Recipient Organization
Precision Combustion, Inc.
410 Sackett Point Road
North Haven,CT 06473
Performing Department
(N/A)
Non Technical Summary
The U.S. strawberry crop centered on 40,000 acres in California supplies 30% of the worlds strawberries, a marvel of American agricultural productivity. It is also emblematic of fumigation-supported high U.S. agricultural productivity, achieving soil sterilization of soil-borne pests necessary for high yield by using as much as 400 pounds per acre (at an average cost of $3500/acre) of ozone-depleting greenhouse gas methyl bromide. Although methyl bromide use is being phased out, California strawberries and some other crops are currently operating under critical use exemptions. A viable alternative for soil fumigation is steam, which is known to be highly effective and environmentally safe. However, steam has not been embraced for outdoor applications due to multiple disadvantages including size and capital cost of equipment, slow steam rates and operating costs, water quality requirements, and low fuel efficiencies. Mobile steam applicators, such as the steam rake and the steam blade have been deployed, both being pulled through the soil either by a winch or by a self-propelled unit containing a boiler to produce steam. Typical treatment rates of only around 0.5 acres per day, and costs notably above methyl bromide. The drawbacks to this method again are size, weight, speed and cost. Precision Combustion, Inc. (PCI) supported by the University of California Davis and University of Connecticut proposes to develop a compact direct-fire and high-heat-rate steam generator that can be configured into a cost-effective soil steam sterilization system for agricultural use. PCIs compact, high efficiency steam generator will enable the use of steam on a large and economic scale, providing an improved means of protecting agricultural production systems from diseases and pests. We estimate that costs will be at or below that of methyl bromide, and test results have shown that strawberry yield can be increased by as much as 15%. In Phase I, we will develop the technology to run on farm-available fuels, propane or natural gas,, using available field water, and create engineering solutions to enable the steam generators use on mobile agriculture equipment. We will develop designs resolving the trade-offs between steam generation rates, soil application rates, and support equipment requirements. In addition to significant weight savings and significantly higher heat rates, advantages of the PCI approach includes over 95% fuel energy efficiency, and the use of untreated well water. If successful, we anticipate being able to effectively treat acreage on a costs competitive basis with methyl bromide applications, and potentially with increased yield. Phase I success will lead to a Phase II field trial with strawberries. Success in the field trial with favorable economics could lead to rapid deployment of the technology, including for application with other high-valued crops. The use of steam rather than pesticides and chemical fumigants addresses NIFA / USDA priority research areas as well as Societal Challenge areas of global food security and climate change.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The overall objective of the Program is to develop a compact high heat rate steam generator technology that can be configured into a cost-effective soil steam disinfestations system. The core direct-fired burner technology has been proven in gas turbine environments and is being developed for steam generation for high pressure steam generation applications such as the production of heavy oil or methane hydrate, and also for in-situ thermal soil remediation. Phase I of this project will be to understand heat and steam volume requirements, mobile steam generator constraints, and commercial considerations. A subsequent Phase II of the Program will expand the Phase I results into testing of a full scale steam generator on mobile equipment at an appropriate field test site. Milestones for the Program are: M1: Complete System Study - 5 months after start of project M2: Complete Support Equipment Specification - 7 months after start of project Expected outputs include but are not limited to: soil processing requirements, outlet and operating conditions, specific mechanism of heat transfer; required heat production rate, choice of fuel, and desired arrangement of steam generator components. From these specifications, PCI will perform initial sizing and trade-off analysis and down-select to meet requirements. In addition, PCI will determine and specify required support equipment. PCI will investigate methods of operation of the steam generator including startup/shutdown procedures, system health monitoring and control, and modes of failure and risk mitigation. This assessment would utilize internal PCI resources and our collaborators. PCI will share the results of the analysis with interested commercial developers of the technology and, based on results and feedback, will modify the steam generator system design. This work will strengthen the Program, and ultimately the success of the steam generator, through determination of the appropriate sizing and operation for successful test/field operation.
Project Methods
PCI will estimate an appropriate heat rate determined through examination of required soil temperature increase, dwell time, and desired processing rate, in terms of cubic foot of soil per hour. We will address whether the configuration will consist of one generator connected to a distribution network, or multiple generators mounted on swing arms, for example. With a target heat rate determined, the operating and outlet conditions of the steam generator. Will be examined, including variable operating pressures (from 0 to 150 psi) to allow for steam injection at depth into the soil, fuel specification and ability for fuel flexibility between natural gas, propane, and liquid fuels likely available (kerosene and diesel), emission requirements, and outlet temperature/steam quality (wet steam, saturated steam, and supercritical steam). PCI will develop relations indicating required flow rates of fuel, air, and water to meet the target soil processing rates. This will take the form of an operating window of target rates/system sizes. Based on this, the preliminary envelope of overall dimensions of the direct-fired steam generator or generators will be developed. We need to achieve even distribution of water to not only achieve target temperature, but do so rapidly and in a means that avoids unmixed regions and scale deposition onto solid surfaces. Rapid mixing is important to avoid excessive size and weight, with consequences of not meeting requirements related to mounting on mobile equipment or excessive costs. Unmixedness will lead to high temperature combustion gases contacting the soil, which could lead to soil damage, destruction of beneficial soil organisms, and in worst-case scenario, combustion of soil components. Deposition of scale on burner or steam generator components will lead to loss of function and reduction in efficiency. We will use computational-fluid dynamics to assist in this subtask. PCI will preliminarily specify and identify the support equipment for field application. Varying configurations of the steam generator and support equipment will be considered. This will include fuel/air/water supply chains (including required air/fuel/water compressors/pumps and supply piping), required controls and integration into the mobile platform, and water quality requirements. In order to match specific applications, a family of sizes and heat outputs of steam generators may be considered, but efforts will be made to achieve maximal commonality. PCI will identify and evaluate configurations and designs of the overall steam generator system including steam generator, and supplies for air, fuel, and water to the steam generator with emphasis on using existing methods, equipment, and techniques during deployment. Configuration to be considered include an integrated system where all components are located on the mobile steam generator platform versus having the steam generator mobile with fuel, air, and/or water supplies located in a fixed location with connections provided by a flexible line. Evaluation will be performed based on available power sources, system weight, and overall complexity.