Patent Description:
Document <CIT> relates to a method for producing biogas from crude biogas, wherein an exhaust gas stream occurring during the processing of crude biogas is treated using a catalyst. Furthermore, document <CIT> relates to the use of a catalyst for treating an exhaust gas stream occurring during the production of biogas.

Document <CIT> proposes a method for transporting waste from one location to another, treating the waste to produce a biogas, and utilizing a portion of that biogas to enhance plant growth and/or as a fuel source. The waste is loaded into a bladder included in a railroad car, and the waste is transported to a remote treatment facility for unloading. The waste is then treated by anaerobic digestion to produce the biogas.

Document <CIT> proposes a process and equipment for oxidizing components of a feed gas mixture in a regenerative heat reactor. The reactor consists of a vessel with two ends, containing a gas-permeable bed made of heat exchange material where the components of the feed gas mixture undergo oxidation. A gas handling system controls the entry and exit of the gas mixture, allowing the direction of gas flow through the vessel to be reversed. A bypass system directs the feed gas mixture to an intermediate point in the vessel, bypassing part of the gas-permeable bed. Meanwhile, a purging system cleans out any remaining unreacted feed gas mixture from the heat exchange zone.

Landfill drain water is collected and treated due to its high pollution with organic and/or other substances. Processes for water treatment such as, e.g., the Fenton process require temperatures above ambient temperate and, hence, a significant amount of energy. Similarly, processes for mechanical biological treatment of waste or processes for water treatment in a sewage treatment plant require controlled temperatures at levels higher than ambient temperature and, hence, a significant amount of energy.

Furthermore, landfill gas emissions or gas emissions of waste treatment plants are treated separately using various purification techniques to comply with statutory emission limits.

There may be demand for improved waste treatment.

The demand may be satisfied by the subject-matter of the appended claims.

An example relates to a synergetic system for waste treatment. The synergetic system comprises a waste treatment system configured to perform biological treatment of waste. Additionally, the synergetic system comprises a gas purification system configured to purify exhaust gas generated during the biological treatment of the waste. The synergetic system further comprises a feeding system configured to feed excess heat from the gas purification system back to the waste treatment system. The waste treatment system is further configured to use the fed back excess heat for the biological treatment of the waste. The gas purification system is configured to purify the exhaust gas by regenerative thermal oxidation or regenerative catalytic oxidation. The gas purification system comprises a single heat-transfer bed filled with ceramic material and an electrical heater configured to initially heat the ceramic material to a predefined temperature. Additionally, the gas purification system comprises a gas flow control system configured to cause the exhaust gas to flow through the heated ceramic material such that the exhaust gas heats up and oxidates while flowing through the ceramic material. The ceramic material is configured to store heat released by the exhaust gas during oxidation. The gas flow control system is further configured to periodically reverse a flow direction of the exhaust gas through the ceramic material. The gas purification system further comprises a heat exchanger arranged in the heat-transfer bed. The heat exchanger is configured to transfer heat from the ceramic material to a heat transport medium flowing through the heat exchanger. The feeding system is configured to feed the heated heat transport medium to the waste treatment system.

Another example relates to a method for waste treatment. The method comprises performing biological treatment of waste using a waste treatment system. Additionally, the method comprises purifying exhaust gas generated during the biological treatment of the waste by regenerative thermal oxidation or regenerative catalytic oxidation using a gas purification system. The method further comprises feeding excess heat from the gas purification system back to the waste treatment system using a feeding system. In addition, the method comprises using the fed back excess heat for the biological treatment of the waste in the waste treatment system. The gas purification system comprises a single heat-transfer bed filled with ceramic material. The method further comprises initially heating the ceramic material to a predefined temperature using an electrical heater. In addition, the method comprises causing, using a gas flow control system, the exhaust gas to flow through the heated ceramic material such that the exhaust gas heats up and oxidates while flowing through the ceramic material. The ceramic material stores heat released by the exhaust gas during oxidation. A flow direction of the exhaust gas through the ceramic material is periodically reversed by the gas flow control system. The gas purification system further comprises a heat exchanger arranged in the heat-transfer bed. The method further comprises transferring, by the heat exchanger, heat from the ceramic material to a heat transport medium flowing through the heat exchanger. Feeding the excess heat from the gas purification system back to the waste treatment system comprises feeding the heated heat transport medium to the waste treatment system using the feeding system.

Feeding back the excess heat from the gas purification system to the waste treatment system and using the fed back excess heat for the biological treatment of the waste in the waste treatment system may allow synergetic operation of the gas purification system and the waste treatment system. In particular, the use of the fed back excess heat for the biological treatment of the waste in the waste treatment system may allow to cover at least part of the energy demand of the waste treatment system. Accordingly, an overall energy consumption for the waste treatment may be reduced according to the proposed technology. Furthermore, the fed back excess energy may allow to optimize the process conditions for the biological treatment of the waste and, hence, allow to perform the biological treatment of the waste with high efficiency.

When two elements A and B are combined using an "or", this is to be understood as disclosing all possible combinations, i.e., only A, only B as well as A and B, unless expressly defined otherwise in the individual case.

<FIG> schematically illustrates an exemplary synergetic system <NUM> for waste treatment. The synergetic system <NUM> comprises a waste treatment system <NUM> for treating waste <NUM>. In particular, the waste treatment system <NUM> is configured to perform biological treatment of the waste <NUM>.

The waste <NUM> may in general be any type of waste that can be treated by means of a biological process. For example, the waste <NUM> may be solid waste, liquid waste, gaseous waste or a combination thereof. Biological treatment of waste may be any treatment of the waste <NUM> that comprises one or more biological processes and/or involves one or more organisms to convert organic components and/or inorganic components of the waste <NUM>. For example, a biodegradable component of the waste <NUM> may be broken down by the biological treatment (e.g. composting, anaerobic digestion or aerobic digestion). In other examples, the biological treatment may be used for denitrification of the waste <NUM>, i.e., for reducing nitrate in the waste <NUM>. Similarly, the biological treatment may be used for reducing other inorganic components in the waste <NUM>. The waste treatment system <NUM> may use various organisms, in particular microorganisms such as algae, fungi, bacteria or ciliates, for the biological treatment of the waste <NUM>. For example, the waste treatment system <NUM> may be a wastewater treatment system for treating wastewater such as, e.g., landfill drain water, domestic wastewater, municipal wastewater or industrial wastewater. In other examples, the waste treatment system <NUM> may be solid waste treatment system such as a mechanical biological treatment system using mechanical waste sorting and biological treatment for treating solid waste such as domestic solid waste, municipal solid waste or industrial solid waste. However, it is to be noted that the waste treatment system <NUM> is not limited to the above examples.

