中文
EnglishBacked by over 20 years of engineering and operational experience in building material and metallurgical thermal processes, the Sequoia team has developed a series of customized thermal calcination systems for diversified industrial mineral processing and solid waste valorization scenarios.
1. Suspension Calcination Technology for Reactive Lime Production
Conventional mineral calcination facilities, including vertical kilns, rotary kilns, updraft kilns, tunnel kilns and pusher kilns, are widely applied for the thermal treatment of limestone, bauxite, dolomite, magnesite and other non-metallic minerals. These static or semi-static calcination modes fail to implement precise temperature-rise and cooling profiles matching mineral phase transformation characteristics. Such technical limitations restrict the full activation of crystal lattice activity, resulting in low production efficiency, high specific energy consumption and inconsistent product quality in industrial practice.
Rotary kiln technology dominates domestic lime production owing to stable operation and qualified product performance. In typical industrial workflows, 10–60 mm limestone particles are preheated to approximately 800 °C in a dedicated vertical preheater, achieving a preliminary decomposition rate of around 30%. The preheated feedstock is then delivered into the rotary kiln and calcined at a steady temperature of 1250 °C to complete calcium carbonate decomposition.
Nevertheless, granular feedstock adopted in vertical preheating systems exhibits limited gas-solid heat transfer efficiency compared with powdery materials under suspension fluidization conditions. Additionally, rotary kilns primarily rely on radiative heat transfer with low thermal utilization efficiency. Substantial surface heat dissipation from the kiln cylinder further elevates overall system energy consumption.
Double-chamber kilns represented by the Maerz kiln deliver low heat loss and mature technical performance, yet they are constrained by low single-line throughput and high upfront capital investment, limiting large-scale industrial promotion.
To overcome the inherent drawbacks of traditional calcination equipment, Sequoia has independently developed a full-set suspension calcination and cooling system for reactive lime production. This technology is compatible with both high-purity limestone raw materials and calcium-bearing industrial solid wastes, including dry and wet discharged carbide slag, with stable and reliable industrial application records. The integrated system features low thermal consumption, ultra-low pollutant emission, compact footprint and cost-effective investment.
Key technical performance indicators of the suspension calcination process for reactive lime powder are listed below:
Heat Consumption: < 1000 kcal/kg (limestone calcination); < 600 kcal/kg (carbide slag calcination)
Comprehensive Power Consumption: < 55 kWh/t (limestone calcination); zero grinding power consumption for carbide slag processing
Calcium Carbonate Decomposition Rate: > 95%
Lime Activity Value: > 320
Finished Particle Size: 90% of particles finer than 200 μm
Emission Compliance: Fully compliant with national and local environmental protection standards
Lime products produced via suspension calcination present stable quality and high chemical activity. The optimized particle size distribution perfectly satisfies pelletizing requirements for iron ore sintering, effectively improving sinter grade and comprehensive utilization efficiency of mineral resources.
2. Coal-series Kaolin High-temperature Calcination Process for Mullite Preparation
This process adopts high-purity coal-series kaolin with kaolin content exceeding 90% as the primary feedstock. With a Mohs hardness of 3–4, the raw material exhibits superior machinability compared with flint clay. Inherent trace moisture in raw ore effectively suppresses dust generation during crushing and conveying. The crushed material is delivered to a fully enclosed air classifier for particle grading. Fine fractions below 80 mesh are collected synchronously via cyclone separators and bag dust collectors. Oversized particles (+80 mesh) pass through a 10-mesh screening unit, with +10 mesh coarse materials returned to the crushing system for reprocessing, while qualified 10–80 mesh fractions are fed into a direct-fired rotary kiln.
