METHODOLOGY FOR WASTEWATER MINIMIZATION IN INDUSTRIES IN THE PETROCHEMICAL COMPLEX

Transcription

1 METHODOLOGY FOR WASTEWATER MINIMIZATION IN INDUSTRIES IN THE PETROCHEMICAL COMPLEX Fontana, D. 1 *, Kalid, R. 1, Kiperstok, A. 1, Silva, M. A. S. 2 1 Escola Politécnica Departamento de Engenharia Ambiental - Departamento de Engenharia Química Rede de Tecnologias Limpas (TECLIM) - Universidade Federal da Bahia 2 Unidade de Insumos Básicos (UNIB) Braskem Abstract. Industrial processes make intensive use of water during their normal operation. As a result, flows of liquid wastewater containing several pollutants (phenols, benzene, oil, dissolved metals,...) are generated which pose serious problems of environmental pollution. The recovery of water from the liquid wastewater has been the objective of many improvement programs in industry, and there is environmental legislation to regulate and to establish goals for this work. Due to pressure from environmental organizations, as well as demands for greater competitively in the market, industries are increasingly trying to participate in programs to reduce the environmental impact they themselves generate. This work introduces a methodology created in TECLIM/UFBA and developed in partnership with industry for wastewater minimization in industries at the Petrochemical Complex of Camaçari - Bahia. The methodology is based on techniques of mass integration described in the literature. The applicability of these techniques for wastewater reduction requires information such as flow rate, concentration of pollutants in the flow to be reused, and the levels of contamination permitted in the systems where it will be reused. However, the information connecting wastewater sources and water consumption points is not always available in the databases of the industries. The contribution of this work is the methods adopted for data collection for the applicability of these techniques inside industries. In this work we review reuse, recycle, regeneration techniques, including the description of the following stages: mapping of sources of contaminants and water consumers, ratification and/or rectification of flow rates and compositions, noting operational restrictions. A bank of ideas with opportunities for wastewater minimization is also part of the described methodology. Keywords: wastewater minimization, reduction in water consumption, data collection, mass integration. 1. Introduction Industrial processes make intensive use of water when functioning normally. As a result flows of liquid wastewater containing various pollutants (phenols, ammonia, benzene, oil, dissolved metals etc.) are generated which cause a serious environmental pollution problem. The recuperation of water from the liquid effluent has been the subject of many improvements in industry and environmental legislation exists to regulate and establish targets for this work. Due to pressure from environmental organizations as well as demands for greater competitiveness in the market industries are increasingly aware of the need to participate in programs to reduce the environmental impact generated by them. The work presents a method created in TECLIM/UFBA in the course of such a program carried out in partnership with industry to minimize wastewater at the Camaçari, Bahia Petrochemical Complex. The methodology created was based on mass integration techniques described in literature. The applicability of these techniques for the reduction of wastewater require information such as: flows, concentration of contaminants in the stream to be reused, the level of contamination permitted in the systems where reuse will occur, the logistics between the source of wastewater and the water consumer; information which is not always * To whom all correspondence should be addressed. Address: Escola Politécnica, UFBA Rede TECLIM, Salvador Brazil fontana@ufba.br 1

2 available in the data bases of the industries. This paper describes the methods adopted for the acquisition of this data for the applicability of these techniques in industrial plants. 2. Methodology The methodology developed for the minimization of wastewater described in this paper comprises the following stages: a) mapping the sources of wastewater and water consumers; b) ratifying and rectifying flows and their composition; c) detailing operational restrictions; d) drawing up the Water Balance; e) compiling the Ideas Bank; Below is a detailed description of each of these stages and an introduction to the techniques which serve as a base for the development of this methodology How to reduce the generation of wastewaters? Mass integration techniques for the minimization of wastewater found in the literature, Fontana (2002), and Pessoa (2001), are summarized below: Reduction at source: reduction in the consumption of water with changes and/or improvements in the processes or operating procedures. Some examples of this technique: Elimination of leakages; Changes in operational procedures; Reformulation of products; Modification of equipment; Purification of raw materials and supplies. Reuse: reuse of wastewater directly in another operation or process; Fig. 1: Reuse of wastewater from process 2 to process 1. Reuse with regeneration: total or partial removal of contaminants from the wastewater to reuse this stream in another operation or process. Regenerator: Equipment for the removal of the contaminant: 2