The waste treatment system <NUM> is configured to output biologically treated material <NUM> resulting from the biological treatment of the waste <NUM>. For example, the biologically treated material <NUM> may be purified wastewater, compost, digestate, residual unusable material, renewable fuel, recovered recyclable materials such as metals, paper, plastics, glass etc., or a combination thereof. The output biologically treated material <NUM> may, e.g., be reused, further treated (e.g. thermal treatment or recycling) or deposited in a landfill.

In addition to the biologically treated material <NUM>, the biological treatment of the waste <NUM> generates exhaust gas <NUM> (e.g. an exhaust gas stream). The synergetic system <NUM> additionally comprises a gas purification system <NUM> coupled to the waste treatment system <NUM> and configured to purify the exhaust gas <NUM> generated during the biological treatment of the waste.

The gas purification system <NUM> is a system that receives the exhaust gas <NUM> at an inlet and removes impurities or one or more pollutants from the exhaust gas <NUM> so that a purified (cleaned) exhaust gas <NUM> is output (emitted/released) at an outlet of the gas purification system <NUM>. The purified exhaust gas <NUM> may be released to the environment. A pollutant can be understood in this context as a substance that harms systems, animals, humans and/or the environment when occurring in a specific quantity or concentration (e.g. defined as mass of the pollutant per unit volume of the exhaust gas <NUM> or as number of pollutant particles per unit volume of the exhaust gas <NUM>). Accordingly, the purification of the exhaust gas <NUM> may include, e.g., a detoxification, denitrification, deacidification, desulfurization, de-dusting or a combination thereof. For example, organic and/or inorganic pollutants may be removed from the exhaust gas <NUM> by the gas purification system <NUM>. The organic and/or inorganic pollutants may, e.g., be nitrogen oxides (NOx), methane (CH<NUM>), sulfur oxides (SOx), hydrogen fluoride (HF), ammonia (NH<NUM>), hydrogen chloride (HCl), dioxins, furans or pollutants of the basic structure CxHyOz (C denotes carbon; H denotes hydrogen; O denotes oxygen; x, y, and z are natural numbers).

The gas purification system <NUM> may use various methods to purify the exhaust gas <NUM>. For example, the gas purification system <NUM> may use known concentration methods/processes (e.g., by means of absorption, adsorption or membranes), condensation methods, catalytic methods, non-catalytic-chemical methods, methods using a non-thermal plasma (cold oxidation), biological methods (e.g., bioscrubbers, biofilters), mechanical methods, electromechanical methods, thermal methods or a combination of several of the above-mentioned methods. According to some examples, the gas purification system <NUM> may be configured to purify the exhaust gas <NUM> by a thermal method such as Regenerative Thermal Oxidation (RTO) or a catalytic method such as Regenerative Catalytic Oxidation (RCO). The gas purification system <NUM> may use one or more flames or a flameless process for purifying the exhaust gas <NUM>. For example, the gas purification system <NUM> may be configured to purify the exhaust gas <NUM> by flameless RTO or flameless RCO. However, it is to be noted that the gas purification system <NUM> is not limited to the above exemplary gas purification techniques.

An efficiency of the one or more biological processes taking place in the waste treatment system <NUM> for treating the waste <NUM> depends on the environmental conditions within the waste treatment system <NUM>. In particular, the efficiency of the one or more biological processes depends on the ambient temperature within the waste treatment system <NUM>. A biological process is most efficient in a specific temperature range. In case the ambient temperature is above or below the specific temperature range, the efficiency of the biological process decreases. Accordingly, adjusting the ambient temperature within the waste treatment system <NUM> to the specific temperature range may allow to optimize the efficiency of the biological waste treatment.

Adjusting the ambient temperature within the waste treatment system <NUM> requires heat. In many conventional systems, heat is not available such that the ambient temperature within the waste treatment system <NUM> is below the specific temperature range. Accordingly, the efficiency of the biological processes taking place in the waste treatment system <NUM> is decreased. For example, the efficiency of the biological processes may vary with the seasons of the year (e.g. be more efficient in summer than in the winter due to the higher temperatures in summer). In other conventional systems, the heat is generated using external energy such as electrical energy or fossil fuels. For example, electrical energy or fossil fuel may be converted to heat for heating the waste <NUM> prior to or during the biological treatment of the waste <NUM>. Alternatively or additionally, a treatment space of the waste treatment system <NUM> in which the biological treatment of the waste <NUM> takes place may be heated. The conventionally used external energy increases the efficiency but also the costs for waste treatment. Further, in case fossil fuel or electric energy from non-regenerative sources are used for heating, the waste treatment causes greenhouse gas emission.

The gas purification system <NUM> generates excess (surplus) heat <NUM> during operation. The excess heat <NUM> is heat energy recovered at the gas purification system <NUM> from the purification process for purifying the exhaust gas <NUM>. The excess heat <NUM> may be understood as waste heat of the gas purification system <NUM> as it is a "waste product" of the purification process. For example, the excess heat may be recovered in a process chamber of the gas purification system <NUM> or from a gas stream processed by the gas purification system <NUM> such as the purified exhaust gas <NUM>.

According to the proposed architecture, the excess heat <NUM> of the gas purification system <NUM> is synergistically used for the waste treatment system <NUM>. In particular, the synergetic system <NUM> comprises a feeding system <NUM> configured to feed the excess heat <NUM> from the gas purification system <NUM> back to the waste treatment system <NUM>. The waste treatment system <NUM> is further configured to use the fed back excess heat <NUM> for the biological treatment of the waste <NUM>.

