• 동력기계공학회지
• /
• 제13권6호
• /
• pp.76-81
• /
• 2009

Thermal desorption systems are designed to remove organic compounds from solid matrices such as soils, sludges and filter cakes without thermally destroying them. It is a separation technology, not a destruction technology. Since it is a thermal process, there is a common belief that temperature is the only significant parameter to be monitored. While it is true that better removal efficiencies are usually achieved at higher temperatures, other factors must be considered. Since the process is governed by mass transfer, heating time and the amount of mixing are also key parameters in optimizing removal efficiency. Thermal desorption have been successfully used for just about every organic contaminant found to date. It has also been used to remove mercury. In the present study, the numerical simulation has been performed to investigate the characteristics of heat transfer of LTTD(low temperature thermal desorption). The commercial software, AMESIM was applied for analyzing the heat transfer process in the LTTD.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2002년도 추계학술발표회
• /
• pp.44-52
• /
• 2002

Low temperature thermal desorption (LTTD) has become one of the cornerstone technologies used for the treatment of contaminated soils and sediments in the United States. LTTD technology was first used in the mid-1980s for soil treatment on sites managed under the Comprehensive Environmental Respones, Compensation and Liability Act (CERCLA) or Superfund. Implementation was facilitated by CERCLA regulations that require only that spplicable regulations shall be met thus avoiding the need for protracted and expensive permit applications for thermal treatment equipment. The initial equipment designs used typically came from technology transfer sources. Asphalt manufacturing plants were converted to direct-fired LTTD systems, and conventional calciners were adapted for use as indirect-fired LTTD systems. Other innovative designs included hot sand recycle technology (initially developed for synfuels production from tar sand and oil shale), recycle sweep gas, travelling belts and batch-charged vacuum chambers, among others. These systems were used to treat soil contaminated with total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs), pesticides, polychlorinated biphenyls (PCBs) and dioxin with varying degrees of success. Ultimately, performance and cost considerations established the suite of systems that are used for LTTD soil treatment applications today. This paper briefly reviews the develpoment of LTTD systems and summarizes the design, performance and cost characteristics of the equipment in use today. Designs reviewed include continuous feed direct-fired and indirect-fired equipment, batch feed systems and in-situ equipment. Performance is compared in terms of before-and-after contaminant levels in the soil and permissible emissions levels in the stack gas vented to the atmosphere. The review of air emissions standards includes a review of regulations in the U.S. and the European Union (EU). Key cost centers for the mobilization and operation of LTTD equipment are identified and compared for the different types of LTTD systems in use today. A work chart is provided for the selection of the optmum LTTD system for site-specific applications. LTTD technology continues to be a cornerstone technology for soil treatment in the U.S. and elsewhere. Examples of leading-edge LTTD technologies developed in the U.S. that are now being delivered locally in global projects are described.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제17권3호
• /
• pp.76-85
• /
• 2012

Geochemical and ecological properties of remediated soil and gas exhausted from a low-temperature thermal desorption (LTTD) process were analyzed to assess the environmental impact of LTTD treatment. Soil characteristics were examined with regard to the chemical (EC, CEC, and organic matter) and the ecological (dehydrogenase activity, germination rate of Brassica juncea, and growth of Eisenia andrei) properties. The exhaust gases were analyzed based on the Air Quality Act in Korea as well as volatile organic compounds (VOCs) and mixed odor. Level of organic Organic matter of the soil treated by LTTD process was slightly decreased compared to that of the original soil because the heating temperature ($200^{\circ}C$) and retention time (less than 15 minutes) were neither high nor long enough for the oxidation of organic matter. The LTTD process results in reducing TPH of the contaminated soil from $5,133{\pm}508$ mg/kg to $272{\pm}107$ mg/kg while preserving soil properties. Analysis results of the exhaust gases from the LTTD process satisfied discharge standard of Air Quality Law in Korea. Concentration of VOCs including acetaldehyde, propionaldehyde, butyraldehyde and valeraldehyde in circulation gas volatilized from contaminated soil were effectively reduced in the regenerative thermal oxidizer and all satisfied the legal standards. Showing ecologically improved properties of contaminated soil after LTTD process and environmentally tolerable impact of the exhaust gas, LTTD treatment of TPH-contaminated soil is an environmentally acceptable technology.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제13권4호
• /
• pp.62-68
• /
• 2008

본 연구에서는 토양 이송 장치, 로터리킬른, RTO, 사이클론 및 백필터 등으로 구성되어 있고 이동이 가능한 저온열탈착 장치를 제작하여 현장유류오염토양의 처리시험을 수행하였다. 제작된 열탈착장치는 LPG를 연료로 사용하고 배출되는 가스를 RTO를 통하여 재순환하는 방식을 적용하여 경제적인 운전이 가능하도록 하였다. 장치의 현장시험을 위하여 경유와 $C_30$ 이상의 heavy oil로 혼합 오염된 현장토양(2,690 mg TPH/kg soil) 을 먼저 선별기를 통해 50 mm 이하의 입경을 가진 토양으로 채 분리한 후, LTTD 장치의 로터리킬른에 체류시간 15분 조건에서 시간당 7$m^3$의 양으로 투입하였다. 열탈착장치의 온도를 각각 평균 $567^{\circ}C$와$692^{\circ}C$로 조정한 후 오염토양의 정화 운전을 수행한 결과, 배출되는 정화토양의 TPH 농도는 각각 46 mg/kg과 32 mg/kg로서 각각 평균 98.3과 98.9%의 높은 정화 효율을 얻을 수 있었다.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제14권5호
• /
• pp.62-70
• /
• 2009

본 연구에서는 lab-scale의 열탈착 장치를 설계 및 제작하고 실제 유류오염 토양을 대상으로 다양한 운전조건에 따른 오염토양정화성능을 비교하였다. 대상 토양은 군부대로 사용되던 부지 내 유류저장소 부근 고농도 오염토로 선정하였고, 10 L 용적의 원통형 batch 형태의 직접 가열식 열탈착기를 사용하여 초기 TPH 농도 4476 ppm의 고농도 오염 토양시료를 다양한 운전조건에서 열탈착하여 처리효율 분석을 수행하였다. 열중량 분석을 통해 열탈착 실험에서 대상 오염물질을 제거하기 위한 토양 시료의 평균 가열온도는 $200-300^{\circ}C$가 적합한 것으로 확인하였다. Batch 형식의 운전을 통한 처리효율 분석 결과 토양 내 오염물질을 90% 이상 제거하기 위해서는 약 $200^{\circ}C$에서는 10분, 약 $300^{\circ}C$에서는 5분 이상의 처리 시간이 요구되었다. 함수율이 높고 덩어리진 토양일수록 처리효율, 특히 고분자 오염물질의 처리효율이 크게 감소함을 보였다. 따라서 풍건을 통하여 오염토양 내 수분을 저하시킨 후 분쇄 처리하여 열탈착기에 주입하는 것이 효과적이라 판단된다. 또한 처리 전 토양과 처리 후 토양의 물리화학적 특성 비교한 결과 고온에 의해 증발된 수분함량을 제외하고 나머지 특성들은 거의 변화가 없어 실제 복원현장에서 오염토양을 열탈착 공정을 이용하여 오염물질을 제거한 후 추가적인 후처리 과정 없이 처리토양을 원래 위치에 복원하는 것이 가능함을 확인하였다. 본 연구결과는 현장운전에서 오염물질의 제거 효율을 극대화하기위한 인자 결정 및 검증을 위한 기초자료로 활용될 수 있을 것으로 사료된다.