Feed Mill Boiler Efficiency and Heat Recovery Project
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Currently, the Landmark Feed Mill has many critical areas where modern technologies could be adopted to improve processes while creating a significantly more environmentally-friendly facility. At the time of construction over 50 years ago, sustainability was not a serious consideration in the mechanical systems nor the pelleting process. Any changes to components since have been purely out of necessity. As the Landmark Feed Mill consists of relatively inefficient equipment by modern standards, the mechanical systems could benefit from contemporary practices to improve overall energy usage. The key component in nearly all processes within the facility is the steam-generating boiler. The current setup does not exercise any means of heat recovery in the boiler circuit, resulting in excessive natural gas consumption and translating to increased financial cost as well as environmental impact. This project focuses on analyzing the boiler system of the Landmark Feed Mill, including the boiler, boiler exhaust stack, blowdown system, and all relevant piping. The main objective is to provide Maple Leaf with a design to decrease overall natural gas consumption, primarily through implementing heat recovery initiatives, and increasing plant efficiency as a secondary measure. As a result, the proposed final design minimizes the annual greenhouse gas emissions from the plant. The detailed design consists of five primary components to be implemented in individual phases. These components include a blowdown feedwater booster pump, linkage-less burner controls, an indirect condensing economizer, insulation of exposed piping, and consideration toward a new boiler in the near future. The concepts are presented in the recommended implementation order and are based on relative savings, costs, and complexity of implementation. The blowdown feedwater booster pump is a simple and economical solution, with a total system cost of $1,745.00 and an annual natural gas savings of 11,173 m3. The booster pump is placed in-line with the feedwater tank re-circulation line, increasing the flow rate through the existing wall-mounted heat exchanger. By increasing the flow rate on the feedwater side, an additional 57,753 Btu/hr of heat is recovered from the automatic blowdown line; this solution results in a system heat savings increase of 871%, an overall plant carbon dioxide emission reduction of 1.52%, and an annual cost savings of $1,914.67. Installation of linkage-less controls is recommended to increase combustion efficiency of the existing boiler while it remains operational. This process is performed by using computerized controls to optimize fuel-to-air ratio, resulting in a 4.00% increase in combustion efficiency. This equipment costs approximately $15,000.00 and saves 29,435 m3 of natural gas per year. This improvement also saves Maple Leaf $5,257.14 in annual natural gas costs. An indirect condensing economizer serves to recover sensible and latent energy from the boiler exhaust stack, transferring the energy to preheat feedwater. At a cost of $35,383.75, this concept saves the greatest amount of natural gas of any heat recovery system in this report at 90,759 m3 per year. A natural gas saving of this magnitude results in a carbon dioxide reduction of 12.33% and an annual cost savings of $16,209.52. Insulation of exposed piping is recommended alongside other improvements to retain the effects of the proposed heat recovery initiatives. In addition to preserving heat recovery, insulation increases overall safety for facility personnel by encapsulating exposed, high-temperature surfaces. Since pipe insulation is relatively inexpensive, it is recommended to be installed in the existing system as soon as possible and to be upgraded as additional heat recovery elements are installed in the plant. The total cost of the insulation for the complete heat recovery system is $2,796.84, saving $1,151.38 per year and 6,447 m3 of natural gas annually. This design component reduces overall carbon dioxide emissions by 0.88%. The existing firetube boiler at Landmark Feed Mill is 30 years old and requires replacement in approximately five years. At the time of replacement, it is recommended that a watertube boiler be sourced. A brand new boiler may be considered to be a profit maintenance project, costing approximately $243,750.00. An upgraded boiler results in savings of 45,993 m3 of natural gas and $8,214.28 annually. These savings translate to an efficiency increase of 6.25%. The total cost of these design concepts is $297,170.59. Due to a phased implementation plan, this cost will not be incurred all at once. Implementing one heat recovery initiative per year over the next five years provides a capital investment return of 12 years. If, as mentioned, the boiler is considered to be a profit maintenance project, the return on heat recovery initiatives is witnessed in year 4. With all concepts implemented, Landmark Feed Mill reduces natural gas consumption by 154,272 m3 per year, which provides a 20.96% increase in efficiency. Carbon dioxide emissions are decreased by 330,163 kg annually, equivalent to removing 72 cars from the roads in Manitoba. This motion helps propel Maple Leaf Foods down a path of sustainability for many years to come.