The use of the fed back excess heat <NUM> for the biological treatment of the waste <NUM> in the waste treatment system <NUM> may allow to optimize (increase) the efficiency of the biological waste treatment as the fed back excess heat <NUM> may be used for adjusting (increasing) the ambient temperature within the waste treatment system <NUM>. Hence, an efficiency of the biological treatment of the waste <NUM> may be increased compared to conventional systems not using heat for temperature optimization. Further, compared to conventional systems using external energy for adjusting the ambient temperature within the waste treatment system <NUM>, the fed back excess heat <NUM> may allow reduce the consumption of external energy for adjusting the ambient temperature within the waste treatment system <NUM> as the fed back excess heat <NUM> may allow to cover at least part of the heat demand of the waste treatment system <NUM>. Accordingly, an overall energy consumption and an overall greenhouse gas emission of the synergetic system <NUM> for the treatment of the waste <NUM> may be reduced compared to conventional approaches. Additionally, the biological treatment of the waste <NUM> may be performed by the waste treatment system <NUM> at high efficiency and/or at shorter time with reduced energy consumption.

The waste treatment system <NUM> may use the fed back excess heat <NUM> in various ways. For example, the waste treatment system <NUM> may be configured to use the fed back excess heat <NUM> for heating the treatment space in which the biological treatment of the waste <NUM> takes place. Alternatively or additionally, the waste treatment system <NUM> may be configured to use the fed back excess heat <NUM> for heating the waste <NUM>. By heating the treatment space and/or the waste <NUM>, the efficiency of the biological treatment of the waste <NUM> may be increased as described above.

The feeding system <NUM> may feed the excess heat <NUM> in various ways back to the waste treatment system <NUM>. For example, feeding system <NUM> may feed a heat transport medium such as a fluid (e.g. water or thermal oil) or a gas (e.g. air or steam) from the waste treatment system <NUM> to the gas purification system <NUM> such that the heat transport medium is heated by the excess heat <NUM> and feed the heated heat transport medium back to the waste treatment system <NUM>. The waste treatment system <NUM> may use the heat stored in the heated heat transport medium for the biological treatment of the waste <NUM> (e.g. as described above).

The synergetic system <NUM> further comprises an exhaust gas transport system <NUM> configured to transport the exhaust gas <NUM> from the waste treatment system <NUM> to the gas purification system <NUM>. The exhaust gas transport system <NUM> may be a separate system (as illustrated in <FIG>) or be part of one of the waste treatment system <NUM> and the gas purification system <NUM>. The exhaust gas transport system <NUM> collects the exhaust gas <NUM> at the waste treatment system <NUM> and transports the exhaust gas <NUM> to the gas purification system <NUM>. The exhaust gas transport system <NUM> may comprise piping and optionally one or more further elements such as a pump, a ventilator, a blower or a compressor for transporting the exhaust gas <NUM>.

As indicated in <FIG>, the gas purification system <NUM> may be further configured to receive and purify further exhaust gas <NUM>. The further exhaust gas <NUM> is received from a different source than the waste treatment system <NUM>. In some examples, another source of exhaust gas may be located nearby the waste treatment system <NUM> such that the gas purification system <NUM> may be used for purifying the exhaust gases <NUM> and <NUM> of both sources. For example, if the waste treatment system <NUM> is a wastewater treatment system for treating drain water of a landfill, not only the exhaust gas <NUM> of the waste treatment system <NUM> may be purified by the gas purification system <NUM> but also gas emissions of the landfill itself.

According to some examples, also the purified exhaust gas <NUM> may be used by the waste treatment system <NUM> for the biological treatment of the waste. Accordingly, the synergetic system <NUM> may optionally further comprise a purified exhaust gas transport system <NUM> coupled to the outlet of the gas purification system <NUM> and configured to transport the purified exhaust gas <NUM> to the waste treatment system <NUM>. The purified exhaust gas transport system <NUM> may comprise piping and optionally one or more further elements such as a pump, a ventilator, a blower or a compressor for transporting the purified exhaust gas <NUM>. For example, the waste treatment system <NUM> may be configured to use the purified exhaust gas <NUM> for heating the treatment space in which the biological treatment of the waste <NUM> takes place. Alternatively or additionally, the waste treatment system <NUM> may be configured to use the purified exhaust gas <NUM> for heating the waste <NUM>. The waste treatment system <NUM> may, e.g., heat wastewater by bubbling or blowing the purified exhaust gas <NUM> into the wastewater. In other examples, the waste treatment system <NUM> may be configured to use the purified exhaust gas <NUM> for adjusting one or more other environmental conditions within the waste treatment system <NUM> (e.g. a respective concentration of one or more substances such as oxygen in the environment air within the waste treatment system <NUM>).

<FIG> schematically illustrates another exemplary synergetic system <NUM> for waste treatment. The synergetic system <NUM> is used for treating wastewater <NUM> of a landfill. In other words, the treated waste is the wastewater <NUM> of the landfill. For example, the wastewater <NUM> may be drain or leak water of the landfill.

A waste treatment system <NUM> of the synergetic system <NUM> may, e.g., be coupled to a basin or dam used for collecting the drain or leak water of the landfill. The waste treatment system <NUM> receives the wastewater <NUM> and feeds the wastewater <NUM> into a treatment space <NUM> such as, e.g., a tank or a basin. The wastewater <NUM> is biologically treated (e.g. by means of Fenton process) in the treatment space <NUM> to reduce or remove organic or other substances polluting the landfill drain water.

Purified wastewater <NUM> is output (emitted, released) by the waste treatment system <NUM>. For example, the purified wastewater <NUM> may be returned to the basin or dam used for collecting the drain or leak water of the landfill.

Exhaust gas <NUM> is generated during the biological treatment of the wastewater <NUM>. For example, the exhaust gas <NUM> may comprise methane or other odorous substances generated during the biological treatment of the wastewater <NUM>. Further, evaporation of the wastewater <NUM> from the treatment space <NUM> may cause part of the exhaust gas <NUM>.

An exhaust gas transport system <NUM> of the synergetic system <NUM> is configured to collect and transport the exhaust gas <NUM> from the waste treatment system <NUM> to a gas purification system <NUM> of the synergetic system <NUM>. The gas purification system <NUM> is configured to receive the exhaust gas <NUM> at an inlet and purify the exhaust gas <NUM>. The gas purification system <NUM> in the example of <FIG> is configured to purify the exhaust gas <NUM> by RTO. However, it is to be noted that is merely an example. In general, any other suitable technique (e.g. RCO) may be used as well for purifying the exhaust gas <NUM>. The gas purification system <NUM> is further configured to release the purified exhaust gas <NUM> at an outlet. For example, the purified exhaust gas <NUM> may be released to the environment. Heat energy is recovered at the gas purification system <NUM> and is available as excess heat <NUM> for other purposes.

