Measuring instrumentation

Summary: For years now, and increasingly so, product quality standards for the commodity lime and for an already wide diversity of lime-base products plus, above all, the environmental protection requirements to be met by lime production plants have been intensifying. For the production plants themselves, this necessitates continuous optimization of their processes and all the requisite auxiliary circuits, up to and including investments in new combustion technology. The data of interest must be acquired automatically, accurately and subject to close tolerances.

1 Measuring instrumentation for lime plants

Measuring instrumentation is required for the following aspects of lime production processes: level, flow, pressure, temperature and analysis. The required number of analyzing instruments varies from case to case. The basic requirements for safe, dependable plant operation apply to all measuring instruments: reliable physical principles of measurement, robust technology and easy-to-use field devices. The ambient conditions prevailing at your typical lime plant are very harsh: sun, wind, rain, dust, heat, cold and sometimes even vibrations constantly impact the instruments. Measuring instrumentation from Endress+Hauser, however, has proven dependable in sustained service at widely diverse locations.

2 Temperatures above 800 °C

The kiln, as the core component of the production process, requires for its control various temperature and pressure sensors as well as flow and level sensors. Since the kiln requires a supply of outside energy for expelling carbon dioxide, a vitally important part of process monitoring is to surveil the temperature in the individual zones. At the Istein lime plant in South Baden, the temperatures at various points of interest on the new kiln are tracked with the aid of Omnigrad S thermometers by Endress+Hauser. Measured-data acquisition points are installed at all important places around the kiln, e.g., on the crossover channel and in various planes of the double-shaft kiln.

Some of the applications involve operating temperatures situated well above 800 °C. In addition to coping with the high temperatures, the material also has to contend with abrasion and aggressive gases. The prevailing service conditions emburden the protective sheathes and thermocouples to their limits of endurance.

Over the past few years, material research has yielded numerous new kinds of material – both as metal alloys and as ceramic substances. At Endress+Hauser, the results of such research have been incorporated into their high-temperature line of TAF thermometers. The Omnigrad category, with its broad array of thermometers, enables optimal thermometry for any application. Omnigrad TAF16 and TC65 models, for example, are now in service on the new double-shaft kiln in Istein.

3 Ceramic sensor for high temperatures

The pneumatic infeed of solid fuel also has to be monitored to ensure a good burning process for producing high-quality lime. In order for the data to remain comparable under all conditions of operation, the volumetric flow of gas in the pneumatic system has to be measured in terms of standard volume. In this case, the instrumentation consists of a vortex flowmeter, a pressure sensor and a temperature sensor. This additional information regarding the momentary pressure and temperature conditions enables conversion of the conveyed compressed air as a standard-volume flow [Nm3/h or SCMH].

The pressure sensor’s ceramic measuring cell has thoroughly proven itself under such ambient conditions, particularly since it possesses an up to 40-fold overload tolerance. Equipped with their own ceramic sensors, Cerabar S and Cerabar M pressure transmitters are suitable for use in media with high abrasive-solid contents. At the Istein lime plant, a Cerabar S PMC71 was installed in the pressure line to obtain permanently stable pressure data under the demanding set of local ambient conditions.

4 Convenient handling

The 3-key operation concept is the same as that used by the vortex flowmeter. It enables simple, reliable starting, and all adjustments and queries can be conveniently made from outside, therefore requiring no interference with the measuring instrument. In addition, thanks to the HistoROM/M-DAT data module, the device’s configuration can be quickly, easily, reliably and securely duplicated onto other measuring instruments simply by replugging the module. Since the casing can be rotated 380° with no affect on the process connector, the pressure transmitter readily adapts to any process environment.

5 Reliable and accurate

The Prowirl vortex flowmeter guarantees permanently stable sustained operation and steady accuracy of volume-flow measurement, even at high pressures and temperatures. Unlike conventional piezo-based vortex sensors, fine-tuned differential switched capacitance (DSC) sensors ensure high-level insensitivity to vibrations. That is an important point for pneumatic conveyance involving potential load changes, varying product properties and, hence, transient pressures. Much like a flag in the wind, the sensor paddle in the pipe flatters in the vortex behind the orifice. This alters the distance between the centre and outer electrodes. The electronic evaluating unit counts the number of changes in capacitance.

This approach is both reliable and accurate. For gases, the maximum measuring error is +/- 1 % of the momentary value. In addition, the presence of dirt or moisture on the front side of the orifice has, if at all, negligible influence on the readings. Moreover, the Proline Prowirl flowmeter meets all functional safety requirements (SIL) for burner control objectives. Together with an Omnigrad S thermowell in the pipe, this setup enables standard-volume computation at will.

Omnigrad resistance thermometers are ideally suited for critical and safety-related mensuration tasks. This measuring instrument is intended for use in applications with explosion-hazard exposure, such as in the present case of coal-dust infeed to the kiln. A clamp fastener enables quick installation and replacement.

6 Simple operation

In many branches of industry, including bulk material is processing, plant operators are having to deal with more and more tasks in addition to production supervision. The electrotechnologists are responsible for keeping the plant’s automation working smoothly, the supply of power secure in every detail, and the various driving-terminal frequency inverters, sensors, and even the plant’s own internal communication technology in good order. Consequently, user friendliness is becoming an increasingly important decision-making factor in the product selection process. Intuitive, uniform operating procedures promote workplace safety while reducing the workload.

Endress+Hauser achieve all this by standardizing the equipment operating procedures above and beyond individual product families and types of data. The new loop-powered level and flow measuring devices are characterized by uniformity with regard to: local control elements, common data interface (CDI) for parameterization, FieldCare configurating software to DTM standard, operating menu with three user groups (system operator, maintenance personnel and experts/service). This makes everything less complicated for the user and simplifies the workaday routine. Fast, uncomplicated commissioning thanks to quick setup via measuring instrument saves the operator time and money. However, an optimal combination of well-chosen measuring principle and flawlessly matched technology alone does not suffice for sustainably reliable data acquisition: it all has to be installed correctly, too.

7 Full liner Endress+Hauser

“Profitability analyses encompass more than just measuring instruments,” explains Rudolf Eichin, who heads the engineering department and is responsible for energy management at the Istein lime plant. “Thanks to simple, uniform operation,” the project manager continues, “the commissioning periods and training measures can be reduced to a minimum. Universally applicable components also help minimize the necessary stock reserves and spare-parts management inputs.” More and more customers are coming to appreciate Endress+Hauser as a full-range supplier with a complete service spectrum for the bulk-material processing industry, from a full array of field instrumentation and relevant services to automation solutions and attractive life-cycle management. All instruments, components and systems are precisely matched and work together perfectly. The benefits of relying on a full-range supplier are obvious: A single partner supplies all that is needed while adding all kinds of value to all the client’s own processes.