HYDRAULICS 18 HYDRAULICS & PNEUMATICS September 2023 www.hpmag.co.uk cycles. After the final stage the steam is condensed back to water and this heat is used to pre-heat the incoming product before the first stage of evaporation. Heat recovery is not limited to systems dealing with liquids. HRS recently supplied a large G Series gas-to-gas heat exchanger to recapture heat from the high temperature exhaust gases leaving a large chemical reactor. This recovered heat is then used to help pre-heat the chemicals entering the reactor to around 500 °C. As well as helping to improve energy efficiency at the plant, the new unit has been designed to cope with challenging operating conditions in order to provide a suitable working life. These examples show that where the situation allows, HRS corrugated heat exchangers have significant potential to reduce the energy consumption (and therefore GHG emissions) of thermal processes in a wide range of industries. The capital costs of including energy recovery in a heat exchanger system is likely to be higher than similar systems without heat recovery, but these will be recovered over the working life of the unit, particularly at today’s high energy prices. 1 https://www.iea.org/commentaries/how-energy-efficiency-willpower-net-zero-climate-goals can be recaptured to be used elsewhere. Many anaerobic digestion (AD) plants use heat exchangers to pasteurise the digestate produced during the AD process, so that it can be sold as an agricultural fertiliser. The ‘surplus’ heat which is generated after the system has been running for two hours is used to preheat the digestate, reducing total heat load and improving overall plant efficiency by increasing the amount of generated energy, which is available for export or other uses, as opposed to being required for pasteurisation. Finally, combining multiple heat exchanges can often provide the greatest energy benefits, for example, in a multi-effect evaporation system such as the HRS DCS Digestate Concentration System. This uses heat exchangers and evaporation to reduce the volume and increase the concentration of sludges and digestate. The first evaporation stage heats liquid digestate and uses a cyclone separator; the steam produced from this first cycle (usually available at 70˚C) is then used as the heating media for the second effect, whereby the process is repeated. The subsequent steam (usually available at 60˚C) is then used as the heating media for the third cycle. The number of effects is determined by the level of dry solids required and the amount of surplus heat available, up to a maximum of four Analyser provides real-time output of VOC leaks KECO’s Model 204 PermaStream Process Analyser provides real-time measurement of VOC leaks in clean or dirty water. More economical and accurate than lab analysers prone to analytical errors, the company says it precisely measures total VOCs including aliphatic and aromatic hydrocarbons without false high readings or high alarms associated with UV fluorescence methods. Requiring no filters or liquid sample conditioning, the 204 PermaStream strips hydrocarbons as water samples continuously flows through it. Carrier air sweeps hydrocarbons at a rate of 200 ml/min to an advanced VOC sensor for quantitative analysis in ppb, ppm, or “up to” saturation levels. KECO’s PermaStream membrane technology creates an ultra-clean sample for the VOC sensor that has an average life of 5 to 10 years. No costly consumables are needed for analysis. The sensor quantities and displays values on a full color touch-screen HMI system, through a 4-20mA output loop or via RS-485, TCP/IP Ethernet, and Modbus. The analyser offers remote and web-based monitoring along with optional concentration relay alarms and diagnostic/fault alarms providing better control over operations. This ultra-low maintenance, solid state analyser is ideal for use in the chemical, environmental, gas processing, refinery, and wastewater treatment industries in monitoring environmentally-harmful VOCs in holding ponds, cooling tower water, produced water, storm runoff water, building water discharge, effluent water, boiler condensate, engine cooling water, and wastewater. In one application, the Model 204 Hydrocarbons in Water Analyser saved an ethylene plant thousands of dollars in lost product through early leak detection of hydrocarbon leaks in the cooling water of heat exchangers/cooling towers. The company says the analyser can pay for itself in weeks or several months in many applications. With no moving parts or need for routine calibration, the 204 PermaStream requires minimal upkeep and operates with high uptime. The process analyser offers typical accuracy and repeatability at better than 3% of the full-scale range.
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