A feeding system <NUM> of the synergetic system <NUM> is configured to feed the excess heat <NUM> from the gas purification system <NUM> back to the waste treatment system <NUM>. As in indicated in <FIG>, the feeding system <NUM> may feed a heat transport medium from the waste treatment system <NUM> to the gas purification system <NUM> such that the heat transport medium is heated by the excess heat <NUM> and feed the heated heat transport medium back to the waste treatment system <NUM>.

The waste treatment system <NUM> comprises a heat exchanger <NUM>. The heat exchanger <NUM> receives the heated heat transport medium from the feeding system <NUM> and uses the excess heat <NUM> stored in the heated heat transport medium for heating the wastewater <NUM> such that heated wastewater <NUM> is feed into the treatment space <NUM>.

As the wastewater <NUM> is heated before it is fed into the treatment space <NUM>, the ambient temperature in the treatment space <NUM> may be increased. In particular, the ambient temperature in the treatment space <NUM> may be adjusted to be in a specific temperature in order to increase (optimize) the efficiency of the biological treatment. Accordingly, the treatment of the wastewater <NUM> may be improved. Further, as the excess heat <NUM> recovered at the gas purification system <NUM> is used, no or a smaller amount of external energy is needed for heating the wastewater <NUM> in the treatment space <NUM>.

In other words, waste heat from the exhaust gas treatment is used to optimize the upstream biological process (in particular the climate conditions) for an optimized waste processing by biological treatment. Further, heating the wastewater <NUM> by means of the excess heat <NUM> may allow to reduce the risk that the wastewater <NUM> freezes in winter such that biological treatment of the wastewater <NUM> is possible the whole year with increased efficiency. As the exhaust (waste) gas <NUM> of the biological treatment of the wastewater <NUM> is used to improve the biological water treatment process, the water treatment may be performed more efficient and with reduced greenhouse gas emission.

In the example of <FIG>, the gas purification system <NUM> not only receives and purifies the exhaust gas <NUM> from the waste treatment system <NUM>. In addition, the gas purification system <NUM> is configured to receive and purify further exhaust gas <NUM> from another source such as the landfill itself. Also the landfill emits exhaust gas polluted with harmful and/or odorous substances such as methane. Accordingly, the gas purification system <NUM> may additionally be used to purify the gaseous emission of the landfill itself.

One component of the exhaust gas <NUM> as well as the further exhaust gas <NUM> is methane. The content of organic material in the waste dumped in the landfill decreases over time, so does the methane content of the exhaust gas <NUM> and the further exhaust gas <NUM>. If a conventional gas burner is used for the exhaust gas purification treatment, a methane content of approx. <NUM> % would be needed to maintain a temperature in the gas purification system required for the oxidation of the exhaust gas(es). In case covered flares without heat recovery for external use would be used for the exhaust gas purification treatment, a methane content of at least <NUM> - <NUM> % would be needed to maintain the temperature. In case, the methane concentration is lower, external fuel is needed to maintain the temperature required for oxidation. However, the methane content of the exhaust gas <NUM> and the further exhaust gas <NUM> may go below <NUM> % over the lifetime of the landfill such that these techniques are not suitable for the gas purification treatment. On the other hand, RTO may allow autothermal gas purification treatment and heat recovery for gas having a very low energy content (i.e. a very low content of impurities). In particular, RTO may allow autothermal gas purification treatment and heat recovery for methane contents of less than <NUM> %, which makes RTO a suitable purification technique for the gas purification system <NUM>. For example, the RTO may allow to run the synergetic system <NUM> for more than <NUM> year. RCO provides similar advantages as RTO may, hence, be used as an alternative by the gas purification system <NUM>.

Similar to what is described above with respect to <FIG>, the purified exhaust gas <NUM> may optionally be fed back to the waste treatment system <NUM>. For example, the purified exhaust gas <NUM> may be injected into the treatment space <NUM> for temperature optimization. For example, the purified exhaust gas <NUM> may be bubbled into the wastewater <NUM> to heat the wastewater <NUM>.

As indicated in <FIG>, the waste treatment system <NUM> may be configured to feed fresh air <NUM> from the surrounding environment to the treatment space <NUM> for supporting or improving the biological treatment of the wastewater <NUM>.

The treatment of exhaust from a landfill as illustrated in <FIG> is merely one exemplary application of the proposed architecture. Similar to what is described above with respect to <FIG>, the proposed architecture may, e.g., be used for the exhaust gas treatment for wastewater treatment plants using RTO to oxidize the emissions. The proposed energy recovery (e.g. by hot water) may be used to provide heat for processes of the water treatment and, hence, to increase the efficiency of these processes.

While the above description of <FIG> and <FIG> focused on the overall structure of the proposed architecture, the following description will focus on various aspects of the gas purification system. In particular, various exemplary gas purification techniques and their implementations will be described in the following with respect to <FIG>.

<FIG> schematically illustrates a sectional view of a gas purification system <NUM> for flameless RTO of exhaust gas <NUM>. The gas purification system <NUM> comprises an inlet <NUM> for receiving the exhaust gas <NUM>. Subfigure (a) of <FIG> illustrates a first flow direction of the exhaust gas <NUM> through the gas purification system <NUM>, whereas subfigure (b) of <FIG> illustrates a reverse second flow direction of the exhaust gas <NUM> through the gas purification system <NUM>.

Further, the gas purification system <NUM> comprises a single (i.e. exactly/only one) heat-transfer bed <NUM> filled with porous ceramic material <NUM> serving as heat-transfer material. The ceramic material <NUM> may be packed structured or randomly in the heat-transfer bed <NUM> to form regular or irregular patterns (e.g. ceramic honeycombs or ceramic saddles may be used).

Additionally, the gas purification system <NUM> comprises an electrical heater <NUM> (e.g. a grid of electrical coils) configured to initially heat the ceramic material <NUM> to a predefined temperature (range) suitable for thermal oxidation of the exhaust gas <NUM>. For example, the electrical heater <NUM> may heat the ceramic material <NUM> to approx. <NUM> suitable for thermal oxidation of the exhaust gas <NUM>.

