Use of biomass fuels for energy purposes has gained increasing importance as a method to reduce greenhouse gas emissions. In comparison to gaseous and liquid fossil fuels, the emissions of particulate matter are higher, leading to concerns about the availability of cost-effective techniques to reduce aerosol emissions in small-scale biomass combustion plants. In this work, the applicability of reducing aerosol emissions by stimulating condensation of aerosol-forming vapors on the heat-exchanger furnaces is investigated. A first-order estimation indicates that the heat-exchanger passage has to be in the order of millimeters to obtain a higher wall condensation rate compared to heterogeneous condensation, a result verified with purpose-built heat exchangers connected to a grate furnace. The measurements show that heat exchangers with an equivalent tube diameter of approximately 2 mm can reduce the aerosol emissions by approximately 70% compared to conventional boiler designs.

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Condensed rotational separation (CRS) is a novel method of gas-gas separation. It is based on pressure distillation at semi-cryogenic temperatures whereby one of the components is condensed, thereby forming a mist of micron-sized droplets. These are separated by applying the rotational particle separator (RPS). The RPS is a compact device for separating micron-sized particles from gases by centrifugation. In this paper, CRS is presented as an efficient method to upgrade natural gas fields contaminated with H 2 S=CO 2 : The process consists of two pressure reduction steps. The first step results in maximizing the methane concentration of the gas. The pressure of the separated liquid is further reduced to maximize the concentration of liquid H 2 S=CO 2 whereby the released gas is re-fed to the inlet of the first step. Basic principles, process lay-outs and equipment are discussed. Compared to conventional processes, CRS excels in compactness and minimum usage of energy.

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Natural gas is expected to be an important energy source for decades to come. About 40 % of the known natural gas reserves is known to be sour with the acid gases H 2 S and CO 2 . 16 % is highly sour with more than 20 % acid gas. [1,2] As the energy costs of conventional amine sweetening increase almost linearly with the contamination level, processes are developed that use cooling and selective condensation of the acid components; that is, SPREX by TOTAL and CFZ by EXXON.[3] The energy use in these processes is greatly reduced compared to conventional amine treatment but the equipment-large distillation towers under pressure-is still voluminous. The newly developed process of condensed rotational separation (CRS) is a compact alternative to the distillation tower. [3] In this communication we compare the amine treatment and CRS processes, considering energy and volume use for a binary mixture of CH 4 and CO 2 . Details of the assumptions and models can be found in the supplementary report to this communication. [4] Condensed rotational separation is based on two innovative ideas. The first innovation is the fast cooling of the gas mixture in the two-phase region by cooling and expansion (EXP1 in Scheme 1), whereby one component becomes a mist of fine droplets and the other remains in the gaseous phase. The second innovation is the rotational particle separator (RPS, and RPS1 in Scheme 1). It is an efficient and compact demister that is able to remove the fine droplets from the gas.[5] A representation of such a component is shown in Figure 1.The pressure and temperature at point A in Figure 2 are chosen such that the methane recovery is maximized. The separated liquid CO 2 still contains a considerable amount of methane, however. The liquid produced in the first condensation step is flashed in a second expansion (EXP2 in Scheme 1) to point B in Figure 2 where the liquid CO 2 recovery is maximized.The contaminated gas produced is compressed (COM in Scheme 1) and re-fed prior to the first step. In this way optimal gas and liquid purity is achieved. For a binary mixture of CH 4 -CO 2 the methane can be purified to a contamination level of 14 %, and the CO 2 leaves the process as a liquid of 98 % purity.The compressor is the main energy consumer in CRS. The compressor work scales with the mass flow, which in turn Scheme 1. Process scheme of a two-step condensed rotational separation. The gas is cooled and expanded over the first expansion stage (EXP1) whereby a mist of small droplets are formed. The cleaned gas is separated in RPS1. The liquid is expanded in EXP2 to produce a clean liquid that is removed by RPS2. The gas in the second stage is re-fed prior to the first expansion stage. Figure 1. Principle of the rotational particle separator. The gas, which contains droplets, enters in a swirling motion. Large droplets are collected in the pre-separator and the micrometer-sized droplets enter the small channels of the rotating element. They form a film that breaks up in large droplets, which are separated in the po...

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The increasing amount of liquid, especially water, in the product stream of offshore gas wells, requires improvement of current separation methods. Nowadays, separation methods are mainly based on gravitational settling of the dispersed phases. In these separators low gas velocities are required to achieve a sufficient separating efficiency. As a result these devices are voluminous, heavy, and expensive. As platforms are restricted to space and weight and the liquid amount is increasing, compact and efficient phase separation equipment is required to keep the exploitation of the wells profitable. A device which fulfils these requirements is the naturally driven Rotational Particle Separator (RPS). In this study the operating characteristics of such a separator was measured. For this purpose a full-scale prototype was built, which is capable to handle the volume flow of one typical wellhead under high pressure (80 bar) and which separates droplets down to 2 micron. In order to validate the operating characteristics of the prototype both hydrodynamic and separation performance measurements were performed. Overall, the performance of the prototype agrees well with expectations.

Membranes are used to upgrade heavily contaminated methane gas to pipeline specifications. However, the typical membrane process suffers from a considerable methane slip in the permeate flow. In the hybrid system considered in this Communication, the methane is removed from the permeate stream by using a low‐temperature distillation process with condensed rotational separation (CRS). Compared to a hybrid amine‐CRS process, the energy and volume use are reduced by a factor of two.