Introduction. Effluents. Smar Guided Wave Level Transmitter. Application in Plants and Distilleries.

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1 Smar Guided Wave Level Transmitter. Application in Plants and Distilleries. Introduction Many industrial applications are run in the presence of vapors, density and process temperature change, as well as access difficulties and installation in the bottom part of reservoirs. The same applies for the sugar/ethanol sector. In many cases, the job is measuring the process level as described above, and solutions as load cells or free wave meters require special installation cares, or simply are not fit for some applications. The level meter technology by the TDR (Time Domain Reflectometry) principle, also known as Guided Wave Radars, is one of the most modern existing in the industrial automation market. This technology appeared as a solution to fill gaps that other meters did not entirely do. The new RD400, Smar s Guided Wave Radar, has already been installed at several sugar plants and distilleries, in all over Brazil. These notes clarify some points that made successful RD400 cases in this segment. Effluents Location: JPilon S/A Açúcar e Álcool - Cerquilho-SP Besides the vinaza, which is supplied to farm areas as fertilizer, many industrial effluents are deposited in plant tanks and have the same use. Usually, they are composed by such elements as: residual water from distillation (flegmaça); boiler discharge water; wash of the sugar production section. At Usina J. Pilon S/A Açúcar e Álcool, located in Cerquilho, São Paulo state, a tank stores all those effluents. Next, the effluents are pumped to cooling towers, where a water spray cools them down and they are sent for irrigation. Both at the cooling tower and in the last tank, the level control should be careful, because it cannot overflow and cause the process to stop. In the first tank, where the effluents are received from the plant, a minimum level must be kept at to avoid pump cavitation. The RD400 is installed in the first effluent tank, as shown in the following sketch.

2 At Plant Vale do Rosário, that installation was accomplished in 2004, and it characterized the first beta test performed by the transmitter. The level control in the evaporation area is of utmost importance. A very high level in the pre-evaporator can contaminate the vegetable vapor that feeds that area. At the same time, the pre-evaporator efficiency, directly associated with the broth level, must be the best possible, so that the evaporation boxes work as expected. This control allows working with an optimum evaporation level. If the level is too low, the pipes heating surface won t be fully used, and the pipes can dry in the upper part. If the level is too high, the lower part of the pipe is drowned by the broth that moves very slowly, and don t reach the desired evaporation rate. The optimum level is when the liquid reaches the top of the pipes through the vapor bubbles, with only a small flow in the upper part of the face. This level varies with the size of the pipes, the broth temperature, heat transfer rate, incrustations and viscosity. Open installation in effluents. Detail of the installation sketch. Process like these are easy to install equipments and guarantee the continuity of the measurement, because besides the presence of water, which causes better reflection to guided waves, the presence of vapors, foam or other elements that absorb the waves is low. So, a single flexible probe was used in that application, with a support that can also be supplied by Smar. Pre-Evaporators and Evaporators Locations: Plant Vale do Rosario, Orlândia-SP; Plant Alvorada de Bebedouro, Guaxupé-SP; other places, soon. Plant pre-evaporators and evaporators have calenders inside that interfere with level measurement. Free-wave meters are disturbed by false echoes and ambient vapors that impair their work, and hydrostatic pressure level meters have to cope with density and temperature variations in the process. On the other hand, communicating vessels are practical devices that fully aid the guided-wave transmitter, even though the free-wave transmitters inside those vessels can also create false echoes due to the walls of the vessel and to the vapours - a thing that has been reported by many users. With the RD400, the electromagnetic waves keep in the path of the reflection without external interferences, as they are guided continually in a probe. Installation in the Pre-Evaporator. On the left the bottom of the vessel with the probe passing through it. 02