The gas purification system <NUM> further comprises a gas flow control system <NUM>. Once the ceramic material is heated by the electrical heater <NUM>, the gas flow control system <NUM> is configured to cause the exhaust gas <NUM> to flow through the heated ceramic material <NUM> such that the exhaust gas <NUM> heats up and oxidates while flowing through the ceramic material <NUM>. In subfigure (a) of <FIG>, the gas flow control system <NUM> causes the exhaust gas <NUM> to flow from the top to the bottom through the heated ceramic material <NUM>. As the exhaust gas <NUM> passes from the top part to the bottom part of the porous ceramic material <NUM>, Volatile Organic Compounds (VOCs) in the exhaust gas <NUM> get hot enough to undergo thermal oxidation to water vapor and carbon dioxide. The ceramic media <NUM> at the bottom part recovers the heat energy in the purified exhaust gas <NUM>. In other words, the ceramic material <NUM> is configured to store heat released by the exhaust gas <NUM> during oxidation. The purified exhaust gas <NUM> is released at an outlet <NUM> of the gas purification system <NUM>. For example, a temperature of purified exhaust gas <NUM> may be less than <NUM> higher than that of the exhaust gas <NUM> (e.g. the temperature may be only <NUM> to <NUM> higher).

The gas flow control system <NUM> is further configured to periodically reverse a flow direction of the exhaust gas <NUM> through the ceramic material <NUM> (e.g. every <NUM> to <NUM> seconds).

This is illustrated in subfigure (b) of <FIG>. In subfigure (b) of <FIG>, the gas flow control system <NUM> causes the exhaust gas <NUM> to flow from the bottom to the top through the ceramic material <NUM>. The heat energy previously stored in the bottom part of the ceramic material <NUM> while the gas flow control system <NUM> caused the exhaust gas <NUM> to flow from the top to the bottom through the ceramic material <NUM> is now used to heat the exhaust gas <NUM> to the oxidation temperature. Accordingly, the ceramic media <NUM> at the top part recovers the heat energy in the purified exhaust gas <NUM>.

The periodic reversion of the flow direction of the exhaust gas <NUM> through the ceramic material <NUM> may allow to maintain a high heat exchange efficiency of the ceramic material <NUM> (e.g. higher than <NUM> %). Accordingly, the gas purification system <NUM> may recover substantially all the heat needed for sustaining the needed oxidation temperature of the heat-transfer bed <NUM>. Further, the periodic reversion of the flow direction of the exhaust gas <NUM> may allow to maintain a predetermined temperature profile of the heat-transfer bed <NUM> along the vertical extension of the heat-transfer bed <NUM>. In particular, the periodic reversion of the flow direction of the exhaust gas <NUM> may allow to keep the hottest zone in the center of the of the heat-transfer bed <NUM> along the vertical extension of the heat-transfer bed <NUM>.

The gas flow control system <NUM> is formed by plenums <NUM>, <NUM> located above and below the heat-transfer bed <NUM> and a plurality of valves <NUM>, <NUM> in the example of <FIG>.

The gas purification system further comprises a heat exchanger <NUM> arranged in the heat-transfer bed <NUM>. The heat exchanger <NUM> is configured to transfer heat from the ceramic material <NUM> to a heat transport medium <NUM> flowing through the heat exchanger <NUM>. As indicated in <FIG>, the heat exchanger <NUM> may be formed by one or more tubes running through the heat-transfer bed <NUM> such that the and one or more tubes are surrounded by the ceramic material <NUM>. For example, a plurality of tubes may be arranged in one or more layers in the heat-transfer bed <NUM> to extract heat from the heat-transfer bed <NUM>. The heat transport medium is flowing through the one or more tubes. The vertical position(s) of the one or more tubes or layers may be selected according to the temperature profile of the heat-transfer bed <NUM>. The heat extraction by the heat exchanger <NUM> may further allow to stabilize a temperature of the purified exhaust gas <NUM> (e.g. reduce a dependency of the purified exhaust gas <NUM>'s temperature from a VOC concentration in the exhaust gas <NUM>).

The heat transport medium may be a gas or a fluid such as water or thermal oil. Using a fluid heat transport medium may be advantageous to using a gaseous heat transport medium as the heat transfer from the solid tube wall to a fluid medium is superior compared to the heat transfer from the solid tube wall to a gaseous medium.

A vertical extension of the hottest zone in the center of the of the heat-transfer bed <NUM> may depend on a VOC concentration in the exhaust gas <NUM>. A higher VOC concentration in the exhaust gas <NUM> may result in a greater vertical extension of the hottest zone. Accordingly, more heat energy may be extracted for higher VOC concentrations in the exhaust gas <NUM>.

The heated heat transport medium <NUM> is transported to the waste treatment system by the feeding system of the proposed synergetic system such that the waste treatment system is able to use the excess heat recovered from the heat-transfer bed <NUM> for the biological treatment of the waste. In other words, the feeding system is configured to feed the heated heat transport medium <NUM> to the waste treatment system. Both a closed and an open loop may be used for the heat transport medium.

The gas purification system <NUM> may, e.g., allow to recover all thermal energy in case the content of methane in the exhaust gas <NUM> is just parts of a percent.

<FIG> illustrates an extended variation of the gas purification system <NUM>. In particular, <FIG> illustrates a sectional view of a gas purification system <NUM>. In comparison to the gas purification system <NUM>, the gas purification system <NUM> additionally comprises a heat exchanger <NUM> coupled to the outlet <NUM> for releasing the purified exhaust gas <NUM>. The heat exchanger <NUM> is configured to transfer heat from the purified exhaust gas <NUM> to a heat transport medium <NUM> flowing through the heat exchanger <NUM>. The heat transport medium <NUM> may be a gas or a fluid such as water, steam or thermal oil.

The heat transport medium <NUM> is fed to the heat exchanger <NUM> via a piping <NUM>. Optionally, one or more further elements such as a pump <NUM>, a ventilator, a blower or a compressor may be used for transporting the heat transport medium <NUM> to the heat exchanger <NUM>.

The heat exchanger <NUM> may allow to recover excess heat from the purified exhaust gas <NUM> released at the outlet <NUM>.

The heated heat transport medium <NUM> is transported to the waste treatment system by the feeding system of the proposed synergetic system such that the waste treatment system is able to use the excess heat recovered from the purified exhaust gas <NUM> for the biological treatment of the waste. In other words, the feeding system is configured to feed the heated heat transport medium <NUM> to the waste treatment system. Both a closed and an open loop may be used for the heat transport medium.

