Gattrell M.,NORAM Engineering and Constructors Ltd. |
Louie B.,BC Research Institute
ACS Symposium Series | Year: 2013
Adiabatic nitration has revolutionized mononitrobenzene (MNB) production, but has not similarly impacted the production of other nitro-aromatics. The issues related to changing to adiabatic nitration are discussed by comparing the nitration of toluene versus benzene using literature data and adiabatic stirred reactor nitration tests. The topics discussed include nitration rates, isomer distribution, and by-product formation. The homogeneous chemical reaction rate for the nitration of toluene is faster than benzene, but the overall rate for interphase mass transport and reaction is found to be fairly similar. The MNT isomer distribution is found to be a function of sulfuric acid strength, temperature, and nitric acid strength. The easier oxidation of toluene versus benzene results in a greatly increased number of oxidation by-products. This presents analytical difficulties in quantifying total by-products. Deeply colored, oxidized by-products can also accumulate in the recycled spent acid producing so called "black acid". However, once understood, the issues related to implementing adiabatic MNT production appear manageable. © 2013 American Chemical Society.
Berretta S.,NORAM Engineering and Constructors Ltd. |
Louie B.,BC Research Inc.
ACS Symposium Series | Year: 2013
Two main impurities are made in the industrial production of MNB. These impurities are nitrophenols and dinitrobenzene (DNB). The formation rates of these impurities are significantly affected by the initial reaction conditions. Understanding these effects is an important first step in the continuous on-going research aimed towards reducing the formation of these impurities. However, very limited work has been published on this subject. This paper presents the findings of a study done by the authors, conducted in a laboratory setting, examining the effect of relevant industrial operating conditions on the formation rates of nitrophenols and DNB. The selected operating conditions, which can usually be manipulated in most industrial production MNB facilities, are: initial sulfuric acid concentration, average reaction temperature, and nitric acid concentration in the mixed acid feed. © 2013 American Chemical Society.
Bandekar R.,NORAM Engineering and Constructors Ltd. |
Frederick J.,Table Mountain Consulting LLC |
Stavik J.,AV Nackawic Inc.
Tappi Journal | Year: 2016
This study addresses the challenges a dissolving-grade pulp mill in Canada faced in 2014 in meeting its total reduced sulfur (TRS) gas emission limit. These emissions from the recovery boiler exit are controlled by passing the boiler exit gas through a TRS scrubber system. The mill employs a cyclonic direct contact evaporator to concentrate black liquor to firing solids content. The off-gases from the direct contact evaporator flow to the effluent gas control system that consists of a venturi scrubber, a packed bed scrubber, and a heat recovery unit. Emissions of TRS greater than the regulated limit of 15 ppm were observed for a 4-month period in 2014. The level of emissions measured during this period was significantly higher than about 12 ppm, the expected average value based on historic experience. The problem persisted from mid-June 2014 until the annual mill shutdown in October 2014. The main TRS components detected and the performance of the Teller scrubber in capturing them are examined. Other potential causes for these emissions are identified, including mechanical problems such as broken packing in the TRS packed bed scrubber, broken baffle plates in the scrubber, and cyclone evaporator leaks causing air ingress. Repairs were carried out during the mill shutdown, which eliminated the TRS emissions problem.
NORAM Engineering and Constructors Ltd. | Date: 2012-08-21
NORAM Engineering and Constructors Ltd. | Date: 2012-03-20
chemicals for treating contaminated soils and water.