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Waste Heat Recovery: Principles And Industrial ...

A waste heat recovery unit (WHRU) is an energy recovery heat exchanger that transfers heat from process outputs at high temperature to another part of the process for some purpose, usually increased efficiency. The WHRU is a tool involved in cogeneration. Waste heat may be extracted from sources such as hot flue gases from a diesel generator, steam from cooling towers, or even waste water from cooling processes such as in steel cooling.

Waste Heat Recovery: Principles and Industrial ...

Waste heat found in the exhaust gas of various processes or even from the exhaust stream of a conditioning unit can be used to preheat the incoming gas. This is one of the basic methods for recovery of waste heat. Many steel making plants use this process as an economic method to increase the production of the plant with lower fuel demand. There are many different commercial recovery units for the transferring of energy from hot medium space to lower one:[1]

According to a report done by Energetics Incorporated for the DOE in November 2004 titled Technology Roadmap[2] and several others done by the European commission, the majority of energy production from conventional and renewable resources are lost to the atmosphere due to onsite (equipment inefficiency and losses due to waste heat) and offsite (cable and transformers losses) losses, that sums to be around 66% loss in electricity value.[3] Waste heat of different degrees could be found in final products of a certain process or as a by-product in industry such as the slag in steelmaking plants. Units or devices that could recover the waste heat and transform it into electricity are called WHRUs or heat to power units:

Against the backdrop of rising energy prices, generating or recovering steam using a heat pump is an attractive option. The basic principle of the PILLER Industrial Heat Pump is to recover waste heat and provide it at a usable temperature level.

If it is not a gaseous waste heat stream or if the vapor cannot be compressed, the innovative heat pump cycle with evaporator can be used. The special aspect here is the steam generation in the first step. For this, PILLER uses water as a working fluid, which is evaporated at low pressure and temperature in the steam generator (Evaporator). The high-performance blowers by PILLER lift the steam to the pressure and temperature to drive the process or heating system needs.

There is a simple answer to this question: If vapors from the process can be compressed directly and then be used for heating, the basic principle is mechanical vapor compression. If the waste heat stream can or should not be compressed in order to utilize the waste heat, the heat pump cycle with evaporator is the solution.

The heat pump cycle with evaporator is the right choice when there are no gaseous waste heat sources or if the vapor can or should not be compressed. The difference: the heat pump process thus begins with the generation of steam in a specifically developed heat exchanger. PILLER relies on the use of water as working medium, so that steam at low pressure and temperature is generated in the evaporator. Here too, the main component is a PILLER MVR blower system: High-performance blowers concentrate the steam to the required pressure level in a multi-stage process and thus reach the usable boiling temperature. The heat pump system uses this recovered heating steam to supply either the same process or other processes by feeding it into a steam network.

Since 2019, the Group has a partnership with Qarnot Computing, a pioneer in the heat waste recycling from data centres, decided to commit further by participating to the latest fund-raising exercise carried out by Qarnot.

How exactly does it work?Industrial processes can be combined with each other: the heat recovered in one process can, for example, be used to power another. They can also become a source of heat for a tertiary sector, a residential sector or for an industrial activity basin.

CHP is a technology that produces electricity and thermal energy at high efficiencies using a range of technologies and fuels. With on-site power production, losses are minimized and heat that would otherwise be wasted is applied to facility loads in the form of process heating, steam, hot water, or even chilled water. CHP can be located at an individual facility or building or it can be a district energy, microgrid, and/or utility resource that provides power and thermal energy to multiple end-users. CHP equipment can provide resilient power 24/7 in the event of grid outages, and it can be paired with other distributed energy technologies like solar photovoltaics (PV) and energy storage.

Waste Heat Recovery Boiler is a system which recovers various kinds of waste heat generated from the production process of steel, non-ferrous metal, chemical, cement etc and those equipment of industrial furnaces, refuse incinerators, industrial waste incinerators, and convert such recovered heat into useful and effective thermal energy. Waste Heat Recovery Boiler is contributing to industrial society in terms of improvement of thermal efficiency, energy saving, environmental protection etc.