In the example of <FIG>, heat is recovered from the heat-transfer bed <NUM> via the heat exchanger <NUM> and additionally from the purified exhaust gas <NUM> via the heat exchanger <NUM>. The gas purification system <NUM> may allow to recover more excess heat than the gas purification system <NUM> and, hence, provide an increased amount of excess heat for the biological treatment of the waste.

In some examples, the heat exchanger <NUM> for recovering heat from the heat-transfer bed <NUM> may be omitted. In other words, gas purification system according to the present disclosure may only comprise the heat exchanger <NUM> but not the heat exchanger <NUM>.

<FIG> schematically illustrates a sectional view of another gas purification system <NUM> for RTO of exhaust gas <NUM>. The gas purification system <NUM> is a three bed tower RTO system.

The gas purification system <NUM> comprises three vertical heat-transfer beds <NUM>, <NUM> and <NUM> each filled with porous ceramic material <NUM> serving as heat-transfer material. The ceramic material <NUM> may be packed structured or randomly in the respective heat-transfer bed to form regular or irregular patterns.

A gas flow control system of the gas purification system <NUM> causes exhaust gas <NUM> to flow through the heated ceramic material of one of the heat-transfer beds <NUM>, <NUM> and <NUM>. In the example of <FIG>, the exhaust gas <NUM> is caused to flow through the heat-transfer bed <NUM>. As the exhaust gas <NUM> travels through the heat-transfer bed <NUM>, heat is transferred from the ceramic material <NUM> to the exhaust gas <NUM>. The heated exhaust gas <NUM> exits the heat-transfer bed <NUM> and enters an oxidation chamber <NUM>. A burner <NUM> heats the oxidation chamber <NUM> such that the heated exhaust gas <NUM> oxidates to water and carbon dioxide.

As indicated in <FIG>, the burner <NUM> is fed with fuel <NUM> and air <NUM> for heating the oxidation chamber <NUM> to a predefined temperature (range) for the oxidation.

The purified exhaust gas <NUM> is caused by the gas flow control system to flow through the ceramic material <NUM> of one of other heat-transfer beds <NUM> and <NUM> towards an outlet <NUM> for releasing the purified exhaust gas <NUM>. In the example of <FIG>, the purified exhaust gas <NUM> is caused to flow through the heat-transfer bed <NUM>. As the purified exhaust gas <NUM> travels through the heat-transfer bed <NUM>, the purified exhaust gas <NUM> transfers most of its heat to the ceramic material <NUM> of the heat-transfer bed <NUM> for recovery in a second, reverse cycle.

During this reverse cycle, the gas flow control system causes the exhaust gas <NUM> to flow through the previously heated ceramic material of the heat-transfer bed <NUM> and further causes the purified exhaust gas <NUM> to flow through the ceramic material <NUM> of the heat-transfer bed <NUM> towards the outlet <NUM>. The gas flow control system causes purge case <NUM> to flow through the heat-transfer bed <NUM> during the initial cycle to purge residual gas of a previous cycle from the heat-transfer bed <NUM>. Similarly, the gas flow control system causes the purge case <NUM> to flow through the heat-transfer bed <NUM> during the reverse cycle.

In a third cycle, the gas flow control system causes the exhaust gas <NUM> to flow through the previously heated ceramic material of the heat-transfer bed <NUM> and further causes the purified exhaust gas <NUM> to flow through the ceramic material <NUM> of the heat-transfer bed <NUM> towards the outlet <NUM>. The heat-transfer bed <NUM> is purged during the third cycle.

The three cycles are repeated continuously to alternately cool one of the heat-transfer beds <NUM>, <NUM> and <NUM>, heat another and purge the third.

The gas flow control system is provided in the example of <FIG> by the piping <NUM> and the plurality of valves <NUM> for controlling the flow of the exhaust gas <NUM> and the purge case <NUM> into the heat-transfer beds <NUM>, <NUM> and <NUM> and for controlling the flow of the purified exhaust gas <NUM> out of the heat-transfer beds <NUM>, <NUM> and <NUM>.

Excess heat may be recovered in various ways. For example, similarly to what is described above with respect to <FIG>, a heat exchanger <NUM> may be coupled to the outlet <NUM>. The heat exchanger <NUM> is configured to transfer heat from the purified exhaust gas <NUM> to a heat transport medium <NUM> flowing through the heat exchanger <NUM>. The heat transport medium <NUM> may be a gas or a fluid such as water or thermal oil. The heat exchanger <NUM> may allow to recover excess heat from the purified exhaust gas <NUM> released at the outlet <NUM>. The heated heat transport medium <NUM> is transported to the waste treatment system by the feeding system of the proposed synergetic system such that the waste treatment system is able to use the excess heat recovered from the purified exhaust gas <NUM> for the biological treatment of the waste. Both a closed and an open loop may be used for the heat transport medium.

Optionally, a three bed tower RTO system such as the gas purification system <NUM> may comprise a bypass <NUM> configured to divert part of the purified exhaust gas <NUM> for bypassing the respective one of the heat-transfer beds <NUM>, <NUM> and <NUM> used for guiding the remaining purified exhaust gas <NUM> to the outlet <NUM>. The bypass <NUM> may also be referred to as "hot bypass" since the purified exhaust gas <NUM> running (flowing) through the bypass <NUM> exhibits a significantly higher temperate than the purified exhaust gas <NUM> released by the respective one of the heat-transfer beds <NUM>, <NUM> and <NUM> to the outlet <NUM>. The bypass <NUM> bypasses the heat-transfer beds <NUM>, <NUM> and <NUM> and directly couples the oxidation chamber <NUM> with the outlet <NUM>.

The gas purification system <NUM> comprises a heat exchanger <NUM> coupled to the bypass <NUM>. The heat exchanger <NUM> is configured to transfer heat from the purified exhaust gas <NUM> running through the bypass <NUM> to a heat transport medium <NUM> flowing through the heat exchanger <NUM>. The heat transport medium <NUM> may be a gas or a fluid such as water or thermal oil. The heat exchanger <NUM> may allow to recover excess heat from the hot purified exhaust gas <NUM> running through the bypass <NUM>. The heated heat transport medium <NUM> is transported to the waste treatment system by the feeding system of the proposed synergetic system such that the waste treatment system is able to use the excess heat recovered from the purified exhaust gas <NUM> for the biological treatment of the waste. Both a closed and an open loop may be used for the heat transport medium.