Continuous calcination is performed at 1100–1500 °C with a holding time of 1–4 hours to complete dehydroxylation, phase transformation and sintering of kaolin. Post-calcination treatment includes targeted depolymerization and particle shaping to disperse sintered agglomerates, eliminate sharp particle edges and unify the aspect ratio of finished grains. High-intensity magnetic separation is subsequently implemented to remove iron-bearing inclusions and low-temperature fusible impurities. The purified materials are classified into commercial grades of 10–16 mesh, 16–30 mesh, 30–60 mesh and 60–80 mesh. The combined shaping and impurity removal process increases screening efficiency by 3–4 times compared with conventional workflows.
Final products feature uniform particle morphology and ultra-low micro-powder impurity content, with impurity residues controlled below 0.3% (ppm level), far exceeding the industrial threshold for precision casting applications. The integrated process reduces comprehensive production costs by approximately 50%. Sequoia’s customized coal-series kaolin calcination equipment enables directional mullitization reaction under precise thermal control, achieving high-value-added mullite material production from low-cost coal-series kaolin resources.
3. Resource Utilization Technology for Aluminum-bearing Solid Waste
Sequoia has developed serialized complete production lines covering aluminate clinker calcination and aluminum slag valorization for calcium aluminate and alumina preparation. All proprietary process technologies and supporting equipment packages have been fully validated and stably operated in commercial industrial projects, realizing efficient and large-scale recycling of aluminum industrial solid wastes.
4. Sulfuric Acid Production Process via Gypsum Resource Recycling
Conventional sulfuric acid production predominantly relies on sulfur ore and pyrite resources, which are associated with high raw material costs, resource supply constraints and poor economic flexibility. Meanwhile, massive stockpiles of industrial by-product gypsum (phosphogypsum, flue gas desulfurization gypsum) occupy land resources and induce soil and water environmental risks. Traditional disposal methods fail to achieve efficient resource recovery, resulting in low utilization rate and poor economic returns.
Sequoia’s optimized co-production process is adaptable to natural gypsum and various industrial secondary gypsum wastes. The integrated technical route consists of raw material pretreatment and purification, multi-stage suspension preheating and decomposition, high-temperature reduction calcination, and double-conversion & double-absorption refining. This systematic workflow realizes synchronous recovery of sulfur and calcium resources, achieving harmless disposal and high-value utilization of gypsum solid waste.
Raw gypsum undergoes purification, filter pressing and drying to remove free moisture and surface impurities, producing qualified anhydrous calcium sulfate raw meal. After homogeneous blending with quantitatively proportioned reducing agents and fluxing agents, the mixed feedstock is preheated in a multi-stage suspension system and then sent to a high-temperature rotary kiln. Reduction and decomposition reactions occur steadily at 1200–1350 °C to generate high-concentration sulfur dioxide flue gas. Kiln tail slag is cooled, screened and further processed to produce by-products such as calcium oxide and calcium-based building materials.
Sulfur-containing flue gas is purified through sequential dust removal, water washing, defogging and deep drying procedures before entering the catalytic conversion unit. Adopting vanadium catalyst-based double-conversion and double-absorption technology, the system produces high-purity industrial sulfuric acid with zero secondary pollutant discharge throughout the process.
Compared with traditional acid production routes, Sequoia’s gypsum-based process eliminates reliance on traditional sulfur mineral resources and fundamentally resolves environmental hazards caused by gypsum stockpiling. The system integrates full waste heat recovery, with recovered kiln waste heat applied for raw material drying and on-site power generation, cutting comprehensive energy consumption by 25%–30%. Featuring compact layout, high automation, stable operational status and low investment cost, the technology supports flexible capacity configuration and fully complies with national ultra-low emission and low-carbon industrial policies, delivering prominent environmental, social and economic benefits.