3 Fig. 2: Regeneration of the wastewater from process 2 to be reused in process 3. Recycling with regeneration: total or partial removal of contaminants from the wastewater to reuse this same stream in the same operation or process; Fig. 3: Regeneration of wastewater to be recycled in the same process. The application of the techniques described above has the following advantages: Reduction in the final wastewater flow generated and consequent reduction in cost of wastewater disposal; Reduction in the consumption of an exhaustible natural resource - water - reducing the cost of water intake; The feasibility of the application of the techniques of reuse and recycling basically depend on: 1. The availability of sources of wastewater with physical/chemical characteristics which are compatible with the water consumers; 2. The logistics between the source and consumer should be economically viable. The availability of sources and consumers with compatible physical/chemical characteristics means that the restrictions of the inflow into the consumers as regards the level of contamination from the source of wastewater which is intended for reuse should be sufficient not to endanger the integrity of the process downstream. This type of restriction can be overcome by inserting regeneration equipment to remove the contaminant leaving the flow to be reused with a level of contamination permissible for reuse. Logistical criteria such as the distance between the source and consumer, the existence of pipe rack, the availability of storage tanks (e.g. reuse of source with intermittent flow and a continuous consumer), and the need for pumping should all be taken into account as they could adversely affect, in economic terms, the implementation of these techniques in the plant. The methodology for data collection described here was guided by previous knowledge of mass integration mentioned above. The stages of data collection for the application of these techniques are described below. 3

4 2.2. Mapping of sources of wastewaters and water consumers The mapping of sources of wastewater and water consumers was done by studying technical reports, fluxograms of the distribution of utilities, fluxograms of the processes (PFD s), technical field visits, interviews with operators and engineers. For each source of wastewater and each consumers identified the following information was collected: tag (code) of the generating piece of equipment, type of water supply required by the consuming equipment, type of wastewater (organic or inorganic), flow rates, Quality of Information (QI) associated with the flow data (a tool to associate the information to levels of certainty) and frequency of operation (continuous or sporadic). A database with this information was then compiled Ratification of the flows and their composition Ratification or rectification of flows With the main sources of effluents and the main water consumers with their respective flow rates identified, each with their QI value (see item 2.5.1) mapped in the first stage of the work, it is then necessary to ratify and rectify these flows. The aim of this stage is to improve control or management of wastewater sources as well as improve the Water Balance. Taking as reference the mapping of the first stage, and taking into account the resources available, some points were selected for QI improvement. The ratification or rectification of flow stage was carried out using: Flow measurements on site; Checks and requesting calibration of existing flow instruments in the plant; Flow calculations via mass and energy balance; Designed flow, found on the datasheets or in PFDs; Flow obtained by using meters in the plant from data collected by the database of the automation system and internal plant controls; To guarantee accurate readings from the existing meters in the plant calibration of the flow indicators of the water flow was requested and confirmed. From the list of points to be improved in terms of QI, the measurement stage was planned according to the following procedure: a) Verification on site of the points to be measured; b) Choice of type of measuring device: standard volume cup and chronometer or portable ultrasonic flowmeter; c) A list of the additional resources required to carry out measurement; On site inspection was carried out to evaluate the type of measuring device better suited for the job. The points where the measurement was to take place were photographed and described (location, pipeline leveling, 4