Optionally, the gas purification system <NUM> may comprise another heat exchanger <NUM> coupled to the bypass <NUM> upstream of the heat exchanger <NUM>. The other heat exchanger <NUM> is configured to transfer heat from the purified exhaust gas <NUM> running through the bypass <NUM> to another heat transport medium <NUM> flowing through the other heat exchanger <NUM>.

The other heat transport medium <NUM> may be a gas or a fluid such as water or thermal oil. Like the heat exchanger <NUM>, the other heat exchanger <NUM> may allow to recover excess heat from the hot purified exhaust gas <NUM> running through the bypass <NUM>. The other heat exchanger <NUM> may allow to recover excess for a heat consuming system different from the above described waste treatment system. For example, the heat consuming system different from the above described waste treatment system may be an industrial system of an industrial plant or a district heating system nearby the gas purification system <NUM>. Accordingly, the proposed synergetic system may in some examples comprise another feeding system configured to feed the heated other heat transport medium <NUM> to the heat consuming system different from the waste treatment system. Both a closed and an open loop may be used for the other heat transport medium <NUM>. Accordingly, not only the waste treatment system but also another heat consuming system may be provided with the available excess heat from the gas purification.

In the example of <FIG>, the heat exchanger <NUM> may allow a high temperature extraction of excess energy and the heat exchanger <NUM> may allow a low temperature extraction of excess energy.

According to some examples, the gas purification system <NUM> may comprises a mixer (not illustrated) configured to mix at least part of the purified exhaust gas <NUM> running through the bypass <NUM> with a gas stream in order to generate a heated gas stream. The gas purification system <NUM> may comprise the mixer additionally to the heat exchanger <NUM> or alternatively to the heat exchanger <NUM>. The gas stream may, e.g., be an air stream. However, it is to be noted that other gases may be used as well. Also the mixer may allow recover excess heat from the hot purified exhaust gas <NUM> running through the bypass <NUM>. The heated gas stream is transported to the waste treatment system by the feeding system of the proposed synergetic system such that the waste treatment system is able to use the excess heat recovered from the purified exhaust gas <NUM> for the biological treatment of the waste. Both a closed and an open loop may be used for the heated gas stream. For example, the waste treatment system may use the heated gas stream as process gas for the biological treatment or for heating the processed waste or the treatment space.

It is to be noted that other RTO systems may be used as well for the proposed synergetic system for waste treatment. For example, a three bed tower RTO system with hot gas flushing instead of the purge gas flushing illustrated in <FIG> may be used. Similarly, a two bed tower RTO system may be used. For example, the two bed tower RTO may be equipped with a buffer tank or be equipped with lying (i.e. horizontally aligned) beds instead of the vertically aligned beds illustrated in <FIG>. In general, any multi bed RTO system may be used. Also one bed RTO systems may be used. In some examples, RTO systems with a rotating heat-transfer bed may be used. Alternatively, the heat-transfer bed may be fixed and a distribution and collection system for injecting the exhaust gas into the heat-transfer bed and for collecting the purified exhaust gas leaving the heat-transfer bed may rotate. These gas purification systems for RTO have in common that they comprise a respective gas flow control system configured to:.

Similar to what is illustrated in <FIG>, these gas purification systems for RTO may comprise a bypass configured to divert part of the purified exhaust gas for bypassing the second ceramic material.

Excess heat may be recovered in these gas purification systems for RTO in various ways. Similar to what is described above with respect to <FIG>, a heat exchanger may be coupled to the outlet of the respective gas purification system for RTO to transfer heat from the purified exhaust gas to a heat transport medium flowing through the heat exchanger. In case the respective gas purification system for RTO comprises a bypass, one or more heat-exchangers may be coupled to the bypass (analogously to the heat exchangers <NUM> and <NUM> illustrated in <FIG>) to transfer heat from the purified exhaust gas running through the bypass to a respective heat transport medium flowing through the respective heat exchanger. Additionally or alternatively, a mixer may be coupled to the bypass to mix at least part of the purified exhaust gas running through the bypass with a gas stream in order to generate a heated gas stream. Similar to what is described above with respect to <FIG>, the heated heat transport medium and the heated gas stream may be feed to the waste treatment system and optionally other heat consuming systems.

The ceramic material in the examples described herein may, e.g., be alumina porcelain, mullite, fireclay (chamotte), cordierite, zircon or a mixture thereof. However, the present disclosure is not limited thereto. Other types of ceramic material may be used as well.

Catalyst material may be provided in addition to the one or more heat-transfer beds of the gas purification systems described above with respect to <FIG>. Accordingly, the needed temperature for oxidizing the exhaust gas may be lower such that the gas purification systems may operate at lower temperatures. For example, one or more layers of catalyst material may be attached to one or both ends of the respective heat-transfer bed along a (possible) flow direction of the exhaust gas. Alternatively or additionally, the ceramic material in the one or more heat-transfer beds (e.g. cordierite) may at least in part be coated with catalyst material. Further alternatively or additionally, catalyst material may be admixed to the ceramic material in the one or more heat-transfer beds. For example, one or more oxidation catalysts and/or one or more reduction catalysts may be used. However, the present disclosure is not limited thereto. Also other types of catalysts may be used. Such gas purification systems may be understood as RCO systems.

For further illustrating the proposed architecture for waste treatment, <FIG> illustrates a flowchart of a method <NUM> for waste treatment. The method <NUM> comprises performing <NUM> biological treatment of waste using (in) a waste treatment system. Additionally, the method <NUM> comprises purifying <NUM> exhaust gas generated during the biological treatment of the waste using (in) a gas purification system. The method <NUM> further comprises feeding <NUM> excess heat from the gas purification system back to the waste treatment system using a feeding system. In addition, the method <NUM> comprises using <NUM> the fed back excess heat for the biological treatment of the waste in the waste treatment system.

The method <NUM> may allow synergetic operation of the gas purification system and the waste treatment system. In particular, the use of the fed back excess heat for the biological treatment of the waste in the waste treatment system may allow to cover at least part of the energy demand of the waste treatment system. Accordingly, an overall energy consumption for the waste treatment may be reduced according to the proposed technology. Furthermore, the fed back excess energy may allow to optimize the process conditions for the biological treatment of the waste and, hence, allow to perform the biological treatment of the waste with high efficiency.

For example, purifying <NUM> the exhaust gas may comprise purifying the exhaust gas by (e.g. flameless) RTO or (e.g. flameless) RCO.