Conditions of the origin of waste heat depend upon each kind of facility which discharges waste heat. Conditions like gas temperature, pressure, corrosiveness, dust content etc vary depending on the conditions of each case. Therefore, deign and fabrication of waste heat recovery boiler require rich experience and technical capability. Kawasaki is able to provide waste heat recovery boilers suitable to extremely tough conditions such as gas temperature of 1,500 degree C (2732 F) dust content of 400g/Nm3 (174 gr/dscf) and SOx content 40%. Kawasaki has delivered more than 500 units of various kinds of waste heat recovery boiler, of which quality and reliability are highly reputed by the customers.

The UK government plans to introduce the Industrial Heat Recovery Support programme to increase industry confidence in identifying and investing in opportunities for recovering and reusing waste heat from industrial processes. Heat that is generated in or for an industrial process can be reused within the same industrial facility for heating or cooling, by another end-user, or by converting the waste heat to power. Collecting and reusing this heat increases efficiency and can lead to fossil fuel, carbon and cost savings.

In October 2017 the Department for Business, Energy & Industrial Strategy announced its consultation on the Industrial Heat Recovery Support programme. This paper sets out a response to a selected question on overcoming potential barriers to the uptake of recoverable heat technologies in industry. It concludes that the programme should take into consideration the interactions with existing policies on heat such as the EU emissions trading system and ensure a level playing field with non-industrial heat generators.

Captured and reused waste heat provides a low-cost substitute for high-cost fuels or electricity. Numerous technologies are available for transferring waste heat to usable energy for a process. Lathrop Trotter has extensive experience in developing heat recovery solutions, including two highly effective options: HRSG & Stack Economizers and Waste Heat Boilers.

Industrial waste heat resources are widely distributed in many industries such as iron and steel, metallurgy, building materials, non-ferrous metals, petrochemicals, light industry, etc. It is currently a recyclable resource with the most widespread distribution and the greatest application potential in industrial production. Industrial waste heat is a kind of secondary energy. It is the heat lost in the industrial production process of primary energy. It is generally discharged into the external environment in the form of flue gas, waste gas, and wastewater1. According to statistics, the total amount of waste heat resources in the metallurgy, building materials and chemical industries is relatively large, reaching about 80%; medium and low-quality waste heat resources account for about 54%, and the annual utilization rate is about 2.7 million tons of standard coal2. As shown in Fig. 1, high-, medium-, and low-temperature waste heat accounted for 40%, 26%, and 34%, respectively, but their secondary utilization rates are quite different. Among them, the medium and low temperature waste heat is widely distributed, but due to its low quality, the recovery rate is much lower than the high temperature waste heat, which limits the further improvement of the overall utilization rate of industrial waste heat3. Research on low-quality waste heat recovery technology is conducive to comprehensive conservation and efficient use of resources, promote the development of low-carbon cycles, advance the energy revolution, accelerate energy technology innovation, and build a clean, low-carbon, safe and efficient modern energy system. Energy saving, emission reduction and environmental protection will be an important part of economic development in the future.

At present, the research on low-quality waste heat recovery in universities and scientific research institutions mostly uses screw expanders and scroll expanders as core equipment, and most of the research on waste heat recovery is the improvement and optimization of existing solutions. However, these studies have obvious shortcomings when applied to low-quality waste heat recovery, which are mainly manifested in the complex structure of the core equipment, high processing costs, inconvenient maintenance, and high operating costs. As a result, these technologies and equipment are not widely used in low- and medium-quality waste heat utilization systems, and they cannot meet the needs of small and medium-sized enterprises for energy-saving technologies4. In addition, while the mechanical structure of waste heat recovery device is studied abroad, it is also gradually studied in the micro direction. On the one hand, the heat transfer effect can be improved by adding nano-particles or nano-fluids; on the other hand, the heat transfer efficiency can be improved by improving the radiator at the nano-level. Ibrahim Muhammad studied stretchable rotating discs with heat transfer functions and carried out numerical analysis of their fluids5,6. Zhixiong Chen et al. tested 27 refrigerants and studied a thermal conductivity model with better accuracy7. Subsequently, nano-particle fluids such as copper oxide or alumina were added into the heat transfer system, and thermodynamics laws and exergy were analyzed. The analysis results show that adding nanoparticles into the heat exchanger fluid can reduce exergy loss and reduce the efficiency of the second law of thermodynamics, so as to improve energy conversion efficiency8,9,10,11,12,13. This kind of method also plays a positive role in waste heat utilization technology, but also has the disadvantage of high cost. 041b061a72


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