5 type of liquid, type of line material and diameter) as regards necessary specifications, mainly those related to the use of the portable ultrasound flowmeter in liquid flows. Some measurement points required the use of additional resources so that measurement could be carried out such as: man lift, scaffolding, flange removal in piping. To guarantee the accuracy of the measurements, care was taken to make a note of the operational condition of the plant (the unit s load) and the time (seasonal variation) while measuring. An attempt was made to make the measurements at times of normal operation (normal load). The results from this stage were tabulated and served as a base to update the data of the water balances Ratification or Rectification of the composition of the wastewaters For reuse and recycling to be viable it is necessary to ascertain the quantity of each contaminant present in the wastewater flow to be reused. With the data from the flow and a qualitative description some of the sources of wastewater, which had not been routinely analyzed were selected for sample collection and subsequent analysis for their physical/chemical parameters. The stage for the ratification or rectification of the composition of the wastewater was as follows: Qualitative evaluation of the streams, from previous knowledge of the process obtained together with the mapping of the streams; Quantitative evaluation of the parameters (ph, temperature, conductivity, salinity, dissolved oxygen etc.) using a multi-parameter measuring instrument on site; Collection of samples on site; Laboratory analysis of the physical/chemical parameters of the samples collected. The laboratory analysis of the sources of wastewater is essential to verify the physical/chemical compatibility of the sources and consumers, allowing us to evaluate the viability of reuse of this stream Identifying the operational restrictions An important stage to make reuse feasible, having already ascertained the sources of wastewater and their respective characteristics, is a study of restrictions on input (Cins) for the consumers. In this stage the maximum concentration of contaminants acceptable by the consumer without compromising the integrity of the process has to be identified. The identification of Cins was carried out using: A study of the processes and the drawing up a checklist to guide interviews with the technicians on site; Interviews with technicians from the company answering the questions on the checklist; Looking up references in the literature; The checklist included questions such as: Which contaminants pose a critical threat to the system? Is there a record of the use of any other supplies in the consumer in question? What type of low quality, in terms of contaminant load, liquid could be used in the process? 5

6 Once the availability of sources of base or acid wastewater and the consumers had been identified, the soda and acid consumers in the plant were traced. The results of this stage and the ratification or rectification of the wastewater content enabled the assessment of the compiled ideas regarding the physical/chemical compatibility between sources and consumers Water Balance (WB) A useful tool for the management and use of water in a productive process is a Water Balance. The liquid flow representing streams of water, steam, condensation and wastewater are put into the balance. The flow data in the water balance refer to a particular period. The average flow data or the flow that best represented the period was selected. An example was the average flow: flows obtained using meters installed in the plant which send data to the automation systems in the plant with measurements taken each minute. To be able to compare flow, particularly from sources of wastewater such as sporadic drains, all the flows were continuously compiled taking into account specific flows and the duration and frequency in the evaluation period. Another criterion adopted to facilitate comparison among the flow amounts was the selection of a base of data flow to be inserted into the water balance. Because there were both liquid and steam flows, the base chosen was mass, represented by t/h Quality of Information (QI) One of the great difficulties of drawing up the water balance for this petrochemical industry, designed 20 to 30 years ago when there were few concerns as regards the use of natural resources and water was considered an inexhaustible resource, is the difficulty in acquiring information regarding flows. The high cost of instruments at the time of the plants design meant that only petrochemical flows were measured. Because of this, most other liquid flows lacked installed flow meters. Therefore the flows which were measured were insufficient to draw up the Water Balance of the plant. To overcome this obstacle, the flow data was collected in various ways: measured, calculated using balances and using design documentation. Given this, there was a need to associate a degree of certainty to the way in which the data was obtained. A tool which associates a value to a flow with a degree of certainty was used, it is called Quality of Information (QI). In this system the maximum quality value is given to measurements made with totalizing equipment installed on the pipeline and the minimum value is given when there is a lack of flow information. Figure 4 shows the scale of values proposed in Quality of Information. 6

7 Fig. 4: Quality of Information Scale. This scale was developed after various tests with other scales, taking into account the final result from the reconciliation of data of flow so as to obtain a result which was coherent with the reality of the plant. One of the advantages of this tool is that it allows us to make up the water balance with the data from the flows without initially having to worry about the unknown flows. Having the water balance already set up with flows associated with their QI, the next step is QI improvement. One of the great advantages of this tool is that it gives us the opportunity to improve the water balance via the identification of critical points which require QI improvement. Throughout the stages of the project, in practical terms, the following QI values were attributed to obtain the flow data. Amounts obtained from estimates from operators and engineers were given a QI value of 0.23; Amounts obtained from the equipment s datasheets, i.e. amounts specified in the design were given a QI value of 0.19 ( for old design or before the revamp or project level B) and 0.38 ( for recent design or project level A); Amounts obtained by using a routine volume measuring recipient and a chronometer were given a QI value of 0.9; Amounts obtained from measurements made using a portable ultrasonic flowmeter were given a QI value of 1.78; Amounts obtained from the database of the plant s automation system were given a QI value of 100 as this data collection of installed meters in the production process as well as totaling the flow data. 7