In some examples, the gas purification system may comprise a single heat-transfer bed filled with ceramic material. In this case, purifying <NUM> the exhaust gas may comprise initially heating the ceramic material to a predefined temperature using (by) an electrical heater. Further, purifying <NUM> the exhaust gas may comprise causing the exhaust gas to flow through the heated ceramic material such that the exhaust gas heats up and oxidates while flowing through the ceramic material. The ceramic material stores heat released by the exhaust gas during oxidation. In addition, purifying <NUM> the exhaust gas may comprise periodically reversing a flow direction of the exhaust gas through the ceramic material.

Optionally, the gas purification system may further comprise a heat exchanger arranged in the heat-transfer bed. In this case, the method <NUM> may further comprise transferring heat from the ceramic material to a heat transport medium flowing through the heat exchanger. Further, feeding <NUM> the excess heat from the gas purification system back to the waste treatment system may comprise feeding the heated heat transport medium to the waste treatment system. As described above, the heat exchanger may comprise one or more tubes running through the heat-transfer bed and being surrounded by the ceramic material. The heat transport medium is flowing through the one or more tubes.

In other examples, purifying <NUM> the exhaust gas may comprise causing the exhaust gas to flow through heated first ceramic material such that the exhaust gas heats up and oxidates. Further, purifying <NUM> the exhaust gas may comprise causing purified exhaust gas to flow through second ceramic material towards an outlet for releasing the purified exhaust gas. In addition, purifying <NUM> the exhaust gas may comprise using a bypass to divert part of the purified exhaust gas for bypassing the second ceramic material.

In some examples, the gas purification system may comprise a heat exchanger coupled to the bypass. In this case, the method <NUM> may further comprise transferring heat from the purified exhaust gas running through the bypass to a heat transport medium flowing through the heat exchanger. Further, feeding <NUM> the excess heat from the gas purification system back to the waste treatment system may comprise feeding the heated heat transport medium to the waste treatment system.

Optionally, the gas purification system may comprise another heat exchanger coupled to the bypass upstream of the heat exchanger. In this case, the method <NUM> may further comprise transferring heat from the purified exhaust gas running through the bypass to another heat transport medium flowing through the other heat exchanger. In addition, the method <NUM> may comprise feeding the heated other heat transport medium to a heat consuming system different from the waste treatment system using (by) another feeding system.

Additionally or alternatively, the gas purification system may comprise a mixer. In this case, the method <NUM> may further comprise mixing at least part of the purified exhaust gas running through the bypass with a gas stream in order to generate a heated gas stream. Further, feeding <NUM> the excess heat from the gas purification system back to the waste treatment system may comprise feeding the heated gas stream to the waste treatment system.

According to some examples, the gas purification system may comprise an outlet for releasing purified exhaust gas, and a heat exchanger coupled to the outlet. In this case, the method <NUM> may further comprise transferring heat from the purified exhaust gas to a heat transport medium flowing through the heat exchanger. Further, feeding <NUM> the excess heat from the gas purification system back to the waste treatment system may comprise feeding the heated heat transport medium to the waste treatment system.

In some examples, the gas purification system further comprises an outlet for releasing purified exhaust gas. In this case, the method <NUM> may further comprise transporting the purified exhaust gas to the waste treatment system using (by) a purified exhaust gas transport system. Further, using <NUM> the fed back excess heat for the biological treatment of the waste may comprise using the purified exhaust gas for the biological treatment of the waste.

According to examples, the method <NUM> may further comprise transporting the exhaust gas from the waste treatment system to the gas purification system using (by) an exhaust gas transport system.

In some examples, the method <NUM> may further comprise receiving and purifying further exhaust gas from a different source than the waste treatment system at the gas purification system.

As described above, the waste treatment system may comprise a treatment space in which the biological treatment of the waste takes place. In this case, using <NUM> the fed back excess heat for the biological treatment of the waste may comprise using the fed back excess heat for heating the treatment space.

Additionally or alternatively, using <NUM> the fed back excess heat for the biological treatment of the waste may comprise using the fed back excess heat for heating the waste.

More details and aspects of the method <NUM> are explained in connection with the proposed technique or one or more examples described above (e.g. <FIG>). The method <NUM> may comprise one or more additional optional features corresponding to one or more aspects of the proposed technique or one or more examples described above.

Claim 1:
A synergetic system (<NUM>) for waste treatment, comprising:
a waste treatment system (<NUM>) configured to perform biological treatment of waste (<NUM>);
a gas purification system (<NUM>) configured to purify exhaust gas (<NUM>) generated during the biological treatment of the waste (<NUM>); and
a feeding system (<NUM>) configured to feed excess heat (<NUM>) from the gas purification system (<NUM>) back to the waste treatment system (<NUM>),
wherein the waste treatment system (<NUM>) is further configured to use the fed back excess heat (<NUM>) for the biological treatment of the waste (<NUM>),
wherein the gas purification system (<NUM>) is configured to purify the exhaust gas (<NUM>) by regenerative thermal oxidation or regenerative catalytic oxidation,
wherein the gas purification system (<NUM>) comprises:
a single heat-transfer bed (<NUM>) filled with ceramic material (<NUM>);
an electrical heater (<NUM>) configured to initially heat the ceramic material (<NUM>) to a predefined temperature; and
a gas flow control system (<NUM>, <NUM>, <NUM>, <NUM>) configured to cause the exhaust gas (<NUM>) to flow through the heated ceramic material (<NUM>) such that the exhaust gas (<NUM>) heats up and oxidates while flowing through the ceramic material (<NUM>),
wherein the ceramic material (<NUM>) is configured to store heat released by the exhaust gas (<NUM>) during oxidation,
wherein the gas flow control system (<NUM>, <NUM>, <NUM>, <NUM>) is further configured to periodically reverse a flow direction of the exhaust gas (<NUM>) through the ceramic material (<NUM>),
wherein the gas purification system (<NUM>) further comprises a heat exchanger (<NUM>) arranged in the heat-transfer bed (<NUM>),
wherein the heat exchanger (<NUM>) is configured to transfer heat from the ceramic material (<NUM>) to a heat transport medium (<NUM>) flowing through the heat exchanger (<NUM>), and
wherein the feeding system (<NUM>) is configured to feed the heated heat transport medium (<NUM>) to the waste treatment system (<NUM>).