3 The RD400 was installed in a communicating vessel on the turbine condensed tank, with 1.5 meter for measuring a range of approximately 1 meter. The process, while being critical, is applied with excellent results on the RD400, due to good reflection quality of the waves, the high dielectric of the process and the installation condition on communicating vessel (that makes possible a good capture of the electromagnetic pulses). Details of the installation in the Pre-Evaporator on communicating vessel. Condensed Tank of the Condensation Turbine Generator Location: Plant Caeté, São Miguel dos Campos-AL This application is one of the most critical on a plant. The generators stand for the heart of the plant, and their turbines should have rotations for the boiler steam to be used to generate electric energy and to be distributed to other areas, or then turn into condensed again, characterizing a cycle entirely closed of use and energy balance. The Caeté Plant has two generators, and the level control of the steam that was condensed is extremely important, because if its reservoir dries, the turbine turns off and the plant stops. The same happens if there is overflow: the water enters in the turbine, causing a thermal shock that turns it off. RD400 Installation in a communicating vessel Installation by communicating vessel in the turbine generator condensed box. Fermentation Tank Location: Santa Elisa Plant, Sertãozinho-SP The final molasses from the sugar production process will be used for alcohol production. But for that, it is diluted in water and/or broth to form the must for the process of alcoholic fermentation to become wine, a sub product sent to the distillation columns for hydrated and anhydrous alcohol production. The fermentation tanks have particularities that makes it difficult to measure the must level. One particularity, for example, is the large quantity of foam accumulated in the surface of the process. In the fermentation peak phase, the foam reaches high levels, sufficient enough to absorb the free waves from meters that use that technology. Besides, measurements by the hydrostatic pressure principle are limited by the temperature and process density variation. At Cia. Energética Sta Elisa, a RD400 with single rod was installed in a communicating vessel, as in the case 03

4 of the evaporators in other plants already mentioned. The equipment will be next installed on the internal wall of the tanks. That sensibility can be understood on the following graphs Low Reflection - Measurement in Soy Oil (low dielectric) Installation in a communicating vessel in the fermentation tank. On the graph above, the horizontal line cuts the wave reflection that reaches the process surface (soy oil, with low dielectric constant). It is noticed that the same line almost cuts noises to the left. That generates imprecision on the measuring, and it requires more installation cares, in order to attenuate the noises in general. On the following graph, another type of behavior is noticed. Other Applications The RD400 can also measure the level of hydrated and anhydrous alcohol, soaking water, cane broth, vinaza, lime broth among other points. Most plant processes are in liquid state, and that facilitates the measurement, because the Sensor Threshold Level parameter of the radar is its sensibility, and it can vary in a wider range of values, with greater equipment autonomy and applicability in those many processes. High Reflection Graph Measuring in Secondary Sugar cane Broth (high dielectric) On that last graph, the horizontal line has a very larger area to detect the reflection in the process surface. That happens because there is a strong presence of water in it. It is the secondary sugar cane broth, composed by the soaking water added in the grinding area. The soaking consists of pulp diluted in the press. Therefore, generally, all the plant processes have the form of liquids or semi-liquids, with the presence of added water or sugar-cane water. Graphs as the last one are more common, therefore, when applying the RD400 in level measuring in several plant and distillery processes. 04

5 Conclusion The RD400 guarantees reliability and accuracy in level measuring in sugar and ethanol plants, as well as in other segments. Free from density and temperature variations, the presence of bubbles, false echoes common in non-guided waves (as in microwaves or ultrasound transmitters), and the possibility of being installed on the lower part of the tanks, the RD400 just needs that its probe is submerged in the process to be measured, and that process needs a minimum dielectric constant so that the guided waves reflect back to the equipment. The presence of water, as mentioned before, is a guarantee of high dielectrics. Besides, the RD400 has the advantage of being installed on top, which makes possible to easily access its electronics, as well as its simplified maintenance. Most industrial tanks already have on their top sockets, inspection points or flanges for installing other equipments, where the radar can be adapted. RD400 provides a new measuring technology for the industrial automation market, but one that is already in use in civil construction, telecommunications, agriculture, chemistry, among other areas. The Time Domain Reflectometry (TDR) concept, based on the reflection of electromagnetic waves in process surfaces offers them impedance change. It is a world accepted principle and one totally adapted to industries, to supply what other level measuring types could not meet. For each type of process there will be the need for a different probe, which can be a single or dual rod, a single or dual cable or a coaxial terminal. Parameters as tank height, the installation or not of the RD400 in a communicating vessel to a reservoir, the dielectric constant of the process, etc. will determine which type of probe it will be. Consult our representatives for more information. Coaxial (1-3m) Single Rod (1-8m) Dual Rod (1-8m) Tri-Clamp Connection with Polished Rod (1-4m) Single Cable (1-14m) Dual Cable (1-14m) 05

6 smar Specifications and information are subject to change without notice. Up-to-date address information is available on our website. web: Copyright Smar International - all rights reserved. - May/2008