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In this study, we adopted steam gasification of biomass, and pine fuel rods as the experimental objects. We used gas chromatography and Fourier transform infrared spectrometer to analyze components of gas and tar change during the process of gasification. We also determined catalytic performance of modified dolomite (bentonite as the carrier, dolomite as the active component and a small amount of load limonite) as temperature rose. Our experiment results showed that, high-temperature made steam gasification of biomass intensified so that steam reforming reaction intensified and thus contributing to H2 gas volume fraction in the overall upward trend in the gasification components, but hydrocarbon gas volume fraction in downward trend. Gasification gas carries gasification tar into the catalyst layer, which makes tar catalytic cracked, promotes steam reforming reaction intensified and thereby changes the composition of gasification gas. Under the condition of steam gasification with modified dolomite catalyst at 750 ℃, H2 volume fraction was 45.77%±0.23%. Compared to hydrogen-rich action of catalytic and non-catalytic conditions dolomite, gasification temperature dropped to 100oC. With the rise of temperature, modified dolomite promoted the increase of carbon oxides and hydrocarbons volume fraction, but hydrogen-rich degree weaken. The calcined dolomite contained MgO/CaO as active ingredients can cause the long carbon chain cracked in aliphatic hydrocarbons, conducive to the production of radical hydrogen ion, and be helpful to generate hydrogen. When Fe as a promoter was used, it was activated to Fe3+ by high temperature steam, and converted to Fe2+ after promoting tar cracking. Modified dolomite not only promoted the scission of carbon chain length on the hydrocarbon side chain and the formation of H2, but also promoted opening reactions of aromatic ring, decarboxylation and dehydroxylation reactions, thereby making tar after pyrolysis easily to be converted into small molecule gas carbon containing, which helped to reduce the production of tars gasified and improved the gasification efficiency. The catalyst active center Fe3+ decreased at higher temperature, which made the gaining weight of homemade catalyst after catalysis reduced to a minimum of 900 ℃, but compared to dolomite, the change of color and shape of modified dolomite between front and rear catalytic was small, which reflected the mechanical strength and surface area carbon optimized. The catalytic activity of dolomite was secondly to nickel-based catalyst, but it had potential economic value with cheaper price. In this study, we compared to steam gasification of biomass with dolomite catalyst, explored the catalytic properties of modified dolomite, which would provide useful information of dolomite modification method and studies of steam gasification of biomass. The purpose of this research was to promote the use of dolomite catalysts, and our results showed that they can be used for the treatment of tailings and to deepen the study of biomass steam gasification. [ABSTRACT FROM AUTHOR]

Grasping the change rule and the distribution of rural settlements in farming-pastoral zone has significant meaning to rectifying residential areas, optimizing layout, and implementing rural revitalization strategic planning. This paper took Damao Banner of Baotou city in Inner Mongolia, a typical farming-pastoral ecotone in the north of Yinshan Mountain, as the study region, and we used historical data materials such as land cover types, toponymy records, scoio-economic data came from the Statistical Yearbook of Damao Banner in 1996, 2012 and 2016, based on Kernel density analysis and model of Gravity Migration to explore and reveal the spatial distribution characteristics and evolution of rural settlements. Meanwhile, its influencing factors mainly include elevation, slope, aspect, distance to water, distance to road, distance to towns, national culture, population and government policies, etc. We analyzed the intrinsic relationship between the spatial distribution of the rural settlements and the factors by using GIS (geographic information system) spatial analysis software. The results showed that: 1) the distribution characteristic of rural settlements in Damao Banner in 2012 was obvious, reaching a peak of 1.416/km2. From 1996 to 2016, the distribution center of Damao Banner’ rural settlements moved to the southeast and gradually approached Bailingmiao Town. 2) The influence of DEM and slope on the distribution of rural settlements was inverted U-shaped. It increased first and then decreased gradually. The peak value of DEM was 1 400-1 600 m, and the peak value of slope was 3.056°-5.446°. The choice of aspect was gradually inclined to the south aspect, southwest aspect and the proportion increased year by year, but some rural settlements were still distributed on the shady aspect, for example north aspect and northeast aspect, which was affected by geographical environment, national culture, and government policy. The spatial distribution of the rural settlements of Damao Banner did not show obvious near-water characteristic in terms of the distance to water area, but they mostly distributed in 7-10 km away from the water. 3) The road distance showed obvious near-road orientation. In 2016, the number of rural settlements distributed within the range of 0-1 000 m from the road accounted for 98.77%, indicating that the roads and settlements had mutual influence and interaction. Traffic significantly changed the spatial pattern of the rural settlements, and had evident distance attenuation effect. The number of the spatial distribution of rural settlements occupied the largest proportion when it was 20-40 km away from the town in 2012 and 2016. It meant that the radiation effect of central town on rural settlements was limited to a certain extent, and the spatial distribution of rural settlements was far away from central town. In agricultural region and pastoral region of Damao Banner, the number of rural settlements had different characteristics with their population. In 1996 and 2016, the number of Mongolian population in the pastoral region was significantly positively correlated with the number of rural settlements. The Mongolian nomadic culture promoted the distribution of residential areas with a highly dispersed feature of “Giant Stars”. Also government policies had an important impact on the spatial distribution and pattern of rural settlements in Damao Banner. Therefore, the results of this study can provide a reference for rectifying residential areas, optimizing layout, and implementing rural revitalization strategic planning in these ethnic areas. [ABSTRACT FROM AUTHOR]