Core Technical Indicators:
Total Sulfur Conversion Rate: ≥ 96%
Sulfur Dioxide Conversion Efficiency: ≥ 99.8%
Comprehensive Energy Consumption: 25%–30% lower than conventional sulfuric acid production processes
Product Purity: Meeting premium industrial standards and battery-grade raw material specifications
Flue Gas Emission: Exceeding national and local ultra-low emission criteria
Solid Waste Utilization Rate: ≥ 98% with zero solid waste discharge
5. Advanced Suspension Calcination Process for Magnesite
Magnesite serves as the core raw material for light-burned magnesia, refractory products and magnesium-based chemical materials. Traditional magnesite calcination equipment including vertical kilns and conventional rotary kilns adopts static stacking calcination mode. Such equipment cannot achieve precise regulation of heating, holding and cooling curves matching magnesite phase transformation, leading to uneven material heating, insufficient decomposition, low magnesia activity, high energy consumption, limited single-line capacity and severe dust pollution. These defects render traditional technologies incapable of meeting quality requirements for high-end magnesium functional materials.
Based on long-term suspension fluidization and thermal calcination research, Sequoia has developed a dedicated high-efficiency suspension flash calcination system for magnesite. After crushing and precise grading, qualified magnesite fine powder is transported to a multi-stage suspension preheating unit. Materials are fully fluidized and dispersed in high-temperature flue gas, realizing uniform and rapid heat transfer through intensive gas-solid contact.
Preheated materials enter a specialized calcination reactor for constant-temperature pyrolysis within a controllable temperature range of 850–1100 °C. Calcination temperature, material residence time and flow field parameters are precisely adjustable to eliminate under-burning and over-burning phenomena caused by uneven heat transfer in conventional kilns. Post-calcination materials are cooled gradually via multi-stage suspension cooling according to optimal thermodynamic cooling profiles, maximizing the retention of magnesia crystal activity. Final high-performance light-burned magnesia products are obtained through subsequent screening and impurity refining procedures.
This technology is adaptable to raw magnesite, magnesite tailings and low-grade magnesite resources, significantly improving overall resource utilization efficiency. It supports continuous, automated and large-scale industrial production with flexible single-line annual capacity ranging from 100,000 to 1,000,000 tons. The fully enclosed negative-pressure operation structure ensures ultra-low dust emission. Compared with traditional calcination facilities, the system improves thermal efficiency by over 30% and reduces comprehensive energy consumption by 20%–30%, with substantially decreased labor and operational costs.
Finished products achieve a magnesite decomposition rate above 98%, featuring high chemical activity, uniform particle size distribution and ultra-low impurity content. The products are widely applicable to high-end refractories, metallurgical auxiliary materials, chemical building materials and environmental water treatment industries.
Core Technical Indicators:
Magnesite Decomposition Rate: ≥ 98%
Active Magnesia Content: ≥ 92%
Comprehensive Heat Consumption: 20%–30% lower than traditional magnesite calcination technologies
Particle Size Uniformity: Precisely adjustable with dimensional deviation ≤ 1%
Production Capacity: Customizable annual output of 100,000–1,000,000 tons per single line
Operation System: Full DCS automatic control, continuous stable operation with low failure rate
Environmental Performance: Dust and flue gas emissions superior to national and local ultra-low emission standards
Should you have any inquiries regarding our technologies, equipment packages and customized industrial solutions, please feel free to contact our team for further communication.
