by our experience since 1975 in the process industry, together with the support of  Heat Transfer Research, Inc. (organization we are members of since 1.998) carried out a customized and reliable engineering solution adapted to the system of our client.

Our solution: Methanol Evaporators and Condensers

Given the process data, our Engineers did the thermal design both for the condensers and the evaporators, checking for every case different alternative, with the aim to offer the best solution to our client.

With this is mind, we describe as follows the most important points considered in the design of the process equipment:

• • Methanol Vapourisers: Boiling is one of the thermal processes requiring a deeper knowledge by the designer. In this case the evaporation was done by heating the methanol vapors using water steam as service media. Our engineers chose a suitable design to avoid mist flow (what can make it difficult to fully evaporate the entering stream) and oversized suitably the process flowrate, thus ensuring that the required boiling capacity was reached. Our designers chose a suitable design to avoid dry wall mist flow, as it could lead to high tube wall temperatures.

• • Methanol Condensers:  The condensation hasn’t got so sensitive issues in the thermal calculation, although it is important to take care in the design to choose a suitable baffle geometry and spacing, to ensure a good draining of the condensates and to avoid also vibration risks in the shellside. In this regard, our Technical Department used the latest version of HTRI software that has a specific module for the checking of vibrations.

Biodiesel Production Process

The biodiesel is produced by chemical reactions of transesterification and esterifications, starting from vegetable or animal fats and oils (pure or recycled) that react with short-chain alcohols, as methanol or ethanol. 

Along this reaction, whose main step takes place in a reactor, other products and byproducts are processed or generated, as glycerol (useful in the cosmetic industry), soaps or residual water.

Product Specifications

Biodiesel is a vegetable oil (sometimes it can also be animal-fat based oil) diesel fuel, that is composed by long-chain alkyl esters.

It can be used either alone (known in this case as B100 biodiesel) or blended in any proportions with conventional hydro-carbon.

Diesel coming from petrol (in this case it is labeled depending on the biodiesel content, i.e. B20 for 20% biodiesel content, etc.).

In our project the lipid raw material was palm oil, although biodiesel can also be obtained from other vegetable oils with or without prior use, as rapeseed or soya oil.