8 The QI values of the flows obtained by mass balance were obtained: QI N QI i= 1 ponderado = N i= 1 i F F i Where: QI = quality of information about the flow; F = amount of flow; i= refers to the current associated with the flow; N = Number of streams involved. i, (1) E.g. Scheme of any process with their streams: 2646, ,62 2,6 QI 3 = = 9,6 2646, , Flow data reconciliation of the Water Balance The difference between the total flow of the intake streams and the output in the industrial unit is rarely zero, indicating non-closure of the balance. The recommended way to make the balances consistent is the reconciliation of data, which also helps in the detection of gross errors in flow. By having the flows associated with their degree of certainty, the reconciliation looks for new flows that can satisfy the balance equation through the distribution of uncertainty. From a knowledge of the common problems found in the reconciliation of data from existing water balances and using the QI tool, it is possible to adapt this formulation to the methodology of Water Balance. The methodology used in the implementation of the Water Balance, the reformulation of the QI scale and the reconciliation are described in greater detail in Fontana et al. (2004) Ideas Bank Despite the fact that the Water Balance is important in the management of water resources, the minimization of wastewater and the reduction in the consumption of water depends on the identification of pairs of source/consumers of wastewater. To classify this information a tool accessed via the Internet was set up called the Ideas Bank. 8

9 A form was drawn up to register the ideas of technician and engineers at the plant and these were compiled in the Ideas Bank. The best opportunities in terms of positive environmental impact were evaluated and will go on to aid the conceptual design and changes in operational procedure. The expected benefit from implementing a minimization of wastewater project is at least a reduction in the cost of wastewater disposal, reduction in the cost of water intake and minimizing treatment from the supply source. 3. Results As a result of the application of these techniques in the UNIB Braskem an effective reduction in the flow of wastewater generated has been achieved. The reduction in volume was of m 3, which translates into a reduction in costs of US dollars/year (at dollar/real exchange rates on ). Figures 05 and 06 shows a reduction in the generation of inorganic and organic wastewater respectively, weighted by the raw material of the petrochemical process in the course of the application of the methodology described here. Fig. 5: Changes in the generation of organic wastewater. Fig. 6: Changes in the generation of inorganic wastewater. 9

10 As well as the reduction of wastewater shown above, over a year 48 opportunities for minimization of water consumption and reduction in the generation of wastewater were registered some of which have given rise to other projects. More detail on these can be found in Motta et al Another important result was the training in the management of water resources given to the technicians in companies at the petrochemical complex. 4. Conclusions and future work The techniques described in this paper were effective in the reduction of wastewater and minimization of the consumption of water at the petrochemical industry under study. The methodology used in this work is being used and perfected in other cooperative projects with industries such as Deten Química, Caraíba Metais and Lyondell, also located in the petrochemical complex. References Fontana, D., Kalid, R., Kiperstok, A. et. al. (2004). Balanço Hídrico Uma nova sistemática. XV Congresso Brasileiro de Engenharia Química. Curitiba, PR. Fontana, D. (2002). Recuperação de águas de processos Desenvolvimento de um problema padrão. Porto Alegre, RS. Motta, R., Kalid, R., Kiperstok, A., Fontana, D. et. al. (2005). Water reuse at Camaçari Petrochemical Complex: Eco- Braskem Project. ENPROMER Costa Verde, RJ, submitted. Mustafa, G.S. (1998). Reutilização de Efluentes em Indústria Petroquímica. Dissertação de Mestrado em Engenharia Química. Escola Politécnica, Universidade Federal da Bahia. Salvador, BA, 104. Pessoa, F. L. P. (2001A). Apostila do curso: Pinch Massa. Rio de Janeiro, RJ, 92. Pessoa, F. L. P. et. al. (2001B). Design procedure for water/wastewater minimization: single contaminants. Rio de Janeiro, RJ, 20. Silva, M. A. S., Pereira, A. C. (2000). Processos de Produção da COPENE. Camaçari, BA, 115. Acknowledgments I would like to thank the FINEP and Braskem for the opportunity to carry out this project. 10