Sequoia 团队根据自身在建材、冶金行业超过20年的经验，先后开发了多台套应用于不同领域的热工煅烧设备。
一、悬浮态煅烧活性石灰工艺
目前，对非金属矿物（石灰石、铝土矿、白云石、菱镁矿等）的煅烧主要有以下几种方法，竖窑、回转窑、倒烟窑、隧道窑、推板窑等，这些煅烧方式很难按照矿物最佳的加热和冷却曲线进行，使晶体的应用特性不能完全体现，具有生产效率低、能耗大、产品性能不稳定等缺点。
以国内使用较多的回转窑煅烧石灰石的工艺为例，其煅烧所得产品具有性能相对较好、系统较稳定等优点。首先通过专用的竖式预热器将10~60mm的细粒级的石灰石颗粒预热到800℃左右，此时，石灰石分解率在30%左右，经过预热的石灰石随后进入回转窑进行煅烧，在约1250℃的高温煅烧下完成石灰石的分解。
但是，喂入竖式预热系统的物料为粒状物料，相较于粉状物料在悬浮预热器中的表现，其换热仍属于较差水平；同时，回转窑内主要是热效率不高的辐射换热，回转窑筒体的表面散热过大，造成系统能耗过高。
以麦尔兹窑为代表的双膛窑技术先进，热耗较低，但单条线合理规模较小，投资较大。
Sequoia 开发了一种既能利用石灰石生产活性石灰的悬浮态煅烧、冷却装置，也可以用于煅烧干排、湿排电石渣等含钙固废，得到了成功应用。该生产线优势在于：热耗低、污染物排放浓度低，占地面积小，投资小。
采用悬浮态方法煅烧活性石灰石粉的主要技术指标如下：
热耗: <~1000kcal/kg（煅烧石灰石） <~600kcal/kg（煅烧电石渣）
综合电耗：<55kwh/t（煅烧石灰石），煅烧电石渣时，无粉磨电耗
碳酸钙分解率：>95%
石灰活性：>320
煅烧物料粒度：90% <200μmm
排放标准：满足国标、地标要求
悬浮态煅烧的产品性能稳定，活动度高，对铁矿烧结品味的提高很有帮助，并且产品细度刚好能满足烧结成球的的要求。
二、煤系高岭土煅烧
用高岭土含量大于90%的矿物作为原料，首先将生产原料破碎，因为原料硬度为3-4级（摩氏），相对焦宝石更容易加工，原料中的少量水份降低了扬尘量，进入密闭式气流分级机，80目以细的颗粒经旋风除尘和布袋收尘器收集，＋80目的颗粒出来过10目筛网，+10目的返回破碎机，将自10-80目的砂料送入直燃式回转窑进行锻烧，般烧温度为1100-1500℃，般烧时间为1-4小时，般烧后对该产品进行解聚、整形，如将烧结的假团块打散，颗粒去尖棱，整形为长径比均一的颗粒，再经除杂，如经高强磁选机除去铁渣等低温烙融物质后，再筛分成10-16目，16-30目，3060目，60-80目各种产品，整形、除杂后筛分效率可提高3-4倍。本方法制备的产品的特点是粒形好、杂粉含量特别低，以PPm计算，低于0.3%的精铸行业标准上限，产品的制作成本平均可降低二分之一。
Sequoia 开发了专用的煤系高岭土煅烧装置，用于煅烧并形成高附加值的莫来石。
三、含铝固废资源化工艺（系统装备）
Sequoia团队开发了铝酸盐熟料煅烧生产线、铝灰制铝酸钙（氧化铝）生产线，并形成了系列化的成套装备，上述工艺装备都在生产实践中得到了成功应用。
四、石膏制硫酸资源化工艺
国内传统硫酸生产多依赖硫磺、硫铁矿原料，存在原料成本高、资源受限、固废处置压力大等问题，同时工业生产产生的磷石膏、脱硫石膏等副产石膏大量堆存，易造成土地占用、水土污染等环境问题，常规处置方式资源化利用率低、经济效益差。针对行业痛点，Sequoia团队优化升级石膏制硫酸联产工艺，适配天然石膏、磷石膏、脱硫石膏等多种含钙硫固废原料，打造高效、低碳、资源化的成套生产工艺及装备，实现固废变废为宝、硫钙资源双重回收。
本工艺核心采用预处理净化+悬浮预热分解+高温还原煅烧+两转两吸精制的一体化流程，首先对原料石膏进行除杂、压滤、烘干脱水处理，去除游离水与杂质，制成无水硫酸钙生料；搭配定量配比的还原剂、助熔剂均匀混磨后，送入多级悬浮预热系统完成低温预热，充分提升物料温度、预判分解效率；随后进入高温回转窑，在1200-1350℃恒温区间完成还原分解反应，析出高浓度二氧化硫窑气，窑渣经冷却、筛分、深加工可产出氧化钙、钙基建材辅料等副产品。含硫窑气经除尘、洗涤、除雾、干燥净化后，进入催化转化系统，通过钒触媒完成二氧化硫高效转化，经两次转化、两次吸收工艺精制，产出高品质工业硫酸，全程密闭无二次污染。
相较于传统工艺，Sequoia石膏制硫酸工艺核心优势突出，彻底摆脱对硫磺、硫铁矿原料的依赖，适配各类工业副产石膏固废处置，有效解决固废堆存环保难题；系统采用余热回收集成设计，窑尾余热可用于原料烘干、厂区供电，综合能耗较传统工艺降低25%-30%，硫综合转化率≥96%，硫酸产品纯度高，可满足工业、锂电磷酸生产等高端场景使用需求。同时整套生产线占地面积小、自动化程度高、运行工况稳定，单线生产规模灵活可控，投资成本低，适配大中小型规模化生产，完全契合双碳政策与环保排放标准，兼具环保效益与经济效益。
核心技术指标：
硫综合转化率：≥96%
二氧化硫总转化率：≥99.8%
系统综合能耗：较传统制酸工艺降低25%-30%
产品硫酸纯度：符合工业优等品、电池级原料使用标准
尾气排放：完全满足国家及地方环保超低排放标准
固废利用率：原料石膏综合利用率≥98%，无固废外排
五、菱镁矿悬浮煅烧工艺
菱镁矿是制备轻烧氧化镁、耐火材料、镁基化工产品的核心原料，传统菱镁矿煅烧多采用竖窑、普通回转窑、多层炉等设备，存在物料受热不均、煅烧反应不充分、产品活性偏低、能耗高、产能受限、粉尘污染大等行业痛点，传统工艺物料静态堆积煅烧，无法匹配菱镁矿最优升温、保温、冷却曲线，导致成品品质参差不齐、资源利用率低，难以满足高端镁质材料的生产需求。
Sequoia团队依托多年悬浮煅烧技术积淀，自主研发菱镁矿专用悬浮态高效煅烧工艺及成套装备，突破传统煅烧工艺瓶颈。工艺采用粉体悬浮闪速煅烧原理，将破碎筛分后的菱镁矿细粉料送入多级悬浮预热系统，物料在悬浮状态下与高温热风充分接触，实现快速、均匀预热；随后进入专用煅烧反应器，在可控高温区间完成恒温煅烧分解，煅烧温度控制在850-1100℃，可根据产品需求精准调控煅烧温度、停留时间与风速参数，物料全程悬浮流化、气固接触充分、换热效率极高，彻底解决传统煅烧受热不均、局部过烧、欠烧问题。煅烧完成后，物料经多级悬浮梯度冷却，按照最优冷却曲线快速降温，最大程度保留氧化镁晶体活性，最后经筛分、除杂、精制得到高品质轻烧镁系列产品。
本工艺可适配原矿菱镁矿、菱镁矿尾矿、低品位菱镁矿等多种原料，资源化利用率大幅提升，适配规模化、连续化、自动化生产，单线产能可实现10-100万吨/年灵活配置。整套系统采用全封闭负压运行结构，粉尘超低排放，环保性能优异；相较于传统炉窑，热效率提升30%以上，综合能耗降低20%-30%，用工成本大幅下降。成品氧化镁分解率≥98%，产品活性高、粒度均匀、杂质含量极低，性能稳定性远超传统工艺产品，可广泛应用于高端耐火材料、冶金辅料、化工建材、环保水处理等多个领域。
核心技术指标：
菱镁矿分解率：≥98%
活性氧化镁含量：≥92%
综合热耗：较传统菱镁矿煅烧工艺降低20%-30%
产品粒度：可精准调控，成品均匀性误差≤1%
产能规模：单套设备年产10-100万吨，支持定制化配置
运行模式：全自动化DCS控制，连续稳定生产，故障率低
环保指标：粉尘、废气排放均优于国标、地方超低排放标准
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